Patent ID: 7637440

Claim:
A suck back valve comprising: a joint section which has a fluid passage and which includes a first port formed at one end and a second port formed at the other end; an ON/OFF valve which opens and closes said fluid passage by means of a valve plug displaceable in accordance with a pilot pressure; a suck back mechanism, which includes a displacement member displaceable in accordance with a pilot pressure and a flexible member connected to said displacement member to make displacement integrally, and which sucks a pressure fluid contained in said fluid passage under a negative pressure action of said flexible member; and a suction amount-adjusting mechanism which adjusts a flow rate of said pressure fluid to be sucked under said negative pressure action of said flexible member, wherein said suction amount-adjusting mechanism includes a stopper member which regulates a displacement amount of said displacement member in accordance with abutment of said displacement member, a driving mechanism, comprising a rotary driving section which has a non-threaded rotary shaft engaged with one end surface of said stopper member via a groove provided in said one end surface, which effects an energizing or deenergizing operation based on an electric signal so that, upon rotation of said rotary shaft, said stopper member is allowed to move toward or away from said displacement member, and a detecting mechanism which detects a displacement amount of said stopper member under a driving action of said driving mechanism, wherein said displacement member remains out of contact with said stopper member during displacement of said displacement member and said flexible member, and wherein said rotary shaft is not displaced linearly along the axial direction of said rotary shaft, one end of said rotary shaft being loosely fitted into said groove.