Abstract: A valve for controlling a flow of a fluid between a source, reservoir, a vent, and pressure-based device. The valve has multiple positions each having a source port fluidly coupleable to the source, reservoir port fluidly coupleable to the reservoir, device port fluidly coupleable to the pressure-based device, and venting port configured to vent the fluid. The multiple positions are separately selectable and include a fill position having a fill conduit fluidly coupling the source port and device port, a recycle position having a recycle conduit fluidly coupling the reservoir port and device port, and a vent position having a vent conduit fluidly coupling the vent port and device port. The fill conduit, recycle conduit, and vent conduit each communicate the fluid only when a corresponding one of the multiple positions is selected, and the multiple positions are configured to prevent selection of more than one at a time.

Abstract: An autarkic hydraulic linear drive with a hydraulic arrangement and a method for operating the same. The hydraulic arrangement a pump unit, an equalizing reservoir, a load switching valve configured to switch between a fast extension and a load extension, and a hysteresis circuit. The hysteresis circuit is configured for triggering a first switching process of the load switching valve at a first control pressure and a second switching process of the load switching valve at a second control pressure that is different than the first control pressure.

Abstract: A system for reducing pressure in a subsea operator. In one embodiment, a subsea system includes an operator and a deintensifier. The operator includes a housing and a piston. The piston is movably disposed within the operator housing and divides an inner volume of the operator housing into a closing chamber and a second chamber. The deintensifier is fluidically coupled to the operator. The deintensifier includes a housing and a piston. The piston includes a closing surface and an opening surface. The closing surface is fluidically coupled to the second chamber of the operator housing. The opening surface is fluidically coupled to ambient pressure. The area of the closing surface is greater than an area of the opening surface so as to increase the pressure differential between the closing chamber and the second chamber and assist in moving the operator piston to the closed position.

Abstract: An integrated unit for air treatment in pneumatic systems comprises a box-shaped body provided with an inlet for the air to be treated and at least one outlet for the treated air and holds devices for treatment and regulation of the air flow between the inlet and outlet. The devices consist of at least one filter device, one pressure regulator and one progressive-starting device.

Abstract: A drivetrain for a motor vehicle has a friction clutch for transmitting drive torque for the motor vehicle and has an actuator arrangement for actuating the friction clutch. The actuator arrangement has a first actuator which is designed to close the friction clutch quickly with little force expenditure in order to thus quickly close up the play which is present in the open state of the friction clutch. The actuator arrangement has a second actuator which is designed such that, with a small stroke, it applies a large force for actuating the friction clutch in order to keep the friction clutch closed with little energy expenditure.

Abstract: What is disclosed is a hydraulic drive mechanism for a blanking or forming machine comprising a working cylinder having several pressure chambers, the piston of which acts directly or indirectly on a workpiece to be processed, wherein at least one pressure chamber of the working cylinder for retracting and extending the piston is adapted to be subjected to a tank pressure or a supply pressure via a continuously adjustable valve, and comprising a valve assembly arranged upstream of the continuously adjustable valve, whereby an inlet port of the continuously adjustable valve may be subjected to a higher or lower supply pressure, wherein the valve assembly comprises a switching valve adapted to be switched over between a basic position and a switching position in dependence on the load pressure at the working cylinder in order to tap the supply pressure from a low-pressure source or from a high-pressure source.

Abstract: A method and a device for controlling a downhole hydraulic sequential control system (1) in which a number of pressure relief valves (20, 22) are arranged to open sequentially directly or indirectly for corresponding actuators (26, 34) through introduction of a hydraulic fluid, wherein the pressure of working fluid supplied to the control system is transmitted to hydraulic fluid in the control system (1). The pressure transfer may be effected by means of a dividing piston (6).

Abstract: A progressive-starting unit for pneumatic circuits comprises a line inlet and a line outlet interconnected with each other by a regulating valve that is piloted by a pneumatic piloting inlet. The piloting inlet is controlled by the outlet of a progressive-starting device having an inlet connected upstream of said regulating valve. In this manner a progressive-starting unit is obtained which is insensitive to the conditions downstream of its line outlet.

Abstract: An actuator device self-contained within a housing and adapted to move an object. The actuator device includes a movable piston positioned in a cylinder portion of the housing. The cylinder portion defines a longitudinal axis, whereby the piston is movable along the longitudinal axis in response to an accumulation of air pressure within the cylinder portion. The actuator device also includes a rod coupled to the piston for movement with the piston. The rod at least partially extends outside of the housing to couple to the object. Further, the actuator device includes an air compressor located within the housing. The air compressor transfers air from a location in the housing outside the cylinder portion to a location inside the cylinder portion.

Abstract: A servo assembly 22 for selectively engaging a brake band 14 in an automotive vehicle is disclosed. Servo assembly 22 includes a piston 26 at least partially encased in a housing 24 and a first and second supply 111, 132 of hydraulic fluid which selectively actuate the piston to engage the brake band.

Abstract: A hydraulic jack includes a moveable base seat. A lift arm, a handle and a hydraulic driver each mounted on the base seat. The hydraulic driver is driven by the handle to push the lift arm to lift an object. The hydraulic jack has a compound piston assembly and a hydraulic driver with fluid paths by which the jack can adjust the lift capacity so as to lift quickly and lower slowly.

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 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: A servo for operating a brake band in an automatic transmission includes a transmission casing and servo cover defining a servo cylinder, a servo piston supported for displacement within the cylinder, first and second sealed volumes within the cylinder, a valve for connecting the fluid sump to one pressure area and for closing that connection and opening a connection to line pressure while maintaining the first pressure area connected to line pressure.

Abstract: A fluid control valve includes an adjustable soft start capability. The fluid control valve isolates an input port and connects an outlet port to an exhaust port when the fluid control valve is in its closed position. A system is provided for locking the fluid control valve in the closed position. When the fluid control valve is moved to an open position, the exhaust port is isolated and full communication between the input port and the outlet port is delayed by a piston which continues to block fluid flow between the input port and the outlet port. An adjustable by-pass passage bleeds pressurized fluid from the input port around the piston to the outlet port until a specified pressure is built up at the outlet port. When the pressure at the outlet port reaches the specified pressure, the piston is moved from a position which blocks the flow from the input port to the outlet port to a position which allows full communication between the input port and the outlet port.

Abstract: A slow start valve has a first valve member for opening and blocking a flow passage between an inlet port and an outlet port and a second valve member for opening and blocking a flow passage between the outlet port and an exhaust port, both being integrally formed in a spool without adopting a poppet construction, wherein the actuation of the spool by force of compressed air causes slow supply, quick supply and exhaust. Compressed air supplied via a solenoid three-way valve causes a piston to move downward along with the spool in contact therewith and then compressed air supplied via a passage causes the spool to move further downward, a second valve opening being immediately shut off with the second valve member.

Abstract: In a neutral to drive shift timing control mechanism, a flow control arrangement is utilized in an electro-hydraulic control system for controlling a clutch fill period of a neutral to drive shift sequence. The hydraulic control system provides a pressure pulse of predetermined time which opens a valve to permit fluid flow to bypass an accumulator feed orifice to pressurize the clutch apply cylinder and piston to a value substantially equal to the piston return spring force without providing excess flow to the accumulator. The clutch apply pressure is then permitted to increase at a more normal rate which is controlled by the accumulator. The engagement time is determined so that the pulse time can be adjusted if the neutral to drive shift is not within a predetermined time range.

Abstract: This hydraulic safety and regulating system for a steam feed of a turbine has a rapid-action (4) and a steam regulating valve (3), and a line system monitored by a safety downward-control unit (22). The monitored line system is designed as both a power oil supply and as a safety oil system. This results in a hydraulic safety regulating system which is simple to build and has a reduced number of possible leakage points.

Abstract: An improved safety valve includes piston-actuated provisions for gradually pressurizing a fluid-actuated motor during start-up of the system, preferably by way of a changeable flow restriction. In addition such improved safety valve preferably includes a floating exhaust valve actuating apparatus movable in an exhaust closure chamber and that operates in response to the presence or absence of line pressure in the exhaust closure chamber for respectively blocking off or opening fluid communication between the safety valve's outlet port and exhaust port. A pilot operator is also included for selectively permitting or cutting off line pressure flow to actuate the piston actuator and the exhaust valve actuating apparatus. The preferred safety valve also includes a check valve for preventing back-flow from the safety valve's outlet port back to the piston actuator and back to the exhaust valve actuating apparatus.

Abstract: In order to improve a machine tool comprising at least one hydraulic drive for working motion or rapid motion operation connected via a supply pipe to a high-pressure network supplied by a high-pressure pump so that the drives can be operated with high pressure for working motion and to a substantial degree with low pressure for rapid motion, it is proposed that a low-pressure network supplied by a low-pressure pump be provided for operating the drive for rapid motion, that a flow-limiting member be arranged between the high-pressure network and the supply pipe for bringing about a pressure drop in the supply pipe during the rapid motion by limiting the flow of a hydraulic medium under high pressure and for maintaining the high pressure to a substantial degree during the working motion, and that the low-pressure network be connected to the supply pipe via a check valve which is open on account of the pressure drop during the rapid motion and closed during the working motion.

Abstract: A hydraulic control system for the drive control of a double-acting hydraulic cylinder with a larger driving surface and a smaller countersurface, in which the direction- and movement-controlling valve is provided in the form of a follow-up adjusting valve that operates with an electrically-controlled indication of the set value and with a mechanical announcement of the actual position. The pressure source provides two different supply pressures P.sub.N and P.sub.H. A pressure-controlled pressure-reversing valve is provided to switch to the higher supply pressure as and when this is called for by a growing load. A similarly pressure-controlled surface-reversing valve is also provided and, after the pressure-reversing valve has switched to the higher pressure, will itself switch the hydraulic cylinder from a differential operating mode to a mode in which pressure is applied only to the larger working surface of its piston.

Abstract: A control circuit for a hydraulic actuator which allows the hydraulic actuator to be operated readily without much skill and at a suitable speed in accordance with a load applied thereto. The control circuit includes a change-over valve provided intermediately of a pilot pipe line communicating with a pilot oil chamber of a hydraulic change-over valve which belongs to one of a pair of hydraulic change-over valve sets of a hydraulic operating circuit for the hydraulic actuator. The change-over valve is normally urged to a position wherein the pilot oil chamber of the hydraulic change-over valve is communicated with a tank, but is changed over, when a hydraulic pressure higher than a predetermined value acts upon a pilot oil chamber of the change-over valve, to another position in which the pilot oil chamber of the hydraulic change-over valve is communicated with the pilot pipe line.

Abstract: A fluid control circuit and method of operating equipment such as a blowout preventer having a two-way hydraulic piston and cylinder assembly. The circuit includes various features such as a dual pressure level independently controlled fluid supply, a dedicated secondary fluid supply reserved for supplemental use, a dedicated fluid supply reserved for exclusive use in one operating branch, automatic sensor for applying a reserve fluid supply on a sensed demand, a pressure intensifier for increasing available operating force, and control circuitry for preventing loss of enhanced secondary operating energy into a primary circuit.

Abstract: A hydraulic control circuit and method of operating a blowout preventer having a two-way hydraulic piston and cylinder assembly including an open and close port. An adjustable hydraulic supply is connected to a control valve which is in turn connected to the open and close ports. A pressure booster having an input and an output is connected to the close port and a control circuit is connected to the input of the booster and to the close port for actuating the booster and also blocking flow from the control valve to the closed port when the hydraulic supply increases to a predetermined value.

Abstract: A hydraulic control apparatus for a vehicle capable of being significantly simplified in structure and stabilizing its control characteristics. The apparatus includes a variable constriction provided in a first flow passage arranged between a steering pump and a steering cylinder and a steering spool for changing over the first flow passage and controlling the degree of opening of the variable constriction. The apparatus also includes a single flow control valve spool which changes over depending on a variation of pressure on an upstream side of the variable orifice and accomplishes an increase and a decrease in the degree of opening of a second flow passage arranged between a switch pump and an implement circuit corresponding to an increase and a decrease in pressure on the upstream side of the variable constriction.

Abstract: A self-regulating hydraulic control circuit for controlling the flow of fluid to and from the cylinder of a double-acting hydraulic motor employs two pumps, one of which supplies fluid at a relatively high pressure and low displacement while the second pump is a relatively high displacement pump which operates only against a relatively low pressure requirement. The system is especially adapted for applications where, during a working stroke, the piston of the hydraulic motor moves from a start position through a first portion of the stroke during which the piston encounters but a minimal resistance to movement and then suddenly encounters a high resistance to movement. One example of such an application would be a press in which, at some point during the stroke of the piston, a tool carried by the piston initially encountered a workpiece.

Abstract: An improved hydraulic circuit for automatically sequencing a pair of hydraulic cylinders through alternate extension and retraction cycles. A manually operated control valve initiates addition and withdrawal of fluid within the circuit and a logic valve determines which cylinder will be in communication with the control valve. The circuit uses an improved flow restrictor arrangement for creating the pressure drop which automatically shifts the logic valve. The restrictor consists of an orifice, a simple check valve and a constant pressure relief valve, all arranged in parallel. The functions of these various restrictor elements can all be performed by a single multifunction valve disclosed herein.

Abstract: For connecting servohydraulic linear or rotation drives to a line with impressed pressure a valve means is provided which shuts off the pressure-carrying lines in leakage-free manner and connects the consumer line pressure-free to the tank. For a trial setting operation a fluid flow of reduced pressure and amount can be supplied to the consumers via an auxiliary means. The connection of the consumers is surge-free.

Abstract: Apparatus for controlling fluid communication with a fluid pressure system includes parallel flow paths connected to the system. A first flow path includes first valve apparatus for selectively closing the flow path. The second flow path includes relief valve apparatus responsive to fluid pressure in the second flow path to move from a closed configuration to an open configuration. Switching apparatus, including sensors for detecting the condition of the system, operate to close the first valve apparatus in response to pre-determined threshold values of such condition. Fluid communication from the system may thereafter occur along the second flow path at the relief valve apparatus opens in response to pressure buildup in the flow path. A third flow path, parallel to the first two flow paths, may be provided with throttling apparatus for controlled communication of fluid along such third flow path.

Abstract: A valve assembly is provided for use with a hydraulic mine roof support, the assembly having uni-directional control means 49 interconnecting first and second pressure sectors of the valve assembly, and further control means 20 embodied in the first pressure sector which further control means is arranged for activation by fluid pressure in the first pressure sector to allow pressure fluid to flow from the second pressure sector to the first pressure sector until the fluid in the first pressure sector is equal to or exceeds the fluid pressure in the second pressure sector.

Abstract: Fluid systems having modulating pressure relief valves are normally needed in systems having clutches that require smooth engagement. It is also desired in many systems to maintain a difference in pressure levels between the fluid in different clutches, such as, speed and directional clutches during initial engagement in order to ensure that only one of the clutches absorbs the initial load. In order to reduce power losses and improve system efficiency, it is desirable to reduce the pressure level of the higher clutch once the clutches are fully engaged. The present modulating pressure relief valve assembly provides a valve device that is effective to limit the maximum pressure in the system and change the pressure difference between the clutches upon full engagement thereof. The valve device is located in a single bore thus reducing total valve size and manufacturing costs.

Abstract: An apparatus for controlling fluid flow to a steering motor and an auxiliary apparatus is capable of smoothly changing between conditions in which it directs relatively small and relatively large flows of fluid to the auxiliary apparatus. The apparatus includes a priority valve assembly having a valve member positioned in accordance with variations in the demand for steering fluid. A land on the valve member cooperates with a fixed valve surface to form a variable size orifice through which fluid flows to a steering controller. A second land on the valve member cooperates with a fixed valve surface to form a variable size main auxiliary flow control orifice through which all of the fluid flow to the auxiliary apparatus is directed during relatively low fluid flow rates to the auxiliary apparatus.

Abstract: A power steering apparatus with a pressure supply for additional loads, the steering pump of which has a plurality of feed chambers separate from one another. The additional loads, such as a brake booster and/or a level regulating device, are connected to one of these separate feed chambers. A reversing valve enables a greater supply capacity to the steering gear by shutting off the additional loads.

Abstract: A hydraulic pressure modulation device disposed between a hydraulic pressure source and a selector valve comprising a cylinder; a spool fitted into the cylinder; an accumulator; an actuation chamber formed in the cylinder; a passage openly connecting the chamber to the selector valve; a spring forcing the spool against a pressure in the chamber; a first passage openly connecting the pressure source to the selector valve; a second passage operable to introduce the oil from the pressure source into the accumulator while the outlet pressure of the device increases from a first value to a second value; and a third passage operable to connect the accumulator to an oil tank substantially after the second passage is closed, the passages being formed in the cylinder and the spool.

Abstract: Pipe thrust-jacking apparatus includes a pressure ring 5 which is advanceable by a plurality of hydraulic rams 3. The rams are controlled by hydraulic control means having a plurality of hydraulic control valves 19. Each control valve is associated with a respective hydraulic ram, and is connected to a first input line and to a second input line. Each of the first input lines is connected to a respective hydraulic fluid feed line 9, and each of the second input lines 17 is connected to a common hydraulic fluid supply line 11 and to an auxiliary pump P2. The common supply line is connected to all of the feed lines. Means 12,15 are provided for selectively connecting each of the hydraulic control valves to its first input line and/or its second input line.

Abstract: A modulation valve for controlling flow to a fluid consuming device which valve provides a gradual buildup of fluid pressure and during at least part of the buildup restricts flow to the consuming unit. The valve includes a slide movable by a spring on one end and fluid pressure on the other. The slide has a blind bore on the pressure end which is adapted to move over a projection having a restricted passage therethrough. In at least one position of the slide, fluid flow to the consuming unit is through the projection and through a passage in the slide to the consuming unit. In another position of the slide, fluid flow is through the blind bore and through the passage in the slide to the consuming unit.

Abstract: The invention relates to a steering control unit for a bidirectional servomotor which is connectable to steerable wheels. A steering wheel controlled quantity setting unit of a known type has ports connectable to a pump and a return tank and two control ports through which metered quantities of fluid flow to opposite sides of the servomotor and to other parts of the apparatus for actuating the servomotor. A directional control valve for selectively directing pressurized fluid from a power circuit to opposite sides of the servomotor is controlled by a control circuit containing the setting unit. A utility valve having the pressure regulating and control and power valve capabilities required for this type of apparatus is characterized by having only a single slide spool for performing all of these functions.

Abstract: The present invention relates to a device for shutting off a supply of pressurized motive fluid to an associated fluid driven motor in response to a predetermined motor back pressure indicating a predetermined load on the motor. The device comprises a housing having a fluid inlet connected to a supply of motive fluid and a fluid outlet connected to supply pressurized fluid to the associated fluid driven motor. A passageway extends through the housing between the fluid inlet and the fluid outlet. A shut-off piston is slidably mounted with the housing and is shiftable to close the housing passageway and shut off the supply of pressurized fluid to the motor in response to a predetermined motor back pressure. An orifice of variable size is provided in the housing passageway and is utilized to reduce the pressure of the fluid supplied to the motor.

Abstract: Hydraulic control apparatus serves to operate roof support props of a mineral mining installation. An automatic setting arrangement with a valve device ensures the props become set against the roof with a high uniform force by connecting a prop pressure chamber to a pressure fluid source once a threshold pressure is exceeded signifying the prop has been extended. To disable the automatic setting arrangement during prop retraction the valve device thereof is provided with a control piston which is subjected to pressure during retraction to oppose the action of another control piston which responds to the threshold pressure.

Abstract: A control valve for the application of a desired pressure in a working circuit, having a pressure chamber connected with a pressure source, a control chamber separated during the rest position of the valve from the pressure chamber by a first seat valve which connects with a working circuit and a pressureless connection during the rest position of the valve, and finally the control valve has an activating piston 14, by means of which, when the control valve is operated, first the connection between the control chamber and the pressureless connection is interrupted and then the first seat valve is opened. Additionally, a further seat valve is interposed into the connection between the pressure source and the pressure chamber, and a control piston 7 is provided to open seat valve 6 when exposed on the one side to the pressure in the pressure chamber 9 and on the other side to the pressure applied in the working circuit.

Abstract: A hydraulic control circuit for a cylinder-and-piston unit includes a relatively small electrohydraulically operated servo-control valve, a main pressure conduit including a measuring throttle, an auxiliary control valve cooperating with an additional pressure conduit connected parallel to the main pressure conduit to branch the pressure fluid in response to a predetermined level of pressure difference occurring across the measuring throttle. In this manner the servo-control valve can control a system of pressure fluid which is substantially larger than the nominal flow rate of the servo-control valve.

Abstract: A hydraulic system is disclosed for use in an automotive vehicle including an engine, a power steering gear, and a brake booster. The system includes a single engine driven pump in fluid communication with first and second fluid flow control means. The first fluid flow control means responsive to fluid inputs for discharging a small or large predetermined amount of hydraulic fluid to control the operation of the power steering gear. The second fluid flow control means supplies a constant amount of hydraulic fluid to control the operation of the brake booster.

Abstract: A progressive pneumatic starter device delivers at its outlet an increasing pressure of low flow rate, then a working pressure at a high flow rate. The starter device is provided with a distributor member adapted to connect, in parallel with a calibrated bore, a channel of large section, when a pressure which is greater than a predetermined threshold and which is not derived from the outlet is applied to the distributor member. The starter device is advantageously placed upstream of a pneumatic switch to which it is directly associated for the purpose of shortening its channels for transfer of fluid.

Abstract: A hydraulic control system, particularly for controlling the operation of roof support props of a mine working, employs control devices operated manually to feed pressure fluid to the working chambers of the props to effect extension or retraction thereof. A two-state valve device is operated when the props are extended to ensure that the correct setting pressure is established. This valve device has a control piston which is actuated to cause the device to establish independent connection between the main fluid pressure line and the associated working chambers of the props charged with fluid by the initial operation of the control devices. The connection established by the valve device is maintained even if the control devices break connection between the chambers and the pressure line. When the correct setting pressure is reached, a further control piston of the valve device is actuated to break the connection established by the valve device ready for the next operative cycle.

Abstract: The invention relates to a steering control unit for a bidirectional servomotor which is connectable to steerable wheels. A steering wheel controlled quantity setting unit of a known type has ports connectable to a pump and a return tank and two control ports through which metered quantities of fluid flow to opposite sides of the servomotor and to other parts of the apparatus for actuating the servomotor. A directional control valve for selectivity directing pressurized fluid from a power circuit to opposite sides of the servomotor is controlled by a control circuit containing the setting unit. A utility valve having the pressure regulating and control and power valve capabilities required for this type of apparatus is characterized by having only a single slide spool for performing all of these functions.

Abstract: Prior art interrupted series type load sensitive hydraulic systems have not had the capability of both providing full speed simultaneous vehicle cornering and implement correction while preventing the same when the implements are operating at a high pressure level, and preventing low torque motor stall. Herein, an input flow path (22) delivers pressurized fluid flow from a source (12) to a first priority (steering) circuit (14). A series flow path (24) delivers the output flow from the circuit (14) to an implement circuit (16). A parallel flow path (26) delivers a portion of the flow from the source (12) to the implement circuit (16). A valving structure (42) is in the series flow path (24). The valving structure (42) is opened in response to load pressure in the implement circuit (16) being at or below a selected value and is closed in response to the load pressure in the implement circuit being above said value.

Abstract: In a hydraulic apparatus, operating oil delivered from a fixed delivery hydraulic pump is divided into two parts, one end of which is discharged into an oil tank by passing through a serial circuit of a normally open valve and an orifice and the other end of which is supplied to a piston-cylinder mechanism by passing through a parallel circuit of a normally closed valve and a check valve. When the normally closed valve is closed and the normally open valve is gradually closed, the piston is raised while gradually increasing in velocity. On the other hand, when the normally open valve is totally opened to stop the piston and the normally closed valve is gradually opened, the piston is lowered while gradually increasing in velocity. When the valves are operated to cause the piston to move vertically, the impact applied thereto at the time when the valve opening is large is largely mitigated by using the orifice.

Abstract: A servo mechanism for adjusting the position of a biased control member of a sliding ring for controlling pressure fluid in a main conduit of a hydraulic machine, comprises a manually adjustable sleeve, a setting piston arranged for reciprocating movement in the sleeve and being hydraulically connected thereto to resume a position preset by the sleeve, a follower piston coupled between the setting piston and the biased control member of the recoiling device, a control pressure space provided above the follower piston, a unidirectional first control conduit delivering a regulating stream of pressure fluid from the main conduit to actuate the setting piston, a second control conduit between the main conduit and the pressure space, and a flow controlling valve controlled by pressure in the first control conduit for equalizing pressure between the pressure space and the main conduit thus allowing override of the setting piston during the pressure setting operation.

Abstract: A wheel cylinder includes a housing defining a bore. A piston is reciprocably received in the bore and cooperates with the housing to define a pressure chamber. The wheel cylinder comprises a passage for supplying pressurized fluid to the pressure chamber from a fluid pressure source. The supply passage includes a first portion defined by an annular groove on the piston and a blind axial bore in the piston which communicates with both the annular groove and with the pressure chamber. A valve apparatus is received in the blind bore and modulates the fluid pressure supplied to the pressure chamber as a function of the fluid pressure provided by the pressure source.

Abstract: The invention relates to hydraulic control apparatus for a servomotor of the type utilized for vehicle steering systems. Such apparatus has a control circuit controlled by a manually operated device such as a steering wheel and a power circuit connected between the servomotor and a power source such as a hydraulic pump. The power circuit includes resetting apparatus for throttling the return flow branch in a manner so that forces applied to the servomotor in the same direction as actuation are absorbed with a minimum of reactionary movement by the valves on the return flow side of the apparatus.