Abstract: A spool valve is provided. A valve housing has a pilot fluid passage, and a first portion and a second portion lengthwisely spaced apart from each other. A spool is movably inserted in the valve housing, and includes a plug able to enter the pilot fluid passage between the first portion and the second portion to change a flow area of the pilot fluid passage following movement of the spool. A hydraulic machine provides that when pilot fluid is supplied to the pilot fluid passage through the first portion, at least a portion of the supplied pilot fluid is provided to the holding valve through the second portion. The holding valve allows a flow of working fluid from the first chamber to the spool valve, and the spool moves to a third position to forward working fluid to the second chamber.

Abstract: A shovel according to an embodiment of the present invention includes a lower traveling body, an upper turning body pivotally mounted on the lower traveling body, a hydraulic pump mounted on the upper turning body, a hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump, an operating device used to operate the actuator, and a control device configured to control an acceleration/deceleration characteristic of the hydraulic actuator in response to an operation of the operating device depending on a work mode.

Abstract: Disclosed herein is a linear compressor. The linear compressor includes a piston, a cylinder, a frame, a first bearing gap formed between an inner circumferential surface of the frame and the outer circumferential surface of the cylinder, a second bearing gap formed between an inner circumferential surface of the cylinder and the outer circumferential surface of the piston, a bearing inflow passage and a bearing side passage formed in the cylinder such that fluid flows from the first bearing gap to the second bearing gap.

Abstract: A hydraulic system is disclosed. The hydraulic system may include a source of pressurized fluid; a tank; a hydraulic actuator including a first chamber and a second chamber; a first independent metering valve disposed between and fluidly connected to the source, the tank, and the first chamber of the hydraulic actuator; and a second independent metering valve disposed between and fluidly connected to the source, the tank, and the second chamber of the hydraulic actuator. Each of the first independent metering valve and the second independent metering valve may include a spool and a valve actuator disposed on one side of the spool. The valve actuator may include a push coil, a pull coil, and a force feedback mechanism configured to balance a force of the push coil and the pull coil.

Abstract: Methods and apparatus to bias spool valves using supply pressure are disclosed. An example apparatus includes a housing of a spool valve, the housing including a first port to receive a fluid at a supply pressure. The example apparatus further includes a spool within the housing. A position of the spool is to be selectively controlled via an input force acting on the spool, the position of the spool to define a path of a flow of the fluid through the spool valve from the first port to a second port of the housing. A biasing force is to bias the spool opposite the input force, the biasing force to be generated from the supply pressure applied to an end of the spool.

Abstract: The injection apparatus, which injects a molding material into a mold by operating an injection cylinder and fills the mold with the molding material, includes a plurality of actuating mechanisms that is connected to the injection cylinder. Each actuating mechanism includes an actuating cylinder that supplies an incompressible fluid to the injection cylinder, and a drive part that drives a piston of the actuating cylinder. In a low-speed step and a high-speed step for injecting the molding material, the piston of each actuating cylinder is driven forward, and hydraulic oil is supplied to the injection cylinder. In a pressure-increasing step, the pistons of the actuating cylinders are driven forward, and hydraulic oil is supplied to the injection cylinder. As the injection apparatus includes a plurality of actuating mechanisms, the speed and pressure of the injection cylinder can be increased without requiring high performance from the drive parts.

Abstract: An injection apparatus includes an actuating cylinder, an accommodating chamber, and a volume changing part capable of changing the volume of the accommodating chamber. The actuating cylinder has an operation chamber and a piston accommodated in the operation chamber, and supplies an incompressible fluid to the injection cylinder by forcing out the incompressible fluid inside the operation chamber with the piston. The accommodating chamber is connected to the operation chamber, and holds at least some of the incompressible fluid that flows out from the operation chamber due to the piston being pushed out. The volume changing part expands the volume of the accommodating chamber, at the latest simultaneously with the start of acceleration of the actuating cylinder, and stops the expansion of the volume when the operating speed of the piston of the actuating cylinder has reached a desired speed.

Abstract: A compressor including a hollow housing having a suction chamber, a discharge chamber, and a crank chamber formed therein. A first fluid flow path provided within the compressor facilitates a flow of the working fluid from the crank chamber to the suction chamber. A second fluid flow path provided within the compressor facilitates a flow of a mixture of the working fluid and a lubricating fluid from the crank chamber to the suction chamber, wherein the second fluid flow path is selectively opened and closed by an annular sleeve.

Abstract: A hydraulic system for a working machine includes a hydraulic actuator and a first hydraulic machine for supplying fluid to the hydraulic actuator. The hydraulic system further includes a hydraulic transformer for supplying fluid to the hydraulic actuator in parallel with the first hydraulic machine, and an accumulator for fluid. The hydraulic transformer includes a first port and a second port and the transformer is adapted to transform a first pressure and a first flow at the first port to a second pressure and a second flow at the second port. The second port of the hydraulic transformer is in fluid communication with the hydraulic actuator and the first port is in communication with the accumulator.

Abstract: A traction-type actuator includes a frame, a first actuating unit, a second actuating unit, a rotatable member and a traction member. The rotatable member is disposed on the frame. The first actuating unit and the second actuating unit are located at two sides of the rotatable member. The traction member has a strip shape and can be curved and wound. The traction member has two ends fixed to the frame and is in a tightened state. The traction member winds through the first actuating unit, and then winds on the rotatable member, and finally winds through the second actuating unit. When the first actuating unit is actuated, the second actuating unit will be towed, vice versa, the first actuating unit and the second actuating unit are push-pull by the traction member so that the rotatable member is turned clockwise and counterclockwise.

Abstract: An apparatus for hydraulically adjusting the blades of an impeller of an axial-flow fan, comprising an adjustment cylinder that on both sides of a piston displaceably disposed in the cylinder has a first chamber and a second chamber respectively provided with a connection to control oil lines connected to four-way valves. Not only a feed line leading to one of the control oil lines, but also a return line connected to the other control oil line, is each divided into two parallel branch lines. Two redundant four-way valves are provided, each being disposed in one of the parallel branch lines. Disposed in each branch line of each control oil line, between the respective connection and the respective four-way valve, is a seat valve that closes by spring force.

Abstract: An actuator using a fluid cylinder in which rigidity may be attained with a simple configuration, includes a fluid cylinder, a first choke valve device, and a second choke valve device. The first choke valve device is disposed between a fluid pressure source and a first chamber, and the second choke valve device is disposed between the fluid pressure source and a second chamber. An opening of a valve of a discharge valve mechanism included in each of the choke valve devices is set so as to be in inverse proportion to a target pressure in the chamber in which the fluid pressure is adjusted by the choke valve device.

Abstract: The invention concerns a hydraulic steering (1) with a steering unit (2) with feedback behavior, a steering motor (8) connected to the steering unit (2) via working pipes (L, R), a steering member (6) and a feedback suppression device (9), which is located in at least one working pipe (L, R). It is endeavored to change the feedback behavior of such a steering in a simple manner. For this purpose, the feedback suppression device (9) has a valve arrangement (10) with hydraulic control inlet (C).

Abstract: The invention concerns a hydraulic steering arrangement (1) with a supply connection arrangement (P, T), a working connection arrangement (A, B) connectable to a steering motor (5), a steering unit (6) located between the supply connection arrangement (P, T) and the working connection arrangement (A, B), and a steering valve (14) whose outlet is connected to the working connection arrangement (A, B). It is endeavored to keep the load of such a steering arrangement small. For this purpose, the steering unit (6) is made as an open-center steering unit, an inlet (20) of the steering valve (14) being connected to a pressure supply arrangement (22) that can be activated by an activation of the steering valve (14).

Abstract: A servo for hydraulically operating a brake band of an automatic transmission includes a housing having a bore engaging portion for engaging an existing servo bore in a case of the automatic transmission and an external portion for positioning externally of the servo bore, the external portion of the housing including an interior bore. The servo also includes a piston disposed in the interior bore of the external portion of the housing for reciprocating movement, the piston being externally remote from the servo bore and having an outer diameter greater than an outer diameter of the servo bore. An actuator rod for engaging and operating the brake band of the automatic transmission is attached to the piston to reciprocate with the piston. The servo connects to existing hydraulic circuits within the servo bore to supply pressurized fluid for operating the servo.

Abstract: The invention provides a method and a system for moving an element, e.g. a rudder of a ship or a wheel of a vehicle. The element is moved by a hydraulic fluid. According to the invention, an operator indicates a desired movement, and in accordance with the desired movement, at fluid is provided from at least three fluid providers each providing a share of the fluid in parallel streams and only considering the desired movement not the shares provided by the other fluid providers. The invention allows continuation of a steering task even if one fluid provider is disabled, and the invention allows the continuation even without having to notice that one provider is disabled. Accordingly, the invention provides an improvement and simplification relative to the known hydraulic steering systems.

Abstract: A fluid control or actuation system providing selective recruiting of actuators antagonistic to one another to provide variable output power, such as that used to drive a load. The actuators are intended to comprise different sizes, and to be operable with one or more pressure control valves capable of providing displacement of a non-recruited actuator without requiring active input to cause such displacement. Being able to selectively recruit different sized actuators to drive the load, and being able to displace non-recruited without active input, effectively incorporates a gearing function into the fluid control system.

Abstract: A hydraulic system comprises: a first fluid distribution line (A) and a second fluid distribution line (B) communicating with a stem chamber (11) of a double-acting cylinder (10) destined to move two reciprocally mobile parts; a third fluid distribution line (O) communicating with a single-acting cylinder (20) for blocking the mobile parts; a solenoid distributor (2) which intercepts the third line (O) and switches the third line (O) between a first position in which it pressurises the single-acting cylinder (20) and a second position in which it discharges the single-acting cylinder (20); a first bistable selector valve (7) sending in outlet a pressure signal when a pressure difference between the first line (A) and the second line (B) exceeds a certain value; a pressure sensor (8) communicating with the first selector valve (7) and associated to the solenoid distributor (2) such as to switch the solenoid distributor (2) into the second position when the fluid pressure coming from the outlet of the first

Abstract: The present invention relates to a hydraulic pressurization system, in particular for application to pressurization devices operating in accordance with the high hydrostatic pressure principle. In particular, the present invention provides a pressurization system for modifying the pressure in a pressurization device. The system comprising a first hydraulic circuit in which one or more primary pressure accumulators are connected to the pressurization device in controlled manner in order to permit a substantially incompressible fluid to be admitted to and removed from the pressurization device at a first pressure, the primary pressure accumulators being precompressed-gas pressure accumulators.

Abstract: For connection to a hydraulic power supply of a tractor, wherein the tractor comprises a plurality of hydraulic supply circuits, and wherein each hydraulic supply circuit comprises a pair of quick couplers for connecting the hydraulic supply circuit to a hydraulic device, a hydraulic motor apparatus comprises a first pair of hydraulic lines adapted for connection to the quick couplers of a first hydraulic supply circuit; a second pair of hydraulic lines adapted for connection to the quick couplers of a second hydraulic supply circuit; and a hydraulic motor connected to both the first and second pairs of hydraulic lines such that fluid can flow from both the first and second hydraulic supply circuits through the hydraulic motor to drive the hydraulic motor.

Abstract: A driving system using an intercalation substance as a novel mechanochemical system includes an actuator using the intercalation substance and driven by exchange of solutions or by changing concentration of a solution, and a solution supplier that supplies the actuator with the driving solution or solutions. The actuator is composed of one or more cylindrical or fiber-shaped elements each extending in the expanding and contracting direction of the intercalation substance, or one or more film-shaped or plate-shaped elements each having a major surface extending vertically of the expanding and contracting direction of the intercalation substance. The driving system is used as artificial muscle, for example.

Abstract: An hydraulic system comprising an air sucking hydraulic circuit 8, an air sucking control valve 5, and a check valve 6 provided in or before and after the air sucking hydraulic circuit 8, allowing a flow of a hydraulic fluid from the air sucking control valve 5 to the hydraulic actuator 4 and preventing a flow of a hydraulic fluid from the hydraulic actuator 4 to the air sucking control valve 5.

Abstract: The present invention concerns a method for controlling the speed of motion of a hydraulically operated machine, an operating system and a control device of the machine. The flow line (3) of the medium from the pump (2) to the machine (1) is divided into two branches (10, 11). By means of a valve (8), the second branch (11) can be set to feed medium either to the machine (1) or to return the medium to the tank (4) of the pump. Such a flow is led to the second valve (8), that at a speed of rotation of the pump lower than the highest speed of rotation, the difference between the flow supplied by the pump and the flow through the second branch produces the desired slowest speed on motion of the device. When the valve (8) is set to return the medium to the tank (4) of the pump, the flow from the pump (2) is adjusted by changing the speed of rotation of the pump.

Abstract: A pneumatic sequential control valve for successive aeration and deaeration of two consumers, wherein for purposes of aeration compressed air is initially applied to the first consumer and only subsequently to the second consumer, and for deaeration the compressed air is initially let off from the second consumer and only subsequently from the first consumer, comprises a valve body with connections for a compressed air line and a first consumer and second consumer, wherein a cavity is provided in the valve body, bore holes extend from the connections for the consumers and for the compressed air line to this cavity.

Abstract: A system for remotely controlling an undersea device. The system employs a gas-pressurized liquid reservoir that can be recharged from at least one replaceable gas bottle. A pressure-regulating valve is employed to control the pressure of the liquid leaving the reservoir. A number of one-shot units, each in the form of a squib-actuated valve coupled with a piston accumulator, are employed to create a hydraulic pilot for a hydraulic direction control valve. The control valve functions to direct pressurized liquid from the reservoir to a hydraulic actuator or other type of hydraulic device.

Abstract: A hydraulic control circuit for a hydraulic actuator, including a high-low pilot valve having a sensing port for connection to a flow line. A single pressure line connects the high-low pilot to a hydraulic actuator. A second line connects the high-low pilot to a reservoir. A normally closed relief valve is connected to the single pressure line for relief of excessive pressure. A normally closed override valve is connected to the single pressure line for manual override of circuit controls. A pump is connected to the single pressure line for pressuring the single pressure line. The hydraulic control circuit has a normally open time out valve on the single pressure line, the time out valve being set to close a pre-set time interval after being manually activated, to isolate the high-low pilot, from the single pressure line to the hydraulic actuator, until the time out period has elapsed. The override valve is connected to the single pressure line between the time out valve and the hydraulic actuator.

Abstract: A dual function throttle control system is disclosed for earthmoving machines. The throttle control system includes a hand lever that is electrically connected to a proportional directional hydraulic valve. Rotation of the hand lever controls actuation of an engine speed actuator and thus the speed of the engine. A foot pedal is connected through a three position spring-centered hydraulic valve to the engine speed actuator. The direction of flow of hydraulic fluid through the three position spring-centered hydraulic valve is controlled by the position of the hand lever. When the hand lever is set at the lowest speed setting, rotation of the foot pedal in a first direction increases the engine speed. When the control lever is set at the highest speed setting, rotation of the foot pedal in the first direction decreases the speed of the engine. Thus, the foot pedal operates both as a decelerator or an accelerator depending on the position of the hand lever.

Abstract: A flow reinforcement directional control valve that is capable of reinforcing a pressure fluid to two actuators, can be formed as compact and yet is capable of flowing a return fluid out of a single actuator into a tank is provided, wherein a valve block 20 has a spool bore 21 in which a first spool (22) and a second spool (23) are slidably inserted; in which the first spool (22) is adapted to be held at a neutral position thereof by a first spring (36) and to be displaced by a pressure fluid in a second pressure receiving chamber (47) to a position thereof for supplying the fluid to an actuator; and in which the above mentioned second spool (23) is adapted to be held at a neutral position thereof by a second spring (41) and to be displaced by a pressure fluid in a first pressure receiving chamber (42) to a position thereof for flowing a return fluid into a tank and to be displaced by a pressure fluid in a third pressure receiving chamber (52) to a position thereof for supplying a pressure fluid to an actuato

Abstract: An automatically controlled braking system comprising a pneumatic vacuum servo and a pneumatic solenoid valve capable of selectively connecting the serov to first or second sources of pressure. The solenoid valve includes a flap valve which is subjected to a suction force proportional to the difference between the first and second source of pressured and acts in the same direction as an electromagnetic actuating force. Elastic means act on and apply a greater force to the flap valve to oppose the suction force. A current generator supplies a current having a predetermined maximum intensity to the solenoid to develop an actuation force overcome the elastic force and effect actuation of the vacuum servo.

Abstract: A steering control system for an autonomous machine has a manual steering control valve for directing fluid from a pump to either a head end chamber or a rod end chamber of a hydraulic steering actuator. In one embodiment, an electrically actuated steering valve device is disposed in series flow relationship between the pump and the manual steering control valve and is operative to direct fluid from the pump to the head end and rod end chambers. In another embodiment, a electrically actuated device mechanically actuates the manual steering control valve for steering the machine.

Abstract: An exhaust manifold (25) of a fluid power and control system, the pressure of which is varied when the fluid motor (10) is subjected to a bidirectional positive or negative type load (W). This exhaust manifold (25) is also supplied from a source of exhaust manifold pressurizing oil (29) other than the system pump (18). This source of exhaust manifold pressurizing oil (29) may include a flow amplifying device (57) which is activated when the fluid motor (10), in the form of a cylinder, moves a load in the direction of its piston rod end (11) and when the piston rod end (11) of cylinder (10) is subjected to a negative load pressure and when the pressure in the exhaust manifold (25) drops below a certain minimum preselected level.

Abstract: A vacuum type brake booster includes a housing including a front shell and a rear shell in which a constant negative pressure chamber and a variable pressure chamber are defined by a power piston and a diaphragm, a partition for dividing the variable pressure chamber into a first variable chamber next to the constant negative pressure chamber and a second variable chamber, a normally opened valve mounted on the partition for establishing or interrupting of the fluid communication an output rod movable together with the power piston, an input rod for urging the output rod, a valve mechanism disposed with in the power piston to be operated by the input rod and used for controlling the differential pressure between the constant negative pressure chamber and the variable pressure chamber by controlling the fluid communication of the second variable chamber with the constant negative pressure chamber and the atmosphere and a normally closed valve mounted on a rear shell and the partition and disposed between the f

Abstract: The hydraulic cylinder comprises a cylinder jacket (1), a piston-rod guide flange (2), and a cylinder bottom (3). Disposed within the cylinder are a primary piston (4) provided with a piston rod (6) and a secondary piston (11) connected to two plungers (7, 8). The plungers enter two bores (5, 6) in the primary piston. Two spring-biased (19, 20), openable check valves (17, 18) are disposed in the cylinder bottom. In each valve there is a bore (41, 42) connecting the front and rear sides of the valve. The rear portions (24, 25) of the valve chambers (26, 27) each contain a spherical unstopping piston (21, 22). Two supply ducts (23, 30) for the hydraulic fluid are connected to the valve chambers, these chambers in turn having supply ducts at various locations (36, 40, 45) of the interior of the cylinder. A very compact construction is possible for the hydraulic cylinder with pressure transmission.

Abstract: A switch-over valve 6 is provided in a pressure circuit 31 between a hydraulic pump 2a and a clutch 7, and a pressure limiting valve 5 is provided between a reflux circuit 9 for the valve 6 and the pressure circuit 31. The clutch actuating hydraulic circuit includes another hydraulic pump 2b, and a switch-over valve 8 for switching over a discharged fluid of the hydraulic pump 2b. A downstream side of the switch-over valve 8 is connected to the pressure circuit 31 and to the reflux circuit 9. Consequently, when the clutch is engaged or disengaged, the discharged fluid of the hydraulic pump 2b is combined with the discharged fluid of the hydraulic pump 2a so as to increase the flow rate to the clutch 7.

Abstract: A hydraulic control valve which is equipped with two direction change-over valve groups individually having traveling change-over valves, and first and second hydraulic pumps corresponding to those direction change-over valve groups. The traveling section valve of one of the change-over groups is equipped with a communication valve. Each section valve has its valve body formed therethrough with signal conduits individually extending perpendicular to spool bores. The two traveling section valves are formed with annular grooves in spool bores positioned to correspond to said signal conduits. The individual working machine section valves other than the traveling section valves are formed with annular grooves in the spool portions corresponding to the signal conduits to provide the communications between the upstreams and downstreams of the signal conduits only when the spools are in their neutral states.

Abstract: A liquid pressure booster which may be used in a brake booster or the like is disclosed. A second supply passage is provided which allows a power chamber of the liquid pressure booster to communicate with an external source of pressure fluid without passing through a valve mechanism of the liquid pressure booster. A first open/close valve is operative to open or close the second supply passage, and a second open/close valve is effective to open or close a discharge passage of the liquid pressure booster. A controller controls the first and the second open/close valve. With this construction, the controller may be caused to open the first valve and to close the second valve to allow the pressure fluid to be introduced into the power chamber through the second supply passage without depressing a brake pedal to cause a forward movement of an input shaft. In this manner, the liquid pressure booster can be operated automatically, and thus such booster can be advantageously used in an automatic braking unit.

Abstract: A means for receiving and subsequently emptying hydraulic fluid from a hydraulic system is described. It comprises a working cylinder (1) and a supply conduit (8) disposed between a pump and the working cylinder for supplying hydraulic fluid at high pressure within a predetermined interval. According to the invention the means also comprises a receiving cylinder (12) with a piston (19), which on one side defines a liquid space (22) for the receipt of hydraulic fluid from the working cylinder with an emptying pressure essentially lower than said high pressure, the piston (19) on the other side defines a chamber (21) containing gas at low pressure, and a high-pressure cylinder (13), which has a liquid space (28) and a plunger (30) movable therein, said liquid space (28) being connected to said supply conduit (8) to receive and return hydraulic fluid at high pressure therefrom and thereto, respectively.

Abstract: A remote control modification (11) for a hydraulic steering system (13) of the type used to steer underground loaders and the like is disclosed. The remote control modification comprises a bidirectional, spring-loaded remote control valve (51) connected in parallel with the bidirectional, spring-loaded control valve (19) that normally responds to steering inputs created by the manual movement of a steering arm (25). The remote control valve (51) has outlet ports (75 and 77) that are smaller than the outlet ports (39 and 41) of the manual control valve (19). Movement of the piston of the remote control valve (51) is controlled by a slave hydraulic actuator (53). The flow of hydraulic fluid to the slave hydraulic actuator (53) is controlled by a solenoid-actuated valve (59). The solenoid (61) of the solenoid-operated valve (59), in turn, is controlled by a receiver (63) that responds to radio frequency control signals (105) generated by a remotely located transmitter (65).

Abstract: An open/close valve which opens or closes a passage providing a communication between a valve mechanism and a constant pressure chamber of a brake booster is disclosed. The valve comprises a valve seat formed in surrounding relationship with a passage, a valve element disposed within a casing which is mounted on the valve body so as to be reciprocably movable therein, and a pressure chamber defined within the casing for urging the valve element toward the valve seat. Pressure fluid supply means supplies a pressure fluid into the pressure chamber from the outside of a shell to cause the valve element to be seated upon the valve seat. As compared with the solenoid-operated valve, an axial size of the open/close valve can be reduced while avoiding any heating effect.

Abstract: The hydraulic piston cylinder assembly which operates the governor of a turbine which powers a hydropower generator has a servo valve capable of flowing only a portion of its flow requirements during normal low power fluctuation conditions of the turbine's operation. During high power fluctuation conditions of the turbine's operation, such as during start-up, hydraulic fluid also flows to and from the piston and cylinder assemblies through high flow pressure and return conduits that bypass the servo valve. Control of fluid flow in the high flow conduits is accomplished by a proportional throttling valve located in the high flow return line. The servo valve and proportional throttling valve together have a flow capacity which is equal to the flow requirements of the piston and cylinder assembly and they are both actuated by the same electronic controller.

Abstract: A flow amplifier in the hydraulic steering system of a transport vehicle comprises a three-position hydraulically operated hydraulic directional control valve having a single sliding spool valve and internal hydraulic pilot lines connected, when in the crossover position, to external portholes made in a sleeve of the three-position hydraulically operated hydraulic directional control valve provided with plungers spring-loaded on their outside end faces. The flow amplifier incorporates also a pair of intensifying chokes, a air of pilot chokes, and a pair of regulating chokes made in the sliding spool valve with a possibility of varying their restriction areas along the direction of travel of the sliding spool valve.

Abstract: A system for controlling the amount of torque applied by a hand-held power tool to fasteners during an assembly of parts. In the preferred embodiment, a torque control circuit is operated by air to deliver a selected volume of air under selected pressure to the tool and to stop the delivery of air when the desired torque has been applied to the fastener. The system can operate one or more torque control circuits. Visual color coded signals can be used to indicate the active circuit and the tools intended to be used with that circuit.

Abstract: A brake actuating device for automotive vehicles comprises a hydraulic brake force booster and a hydraulic tandem master cylinder to which pressure is applied by the brake force booster and which is in communication with the hydraulic wheel brake circuits. The hydraulic piston of the brake force booster applies pressure to the primary master piston of the said hydraulic tandem master cylinder. Pressure is applied to the hydraulic piston of the hydraulic brake force booster from a hydraulic pressure source through a normally closed opening valve which, through a function electronic unit receiving by way of a control input in the form of a guide quantity, an input signal representative of the pedal travel is alternately opened and closed. Accordingly the hydraulic brake pressure build-up is effected in accordance with a predetermined function stored in the function electronic unit between pedal travel and brake pressure with no lost motion of the brake pedal.

Abstract: In a pneumatic actuator wherein air pressure in a diaphragm compartment (38) is changed by controlling solenoid valves (39, 39 and 41) thereby to output a displacement; an intake solenoid valve (39) has a spring (30h) which penetrates a center part of a fixed iron core (39e) and urges a movable iron core (39f), and the solenoid valves (39, 39 and 41) are mounted on a housing (31) in a triangular disposition with terminal side thereof faced to the housing (31), and besides, one of terminals of each solenoid valve (39 or 41) is secured with each other at a center part of the triangular disposition, and the other terminals are disposed outward of the triangular disposition.

Abstract: A hollow cylindrical amplifier driven actuator spool has first and second vortex chambers divided by an internal piston. A shaft is attached to the pistion and extends out the cylinder. Fluid logic controls the fluid flow in the vortex chambers so that the resulting chamber pressure causes the piston to accelerate. The use of beam deflection amplifiers for fluid control in connection with a push-pull vortex amplifier arrangement results in a device with low fluid flow leakage.

Abstract: A hydraulic booster equipped with an emergency accumulator, wherein reaction and power pistons are slidably fitted in a housing such that the two pistons define a power chamber therebetween. The booster includes a control valve having a normally closed power chamber passage formed therethrough so as to communicate with the power chamber, and a normally open passage connecting a pump and a reservoir. The valve is operated in response to an operation of the reaction piston, so as to restrict a fluid flow through the normally open passage from the pump toward the reservoir, thereby raising a pressure of the fluid delivered from the pump, and open the power chamber passage to apply the raised pressure to the power chamber. A pressure reducing device is provided in the power chamber passage, for reducing a fluid pressure in the power chamber passage and applying the reduced pressure to the power chamber, at least while a rate of fluid flow through the power chamber passage is higher than a preset limit.

Abstract: The drive is controlled such that reduced pressure is applied during a forward motion phase and venting flow from the drive is used as dynamic control pressure to hold off application of full driving pressure until, through physical impediment, piston movement stops. This way rebounding is prevented and strong holding pressure (e.g. on welding electrodes) is made available after a low power motion phase.

Abstract: The present invention is directed to a hybrid hydraulic system for a work vehicle having both an open center hydraulic circuit and a close center hydraulic circuit. An internal combustion engine drives a fixed displacement pump and a variable displacement pump. The fixed displacement pump provides hydraulic fluid to the open center circuit which directs hydraulic fluid to a steering circuit and the working circuit through a priority valve. The variable displacement pump provides hydraulic fluid to the close center circuit which directs hydraulic fluid to a braking circuit and a pressure reduction circuit. The pressure reduction circuit directs hydraulic fluid to a pilot control system, a clutch cutoff and a differential lock out. Both pumps receive hydraulic fluid from a common sump and a common suction line. The braking circuit comprises two independent braking circuits.

Abstract: A hydraulic drive system for a construction machine in which a hydraulic circuit has at least one hydraulic pump, at least first and second hydraulic actuators driven by a hydraulic fluid discharged from the pump, and at least first and second directional control valves connected to the pump in parallel with each other for controlling flows of hydraulic fluid supplied from the pump to the first and second actuators, respectively, and a control unit is responsive to first and second operation signals for driving the first and second actuators, respectively, to produce first and second control signals for actuating the first and second valves and deliver such control signals thereto, respectively, each of the first and second valves having a degree of opening changed in accordance with a level of the corresponding one of the first and second control signals for controlling a flow rate of hydraulic fluid supplied to the corresponding one of the first and second actuators.

Abstract: Method and apparatus of controlling and positioning a fluid actuator by supplying pressurized fluid to right and left actuating chambers of the actuator through an on-off control valves. To drive and position the actuator rapidly and accurately, the actuator can be driven at a higher speed by an initial driving force until it reaches near the desired position and continuously moved at a low speed by gradually increasing the fluid pressure to be supplied to the right and left actuating chambers of the actuator. The initial driving force in the high-speed range becomes maximum when the pressure is applied to one of the right and left actuating chambers while at the same time the other actuating chamber is exhausted. In the low-speed range and near the target position, the one actuating chamber is continuously supplied with the pressure while at the same time the other actuating chamber is gradually closed.