Patent ID: 7066443

Claim:
A gate valve including: a valve body having a transfer chamber opening and a process chamber opening formed in mutually opposing walls thereof, respectively; and a transfer chamber-side valve element and a process chamber-side valve element provided in said valve body, said transfer chamber-side valve element and process chamber-side valve element being connected to a single shaft; wherein said transfer chamber-side valve element and said process chamber-side valve element are controlled by actuation of said single shaft so that said transfer chamber-side valve element closes said transfer chamber opening, or said process chamber-side valve element closes said process chamber opening, or both said transfer chamber-side valve element and said process chamber-side valve element fully open said transfer chamber opening and said process chamber opening, respectively, to allow an object to pass therethrough; said gate valve comprising: a lever member secured to said single shaft; a roller supported by said lever member, said roller being kept in engagement with a cam groove of a cam member, said cam groove having a position A, a position B, and a position C; a cam support member for supporting said cam member, said cam support member being connected to a piston rod of a three-position air cylinder, said piston rod having a first position, a second position, and a third position; and a spring interposed between said lever member and said cam support member; wherein when said piston rod is in the first position, said transfer chamber-side valve element and said process chamber-side valve element fully open said transfer chamber opening and said process chamber opening, respectively, and as said piston rod shifts from the first position to the second position, said transfer chamber-side valve element and said process chamber-side valve element half open said transfer chamber opening and said process chamber opening, respectively, and thereafter, said roller shifts from engagement with the position A of said cam groove to engagement with the position B, causing said process chamber-side valve element to close said process chamber opening, and as said piston rod shifts from the second position to the third position, said roller shifts from the engagement with the position B of said cam groove to engagement with the position C, causing said transfer chamber-side valve element to close said transfer chamber opening.