Abstract: A magnetic detent housed in an end cap adapted for mounting to a hydaulic control valve having a reciprocally actuated spool movable from a neutral to a detented position. The magnetic detent including a spool extension formed with a detent groove and slidably supported in a retainer mounting a plurality of radially movable balls. A centering spring exerting a biasing force for urging the extension to the neutral position. A clapper movably mounted on and in driving contact with the balls and spaced from a magnet member generating a magnetic force. A spring member exerting a relatively light pre-load force for urging the balls against the periphery of the extension and driving the clapper into magnetically held contact with the magnet member. The pre-load and magnetic forces combining to form a detenting force locking the balls against the biasing force of the centering spring. The biasing and pre-load forces combining to form a shifting force resisting movement of the extension from the neutral position.

Abstract: A hydraulic pressure relief circuit including a main valve, a bleed flow orifice to provide stability to the main valve, a pilot valve having a differential area piston and a damping orifice in conjunction with an accumulator chamber. System pressure is limited by opening the main valve and allowing fluid flow from the system back to tank. The main valve is controlled as a bleed flow servo wherein the pilot valve meters the bleed flow from the bleed flow orifice to tank thereby controlling the opening of the main valve. Fluid flow through the damping orifice in conjunction with the accumulator chamber acts on the pilot valve to provide damping forces acting on the pilot valve with both rising and falling system pressures thereby limiting the maximum rate of pressure increase in the circuit.

Abstract: In a rotary sliding vane pump having a non-circular cam ring which expands and contracts radially, a cheek plate is clamped against the end face of the cam ring and lies in rubbing contact with the rotor and vanes. The cheek plate has a wearing face of low friction material such as bronze. Unwanted wear between the cheek plate and the cam ring due to its expansion/contraction movements is reduced by the provision of one or more areas of hard metal adjacent the cam ring.

Abstract: A fluid reservoir for hydraulic power systems comprises a tank divided into a liquid compartment and an air compartment by a flexible diaphragm so that the liquid will be pressurized by compressed air in the air compartment. The tank is supported in a stationary frame upon horizontal pivots and a balancing spring. The liquid inlet and outlet connections pass through the pivots. An indicator is provided for showing the vertical position of the tank relative to the frame on the balancing spring and thus indicating the amount of liquid in the tank.

Abstract: A cartridge type sleeve and plunger hydraulic valve is retained in a blind bore along with a biasing spring by a closure plug. Spaced transverse passages intersecting the bore are either separated or connected depending upon whether the plunger is either shifted by the spring bias or by fluid pressure overcoming the spring bias. An elastomeric seal eliminates leakage when the valve is in closed position. To insure against accidental fall out of any loose parts when the valve is disassembled under difficult working conditions, as in mines, O-rings are utilized as retainers for the spring and other parts.

Abstract: A solenoid of the wet armature type for operating valves has the usual closed end tube within which a stationary pole piece and a slidable armature are mounted with a push pin extending through the pole piece. A bobbin-mounted energizing coil surrounds the tube. A generally barrel-shaped housing surrounds the coil and the tube. The housing has thick walls and is formed of magnetically permeable material to provide a low reluctance path extending substantially completely around the outside of the coil and along its two ends. The housing is formed in the plurality of sections spaced from one another along axial planes and clamped together against the tube by clamping members at either end. The housing is provided with conical clamping surfaces. The housing members are formed from sintered powdered magnetic iron.

Abstract: A solid state switching circuit for applying rectified alternating current to one or the other of two solenoid valve actuators and modulating that current from a pull-in value to a lower holding value has a separate power circuit for each solenoid and a common timing and trigger circuit. Each power circuit contains a pair of diodes and a pair of silicon controlled rectifiers connected in a bridge circuit to supply its solenoid. The common timing and triggering circuit is connected to be energized whenever either power circuit is energized and contains a first DIAC control circuit for supplying triggering pulses early in each AC cycle and a second DIAC circuit for supplying pulses late in each AC cycle. The DIACs feed a coupling transformer which is coupled to the silicon controlled rectifiers of both power circuits. A time delay circuit biases a transistor to the on state after a predetermined time interval to disable the first DIAC control circuit.

Abstract: The suppression of bubble formation and cavitation in the fluid passing through a high pressure relief valve is achieved by a back pressure valve in the relief valve discharge line. The back pressure valve has differential area pistons which maintain a back pressure of a fixed ratio to the high pressure at the relief valve inlet, this ratio being at least 1:3.

Abstract: A balanced rotary sliding vane pump has a flexible cheek plate slightly spaced from the rotor and vanes. A hydrostatic pressure pad exposed to outlet pressure urges the cheek plate to deflect toward the rotor and is fully effective at low speeds. A pressure force opposing this deflection at higher speeds is produced by restricting the outlet for fluid discharged by the inwardly moving vanes, thus augmenting the pressure field applied in the clearance space between the rotor and the cheek plate. This speed responsive change in the cheek plate deflection provides for a high volumetric efficiency at slow speeds and also reduces the possibility of cheek plate wear and seizure at higher speeds when volumetric efficiency is less important.

Abstract: A speed controller for a rotary pump and motor hydraulic power transmission comprises a pair of pulse generators, one driven at a reference speed and the other proportionally to motor speed. An algebraic summing circuit connects the two pulse generators to the displacement regulator of the hydraulic pump. Error signals produced by the changes in phase of the pulse generators adjust the pump displacement to maintain the motor speed in step with the reference speed.

Abstract: A rotary sliding vane type of fluid pump or motor has a rotor with loosely fitted vanes radially slidable in the rotor slots to follow the varying contour of the cam ring. Hydraulic pressure to project the vanes outwardly is fed to their inner ends along three paths comprising the side clearance between the slot and the vane which is open directly to one of the working chambers, a first set of pressure feed holes communicating with the bottom of each slot in turn, and a second set of pressure feed holes communicating with a widened portion of each slot in turn intermediate its ends.

Abstract: A pilot operated fluid pressure relief valve has a main valve operable by opposed piston areas, both normally exposed to inlet pressure whenever that is below the maximum pressure setting of the valve. A pressure responsive pilot valve is exposed to inlet pressure through a restricted path and when open, exhausts fluid from the piston area which holds the main valve closed. The restricted pathway contains two laminar flow orifices one of which is between the inlet and the valve closing piston area and the other is between the valve closing piston area and the outlet through the pilot valve. This arrangement provides good damping of oscillations, while minimizing any changes in effective opening pressure which are otherwise caused by the use of a single laminar flow orifice for damping purposes.

Abstract: A directional valve for hydraulic power transmission systems of the closed center type has a spool for directing fluid from inlet to either of two motor ports through one or the other of a pair of check valves for holding the load against dropping. A second pair of check valves connect from each motor port directly to a fluid return port independently of the spool. The second check valves have control chambers the maximum pressure in which is limited by a pilot relief valve to cause the check valve to act as a maximum pressure limiting valve for its motor port. A small pilot piston responsive to operating pressure in the opposite motor port can mechanically open the pilot relief valve thereby causing the second check valve to act as a counterbalance valve to prevent the motor from being driven by an overhauling load.