Abstract: A hydraulic recoil and belt tension control system is connected to a hydraulic motor of an endless belt propulsion device so that a common source of fluid is used to both drive the hydraulic motor and maintain proper tension in a drive belt of the propulsion device. The hydraulic recoil and belt tension control system includes first and second check valves to direct pressurized fluid from the appropriate one of first and second motor conduits to an actuating chamber of a belt tension actuator. A relief valve relieves excessive pressure in the actuating chamber and returns fluid exhausted from the actuating chamber during recoil through either of third and fourth check valves to the appropriate one of the first and second motor conduits. Utilizing the hydraulic motor drive circuit as the source of fluid for the hydraulic recoil and belt tension control systems eliminates at least two conduits between the propulsion device and the vehicle to which the propulsion device is mounted.

Abstract: An endless elastomeric belt includes a plurality of longitudinally separated guide blocks each having a longitudinally extending slot in a tip portion thereof. The slot reduces the mass of the guide block at a location most effective for reducing acceleration forces generated in the belt at a position where the belt separates from the entrained wheels at high rotational speeds. Reducing the acceleration forces reduces fatigue failures tending to occur in the bond joint between the guide block and a belt body.

Abstract: Centering spring devices are useful in hydraulic control valves for returning the valve to the neutral position under both normal and abnormal operating conditions. Since the actuator moving the valve spool must work against the spring centering device, electrically actuated hydraulic valves have been limited to small sizes. The subject hydraulic control valve incorporates a centering spring device that can be controllably disabled so that the valve spool can be freely moved between the neutral and operating positions. In one embodiment, a centering spring is disabled by hydraulically moving the spring retainers toward each other to compress the spring with hydraulic fluid controlled by a solenoid valve. Maintaining the spring in a compressed condition permits the valve spool to be moved with a smaller actuator thereby making it feasible to control the valve position with an electrical actuator.

Abstract: A hydraulic control system has first and second actuators that can be selectively moved to a second operating position dependant upon the pressure of hydraulic fluid being simultaneously transmitted thereto through a common conduit. The force of the springs of the first and second actuators is selected so that when the pressure of the hydraulic fluid is at a preselected low pressure, only one of the actuators is moved to its second position and both of the actuators is moved to their second positions when the fluid is at a preselected high pressure. The use of a common conduit for carrying fluid to the actuators eliminates the expense and complexity of providing another flow path between rotatable parts of a vehicle.

Abstract: Steering systems are normally incorporated into hydrostatic drive systems for use on track-type vehicles. The currently available steering systems do not take advantage of the potential energy created by slowing down the inside track during a steering maneuver. The subject regenerative steering system includes positioning a pair of reversing valves between a source of pressurized fluid and a pair of motor/pump units drivingly connected to a pair of tracks. Each of the variable displacement motor/pump units includes a displacement controller for controlling the displacement of the motor/pump unit. To initiate a steering maneuver, a control signal is directed to the displacement controller of one of the motor/pump units to change the displacement of the motor/pump unit causing the track to slow down and start driving the motor/pump unit.

Abstract: Axial piston fluid translating units commonly experience undesirable shaft deflections and barrel tilting during operation. A fluid translating unit includes a barrel plate interposed the end of a barrel and a porting surface defined within a housing thereof. The barrel plate is axially spaced from an end of the barrel and is in face sealing engagement with the porting surface. The barrel plate defines a plurality of fluid ports, each communicating between one of a plurality of barrel cylinder bores and the porting surface. In one aspect a plurality of counterbores are provided in the barrel in surrounding relation to the fluid ports. A plurality of seal rings having a sealing end defining an annular seal face of a predetermined width for face sealing engagement with the barrel plate. The seal rings are each disposed in one of the counterbores in circumferential sealing relation of a predetermined length which is no greater than the width of the sealing face.

Abstract: Variable displacement axial piston pumps are useful in outputting pressurized fluid to operate fluid actuators. The currently available center pivoted variable displacement axial piston pumps waste energy by compressing trapped volumes of oil during operation. The present variable displacement axial piston pump has first and second opposite sides of a swash plate pivotally connected to a pump housing by a pair of off-center pivots with the angle of the swash plate being controlled by first and second actuators connected to the opposite sides of the swash plate. Each of the off-center pivots includes a pair of pivot pins connected to the housing and releasably pivotally seated in a pair of semi-cylindrical pockets formed in the opposite sides of the swash plate. The first actuator at the first side of the swash plate holds the semi-cylindrical pocket seated against the pivot pin while the second actuator controls pivotal movement of the swash plate about the first off-center pivot.

Abstract: Vehicles having front and rear pairs of steerable wheels are sometimes provided with large springs for moving one pair of the wheels to a straight-ahead position during emergency steering. Large amounts of hydraulic energy are expended solely for the compression of such springs every time the pair of wheels are steered. A back-up steering control system (19) of the present steering control arrangement (10) has a servo valve (76) operative to control the flow of pressurized fluid from a back-up pump (60) to a steering control valve (21) which in turn controls the flow of pressurized fluid from the back-up pump to a hydraulic actuator (13) to hydraulically move a first pair of steerable wheels (11) to a straight-ahead position during emergency steering conditions.

Abstract: Reversible hydraulic motors driven by fluid from variable displacement pumps are useful in driving various mechanisms of earthmoving machines. The subject pilot control circuit includes a pilot operated valve in each of a pair of signal passages which communicate a pilot signal from a control valve to a pump displacement control. The pilot operated valve in one of the signal passages is shifted to a position blocking fluid flow therethrough by the pilot signal in the other signal passage. An accumulator means stores a portion of the pilot signal from the other signal passage and causes the pilot operated valve in the one signal passage to remain in the blocking position for a predetermined time after the pilot signal is vented from the other signal passage.

Abstract: A steering control system is provided in which one pair of wheels of an articulated steer vehicle are steered in synchronization with the articulation steering. This is accomplished by providing a first two-position valve for directing the fluid exhausted from the rod end of one articulation steer jack to the head end chamber of one of the rear wheel steering jacks and to the rod end chamber of the other rear wheel steering jack for steering the rear wheels in a first direction and another two-position valve for directing the fluid exhausted from the rod end chamber of the other articulation steering jack to the rod end chamber of the one rear wheel steering jack and the head end chamber of the other rear wheel steering jack for steering the rear wheels in the opposite direction.

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: The fluid seals on the currently available piston assemblies are ineffective for blocking the leakage of electrical signals between the piston and the cylinder. The present invention utilizes an electrically conductive split ring seated in an annular groove in a piston and an electrically conductive annular spring disposed between the split ring and the piston to resiliently urge the split ring into conductive engagement with the hydraulic cylinder while providing continuous electrical contact between the split ring and the piston to block the leakage of electrical signals.

Abstract: Fluid regeneration circuits are useful for filling expanding sides of a hydraulic motor with fluid being exhausted from the other side. The components of the currently available regeneration circuits are disposed in or adjacent to the directional control valve such that the fluid used for regeneration must pass through relatively long motor conduits between the control valve and the hydraulic cylinder. The regeneration circuit of the present invention includes a load check valve which forces the fluid exhausted from the head end chamber of a hydraulic motor to pass through a poppet valve controllably opened by a control signal. A low pressure relief valve causes an increase in the fluid pressure of the exhausted fluid passing through the poppet valve such that when the pressure level exceeds the pressure level of the fluid in an expanding side rod end chamber of the hydraulic motor, the exhausted fluid passes through a regeneration check valve and fills the expanding rod end chamber.

Abstract: Hydraulic control systems are useful for controlling actuation of hydraulic motors. Some such systems use spool type valves while other systems use poppet type valves, both of which have their advantages and disadvantages. The present hydraulic control system is a hybrid system utilizing a combination of both a spool type control valve and poppet type control valves in a single work circuit. Specifically, a spool type control valve has an inlet port connected to a variable displacement pump and a pair of flow amplifying poppet type valves are serially disposed between a pair of motor ports of the spool type valve and a pair of actuating chambers of a double acting hydraulic motor. The spool type control valve is operative to control pump-to-motor flow while one of the poppet type valves is operative to control motor-to-tank flow.

Abstract: Detent mechanisms are useful for retaining a stem of a control valve at predetermined operating positions. The ball type detents commonly used in control valves tend to slide thereby causing the operator to extend additional energy to overcome the sliding friction. The subject detent mechanism includes a roller rotatably disposed on a pin carried by a roller carrier. The roller has an annular arcuate surface in rolling contact with the peripheral surface of the stem. The arcuate surface increases the contact surface between the roller and the stem to thereby insure that the roller rolls on the stem and minimizes the lever effort necessary to move the stem.

Abstract: High pressure cutoff controls are useful for variable displacement hydraulic pumps for reducing power losses at high pressure levels. Some operators, however, believe that they get more work from pumps not having the high pressure cutoff control. The subject on-off high pressure cutoff control includes an on-off valve disposed in a pilot passage connected to an output port of a pump and to an end of a high pressure cutoff valve. The on-off valve is selectively movable between a first position at which pressurized fluid passes through the pilot passage to the end of the high pressure cutoff valve to prevent it from functioning as a high pressure cutoff valve. Thus, an operator has the option of operating the hydraulic pump with or without the high pressure cutoff control.

Abstract: Cylinder position sensor apparatuses are useful for monitoring the location of a piston within a hydraulic cylinder. The present position sensor mounting apparatus includes a resilient tubular electrical insulator positioned in a bore of a housing and has a leg of a sensor element extending therethrough. The sensor element is fixedly retained relative to the housing in one embodiment by a bolt which squeezes the insulator radially inwardly to clamp against the leg of the sensor element. In another embodiment, an insert slidably engages a tapered portion of a bore and is urged radially inwardly to squeeze the insulator inwardly to clamp against the sensor element. Thus, the insulator serves the dual purpose of electrically insulating the sensor element from the housing and the hydraulic cylinder while being utilized to clamp against the sensor element for retaining the sensor element within the housing.

Abstract: Ignition system wiring harnesses are used to carry discrete electrical signals to the fuel igniter devices of spark ignited engines. Externally mounted wiring harnesses are subjected to damage which can cause the engine to run inefficiently. The subject ignition system wiring harness extends through internal passageways in an engine block and a plurality of cylinder heads mounted thereon. The wiring harness is retained at fixed locations by a plurality of spring clip retainers, each of which has a normally flat elongate spring clip deflected around the wiring harness and slidably extending through a pair of slots in a bracket. The spring clip exerts a nearly constant force on the wiring harness as it tries to straighten to its normally flat condition regardless of the cross sectional size of the wiring harness. Thus, one size of spring clip retainer can be used for various sizes of wiring hearness.

Abstract: Hydraulic control of reversible hydraulic motors typically requires several different valves to provide for the various operating parameters. The subject hydraulic control circuit has only a pair of electrohydraulic control valves to provide all the typical operating parameters. Operation of the control valves is controlled by a microprocessor in response to receiving command signals from a manually controlled command signal outputting device which establishes a desired fluid flow rate and direction of flow through the control valves.

Abstract: Flow amplifying poppet valves are useful in hydraulic circuits requiring low leakage when the circuit is in a load holding condition. Pressure compensation of the known flow amplifying poppet valves has not been totally successful and thus, the output flow varies somewhat with changing pressure drops across the poppet valve. The subject pressure compensated flow amplifying poppet valve utilizes a pressure compensating valve and a compensating orifice disposed in a compensating flow path disposed in parallel with a valve device for controllably regulating fluid flow through a flow regulating passage. Fluid flow through the compensating flow path is restricted by the orifice to a flow rate substantially equal to the amount of fluid that can flow through a flow control slot in a valve element at a closed position of the valve element.