TECHNICAL FIELD

The present invention relates to a fluid actuator arrangement according to the preamble of claim 1.

The present invention concerns the industry using hydraulic and pneumatic actuators for different types of applications and concerns the manufacture industry producing such arrangements.

The invention is not limited thereto, but can also be used for replacing electrical actuator arrangements and can be adapted for application of a wide range of different types industries.

BACKGROUND ART

There is a desire to provide a fluid actuator arrangement that can distribute control functionality regarding force and motion rate of the piston rod arrangement. Current technology uses fluid actuator arrangements that are designed with specific features for achieving optimal pressure. This may imply overweight and over-dimension materials, which for a specific operating mode may be regarded as superfluous.

Current technology also often uses a centrally controlled operation of maximum motion rate (speed) and force of the piston rod arrangement by means of controlling the fluid flow and pressure of the fluid supply device. Such centrally controlled feeding of fluid makes the current arrangement ineffective.

There is a desire to eliminate inefficient throttling processes performed by servo valves controlling prior art fluid actuator arrangements. Such throttling involves wasted energy through heat dissipation and high energy costs. US 4 506 867 discloses a jacking apparatus for effecting motion of loads by means of two double-acting hydraulic cylinders for providing increased force of a power stroke. Hydraulic fluid pressure is controlled to a predetermined flow rate to the hydraulic cylinders for increasing the speed of a repositioning stroke of the apparatus.

US 3220317 discloses a servo system having a hydraulic motor system with two pistons arranged in tandem for each motor. The system uses two motors connected in parallel so that their motions are in fixed proportions and their forces are added. The system may also be arranged with the motors in series so that forces are in fixed proportions and motion added.

There is an object to reach more efficient control of speed and force of a fluid actuator arrangement.

Yet another object is to reduce power output of the fluid supply device (pump). There is also an object to reduce energy losses.

A further object is to develop an energy saving fluid actuator arrangement comprising compact cylinders promoting the benefits of longer piston rod arrangements having longer piston rod path compared with prior art fluid actuator arrangements.

A yet further object is thus to provide a more compact fluid actuator arrangement.

An object is to provide a fluid actuator arrangement exhibiting a lower weight compared with prior art fluid actuator arrangements.

An object is to improve current fluid actuator arrangements in mobile and industrial applications.

An object is to provide fluid actuator arrangements to accomplish work with only a small amount of input force.

A further object is to increase energy efficiency for a fluid actuator arrangement operating under various motion/movement and force performance selected from actual requirement or condition, without need of additional energy consuming throttling valves.

Furthermore, an object is to reduce the size of components and systems of a fluid actuator arrangement, while maintaining or increasing power output.

A further object is to provide a fluid actuator arrangement, which can be used in smart fluid power component systems including self-diagnostics and plug-and-play (easy to use) functionality.

A yet further object is to minimize the environmental impact by lowering noise and eliminating large leaks.

An object is to provide a fluid actuator arrangement that can be used cost-effective in material handling equipment applications. Material handling equipment, such as electronic overhead travelling cranes, level luffing cranes and stackers can thus make use of the present fluid actuator arrangement. Also other types of cranes may make use of the arrangement, such as overhead cranes, mobile cranes, tower cranes, telescopic cranes, loader cranes, which cranes comprise long hydraulic cylinders. Also forklifts, telehandlers and production line conveyors may make use of the present fluid actuator arrangement. The application of the present fluid actuator arrangement covers a major range of industries, such as oil refineries, power and energy facilities, food and beverage industries, retails, container terminals aiming at faster solutions for container logistics offering shorter time for container ships in harbour. Also elevators for buildings may make use of the present fluid actuator arrangement. Also offshore/marine applications, paper and steel industry machinery, pneumatic industry may make use of the present fluid actuator arrangement.

A further object is to provide a fluid actuator arrangement that can be used for the production of agricultural equipment, including tractors, combine harvesters, loaders, hay balers, mulching machines and lawn and garden equipment, such as earth mowers, forest harvesters, etc. One aspect of the present invention is to adapt the arrangement to 3D-printing in plastic, composite and/or metal applications for aircraft and automotive industry. This promotes high process speed and high accuracy for prototypes (rapid prototyping), demonstration units and small volume production.

A further object is to provide an arrangement that can be used in 3D-printing of entire buildings.

An object is to provide an arrangement that can be used in automated storage and retrieval systems for car parking and rough-terrain robots, so called legged robot systems.

A yet further object is to provide a fluid actuator arrangement that can be used in the construction end-market, including vehicles such as excavators, steam rollers, backhoe loaders, concrete machines, drilling rigs, and wheel loaders used adapted for construction of infrastructure, e.g. roads, bridges, buildings or tunnels.

Furthermore, an object is to provide a fluid actuator arrangement that can be used in the upstream oil and gas industry, primarily at the wellhead and including jacking systems used to raise and lower oil well drilling and service platforms, excavators, off-road dump trucks and rigs.

A further object is to provide a fluid actuator arrangement that can be put into use in light, medium and heavy hydraulic presses used for metal forming, including die casting, forging, extrusion, drawing, pressing machines, mould making, casting, etc. A yet further object is to provide a fluid actuator arrangement adapted for aerospace vehicles. There is a need for weight saving and less bulky arrangements. The present fluid actuator arrangement can be used in systems for landing gears, engines, ramps, door actuation devices, brakes and wheels, flight controls and fuel systems etc. The arrangement can also be used in ground handling equipment, baggage handling equipment and specialty aircraft repair equipment. The aerospace segment has always been a major consumer of heavy duty hydraulic cylinders and arrangements for saving weight have been developed over long time. The weight saving of commercial aircraft is extremely important today regarding so called "green aviation" as less weight of the aircraft will reduce fuel consumption and thus less NOx and C02 emissions. One aspect is thus to put the present fluid actuator arrangement in use in both civil and military applications, in manned and unmanned aircrafts, and especially for large civil aircraft.

Additionally, an object is to provide a fluid actuator arrangement that can be used in military equipment utilizing hydraulic and/or pneumatic mechanisms. This includes armoured personnel carriers, aircraft material handlers, cranes and loaders, hook lifts, track adjusters and truck-mounted bridge layers.

Large milling (CNC) machines and hydraulic robots for aircraft, automotive may make use of the fluid actuator arrangement.

An object is to provide an arrangement that can be adapted to mining machines, mine and mountain drilling rigs, etc.

A further object is to provide a fluid actuator arrangement that can be used in mining drills and breakers, crushing, pulverizing and screening equipment, mineral processing machinery, surface mining equipment, underground mining machinery and other mining equipment.

SUMMARY OF THE INVENTION This has been achieved by the arrangement defined in the introduction and being

characterized by the features of the characterizing part of claim 1.

Thereby is achieved that the first chamber can be pressurized with a first pressure, wherein the first piston device will be secured to the piston rod arrangement by means of the piston rod engagement and disengagement means actuated by the first pressure. Disengagement of the first piston device from the piston rod arrangement is performed when the first chamber is pressurized with a second pressure or not being pressurized.

Preferably, the second pressure being lower than the first pressure. Thereby is achieved a fluid actuator arrangement comprising at least one actuator, the definition of which corresponds to a cylinder comprising a piston device and piston rod arrangement, using a releasable piston allowing discrete adjustability of the total cross- section piston force area. In such way it is possible to provide precise motion control without the need of current inefficient throttling process. There is therefore provided less inefficient throttling for the present arrangement than for prior art arrangements. Current motion control often involves wasted energy through heat dissipation and required heavy and expensive cooling systems.

Preferably, the valve member means is adapted to control that the first pressure is higher than the second pressure and alternatively (in case of pneumatic actuator arrangement) the second pressure is reservoir pressure.

It is thus provided a modular fluid actuator arrangement that comprises three main functionalities. Firstly, a hybrid actuator comprising at least one conventional piston constantly in engagement with the piston rod may be used. Secondly, there is a possibility to use two or more cylinders in tandem using one common piston rod and wherein respective piston of each cylinder comprises a piston rod engagement and disengagement means, which is adapted to engage or disengage the piston from the piston rod. Thirdly, a locking arrangement mode is possible, wherein a piston-like clamping device using the fluid supply system or external fluid supply systems (or wherein both chambers of respective cylinder may optionally be pressurized for activating the piston engagement means in a locked position) is used. Such application may be advantageous in case of error in operation. Said three function modes can also be combined. Such combinations may regard different force areas of the cross-sections of the pistons.

In such way is achieved that unlimited lengths of piston rods can be used that opens up for various types of industrial areas.

Thereby is achieved a possibility to control the fluid actuator arrangement in an efficient way depending upon the actual need of fluid power for a specific situation.

In such way is achieved a major reduction in power losses, when compared to prior art arrangements. Thereby, no or less throttling losses are present and it is achieved that the fluid actuator arrangements. This implies, e.g. for mobile applications, that significant fuel savings can be made and less C02 emissions.

According to current technology, a designer must adapt prior art arrangement to match force and speed requirements - e.g. to match high force and slow speed or low force and high speed - by introducing servo valves. Such servo valves throttle one or several actuators depending upon desired force and rate of motion and acceleration of the piston rod.

By means of the claimed features, the designer will have a unique possibility to

adjustment/management of the cylinder area of the arrangement by engaging/disengaging one or several pistons to the piston rod arrangement, thereby optimizing the performance of the actuator arrangement to varying speed and force requirements.

By means of the piston rod engagement and disengagement means, which is adapted to engage the piston device to the piston rod arrangement, there is achieved that a precise motion of the piston rod arrangement can be made in combination with a less energy consuming throttle valve.

In such way is achieved a fluid actuator arrangement that has substantially higher power to weight ratio resulting in higher machine frame resonant frequencies for a given power level and high stiffness of the control system of the present arrangement.

Thereby is provided a fluid actuator arrangement operating in a stiff manner and that achieves high loop gain capability, great accuracy and frequency response.

In such way is achieved a fluid actuator arrangement performing smooth performance at low speed and which have a wide speed range by changing the force area of the present arrangement.

This means that a fluid actuator arrangement is provided that to a great extent is self-cooling and that can be operated in stall condition indefinitely without damage.

In such way is achieved a compact, short and light-weight cylinder having a smaller volume of oil (in case of being a hydraulic actuator) in the first and second chamber of the cylinder than that of conventional hydraulic cylinders. Elongated and heavy prior art cylinders can thus be eliminated. Additional oil volume in bulky reservoir tanks is needed for prior art cylinders. Extraction and extension of prior art actuators requires large oil volume. By means of the claimed features it is provided that less bulky oil reservoir tanks can be used for the arrangement.

Preferably, the first and second cylinder are arranged in tandem and the first and second piston device being associated with a common piston rod of the piston rod arrangement. In such way there is provided a less bulky arrangement using a common piston rod. Current control of prior art arrangements for changing working point involves the use of energy consuming throttling valves. Such prior art throttling results in wasted energy through heat dissipation and thus requires heavy and expensive cooling systems. By means of the claimed features a cooling system of the present arrangement can be designed to be less bulky than prior art cooling systems.

Thereby are achieved reductions in weight and volume. This involves smaller components (cylinder, oil reservoir, oil cooler and fuel tank) than prior art and thus more cost-efficient assembly. In such way is achieved an arrangement having less gross weight, requiring less manufacture costs, and having a very compact design. Suitably, the second piston device comprises a piston rod engagement and disengagement means adapted to be able to engage or disengage the second piston device to/from the piston rod arrangement.

In such way is achieved an optimal and secure functionality providing accurate performance.

Thereby is provided a compact and low-weight (and energy saving) fluid actuator arrangement that can propel a piston rod arrangement a major distance and back again, wherein the respective piston device in turn is engaged with the piston rod arrangement.

Thereby is achieved that both piston devices can be engaged with the piston rod

arrangement for generating a larger force area of the piston devices. Such additional force is suitable for achieving that the piston rod arrangement can accelerate a heavy load. Preferably, the piston device (when not in engagement with the piston rod) is centrally positioned in the cylinder for operating the fluid actuator arrangement in a symmetrically manner in opposite directions.

Optionally, this can be achieved by two spring elements provided at each side of the piston device, seen in a direction corresponding with the elongation of the piston rod arrangement. Alternatively, this can be achieved by an electromagnetic means.

Suitably, a third cylinder comprising a third piston device is arranged in tandem with the first and second cylinder (preferably using a common piston rod).

Thereby a unique maximal long piston rod can be used for a wide range of applications, e.g. elevators, forklifts, cranes, 3D printing/CNC machines, mine drilling rigs, container terminals, profile rail guides etc. Such use of long piston rods opens up new areas for hydraulic actuators and pneumatic actuators. The length of the piston rod is not dependent on cylinder length. Also an aspect of the invention disclosing only two cylinders may involve such unique maximal long piston rod.

Alternatively, the piston rod engagement and disengagement means additionally being adapted to engage the first piston device to the piston rod arrangement, when the second chamber is pressurized.

In such way there is achieved high flexibility in speed and force. The achieved arrangement can be seen as a hydraulic "gear box". Heavy loads can be moved at high speed with high acceleration and retardation in combination with very accurate motions at low speed.

Preferably, the piston rod engagement and disengagement means is adapted for stiff/rigid engagement (rigidity in axial direction).

This implies safe operation of the fluid actuator arrangement and optimal precision of motion.

Suitably, the piston device and the piston rod arrangement (piston rod) are free to move relative each other and also relative the cylinder per se encompassing the piston device and a portion of the piston rod. Alternatively, the piston rod engagement and disengagement means comprises a cavity means forming a flexible piston inner wall portion adapted for releasable engagement with the piston rod arrangement.

Preferably, the cavity means extends around the longitudinal axis of the piston device parallel with the circumference of the bore hole of the piston device and at a proper distance from the latter so that a suitable mass of material (e.g. same material as the rest of the piston device) constitutes said piston inner wall portion. Said mass of material forming the piston inner wall portion is such flexible that increased pressure in the cavity means expands the piston inner wall portion thereby clamping upon the piston rod arrangement.

By means of said flexible piston inner wall adapted for only minor movement in radial direction for clamping (secure) the piston arrangement, the number of motions is high and the arrangement can be classified as a long-life arrangement.

Thereby is achieved that a portion (comprising a section of the piston inner wall) of the material of the piston device can be used for radially clamping said portion of the piston device onto the piston rod arrangement outer surface (envelope surface) by introducing a high pressure in the cavity, thus expanding the portion (i.e. the piston inner wall of the piston device) in direction radially inwardly in engagement with the piston rod arrangement. Vice versa, the piston device is disengaged from the piston rod arrangement when the fluid not being pressurized in the cavity, wherein said portion will retract to its original state and said section of the piston inner wall moves outwardly in a radial direction from the piston rod and disengages the piston device from the envelope surface of the piston rod.

Preferably, the piston rod engagement and disengagement means comprises a membrane means adapted for releasable engagement with the piston rod arrangement.

In such way is achieved a membrane used between the piston rod and the piston device. By applying a pressurized fluid to the membrane by means of a logic valve being in fluid communication with the pressurized fluid in the actual chamber of the cylinder comprising the releasable piston device, the piston device will be connected with maximum secure, fast and reliable clamping to the piston rod arrangement. Such membrane also promotes fast disconnection (disengagement) of the piston device from the piston rod arrangement.

Preferably, the piston rod engagement and disengagement means comprises a clamping device and/or locking member

The speed and force of the piston rod can thus be controlled in an efficient way by varying the active total piston area in discrete steps. Multiple cylinder chambers with releasable pistons can be combined in several ways in order to find the most suitable speed-and-force solution for a specific application.

Suitably, the piston rod engagement means comprises a pressure strengthening device, which is provided to strengthening the engagement of the first piston device to the piston rod arrangement.

In such way is achieved that the piston device is rigidly secured to the piston rod

arrangement and which can be performed a short time period.

Preferably, the pressure strengthening device is arranged within the piston device and comprises a movable micro piston rod having a first micro pressure area and a second micro pressure area. The first micro area being larger than the second micro pressure area, and is in fluid communication with the pressurized (main) fluid. The second micro pressure area may be arranged in communication with a separate high pressure fluid provided in a cavity means (for membrane functionality) of the piston device forming the cavity means of the piston rod engagement and disengagement means. Suitably, the arrangement comprises a hydraulic actuator arrangement.

Thereby is achieved that a secondary control is provided. Such secondary control is one of the most efficient control methods for hydraulic systems. Such secondary control of the present hydraulic actuator arrangement also presents low hydraulic capacitance, which additionally saves power.

In such way is achieved energy saving and reduced power demand of the primary hydraulic supply device (such as a power unit). In such way fuel consumption and operative costs being reduced. There is also achieved that cooling capacity will comply with current emission regulations.

According to one aspect of the present invention, so called secondary control of hydraulic cylinders can be realized by utilizing a multi-chamber cylinder approach with releasable (possible to disconnect/disengage) pistons. The principle of such a secondary control is to control the torque of the hydraulic motor by controlling the displacement of the motor. By means of this aspect, a variable displacement unit can be provided for a hydraulic cylinder, but also in this case the present arrangement with variable cross-sectional force area.

By means of the claimed features, the need for prior art emission reduction technology is reduced. Such prior art emission reduction technology usually is complicated, expensive and difficult to integrate into machine application and apparatuses to be used. Furthermore, by means of the claimed features is achieved that energy waste through heat dissipation is decreased and lighter, smaller and less expensive cooling systems can be used. The impact on the environment is thus less vulnerable and the present fluid actuator arrangement can be regarded as "Green" technology. In such way is provided a high stiffness and high natural frequency (compared with prior art actuator arrangements) due to less volume used in the present cylinder chamber (compared to conventional cylinders). These factors are favourable in control design.

Preferably, a first cross-sectional force area of the first piston device differs from a second cross-sectional force area of the second piston device. There is thus possible to control the fluid actuator arrangement performance by altering the fluid actuator arrangement's effective force area during operation. This introduces a new level of energy efficiency to hydraulic/pneumatic systems used in current power

transmissions.

Suitably, the arrangement comprises a first actuator provided with a first force area, a second actuator provided with a second force area corresponding with the first force area, a third actuator provided with a third force area, a fourth actuator provided with a fourth force area, the third force area is twice as large as the first force area, the fourth force area is twice as large as the third force area. In such way is achieved that a fast piston motion can be achieved with minor piston force. The respective force area is defined as the cross-sectional area of the respective piston device. For reaching such fast piston motion and minor force, the first force area (e.g. 1 area unit) is activated by alternating engagement of the first and second actuator to the piston rod arrangement. For achievement of an alternative performance of the arrangement, for example a slow piston motion with high force, all activators are activated. The high force may be achieved by activating all four force areas (e.g. 8 area units = 1 + 1 + 2 + 4, i.e. the respective force area of the first, second, third, fourth actuator). This implies an optimal combination of eight different force area units, which can be selected from required piston motion rate and force of piston device. Prior art actuators can be built for 8 area units and being determined for slow piston motion with high force. However, such prior art actuator will, when used for fast motion and minor force, require that the entire cylinder volume must be pressurized and a part of the pressurized fluid (fed from the fluid supply device) must be throttled for decreasing the force. Prior art arrangements thus will generate energy losses. Preferably, also other force area combinations are possible. For example 1+1+1 +1 +1+1 or 1 +2+4+8+16+32 or 1 +1 +2+4+8+16+32 or others.

Alternatively, the arrangement comprises a plurality of actuators.

By controlling the total cross-sectional force area of the arrangement, the motion rate and the force of the piston rod can be changed and optimized in an efficient way. The actual needs of operation for a certain situation can be satisfied by changing said total cross-sectional force area of the arrangement. This is due by the formula V = Q / A and the formula F = P * A, wherein "V" is the motion rate of the piston device, "Q" is the fluid flow, "A" is the area of the piston device, "F" is the force of the piston device and "P" is the pressure of the fluid. For example, by decreasing the area "A" (e.g. by disengaging one piston), the motion rate "V" is increased at the same time as the force "F" is decreased.

In such way is achieved that a modular actuator arrangement can be assembled from desired provisions regarding force and speed of the piston rod arrangement - for example high force and slow speed or low force and high speed - and furthermore desired distance for piston rod arrangement motion, braking action, precision adjustment of the piston rod arrangement to a predetermined accurate position etc. Such modular actuator arrangement can operate with less throttling compared with prior art. According to one aspect of the present invention there is provided that engagement and disengagement of piston devices to/from the piston rod arrangement will imply flexibility and less energy losses compared with prior art. Preferably, the arrangement comprises an electro-hydraulic cylinder apparatus.

In such way is achieved accuracy, enhanced functionality, improved ease-of-use and controlled performance. Electro-hydraulic cylinders incorporate servo valves and electronic controls such as transducers to provide rod position feedback and to ensure efficient machine operations. This enables sophisticated control of speed and position of loads in several applications of the arrangement according to this aspect.

The arrangement is suitable adapted for an aircraft comprising the arrangement according to any of claims 1-13.

Suitably, the aircraft is a commercial aircraft designed for long distance flights. The arrangement is preferably adapted for any of the following industrial segments;

construction industry, jacking systems for oil well drilling and service platforms, agricultural equipment industry, marine industry, crane manufacture industry, paper and steel industry, rough-terrain robot manufacture industry or others.

Alternatively, the arrangement comprises a pneumatic actuator arrangement. 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:

Figs. 1a to 1 d illustrate one aspect of the present invention;

Figs. 2a to 2d illustrate a prior art actuator arrangement; Fig. 3a shows a flight envelope diagram illustrating needs of performance related to Mach number;

Fig. 3b shows a graph illustrating a central pump working point relative different fluid actuator arrangements presenting different operational requirements;

Figs. 4a to 4b illustrate an example of mounting of a prior art application versus the mounting of an arrangement according to one aspect of the invention;

Figs. 5a to 5f illustrate the operating of a hydraulic actuator arrangement, according to one aspect of the present invention;

Figs. 6a to 6c illustrate a lift cage and a piston rod device using the arrangement according to one aspect of the present invention; Figs. 7a to 7c illustrate different piston rod engagement and disengagement means according to one aspect;

Figs. 8a to 8e illustrate a piston rod engagement and disengagement device according to several aspects of the present invention; Figs. 9a to 9k illustrate a method for operating an arrangement according to one aspect of the present invention;

Figs. 10a to 10b illustrate further aspects of the present invention;

Figs. 1 1a to 11f illustrate yet further aspects of the present invention; and

Figs. 12a to 12j illustrate different aspects of the present invention. DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described in detail 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. The fluid actuator arrangement is also herein called arrangement. Fig 1a schematically shows a fluid actuator arrangement 1 comprising a first 3 and second 5 cylinder of a cylinder arrangement 7. The first 3 and second 5 cylinders are arranged in tandem and rigidly fit to each other by using a common cylinder housing. A partition wall 6 is provided between the cylinders 3, 5. The arrangement 1 further comprises a common piston rod 9 and a first 11 and second 13 piston, each being coupled to the piston rod 9. The first piston 11 is arranged in the first cylinder 3 and divides the latter into a first 15 and second 17 chamber. The second piston 13 is arranged in the second cylinder 5 and divides it into a first 15 and second 17 chamber and is rigidly connected to the piston rod 9. The respective chamber 15, 17 is connected for fluid communication with a fluid pump 19 via a valve member 21 comprising a control valve 23 and a logic valve 25. The fluid pump 19 is connected to the control valve 23 by means of a fluid (hydraulic) feeding line 27. The control valve 23 is in turn connected for fluid communication with the first chamber 15 of the second cylinder 5 by means of a first fluid line 29 and also connected to the second chamber 17 of the second cylinder 5 by means of a second fluid line 31. A control unit 33 (such as a CPU) controls the control valve 23 and directs the fluid flow to the second cylinder 5 providing fast motion and low force of the piston rod 9 as is shown in Fig. 1 b. In Fig. 1 c is shown that the control unit 33 has made a command to the logic valve 25 to open also a third fluid line 35 provided between the first chamber 15 of the first cylinder 3 and the first fluid line 29, thereby activating the arrangement from the state shown in Fig. 1 a. The first chamber 15 of the first cylinder 3 will thus also be pressurized. The first piston 11 is provided with a piston rod engagement and disengagement means 37 adapted to engage (secure) or disengage (release) the first piston 1 1 to/from the piston rod 9. The piston rod engagement and disengagement means 37 comprises a membrane 39 arranged adjacent a wall of an inner piston surface of said first piston 11 , which membrane 39 is provided to expand and retract depending upon actual pressure fed into interior fluid guide channels (not shown) of the first piston 11. The piston rod engagement and disengagement means 37 is thus adapted to engage or disengage the first piston 11 to or from the piston rod 9 depending upon actual pressure in the respective chamber 15, 17 in the first cylinder 3. As the first chamber 15 of the first cylinder 3 being pressurized, the membrane 39 will expand and press tightly (clamp) against the piston rod 9. Such tight engagement of the first piston 11 to the piston rod 9 implies that the first piston 1 1 will contribute adding force (double force area) to the piston rod 9. Such contribution is shown with arrow C marking that the force now generated by the arrangement 1 is larger. In Fig. 1 d is shown that the control unit 33 has shut down the feeding of fluid to the first cylinder 3 by closing the logic valve 25. As no pressure prevails in the first chamber 15 of the first cylinder 3, the membrane 39 will retract and the first piston 1 1 will disengage from the piston rod 9. The first piston 11 is (shortly after disengagement) positioned in symmetrical position (middle position of the second cylinder 5 seen in the longitudinal direction) be means of a spring arrangement 41. The control valve 23 is controlled to feed fluid flow to the second chamber 17 of the second cylinder 5 for pressurizing the second chamber 17 of the second cylinder 5 and returning the piston rod 9 with high motion rate and low force.

Fig. 2a shows a hydraulic actuator arrangement 100 according to prior art. The arrangement 100 comprises a cylinder 101 and a piston 102 rigidly connected to a piston rod 103. A pump 104 provides a flow of fluid to a control valve 105. The arrangement 100 is designed for highest expected motion force/load. This means that if a lower force has to be generated, a major throttling is made for decreasing the pressure in the pressurized chamber 108. This excess fluid is led to an external reservoir 109. One way to solve this is to decrease the pump action. This is however also ineffective. Especially if another prior art arrangement (not shown) is coupled to the pump 104, which prior art arrangement must perform a high force/load motion adapted to the maximal pump performance. Thereby a not efficient throttling must be performed for the hydraulic actuator arrangement 100. In Fig. 2b is shown that no throttling is performed for achieving that the arrangement 100 is maximally pressurized for motion of a high load. Fig. 2c shows another prior art actuator arrangement 200 having two cylinders, each having a piston 201 being rigidly coupled to a common piston rod arrangement 202. In case a lower force is needed, only one cylinder is active. This arrangement is bulky for low force mode involves unnecessary motion of all pistons in the cylinders.

Fig. 2d shows a further prior art actuator arrangement 300 of a jet fighter wing. An elevator 301 is controlled by the actuator arrangement 300 having two parallel actuators 302. In case of high aircraft speed (e.g. supersonic speed) (high force is required to move the elevator 301), both actuators 302 are activated. At low speed (for example at take-off and landing) there are required a low force and high motion rate to move the elevator 301 , wherein high energy losses are present.

Fig. 3a schematically shows a flight envelope diagram illustrating the performance of an actuator arrangement related to Mach number. It is herein shown that with increasing Mach number (VEL.) and decreasing altitude (ALT.), the control surface motion requirements result in that the pump pressure increases from Low Pump Pressure LPP to High Pump Pressure HPP. At the same time the required motions of an actuator arrangement are different upon actual position of the aircraft in the flight envelope. At low Mach numbers are needed High Rates HR and at high Mach numbers are needed Low Rates LR. Low Hinge Moments are marked with LHM. High Hinge Moments are marked with HHM. There is thus a need for high pump pressure and low rate actuator motion at high velocity - and low pump pressure and high rate actuator motion at low velocity - of the aircraft. According to one aspect of the present invention there is provided that rapid change of force area of the piston device can be made for achieving high force performance of the arrangement or high rate motion of the arrangement in accordance with actual operation of the aircraft.

Fig. 3b schematically illustrates a diagram (P=fluid pressure; F=force; Q=fluid flow; v=motion rate) of the working point WP of a central pump relative a set (two) of different fluid actuator arrangements (not shown) having different operational requirements regarding High

Force/Low Motion Rate (Requirement R1) and High Motion Rate/Low Force (Requirement R2). For example, a first arrangement (not shown) requires High Force and Low Motion Rate and a second arrangement (not shown) requires High Motion Rate and Low Force, wherein the arrangements are connected to a common central pump proving a constant high pressure P. By means of just changing the cross-sectional force area (active piston area) of each arrangement, the Requirement R1 and Requirement R2 will be possible to full fill in an energy saving way. In such way is provided an effective, intelligent and local/distribution control of motion rate and force for each arrangement independently of each other and providing less C02 emissions and saving energy. This aspect of the present invention also implies a total lower (relative prior art) power output of the central pump and thus lower energy losses. Figs. 4a to 4b illustrate an example of mounting of a prior art application versus the mounting of an arrangement 1 according to one aspect of the invention. As shown in Fig. 4a the prior art arrangement 400 is designed for only High Pump Pressure HPP, but throttled to Low Hinge Moments LHM for providing lower forces. As shown in Fig. 4b the arrangement 1 according to one aspect of the present invention is less bulky and is of lower weight. By means of the arrangement in Fig. 4b according to one aspect there is thus possible to change between high force and high velocity of the piston 9. There is a possibility to change to double force area and thus double force for a short distance by activating both cylinders in tandem. Large forces and short distance motions of being required for the piston rod in high speed and/or supersonic speed.

Fig. 5a to 5d 5f schematically shows the operating of a hydraulic actuator arrangement V according to one aspect of the present invention. Fig. 5a illustrates the arrangement V comprising a first cylinder 3 and a second cylinder 5. A first piston 1 1 is arranged in the first cylinder 3 and a second piston 13 is arranged in the second cylinder 5. A spring mechanism 42 is arranged in respective cylinder 3, 5 for positioning respective piston 1 1 , 13

symmetrically (seen in a longitudinally direction between end walls of the cylinder) in the cylinder 3, 5, when respective cylinder chamber 15, 17 is not pressurized. Only one of the spring mechanisms is shown in the Figs. 5a to 5f for sake of clarity. A common piston rod 9 protrudes through the cylinders 3, 5 along a central longitudinal axis X. The cylinders 3, 5 are arranged in a tandem assembly and at outside ends of the assembly there is arranged a respective scraper means (not shown) for removing eventual dust and dirt from the piston rod 9 outside the cylinders 3, 5. Respective piston 1 1 , 13 is provided with a piston rod engagement and disengagement means 37 adapted to engage (secure) or disengage (release) the pistons 1 1 , 13 to/from the common piston rod 9. A pump 19 is connected to a control valve 23, which in turn is connected to respective chamber 15, 17 of the assembly via logic valves 25. The second cylinder 5 is connected to the control valve 23 via the right (as seen in the Figs. 5a to 5f) positioned logic valve 25 adapted for directing the hydraulic flow to the respective chambers 15, 17 of the second cylinder 5. In Fig. 5b is shown that the first piston 11 is actuated by pressurizing the first chamber 15 of the first cylinder 3. The direction of motion is operated by controlling the control valve 23 and the activating of the respective cylinder 3, 5 is made by operating the respective logic valve 25. Such control of fluid flow to the arrangement promotes for efficient selection of working points regarding motion rate and force of the arrangement. By pressurizing the first chamber 15 of the first cylinder 3, the first piston 11 engages the common piston rod 9 by means of the piston rod engagement and disengagement means 37. The second cylinder 5 is not pressurized and no engagement is performed between the piston rod 9 and the second piston 13. The second piston 13 is not engaged with the common piston rod 9, which slides through the second piston 13 and its piston rod engagement and disengagement means 37, thus slides adjacent the piston bore inner wall of the second piston 13. Low force and high motion of the common piston rod 9 is achieved. In Fig. 5c is shown that the control valve 23 is operated to direct the hydraulic flow from the pump 19 to the second chamber 17 of the first cylinder 3. The first piston 1 1 is again in engagement with the common piston rod 9 for returning the latter with a low force.

In Fig. 5d is shown that both logic valves 25 is are operated to open fluid communication with the second cylinder 5 as well. The first chamber 15 of the second cylinder 5 is pressurized and the second piston 13 will engage with the common piston rod 9 in similar same way as the first piston 1 1. There will thus be added performance in force F acting upon the piston rod 9. Double load motion/fast accelerating heavy loads is thus achieved by the arrangement V in this state.

In Fig. 5e is shown that the control valve 23 is changed for feeding hydraulic oil to re-direct the common piston rod 9 by means of engagement of the both pistons 1 1 , 13 by pressurizing the second chamber 17 of the first cylinder 3 and the second chamber 17 of the second cylinder 5. In Fig. 5f is shown that the right logic valve 25 is closed and the second piston 13 is disengaged from the common piston rod 9, wherein the second piston 13 is returned to mid-position by means of the spring mechanism 42. The first piston 11 is engaged with the common piston rod 9 and propels the latter with minor force for accurate and fine adjustment of the common piston rod 9.

Figs. 6a to 6c schematically illustrate a lift cage 45 and a piston rod 9 for use of an arrangement 1 " according to one aspect of the present invention. A further parallel arrangement (not shown) is also adapted to the lift cage 45. The piston rod 9 is arranged through a cylinder arrangement comprising four cylinders 4', 4", 4"', 4"" (see Fig 6b).

Respective cylinder is provided with a piston comprising a piston rod engagement and disengagement member 37 adapted for releasable engagement with the piston rod 9. As seen in Fig. 6a the arrangement 1 " is mounted in a structural portion of the lift cage 45. The operation of the arrangement 1 " is performed by a user 8 operating a control unit 33'. Fig. 6b illustrates the arrangement 1 " in closer view taken instantaneously. The arrangement 1 " comprises the first 4', second 4", third 4"' and fourth 4"" cylinder with respective first 1 1 ', second 11 ", third 11 "' and fourth 1 1"" piston. An upper chamber 15' of the second cylinder 4" is pressurized, wherein the second piston 1 1 " is engaged with the piston rod 9. The arrangement 1 " and lift cage 45 will thus be moved in direction L, as the upper wall w of the second cylinder 4" is forced (pressed) in said direction. A spring 44 is arranged in each cylinder in its lower cylinder chamber 15". The spring 44 in the second cylinder 4" being compressed during said pressurization. Optionally, during lift start for accelerating the lift cage 45, all cylinders 4', 4", 4"', 4"" may be active, generating a large force. In Fig. 6c is shown that the third piston 1 1"' is engaged with the piston rod 9 by pressurizing the upper chamber 15' of the third cylinder 4"'. The second cylinder 4" is not pressurized and the piston 1 1 " is returned to its upper position in the cylinder 4" by said spring 44. For operating the lift cage 45 going down, the lift cage 45 is provided with a system adapted for such functionality.

Figs. 7a to 7c schematically illustrate a piston rod engagement and disengagement means 37 according to one aspect. Fig. 7a shows a piston 11 in a front view. A bore 61 (exhibiting an inner wall section 63) is provided centrally in the piston 11 for encompassing a piston rod 9. An interior channel 65' is arranged in the piston 1 1 , which channel 65' is provided with six tangent section portions. The interior channel 65' is adapted for fluid communication with a fluid pressurized cylinder chamber (not shown) according to one aspect. Pressurized fluid is fed into the interior channel 65' wherein the inner wall 63 expands in a radial direction inwardly according to arrows AR in Fig. 7b. In such way the piston 1 1 will engage the piston rod 9, when the cylinder chamber (see e.g. Fig. 6c) is pressurized for action. In Fig. 7c is illustrated a cross-section A-A taken in Fig. 7a.

Fig. 8a schematically illustrates a piston rod engagement and disengagement device 37 of a piston 1 1 according to one aspect. The device 37 comprises a membrane means 39' adapted for providing releasable engagement for the piston 1 1 with a piston rod 9. The device 37 further comprises a pressure strengthening device 67, which is provided for strengthening the engagement of the piston 1 1 to the piston rod 9. The pressure

strengthening device 67 is arranged within the piston 1 1 and is shown in an enlarged view in Fig. 8c according to one aspect. It comprises a movable micro piston rod 69 having a first micro pressure area mpa1 and a second micro pressure area mpa2. The first micro pressure area mpa1 being larger than the second micro pressure area mpa2, and is in fluid

communication with the pressurized fluid of the pressurized cylinder chamber 15. The second micro pressure area mpa2 is arranged in communication with a pressure

strengthening fluid provided in a cavity means 65"' for acting upon the membrane means 39' of the piston 11. Fig. 8b schematically illustrates one aspect of the invention, wherein a piston 11 is provided with two piston rod engagement and disengagement devices 37, each adapted for fluid communication with respective first 15 and second 17 chamber of a cylinder. Fig. 8d schematically shows a front view of a portion of a piston 11 having a central bore 61 forming an inner wall section 63. An interior circular cavity 65" is provided in the piston 11 extending parallel with the inner wall section 63 extension. The interior circular cavity 65" is arranged for fluid communication with corresponding cylinder chamber for pressurizing the interior circular cavity 65", thereby expanding the inner wall section 63 for engagement functionality. Fig. 8e schematically illustrates a piston 1 1 comprising a common membrane using a channel system (alternatively at least one channel) adapted for a respective micro piston for alternately actuating said common membrane. The use of a common membrane involves the benefit of an optimal friction area (clamping area) of the membrane.

Figs. 9a to 9I schematically illustrate a method for operating the motion of a piston rod 9 of an arrangement 1 according to one aspect of the present invention. Fig. 9a illustrates that first chamber 15 of respective cylinder (first 3 and second 5) being pressurized for accelerating a heavy load F. Fig. 9b shows that the overall force area is smaller, as the second cylinder 5 is not pressurized. However, the motion of the piston rod 9 is performed by pressurizing the first cylinder 3. Fig. 9c shows when both first 1 1 and second 13 pistons are in engagement with the piston rod 9. The first piston 1 1 is shortly held in engagement with the piston rod 9 during change of engagement to the second piston 13. Fig. 9c thus shows a way to manage operation of the arrangement to engage the piston rod 9 and simultaneously propel the latter without faltering during switch between pistons 11 and 13.

Fig. 9d shows that the second piston 13, which is in engagement with the piston rod 9, has moved the latter, at the same time as the first piston 1 1 is disengaged (as the first cylinder chamber 15 not being pressurized) and has been moved to a mid-portion of the first cylinder 3 by means of a spring arrangement (not shown). Further motion of the piston rod 9 is performed in Fig. 9e, wherein the controlled pressure acts upon the piston rod 9 via the first piston 11. Fig. 9f shows further motion the first piston 11. Fig. 9g shows complementary motion by means of providing pressure to the second cylinder 5. Fig. 9h shows that yet further motion is achieved by means of the first cylinder 3. Figs. 9i and 9j shows return of the piston rod 9 by activating the first cylinder 3 second chamber 17 and fine adjustment by activating the first chamber 15 of the first cylinder 3 to an accurate position of the piston rod 9. A major force F is generated upon the piston rod 9 as shown in Fig. 9k by pressurizing the second chambers 17 of the respective first 3 and the second 5 cylinder. Fig. 10a schematically illustrates a further aspect of the present invention. The arrangement 1 comprises a first and a second cylinder. The first cylinder is shorter than the second cylinder.

Fig. 10b schematically illustrates a further aspect of the present invention. The arrangement 1 comprises a plurality of cylinders arranged in tandem and with a distance therebetween. Figs. 1 1a to 1 1f schematically illustrate yet further aspects of the present invention. Fig. 11 a shows an arrangement 1 comprising two cylinders 3, 5 with a respective piston 1 1 , 13. By pressurizing both first chambers 15, the pressure makes the cylinder arrangement 7 to move providing a major force F. For providing less force and higher motion rate of the cylinder arrangement 7, only one cylinder is pressurized. The respective piston being symmetrically positioned in the respective cylinder by means of an electro-magnetic device E. Fig. 1 1 b illustrates an aspect wherein four cylinders 3', 3", 3"', 3"" are used for propelling a piston rod arrangement 9 comprising four piston rods 9' and a four-armed-wheel 10. In Fig. 11 b only two cylinders 3', 3"' are pressurized. Fig. 1 1c shows a further aspect wherein the

arrangement 1 is provided for telescope functionality. Fig 1 1d shows an arrangement 1 comprising an integrated logic valves unit VU. The valve unit VU transforms an electrical signal to an analogous hydraulic quantity. In the figure is shown that fluid F is fed into a first cylinder 3' via a port 91 and at the same time into a second cylinder 3" via a port 92. Return fluid is fed from the first cylinder 3' via port 93 and from the second cylinder 3" via port 94. For changing direction of motion a control valve (not shown) is operated to change fluid to be fed into ports 93 and 94. The integrated logic valves unit VU is for changing direction not operated. For changing a force/motion rate of the arrangement 1 , the integrated logic valves unit VU is operated to change so that port 92 is opened for feeding fluid to the second cylinder 3" at the same time as port 91 not being fed with fluid and the piston of the first cylinder 3' is disengaged.

Fig. 1 1e shows an embodiment wherein the force area of the arrangement 1 can be changed in an optimal way. For reaching fast piston motion and minor force, a first force area A1 (e.g. 1 area unit) is activated by alternating engagement of the first 18' and second actuator 18" to the piston rod 9. For achievement of slow piston motion with major force, all activators 18', 18", 18"', 18"" are activated. This major force can be achieved by activating all four force areas A1 , A2, A3 and A4. This means that eight area units are used, i.e. the force areas of the first, second, third, fourth actuators 18', 18", 18"', 18"" are all used together. This implies an optimal combination of eight different force area units, which can be selected from required piston motion rate and force of the piston device. Fig. 1 1f shows an aspect wherein four cylinder arrangements 7', 7", 7"', 7"" of a fluid actuator arrangement 1 share one common fluid pump 19. If the first arrangement 7' must provide high force and the second must provide high velocity, this is possible by the arrangement using the common fluid pump 9 by changing force area of the respective arrangement 7' and 7". Fig. 12a schematically shows a supersonic fighter aircraft 70, which comprises the arrangement 1 according to one aspect. A canard 71 of the fighter aircraft 70 is adapted for one aspect of the arrangement 1 providing the left and right canard 71 with fast motion rate and low force in low aircraft velocity and low motion rate and high force in supersonic speed. Fig. 12b schematically illustrates a forestry machine 72 comprising a lift arm which is adapted with the arrangement 1 according to one aspect of the invention. Fig. 12c schematically shows a portion of a container terminal 73 comprising a container crane adapted to further arrangements 1 according to further aspects, offering shorter time for container ships in harbour. Fig. 12d schematically shows a commercial aircraft 74 designed for long distance flights. The landing gear retraction system 75 of the aircraft 74 is adapted for a hydraulic actuator arrangement 1 according to one aspect of the present invention. By using the arrangement, the weight of the aircraft 74 can be saved whereby improved performance is achieved, especially fuel consumption of the aircraft 74 is reduced which can be a part of "Green aviation" concept, aiming at the reduction of the operational

environmental footprint of the aircraft 74. Fig. 12e schematically shows a mobile crane 76 adapted with an arrangement 1 according to yet a further aspect of the present invention. Fig. 12f schematically shows an offshore platform 77 including jacking systems used to raise and lower oil well drilling. The jacking system comprises an arrangement 1 according to one aspect. Fig. 12g schematically illustrates a forklift 78 comprising an arrangement 1 according to a further aspect. By using more compact arrangement 1 , a driver will have better view which increases certainty and reduces risks. Fig. 12h schematically illustrates a bascule bridge 79 adapted with the arrangement 1 according to a further aspect. The bridge counterweight chamber 80 is adapted for encompassing the piston rod arrangement of the hydraulic actuators and thus protected from outdoor environment. Fig. 12i schematically shows a further aspect used in a 3D-printing apparatus 81 for printing of entire buildings. Fig. 12j schematically shows an automated storage and retrieval system 82 for car parking DP3, which system comprises an arrangement 1 according to a further aspect. Fig. 12k schematically shows a mobile scissor lift 83 comprising a hydraulic actuator arrangement 1 according to a further aspect. The arrangement according to different aspects can thus be adapted to one or several of following industrial segments; construction industry, jacking systems for oil well drilling and service platforms, agricultural equipment industry, marine industry, crane manufacture industry. The arrangement is not limited to be used in such segments, but also other industrial segments are possible. The present invention is of course not in any way restricted to the preferred embodiments described above, but many possibilities to modifications, or combinations of the described embodiments, 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. One aspect involves that the arrangement can be adapted for momentary disengaging all pistons from the piston rod in case the piston rod propels a large mass using the kinetic energy of the mass (in a way reminding of a freewheel clutch). The valve member means may comprise a logic valve of suitable type. The valve member may comprise a 5 ports/2 valve positions, so called 5/2 valve or others. The valve member may comprise a two-way valve of any type suitable for the arrangement. The manoeuvring of the valve member may be performed by means of a solenoid connected to a control unit adapted for controlling the valve member and thereby the arrangement. The arrangement may be adapted for fast and high clamp force engagement of the piston device for propelling the latter accurate also for acceleration of heavy loads. By manoeuvring the valve member, such as a logical valve, the same arrangement can perform also lower force and slow motion rate of the piston rod

arrangement. A logical valve can be manoeuvred by the control unit to shut down the fluid flow to excluded cylinder/cylinders and only direct fluid flow to only one cylinder. There are different types of valves that can be used for providing the above-mentioned aspects and other aspects. Electro-hydraulic controlled valves, other types of directly controlled electro- hydraulic logical valves, etc. The arrangement can be used in civil and military, manned and unmanned aircraft: Leading/Trailing Edge Flap Actuators; Landing Gear Actuators; Air Brakes; Primary Servo Actuators (PSA); Electro-Hydrical Actuator (EHA) applications etc.