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: A pressure-compensated flow-control valve with an adjustable limiting device controls the maximum speed of a fluid motor and eliminates an additional valving element found in prior art device. The flow control valve includes a flow limiting throttle opening integral with the flow control spool. The spool can be selectively rotated to adjust the effective size of the throttle opening thereby limiting flow through the valve. The spool establishes a constant rate of flow determined by the throttle opening or a directional control valve. By incorporation of the flow limiting function within the flow control spool, the overall cost and complexity of the pressure compensated flow control valve is reduced.

Abstract: Disclosed herein is a hydraulic jack comprising a cylinder and a piston rod assembly which is movable between a retracted position and an extended position relative to the cylinder. The jack also has mechanical locking means including a rotatable shaft and movable into engagement with the piston rod assembly in response to rotation of the shaft, thereby to lock the piston rod assembly in its extended position. The locking means reinforces the piston rod assembly in its extended position along substantially the entire length of the piston rod assembly.