Abstract: Quick drop valves are useful in directing fluid expelled from a contracting chamber of a hydraulic actuator to its expanding chamber under gravity load conditions. The present electro-hydraulic quick drop circuit improves the efficiency of the quick drop valve by energizing a solenoid valve to direct load generated pressure from the rod end chamber of the hydraulic actuators to an end of a quick drop valve for moving the quick drop valve to the quick drop position when a control valve is at or between a preselected intermediate operating position and its fully open position. The quick drop valve is moved to the quick drop position immediately upon the control valve reaching the preselected operating position so that the fluid expelled from the rod end chamber is directed to the head end chamber almost immediately after the blade begins to freefall.

Abstract: A valve assembly (16) for use in a fluid system (10) includes a flow control valve (82) which controls fluid flow between a fluid inlet port (34) and a fluid supply passage (36) in response to the load requirements. A main control spool (96) is selectively movable between a neutral position and first and second actuated positions. A load sensing passage (78) communicates a load signal from an actuator (26) to the spring chamber (50) of the flow control valve (82). A drain passage (80) communicates the load sensing passage (78) with the reservoir (14) when the main control spool (96) is in the neutral position. A blocking mechanism (138) blocks the load sensing passage (78) when the main control spool (96) is in the neutral position and opens one of the inlet port (34) and the supply passage (36) to the spring chamber (50) so that the flow control spool (82) is held in an open position.

Abstract: Fluid in the relatively long lines (22, 24) between a control valve (16) and a fluid actuator (14) can become overly viscous in cold weather. Herein, fluid is circulated through such lines (22, 24), at least during cold weather, even when the fluid actuator (14) is not being used. This flowing is discontinued in response to shifting of the control valve (16) to a position where it motivates the actuator (14) and in response to pressure in the circulating path (20) exceeding a selected level.

Abstract: A fluid control system for selectively holding a work implement, such as a blade in a motor grader or the like, in a fixed position in a first operation mode, and for selectively providing a shock absorbing system (70,72) for the implement in a second operating mode. In the fixed position mode, lock valves (36,38,68) are operative to provide positive locking for an implement actuator (24,26), while in the shock absorbing mode, longstem lock valves (82,84) are operable to maintain one check valve (102) of a dual valve structure (96,98) unseated at all times. Each unseated check valve (102) provides a connection of one end of an implement actuator (24,26) to vent to insure that the shock absorbing system (70,72) maintains a full shock absorbing capacity.

Abstract: A variable displacement auxiliary front wheel drive system (10) is provided which includes a variable displacement fluid motor (12, 14, 16) for driving at least one vehicle wheel. The fluid motor (12, 14, 16) receives fluid under pressure from a supply source (30, 32) connected to a variable displacement pressure compensated pump which supplies fluid to a hydraulic system for the vehicle accessories. To render the variable displacement fluid motor (12, 14, 16) inoperative, a fluid control system (34, 36, 40) may be selectively operated to block fluid flow from the supply source (30, 32) to the variable displacement fluid motor (12, 14, 16) and to a pressure compensating system (44) for the fluid motor (12, 14, 16). With fluid from the supply source (30, 32) blocked, a plurality of spool valves (46, 48, 50) in the pressure compensating system (44) are drained.

Abstract: An improved emergency system (10) for a vehicle having a closed center steering valve (12), a pump (14) normally supplying fluid to the valve, and an accumulator (16) for supplying emergency pressurized fluid to the valve when the pump fails. The improvement is a flow directing circuit (18) connecting the accumulator to the valve in parallel relationship to the pump and apparatus for blocking flow from the accumulator to the valve responsive to proper operation of the pump. Adequate emergency steering is provided to a closed center steering valve system by the above arrangement.

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 vehicle drive and work performing system including a rotary output, variable displacement, hydraulic drive motor (22) adapted to drive a vehicle, at least one hydraulic implement motor (14,16 and 18) adapted to power a work performing implement, a hydraulic pump (10) providing hydraulic fluid under pressure to the motors, a flow control valve (12) for controlling the fluid flow from the pump to at least the drive motor, and a pressure control valve (30) for controlling the displacement of the drive motor to achieve a desired fluid pressure level at the drive motor, and including the improvement wherein a load sensor (60,62) is connected to the implement motor for providing a signal representing the load thereon and a piston (54) is responsive to the signal for causing the pressure control valve to change the displacement of the drive motor to thereby change the fluid pressure level thereat to a value different from the desired fluid pressure level.

Abstract: A vehicle drive system including a wheel adapted to at least partially propel a vehicle over underlying terrain and a hydraulic motor coupled to the wheel to drive the same. A flow and pressure compensated pump has an output for providing hydraulic fluid under pressure to the motor and includes a control system having an input for receiving a hydraulic signal and for controlling pressure and flow output characteristics of the pump. A manually settable, pressure reducing valve interconnects the pump output and the control system input to provide a substantially constant, but adjustable, pressure signal to the control system so that output pressure from the pump to the motor may be controlled independently of loading on the motor to set the maximum torque delivery of the motor at a desired value.

Abstract: A locking mechanism is provided for an apparatus having a first member movable relative to a second member providing a plurality of spaced holes therein including: a housing secured to the first member; a lock pin extendably retractably mounted in the housing for insertion into the holes in the second member; and a powered control circuit having an actuated member movably mounted within the housing and connected to the lock pin, the actuator member providing differential force applying surfaces selectively exerting a predetermined locking force to hold the lock pin in the holes and a lower indexing force permitting substantially unrestricted relative movement between the first and second members and automatic insertion of the pin into one of the aligned holes.

Abstract: A multi-range pressure compensated fluid delivery system gives output flow over at least two pressure ranges. The system comprises a prime mover driven variable displacement pump having an inlet from a source of hydraulic fluid and a delivery outlet. A delivery circuit from the output has at least two work circuits selectively connected thereto. A first of the circuits is operable up to a first pressure and a second of the circuits is operable only up to a second lower pressure. An actuator system controls pump displacement responsive to a pressure applied thereto. A system selectively applies a first signal determined by the first pressure to the actuator system to adjust the operating pressure of the pump. A device reduces the first pressure to the second pressure responsive to connection of the second circuit to the delivery circuit to thereby decrease the maximum compensated pressure setting of the pump.

Abstract: A motor grader including a main frame mounted on steerable wheels, a drawbar frame mounted on the main frame, a working implement carried by a circle gear rotatably mounted on the drawbar frame and a hydraulic control circuit is described. An improvement in the control of the working implement is disclosed in which continuous downward force is exerted on the circle gear at all times during operation by hydraulic rams. Preferred embodiments of the invention are described wherein the force is exerted by hydraulic means including wear surfaces in contact with the circle gear and wherein the hydraulic control circuit is adapted to provide automatic operation.

Abstract: The invention is concerned with an improvement in a hydrostatic auxiliary front wheel drive system for a vehicle which comprises a hydraulic implement pump, a hydraulic implement powered by the pump and motors drivingly connected to a front wheel shaft rotatable in a forward or a reverse direction, the motors being powered via motor conduits by the pump. The improvement of the invention comprises an electrical switch operating responsive to hydraulic pressure developed by the implement pump, the electrical switch a including biasing spring preventing switching thereof into a closed circuit position until the hydraulic pressure reaches a predetermined value and forcing the switch into an unswitched open circuit position when the hydraulic pressure drops below the predetermined value.

Abstract: A vehicle such as a motor grader includes a hydrostatic auxiliary front wheel drive system which utilizes implement system pressurized fluid flow to drive a pair of fixed displacement hydraulic motors, such motors being drivingly connected to cause rotation of the front wheels. A pilot operated series-parallel valve in combination with a flow divider allows the motors to be driven in series or in parallel. A directional control valve is selectively responsive to operator control, and clutch actuation is accomplished automatically by directing a controlled portion of system fluid to such clutches to overcome the normal spring bias thereof.

Abstract: A construction vehicle, such as a motor grader, comprises a work tool mounted thereon and adapted to be selectively moved by at least one double-acting hydraulic cylinder. A fluid circuit comprises a pressurized fluid source adapted to communicate fluid to the cylinder via a first control valve. A normally closed second control valve is operatively connected between a storage tank of the fluid source and the rod and head ends of the cylinder for exhausting fluid therefrom to the tank directly upon actuation of an independent actuation means. Opening of the second control valve will thus place the cylinder in a "float" condition of operation.

Abstract: A hydraulic fluid circuit comprises an engine-driven pump for communicating pressurized fluid through a combined unloading and relief valve and to an implement control circuit of a construction vehicle. Actuating means are provided for selectively opening the valve during engine start-up to reduce fluid pressure in the valve and implement control circuit to a first predetermined level. An override means is operatively connected to the actuating means for preventing the valve from opening when the fluid pressure exceeds a second predetermined and operating level which is higher than the first predetermined level.

Abstract: A vehicle such as a motor grader includes a hydrostatic auxiliary front wheel drive system which utilizes implement system pressurized fluid flow to drive a pair of fixed displacement hydraulic motors, such motors being drivingly connected to cause rotation of the front wheels. A pilot operated series-parallel valve in combination with a flow divider allows the motors to be driven in series or in parallel. A directional control valve is selectively responsive to operator control, and clutch actuation is accomplished automatically by directing a controlled portion of system fluid to such clutches to overcome the normal spring bias thereof.

Abstract: A tandem axle suspension system for a vehicle includes a first axle including non-adjustable fixed spring means for connecting the axle for support of the frame of the vehicle, and a second axle including an adjustable hydraulic spring means and including leveling valve means responsive to the distance between the second axle and the frame means for controlling communication of fluid to the second or adjustable hydraulic spring means.

Abstract: An apparatus and method for preparing a hydraulic work machine for towing in response to a dead engine condition. The apparatus includes a source of hydraulic fluid, a standby pump system hydraulically connected to the source, a plurality of pilot controls adapted for electrical activation by the standby pump system, and a hydraulic brake system. The apparatus also includes a supply valve connected to the pilot controls, and at least one lift cylinder connected to the supply valve and adapted to lift an implement on the work machine. The hydraulic brake system and the lift cylinder are enabled for hydraulic control in response to activation of the standby pump system.