Patent ID: 7192002

Claim:
A flush valve including a body having an inlet and an outlet, a valve seat in the body between the inlet and outlet, the valve seat defining an opening, a cover attached to the body, a piston movable within the body and cover, the piston, body and cover defining a pressure chamber, an exterior seal carried by the piston and bearing against an inside wall of the cover during movement of the piston, a refill orifice in the piston connecting the pressure chamber with the inlet, pressure in the pressure chamber maintaining the piston closed upon the main seat assembly, a relief valve in the piston for venting the pressure chamber to the outlet, and an actuator mounted in the body and selectably engageable with the relief valve to vent the pressure chamber causing the piston to move away from the valve seat and open flow from the inlet to the outlet, one of the cover and body having a stop engageable with the piston for limiting upward movement of the piston to a predetermined piston travel, the piston having a guide portion which extends downstream through the valve seat opening, the guide portion having a plurality of outwardly extending axial ribs, the outer surface of which are radially in alignment with the opening in the valve seat, the piston area between the ribs being closed by a skirt, the axial extent of both the ribs and the skirt being greater than said predetermined piston travel.