Abstract: A hydraulic control circuit arrangement for a single-acting cylinder provided with bottom and rod chambers separated by a piston having a piston rod extending the rod chamber, the arrangement including a directional control valve for controlling a supply of an operating oil from a hydraulic pump to the bottom chamber and an evacuation of the operating oil from both the bottom and rod chambers, a first pilot-operated valve for controlling the type of operation of the single-acting cylinder from a ram type to a piston type, and vice versa, in response to a change in an extent of a load applied to the single-acting cylinder during the lifting thereof, a short-circuiting conduit arranged between the bottom and rod chambers of the cylinder to short-circuit a flow of the operating oil from the bottom to rod chamber, and vice versa, a second pilot-operated valve located in the short-circuiting conduit to control the short-circuiting of the flow of operating oil, and a flow control valve for generating a pressure in

Abstract: A double-cylinder construction which can be used not only in large-sized compression molding machines but also in small-sized or medium-sized compression molding machines. In the double-cylinder construction of the present invention, a ram slidably fitted within an outer cylinder is provided in the center thereof with a hollow part. A rod slidably fitted in said hollow part is fixed to the bottom of said outer cylinder without penetrating said bottom thereof, and said rod does not contain an oil passage within. The double-cylinder construction always contains a certain amount of oil within and this self-contained oil is moved back and forth within the double-cylinder construction when the ram is being moved up and down. Therefore, the amount of oil supplied to the double-cylinder construction from outside is very small.

Abstract: A double operate check valve used in a hydraulic pressure circuit for locking and unlocking a vibration absorbing hydraulic cylinder included in a wheel suspension mechanism of a vehicle, which includes an improvement in its structure for providing the suspension with improved compliance with respect to road surface undulation and corresponding comfortable drive of the vehicle. The check valve pilot pistons have fluid conducting surfaces which are connected by a valve body passageway and which communicate the main fluid paths when hydraulic pressure in the pilot chamber urges the pilot pistons to open the check valves.

Abstract: A check valve assembly having first and second check valves and an unseating spool is positioned between a control valve and a rotary motor. The unseating spool is elongated so that it continually contacts the valve elements of the check valves. The check valve hydraulically coupled to the higher pressure supply/return line drives the unseating spool against the valve element of the other check valve opening it and connecting the associated supply/return line having lower hydraulic pressure to reservoir through the direction control valve.

Abstract: A control system for the hydraulic operating circuit associated with a vehicle lifting device in which the circuit is provided with pressure fluid control valves and flow sensors which are operative on the vehicle lowering cycle to establish substantial evenness of the lowering mechanism and protection against malfunction of an operating component to arrest the travel of the vehicle lifting device in its lowering cycle.

Abstract: A hydraulic circuit suitable for use in a hydraulic operating circuit of a power shovel includes a hydraulic cylinder for driving a working component and a hydraulic change-over valve for selectively supplying the cylinder with a discharge oil pressure of a hydraulic pump driven from an engine.

Abstract: A shaking control unit for a hydraulic cylinder, wherein a first predetermined pressure is admitted to the piston space of the cylinder through a first hydraulic line. A three/two-way valve connects in its zero position a second hydraulic line to a return tank, the second hydraulic line being connected to the first hydraulic line through a check valve. A first control line leads from the first hydraulic line to a first control area of the three/two-way valve. A second control line leads from the second hydraulic line to a second control area of the three/two-way valve. The three/two-way valve is constructed in such a way that, when the pressure in the first hydraulic line reaches a second predetermined pressure which is greater than the first predetermined pressure, the three/two-way valve switches and connects the first hydraulic line to the second hydraulic line. If the piston of the hydraulic cylinder meets an obstacle, the pressure in the first hydraulic line rises above a certain limit value.

Abstract: A lifting apparatus has two posts on either side. A lifting or cross member extends between them and is supported on carriages slidably mounted on the posts. Support arms or the like extend out from the support carriages for supporting a vehicle or other load. Actuators are provided for driving the carriages up and down. The actuators can be hydraulic cylinders connected in a master and slave relationship with a hydraulic connection between them through the cross member. Additionally, mechanical safety catches can be provided which are connected by a cable or the like through the cross member, to permit a single handed operation of them. In the further aspect of the invention, a mechanism is provided for locking the support arms angularly, which mechanism includes plungers that contact the ground and automatically free the support arms when the apparatus is lowered.

Abstract: A hydraulic safety brake valve arrangement for a motor controlled by a directional control valve. The safety brake valve arrangement has a main valve closing the load lowering conduit in a rest position. Pump pressure opens the main valve to throttle exhausted fluid and at the same time throttle fluid through the supply conduit to the opposed motor chamber. A compensating valve is placed in series with the main valve throttle for the loaded side of the motor. Motor speed is thereby controlled independent of the external loading on the motor.

Abstract: A hydraulic drive mechanism for a punching or an embossing tool, with a double-acting drive hydrocylinder with differently large piston areas, the rapid feed operation, the working feed operation, as well as the rapid retraction operation being controllable by the joint or alternative pressurization of these piston areas. For effecting switchover, an area switching valve is provided which switches over, once the driving pressure exceeds, for example, 90% of the maximum initial pressure of the pressure supply unit, from differential operation to unilateral pressurization of the larger drive area. The area switching valve comprises a check valve acted upon, in the opening direction, by the operating pressure in the smaller driving pressure chamber. A locking spring force of the check valve is equivalent to an opening pressure of about 90% of the supply pressure.

Abstract: A hydraulic differential cylinder comprises a cylinder, a piston slidably fitted in a cylinder chamber, a piston rod with one end coupled to said piston and an inner valve disposed in said piston rod. The cylinder chamber is divided by the piston into a rod-side cylinder chamber and a head-side cylinder chamber. The piston-pressure-bearing area of the head-side cylinder chamber is greater than the piston-pressure-bearing area of the rod-side cylinder chamber. The rod-side cylinder chamber is connected via the inner valve to a constant hydraulic pressure source. The head-side cylinder chamber is connected to a control hydraulic pressure source.

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: Hydraulic drive mechanism for a machine element with rapid feed movement and under-load feed movement, comprising a double-acting hydrocylinder power drive and a pressure switching valve responding to the pressure at least in a larger operating chamber of the hydrocylinder when the pressure in the operating chamber exceeds a threshold value higher than 1/4 of the operating pressure of the pressure supply source, but lower than half the operating pressure thereof, switches to under-load feed operation and, when the pressure in the drive pressure or operating chamber falls below the threshold value, switches back to rapid feed operation. The pilot valve for the main control valve is equipped with two windings effective in opposite directions.

Abstract: A hydraulically operating actuating device for a lift valve, in particular in an internal combustion engine, has a piston which is connected to the valve stem. The piston is positioned in a cylinder and separates two stroke spaces which are connectable, in each case via inlet and outlet openings which can be occluded by the piston, to a pump for the working fluid or a reservoir. In order to reduce the energy requirement of the actuating device, the two inlet openings, which in a central actuation range of the piston are open, are connected to one another directly by a line, and two springs which act in opposite directions and, in equilibrium, hold the piston in a central position relative to two end positions engage on the piston or valve stem.

Abstract: A weight-balancing system for a farm implement, such as a disk harrow with foldable wings operated by wingfold cylinders, includes a selective control valve for controlling fluid communication to the head and rod ends of the wingfold cylinders. A pair of pressure-reducing/relieving valves permit individual adjustment of the pressures in both the head and rod ends to achieve the desired balance. In a preferred embodiment, a pilot-operated, two-position valve is connected between the rod ends and one of the pressure-responsive valves. The two-position valve is operated by pressure signals generated by a flow-responsive switching valve connected between the two-position valve and the selective control valve. The switching valve and the two-position valve cooperate to block the pressure-controlled outlet of the one pressure-responsive valve and the rod ends and to bypass return fluid flow from the rod ends to sump when the cylinders are being extended.

Abstract: A shaking control unit for a hydraulic cylinder, wherein a first predetermined pressure is admitted to the piston space of the cylinder through a first hydraulic line. A three/two-way valve connects in its zero position a second hydraulic line to a return tank, the second hydraulic line being connected to the first hydraulic line through a check valve. A first control line leads from the first hydraulic line to a first control area of the three/two-way valve. A second control line leads from the second hydraulic line to a second control area of the three/two-way valve. The three/two-way valve is constructed in such a way that, when the pressure in the first hydraulic line reaches a second predetermined pressure which is greater than the first predetermined pressure, the three/two-way valve switches and connects the first hydraulic line to the second hydraulic line. If the piston of the hydraulic cylinder meets an obstacle, the pressure in the first hydraulic line rises above a certain limit value.

Abstract: A fluid operated circuit for controlling the movement of pistons contained in the drive and idler cylinders of a conventional dual post vehicle lift assembly of the type wherein the cylinders are hydraulically connected in tandem so that movement of the idler cylinder piston is dependent upon movement of the drive cylinder piston and wherein the pistons, while operative to lift and lower movable article supporting structures, are not fixedly connected thereto.

Abstract: A valve for retaining a jack which retains a drive load. The braking valve includes a pressure reducing valve and safety valve, one of which ensures that the pressure in the chamber is retained, while the other modulates the pilot-control pressure P.sub.p. Thus, at each moment, the pilot-control pressure P.sub.p is adjusted to the value of the retaining pressure P.sub.l.

Abstract: In an industrial, agricultural, or earth-moving vehicle, a charging pump, which delivers hydraulic fluid under pressure remaining substantially constant while the vehicle is operating and a coupler are combined. In the coupler, a hydraulically actuated piston-cylinder mechanism is used to wedge a pin into an orifice in an implement, thereby to couple the implement to the vehicle, and to withdraw the pin, thereby to uncouple the implement from the vehicle. A directional valve, which is connected between the pump and the piston-cylinder mechanism, is switchable by an operator of the vehicle between a first stage wherein the directional valve allows hydraulic fluid delivered by the pump to actuate the piston-cylinder mechanism in a forward direction, thereby to wedge the pin into the orifice, and a second stage wherein the directional valve allows hydraulic fluid delivered by the pump to actuate the piston-cylinder mechanism in a reverse direction, thereby to withdraw the pin.

Abstract: A locking valve assembly for use with air cylinder and in pneumatic circuits and including a locking valve for selectively locking air pressure in the air cylinder. The locking valve is pilot operated to provide for release of air pressure from the air cylinder and also includes a manual override apparatus for providing for release of the locking valve in the absence of pilot pressure.

Abstract: An improved compact pilot-assisted pressure relief valve is disclosed. The invention includes a vent piston or the like hydraulically dividing the valve body bore into a hydraulic fluid chamber and a spring chamber which is vented to atmosphere, such that backpressure is eliminated entirely for both faster reaction to pressure impulses and improved accuracy in pre-load setting of the valve assembly.

Abstract: A control switching arrangement for a hydraulic power lift control system comprises a power lift control valve which is controlled via control lines in a low pressure section. The main hydraulic section is controlled by the said control valve via a check valve which is hydraulically openable, at least for carrying out lowering movement by the power lift. The check valve is opened via the said control valve itself, which furnishes the switching line a pressure generally equal to the circulation pressure of the main hydraulic section. Further, means are provided whereby, in the switching state corresponding to lowering movement of the power lift, the circulation pressure of the main hydraulic section can be increased. With this control system the low pressure control section is simplified, and energy losses in the control system are kept as low as possible.

Abstract: The hydraulic control is constructed for time-sharing of the pump which normally controls the turning mechanism, to operate other hydraulic equipment in conjunction with other pumps.

Abstract: A power steering system for automotive vehicles includes devices for decreasing reaction force and for increasing assisting force applied to the steering wheel in cases where steering operation is performed while the vehicle is stopped. The device comprises a cut-off valve and a bias spring biasing the cut-off valve upwardly. The area of the upper surface of the cut-off valve is larger than that of the lower surface thereof. Therefore, the cut-off valve can move downwardly against the biasing force of the bias spring to block fluid communication between a fluid pressure source and chambers of a power cylinder when fluid pressure exceeding a predetermined value is applied to the upper and lower surfaces of the cut-off valve.

Abstract: The device comprises a pilot slide (27) controlled by a pressure differential (P-P') determined by an electromagnetic pilot valve element (43) located in a return circuit to a tank (7) which is common to both the hydraulic installation and a branch pipe (8). The device preferably includes an isolating valve (40) connected to the pilot valve element (43) so as to isolate a pilot chamber (30) in the event of a failure of the electromagnetic actuator.

Abstract: An actuator has a pilot valve incorporated in a piston thereof which is slidably disposed in a cylinder tube, the piston having first and second piston lands slidably disposed in first and second coaxial cylinder chambers. A spool valve body has first and second spool lands slidably disposed in an inner hole in the piston. When the spool valve body is moved in one direction, a first axial passage in the piston communicates with a pressure sink through a first return port which is opened by the first spool land, and a second axial passage in the piston communicates with a portion of the inner hole in front of the second spool land through a second supply port which is opened by the second spool land.

Abstract: The annular transmission block (13) is pressed against the transmission face (8) of the cylinder (5) when the oil pressure arrives via the duct (17). At that moment, one of the two grooves (19 or 10) can supply one of the two ducts (9 or 10) in such a way that the oil pressure is transmitted across the fluid-retaining devices (11and 12) to one of the two ends of the chamber (4). The pressure-maintaining device (25) is then charged by stressing its spring (27) and the piston (6) moves into the chamber (4) of the cylinder, carrying along the clamp chuck (7).

Abstract: A valve for cooling a reversible hydraulic machine includes a valve piston in a connecting channel extending between supply and discharge passages. Pressure in these passages displaces the spring-centered piston from neutral position to an end position. A central reduced-diameter portion of the piston carries a spring-centered closing member which closes a discharge conduit leading to a leakage space when the piston is in its central position. When the piston is displaced out of the neutral position toward one of the end positions, pressure from one of the connecting passages which has the lower pressure prevailing therein is permitted to propagate through one of the spring-receiving spaces delimited by the closing member and through an annular throttling gap present between the closing member and the central portion of the piston into the other spring receiving space and from there into the discharge conduit and into the leakage space.

Abstract: In a rotary fluid cylinder for operating a chuck of the type comprising a piston rod, guide rods disposed in parallel with the piston rod, spring biased check valve mechanism and pilot valve mechanism operating the check valve mechanism both contained in each guide rods, there are provided a pair of diametrically opposed annular pistons concentric with the piston rod, guide rods being received in the annular pistons for guiding longitudinal movements thereof, a cylinder head rotatably mounted on the piston rod, a rotary valve connected to the cylinder head for defining cylinders for accommodating the pair of annular pistons, a sleeve rotatably mounted on the rotary valve, and valve means for alternately admitting operating fluid in the opposite sides of each annular piston.

Abstract: A flow regulating device is placed between a compressed air distributor and a double-acting jack for regulating the admission and exhaust flow of compressed air. The device includes a body with a cylindrical housing in which is mounted for axial sliding a movable member, and within which are two passageways transversed perpendicular to the body. Each passageway issues into a chamber defined by a bottom, the housing and the movable member. The two chambers are isolated by the movable member which comprises a central seal. The opening of the passageways are defined by stop members placed at both ends of the housing.

Abstract: A chuck actuator has a cylinder extending along an axis and having an axially extending stem whose outer surface is formed with a pair of central radially outwardly open and axially spaced intake ports, a piston axially displaceable in the cylinder and forming therein two compartments connected via respective passages connected to the intake ports, two axially spaced bearings on the stem, and a connector supported by the bearings on the stem. This connector normally is restrained against rotation relative to the axis and has an inner surface closely juxtaposed with and forming with the stem surface an interface. Respective radially inwardly open and axially spaced inner feed grooves open at the interface level with the respective intake ports. Two independent hydraulic fittings communicating with the inner feed grooves can pass pressurized liquid to the respective compartments.

Abstract: A compensating valve arrangement is connected between a throttling direction control valve or proportioning valve which controls fluid flow from a pressure source to a load. The compensating valve is provided with a pressure reducing valve, check valves and throttling points between the pressure supply and the control piston of the compensating valve to compensate for surges, prevent sudden driving of the load and prevent leakage.

Abstract: A hydraulically controllable, leakproof holding valve is disclosed, and which is adapted to be attached in the lifting hydraulic line leading to a working cylinder or the like. The holding valve includes a slidably mounted control piston, which functions as a controlled non-return valve during periods when the working cylinder is stationary or being lifted, and the piston also functions as a throttling valve during periods when the working cylinder is being lowered.

Abstract: The invention contemplates hydraulic-lift mechanism which employs a power integrator in the connection between a charged hydraulic accumulator and the actuator for a vertically positionable load; the power integrator, additionally, has a prime-mover connection, and the pressurized charge of the accumulator is advisedly set to fully accommodate a preselected level of average load upon the actuator. The hydraulic circuit importantly includes check valves, with a pilot-operated check valve interposed between the power integrator and the accumulator and another pilot-operated check valve interposed between the power integrator and the load actuator. The pilot-operated check valves cooperate with other check valves to assure automatic transfer of hydraulic fluid under pressure from the accumulator to the load actuator, and vice versa, as may be determined by selected control of or via the power integrator.

Abstract: The invention relates to a coaxial multi-function insertable hydraulic distribution cartridge valve including various inlet and outlet ports (P1,X1,R1,S1,s1,D1,B1), a first compensating slide (N1) urged towards a position of full opening by a first spring (r1), a second internal slide (J1), concentric with the first, providing the principal regulation of the oil inlet flow rate, urged by a second spring (r2), against the control pressure delivered by the inlet port (X1), towards the position of closure of the communication between the oil pressure inlet port (P1) and the outlet port (R1) delivering the actuating pressure, and isolating (C) check valve and a backfeed (G) check valve, which are urged by a third spring (r3) to return these two check valves into the position of closure of communication towards (S1) for the check valve (C) and towards (T1) for the check valve (G), a third balancing slide (E1) urged by a fourth spring (r4), against the pressure delivered by the balancing pressure port (B1) and the

Abstract: A fluid cylinder control method for monitoring the position or controlling the movements of a piston which is slidably guided in a cylinder tube and is acted upon on at least one side by a pressure medium, in particular, maintaining the piston in a predetermined position against the action of eventual disturbance forces. This is attained in that the force which is transmitted between the piston and the cylinder by way of the parts which are slidingly guided on each other, and in particular the friction force acting by way of the seal gaskets of the piston and/or of the rod, is measured and the loading of the piston by a pressure medium is varied in the sense of reducing the measured force.

Abstract: There is disclosed a spool type direction control valve for controlling the oil flow direction in a hydraulic circuit including a pressure source, a hydraulic cylinder and a spool member. A flow control mechanism is provided in an oil passage connecting one of the oil chambers of the hydraulic cylinder to the spool member. The flow control mechanism comprises a poppet type piston adapted for opening and closing the oil passage. When the spool member is switched over for supplying the pressure fluid to the other oil chamber of the hydraulic cylinder, the pilot pressure from the pressure source is caused to act on the piston in the valve opening direction, while the back pressure of the discharge side pressure fluid corresponding to the load acting on the one oil chamber is caused to act on the piston in the valve closing direction, so as to control the discharge flow of the pressure fluid from the one oil chamber.

Abstract: A compensated control valve assembly for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load the controlled pressure level of a pressure reducing valve mechanism handling the fluid flow at negative load pressure is varied upstream of an outflow metering orifice arrangement, positioned at the outlet of the fluid motor, in response to pressure at the inlet of the fluid motor, while maintaining this controlled pressure constant at each specific level. The pressure differential across an inflow metering orifice arrangement, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by a positive load pressure compensating control device.

Abstract: A compensated direction flow control valve assembly for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load, the negative load compensating control varies the level of the pressure differential across a metering orifice, positioned at the outlet of the fluid motor, in response to pressure at the inlet of the fluid motor, while maintaining this pressure differential constant at each specific level. The pressure differential across a metering orifice, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by the positive load compensator control assembly.

Abstract: A hydraulic lock valve assembly (10) includes a valve body (16) having an axially extending main bore (18) and first and second axially spaced pump ports (20, 22). A tank passage (23) is in communication with said main bore (18) and first and second valve chambers (24, 26). The assembly (10) includes a spool valve (74) for opening either of the first and second check valve (36, 38) to allow fluid flow from the cylinder ports (28, 30) through the check valve (36, 38) and the inner passage (32, 34) to the pump ports (20, 22) to define a first return flow passage and for opening either of the first and second return ports (84, 86) to allow fluid flow to and from the tank passage (23) to and from the pump port (20, 22) through the return port (84, 86) to define a second return flow passage, whereby the spool valve (74) opens either of the first and second check valves (36, 38) in response to a predetermined delivery pressure in the delivery flow passage in opposite check valve chamber.

Abstract: A first path extends through the combined blocking and relief valve (10) from a first inlet/outlet port (44) to a first actuator port (88), and a second path extends from a second inlet/outlet port (46) to a second actuator port (82). The first path includes a spring biased poppet valve member (64) positioned to open in response to system pressure introduced into the valve (10) via the first inlet/outlet port (44). The second path extends between one end of a pilot piston (68) and one end of a relief piston (74). Pressure in the first path from port (44) acts on an area (A2) of the pilot piston (68) to produce a force on the pilot piston (68) tending to bias it away from the closure member (64). This same pressure is applied against an opposite side area (A5) on relief piston (74). This area (A5) is equal to the difference between the pilot valve area (A2) and the poppet valve area (A1) so that the pressure forces on the pistons (68) and (74) cancel each other out regardless of the pressure in the first path.

Abstract: A compensated direction flow control valve arrangement provided with a direction control spool for control of fluid flow to and from a fluid motor, which may be of a cylinder type and is subjected to positive and negative loads. During control of negative load the upstream of the outflow metering orifice, positioned at the outlet of the fluid motor, is maintained at a controlled constant pressure level by a pressure reducing valve handling the fluid flow at negative load pressure. The outflow metering orifice is made independent of the direction control spool and its effective flow area is made responsive and varies with the pressure at the inlet of the fluid motor. The pressure differential across a metering orifice, positioned at the inlet of the fluid motor, is maintained at a constant preselected level by the positive load compensator.

Abstract: An improved sequence-and-relief valve comprises a housing (60), a plurality of conduits (42/44, 46, 53) opening into a bore (62) within the housing, a valve cartridge (64) with the bore, the valve cartridge having a central bore (66) in which a valve element (76) may be moved into and out of contact with seat (74) to control flow from a cylinder port (70) to a tank port (72) in response to changes in pressure acting at pump port (68) or at cylinder port (70). See FIG. 2.

Abstract: A hydraulic control arrangement for height regulation of an agricultural vehicle has a control valve with a control slider provided with a first piston portion with a control edge and a second piston portion with a throttle point. In the positions of neutral and lifting of the control slider the control edge blocks the communication from a control chamber to a working chamber which is connected with a spring chamber of a throttle valve. In the position of lifting the control edge opens and the pressure medium flows via the throttle point from the working chamber in the control chamber. Thereby the pressure in the spring chamber of the throttle valve is lifted. Therefore a lower neutral circulating pressure and a higher pressure level in the position of lifting is possible.

Abstract: A reversing and adjustment mechanism, especially for a reversible plough adapted for hydraulically adjustable furrow width and hydraulic reversing of the plough, wherein the reversing and adjustment mechanism comprises a hydraulic cylinder (8) with a "hydraulic memory" for adjustment of the furrow width. The oil chambers on both sides of the ordinary piston (15) in the adjustment cylinder (8) communicate with a reservoir (24) via two pilot-controlled check valves (26, 25) with open passage toward the adjustment cylinder (8) and a second direction-control valve (10). The chamber (31) in the adjustment cylinder (8) between the rear head and a freely movable piston (17) communicates on the one hand with a hydraulic cylinder (7) for reversing the plough, preferably with the rod end thereof, via a first check valve (14) with open passage toward the reversing cylinder (7), and on the other hand communicates with the reservoir (24) via a flow-control valve (28) and a first direction-control valve (9).

Abstract: This invention relates to small-sized electrohydraulic actuators for use in adjusting aircraft control surfaces. A problem associated with such actuators is that they must be of a light-weight and efficiently packaged design. The present invention is designed to operate at relatively low hydraulic pressures. A balanced, double-acting hydraulic ram (10), connectable between a support (14) and a member to be moved relative to the support, includes a cylinder (18) divided into first and second chambers (20, 22) by a movable piston (19). A pump (26) having high and low pressure ports (38, 40) is connected to the cylinder (18) by first and second conduits (42, 44). A third conduit (48) connects an accumulator (46) to the first and second conduits (42, 44). A valve (52) is positioned in the third conduit (48), and blocks high pressure flow from a high pressure port in the pump to the third conduit (48).

Abstract: The invention is a lockout valve used in a hydraulic circuit to prevent leakage in a static condition; the lockout valve does not require outside force to hold the lockout open once flow across the lockout is established due to the positioning of an orifice ring around the poppet upstream of the poppet seat with the closing area acting on the poppet in conjunction with a spring which senses the pressure downstream of the orifice ring so that when there is sufficient flow across the orifice ring, the force created by the opening area on the poppet, which is located upstream of the orifice ring, will exceed the combined force of the spring and the closing area so that the lockout valve will remain open without an outside force so long as sufficient flow is maintained across the poppet.

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 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, a pilot operated meter-in valve to which the fluid form the pump is supplied for controlling the direction of movement of the actuator, and pilot operated meter-out valves associated with each 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 is sensed and caused to produce a force opposing the movement of the meter-out valve controlling flow from the actuator.

Abstract: A load control system is disclosed for preventing the uncontrolled lowering of a load should a line failure occur in a hydraulic system. The system is designed to be used with a hydraulic cylinder having a movable piston therein which divides the cylinder into a head end and a rod end. Attached to the piston and extending out of the hydraulic cylinder is a piston rod which has a load secured to its free end. The load control system includes a source of pressurized fluid, the flow of which is selectively controlled to the hydraulic cylinder by a control valve. Positioned between the control valve and the head and rod ends of the hydraulic cylinder, respectively, are first and second valves each of which is normally biased towards a closed position by a common pressure. The first and second valves are urged toward an open position by fluid pressure taken between the control valve and the first valve and are movable by this fluid pressure in a proportional manner with the second valve being opened first.