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...http://www.google.co.uk/patents/US7637440?utm_source=gb-gplus-sharePatent US7637440 - Suck back valve
