Abstract: An overspeed control for a hydrostatic transmission of a mobile machine includes a speed control valve arrangement connected to a fixed displacement pump through a supply line and to a pressure responsive displacement controller of a variable displacement hydraulic pump of the transmission. An overspeed control valve is connected to the supply line and is operative for reducing the fluid pressure level in the displacement controller when the speed control valve arrangement is in an operative position and the rotational speed of the engine exceeds a predetermined level. This reduces the displacement of the variable displacement pump (which acts as a motor in a downhill situation) and thus increasing engine retarding and transmission losses for preventing the positive grade from accelerating the machine, engine and/or the components of the hydrostatic transmission to speeds exceeding their designed limits.

Abstract: A fluid metering valve adaptable for outputting a fixed volume of lubricating oil from a diesel engine into an engine fuel system includes a sleeve slidably disposed in a body and a piston valve slidably disposed within the sleeve. A spring resiliently biases the sleeve to a default position blocking communication between a chamber and an outlet and the piston valve to a default position communicating an inlet with the chamber. The default position of the sleeve is established by a annular member resiliently biased into engagement with the body by another spring while the default position of the piston valve is established by another annular member urged into engagement with the body by a third spring.

Abstract: A hydraulic control valve for minimizing fluid leakage from a load actuating cylinder and for protecting the cylinder from damage has a composite valve body with a poppet slidably disposed in a bore and biased to the closed position. A pilot spool, controllable by a proportional solenoid regulates pilot pressure. Regulated pilot pressure allows for accurate control of the poppet for metering fluid from cylinder to tank. A force feedback spring disposed between the poppet and the pilot spool exerts a force on the pilot spool equivalent to the force from the proportional solenoid keeping the forces in equilibrium. Pilot pressure is adjusted to establish the relief pressure setting for the hydraulic control valve while conical sealing surfaces, minimize fluid leakage from cylinder to tank.

Abstract: A hydraulic deceleration control for a hydraulic motor includes a pilot operated control valve for controlling fluid flow through a pair of motor lines connected to the opposite sides of the hydraulic motor. A valve device is disposed to communicate a source of pressurized fluid to a fluid energy storage device when the control valve is in its open position and to release the pressurized fluid contained in the storage device when the control valve is moved from the open position to its closed position. A throttle orifice releases the fluid from the storage device at a controlled flow rate. A pilot operated diverter valve is disposed in series with an orifice disposed between the motor lines to control fluid flow through the orifice and has a spring disposed at a first end resiliently biasing the diverter valve to its closed position.

Abstract: A blade control system includes a directional control valve, a fluid regeneration valve and a selector valve for selectively controlling fluid flow between a pump and first and second hydraulic cylinders and between the cylinders. With the valves positioned at preselected operative positions, pressurized fluid from the pump is directed to the head end chamber of the first cylinder, fluid expelled from the rod end chamber of the first cylinder is diverted to the head end chamber of the second cylinder, and fluid expelled from the rod end chamber of the second cylinder is combined with the fluid being directed to the head end chamber of the first cylinders to provide two stages of fluid regeneration for increasing the extension speed of the cylinder.

Abstract: A swash plate actuating device for an axial piston unit has a swash plate tiltably mounted within the housing. A pair of axially aligned actuating chambers defined in the housing slidably receive the opposite ends of an elongate actuator and are disposed on opposite sides of a distal end portion formed on an actuator lever connected to the swash plate. A connector has a mounting portion spanning a transverse slot in the actuator and seated on a planar surface of the actuator. A guide portion of the connector is disposed within the transverse slot and has a bearing slot slidably receiving the distal end portion of the actuator lever.

Abstract: Oil coolers are commonly used in hydraulic systems for maintaining oil below a preselected temperature under normal operating conditions. The subject oil cooler circuit includes a pilot operated valve disposed in a conduit connecting the hydraulic system to the cooler and an electromagnetic pilot valve connected to one end of the pilot operated valve. The pilot valve is spring biased to its closed position when the temperature of the oil is above a predetermined temperature and is moved to an open position when the oil temperature is at or below the predetermined temperature. The end is vented to a tank at the open position of the pilot valve so that the pilot operated valve is maintained at the closed position to prevent cold viscous oil from being transmitted to the oil cooler when the oil temperature is below the predetermined temperature.

Abstract: A flow amplifying poppet valve has a main poppet for controlling fluid flow from an inlet port to an outlet port of a main fluid passage. The position of the main poppet is controlled by controlling the pressure in a first control chamber adjacent the main poppet with a second stage poppet of a two-stage pilot valve disposed within a pilot passage communicating the first control chamber with the outlet port. The position of the second stage poppet is controlled by controlling the pressure in a second control chamber adjacent the second stage poppet with a pilot stage poppet that has a frusto-conical section urged into sealing engagement with the second stage poppet by a spring. A device selectively exerts a control force to move the first stage poppet in a valve opening direction to establish a variable flow control orifice between the frusto-conical section and the second stage poppet.

Abstract: A control logic for a multiple use hydraulic system includes a selector switch having a first position connecting a battery to a treadle switch operable to energize a solenoid pilot valve for communicating pilot fluid to an end of a first directional control valve. The selector switch has another position connecting the battery to a bi-directional push button switch operable to selectively energize a pair of solenoids of a second pilot valve. Energizing one of the solenoids moves the second pilot valve in one direction to communicate pilot fluid to an end of the first and a second control valve. Energizing the other solenoid moves the second pilot valve in the opposite direction to communicate pilot fluid to the other end of the control valves. The selector switch has a third position connecting the battery to a pair of pressure switches connected to a pair of lines connecting a manually actuated pilot valve to a pair of solenoid blocker valves.

Abstract: A two-stage electrohydraulic pressure control valve modulatably controls engagement of a spring applied, pressure released brake when electrical power directed thereto is suddenly lost. The control valve includes a shutdown valve mechanism between a pilot stage and a main stage to controllably reduce the fluid pressure in an accumulator storage chamber in three distinct stages. The first stage is the immediate blocking of fluid flow from the storage chamber by a flow control valve when fluid passing therethrough in one direction exceeds a predetermined flow rate. The second stage is reducing the fluid pressure in the storage chamber to a predetermined level by a relief valve when the flow control valve is in its flow blocking position. The third stage is accomplished by restricting fluid flow from the storage chamber at a predetermined flow rate through an orifice so that the main stage modulatably controls the reduction of fluid pressure in the brake chamber.

Abstract: An axial piston hydraulic unit has a valve plate assembly positioned between a head and a rotatable cylinder barrel. The assembly includes a pair of valve plates stacked together to function as a single valve plate. The valve plate assembly defines a restricted flow path for providing initial communication between an approaching piston bore of the rotatable barrel and an intake port and a discharge port extending through the pair of plates. A first portion of the flow path is defined in the valve plate adjoining the head and a second portion of the flow path is defined in the valve plate adjacent the barrel. The stacked valve plates are hydraulically held together by a pair of pressure balancing devices.

Abstract: A cylinder barrel includes a casting having a plurality of ceramic bore liners cast in situ within the casting. The cylinder barrel is made by positioning the ceramic bore liners at predetermined locations within a casting mold and pouring a molten ferrous metal into the mold so as to envelope the bore liners.

Abstract: A piston for a variable displacement axial piston hydraulic pump has a vibration absorber disposed within a chamber of the piston. The vibration absorber includes a vibration absorber mass suspended between a pair of springs. The vibration absorber offsets the piston inertia created from the oscillatory displacement of the pistons for stabilizing the pump.

Abstract: A three position four way directional control valve having a single spool is typically used for controlling fluid flow from a pump to a cylinder and from the motor to a tank. The present invention includes a pair of electrohydraulic control valves with one of the control valves controlling pump-to-cylinder communication between a pump and the rod end and head end chambers of a hydraulic cylinder while the other control valve controls cylinder-to-tank communication between the rod end and head end chambers and the tank. Each of the control valves includes a displacement controlled proportional valve for controlling the position of a pilot operated valve member. Actuation of the hydraulic cylinder requires moving the valve member of one control valve to control pump-to-cylinder communication to one of the chambers while simultaneously moving the valve member of the other control valve for establishing cylinder-to-tank communication between the other chamber and the tank.

Abstract: A pump displacement control for a variable displacement pump includes a torque control valve disposed between a variable torque limiter and a force applying device disposed in axial alignment within a common bore. A sleeve and a valve spool are movable relative to each other to establish a first condition communicating discharge pressure into an actuator chamber to move a swashplate toward a minimum displacement position against the bias of a spring or a second condition communicating the actuating chamber with an exhaust passage to allow the spring to move the swashplate toward its maximum displacement position. A torque control piston disposed between opposing springs resiliently bias the valve spool in a direction to establish the second condition when control fluid is directed into a control chamber.

Abstract: A variable displacement axial piston hydraulic unit includes a flat port plate disposed between a stationery head and a rotatable cylinder barrel. An arcuate actuator piston extends from the port plate and is slidably disposed within an arcuate pocket in the head to define an actuator chamber. Similarly, an arcuate biasing piston extends from the port plate and is slidably disposed within an arcuate pocket defining a biasing chamber which continuously communicates with a discharge passage in the head. By selectably rotating the port plate relative to the head, the amount of fluid pressure carryover through TDC and BDC can be varied, thereby changing the swivel torque acting on the swashplate so that the swivel torque can be utilized to actually control the position of the swashplate. The rotational position of the port plate is controlled by controllably introducing pressurized fluid into the actuating chamber.

Abstract: A two stage electrohydraulic pressure control valve includes a pilot stage for providing regulated pressure at lower flows to a larger main stage that handles the higher control flows to and from a pressure applied clutch or pressure released brake. The regulated pressure from the pilot stage acts on an end of the main stage for controlling the position of the main stage. An energy storage device in the form of either an accumulator or a load piston device is connected to the end of the main stage to permit instantaneous independent movement of the main stage relative to the pilot stage. The energy storage device quickly provides for or accepts displaced fluid from the main stage much faster than the limited flow capacity and response time of the pilot stage. This permits the main stage to quickly adjust to flow changes to the clutch or brake with minimal change in pressure until the pilot stage can respond.

Abstract: A pump displacement control for a variable displacement pump includes a torque control valve serially disposed between a remotely controllable displacement control valve and a variable torque limiter in axial alignment within a common bore. A displacement control sleeve is disposed within the bore for normally controlling the fluid pressure in an actuating chamber of an actuator connected to a swashplate of the pump when the pump discharge pressure is below a predetermined high pressure. The torque control valve assumes control of pump displacement when the pump discharge pressure exceeds the predetermined high pressure and includes a sleeve and a valve spool movable relative to each other to establish a first condition communicating discharge pressure into the actuator chamber to move the swashplate toward a minimum displacement position or a second condition communicating the actuating chamber with an exhaust passage so that the swashplate is moved toward its maximum displacement position.

Abstract: A variable displacement axial piston hydraulic unit includes first and second control pockets individually disposed between first and second arcuate shaped fluid passages, a first electrohydraulic valve for controlling fluid flow between the first control pocket and the first fluid passage and a second electrohydraulic valve for controlling fluid flow between the second passage and the second control pocket. A controller outputs first and second control signals to the first and second electrohydraulic valves in response to receiving a command signal so that the tilt angle of a swashplate is controlled to obtain a desired operating parameter. An angle detector, a pressure detector, and a speed detector provide feedback signals to the controller for determining when the desired operating parameter has been obtained.

Abstract: A hydraulic cylinder snubbing arrangement includes a pilot operated control valve having a predetermined snubbing position at which flow exhausted from a hydraulic cylinder actuating chamber must pass through a plurality of flow restricting orifices in a valve spool when the hydraulic cylinder is retracted to a predetermined position. The valve spool is shifted to the snubbing position automatically by reducing the fluid pressure in a pilot chamber at the end of the valve spool to a predetermined level so that a snubber spring device resiliently moves the spool from a lower or float position. By forcing the fluid to pass through the restricted flow path created by the orifices, the gravity induced velocity of the hydraulic cylinder is greatly reduced as the hydraulic cylinder approaches its end of stroke position.