Abstract: A multiple section control valve bank is provided having a control valve section and an inlet section operatively connected to provide smooth proportional metering control over a wide band of operating pressures while simultaneously metering the operation of two or more fluid actuated devices from a single fluid source. This is accomplished by providing metering and logic elements in the control valve section connected to a signal chamber in the inlet section to vary the flow of fluid through the inlet section to the control section in accordance with signals from the meter and logic elements.

Abstract: A linear solid state servo amplifier operated from a low voltage source and which develops a voltage across the servo motor equal to the source voltage diminished only by the saturation voltages of two of its output transistors has a bridge output stage of complementary transistors and a bridge driver stage of complementary Darlington transistors having as its load a preselected resistor.

Abstract: A valve structure is provided for use in an integral hydraulic pump and valve assembly having a housing adapted to be integral with a pump housing with spaced apart low pressure and high pressure ports corresponding to the low pressure inlet port and high pressure outlet port of said pump, a low pressure chamber, a high pressure chamber and a cylinder chamber in said housing spaced apart and generally parallel to one another, a transverse bore in said housing intersecting said chambers, valve means movable axially in said bore, said valve means having an annular groove intermediate its ends capable of connecting said low pressure and high pressure chambers in a first neutral position, capable of connecting all of said chambers in a second position and connecting only the low pressure chamber in a third position, detent means in said housings extending into said bore and annular groove in the valve member, detent engaging means in said groove intermediate its ends and stroke limiting means extending into the b

Abstract: A control valve bank is provided having a working section and an inlet section wherein inlet fluid from a pump is proportionally metered at the inlet of each valve section so that the input volume to each work port is generally uniform regardless of pressure variations.

Abstract: A variable displacement fluid pump system is provided having a pressure and flow compensated control system with constant torque and viscosity sensing over-ride acting on the control system.

Abstract: A pump control valve and relief valve assembly are provided in the form of a valve housing having a main bore therethrough, a spool movable in said bore and having a pair of spaced annular grooves therein, a spaced relief bore in said housing, a pump chamber and a work chamber in said housing intersecting both bores, a pair of tank chambers, one on each opposite side of the pump and work chambers intersecting said main bore, said tank chamber adjacent the work chamber intersecting the relief bore, a tank bore connecting said tank chambers, an inlet return bore intersecting said tank chamber adjacent the work chamber, an inlet port connected to said relief bore and jump chamber and adapted to connect to a pump outlet port, a tank port connected to said tank bore, a pump inlet port and a return port connected to said inlet return bore, said pump inlet port adapted to connect to a pump inlet port and the return port adapted to be connected to a source of return fluid, and a combination check and relief valve ass

Abstract: A rotary impeller pump or motor is provided having a case, a pair of rotary impellers in said case, a plate having a first face divided by lands into a plurality of chambers against corresponding ends of the impellers and a second face having two counterbores around the rotary impellers, annular seal means intermediate the ends of each counterbore forming a pair of chambers within the counterbore, opposed inlet and outlet ports in said case whereby said plate is balanced in pressure on opposite sides by fluid in said chambers on the first face and the counterbores.

Abstract: A rotary impeller pump or motor is provided having a case, a pair of rotary impellers in said case, a plate having a first face divided by lands into a plurality of chambers against corresponding ends of the impellers and a second face divided by sealing means into a similar plurality of chambers between the plate and case, opposed inlet and outlet ports in said case whereby said plate is balanced in pressure on opposite sides by fluid in said chambers on the first and second faces.

Abstract: A low friction drag seal is provided for use between a housing and a linearly movable cylindrical member subject to fluid pressure in the form of an annular chamber surrounding the cylindrical member in one of the housing and cylindrical member, a generally right triangular cross section elastomer ring in said annular chamber surrounding said cylindrical member and in contact with a relatively movable surface on one of the cylinder and housing at an apex of said elastomer ring and a generally rigid back up ring having an inclined surface extending away from said relatively movable surface and in contact with the hypotenuse of the generally triangular member.

Abstract: A rotary to linear servo mechanism for converting low force mechanical rotary motion into hydraulic motion is provided which includes a piston linearly movable in one end of a bore and a valve rotatably mounted in the other end of the bore for cooperation with the piston to selectively deliver pressure fluid to opposite sides of the piston to move said piston selectively in either direction in said bore.

Abstract: A gear pump or motor and a thrust plate therefor are provided having a case, a pair of rotary gears in said case, said gears having axial stub shafts journaled in said case, a unitary thrust plate for the corresponding ends of the pair of rotary gears adapted to lie between the case and the ends of the gears, said thrust plate being of a metal softer than the gears and having a front face adapted to abut the gear ends and a rear face abutting the case, a pair of spaced openings extending through said plate to receive the gear stub shafts, a pair of annular grooves in the rear face spaced from and surrounding each of said openings, a groove in the rear face connecting said annular grooves at their closest points, at least one groove in the rear face extending radially from each annular groove to the periphery of the body generally opposite the groove connecting the annular grooves defining at least two substantially identical areas on opposite sides of the body, a generally U-shaped elastomer gasket having the

Abstract: A relief valve assembly particularly in combination with yieldable pit posts is provided having an elongate housing, a first load chamber at one end of said housing, an inlet aperture into said housing, a non-return valve in said inlet aperture for admitting fluid non-returnably into said load chamber, a first valve seat in said housing communicating with said load chamber, a spring loaded relief valve movable lengthwise of the housing and normally engaging said seat to close the load chamber, a second valve seat in said housing spaced lengthwise from said first valve seat and relief valve and forming therebetween a balancing load chamber, a spring loaded pilot relief valve movable lengthwise of the housing and normally engaging said second seat to close the same, and a regulated orifice means in said relief valve connecting the first load chamber and the balancing load chamber whereby said balancing load chamber is normally pressurized to the pressure of the load chamber.

Abstract: A compensated work port fluid valve is provided wherein a directional control valve having an inlet chamber, an outlet chamber and a work chamber is provided with a compensator valve connected to the work chamber and having a pressure sensing compensator valve controlling the flow of fluid from the work chamber to a work port to maintain constant pressure at the work port.

Abstract: The invention relates to a high pressure control valve of the spool type. The valve contains a series of fluid passageways which drain off the high pressure fluid before it reaches the sealed area of the spool thus allowing the spool to be shifted with a minimum of force even though under high internal fluid pressure. The invention thus increases the life of elastomer seals used in high pressure fluid control valves.

Abstract: A swash plate pump or motor is provided having a swivel plate surrounding the slippers and a positive hold down ring connected to the swash plate and bearing on said swivel plate to maintain it at a fixed distance from the slipper plate, said hold down ring having a series of successive controlled wedge angles on the face bearing on the swivel plate and oil feed means connected to each wedge angle whereby a hydrodynamic force is created holding the swivel plate and hold down ring apart.

Abstract: A pressure compensated directional control valve is provided which automatically regulates the position of the valve depending upon the load so as to maintain a constant flow of fluid by means of check valve members in the spool in the form of a resilient or flexible band in a groove surrounding the valve spool and covering the outer ends of the radial passages from the internal spool chambers.

Abstract: A hydraulic drive circuit for tracked vehicles is provided in the form of two hydrostatic transmissions, one for each track with a control system for one track acting as a master control and the other transmission control following as a slave unit, except as modified by the signal from a manual steering control.

Abstract: A tunnel liner and segment are provided for simplifying changes in direction. The segment comprises a pair of liner plates each having a curved elongated skin with spaced parallel dependent sidewalls bent at an angle thereto, said liner plates being in spaced side-by-side relationship, spaced apart a selected greater distance at one end than at the other end, a pair of wedge shaped gusset plates in spaced parallel planes fixed to the sidewalls between said liner plates adjacent the top and bottom respectively of the adjacent sidewalls and an end plate at each end of said pairs of liner plates extending the remote sidewalls of each segment and connected to the sidewalls, gusset plates and skins to form a unitary whole.