Abstract: A hydraulic machine includes an actuator, a tank, a directional control valve disposed between the actuator and the tank, and an adjustable return check valve disposed between the directional control valve and the tank. The directional control valve includes an attachment actuator directional control valve disposed between an attachment actuator of the actuator and the tank and a swing actuator directional control valve disposed between a swing actuator of the actuator and the tank. The adjustable return check valve allows fluid to flow from the attachment actuator directional control valve toward the tank while applying the low back pressure but blocks a flow, and allows fluid to flow from the swing actuator directional control valve toward the tank while applying the high back pressure but blocks a reverse flow.

Abstract: An actuator system can include a first actuator, a second actuator, a first actuator control device configured to control the first actuator, a second actuator control device configured to control the second actuator, a shared redundant actuator control device, and at least one transfer device operatively connected to the first, second, and shared redundant actuator control devices.

Abstract: Distributed trailing edge wing flap systems are described. An example wing flap system for an aircraft includes a flap, an actuator, a first hydraulic module, and a second hydraulic module. The flap is movable between a deployed position and a retracted position relative to a fixed trailing edge of a wing of the aircraft. The actuator is to move the flap relative to the fixed trailing edge. The first hydraulic module is located at the actuator. The second hydraulic module is located remotely from the first hydraulic module and includes a local power unit. The actuator is hydraulically drivable via first pressurized hydraulic fluid to be supplied from a hydraulic system of the aircraft to the actuator via the second hydraulic module and further via the first hydraulic module. The actuator is also hydraulically drivable via second pressurized hydraulic fluid to be supplied from the local power unit to the actuator via the second hydraulic module and further via the first hydraulic module.

Abstract: A redundant steering system for watercraft that transfers rudder control to an electronic steering system when a hydraulic steering system either fails or is under repair. The electronic steering system utilizes either a fueled generator or a battery or series of batteries to power electric steering and flanking motors that serve control the angular position of the rudders.

Abstract: An electronically pressure-controllable braking system and methods for controlling an electronically pressure-controllable braking system. Each wheel brake of the braking system is connected respectively to at least two brake circuits, pump units and valve devices of one brake circuit are operable respectively independently of the pump units and the valve devices of the respective other brake circuit. This provides a cost-effectively and compactly designed redundant braking system, which is suitable for use in autonomously, i.e., driverlessly drivable, motor vehicles.

Abstract: The purpose of the present invention is to provide a cooling fan control device for a construction machine, whereby the effects of heat caused by warm-up operation can be suppressed. This cooling fan control device is equipped with a control unit (10a) that controls the rotational speed of a cooling fan (21) in accordance with a main pump discharge pressure (P) detected by a main pump discharge pressure sensor (25), an engine cooling water temperature (Tw) detected by an engine cooling water temperature sensor (26), a hydraulic oil temperature (To) detected by a hydraulic oil temperature sensor (27), and an engine rotational speed (E) detected by an engine rotational speed sensor (28). The cooling fan (21) is rotated at the rotational speed controlled by the control unit (10a), thereby sending the generated cooling air to an oil cooler (19) and a control valve (13).

Abstract: Two control systems are provided to run in parallel between a surface location and the final controlled element, in this case a subsurface safety valve. The primary control circuit is controlling until a predetermined signal is given to the secondary control line which has the effect of actuating the valve a single time against the force of a bias or a shear pin that breaks. The movement of a shuttle in the housing due to the predetermined signal being provided in the secondary line puts the secondary control system in the position of running the tool. The primary system is valved off and cannot return into service. There are just two lines into and out of the housing to make the valve operate at the desired location. A test port is provided for surface testing.

Abstract: Hydraulic apparatus for recovering energy, said apparatus comprising a hydraulic motor, and a high-pressure fluid source and a low-pressure fluid source. The apparatus has: an energy consumption mode, in which the fluid is transferred from the high-pressure fluid source to the low-pressure fluid source while driving the motor in rotation; and an energy accumulation mode, in which, by the action of the motor operating as a pump, the fluid is transferred from the low-pressure source to the high-pressure fluid source. The apparatus further comprises a pressure reducer disposed on a duct interconnecting the two fluid sources. In energy accumulation mode, if the level of the low-pressure source is tending to become excessively low, the reducer opens, enabling fluid to reach the low-pressure fluid source via the first duct.

Abstract: A hydraulic control system is disclosed for use in a machine. The hydraulic control system may have a work tool, a motor configured to swing the work tool, a tank, a pump configured to draw fluid from the tank and pressurize the fluid, and a control valve operable to control fluid flow from the pump to the motor and from the motor to the tank via first and second chamber passages to affect motion of the motor. The hydraulic control system may also have an accumulator, and an accumulator circuit configured to selectively direct fluid discharged from the motor to the accumulator for storage and to direct stored fluid from the accumulator to the motor to assist the motor. The hydraulic control system may further have a selector valve configured to selectively connect a higher pressure one of the first and second chamber passages with the accumulator, and a single pressure relief valve disposed within the accumulator circuit and configured to relief pressure from opposing sides of the motor.

Abstract: The present disclosure relates to isolation and reconfiguration schemes, architectures and methods for use in aircraft hydraulic systems. The main hydraulic system of each hydraulic section of the aircraft hydraulic system can be isolated from one or more consumers in the event of a leak without the use pressure from the backup system. Further, in some embodiments, the main hydraulic system of each hydraulic section of the aircraft hydraulic system can be isolated from one or more consumers in the event of a leak without the use pressure from the backup system and the main system.

Abstract: The present disclosure relates to construction machinery such as an excavator or a wheel loader, and more particularly, to an emergency steering apparatus for construction machinery, capable of controlling a steering operation at the time of emergency in which a part of equipment malfunctions or is in an inoperable state. More specifically, an emergency steering apparatus for construction machinery according to an exemplary embodiment of the present disclosure includes: a steering actuator; an emergency hydraulic pump connected to the steering actuator through a pair of driving flow paths; an emergency steering unit configured to receive working oil, which is discharged from the emergency hydraulic pump, and operate a steering means; and an emergency steering controller configured to control whether or not the emergency hydraulic pump is operated.

Abstract: A control system for a swashplate pump is disclosed. The control system may have a tiltable swashplate, at least one actuator movable to tilt the swashplate, a supply of pressurized fluid, and a drain. The control system may also have a first circuit connectable to the supply of pressurized fluid and to the drain and configured to control operation of the at least one actuator, and a second circuit connectable to the supply of pressurized fluid and to the drain and configured to control operation of the at least one actuator. The control system may further have a failsafe valve configured to connect the first circuit to at least one of the supply and the drain only during a normal operating condition, and to connect the second circuit to the supply and to the drain only during a failsafe condition.

Abstract: A first actuator drives a control surface by being operated by supply of pressure oil from a first aircraft central hydraulic power source including a first aircraft central hydraulic pump. A second actuator drives the control surface by being operated by supply of pressure oil from a second aircraft central hydraulic power source including a second aircraft central hydraulic pump. A backup hydraulic pump is installed inside a wing of the aircraft and is provided so as to be able to supply pressure oil to the first actuator when a loss or degradation in a function of at least one of the first aircraft central hydraulic power source and the second aircraft central hydraulic power source occurs. A maximum discharge pressure of the backup hydraulic pump is set to be greater than maximum discharge pressures of the first aircraft central hydraulic pump and the second aircraft central hydraulic pump.

Abstract: A pump unit installed inside a wing, and a panel body constituting part of a wing structure portion forming a surface structure of the wing are provided. The pump unit includes a backup hydraulic pump that can supply pressure oil to an actuator when a loss or reduction occurs in the function of an aircraft central hydraulic power source and an electric motor that drives this pump. Except for at least the panel body, the wing structure portion is formed from fiber reinforced plastics. The panel body is formed of a metallic material.

Abstract: A backup system is provided that has a local electric motor and pump for some or all of hydraulic actuators. A local backup hydraulic actuator has two power sources, hydraulic as primary and electrical as backup. During normal operation, the hydraulic actuator receives pressurized fluid from a hydraulic system and the fluid flow to the chambers is controlled by a servo valve. If the hydraulic system fails, the electronic controller detects the failure by observing the signal indicative of the pressure from the pressure sensor, and the controller powers the local hydraulic pump to provide high pressure hydraulic fluid to the hydraulic actuator via the servo valve.

Abstract: A first actuator drives a control surface by being operated by supply of pressure oil from a first aircraft central hydraulic power source including a first aircraft central hydraulic pump. A second actuator drives the control surface by being operated by supply of pressure oil from a second aircraft central hydraulic power source including a second aircraft central hydraulic pump. A backup hydraulic pump is installed inside a wing of the aircraft and is provided so as to be able to supply pressure oil to the first actuator when a loss or degradation in a function of at least one of the first aircraft central hydraulic power source and the second aircraft central hydraulic power source occurs. A maximum discharge pressure of the backup hydraulic pump is set to be greater than maximum discharge pressures of the first aircraft central hydraulic pump and the second aircraft central hydraulic pump.

Abstract: A double redundancy electro hydrostatic actuator system includes two hydraulic pumps; two fail safe valves connected with the two hydraulic pumps, respectively; one dual tandem hydraulic cylinder connected with the two fail safe valves and having a piston rod, wherein the piston rod is moved by switching supply and discharge of the fluid; two switching valves connected with the two fail safe valves; two accumulators connected with the two switching valves and the two hydraulic pumps, respectively; and two chambers connected with the two switching valves, respectively. Each of the two accumulators accumulates the fluid from a corresponding one of the two hydraulic pumps, and sends the fluid to a corresponding one of the two fail safe valves. The two chambers receive the fluid from the two fail safe valves, respectively.

Abstract: An assembly for the hydraulic actuation of safety equipment includes a hydraulic pump disposed between a fluid feed line and a supply line in fluid communication with the safety equipment. A pump valve in the supply line downstream of the hydraulic pump is adjustable between open and closed positions for providing hydraulic fluid to supply line. A fluid source communicates with a bypass line in fluid communication with the supply line. A bypass valve is disposed between the fluid source and the supply line and is lockable between open and closed positions for providing other hydraulic fluid to supply line.

Abstract: A backup system is provided that has a local electric motor and pump for some or all of hydraulic actuators. A local backup hydraulic actuator has two power sources, hydraulic as primary and electrical as backup. During normal operation, the hydraulic actuator receives pressurized fluid from a hydraulic system and the fluid flow to the chambers is controlled by a servo valve. If the hydraulic system fails, the electronic controller detects the failure by observing the signal indicative of the pressure from the pressure sensor, and the controller powers the local hydraulic pump to provide high pressure hydraulic fluid to the hydraulic actuator via the servo valve.

Abstract: A hydraulic vehicle provided with a running-system hydraulic unit 10 that includes a hydraulic pump 11 being configured to be driven by an engine E, a hydraulic motor 12 being configured to be driven by pressure oil discharged from the hydraulic pump 11, and a pair of running-system oil passages 13a and 13b connected between the hydraulic pump 11 and the hydraulic motor 12 for forming a closed circuit. The hydraulic vehicle is configured to be driven by the hydraulic motor 12 for running. The hydraulic vehicle includes: a backup pump 40 being configured to be driven by the engine E; a backup control valve 30, a backup oil passage 47, a high-pressure selection valve 47b that are configured to allow pressure oil discharged from the backup pump 40 to flow to one of the running-system oil passages that is higher in pressure than the other.

Abstract: A backup system is provided that has a local electric motor and pump for some or all of the hydraulic actuators on an aircraft. A local backup hydraulic actuator has two power sources, hydraulic as primary and electrical as backup. During normal operation, the hydraulic actuator receives pressurized fluid from a hydraulic system and the fluid flow to the chambers is controlled by a servo valve. If the hydraulic system fails, the electronic controller detects the failure by observing the signal indicative of the pressure from the pressure sensor, and the controller powers the local hydraulic pump to provide high pressure hydraulic fluid to the hydraulic actuator via the servo valve.

Abstract: A double redundancy electro hydrostatic actuator system includes two hydraulic pumps; two fail safe valves connected with the two hydraulic pumps, respectively; one dual tandem hydraulic cylinder connected with the two fail safe valves and having a piston rod, wherein the piston rod is moved by switching supply and discharge of the fluid; two switching valves connected with the two fail safe valves; two accumulators connected with the two switching valves and the two hydraulic pumps, respectively; and two chambers connected with the two switching valves, respectively. Each of the two accumulators accumulates the fluid from a corresponding one of the two hydraulic pumps, and sends the fluid to a corresponding one of the two fail safe valves. The two chambers receive the fluid from the two fail safe valves, respectively.

Abstract: An electro-hydraulic steering control system for directing fluid to steering actuators on a work machine may include a main valve configured to control fluid flow to the steering actuators. Left and right primary steering valves may be in communication with and configured to affect the main valve to control fluid flow to the steering actuators. Left and right redundant steering valves may be in communication with and configured to affect the main valve to control fluid flow to the steering actuators. A shuttle valve may be operably disposed between one of the right primary and the right redundant steering valves and the left primary and left redundant steering valves. The shuttle valve may be operable to selectively control fluid from the one of the right primary and the right redundant steering valves and the left primary and left redundant steering valves to the main valve to control the main valve.

Abstract: An auxiliary tank is filled by a pitch control system, which enables the size of the auxiliary tank to be reduced.

Abstract: A steering system for a work machine having a hydrostatic transmission is disclosed. The steering system has a primary source of pressurized fluid and a steering control valve. The steering system also has a first fluid passageway fluidly connecting the primary source of pressurized fluid to the steering control valve and a second fluid passageway fluidly connecting the hydrostatic transmission to the steering control valve.

Abstract: A hydraulic steering arrangement includes a steering valve, a steering motor, connected with a high-pressure connection and a low-pressure connection via the steering valve, and with a steering unit, connected via the steering valve with a pilot pressure valve, whose outlet is connected with the low-pressure connection. It is endeavoured to improve the steering behaviour. For this purpose, the pilot pressure valve is opened, before the steering valve creates a connection between the high-pressure connection and the steering motor.

Abstract: A control for parallel hybrid transmission has a valve mechanism, which is operable to supply fluid pressure to a torque-transmitting mechanism with or without the operation of the vehicle engine. The valve mechanism is responsive to an electrically driven pump to supply fluid pressure whenever the engine is discontinued and the electric driven pump is operated.

Abstract: A hydraulic circuit for a hydraulic excavator having a motor drive which acts on at least two closed drive circuits which are connected in parallel, each have a hydraulic pump and a hydraulic motor and which operate on a common output drive, connecting lines being provided between the hydraulic pump and the hydraulic motor of a respective drive circuit, is intended to be improved such that mutual contamination of the components of different driving means with particles in the event of damage is largely avoided and it is also made easier to ascertain the damage. This is achieved by the connecting lines (L11, L12; L21, L22) of each drive circuit (A1, A2) being arranged only between the hydraulic pump (P1, P2) and the hydraulic motor (HM1, HM2) of the respective drive circuit (A1, A2) in such a way that there is no hydraulic connection between the different drive circuits (A1, A2), the respective drive circuit (A1, A2) each having its own control valve (S1, S2) connected to it.

Abstract: A rotary flow combiner allows flow from multiple pressure compensated hydraulic pumps; with or without load sensing to be combined into a single outlet. The flows are combined in such a way that each input to the rotary flow combiner has equal flow. The flow from each pump is optimized in such a way that the output from the rotary flow combiner can achieve the maximum range of flow and pressure and so that all the pumps in the multiple pump system are supplying fluid flow at all times. A check valve can allow the rotary flow combiner to pull hydraulic fluid direct from a reservoir in parallel to a lower flow pump such that the volume of flow from the lower pump combined with the fluid drawn directly from the reservoir will match the flow from the higher flow pump.

Abstract: An electro-hydrostatic actuator unit that contains a sealed pressurized housing filled with a dielectric fluid. A bi-directional motor is immersed in the fluid and drives a gear pump for exchanging fluid via a control circuit between the chambers of a bi-directional hydraulic actuator in response to an input from a controller. The chambers are separated by a piston and a piston rod is connected to an external load such as a plunger type valve. A failsafe circuit is also provided which is arranged to override the control circuit in the event a failsafe condition is detected by the unit controller. The failsafe circuit contains a motor driven pump that provides high pressure fluid from the pressurized reservoir to an accumulator. Valves are arranged to shut down the control circuit and deliver fluid from the accumulator to one of the cylinder chambers to rapidly move the actuator to a desired failsafe position.

Abstract: A last chance aircraft back-up hydraulic system in which fuel from the fuel tanks of the aircraft is injected into the return line of a leaking hydraulic system by use of a pump activated by a guarded switch by the aircraft's pilot. The fuel serves as hydraulic fluid to operate the pumps of the system as it is injected upstream from the fluid being lost to extend the operating time of the system and prevent failure so the aircraft can be landed at a site.

Abstract: A hydraulic transfer valve system has a main valve selectively placing one of a primary and secondary hydraulic system in communication with a hydraulic load. A pilot valve provides a toggling action between the primary and secondary systems with respect to pressure changes in such systems.

Abstract: The invention relates to a hydraulic steering system architecture comprising at least one steering control actuator having chambers connected to the outlets of a directional-control valve, an accumulator, and an electrically-driven pump unit associated with an emergency supply. The hydraulic system also comprises a general selector arranged, in a normal mode of operation, to connect the feed port of the directional-control valve to a pressure-generator device and the return port of the directional-control valve to a main supply associated with the pressure-generator device, while also ensuring that the emergency supply is filled, and in an alternate mode of operation, to connect the feed port of the directional-control valve to the accumulator.

Abstract: A hydraulic transfer valve system has a main valve selectively placing one of a primary and secondary hydraulic system in communication with a hydraulic load. A pilot valve provides a toggling action between the primary and secondary systems with respect to pressure changes in such systems.

Abstract: The invention relates to an architecture for a hydraulic steering control system including at least one actuator; the hydraulic system comprises a directional-control valve connected to a pressure-generator device and to an associated main supply, the hydraulic system further comprising a reversible electrically-driven pump unit having two ports and being fitted with a general selector arranged, in a normal mode of operation, to put the chambers of the actuator into communication with the directional-control valve, and in an alternate mode of operation to put the chambers of the actuator into communication with the ports of the pump unit. A compensation device makes it possible in the alternate mode to compensate for any flow differential between the flow drawn in by the pump unit from one of the chambers of the actuator and the flow delivered by the pump unit into the other chamber of the actuator.

Abstract: The invention relates to a hydraulic steering system architecture comprising at least one steering control actuator having chambers connected to the outlets of a directional-control valve, an accumulator, and an electrically-driven pump unit associated with an emergency supply. The hydraulic system also comprises a general selector arranged, in a normal mode of operation, to connect the feed port of the directional-control valve to a pressure-generator device and the return port of the directional-control valve to a main supply associated with the pressure-generator device, while also ensuring that the emergency supply is filled, and in an alternate mode of operation, to connect the feed port of the directional-control valve to the accumulator.

Abstract: The invention relates to an architecture for a hydraulic steering control system including at least one actuator; the hydraulic system comprises a directional-control valve connected to a pressure-generator device and to an associated main supply, the hydraulic system further comprising a reversible electrically-driven pump unit having two ports and being fitted with a general selector arranged, in a normal mode of operation, to put the chambers of the actuator into communication with the directional-control valve, and in an alternate mode of operation to put the chambers of the actuator into communication with the ports of the pump unit. A compensation device makes it possible in the alternate mode to compensate for any flow differential between the flow drawn in by the pump unit from one of the chambers of the actuator and the flow delivered by the pump unit into the other chamber of the actuator.

Abstract: A manifold assembly for pneumatically interconnecting a brake booster to an engine and to an electrically-driven vacuum pump. A manifold housing has an engine port pneumatically communicable with the engine, a separate booster port pneumatically communicable with the brake booster, and an orifice pneumatically communicable with the vacuum pump inlet. An engine check valve substantially blocks pneumatic flow from the engine port to the booster port. A vacuum-pump check valve substantially blocks pneumatic flow from the engine port to the vacuum pump outlet.

Abstract: A redundant control actuation system (100) provides hydraulic logic cross-coupling between physically-separate servoactuators (101A, 101B). Each servoactuator has a control valve (102A, 102B) arranged to provide a hydraulic output in response to a control signal. Each actuator also has a hydraulic actuator (106A, 106B) arranged to move a load in response to the hydraulic output from its associated control valve. Logic valve means (103A, 104A, 105A, 103B, 104B, 105B) are operatively associated with the control valves (102A, 102B) and actuators (106A, 106B). Each logic valve means is supplied with hydraulic and electrical input signals.

Abstract: A redundant control actuation system (100) provides hydraulic logic cross-coupling between physically-separate servoactuators (101A, 101B). Each servoactuator has a control valve (102A, 102B) arranged to provide a hydraulic output in response to a control signal. Each actuator also has a hydraulic actuator (106A, 106B) arranged to move a load in response to the hydraulic output from its associated control valve. Logic valve means (103A, 104A, 105A, 103B, 104B, 105B) are operatively associated with the control valves (102A, 102B) and actuators (106A, 106B). Each logic valve means is supplied with hydraulic and electrical input signals.

Abstract: A switching valve (50) for a hydraulic power steering system (10) includes a longitudinally movable valve spool (80). A spring (86) biases the spool (80) to a neutral position. The switching valve (50) is configured to direct hydraulic fluid from a primary pump (34) to a steering control valve (14) when the spool (80) is in a primary position, and to direct hydraulic fluid from an auxiliary pump (38) to the control valve (14) when the spool (80) is in an auxiliary position. The spool (80) is movable against a bias of the spring (86) from the neutral position to the primary position under the influence of a hydraulic fluid pressure differential between the opposite ends of the spool (80). The switching valve (50) defines a flow path for directing hydraulic fluid from the primary pump (34) to an end of the spool (80) when the spool (80) is in the neutral position. The flow path extends axially over a flat portion (124) of an outer surface of the spool (80).

Abstract: A hydrostatic steering device having substantially identical first and second steering systems, each including a pump connected to a steering unit, which is connected to a steering motor by two motor hoses. A steering wheel is common to both steering units. The device includes a change-over valve which has an operation position hydraulically coupling together the two motor hoses of the second steering system, while hydraulically isolating from each other the two motor hoses of the first steering system, and an emergency position hydraulically coupling together the two motor hoses of the first steering system, while hydraulically isolating from each other the two motor hoses of the second steering system. A switching device switches the change-over valve from the operation position to the emergency position, when a fault occurs in the first steering system.

Abstract: A method and an apparatus control a car equipped with an automatic transmission having a lockup clutch. When the lockup clutch is in the lockup state, a variation of a generated torque is detected. When the range of the torque variation detected exceeds a predetermined value, an engine torque is reduced by controlling the engine, and the automatic transmission is controlled to compensate for a reduction of the driving torque due to a reduction of the engine torque. Thus, the speed change ratio is changed to the low gear side.

Abstract: A vacuum back-up system for diesel vehicles, and a primary vacuum system for high performance vehicles, which vacuum system includes a vacuum pump for creating a vacuum in an associated reserve vacuum tank connected to the vacuum booster of the vehicle. A relay is attached to the vacuum pump or to a mount bracket which mounts the vacuum pump and the reserve vacuum tank and the relay is electrically connected to a vacuum switch on the vacuum booster and to the vehicle battery and the vacuum pump to facilitate operation of the vacuum pump and maintaining a vacuum of preselected magnitude in the reserve vacuum tank and the vacuum booster.

Abstract: A hydraulic actuating apparatus for opening and closing a movable cover (convertible top) of a vehicle includes a piston/cylinder device, a reversible, motor driven pump for supplying hydraulic fluid to the piston/cylinder device to cause it to open or close the vehicle cover, and an auxiliary manual pump for supplying hydraulic fluid to the piston/cylinder device in the event of failure of the reversible pump.

Abstract: A fail safe hydraulic system which includes a pressurized fluid storage which is capable of delivering fluid to the actuator to return it to its inoperative position should the actuator system suffer a loss of power and a apparatus for signaling a controller when the pressurized fluid storage has been charged with fluid, wherein fluid from the reservoir cannot be delivered to the actuator until the pressurized fluid storage has been charged with fluid.

Abstract: A control system for hydraulically controlling variable engine structures is disclosed in which the control system utilizes hydraulic fluid identical to that used by the aircraft hydraulic control circuit. A high pressure hydraulic pump, driven by the aircraft engine, may be interconnected with the aircraft hydraulic control circuit, or may be associated with a separate fluid reservoir, to supply pressurized hydraulic fluid to the actuators for controlling the variable engine structures. The engine control circuit also includes a hydraulic pressure modulator to modulate the pressure of the fluid supplied to the actuator and a selector connected between the high pressure pump and, the modulator and the aircraft control circuit to selectively supply the high pressure hydraulic fluid from the pump to either the engine control circuit, or to the aircraft control circuit.

Abstract: Vehicles having front and rear pairs of steerable wheels are sometimes provided with large springs for moving one pair of the wheels to a straight-ahead position during emergency steering. Large amounts of hydraulic energy are expended solely for the compression of such springs every time the pair of wheels are steered. A back-up steering control system (19) of the present steering control arrangement (10) has a servo valve (76) operative to control the flow of pressurized fluid from a back-up pump (60) to a steering control valve (21) which in turn controls the flow of pressurized fluid from the back-up pump to a hydraulic actuator (13) to hydraulically move a first pair of steerable wheels (11) to a straight-ahead position during emergency steering conditions.

Abstract: An engine-driven pump supplies pressurized hydraulic fluid to vehicle brake and steering circuits. A ground driven variable displacement pump controlled by a control circuit is de-stroked when the engine-driven pump is operational. The variable displacement pump includes a movable piston which divides a bore into a pilot chamber and a pump chamber. An outlet line with a check valve communicates fluid one way from the pump chamber to the vehicle circuits. An inlet line with a check valve communicates fluid one way from a reservoir to the pump chamber. A ground-driven rotatable cam member reciprocates the piston. A spring urges the piston towards the cam member and towards a full stroke position. A pilot line which communicates fluid pressure from an outlet of the engine-driven pump to the pilot chamber. When the engine-driven pump is operational the pressure in the pilot line moves the piston away from the cam member, thus de-stroking the variable displacement pump.

Abstract: A hydraulic brake booster (10) includes a housing (12) which defines a pressure chamber (16) and a piston (18) within the housing (12) is movable in response to pressurized fluid within the pressure chamber (16) to effectuate a brake application. The piston (18) encloses a storage chamber (60) and forms a pair of passages (80, 90) communicating the storage chamber (60) with the pressure chamber (16). A valve member (100) is disposed within the first passage (80) in order to control communication between the storage chamber (60) and pressure chamber (16). The valve member (100) permits pressurized fluid within the pressure chamber (16) to be communicated to the storage chamber (60) in order to charge the storage chamber (60). The valve member (100) also permits high pressure fluid above a predetermined pressure level within the storage chamber (60) to be communicated to the pressure chamber (16).