Technical field

The present invention relates to dock levellers. It specifically relates to a dock leveller comprising a platform, at least one lift cylinder connected to the platform and arranged to move/rotate the platform, an electrically controllable valve and a safety arrangement.

Backpround of the invention

At a loading dock, one problem to overcome is the problem of bridging the gap between a truck and the dock or warehouse floor. Not all trucks are the same height, and the height of the trailer floor within a truck can vary according to how heavily the truck is loaded. Thus, there is not only a gap to bridge but also a height difference to overcome. Various devices are employed in order to achieve this: dock plates, dock levellers, dock boards, and various forms of lift. Dock levellers are stronger than dock plates and have similar ranges to dock boards, making them suitable not only for motorized forklift trucks but also for master conveyors. Safety requirements is very high for products like dock levellers. There are some standards specifying safety rules for dock levellers. One example of such a standard is EN1398 (European Standard). This standard specifies that unsupported power operated dock levellers shall be secured automatically against uncontrolled and dangerous lowering when carrying more than 25 % of the rated load.

One safety device used to secure against uncontrolled and dangerous lowering is a hose break valve. The hose break valve is a low cost, simple

mechanical device, which avoids undesirable movements of an actuator or a hydraulic/lift cylinder due to a hose rapture or breakage. However, there are some disadvantages associated with the use of hose break valves for securing against uncontrolled and dangerous lowering, such as that annual field-testing is not feasible, since the safety valve is a one-time use device, which needs to be replaced after use. Other disadvantages are that temperature fluctuation influences the viscosity of the oil which directly affects the reliability of the valve, that a complete actuator or cylinder must be changed if a valve is broken, that there may be different kind of valves in different cylinders, which may affect symmetry etcetera, that the valves are easy to remove and may therefore not be present when needed, that the valves may be blocked due to oil contamination and that the valves need to be replaced after activation/use.

Summary of the invention

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies/disadvantages in the prior art and/or other

deficiencies/disadvantages singly or in any combination.

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which can be tested at any time with non-destructive testing.

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which is less prone to temperature changes and/or is operational under all circumstances or at any temperature.

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which is fail safe and/or which ensures that the dock stops in case of power failure and/or wire damage.

An object of the present disclosure is to provide a safety arrangement for a dock leveller, which may be retrofitted to existing dock levellers.

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which may give visual and/or auditory warnings.

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which is easier to test and/or reuse after activation of the safety arrangement.

An object of the present disclosure is to provide a dock leveller having a safety arrangement, which is more reliable and have higher precision.

An object of the present disclosure is to provide a dock leveller, which is safe under more or all circumstances. An object of the present disclosure is to provide a dock leveller, which is more or completely independent from oil viscosity, valve adjustments, oil quality and/or contaminations.

An object of the present disclosure is to provide a dock leveller, which has a safety arrangement that is more complicated to disengage.

An object of the present disclosure is to provide a dock leveller, having a safety arrangement, which is easier and/or faster to restore after an incident.

An object of the present disclosure is to provide or retrofit a dock leveller with a new safety arrangement, without replacement of other parts of the dock leveller, such as the hydraulic cylinder.

An object of the present disclosure is to provide a dock leveller, having a safety arrangement, which is easier and/or more convenient to test.

According to a first aspect, this is achieved by a dock leveller comprising a platform; at least one lift cylinder connected to the platform and configured to move/rotate the platform; an electrically controllable valve; and a safety arrangement, the safety arrangement comprising: a sensor, the sensor being configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform, angular platform velocity, angular platform acceleration and travel length of the front edge of the platform; and a control unit, the control unit being operatively connected to the sensor and the valve; and wherein the control unit is configured to provide a control signal to control the valve to stop or reduce a movement of the platform upon receiving a sensor signal, from the sensor, the sensor signal being indicative of a higher value than a threshold value.

In some embodiments, the electrically controllable valve is a normally closed, NC, magnetic valve, and the control signal is a power off signal for closing the valve and the electrically controllable valve is configured to stop or reduce a movement of the platform when closed.

In some embodiments, the sensor is a motion sensor, such as a gyroscope and/or an accelerometer. In some embodiments, the control unit is operatively connected via wire and/or wirelessly to the sensor and the control unit is operatively connected via wire and/or wirelessly to the valve.

In some embodiments, the sensor is mounted at a front edge of the platform.

In some embodiments, the control unit is configured to log information related to movements of the platform, such as fall speed, fall angle, fall time, and/or travel length of the front edge of the platform.

In some embodiments, the control unit is configured to provide the control signal to control the valve upon receiving a sensor signal, from the sensor, the sensor signal being indicative of a platform fall speed value higher than a first threshold value and/or a value of an angle of rotation of the platform higher than a second threshold value.

In some embodiments, the first and/or the second threshold value is preset. According to a second aspect, one or more of the objects is achieved by a safety arrangement for a dock leveller, the dock leveller comprising a platform, at least one lift cylinder connected to the platform and arranged to move/rotate the platform and comprising an electrically controllable valve; the safety arrangement comprising: a sensor, such as a gyroscope and/or an accelerometer, the sensor being configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform, angular platform velocity, angular platform acceleration and travel length of the front edge of the platform; a control unit, the control unit being operatively connected to the sensor and the valve; and wherein the control unit is configured to provide a control signal to control the valve to stop or reduce a movement of the platform upon receiving a sensor signal, from the sensor, the sensor signal being indicative of a higher value than a threshold value.

According to a third aspect, one or more of the objects is achieved by a control unit for a dock leveller, the dock leveller comprising a platform; a sensor, mounted at the platform, the sensor being configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform, angular platform velocity, angular platform acceleration and travel length of the front edge of the platform; and at least one lift cylinder comprising an electrically controllable valve, the control unit being operatively connectable to the valve and to the sensor and configured to provide a control signal to control the valve upon receiving a sensor signal from the sensor, the sensor signal indicating a higher value than a first threshold value. In some embodiments, the control unit is configured to provide the control signal to control the valve upon receiving the sensor signal, from the sensor, the sensor signal being indicative of a platform fall speed value higher than a first threshold value and/or a value of an angle of rotation of the platform higher than a second threshold value.

In some embodiments, the electrically controllable valve is a normally closed, NC, magnetic valve, and the control signal is a power off signal for closing the valve and the electrically controllable valve is configured to stop or reduce a movement of the platform when closed.

In some embodiments, the control unit is operatively connected via wire and/or wirelessly to the sensor and the control unit is operatively connected via wire and/or wirelessly to the valve.

In some embodiments, the control unit is further configured to log information related to movements of the platform, such as fall speed, fall angle, fall time, and/or travel length of the front edge of the platform.

According to a fourth aspect, one or more of the objects is achieved by a method of controlling a dock leveller, the dock leveller comprising a platform, a sensor, such as a motion sensor, such as gyroscope and/or an accelerometer, mounted at the platform, preferably at the front edge of the platform, and at least one lift cylinder comprising an electrically controllable valve, preferably a normally closed, NC, magnetic valve, the method comprising: receiving a sensor signal from the sensor; determining whether the sensor signal indicates a value higher than a threshold value; if the sensor signal indicates a value higher than a threshold value, providing a control signal for controlling the valve; if the sensor signal does not indicate a value higher than a threshold value, providing no control signal for controlling the valve; and repeating the steps until a finishing criteria is met.

According to a fifth aspect, one or more of the objects is achieved by a computer program product comprising a non-transitory computer readable medium, having thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to the fourth aspect when the computer program is run by the data processing unit.

According to a sixth aspect, one or more of the objects is achieved by a method for servicing a dock leveller with a service tool, the method comprising: operating the dock leveller with regular controls to lower the platform; pressing a button or touching a specific area of a touchscreen of the service tool to simulate an increase of a platform fall speed to above a first threshold value; reading logged information; comparing a value of the logged information with a third threshold value; and deciding if a sensor function and/or a valve function needs repair or replacement, based on the comparing.

According to a seventh aspect, one or more of the objects is achieved by an apparatus for control of an dock leveller, the dock leveller comprising a platform, a sensor, such as a motion sensor, such as gyroscope and/or an accelerometer, mounted at the platform, preferably at the front edge of the platform, and at least one lift cylinder comprising an electrically controllable valve, preferably a normally closed, NC, magnetic valve, the apparatus comprising controlling circuitry configured to cause: reception of a sensor signal from the sensor; determination of whether the sensor signal indicates a value higher than a threshold value; if the sensor signal indicates a value higher than a threshold value, provision of a control signal for controlling the valve; if the sensor signal does not indicate a value higher than a threshold value, no provision of a control signal for controlling the valve; and repetition of the steps until a finishing criteria is met.

In some embodiments, any of the above aspects may additionally have features identical with or corresponding to any of the various features as explained above for any of the other aspects or embodiments.

Brief description of the drawinps

The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments and aspects.

Figure 1 A is a schematic side view drawing of a dock leveller, according to an aspect of the invention, with a truck arranged in the vicinity of the dock leveller and the dock leveller being attached to a dock or a warehouse floor. Figure 1 B is a schematic side view drawing of a dock leveller, according to another aspect of the invention, with a truck arranged in the vicinity of the dock leveller and the dock leveller being attached to a dock or a warehouse floor.

Figure 2A is a schematic drawing of some different units of the safety arrangement and the dock leveller and connections there-between according to an aspect of the invention.

Figure 2B is a schematic drawing of some different units of the safety arrangement and the dock leveller and connections there-between according to another aspect of the invention.

Figure 3 is a flowchart illustrating example method steps according to an aspect of the invention.

Figure 4 is a schematic drawing illustrating an example computer readable medium.

Figure 5 is a flowchart illustrating example method steps of a method for servicing a dock leveller.

Figure 6 is a schematic top view drawing of a service tool.

Figure 7 is a flowchart illustrating example method steps implemented in an apparatus according to an aspect of the invention.

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying figures. The assembly disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein.

The terminology used herein is for the purpose of describing particular aspects of the disclosure only, and is not intended to limit the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Embodiments of the present disclosure will be described and exemplified more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the embodiments set forth herein.

Below, reference is made to angle of rotation of a platform, angular platform velocity, angular platform acceleration and travel length of a front edge of a platform. Such measured variables may comprise a value and a direction.

Below, reference is made to thresholds or threshold values. Any of the thresholds or threshold values may be preset.

The term“sensor” used below is intended to mean a sensor unit, which comprises one or more sensors.

The term“configured” used below is interchangeable with adapted, and may below mean set up, arranged, placed, located, shaped, formed etcetera.

The present invention relates to a dock leveller. Figure 1 A is a schematic side view drawing of a dock leveller 200. The dock leveller 200 is attached to a dock 294. The dock 294 is a loading dock or a floor of a warehouse. Furthermore, the dock leveller is arranged in a location, such that trucks and other vehicles have easy access to the dock leveller 200. In an embodiment, the dock leveller 200 is provided with a lip 296. The lip 296 is attached to the dock leveller 200 at a front edge 212 of the dock leveller 200. The front edge 212 of the dock leveller 200 is the edge of the dock leveller 200, which is parallel to the dock 294 and furthest away from the dock 294. The lip 296 comprises a simple metal plate, which is raisable from a stowed position and then lowerable onto the back/floor 298 of a truck 290 or onto a trailer floor. The lip 296 is hinged or of a telescopic type. The lip 296 is operated either manually, via a simple pull chain, or hydraulically with an electric pump driving a piston to lift the plate and another electric pump to move the lip. The dock leveller 200 comprises a platform 210 and at least one lift cylinder 220. The dock leveller 200 comprises two lift cylinders. Alternatively, the dock leveller 200 comprises four lift cylinders. Each of the one or more lift cylinders 220 are connected to the platform. Furthermore, each of the one or more lift cylinders 220 are configured to move and/or rotate the platform. Moreover, dock leveller 200 comprises an electrically controllable valve 230. The electrically controllable valve 230 is integrated in a fluid/hydraulic line of an actuation arrangement comprising a lift cylinder 220, such as a hydraulic cylinder, a pump and a tank. If the dock leveller 200 is provided with more than one lift cylinder 220, each of the lift cylinders is provided with an electrically controllable valve 230. Thus, each of the lift cylinders 220 are in connection with an electronically controlled valve 230. In case that the electrically controllable valve 230 is activated or powered up, the electrically controllable valve 230 is opened and the fluid of the actuation arrangement can flow into and out of the cylinder 220. In case the electrically controllable valve 230 is deactivated or powered off, the electrically controllable valve 230 is closed to prevent, block or stop any fluid flow. Thus, when an electrically controllable valve 230 is deactivated, the lift cylinder 220 connected thereto is prevented from moving. Preferably, the electrically controllable valve 230 is a magnetic valve. In an embodiment, the electrically controllable valve 230 is a normally closed, NC, magnetic valve. In this case, a power off signal is used as a control signal 124 (shown in figure 2A) for closing the electrically controllable valve 230. Furthermore, the electrically controllable valve 230 is configured to stop or reduce a movement of the platform 210 when a control signal 124, such as a power off signal, is received. When the control signal 124 is received at the valve 230, the valve 230 is closed. By closing the valve 230, the fluid of the actuation arrangement is prevented from flowing into and out of the cylinder 220. When, the fluid of the actuation arrangement is prevented from flowing into and out of the cylinder 220, the movement of the platform 210 is reduced or stopped. Alternatively, other control signals 124, such as a power on signal, is used for closing the valve 230. An example of a valve 230 used with a power on signal is a normally open valve.

Alternatively, the valve is a shutdown valve. In an embodiment, the valve 230 is not electrically controllable, instead the valve 230 is hydraulically or pneumatically controlled. In an embodiment, more than one electrically controllable valve 230 is present for stopping or reducing a movement of the platform 210. Furthermore, the dock leveller 200 comprises a safety arrangement 100. The safety arrangement 100 comprises a sensor 1 10. The sensor 1 10 is configured to sense at least one of:

platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration and travel length of a front edge 212 of the platform 210. The safety arrangement 100 comprises a control unit 120. The control unit 120 is operatively connectable or connected to the sensor 1 10 and/or the valve 230. The control unit 120 is configured to provide a control signal 124 (shown in figure 2) to control the valve 230 to stop or reduce a movement of the platform 210. Such a control signal 124 is provided when the control unit 120 receives a sensor signal 1 14 (shown in figure 2A), from the sensor 1 10, which sensor signal 1 14 is indicative of a higher value than a threshold value. When the sensor signal 1 14 is indicative of a lower value than or the same value as a threshold value, a zero Volt signal is provided instead. Alternatively, a non-zero Volt control signal is provided when the sensor signal 1 14 is indicative of a lower value than or the same value as a threshold value, whereas a 0 Volt signal is provided when the sensor signal 1 14 is indicative of a higher value than a threshold value. The threshold value is set empirically so that a travel length of the front edge 212 of the platform 210 does not exceed 6 percent of the length of the platform, as specified in the European Standard EN1398. The length of the platform or bridge may be 2 m. Alternatively, the threshold value is set empirically so that an angle of rotation of the platform 210 does not exceed a certain angle value. This certain angle value is an angle value

corresponding to the limit set in the European Standard EN1398, i.e. 3,438 degrees. As another alternative, the threshold value is set to be a platform fall speed of 0.120 m/s. Thus, when the sensor 1 10 detects an increase of platform fall speed greater than 0.120 m/s, the platform 210 stops since the control unit 120 provides a control signal 124 to control the valve 230 to stop the movement of the platform 210 or the speed of the platform 210 is reduced to below 0.05 m/s, as specified in the European Standard EN1398, since the control unit 120 provides a control signal 124 to control the valve 230 to partly close and thereby reduce the movement of the platform 210 to below 0.05 m/s. The valve 230 is controlled to stop by cutting of the power.

Whenever the control unit 120 provides a control signal 124 to control the valve 230 to stop the movement of the platform 210, a visual or audible warning is provided during the stopping of the movement of the platform 210.

In an embodiment, a safety arrangement 100 for a dock leveller 200 is provided. Such a safety arrangement 100 may be advantageous for retrofitting, i.e. when older safety arrangements for dock levellers needs to be replaced due to e.g. new requirements or aging. The dock leveller 200 comprises a platform 210. The dock leveller 200 comprises at least one lift cylinder 220 connected to the platform and arranged to move/rotate the platform. The dock leveller 200 also comprises an electrically controllable valve 230. Alternatively, the electrically controllable valve 230 is part of the safety arrangement 100. The safety arrangement 100 comprises a sensor 1 10. The sensor 1 10 is a gyroscope, an accelerometer or a gyroscope with an accelerometer. The sensor 1 10 is configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration and travel length of the front edge 212 of the platform 210. The platform fall speed is the vertical speed of the platform 201 as the platform is falling. The platform fall time is the time from when the platform movement started or the time from when the platform movement exceeded a certain value, such as 0.05 m/s or 0.12 m/s. The angle of rotation of the platform 210 is the angle of the platform 210 compared to a level parallel to the dock 294 or the difference in angle of the platform 210 from an angle of the platform 210 when the platform movement started or from an angle of the platform 210 when the platform movement exceeded a certain value, such as 0.05 m/s or 0.12 m/s. The angular platform velocity is the angular velocity of the platform. The angular platform acceleration is the angular acceleration of the platform. The travel length of the front edge 212 of the platform 210 is the vertical distance travelled by the front edge 212 of the platform 210 from a position of the front edge 212 of the platform 210 when the platform movement started. Furthermore, the safety arrangement 100 comprises a control unit 120. The control unit 120 is operatively connected to the sensor 1 10. Moreover, the control unit 120 is operatively connected to the valve 230. The control unit 120 is configured to provide a control signal 124 (shown in figure 2A) to control the valve 230 to stop or reduce a movement of the platform 210 upon receiving a sensor signal 1 14, from the sensor 1 10, which sensor signal 1 14 is indicative of a higher value than a threshold value. The use of the control signal 124 and/or the setting of the threshold value is as explained above for the safety arrangement 100 comprised by the dock leveller 200.

In an embodiment, a control unit 120 for a dock leveller 200 is provided. This is illustrated in figure 1 B, which is a schematic side view drawing of a dock leveller 200 attached to a dock 294 or a warehouse floor. The dock leveller 200 comprises a platform 210 and a sensor 240. The sensor is mounted at the platform 210, preferably at a front edge 212 of the platform 210. The sensor 1 10 is configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration and travel length of the front edge 212 of the platform 210. The dock leveller 200 comprises at least one lift cylinder 220 and an electrically controllable valve 230 associated with the lift cylinder. The control unit 120 is operatively connectable or connected to the valve 230 and to the sensor 240. The control unit 120 is configured to provide a control signal 124 (shown in figure 2B) to control the valve 230 upon receiving a sensor signal 244 (shown in figure 2B) from the sensor 240, the sensor signal 244 indicating a higher value than a first threshold value. The use of the control signal 124 and/or the setting of the threshold value is as explained above for the safety arrangement 100 comprised by the dock leveller 200.

Figure 2A is a schematic drawing of an example of connections between different units of the safety arrangement 100 and of the dock leveller 200. The sensor 1 10 is configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration and travel length of the front edge 212 of the platform 210. In an embodiment, the sensor is configured to sense angular platform position or angle of rotation of the platform 210. Additionally or alternatively, the sensor 1 10 is configured to sense angular platform velocity. Additionally or alternatively, the sensor 1 10 is configured to sense angular platform acceleration. In one example, the sensor 1 10 is a combined gyroscope and accelerometer. Such a sensor may simultaneously measure angular platform position, angular platform velocity and angular platform acceleration. The sensor 1 10 provides a control unit 120 with a signal 1 14. In an embodiment, the signal 1 14 is more than one signal, such as three different signals. The one or more signals 1 14 provides one or more values of the measured/sensed variables. The control unit 120 is operatively connected to the sensor 1 10 via wire. Alternatively or additionally, the control unit 120 is operatively connected to the sensor 1 10 wirelessly. The control unit 120 receives the one or more values from the one or more signals 1 14. Upon reception of the values, the control unit 120 compares the one or more received signal values with thresholds. In one example, a value indicative of platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration or travel length of the front edge 212 of the platform 210 is compared to a threshold. In another example, a value indicative of a platform fall speed value is compared with a first threshold value and a value indicative of an angle of rotation of the platform is compared with a second threshold value. In yet another example, each of measured angular platform position, measured angular platform velocity and measured angular platform acceleration is compared with a threshold. When one or more of the measured values of position, velocity and acceleration exceeds the associated threshold, the control unit 120 will transmit a control signal 124 to close the electrically controllable valve 230. This control signal is a zero Volt signal as opposed to the signal, which is feed to the electrically controllable valve 230 when no threshold value has been exceeded. Alternatively, the control signal is a non-zero Volt signal, whereas the signal feed to the electrically controllable valve 230 when no threshold value has been exceeded is a zero Volt signal. By comparing a plurality of signals from the sensor with thresholds associated with the different signals, a more reliable safety arrangement with higher precision may be achieved.

In an embodiment, the electrically controllable valve 230 is a normally closed, NC, magnetic valve. The control signal 124 is a power off signal for closing the valve 230. Such a power off signal is feed to a power-controlling unit 232 of the electrically controllable valve 230. The power off signal will shut off the power 236 to the electrically controllable valve 230. Alternatively the power 236 to the electrically controllable valve 230 is govern directly from the control unit 120, in which case the power 236 is delivered to the electrically controllable valve 230 prior to the control unit 120 receiving a sensor signal 1 14 indicative of a value higher than a threshold value and no power 236 is delivered to the electrically controllable valve 230 after the control unit 120 receives a sensor signal 1 14 indicative of a value higher than a threshold value. When the power 236 has been shut off, the electrically controllable valve 230 will close. When the electrically controllable valve 230 is closed, a movement of the platform 210 will stop, since the at least one cylinder 220 is prevented to move due to the fact that the fluid of the actuation arrangement cannot flow into and out of the cylinder 220 when the electrically controllable valve 230 is shut/closed. The control unit 120 is operatively connected to the valve 230 via wire. Alternatively or additionally, the control unit 120 is operatively connected to the valve 230 wirelessly.

Figure 2B is a schematic drawing of an example of connections between a control unit 120 and units associated with the dock leveller 200. The sensor 240 is configured to sense at least one of: platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration and travel length of the front edge 212 of the platform 210. In an embodiment, the sensor is configured to sense angular platform position or angle of rotation of the platform 210. Additionally or alternatively, the sensor is configured to sense angular platform velocity. Additionally or alternatively, the sensor is configured to sense angular platform acceleration. In one example, the sensor 240 is a combined gyroscope and accelerometer. Such a sensor is capable of simultaneously measuring angular platform position, angular platform velocity and angular platform acceleration. The sensor 240 provides a control unit 120 with a signal 244. In an embodiment, the signal is more than one signal, such as three different signals. The one or more signals 244 provides one value of each of the measured/sensed variables. The control unit 120 receives the one or more values from the one or more signals 244. The control unit 120 is operatively connected to the sensor 240 via wire. Alternatively or additionally, the control unit 120 is operatively connected to the sensor 240 wirelessly. Upon reception of the values, the control unit 120 compares the one or more received signal values with thresholds. In one example, a value indicative of platform fall speed, platform fall time, angle of rotation of the platform 210, angular platform velocity, angular platform acceleration or travel length of the front edge 212 of the platform 210 is compared to a threshold. In another example, a value indicative of a platform fall speed value is compared with a first threshold value and a value indicative of an angle of rotation of the platform is compared with a second threshold value. In yet another example, measured angular platform position, angular platform velocity and angular platform acceleration may each be compared with a threshold. When one or more of the measured values of position, velocity and acceleration exceeds the associated threshold, the control unit 120 will transmit a control signal 124 to close the electrically controllable valve 230. This control signal is a zero Volt signal as opposed to the signal, which is feed to the electrically controllable valve 230 when no threshold value has been exceeded. Alternatively, the control signal is a non-zero Volt signal, whereas the signal feed to the electrically controllable valve 230 when no threshold value has been exceeded is a zero Volt signal. By comparing a plurality of signals from the sensor with thresholds associated with the different signals, a more reliable safety arrangement with higher precision may be achieved.

The electrically controllable valve 230 is in an embodiment a normally closed, NC, magnetic valve. The control signal 124 is a power off signal for closing the valve 230. Such a power off signal is feed to a power-controlling unit 232 of the electrically controllable valve 230. The power off signal will shut off the power 236 to the electrically controllable valve 230. When the power 236 has been shut off, the electrically controllable valve 230 will close. When the electrically controllable valve 230 is closed, a movement of the platform 210 will stop, since the at least one cylinder 220 is prevented to move due to the fact that the fluid of the actuation arrangement cannot flow into and out of the cylinder 220 when the electrically controllable valve 230 is shut/closed. Alternatively or additionally, the control unit 120 is operatively connected to the valve 230 wirelessly.

Figure 3 is a flowchart illustrating example method steps of a method of controlling a dock leveller 200. The method 300 comprises receiving 310 a sensor signal 1 14, 244 from the sensor 1 10, 240. Such receiving 310 is performed by a reception unit. Furthermore, the method 300 comprises determining 320 whether the sensor signal 1 14, 244 indicates a value higher than a threshold value. Such determining 320 is performed by a determination unit. If the sensor signal 1 14, 244 indicates a value higher than a threshold value, i.e. if it is determined during determining 320 that the sensor signal 1 14, 244 indicates a value higher than a threshold value, a control signal 1 14 for controlling the valve 230 is provided 330. Such providing 330 is performed by a provision unit. If the sensor signal 1 14, 244 does not indicate a value higher than a threshold value, i.e. if it is determined during determining 320 that the sensor signal 1 14, 244 does not indicate a value higher than a threshold value, no control signal or a zero control signal for controlling the valve 230 is provided 340. The method 300 comprises repeating 350 the steps until a finishing criteria is met. Such repeating 350 is performed by a repetition unit. A finishing criterion is that an operator has turned the system off. As an alternative to the repeating step 350, the method steps are repeated endlessly until the system is no longer in use.

Figure 4 is a schematic drawing illustrating an example computer readable medium in the form of a compact disc (CD) ROM 400. The computer readable medium may instead of a CD be a USB stick or any other suitable memory. The computer readable medium has stored thereon a computer program comprising program instructions. The computer program is loadable into a data processor (PROC) 420, which may, for example, be comprised in a mobile device 410, such as a laptop computer, a tablet computer, a smart phone or a service tool 600 (shown in figure 6). When loaded into the data processing unit, the computer program is stored in a memory (MEM) 430 associated with or comprised in the data-processing unit. According to some embodiments, the computer program may, when loaded into and run by the data processing unit, cause execution of method steps according to, for example, any of the methods illustrated in Figures 3 or 5 or otherwise described herein. Figure 5 is a flowchart illustrating example method steps of a method for servicing a dock leveller 200. The method 500 for servicing a dock leveller 200 with a service tool 600 (shown in figure 6) comprises operating 510 the dock leveller 200 with regular controls for adjusting the height of the platform 210 to lower the platform 210. Furthermore, the method 500 comprises pressing 520 a button 602 (shown in figure 6) or touching 520 a specific area 604 (shown in figure 6) of a touchscreen 606 (shown in figure 6) of the service tool 600 (shown in figure 6) to simulate an increase of a platform fall speed to above a first threshold value. The pressing or touching 520 is preferably performed during the operating 510 of the dock leveller 200 with regular controls. Moreover, the method 500 comprises reading 530 logged information, such as the platform fall speed, whether the power to the electrically controlled valve 230 was cut off, platform fall angle, platform fall time and/or travel length of the front edge 212 of the platform 210. This logged information has been logged for a period of time and at least since the platform 210 started being lowered. The method 500 comprises comparing 540 a value of the logged information with a third threshold value. The logged value is a platform fall angle and the third threshold value is 3.438 degrees. Alternatively, the logged value is platform fall speed, whether the power to the electrically controlled valve 230 was cut off, platform fall time and/or travel length of the front edge 212 of the platform 210. The third threshold may be the same as the first or the second threshold. Furthermore, the method 500 comprises deciding 550 if a sensor function, such as one or more sensors 1 10, 240, and/or a valve function, such as one or more electrically controlled valves 230, needs repair or replacement, based on the comparing 540. In an embodiment, the deciding is based on whether or not the electronically controlled valve 230 was powered off and on whether or not the logged platform fall angle exceeds a third threshold value, such as 3.438 degrees. As an example, if the electronically controlled valve 230 was powered off and the logged platform fall angle does not exceed a third threshold value, it is decided that neither the sensor function nor the valve function need repair or replacement. However, if the electronically controlled valve 230 was not powered off and the logged platform fall angle exceeds a third threshold value, it is decided that at least the valve function needs repair or replacement. With the method 500 for servicing a dock leveller 200, all electronically controlled valves 230 and all sensors 1 10, 240, such as all motion sensors or all different sensors of a sensor unit may be tested. Figure 6 is a schematic top view drawing of an example service tool. The service tool 600 comprises a display, such as a touch screen 606. The touch screen 606 comprises one or more different areas 604, which function as virtual buttons and when touched, these specific areas 604 may invoke a specific function, such as simulation of an increase of a platform fall speed to above a first threshold value. Furthermore, in an embodiment, the service tool 600 comprises one or more pressable buttons 602. Moreover, the service tool comprises one or more processors, one or more transceivers, one or memory units and/or one or more input/output units. As an example, the service tool 600 comprises a smartphone, a laptop or a tablet computer.

Furthermore, in an embodiment the service tool 600 comprises an APP and/or may connect with the control unit 120 via Wi-Fi or via a Bluetooth connection.

Figure 7 discloses a flowchart illustrating example method steps implemented in an apparatus for control of a dock leveller 200. The apparatus 700 for control of a dock leveller 200 comprises controlling circuitry. The controlling circuitry is one or more processors or the control unit 120. The controlling circuitry is configured to cause reception 710 of a sensor signal 1 14, 244 from the sensor 1 10, 240.

Furthermore, the controlling circuitry is configured to cause determination 720 of whether or not the sensor signal 1 14, 244 indicates a value higher than a threshold value. Moreover, the controlling circuitry is configured to cause provision 730 of a control signal 1 14 for controlling the valve 230, such as controlling the valve 230 to close if the sensor signal 1 14, 244 indicates a value higher than a threshold value. The controlling circuitry is configured to cause no provision 740 of a control signal 1 14 for controlling the valve 230 if the sensor signal 1 14, 244 does not indicate a value higher than a threshold value. Furthermore, the controlling circuitry is configured to cause repetition 750 of the steps either until a finishing criterion is met or until the apparatus is no longer in use.

In an embodiment, the control unit 120 is configured to log information related to movements of the platform 210, such as fall speed, fall angle, fall time, and/or travel length of the front edge 212 of the platform 210. Furthermore, the control unit 120 is configured to log information regarding whether or not (or when) the electrically controllable valve is closed. Moreover, the control unit 120 may log all incidents and all usage of the dock leveller. The logged information is saved in a memory of the control unit 120. The control unit may also comprise a transceiver for communicating with a service tool 600. Such communication is performed via Wi-Fi or via Bluetooth.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

The description of the aspects of the disclosure provided herein has been presented for purposes of illustration. The description is not intended to be exhaustive or to limit aspects of the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided aspects of the disclosure. The examples discussed herein were chosen and described in order to explain the principles and the nature of various aspects of the disclosure and its practical application to enable one skilled in the art to utilize the aspects of the disclosure in various manners and with various modifications as are suited to the particular use contemplated. The features of the aspects and the embodiments of the disclosure described herein may be combined in all possible combinations of methods, apparatuses, dock levellers, modules, safety arrangements, systems, control units and computer program products. It should be appreciated that the aspects of the disclosure presented herein may be practiced in any combination with each other.

It should be noted that the word“comprising” does not necessarily exclude the presence of other elements or steps than those listed. It should further be noted that any reference signs do not limit the scope of the claims.