Abstract: A valve includes a distributor with four ports and two positions. In a first position, a first non-return valve allows only circulation of a fluid from the first port toward the third port, while the second port and the fourth port are directly in communication with one another. In a second position, the third port and the fourth port are directly in communication with one another, while a second non-return valve allows only circulation of fluid from the third port and the fourth port in communication toward the first port.

Abstract: A 2-position, 3-way directional control valve is described which prevents reverse flow from an actuator port to a pressure port in one position. In the preferred embodiment described, the valve is solenoid actuated and is spring biased to a drain position, wherein an extension central to a spool assembly penetrates through a check valve seat and lifts a check valve ball from its seat to permit flow from an actuator port to a drain port. In the actuated or energized position, an armature assembly is shifted by a solenoid, drawing the spool assembly within the valve body and establishing a fluid path between a pressure port and the actuator port. In this position the extension of the spool assembly is withdrawn from the check valve seat. The check valve can be unseated by pressure from the pressure port to permit flow from the pressure port, through the spool and the check valve assembly.

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

Abstract: A pressure-responsive hydraulic control system (10) has a load-sensing flow-compensated pump (S) connected to a plurality of work sections; with a direction control valve (26, 26') and a pressure compensator valve in each work section; and with a flow-regulated logic check system (45); a flow-metered logic check system (40); an isolation circuit (60, 160, 260); and an induced load check system (70). Each pressure compensator valve is supplied flow-metered fluid from the respective direction control valve and supplies flow-regulated fluid to a hydraulic motor. The flow-regulated logic check system (45) provides a flow-regulated maximum output signal, and the flow-metered logic check system (40) provides a flow-metered maximum output signal.

Abstract: A hydraulic control device having a directional valve by means of which the direction of movement and the speed of a hydraulic consumer, especially a mobile working device can be modified. The hydraulic control device has a hydraulic pre-control device by which a control pressure can be applied, via a first control line, to a first control chamber and, via a second control line, to a second control chamber of the directional valve, and having valve arrangement in a first control line by which a largely free flow of control oil is admitted to a first control chamber and by which, by a throttling of the discharge of control oil, the movement of a control slide of the directional valve can be damped.

Abstract: A hydraulic control valve formed as a magnet valve with several connections and switching positions, comprises a housing provided with several connections, a valve slider displaceable in the housing, an electromagnet provided with an extensible plunger for controlling the valve slider, a valve seat provided in the housing, a ball movable between a closing position and an opening position with respect to the valve seat, a closing spring which urges the ball to the closing position. The ball is bringable by the valve slider to the opening position under the action of a force of the electromagnet, a valve body is firmly but exchangeably inserted in the valve housing so that the valve slider is guided in the valve body. The valve body accommodates the valve slider, the ball and a closing spring which presses the ball against the valve seat. A plurality of conduits are provided, including a pressure conduit, a control conduit and a consumer conduit.

Abstract: An operating valve assembly with a pressure compensation valve, comprises a spool for selectively establishing and blocking communication between a pump port, an output port and a main tank port, being disposed within a spool bore of a valve body, and a pressure compensation valve being provided between the output port and the actuator port. The pressure compensation valve has a piston pressed in the closing side by a load pressure acting on a compensation pressure acting portion, and a valve provided integrally with the piston for selectively establishing and blocking communication between the output port and the actuator port, and actuated for opening by the output port pressure acting on a portion to be compensated, the compensation acting area being equal to the area to be compensated.

Abstract: A control is proposed for dividing the output flow in hydraulic systems made available by at least one pump to a plurality of users according to the load pressure-independent principle in case of output flow undersupply of the users, wherein a compensator is connected downstream of each control slide valve provided with a predeterminable control cross section, with the compensator including a piston and actuating element and each user connected downstream of the compensator receiving a predeterminable portion of the output flow as a function of the degree of undersupply by the pistons of the compensators, with the piston being acted upon by different forces which bring about different opening pressures.

Abstract: A gas operated release or ejection system which compensates for changes in pressure applied to a load being ejected. The pressure regulator compensates for decreases in pressure through a pressure regulating valve, and compensates for increases in pressure through a pressure relief valve.

Abstract: A hydraulic elevator up direction control system is provided that has a circulating valve connected between the supply and the return of a source that normally supplies pressure to the cylinder of an elevator. The circulating valve is controlled by a computer regulated stepless variable solenoid valve that influences the pilot fluid pressure in the operating chamber of the circulation valve to control the size of the opening of the circulating valve and thereby the volume of fluid passing through the circulating valve. This affects inversely the volume of fluid passing through a fluid flow measuring valve, to the cylinder, to provide selectably variable up speeds of travel facilitating a fast, smooth, accurate ride of the elevator car as it approaches a stopping point relative to an upper floor of a building. Such operation is substantially independent of the system pressure and fluid viscosity. A selectably variable speed down direction control system operates on largely the same principle.

Abstract: In a hydraulic device including at least two actuators both adapted to be operated by a single pump, one of the actuators having priority over the other actuator, a control valve for the one actuator including a load hold check valve adapted to assign a variable priority function to the one actuator over the other actuator, the load hold check valve including a valve body provided with a pair of ports respectively communicating with the actuators and a parallel fluid passage communicating with the pump, the parallel fluid passage also communicating with a selected actuator port in an opened state thereof, a poppet disposed in the valve body and adapted to fully open the parallel fluid passage at a full stroke thereof and partially opening the parallel fluid passage at a limited stroke thereof, and a pressure setting spring adapted to always urge the poppet toward the initial position for closing the parallel fluid passage.

Abstract: A hydraulically supported power steering system is disclosed for motor vehicles including a double-acting hydraulic displacement unit or piston/cylinder unit for generating an auxiliary hydraulic force. For this purpose, the displacement body working spaces or piston working spaces can be acted upon by controllable hydraulic pressure or relieved of hydraulic pressure by means of associated conduits controlled by a servo-valve. The displacement unit or piston/cylinder unit also undertakes the function of a steering damper by means of damper valves arranged on the conduit connections. The damper valves include a perforated disc type of support part which can be clamped in the manner of a spacer ring between a bearing surface of a connecting mouthpiece arranged on a housing of one of the servo-valve and the displacement unit and an opposite bearing surface of a connecting part of a conduit, said connecting part being detachably connected to the connecting mouthpiece.

Abstract: A control arrangement for at least one hydraulic consumer in which the consumer can be controlled with respect to direction and speed via a directional control valve device, in which two consumer lines lead from the directional control valve device to the consumer, each of which consumer lines can be connected to a pump and a tank respectively via a directional control valve piston and a metering restrictor and in which a throttle valve having a servo-piston is associated with each consumer line. The consumer is to be held free of leakage oil in a given position.

Abstract: An operating valve assembly incorporates a pressure compensation valve and is capable of contributing down-sizing of a hydraulic circuit. The valve assembly includes an operating valve, compensation valves and a load pressure detecting portion. A valve body of the operating valve defines a spool bore extending laterally through the valve body at a vertically intermediate portion of the valve body, a load pressure detecting port at a laterally intermediate portion of the spool bore, and a respective pump port, actuator port and tank port at each side of the load pressure detecting port. The operating valve also includes a spool within the spool bore. The pressure compensation valves are arranged at left and right sides of an upper portion of the valve body and the load pressure detecting portion for supplying load pressure to the load pressure detecting port is formed in the spool.

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

Abstract: Simultaneous operation efficiency in a case where a plurality of actuators are operated by one or a plurality of hydraulic pumps is improved. A delivery pressure passage (1a) of one hydraulic pump (1) and that (1a) of the other hydraulic pump (1) communicate with each other through a first short-circuit passage (39) via a pair of check valves (38, 38), and an unload valve (40) is provided in this first short-circuit passage (39). The load pressure introduction passages (6, 6) on the left and right hydraulic pumps (1, 1) communicate with each other through a second short-circuit passage (36) via a pair of check valves (35, 35), and a relief valve (37) is provided in this short-circuit passage (36).

Abstract: This actuating drive (1) for a control valve (2) has a control circuit which sets the actuating drive (1) to correspond with a specified required value from an overriding installation control system. It has, in addition, a main piston (6) sliding in a main cylinder (5) with a drive volume (7), on one side of the main piston (6), which can be acted on in a controlled manner by oil under pressure and has a plate valve (17) fitted upstream of the drive volume (7).The intention is to create an actuating drive, for a control valve, whose dynamic behavior can be improved by relatively simple means. This is achieved by the plate valve (17) being provided with a separate reservoir volume, connected to a drain appliance, for the oil emerging from the plate valve (17).

Abstract: An operating valve device for supplying fluid under pressure to an actuator comprises: a first hole (3) and a second hole (4) for allowing fluid under pressure supplied by a pump (P) into an inlet port (2) connected with the pump to selectively flow into pressure chambers (B.sub.1, B.sub.

Abstract: A holding valve for use in a hydraulic operating system of a machine which is adapted to perform both lifting and digging functions is disclosed. The holding valve includes a conventional poppet assembly for modulating the rate at which hydraulic fluid flows from a hydraulic cylinder when the machine is used for lifting functions. The poppet assembly regulates the speed at which a heavy load can be lowered. The holding valve further includes a pilot actuated piston assembly which is operated only when the machine is used for digging functions. When so actuated, the piston assembly engages the poppet assembly and moves it to a fully opened position. In this fully opened position, the poppet assembly is prevented from modulating the flow rate of hydraulic fluid therethrough, effectively removing the holding valve from the hydraulic circuit. Consequently, hydraulic fluid can flow to and from the digging device without interference from the holding valve.

Abstract: A valve for slowly starting an actuator includes a block having an inlet port, an outlet port, and a passage providing communication between the inlet and outlet ports. A first valve body is disposed in the passage for selectively opening and closing the passage, and a second valve body is disposed downstream of the first valve body with respect to the passage for selectively opening and closing the passage. A needle valve is disposed in the block parallel to the second valve body between the passage and the outlet port for restricting the fluid under pressure discharged from the outlet port. The second valve body has a passage defined therein and communicating from one end to the other end thereof, and first and second pressure-bearing surfaces on the one and other ends, respectively, the first pressure-bearing surface is wider than the second pressure-bearing surface.

Abstract: A counterbalance valve has a first port connected to a hydraulic cylinder and a second port connected to a four-way controller, such as a four-way control valve. Disposed between the ports is a poppet biased to a closed position. The poppet opens to allow operating hydraulic fluid to drain from the hydraulic cylinder and also opens if excessive pressure builds up in the hydraulic cylinder due to thermal conditions. When an operator decides to move the piston within the hydraulic cylinder, hydraulic fluid must be drained from the cylinder. This is accomplished by moving the poppet from a blocking position to an open position with pressurized pilot fluid. On occasion, confusion caused by operator error can cause a build-up of valve backpressure from the four-way control valve, which prevents the poppet from moving upon applying pilot pressure thereto. The resulting excess pressure in the hydraulic cylinder can rupture the hydraulic cylinder.

Abstract: A hydraulic circuit for a swivel working machine, in which the operation of the working unit is speeded up when the swiveling body and the working unit are simultaneously operated, includes, for this purpose, first and second operating valves (15.sub.1 and 15.sub.2) connecting the delivery conduit of a hydraulic pump (10) to a swiveling hydraulic motor (16.sub.1) and to a working unit cylinder (16.sub.2), and pressure compensating valves (18) provided between the first operating valve (15.sub.1) and the swiveling hydraulic motor (16.sub.1) and between the second operating valve (15.sub.2) and the working unit cylinder (16.sub.2), the load pressure of the swiveling hydraulic motor (16.sub.1) and the load pressure of the working unit cylinder (16.sub.

Abstract: An operation valve having a pressure compensation valve of relatively simple non-complicated internal body structure. In the valve body, a load pressure introducing passage, a check valve and a restriction are formed inside the spool comprising the operation valve. An intermediate pressure between an inlet pressure and an outlet pressure of the compensation valve which is arranged in the valve body, may be supplied to a pressure receiving section of the pressure compensation valve through an oil hole of the spool. The operation valve with the pressure compensation valve is of simple construction and may be easily manufactured.

Abstract: In the hydraulic apparatus (1) according to a first aspect of the present invention, mid-pressures between the inlet side and outlet side pressures of a first and a second pressure compensating valves (4, 4') are permitted to act on the flow rate decreasing side pressure receiving surfaces (4b, 4b') thereof through first and second mid-pressure supplying means (13, 13'), thereby restraining operational error and malfunction of the pressure compensating valves (4, 4'). In the hydraulic apparatus (20) according to a second aspect of the present invention. when actuating valves are made to assume neutral position, holding pressures of hydraulic actuators (5, 5') are permitted to act on flow rate decreasing side pressure receiving surfaces (4b, 4b') of pressure compensating valves (4), (4') so that spools of the pressure compensating valves are held at compensating position, thereby improving the response of the hydraulic actuators (5, 5') to lever actuation.

Abstract: In a control device (S) for a hydraulic motor (V) which is adapted to be ed upon at both sides, there are provided working conduits (4, 5) which are alternately connectable via a directional control valve (C) to a pressure source (P) and a tank (T), a load holding valve (H) which is hydraulically openable in a controlled way and is arranged in at least one working conduit (4), as well as a control pressure conduit (13) which is connected to the opening side (16) of said load holding valve (H), with pressure variations arising during the controlled opening of the load holding valve, and the amplitudes of the pressure variations being adapted to be dampened in the control pressure conduit (13) at least via a damping throttle (D).

Abstract: This invention provides a hydraulic circuit system capable of reducing the flow rate distribution error in supplying pressurized fluid from a single hydraulic pump into a plurality of hydraulic actuators, and also supplying pressurized fluid quickly. The circuit is simplified to reduce manufacturing costs.

Abstract: In a hydraulic control device (S) comprising a double-acting hydraulic consumer (V) which is actuable by pressure via two working conduits (4, 5) and secured in at least one working direction by a load holding valve (H) which is hydraulically openable and closable in a controlled way, further comprising a control pressure conduit (12) which is connected to a control connection of the load holding valve and selectively actuable, as well as a damping throttle (13) arranged in control pressure conduit (12), there is provided a valve (15, 15', 15", 15'", 15.sup.IV) which during the controlled closing movement of load holding valve (H, 6) is automatically responsive to a delay of the controlled closing movement which is caused by the instantaneous viscosity of the pressure medium and/or a too tight setting of damping throttle (13) and is critical as to the after-running of hydraulic consumer (V) under a load (F), with the valve switching in such a case to passage and bypassing damping throttle (13).

Abstract: When a hydraulic circuit for driving actuators of a construction machine or the like includes a single hydraulic pump and a plurality of direction changeover valves connected to the hydraulic pump for controlling the respective actuators, operation of one of the direction changeover valves may result in undesirable change in the output oil pressure of the other direction changeover valves. The inventive hydraulic circuit includes means for driving a regulator of the hydraulic pump in response to any oil puressure change at the inlets of the direction changeover valves corresponding to the output oil pressure change, thereby compensating for the pressure change.

Abstract: This invention provides a hydraulic circuit apparatus for operating a work-implement actuating cylinder arranged such that, during an earth compacting operation using a bucket, a work implement or boom is lowered by its own weight, and during other operations, a part of the fluid under pressure in a lifting chamber of the actuating cylinder is supplied together with pressurized fluid discharged by a pump into a lowering chamber to increase the retracting speed of a piston rod in the work-implement actuating cylinder. The apparatus comprises a spool slidably inserted in a valve bore formed in an operating valve body so that it may be moved between a first actuating position, where a second port connected to the lowering chamber is communicated with a second tank port and a first port connected to the lifting chamber is communicated with a first pump port; and a second actuating position, where the second port is communicated with a second pump port and the first port is communicated with a first tank port.

Abstract: A hydraulic circuit arranged to prevent the load pressure in one of the hydraulic actuators at the time of starting from becoming abnormally high thereby preventing fluid under pressure from being relieved by the safety valve when a plurality of hydraulic actuators are operated at the same time, wherein the function of one of the pressure compensating valves is temporarily enhanced by introducing the load pressure in the hydraulic actuator so as to supply a large quantity of fluid under pressure to the hydraulic actuator connected to the pressure compensating valve so that the operating speed of the hydraulic actuator can be increased.

Abstract: An extensible mechanism, in which a first hydraulic cylinder and piston has a fixed reference for movement in an extension direction and also in a retraction direction. A second hydraulic cylinder and piston is moveable in both of these directions. Hydraulic fluid actuates the first and second hydraulic units in series, whereby actuation in the extension direction sequentially moves the first and second hydraulic piston and actuation in the retraction direction reverses the sequential order of movement of the two hydraulic pistons.

Abstract: A hydraulic drive system for construction machines includes a hydraulic pump (1), a plurality of hydraulic actuators (2, 3) driven by a hydraulic fluid supplied from the hydraulic pump, a plurality of flow control valves (4, 5) for controlling flow rates of the hydraulic fluid supplied to the actuators, respectively, and a plurality of distribution compensating valves (6, 7) for controlling differential pressures across the flow control valves, respectively, the plurality of actuators including a first actuator (2) which undergoes a relatively large load pressure and a second actuator (3) which undergoes a smaller load pressure than that of the first actuator.

Abstract: A speed control device for a pneumatic cylinder of the invention is characterized in that a speed control of the pneumatic cylinder can be changed from air pressure to air mass flow by a two-way valve and an airflow control valve. Therefore, an ordinary and low moving speed of a load is maintained even if the load changes its speed or stops moving, and thus any accidents caused by a change of the moving speed of the load are prevented beforehand. Additionally, since in this invention only a two-way valve and an airflow control valve are added to a conventional pneumatic cylinder and high relief type pressure reducing valve, the device of the invention is simply constructed and has a wide variety of usage. Furthermore, since the device of the invention is provided with a pressure accumulator and a checking valve, the pneumatic cylinder can be stably controlled even when the load moves at a high speed.

Abstract: A counterbalance valve including a spool (62) divided into two spool pieces (63, 64) at its axial center, return springs (71, 72) for urging the spool pieces inwardly along the axial direction toward their innermost positions, a first passage (90) for introducing an inside pressure in a supply and exhaust passage (48) to an outermost end of the spool piece (63), a second passage (91) for introducing an inside pressure in the supply and exhaust passage (49) to an outermost end of the spool piece (64), a pressure selecting member (88) for selecting higher inside pressure among the inside pressures in the supply and exhaust passages (48, 49) and for introducing the selected pressure via a choke (87) to a pressure chamber (73) formed between the spool pieces (63, 64), and a communicating passage (95) formed for communicating the supply and exhaust passages (48, 49) with each other when both the spool pieces (63, 64) are moved outwardly in the axial direction from the innermost positions due to fluid in the pressu

Abstract: A control system for longwall face support frames as used in mines, the system comprising pushing rams which are adapted to be actuated at two different pressures (for example, a low pressure of about 70 to 120 bar for non-defined cutting and a high pressure of 120 to 350 bar for defined cutting) with each pushing ram being individually actuatable by a respective non-return valve arrangement, the pushing rams being connected by a common pressure line to an hydraulic pressure unit.

Abstract: A check valve (14) with a valve opening actuator function and a bypass opening/closing valve (17) are disposed in parallel in a pressure oil supply/discharge passage (3) connected in communication with a hydraulic actuation chamber (2). The opening/closing valve (17) is adapted to be held at a valve opened position (Y) against a residual pressure holding spring (19) when the pressure on the check valve inlet (14a) side is normal and to be changed over to a valve closed condition (X) by means of the spring (19) when the pressure has lowered to a predetermined value. The pressure oil supply/discharge passage (3) and a pressure discharge passage (7) are connected in communication with each other through a pressure compensation valve (12). The opening/closing valve (17) is composed of a piston valve member (38) resiliently biased against a bypass valve seat (40) by means of the spring (19).

Abstract: A check valve (14) with a valve opening actuator and a bypass passage (16) are disposed in parallel in a pressurized oil supply/discharge passage (3) connected in communication with a hydraulic actuation chamber (2). A residual pressure holding valve (17) and a flow restrictor (21) are disposed in series in the bypass passage (16). The supply/discharge passage (3) and a discharge passage (7) are connected in communication by a pressure compensation valve (12). While the valve (17) is adapted to be moved to a valve closing position by means of pressure supplied at a check valve inlet (14a) and a residual pressure holding spring (19), it is adapted to be moved to its valve opening position by means of pressure supplied at a check valve outlet (14b). The valve (17) includes a valve member (38) resiliently urged to a valve seat (40) by means of a spring (19).

Abstract: A hydraulic circuit system comprising a hydraulic-fluid supply source, at least one hydraulic actuator operated by hydraulic fluid from the hydraulic-fluid supply source, a flow control valve for controlling the flow of the hydraulic fluid to be supplied to the actuator and a pressure control element for maintaining the differential pressure across the flow control valve at a predetermined value.

Abstract: Described is a control circuit for a hydraulic power lift driven by a displacement pump which has a check valve releasable at least for lowering movements of the power lift, a actuation means switching the check valve off and on to control the flow from a pump line into an operating line leading to the power lift and vice-versa, and a load-sensing line carrying the load pressure and connected to the operating line, by which the variable-displacement pump is capable of being activated. The actuating means has an actuating unit switching the check valve off and on and a servo valve, activated simultaneously and controlling the flow to and from the power lift, with at least three switch positions. In the starting position of the actuating means, the latter connects the load-sensing line and the operating line, by way of the servo valve, with the tank and, after passage through a central position, the operating line with the pump line.

Abstract: A locking valve for selectively locking fluid pressure in a fluid cylinder in the event of failure of the source of fluid pressure to the cylinder and including an integral fluid flow control valve, the locking valve also including a fluid pressure seal between the fluid supply port and the pilot port of the locking valve to prevent back pressure on the pilot pressure operated valve components.

Abstract: A counterbalance valve with a relief function, disposed in a pair of supply and exhaust lines communicating a directional control valve with a fluid actuator for adjusting a flow area at an exhaust side of the supply and exhaust lines in response to a pressure at a supply side of the supply and exhaust lines, which includes two divided spools, corresponding to the supply and exhaust lines, respectively, as a spool of the counterbalance valve, a device for moving one of the divided spools at the supply side of the supply and exhaust lines in such a direction that the flow area increases in response to an increased pressure at the exhaust side of the supply and exhaust lines, when the pressure increases beyond a predetermined pressure due to a pumping function of the fluid actuator, and a communicating passage for communicating the exhaust side of the supply and exhaust lines with a supply side of the supply and exhaust lines when the moving device is actuated so that the fluid at the increased pressure at the

Abstract: Pressure compensating valves located downstream of the directional control valves are useful in providing load independent, proportional flow control hydraulic systems and normally serve as load checks. The subject load check and pressure compensating valve is designed for use in a hydraulic system in which the pressure of a common pressure signal directed to all the pressure compensating valves of the system is limited to a predetermined maximum level. The pressure compensating valve includes a valve element disposed downstream of a metering orifice, a separate load piston disposed in end-to-end relationship with the valve element in a common bore and a pressure compensating spring disposed in a chamber behind the load piston and biasing the load piston and valve element to the load check position.

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: A linear drive mechanism has a combination of a drive cylinder, a drive rod stroke-limiting element, position sensors, a solenoid, and a terminal strip, together with internal wirings and hose connections. The drive mechanism can be arbitrarily arranged quickly and simply at a processing apparatus or assembly structure as a unit, and only a cable having the external signal and control lines as well as a supply line for the pressure agent need be connected thereto. No disturbing and involved wirings and position sensing elements therefore need be arranged in the actual tool region.

Abstract: A control device for a cylinder including a spool type valve which includes a spool and is formed therein with a cylinder port. In the spool type valve is arranged an operation check valve for permitting only flowing of fluid to the cylinder. An orifice is formed so as to communicate a pilot chamber of the operation check valve and the cylinder port with each other. The spool is formed with a first control port and a second control port for selectively carrying out communication between the pilot chamber and the return passage. Thus, when the spool is moved to communicate the first control port with the pilot port, the pilot chamber is communicated with the return passage. This causes fluid to flow through the orifice to lead to a difference in pressure between both sides of the orifice, resulting in a poppet of the operation check valve being opened.

Abstract: By providing the work blade of a grader with a hydraulic regulation system where pressure limiting valves (14, 15, 16, 17) guide pressure reducing valves (10, 11, 12, 13) a constant pressure regulation of the work blade is achieved so that the work pressure set by the operator from his cab is maintained almost independent of the irregularities of the underlying surface.

Abstract: A hydraulic lift is raised by hydraulic fluid which passes through a servo valve and is lowered when the servo valve exhausts the hydraulic lift to a reservoir. The hydraulic fluid travels to and from the lift through a service line in which a blocking valve is disposed. A control unit opens the blocking valve against a spring bias in response to the application of a control pressure to a control element disposed on one side of the control unit. The control pressure is supplied via a control line which also actuates the servo valve. A branch control line branches from the control line and applies pressure to another control element which acts counter to the first-mentioned control element. The branch control line includes tow throttles between which a discharge line is connected and communicates with the reservoir.

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 control system for a hydraulic lift driven by a variable displacement pump is disclosed. It is comprised of a blocking valve which may be opened at least for lowering movement of the hydraulic lift. A control device is provided for opening and closing the blocking valve and for regulating the volumetric flow from a pump line to an operating line leading to the hydraulic lift, and the flow from the hydraulic lift to a tank line leading to a tank. In addition, a load indicating line is provided which transmits the load pressure. The control device is comprised of a servo valve with three valve positions, and is further comprised of an actuator unit which opens and closes the blocking valve. The servo valve regulates the volumetric flow to and from the hydraulic lift. The load registering line is connected to the operating line, and in the initial position of the control device the load registering line is connected via the servo valve to the tank.

Abstract: A spool type directional control valve switches flow of oil discharged from an oil hydraulic pump to a hydraulic actuator, and decreases internal leak of a cylinder. Two sets of separated cylinder passages are formed on a valve body provided with a main spool, and a nonleak valve is provided across them. The nonleak valve is equipped with a main passage switching puppet having a throttle on the nose, a spring for energizing it to a close side, a pilot poppet for controlling pressure of a spring chamber in which the spring is enclosed, and a piston for operating the poppet.