Abstract: A working fluid supply system is provided with: a first oil pump and a second oil pump driven by an engine; a switching valve configured to cause a discharge passage of the second oil pump to communicate with at least one of a supply passage and a first drain passage; and a controller configured to switch the switching valve. The controller is configured to switch the switching valve by spending a switching time that is set in accordance with a degree of pressure variation predicted to be caused in the supply passage when the switching valve is switched instantaneously.

Abstract: A pressure supply device for prioritised volume flow splitting, in particular in mobile working machines, includes at least one adjusting pump (2) controllable by an LS signal as main pump, a constant-displacement pump (4) as an auxiliary pump, and two pressure balances. A system is supplied primarily, in particular in the form of steering hydraulics (PL), which outputs an LS signal. A system is supplied secondarily, which outputs a further LS signal, in particular in the form of working hydraulics (PA). A further system is supplied hydraulically, in particular in the form of brake hydraulics (PB).

Abstract: A mechanism (100) for raising and lowering lifting arms (104) of a work vehicle includes an operating lever (111) that is secured at the column (103) of the steering wheel (102) of the work vehicle, a hydraulic arrangement and at least one linkage for operating the lifting arms (104). The hydraulic arrangement further includes a plurality of piston-cylinder pairs (105a-105b, 110a-110b, 115a-115b, 120a-120b, and 125a-125b) provided between the operating lever (111) and the linkage, for controlling the raising and lowering operation of the lifting arms (104). The operating lever (111) permits an effective and easy control of the raising and lowering operation of the lifting arms (104).

Abstract: Hydraulic workover system having at least two sets of hydraulic cylinders coupled with a single load. A plurality of control valves transitionable between a closed position and an open position, the plurality of control valves having at least one extend control valve disposed between each set of hydraulic cylinders and an extend supply pump, at least one retract control valve disposed between each set of hydraulic cylinders and a retract supply pump, and at least one float control valve disposed between each set of hydraulic cylinders and a float supply pump. A logic control system coupled with the plurality of control valves and configured to transition the plurality of control valves between the closed and open position, thereby controlling flow between the at least two sets of hydraulic cylinders and the extend supply pump, retract supply pump, and float supply pump.

Abstract: A routing plate assembly is provided and includes a gearbox having an aft surface, first and second hydraulic components, a routing plate comprising a forward side affixable to the aft surface of the gearbox, an aft side to which the first and second hydraulic components are affixable and a body. The body is formed to define interfacial pathways by which the gearbox and the first and second hydraulic components are communicative.

Abstract: A hydrostatic drive includes a hydraulic pump configured to drive at least two hydraulic motors. The hydraulic motors each include an inlet side and an outlet side. The hydraulic motors are each connected on the inlet side to a respective outlet of a flow divider, which is arranged downstream of the hydraulic pump. The hydraulic motors are each connected on the outlet side to a respective inlet of a flow divider, which is arranged upstream of the hydraulic pump.

Abstract: The present disclosure provides embodiments directed towards a system for the control of hydraulic output by a hydraulic power source. In one embodiment, a system is provided. The system includes a hydraulic supply system having a drive, a hydraulic pump coupled to the drive, a first hydraulic output configured to supply a first flow of a hydraulic fluid from the hydraulic pump to a hydraulic lift, a second hydraulic output configured to supply a second flow of the hydraulic fluid from the hydraulic pump to a first hydraulic tool, and a controller configured to adjust a speed of the drive in response to a feedback indicative of a first load by the hydraulic lift, a second load by the first hydraulic tool, or a combination thereof.

Abstract: Disclosed embodiments of power machines, implements and hydraulic systems utilize a hydraulic flow control circuit and method to implement multiple modes of operation while optimizing hydraulic fluid flow to either or both of primary and secondary function devices.

Abstract: A system for operating a single acting hydraulic cylinder includes a directional valve that has one extreme position in which a workport is connected to a tank return conduit, another extreme position where the workport is connected to a pump supply conduit, and a closed intermediate a position where the workport is disconnected from both the pump and the tank. The directional valve is pilot operated and is biased toward the one extreme position by a spring. An electrically operated primary applies pilot pressure to the directional valve alternately from the pump supply conduit and the tank return conduit. A pilot operated check valve has a first state which restricts fluid flow only from the workport toward the chamber and a second state in which fluid can flows from the chamber to the workport. The system has a pressure compensation that also provides self priming of the directional valve.

Abstract: The invention relates to a hydraulic control arrangement for a mobile machine tool, particularly for a forklift, comprising at least two hydraulic loads (10, 12), one of them having a lifting function. According to the invention, the two loads are each controlled via a LUDV valve with inflow measuring diaphragm (36, 44) and LUDV pressure regulator (46) connected downstream.

Abstract: In a hydraulic pressure circuit including an introduction section through which oil is introduced, a main passage section installed at a downstream side of the introduction section to be communicated with a supply section through which oil is supplied to each of slide sections of an internal combustion engine, a branch passage branched from the main passage section to supply oil to a hydraulic pressure actuator, and a control valve having a valve body which is moved in accordance with a pressure of an upstream side thereof, and a variable capacitance pump configured to drain oil to the introduction section, the variable capacitance pump is configured to vary a drained flow quantity in accordance with the drained pressure of oil and a pressure under which the oil drained flow quantity is started to be varied is higher than a pressure under which the valve body is started to move.

Abstract: A hydraulic system for a machine is disclosed. The hydraulic system may have a first pump with variable displacement and being load-sense controlled, and a first hydraulic circuit associated with the first pump. The hydraulic system may also have a second pump with variable displacement and being electro-hydraulically controlled, and a second hydraulic circuit associated with the second pump. The hydraulic system may further have a flow-sharing valve arrangement configured to selectively share fluid flow between the first and second hydraulic circuits.

Abstract: Disclosed embodiments of power machines, implements and hydraulic systems utilize a hydraulic flow control circuit and method to implement multiple modes of operation while optimizing hydraulic fluid flow to either or both of primary and secondary function devices.

Abstract: The invention relates to the field of load sensing, flow sharing directional control valves for controlling an operating machine, such as an excavator. The directional control valve of the present invention is particularly characterized by the addition of at least one element (E4) wherein the provision of a bore (16) and the replacement of components (30), (50), (M1) with a compensator (9), having a spring (14) operating on one side thereof (9a), and a piston/load sensing signal selector (8) impart to this single element (E4) the feature of non participating in flow-rate reduction under saturation conditions, while preserving the feature of maintaining a constant flow-rate to the user, irrespective of the variation of the load.

Abstract: Embodiments of a hydraulic brake system are disclosed. In one embodiment, a priority flow control valve for supplying operating pressure has a first orientation in which operating pressure is provided at a controlled flow port and a second orientation in which operating pressure is provided at the controlled flow port and an excess flow port. A steering control unit has an inlet port for receiving operating pressure and an outlet port for communicating a steering control load sense signal. A brake control unit has an inlet port for receiving operating pressure and an outlet port for communicating a braking control load sense signal. The inlet port of the brake control unit and the inlet port of the steering control unit are connected to the controlled flow port.

Abstract: According to the present disclosure, a hydraulic control apparatus for construction machinery comprises: hydraulic pumps; first and second control valve units which control the flow directions of working oil discharged from the hydraulic pumps to supply the working oil to first and second work machines, respectively, and which control the degree of opening of flow channels which interconnect the first and second work machines and the hydraulic pumps, respectively; and a control unit which controls the first and second control valve units in accordance with operating signals inputted from first and second operating units.

Abstract: A hydraulic control system for controlling at least two consumers (2, 4) includes a pump (6) with an adjustable delivery quantity. The consumers are each associated with an adjustable metering orifice (24, 38), having a power beyond connection (72) to which at least one power beyond consumer (74) is connectable. An inlet pressure governor unit (60) is connected downstream of the pump (6) and opens a connection to a tank (T). Its setting occurs as a function of a load pressure of the consumers (2, 4) or of the at least one power beyond consumer (74). The inlet pressure governor (60) is provided in the pressure fluid flow path between the pump (6) and one of the two consumers (2, 4), while the power beyond connection (72) branches off from the pressure fluid path between the pump (6) and the inlet pressure governor (60).

Abstract: A hydraulic control device according to the invention is of load-sensing design and serves to actuate a first hydraulic load and a second hydraulic load. Also provided are a first control valve for actuating the first hydraulic load and a second control valve for actuating the second hydraulic load. A first load signal can be measured on the basis of a load pressure with which the first hydraulic load is acted on, and a second load signal can be measured on the basis of a load pressure with which the second hydraulic load is acted on. Pressure medium from a pressure medium source can be supplied in parallel to the first control valve and to the second control valve. A load signal path can, in order to actuate an adjusting element which is assigned to the pressure medium source, be acted on with a highest presently measured load signal. A limiting device allows the second load signal to be limited to a predefined signal limit value.

Abstract: A priority hydraulic flow diverter control assembly for a refuse collection vehicle hydraulic system provides proper and efficient flow in an auxiliary hydraulic circuit regardless of the primary flow so that refuse cart lifters and the refuse cart operate safely and efficiently. A pressure sequence valve diverts hydraulic fluid flow from the refuse cart lifter circuit into the downstream main hydraulic system when downstream back pressure is low, and into the system tank when back pressure is high. This allows all hydraulic operated equipment to operate at their intended speed whether at high or low system back pressure. A differential pressure sensing valve and flow regulating valves provide a precision flow. Harmful and undesirable vibrations and noise associated with pulses in hydraulic system pressure are reduced using a control orifice located in the valve body. A relief valve ensures that the diverter control assembly is compatible with other manufacturer's products.

Abstract: The invention relates to a hydraulic control device for a priority, first hydraulic consumer and a subordinate, second hydraulic consumer, pressure medium being deliverable to the first or the second consumer via a first or a second metering diaphragm. A pressure scale which allows a constant pressure difference to be adjusted above the first metering diaphragm is mounted upstream from the first metering diaphragm. For this purpose, said pressure scale is provided with a valve piston encompassing a first control edge, by means of which a first flow area between a feeding duct and the first metering diaphragm can be controlled. A second control edge which allows a second flow area to be controlled between the feeding duct and a load signaling line is provided on the valve piston of the first pressure scale.

Abstract: The dynamic fluid device has a first pumping arrangement and second pumping arrangement arranged in parallel with each other to pump a pressurized fluid to user devices; at least a distributor member interposed amongst the first pumping arrangement, second pumping arrangement and the user devices and connected to them with connection arrangements, the at least a distributor member being arranged to connect singly and/or jointly and/or according to predetermined sequences, the first pumping arrangement and/or the second pumping arrangement to the user devices.

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 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 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 vehicular hydraulic system having a pump, flow-splitting valve, first application and second application arranged in series. The flow-splitting valve diverts a portion of the primary fluid flow to the second application when the pressure exceeds a threshold value. A valve member disposed in the flow-splitting valve defines a pressure-reducing orifice that communicates fluid across the valve member. A one-way relief valve prevents fluid 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 relief valve and the pressure reducing orifice resulting in the movement of the valve member and exposure of a bypass port to thereby divert a portion of the primary fluid flow to the second application. The relief valve may be selectively variable to thereby provide for the adjustment of the threshold value.

Abstract: A hydraulic system including a control valve and a steering control assembly. The steering control assembly includes a steering control unit and a priority flow divider contained in a single unitary casing. The steering control assembly is attached adjacently with and directly to the control valve by means of an interface that fluidly connects the control valve with the steering control assembly.

Abstract: A priority flow rate control valve (4) increases a distribution ratio of pressurized oil to a power steering device (1) of a fork-lift track via a power steering oil passage (9) as a differential pressure between a power steering pressure (PS) in the power steering oil passage (9) and a pilot pressure (LS) decreases. A load signal port (24) which outputs a pressure indicative of a load exerted on the power steering device (1) and the power steering oil passage (9) are connected via two orifices (26A, 26B), and the pilot pressure (LS) pressure is extracted from a point between the two orifices (26A, 26B). By providing a bypass passage (31, 35) which bypasses one of the two orifices (26A, 26B) and a bypass valve (30) which opens and closes the bypass passage (26A, 26B), a response of the priority flow rate control valve (4) can be increased temporarily.

Abstract: A fluid system comprises a static LS valve, a dynamic LS valve, a priority valve biased to preferentially supply pressurized fluid to both the static LS valve and the dynamic LS valve, and a signal-mimicking device fluidly coupled to a static LS port of the static LS valve, a dynamic LS port of the dynamic LS valve, and a dynamic LS pilot port of the priority valve for mimicking a static LS signal from the static LS port of the static LS valve into a dynamic LS signal from the dynamic LS port of the dynamic LS valve to produce a combined LS signal communicated to the dynamic LS pilot port of the priority valve. Such a fluid system may be applied to a steering system. An associated method is disclosed.

Abstract: The invention relates to a hydraulic control device for a priority, first hydraulic consumer and a subordinate, second hydraulic consumer, pressure medium being deliverable to the first or the second consumer via a first or a second metering diaphragm. A pressure scale which allows a constant pressure difference to be adjusted above the first metering diaphragm is mounted upstream from the first metering diaphragm. For this purpose, said pressure scale is provided with a valve piston encompassing a first control edge, by means of which a first flow area between a feeding duct and the first metering diaphragm can be controlled. A second pressure scale which can be impinged upon in the closing direction by control pressure prevailing in a control chamber while being impinged upon in the opening direction by the pressure applied downstream from the second measuring diaphragm is mounted downstream from the second measuring diaphragm.

Abstract: A fluid system comprises a static LS valve, a dynamic LS valve, a priority valve biased to preferentially supply pressurized fluid to both the static LS valve and the dynamic LS valve, and a signal-mimicking device fluidly coupled to a static LS port of the static LS valve, a dynamic LS port of the dynamic LS valve, and a dynamic LS pilot port of the priority valve for mimicking a static LS signal from the static LS port of the static LS valve into a dynamic LS signal from the dynamic LS port of the dynamic LS valve to produce a combined LS signal communicated to the dynamic LS pilot port of the priority valve. Such a fluid system may be applied to a steering system. An associated method is disclosed.

Abstract: An electro-hydraulic system for a machine may include a brake charging system including at least one accumulator. A fan drive system may include a fan and a fan motor. A fluid source may be in communication with the brake charging system and the fan drive system. The fluid source may be configured to provide pressurized fluid to the brake charging system and the fan drive system to charge at least one accumulator and to drive a fan motor. A priority valve may be configured to provide pressure from the fluid source to the brake charging system, such that the fluid pressure at the accumulator is maintained at a substantially constant level during normal operating conditions.

Abstract: Fluid-dynamic circuit for supplying primary and auxiliary uses with preset priorities comprises a pressurised fluid source, at least one first use with primary priority, at least one second use with secondary priority, at least one third use with low priority; said first use is directly connected to said source by a relative first pipe and said second use and third use are connectable to said source with respective second and third pipes by interposing a valve equipped with an internal distributor member to control said second and third pipes and movable according to at least three connection configurations, in a first configuration said second use and third use being shut, in a second configuration said second use being open and said third use being shut, in a third configuration said second use being open and said being open.

Abstract: A hydraulic circuit for use with a backhoe includes first, second and third pumps; left and right traveling unit valve sections-receiving pressure oil from the first and second pumps independently of each other; a front implement valve section receiving combined pressure oil including oil from respective center oil passages of the left and right traveling unit valve sections; and a swiveling valve section receiving pressure oil from the third pump. A parallel oil passage having a restrictor extends parallel to a center oil passage of the swiveling valve section. The front implement valve section also receives pressure oil from the center oil passage of the swiveling valve section and the parallel oil passage. A load sensing system controls flow amounts of the first and second pumps according to a hydraulic load generated in a front implement operation.

Abstract: A hydraulic booster brake system includes a flow priority valve connected to a discharge portion of a hydraulic pump. To the flow priority valve are connected a brake booster and a power steering booster in parallel. The flow priority valve supplies a stipulated flow quantity of a hydraulic fluid in a total flow quantity of the hydraulic fluid discharged by the hydraulic pump to the brake booster by priority. A relief valve is provided between a brake port and a drain port. A valve body of the relief valve can adjust a relief pressure by turning a screw shaft for relief pressure adjustment.

Abstract: A priority circuit is provided that is in communication with an open circuit pump and priority and auxiliary systems. The circuit comprises a first valve with an inlet in communication with the pump, an outlet in communication the priority system, and a load sensing inlet in communication with the priority system, wherein the first valve modulates to maintain a predetermined pressure differential between pressure at the load sensing inlet and pressure at the outlet. The circuit further comprises a second valve with an inlet in communication with the pump, an outlet in communication with the auxiliary system, and a load sensing inlet in communication with the priority system, wherein the second valve is normally closed and opens when pressure at the load sensing inlet of the second valve is less than pressure at the inlet of the second valve minus the predetermined pressure differential of the first valve.

Abstract: An apparatus and method for controlling hydraulic output to a plurality of actuatable devices are disclosed. The apparatus includes a plurality of main valves coupled, respectively, to the actuatable devices and to respective secondary valves, and also an adjustment valve that is coupled between a pressure source and one or more of the secondary valves. The adjustment valve receives a first indication of a pressure at the one or more secondary valves, and a second indication related to a highest load pressure. The adjustment valve allows pressure to be provided from the pressure source to the one or more secondary valves when the second indication exceeds the first indication, such that an equal amount of fluid flow occurs with respect to each of those secondary valves that is reduced in comparison with the fluid flow to any other secondary valves that are not connected to the adjustment valve.

Abstract: A fan drive system includes a pump, at least one implement arrangement in fluid communication with the pump and a fan drive unit driveably connected to the pump. The fan drive unit is in fluid communication with the pump through a modulation valve. A signal operator is structured and arranged to receive at least one implement signal and a fan drive signal and generate a load signal output, wherein the pump is adapted to modify an output flow of the pump in response to the load signal. A control valve is urged to respond under the influence of a sensed condition and is in fluid communication with the modulation valve and the signal operator through a signal conduit.

Abstract: A hydraulic system includes a pressurized fluid supply, a plurality of non-priority elements each including a signal port and a supply port, at least one priority implement including a signal port and a supply port and a priority valve arrangement. The priority valve arrangement is adapted to receive fluid from the pressurized fluid supply and selectively apportion fluid between the supply port of the priority implement and the supply ports of the plurality of non-priority elements. The valve arrangement includes a signal circuit operative to establish a flow priority between the priority implement and the plurality of non-priority implements and the signal circuit is in fluid communication with the priority supply. The signal circuit includes a pilot portion and a dynamic load portion and the signal port of the priority implement is in fluid communication with the priority valve arrangement through the dynamic load portion of the signal circuit.

Abstract: A hydraulic system includes a pressurized fluid supply, a plurality of non-priority elements each including a signal port and a supply port, at least one priority implement including a signal port and a supply port and a priority valve arrangement. The priority valve arrangement is adapted to receive fluid from the pressurized fluid supply and selectively apportion fluid between the supply port of the priority implement and the supply ports of the plurality of non-priority elements. The valve arrangement includes a signal circuit operative to establish a flow priority between the priority implement and the plurality of non-priority implements and the signal circuit is in fluid communication with the priority supply. The signal circuit includes a pilot portion and a dynamic load portion and the signal port of the priority implement is in fluid communication with the priority valve arrangement through the dynamic load portion of the signal circuit.

Abstract: A hydraulic drive system includes a pump control unit 18 for controlling a pump delivery rate such that a pump delivery pressure is held at a predetermined value higher than a maximum load pressure among actuators 2-6. Pressure compensating valves 12-16 are each constructed to set, as a target compensation differential pressure, a differential pressure between the delivery pressure of a hydraulic pump 1 and the maximum load pressure among the actuators 2-6. The pressure compensating valve 12 is given such a load dependent characteristic that the target compensation differential pressure is reduced when a load pressure rises. A lower limit setting spring 55 for limiting the target compensation differential pressure from becoming smaller than a predetermined value is provided in the pressure compensating valve 12 for the swing section.

Abstract: A fluid pump has a housing (4), a main output port (10), an auxiliary output port (14) and a priority pressure regulating valve contained with the housing (4). The priority pressure regulating valve has a spool (20) to direct fluid to one or both of the of the output ports (10,14), a force means (34,36) associated with the spool to bias the spool (20) to a position where it causes fluid to flow to the main output port (10) exclusively, and a pressure release means (40) which enables the spool (20) to move to a position where it permits fluid to flow to the auxiliary output port (14) when the pressure at the main output port (10) is at or greater than a predetermined pressure.

Abstract: A hydraulic system (10) having a pump (12) for sequentially supplying a brake booster (14) and a steering gear (16) with hydraulic fluid to an assist in effecting a brake application and/or a steering application. The brake booster (14) has a housing (100) with a chamber (102) therein connected to a first bore (104) which retains a piston (108) connected to a master cylinder (112) and a second bore (106) which retains a control valve (114). The second bore (106) has an inlet port (118) connected to the pump (12) for receiving supply hydraulic fluid, an outlet port (120) connected to the steering gear (16) and a return port (120) connected to the pump (12).

Abstract: The invention concerns a hydraulic control circuit in which the pressure medium conveyed by a hydraulic pump of variable delivery (10) is fed, in each case via a metering aperture (17, 31), as a priority to a first hydraulic consumer (14) and only secondly to a second hydraulic consumer (15). A priority control system is now produced without additional delivery losses and with sufficient amounts of pressure medium being conveyed in that the valve member (48) of the priority valve (45) can be acted upon in the closure direction of the connection between the first connection (46) and the second connection (47) by a pressure prevailing in a line section (13) upstream of the first metering aperture (17).

Abstract: A hydraulic system for a vehicle including a distributor, or switch, valve for actuating at least two operational areas and supplying the two areas with sufficient amounts of hydraulic medium is provided. The distributor, or switch, valve preferably comprises a flow regulator valve and a solenoid valve, which function so that the supply of hydraulic medium to the steering system always has priority, ensuring that the vehicle is steerable in any situation. When the steering system is operational, the supply of hydraulic medium to other operational areas, such as the clutch and transmission systems, is completely blocked by operation of the switch valve. If, however, the clutch and transmission systems should require hydraulic medium during operation of the steering system, the switch valve allows a small portion of hydraulic medium to be supplied to the clutch and transmission as well.

Abstract: A hydraulic control circuit for, for example, working members of earth-moving machines such as backhoe loaders. A first and a second control section (9,10) are coupled to first and second linear hydraulic actuators (1,2; 3-8) through respective first a second hydraulic spool valves (21,22; 23-28), and supply (11) of a hydraulic fluid under pressure is connected in parallel with the two control sections (9,10) via a feed line (13). A load sensing circuit (16) is associated with the first and second spool valves. The control circuit includes a series-parallel connection circuit (36) of the load sensing circuit (16), and additional optional devices ensuring a higher operative functionality of the working members of the machine.

Abstract: An automotive hydraulic system having a power steering unit of a vehicle connected in parallel with an externally mounted, hydraulic-cylinder-powered accessory, such as a liftgate, snow plow or dump bed. The vehicle's power steering pump supplies the required hydraulic fluid to the power steering unit and to a cylinder in the accessory, simultaneously in the preferred embodiment and alternately in another. A preferred valve assembly is disclosed which includes a priority flow control valve and a three-position, four-way accessory control valve mounted together in a manifold designed for connection to the vehicle's power steering pump, power steering unit, and hydraulic fluid reservoir, and to a double-acting hydraulic cylinder in the accessory.

Abstract: A hydrostatic drive system is provided for a vehicle, in particular an industrial truck having a hydrostatic traction drive system (16), a hydraulic work system (20) and a hydraulic steering system (8). The drive system is compact and the energy utilization in the drive system is improved by providing a hydraulic pump (1) with an adjustable delivery volume working in an open circuit to supply the traction drive system (16), the hydraulic work system (20) and the steering system (8). In one configuration of the invention, there is at least one traction drive control valve (23) in the delivery line (5b) of the pump (1), whereby upstream of the traction drive control valve (23) in the delivery line (5b) of the pump (1) there is a priority valve (18) for the hydraulic work system (20), and upstream of the priority valve (18) of the hydraulic work system (20) there is a priority valve (6) for the steering system (8).

Abstract: A fluid supply system provides hydraulic fluid to a series combination of an automotive fan motor and a power steering unit. There is a bypass line around the fan motor for prioritizing the operation of the power steering unit. A normally closed pressure sequencing valve opens the bypass line when the pressure across the overall series combination exceeds a predetermined limit. Optional second and third bypass lines are disclosed for respectively bypassing either the power steering unit or the fan motor in case of abnormal conditions therein.

Abstract: A boom and drive train hydraulic system is described having a pressure source, preferably a pump operated by a motor, said pressure source providing hydraulic fluid at a high pressure to a first set of valves used to operate the drive train of the system. The first set of valves is equipped with a power beyond for allowing the hydraulic fluid to flow from the first set of valves to a second set of valves. At the second set of valves a pressure control is provided to reduce the pressure to a desired lower pressure. The second set of valves provides the hydraulic fluid at this reduced pressure to the boom portion of the system. The differential of the pressures is approximately 5,000 psi for the track system and approximately 2,500 psi for the boom system.

Abstract: A hydraulic system for use in an automotive vehicle. A source of hydraulic pressure selectively operates in two modes. In one mode, it feeds a radiator cooling fan and a power steering system in parallel when a system pressure or flow exceeds a predetermined pressure rate. In another mode, it feeds the radiator cooling fan and the power steering system in series when the system pressure or flow is less than the predetermined pressure or flow.