TECHNICAL FIELD

The present invention relates to an electro-hydraulic linear actuator. The present invention further may relate to compact self-contained electro-hydraulic linear actuators.

The present invention further may relate to compact self-contained electro-hydraulic intermittent operation linear actuators.

The present invention further relates to an electro-hydraulic linear actuator configured for moving a solar tracking device.

The present invention further relates to a solar tracking device.

The present invention further relates to a heliostat.

The present invention also relates to a method of controlling the operation of the electro- hydraulic linear actuator.

The present invention also relates to a method of controlling the motion of a solar tracking device.

The present invention also relates to a method of controlling the motion of a heliostat.

The present invention concerns the industry making use of electro-hydraulic linear actuators for different types of applications and concerns the manufacture industry producing electro- hydraulic linear actuators.

The present invention may be applied to seeder arrangements, seed drills and planter machines/vehicles comprising the electro-hydraulic linear actuator configured to move planter/seeder units or may relate to load (e.g. timber) carrying vehicles and configured to move stake bars along the carrying vehicle.

The present invention may relate to pallet trucks.

BACKGROUND

Current electro-hydraulic linear actuators are bulky, energy consuming and heavy.

Actuator arrangements for current planter/seeder machines comprising movable planter/seeder units or current load carrying vehicles comprising movable stake bars, may be bulky, energy consuming and heavy. Current electro-hydraulic linear actuators are complex and involve high service and maintenance costs.

Current electro-hydraulic linear actuators are subject to rough environment.

Current electro-hydraulic linear actuators have poor efficiency and use a major part of energy consumption.

Solar tracking devices and/or heliostats of today use expensive electro-mechanical actuator systems, which imply high installation and maintenance costs. As solar cells and heliostats become more common, the expensive solar tracking devices and heliostats of today may hinder the use solar tracking devices and/or heliostats and thus fossil free energy production.

SUMMARY OF THE INVENTION

There is an object to provide an electro-hydraulic linear actuator and/or compact self- contained electro-hydraulic linear actuator of the type defined in the introduction, which is less bulky than prior art actuators.

There is an object to provide a self-contained electro-hydraulic intermittent operation linear actuator, which is less bulky than prior art actuators.

There is an object to provide a self-contained electro-hydraulic intermittent operation linear actuator, which can be designed compact and being light.

There is an object to provide storability and easy mounting and positioning of e.g. planter/seeder units, and/or stake bars.

There is an object to provide easy and cost effective testing and handling of the electro- hydraulic linear actuator.

There is an object to provide an electro-hydraulic linear actuator that operates intermittently and is of as few valves as possibly for saving space.

There is an object to provide an electro-hydraulic linear actuator configured for moving a solar tracking device configured to orient a panel device, such as a solar panel, a parabolic trough, a reflector etc., toward the sun.

There is an object to provide an electro-hydraulic linear actuator configured for moving a heliostat reflecting sunlight toward a concentrator device.

Alternatively, the solar tracking device and/or heliostat comprises at least one electro- hydraulic linear actuator. The word “panel device” may be replaced by the words “wind load up taking device” or by the word “object”.

The word “panel device” may be defined as a panel having a surface extension facing the sun.

The definition of a heliostat means a device that includes a mirror, usually a plane mirror, which is configured to pivot so as to keep reflecting sunlight toward a predetermined target or concentrator, compensating for the movement of the sun.

There is an object to provide an electro-hydraulic linear actuator that is configured for managing relatively slow rod movements and very long rod strokes (e.g. 2 to 10 m) and where the movement pattern is very well-defined and repeated, as is the case regarding a heliostat or solar tracking device.

There is an object to provide an electro-hydraulic linear actuator that is configured to make use a small volume of hydraulic fluid for one piston stroke.

There is an object to provide an electro-hydraulic linear actuator that is configured to hold the rod in a holding state under high axial forces.

There is an object to provide an electro-hydraulic linear actuator that does not make use of pipes or hoses.

There is an object to provide an electro-hydraulic linear actuator that provides movements without any slack and/or backlash.

There is an object to provide an electro-hydraulic linear actuator that implies use of cost- effective control circuitry system compared to servo-based systems.

There is an object to provide an electro-hydraulic linear actuator that renquires less service than prior art systems.

There is an object to provide an electro-hydraulic linear actuator that provides long strokes and/or large levers and/or large locking forces, wherein large torques can be handled.

There is an object to provide an electro-hydraulic linear actuator that provides high resolution.

There is an object to provide a solar tracking device and/or heliostat that comprises a robust linear actuator for controlling the panel device.

For the structural dimensioning of solar panels and heliostats, wind loading and deformation due to gravity are decisive. There is an object to provide a solar tracking device and/or heliostat not being prone for tracking errors due to backlash (play) of the linear actuator.

There is an object to provide a solar tracking device and/or heliostat that overcome breakaway torques due to wind loads (e.g. caused by turbulence) affecting the panel device to fluctuate implying high forces on the solar tracking device and/or heliostat.

There is an object to provide a solar tracking device and/or heliostat providing tracking accuracy.

There is an object to provide a solar tracking device and/or heliostat that resists heavy wind loads and promotes that the panel device easy can be oriented in stow position during storms.

There is an object to provide a solar tracking device and/or heliostat that is light.

This or at least one of said objects has been achieved an electro-hydraulic linear actuator comprising; one single cylinder housing extending along a central axis; one single piston body dividing the cylinder housing in a first and second cylinder chamber; a rod extends along the central axis through the cylinder housing and through a first rod clamping device of the piston body; the first rod clamping device comprises a first expandable cavity configured to deform a first flexible inner wall of the piston body (by pressurizing the first expandable cavity); wherein the electro-hydraulic linear actuator is configured as a self-contained electro- hydraulic linear actuator comprising a hydraulic fluid supply; which comprises a channel arrangement arranged between a hydraulic pump and the cylinder housing and between the hydraulic pump and the first expandable cavity; a valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid; and an electrical power device for operating the electro-hydraulic linear actuator (for operating the electro- hydraulic linear actuator).

Alternatively, the electro-hydraulic linear actuator comprises a second rod clamping device, through which the rod extends along the central axis.

Alternatively, the first rod clamping device comprises a first expandable cavity configured to deform a first flexible inner wall of the piston body, wherein the piston body is configured to clamp around the rod and move the rod by making a piston body stroke.

Alternatively, the piston body stroke is defined as a working stroke made by the piston body from a second cylinder cap end position to a first cylinder cap end position.

Alternatively, the first and second rod exhibit a rod diameter of 50-100 mm and being hollow for saving weight. In such way is achieved that also large solar tracking devices, solar panels and heliostat mirrors, can be rigidly supported by the first and second rod of the respective first and second electro-hydraulic linear actuator.

Alternatively, the electro-hydraulic linear actuator is configured to perform a movement pattern controlled by a Bang-Bang control algorithm adapted to the control circuitry for providing a feedback loop procedure.

Alternatively, the Bang-Bang control algorithm is a 2-step or on-off control performed by the control circuitry, wherein the control circuitry is coupled to the valve arrangement and configured to control the operation of the electro-hydraulic linear actuator in a feedback loop procedure, wherein the control circuitry may be configured to switch instantly between a first rod engaging state of the first rod clamping device and a first rod disengaging state of the first rod clamping device, and alternatively the control circuitry may be configured to switch instantly between a second rod engaging state of the second rod clamping device and a second rod disengaging state of the second rod clamping device

In such way is achieved a compact electro-hydraulic linear actuator making use of 2-step control in a feed loop system for moving a long rod along the central axis, in a robust and stable manner.

Alternatively, the electro-hydraulic linear actuator comprising the second rod clamping device comprising a second expandable cavity configured to deform a second flexible wall of the second rod clamping device.

Alternatively, the electro-hydraulic linear actuator comprises one single cylinder housing extending along the central axis and comprises one single piston body dividing the cylinder housing in a first and second cylinder chamber, whererin the rod extends along the central axis through the first rod clamping device of the piston body and through the second rod clamping device.

Alternatively, a hydraulic accumulator of the electro-hydraulic linear actuator is configured for storing pressurized fluid for use in pressurizing the first and/or second expandable cavity.

Alternatively, the valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid to the respective first and second expandable cavity in accordance with said Bang-Bang control algorithm in a 2-step or on-off configuration performed by the control circuitry in such way that when the first expandable cavity is controlled to be pressurized for clamping, the second expandable cavity is controlled to be de-pressurized for permitting sliding of the rod through the second rod clamping device. Alternatively, the valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid to the respective first and second expandable cavity in accordance with said Bang-Bang control algorithm in a 2-step or on-off configuration performed by the control circuitry in such way that when the first expandable cavity is controlled to be de pressurized for permitting sliding of the rod through the first the one single piston body, the second expandable cavity is controlled to be pressurized for clamping.

In such way, the one single piston body can be returned to a starting position in a return stroke, whilst the rod is held stationary by the second rod clamping device.

Alternatively, the second rod clamping device comprises a second expandable cavity configured to deform a second flexible wall of the second rod clamping device.

Alternatively, the valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid to the respective first and second expandable cavity in accordance with said Bang-Bang control algorithm in a 2-step or on-off configuration performed by the control circuitry in such way that when the first cylinder chamber of the one single piston body is controlled to be pressurized for moving the piston body in a working stroke, the first expandable cavity of the one single piston body is controlled to be pressurized for clamping around the rod, for providing engagement of the one single piston body to the rod.

Alternatively, the valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid to the respective first and second expandable cavity in accordance with said Bang-Bang control algorithm in a 2-step or on-off configuration performed by the control circuitry in such way that when the second cylinder chamber of the one single piston body is controlled to be pressurized for moving the piston body in said return stroke, whereas the first expandable cavity of the one single piston body is controlled to be de-pressurized for providing that the one single piston body slides along the rod.

Alternatively, the piston body stroke is defined as a return stroke made by the piston body from a first cylinder cap end position to a second cylinder cap end position.

Alternatively, the piston body stroke is defined as a working stroke made by the piston body from a second cylinder cap end position to a first cylinder cap end position.

Alternatively, the valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid to the respective first and second expandable cavity in accordance with said Bang-Bang control algorithm in a 2-step or on-off configuration performed by the control circuitry.

Alternatively, the control circuitry may be configured to switch instantly between a first rod engaging state of the first rod clamping device and a first rod disengaging state of the first rod clamping device, and alternatively the control circuitry may be configured to switch instantly between a second rod engaging state of the second rod clamping device and a second rod disengaging state of the second rod clamping device

In such way is achieved that e.g. a total rod stroke of 3500 mm can be provided, wherein each made piston body stroke being e.g. 2 mm for each individual stroke, which implies 1750 piston body strokes for making said total rod stroke.

Alternatively, the electro-hydraulic linear actuator of the solar tracking device is configured to provide a piston body stroke of 10-30 mm, preferably 5-25mm.

Alternatively, the electro-hydraulic linear actuator of the heliostat is configured to provide a piston body stroke of 1-3 mm or 1-5mm.

In such way is achieved an electro-hydraulic linear actuator that supports a robust and cost- effective solar tracking device.

In such way is provided an electro-hydraulic linear actuator that is configured to make stepwise motion until end stop.

In such way is achieved robust control using on-off configuration for the second rod clamping device in cooperation with pressurization or depressurization of the respective first and second cylinder chamber for moving the one single piston body in said working stroke or return stroke.

In such way is achieved a compact, reliable, cost-effective in service maintenance and less complex electro-hydraulic linear actuator and control circuitry.

The definition “first rod clamping device” may be interpreted as a first clamping device configured to alternately clamp around the rod.

The definition “second rod clamping device” may be interpreted as a second rod clamping device configured to alternately and/or stationary clamp around the rod.

In such way is achieved a solar tracking device providing very long strokes for moving the panel device, and taking care of medium forces and high moments.

In such way is achieved a solar tracking device and/or heliostat performing slow but precise movements with no backlash.

In such way is achieved a solar tracking device and/or heliostat comprising a robust and simple control circuitry compared with servo-based systems. In such way is achieved a solar tracking device and/or heliostat that promotes easy stow position of the panel device.

In such way is achieved a solar tracking device and/or heliostat that handles tough environments regarding vibration, shock, dust, moisture, temperature, etc.

In such way is achieved a cost-effective and compact solar tracking device and/or heliostat.

Alternatively, the solar tracking device and/or heliostat configured to carry the panel device comprises three leg members (a first leg member, a second leg member, a third leg member) forming a tripod.

Alternatively, the solar tracking device configured to carry the panel device comprises two leg members (a first leg member, a second leg member) and a joint member.

Alternatively, the joint member comprises a universal joint about which the panel device and/or heliostat can pivot in a circular sector, e.g. defined by a sector from 0 degrees to 100 degrees to horizontal line.

Alternatively, the joint member comprises a universal joint about which the panel device and/or heliostat can pivot for positioning the panel device and/or heliostat in a storm position.

Alternatively, the panel device comprises a first through hole and/or a second through hole.

Alternatively, the first rod extends through the first through hole.

Alternatively, the second rod extends through the second through hole.

Alternatively, the panel device comprises a first peripheral coupling arranged on a first side edge of the panel device and configured to be coupled to the first electro-hydraulic linear actuator.

Alternatively, the panel device comprises a second peripheral coupling arranged on a second side edge of the panel device and configured to be coupled to the second electro- hydraulic linear actuator.

Alternatively, a first single cylinder housing and/or a static clamping body of the first electro- hydraulic linear actuator and /or a first fitting of the first electro-hydraulic linear actuator is coupled to the panel device adjacent the first through hole via a first universal joint coupling.

Alternatively, a second single cylinder housing and/or a static clamping body of the second electro-hydraulic linear actuator and /or a second fitting of the second electro-hydraulic linear actuator is coupled to the panel device adjacent the second through hole via a second universal joint coupling. The wording “panel device” may be replaced by the word heliostat.

When “lowering” the panel device, the panel device will pivot about the joint member coupled to a base portion of the panel device and to a foundation base on the ground.

At the same time, also the first single cylinder housing will pivot about the first universal joint coupling. At the same time, also the second single cylinder housing will pivot about the second universal joint coupling.

Alternatively, the first leg member constitutes a first rod of a first electro-hydraulic linear actuator, similar to the electro-hydraulic linear actuator as defined by claim 1.

Alternatively, the second leg member constitutes a second rod of a second electro- hydraulic linear actuator, similar to the electro-hydraulic linear actuator as defined by claim 1.

Alternatively, a first cylinder housing of the first electro-hydraulic linear actuator is mounted adjacent the first through hole of the panel device.

Alternatively, a second cylinder housing of the second electro-hydraulic linear actuator is mounted adjacent the second through hole of the panel device.

Alternatively, the first electro-hydraulic linear actuator comprises a rod clamping device similar to the second rod clamping device of the electro-hydraulic linear actuator, which rod clamping device is mounted adjacent the first through hole of the panel device and coupled to the first cylinder housing.

Alternatively, the second electro-hydraulic linear actuator comprises a rod clamping device similar to the second rod clamping device of the electro-hydraulic linear actuator, which rod clamping device is mounted adjacent the second through hole of the panel device and coupled to the second cylinder housing.

In such way, by positioning the actuators of the first and second electro-hydraulic linear actuator adjacent to and/or coupled to the panel device, and arranging the first and second rod running there through, optimal attachment points is achieved for moving the panel device and low energy consumption.

The proposed positioning of the actuators is feasible due to the long rod strokes of the respective actuator relative the first and second rod. In such way is achieved that pedestals, torque-taking beams and actuators of the solar tracking device can be made light and thus cost-effective to operate and to provide maintenance service.

Alternatively, the electro-hydraulic linear actuator may be defined as a linear linear stepper motor that switches between two well defined locations (positions).

Alternatively, the two well defined locations may be defined as a first location and a second location.

Alternatively, the first location may be a position in which the one single piston body being configured to abut the first cylinder cap end.

Alternatively, the second location may be a position in which the one single piston body is configured to abut the second cylinder cap end.

Alternatively, the first and second electro-hydraulic linear actuator may be controlled by a train of input pulses that are converted into incremental movement of the respective actuator along the first and second rod.

In such way is achieved that the electro-hydraulic linear actuator (e.g. the first and second electro-hydraulic linear actuator) may not need any position senor for feedback, as the electro-hydraulic linear actuator operates in an open loop system.

Alternatively, the first and second electro-hydraulic linear actuator of the solar tracking device comprises a control circuitry and/or programmable logic control system, wherein the valve arrangement comprises logic on/off valves for position the actuator relative the rod at a desired position be means of the open loop control system and open loop algorithm.

In such way is achieved an electro-hydraulic linear actuator and/or solar tracking device of low cost operating in an open loop control system.

In such way is achieved an electro-hydraulic linear actuator and/or solar tracking device that is robust and that can operate in demanding environment.

In such way is achieved an electro-hydraulic linear actuator and/or solar tracking device that exhibits a simplified structure and/or construction.

In such way is achieved an electro-hydraulic linear actuator and/or solar tracking device that does not use any energy for holding an object or panel device in a stationary position.

In such way is achieved a solar tracking device using no energy to hold a position for an extended period of time by means of closing (off) the valve arrangement (the selection valve device) for keeping the fluid pressure in the second rod clamping device (and optionally in the first clamping device).

In such way is achieved a solar tracking device configured for precise positioning and high repeatability of movement.

In such way is achieved a light solar tracking device as reinforcement structures and thicker material of the structure of the solar tracking device not being necessary.

In such way, in case of wind gusts and momentarily high wind speeds, the first and/or second electro-hydraulic linear actuator slides on the respective first and/or second rod, thus enabling a weaker design of the beam structure of the actuator and solar panel/heliostat.

Alternatively, the respective electro-hydraulic linear actuator of the solar tracking device is coupled to a remote energy source via a respective electrical wire.

In such way is achieved a solar tracking device not requiring long tubes and pipes coupled to the actuator. As the respective electro-hydraulic linear actuator does not require any heavy tubes and pipes for operation, the respective electro-hydraulic linear actuator can be positioned adjacent the panel device. This is beneficially from installation and service point of view.

Alternatively, a pressure switch unit of the electro-hydraulic linear actuator is arranged to be in fluid communication with the first cylinder chamber and/or the second cylinder chamber.

Alternatively, in case the pressure in the first cylinder chamber and/or the second cylinder chamber, detected by the pressure switch unit, exceeds a pre-set pressure value, it is obvious that the panel device has been moved out from position (e.g. due to a wind gust), wherein the control circuitry operates the panel device back into the correct position.

Alternatively, the pressure switch signals to the control circuitry commanding the electro- hydraulic linear actuator to provide a new reference value, e.g. moving the cylinder housing to a stop position for reference. Subsequently, the control circuitry commands the electro- hydraulic linear actuator to move the rod or cylinder housing to the desired position, thereby operating the panel device back into the correct position.

In such way is achieved that eventual heavy wind load making the rod to slide relative the cylinder housing and displacing the panel device can be detected.

Alternatively, the clamping force of the first rod clamping device (of the first and/or second electro-hydraulic linear actuator) is set to such low value that a specific wind load (e.g. upper limit load) generating an axial force on the panel device and thus on the respective electro- hydraulic linear actuator will provide that the rod (the first rod/or second rod) slides in said first rod clamping device/s. This provides a storm stowing mode.

Alternatively, the clamping force of the first and second rod clamping devices of each electro- hydraulic linear actuator is set to such low value that a specific wind load (e.g. upper limit load) generating an axial force on the respective cylinder housing and/or static clamping body, providing that the respective rod (the first and/or second rod) slides in the rod clamping device/s even though the respective electro-hydraulic linear actuator being operated to clamp around the rods. This provides a storm stowing mode.

Alternatively, the clamping force of the second rod clamping device is set to such low value that a specific wind load generating an axial force on the rod will provide that the rod slides in the second rod clamping device.

In such way a storm managing performance is provided.

The panel device is preferably moved to a storm stowing position, which position is reached by operation of the control circuitry.

Alternatively, a cylinder pressure switch is configured to feed a signal to the control circuitry informing that the wind load acting upon the panel device increases, whereby the control circuitry moves the panel device to a stow position.

Alternatively, the control circuitry is configured to move the panel device into stow position in a horizontal orientation, i.e. providing that the structural load on the panel device decreases in stormy weather.

Alternatively, in service maintenance mode, the first and second rod clamping device of the first electro-hydraulic linear actuator, and the first and second rod clamping device of the second electro-hydraulic linear actuator, may be set in a “free-wheel” or “overrunning mode” achieved by depressurizing the respective first and second rod clamping device, whereas the first and second electro-hydraulic linear actuator can slide over the respective first and second rod.

This implies that the panel device easily can be “lowered” to horizontal position for service maintenance and for mounting/demounting of the electro-hydraulic linear actuator to the panel device.

Alternatively, a first flexible wall is positioned between the rod envelope surface and the first expandable cavity.

Alternatively, the second flexible wall is positioned between the rod envelope surface and the second expandable cavity. Alternatively, the second rod clamping device is partly or entirely encompassed by the first piston portion of the one single piston body.

Alternatively, the first rod clamping device is entirely encompassed by the cylinder housing.

Alternatively, the first expandable cavity extends coaxially around the rod and extends in a direction along the axial direction.

Alternatively, the second expandable cavity extends coaxially around the rod and extends in a direction along the axial direction.

Alternatively, the extension of the first expandable cavity is longer than the extension of the second expandable cavity seen in a direction along the central axis.

Alternatively, the clamping force, of the first rod clamping device, that is needed to tightly hold the rod by the one single piston body during movement of the one single piston body (and holding the rod) in the cylinder housing is higher than the clamping force, of the second rod clamping device, that is needed to tightly hold the rod by the second rod clamping device in fixed position.

Alternatively, the cylinder housing of the electro-hydraulic linear actuator preferably is coupled to the second rod clamping device.

Alternatively, the cylinder housing of the electro-hydraulic linear actuator preferably is coupled to the second rod clamping device via a cover housing.

Alternatively, the cylinder housing of the electro-hydraulic linear actuator preferably is coupled to the second rod clamping device via a releasable mechanical coupling.

Alternatively, the electro-hydraulic linear actuator comprises a hydraulic fluid supply configured to feed hydraulic fluid to the cylinder housing and to the first expandable cavity.

Alternatively, the piston body comprises a first piston portion partly arranged in the cylinder housing, which first piston portion is coupled to a second piston portion and configured to extend through a first opening of the cylinder housing along the central axis.

Alternatively, the second piston portion is configured to extend through a second opening of the cylinder housing along the central axis.

Alternatively, the electro-hydraulic linear actuator comprises a hydraulic fluid reservoir.

Alternatively, the electro-hydraulic linear actuator is coupled to a remote hydraulic fluid reservoir. Alternatively, the electro-hydraulic linear actuator comprises an electric motor mechanically coupled to a hydraulic pump.

Alternatively, the electrical power device is electrically coupled to an electric motor.

Alternatively, the electro-hydraulic linear actuator comprises a hydraulic accumulator configured for storing pressurized fluid for pressurizing the first expandable cavity.

Alternatively, the rod further extends through a second rod clamping device configured as a semi-rigid clamping device, such as a friction bearing member configured to slide along a linear guide or along the rod.

Alternatively, the friction between the friction bearing member and the guide or rod is predetermined to such friction characteristic that the friction bearing member is movable along the guide by means of the cylinder housing motion along the rod.

Alternatively, the friction between the friction bearing member and the guide is predetermined to such friction characteristic that the friction bearing member remains stationary on the guide when the cylinder housing not affects the friction bearing member.

Alternatively, the cylinder housing is configured to be coupled to the second rod clamping device for pushing the second rod clamping device.

Alternatively, the cylinder housing is configured to be releasable coupled to the second rod clamping device via a coupling.

Alternatively, the second rod clamping device is coupled to a stake bar or planter/seeder unit.

Alternatively, the second rod clamping device may be called second guide clamping device.

Alternatively, the second rod clamping device comprises a second expandable cavity configured to deform a second flexible wall of the second rod clamping device.

Alternatively, the hydraulic fluid supply is configured to feed fluid to the second expandable cavity.

Alternatively, the channel arrangement is arranged between the hydraulic pump and the second cavity.

This or at least one of said objects has been achieved by; an electro-hydraulic linear actuator comprising: one single cylinder housing extending along a central axis; one single piston body dividing the cylinder housing in a first and second cylinder chamber; a first piston portion arranged in the cylinder housing, which first piston portion is coupled to a second piston portion and configured to extend through a first opening of the cylinder housing; a rod extends along the central axis through a first rod clamping device of the piston body and through a second clamping rod device; the first rod clamping device comprises a first expandable cavity configured to deform a first flexible inner wall of the piston body; the second rod clamping device comprises a second expandable cavity configured to deform a second flexible wall of the second rod clamping device; a hydraulic fluid supply for feeding hydraulic fluid to the cylinder housing and to the first and second expandable cavity; the electro-hydraulic linear actuator is configured as a self-contained electro-hydraulic linear actuator; the hydraulic fluid supply comprises: a hydraulic fluid reservoir; an electric motor mechanically coupled to a hydraulic pump; a channel arrangement arranged between the hydraulic pump and the cylinder housing and between the hydraulic pump and the first and second cavity; a valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid; and an electrical power device electrically coupled to the electric motor.

Alternatively, the cylinder housing is configured to be rigidly coupled to the second rod clamping device.

Alternatively, the cylinder housing is configured to be rigidly coupled to the second rod clamping device, wherein the cylinder housing and the second rod clamping device are integrally arranged as an integrally parts of the self-contained electro-hydraulic linear actuator.

Alternatively, the electro-hydraulic linear actuator comprises a hydraulic accumulator configured for storing pressurized fluid for pressurizing the first and/or second expandable cavity.

Alternatively, the cylinder housing and second rod clamping device are rigidly fixed to and demountable arranged in the cover housing, covering the cylinder housing and/or the second rod clamping device.

Alternatively, the electrical power device is electrically coupled to the valve arrangement.

Alternatively, the channel system is formed in an intermediate channel block configured to be fixedly mounted to, and configured removable from, the cylinder housing and the valve arrangement.

In such way is achieved a compact, reliable, cost-effective in service maintenance and less complex electro-hydraulic linear actuator.

Alternatively, the valve arrangement is mounted in the intermediate channel block. Alternatively, the hydraulic fluid reservoir, the electric motor, the hydraulic pump, the channel arrangement, the valve arrangement and the electrical power device is mounted in the cover housing.

Alternatively, the hydraulic fluid supply comprises a first pressure supply system and a second pressure supply system.

Alternatively, the second pressure supply system is configured to generate a second hydraulic pressure being higher than a first hydraulic pressure generated by the first pressure supply system and/or by the hydraulic fluid supply and/or by the hydraulic pump.

Alternatively, the second pressure supply system is configured to feed hydraulic fluid to the first and/or second expandable cavity.

Alternatively, the first pressure supply system is configured to feed hydraulic fluid to the respective first and second cylinder chamber.

Alternatively, the hydraulic fluid supply and/or the first pressure supply system is configured to feed hydraulic fluid to the respective first and second cylinder chamber for moving the piston body back and forward in the cylinder housing by means of the first hydraulic pressure.

Alternatively, the second pressure supply system comprises the hydraulic accumulator.

Alternatively, the hydraulic pump of the first pressure supply system is configured to transfer hydraulic fluid to the hydraulic accumulator.

Alternatively, the hydraulic accumulator is configured to be charged and/or pre-charged to a charge pressure corresponding to the second hydraulic pressure.

Alternatively, the hydraulic fluid is pressurized in the hydraulic accumulator for generating said second hydraulic pressure to be used for pressurizing the first and/or second expandable cavity providing the clamping action.

Alternatively, the hydraulic accumulator is configured to be charged with hydraulic fluid fed from the hydraulic pump.

Alternatively, the second pressure supply system comprises a non-return valve arrangement.

Alternatively, the non-return valve arrangement is arranged in a channel or line arrangement between the hydraulic pump and a directional valve device of the second pressure supply system, such as a 3/2 directional valve device, or 4/2 directional valve device, or 4/3 directional valve device or two 3/2 valves or four 2/2 valves. Alternatively, the non-return valve arrangement comprises a check valve, a non-return valve or any one-way valve being a valve that normally allows fluid to flow through in only one direction.

Alternatively, the check valve is a two-port valve comprising two openings in the body, one for fluid to enter and the other for fluid to leave.

Alternatively, the hydraulic accumulator is configured to be charged to a pressure being larger than a precharge pressure.

Alternatively, the precharge pressure corresponds with the second pressure generated by the second pressure supply system.

Alternatively, the hydraulic accumulator is a component of the second pressure supply system.

By providing an additional pressure supply system with higher fluid pressure than that being momentary generated by the fluid pump, the higher fluid pressure (second pressure) provides that less clamping area of the rod clamping devices is needed, which in turn implies that the rod clamping devices can be designed less bulky and compact.

Alternatively, during charging of the the hydraulic accumulator, the hydraulic fluid is compressed to store energy.

Alternatively, the hydraulic accumulator comprises a space for storing compressed hydraulic fluid configured to store energy and/or stored at a second pressure.

Alternatively, the second pressure supply system comprises a pressure amplifier configured to amplify the first pressure of the hydraulic fluid to the second pressure.

Alternatively, the second pressure supply system comprises the hydraulic accumulator configured to store pressurized hydraulic fluid supplementary to the hydraulic pump.

Alternatively, the hydraulic pump feeds hydraulic fluid to the hydraulic accumulator during idle periods of a work cycle.

Alternatively, the control circuitry (e.g. PLC system) is coupled to the valve arrangement and configured to control the operation of the electro-hydraulic linear actuator in a non-feedback and/or a feedback loop procedure.

Alternatively, the electrical power device is electrically coupled to the control circuitry.

Alternatively, the cylinder housing is rigidly fixed and demountable arranged to a cover housing rigidly fixed and demountable arranged also to the second clamping rod device. Alternatively, the cover housing exhibits a circular cross section and/or quadratic cross section and/or rectangular cross section.

In such way it is easy to mount the actuator to a planar fundament.

Alternatively, the hydraulic fluid supply and/or the electro-hydraulic linear actuator is formed as a self-contained unit.

Alternatively, the cover housing, also encasing the hydraulic fluid supply, is formed as a cover forming the outermost surface of the electro-hydraulic linear actuator.

Alternatively, the one single cylinder housing comprises a first cylinder cap end and a second cylinder cap end.

Alternatively, the first cylinder cap end is arranged opposite to the second cylinder cap end seen along the central axis.

Alternatively, the first cylinder cap end comprises the first opening and the second cylinder cap end comprises the second opening.

Alternatively, the electro-hydraulic linear actuator comprises a sensor arrangement coupled to the control circuitry of the hydraulic fluid supply.

Alternatively, the sensor arrangement comprises a potentiometer and/or a linear variable differential transformer (LVDT), and/or a resolver and/or an optic sensor and/or a magnetic sensor and/or an accelerometer or other.

In such way is achieved that the electro-hydraulic linear actuator can be used in a feedback loop control system or closed loop system.

Alternatively, the sensor arrangement is configured to provide information regarding the position of the piston body relative the cylinder housing and/or the position of the rod relative the position of the cylinder housing.

Alternatively, the information regarding said position is used by the control circuitry for generating a control command, which control command is generated in response to an actual position value of the piston body relative the cylinder housing and/or the position of the rod relative the position of the cylinder housing, in view of a desired position value of the piston body relative the cylinder housing and/or the position of the rod relative the position of the cylinder housing.

Alternatively, the electrical power device is an electrical circuit component, such as an electrical plug and play connection, configured to be connected to an electrical power supply.

In such way is achieved a cost-effective handling of the electro-hydraulic linear actuator. Alternatively, the electrical plug and play connection comprises connection for electrical supply and/or data transfer.

In such way the electro-hydraulic linear actuator can used in a vehicle, e.g. a timber truck, an agricultural machine, and coupled to the computer and supply system of the vehicle.

Alternatively, the data transfer comprises transfer of test signals and/or command signals for testing and/or controlling the channel arrangement.

Alternatively, the data transfer comprises transfer of test signals and/or command signals for testing and/or controlling the channel arrangement via the control circuitry.

Alternatively, the electrical power device comprises an electrical battery power pack.

In such way is achieved a mobile electro-hydraulic linear actuator, which is configured for remote use.

Alternatively, the valve arrangement comprises a selection valve device, configured for pressurization of the respective first and second expandable cavity, and a directional valve device configured for pressurization of the first and second cylinder chamber.

Alternatively, the selection valve device comprises a first logic valve configured for pressurization of the first expandable cavity and a second logic valve configured to manage pressurization of the second expandable cavity.

In such way is achieved that both the first and second expandable cavity can be pressurized for achieving an instant and redundant stop/holding of the rod relative the cylinder.

In such way is achieved that both the first and second expandable cavity simultaneously can be pressurized for achieving an instant and redundant stop/holding of the rod relative the cylinder, even though neither of the first and second cylinder chamber is pressurized and the piston abuts either of the first or second cylinder cap end.

Alternatively, the valve arrangement comprises a shift valve, for example a 4/2 valve, wherein the shift valve is configured to select the flow of fluid for pressurization of either of the first expandable cavity or the second expandable cavity.

Alternatively, the shift valve being configured to be controlled by the control circuitry of a computer.

Alternatively, the selection valve device and/or the directional valve device each being configured to be controlled by the control circuitry.

Alternatively, the sensor arrangement of the electro-hydraulic linear actuator is configured to obtain a first position information regarding mutual relation between the cylinder and the piston body indicating that the piston body passes or reaches a first position relative the cylinder along the piston body stroke.

Alternatively, the piston body stroke is defined as a return stroke made by the piston body from a first cylinder cap end position to a second cylinder cap end position.

Alternatively the first cylinder cap end position comprises a first piston body damper device.

Alternatively the second cylinder cap end position comprises a second piston body damper device.

Alternatively, the piston body stroke is defined as a working stroke made by the piston body from a second cylinder cap end position to a first cylinder cap end position.

Alternatively, the sensor arrangement of the electro-hydraulic linear actuator is configured to obtain a second position information regarding mutual relation between the cylinder and the piston body indicating that the piston body passes or reaches a second position relative the cylinder along the piston body stroke.

Alternatively, a piston body control circuitry of the control circuitry is configured to control the back and forward movement of the piston body in the cylinder housing based on the obtained first position information.

Alternatively, a piston body control circuitry of the control circuitry is configured to control the back and forward movement of the piston body in the cylinder housing based on the obtained second position information.

Alternatively, the sensor arrangement coupled to the control circuitry further comprises a rod position detector.

Alternatively, the clamping control circuitry of the control circuitry is configured to control the engagement or disengagement of the respective first and second clamping rod device.

Alternatively, the clamping control circuitry of the control circuitry is configured to control the engagement or disengagement of the first rod clamping device based on the obtained first position information and/or obtained second position information.

Alternatively, the clamping control circuitry of the control circuitry is configured to control the engagement or disengagement of the second rod clamping device based on the obtained first position information and/or obtained second position information.

Alternatively, the control circuitry is configured to receive the first and second position information, the control circuitry comprises a signal port configured for delivery of the first and second position information to a communication port of the electro-hydraulic linear actuator, wherein the communication port is configured to be coupled to an electronic network device comprising a processor unit adapted for communication with a digital user interface.

Alternatively, the processor unit of the electronic network device is coupled to a connection point of the electronic network device.

Alternatively, the connection point is configured to be coupled to the communication port.

Alternatively, the communication between the communication port and the connection point is wireless and/or uses wire-based technology.

Alternatively, the communication between the sensor arrangement and the control circuitry is wireless and/or uses wire-based technology.

Alternatively, the communication port is adapted to deliver the first and second position information to the processor unit via the connection point, wherein the processor unit generates information to be presented on the digital user interface (e.g. of a vehicle, such as e.g. a timber truck, an agricultural machine)

Alternatively, the processor unit presents information at a touchscreen display of the digital user interface.

Alternatively, the digital user interface is adapted for presentation of information to operation and/service personnel.

Alternatively, the electronic user device is embodied by a mobile smart phone or tablet having dedicated smart phone application or tablet application software adapted to display the first and second position information.

This or at least one of said objects has been achieved by a method of controlling the operation of an electro-hydraulic linear actuator comprising; one single cylinder housing extending along a central axis; one single piston body dividing the cylinder housing in a first and second cylinder chamber; a rod extends along the central axis and through the cylinder housing and through a first rod clamping device of the piston body; the first rod clamping device comprises a first expandable cavity configured to deform a first flexible inner wall of the piston body; the electro-hydraulic linear actuator is configured as a self-contained electro- hydraulic linear actuator coupled to a hydraulic fluid supply, the hydraulic fluid supply which comprises; a channel arrangement arranged between a hydraulic pump of the hydraulic fluid supply and the cylinder housing and between the hydraulic pump and the first expandable cavity; a valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid to the first and second cylinder chamber and to the first expandable cavity; an electrical power device; wherein the method comprises; engaging the first rod clamping device to the rod for preparing a working stroke of the piston body; pressurizing the first cylinder chamber and making the working stroke; depressurizing the first cylinder chamber; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the second cylinder chamber making the return stroke; and engaging the first rod clamping device for preparing a working stroke of the piston body.

Alternatively, a control circuitry of a vehicle may be coupled (by wire and/or wireless) to the valve arrangement and to a first sensor arrangement of the the piston body and/or cylinder housing and to an electrical network of the vehicle via a plug and play connection.

Alternatively, the channel arrangement of the electro-hydraulic linear actuator is configured to be coupled to a hydraulic pump of a vehicle

Alternatively, the step of pressurizing the first cylinder chamber and making the working stroke involves to moving of a second rod clamping device comprising a semi-rigid clamping device comprising a friction bearing member configured to slide along the rod and/or a guide, which means that the second rod clamping device is semi-clamped thereto.

The friction between the friction bearing member (a semi-rigid clamping device) and the rod and/or the guide is predetermined to such low friction characteristic that the friction bearing member can be movable along the guide by means of the cylinder housing motion along the rod (the cylinder housing is configured to be coupled to the second clamping rod device), but predetermined to such high such friction characteristic that the friction bearing member remains stationary on the guide when the cylinder housing not moves the friction bearing member.

Alternatively, during the step of pressurizing the second cylinder chamber for making the return stroke, the second rod clamping device coupled to the cylinder housing provides that the cylinder housing remains in position on the rod, despite that the first rod clamping device is disengaged from the rod in preparing a return stroke of the piston body.

Alternatively, the cylinder housing is configured to be releasable coupled to the semi-rigid clamping device via a releasable coupling.

This or at least one of said objects has been achieved by a method of controlling the operation of an electro-hydraulic linear actuator comprising; one single cylinder extending along a central axis; one single piston body dividing the cylinder in a first and second cylinder chamber; a first piston portion arranged in the cylinder, which first piston portion is coupled to a second piston portion and configured to extend through a first opening of the cylinder; a rod extends along the central axis through a first rod clamping device of the piston body and through a second rod clamping device; the first rod clamping device comprises a first expandable cavity configured to deform a first flexible inner wall of the piston body; the second rod clamping device comprises a second expandable cavity configured to deform a second flexible wall of the second rod clamping device; a fluid supply for feeding hydraulic fluid to the cylinder and to the first and second expandable cavity; wherein the hydraulic fluid supply is formed as a self-contained unity rigidly coupled to the cylinder and at least partially enclosing: a hydraulic fluid reservoir; an electric motor mechanically coupled to a hydraulic pump; a channel arrangement arranged between the hydraulic pump and the cylinder and between the hydraulic pump and the first and second cavity; a hydraulic accumulator configured for storing pressurized fluid for use in pressurizing the first and/or second expandable cavity; a valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid; a control circuitry coupled to the valve arrangement and configured to control the operation of the electro-hydraulic linear actuator in a non-feedback and/or a feedback loop procedure; and an electrical power device electrically coupled to the electric motor, the control circuitry and the valve arrangement; the method comprises, subsequently the step of engaging the second rod clamping device, the steps of: pressurizing the first cylinder chamber; engaging the first rod clamping device for preparing a working stroke; disengaging the second rod clamping device; pressurizing the second cylinder chamber; engaging the second rod clamping device synchronous or after the piston body fulfilled the working stroke; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the first cylinder chamber; engaging the first rod clamping device synchronous or after the piston body fulfilled the return stroke for preparing a working stroke.

Alternatively, the electro-hydraulic linear actuator comprises a sensor arrangement coupled to the control circuitry which sensor arrangement is configured to detect the actual obtained first and/or second position regarding mutual relation between the cylinder and the piston body.

Alternatively, the steps of disengaging the first rod clamping device and disengaging the first rod clamping device are followed by the steps of; pressurizing the first cylinder chamber so that the piston abuts the second cylinder cap end in a working stroke start position; engaging the first rod clamping device for preparing a working stroke; disengaging the second rod clamping device; pressurizing the second cylinder chamber so that the piston makes the working stroke from the working stroke start position to a working stroke end position; engaging the second rod clamping device synchronously with or after that the piston body has fulfilled the working stroke and has reached the working stroke end position and abuts the first cylinder cap end; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the first cylinder chamber so that the piston makes a return stroke from the working stroke end position to the working stroke start position and abuts the second cylinder cap end; engaging the first rod clamping device synchronous with or after that the piston body fulfilled the return stroke for preparing a working stroke.

Alternatively, the method comprises the steps of disengaging the second rod clamping device and disengaging the first rod clamping device and comprises the following step of pressurizing the first cylinder chamber so that the piston abuts second cylinder cap end, wherein the rod is manually or automatically pushed or pulled to a reference starting position.

Alternatively, the rod and/or cylinder housing being configured to be automatically pushed or pulled to the reference starting position by means of an automatic actuator apparatus configured to move the rod.

Alternatively, the steps of disengaging the first rod clamping device and disengaging the first rod clamping device are followed by the steps of; pressurizing the first cylinder chamber so that the piston abuts the second cylinder cap end in a working stroke start position; engaging the first rod clamping device for preparing a working stroke; disengaging the second rod clamping device; pressurizing the second cylinder chamber so that the piston makes the working stroke from the working stroke start position to a working stroke end position; engaging the second rod clamping device synchronously with or after that the piston body has fulfilled the working stroke and has reached the working stroke end position and abuts the first cylinder cap end; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the first cylinder chamber so that the piston makes a return stroke from the working stroke end position to the working stroke start position and abuts the second cylinder cap end; engaging the first rod clamping device synchronous with or after that the piston body fulfilled the return stroke for preparing a working stroke.

Alternatively, the steps of disengaging the first rod clamping device is followed by the step of pressurizing the first cylinder chamber.

Alternatively, the following step comprises engaging the first rod clamping device for preparing a first working stroke.

Alternatively, the following step comprises disengaging the second clamping rod device.

Alternatively, the following step comprises pressurizing the second cylinder chamber so that the piston makes the first working stroke.

Alternatively, the following step comprises depressurizing the second cylinder chamber. Alternatively, the step of depressurizing the second cylinder chamber is made synchronous with or after that the second rod clamping device is engaged or before that the second rod clamping device is engaged.

Alternatively, the following step comprises pressurizing the first cylinder chamber so that the piston makes a second working stroke in a direction opposite a direction of the first working stroke.

Alternatively, the step of pressurizing the first cylinder chamber is made synchronous with the depressurizing the second cylinder chamber.

Alternatively, the following step comprises pressurizing the first cylinder chamber for balancing the piston body in a position between the first cylinder cap end and the second cylinder cap end.

Alternatively, the step of pressurizing the first cylinder chamber, for balancing the piston body in a position between the first cylinder cap end and the second cylinder cap end, is provided simultaneously with a step of engaging the second clamping rod device.

In such way is achieved a redundant clamping to the rod.

In such way is provided an electro-hydraulic linear actuator configured for redundant clamping along a vertical rod.

Alternatively, the method comprises the steps of: subsequently a step of engaging the second rod clamping device, the steps of; pressurizing the first cylinder chamber; engaging the first rod clamping device for preparing a working stroke of the piston body; disengaging the second rod clamping device; pressurizing the second cylinder chamber; engaging the second rod clamping device synchronous or after the piston body fulfilled the working stroke; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the first cylinder chamber; depressurizing the first cylinder chamber; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the second cylinder chamber; and engaging the first rod clamping device for preparing a working stroke of the piston body.

Alternatively, the method comprises the steps of: disengaging the second rod clamping device; pressurizing the second cylinder chamber; engaging the second rod clamping device synchronous or after the piston body fulfilled the working stroke; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the first cylinder chamber; engaging the first rod clamping device synchronous or after the piston body fulfilled the return stroke for preparing a working stroke; disengaging the second rod clamping device; pressurizing the second cylinder chamber; engaging the second rod clamping device synchronous or after the piston body fulfilled the working stroke.

Alternatively, the method comprises the steps of: pressurize the second cavity; pressurize the first cavity; depressurize the second cavity and subsequently pressurize the first cylinder chamber CC or pressurize the first cylinder chamber and subsequently depressurize the second cavity; depressurize the first cylinder chamber; pressurize the second cavity; depressurize the first cavity; pressurize the second cylinder chamber; depressurize the second cylinder chamber; pressurize the first cavity and repeating the method.

Preferably, the electro-hydraulic linear actuator is configured to vertically lift a load.

Preferably, the control circuitry and valve arrangement is configured to, when changing clamping action of the clamping member of the static clamping unit to clamping action of the clamping member of the piston body, provide an overlapping sequence whereas the clamping member of the static clamping unit and the clamping member of the piston body simultaneously clamp around the rod.

F piston ⁼ P system X Apiston P system ⁼ F piston / Apiston

Fpi _ston = mass x gravitation acceleration (g)

P system ⁼ maSS X g / Apiston

Preferably, for provision of the electro-hydraulic linear actuator applied to vertical motion, the system pressure P _sy stem is determined to be at least of such value, in respect to the actual dimension of the piston area A _piston , that the mass can be moved upward by the piston body when the clamping member of the piston body clamps around the rod.

Preferably, the mass includes the load to be lifted, the mass of the piston body comprising the clamping member of the piston body and optionally the rod and/or the cylinder housing.

Preferably, the accumulator is configured to be pressurized by the fluid pump and charged with pressurized fluid so that the following proportion is valid:

P system £X P clamp

For example, the clamping pressure P _C iam is set to be twice the system pressure P _sy stem.

P clamp — 2 X P system

In such way is achieved that the area of the piston area A _piston can be made smaller or sufficient small to generate at least the same force F _piston generated by the piston during the working stroke, which in turn will promote the design of a piston body with smaller diameter, which supports a very compact electro-hydraulic linear actuator.

Alternatively, the electro-hydraulic linear actuator comprising the electronic network device, wherein the processor unit is configured.

Alternatively, the first rod clamp and piston body being entirely encompassed by the cylinder housing.

Alternatively, the second rod clamp is shorter (seen in the axial direction X) than the first rod clamp.

This is achieved by that the clamping force needed to rigidly hold the rod by the piston body during movement of the piston body occasionally is higher than the clamping force needed to rigidly hold the rod by the second rod clamp.

In such way, the electro-hydraulic linear actuator can be made less bulky.

The wording “electro-hydraulic linear actuator" may be replaced by the wording “compact self-contained electro-hydraulic linear actuator “ or “compact self-contained electro-hydraulic intermittent operation linear actuator”.

The definition of “an intermittent operation linear actuator” is an actuator that intermittently moves the piston or cylinder for each working stroke.

The definition of “clamping action” means when the rod clamping device is clamped around the rod for rigidly connecting the piston body and/or the second rod clamping device to the rod.

The definition of “clamping action” may also mean frictional engagement between the second rod clamping device and the rod (or the guide).

The definition of “clamping action” may also mean a semi-rigid clamping device comprising a friction bearing member configured to slide along a guide semi-clamped thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of examples with references to the accompanying schematic drawings, of which:

Fig. 1 illustrates, in a perspective view, an electro-hydraulic linear actuator according to a first example;

Fig. 2a illustrates an electro-hydraulic linear actuator according to a second example; Fig. 2b illustrates an electro-hydraulic linear actuator according to a third example;

Fig. 3 illustrates an electro-hydraulic linear actuator according to a fourth example;

Fig. 4 illustrates an actuator arrangement comprising two co-working electro-hydraulic linear actuators according to a fifth example; Figs. 5a and 5b illustrate an electro-hydraulic linear actuator according to a sixth example;

Fig. 6a illustrates the relative motion between a piston body and a cylinder housing of an electro-hydraulic linear actuator according to a seventh example;

Fig. 6b illustrates a closed loop control system of an electro-hydraulic linear actuator according to an eight example; Fig. 6c illustrates an electronic network device coupled to an electro-hydraulic linear actuator according to a ninth example;

Fig. 6d shows an electro-hydraulic linear actuator comprising a semi-rigid clamping device according to a further aspect;

Fig. 6e illustrates an open loop control system of an electro-hydraulic linear actuator according to an example;

Fig. 7 illustrates a first and second pressure supply system of an electro-hydraulic linear actuator according to a tenth example;

Figs. 8a to 8c illustrate the operation of a valve arrangement of an electro-hydraulic linear actuator according to an eleventh example; Figs. 9a to 9b illustrate exemplary flowcharts of operating an electro-hydraulic linear actuator according to a twelfth example;-and

Fig. 10 illustrates a control unit of an electro-hydraulic linear actuator according to a thirteenth example; and

Fig. 10a illustrates a solar panel coupled to a first and second electro-hydraulic linear actuator configured for moving an exemplary solar tracking device;

Fig. 10b illustrates a solar panel coupled to a first and second electro-hydraulic linear actuator configured for moving an exemplary solar tracking device;

Fig. 11 illustrates the first electro-hydraulic linear actuator in Fig. 10a in detail;

Fig. 12 illustrates movement pattern with Bang-Bang control; and Figs. 13a to 13c illustrate an exemplary solar tracking device configured to orient a panel device.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein for the sake of clarity and understanding of the invention some details of no importance may be deleted from the drawings.

Fig. 1 shows, in a perspective view, an electro-hydraulic linear actuator 1 according to a first example. The electro-hydraulic linear actuator 1 comprises one single cylinder housing 3 extending along a central axis X. The electro-hydraulic linear actuator 1 further comprises one single piston body 5 dividing the cylinder housing 3 in a first and second cylinder chamber 7, 9.

A first piston portion 11 is arranged in the cylinder housing 3 and is coupled to a second piston portion 13 via an intermediate portion of the one single piston body 5 and is configured to extend through a first opening 15’ of the cylinder housing 3.

A rod 17 extends along the central axis X through a first rod clamp 19 of the piston body and through a second rod clamp 21.

The first rod clamp 19 comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the one single piston body 5.

The second rod clamp 21 comprises a second expandable cavity (not shown) configured to deform a second flexible wall (not shown) of the second rod clamp 21.

A hydraulic fluid supply 23 is configured for feeding hydraulic fluid to the cylinder housing 3 and to the first and second expandable cavity.

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator.

The hydraulic fluid supply 23 comprises: a hydraulic fluid reservoir 25; an electric motor 27 mechanically coupled to a hydraulic pump 29; a channel arrangement 31 arranged between the hydraulic pump and the cylinder housing and between the hydraulic pump 29 and the first and second cavity; a hydraulic accumulator 30 configured for storing pressurized fluid for use in pressurizing the first and/or second expandable cavity.

A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid. An electrical power wire 35’ (an electrical power device 35) is electrically coupled to the electric motor 27 and configured to be connected to an electrical network (not shown).

Alternatively, the electrical power device 35 comprises a battery pack that can be connected and charged by the electrical network.

Fig. 2a illustrates an electro-hydraulic linear actuator 1 according to a second example. The electro-hydraulic linear actuator 1 comprises one single cylinder housing 3. The electro- hydraulic linear actuator 1 further comprises one single piston 5. A rod 17 extends along a central axis X through a first rod clamp 19 of the piston 5 and through a second rod clamp 21.

The first rod clamp 19 comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the one single piston body 5.

The second rod clamp 21 comprises a second expandable cavity (not shown) configured to deform a second flexible wall (not shown) of the second rod clamp 21.

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator.

A hydraulic fluid supply 23 configured to pressurize the first and second rod clamp for clamping action.

The hydraulic fluid supply 23 comprises a hydraulic fluid reservoir 25, an electric motor 27 mechanically coupled to a hydraulic pump 29, a channel arrangement 31 arranged between the hydraulic pump 29 and the cylinder housing 3 and between the hydraulic pump 29 and the first and second rod clamp 19, 21.

The hydraulic fluid supply 23 further comprises a hydraulic accumulator 30 configured for storing pressurized fluid for use in pressurizing the first and second rod clamp 19, 21.

A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid.

An electrical power pack 35 is electrically coupled to the electric motor 27 and configured to be connected to an electrical network (not shown).

Fig. 2b illustrates an electro-hydraulic linear actuator according to a third example. The electro-hydraulic linear actuator 1 comprises one single cylinder housing 3 and one single piston 5.

A first rod clamp 19 of one single piston comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the one single piston body. The second rod clamp 21 comprises a second expandable cavity (not shown) configured to deform a second flexible wall (not shown) of the second rod clamp 21.

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator.

A hydraulic fluid supply 23 configured to pressurize the first and second rod clamp for clamping action.

The hydraulic fluid supply 23 comprises a hydraulic fluid reservoir 25; an electric motor 27 mechanically coupled to a hydraulic pump (not shown) a channel arrangement 31 arranged between the hydraulic pump and the cylinder housing 3 and between the hydraulic pump and the first and second rod clamp 19, 21.

The hydraulic fluid supply 23 further comprises a hydraulic accumulator (not shown) configured for storing pressurized fluid for use in pressurizing the first and second rod clamp 19, 21.

A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid.

An electrical power pack 35 is electrically coupled to the electric motor 27 and configured to be connected to an electrical network (not shown).

Fig. 3 illustrates an electro-hydraulic linear actuator 1 according to a fourth example. The electro-hydraulic linear actuator 1 comprises one single cylinder housing 3 and one single piston 5. A first rod clamp 19 of the single piston 5 comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the one single piston 5.

Alternatively, a first piston portion 11 of the single piston 5 is partly arranged in the cylinder housing 3 and is configured to extend through a first opening 15’ of the cylinder housing 3.

Alternatively, a second piston portion 13 of the single piston 5 is partly arranged in the cylinder housing 3 and is configured to extend through a second opening 15” of the cylinder housing 3.

The central axis X extends through the first and second opening 15’, 15”, being on opposite positioned cap ends of the cylinder housing 3.

Alternatively, a first rod clamp 19 of the single piston 5 comprises a first expandable cavity 20 configured to deform a first flexible wall 1 FW of the first rod clamp 19.

Alternatively, a second rod clamp 21 comprises a second expandable cavity 22 configured to deform a second flexible wall 2FW of the second rod clamp 21. Alternatively, the first flexible wall 1 FW is positioned between the rod 17 envelope surface and the first expandable cavity 20.

Alternatively, the second flexible wall 2FW is positioned between the rod 17 envelope surface and the second expandable cavity 22.

Alternatively, the second rod clamp 21 is partly or entirely encompassed by the first piston portion 11 of the single piston 5.

Alternatively, the first rod clamp 19 is entirely (see Fig. 6d) encompassed by the cylinder housing 3.

Alternatively, the first expandable cavity 20 extends coaxially around the rod 17 and extends in a direction along the axial direction X.

Alternatively, the second expandable cavity 22 extends coaxially around the rod 17 and extends in a direction along the axial direction X.

Alternatively, the extension of the first expandable cavity 20 is longer than the extension of the second expandable cavity 22 seen in a direction along the central axis.

The clamping force that is needed to tightly hold the rod 17 by the piston 5 during movement of the piston (and holding the rod) may be higher than the clamping force needed to tightly hold the rod 17 by the second rod clamp 21 in fixed position.

By providing a shorter second rod clamp 21 (seen in the axial direction X), the electro- hydraulic linear actuator 1 can be made less bulky.

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator.

A hydraulic fluid supply 23 configured to pressurize the first and second rod clamp for clamping action.

The hydraulic fluid supply 23 comprises a hydraulic fluid reservoir 25; an electric motor 27 mechanically coupled to a hydraulic pump 26; a channel arrangement 31 arranged between the hydraulic pump 26 and the cylinder housing 3 and between the hydraulic pump 26 and the first and second rod clamp 19, 21.

The hydraulic fluid supply 23 further comprises a hydraulic accumulator30 configured for storing pressurized fluid for use in pressurizing the first and second rod clamp 19, 21.

A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid generated by the hydraulic pump 26. An electrical power pack 35 is electrically coupled to the electric motor 27 and configured to be connected to an electrical network 36.

Alternatively, a pair of scrapers S are arranged to a cover housing 39 for removing eventual dirt and dust from the rod 17 entering the cover housing encompassing the first and second rod clamp 19, 21.

A pair of sealings 38 are arranged between the cylinder housing 3 and the piston 5.

Sealings S’ are arranged between the cylinder housing 3 and the piston 5.

The electro-hydraulic linear actuator 1 comprises a first sensor arrangement 90 configured to sense the position of the piston 5 relative the cylinder housing 3. The first sensor arrangement 90 is coupled to a control circuitry 100.

The control circuitry 100 is coupled (by wire and/or wireless) to the valve arrangement 33 and to the first sensor arrangement 90 and the electrical network 36 via a plug and play connection.

The first sensor arrangement 90 is configured to obtain a first position information regarding mutual relation between the cylinder housing 3 and the piston 5 indicating that the piston 5 passes or reaches a first position relative the cylinder housing 3 along the piston body stroke.

In this application, the detection of the position of the piston 5 relative the cylinder housing 3 is achieved as a relative/relative position information for controlling the motion of the piston 5.

The first sensor arrangement 90 is further configured to obtain a second position information regarding mutual relation between the cylinder housing 3 and the piston body 5 indicating that the piston 5 passes or reaches a second position relative the cylinder housing 3 along the piston body stroke.

The control circuitry 100 is configured to receive the first and second position information, the control circuitry 100 comprises a signal port (not shown) configured for delivery of the first and second position information to a communication port (not shown) of the electro- hydraulic linear actuator, wherein the communication port is configured to be coupled to an electronic network device (not shown).

In other applications, the detection of the position of the piston 5 relative the cylinder housing 3 and/or a path (e.g. a guide) that the cylinder housing 3 and/or piston 5 reaches is provided as an absolute position information for controlling the motion of the piston 5.

Fig. 4 illustrates an actuator arrangement comprising two co-working electro-hydraulic linear actuators according to a fifth example. A first electro-hydraulic linear actuator is configured to move along a first guide. A second electro-hydraulic linear actuator is configured to move along a second guide. The electro- hydraulic linear actuators are configured to propel a respective cross-bar 50 along the first and second guides.

It is important that the cross-bar 50 is moved by same motion pattern generated by both electro-hydraulic linear actuator for avoiding drawer effect and unwanted tilting.

A plurality of position sensor markers 71 are arranged along the first and second guides.

A respective sensor unit 73 configured to detect the position of each position sensor marker 71 is mounted on both electro-hydraulic linear actuator.

A distance a between two adjacent position marker is shorter than a distance b corresponding to the working stroke length of the respective piston 5 of the electro- hydraulic linear actuator 1 in the respective cylinder housing 3.

As the respective electro-hydraulic linear actuator 1 moves the first distance a, the respective sensor unit 73 detects the following position sensor marker 71 , wherein the respective electro-hydraulic linear actuator 1 stops.

By arranging the plurality of position sensor markers 71 identically along the respective guide and providing the distance a, the respective electro-hydraulic linear actuator 1 can stop synchronously.

By arranging two opposite position sensor markers 71, each positioned on respective guide and intersecting an imaginary line oriented perpendicular to the prolongation of the guides, the respective electro-hydraulic linear actuator 1 can stop synchronously.

The respective electro-hydraulic linear actuator 1 stops for permitting the respective piston 5 to perform a return stroke, while a respective rod clamping unit of each electro- hydraulic linear actuator 1 holds the electro-hydraulic linear actuator 1 in position at the same position on the imaginary line perpendicular to the guides.

In this application, the detection of the position of the cylinder housing 3 has been made along the guide G, and is performed by means of the sensor markers 71 and the sensor unit 73 according an absolute position information for controlling the motion of the piston 5.

Figs. 5a and 5b illustrate an electro-hydraulic linear actuator 1 according to a sixth example. The electro-hydraulic linear actuator 1 comprises a hydraulic accumulator 30. The electro- hydraulic linear actuator 1 comprises a sensor arrangement 90 coupled to a control circuitry 100 of the hydraulic fluid supply 23. An electrical power device 35 of the electro-hydraulic linear actuator 1 may comprise an electrical battery power pack 35PP.

A valve arrangement 33 comprises a selection valve arrangement 36 (e.g. two 3/2 valves 36”), configured for pressurization of each first and second expandable cavity (not shown) of the respective rod clamp 19, 21, and a directional valve 38 configured for pressurization of the first 7 and second 9 cylinder chamber of the single cylinder housing 3 encompassing the single piston body 5.

The selection valve arrangement 36 and the directional valve 38 each being configured to be controlled by a control circuitry 100 of a computer.

Alternatively, the control circuitry 100 of a computer may be associated with a mobile smart phone (not shown) or tablet having dedicated smart phone application or tablet application software adapted to display the first and second position information.

Alternatively, a sensor arrangement 90 of the electro-hydraulic linear actuator is configured to obtain a first position information regarding mutual relation between the single cylinder housing 3 and the single piston body 5 indicating that the single piston body 5 passes or reaches a first position relative the single cylinder housing 3 along a first piston body stroke.

Alternatively, the sensor arrangement 90 of the electro-hydraulic linear actuator 1 is configured to obtain a second position information regarding mutual relation between the single cylinder housing 3 and the single piston body 5 indicating that the single piston body 5 passes or reaches a second position relative the single cylinder housing 3 along a second piston body stroke

Fig. 5b illustrates a cross-section A-A passing through the single piston body 5 in Fig. 5a. A rod 17 extends along the central axis X and through the single cylinder housing 3 and through a first rod clamping device 19 of the single piston body 5. The first rod clamping device 19 comprises a first expandable cavity 20 configured to deform a first flexible inner wall FW of the single piston body 5. The hydraulic fluid supply 23 is configured to pressurize the first expandable cavity 20 with hydraulic fluid for deforming the first flexible inner wall FW so that the single piston body 5 is able to clamp around the rod 17.

Alternatively, a groove GG is formed in the envelope surface of the single piston body 5 and extends in the direction parallel with the central axis X. An inlet bore 77 of the single cylinder housing 3 is in contact with the groove GG for fluid communication in every position of the single piston body 5 relative the single cylinder housing 3 when the single piston body 5 moves along the central axis X. The groove GG is arranged for fluid communication with the first expandable cavity 20. Fig. 6a illustrates the relative motion between a piston body and a cylinder housing of an electro-hydraulic linear actuator according to a seventh example. The electro-hydraulic linear actuator is preferably used in a vertical application, but may be used in any orientation of the rod.

The first rod clamping device of the piston body rod and the second rod clamping device alternatively clamp and hold the rod in overlapping sequence, so that shortly before the piston body is unclamped from the rod after making its working stroke, the second rod clamping device is controlled to clamp around the rod for holding the rod while the unclamped piston body makes its return stroke.

Alternatively, in horizontal applications, wherein the rod extends horizontally, there may be no overlapping sequence, meaning that at the same time, or subsequently, as the piston body is unclamped from the rod after making its working stroke, the second rod clamping device is controlled to clamp around the rod for holding the rod while the unclamped piston body makes its return stroke.

The positon A represents a first end position of the piston body relative the cylinder housing. The positon B represents a second end position of the piston body relative the cylinder housing. In position B, the V3 logic valve is controlled to permit flow of hydraulic fluid to the second rod clamping device for holding the rod. The first rod clamping device is pressurized for clamping action, by that the V2 logic valve is controlled to permit flow of hydraulic fluid to the first rod clamping device of the piston body for holding the rod and making a working stroke of the piston body. The cylinder is then pressurized to opposite cylinder chamber by shifting direction of hydraulic flow in directional valve V1 , but subsequently the V3 logic valve is closed for releasing the rod from the second rod clamping device. When the piston body reaches the position in A, i.e. the piston body reaches the first end position, the second rod clamping device is controlled to provide clamping action of the second rod clamping device for holding the rod and subsequently releasing the piston body from the rod by closing V2 and subsequently pressurize opposite cylinder chamber by shifting direction of hydraulic flow in directional valve V1 for making a return stroke of the piston body.

Fig. 6b illustrates a closed loop control system of an electro-hydraulic linear actuator according to an eight example. A desired position value (set value), related to the piston body position relative the cylinder housing and/or relative a desired position of the rod, is fed as an input signal IN to the control circuitry CC of the electro-hydraulic linear actuator.

The desired position value (set value) represents a position that the piston body/the cylinder housing/rod being controlled by the control circuitry CC to reach by a control command executed by the control circuitry CC. The motion and performance of the piston body and the first and second rod clamping devices is controlled by the control circuitry CC. The piston body is moved by controlling the valve arrangement for performing a working stroke or working strokes WS for moving the rod ROD toward the desired position value (set value) in accordance with the input signal.

A sensor arrangement SA, arranged to e.g. the piston body and/or cylinder housing and/or rod and/or guide, detects an actual value ACT of the piston body position relative the cylinder housing and/or actual position of the rod relative the cylinder housing and/or piston body, and signals the actual value ACT to the control circuitry CC.

The control circuitry CC compares the actual value ACT with the desired position value (set value) and calculates a correction signal and executes a correction control command extracted from the comparison between the set value and the actual value. The control circuitry commands the valve arrangement to move the piston body/cylinder housing/rod in accordance with said correction control command.

The control circuitry CC thus executes a comparison calculation between the actual value ACT with the desired position value (set value) SET and controls the electro-hydraulic linear actuator to move the piston body/cylinder housing/rod toward the desired position value (set value) taking into account the detected actual value ACT and comparison calculation for making the correction control command and repeats the closed loop until the desired position value (set value) SET is reached. The closed loop control system thus is configured to correct for factors, such as gravity influencing the position of mass of gravity of the panel device, wind loads, etc.

In such way, the electro-hydraulic linear actuator is provided with high reliability and redundancy.

Alternatively, the control circuitry of the electro-hydraulic linear actuator 1 is configured to compare, in a back-up comparison execution, a real time movement of the piston body and/or rod detected by the sensor arrangement, with a predetermined and desired movement of the piston body and/or rod.

The closed-loop control system is suitable for a heliostat. The movement of a heliostat requires very accurate operation.

Fig. 6c illustrates an electronic network device coupled to an electro-hydraulic linear actuator 1 according to a ninth example. A control circuitry 100 is configured to receive first and/or second position information data regarding the rod and/or the piston body. The control circuitry 100 comprises a signal port 999 configured for delivery of the first and/or second position information to a communication port 888 of the electro-hydraulic linear actuator 1 , wherein the communication port 888 is configured to be coupled to an electronic network device 110 comprising a processor unit 112 adapted for communication with a digital user interface 114.

Fig. 6d shows an electro-hydraulic linear actuator 1 comprising a semi-rigid clamping device 221, such as a friction bearing member configured to slide along a linear guide. The electro- hydraulic linear actuator 1 comprises one single cylinder housing 3 extending along a central axis X. A piston 205 is encompassed in the cylinder housing 3 and divides the cylinder housing 3 in a first 7 and second 9 cylinder chamber. A rod 17 extends along the central axis X through a rod clamping device 219 of the piston 205.

The semi-rigid clamping device 221 is configured to weakly clamp around, and to be moved along, a guide 224 extending parallel with a rod 17 of the electro-hydraulic linear actuator 1.

The rod clamping device 219 comprises an expandable cavity 20 configured to deform a first flexible inner wall of the piston 205 when pressurizing the expandable cavity 20.

A hydraulic fluid supply (not shown) may be part of a vehicle fluid supply system (not shown) carrying the electro-hydraulic linear actuator 1.

A communication port (not shown) of the control circuitry (not shown) of the electro- hydraulic linear actuator 1 may be adapted to deliver a first and second position information to a processor unit of the vehicle, wherein the processor unit generates information to be presented on a digital user interface of the vehicle.

Alternatively, the processor unit presents information at a touchscreen display of the digital user interface.

The fluid supply is configured to feed hydraulic fluid to the cylinder housing 3 and to the expandable cavity 20.

The electro-hydraulic linear actuator 1 is configured as to be mounted to the vehicle and is configured as a self-contained electro-hydraulic linear actuator.

The electro-hydraulic linear actuator 1 may be configured to position e.g. stake bars or planter/seeder units along guide members or a rod.

The hydraulic fluid supply may comprise a hydraulic fluid reservoir (not shown), an electric motor (not shown) mechanically coupled to a hydraulic pump (not shown).

The electric motor may use electrical power also used by a vehicle.

A channel arrangement 31 is arranged between the hydraulic pump and the cylinder housing 3 and between the hydraulic pump and the expandable cavity 20. The hydraulic fluid supply may comprise a hydraulic accumulator (not shown) configured for storing pressurized fluid for use in pressurizing the first expandable cavity.

A valve arrangement (not shown) of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid and is controlled by the control circuitry.

The control circuitry may be coupled to a plug and play connection (not shown) and the plug and play connection may be configured to transfer electric current to the electric motor from the energy supply system of the vehicle.

Alternatively, the friction between the friction bearing member (semi-rigid clamping device 221) and the guide is predetermined to such low friction characteristic that the friction bearing member can be movable along the guide by means of the cylinder housing motion along the rod, but predetermined to such high such friction characteristic that the friction bearing member remains stationary on the guide when the cylinder housing not moves the friction bearing member.

Alternatively, the cylinder housing is configured to be releasable coupled to the semi-rigid clamping device 221 via a releasable coupling 240.

There may be provided a method of controlling the operation of an electro-hydraulic linear actuator 1 comprising: one single cylinder housing 3 extending along the central axis X; one single piston body 205 dividing the cylinder housing 3 in the first 7 and second 9 cylinder chamber; the rod 17 extends along the central axis X and through the cylinder housing 3 and through the first rod clamping device 219 of the piston body 205; the first rod clamping device219 comprises a first expandable cavity 20 configured to deform a first flexible inner wall of the piston body 205; the electro-hydraulic linear actuator 1 is configured as a self- contained electro-hydraulic linear actuator 1 coupled to a hydraulic fluid supply of a vehicle (not shown) or to an internal fluid supply (not shown) of the electro-hydraulic linear actuator 1, the hydraulic fluid supply comprises a channel arrangement 31 arranged between a hydraulic pump (not shown) of the vehicle and/or the of the hydraulic fluid supply and the cylinder housing 203 and between the hydraulic pump and the first expandable cavity 20; a valve arrangement (not shown) of the channel arrangement is configured for controlling the flow of hydraulic fluid to the first 7 and second 9 cylinder chamber and to the first expandable cavity 20; an electrical power device of the vehicle and/or of the electro-hydraulic linear actuator 1; wherein the method comprises engaging the first rod clamping device to the rod for preparing a working stroke of the piston body; pressurizing the first cylinder chamber and making the working stroke; depressurizing the first cylinder chamber; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the second cylinder chamber making the return stroke; and engaging the first rod clamping device for preparing a working stroke of the piston body 205.

Alternatively, a control circuitry of a vehicle may be coupled (by wire and/or wireless) to the valve arrangement and to a first sensor arrangement (not shown) of the the piston body 205 and/or cylinder housing and to an electrical network of the vehicle via a plug and play connection.

Alternatively, the channel arrangement 31 of the electro-hydraulic linear actuator 1 is configured to be coupled to a hydraulic pump of a vehicle

Alternatively, the step of pressurizing the first cylinder chamber and making the working stroke involves to moving of a second rod clamping device comprising a semi-rigid clamping device comprising a friction bearing member configured to slide along the rod and/or a guide, which means that the second rod clamping device is semi-clamped thereto.

The friction between the friction bearing member (a semi-rigid clamping device) and the rod and/or the guide is predetermined to such low friction characteristic that the friction bearing member can be movable along the guide by means of the cylinder housing motion along the rod (the cylinder housing is configured to be coupled to the second clamping rod device), but predetermined to such high such friction characteristic that the friction bearing member remains stationary on the guide when the cylinder housing not moves the friction bearing member.

Alternatively, during the step of pressurizing the second cylinder chamber for making the return stroke, the second rod clamping device coupled to the cylinder housing provides that the cylinder housing remains in position on the rod, despite that the first rod clamping device is disengaged from the rod in preparing a return stroke of the piston body.

Alternatively, the electro-hydraulic linear actuator is configured to perform a movement pattern controlled by a Bang-Bang control algorithm adapted to the control circuitry for providing a feedback loop procedure.

Alternatively, the Bang-Bang control algorithm is a 2-step or on-off control performed by the control circuitry, wherein the control circuitry is coupled to the valve arrangement and configured to control the operation of the electro-hydraulic linear actuator in a feedback loop procedure, wherein the control circuitry may be configured to switch instantly between a first rod engaging state of the first rod clamping device and a first rod disengaging state of the first rod clamping device, and alternatively the control circuitry may be configured to switch instantly between a second rod engaging state of the second rod clamping device and a second rod disengaging state of the second rod clamping device. As shown in Fig. 6e, an exemplary electro-hydraulic linear actuator works in an open loop control system, whereas the desired motion of the piston body and/or cylinder housing and/or rod position is set beforehand and/or predetermined and the valve arrangement is controlled to operate the electro-hydraulic linear actuator, without any sensor arrangement and no feed back signals are generated for actual position values.

In the open-loop control system, may also be called a non-feedback system, control action WS (working stroke) and ROD (rod motion) command from the control circuit CC is independent of the output OUT. The open-loop control system does not use feedback to determine if its output has achieved the desired goal of the input value.

The open-loop control system may use on/off valves, where the control result is known to be approximately sufficient under normal conditions without the need for feedback. The advantage of using open-loop control in these cases is the reduction in components and complexity.

In the open-loop control system, a reference input IN may be given to the system in order to provide the desired output OUT. However, the true output OUT not being used for further reference input.

The open-loop control system is suitable for a solar tracking device coupled to a movable solar panel. A movable solar panel or panel device pivots at large angles of impact and does not require as high accuracy as a heliostat.

Fig. 7 illustrates a first and second pressure supply system of an electro-hydraulic linear actuator according to a tenth example.

The electro-hydraulic linear actuator 1 can be made less bulky than prior art electro- hydraulic linear actuators. This is achieved by increasing and strengthening the clamping pressure Pciamp for decreasing the clamping area A _C iam of the clamping member. The increased clamping pressure P _ciamp is achieved in a simple and cost-effective way at the same time as the pressure produced by the fluid pump, the system pressure P _sy stem , is kept sufficient low to provide that the piston force F _PiSton acting on the piston moves the piston in the cylinder.

That is, at the same time as the first and second rod clamping device can be designed as compact as possible, it is also achieved that a lower system pressure P _system promotes lower energy consumption.

For maintaining the clamping pressure Pciamp in the accumulator, the accumulator is intermittently pressurized by the system pressure P _sy stem generated by the fluid pump. The system pressure P _sy stem is lower than the clamping pressure Pciamp generated by the pressurized accumulator.

For example, the accumulator is pressurized by means of the fluid pump for charging the accumulator with a clamping pressure P _Ciam that is three times higher than the system pressure P _sy stem generated by the fluid pump:

P clamp — 3 X P s _y stem

Aclamp ^_ TT X D X L

A _ciamp = the clamping area of the respective first and second rod clamping device configured to clamp around the rod

D = the diameter cross-section of the cylinder shaped clamping surface L = the length of clamping surface along the longitudinal axis

That is, if the clamping area is possible to decrease, by decreasing the diameter and/or the length of the rod clamping device, the electro-hydraulic linear actuator 1 can be made compact.

Thus, by means of the increased clamping pressure Pciamp , the clamping area A _C iam can be decreased for providing a compact electro-hydraulic linear actuator 1 , still maintaining sufficient clamping force F _C iam . Thus, the clamping force F _C iam acting on the clamping area A _ciamp is sufficient to lock the first and second rod clamping device.

By decreasing the clamping area A _C iam , a compact and less bulky first and second rod clamping device being achieved.

F clamp ⁼ P clamp X Aciamp X P

F _ciamp = the clamping force acting on the A _Ciam for providing a clamping action.

Pciamp = the clamping pressure produced by the accumulator

A _ciamp = the clamping area of the clamping member configured to clamp around the rod h = the frictional coefficient

F piston ⁼ P s _y stem X Apiston

F _piston = the piston force acting on the piston for moving the piston in the cylinder

P _sy stem = the system pressure, the pressure produced by the fluid pump

A _piston = the piston area of the piston, which piston area is effected by the system pressure The force acting on the rod for clamping the clamping member to the rod is higher than the force acting on the piston body for moving the piston body in the cylinder, whereas the piston body is clamped to the rod and moves a load.

F clamp ^ F piston

P clamp X Aclamp X P > P system X Apiston

It shall be noted that the clamping force F _C iam is non-existent when initially pressurizing the first and/or second rod clamping device due to the bias pressure.

Fig. 7 further shows the electro-hydraulic linear actuator 1 comprising one single cylinder housing 3 extending along a central axis. The electro-hydraulic linear actuator 1 further comprises one single piston body 5 dividing the cylinder housing 3 in a first and second cylinder chamber.

A first piston portion 11 is arranged in the cylinder housing 3 and is coupled to a second piston portion 13 via an intermediate portion of the one single piston body 5 and is configured to extend through a first opening 15’ of the cylinder housing 3.

A rod 17 extends along the central axis through a first rod clamping device P of the piston body and through a second rod clamping device S.

The first rod clamping device P comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the one single piston body 5.

The second rod clamping device S comprises a second expandable cavity (not shown) configured to deform a second flexible wall (not shown) of the second rod clamping device.

A hydraulic fluid supply 23 is configured for feeding hydraulic fluid to the cylinder housing 3 and to the first and second expandable cavity of the respective first and second rod clamping device P, S.

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator.

The hydraulic fluid supply 23 comprises a first pressure supply system 701 and a second pressure supply system 702. The first pressure supply system 701 generates a first hydraulic pressure being higher than a second hydraulic pressure generated by the second pressure supply system 702 and/or by the hydraulic fluid supply 23.

The hydraulic fluid supply 23 comprises a hydraulic fluid reservoir 25, an electric motor 27 mechanically coupled to a hydraulic pump 29, a channel arrangement 31 arranged between the hydraulic pump 29 and the cylinder housing 3 and between the hydraulic pump 29 and the first and second cavity of the respective first and second rod clamping device P, S.

The second pressure supply system 702 comprises a hydraulic accumulator 30 configured for storing pressurized fluid for use in pressurizing the first and/or second expandable cavity of the respective first and second rod clamping device P, S.

A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid.

An electrical power unit (not shown) is electrically coupled to the electric motor 27 and configured to be connected to an electrical network (not shown).

The second pressure supply system 702 is configured to feed hydraulic fluid to the first and/or second expandable cavity of the respective first and second rod clamping device P, S.

Alternatively, the second pressure supply system 702 is configured to feed hydraulic fluid to the respective first and second cylinder chamber.

Alternatively, the hydraulic fluid supply 23 and/or the second pressure supply system 702 is configured to feed hydraulic fluid to the respective first and second cylinder chamber of the cylinder housing 3 for moving the piston body 5 back and forward in the cylinder housing 3 by means of the second hydraulic pressure.

Alternatively, second first pressure supply system comprises the hydraulic accumulator 30.

Alternatively, the hydraulic pump 29 is configured to transfer hydraulic fluid to the hydraulic accumulator 30 and charge the hydraulic accumulator 30 into the second hydraulic pressure.

Alternatively, the hydraulic accumulator 30 is configured to be charged and/or pre-charged to a charge pressure corresponding to the second hydraulic pressure.

Alternatively, the hydraulic fluid is pressurized in the hydraulic accumulator 30 for generating said second hydraulic pressure to be used for pressurizing the first and/or second expandable cavity providing said clamping action.

Alternatively, the hydraulic accumulator 30 is configured to be charged with hydraulic fluid fed from the hydraulic pump.

Alternatively, the first pressure supply system and/or second pressure supply system comprises a non-return valve arrangement 705.

The non-return valve arrangement 705 may be arranged between the second pressure supply system 702 and the hydraulic pump 29. The non-return valve arrangement 705 may be arranged between the hydraulic accumulator 30 and the hydraulic pump 29.

Alternatively, the non-return valve arrangement 705 is arranged in a channel or line arrangement and between the hydraulic pump 29 and a directional (selection) valve device 707, such as a 3/2 directional valve device, or 4/2 directional valve device, for directing the pressurized hydraulic fluid of the second pressure supply system to either of the first and second rod clamping device P, S.

The valve arrangement may comprise a directional valve for directing pressurized fluid to either of the cylinder chambers.

Alternatively, the non-return valve arrangement comprises a check valve, a clack valve, a non-return valve, a reflux valve, a retention valve or any one-way valve is a valve that normally allows fluid to flow through in only one direction.

Alternatively, the check valve is a two-port valve comprising two openings in the body, one for fluid to enter and the other for fluid to leave.

Alternatively, the hydraulic accumulator 30 is configured is configured to be charged to a second hydraulic pressure being larger than a precharge pressure.

Alternatively, the precharge pressure corresponds with the second pressure generated by the second pressure supply system.

Alternatively, the hydraulic accumulator 30 is a component of a second pressure supply system.

Alternatively, during charging of the the hydraulic accumulator 30, the hydraulic fluid is compressed to store energy.

Alternatively, the hydraulic accumulator 30 comprises a space for storing compressed hydraulic fluid configured to store energy and/or stored at a second hydraulic pressure.

Alternatively, the second pressure supply system comprises a pressure amplifier configured to amplify the second pressure of the hydraulic fluid.

Alternatively, the second pressure supply system comprises the hydraulic accumulator 30 configured to store pressurized hydraulic fluid supplementary to the hydraulic pump 29.

The second pressure system 702 comprises a pressure switch PS configured to regulate the charging and/or precharging of the hydraulic accumulator 30 so that the hydraulic accumulator 30 is charged with the second hydraulic pressure or with at least the second hydraulic pressure. Figs. 8a to 8c illustrate the operation of a valve arrangement 33 of an electro-hydraulic linear actuator according to an eleventh example. The valve arrangement is configured to operate the first and second rod clamping devices for performing overlapping sequences.

Figs. 9a-9b illustrate exemplary flowcharts of operating an electro-hydraulic linear actuator according to a twelfth example.

Fig. 9a shows step 801 for starting the method of controlling the operation of an electro- hydraulic linear actuator. Step 802 shows the method being executed. Step 803 stops the method. Step 802 may comprise the method steps of; engaging the second rod clamping device; pressurizing the first cylinder chamber; engaging the first rod clamping device for preparing a working stroke; disengaging the second rod clamping device; pressurizing the second cylinder chamber; engaging the second rod clamping device synchronous or after the piston body fulfilled the working stroke; disengaging the first rod clamping device for preparing a return stroke of the piston body; pressurizing the first cylinder chamber; and engaging the first rod clamping device synchronous or after the piston body fulfilled the return stroke for preparing a working stroke.

Fig. 9b shows step 901 for starting an exemplary method of controlling the operation of an electro-hydraulic linear actuator. Step 902 shows pressurizing the first cylinder chamber so that the piston abuts a second cylinder cap end in a working stroke start position. Step 903 shows engaging the first rod clamping device for preparing a working stroke. Step 904 shows disengaging the second rod clamping device. Step 904 shows pressurizing the second cylinder chamber so that the piston makes the working stroke from the working stroke start position to a working stroke end position. Step 905 shows the engaging of the second rod clamping device synchronously with or after that the piston body has fulfilled the working stroke and has reached the working stroke end position and abuts the first cylinder cap end. Step 906 shows disengaging the first rod clamping device for preparing a return stroke of the piston body. Step 907 shows pressurizing the first cylinder chamber so that the piston makes a return stroke from the working stroke end position to the working stroke start position and abuts the second cylinder cap end. Step 908 shows engaging the first rod clamping device synchronous with or after that the piston body fulfilled the return stroke for preparing a working stroke. Step 909 stops the method.

Fig. 10 illustrates a control unit of an electro-hydraulic linear actuator according to one aspect. The electro-hydraulic linear actuator comprises a control circuitry 100 configured to control an exemplary method described herein. The control circuitry 100 may comprise a non-volatile memory NVM 1020, which is a computer memory that can retain stored information even when the control circuitry 100 not being powered. The control circuitry 100 further comprises a processing unit 1010 and a read/write memory 1050. The NVM 1020 comprises a first memory unit 1030. A computer program (which can be of any type suitable for any operational database) is stored in the first memory unit 1030 for controlling the functionality of the control circuitry 100.

Furthermore, the control circuitry 100 comprises a bus controller (not shown), a serial communication port (not shown) providing a physical interface, through which information transfers separately in two directions. The control circuitry 100 also comprises any suitable type of I/O module (not shown) providing input/output signal transfer, an A/D converter (not shown) for converting continuously varying signals from the sensor arrangement and different monitoring units (not shown) into binary code suitable for the control circuitry 100.

The control circuitry 100 also comprises an input/output unit (not shown) for adaption to time and date. The control circuitry 100 also may comprise an event counter (not shown) for counting the number of event multiples that occur from independent events regarding piston body stroke operation. Furthermore, the control circuitry 100 includes interrupt units (not shown) associated with the computer for providing a multi-tasking performance and real time computing. The NVM 1020 also includes a second memory unit 1040 for external controlled operation.

A data medium storing program P comprising driver routines adapted for commanding the operating of the electro-hydraulic linear actuator in response to desired operating of the electro-hydraulic linear actuator.

The data medium storing program P may be provided for operating the control circuitry 100 for performing any exemplary method described herein. The data medium storing program P comprises routines for causing said command. The data medium storing program P comprises a program code stored on a medium, which is readable on the control circuitry 100, for causing the control circuitry 100 to perform said method.

The data medium storing program P further may be stored in a separate memory 1060 and/or in a read/write memory 1050. The data medium storing program P is in this embodiment stored in executable or compressed data format.

It is to be understood that when the processing unit 1010 is described to execute a specific function that involves that the processing unit 1010 executes a certain part of the program stored in the separate memory 1060 or a certain part of the program stored in the read/write memory 1050.

The processing unit 1010 is associated with a signal port 999 for communication via a first data bus 1015. The non-volatile memory NVM 1020 is adapted for communication with the processing unit 1010 via a second data bus 1012. The separate memory 1060 is adapted for communication with the processing unit 1010 via a third data bus 1011. The read/write memory 1050 is adapted to communicate with the processing unit 1010 via a fourth data bus 1014. The signal (data) port 999 may be connectable to data links of e.g. a network device comprising the control circuitry 100.

When data is received by the signal port 999, the data will be stored temporary in the second memory unit 1040. After that the received data is temporary stored, the processing unit 1010 will be ready to execute the program code, in accordance with the above-mentioned method. Preferably, the signals (received by the signal port 999) comprise information about operational status of thee electro-hydraulic linear actuator, such as status of the hydraulic accumulator, sensor arrangement and/or status of the hydraulic fluid.

The received signals at the signal port 999, such as a serial bus, may be used by the control circuitry 100 for controlling and monitoring the he electro-hydraulic linear actuator 1 in a cost- effective way.

The signals received by the signal port 999 can be used for historic data and data regarding the operation of the he electro-hydraulic linear actuator.

The electro-hydraulic linear actuator may be configured to be coupled to a network device via the signal buss configured for electrical interface explicitly providing electrical compatibility and related data transfer, which data may include information about status of the hydraulic accumulator, sensor arrangement and/or status of the hydraulic fluid.

Data may also be manually fed to or presented from the control circuitry via a suitable communication device, such as a personal computer display (not shown).

Separate sequences of the method can also be executed by the control circuitry 100, which control circuitry runs the data medium storing program P being stored in the separate memory 1060 or the read/write memory 1050. When the the control circuitry 100 runs the data medium storing program P, suitable method steps disclosed herein will be executed. A data medium storing program product comprising a program code stored on a medium is provided, which product is readable on a suitable computer, for performing the exemplary method steps herein, when the data medium storing program P is run on the the control circuitry 100.

Fig. 10a illustrates a solar panel 52 coupled to a first T and second 1” electro- hydraulic linear actuator constituting an exemplary solar tracking device 51. The first T and second 1” electro-hydraulic linear actuator each being coupled to an electrical supply 53 via electrical wires 54. The solar tracking device 51 comprises a first leg member 56’, a second leg member 56” and a universal joint 55, which support the solar panel 52. A first rod 17’ of the first electro-hydraulic linear actuator 1’ comprises the first leg member 56’.

A second rod 17” of the second electro-hydraulic linear actuator 1” comprises the second leg member 56”. The solar panel 52 comprises a first through hole 57’ and a second through hole 57”. The first rod 17’ extends through the first through hole 57’. The second rod 17” extends through the second through hole 57”.

A first single cylinder housing 3’ of the first electro-hydraulic linear actuator T is coupled to the solar panel 52 adjacent the first through hole 57’ via a first universal joint coupling 58’. A second single cylinder housing 3” of the second electro-hydraulic linear actuator 1” is coupled to the solar panel 52 adjacent the second through hole 57” via a second universal joint coupling 58”.

Fig. 10b illustrates a solar panel 52 coupled to a first T and second 1” electro- hydraulic linear actuator at the periphery of the panel device. The respective side edge of the panel device comprises the first T and second 1” electro-hydraulic linear actuator and the respective first and second rod passes the side edges outside the panel device.

Fig. 11 illustrates the first electro-hydraulic linear actuator T in Fig. 10 more in detail. The first electro-hydraulic linear actuator T comprises the first single cylinder housing 3’ extending along a central axis X. The first electro-hydraulic linear actuator T further comprises a first single piston body 5’ dividing the first single cylinder housing 3’ in a first and second cylinder chamber 7, 9.

A first piston portion 11 is arranged in the first single cylinder housing 3’ and is coupled to a second piston portion 13 via an intermediate portion IP of the first single piston body 5’ and is configured to extend through openings 15 of the cylinder housing 3.

A first rod 17’ extends along the central axis X through a first rod clamp 19 of the first single piston body 5’ and through a second rod clamp 21 of a static clamping body 59 of the first electro-hydraulic linear actuator T. The first rod clamp 19 comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the first single piston body 5’. The second rod clamp 21 comprises a second expandable cavity (not shown) configured to deform a second flexible wall (not shown) of the static clamping body 59. A hydraulic fluid supply 23 is configured for feeding hydraulic fluid to the first single cylinder housing 3’ and to the first and second expandable cavity.

The first electro-hydraulic linear actuator T is configured as a self-contained electro- hydraulic linear actuator. The hydraulic fluid supply 23 comprises a hydraulic fluid reservoir 25, an electric motor 27 mechanically coupled to a hydraulic pump 29, a channel arrangement (not shown) between the hydraulic pump 29 and the first single cylinder housing 3’ and between the hydraulic pump 29 and the first and second cavity. An electrical power wire 35’ (an electrical power device) is electrically coupled to the electric motor 27 and configured to be connected to an electrical network (not shown).

Alternatively, the first single cylinder housing 3’ and/or the a static clamping body 59 of the first electro-hydraulic linear actuator T and /or a fitting (not shown) of the first electro- hydraulic linear actuator T is coupled to the solar panel 52 adjacent the first through hole 57’ via a first universal joint coupling 58’.

Fig. 12 schematically illustrates a movement pattern diagram with a Bang-Bang control. An exemplary electro-hydraulic linear actuator is configured to perform a movement pattern controlled by a Bang-Bang control algorithm adapted to a control circuitry of the electro- hydraulic linear actuator for providing a feedback loop procedure.

The Bang-Bang control algorithm may be a 2-step or on-off control performed by the control circuitry, wherein the control circuitry is coupled to a valve arrangement of the electro- hydraulic linear actuator and configured to control the operation of the electro-hydraulic linear actuator in a feedback loop procedure, wherein the control circuitry may be configured to switch instantly between a rod engaging state of the first rod clamping device and a rod disengaging state of the first rod clamping device, and alternatively the control circuitry may be configured to switch instantly between a rod engaging state of the second rod clamping device and a rod disengaging state of the second rod clamping device.

As shown in Fig. 12 the position POS of the rod changes over a long distance, using short individual strokes (requiring a small amount of hydraulic fluid). The short individual strokes performed by the one single piston body is marked with PIS.

For example, the total displacement of the rod achieving the position POS of 3500 mm requires 1750 working strokes of the piston body over time t, each working stroke being 2 mm.

In such way is achieved a robust and cost-effective electro-hydraulic linear actuator.

Figs. 13a to 13c illustrate an exemplary solar tracking device 51 configured to orient a panel device 52, such as a solar panel or a heliostat. The solar tracking device 51 comprises a base joint 62 providing a universal pivot for the panel device 52 relatively a foundation 63.

The panel device 52, as shown in Fig. 13a, is coupled to a first T and second (not shown) electro-hydraulic linear actuator. The solar tracking device 51 comprises a first leg 56’, a second leg member (not shown) and the base joint 62, which support the panel device 52. A first rod 17’ of the first electro-hydraulic linear actuator T constitutes the first leg 56’. The base joint 62 comprises a universal joint about which the panel device 52 can pivot in a circular sector S, e.g. defined by the sector S (90 degrees) from 0 degrees to 90 degrees from horizontal, as shown in Fig. 13b. As shown in Fig. 13c, the panel device 52 also has been tilted about the base joint 62 by driving the respective electro-hydraulic linear actuators different distances on the respective rod.

Alternatively, in case the pressure in the first cylinder chamber and/or the second cylinder chamber, detected by a cylinder pressure switch unit (not shown), exceeds a pre-set pressure value, it is obvious that the panel device has been moved out from the position in Fig. 13a (e.g. due to a wind gust), wherein the control circuitry operates the panel device back into the correct position.

Alternatively, the pressure switch signals to a control circuitry (not shown) commanding the respective electro-hydraulic linear actuator T, 1” to provide a new reference value, e.g. moving the cylinder housing to a stop position for reference. Subsequently, the control circuitry commands each electro-hydraulic linear actuator to move the respective rod or cylinder housing to the desired position, thereby operating the panel device back into the correct position. In such way is achieved that eventual heavy wind load making the rod to slide relative the cylinder housing and displacing the panel device can be detected.

Alternatively, the clamping force of the first and second rod clamping devices (not shown) of each electro-hydraulic linear actuator is set to such low value that a specific wind load (e.g. upper limit load) generating an axial force on the respective cylinder housing and/or static clamping body, providing that the respective rod (the first and/or second rod) slides in the rod clamping device/s.

Alternatively, the clamping force of the second rod clamping device is set to such low value that a specific wind load generating an axial force on the rod will provide that the rod slides in the second rod clamping device.

In such way the panel device is configured to be moved between a horizontal position and an upstanding position, i.e. providing that the structural load on the panel device decreases in stormy weather.

Alternatively, the control circuitry is configured to move the panel device into a stow position according to a horizontal orientation, i.e. providing that the structural load on the panel device decreases in stormy weather.

The present invention is of course not in any way restricted to the preferred examples described above, but many possibilities to modifications, or combinations of the described examples, thereof should be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention as defined in the appended claims.

The term ‘battery pack’ may denote a plurality of battery modules interconnected to achieve required voltage for an application. In some designs, battery pack consists of plurality of individual batteries without some additional grouping forming battery module.

One aspect may involve that the rod clamping devices are adapted and arranged for momentary disengaging the rod for providing a free-wheel performance using the kinetic energy of the mass being moved.