Abstract: A control system for a hydraulic pump in a hydraulic drive circuit includes at least one hydraulic pump whose displacement volume is variable, at least one hydraulic actuator driven by a hydraulic fluid delivered from the hydraulic pump, and a flow control valve connected between the hydraulic pump and the actuator for controlling a flow rate of the hydraulic fluid supplied to the actuator. In the control system, the target value of the differential pressure between the delivery pressure of the hydraulic pump and the load pressure of the actuator is preset, and the displacement volume is varied dependent on the deviation between the differential pressure and its target value for controlling a pump delivery rate so that the differential pressure is held at the target value.

Abstract: An improved pneumatic control system is selectively deactuable and actuable for controlling movement of the armature of a pneumatically-operated device between first and second working positions and includes a timing subsystem that enhances the efficiency of the overall system by stabilizing the control system at a pressure necessary to maintain certain static conditions in the pneumatically-operated device, while still providing for full control air pressure when dynamic operations are required. In addition, such a control system compensates for system leakage in an efficient manner by using full control air pressure only when needed for proper operating functions of the overall system.

Abstract: Disclosed is a hydraulic control valve system, for driving a plurality of hydraulic actuators by a single pump, including pressure compensation valves and a shuttle valve disposed in a vertical bore orthogonal to a lateral bore of a valve body, into which a spool of a direction switching valve is fitted. A load sensing chamber for introducing a load pressure of an actuator is formed at an intersection between the lateral bore and the vertical bore. An opening-side first pressure receiving surface of the pressure compensation valve confronts the load sensing chamber. The pressure compensation valve has an opening-side second pressure receiving surface contacting a pilot pressure in the vicinity of the opening-side first pressure receiving surface. Formed on the upper side of the pressure compensation valve are a closing-side first pressure receiving surface on which a bridge pressure acts and a closing-side first pressure receiving surface on which an external control pressure acts.

Abstract: There is disclosed a direction selector valve having function of detecting load. The valve is used in a hydraulic system. A spool has two passage holes extending axially partially through the spool from both side ends. These two passage holes have their respective high-pressure holes. When the spool is in its neutral position, the high-pressure holes are closed off by spool hole walls between bridge ports and actuator ports. The two passage holes further include low-pressure holes which are in communication with tank ports via load check valves mounted in the passage holes, respectively. Guide holes are formed near the front end of one passage hole and in communication with a load-sensing port. A restriction portion is formed on the outer surface of the spool adjacently to the guide holes to control the flow from the load-sensing port to the tank ports. First guide holes and second guide holes which are close to each other are formed near the front end of the other passage hole.

Abstract: A fluid distributor for sequentially distributing pressurized fluid from at least one inlet port to a plurality of distribution ports and exhausting fluid from said distribution ports to at least one exhaust port, said distributor having a valve actuated by pressure of fluid supplied at said inlet port and arranged to close said exhaust port when said fluid pressure drops below a predetermined minimum. The distributor is suitable for use in conjunction with an inflatable human body support.

Abstract: A hydraulic drive system has a hydraulic pump (1), an actuator (2), a flow control valve (5) disposed between the hydraulic pump and the actuator, a pressure compensating valve (8; 8A; 8B) having a valve spool (23; 23A; 23B) that controls the differential pressure (Pz-PLS) across the flow control valve, and a pump delivery rate control device (9) for controlling a flow rate of the hydraulic fluid delivered from the hydraulic pump dependent on a differential pressure (Pd-PLS) between a pump pressure and a load pressure of the actuator.

Abstract: Compensated controls for a negative type load which, without degrading the quality of the control, permit direct use of the fluid power energy of the negative load for control of a resistive or positive type load, thereby greatly increasing the efficiency of the control system.

Abstract: An automatic shuttle valve having a valve body with a bore defined in it. A piston slide in the bore between first and second and positions and a third intermediate position. The valve distributes hydraulic fluid from a fluid supply through first and second branch conduits to respective first and second fittings leading respectively to first and second selectively operable driven mechanisms. A high pressure fitting at each end of the bore. The piston having respective first and second circular cross section, conical end blocks which are seated in the first seat of the first fitting when the piston is in the first position and the second seat of the second fitting when the piston is in the second position while the cylinder blocks are out of both of the seats when the piston is in the third position. The first and second driven mechanisms include respective first and second valves operable to receive hydraulic fluid from the first fitting or from the second fitting.

Abstract: A hydraulic drive system for a construction machine has a flow control valve (5) disposed between a hydraulic pump and an acutator, a pressure compensating valve for controlling a differential pressure across the flow control valve, and a pump delivery rate regulator for controlling a flow rate of the hydraulic fluid delivered from the hydraulic pump dependent on a differential pressure (Pd-PLS) between a pump pressure and a load pressure of the actuator. The pressure compensating valve has a valve body subjected to control forces. A first control force based on the differential pressure across the flow control valve to the valve body urges the valve body in the valve-closing direction. A second predetermined control force urges the valve body in the valve-operating direction; and a third control force based on the differential pressure (Pd-PLS) between the pump pressure and the load pressure of the actuator urges the valve body in the valve-opening direction.

Abstract: A valve apparatus (10; 10A) has at least one directional control valve (31; 31A) having a pair of variable restricting sections (43, 44) disposed between a supply passage (35) communicating with a hydraulic fluid supply source (11) and a pair of load passages (36, 37) communicating with an actuator (12). A pressure controller (32) or a pressure compensating valve (32A) is provided for holding a differential pressure across the variable restricting sections at a predetermined value. A detection line (57; 57A) is branched from a first passage (32; 86, 87) located between the pair of variable restricting sections and the pair of load passages for receiving a load pressure produced upon operation of the actuator. A check valve (59) or shuttle valve (90, 91) is provided for selecting a maximum load pressure and a control line (61, 62) introduces the selected maximum load pressure, as a control pressure, to the pressure controller or pressure compensating valve.

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

Abstract: 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 hydraulic drive system for a civil engineering and construction machine of the present invention comprises a hydraulic pump (11, 11A), a plurality of actuators (4-6) driven by a hydraulic fluid supplied from the hydraulic pump and including an arm cylinder (5) and a boom cylinder (4), a plurality of flow control valves (12, 14, 16) for controlling flows of the hydraulic fluid supplied to the respective actuators and including an arm directional control valve (14) and a boom directional control valve (12) and a plurality of distribution compensating valves (13, 15, 17; 13A, 15A, 17A) for controlling differential pressures across the respective flow control valves, the distribution compensating valves each having a first device (13d,15d, 17d; 13e, 13f, 15e, 15f, 17e, 17f) to set a target value of the differential pressure across the associated flow control valve.

Abstract: A flow control device includes a control valve having a discharge line to be connected to a hydraulic motor, a supply line to be connected to a hydraulic pump, a first bleed-off control passage having a line connected to a tank, and a second bleed-off control passage having a line connected to the tank through a secondary control valve, a flow dividing valve provided in the supply line and having a first position for allowing a first desired flow of oil discharged from the hydraulic pump and a second position for allowing a second desired flow of the oil, and a selector valve operable for the secondary control valve and the flow dividing valve and having a first selection position for closing the secondary control valve and shifting the flow dividing valve to the first position and a second selection position for opening the secondary control valve and shifting the flow dividing valve to the second position.

Abstract: A control valve assembly for a pressurized oil has a valve chamber (4) within which a pressure supply valve seat (15), a first chamber (11), a short-circuit prevention valve seat (17), a second chamber (12) and a return valve seat (16) are arranged in order. A check valve member (19) inserted into the first chamber (11) is adapted to be resiliently urged to the pressure supply valve seat (15) for valve closing by means of a valve closing spring (19) through a resilient sealing member (21). A return valve member (22) and a short-circuit prevention valve member (23) are inserted into the second chamber (12) in series. The return valve member (22) is adapted to be resiliently urged to the return valve seat (16) for valve closing by means of another valve closing spring (30).

Abstract: A device is provided for controlling the initial pressurization of a pneumatic system having a pressure supply line with an inlet end and a tail end and at least one pneumatic actuator in the system. The device includes a pneumatic valve having a first and second inlet port and an outlet port. The valve is movable between a first position in which a first fluid passageway connects the first inlet port to the outlet port, and a second position in which a second fluid passageway connects the second inlet port to the outlet port. A user variable orifice is connected in series between the source of pneumatic pressure and the first inlet while the source is fluidly connected directly to the second inlet. Similarly, the outlet from the valve is connected to the inlet end of the pressure supply line of the pneumatic system.

Abstract: A control valve is disclosed for use in controlling flow of hydraulic fluid from a hydraulic pump to a plurality of actuators. The control valve includes a valve housing within which are formed control bores, pressure-compensating bores, a feed passage communicating between the pressure-compensating bores, a selected-load pressure transmitting passage communicating between the pressure-compensating bores, a pair of return passages communicating between the control bores and a reservoir tank, control passages communicating respectively between each of the control bores and each of the pressure-compensating bores, and feeding and exhausting passages, as well as actuator ports, communicating between the control bores and the actuators. Control valve spools are slidably mounted, respectively, in the control bores, and pressure-compensating valves are slidably mounted, respectively, the pressure-compensating bores.

Abstract: A hydraulic control system for driving a plurality of actuators basically includes directional control valves, and pressure compensation valves, and at least one detection valve, the directional valves and the pressure compensation valves both corresponding in number to the actuators. These valves are mounted or incorporated in a body. The body has a plurality of regions corresponding in number to the actuators. Each of the regions of the body has a first hole, and a second hole substantially perpendicularly intersecting the first hole. A load pressure chamber for receiving a load pressure of the corresponding actuator is formed at the intersection between the first and second holes of each region. A spool of the directional control valve is received in the first hole. A balance piston of the pressure compensation valve is received in that portion of the second hole disposed on one side of the load pressure chamber.

Abstract: A hydraulic drive system is equipped with an engine, a plurality of hydraulic pumps adapted to be driven by the engine and including a variable displacement hydraulic pump provided with a displacement varying mechanism, a hydraulic motor connected to the variable displacement pump, a hydraulic actuator for actuating the displacement varying mechanism of the variable displacement hydraulic pump, a working fluid feeding means for feeding the hydraulic actuator with a hydraulic fluid of a pressure according to the degree of control of an accelerator lever which is adapted to instruct a target revolution number of the engine, and a low-pressure circuit for allowing the hydraulic fluid to be discharged therethrough from the hydraulic actuator.

Abstract: There is provided control apparatus for controlling fluid flow between a bidirectional motor, a pump and a container, and includes a control valve that has a slide operative between neutral and first and second operative positions. A compensating valve is provided in the supply conduit that holds the upstream pressure drop at the control valve substantially constant and is controlled by load pressure sensing circuitry. The load pressure circuitry includes two branches that are connected through a change over valve to the compensating valve. There is provided an over pressure valve and a throttle point in each branch, each branch being connected to a load pressure sensing orifice of the control valve housing and fluidly connected through the slide to one of the housing motor orifices, the one depending upon whether the slide is in its first or in its second position.

Abstract: A hydraulic control valve and sensing mechanism for controlling flow between a motor and a pump and container that includes a slide mounted in a housing bore for movement between a neutral position and two operative position. The slide has a central collar separated from end collars by slide grooves, profilings on diametric opposite sides of the slide grooves intersecting each groove. The housing bore has a pump groove supplied with pressure medium, axially opposite motor grooves connectable to motor conduits, and axially opposite the motor grooves from the pump grooves there are container grooves connectable to the container. The pressure sensing mechanism includes at least one pressure sensing orifice that is connected to the pressure to be sensed in an operative position of the slide but not being fluidly connected thereto when the slide is in its neutral position.

Abstract: Control system for a load-sensing hydraulic drive circuit comprising; at least one hydraulic pump; hydraulic actuators driven by the hydraulic pump; and a pressure compensated flow control valve between the pump and each of the actuators, for controlling a flow rate of fluid to each actuator in response to a control signal. The control system has first detection means for detecting a differential pressure between the pump delivery pressure and the maximum load pressure; second detection means for detecting the pump delivery pressure; first means for calculating a differential pressure target pump delivery amount Q.DELTA.p to hold the differential pressure constant; second means for calculating an input limiting target pump delivery amount QT based on at least a pressure signal from the second detection means and an input limiting pump function; third means for selecting one of the differential pressure target delivery amount Q.DELTA.

Abstract: The invention concerns a valve structure comprising a valve body, a chamber space disposed within the valve body, two running spindles and seats disposed to cooperate and placed within the chamber space, each running spindle enabling the aperture in the respective seat to be controlled. The valve structure comprises an input duct, a return duct and a working duct, the ducts being connected to the chamber space, a pressurized fluid being supplied through the input duct in the chamber space and the fluid being conducted through the controllable apertures with the aid of the running spindles either through the return duct out from the valve means to a tank or equivalent, or through the working duct to at least one power cylinder or equivalent, and the position of the running spindles and the size of the apertures being controlled with the aid of pilot valves.

Abstract: The feedback chamber of the pilot pressure valve is supplied with its discharge after it has been filtered whereby the pressure which is supplied to the feedback chamber is subject to the flow restricting effect of the strainer and increases the valve output to compensate for the flow restrictive nature of the strainer.

Abstract: Fluid systems for controlling clutch engagement of a vehicle drive train normally have modulating pressure relief valves to aid in smooth clutch engagement. It is desired in such systems to ensure that the system pressure is reduced during a shift so that the load piston of the modulating pressure relief valve is fully reset prior to engagement of the vehicle drive train. In this arrangement, a fluid system is provided which has a plurality of clutches. In order to ensure that the load system is fully reset, a load piston reset control mechanism is provided which establishes a path to vent the pressurized fluid from a load piston pressure chamber of a modulating presure relief valve in response to the pressure of the fluid in one of the clutches being below a predetermined pressure level.

Abstract: Lift structure particularly useful with front mounted implements for providing both lift and weight transfer functions from a single valve. The valve acts as an adjustable bleeder for the lift cylinder and includes a control knob which is movable both axially and rotationally to respectively provide lift and adjustable flotation. The valve is normally biased to an adjustable orifice position for operating the implement in a lowered, flotation position. To momentarily lift the implement, the operator moves the control knob against the bias to direct flow to the lift cylinder thereby raising the implement off the ground. When the operator releases the valve, it automatically returns to the preset orifice position to provide the desired flotation.

Abstract: In a fluid control valve, a check valve is provided between the pump port and the first fluid chamber and allows the fluid to pass therethrough only in a direction from the pump port to the first fluid chamber, a down control valve is provided between the first fluid chamber and the second fluid chamber, an up control valve is provided between the first fluid chamber and the third fluid chamber, the fluid is allowed to flow from the pump port to the cylinder port through the check valve and through the down control valve when they are opened, and the fluid from the cylinder port to the tank port is allowed to flow through the down control valve, through the first fluid chamber and through the up control valve when they are opened. The fluid control valve can be obtained simple in structure and high in precision, and be allowed a reduction in cavitation and noise.

Abstract: An individual segment flow regulator is shown having a two landed spool and two landed bore, all with the same nominal diameter, a plug, a spring and a sensing passage from the main spool of the valve. Supply oil entering between the two lands of the bore is separated from a sensing pressure by one spool land which is slidable within the bore. The other spool land meters the supply fluid. The metering land of the regulator spool opens away from the valve bore land to allow supply fluid through and can shut off the supply. A spring chamber above the spool senses the load pressure which opens the metering spool, thereby increasing the flow and therefore the pressure drop across the main spool area opening. Feedback pressure developed at the bottom of the metering land of the spool is used to close down the regulator spool as the flow, and therefore the pressure drop, across the main spool increases beyond the pre-load force of the bias spring.

Abstract: A flow control valve includes a cylinder in which an inflow port, an outflow port and a return port are formed. A spiral choke is formed between the inflow and outflow ports. A working oil introduced from the inflow port into the cylinder flows out from the outflow port through the spiral choke. An actuating valve is arranged in the cylinder so as to open and close the return port in accordance with a difference in pressure between the inflow and outflow port sides of the spiral choke. When the pressure difference exceeds a predetermined value, the actuating valve opens the return port so that a part of the working oil introduced into the cylinder is returned to the inflow side of the flow control valve.

Abstract: A distributor for hydraulic cylinders (2), especially applicable to crane drive cylinders, which comprises an axial sliding runner (4) for selection of the oil circuit. Said runner (4) is hollow, forming two separate chambers (19,20) adjacent to the cylinder chamber supply and return ducts with which it is connected through holes in the wall of the said runner. One of the chambers (19) includes means for varying the degree to which the holes are opened, according to the return oil pressure from the cylinder withdrawal chamber. The other chamber (20) incorporates means for opening or closing the connection through it, according to the pressure being delivered by the pump, to the cylinder withdrawal chamber oil supply duct. Thus it is possible to regulate the flow as an inverse function of the load and to reduce the effect of induced pressure.

Abstract: According to the parent patent on inadequate power of the delivery pump the flow rate set at the directional control valves for the consumers is reduced in equal proportions in that electrical signals proportional to the flow rates are supplied to a summation stage and the sum voltage is compared in a comparison stage with a limit value corresponding to the maximum pump delivery flow. When the limit value is exceeded a control signal is generated with which the stroke of all the driven directional control valves can be jointly reduced. According to the application of addition the signal voltage supplied to the summation stages and corresponding to the respective flow rate can be obtained in a displacement pickup associated with each directional control valve or in a pressure pickup measuring the pilot pressure if the directional control valves are not controlled electrically but hydraulically.

Abstract: A proportional type hydraulic distributor incorporates a distributor slide valve including a feed chamber. It is provided with a pressure compensator device for regulating the feed pressure to the feed chamber according to the output (load) pressure of the slide valve. This device includes an inlet channel, an outlet channel communicating with the feed chamber and a stator communicating with the inlet and outlet channels. A compensator slide valve slides in a housing in the stator. A spring exerts an axial force on the compensator slide valve in the same direction as the force exerted on it by the output pressure and in the opposite direction to the force exerted on it by the feed pressure. An annular obturator member on the compensator slide valve isolates the inlet and feed channels and is acted on by a return spring on the compensator slide valve. The latter has a recessed part on which the obturator member slides without clearance.

Abstract: A control system for an actuator used to position a control surface on an aircraft such as a horizontal stabilizer, including a source of pressurized fluid, a pressure control for establishing a predetermined pressure level that is substantially one-half source pressure, a blocker valve and at least one direction control valve for controlling the application of fluid pressures to the actuator. During idle periods, the blocker valve supplies substantially equal control pressures to the actuator so that the control system remains pressurized to substantially one-half source pressure. When the actuator is being energized, the direction control valve determines the direction of actuation and the blocker valve controls the fluid flow rate to and from the actuator to maintain a constant actuation rate regardless of load.

Abstract: A regulator arrangement (14) for a servo system (10) having a first stage valve spool piston (44) for developing a primary operational fluid (P.sub.c) and a second stage valve spool piston (70) for developing secondary operational fluid P.sub.cr having a constant fluid pressure. A control valve (109) selectively connects a first chamber (100) of a cylinder housing bore to either the primary operational fluid pressure P.sub.c or a reference fluid pressure P.sub.B to develop a fluid pressure P.sub.x in first chamber (100) while a second chamber (102) is connected to the secondary operational fluid (P.sub.cr). A load piston (96) responds to a pressure differential (P.sub.x -P.sub.cr) by moving to either expand or contract the second chamber (102) and produce a fluid pressure (P.sub.crx) in the secondary operational fluid. The fluid pressure P.sub.crx is communicated to the second valve piston (70) to correspondingly allow either additional primary fluid (P.sub.

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 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: A bidirectional flow communication passageway is provided by the present invention in a multiple-circuit fluid pressure responsive system on a motor vehicle to allow a gradual reduction of pressure in a parking brake circuit which is a part of such system. The passageway is restricted to limit such bidirectional flow to a predetermined level. The pressure reduction permitted is sufficient to activate a parking brake valve in such parking brake circuit when a defect occurs in an operating service brake circuit which is also a part of such system.

Abstract: A bidirectional flow communication passageway is provided by the present invention in a multiple-circuit fluid pressure responsive system on a motor vehicle to allow a gradual reduction of pressure in a parking brake circuit which is a part of such system. The passageway is restricted to limit such bidirectional flow to a predetermined level. The pressure reduction permitted is sufficient to activate a parking brake valve in such parking brake circuit when a defect occurs in an operating service brake circuit which is also a part of such system.

Abstract: A bidirectional flow communication passageway is provided by the present invention in a multiple-circuit fluid pressure responsive system on a motor vehicle to allow a gradual reduction of pressure in a parking brake circuit which is a part of such system. The passageway is restricted to limit such bidirectional flow to a predetermined level. The pressure reduction permitted is sufficient to activate a parking brake valve in such parking brake circuit when a defect occurs in an operating service brake circuit which is also a part of such system.

Abstract: A load responsive control system using on a selective basis the energy derived from a negative type load for operation of system controllers, which may be of various types, including electro-hydraulic multi-stage controls, for use in positioning of the main control spools and in control of other system components.

Abstract: A load sensing circuit of a load responsive direction control valve including a device for sensing load pressure signals, identifying those pressure signals as positive or negative and transmitting those identified positive or negative load pressure signals to the throttling compensator controls of the load responsive valve. The load pressure signal identifying circuit responds to the control pressure signals, which determine the desired direction of displacement of the spool of the direction control valve, while those control pressure signals are selectively isolated from the identifying circuit, in response to the direction of spool displacement from its neutral position.

Abstract: The invention relates to a pressurized hydraulic fluid spool valve intended to be stacked against other similar spool valves, having a valve body (1) with a spool (4) adapted for sliding in a bore (5) into which open in the following order: a first intake recess (19) in a central position, two second recesses (21A, 21B) for connection to a hydraulic apparatus situated on each side of the preceding one; two third recesses (T.sub.1, T.sub.2) situated respectively beyond the second recesses, and two fourth recesses (22.sub.1, 22.sub.2) situated respectively beyond the third recesses.

Abstract: A pressure-compensated flow-control valve with an adjustable limiting device controls the maximum speed of a fluid motor and eliminates an additional valving element found in prior art device. The flow control valve includes a flow limiting throttle opening integral with the flow control spool. The spool can be selectively rotated to adjust the effective size of the throttle opening thereby limiting flow through the valve. The spool establishes a constant rate of flow determined by the throttle opening or a directional control valve. By incorporation of the flow limiting function within the flow control spool, the overall cost and complexity of the pressure compensated flow control valve is reduced.

Abstract: Fluid systems for controlling clutch engagement normally have modulating pressure relief valves to aid in smooth clutch engagement. It is also desired in such systems to ensure that the system pressure is reduced to a low level so that the load piston is fully reset prior to initial engagement of the newly filled clutch. In this arrangement, in order to ensure that the load piston is fully reset, a mechanism is provided which establishes a ratio between the pressure of the fluid being directed to the clutch and the pressure of the fluid acting on the load piston of the modulating pressure relief valve so that the pressurized fluid acting on the load piston during the filling of the clutch is vented to the reservoir to reset the load piston even though the pressure of the fluid available to the clutch is still at a higher pressure level.

Abstract: A load responsive system is provided with two synchronizing systems for positive and negative load compensation. One of the synchronizing systems varies the flow through a negative load compensator, during control of a negative load, in response to the inlet pressure of a fluid motor which is controlled by a positive load compensator. The other synchronizing system isolates the system pump from the fluid motor during control of the negative load while make-up flow to the fluid motor is supplied from the fluid exhaust system. In a more specific arrangement, the system pump is isolated from the fluid motor through the use of the positive load compensator and totally independent of any negative load compensating action. The synchronizing systems function in response to an external signal(s), which can be a function of any selected specific parameter of the system.

Abstract: A multiway valve is provided having a load feedback wherein a pressure-reducing element that reduces the pressure conveyed to a connection through the valve with a control pressure signal line is controlled as a function of the displacement of a valve piston in the multiway valve.

Abstract: A progressive hydraulic distributor with a slide for controlling a hydraulic actuator. The distributor has an internal load sensing passage that detects the operating pressure in the hydraulic fluid inlet or outlet passage and superimposes this pressure on the action of the spring of a feed valve. Thus, the difference between the up-flow and the down-flow of progressivity in the slide of the distributor is constant.

Abstract: A regenerative valve which includes a valve body having a bore therein intersected by first and second control passages connected respectively to a four-way directional control valve; the bore is also intersected by first and second cylinder control cavities connecting with the head end and rod end respectively of a double-acting cylinder; a check valve poppet is seated in said bore blocking flow to the head chamber of the cylinder. A shuttle spool is also positioned in said bore and is movable between a first working position allowing the cylinder to retract its piston and a regeneration position opening flow across the first and second cylinder control cavities while blocking flow to the second control passage. The shuttle spool engages the poppet member in its regeneration position causing the poppet to open a flow path from the first control passage to the first cylinder control cavity and thereby allow regeneration flow.

Abstract: A valve unit for use in a load sensing system having a fluid operated cylinder. The valve unit permits positioning of an implement between the raise, lower, neutral and float positions and also provides for throttling of fluid flow to the cylinders as well as priority flow to the system. Float is obtained through a lock check valve which includes a main poppet maintained in a seated position by a spring biased pilot poppet. A pilot piston is positioned coaxially opposite the main poppet and is responsive to fluid pressure in the valve to act upon the pilot poppet and unseat the main poppet. In the float position, the fluid pressure within the valve may be stand-by pressure which acts upon the pilot piston to allow it gradual decent of the implement. The pilot pressure is communicated to the pilot piston through a centrally located passage. The location of the passage permits additional lock check valves to be easily added as needed.