US Patent 7143956 Suck back valve

A suck back valve includes an ON/OFF valve mechanism which opens/closes a fluid passage by displacing a valve member together with a first piston under an action of a pressure fluid supplied into a first cylinder chamber, and a suck back mechanism which has a suction member formed deformably in a flow chamber to suck a pressure fluid contained in the fluid passage by displacing the suction member together with a second piston under an action of the pressure fluid supplied to a second cylinder chamber. The ON/OFF valve mechanism and the suck back mechanism are assembled coaxially and integrally.