Patent ID: 7077378
Filing Date: 2006-07-18
Classification: F16K

Abstract:
1. A valve assembly operable to allow or prevent the flow of fluid to or from a working chamber of a fluid-operated machine, the valve assembly comprising radially spaced apart inner and outer annular valve seats defining an annular passage therebetween for the flow of fluid therethrough, a valve member comprising a sealing ring, valve moving apparatus for moving the valve member axially between a first position in which the sealing ring is in seating engagement with said annular valve seats to close said annular passage to fluid flow therethrough and a second position in which the sealing ring is spaced from said annular valve seats so that said annular passage is open to fluid flow therethrough, wherein the valve moving apparatus comprises a ferrous annular moving pole member attached to the valve member, a permanent magnet arranged to magnetically urge the moving pole member so that the valve member is in its second position and an electromagnetic coil which can be energised to oppose the magnetic force of the permanent magnet acting on the moving pole member to cause the valve member to move to its first position.