Abstract: A valve arrangement for hydraulic control of a piston-cylinder of a power switch contains a main stage having a first main valve and a second main valve, and a pilot stage having at least one pilot valve. In order to permit the first main valve to remain securely in the opened state, even in the event of pressure oscillations, the main valve has a total of four control surfaces, of which a second and a third control surface operate in a closing manner and a fourth control surface operates in an opening manner. For this purpose, the second control surface is connected to the high-pressure line, the third control surface is connected to the low-pressure line, and the fourth control surface is connected to the output-side valve connection of the first main valve.

Abstract: An electrohydraulic implement pressure cutoff system is disclosed that includes a pump, one or more hydraulic functions, at least one valve, sensors and control unit. The pump powers the functions, and the valves control flow between the pump and their associated function. The sensor readings indicate system parameters. The control unit receives the readings and controls the valves. When the readings indicate a function is at or beyond a threshold, the control unit closes the associated valve to prevent flow to or from that function. The sensors can be pressure, position or other types of sensors. Operator control signals can be provided to control the functions. When the readings indicate a function is at or beyond a threshold in a stalled direction and the operator signals keep commanding the function in the stalled direction, the control unit can close the associated valve regardless of the operator signals.

Abstract: A valve system, for use with a cylinder having an extensible rod, includes a first valve assembly having a first inlet/outlet port, a check valve biased toward a closed state, the check valve having a check valve body at least partially receivable within a first port of the cylinder, a flow control valve positioned in series between the first inlet/outlet port and the check valve, and a first pilot port selectively communicable with a source of pressurized gas for opening the check valve. The valve system further includes a second valve assembly having a second inlet/outlet port, a second pilot port through which the pressurized gas must flow before being introduced to the first pilot port, and a valve body at least partially receivable within a second port of the cylinder.

Abstract: The disclosure relates to a method for actuating a hydraulic valve arrangement, having a hydraulic continuously adjustable valve and having a hydraulic switching valve for providing a variable opening cross section, wherein an opening cross section threshold value is predefined, wherein, above the opening cross section threshold value, the switching valve is placed into a defined switching position and only the continuously adjustable valve is actuated, and wherein, below the opening cross section threshold value, the continuously adjustable valve is placed into a defined switching position and only the switching valve is actuated.

Abstract: A load sense connection is provided between the implement rockshaft cylinders and the load-sensed power source. However, to avoid tractor starting difficulty, a valve structure is provided in the power beyond fluid line to keep the fluid line closed when starting the tractor. This valve structure provides a hydraulic latching function that allows the load-sensed power source to be activated and deactivated depending on the SCV function. The load-sensed power source is activated when the rockshaft cylinder(s) is fully extended and remains activated or latched when the SCV is returned to neutral. The load-sensed power source is deactivated or unlatched when the rockshaft cylinder is retracted.

Abstract: A line connects the tractor hydraulic power beyond supply to the pressure reduction valve that is connected to the implement cylinder ends and automatically controls implement down pressure. Fluid under pressure is supplied from a line independently of the tractor selective control valve during automatic down pressure mode operation, the selective control valve can be positioned in a float mode when the down force circuit is controlling implement down pressure. The circuit eliminates a stall signal from the selective control valve to the hydraulic pump that otherwise would cause the pump to rise to the high, heat-producing stall pressure if the selective control valve operated in an active pressure mode.

Abstract: The invention relates to a method and an apparatus for controlling an actuator (7, 8) of a crane by control means (10) in a situation where the lifting power of the actuator (7, 8) of the crane is increased temporarily by an auxiliary valve arrangement (11). In the invention, control properties of the actuator (7, 8) are changed when the temporarily increased lifting power is applied to limit the speed of the actuator (7, 8).

Abstract: A hydraulic actuator for a hydraulic servomotor (4) is disclosed. The hydraulic servomotor (4) is of a kind having at least one defined end position, and has a first chamber (5) and a second chamber (6) associated therewith. The actuator is connected to a fluid source (2) and a fluid drain (3). The actuator comprises a first valve (7) fluidly connected between the fluid source (2) and the first chamber (5), a second valve (8) fluidly connected between the first chamber (5) and the fluid drain (3), and a third valve (9) fluidly connected between the fluid source (2) and the second chamber (6). The actuator further comprises a flow channel (10, 17), preferably comprising a flow restrictor (12, 18), in fluid communication with the second chamber (6). The valves (7, 8, 9) are such that, in the case of a power cut off, they will prevent a fluid flow out of the first chamber (5), and a fluid flow out of the second chamber (6) takes place via the flow channel (10, 17).

Abstract: The invention concerns a control device for adjusting the relative angular position of a driven shaft, particularly a camshaft of an internal combustion engine, said device comprising a drive pinion that is rotatably connected to the shaft, an adjusting element (1) for the angular adjustment of the drive pinion relative to the shaft, two chambers (2, 3) that are alternately supplied with hydraulic fluid and a control valve (6) for actuating the adjusting element (1), said control valve being connected to the chambers (2, 3) of the adjusting element (1) through pressure medium channels (4, 5). The control valve (6) comprises a valve body (7) that has two working connections A and B for the pressure medium channels (4, 5), a delivery connection P for the supply of hydraulic fluid and a discharge connection T for the discharge of hydraulic fluid, and the control valve (6) further comprises a sliding valve control piston (8) for setting different hydraulic resistances W between the individual connections.

Abstract: The invention concerns a control device for adjusting the relative angular position of a driven shaft, particularly a camshaft of an internal combustion engine, said device comprising a drive pinion that is rotatably connected to the shaft, an adjusting element (1) for the angular adjustment of the drive pinion relative to the shaft, two chambers (2, 3) that are alternately supplied with hydraulic fluid and a control valve (6) for actuating the adjusting element (1), said control valve being connected to the chambers (2, 3) of the adjusting element (1) through pressure medium channels (4, 5). The control valve (6) comprises a valve body (7) that has two working connections A and B for the pressure medium channels (4, 5), a delivery connection P for the supply of hydraulic fluid and a discharge connection T for the discharge of hydraulic fluid, and the control valve (6) further comprises a sliding valve control piston (8) for setting different hydraulic resistances W between the individual connections.

Abstract: An air pressure actuator has a partition wall provided on one of a slider and a guide shaft to form two cylinder chambers between the guide shaft and the slider. Intake/exhaust systems are connected with the two cylinder chambers for supplying a compressed air into the cylinder chambers or discharging the same therefrom. Two servo valves including a large capacity servo valve and a small capacity servo valve are respectively connected with the intake/exhaust systems. A position detector for detecting the position of the slider is provided on the slider. A control device receives the detection results of the position detector and a position instruction value, to select the large capacity servo valve or the small capacity servo valve in accordance with an acceleration or deceleration zone and a constant speed zone of the slider, and to control an opening degree of a selected servo valve.

Abstract: The invention concerns a control device for adjusting the relative angular position of a driven shaft, particularly a camshaft of an internal combustion engine, said device comprising a drive pinion that is rotatably connected to the shaft, an adjusting element (1) for the angular adjustment of the drive pinion relative to the shaft, two chambers (2, 3) that are alternately supplied with hydraulic fluid and a control valve (6) for actuating the adjusting element (1), said control valve being connected to the chambers (2, 3) of the adjusting element (1) through pressure medium channels (4, 5). The control valve (6) comprises a valve body (7) that has two working connections A and B for the pressure medium channels (4, 5), a delivery connection P for the supply of hydraulic fluid and a discharge connection T for the discharge of hydraulic fluid, and the control valve (6) further comprises a sliding valve control piston (8) for setting different hydraulic resistances W between the individual connections.

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 manually controlled lifting device is provided including a pneumatic lifting drive, a lifting member, a load carrying means, a pressure source, a pressure line, a flow control device, a pneumatic pressure switch and a vent drive. The lifting member is arranged on the pneumatic lifting drive and is a load transmitting component of at least two parts. The load carrying means is attached to the lifting member for carrying a load. The pressure line has a first end and a second end where the first end is in communication with the pressure source and the second end is in communication with the pneumatic lifting drive. The flow control device is in communication with the pressure line and integrated between the two parts of the load transfer component and the pressure source. The flow control device automatically varies a cross section of flow in the pressure line in relation to a load acting on the load carrying means.

Abstract: A water well recharge throttle valve (1) is configured as a hydraulic actuated flow control device (5) that permits calibrated throttling of water used in Artificial Storage and Recovery (ASR), Salt Water Barrier, Dedicated Recharge and Injection Wells to prevent the free cascading of water and thereby eliminating the entrainment of air which may cause air fouling, bio-fouling, calcite formation with a resultant reduction in permeability of the aquifer.

Abstract: An off-line teaching apparatus includes an operation command-receiving device for receiving an operation command inputted via an input/output port from a key input device or a coordinate input device and successively storing the operation command in a buffer; an operation command-reading device for successively reading the operation command stored in the buffer; an operation command-counting device for counting a number of operation commands stored in the buffer; and a confirmation sound-generating device for generating confirmation sound upon receipt of the operation command by the operation command-receiving device when a counted value obtained by the operation command-counting device is not less than a predetermined number. Accordingly, the operator is informed, in real time, of the fact that the system responds to the input of the operation command from the operator. Thus, it is possible to improve the operability of the off-line teaching.

Abstract: A machine, in particular an industrial truck, is provided with a hydraulic system that has at least one reservoir (1) for hydraulic fluid and at least one hydraulic pump (5). The hydraulic pump (5) is located inside the reservoir (1). A priority valve (8a) is connected to the hydraulic pump (5) by a flange connection. An electric drive motor (3) of the hydraulic pump (5) can also be located inside the reservoir (1).

Abstract: A construction machine, e.g., a backhoe, has a chassis and a digging tool mounted for movement, e.g., swinging movement, with respect to such chassis. A machine hydraulic circuit includes a pump, a hydraulic actuator coupled to the tool for tool movement, and a directional valve between the pump and the actuator. In several specific embodiments, the circuit includes first and second flow restrictors coupled between the pump and the actuator. There is also a valve device for selectively disabling the second flow restrictor, thereby configuring the circuit to provide either of two maximum rates of tool movement. In other embodiments, the circuit uses a variable delivery, fluid-pumping power source and a load-sensing line coupled between the pump and the actuator. The valve device is in series with the load-sensing line and includes a restriction-free path and a flow-restricted path therethrough, thereby configuring the circuit to provide either of two maximum rates of tool movement.

Abstract: A controller for controlling the flow rate of compressed air to a spray paint gun as well as to a comparable tool which is optimally operative dependant upon receiving a specified flow rate of air includes a flow control valve which regulates the air flow rate therethrough based on a pressure differential signal received from an air flow meter. The pressure differential signal transmitted to the air flow controller is balanced against an opposing spring biased needle in the flow controller.

Abstract: An assembly for reversing a fluid driven motor. The assembly includes a fluid driven motor, and a reversing valve that reverses inlet and exhaust porting to and from the fluid driven motor. An actuation device opens an actuation valve and a fluid supply valve. The actuation valve causes the reversing valve to reverse the inlet and exhaust porting to and from the fluid driven motor when the actuation device opens the actuation valve. The fluid supply valve allows fluid to flow through the fluid supply valve to the motor when the actuation device opens the fluid supply valve. The fluid supply valve also prevents fluid flow through the fluid supply valve to the fluid driven motor when the fluid supply valve is closed.

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 hydraulic directional-control valve comprises a first inlet part, a second inlet part, a tank port, a work part and a valve member which is movable from a neutral position to a operating position. In the neutral position, the valve member connects the first inlet port with the tank port and blocks the second inlet port. In the operating position, it blocks the first inlet port and connects the second inlet port with the work port. A third inlet port is provided and the valve member in the neutral position blocks the third inlet port and in the operating position connects it with the work port. The third inlet port may be supplied with hydraulic fluid in parallel with the second inlet port when an additional fluid flow is required.

Abstract: The invention concerns a device in an piston cylinder aggregate including a valve element (8) which comprises a valve body (9) for choking the flow in a fluid channel (6) in co-operation with a valve opening (7), wherein the device is arranged in a bore (11) in an end wall (1) of the piston cylinder aggregate and wherein the valve element (8) is provided with a setting means (10) to allow adjustment from the outside of the end wall.

Abstract: It is intended to dispense with the pipe welding work, thereby improve the pipe mounting performance and prevent contamination which results from welding, and elimination the waste of oil.A spigot portion 34 is mounted upright integrally in the center of the upper end portion of a piston 17, the base end of a piston rod 18 is fitted on the outer periphery of the spigot portion 34, and the outer periphery of the base end of a pipe 41 is press-fitted into an upper hollow part of the spigot portion 34.

Abstract: In a hydraulic power steering for a motor vehicle with a hydraulic servomotor and a servovalve arrangement in communication with opposite servomotor actuating chambers by way of separate communication conduits through which the actuating chambers can be pressurized or depressurized for the operation of the servomotor depending on a force applied by an operator to a steering means, the communication conduits include valve arrangements permitting, when they are open, the release of hydraulic fluid from the actuating chambers but blocking the release of hydraulic fluid when they are closed thereby hydraulically locking the power steering.

Abstract: In order to improve speed controllability both in low and high speeds, thereby stabilizing the speed of a hydraulic cylinder, both the flow-in amount of hydraulic operating fluid flowing from a hydraulic source to the hydraulic cylinder having a run-around circuit and the flow-in amount of hydraulic operating fluid flowing from the run-around circuit to the hydraulic cylinder are controlled simultaneously by a control valve, so that the speed of the hydraulic cylinder is controlled.

Abstract: A flotation control system for controlling the boom of a tractor or brush cutting machine. Three hydraulic valves operate together and work in conjunction with the existing main valve of the tractor or brush cutting machine to provide flotation control or automatic movement up and down of the boom in response to ground surface variations. The system also allows the amount of weight that the cutter or other attachment exerts against the ground to be increased or decreased. The first valve is a flow control valve or a flow restricting or dividing valve that divides hydraulic flow from the pump of the tractor to the flotation control system. The second valve is a pressure reducing valve that provides the general operation of the flotation control system. The third valve is a directional valve and functions as an on/off for the flotation control system.

Abstract: A return fluid regeneration device for construction vehicles is provided. The regeneration device includes an orifice disposed on a return-side internal line of a directional control valve of an actuator. A regeneration line is arranged between the return-side internal line and a return line extending to a return tank and is further selectively connected to the return-side internal line during a weight operation of the actuator. A regeneration branch line is branched from the return-side internal line and is connected to a supply-side internal line of the valve, thus selectively feeding the return fluid from the return-side internal line to the supply-side internal line and thereby regenerating the return fluid. First and second check valve are also provided on the regeneration line and branch line, respectively. The regeneration device regulates the moving speed of the actuator while simultaneously preventing the generation of high pressure in a fluid supply line.

Abstract: An add-in device for a hydraulic control arrangement provides a function unit (24) to be arranged between successive modules, which function unit takes the connection between the pump channels of the preceding and the subsequent module by way of at least one function slide valve (117, 217) which is arranged to be displaced into several positions. In its positions this function slide valve initiates different functions, by which fluid under pressure is arranged to be admitted to the subsequent control module in at least two different amounts and/or in at least two different levels of pressure. In this manner operation of the subsequent control modules can be better matched to the particular operating conditions that obtain.

Abstract: A hydraulic control apparatus for a hydraulically operated vehicular transmission has control valves corresponding to hydraulic engaging elements provided in the transmission. The supply and discharge of hydraulic oil to and from the corresponding hydraulic engaging elements are controlled by the control valves. The hydraulic control apparatus has an oil supply passage which is connected to a hydraulic oil source and into which a throttle is interposed. The oil supply passage is connected to oil passages which are on a downstream side of each of the control valves and which are to be communicated with the hydraulic engaging elements. Check valves are interposed in the oil supply passage to allow for the hydraulic oil flow only from the oil supply passage to the oil passages on the downstream side of each of the control valves.

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: The Variable Orifice Valve is disclosed and the preferred embodiment of a hydraulically acruated.sub.-- flow control device that permits the calibrated throttling of water used in a Artificial Storage and Recovery (ASR), Dedicated Recharge, Injection, Salt Water Barrier Wells used in aquifer storage.sub.-- or utilized in other industries where fluid flow control is required and desired. Aquifer storage of treated drinking water is the placement of water in aquifers during periods of surplus water for recovery of the water during peak demands or forming a barrier to protect a fresh water aquifer. This invention, when installed in a recharge well, is a device installed below the static water level and at or near the bottom of the drop pipe and near the top of the well screen. The size of the orifice and the liquid flow is varied by the axial positioning or adjustment of a double acting hydraulic actuator connected to valve piston.

Abstract: A variable priority device for heavy construction equipment for establishing a priority of the boom over the bucket by limiting an amount of fluid passing through a bucket-side parallel fluid line when the boom operates alone and thereby decreasing the amount of fluid supplied to the bucket actuator. The device is installed in the bucket-side parallel fluid line and adapted to be switched between an orifice state and an orifice release state, the priority control valve being initially maintained at the orifice release state by a resilience device while being switched from the orifice release state to the orifice state against a resilience of the resilience device in response to a pilot pressure for moving the spool of a boom-side switching valve communicating with the boom actuator.

Abstract: A switching arrangement for controlling the speed of hydraulic drives, wherein a speed of the drive is assigned to a corresponding flow rate of a hydraulic medium. The flow rate is determined by a preselected pair of phased nozzles placed in the inlet and outlet lines. The nozzle flow rates are selected such that switching between a series of nozzle pairs creates a smoothly changing speed of the hydraulic drive, thus eliminating jolting during starting and braking.

Abstract: A hydraulic drive passenger lift with distinct lifting "up and down" (loading, unloading) and "fold-unfold" (storage) motion patterns, includes a flow control structure that accommodates various hydraulic flows, somewhat unrestricted for "up-and-down" movement, and different for "fold" and "unfold" movements. The flow control structure includes multiple paths between a source and an actuator, with control for selecting the appropriate path to yield predetermined flow rates. A solenoid driven spool valve and a biased movable orifice member select the desired path. Accordingly, while the flow is substantially unrestricted during "up-and-down" movement, it is somewhat restricted for reduced speed during the "unfold" movement and is more restricted during the power-driven "fold" movement.

Abstract: A control arrangement for regulating the speed of a pressure cylinder increases the controllable flow volume through a proportional-action (control) valve, while avoiding a larger valve or two valves of the same type that must be connected in parallel. A control valve is used which has at least two flow paths connected in parallel. At least one controllable valve is connected in series with a first of the flow paths for the blocking or release of the delivery pipe. The connected first flow path and the controllable valve are connected in parallel to the second flow path.

Abstract: A motion control system for hydraulically operated lifting devices. The system provides for the dynamic weighing of a loaded container by controllably directing hydraulic flow through a bypass chamber of a two-way valve. An analog output signal is generated by a hydraulic pressure transducer fluidly communicating with the two-way valve or by a tensiometer mounted on the arms of the lifting device. The two-way valve further provides a second bypass chamber which receives fluid under gravity from the lift circuit line of the hydraulic cylinder for controllably lowering the lifting device. The pressure transducer or tensiometer generate an analog signal proportionate to the weight being lowered and whereby the hydraulic fluid is returned to the reservoir of the hydraulic system independently and downstream of the main operating valve.

Abstract: A pressure holding valve for pressure-fluid-actuated leveling systems in vehicles, having at least one seat valve with a valve opening, a valve seat and a valve member in which the valve member is opened by a control piston acted upon by pressure fluid. In order to achieve an absolutely pressure-tight seat valve with a long service life, an elastomer seal which seals off from the valve member is disposed on the valve seat, and pressure equalizing means are provided such that upon an impingement of pressure on the control piston in an opening direction of the seat valve, pressure build up upstream of the valve member is such that only a slight pressure difference arises at the seal at the onset of opening. In addition, the valve member is embodied such that upon displacement in a closing direction of the seat valve, the valve member substantially closes the valve opening in advance of the valve member becoming seated upon the seal.

Abstract: A motion control system for hydraulically operated lifting devices. The system provides for the dynamic weighing of a loaded container by controllably directing hydraulic flow through a bypass chamber of a two-way valve. An analog output signal is generated by a hydraulic pressure transducer fluidly communicating with the two-way valve or by a tensiometer mounted on the arms of the lifting device. The two-way valve further provides a second bypass chamber which receives fluid under gravity from the lift circuit line of the hydraulic cylinder for controllably lowering the lifting device. The pressure transducer or tensiometer generates an analog signal proportionate to the weight being lowered and whereby the hydraulic fluid is returned to the reservoir of the hydraulic system independently and downstream of the main operating valve.

Abstract: Piston sealing and dampening device in a pressurized-fluid cylinder, where a piston (3) has a central recess (3a) facing towards a cylinder end cap (1a) and disposed such that when the piston is in the vicinity of its end position, said recess accommodates a sleeve portion (5) provided with an internal pressurized-fluid connection (6) and projecting from the cylinder end cap. An integrated sealing ring (10) seals against the outside of the sleeve portion (5) with an inner sealing ring lip (10e) and against the inside of the cylinder tube (2) with an outer sealing ring lip (10c).

Abstract: The pressure-regulating system for a hydraulic circuit, comprises at least one generator (22) of fluid under pressure, a hydraulic motor (20), a reservoir (24) of fluid under low pressure and a solenoid valve controlled by a computer and comprising an electrical coil (1) and a sliding magnetic core (3) controlling a slide (7) which slides in a bore provided in a body (9). The slide (7) defines two chambers (11, 15) arranged on either side of the slide (7) in the bore, and it comprises a hydraulic cell (26) communicating with the hydraulic motor (20) and determining a reaction force added to the force generated by the coil (1), counter to a prestressed elastic means (131) and to a return spring (132) returning the slide (7) and the core (3) to the rest position.

Abstract: A transmission equipped with torque converter having a forward/backward change valve for supplying working oil selectively to any one of a forward clutch or a backward clutch. A shock diverter valve is installed between the forward/backward change valve and a working oil supply source. The shock diverter valve is so designed as to include plural throttles having different bore diameters through which working oil is passed to reduce a rise speed of downsteam side hydraulic pressure. A lever for changing the shock diverter valve is installed at an outside of clutch. An operator can select a drive feeling easily from at least two kinds of feeling by operating a lever.

Abstract: Disclosed is an arrangement that includes a piston cylinder unit having pressure chamber in which fluid acts in opposition to a spring piston combination, a pressure generator and a fluid conduit extending between a tank and the tank. A first and a second valve are connected in series between the pressure generator and tank with the pressure chamber being in fluid communication with the connection between the valves. In known arrangements of the above type there is dead play wherein not every control signal corresponds to a defined position of the piston in the cylinder. However as disclosed herein the setting accuracy is improved by a throttle in parallel with valve that is fluidly connected between the pressure chamber and the piston cylinder unit. Also third and fourth valves may be connected in series between the pressure generator and tank and have a fluid connection between the third and fourth valves to the unit pressure chamber that is opposite the first chamber to provide a bridging circuit.

Abstract: A load-referenced, pressure reducing valve, and a system which incorporates one or more of such valves provide needed response to rapidly changing hydraulic system load demands which are experienced with automatic control systems. The valve provides rapid response for pressure regulation by providing the load pressure to one side of the valve so that immediate, load referenced valve adjustment occurs instantly upon change of load conditions at a system load, and pressure regulation begins immediately without need for fluid flow.

Abstract: A variable assist power steering system for an automotive vehicle, the system having a source of hydraulic fluid (10), a power steering assembly (30) having a low speed inlet (32) and a high speed inlet (34), and a control valve (50) for continuously delivering hydraulic fluid to the low speed inlet and for delivering fluid to the high speed inlet only at vehicle speeds above a predetermined level. The control valve has an annular spool (64) which moves freely within a cylindrical housing (52), and it has a second spool (74) which is caused to move linearly by a solenoid (86) which acts on the one end thereof and a spring (88) which acts on the other end thereof. The second spool has a central portion (76) which is positioned within the annular spool and which defines an annular passage (68) therewith. The second spool further has enlarged end portions (78, 80) positioned outside of the ends of the annular spool to permit fluid to flow into the annular passage from each end.

Abstract: Hydraulic pressure representing engine throttle position is applied to a valve spool having two control surfaces. In opposition to the force of a control spring, a pressure line, which opens to the valve chamber between the two control surfaces, carries regulated line pressure through a flow orifice in a first connecting line and through an aperture stop in a second connecting line. The flow orifice of the first connecting line is arranged in parallel with an aperture of the second connecting line, both the first and second connecting lines being connected directly to the valve chamber.

Abstract: An improved fluid controller (15) is provided having both rotary valving (47) actuated by the steering wheel (17), and axial valving (49) controlled by an electro-hydraulic valve (113) in response to a correction signal (31). In one embodiment, both the rotary valving and the axial valving are achieved by a primary valve member (63) and a follow-up valve member (65), and both the rotary and axial valving can be actuated simultaneously. Also disclosed is a logic control system for closed-loop control of the electro-hydraulic valve, whereby performance problems such as self-steering wander, drift, and others are substantially eliminated.

Abstract: A telescopic pneumatic hoist has a flexible stationary hollow probe on its base arranged to unseat a check ball in the piston of the lowest intermediate stage when the piston is near the base. When such a condition exists, the probe closely interfits with the piston and has a radial port communicating with the underside of the piston. The probe connects at the bottom with a supply and exhaust passage which also communicates with the underside of the piston via a check valve controlled secondary passage.

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 hydraulic system is provided including a hydraulic pump which is continuously coupled with the engine of a utility such as a dump truck utilized for snow-ice removal. When hydraulic implements employed on the truck are not actuated, the pump operates in a cavitation mode. During this cavitation mode of operation, there is no ingress of air through seals or the like to a venting of the gear pump chamber essentially to tank or atmosphere. A poppet valve is actuated in conjunction with periodic use of hydraulic elements on the truck to actuate the pump to an operational or pressurized mode. A key actuated calibrating system is employed to calibrate snow-ice removal components in a secure manner. Calibration is provided in conjunction with EEPROM memory.