Patent ID: 8133042

Claim:
A chemical liquid supplying apparatus comprising: a pump case having a liquid inflow port and a liquid discharge port formed therein; a cylindrical body mounted in the pump case; an axially reciprocable piston which is incorporated in the cylindrical body, the piston having a piston main body having a sliding surface which slidably contacts with an inner circumferential surface of the cylindrical body; an elastically deformable pump bellows attached to a tip portion of the cylindrical body, the pump bellows partitioning and forming a pump chamber communicating with the liquid inflow port and the liquid discharge port in the pump case, the pump bellows partitioning and forming a drive chamber in which an incompressible indirect medium is enclosed between a tip of the piston and the pump bellows; a flexible cover member elastically deformed axially, attached between a base end portion of the piston and the cylindrical body, the flexible cover member forming a seal chamber which continues with the sliding surface of the piston and in which the incompressible indirect medium is enclosed, the flexible cover member being composed of an axially elastically deformable bellows having an average effective diameter which is substantially identical to an outer diameter of the piston main body; and a drive unit mounted in the pump case, a drive shaft for reciprocating axially the piston being incorporated in the drive unit, wherein the piston base end portion is smaller in diameter than the piston main body.