Abstract: A hydraulic door opener provides a simplified mechanism for two-speed operation and for controlling the release of a brake that normally holds the door against movement. The mechanism includes a bypass valve between a fluid reservoir feeding the pump and the close control line running between the pump and the hydraulic motor. Fluid flow is directed from the close control line so that the door can be closed at slower rate than it is opened using a single speed motor. A brake control valve releases the brake when the control lines are pressurized.

Abstract: A system operated by what is referred to as a clutch pedal, which adjusts the traction power of an infinitely variable, hydrostatic-mechanical transmission. The transmission contains at least one pump (1) and at least one motor (2), arranged in a hydraulic circuit. In order to reduce the traction power, pressure is leaked between the two sides of the motor (2) by reducing the pressure at the control parts (14a) of two proportional valves (14, 15) in respective lines bridging the motor (2). The control parts (14a) of the proportional valves (14, 15) are connected via a shift valve (19) to an intermediate valve (24), the closing force of which is reduced as the clutch pedal (26) is opened by means of a closing spring (36).

Abstract: A hydrostatic vehicle drive has a control (5) for controlling an output torque of the drive and another control device (5) for controlling the output torque of a hydrostatic drive, the control device (5) having a controllable pressure-limiting valve (6) by means of which the working pressure can be adjusted and which is used for sensitive control of the output torque of a hydraulic motor (3). The pressure-limiting valve (6) can be controlled by a proportionally adjustable pressure-reducing valve (7).

Abstract: A loop flushing circuit for a hydrostatic transmission module includes a three position, three port pilot pressure operated loop flushing valve having a first inlet port fluidly connected to the first system pressure line, a second inlet port fluidly connected to the second system pressure line and an outlet port fluidly connecting the loop flushing valve to the case drain through a drain line having a drain orifice therein. A loop flushing and lubrication line fluidly connected to the drain line upstream of the drain orifice extends within the casing and has an open end directed toward the rotating elements of one of the pump and motor. The three position valve has an intermediate position operatively located between the opposite end positions. System pressure from at least one of the first and second system pressure lines is always routed to the loop flushing and lubrication line through the valve regardless of which of the three positions the valve is in.

Abstract: A fluid control system (50) is provided for a work machine (10) having first and second compacting drums (14,16). First and second hydraulic motors (28,32) are connected in series and power first and second vibratory mechanisms (26,30) located within the first and second compacting drums (14,16). A control valve (60) supplies pressurized fluid to the first hydraulic motor (28). The pressurized fluid is transferred through a bypass circuit (74) around the second hydraulic motor (32). A sequencing device (80) closes the bypass circuit (74) transferring the pressurized fluid to the second hydraulic motor (32) after actuation of the first hydraulic motor (28).

Abstract: The present invention provides a lubrication system and method for a work vehicle having a lubricant reservoir and a lubricant using attachment that comprises a single bi-directional pump/motor set, a single three-position/four way control valve that directs hydraulic fluid, through one of two flow limiting devices, to the hydraulic motor to power the pump. In one mode the pump, at a slow rate of approximately one gallon per minute, moves lubricant from the reservoir to the attachment. In the other mode the pump, at a fast rate of approximately six gallons per minute, moves lubricant from a lubricant source to fill the lubricant reservoir. The flow limiting devices can be either a fixed flow rate device or a multiple flow rate device as selected by an operator of the work vehicle. The various positions of the control valve can be actuated by a solenoid, a hydraulic cylinder, a pneumatic cylinder or a cable, all of which can be operated from the cab of the work vehicle.

Abstract: The present invention relates to a speed changing device for a hydraulic driving apparatus and a speed change control method thereof, which provide excellent controllability, traveling efficiency, and reliability without occurrence of cavitation. To this end, the device comprises a shifter selected position sensor (63a) for detecting a shift lever change, a motor rotational speed sensor (52) for detecting a rotational speed of a hydraulic motor (50), and a control device (60); and the control device (60) judges and controls either a powering control or a brake control, based on the change of the shift lever selection and on the comparison of the detected motor rotational speed with a memorized motor rotational speed. In addition, a two-stage back pressure valve (23) can be provided between a directional control valve (21) and an oil tank.

Abstract: A hydraulic system for propelling a vehicle, and with the system arranged with a pump and vehicle drive motors and valves and pilot lines. The operator can select an all-wheel drive or a lesser number of wheel drives. Also, there is a system automatic response to certain conditions of vehicle drive, whereupon the system activates to alter the drive to the various vehicle wheels, including changing from a four-wheel drive mode to a two-wheel drive mode. Further, the operator can override the system's own activation and thereby establish the two-wheel drive mode desired.

Abstract: The invention concerns a hydraulic device for controlling the hydraulic-fluid flow to and from a single-acting cylinder (3) on which a load (4) acts. Located between a pump (1) and the cylinder (3) is a controlled valve array (5) which, together with a controlled on-off valve (9) which in one position allows hydraulic fluid to pass back into the reservoir (2), controls the flow of hydraulic fluid to and from the cylinder (3). In order to be able to lift the piston slowly and at constant speed in the cylinder (3), independently of the load (4) acting on the piston, the invention calls for a throttle (6) and a non-return valve (7) to be connected in series, by-passing the valve array (5). A pressure regulator (10) maintains the pressure difference through the throttle (6) constant and feeds the fluid not required to maintain the pressure difference through the throttle (6) back to the reservoir (2).

Abstract: A steering power assist apparatus is comprised of a power cylinder whose operation is controlled by the a flow rate control valve, a first control valve and a second control valve. The flow rate control valve is connected to a discharge side of a hydraulic pump and controls the amount of the hydraulic oil to be supplied to the first and second control valves according to a load pressure. The first control valve constituted by choke valves is disposed downstream of the flow rate control valve and controls the amount of the hydraulic oil supplied to the second control valve according to a steering torque. The second control valve constituted by choke valves is disposed downstream of the flow rate control valve and controls the amount of the hydraulic oil to the power cylinder according to a steering torque. The choke valves of the second control valve are fully closed after the choke valves of the first control valve are fully closed.

Abstract: A hydraulic power unit for an auto-hoist lift having improved noise characteristics and a more compact design. A motor and pump driving the power unit are located inside a hydraulic fluid reservoir to thereby reduce the amount of noise reaching the immediate vicinity of the power unit. The motor and pump are submerged in the hydraulic fluid to advantageously utilize the hydraulic fluid to cool the motor. The power unit may further incorporate a delay valve for reducing the start-up torque load on the motor, thereby allowing the motor to be sized for normal operating requirements rather than oversized for start-up requirements.

Abstract: A variable flow hydraulic system including a fixed displacement pump and a variable displacement pump for supplying pressurized hydraulic fluid in a machine is disclosed herein. Along with the dual pumps, the system includes a reservoir, a flow sensitive unloading valve, and a conduit system for distributing fluid flow between the system components. The reservoir stores fluid for use in a work circuit with an actuator for performing work in response to applied fluid flow. The fixed and variable displacement pumps are driven by a power source (e.g., an engine) to provide a fixed and a variable fluid flow, respectively. The variable flow is applied to the work circuit. As for the fixed flow, the unloading valve switches the fixed flow to either bypass or be applied to the work circuit in response to a flow signal, which depends upon the fluid flow being applied to the work circuit.

Abstract: In machines having a bucket that is capable of carrying a load of material, it is well known that when the machine encounters a bump or other obstacle that the effects thereof may result in a shock or jolt being subjected to the machine due to the sudden change in forces acting on the actuator of the lift mechanism. In the subject invention, an accumulator arrangement is connected through a first valve mechanism to the loaded end of an actuator to provide a cushion or damping of the sudden changes in the forces. The first valve mechanism controls the magnitude of the damping in response to the rate of flow between the actuator and the accumulator arrangement. This is accomplished by sensing the pressure drop across a flow restriction mechanism located upstream of the first valve mechanism and controlling the degree of fluid communication between the actuator and the accumulator arrangement in response thereto.

Abstract: A hydraulic power steering apparatus includes a pump for discharging pressurized operation fluid, a power cylinder for generating assisting force, a control valve connected to the pump via a fluid path for receiving the operation fluid from the pump and adapted to supply the operation fluid to the power cylinder in accordance with operation of a steering wheel, a rubber hose disposed in the fluid path. A check valve is disposed between the rubber hose and the control valve. Since reverse flow of the operation fluid due to input of kick-back force is prevented, tires to be steered are prevented from undesirably steered against the driver's intention. Further, a pressure relieving mechanism is provided to relieve part of the operation fluid when the check valve operates. Therefore, the oil pressure within the power cylinder and the control valve is prevented from increasing excessively, so that the oil pressure within the pump does not reach a preset relief pressure.

Abstract: A hydraulic motor driving apparatus includes a directional control valve for supplying discharge pressure fluid from a hydraulic pump into a first or second port of a hydraulic motor and returning the hydraulic fluid from the second or first port into a tank, and a pilot pressure applying valve for controlling the directional control valve. The directional control valve is urged to its neutral position by springs, to its first position by hydraulic pressure against its first pressure receiving portion and to its second position by hydraulic pressure against its second pressure receiving portion. Discharge pressure fluid from the hydraulic pump is supplied via a check valve into the first and second ports of the hydraulic motor when the directional control valve is at the neutral position. The discharge pressure fluid is supplied into the first port of the hydraulic motor and a hydraulic pressure fluid of the second port flows into the tank, when the directional control valve is at the first position.

Abstract: A fluid control system for powering vehicle accessories includes a pump for generating a supply flow of hydraulic fluid. The system also includes a fluid valve assembly having a housing which includes an inlet, a first outlet, a second outlet, and a third outlet defined therein. The inlet is in fluid communication with the supply flow of fluid. The fluid valve assembly provides (1) a first fluid path between the inlet and the first outlet, (2) a second fluid path between the inlet and the second outlet, and (3) a third fluid path between the inlet and the third outlet. The system also includes a fan motor for rotating an engine cooling fan. The fan motor is in fluid communication with the first outlet. Moreover, the system includes a steering control circuit which is in fluid communication with the second outlet. The system further includes a reservoir which is in fluid communication with the third outlet. A method of controlling fluid flow between a plurality of vehicle components is also disclosed.

Abstract: An energy recovery device, in particular of static and kinetic energy, has at least one hydraulically controlled working cylinder (110) or a hydraulic engine (210) that moves tools back and forth, preferably up and down. The working cylinder (110) or the hydraulic engine (210) can be connected to a hydraulic circuit (132) with a pump (134) and to a hydraulic accumulator (138) by a connection line (136). The connection line (136) contains two hydraulically controlled check valves (140, 142) controlled by a control unit, in particular a distributing valve (144), depending on the displacement of the tools or on the state of motion of the working unit. This energy recovery device does not have the disadvantages due to the use of conventional cartridge valves, and is cheap and reliable to operate.

Abstract: A reverse rotation preventing apparatus for a hydraulic actuator includes a hydraulic actuator for driving an inertia member, a main valve which is switched to a driving position in which a pressure oil is supplied to one of first and second ports of the hydraulic actuator and another one thereof is communicated with a tank and to a neutral position in which the first and second ports are shut off, a relief valve adapted to flow out a pressure oil in the first or second port to the tank at a time when a pressure on the side of the first or second port is higher than a set high pressure, a suction valve adapted to suck the pressure oil to the first or second port at a time when the pressure on the side of the first or second port is negative, and a reverse rotation preventing valve adapted to communicate the first and second port sides with the tanks respectively at a time when the pressure on the sides of the first and second ports is higher than a set pressure which is a pressure lower than the set high pres

Abstract: A hydraulic system for a construction machine includes a hydraulic pump driven by a prime mover, actuators driven by a hydraulic fluid delivered from the hydraulic pump, flow control valves for controlling flow of the hydraulic fluid to the actuators and operation means for operating the flow control valves. A relief value sets a relief pressure for limiting the maximum delivery pressure of the hydraulic pump and relief pressure change means increase or decrease the relief pressure set by the relief valve. The relief pressure change means automatically increase or decrease the relief pressure in accordance with the input amount of the operation means.

Abstract: A hydraulic system for driving an axial piston type hydraulic motor wherein a swash plate can tilt at a right angle relative to a shaft.

Abstract: A hydraulic control for a dividing machine tool, in particular a shear or cutting press, in which a damping device is provided in order to counteract a sudden downward movement of the working piston upon the cutting through of a workpiece during an operating stroke.

Abstract: A motor vehicle hydraulic system including a power steering pump, a reservoir, a steering assist fluid motor, and a second fluid motor for a radiator cooling fan. A flow control valve remote from the power steering pump divides the total fluid flow from the power steering pump into a high flow branch and a low flow branch. Fluid circulates in the low flow branch at a substantially constant flow rate for a proportional control valve for the steering assist fluid motor and returns to the reservoir through an unrestricted tubular boss on the reservoir. Fluid in the high flow branch issues as a jet stream from a nozzle on the reservoir into a venturi passage submerged in fluid in the reservoir. The venturi passage is connected to an inlet port of the power steering pump. The jet stream aspirates fluid from the reservoir into the venturi passage. The kinetic energy of the jet stream is converted into superatmospheric pressure at the inlet port of the power steering pump to suppress cavitation.

Abstract: A hydraulic system for a mobile machine, in particular a wheel loader, has a longitudinal oscillation damping function. The hydraulic system has at least one hydraulic cylinder (13) with which a tool can be operated and whose inner space is divided by a piston (15) into two pressure chambers (17, 18); a stop valve (12) which connects one of the two pressure chambers (17, 18) to a hydraulic reservoir (42) which can be filled via a filling pipe; and a distributing or directional control valve (11) with a spool or slide valve (40) for the separate pressurization of the two pressure chambers (17, 18) in the hydraulic cylinder (13) and/or for connecting them to a tank (29). To facilitate low-cost and space-saving construction of a system of this type, the stop valve is incorporated in the distributing valve (11) in such a way that the hydraulic reservoir (42) and the first pressure chamber (17) of the hydraulic cylinder (13) can be connected to each other via the spool valve (40) of the distributing valve (11).

Abstract: An automatic hydrostatic transmission in which two vane pumps have their pumping chambers coupled together in a closed circuit with a constant volume of hydraulic fluid, the volume of each pump being changed by the axial displacement of a moving side of the chamber and the respective rotor toward and away from a diaphragm through which the vanes can extend so that either pump can act as the displacement inducer or as the driven member. One of the rotors has a nut provided on a large-pitch screw for automatic adjustment of the pump chamber volume in accordance with load conditions while the other moving side assembly has a key and keyway connection to its shaft.

Abstract: An engine/pump control device for loaders is disclosed. The control device controllably distributes the output power (rotating force) of an engine to the travelling and working units of a loader in accordance with operational conditions of the loader, thus remarkably improving work efficiency of the loader. When the loader performs an operation requiring a high tractive force prior to the driving force of the working members, the control device opens the unloading valve thereby partially returning the output fluid of a hydraulic pump to a return tank while transmitting the surplus output power of the engine to the traveling unit. Meanwhile, when the loader performs an operation requiring a high driving force of the working members prior to the tractive force, the control device closes the unloading valve, thereby totally supplying the output fluid of the hydraulic pump to the actuators in order to generate a high moving speed of the working members.

Abstract: A hydraulic emergency circuit for a hydraulically-operated friction clutch disposed as a part as an electro-hydraulic clutch control between an internal combustion engine and a transmission has a hydraulic pump provided for supplying at least one working line and connected with a power take-off shaft of the internal combustion engine, a throttle valve disposed in the working line, two control lines branching off upstream and downstream of the throttle valve, and a switch valve connected with the control lines and provided for controlling and operating a supply of pressure for the friction clutch, the control line upstream of the throttle valve being connected to a first control input of the switch valve, the control line disposed downstream of the throttle valve being in hydraulic connection with a second control input of the switch valve which is located approximately opposite to the first control input, and a restoring string disposed on a control piston side adjoining the second control input.

Abstract: A hydraulic power steering apparatus includes a fluid pump, a power cylinder, a reservoir, and a control valve connected to the pump via a supply passage including a high pressure hose and connected to the reservoir via a drain passage. The power steering apparatus also includes a bypass passage provided between the supply passage and the drain passage, and a check valve which is disposed in the bypass passage to allow operation fluid to flow only in a direction from the drain passage to the supply passage. The power steering apparatus can supply a sufficient amount of operation fluid to the power cylinder even when a steering wheel is abruptly turned or when an opposing force is input from a tire.

Abstract: An air turbine flow restrictor comprises a sensor for determining the rotational velocity of the turbine wheel. In response to a detected speed above a predetermined threshold, particles are injected into the inlet airstream. In one embodiment of the invention, the particles are metal disks. The disks, carried by the airstream become lodged in the nozzles of the air turbine, thereby restricting the flow of air to the turbine wheel.

Abstract: A switching device controlling at least one hydraulically operating apparatus has two check valves working in opposition to one another in a feed conduit and a discharge conduit, respectively. The conduits are connected to the operating apparatus, as well as to a pilot valve. Two openable nonreturn valves are connected parallel to the two check valves. The control line of one openable nonreturn valve is connected to the blocking connection of the other openable nonreturn valve. The switching device is especially for controlling a hydraulic cylinder to provide a float setting at low cost, with reliable operation, and with few components.

Abstract: The variable speed drive mechanism includes an input member (17) and an output member (18), each rotatable within a housing (11) filled with fluid. The input and output members each have helical vanes (26) that are in a close running fit with sleeves (21, 22) within the housing. The amount of axial overlap of the sleeves with the helical vanes of either the input member or the output member is adjustable. Rotation of the input member causes the helical vanes of the input member to pump the fluid towards the helical valves of the output member, causing the output member to rotate. The ratio of the speed of the output member with respect to the input member is varied, by varying the axial length of overlap.

Abstract: A power steering apparatus of the present invention which includes a pump, a power cylinder, a control valve, an orifice arranged in a supply passage leading an operating fluid discharged from the pump to the control valve, a flow control valve, and a switching valve. A spring chamber of the flow control valve is connected to the supply passage downstream of the orifice, and is responsive to the pressure difference across the orifice for regulating the flow rate of an operating fluid to the control valve to an almost constant flow rate. The switching valve is actuated in response to the differential pressure across the orifice for switching the communication of the spring chamber between the downstream of the orifice and the reservoir. When the differential pressure across the orifice is relatively low, the switching valve brings the spring chamber into communication with the reservoir.

Abstract: A straight travelling apparatus for heavy construction equipment, equipped with a travel supplement circuit, including a variable orifice disposed in a fluid line connected to the supply-side of the control valve of a bucket and controlled to vary an opening degree thereof by a predetermined pilot signal that is applied to the variable orifice in response to an operation of at least one of right and left travel motors in order to keep the variable orifice at a relatively closed state while being released in response to the travel motors not operating in order to keep the variable orifice in a relatively opened state, thereby capable of supplementing a sufficient amount of fluid to a travelling system when the bucket is operated during, thereby preventing an abrupt reduction in travelling speed caused by operatings the straight travelling apparatus.

Abstract: A hydraulic drive system for a construction machine includes a pump for delivering fluid under pressure from a fluid reservoir, at least one hydraulic actuator selectively driven by the pressurized fluid, and at least one closed-center directional control valve connected in parallel to the pump. The control valve has an "off" position which blocks fluid flow therethrough and at least one "on" position for controlling the flow of fluid to the hydraulic actuator. A control device generates a signal for actuation of the hydraulic actuator. A control unit receives the control device signal for operating the control valve associated with the hydraulic actuator. A bypass line leads from the pump back to the reservoir. A variable position bypass valve is interposed in the bypass line and controls flow through the bypass line. The control unit modulates the bypass valve for optimum operation. A hybrid control senses pressure in the actuator and modifies the control signal in response to the load pressure.

Abstract: A press includes a drive system which includes a brake and a clutch operated by fluid pressure. The brake and clutch control the movement of a crankshaft in relation to a flywheel. A unique control system supplies the pressurized fluid for operation of the brake and clutch. The unique control system includes a pressure relief valve for defining a maximum fluid pressure and a plurality of valve modules which each define a specific fluid pressure. Each valve module is selectively movable between a relief condition and a blocked condition. Thus, by selectively operating the valve modules, it is possible to select the fluid pressure being supplied to the brake and clutch.

Abstract: An hydraulic circuit controlling an actuator including a main signal branch which includes a pump (11), a valve (12) and an actuator (18) coupled in series, the valve being responsive to first and second applied biasing pressures (19,23), the first biasing pressure being operable to bias the valve (12) into a closed position and the second biasing pressure being operable to bias the valve into an open position; an auxiliary branch (20,21,22) connected in parallel with the actuator (18); the first biasing pressure (19) being derived from the main signal branch downstream of the valve (12) and the second biasing pressure being derived from the auxiliary branch.

Abstract: A control system for controlling the movement of the ram of a press or press brake of the type having one or two main cylinders with pistons operatively attach to the ram. The control system comprises a programmable processor with inputs from a pressure transducer indicating the pressure applied to the one or two pistons and a linear potentiometer for each side of the ram to indicate ram position and levelness. The control system further includes a hydraulic circuit operated by outputs from the processor. The hydraulic circuit comprises a variable volume load sense-controlled pump supplying hydraulic fluid through a speed control assembly to a solenoid-actuated directional valve determining upward and downward movement of the ram. The speed control assembly comprises at least two lines connected to the output line of the pump and to the speed control assembly output line to the directional valve. At least one of the at least two speed control assembly lines is provided with a restricting orifice.

Abstract: In a hydraulic driving apparatus with a bladder-type accumulator connected to a fluid supply pipe extending from a hydraulic fluid source to at least one actuator, the apparatus comprises a hydraulic pressure sensor attached to the fluid supply pipe in the vicinity of the bladder-type accumulator and a control unit responsive to a detected pressure detected by the hydraulic pressure sensor for controlling the hydraulic fluid source. The control unit carries out the steps of judging, at the start of the hydraulic driving apparatus, an initial gas pressure supplied to the bladder-type accumulator with reference to a gradient of variation of the detected pressure detected by the hydraulic pressure sensor; monitoring, during a normal operation of the hydraulic driving apparatus, a difference .DELTA.P between the initial gas pressure and the detected pressure; and judging occurrence of a trouble when the difference .DELTA.P becomes smaller than a predetermined first difference .DELTA.P1 or when the difference .

Abstract: A linear hydraulic actuator has a reciprocating pump which provides pressurized hydraulic fluid contained in a reservoir to a hydraulic cylinder in which slides a piston which supplies the actuator output. A diverter valve in flow communication with the pressurized hydraulic fluid has an adjustment shaft allowing manual adjustment of the rate of flow of pressurized hydraulic fluid to the cylinder. Preferably the pump is immersed in the hydraulic fluid held by the reservoir, and the adjustment shaft of the diverter valve penetrates a wall of the reservoir to allow external adjustment of the diverter valve.

Abstract: The hydraulic circuit directional control valve 20 is provided in a line connected with a lower chamber 13 of the hydraulic cylinder 1 and the B-port of the servo valve 3. A check valve 22 permitting oil flowing into the P-port of the servo valve 3 from the lower chamber 13 is provided in the line in parallel with the hydraulic circuit directional control valve 20 and connected with the lower chamber 13 and the P-port of the servo valve 3. When making the ram 15 move downward with high speed, the hydraulic differential circuit is constituted by changing the hydraulic circuit directional control valve 20 such that the delivery oil exhausted from the lower chamber 13 returns to the P-port of the servo valve 3. The hydraulic oil supplied from the hydraulic pump 1 flows into the upper chamber 12 through the servo valve 3. The delivery oil exhausted from the lower chamber 13 returns to the suction side of the P-port of the servo valve 3 through the check valve 22, assisting the flow rate of the hydraulic pump 2.

Abstract: A fluid power transmission for driving automotive accessories at a constant speed with a variable speed input includes a pump driven by a motor vehicle engine in communication with a hydraulic motor which drives the motor vehicle accessories. A working fluid is disposed within a conduit system which communicates the pump driving force with the hydraulic motor. A flow control valve in the return line from the hydraulic motor to the pump provides a constant input flow rate to the pump independent on motor vehicle engine speed and the accessory load on the hydraulic motor to provide a constant output speed at a necessary pressure for the pump to maintain the accessories at a predetermined optimal rotational speed.

Abstract: Cavitation in axial piston motors (20) caused to act as a pump by an aiding load (28), and the related difficulty of loss of hydrostatic film (52), and tipping or hammering of motor slippers (64), can be reduced by a method which includes the step of recirculating hydraulic fluid from the supply port (18) of the motor (20) to the return port (30) of the motor (20) upon the occurrence of an aiding load (28).

Abstract: A device for sensing actuator operating signal in a hydraulic system is disclosed. The device has auxiliary valves directly coupled to the directional control valves respectively, the internal lines of which auxiliary valves are opened or become orifices in accordance with positions of spools of their associated directional control valves. A fluid line extends from a hydraulic pump to a return tank after passing the auxiliary valves in a series. The device also has two elements for detecting fluid pressure at two given points along the fluid line. An additional orifice is formed in the hydraulic line between the auxiliary valves and the pressure detecting elements is provided in the hydraulic line before and after the additional orifice.

Abstract: The present invention provides a swash plate type hydraulic actuator comprising cylinders provided with an inner oil passage, an outer oil passage, cylinder bores, radial valve holes extending between the inner oil passage and the outer oil passages, and ports opening into the cylinder bores and the valve holes, respectively. Distributing valves are slidably fitted in the valve holes for connecting the ports alternately to the inner oil passage and the outer oil passage. Swash plate holders, swash plates and eccentric rings supported on the swash plate holders so as to be engaged with the outer ends of the distributing valves respectively, are provided. Plungers are slidably fitted in the cylinder bores, respectively, in which the displacement can be changed whether or not the inclination of the swash plates is variable.

Abstract: A torque controller which limits the output of a hydraulic motor is provided. The torque controller includes a by-pass circuit which allows the hydraulic fluid in the hydraulic fluid circuit to by-pass the motor. A valve manifold is placed in the by-pass and includes a main chamber having a main valve member and one (and preferably two or more) poppet valves in communication with the main chamber. The pressure at which the poppet valves and the main valve open are individually adjustable and are set for different pressures. Inlets to the poppet valves are closed with electrically operated solenoids such that the inlet to a selected poppet valve can be opened to activate that poppet valve.

Abstract: A compensation system for a hydraulic circuit of a hydraulically driven vehicle for straight traveling, with left and right traveling valves having load detection ports; left and right pressure compensation valves arranged in respective pressurized fluid supply passages between a fluid pressure source and the traveling valves; and a by-pass passage for connecting together the load pressure detecting ports of the left and right traveling valves. There may be an on-off valve in the by-pass passage.

Abstract: In many hydraulic systems, fluid borne noise is generated during operation due to the effects of the hydraulic pump. This fluid borne noise is many times transmitted to the hydraulic valves, hydraulic lines, and other structures that valves and lines are mounted on. The structure then emits vibrations that create the largest portion of the system air borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid borne noise in a hydraulic system. The apparatus includes a fluid vessel having a volumetric space of a predetermined size located in the system generally adjacent a pump and a flow restrictor located in the system downstream of the fluid vessel. In the subject arrangement, the flow restrictor may be adjustable in response to various system parameters so that the fluid borne noise is effectively controlled over wide ranges of system pressures, pump drive speeds, and pump displacements.

Abstract: A windshield washer control system for a vehicle having an air pressure source includes an electrically actuated control valve for controlling communication between the air pressure source and a bladder pump which squirts windshield washer fluid up to the windshield of the vehicle. A fluid restricting orifice is opened and closed by a solenoid actuator such that the pressure communicated to the bladder pump is limited to be below that of the air pressure reservoir. A second orifice controls communication from the pump to ambient atmosphere.

Abstract: A control device provides a reliable way of pressure controlling a hydraulic distributor and an associated first hydraulic circuit when pressurized hydraulic fluid is simultaneously supplied to at least one other hydraulic circuit. Pilot pressure oil enters and exits the distributor through inlet and outlet passages in the pilot line. An apparatus for regulating pilot oil flow rate is interposed between the pilot line inlet passage and the hydraulic fluid line. The device includes a pressure head detection apparatus having inlet ends connected to the pilot line inlet passage and to the hydraulic circuit and an outlet end connected to the hydraulic fluid source for controlling the flow rate of the hydraulic fluid based on the highest pressure requirement.

Abstract: A hydraulic system comprises a mechanical brake assembly having a brake piston engageable with an output rotation shaft of a hydraulic motor, a cylindrical casing having the brake piston slidably received therein and a brake spring resiliently urging the brake piston to engage with the output rotation shaft of the hydraulic motor. The brake piston and the cylindrical casing collectively define a main hydraulic chamber held in fluid communication with a release fluid passageway which is communicable with a hydraulic pump and a reservoir tank through a shuttle valve and a directional control valve. The brake piston and the cylindrical casing further collectively define a secondary hydraulic chamber held in fluid communication with the release fluid passageway through a fluid feed/return passageway on which a brake resistance restrictor provided for restricting flow of the working fluid in the fluid feed/return passageway.

Abstract: A hydraulic system for machines provided with tools, particularly for wheel loaders, fork lifts or the like, including comprising at least one hydraulic accumulator, distributing valves, manometric switches and at least one nozzle for variably adapting the load pressure of the hydraulic accumulator to the load pressure of the lifting cylinder, wherein the load-damping system formed by the hydraulic accumulator is connected to the hydraulic lines responsible for lifting and lowering and extending between the hydraulic cylinder(s) and a control valve.