Patent ID: 7523916

Claim:
A gate valve, comprising: a body having a gate chamber intersected by a flow passage and a stem chamber extending from the gate chamber; a gate carried within the gate chamber for movement between a closed position and an open position; the gate having a neck having a cylindrical outer diameter and extending into the stem chamber; a rotatable member; an interface between the rotatable member and the neck of the gate for effecting movement of the gate between the open and closed positions in response to rotation of the rotatable member; a seal that seals between the stem chamber and the neck, thereby preventing any fluid in the gate chamber from contacting the interface; wherein: the neck has a pressure area defined by the seal; fluid pressure within the gate chamber when the valve is in one position acts against the pressure area to exert a force on the gate urging the gate to the other position and thereby urging the rotatable member to rotate; and the gate valve further comprises: a clutch for selectively preventing rotation of the rotatable member.