Rotary plug valve

Abstract

A rotary plug valve has a valve body member provided with a ported plug seat, and a ported plug member rotatably mounted in the valve body member, the plug member being adapted to be rotated between the position where the ports are aligned and the position where the ports are not aligned, thereby opening and closing the valve. One of the valve body member and the plug member is provided in the surface thereof facing the other member with circumferential grooves at both axial end portions of the member. The circumferential grooves receive respective packing 'O' rings which form tight seals between the opposing seat surfaces of the valve body member and the plug member. The seat surface of either one of the valve body member and the plug member is provided with a plurality of channels extending in the longitudinal direction of the member at both sides of each port, so as to provide communication between two circumferential grooves. The circumferential grooves and the channels in combination constitute a closed lubrication system of the valve. The bottom wall of each circumferential groove is inclined such that the distance between the bottom wall and the opposing seat surface is greater at the end of the groove adjacent to the central region of the plug member than at the end of the same remote from the central region. With this arrangement, it is possible to store and reserve greater energy for pressurizing the lubricant.