US Patent 7637440 Suck back valve

A suck back valve comprises a suction amount-adjusting mechanism including a screw member which regulates a displacement amount of a second piston integrally displaceable with a second diaphragm in accordance with abutment of a disk-shaped member, a rotary driving section which allows the screw member to move toward or away from the disk-shaped member, and a detecting section which detects a displacement amount of the screw member. Accordingly, it is possible to appropriately adjust the flow rate of the pressure fluid to be sucked under the negative pressure action of the second diaphragm.