WO2021112728A1

WO2021112728A1 - A self-contained electro-hydraulic linear actuator and a method for controlling the actuator

Info

Publication number: WO2021112728A1
Application number: PCT/SE2019/051234
Authority: WO
Inventors: Magnus Landberg; Gustav NÄSLUND
Original assignee: Saab AB
Current assignee: Saab AB
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2021-06-10
Anticipated expiration: 2022-06-05
Also published as: WO2021112750A1

Abstract

The present invention regards an electro-hydraulic linear actuator (1) and a method of controlling the operation of the electro-hydraulic linear actuator (1). The electro-hydraulic linear actuator (1) comprises one single cylinder housing (3) extending along a central axis (X). One single piston body (5) dividing the cylinder housing (3) in a first (7) and second (9) cylinder chamber. A rod (17) extends along the central axis (X) and through the cylinder housing (3) and through a first rod clamping device (19) of the piston body (5). The first rod clamping device (19) comprises a first expandable cavity (20) configured to deform a first flexible inner wall of the piston body (5). The electro-hydraulic linear actuator (1) is configured as a self-contained electro- hydraulic linear actuator (1) comprising a hydraulic fluid supply, which comprises a channel arrangement (31) arranged between a hydraulic pump (27) and the cylinder housing (5) and between the hydraulic pump (27) and the first expandable cavity (20), a valve arrangement (33) of the channel arrangement is configured for controlling the flow of hydraulic fluid; and an electrical power device (35). The cylinder housing (3) of the electro-hydraulic linear actuator (1) preferably is coupled to a second rod clamping device (21).

Description

A SELF-CONTAINED ELECTRO-HYDRAULIC LINEAR ACTUATOR AND A METHOD FOR CONTROLLING THE ACTUATOR

TECHNICAL FIELD

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

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

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

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

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

The present invention may relate to pallet trucks.

BACKGROUND

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

Actuator arrangements for current planter/seeder machines comprising movable planter/seeder units or current load carrying vehicles comprising movable stake bars, may be bulky, energy consuming and heavy.

Current electro-hydraulic linear actuators are complex and involve high service and maintenance costs.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Alternatively, the electro-hydraulic linear actuator is coupled to a remote hydraulic fluid reservoir.

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

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

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

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

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

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

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

Alternatively, the cylinder housing is configured to be releasable coupled to the second rod clamping device via a coupling. Alternatively, the second rod clamping device is coupled to a stake bar or planter/seeder unit.

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

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

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

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

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

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

Alternatively, the cylinder housing is configured to be rigidly coupled to the second rod clamping device, wherein the cylinder housing and the second rod clamping device are integrally arranged as an integrally parts of the self-contained electro-hydraulic linear actuator. Alternatively, the electro-hydraulic linear actuator comprises a hydraulic accumulator configured for storing pressurized fluid for pressurizing the first and/or second expandable cavity.

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

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

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

Alternatively, the valve arrangement is mounted in the intermediate channel block.

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

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

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

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

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

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

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

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

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

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

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

Alternatively, the non-return valve arrangement is arranged in a channel or line arrangement between the hydraulic pump and a directional valve device of the second pressure supply system, such as a 3/2 directional valve device, or 4/2 directional valve device, or 4/3 directional valve device or two 3/2 valves or four 2/2 valves.

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

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

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

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

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

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

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

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

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

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

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

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

Alternatively, the cylinder housing is rigidly fixed and demountable arranged to a cover housing rigidly fixed and demountable arranged also to the second clamping rod device.

Alternatively, the cover housing exhibits a circular cross section and/or quadratic cross section and/or rectangular cross section.

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

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

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

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

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

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

Alternatively, the electro-hydraulic linear actuator comprises a sensor arrangement coupled to the control circuitry of the hydraulic fluid supply. Alternatively, the sensor arrangement comprises a potentiometer and/or a linear variable differential transformer (LVDT), and/or a resolver and/or an optic sensor and/or a magnetic sensor and/or an accelerometer or other.

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

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

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

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

In such way is achieved a cost-effective handling of the electro-hydraulic linear actuator.

Alternatively, the electrical plug and play connection comprises connection for electrical supply and/or data transfer.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Alternatively, the sensor arrangement of the electro-hydraulic linear actuator is configured to obtain a second position information regarding mutual relation between the cylinder and the piston body indicating that the piston body passes or reaches a second position relative the cylinder along the piston body stroke. Alternatively, a piston body control circuitry of the control circuitry is configured to control the back and forward movement of the piston body in the cylinder housing based on the obtained first position information.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Alternatively, the method comprises the steps of disengaging the second rod clamping device and disengaging the first rod clamping device and comprises the following step of pressurizing the first cylinder chamber so that the piston abuts second cylinder cap end, wherein the rod is manually or automatically pushed or pulled to a reference starting position. Alternatively, the rod and/or cylinder housing being configured to be automatically pushed or pulled to the reference starting position by means of an automatic actuator apparatus configured to move the rod.

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

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

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

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

Alternatively, the following step comprises depressurizing the second cylinder chamber.

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

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

Alternatively, the step of pressurizing the first cylinder chamber is made synchronous with the depressurizing the second cylinder chamber. Alternatively, the following step comprises pressurizing the first cylinder chamber for balancing the piston body in a position between the first cylinder cap end and the second cylinder cap end.

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

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

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

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

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

Alternatively, the method comprises the steps of: pressurize the second cavity; pressurize the first cavity; depressurize the second cavity and subsequently pressurize the first cylinder chamber CC or pressurize the first cylinder chamber and subsequently depressurize the second cavity; depressurize the first cylinder chamber; pressurize the second cavity; depressurize the first cavity; pressurize the second cylinder chamber; depressurize the second cylinder chamber; pressurize the first cavity and repeating the method. Preferably, the electro-hydraulic linear actuator is configured to vertically lift a load.

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

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

Fpi_ston = mass x gravitation acceleration (g)

P system ⁼ maSS X g / Apiston

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

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

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

P system £X P clamp

For example, the clamping pressure P_Ciam is set to be twice the system pressure P_system.

P clamp — 2 X P system

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

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

Alternatively, the first rod clamp and piston body being entirely encompassed by the cylinder housing. Alternatively, the second rod clamp is shorter (seen in the axial direction X) than the first rod clamp.

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

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

The wording “electro-hydraulic linear actuator" may be replaced by the wording “compact self-contained electro-hydraulic linear actuator “ or “compact self-contained electro-hydraulic intermittent operation linear actuator”. The definition of “an intermittent operation linear actuator” is an actuator that intermittently moves the piston or cylinder for each working stroke.

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

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

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

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

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

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

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

Fig. 4 illustrates an actuator arrangement comprising two co-working electro-hydraulic linear actuators according to a fifth example;

Figs. 5a and 5b illustrate an electro-hydraulic linear actuator according to a sixth example; Fig. 6a illustrates the relative motion between a piston body and a cylinder housing of an electro-hydraulic linear actuator according to a seventh example;

Fig. 6b illustrates a closed loop system of an electro-hydraulic linear actuator according to an eight example;

Fig. 6c illustrates an electronic network device coupled to an electro-hydraulic linear actuator according to a ninth example;

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

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

Figs. 8a to 8c illustrate the operation of a valve arrangement of an electro-hydraulic linear actuator according to an eleventh example;

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

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

DETAILED DESCRIPTION

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

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

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

A rod 17 extends along the central axis X through a first rod clamp 19 of the piston body and through a second rod clamp 21. The first rod clamp 19 comprises a first expandable cavity (not shown) configured to deform a first flexible inner wall (not shown) of the one single piston body 5.

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

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

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

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

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

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

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

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

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

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator. A hydraulic fluid supply 23 configured to pressurize the first and second rod clamp for clamping action.

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

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

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

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

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

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

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

The hydraulic fluid supply 23 further comprises a hydraulic accumulator (not shown) configured for storing pressurized fluid for use in pressurizing the first and second rod clamp A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid.

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

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

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

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

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

Alternatively, a second rod clamp 21 comprises a second expandable cavity 22 configured to deform a second flexible wall 2FW of the second rod clamp 21.

Alternatively, the first flexible wall 1 FW is positioned between the rod 17 envelope surface and the first expandable cavity 20.

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

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

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

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

Alternatively, the second expandable cavity 22 extends coaxially around the rod 17 and extends in a direction along the axial direction X. Alternatively, the extension of the first expandable cavity 20 is longer than the extension of the second expandable cavity 22 seen in a direction along the central axis.

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

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

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

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

A valve arrangement 33 of the channel arrangement 31 is configured for controlling the flow of hydraulic fluid generated by the hydraulic pump 26.

An electrical power pack 35 is electrically coupled to the electric motor 27 and configured to be connected to an electrical network 36.

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

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

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

The electro-hydraulic linear actuator 1 comprises a first sensor arrangement 90 configured to sense the position of the piston 5 relative the cylinder housing 3. The first sensor arrangement 90 is coupled to a control circuitry 100. The control circuitry 100 is coupled (by wire and/or wireless) to the valve arrangement 33 and to the first sensor arrangement 90 and the electrical network 36 via a plug and play connection.

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

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

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

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

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

Fig. 4 illustrates an actuator arrangement comprising two co-working electro-hydraulic linear actuators according to a fifth example.

A first electro-hydraulic linear actuator is configured to move along a first guide. A second electro-hydraulic linear actuator is configured to move along a second guide. The electro- hydraulic linear actuators are configured to propel a respective cross-bar 50 along the first and second guides.

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

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

A respective sensor unit 73 configured to detect the position of each position sensor marker 71 is mounted on both electro-hydraulic linear actuator. A distance a between two adjacent position marker is shorter than a distance b corresponding to the working stroke length of the respective piston 5 of the electro- hydraulic linear actuator 1 in the respective cylinder housing 3.

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

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

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

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

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

Figs. 5a and 5b illustrate an electro-hydraulic linear actuator 1 according to a sixth example. The electro-hydraulic linear actuator 1 comprises a hydraulic accumulator 30. The electro- hydraulic linear actuator 1 comprises a sensor arrangement 90 coupled to a control circuitry 100 of the hydraulic fluid supply 23.

An electrical power device 35 of the electro-hydraulic linear actuator 1 may comprise an electrical battery power pack 35PP.

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

The selection valve arrangement 36 and the directional valve 38 each being configured to be controlled by a control circuitry 100 of a computer. Alternatively, the control circuitry 100 of a computer may be associated with a mobile smart phone (not shown) or tablet having dedicated smart phone application or tablet application software adapted to display the first and second position information.

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

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

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

Alternatively, a groove GG is formed in the envelope surface of the single piston body 5 and extends in the direction parallel with the central axis X. An inlet bore 77 of the single cylinder housing 3 is in contact with the groove GG for fluid communication in every position of the single piston body 5 relative the single cylinder housing 3 when the single piston body 5 moves along the central axis X. The groove GG is arranged for fluid communication with the first expandable cavity 20.

Fig. 6a illustrates the relative motion between a piston body and a cylinder housing of an electro-hydraulic linear actuator according to a seventh example. The electro-hydraulic linear actuator is preferably used in a vertical application, but may be used in any orientation of the rod.

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

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

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

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

The desired position value (set value) represents a position that the piston body/the cylinder housing/rod being controlled by the control circuitry CC to reach by a control command executed by the control circuitry CC.

The motion and performance of the piston body and the first and second rod clamping devices is controlled by the control circuitry CC. The piston body is moved by controlling the valve arrangement for performing a working stroke or working strokes WS for moving the rod ROD toward the desired position value (set value) in accordance with the input signal. A sensor arrangement SA, arranged to e.g. the piston body and/or cylinder housing and/or rod and/or guide, detects an actual value ACT of the piston body position relative the cylinder housing and/or actual position of the rod relative the cylinder housing and/or piston body, and signals the actual value ACT to the control circuitry CC.

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

The control circuitry CC thus executes a comparison calculation between the actual value ACT with the desired position value (set value) SET and controls the electro-hydraulic linear actuator to move the piston body/cylinder housing/rod toward the desired position value (set value) taking into account the detected actual value ACT and comparison calculation for making the correction control command and repeats the closed loop until the desired position value (set value) SET is reached.

Alternatively, the electro-hydraulic linear actuator works in an open loop system, whereas the desired motion of the piston body and/or cylinder housing and/or rod position is set beforehand and/or predetermined and the valve arrangement is controlled to operate the an electro-hydraulic linear actuator without any sensor arrangement and no feed-back signals are generated for actual position values.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The electro-hydraulic linear actuator 1 can be made less bulky than prior art electro- hydraulic linear actuators. This is achieved by increasing and strengthening the clamping pressure Pciamp for decreasing the clamping area A_Ciam of the clamping member. The increased clamping pressure P_ciamp is achieved in a simple and cost-effective way at the same time as the pressure produced by the fluid pump, the system pressure P_system , is kept sufficient low to provide that the piston force F_PiSton acting on the piston moves the piston in the cylinder. That is, at the same time as the first and second rod clamping device can be designed as compact as possible, it is also achieved that a lower system pressure P_system promotes lower energy consumption.

For maintaining the clamping pressure Pciamp in the accumulator, the accumulator is intermittently pressurized by the system pressure P_system generated by the fluid pump.

The system pressure P_system is lower than the clamping pressure P_ciamp generated by the pressurized accumulator.

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

P clamp — 3 X P system

Aclamp ^_ TT X D X L

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

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

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

Thus, by means of the increased clamping pressure P_Ciam , the clamping area A_Ciam can be decreased for providing a compact electro-hydraulic linear actuator 1 , still maintaining sufficient clamping force F_Ciam . Thus, the clamping force F_Ciam acting on the clamping area A_ciamp is sufficient to lock the first and second rod clamping device.

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

F clamp ⁼ P clamp X Aciamp X P

F_ciamp = the clamping force acting on the A_Ciam for providing a clamping action.

Pciamp = the clamping pressure produced by the accumulator

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

F piston ^— P system X Apiston

F_piston = the piston force acting on the piston for moving the piston in the cylinder

P_system ⁼ the system pressure, the pressure produced by the fluid pump

A_piston = the piston area of the piston, which piston area is effected by the system pressure

The force acting on the rod for clamping the clamping member to the rod is higher than the force acting on the piston body for moving the piston body in the cylinder, whereas the piston body is clamped to the rod and moves a load.

F clamp ^ F piston

P clamp X Aclamp X P > P system X Apiston

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

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

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

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

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

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

The electro-hydraulic linear actuator 1 is configured as a self-contained electro- hydraulic linear actuator. The hydraulic fluid supply 23 comprises a first pressure supply system 701 and a second pressure supply system 702. The first pressure supply system 701 generates a first hydraulic pressure being higher than a second hydraulic pressure generated by the second pressure supply system 702 and/or by the hydraulic fluid supply 23.

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

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

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

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

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

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

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

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

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

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

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

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

The non-return valve arrangement 705 may be arranged between the hydraulic accumulator 30 and the hydraulic pump 29.

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

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

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

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

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

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

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

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

The second pressure system 702 comprises a pressure switch PS configured to regulate the charging and/or precharging of the hydraulic accumulator 30 so that the hydraulic accumulator 30 is charged with the second hydraulic pressure or with at least the second hydraulic pressure.

Figs. 8a to 8c illustrate the operation of a valve arrangement 33 of an electro-hydraulic linear actuator according to an eleventh example. The valve arrangement is configured to operate the first and second rod clamping devices for performing overlapping sequences.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Data may also be manually fed to or presented from the control circuitry via a suitable communication device, such as a personal computer display (not shown). Separate sequences of the method can also be executed by the control circuitry 100, which control circuitry runs the data medium storing program P being stored in the separate memory 1060 or the read/write memory 1050. When the the control circuitry 100 runs the data medium storing program P, suitable method steps disclosed herein will be executed. A data medium storing program product comprising a program code stored on a medium is provided, which product is readable on a suitable computer, for performing the exemplary method steps herein, when the data medium storing program P is run on the the control circuitry 100.

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

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

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

Claims

1. An electro-hydraulic linear actuator (1) comprising:

-one single cylinder housing (3) extending along a central axis (X);

-one single piston body (5) dividing the cylinder housing (3) in a first (7) and second (9) cylinder chamber;

-a rod (17) extends along the central axis (X) and through the cylinder housing (3) and through a first rod clamping device (19) of the piston body (5);

-the first rod clamping device (19) comprises a first expandable cavity (20) configured to deform a first flexible inner wall of the piston body (5); wherein the electro-hydraulic linear actuator (1) is configured as a self-contained electro-hydraulic linear actuator (1) comprising a hydraulic fluid supply, which comprises:

-a channel arrangement (31) arranged between a hydraulic pump (27) and the cylinder housing (5) and between the hydraulic pump (27) and the first expandable cavity (20);

-a valve arrangement (33) of the channel arrangement is configured for controlling the flow of hydraulic fluid; and

-an electrical power device (35).

2. The electro-hydraulic linear actuator (1) according to claim 1, wherein the electro- hydraulic linear actuator (1) comprises a sensor arrangement (71, 73, 90) coupled to a control circuitry (100) of the hydraulic fluid supply (23).

3. The electro-hydraulic linear actuator (1) according to claim 1 or 2, wherein the electrical power device (35) is an electrical circuit component, such as an electrical plug and play connection, configured to be connected to an electrical power supply.

4. The electro-hydraulic linear actuator according to claim 3, wherein the electrical power device (35) comprises an electrical battery power pack.

5. The electro-hydraulic linear actuator according to any of the preceding claims, wherein the valve arrangement (33) comprises a logic valve device (707), configured for pressurization of at least the first expandable cavity (20), and a directional valve (33) device configured for pressurization of the first and second cylinder chamber.

6. The electro-hydraulic linear actuator (1) according to claim 5, wherein the logic valve device and the directional valve device each being configured to be controlled by a control circuitry (100) of a computer.

7. The electro-hydraulic linear actuator (1) according to any of claims 2-6, wherein a sensor arrangement (71 , 73, 90) of the electro-hydraulic linear actuator (1 ) is configured to obtain a first position information regarding mutual relation between the cylinder housing (3) and the piston body (5) indicating that the piston body (5) passes or reaches a first position relative the cylinder housing (3) along the piston body stroke.

8. The electro-hydraulic linear actuator according to claim 7, wherein the sensor arrangement (71, 73, 90) of the electro-hydraulic linear actuator (1) is configured to obtain a second position information regarding mutual relation between the cylinder housing (3) and the piston body (5) indicating that the piston body (5) passes or reaches a second position relative the cylinder housing (3) along the piston body stroke.

9. The electro-hydraulic linear actuator (1) according to claim 8, wherein the control circuitry (100) is configured to receive the first and second position information, the control circuitry (100) comprises a signal port (999) configured for delivery of the first and second position information to a communication port of the electro- hydraulic linear actuator, wherein the communication port is configured to be coupled to an electronic network device (110) comprising a processor unit (112) adapted for communication with a digital user interface (114).

10. A method of controlling the operation of an electro-hydraulic linear actuator (1) comprising:

-one single cylinder housing (3) extending along a central axis (X);

-one single piston body (5, 205) dividing the cylinder housing (3) in a first (7) and second (9) cylinder chamber;

-a rod (17) extends along the central axis (X) and through the cylinder housing (3) and through a first rod clamping device (19, 219) of the piston body (5, 205);

-the first rod clamping device(19, 219) comprises a first expandable cavity (20) configured to deform a first flexible inner wall of the piston body (205); -the electro-hydraulic linear actuator (1) is configured as a self-contained electro- hydraulic linear actuator (1) coupled to a hydraulic fluid supply,

-the hydraulic fluid supply comprises:

-a channel arrangement (31) arranged between a hydraulic pump (27) of the hydraulic fluid supply and the cylinder housing (3) and between the hydraulic pump (27) and the first expandable cavity (20);

-a valve arrangement (33) of the channel arrangement is configured for controlling the flow of hydraulic fluid to the first (7) and second (9) cylinder chamber and to the first expandable cavity (20);

-an electrical power device (35, 35’, 36); the method comprises,

-engaging the first rod clamping device (19, 219) to the rod (17) for preparing a working stroke of the piston body (5, 205);

-pressurizing the first cylinder chamber (7) and making the working stroke; -depressurizing the first cylinder chamber (7);

-disengaging the first rod clamping device (19, 219) for preparing a return stroke of the piston body (5, 205);

-pressurizing the second cylinder chamber (9) and making the return stroke; and

-engaging the first rod clamping device (19, 219) for preparing a working stroke of the piston body (5, 205).

11. A method of controlling the operation of an electro-hydraulic linear actuator (1) comprising:

-one single cylinder housing (3) extending along a central axis (X);

-one single piston body (5) dividing the cylinder housing (5) in a first and second cylinder chamber;

-a first piston portion arranged in the cylinder, which first piston portion is coupled to a second piston portion and configured to extend through a first opening of the cylinder; -a rod extends along the central axis through a first rod clamping device of the piston body and through a second rod clamping device; -the first rod clamping device comprises a first expandable cavity configured to deform a first flexible inner wall of the piston body;

-the second clamping device comprises a second expandable cavity configured to deform a second flexible wall of the second clamping device;

-a fluid supply for feeding hydraulic fluid to the cylinder and to the first and second expandable cavity; wherein the hydraulic fluid supply is formed as a self-contained unity rigidly coupled to the cylinder and at least partially enclosing:

-a hydraulic fluid reservoir;

-an electric motor (27) mechanically coupled to a hydraulic pump;

-a channel arrangement arranged between the hydraulic pump and the cylinder and between the hydraulic pump and the first and second cavity;

-a hydraulic accumulator configured for storing pressurized fluid for use in pressurizing the first and/or second expandable cavity;

-a valve arrangement of the channel arrangement is configured for controlling the flow of hydraulic fluid;

-a control circuitry coupled to the valve arrangement and configured to control the operation of the electro-hydraulic linear actuator in a non-feedback and/or a feedback loop procedure; and

-an electrical power device electrically coupled to the electric motor, the control circuitry and the valve arrangement; the method comprises, subsequently a step of engaging the second rod clamping device, the steps of:

-pressurizing the first cylinder chamber;

-engaging the first rod clamping device for preparing a working stroke of the piston body;

-disengaging the second rod clamping device;

-pressurizing the second cylinder chamber;

-engaging the second rod clamping device synchronous or after the piston body fulfilled the working stroke;

-disengaging the first rod clamping device for preparing a return stroke of the piston body;

-pressurizing the first cylinder chamber; -engaging the first rod clamping device synchronous or after the piston body fulfilled the return stroke for preparing a working stroke.

12. An electro-hydraulic linear actuator (1) comprising the electronic network device (110) according to claim 9, wherein the control circuitry (100) and/or the processor unit

(112) is configured to manage the method steps according to claim 10.

13. A data medium, configured for storing a program (P), configured for controlling the electro-hydraulic linear actuator (1) according to claim 1, wherein said data medium comprises a program code stored on the data medium, which program code is readable by the control circuitry (100) and/or the processor unit (112) for performing the method step according to claim 10.

14. A data medium product comprising a program code stored on a data medium, which program code is readable by the control circuitry (100) and/or the processor unit (112) for performing the method step according to claim 10, when the data medium according to claim 12 is run by the control circuitry (100) and/or the processor unit (112).