Abstract: The invention relates to a compressed fluid saving device positioned between the outlet of a distributor and the admission of a pneumatic jack. The device comprises a valve which is kept open, to allow the flow of driving fluid into one chamber of the jack from the start and right through the stroke, by the exhaust back-pressure escaping from the other chamber of the jack, and acting on the piston of said valve. When the back-pressure disappears, the valve closes under the action of a screw-adjustable spring.

Abstract: An hydraulically-controlled non-return valve for the hydraulic cylinders of a walking mine-roof support is provided with a cylindrical valve-closing member which is spring-loaded in the closing direction and is guided in a valve case in a valve housing, the valve-closing member being sealed off therein by means of a seal. A space on one face of the valve-closing member is connected to a circulating duct by way of a stepped bore in the valve case, which bore contains a spring-loaded throttle member having through-flow bores of which one has a throttle-like reduced cross-section. During setting of the hydraulic cylinder pressurized fluid flows past the opened valve-closing member through inclined bores and, by way of the circulating duct, to the stroke space of the hydraulic cylinder. During retraction of the hydraulic cylinder, a control piston in the non-return valve is loaded at the same time as an annular space in the hydraulic cylinder.

Abstract: Disclosed is a representative agricultural implement towed by a tractor equipped by a hydraulic power source connected to a lift mechanism for raising and lowering the implement frame so as to vary the ground-working depth of the working tools. The frame carries a sensor responsive to changes in implement depth above and below a preselected norm. This sensor serves as the input for the inventive control valve and system so as to control the implement lift system automatically. The valve is designed as a four-position valve, with one of the positions serving dual modes so that the system produces fast and slow raising, fast and slow lowering and a neutral or balanced position. The valve has a pressure port connected to the pressure side of the tractor source via a manual valve to afford three of the four active positions with one setting of the manual valve. The fourth active position (fast raise) is achieved by changing the manual valve to reverse the pressure and return ports in the depth control valve.

Abstract: A two-speed, pilot-operated selector valve which directs hydraulic fluid to two motor elements with a common output shaft to obtain a high-torque, low-speed mode, or to one motor element, while recirculating the second element in a loop, to obtain a low-torque, high-speed mode. The spool has a built-in logic mechanism which, while shifting from one position to the other, prevents any momentary condition where a motor discharge port is blocked or a fluid path exists that bypasses both motor elements.

Abstract: A pump 1 supplies hydraulic fluid from a reservoir 2 to hydraulically operated equipment 4 through a main flow line 3, the fluid being returned to the reservoir 2 through a return supply line 5. If the pump 1 should fail the equipment 4 may be supplied from an independent pump unit which can be connected to flow and return lines 6, 7. Because the pump 1 has failed it will be incapable of operating a dump valve 15 so the fluid will not be fed to the reservoir 2. Should there be a blockage in the equipment 4 pressure will build up in a relief valve 13 which will therefore open to allow the fluid to pass directly to the return line 5 (or 7). If the system is to be used as a source of pressurized hydraulic fluid for another unit then a change over valve 12 will be operated to de-couple the unit 4 and allow the fluid to pass to the other unit through the auxiliary supply lines 6, 7.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, and pilot operated meter-out valve associated with at least one opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve means is sensed and caused to produce a force opposing the movement of the meter-in valve means by the pilot pressure and also applied to a device for controlling an overhauling load resulting in a smooth and accurate control of the movement of the actuator.

Abstract: A hydraulic piston cylinder device comprising a cylinder, a piston dividing the cylinder into two cylinder spaces (A and B), and valve members between the cylinder spaces and respective pressure medium pipes. The problem is to achieve a hydraulic piston cylinder device in which the pressure or tractive force of the cylinder is maintained even if the external pressure led into the cylinder would stop. To solve this problem, an elastic material is interposed between two piston parts, and is elastically compressible by the external pressure applied to the cylinder; and the valve members are coupled to each other so that when one of the valve members is closed the other cannot be closed.

Abstract: A device for controlling a consumer, in particular a hydromotor includes a restrictor, preferably an electrohydraulic proportional directional control valve, and a control valve operating on the basis of a releasable non-return valve. The control valve is provided with an actuating cylinder-and-piston unit having control ports and a biasing spring for the piston. The control valve also has a connecting port which is connected with a connecting port of the restrictor. In order to substantially simplify the structural design of the device, a flow regulator is installed between the control port of the control valve and the connecting port of the restrictor which is connected with the consumer. The control sides of the flow regulator and the control valve are connected through a throttle with a supply container. The space of the cylinder-and-piston unit adjoining the control side of the control piston is connected with another connecting port of the control valve and with the restrictor.

Abstract: A hydraulic power source has a main body with a valve body and a valve assembly disposed in it. A reservoir and pump body assembly is connected to a top surface of the main body, and a hydraulic piston/cylinder assembly is connected to a bottom surface of the main body. A hydraulic circuit connects the various elements for fluid flow. The hydraulic power source is compact and can be located remotely on, for example a vehicle, at a point near an object or part to be moved.

Abstract: A marine propulsion device including a member adapted to be connected to a boat hull, and a propulsion assembly pivotally connected to the member for vertical swinging movement when the member is attached to the boat hull. The device also includes a plurality of hydraulic assemblies, each of the hydraulic cylinder assemblies including a hydraulic cylinder and a piston rod slideably received in the cylinder. The hydraulic cylinder assemblies are mounted between the member and the propulsion assembly to effect the vertical swinging movement of the propulsion assembly in response to movement of the piston rods in one direction relative to the cylinders and in the opposite direction relative to the cylinders. The marine propulsion device further includes a reversible pump including a first port and a second port.

Abstract: A metering lockout check valve which lowers gravity loads without chatter. The poppet has a conical concave face which surrounds an annular seat and is shaped so that as the poppet opens, the effective closing force increases requiring higher pressures in the opposite motor port to open the poppet. Conversely an overrun condition is prevented since when the pressure drops in the pump pressure side of the circuit, the poppet will reduce its opening and provide a metering function.

Abstract: An arrangement for controlling a hydraulic motor having supply and discharge sides, has a throttling directional valve having supply and discharge sides and a port, a speed lowering brake valve controlling the discharge side of the hydraulic motor and having a control piston with a control side and a port connected with said port of said directional valve, a control valve arrangement between the control side of the control piston and the supply side of the hydraulic motor and having end sides with end side ports, the control valve having a control slider which selectively connects the control side of the control piston with the supply side of the hydraulic motor and disconnects the control side of the control piston from the latter, is constantly connected at the end side ports with the discharge side of the hydraulic motor prior or after the directional valve and connects the discharge side of the hydraulic motor after the directional valve with the control side of the control piston or disconnect the discha

Abstract: A leak-detecting hydraulic system is disclosed for operation of a fluid actuator associated with a front-end loader, a backhoe, or a like implement on a material handling device. Notably, the system includes a leak-detection circuit which normally acts to prevent movement of the implement associated with the actuator by gravity in the event of a failure in one of the hydraulic fluid lines operatively connected with the actuator. Additionally, the system preferably includes a selectively operable float valve which permits fluid flow which bypasses the leak-detection circuit, thus desirably permitting operation of the implement associated with the actuator in a "floating" mode.

Abstract: A valve combining in a single unit a multiplicity of functions including isolation, thermal and pressure relief, return check and bypass. The valve includes a pair of spool valves, one slidably positioned within the other, disposed with a bore in a housing and interconnected with system pressure and return and an appropriate control valve.

Abstract: An improved machine tool has a chuck assembly which is actuated by a piston and cylinder type motor assembly. When a workpiece is to be gripped by the chuck assembly, high pressure fluid is directed to one chamber of the piston and cylinder motor and is exhausted from the opposite chamber. When the chuck assembly has gripped a workpiece, relative movement between the piston and cylinder is interrupted and fluid is no longer discharged from the motor. A pressure responsive switch assembly detects the reduction in the rate of the flow of fluid from the motor to provide a signal to indicate that a workpiece has been firmly gripped by the chuck assembly. After an initial machining operation in which relatively high forces are applied to the workpiece, such as during a rough cutting operation, the chucking forces applied to the workpiece are reduced prior to initiation of a finish cutting operation.

Abstract: A pumping unit for wells which is hydraulically powered and adapted to replace or used in lieu of conventional pump jacks. The hydraulic system utilized with the hydraulically operated pumping unit includes an accumulator system which stores energy produced by gravity induced downward movement of the pump rod and other pump components during the down stroke and automatically utilizes this stored energy to assist in lifting the pump components and the column of production fluid thereby increasing the efficiency of the pumping unit.

Abstract: A control valve system and method are disclosed for blowout preventers having an actuating piston for actuating the closing of the blowout preventer whereby the piston has an opening side and a closing side. The control valve system and method include a means for selectively directing fluid from the opening side of the actuating piston to the closing side of the actuating piston in order to reduce the fluid requirements for closing the blowout preventer and reduce installed horsepower requirements thereby.

Abstract: A hydraulic circuit for pitch and tilt control of a dozer blade attached to push arms on a vehicle with a pitch ram connected between one push arm and the blade and a dual actuator consisting of a second pitch ram and a tilt ram connected at their head ends. A pitch valve directs hydraulic fluid to and from the pitch rams with a diverter/combiner valve interposed therebetween to assure a flow of fluid either to said rams or from said rams at equal rates. Pilot-operated check valves hydraulically lock the pitch rams until opened by pressure directed from said pitch valve. Tilt and lift valves directs fluid pressure to and from the tilt ram and a lift ram respectively with regeneration capability for both tilt and lift functions.

Abstract: A chuck actuator has a cylinder extending along a main axis and a piston axially displaceable in the cylinder, forming therein two compartments, and having an axially backwardly extending stem also centered on the axis and formed with two respective intake passages each having one end opening into the respective compartment and another end opening at a respective location on the stem. A connector rotatable about the axis on the stem is provided with respective fittings communicating with the locations. First and second axially spaced bearings prevent the connector from moving axially on the stem. Fluid is fed under pressure alternately to the fittings to pressurize and depressurize the respective compartments and thereby axially displace the piston in the cylinder. Normally the cylinder is connected to a chuck body and the piston to a chuck-actuating member for fluid actuation of the member.

Abstract: Pressurization of closing and opening chambers of a door operator is controlled by first and second magnet valves coupled to the source of air. These valves are alternately energized by a switching network, e.g., a flip-flop, when sequentially actuated to close and open the door. The second magnet valve is biased to its vent position but the first valve is operated to its vent position by air through a double check valve when the second magnet valve is energized. Emergency and choke valves are inserted in series in the air supply to the magnet valves and normally pass air without restriction. Operation of the emergency valve, e.g., door blocked, shuts off air from the magnet valves and diverts that air to inhibit all output from the switching network and, through the check valve in opposite position, to operate the first magnet valve to vent position. Door operation is halted in position.

Abstract: A hydraulic system for trimming and tilting an outboard propulsion unit (10) includes both trim piston-cylinder units (22, 23) and a trim-tilt piston-cylinder unit (17). The flow of hydraulic fluid from the reversible pump (49) is controlled by a spool valve (26). A pressure relief valve (71) is mounted in the spool (50) to maintain pressure on one side of the spool (50) when the pump (49) is turned off to rapidly close the return valve (56) and prevent further movement of the piston-cylinder units.

Abstract: The body of the braking valve includes a front chamber, an intermediate chamber and a rear chamber which surround a blocking component and a governing piston. The diameter of the bore, in which slides the governing piston at the rear of the chamber, is equal to the diameter of the line along which the truncated conical bearing surface of the blocking component comes into contact with a seat situated between the front and intermediate chambers. The pressure in the intermediate chamber is connected to an outlet of a distributor which has no effect on the balance position on the blocking component.

Abstract: A counterbalance valve connects a source of hydraulic fluid to a power piston-cylinder unit for positioning and/or holding a load such as a pivoted bucket arm of earth moving equipment. A directional control valve is operable to reverse the supply connection to the cylinder unit and to operatively close the connections thereto to hydraulically lock the cylinder unit and attached load in place, with a highly restrictive bleed passageway. The counterbalance valve has a first valved passageway between a pair of ports which includes a check valve to provide one directional flow between the two ports. A dual poppet valve unit includes a pair of parallel passageways in parallel with each other and with the first passageway. The double poppet valve includes a main poppet valve having a valve stem with a piston head and a spaced member of a larger effective area.

Abstract: A hydraulic blocking valve for use in an aircraft flight power actuator employs a unique stepped piston design referenced to return pressure which provides pressure relief at a fixed value independent of system pressure.

Abstract: A 4-way, 3-position, on-off type electrohydraulic valve includes a pair of solenoid-operated inlet valves for controlling communication between a pump and a valve bore. A pair of adjustable check valves are positioned in opposite ends of the valve bore. A double-acting pilot return valve assembly is operably mounted in a central portion of the valve bore and is movable to engage and open one of the check valves to return fluid flow when pump pressure flows through the other check valve to a fluid motor.

Abstract: A hydraulic isolation valve (10) will not open if leaks are present in the associated utility subsystem (15). The continuity of the hydraulic fluid circuit actuates the valve (10) to the open position by an energized solenoid operated pilot valve (21) sending a small flow through a fuse (23) and one-way restrictor (24) to the utility function (15). If no leaks are present, the utility function (15) begins to actuate sending return flow through a two-way restrictor (31) and moving a continuity actuation piston (28) to push the shut off spool (16) to the open position so that full flow is admitted to actuate the utility function (15). If the continuity of the hydraulic circuit is broken by leaks, the return flow does not reach the continuity actuation piston and the shut off spool (16) remains in the shut off position, the fuse (23) closing to block further flow and then resetting by spring action when the solenoid operated pilot valve (21) is deenergized so that actuation may be attempted again, if desired.

Abstract: A hydraulic jack comprises a base having a vertically disposed cylindrical member attached thereto. A cylindrical movable member is mounted on the fixed member and is vertically movable relative thereto. The base is provided with passages therethrough which are connected in communicating relation to a source of fluid under pressure, such as a reservoir and pump. The fixed and movable members define a pair of variable chambers, each of which is connected in communicating relation with one of the passages by a restricted orifice to reduce the flow of fluid to and from the chambers. When one of the chambers is pressurized, the movable member is raised and will support a load engaged thereby. When the other chamber is pressurized, the movable member is lowered. Fluid in the chambers is prevented from returning to the reservoir by valve elements. A valve actuator is operated by fluid pressure and selectively opens each passage to permit the return of fluid to the reservoir.

Abstract: A combination hydraulic lock and pressure relief valve for use in an actuator system for operating a spoiler control surface is interposed between the retract side of the actuating piston and the servo valve controlling the piston. In this valve a poppet urged closed against a seat member by means of a light spring aided by the fluid pressure in the retract chamber of the piston holds the poppet closed whenever the system is shut down. A piston exposed to supply pressure carries a spring retainer which includes an elongated rod movable to dislodge the poppet from its seat to permit fluid to move toward and from the retract side of the piston during normal operation of the spoiler. A second retainer abuts against the seat and a heavy spring is interposed between the spring retainers. The seat member is loaded by the heavy spring to a predetermined level above normal system pressure.

Abstract: An hydraulic system: a power assisted vehicle steering system which includes such an hydraulic system and a method of alleviating noise in an hydraulic system. The hydraulic system as applied to a vehicle steering gear (1) has an open center valve (3) which directs hydraulic fluid under pressure derived from a pump (12) and in response to a steering maneuver through a shaft (4) to a servo motor of the gear (1). Downstream of the open center valve (3) is a restrictor (8) through which hydraulic fluid from the valve (3) passes to a reservoir (11). The restriction effected by the restrictor (8) to fluid flow from the valve (3) to the reservoir is variable to provide a throttling action and a back pressure in the line (6) to alleviate noise in the valve (3).

Abstract: A tunnel knife shield has a support frame, and a plurality of knives positioned side-by-side on the support frame. Each of the knives is associated with a double-acting hydraulic ram, the rams being used for advancing the knives, and for causing the support frame to follow up the advance of the knives. Hydraulic control means are provided for controlling the extension and retraction of the rams. Each ram has first and second working chambers, pressurization of which is effective to extend and retract that ram. The hydraulic control means comprises respective first supply lines for supplying pressurized hydraulic fluid to the first working chambers, respective second supply lines for supplying pressurized hydraulic fluid to the second working chambers, and respective discharge lines for discharging hydraulic fluid from the first working chambers. Each discharge line is provided with a flow-regulation valve and a pilot-operated non-return valve.

Abstract: A fluid flow controlling device includes a flow control that is interposed between the valve spool of a directional control valve and the work port channel of the directional control valve, and that is effective to control fluid flow to and from one motor port of a fluid motor in proportion to respective sizing of first and second fluid flow paths by the valve spool. The fluid flow controlling device is preferably used in load responsive hydraulic systems.

Abstract: A hydraulic valve for controlling a hydraulically-operated surgical table and the like comprising a body having a piston slidable in a piston chamber. Normally closed outlet check valves communicate with the chamber on opposite sides of the piston. Similarly located on each side of the piston are respective normally-closed inlet valves and relief valves. Slidable plungers are carried by the piston and may be rotated into and out of alignment with the associated check valve. In operation, the piston is rotated to align a selected plunger with an associated check valve and a fluid under pressure is introduced into the chamber on the opposite side of the piston to force the plunger against the associated check valve to open the same and permit the fluid to flow to and operate the load.

Abstract: An improved brake valve for a hydraulically powered winch which has one flow path permitting the relatively unrestricted flow of hydraulic fluid through the valve when the winch is being used to raise a load and a second flow path in which the flow of fluid is controlled in response to the pressure of fluid at the motor inlet when the winch is being used to lower a load. Of particular significance are a fixed area orifice, an annular restrictive passageway and a variable area orifice which cooperate to distribute the pressure drop in the control circuit so as to reduce the sensitivity of the valve to pressure fluctuations in the hydraulic motor circuit. Also of significance are seals used on the spool and damper piston to retard the movement of the spool and to produce a desirable hysteresis effect in its response to pilot pressure.

Abstract: A regenerative valve includes a housing having a valve bore therein intersecting with an extension passage interconnecting a pump and a piston extension chamber, a retraction passage interconnecting a sump and a piston retraction chamber, and a regenerative passage for communicating fluid from the retraction to the extension chamber upon extension of the piston. A poppet member is movable in the bore to open and block fluid flow through the extension passage. A shuttle member is movable in the bore to either open or block one or the other of the regenerative and retraction passages. The shuttle member engages the poppet to cause the poppet to open the extension passage when the shuttle moves to close the retraction passage and open the regenerative passage.

Abstract: The distributor is designed to control the supply of a fluid under pressure into a chamber of a hydraulic actuator and the outlet of fluid from another chamber of said actuator, and comprises a first chamber and a second chamber, which are designed to be communicated with one of said chambers of the actuator, and a slide valve movable in the direction of its axis in a corresponding seat of the distributor; the distributor comprises means which respond to the pressure prevailing inside said first and second chambers of the distributor and means for choking the cross-section of the outlet for the fluid from said first and second chambers of the distributor, said pressure-responsive means being connected to said choking means so that, as a result of a movement of the movable member of said actuator at a velocity higher than a predetermined velocity, said choking means bring about a reduction in the velocity of said movable body.

Abstract: A control mechanism (48) is provided to controllably maintain a constant force on an actuator (18) and provide fluid flow to a downstream control valve (24) by controlling a pilot differential pressure between first and second ends (38,40) of a pilot operated control valve (14). A two position valve (56,66) acting in response to a predetermined pressure level in the actuator (18) modulatably controls the flow of pressurized pilot fluid to the pilot operated control valve (14) to position the pilot operated control valve (14). This maintains the pressure in the actuator (18) at the predetermined pressure level and passes the excess flow of fluid from a source (12) to the downstream control valve (24).

Abstract: A multi-purpose lifting vehicle includes a hydraulic cylinder for controlling the elevation of a boom hoist device operably connected thereto. The device is alternately used in crane or front end loader modes of operation. The vehicle includes a hydraulic system for controlling the operation of the cylinder comprising a multi-position mode selector valve for selecting the specific mode of operation of the boom hoist device for raising, lowering and enabling the boom hoist device to float. The control system further includes a holding valve for locking the hydraulic fluid within the raising end of the cylinder for maintaining the elevation of the boom hoist device. A first bypass circuit is provided about the holding valve for enabling fluid to escape from the raising end of the cylinder while fluid is simultaneously flowing to the lowering end thereof.

Abstract: The invention relates to a fluid pressure supply and exhaust system for controlling a two part servomotor wherein relative loads are anticipated for one side of the servomotor. The system has a switching valve unit for selecting parallel supply and exhaust branches to direct supply fluid to the servomotor side subjected to negative loading. There are pressure regulating and throttling valves in the supply branch and a reducing valve in the exhaust branch. The supply pressure downstream from the throttle valve is directed to the reducing valve with a valve closing effect so that a sharp negative load will simultaneously reduce the supply pressure to the servomotor while increasing the throttling of the return flow.

Abstract: An improved valve in use for underground mining in connection with a piston cylinder unit, such as a hydraulic prop, is disclosed. The valve includes a piston member within a control chamber which is operative to terminate fluid communication between the hydraulic prop and a hydraulic fluid source. The piston is pressure-equalized in a neutral position when the hydraulic prop is set.

Abstract: An electrohydraulic control arrangement comprising at least one terminal plate having an inlet port connected to a pump pumping fluid under pressure from a tank and an outlet port connected to a return conduit leading to the tank and a plurality of consumer plates having consumer ports connected to consumers of pressure fluid. All plates are arranged side by side and held in abutting relationship by tightening screws extending through axially aligned bores through said plates. The plates are further provided with three axially aligned fluid channels therethrough, one to be connected to the inlet port and the two others to the outlet port. The selective connection of the fluid channels to the respective ports is accomplished in the terminal plate by a control slide movable by auxiliary valves, one of which is controlled by an electromagnet and by an additional control slide in each of the consumer plates, the position of which is controlled by two additional auxiliary valves.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, pilot operated meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator,and means for sensing a predetermined drop in a line supplying fluid to one opening of the actuator caused by a runaway load in one direction and operating the meter-out valve means to interrupt flow out of the other opening of the actuator.

Abstract: A control valve system and method are disclosed for blowout preventers having an actuating piston for actuating the closing of the blowout preventer whereby the piston has an opening side and a closing side. The control valve system and method include a means for selectively directing fluid from the opening side of the actuating piston to the closing side of the actuating piston in order to reduce the fluid requirements for closing the blowout preventer and reduce in stalled horsepower requirements thereby.

Abstract: A control valve that can be used as a pilot-assisted pressure relief valve or as a sequence valve, which is substantially insensitive to system back pressure. The valve comprises a valve body 10 defining a multistep bore 36, and a valve member 44 engageable with a coaxial valve seat 46, both supported for reciprocating motion within the bore 36 and cooperating to control the fluid communication between first and second ports 30, 32 defined in the valve body 10. A primary biasing spring 48 enclosed within a vented spring chamber 52 urges the valve member 44 into engagement with the valve seat 46. Fluid pressure at the first port 30 exerts fluid forces on the valve member 44 that opposes the primary spring force. The valve member 44 is a unitary element including first and second annuli 44a, 44b joined by a reduced diameter shank portion 44c. A radial surface on the first annuli 44a defines a net effective pressure area against which fluid pressure at the port 30 is applied.

Abstract: The invention relates to a hydraulic motor assembly which includes a hydraulic servomotor operable in either direction with a control valve. When the motor is operated in a selected direction, as distinguished from the return direction, it is desired that external forces acting on linkage connected to the piston of the hydraulic motor do not alter the speed of the piston. The control valve has two operating positions and two sets of supply and return passages which facilitate operation of the servomotor in either direction. A brake valve between one of the servomotor ports and the control valve has a scanning port which scans or senses the downstream pressure of either of the control valve supply passages, depending on the control position of the control valve.

Abstract: A fluid control system for selectively holding a work implement, such as a blade in a motor grader or the like, in a fixed position in a first operation mode, and for selectively providing a shock absorbing system (70,72) for the implement in a second operating mode. In the fixed position mode, lock valves (36,38,68) are operative to provide positive locking for an implement actuator (24,26), while in the shock absorbing mode, longstem lock valves (82,84) are operable to maintain one check valve (102) of a dual valve structure (96,98) unseated at all times. Each unseated check valve (102) provides a connection of one end of an implement actuator (24,26) to vent to insure that the shock absorbing system (70,72) maintains a full shock absorbing capacity.

Abstract: An electrically controlled hydraulic remote controller for use in piloting the operation of a hydraulic control valve comprising a pair of electrically operated three-way pressure control valves. Each control valve has a supply pressure inlet and a controlled pressure outlet operable in the de-energized position to prevent flow from the supply inlet to said controlled pressure outlet and connect said outlet to tank pressure. Each valve when energized is operable to permit fluid flow from the inlet to the controlled pressure outlet in proportion to the solenoid force operating said valve and simultaneously permit fluid to flow to tank pressure. The controller is responsive to the higher of the controlled pressure of the outlets of the two pressure controlled valves for applying the higher controlled pressure to the valve having the lower controlled pressure to operate the valve in direction increasing the passage of fluid through the other valve to tank.

Abstract: A counterbalance valve for controlling the flow of fluid from a hydraulic motor when a load is lowered has a pilot operated valve which modulates the flow of pressure fluid to and from a control port connected to main valve poppet to thereby set the opening of the poppet.

Abstract: A pilot-assisted pressure relief valve including a valve body 10 defining a first and second plurality of ports 30, 32 and an internal stepped bore 40 that slidably supports an elongate, tubular primary piston 34 engageable with a valve seat 36 mounted at one end of the valve body bore, which cooperate to control fluid communication between the first and second plurality of ports. The piston 34 is biased towards a flow interrupting position by a spring and is biased towards an open position by fluid pressure at the first plurality of ports. A pilot-operated piston 70 is mounted coaxially with the primary piston and is operative to engage the primary piston 34 and oppose the spring force thereby reducing the effective relief setting of the valve.

Abstract: An actuator for a power chuck has a hollow actuator housing having a rearwardly extending housing tube that is centered on an axis and that has a closed rear end. This tube is formed with a pair of axially spaced and radially inwardly open grooves both having axial lengths equal at least to a predetermined axial distance, and the tube is further formed at these grooves with respective radially throughgoing apertures. A piston subdivides the interior of the housing into a pair of compartments and has a stem extending axially rearwardly in the tube. This piston is axially displaceable in the housing through an axial stroke at most as long as the distance corresponding to the axial lengths of the grooves. The piston is formed with a pair of throughgoing passages each having one end opening at the stem into a respective one of the grooves and another end opening into a respective one of the compartments.

Abstract: A throttle valve biased to open position by a spring is interposed in the return line of a steering control valve in a booster steering system. The essential feature of the invention is that one face of the valve is exposed to feed pressure acting against a valve opening bias spring to produce the throttling effect in accordance with construction and design of the valve and the system in which it may be used. The invention is particularly intended for use with booster steering control valves in neutral or steering position and ensures throttling of return flow to the system sump only during a steering operation. The invention is usable in steering mechanisms such as shown in the patent to Wagner et al., U.S. Pat. No. 3,964,371.