Gate valve rotating disc

In a gate valve having a body provided with a flow passageway and having a disc receiving guide slot transversely intersecting the passageway, a valve stem having one end portion axially movable within the disc slot toward and away from the axis of the passageway by a gate wheel rotatable in opposing directions and having a pair of disc seat rings formed from material having a Rockwell scale C hardness of at least forty disposed, respectively, on the upstream and downstream sides of the disc slot coaxial with respect to the flow passageway and defining confronting seat ring surfaces respectively disposed in the planes forming the upstream and downstream sides of the slot, the improvement comprising:

• a metallic disc slidable within the disc slot,
• said disc having a head portion removably secured to said one end portion of said valve stem for moving said disc and opening and closing the flow passageway,
• said disc having a transverse opening, at least equal in area to the transverse cross sectional area of the flow passageway, in its end portion opposite said disc head portion and having a transverse aperture between its head portion and the opening coaxial with the flow passageway when said disc is in valve closed position and being at least diametrically equal to the diameter of the flow passageway;
• a plug formed of material having a Rockwell scale C hardness of at least forty freely received by the disc aperture and slidably interposed between said disc seat rings for coaxially registering and sealing with said disc seat ring on the downstream side of the slot and closing the flow passageway when said disc is moved to a closed position;
• and,
• ratchet means within the gate valve body for angularly rotating said plug through a predetermined arc each time said disc is moved to a flow passageway closed position.