Patent ID: 8757583

Claim:
A hydraulic or pneumatic motor or pump, comprising: a high-pressure line; a working chamber having a piston that is movable to cyclically vary a volume of the working chamber; and a valve arrangement disposed between the high-pressure line and the working chamber for controlling fluid flow from the high-pressure line to the working chamber, the valve arrangement comprising a main valve having a valve element arranged to provide sealing contact with a valve seat, and an auxiliary valve comprising an electromagnetically-movable valve member for equalising pressure on either side of the main valve by placing the working chamber in direct fluid communication with the high-pressure line, wherein the valve element has an internal conduit communicating with an opening defined by the valve seat, and the electromagnetically-movable valve member is adapted to place the internal conduit in direct fluid communication with a space surrounding said valve element such that the internal conduit connects the working chamber with the high pressure line, wherein the valve element is a poppet valve having a poppet shank, and the electromagnetically-moveable member is a moving pole ring slidable on the poppet shank, and wherein a pole compression spring is configured to act on the pole ring and the poppet shank.