Abstract: An actuator has a position encoder provided by a piston rod having a body of magnetic material progressively tapering from one end to another in a direction of relative movement between the piston rod and a cylinder. The piston rod has a coating of non-magnetic material, providing a smooth, uniform exterior surface. An array of Hall effect sensors is mounted in a support located in and radially movable relative to an end cap fixed to the cylinder.

Abstract: An electromagnetic actuator has an armature assembly including a pair of spaced plate springs to locate the magnetic core radially. The springs are formed from concentric rings interconnected by radial bridges so that flexure of the spring does not cause radial displacement. A single coil or double coil may be used and each coil is supported on a pair of bobbins. One bobbin overlies the core and the other has a recess to receive part of the core to maintain a uniform air gap between the core and bobbin.

Abstract: A flow transducer includes a piston movable in a sleeve to vary the area of an orifice. The piston may move in either direction from a position in which flow is prevented. Movement in both directions is opposed by a spring. The piston assumes a unique position for each flow rate and the position of the transducer is sensed to provide a signal indicative of low rate.

Abstract: A hydraulic valve includes a spool movable within a body to regulate flow across the valve. Movement of the spool is controlled by an electromagnetic actuator that operates either directly or through a pilot stage upon the spool. When operating through a pilot stage, the actuator varies pilot pressure by an operating member co-operating with an orifice. A flapper valve may be used to vary a pair of pilot flows in complementary manner. Feedback signals of pressure and spool position are provided to a controller which selectively combines the signals to monitor the operating parameters of the valve. The controller may modify the position signal with the pressure signal to obtain an indication of flow rate through the valve.

Abstract: A diagnostic device for a hydraulic circuit includes a flow transducer to provide an indication of flow rate, a pressure transducer to provide a signal indicative of pressure, and a temperature transducer to provide a signal indicative of temperature. Each transducer provides an output signal calibrated by look-up tables stored in an integrated circuit located in the device.

Abstract: An axial piston pump has multiple pistons and cylinders with a spill port in each piston. A sleeve controls venting from the spill port and an inlet is provided to each cylinder, by way of a check valve from a fluid supply.

Abstract: A pressure transducer has a cylindrical body with a thread formed on at least part of the outer surface. A resistance element is wound in the thread and an internal bore receives pressurized fluid. The resistance element is strained by application of pressure to vary its resistance.

Abstract: An actuator for use in an active suspension system is controlled by a valve responsive to differential pressure across the piston of the actuator. The valve operates to allow movement of the piston so as to reduce the pressure differential. The valve is also controlled by signals indicative of position of and load applied to the actuator.

Abstract: An actuator for use in an active suspension system is controlled by a valve responsive to differential pressure across the piston of the actuator. The valve operates to allow movement of the piston so as to reduce the pressure differential. The valve is also controlled by signals indicative of position of and load applied to the actuator.