Abstract: A locking arrangement for an electric vehicle, that includes a locking unit, an electric motor, and an axle which is driveable by the electric motor. The locking unit can have a piston and serve for locking the movement of the piston which can be acted on with pressure of a fluid. The locking unit has an electromagnet and at least one detent element, and the detent element interacts with the armature or the armature rod of the electromagnet, and the piston has at least one detent receptacle, and the piston can be secured by the retaining interaction of the detent element with the detent receptacle. The piston can be adjustable between a retracted position and an extended position. The piston can act in at least one of the two positions on the axle in such a manner that the rotation of the axle is mechanically blocked.

Abstract: A hydraulic system for a mobile rescue stretcher has a hydraulic cylinder, with first and second working chambers, a tank and pump. The first and second chambers are connected to the pump via first and second line arrangements, respectively, and can be pressurized by the pump. Hydraulic fluid flows out of the first chamber via the first line arrangement when pressure is applied to the second chamber. The first line arrangement has a first check valve which opens when pressure is applied to the second line arrangement. Hydraulic fluid flows out of the second chamber via the second line arrangement when pressure is applied to the first chamber. The second line arrangement has a first branch line connected to the pump and a second branch line connected to the tank. A pressure valve in the second branch line opens when pressure is applied to the second line arrangement.

Abstract: A hydraulic thruster system for providing an axial force. In one embodiment, the system comprises a pump, a motor for driving the pump, and a hydraulic thruster comprising: a cylinder comprising a plurality of cylinder pistons; a shaft comprising a plurality of shaft pistons; a plurality of first pressure chambers; and a plurality of second pressure chambers, wherein the plurality of shaft pistons are positioned inside the cylinder, between the cylinder pistons to form the plurality of first and a second pressure chambers, wherein the shaft further comprises a first fluid passage connected to the pump and to the first pressure chambers, and a second fluid passage connected to the pump and to the second pressure chambers, and wherein the pump may pump fluid into the first pressure chambers and suction fluid from the second pressure chambers providing an axial force between the shaft and the cylinder.

Abstract: A hydraulic drive apparatus includes: an electric motor; a variable displacement pump driven by the electric motor, the pump including a pair of pump ports whose delivery side and suction side are switched with each other in accordance with a rotation direction of the electric motor; a hydraulic actuator connected to the pair of pump ports by a first supply/discharge line and a second supply/discharge line; and a control device that controls the electric motor based on an actuator position command value for the hydraulic actuator. The pump is configured such that a volume of the pump decreases in accordance with increase in a pressure difference between the first supply/discharge line and the second supply/discharge line.

Abstract: The invention relates to a hydraulic drive having a differential cylinder which has a cylinder piston and a piston rod which is connected to the cylinder piston. The cylinder piston is arranged in a displaceable manner in a cylinder chamber in order to extend and retract piston rod. The cylinder chamber is separated by cylinder piston into a piston side, and a ring side with piston rod, each with a variable volume. The piston side and ring side are separated from one another by the piston and are connected to one another in a fluid conducting manner via a short-circuit line. The short-circuit line includes a switching valve for optionally shutting off short-circuit line in a fluid-tight manner. A switching valve can be switched into its blocking position at least indirectly in dependence on the pressure on piston side of cylinder chamber.

Abstract: A method of servicing a pressure relief valve system for a fluid injection system is provided. The method includes providing a skid, with the skid having a frame that supports a horizontal I-beam overhead. The method also includes providing a pressure relieve valve (“PRV”) system supported by a platform of the skid. The PRV system comprises one or more pressure transducers configured to sense fluid pressure within the fluid injection system. The transducers then generate electrical signals representative of fluid pressure readings within the fluid injection system in real time. Signals are received by a controller which compares pressure readings with a stored pressure threshold. An actuation signal is sent upon detecting a signal representative of a pressure that exceeds the stored pressure threshold, causing an electraulically-actuated valve to rotatably move to an open position. Plug valves may be quickly removed for service using a hoist system supported by the skid.

Abstract: Provided is a pump device and a hydraulic actuator that can reduce the number of steps of performance measurement. The pump device includes: a switching valve for switching a flow of oil to a first chamber or a second chamber of a cylinder device, the inside of which is segmented into the first chamber and the second chamber by a piston; an up blow valve (first chamber-side relief valve) that relieves pressure of a first chamber-side flow path connected to the first chamber; and a down blow valve (second chamber-side relief valve) that relieves pressure of a second chamber-side flow path connected to the second chamber.

Abstract: An actuator according to the present invention includes a cylinder, a piston inserted into the cylinder to be free to slide, a rod that is inserted into the cylinder and connected to the piston, a rod side chamber and a piston side chamber defined by the piston within the cylinder, a tank, a first opening/closing valve provided in a first passage that connects the rod side chamber to the piston side chamber, a second opening/closing valve provided in a second passage that connects the piston side chamber to the tank, a pump that supplies a working fluid to the rod side chamber, a motor that drives the pump, an exhaust passage that connects the rod side chamber to the tank, and a passive valve that is provided in the exhaust passage and has a predetermined pressure/flow rate characteristic.

Abstract: A hydraulic system is disclosed. The hydraulic system may have a pump, a rotary actuator, a linear actuator, and a closed-loop circuit fluidly connecting the pump to the rotary and linear actuators. The hydraulic system may also have at least one valve configured to switch fluid flow direction from the pump through the linear actuator during fluid flow in a single direction through the rotary actuator.

Abstract: The invention is an accumulator system in which multiple elastomeric accumulators are attached in series or parallel in order to generate total differential pressure in excess of that generated in a non-series system. Also disclosed is a “stacked” accumulator system. The system stores energy when the accumulators deform from their original shape in response to the flow of a pressurized fluid. The stored energy is available for use when the fluid is released from the accumulators and the accumulators return to their original shape.

Abstract: An electro-hydraulic actuator (EHA) includes a hydraulic circuit having a plurality of pressure compensated flow control valves for limiting the maximum flow rate through the fluid conduits regardless of the loads imparted on the actuator. In one embodiment of the EHA, a plurality of combination manual override/thermal expansion valves that simplify the manufacture of the EHA.

Abstract: A hydraulic system is disclosed. The hydraulic system may have an over-center, variable-displacement pump, an actuator, and first and second passages that create a closed-loop circuit. The hydraulic system may also have first and second check valves disposed in the first and second passages, respectively, to allow flow only from the pump to the actuator. The hydraulic system may further have a first bypass line connecting the first passage at a location between the actuator and the first check valve to the first passage at a location between the first check valve and the pump, and a second bypass line connecting the second passage at a location between the actuator and the second check valve to the second passage at a location between the second check valve and the pump. The hydraulic system may additionally have a valve configured to control flow through the first and second bypass lines.

Abstract: The invention relates to an electrohydraulic actuator comprising a body (1) that defines a cylindrical cavity (2) in which a piston (3) slides in leaktight manner and divides an inside volume of the cavity into two chambers (A, B) of variable volume, the piston being associated with at least one rod (4) passing in leaktight manner through an end wall of the cavity, the actuator including a bidirectional pump (5) having two ports (P1, P2), each connected to one of the chambers, an electric motor (8) for selectively driving the pump in one direction or the other, the pump being placed inside the piston of the actuator so as to move together therewith.

Abstract: A hydraulic system includes an actuator, a pump, rod side and cap side fluid connections between the pump and the rod and cap side chambers, respectively, at least one selectively actuatable regeneration valve that selectively provides flow from the cap side fluid connection to the rod side fluid connection, and a controller. The controller controls the pump to selectively vary the flow rate of the pump in response to a commanded motion to control movement of the piston. The controller actuates the regeneration valve during a retraction of the piston into the cylinder when pump is acting as a motor.

Abstract: A hydraulic system for a marine engine has a fluid reservoir, a bi-directional pump, a valve assembly, and a hydraulic actuator. The valve assembly includes: first and fourth apertures fluidly communicating with the pump, second and third apertures fluidly communicating with the actuator, and a fifth aperture fluidly communicating with the fluid reservoir. Operating the pump to supply hydraulic fluid to the first aperture causes hydraulic fluid to flow from the pump to the actuator and from the actuator to the fluid reservoir, and causes the actuator to move in a first actuator direction. Operating the pump to supply hydraulic fluid to the fourth aperture causes hydraulic fluid to flow from the pump to the actuator and from the actuator to the pump, and causes the actuator to move in a second actuator direction opposite the first actuator direction.

Abstract: First and second mechanical hydraulic valves are disposed between a pump and the cap side chamber of an actuator and the pump and the rod chamber of the pump. The first and second valves are actuated as a result of respective pressure differentials applied across the valves. A controller controls flow from a pump in response to a commanded motion to control movement of the actuator, and cause the valves to open. The valves are disposed in their no-flow positions when the pump is not operative, and when the hydraulic system of off or locked out to hold a load.

Abstract: A hydraulic manifold pump comprising a housing in which is located a first hydraulic circuit and a second hydraulic circuit. A bidirectional motor connectable to the first hydraulic circuit and the second hydraulic circuit, the bidirectional motor being able to activate the first hydraulic circuit when operable in a first direction, and being able to activate the second hydraulic circuit when operable in a second direction. The hydraulic manifold pump further compromises a hydraulic actuator having two hydraulic chambers being connectable to the first hydraulic circuit and to the second hydraulic circuit, and both the first and second hydraulic circuits being connected to and able to vent into a fluid reservoir.

Abstract: A flow management system capable of providing adjustable hydraulic fluid flow or pressure at a common line to supply bidirectional pumps in electro-hydrostatic actuation systems and conditioning re-circulated hydraulic fluid. The system enables flow sharing between multiple actuation systems and minimization of energy consumption by a power-on-demand approach and/or electrical energy regeneration while eliminating the need for an accumulator. The system has particular application to electro-hydrostatic actuation systems that typically include bi-directional electric motor driven pumps and unbalanced hydraulic actuators connected within closed circuits to provide work output against external loads and reversely recover energy from externally applied loads.

Abstract: The present invention is to provide an electro hydrostatic actuator excellent in a snubbing characteristic including a cylinder type actuator main body 1, a piston 2 having a piston rod, the piston slidingly moving in a cylinder of the actuator main body, a motor 18, a pump 19 for supplying fluid according to the rotation of the motor, a mechanism for adjusting a running amount of the fluid into and from the cylinder according to the motion of the piston, and a reservoir 8 for adjusting the supply of the fluid corresponding to a volume difference generated according to the motion of the piston, and a controller 17 which controls the number of revolutions of the motor according to the calculated load torque, and a snubbing control method used for this. An electro hydrostatic actuator of realizing a snubbing mechanism capable of increasing energy efficiency, when used for a landing gear retraction/extension device of an airplane, can be provided.

Abstract: A system and method for controlling the movement of an implement of an earthmoving machine. The system includes a hydraulic actuator adapted to move the implement. A variable displacement pump is coupled to the actuator for delivering a pressurized fluid to and receiving pressurized fluid from chambers within the actuator. A sensor generates an output based on the position of the actuator's piston or piston rod, and a controller controls the displacement of the variable displacement pump in response to the output of the sensor by executing an algorithm to reduce the flow rate of the fluid to and from the actuator's chambers and thereby reduce the velocity of the piston as it approaches an end of a piston stroke thereof and prevent the piston from impacting the actuator at the end of the piston stroke.

Abstract: Actuators suited for use with, for example, vehicular suspension systems. In some embodiments, the present actuators include a reversible hydraulic pump configured to produce variable hydraulic pressure; a hydraulic cylinder assembly having a cylinder bore, and a piston positioned within the cylinder bore that is axially movable relative to the cylinder bore; and a hydraulic circuit hydraulically coupling the reversible hydraulic pump to the hydraulic cylinder assembly. In these embodiments, actuated axial motion of the piston relative to the cylinder bore is accomplished without the use of check valves, pressure regulating valves, or actively controlled valves.

Abstract: A method is provided for controlling a hydraulic cylinder in a work machine, which hydraulic cylinder is arranged to move an implement in relation to a part of a vehicle, with the hydraulic cylinder being controlled by a hydraulic machine. The method includes the steps of detecting initiation of a movement of the implement that is such that the piston of the hydraulic cylinder is moved in a first direction, of driving the hydraulic machine in a first rotational direction, prior to the movement of the implement taking place, so that a line from the hydraulic machine is pressurized, which line is arranged to connect the hydraulic machine to the side of the cylinder toward which the piston will be moved during the movement of the implement.

Abstract: There is disclosed an actuator (5) having an actuator chamber (6) and actuator piston (9) therein defining an extend chamber (10) and a retract chamber (7) separated from the extend chamber by the actuator piston. A first fluid pump (A) is in fluid communication with the extend chamber and the retract chamber and is arranged to transfer therebetween volumes of fluid substantially equal in magnitude to changes in the volume of the retract chamber resulting from movement of the actuator piston within the actuator chamber. A second pump B connected to the extend chamber and to an accumulator (17) allows the differential volume between the extend and retract chambers to be displaced into the accumulator at a pressure. Stored accumulator fluid pressure enables pump B to be back-driven so that it behaves as a motor whenever the pressure in conduit 15 is less than in conduit 16. A pre-charge (20) unit pressurizes the system until full mass counterbalance of the suspended load is achieved.

Abstract: An actuating device for hydraulically actuating at least one setting element comprising a pump, which has an electric pump drive, with reversible pumping direction, at least one double-acting piston-cylinder arrangement, which is connected therewith and the piston of which is operatively connected with the setting element, and a hydraulic fluid reservoir from which the hydraulic fluid can be pumped to the piston-cylinder arrangement in order to hydraulically load the piston thereof for a setting element movement depending on pumping direction on one (effective surface 22) or other (effective surface 24) side. In this connection, the piston-cylinder arrangement is functionally associated with a detent device with a blocking element, which is spring-biased into a blocking position preventing setting element movement and is movable by an electrically activatable actuator from the blocking position into a release position permitting setting element movement.

Abstract: An electric actuator of the present invention includes a hydraulic fluid supply device and an actuator actuated in response to an input of hydraulic fluid from a variable-volume pump. The hydraulic fluid supply device includes an adjustable-speed motor, the variable-volume pump which is driven by the adjustable-speed motor and ejects hydraulic fluid, an electric motor control unit which controls the adjustable-speed motor so as to achieve an intended rotation speed, and a pump control unit which controls the variable-volume pump so that the ejection volume of the variable-volume pump decreases with an increase in the ejection pressure of the variable-volume pump.

Abstract: An actuation system includes a pump assembly configured to form a pump chamber, an actuator having first and second chambers and a movable member and configured to convert pressures applied to the first and second chambers into a movement of the movable member, and a valve section. The valve section has a plurality of positions set by a controller, and the plurality of positions includes a first position in which the valve section opens the first flow path and closes the second flow path, a second position in which the valve section closes the first flow path and opens the second flow path, and a neutral position in which the valve section closes the first and second flow paths.

Abstract: A multi-way valve includes a plurality of parallel combination valves for controlling corresponding actuators (4-1-4-5). Each combination valve comprises proportional throttle valves (2-1-2-5) and reversing valves (3-1-3-5). An oil inlet of the proportional throttle valve is communicated with a main oil inlet (P), and an oil outlet of the proportional throttle valve is communicated with an oil inlet of the reversing valve. An oil outlet of the reversing valve is communicated with the main oil return port (T). Wherein, each combination valve further comprises a one-way control valve (9-1-9-5, 10-1-10-5) for obtaining the load pressure of corresponding actuator. One side of the one-way control valve is communicated with a pipeline between the proportional throttle valve and the actuator. The multi-way valve further includes a control element (8) which receives the load pressure fed back by each one-way control valve and responds to the load pressure to control the supply of hydraulic oil for the actuators.

Abstract: An electro-hydraulic actuator includes a hydraulic pump, an electric motor operatively connected to the hydraulic pump and operable for driving the pump, an actuator moveable in response to fluid flow from the pump, and a housing for the pump, electric motor and actuator. The housing has a base member that is adapted to be modified into various configurations for forming an attachment interface for mounting of the electro-hydraulic actuator.

Abstract: Exemplary embodiments relate to a method for verifying a leak situation in a liquid transfer system a system and a control unit for implementing the method. The liquid is transferred with a frequency-converter-controlled pump from a lower pressure to a higher pressure and where liquid is prevented from being transferred from a higher pressure to a lower pressure with one or more check valves positioned in a pipe system. The method includes generating, for the frequency converter, motion information on the motion of the pump between the motion operations, and indicating a leak situation of the check valve if the direction of operation of the pump is, in the motion information, opposite to the direction of operation during the use of the pump.

Abstract: System for controlling the motion of an actuator of a hydraulic system that may be embodied as a circuit or device that, interposed between a pump and the actuator, controls the motion of the actuator, causing the actuator to follow the movement of the pump. The present invention relates both to a system and a device providing such result just on the basis of the measures of the fluid circulating within the hydraulic circuit or device. The system according to the present invention is suited both with opposing loads and dragging loads.

Abstract: A method for springing a movement of an implement of a work machine during a movement of the work machine is provided, in which at least one hydraulic cylinder is connected to the implement for controlling its movements, comprising the steps of connecting a hydraulic machine to the hydraulic cylinder, and of controlling the hydraulic machine in response to a disturbance acting upon the implement during the movement of the work machine.

Abstract: A hydrostatic drive with first and second hydraulic pumps and a dual-acting hydraulic cylinder. The dual-acting hydraulic cylinder has a first working chamber defined by a first piston surface and a second working chamber defined by a second piston surface. The first working chamber is connected to first connections of the first and second hydraulic pumps. The second working chamber is connected to a second connection of the second hydraulic pump. A second connection of the first hydraulic pump is connected to a hydraulic fluid reservoir. The ratio of the first piston surface to the second piston surface differs from the ratio of the total delivery volume of the two hydraulic pumps relative to the delivery volume of the second hydraulic pump. A tapping valve for removing hydraulic fluid is provided for the volumetric flow equalisation.

Abstract: In a pump device applicable to a power steering apparatus, a pump element is housed within a pump housing and is configured to drain a working oil, an electric motor is configured to drive the pump element, a reservoir tank is installed on the housing and is configured to reserve the working oil supplied to the oil element, a passage is formed within the pump housing and is connected to the pump element, and a control valve is installed in the pump housing, is configured to communicate with the passage, and is configured to control a flow of the working oil caused to flow through the passage.

Abstract: A fluid pressure actuator includes an output cylinder, a fluid pressure pump, an electric motor, a first output cylinder passage, a second output cylinder passage, a return passage and a swash plate control cylinder. The output cylinder includes a first output cylinder chamber, a second output cylinder chamber and an output piston arranged between the first output cylinder chamber and the second output cylinder chamber. The fluid pressure pump includes a first supply and discharge port, a second supply and discharge port and a swash plate for changing displacement of the fluid pressure pump. The electric motor drives the fluid pressure pump. The first output cylinder passage connects the first output cylinder chamber and the first supply and discharge port. The second output cylinder passage connects the second output cylinder chamber and the second supply and discharge port.

Abstract: A hydraulic circuit for actuation of a hydraulic working cylinder (1) having a one-sided piston rod (1a), comprising a reversible pump (4) whereby both sides of said pump are connected via a supply line (5) and a first two-way valve (6) to the tank (7) containing hydraulic medium and through releasable control check valves (8) to the working cylinder (1). Both sides of the arrangement are further connected respectively to a hydraulic closeable valve (21, 31) through a discharge line (20, 30) and also to the tank (7) through a replenishing suction line (22, 32) having a corresponding suction valve (9). Each of said hydraulic closeable valves (21, 31) is controlled by the pump (4) through a second two-way valve (4).

Abstract: The invention relates to a hydraulic drive, comprising a hydraulic cylinder (1), divided into a first operating pressure chamber (4) and a second operating pressure chamber (5), by an operating piston (3). The hydraulic drive further comprises a closed hydraulic circuit (39), with a first hydraulic pump (43), connected to the first operating pressure chamber (4) via a first working line (7), by means of a first connector (10) and to the second operating pressure chamber (5) via a second working line (13), by means of a second connector (12). In addition, an open hydraulic circuit (40) is provided, with a second hydraulic pump (8), connected to the first operating pressure chamber (4), by means of a third connector (11). A fourth connector (14) on the second hydraulic pump (8) is connected to a hydraulic reservoir element (75).

Abstract: The hydraulic linear actuator system of the present invention includes a pump that is configured to rotate in a single direction at a substantially constant velocity. Both the direction and flow rate of fluid through the system is controlled by adjusting the positional relationship between the stator and the rotor of the pump. This positional relationship is adjustable between a forward flow state, a non-flow state and a reverse flow state. The hydraulic linear actuator is responsive to the flow of fluid through the system so as to be displaced in a first direction by the forward flow state of the pump and in a second direction by the reverse flow state of the pump.

Abstract: The present invention relates to an actuation device for the actuating of an adjustment surface of an aircraft such as an elevator, a rudder or the like, of landing gear or another aircraft or surface vehicle actuator, comprising an electrohydraulic actuator having a servo control cylinder, a pump for pressure fluid action on the servo control cylinder as well as an electric motor for the actuation of the pump, with the electric motor having a liquid cooling. In accordance with the invention, the actuation device is characterized in that a leak flow of the pump is guided over a leak passage through the electric motor to cool the electric motor.

Abstract: The hydraulic linear actuator system of the present invention includes a pump that is configured to rotate in a single direction at a substantially constant velocity. Both the direction and flow rate of fluid through the system is controlled by adjusting the positional relationship between the stator and the rotor of the pump. This positional relationship is adjustable between a forward flow state, a non-flow state and a reverse flow state. The hydraulic linear actuator is responsive to the flow of fluid through the system so as to be displaced in a first direction by the forward flow state of the pump and in a second direction by the reverse flow state of the pump.

Abstract: A hydraulic system comprises a plurality of primary hydraulic circuits and a secondary hydraulic circuit for satisfying flow continuity of the primary hydraulic circuits.

Abstract: Hydraulic actuating device comprising a first and a second hydraulic actuator, which actuators have a first and a second connection for the supply and discharge of hydraulic fluid, which connections are in communication with a first and a second chamber, respectively, by way of a first and a second opening, respectively, in the cylinder space. The first opening of the second hydraulic actuator is in communication with the first opening of the first hydraulic actuator. The second opening of the second hydraulic actuator is in communication with the second opening of the first hydraulic actuator via a third connection. The third connection is in communication with the cylinder space in the first hydraulic actuator via a third opening. Damping means are achieved by a restriction of the outflow of hydraulic fluid via the second opening before the piston/piston rod assembly reaches the second end position.

Abstract: A stabilizer system and method that can provide high speed, relatively low force extension and retraction of a stabilizer leg during a first portion of a stroke, and low speed, relatively high force extension and retraction during a second portion of the stroke. Accordingly, the stabilizer system and method takes less time to deploy than conventional stabilizer systems but without sacrificing performance.

Abstract: The invention concerns a hydraulic system for linear drives with a differential cylinder, in particular for mobile machines which through the use of displacement-control of the drives avoids the many and diverse disadvantages of the state of the art and renders possible a precise and energy-efficient control of linear drives with differential cylinders, and which is economical and simple to maintain and which can be well integrated into the total hydraulic system of such machines.

Abstract: A hydraulic pressure supply unit has two exits that are alternately pressurized, a reversible pumping unit including at least two pumps, reversible electric motor that drives all pumps jointly, if necessary with mutually de-locking check valves before the exits, and a supply for hydraulic medium. One pump is a low-pressure pump and one pump is a high-pressure pump, and the pressurized exits of both pumps are placed against the same exit of the pressure supply unit. Both exits of the high-pressure pump can be separated from the low-pressure pump via check valves, and each pump is connected to the supply for hydraulic medium via its own shuttle valve.

Abstract: A dual mode hydraulic actuator, comprising: a housing; a rod secured to a piston, the rod and piston being slidably received within the housing; a first chamber positioned on one side of the piston; a second chamber positioned on another side of the piston; a sealed reservoir; a fluid disposed in the first chamber, the second chamber and the reservoir; a bidirectional pump for moving the fluid between the first chamber, the second chamber and the sealed reservoir; a bi-mode control valve for providing selective fluid communication between the first chamber, the second chamber and the sealed reservoir, wherein the bi-mode control valve is spring biased into a neutral position wherein fluid communication between the first chamber, the second chamber and the sealed reservoir is prevented; and wherein the bi-mode control valve is capable of being manually manipulated into a manual mode position wherein fluid flow from the first chamber to the second chamber is provided and fluid flow from or to the sealed reservo

Abstract: Actuators suited for use with, for example, vehicular suspension systems. In some embodiments, the present actuators include a reversible hydraulic pump configured to produce variable hydraulic pressure; a hydraulic cylinder assembly having a cylinder bore, and a piston positioned within the cylinder bore that is axially movable relative to the cylinder bore; and a hydraulic circuit hydraulically coupling the reversible hydraulic pump to the hydraulic cylinder assembly. In these embodiments, actuated axial motion of the piston relative to the cylinder bore is accomplished without the use of check valves, pressure regulating valves, or actively controlled valves.

Abstract: A closed circuit hydraulic system includes a fluid reservoir, a hydraulic cylinder having a cylinder rod, a bidirectional variable displacement hydraulic pump that pumps fluid to either extend or retract the cylinder rod on demand, a flow control valve for relieving pressure between the variable displacement hydraulic pump and the cylinder, and a low pressure check valve between the variable displacement hydraulic pump and the fluid reservoir. Also included is a charge pump for charging the variable displacement hydraulic pump and an accumulator for saving extra energy and fluid from the hydraulic cylinder during the retraction of an extended cylinder rod and using that fluid and energy during the extension of the hydraulic cylinder to reduce a load on the charge pump. The flow control valve opens on demand to allow floating. The low pressure check valve opens when pressure at an inlet of the variable displacement hydraulic pump is low to provide additional fluid and pressure so as to avoid cavitation.

Abstract: A hydraulic controller in which driving sound and the number of parts can be reduced, and a long service life can be realized, and a hydraulic drive unit provided with said hydraulic controller. The hydraulic controller for a hydraulic drive unit includes a housing that includes an electric motor housing configured to house an electric motor, an oil pump housing configured to house a hydraulic pump, and a valve housing configured to house valves are integrated together.

Abstract: An operate check valve saves space and performs multiple functions by absorbing and integrating a switching valve. A switching valve for controlling the flow of a hydraulic fluid in both normal and reverse directions is coaxially contained with a check valve in a space inside a valve containing housing between a hydraulic pump and a tank for storing the hydraulic fluid. Check valves are located opposite one another on either side of the switching valve, with the switching valve integrated into the operate check valve.

Abstract: A release system, particularly for releasing hydraulic actuators for automatic openings having an articulated arm for swing-door gates, provided in a hydraulic circuit having a hydraulic pump (3), operated by a reversible motor, two cylinder-piston elements (6, 7), alternatively receiving hydraulic liquid (L) from the hydraulic pump (3) through two tubes (4, 5), a valve (9, 10) being provided along the tubes (4, 5), between each cylinder-piston element (6, 7) and the hydraulic pump (3), preventing the return of the hydraulic liquid toward the hydraulic pump (3), the return being permitted only by an inverse rotation of the pump (3) operation motor, the system being characterized in that a normally closed manual opening-closing elements (11) being provided along the tubes (6, 7), connected in parallel with respect to the pump (3).