Smiths Industries Public Limited Company

Don Seddon

An hydraulic valve has a flow/pressure characteristic matched to that of a pump with which it is used. The valve has a housing with a fluid inlet in its side and an outlet at one end. A shuttle is movable along the housing under control of a proportional solenoid, to vary the amount by which an edge of the shuttle covers the inlet and thereby controls flow of fluid through the valve. The shuttle has a flange one end located between the inlet and outlet so that fluid flowing from the inlet to the outlet applies pressure to one side of the flange and displaces the shuttle to close the inlet. In this way, an increase in pressure tends to reduce the effective size of the inlet aperture to compensate for pressure variation.

Self-compensating proportional hydraulic valve

An hydraulic valve has two outlets and is switchable so that fluid can only be supplied to one outlet at a time. A spool with two seals is slidable in a housing under the action of two proportional solenoids and is urged to a central position by two springs where the seals block passage to both outlets. When the spool is moved in one direction it allows flow to one outlet and also allows flow via a bypass channel to an opposite side of the spool counteracting the force applied by the solenoid so that the force applied to an outlet can be controlled gradually.

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Hayling Island, United Kingdom

Don Seddon