Patent ID: 7089960

Claim:
A ball valve comprising: a casing comprising an entrance, a valve chamber, an exit and a discharge orifice, wherein said discharge orifice communicates with ambient air when said ball valve is installed in a piping system; a valve shaft hermetically passing through said casing; a valve ball within said valve chamber connected to said valve shaft within said casing; an entrance-side ring valve seat between said casing and said valve ball on the entrance side of said ball valve; and an exit-side ring valve seat between said casing and said valve ball on the exit side of said ball valve, wherein said exit-side ring valve seat comprises a through hole passing through said exit-side ring valve seat between said valve ball and said discharge orifice in said casing; said valve ball comprising: a circulation hole through the valve ball, wherein said entrance in said casing is connected and disconnected to said exit in said casing by rotate-operating said valve shaft and said valve ball; a first passage hole between said circulation hole and said entrance when said valve ball is positioned in a first disconnection state wherein said valve ball disconnects said entrance from said exit; and a second passage hole between said circulation hole and said through hole in said exit-side ring valve seat when said valve ball is positioned in said first disconnection state.