Abstract: A load responsive fluid control system in which system pump controls permit variation in the level of pressure differential in response to an external control signal and which uses direction control valves equipped with load responsive variable pressure differential positive load controls.

Abstract: A vehicle is provided with right and left traction drives powered by first and second reversible two-speed hydraulic motors. A solenoid-operated speed control valve is coupled to the motors for shifting the latter to high speed operation in response to the valve being energized. Travel control valves for the motor are coupled to switches connected in the circuitry for controlling the speed control valve such that during high speed operation of the vehicle the motors will be automatically downshifted in response to the travel control valves being operated to cause the vehicle to be turned.

Abstract: A direction flow control valve in a load responsive system equipped with a positive load compensator, which in the presence of negative load either blocks the pump flow to the motor above a certain predetermined level of the exhaust manifold pressure, or below that predetermined pressure level acts as a pressure reducing valve throttling sufficient fluid flow from the pump circuit to pressurize the exhaust manifold.

Abstract: A load responsive flow control valve for use in a system controlling a plurality of loads. The system is powered by a single fixed displacement pump equipped with a load responsive bypass valve or a variable displacement pump equipped with load responsive control, which during simultaneous control of multiple loads automatically maintains the pump discharge pressure at a level higher by a constant pressure differential than the pressure required by the largest load being controlled. The load responsive valve is of a four position float type which in the float position while isolating system pump and connecting both of the load chambers to system reservoir blocks pressure sensing ports from inlet chamber and connects them to system reservoir to permit full unloading of the system pump.

Abstract: A direction flow control valve for control of positive and negative loads equipped with a load responsive positive load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between inlet pressure and load pressure. The load responsive control of direction flow control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: Hydraulic system for operation of winches which are associated with powered friction pulleys for hauling a wire, the winch winding the wire onto the drum being provided with valves permitting the friction pulleys to idle freely when it is convenient to use the winch drum proper also for hauling the wire.

Abstract: A load responsive flow control valve for use in a system controlling a plurality of loads. The system is powered by a single fixed displacement pump equipped with a load responsive bypass valve or a variable displacement pump equipped with load responsive control, which during simultaneous control of multiple loads automatically maintains the pump discharge pressure at a level higher by a constant pressure differential than the pressure required by largest load being controlled. The load responsive valve is of a four position regeneration type which in the regeneration position while connecting together both of the load chambers supplies irrespective of the pressure level a constant flow into those chambers from the inlet chamber through a metering orifice.

Abstract: A load responsive flow control valve for use in a system controlling a plurality of loads. The system is powered by a single fixed displacement pump equipped with a load responsive bypass valve or by a variable displacement pump equipped with a load responsive control, which during simultaneous control of multiple loads automatically maintains the pump discharge pressure at a level higher than the pressure required by the largest load being controlled. To transmit to the pump control signal of the highest system load, without creating a back flow, load sensing passages of individual valve spools contain check valves. Upstream of the check valves load sensing passages of individual spools are vented to reservoir with valve spools in neutral position, to prevent accumulation of leakage pressure affecting the pump control and to permit the use of priority type control with selected valve spools.

Abstract: A vehicle drive system including a rotary output, variable displacement, hydraulic motor (22) adapted to drive a wheel or the like, a pump (10) for providing hydraulic fluid under pressure to the motor, a pressure control valve (30) connected to the motor for regulating the displacement thereof to achieve a desired system pressure and having a pressure responsive surface (34) receiving a signal representative of system pressure and a biasing spring (36) acting in opposition thereto. The invention contemplates the improvement wherein a variable, settable, pressure reducing device (60,106) is connected to the pump and to the pressure control valve to apply hydraulic fluid under reduced pressure to the pressure control valve in bucking relation to the system pressure signal.

Abstract: A motor displacement control system (10) has a variable displacement drive motor (38), an auxiliary motor (30), a source (12) of fluid under pressure for operating the motors (30, 38), a first valve (50) for controlling the displacement of the drive motor (38) and maintaining at least a first pressure level thereto, and a second valve (98) for controlling the displacement of the drive motor (38) in response to operation of the auxiliary motor (30) at a second pressure level and overriding the first valve (50). The system is particularly useful on a motor grader.

Abstract: A fluid power system (10) for a lift truck (18) has a movable steering device (12) and a valve (14) which moves in response to movement of the steering device (12) a preselected amount to supply fluid power for steering the lift truck (18). Apparatus (30) is provided for controllably supplying fluid power to the valve (14) prior to the valve (14) moving to supply fluid power for steering. The apparatus (30) eliminates delay between the moving of the valve (14) and the availability of fluid power at the valve (14) to insure quick, responsive steering.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump flow control responding to highest system load. Each direction flow control valve is equipped with a load responsive negative load control to control a constant pressure differential at the motor exhaust. The negative load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A hydraulic system having a reservoir fed charge pump supplying pressurized fluid through a filter to a supply pump for direction controlled fluid devices includes an unloading valve assembly on the return passage from the devices for limiting back pressure therefrom as long as the charge pump supplies sufficient pressurized fluid for the supply pump. The unloading valve assembly includes an unloading valve movable in response to the pressurized fluid at the connection between the supply pump and the filter to unload the return passage by connecting it to the reservoir and further to control the pressurized fluid going to the filter by connecting the charge pump to the reservoir at a predetermined maximum pressure of pressurized fluid. As the decvices require more fluid from the supply pump causing the pressure to the supply pump to drop, the unloading valve first blocks the charge pump from the reservoir and then the return passage.

Abstract: A load responsive fluid power multiple load control system using a first type of load responsive direction control valves responding to upstream pressure differential between inlet and load chambers together with a second type of load responsive direction control valves responding to down stream actuator pressure or pressure differential. Load pressure signals are phased by check valve logic system to the output flow control of fixed or variable displacement pump which maintains a constant pressure differential between pump discharge pressure and highest of the load pressures.

Abstract: A hydraulic follow-up for use with a hydraulic system placed between a rotating input member and a rotating output member. The hydraulic system is a hydrostatic transmission for driving a tractor, and comprises a hydrostatic pump and a hydrostatic motor driven by the pump. When the hydrostatic pump is angularly shifted with respect to the input member, the shifting is controlled by the hydraulic follow-up, which also shifts the motor in relation to the output member.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a single load responsive controller which automatically regulates fluid flow into and out of the fluid motor to maintain a constant pressure in front of a variable flow controlling orifice, during the control of both positive and negative loads. The load responsive controller of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive pressure control which automatically regulates valve inlet pressure to maintain a constant low pressure level at the motor exhaust and a load responsive negative load control to control a constant pressure differential at the motor exhaust. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A method and apparatus are disclosed for mechanically steering vehicles such as crawler tractors and the like or skid steer tractors, which include a pair of independently operable power sources. The apparatus includes a pair of independent first linkage systems interconnected between a single operator control lever and each respective power source to achieve equivalent power outputs from the sources upon movement of the lever. A pair of independent second linkage systems are interconnected between respective links in the first linkage system and respective throttling means. In the method, each throttling means may be operated independently of the other to achieve unequal power outputs from the two sources by virtue of the independent first and second linkage systems.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive pressure control which automatically regulates valve inlet pressure to maintain a constant low pressure level at the motor exhaust and a load responsive negative load control to control a constant pressure differential at the motor exhaust. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: A load responsive direction and flow control valve for use in fluid power load responsive system. The valve maintains a selected constant flow level for control of both positive and negative loads, irrespective of the change in the load magnitude or change in the fluid pressure, supplied to the valve. When controlling positive or negative loads the valve maintains a constant pressure differential across a flow control metering orifice utilizing a single control slide member, first by throttling fluid entering the inlet chamber and then by throttling the fluid leaving the outlet chamber. The valve may be used with fixed displacement pumps, fixed displacement pumps equipped with differential pressure relief valves, with variable pumps equipped with pressure compensators and variable pumps equipped with differential pressure compensators.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump flow control responding to highest system load. Each direction flow control valve is equipped with a load responsive negative load control. The negative load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust while maintaining a constant pressure in front of a variable flow metering land.

Abstract: A load sensitive hydraulic system having a variable displacement pump, a priority dependent work circuit, at least one secondary work circuit, priority means preferencing fluid flow to the priority dependent work circuit over the secondary work circuit, flow and pressure compensating means responsive to requirements of either work circuit for controlling displacement of the variable displacement pump and a relief valve, when overriden, allowing fluid flow to the secondary work circuit.

Abstract: A load responsive fluid power multiple load control system using load responsive direction and flow control valves in combination with pump control responding to highest system load. Each direction flow control valve is equipped with a load responsive positive load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between pump inlet pressure and load pressure at a first level and a load responsive negative load control which automatically regulates valve inlet pressure to maintain a relatively constant pressure differential between pump inlet pressure and load pressure at a second higher level. The load responsive control of each direction control valve blocks the pump flow to the motor while controlling negative load, providing the motor inlet with fluid from the motor exhaust.

Abstract: The invention relates to a hybrid vehicle of the hydrostatic transmission type comprising a main driving engine, a hydraulic, variable volumetric capacity pump driven from said main engine, a hydraulic motor and a hydropneumatic power accumulator mounted in a delivery conduit of said pump. Said vehicle further comprises an auxiliary hydraulic motor hydraulically mounted in parallel relationship to said first hydraulic motor and having a common output shaft therewith, the volumetric capacity of said auxiliary motor being equal to one fraction of the volumetric capacity of said first hydraulic motor.

Abstract: An improved fluid system of a crawler type vehicle has control means for selectively passing fluid in a preselected sequence to a plurality of work elements.

Abstract: Apparatus of a fluid system of a work vehicle for controlling the fluid delivered to parallel work elements of the vehicle in response to the load exerted on the fluid system by the work elements.

Abstract: An improved automatically shiftable direction control valve for a tractor hydraulic system wherein there is provided a charging pump, low pressure priority functions such as cooling and lubrication connected to the charging pump, a main pump, a continuously acting reversible function, a single-acting function, and a double-acting function all connected to the output of the main pump, and a manually operable direction control valve for each of the functions. The improved automatically shiftable direction control valve has a restricted passage causing a pressure drop which shifts the valve so as to direct the exhaust of the continuously-acting and double-acting functions to the charging circuit and to direct the exhaust of the single-acting function to the fluid reservoir.

Abstract: A hydraulic system including a source of pressurized fluid and a multi-speed motor with a directional control valve for selectively directing fluid to the motor for forward and reverse operation thereof and a speed control valve operative to control the flow of the fluid to the motor for selective control of the speed thereof is provided with an override control valve that is operative to override the speed control valve under heavy load conditions to shift the speed control valve to a low-speed high-torque position for low-speed high-torque operation of the hydraulic motor.

Abstract: In a system comprising first and second drive units each including one or more hydraulic motors, a two-position valve is provided in circuit with the motors of one drive unit, the motors of the other drive unit being supplied independently of the valve; the valve has a first operative position for blocking flow of working fluid to the one drive unit and a second operative position for permitting flow of working fluid to the one drive unit, the valve being operable between its first and second positions for selective operation of one or both drive units.

Abstract: A fluid pressure system having a plurality of pumps, valves, and fluid-pressure responsive units. These items are interconnected by fluid lines, and check valves are arranged to control the fluid in only certain directions in some portions of the lines. The entire arrangement permits the utilization of one pump for a respective fluid-pressure responsive unit, or all of the pumps can be directed to one of the fluid-pressure responsive units.