Abstract: A hydraulic actuating unit for raising a hospital bed includes a reservoir, a hydraulic piston cylinder device the cylinder of which has its ends connected to the reservoir through a supply conduit that contains a hydraulic plunger pump with suction and pressure valve means and through a return conduit which contains an orifice in a normally closed relief valve. A branch conduit leads to a hydraulic liquid accumulator from the supply conduit at a location between the cylinder and pressure valve means. A multiple pilot operated check valve of the differential type is provided in the branch conduit towards the accumulator. The largest and smallest end faces of the differential spool member are subject to the pressure in the branch conduit while the differential area of the spool member is subject to the pressure in a conduit which leads from the return conduit at a location between the orifice and the relief valve.

Abstract: Apparatus for driving a medical appliance has a single compressor for generating both the positive and negative pressures. The switching valves are connected to the outlet and inlet terminals of the compressor. The outlet and inlet terminals of the compressor are also connected to the positive pressure accumulator and the negative pressure accumulator, respectively. The apparatus has the pressure sensors to sense the pressures in the positive and negative pressure accumulators. When the pressure in the accumulator reaches a set pressure, at least one of the switching valves is closed. The apparatus further has the relief valves connected to the outlet and inlet terminals of the compressor. These relief valves open when the pressures of the compressor become excessive.

Abstract: A bidirectional pressure supply system for consumers of pneumatic negative pressure and/or positive pressure has a negative pressure line system and a positive pressure line system, to which the respective pressure types are simultaneously admitted from a pressure generator. Upon the electrically triggerable operation of the generator the consumers are connected, via parallel connected directional valves assigned to the consumers, to the respective pressure line system depending on the pressure type required at that moment, individually or in groups. The system provides an arrangement to apply negative pressure to first consumers and, simultaneously, positive pressure to second consumers.

Abstract: A hydraulic unit for a motor vehicle consisting of a housing comprising two housing chambers separated by a wall located inside the housing, in which a reciprocating pump is supported by the wall located inside the housing and is arranged in a first housing chamber which forms a hydraulic fluid reservoir. A drive member for the reciprocating pump is led out of the first housing chamber. A nonreturn valve provided in the wall located inside the housing establishes a fluid communication from the reciprocating pump to a pressure chamber in the second housing chamber, which is separated from a gas pressure reservoir also provided in the second housing chamber by a reservoir piston guided in the second housing chamber.

Abstract: A hydraulic control system for actuating a switch or related device including an actuator assembly having a housing with a member movable therein and connected to the switch for movement therewith between first and second positions responsive to the application of hydraulic pressure in the housing on opposite sides of the movable member.

Abstract: An accumulator designed to alleviate a so-called N-D select shock is connected in a hydraulic control system for an automatic transmission such that it can also alleviate a 3-4 shift shock. The accumulator includes a piston and a spring biasing the piston. The spring force of the spring is appropriately set such that the piston starts moving against the spring in response to small pressure build-up of a drive range select pressure.

Abstract: The invention involves pressure-counterweighted oil-well pumping apparatus in which derrick structure of elemental simplicity involves components which are readily assembled and disassembled, such that a given pumping apparatus can be loaded on a single truck and transported from one to the next desired well-pumping location. For a given capacity pumping system, overall height requirements for the derrick structure are less than one half those of U.S. Pat. No. 4,631,918. And power-integrator complexity is substantially reduced by employment of a fixed-displacement variety in conjunction with a variable speed a-c motor as the prime mover, under control of solid-state devices and pressure-sensitive transducer elements which determine upper and lower limits of the reciprocating stroke.

Abstract: A hydraulic motor vehicle brake system with a master cylinder (61) and a hydraulic power booster (24) connected upstream of the master cylinder (61), in which a pressure medium pump (1) which may be driven by an electric motor is used for providing an auxiliary hydraulic energy. The drive of the pressure medium pump (1) may be switched on by a pressure accumulator (26) which in the unbraked operation of the automotive vehicle is permanently kept on a pressure level sufficient for an initial actuation of the brake. The pressure accumulator (26) is charged by means of a pressure control valve (7) in which a valve passage (15, 17) is operable by a hydraulic pressure in the booster chamber (23) of the power booster (24) such as to ensure that upon pressurization of the booster chamber (23) a connection will be locked between the pressure accumulator (26) and the power booster (24).

Abstract: A double-acting accelerated forging hammer and method of operation are disclosed. The hammer is of the type having a vertically oriented cylinder, a piston slidably mounted within the cylinder having a downwardly depending piston rod extending along the cylinder and attached to a hammer. A gas accumulator communicates with the cylinder above the piston for supplying gas under pressure thereto during a forging stroke, and a fluid accumulator communicating with the cylinder below the piston for supplying fluid thereto at a higher pressure than the gas to dirve the piston upwardly during a return stroke. A fluid tank supplies fluid to recharge the accumulator and receives fluid from the cylinder during the forging stroke. Variable valves control the rate of fluid flow from the cylinder and thereby control the rate at which the piston descends within the cylinder.

Abstract: A device for controlling the pressure in an auxiliary-pressure supply system of a hydraulic brake unit for automotive vehicles, which device comprises a diaphragm-type or bladder-type accumulator equipped with a hydraulic and electric switching arrangement by way of which the hydraulic pressure in the pressure accumulator can be reduced to a predetermined value after the engine of the vehicle has been turned off. An electromagnetic multidirectional control valve is used to divert hydraulic fluid back to a reservoir through a pressure-limiting valve connected downstream thereof. After the engine of the vehicle has been turned off, the multidirectional control valve remains open until the accumulator pressure has decreased to at least the gas inflation pressure of the accumulator. The invention reduces permeation of gas molecules through the diaphragm of the accumulator into the hydraulic fluid and thus effects a longer useful life of the pressure accumulator.

Abstract: A battery-operated electric-motor driven hydraulic-lift mechanism for a fork-lift vehicle employs a hydraulic accumulator which serves an intertia-free counterweight function, designedly to the degree that such counterweight action is a direct offset of a predetermined average-load condition, as seen by the hydraulic-lift actuator of the system. Electric-motor drive is utilized for up/down operation of the fork lift, only to the extend needed to displace hydraulic fluid into or out of the "counterweighted" actuator. In some cases, such displacement will call for expending energy to add to or substract from the counterweight action; in other cases, the necessary fluid displacement results in an energy return to the system, i.e., in restoring energy to the battery.

Abstract: An air compressor pressure adjustment device designed such that any values between two set points are determined and used as first and second standard values. When the air pressure in the reservoir decreases to the first standard value the air compressor is driven at a low speed. When the air pressure increases in the reservoir and reaches an upper limit set point the compressor is turned off. When this air pressure decreases to less than the lower limit set point, the air compressor is started once more.

Abstract: A hydraulic drive system for driving a platen in forward and return reciprocatory strokes includes a hydraulically driven reciprocable piston and a reversible rotary hydraulic motor having a crank coupled to the platen by a link. A hydraulic circuit employs a variable output pump connected via a reversible direction control valve to drive the piston and crank in unison to cooperatively drive the platen. The piston and crank motor are connected in parallel to the pump and the pump output is advantageously distributed variably between the piston and motor during the stroke cycle. Where the stroke of the platen is vertical, the system may include a hydraulic counterbalance circuit to counterbalance the weight of the platen. The pump output may be varied to control the velocity of the platen at selected points in its stroke.

Abstract: A pressure generator having a high-pressure accumulator connected to a high-pressure pump by a high-pressure conduit via a first check valve, to store a high-pressure fluid from the high-pressure pump, a charging accumulator connected to the high-pressure pump, for storing a low-pressure fluid and supplying the high-pressure pump with the low-pressure fluid, and a charging pump for supplying the charging accumulator with the low-pressure fluid. The charging accumulator includes leak means for permitting the low-pressure fluid to leak at a low rate. The high-pressure conduit is connected to a storage chamber of the charging accumulator by a communication passage in which is disposed a second check valve for preventing a flow of the fluid from the high-pressure conduit toward the charging accumulator.

Abstract: A hydraulic brake system for automotive vehicles with a master brake cylinder and with a hydraulic power booster (1) connected upstream of the master brake cylinder, in which a pressure medium pump (6) drivable by an electric motor (9) is employed for providing auxiliary hydraulic energy. The drive of the pressure medium pump (6) may be switched on by a pressure contact (13) of a pressure accumulator (4), on the one hand, and by a brake pedal contact (11), on the other hand. In the unbraked operation of the automotive vehicle, the pressure medium accumulator is permanently kept on a pressure level sufficient for an initial actuation of the brake. A valve assembly is provided which establishes a hydraulic connection between the outlet of the pressure medium pump (6) and the pressure port of the hydraulic power booster (1).

Abstract: A control valve for controlling the distribution of pumped hydrodynamic fluid to the trailer brakes of a tractor and trailer combination in response to hydrostatic pressure applied from the tractor braking system has an inlet for pumped fluid, a spool valve operable in response to a control piston to control the flow of pumped fluid to a first working trailer braking circuit through an outlet and to a tank, or reservoir, through an outlet, a flow control valve which provides a passageway communicating with a first flow path for pumped fluid to the spool valve and which is operable in response to pumped fluid pressure to control the flow of pumped fluid to a second working implement circuit through an outlet, and a second flow path for pumped fluid extending between the inlet and spool valve independent from and parallel with the first flow path, so that the spool valve controls the flow of pumped fluid through the second flow path to the fluid outlet leading to the trailer braking circuit.

Abstract: A piston for a striker is displaceable in a cylinder and forms compartments on opposite sides which can selectively be connected by hydraulically controlled valve elements to a pump and to an accumulator. A hydraulic controller for the valve elements initially connects a compartment on one side of the piston to contribute the pressure from a respective compartment to the accumulator during a lifting operation, cuts off the valve element affording this pressure accumulation to brake the piston, and other such valve elements enable the accumulator to be charged with the piston in its raised position so that, upon triggering by the controller of the valve elements, the pressure which drives the ram is equal to the total pressure delivered by the accumulator and the pump to the piston.

Abstract: A hydraulic system comprises an accummulator for supplying hydraulic fluid to a load, a variable displacement pump for charging the accummulator and a valve means for adjusting the pump to deliver a high pressure for charging the accummulator and then to a low pressure when the load is supplied with fluid from the accummulator. By this operation, in which the pump is switched between the zero stroke positions of high and low pressure, the losses of the pump are decreased and the lifetime is increased.

Abstract: There is described a furrow opener apparatus capable of operating in a furrowing mode and a carrying mode. The apparatus consists of a double acting hydraulic cylinder having one end connected to a furrow opener drag arm and the other end connectable to a drill rig. It incorporates a pressure cushioning system consisting of at least one pressure absorber and hydraulic lines communicating through a mode valve with both the thrust and draw sides of the double acting cylinder. It further communicates through a single or double acting hydraulic valve to the hydraulic pump and reservoir of an associated prime mover such as a tractor. The mode valve is hydraulically connected to both the thrust and draw sides of the double acting cylinder. In a first mode the mode valve is hydraulically connectable to the pressure cushioning system and in a second mode hydraulically connected through a double acting hydraulic valve to the hydraulic pump and hydraulic reservoir of the prime mover.

Abstract: A hydraulic system for a weight-load transferring mechanism for a vehicle in which a pivoted frame carries wheels and the hydraulic system raises and lowers those wheels. The system employs a directional control valve for switching the supply of pressurized hydraulic fluid from one side to the other of the operating cylinder and piston assembly without depressurizing the entire system and an accumulator is continually connected to the pressurized side for supplying the necessary fluid when switching from one mode of operation to another. The desired predetermined pressure in the system is maintained by a pressure switch operating a solenoid dump valve to allow continuous operation of the pump.

Abstract: An electrohydraulic compact drive for turbomachine valves includes: a device for supplying electric power, receiving electrical addressing signals and converting the signals into positioning and control variables; an hydraulic supply system including a fluid tank, pump, motor, accumulator and manifold; an hydraulic power piston/cylinder system including a piston rod connected to a valve, and a spring biasing the piston; an electrohydraulic addressing system generating a pressurized fluid flow opening the valve spindle against the spring dependent upon the variables; control members of the addressing system, the power system and the supply system forming a compact drive block at a valve; the pump being switched as a function of a pressure limit by intermittent charging and discharging operations between the charging pressures; the pump charging the accumulator in charging operation until the upper pressure is reached and, after being switched, returning the fluid to the tank in substantially pressureless circu

Abstract: A hydraulic pressure source device for supplying an actuating hydraulic pressure to an automotive booster, having an accumulator and a hydraulic pump, the pump being interposed in a low-pressure oil passage leading from the control valve of a hydraulic power steering device to an oil tank. In the oil passage is also interposed an electromagnetic valve which is adapted to be opened and closed under control of an intermittent actuator which intermittently energizes the electromagnetic valve when sensing a pressure in the accumulator below a preset level. The pump is actuated by the hydraulic oil which is discharged into the low-pressure oil passage after having actuated the control valve through intermittent opening and closing operation of the electromagnetic valve to replenish the accumulator with the hydraulic pressure.

Abstract: A hydraulically operated, mobile patient transport table useful with a magnetic resonance scanner, which includes a magnet for producing a polarizing magnetic field, employs a hydraulic motor disposed at the base of the magnet and a hydraulic pump disposed at the base of the table. The hydraulic motor and pump are operatively coupled to enable transfer of energy from the motor to the pump without use of hydraulic connections therebetween. In the preferred embodiment, the coupling is implemented with a cone-shaped coupling member attached to the output of the motor and a complementarily-shaped coupling member attached to the input shaft of the pump which frictionally engages the cone-shaped member.

Abstract: The system of this disclosure provides apparatus by which fossil fuel is utilized in the generation of power. The generated power is more efficiently utilized by the apparatus. The system includes an internal combustion process which moves a piston. The piston is directly connected to actuate a special hydraulic pump which provides power fluid to an improved hydraulic motor. Each component of the system is specifically designed respective to the other components of the system to complement one another in a manner to effect an increase in efficiency, and therefore the efficiency gained from each component is added to the efficiency gained by the other components, all of which results in an accumulative gain in power from the total system.

Abstract: A pneumatic control system for machines that provides precise incremental or continuous direction, position, velocity and acceleration control of a variety of machine functions, such as rotary or linear motions, tool positioning and the like. A compressed air supply is maintained accurately at a preselected minimum pressure necessary for a particular operation, by a digitally pulsed air flow control system. Air flow and pressure to the associated actuating mechanisms is also controlled by a digital dithering technique using individual sharp pulses of air, each of which instantly breaks the static friction of the mechanism and causes a discrete precise increment of movement, with rapid consecutive pulses providing continuous motion. The direction, amount, acceleration and speed of travel are controlled by varying the pulse width and rate of air flow and pressure as necessary and for efficiency in air consumption.

Abstract: A fuel delivery system has a leak detector which responds to a low pressure condition in the delivery line for severely restricting the rate of flow of fluid to the delivery line. A temperature contraction compensation accumulator compensates for the contraction of fuel in the delivery line for maintaining the pressure of the delivery line above a minimum value, to avoid erroneous triggering of the leak detector into its slow flow mode in response to thermal contraction of the fuel.

Abstract: A fuel-saving energy storage vehicle drive system which saves fuel, primarily under stop-and-go driving conditions, by collecting, storing and using energy normally lost in the braking or deceleration of the vehicle, by automatically controlled operation of the engine under certain conditions, and by automatically controlled use of the stored energy and engine respectively as alternative or supplemental prime movers for each other for driving the vehicle. Subsystems for preventing waste of deceleration energy and stored energy are provided, and compact transmission layout and packaging are provided which facilitate installation of the new system in existing vehicles.

Abstract: A hydraulic circuit and charging valve arrangement is disclosed for charging an accumulator where the accumulator is used to power an additional function such as a brake valve. The accumulator charging circuit is connected to a load sensing power steering circuit including a flow divider that controls the flow of a fixed displacement pump to selectively effect actuation of a power steering motor and an auxiliary device such as a bucket loader or backhoe control valve. The charging circuit includes a pilot operated charging valve which controls the flow divider of the load sensing steering circuit for the purpose of recharging the accumulator. The charging valve includes a valve member that is biased against a coil spring to a neutral position when the accumulator is charged. When the accumulator pressure drops below a preset level, the valve member is shifted thereby permitting fluid flow through the charging valve to the flow divider in the load sensing steering circuit.

Abstract: Implement and steering actuators are selectively actuated through steering and implement control valves respectively by fluid power output of respective steering and implement pumps. A pressure compensator is provided for at times diverting excess fluid from the steering pump to the implement control valve, and the implement pump applies fluid pressure to the implement valve through an unloading valve that gives the charging of an accumulator by the implement pump preference over operation of the implement actuator. The sensing of loss of fluid power in the steering pump activates an emergency control valve to connect the accumulator to the steering valve and to disconnect the pressure compensator from the implement control valve.

Abstract: The present invention is directed to an improved fail-safe actuator and hydraulic system incorporating the same. The actuator includes energy storage means in the form of a spring adapted to set a control device in a predetermined condition, illustratively in the closed condition, responsive to a failure situation, illustratively, a power failure. The actuator includes a coupling which permits normal operation of the control device without cycling the spring energy storage means, thus increasing the life of the spring and eliminating energy wastage inherent in cocking the spring during each operative cycle.

Abstract: In an hydraulic system an unloader valve is disposed in a supply line between a pump and an hydraulic accumulator. The unloader valve is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value. The unloader valve incorporates a control valve comprising a spool and a pressure responsive slave which is operated by fluid pressure under the control of the control valve. The spool is movable between a first position in which the accumulator is isolated from the slave so that pump pressure is supplied to the accumulator and acts through a membrane on a trapped volume of gas under pressure, and a second position in which fluid pressure from the accumulator acts on the slave to unload the pump. The membrane of the accumulator acts directly on the spool to control movement of the spool between the two positions.

Abstract: A fuel-saving energy storage vehicle drive system which saves fuel, primarily under stop-and-go driving conditions, by collecting, storing and using energy normally lost in the braking or deceleration of the vehicle, by automatically controlled operation of the engine under certain conditions, and by automatically controlled use of the stored energy and engine respectively as alternative or supplemental prime movers for each other for driving the vehicle. Subsystems for preventing waste of deceleration energy and stored energy are provided, and compact transmission layout and packaging are provided which facilitate installation of the new system in existing vehicles.

Abstract: A fuel-saving energy storage vehicle drive system which saves fuel, primarily under stop-and-go driving conditions, by collecting, storing and using energy normally lost in the braking or deceleration of the vehicle, by automatically controlled operation of the engine under certain conditions, and by automatically controlled use of the stored energy and engine respectively as alternative or supplemental prime movers for each other for driving the vehicle. Subsystems for preventing waste of deceleration energy and stored energy are provided, and compact transmission layout and packaging are provided which facilitate installation of the new system in existing vehicles.

Abstract: A hydraulic percussion machine, comprising a body carrying hydraulic passages and valves, and having a gas-filled, hydraulic pressure accumulator for storing the stroke energy which accelerates a piston to strike against a tool. The percussion machine has a separate hydraulic stroke standardizing circuit by action of which the piston stroke is independent of the liquid pressure in the high pressure line supplying the machine and of the volumetric flow.

Abstract: A hydraulic priority switch for preferential feeding of a low consumption primary loop in fluid communication with a hydraulic reservoir which is chargeable from a pressure medium source via a flow control means, against a non-preferential secondary loop which can be switched in with the aid of a priority value when said primary loop is sufficiently pressurized, said hydraulic priority switch having protecting means for protecting both loops from excess pressure comprising a pressure-limiting valve which functions to make an outlet flow path available when pressure is excessive.

Abstract: A fuel-saving energy storage vehicle drive system which saves fuel, primarily under stop-and-go driving conditions, by collecting, storing and using energy normally lost in the braking or deceleration of the vehicle, by automatically controlled operation of the engine under certain conditions, and by automatically controlled use of the stored energy and engine respectively as alternative or supplemental prime movers for each other for driving the vehicle. Subsystems for preventing waste of deceleration energy and stored energy are provided, and compact transmission layout and packaging are provided which facilitate installation of the new system in existing vehicles.

Abstract: An internal combustion engine is connected to a fixed displacement pump normally having its inlet connected to a reservoir and its outlet connected to an accumulator. To start the engine, selectively operable valves connect the inlet of the pump to the accumulator and the outlet to the reservoir to drive the pump as a motor to rotate the engine. Also, a fixed displacement motor has an inlet connected by a forward solenoid valve to the accumulator and pump and connected by a brake solenoid valve to the reservoir. The motor also has an outlet connected to the pump and the accumulator by a reverse solenoid valve and connected to the reservoir by a neutral solenoid valve.

Abstract: A system is disclosed for controlling the flow of fluid from a pair of pumps (15,15') to a steering system (11) and a pair of auxiliary load circuits (13,13'). The steering system includes valving (43) defining a variable flow control orifice (45), and the steering system normally operates with a pressure differential X across the variable orifice, and provides load pressure signals (47,49,49',53,53') representative of demand for fluid by the steering system. Fluid flow from the pumps is controlled by a pair of priority flow control valves (21,21') including a pair of valve members (27,27') each of which is biased by a spring (29,29') toward a position permitting flow to the steering system. The spring (29) exerts a biasing force equivalent to the pressure differential X while the spring (29') exerts a biasing force equivalent to a pressure differential Y, which is less than X.

Abstract: The valve device disclosed includes first, second and third user ports. A pressure accumulator connects with the first user port. With the accumulator fully charged, a pressure port connected to a pump communicates with the second user port. With the accumulator evacuated, the pressure port communicates with the first user port. In the event of a fluid demand at the third user port connected to a closed-center user component, the pressure port will be connected to the third user port via a control valve.

Abstract: In an hydraulic system an unloader valve is located in a line between a pump and an hydraulic accumulator. The unloader valve is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value. The unloader valve incorporates a control valve comprising a spool and a pressure responsive slave which is operated by fluid pressure under the control of the control valve. A single spring acts to bias the spool into a first position against pressure in a control chamber into which fluid is pumped through a first one-way inlet valve. A second one-way exhaust valve located between the first one-way valve and an exhaust port can be opened by the slave to unload the pump.

Abstract: A hydraulic pressure actuated power brake system having a hydraulic power booster with operating pressure on both sides of the power piston power wall. The booster is therefore hydraulic pressure suspended so that the hydraulic pump of the system need not be operating to maintain this pressure while the booster is inactive. An accumulator is also charged by this pressure to provide power brake booster operation for several booster actuations without recharging by the pump. When the pump is operating, a pilot valve which is sensitive to a drop in booster operating pressure will control charging or recharging the accumulator and booster from the pressure generated by the pump to maintain a desired charge pressure. A pressure relief valve will also prevent overcharging of the accumulator and booster. A check valve prevents loss of booster operating pressure toward the pump outlet if the pump pressure falls below the charged pressure.

Abstract: The charging valve comprises a pressure port connected with a pressurized fluid source, a first user port which is connectible to a first user component, a second user port which is connectible to an accumulator and to a second user component of the closed center type and a valve device which is switchable dependent upon the pressure existing in the accumulator. The valve device, below a predetermined pressure in the accumulator, connects the pressure via a throttle with the second user port and, above a predetermined pressure in the accumulator, connects the pressure with the first user port. The valve device includes a closing valve which is controlled by a control pressure and the closing valve closes the connection of the pressure port with the first user port, if the pressure in the accumulator is below the predetermined pressure. Further, the closing valve can only be closed by the control pressure if the center of the second user component is open.

Abstract: A hydraulic accumulator system comprising an accumulator tank (22) for storing hydraulic fluid supplied by a pump (P) from reservoir (10), the stored fluid being pressurized by gas from gas tank (28), a control tank (35)connected at one end to the fluid supply (10) and at the other end to the gas supply (28), and a piston (36) in said control tank (35) having differential areas exposed to said fluid and said gas, said piston having means (41) for actuating a switch (43) to control said pump (P).

Abstract: Electric power is generated from a non-uniformly operating energy source such as wind or water waves by driving hydraulic pump means by a wind wheel or a bobbing float. The pump feeds hydraulic medium into a cylinder to raise a piston loaded by a weight. When the weight rises above a predetermined level, the medium is fed under its constant pressure to drive an hydraulic motor connected to an induction generator. Because the generator is driven at constant power (though intermittently) it can be connected to the public mains supply, eliminating the need to store power, without sophisticated interface arrangements. A second generator connected to a resistive space or water heating load can be cut in at higher energy levels. The hydraulic pump can be arranged to extract power from the source in the most efficient way.

Abstract: The valve includes a control piston axially slidable in a cylindrical bore which controls the cross-sectional area of an orifice of a connection between the cylindrical bore communicating with a pressure port and a user port. The control piston is acted on by a spring and a pressure which is reduced relative to the pressure at the pressure port. A cushioning arrangement acting on the control piston avoids occurrence of pressure surges affecting the control piston behavior.

Abstract: A hydraulic circuit breaker comprising an inlet chamber supplied with pressurized fluid from a pump and connected to a hydraulic circuit of the open-center type through a variable constriction, to a control chamber via a passage of reduced cross-section provided in a differential piston which separates both chambers from each other, and to a hydraulic accumulator through a check-valve, and further comprising a variable-volume vessel in communication with the control chamber and comprising a valve element responsive to the pressure reigning in said chamber for opening or closing a leak passage of restricted cross-section intended to allow the vessel to be discharged. In order to simplify the manufacture of the device and make easier its possible adjustment, the present invention proposes to realize the variable-volume vessel as an interchangeable capsule which is received in the proper control chamber and additionally serves as an abutment for limiting the stroke of the differential piston.

Abstract: An internal combustion engine is connected to a fixed displacement pump normally having its inlet connected to a reservoir and its outlet connected to an accumulator. To start the engine, selectively operable valves connect the inlet of the pump to the accumulator and the outlet to the reservoir to drive the pump as a motor to rotate the engine. Also, a fixed displacement motor has an inlet connected by a forward solenoid valve to the accumulator and pump and connected by a brake solenoid valve to the reservoir. The motor also has an outlet connected to the pump and the accumulator by a reverse solenoid valve and connected to the reservoir by a neutral solenoid valve.

Abstract: In a hydraulic circuit breaker comprising a housing with an inlet orifice connectable to the outlet of a hydraulic pump, a first outlet orifice connectable to the pressure chamber of a hydraulic pressure accumulator, and a second outlet orifice connectable to an open-center hydraulic circuit, a stepped bore in said housing, a piston of the differential type slidable in a fluid-tight manner in said bore and defining therewith an inlet chamber communicating with the inlet orifice and a control chamber, a constriction orifice of variable cross-section being provided between the inlet chamber and the second outlet orifice, and said inlet chamber communicating with said control chamber through a first passage comprising a first restriction and being also connected to the first outlet orifice by a connection comprising a non-return valve, there is further provided a resilient vessel having a variable-volume compartment connected to said control chamber, said vessel being adapted to connect said compartment to a sec

Abstract: In an hydraulic power system for operating a vehicle levelling system and braking system, an accumulator supplies both the levelling system and the braking system. The accumulator is connected indirectly to the braking system through a pressure limiting device, which disconnects the braking system from the accumulator when a predetermined pressure is reached.

Abstract: In an hydraulic system an unloader valve is located in a line between a pump and an hydraulic accumulator. The unloader valve is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value. The unloader valve incorporates a control valve comprising a spool, and a pressure responsive slave which is operated by fluid pressure under the control of the control valve. Two springs bias the spool into a first position in which pump pressure can be supplied to the accumulator, and the second spring is inoperative when the spool is moved into a second position in which fluid pressure from the accumulator can act on the sleeve to reduce the pump pressure to that of the tank for the pump.