Patent ID: 7168676

Claim:
A two-port valve for vacuum operation, comprising: an axis; a main valve portion comprising: a first main port; a second main port; a fluid passage connecting the first and second main ports; a valve seat disposed in the fluid passage; a valve member to be seated on and separated from the valve seat; and a valve shaft extending along the axis of the valve from the valve member; and a cylinder portion connected to the main valve portion along the axis of the valve, and comprising: a cylinder housing defining a piston chamber therein into which the valve shaft extends; a first piston which is slidably disposed in the piston chamber, and has a front end on the side of the main valve portion and a rear end on the side opposite to the main valve portion, the valve shaft slidably extending through a central portion of the first piston; a sleeve which is disposed in the piston chamber to be movable along the axis, and limits an operating stroke of the first piston by being brought into abutting contact with the rear end of the first piston; a positioning member which determines the position of the sleeve; a second piston which is slidably disposed in the sleeve and connected to the valve shaft so as to be in contact with the first piston when the valve member is seated on the valve seat; a first pressure chamber for driving the first piston; a second pressure chamber for driving the second piston; a first pilot port in communication with the first pressure chamber; and a second pilot port in communication with the second pressure chamber.