Abstract: A vehicle, variable spring system and method of operating a corner actuator coupled to wheel of the vehicle. The vehicle includes the corner actuator and the variable spring system. The variable spring system includes a control chamber coupled to the corner actuator, a first spring, a second spring, and a valve. An applied resistance for the corner actuator is selected by selecting an amount of fluid coupling between the control chamber and each of the first spring and the second spring. A force is absorbed at the wheel using the applied resistance.

Abstract: A hydraulic excavator drive system includes a regeneration line, which connects an arm pushing and an arm crowding supply line, each of which extends between an arm cylinder and arm control valve. The regeneration line includes regeneration and switching valves. A release line that is branched off from the regeneration line at a position between the regeneration valve and the switching valve is provided with a release valve. A secondary pressure from a first solenoid proportional valve is fed to a pilot port of the regeneration valve such that the regeneration valve opens at a time of arm crowding. A secondary pressure from a second solenoid proportional valve is fed to a pilot port of the release valve such that release valve opens at a time of arm pushing. An arm pushing pilot pressure for moving the arm control valve is led to a pilot port of the switching valve.

Abstract: A piston type pneumatic engine, including a cylinder block, a piston, a cylinder, a crankshaft, a connecting rod, a camshaft, and a device for controlling the opening or closing of a gas valve. A cylinder cover arranged on the cylinder block is provided with an inwardly-opened type compressed-gas intake valve and an exhaust valve. An intake cam and an exhaust cam are arranged on the camshaft. The opening or closing of the intake and the exhaust valves is controlled by a rocker arm which is driven by the camshaft. The camshaft is driven by the rotated crankshaft via a timing chain or belt.

Abstract: A torsional rigidity control device capable of controlling a moment provided to stabilizers (1f) and (1r) against the moment based on an external moment loaded from the outside to the stabilizers (1f) and (1r), comprising a moment variable mechanism for varying the moment loaded on the stabilizers (1f) and (1r) by regulating a fluid pressure supplied from a fluid pressure source driving rotary actuators (2f) and (2r) connected to the intermediate parts or one ends of the stabilizers (1f) and (1r) or the cylinders (51f) and (51r) connected to one ends of the stabilizers (1f) and (1r), characterized in that the necessary value of the fluid pressure for driving the rotary actuators (2f) and (2r) or the cylinders (51f) and (51r) is calculated based on the value of the external moment, the value of the fluid pressure supplied to the rotary actuators (2f) and (2r) or cylinders (51f) and (51r) is compared with the necessary value of the fluid pressure, and based on the compared result, the fluid pressure is regulate

Abstract: The oil supply device for a change-under-load transmission having a high-pressure circuit and a low-pressure circuit is designed in such a manner that the high-pressure feed line to the consumer devices of the transmission system incorporates an inlet aperture of small size, the low-pressure feed line is connected between the inlet aperture and the consumer device, and the low-pressure feed line can be cut off from the high-pressure feed line by a one-way valve.

Abstract: An hydraulic system comprising an air sucking hydraulic circuit 8, an air sucking control valve 5, and a check valve 6 provided in or before and after the air sucking hydraulic circuit 8, allowing a flow of a hydraulic fluid from the air sucking control valve 5 to the hydraulic actuator 4 and preventing a flow of a hydraulic fluid from the hydraulic actuator 4 to the air sucking control valve 5.

Abstract: A control system is provided with a float condition to permit a double acting hydraulic cylinder to freely extend or retract in response to external forces acting on the hydraulic cylinder. The system includes a pair of pilot operated poppet valves disposed between the opposite sides of the hydraulic cylinder and a directional control valve. The pilot condition is obtained by opening a pair of pilot operated control valves to vent the control chambers of the poppet valves to a tank through a pair of float check valves. The float check valves are operative to prevent higher pressure fluid from being transmitted from the tank to the control chambers of the poppet valves when a negative pressure occurs in the side of the hydraulic cylinder that is connected to the control chamber.

Abstract: A fluid control system including a control valve providing a simple, easy to use regeneration capability in association with a pump, a tank, and a double acting actuator having a first actuating chamber and a second actuating chamber. The control valve has a first actuating chamber port connected to the first actuating chamber, a second actuating chamber port connected to the second actuating chamber, a tank port connected to the tank, a first pump port and a second pump port. The control valve includes a connecting passage connecting the first pump port and the second pump port to the pump, and is operable in a first position to allow fluid flow from the pump through the first pump port and the first actuating chamber port to the first actuating chamber and fluid flow from the second actuating chamber through the second actuating chamber port and the tank port to the tank.

Abstract: A charge pump for a hydrostatic transmission, having a self-charge relief function, in which a first toothed wheel, a second toothed wheel, and a pump casing, housing therein the first and second toothed wheels, are molded of heat resistant resin material, thereby reducing the weight of the charge pump, stabilizing its charge relief function and reducing the wear of the lower surface of a center section. Check valves are housed in the pump casing so that operating oil sealed between a hydraulic pump and a hydraulic motor can always be maintained at a proper level, regardless of whether the charge pump is driven or not.

Abstract: A hydraulic system with a pressure source controllable via a load sensing signal, a pressure sink, at least two working sections, each having a hydraulic consumer and a control valve with a load sensing signal connection and at least one back-pressure valve arranged in a tank pipe between the control valve and the pressure sink. In such a system the pressure required from the pump in the neutral position must be as low as possible. On the other hand, however, oscillations should not occur, when an external force acts on another hydraulic consumer in the neutral position of a control valve. In the neutral position of the control valves the load sensing signal connection is therefore connected with the pressure sink via an auxiliary tank pipe by-passing the back-pressure valve.

Abstract: An axle driving apparatus in which a hydraulic pump and a hydraulic motor which constitute a hydrostatic transmission are disposed on a center section. In a horizontal portion of the center section are provided a pair of linear oil passages in parallel to each other. A pair of arcuate ports are provided on a pump mounting surface formed on the horizontal portion of the center section. The pair of arcuate ports are substantially perpendicular with respect to the direction in which the oil passages extend. The axis of slanting movement of a movable swash plate of the hydraulic pump extends laterally of the vehicle body on which the axle driving apparatus is provided. The rotating direction of an arm provided on a control shaft for slantingly operating the movable swash plate is coincident with the operating direction of a control rod connected with a speed changing member. Thus, the link mechanism for connecting the speed changing member and the control arm for the movable swash plate is simplified.

Abstract: A hydraulic power steering apparatus includes a fluid pump, a power cylinder, a reservoir, and a control valve connected to the pump via a supply passage including a high pressure hose and connected to the reservoir via a drain passage. The power steering apparatus also includes a bypass passage provided between the supply passage and the drain passage, and a check valve which is disposed in the bypass passage to allow operation fluid to flow only in a direction from the drain passage to the supply passage. The power steering apparatus can supply a sufficient amount of operation fluid to the power cylinder even when a steering wheel is abruptly turned or when an opposing force is input from a tire.

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 fluid unit, for example a piston/cylinder unit, is supplied with fluid via a cyclically opened or closed on/off valve. The vacuum peaks occurring on the outlet side of the on/off valve when it is closed and the inertia forces of the flowing fluid are used to supply additional fluid to the fluid unit via a non-return valve leading from a low-pressure connection or reservoir to the fluid unit.

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 hydraulic pressure booster which may be used in a brake system of a vehicle is constructed to allow a brake output to be increased upon ceasing the depression of a brake pedal, thus imparting a brake feeling which is favorable to a driver. Hydraulic pressure from a first power chamber flows into a second power chamber through a passage provided with an orifice in shunt with a check valve, such that flow from the first power chamber to the second power chamber is retarded while flow from the second power chamber to the first power chamber is unrestricted.

Abstract: A braking system for a dumping vehicle having a hydraulic drive system and a hydraulic dump container is disclosed. A two-section control valve is connected by conduit to a hydraulic fluid reservoir and a hydraulic motor. The control valve includes a first valve assembly for controlling the dump container and a second valve assembly for controlling operation and direction of the hydraulic motor. An anti-cavitation valve and relief valve are provided to prevent locking of the vehicle wheels during braking. Walk-behind, riding-step and riding-seat variations of the invention vehicle are disclosed.

Abstract: A pressure relief system for the primary hydraulic system of a large industrial machine wherein the biasing force biasing one of the pressure relief valves is supplied by the pilot hydraulic control system of the machine. A two-position valve is used to selectively change the biasing force in response to a temperature indicator. The two-position valve couples and decouples the pressure relief valve to and from the pilot control system hydraulic pump and the pilot hydraulic system sump. If the pressure relief valve is in communication through the two-position valve with the pilot hydraulic fluid sump, the biasing force is reduced against the pressure relief valve and the pressure in the primary hydraulic system opens the pressure relief valve and directs hydraulic fluid to the primary hydraulic fluid sump.

Abstract: A pallet truck hydraulic jack has a base plate mounting a lift cylinder with a reciprocal piston or lift rod and a pump cylinder with a reciprocal pump piston. A cartridge type directional control valve assembly within the base plate controls the flow of pressurized hydraulic fluid in respective manifold passages so that manual actuation of the pump effects a quick lift of the frame when it is unloaded, effects an additional application of lifting force through the lift cylinder when the frame is loaded, bypasses pressurized hydraulic fluid to the reservoir when the frame is overloaded, and provides a release of pressurized hydraulic fluid from the pump cylinder and the lift plunger and returns it to the reservoir for lowering the frame and forks.

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

Abstract: An energy-saving hydraulic driving arrangement includes a motor having two chambers separated by a reciprocable or angularly movable output element which can accelerate or decelerate a mass. One of the chambers receives pressurized fluid from one of a battery of accumulators containing fluid at different pressures (namely, from the accumulator wherein the pressure is slightly higher than the desired pressure in the one chamber) during acceleration of the output element while the other chamber discharges fluid directly into a sump. During deceleration of the output element, the one chamber draws fluid directly from the sump whereas the other chamber discharges pressurized fluid into that accumulator wherein the pressure is slightly less than the pressure of fluid in the other chamber.

Abstract: A hydraulic system (40) for an excavator (10) which utilizes regeneration, minimizes cavitation, and provides hose break protection is disclosed. A valve assembly (50) is permanently connected to a hydraulic actuator (30) which is to be controlled. A hydraulic power supply (42) remote from the hydraulic actuator is connected to the valve assembly (50) through a pair of flexible hoses (56, 58). Pressurized hydraulic fluid can flow to the valve assembly through either of the flexible hydraulic hoses, but the valve assembly (50) includes a check valve (60) so hydraulic fluid return is only possible through one hose (56). A two position valve (62) is provided in the valve assembly (50) between a pair of operating ports (36, 38) on the hydraulic actuator (30). The two position valve (62) can be opened in response to a signal from the operator, connecting the two ports (36, 38) together to permit regeneration.

Abstract: A hydraulically operated impact motor, e.g. for a jack hammer, has a hammer piston that has a piston surface 19 in a pressure chamber 21 which is constantly pressurized in order to effect the work strokes of the hammer piston, and a larger piston surface 20 in a second pressure chamber 21 which is intermittently pressurized in order to effect the return strokes of the hammer piston. The second pressure chamber 22 is also connected to the exhaust line via a one-way valve that permits flow towards the second pressure chamber 22.

Abstract: A fast acting hydraulically actuated ram (10) especially suitable for use in the punch head of a press uses a first ram area (28) to advance the ram until the load thereon increases, which occurs when punching is about to take place. Then a pressure actuated valve (22), which is responsive to the increase in hydraulic pressure acting upon the first ram area, places pressure on a large area (36) of the ram for a time sufficient to enable penetration of the work. An electrohydraulically controlled valve (20, 98) responsive to the ram position, switches hydraulic pressure which is applied to the first ram area so as to operate the ram under electrical control to provide the desired cycle time and frequency.

Abstract: A fluid control system for controlling a fluid motor (12) wherein a pressure regulating pilot valve (10) controls a directional control valve (11) by manipulation of handle (21) associated with the pilot valve (10). The directional control valve (11) includes a make-up valve (84). The pilot valve (10) includes a spool (26) having a recess (98) providing selective communication between the backside of the movable valve member (86) of the make-up valve and an exhaust recess (100) communicating with the reservoir tank (36). A direct mechanical connection is provided from the handle (21) to the spool (26) as the result of an abutment of an upper end portion (102) of the spool (26) with a surface (49) on the plunger (28) engaged by the control handle in effecting the positive movement of the spool (26) to effect the desired communication between the recess (98) and recess (100). The spool normally is resiliently movable to effect a desired pressure regulation fluid flow through the pilot valve (10).

Abstract: A hydraulic system (9) includes a hydraulic motor (10), a main control valve (17) for controlling said motor (10), a make-up valve (78,79) operatively associated with said main control valve (17) and a vent line (93,94,95,99) for selectively venting said make-up valve (78,79). In such hydraulic systems, and in particular, in prior art hydraulic systems used to raise and lower a load, there is always the possibility that should hydraulic pressure not be maintained in the vent line the make-up valve could come open and the load could unexpectedly move. Such a situation could occur with, for example, air trapped in said vent line and the simultaneous failure of a pump of the system. The present invention solves this problem by providing pressure maintaining arrangement (200) in fluid communication with said vent line (93,94,95,99).

Abstract: A self adjusting actuator system (32/32') has an actuator housing (40), a telescoping piston (52) defining therewith head and rod end chambers (58,60), and a compression spring (66) disposed for biasing the piston (52) in a preselected direction against an external force. A control system supplies fluid selectively to either of the chambers (58,60) and includes control device (33/33') for selectively permitting egress of fluid from the rod end chamber (60) to permit the piston (52) to move in the preselected direction in response to a change in the external force. Such system is particularly useful in a log grapple (10).

Abstract: An improved filling and discharge valve for use with a hydraulic cylinder is provided, the valve comprising a valve body having a first chamber therein supporting a spring-biased main valve piston having an extending portion containing a chamber in which a second spring-biased valve is supported, the valves operationally being interdependent and being capable of being coupled to a hydraulic cylinder so as to control the flow of oil from oil-storage means to said hydraulic cylinder and back to said oil-storage means according to a pre-determined working cycle. Control valves and switches are provided to control the operation of the filling and discharge valve.

Abstract: A hydraulic system including at least one hydraulic cylinder is provided with an anti-cavitation and overload relief valve having a housing, a first chamber within the housing in fluid communication with one end of the cylinder, and a second chamber within the housing in fluid communication with a fluid reservoir. A fluid passageway within the valve housing connects the first and second chambers. A movable valve assembly is positioned within the fluid passageway for operating in a plurality of modes for providing anti-cavitation and overload relief. The valve includes a stationary portion positioned within the fluid passageway between the first and second chambers having a valve seat. The movable valve assembly includes a poppet mechanism for sealingly engaging a valve seat of the movable valve element when the movable valve assembly is operating in first and third modes.

Abstract: A control system for hydraulic servomechanisms comprising a double-acting jack the working chambers of which are selectively and alternately connectable to a source of pressurized fluid and to a fluid discharge through a reactive switching valve which itself is operated by a control member.According to the invention, there are provided between the valve and each working chamber of the jack means for intercepting the passage of fluid toward said chamber as long as the upstream pressure does not reach a predetermined threshold value.The application may be advantageously used in power-assisted steering systems for automotive vehicles.

Abstract: A control valve unit (10) disclosed includes a slide mechanism (14) mounted on a base (40) of the unit, a control member (18) driven by a hydraulic linear actuator (12) controlled by the unit, and a control valve (22) that feeds hydraulic fluid to the actuator and has a deactivator (24) that is engaged and moved by a pair of slides (16a,b) of the slide mechanism under the impetus of the control member movement in order to terminate driving of the actuator at its limits of movement. The slide mechanism includes a slideway on the base and a pair of fixed stops (62a,b) between which the movable slides are supported on the slideway and biased by a helical spring (68) against the stops. The helical spring is aligned with openings (66) in the slides and the control member (18) extends through the spring and the slide openings. Lugs (76a,b) on the control member for moving the slides are preferably adjustable so as to permit adjustment of the limits of actuator movement.

Abstract: A hydraulic system including at least one hydraulic cylinder is provided with an anti-cavitation and overload relief valve having a housing, a first chamber within the housing in fluid communication with one end of the cylinder, and a second chamber within the housing in fluid communication with a fluid reservoir. A fluid passageway within the valve housing connects the first and second chambers. A movable valve assembly is positioned within the fluid passageway for operating in a first mode to block fluid flow between the first and second chambers, for operating in a second mode to permit fluid flow from the first chamber to the second chamber only when the pressure in the first chamber exceeds the pressure in the second chamber by a first predetermined amount, and for operating in a third mode to permit fluid flow from the second chamber to the first chamber only when the pressure in the second chamber exceeds the pressure in the first chamber by a second predetermined amount.

Abstract: A defrost and water drain valve suitable for use with air cylinders, such as used to furnish power to material handling equipment, is connected to receive air from the exhaust side of the piston and direct this air against the inlet end of the cylinder and is constructed so that it can also automatically function to permit drainage of condensed water in the cylinder. The valve includes means to control flow to and from the exhaust side of the piston and the use of its features in a flow control valve and a check valve is also disclosed.

Abstract: A pressure medium control means for hydraulic servo-steering devices with a pressure source and preferably a hydraulic pressure accumulator in which means there is provided a control valve having a four-way control and one or preferably two control pistons for selectively connecting the working spaces of a servo motor with a pressure source or return pipe to a reservoir, in which the servo motor is operably related to a power outlet member affecting the steerable wheels, with the power outlet member per se being connected with a power inlet member via a resilient, preferably pre-stressed coupling means, and in which the control piston or pistons is or are provided with reaction areas stressed by the pressures from the working spaces of the servo motor, or are in operative relation with respective reaction members and are actuable via actuating elements by virtue of relative movements between the power inlet member and the power outlet member.

Abstract: A device for elevating the boom of a side crane has a double acting valve provided in a hydraulic circuit so as to permit natural lowering of the boom of the side crane under its own weight as well as forcible raising and lowering hydraulically, and also so as to maintain the boom without need of further fluid supply from a pump in its forcibly lowered or lifted state for a long period of time through the trapping of hydraulic fluid within the boom cylinders on both the lifting and lowering sides thereof.

Abstract: A valve for rapidly filling and emptying a volume created by rapid displacement of a machine member. The valve has a body to be connected between a reservoir and the machine. The valve has a valve seat with a seating surface that surrounds the flow path of fluid from the volume and an integral valve guide connected to the seat. A valve opening toward the machine is spring urged toward closed position to withstand high pressure of the fluid at the machine. An auxiliary mechanism is provided to open the valve which may be a solenoid, a pilot piston, or fluid cylinder or manual operation. The valve is provided with a dashpot to provide smooth operation.

Abstract: There is disclosed a valve assembly in combination with a hydraulic circuit to operate a motor in the circuit in a forward and reverse direction. The valve assembly includes check valve means for regulating fluid flow to the motor, pilot valve means for operating the check valve means responsive to pressures within the circuit, and relief valve means for relieving overpressure within the circuit. The combination is constructed and arranged so that the valve assembly substantially prevents cavitation of the motor, and is also operative to and isolate the motor from external loading.

Abstract: The steering wheel controlled valve operator in a fluid power steering system, is mechanically held in a neutral position by centering springs associated with fluid pressure controlled reaction pistons yieldably resisting movement of the control valve by the valve operator. Check valves opened in response to suction pressure, conduct fluid in by-pass relation to the control valve between a servo motor chamber and a return fluid line, the control valve connecting both servo motor chambers to the return line in the neutral position.