Pump for supplying chemical liquids

Abstract: An opening 22d of a supply/withdrawal passage 22b is positioned at the center part of the internal wall surface 22c of the operating chamber 26 (concave area 22a), and a cross-shaped venting groove 22e extending from the opening 22d of the passage 22b to the periphery of the wall surface 22c is formed in the wall surface 22c. Thus, an operating air in the chamber 26 is discharged (sucked) through the passage 22b during drawing in the chemical liquid. Since the opening 22d communicates with the venting groove 22e extending to the periphery of the chamber 26, if the center of the diaphragm 23 covers the opening 22d first, the operating air in the chamber 26 can be continuously evacuated (drew out) from the venting groove 22e positioned on the outside of the center part which first comes into contact with the opening 22d (end of abstract)