Abstract: A pressure recovery system according to the present invention comprises a pump, a flow control valve and a flow amplifier. The flow control valve has an inlet connected to the outlet of the pump, an outlet for supplying fluid to the load to which pressurized fluid is to be supplied, and a bypass flow outlet connected to the flow amplifier. The bypass flow drives the flow amplifier for supplying fluid to an inlet of the pump.

Abstract: An axle driving apparatus including a hydrostatic transmission disposed in a housing, with at least one axle extending from a side of the housing and an input shaft extending into the housing to drive the hydrostatic transmission, an output shaft engaged to and driven by the hydrostatic transmission and having one end external to the housing, a brake mechanism engaged to the external end of the output shaft, a trunnion engaged to the hydrostatic transmission and having one end extending from the housing, and a bypass actuator engaged to the hydrostatic transmission and having one end extending from the housing, wherein each of the axle, output shaft, trunnion, and bypass actuator are oriented generally perpendicular to the input shaft, and each of the output shaft, trunnion and bypass actuator extend from the same side of the housing.

Abstract: What is disclosed is a hydraulic controller arrangement for the pressure medium supply of a hydraulic consumer, e.g., of the rotating gear of a mobile work machine. At low pressure medium flow rates, the pressure medium flow rate draining from the consumer is backed up by means of a drain backup valve having the form of a pressure limiting valve and throttled accordingly, so that a back pressure is generated which is capable of preventing an advance of the mass actuated by the hydraulic consumer.

Abstract: A hydropneumatic pressure transmission device having a working piston and a transmitter piston for pressure transmission to the working piston is proposed, with the working piston being guided in a housing space in such a way that, coupled to the movement of the working piston, hydraulic fluid must flow from a first region via a first connecting section into a second region. According to the invention, a switchable second connecting section is provided so as to be connected parallel to the first connecting section.

Abstract: [Object] To materialize a reduction in pump loss, the assurance of sufficient working device speeds and the priority assurance of an adequate steering capacity with simpler construction and at lower cost than a load sensing system.

Abstract: An improved anti-cavitation hydraulic manifold for hydraulically coupling the hydraulic input and output of two, drive coupled, reversible hydraulic motors and a reversible source of hydraulic power for winding and unwinding systems is described wherein a stop confines a shuttle ball within each of two input/output (I/O) chambers receiving driving hydraulic input liquid from the reversible source of hydraulic power between an annular valve seat around a bypass passage communicating between the bases of the input/output (I/O) chambers and any ports penetrating into the respective input/output (I/O) chambers supplying high pressure or driving hydraulic input from the reversible source of hydraulic power where, responsive to supplied high pressure or driving hydraulic input to a particular I/O chamber, the shuttle ball in the chamber seats upon the particular annular valve seat translating a shuttle rod in the bypass passage unseating the particular shuttle ball from the annular valve seat around the passageway

Abstract: To provide a short connection hydraulic path structure with a sufficiently large diameter to adequately lower the pressure in a high-pressure hydraulic path while the clutch is off, in a static hydraulic continuously variable transmission for sliding a clutch valve installed within the transmission shaft, to change the power being transmitted and shorten the high-pressure hydraulic path and low-pressure hydraulic path. A high-pressure fluid path is provided for sending hydraulic fluid from the hydraulic pump side to the hydraulic motor side with a low-pressure fluid path for sending hydraulic fluid from the hydraulic motor side to the hydraulic pump side. A hydraulic circuit includes a switching valve for switching the plungers to the high-pressure path or the low-pressure path as a dual structure within a valve body between the hydraulic pump made from multiple plungers, and a hydraulic motor made from multiple motors.

Abstract: A vehicular hydraulic system with a pump and first and second hydraulic applications arranged in series. The fluid upstream of the first application may be elevated to a first threshold pressure value. A pressure-dump valve is disposed downstream of the first application and fluid entering the valve flows through an inlet port, primary flow channel and outlet port of the valve to the second hydraulic application. The valve includes a valve member that axially slides within an elongate valve chamber, partitioning the primary flow channel from a low pressure volume. The valve also includes a low pressure port and a bypass port that diverts fluid past the second application. The valve member is biased into a position wherein fluid is diverted through the bypass port when the pressure in the primary flow channel exceeds a second threshold value. The first threshold value is greater than the second threshold value.

Abstract: A vehicular hydraulic system with a pump and first and second hydraulic applications arranged in series. A valve is disposed whereby fluid from the pump flows through an inlet port, primary flow channel and outlet port of the valve to the first hydraulic application. The valve includes a body and a valve member that axially slides within an elongate valve chamber, partitioning the primary flow channel from a low pressure volume. The valve also includes a low pressure port and a bypass port. The bypass port is sealed from fluid communication with the valve chamber in a first position and is in fluid communication with the primary flow channel when the valve member is biased into a second position by a threshold exceeding elevated fluid pressure in the primary flow channel. Fluid discharged from the bypass port is diverted past the first application to the second application.

Abstract: A vehicular hydraulic system having a hydraulic pump and first and second hydraulic applications arranged in series. A dual relief valve defines first and second flow channels, a passageway and a bypass port. The first flow channel is disposed between the hydraulic pump and the first hydraulic application and the second flow channel is disposed between the first hydraulic application and the second hydraulic application. A first valve member controls fluid flow through the passageway and allows fluid flow from the first to the second flow channel through the passageway when fluid pressure within the first flow channel exceeds a first threshold pressure. A second valve member controls fluid flow through the bypass port and allows fluid flow from the second flow channel to a return line through the bypass port when fluid pressure within the second flow channel exceeds a second threshold pressure.

Abstract: A vehicular hydraulic system having a pump, first application, pressure-dump valve and second application arranged in series. The pressure-dump valve diverts a portion of the primary fluid flow past the second application when the pressure exceeds a threshold value. A valve member in the pressure-dump valve defines a pressure-reducing orifice that communicates fluid across the valve member. A check valve prevents flow through the pressure-reducing orifice when the pressure in the valve is below the threshold value. When the pressure exceeds the threshold value, fluid flows through check valve and the pressure reducing orifice resulting in the movement of the valve member and exposure of a bypass port thereby diverting a portion of the primary fluid flow past the second application. The check valve may be selectively variable to provide for the adjustment of the threshold value. A priority valve may also be provided upstream of the first application.

Abstract: A hydraulic system for a motor vehicle is provided with a pump suction enhancer includes a body section defining a small chamber, a venturi tube passage exposed to the small chamber at an inner end thereof and connected to the suction port of the oil pump, and a nozzle protruding into the small chamber to face the inner end of the venturi tube passage with a space relative to the venturi tube passage in axial alignment with the same. The flow divider divides the operating oil discharged from the oil pump into a return flow to the pump suction enhancer and a supply flow which passes through a power steering device to return to an oil reservoir. The pump suction enhancer may be integrally formed with the oil reservoir or provided as a discrete component separated from the oil reservoir, oil pump and the flow divider.

Abstract: A hydraulic pump apparatus having an internal sump formed by a housing having an internal portion and an end cap secured to the housing. A rotatable cylinder block is located in the sump and driven by an input shaft extending into the housing. The pump apparatus also has a system of hydraulic porting in fluid communication with the cylinder block. The porting includes a pair of system ports located on a first side of the hydraulic pump apparatus, a fluid inlet on a second side of the hydraulic pump apparatus, opposite the first side, and a bypass valve positioned on the second side adjacent to the fluid inlet.

Abstract: A hydrostatic stepless transmission comprises a hydraulic pump and a hydraulic motor, at least one of the hydraulic pump and motor being variable in displacement; a closed circuit for fluidly connecting the hydraulic pump and motor to each other therethrough, the closed circuit including a pair of oil passages between the hydraulic pump and motor, one of the oil passages being hydraulically higher-pressured and the other being hydraulically depressed when the hydraulic pump delivers oil to the hydraulic motor; a speed change operation device for changing output rotational speed of the hydraulic motor; and a leak valve connected to the speed change operation device.

Abstract: A hydraulic pump apparatus having an internal sump formed by a housing having an internal portion and an end cap secured to the housing. A rotatable cylinder block is located in the sump and driven by an input shaft extending into the housing. The pump apparatus also has a system of hydraulic porting in fluid communication with the cylinder block. The porting includes a pair of system ports located on a first side of the hydraulic pump apparatus, a fluid inlet on a second side of the hydraulic pump apparatus, opposite the first side, and a bypass valve positioned on the second side adjacent to the fluid inlet. A case drain may also be formed on a third side of the pump apparatus.

Abstract: Disclosed is a vehicle comprising a transaxle and a bypass mechanism. The transaxle has a plurality of mounting holes for use in attaching the transaxle to the vehicle. Further, the transaxle has at least one mounting hole more than is used to attach the transaxle to the vehicle. The bypass mechanism comprises a bypass linkage. Finally, the bypass linkage is supported by the mounting hole.

Abstract: A hydraulic control device for a working machine includes hydraulic actuators, a hydraulic pump which functions as a hydraulic power source, control valves which control the actuators on the basis of operations by an operating unit, a common bleed-off valve which returns excess oil to a tank via an unload passage on the basis of the operations by the operating unit, and a control unit which controls the common bleed-off valve. The common bleed-off valve is capable of setting a position for closing the unload passage when the common bleed-off valve is in a non-operating state. The control valves have center bypass passages which function as individual bleed-off passages which open when the control valves are in neutral states. Opening characteristics of the control valves are set such that the center bypass passages are closed in initial stroke periods in which the control valves move toward operating positions.

Abstract: A power unit includes an engine and a static hydraulic continuously variable transmission with a swash plate type hydraulic pump and a hydraulic motor, which are connected via a hydraulic pressure closing circuit. This power unit drives the hydraulic pump to rotate with the engine and performs swash plate angle control of the hydraulic motor. A crankshaft mechanism of the engine and a rotating mechanism of the static hydraulic continuously variable transmission are housed in a transmission housing. A cylinder of the engine is integrated with the transmission housing, and a swash plate control motor for swash plate angle control of the hydraulic motor is positioned at an area adjacent a root of the cylinder in the transmission housing.

Abstract: In a hydrostatic continuously variable transmission, a hydraulic pump and a hydraulic motor are connected through a hydraulic closed circuit and the capacity of the hydraulic motor is varied to vary the speed continuously. The transmission has a valve spool in a spool hole made in a transmission output shaft which rotatably holds the hydraulic pump and hydraulic motor; and the transmission output shaft incorporates outer branch oil paths which are connected with an outer passage and open to the spool hole, and an inner branch oil path which is connected with an inner passage and open to the spool hole.

Abstract: A joining directional control valve 13 is disposed to supply, to an arm cylinder 4, not only a hydraulic fluid delivered from a first hydraulic pump 1, but also a hydraulic fluid delivered from a second hydraulic pump 2 when an arm directional control valve 14 is driven. Respective delivery pressures of the hydraulic pumps 1, 2 are detected by pressure sensors 101, 102, and the opening area of a recovery control valve 6 is controlled depending on a lower one of the detected pressures from the pressure sensors 101, 102 such that, even in the combined operation of the arm cylinder 4 and another actuator 3, 4, the hydraulic fluid can be recovered for return to the arm cylinder 4 when the load pressure of the arm cylinder 4 is low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.

Abstract: The present invention lowers energy loss while at the same time enhancing the responsiveness of a steering control system. When a steering controller is operated rapidly, the aperture area of a steering flow control valve 4 rapidly increases, and the differential pressure (Pp?-PL) across the steering flow control valve 4 rapidly decreases. When the differential pressure (Pp?-PL) across the steering flow control valve 4 rapidly decreases, a flow control valve 6 is biased by the spring force of a spring 6f and quickly moves to the side of a valve position 6b to increase the differential pressure (Pp?-PL) and make it correspond to a set pressure. Thus, the pressure oil of a surplus flow ?, which up to this point has been flowing to a discharge oil line 7, is quickly supplied from the flow control valve 6 to a steering hydraulic cylinder 5 via the steering flow control valve 4. Thus, an output Q? starts quickly relative to an input St.

Abstract: A pump having a symmetric end cap is disclosed. The end cap is attachable in a first position or a second position wherein the second position is rotated relative to the housing. A trunnion arm extends in a first direction and a system port opens in a first orientation when the housing is connected to the end cap in a first position. The end cap includes structure such that the housing may be connected in a second position so that the trunnion arm extends in a second direction while maintaining the system port opening in the first orientation. The end cap may be provided with a symmetric porting system. A control device for affecting movement of the swashplate is disclosed. Methods of locking the swash plate into a predetermined position are also taught.

Abstract: A bypass mechanism is provided for use in a hydrostatic transmission, to enable the user to open or close a valve between the two pressure sides of the hydraulic circuit of the transmission. An electrical mechanism is positioned to open or close the valve based on a signal which may be generated by a switch associated with the hydrostatic transmission.

Abstract: A hydrostatic stepless transmission comprises a hydraulic pump and a hydraulic motor, at least one of the hydraulic pump and motor being variable in displacement; a closed circuit for fluidly connecting the hydraulic pump and motor to each other therethrough, the closed circuit including a pair of oil passages between the hydraulic pump and motor, one of the oil passages being hydraulically higher-pressured and the other being hydraulically depressed when the hydraulic pump delivers oil to the hydraulic motor; a speed change operation device for changing output rotational speed of the hydraulic motor; and a leak valve connected to the speed change operation device.

Abstract: The present invention relates to a hydraulically powered arm system with a hydraulic circuit, which hydraulic circuit (L) comprises a pressure source (6) and a lifting cylinder (1) arranged to an arm which is intended for handling a tool, said hydraulic circuit (L) comprising a partial circuit (45A, 45B), which can be connected into communication with said pressure cource (6) by means of a first valve element (44) and said lifting cyliner (1) by means of a second valve element (43), characterised in that said partial circuit (45A, 45B) comprises a pressure reducing/relieving unit (4) whichis arranged between said valve elements (43, 44), and that said pressure reducing/relieving unit (4) is controlled by a pressure controlling unit (62A) in order to facilitate float control of the tool attached to the arm system, whereby a controlled ground pressure is obtained during the a floating motion.

Abstract: A hydrostatic transmission including a pump, a motor, and a center section provided with a conduit through which the pump and motor are in fluid communication and a valve. The pump, motor and center section are disposed in a housing having a plurality of walls which at least partially define a sump, the conduit being in fluid communication with the sump through the valve when the valve is open. A hydraulic disconnect mechanism is provided which includes a substantially rigid first portion, and a second portion operatively engaged with the first portion and being at least partially resilient. The valve is operably engaged with and opened by the second portion in response to the first portion being in an engaged position, and the valve is not operably engaged with the second portion when the first portion is in a disengaged position.

Abstract: A combination fitting for flow control devices in an automotive power steering system having channels disposed in the fluid receiving end of the fitting.

Abstract: A hydrostatic transmission may be placed in a free-wheeling state by rotating a bypass actuator that lifts the motor from a motor running surface whereby hydraulic fluid flows into a transmission cavity. A bypass arm connected to the bypass actuator and to a bypass rod may be used to engage and disengage the bypass actuator via operation of the rod. Further, a bypass latch may be used to lock the bypass arm in an engaged position whereby the bypass actuator is engaged and the transmission is disengaged. The bypass latch arm is preferably linked to the brake pedal whereby actuation of the brake pedal disengages the bypass actuator through operation of the latching arm. The system may be designed to provide dynamic braking through transmission resistivity prior to application of a brake force to the axles or wheels by unlatching the bypass arm prior to actuating the brake arm.

Abstract: A combination fitting for flow control devices in an automotive power steering system having channels disposed in the fluid receiving in of the fitting.

Abstract: A fluid controller (27) for use with a fluid pressure operated device (45) having an inlet (47) and an outlet (49) and defining a fluid leakage path therebetween. The controller (27) includes valving (61) defining a main fluid path and further defines a fluid bleed passage including a variable bleed orifice (AB), having a substantially zero flow area when the controller valving (61) is in its neutral position (N) and in the normal operating position (R), but beginning to open as the valving approaches its maximum displacement position (R-M).

Abstract: A bypass mechanism for a hydrostatic transaxle comprising a casing in which is carried a hydraulic motor that rotates on a motor running surface of a center section. The bypass mechanism includes a bypass actuator having a first end that extends from the casing and a second end that extends through an opening in the center section adjacent to the motor running surface. Connected to the bypass actuator is a bypass arm that is adapted to rotate the bypass actuator to lift the hydraulic motor from the motor running surface of the center section. A first retaining ring attached to a first groove formed in the bypass actuator adjacent to an exterior surface of the casing and a second retaining ring located in a housing bore adjacent the first retaining ring maintains the position of the bypass mechanism relative to the transaxle components.

Abstract: A control apparatus for a hydrostatic device such as a hydrostatic transmission having a rotatable pump and motor mounted in a housing, a moveable swash plate engaged to the pump and a trunnion shaft engaged to one side of the swash plate and extending out of the housing, wherein the control apparatus comprises a control arm and return arm mounted external to the transmission housing, the control arm engaging the trunnion shaft and having a ball bearing mounted thereon, so that the return arm engages the ball bearing to provide a return force to the control arm.

Abstract: A hydraulic circuit for the hydrostatic transmission of a vehicle, said hydraulic circuit comprising at least one hydraulic motor, two main ducts, a parking brake having brake means, brake release control means suitable for feeding the brake release chamber from a first brake release fluid source, and means for connecting said chamber to a unpressurized reservoir. The circuit has a single short-circuit and selection valve having two main ports connected to respective ones of the two main ducts, and two selection ports connected respectively to the brake release chamber and to the brake release duct, and control means for controlling said valve, which control means are suitable for causing the valve to take up a first configuration in which the main ports are mutually isolated while the selection ports are interconnected, and for causing it to take up a second configuration in which the main ports are interconnected while the selection ports are mutually isolated.

Abstract: A hydrostatic transmission may be placed in a free-wheeling state by rotating a bypass actuator that lifts the motor from a motor running surface whereby hydraulic fluid flows into a transmission cavity. A bypass arm connected to the bypass actuator and to a bypass rod may be used to engage and disengage the bypass actuator via operation of the rod. Further, a bypass latch may be used to lock the bypass arm in an engaged position whereby the bypass actuator is engaged and the transmission is disengaged. The bypass latch arm is preferably linked to the brake pedal whereby actuation of the brake pedal disengages the bypass actuator through operation of the latching arm. The system may be designed to provide dynamic braking through transmission resistivity prior to application of a brake force to the axles or wheels by unlatching the bypass arm prior to actuating the brake arm.

Abstract: A method for providing a bypass for a hydraulic circuit in a hydrostatic transmission enables the user to open or close a bypass between the hydraulic circuit of the transmission and a hydraulic fluid sump. The method uses an electromechanical valve mechanism, and provides an electrical signal thereto to open the bypass and divert the hydraulic fluid from the circuit to the sump.

Abstract: A hydraulic power steering system includes a steering gear having a cylinder, and a piston slidably disposed in the cylinder to divide the cylinder into first and second cavities on opposed sides of the piston. A pair of turn tubes are coupled to the cylinder for connecting the cylinder cavities to a source of hydraulic fluid. An open fluid leakage path extends between the cylinder cavities or between the turn tubes. This open leakage path is sized to damp fluid pressure fluctuations and thereby reduce fluid-induced shudder in the steering system. The open fluid leakage path may comprise a valve or a passage extending between the turn tubes, a passage in the piston or in the seal between the piston and the gear housing cylinder, or a passage in a banjo block connected across the turn tube inputs to the gear housing.

Abstract: A mechanism for bypassing the flow of hydraulic fluid in a hydrostatic transmission comprised of a hydraulic pump and a hydraulic motor in fluid communication through a center section. The mechanism includes a bypass actuator rod that is moved from a first position to a second position to thereby move a plate into the hydraulic motor to lift the hydraulic motor off of the center section. The bypass actuator rod may has a generally flat surface and an opposite arcuate surface wherein the generally flat surface of the bypass actuator is positioned adjacent to the plate in the first position and the arcuate surface of the bypass actuator engages the plate in the second position. When the bypass actuator rod is in the first position the hydraulic motor is in substantial sealed engagement with the center section.

Abstract: A hydraulic system controls the flow of fluid to and from several functions on a machine. Each function has a valve assembly through which fluid is supplied under pressure from a source to an actuator and through which fluid returns from the actuator to a shared return line connected by a return line metering valve to the system tank. There are several regeneration modes of operation in which fluid exhausted from one port is supplied into the other port of the same actuator, which eliminates or reduces the amount of hydraulic fluid that must be supplied from the source. In some regeneration modes, input fluid for an actuator is obtained from another hydraulic function via the shared return line. In these regeneration modes an electronic controller operates the return line metering valve to restrict fluid from flowing into the tank from the shared return line, so that the fluid will be available to be supplied into an actuator port.

Abstract: A transmission with a mechanical cold start valve that dumps the pump output to the suction side of the pump to prevent oil pressure build up and thereby prevent pump toque loads from being applied to the engine during engine cranking. The oil eventually forces the valve closed after oil passes through a long orifice passage. The length of time for this to occur is dependent on the oil temperature and the length and diameter of the orifice passage. In colder temperatures, more time will be required for the valve to close, thus aiding in the cold starting of the engine.

Abstract: A hydraulic circuit cleaning apparatus has a hydraulic circuit that includes an oil pump, an oil passage to which the oil pressure ejected from the oil pump is supplied, and a pressure regulator device connected to the oil passage for regulating the oil pressure in the oil passage. The apparatus cleans the hydraulic circuit by using a cleaning liquid. A discharge oil passage is connected to a discharge port of the pressure regulator device, so that the cleaning liquid is discharged out of the hydraulic circuit via the discharge oil passage.

Abstract: A hydraulic drive with regeneration circuit comprises a pump, a hydraulic actuator and a rotary flow divider which operates in conjunction with valve means to provide regeneration flow for the hydraulic drive.

Abstract: A loop flushing circuit includes a loop flushing valve that is connected to the low pressure system line in a hydrostatic transmission for selectively bleeding fluid therefrom to the case drain without relying on a shuttle valve to identify the low pressure line. The loop flushing valve is adaptable to electrical or electro-hydraulic actuation by a microcontroller. Thus, the timing of loop flushing can be controlled based upon various system operating conditions or input values. Loop flushing with this circuit avoids adversely impacting control characteristics of the transmission, can be defeated around neutral, and can provide single-sided loop flushing.

Abstract: A work machine is disclosed. The work machine includes a work implement and a fluid cylinder mechanically coupled to the work implement. The fluid cylinder is controlled by an apparatus that automatically places the fluid cylinder in a float mode of operation when a control valve fluidly coupled to the fluid cylinder is placed in a neutral position.

Abstract: A hydrostatic transmission may be placed in a free-wheeling state by rotating a bypass actuator that lifts the motor from a motor running surface whereby hydraulic fluid flows into a transmission cavity. A bypass arm connected to the bypass actuator and to a bypass rod may be used to engage and disengage the bypass actuator via operation of the rod. Further, a bypass latch may be used to lock the bypass arm in an engaged position whereby the bypass actuator is engaged and the transmission is disengaged. The bypass latch arm is preferably linked to the brake pedal whereby actuation of the brake pedal disengages the bypass actuator through operation of the latching arm. The system may be designed to provide dynamic braking through transmission resistivity prior to application of a brake force to the axles or wheels by unlatching the bypass arm prior to actuating the brake arm.

Abstract: A hydraulic circuit includes first and second pumps, a first discharge passage receiving hydraulic fluid discharged from the first pump and communicating with a main gallery, a second discharge passage receiving hydraulic fluid discharged from the second pump and communicating with an actuator, a communication passage ensuring communication between the first and second discharge passages, and a relief valve arranged with the communication passage to be opened at a predetermined pressure for the second discharge passage.

Abstract: A mechanism for bypassing the flow of hydraulic fluid in a hydrostatic transmission comprised of a hydraulic pump and a hydraulic motor in fluid communication through a center section. The mechanism includes a bypass actuator rod that is moved from a first position to a second position to thereby move a plate into the hydraulic motor to lift the hydraulic motor off of the center section. The bypass actuator rod may has a generally flat surface and an opposite arcuate surface wherein the generally flat surface of the bypass actuator is positioned adjacent to the plate in the first position and the arcuate surface of the bypass actuator engages the plate in the second position. When the bypass actuator rod is in the first position the hydraulic motor is in substantial sealed engagement with the center section.

Abstract: A hydraulic motor arrangement including a hydraulic motor having an inlet port arranged to receive a driving fluid, and an outlet port whereby fluid can exhaust from the motor, the arrangement incorporating a by-pass line interconnecting the inlet and the outlet ports, a non-return valve being located within the by-pass line and being arranged to permit fluid flow from the outlet port to the inlet port but to substantially prevent fluid flow in the reverse direction.

Abstract: A hydraulic vehicle drive, having a closed hydraulic circuit consists of a variable displacement pump and one or several hydraulic motors. The variable displacement pump is driven by a diesel engine. During the braking or pushing operation of the vehicle, the hydraulic motor becomes a pump and drives the variable displacement pump which, in turn, acts as a motor upon the diesel engine and acts to accelerate the latter. Thus, the intended braking effect prevents the danger that the diesel engine will reach non-permissible high revolutions per unit time, which is particularly dangerous for diesel engines with turbochargers. In order to prevent non-permissible high revolutions per unit time, a pressure regulator acting as a throttle is placed in the return line between the hydraulic motor and the variable displacement pump. The valve throttles the rate of flow when the pressure of the hydraulic fluid in the line exceeds a certain desired value during the braking operation.

Abstract: A hydrostatic loop dump valve for reducing the starting torque required for a hydrostatic unit includes a normally biased open dump valve connecting one or more of the system pressure lines to the reservoir. The dump valve(s) will automatically open and oil will drain out by gravity when the engine is not running. When the engine turns the hydrostatic unit at sufficient speeds to generate significant charge pressure, the dump valves will close and the unit will operate as normal. Thus, the input torque required to start the engine and the hydrostatic unit is minimized without damaging the hydrostatic unit.

Abstract: A fluid controller (17) to control flow to a steering cylinder (19) is modified to include a selector valve assembly (41,73) having two operating positions. In a first position (“R” in FIG. 1), the selector valve (73) permits fluid flow though the main fluid path (53) in the normal manner, as would be used when the vehicle is in a “roading” mode. In a second position (“W” in FIG. 1 and in FIG. 3), the selector valve (73) blocks flow through the fluid meter (43) which normally provides the follow-up movement (51) to the controller valving (31,33), and bypasses the fluid meter in a “working” mode. Thus, the normal flow rate can be achieved by merely rotating the steering wheel (27) an amount which corresponds to the desired deflection of the controller valving (31,33), without the need for the continuous rotation of the steering wheel, as required during normal steering.