US Patent 7255329 Gate valve with offset valve stem

An improved gate valve has a main body defining a flow passage, and a cylindrical gate member, which has a continuous seal disposed within a groove in the gate surface. The gate is actuated by a valve stem movable through a bonnet connected to the main body, with the longitudinal axis of the stem being offset from the longitudinal axis of the gate. The inner end of the stem is retainingly received in a recessed slot in the gate such that the valve stem can rotate relative to the gate and such that longitudinal movement of the stem will cause corresponding movement of the gate. The offset between the stem and gate axes keeps the gate in the same orientation relative to the gate chamber regardless of the gate's longitudinal position.