Abstract: A self energizing one piece seal has an annular seal body and a multiplicity of circumferentially spaced delta shaped resilient tabs extending inwardly from the annular body. The seal is adapted to be placed in an annular groove of a cylindrical member so that a circumferential seal face is initially biased into sealing engagement with a bore of a body and a radial seal face is initially biased into sealing engagement with a radial face of the groove by the resilient tabs.

Abstract: A variable margin pressure control for a variable displacement load sensing pump comprises a body having a bore therein and a valve spool slidably disposed in the bore defining a chamber in continuous communication with a discharge passage in the body. The valve spool is movable in a first direction for communicating the discharge passage with a control port in the body and in a second direction for communicating the control port with an exhaust flow path. The valve spool is biased in the first direction by discharge fluid pressure in the chamber. A spring mechanism biases the valve spool in the second direction against the force generated by the discharge pressure with a biasing force sufficient to establish a predetermined margin pressure. A remotely controllable variable biasing force is applied against the valve spool by a device so that the margin pressure can be selectively varied in response to receiving a pressure signal.

Abstract: A hydraulic track tensioning circuit is connected to an idler wheel of a track drive mechanism to maintain a tension in a track proportional to the drawbar pull of the track drive mechanism. The tensioning circuit includes a variable pressure relief valve having a variable pressure setting controller which controls the tensioning pressure in a supply line connected to a hydraulic tensioning cylinder in response to the highest pressure in a pair of motor ports of a reversible hydraulic drive motor operative to propel the track drive mechanism.

Abstract: A rotary control valve includes a directional control valve having a rotatable valve element for controlling the direction of fluid flow from an input passage to a pair of control ports and from the control ports to a drain passage. A pressure regulating valve is connected to a source of pilot pressure and has a valve spool for controlling the regulated pressure level of pilot fluid in the input passage. A cam is connected to the valve element for unitary rotation therewith. A spring and a plunger are disposed between the valve spool and the cam so that the valve spool is mechanically moved in a rectilinear direction by the cam in either direction from a neutral position to increase the level of the regulated pressure in the input passage proportional to the degree of rotation of the rotatable valve element.

Abstract: A jerk control valve adapted for use in a pilot operated steering system has a pilot operated valve biased to an open position by a spring for communicating left steer and right steer pilot lines to a tank through a pair of orifices. The pilot operated valve is moveable to a closed position blocking communication through the first and second orifices when the highest pressure of the left and right steer pilot lines exceeds a predetermined value. The left and right steer pilot lines are continuously communicated with the tank through a pair of orifice devices.

Abstract: A load sense hydraulic system includes a pilot operated on/off valve disposed within a signal line which communicates a dynamic load sense signal from a steering control valve to a pressure controller of a load sensing pump. Upon actuating a brake valve or applying a brake mechanism, a pressurized fluid signal downstream of a variable flow control orifice in the brake valve is directed to move the on/off valve to its closed position blocking the dynamic load sense signal from a load sense port to the pump controller. This causes the pump controller to stroke the load sensing pump to its high pressure stand-by position so that the brake valve always functions under high pressure operating conditions.

Abstract: A pilot stage of an electrohydraulic control valve controls the position of a pilot actuated main stage by controlling fluid flow through a flow path that connects a supply port to an exhaust port and to an end of the main stage. A proportional valve of the pilot stage has a valve element for establishing a variable flow control orifice to control fluid flow through the flow path and a bleed orifice disposed in the flow path downstream of the proportional valve to generate fluid pressure upstream of the bleed orifice and at the end of the main stage.

Abstract: The present quick drop valve control provides both quick drop and float functions by moving a quick drop valve to a position interconnecting the drop and lift sides of a pair of lift cylinders when a directional control valve reaches a predefined position. The quick drop function valve is established by simultaneously energizing a first solenoid valve to communicate a shift end of the quick drop valve with a resolved pressure port of a resolver connected to the drop and lift sides and a first solenoid of a second solenoid valve to communicate a spring end of the quick drop valve with the drop sides so that the quick drop valve moves to the interconnecting position combining fluid expelled from the lift sides with fluid going to the drop side from a pump.

Abstract: A low cost, electromagnetic efficient integrated electrohydraulic actuator includes a sleeve disposed within a housing and an annular electric coil formed as an integral part of the sleeve so that the coil is deeply integrated in the housing. An armature slidably disposed within an axial bore of the sleeve has the fluid metering functions integrally formed thereon so that the armature functions as a valve spool for controlling communication between an inlet port and an outlet port and between the outlet port and a tank port. The armature is thus the only movable part of the actuator.

Abstract: A variable displacement pump has a discharge passage and a displacement controller disposed to decrease pump displacement in response to an increasing pressure signal and to increase pump displacement in response to a decreasing pressure signal. A load sensing pump control for the pump includes a displacement control valve having an input port connected to the discharge passage and a signal port connected to the displacement controller. A valve spool controls communication between the input and signal ports and is biased in a direction to block the inlet port from the signal port by a spring. The spool has a differential area for exerting a force against the spool in opposition to the spring force proportional to the pump discharge pressure entering the valve through the input port. A variable force can be selectively exerted against the spool in opposition to the spring force to change the displacement of the pump.

Abstract: An electrohydraulic pressure regulating valve comprises a variable orifice disposed between a supply port and a control port and has a fixed size vent orifice disposed downstream of the variable orifice and in parallel with the control port to reduce the flow forces acting on the spool so that the valve is less sensitive to solenoid and spool quality and has improved pressure control capability.

Abstract: A hydrostatic transmission has a pair of overcenter variable displacement pumps, each having a flow control element controlled by a double acting actuator to control direction and flow rate of the pump. Fluid pressure in first and second chambers of each actuator are equal at a neutral position of the transmission. A forward control valve controllably communicates the first chambers of both actuators to a tank through a first orifice to reduce the pressure in the first chambers to simultaneously move the flow control elements in a first direction for forward travel. A reverse control valve controllably communicates the second chambers of both actuators to the tank through a second orifice to reduce the pressure in the second chambers to simultaneously move the flow control elements in a second direction for reverse travel.

Abstract: Fore and aft movement of a lever pivots first and second shafts of a cross shaped member while left and right movement of the lever causes a yoke of the lever to pivot on third and fourth shafts of the cross shaped member. The pivotal movement of the first shaft causes a pair of end portions of a torsion spring to generate forces on a force sensor resulting in the output of electrical signals proportional to the fore and aft movement of the lever. Similarly, left and right pivotal movement of the yoke causes a pair of end portions of another torsion spring to generate forces on another force sensor resulting in the output of electrical signals proportional to the left and right movement of the lever. Selectively energizing a coil device fixed relative to a mounting base pulls a washer anchored to the second shaft into mechanical engagement with the coil device to hold the lever at a fore or aft operational position.

Abstract: A pressure regulating valve usable in combination with a hydraulic steering system has a spring mechanism axially disposed between a pair of axially aligned valve spools. Movement of the spring mechanism in a first direction resiliently moves one of the valve spools to a position for communicating an inlet port with a control port and regulating the pressure in the the control port so that the pressure is proportional to the degree of movement of the spring mechanism. Conversely, movement of the spring mechanism in a second direction resiliently moves the other valve spool to a position for communicating the inlet port with another control port and regulating the pressure in the other control port so that the pressure is proportional to the degree of movement of the spring mechanism.

Abstract: An electrohydraulic displacement controlled valve module is disposed in a bore of a valve body for controlling fluid flow between first and second ports. A main valve element slideably disposed in the bore is biased to a closed position blocking communications between an annular groove of the valve element and the second port. An actuating chamber defined at one end of the valve element receives pressurized pilot fluid for urging the main valve element toward an open position communicating the first and second ports through the annular groove. A passage communicates the actuating chamber with a control chamber disposed at the other end of the valve element through an orifice. A poppet is disposed within the control chamber and is biased into sealing engagement with an annular valve seat of an outlet port by a feedback spring disposed between the valve element and the poppet.

Abstract: An unloader valve is connected to a pump and has first and second ends, a priority flow port communicating with the first end and being connected to a first conduit connected to a first hydraulic circuit, an excess flow port communicating with a tank, and a spring disposed at the second end biasing the unloader valve to a priority flow position with a force sufficient to maintain the pressure in the priority flow port above a predetermined minimum level. The unloader valve is biased toward an unloading position in opposition to the spring force by pressure generated force acting on the second end. A check valve is disposed between the first conduit and a second conduit connected to a second hydraulic circuit. A valve device controls the pressure at the second end of the unloader valve in response to pressure in the second conduit so that pressure in the second conduit is maintained above a second higher predetermined level.

Abstract: An active pitch control is provided for counteracting the pitching motion of a mobile machine. The machine has an apparatus for transmitting driving torque from an engine to a pair of pneumatic tires. The pitch control includes a device for detecting a pitching motion of the machine and responsively outputting a control signal. A device receives the control signal and changes the driving torque transmitted to the tires to counteract the pitching motion.

Abstract: A variable position detent mechanism for latching a control lever at an infinite number of operating positions includes a semi-circular member connected to a support so that its axis coincides with the pivot of the control lever. An electric detent coil is connected to the lever at a location adjacent the semi-circular member so that energizing the detent coil magnetically latches the lever to the semi-circular member.

Abstract: A displacement control valve includes a valve element having a first operative position communicating a displacement controller of a variable displacement hydraulic pump with a tank for increasing the pump displacement and a second operative position communicating a discharge passage of the pump with the control port for decreasing pump displacement. The discharge passage communicates with a first end of the valve element to generate a force biasing the valve element toward the second position. An opposing biasing force is exerted on the valve element in opposition to the pressure generated force acting on the first end of the valve element so that a predetermined pressure level is established in the discharge passage when the forces acting on the valve element are equalized.

Abstract: A check valve normally blocks fluid flow from a bore to a passage and includes a spring normally holding a ball in sealing engagement with a valve seat to form a primary metal-to-metal hard seal. Another spring normally holds a poppet in engagement with another valve seat causing an annular protuberance formed on the poppet to sealingly engage a resilient seal to provide a more positive secondary soft seat seal. The poppet is unseated from the valve seat by a stem of a piston prior to the ball being unseated from the valve seat by a guide stem of the poppet so that the soft seal is opened at essentially zero flow conditions.