Hydraulic valve.

摘要

A pilot actuated hydraulic control valve (1) has a flow setting member in the form of a valve piston (9) an end (61) of which co-operates with radial outlet ports (11) of the valve (1) to form a variable metering orifice. A flow sensor (10) provides a feedback differential pressure proportional to the flow through the valve and that feedback differential pressure is used to control a pilot stage (14) which actuates the flow setting member (9).

Various alternative embodiments are disclosed. In one form of the valve the flow setting member is a stepped valve piston (9) exposed at its smaller end (61) to the pressure at the inlet to the metering orifice, the proportion of the pressure at the inlet which is applied to the large diameter end of the stepped valve piston (9) being controlled by the pilot valve. In another form of the invention the flow control member is a collared valve piston (814) having equal area radial control surfaces.

Feedback from the inlet to the pilot stage may instead be accomplished by converting the feedback pressure differential across the flow sensor into an equivalent electric feed- back signal by means of a pressure transducer (291).