Patent ID: 7293967

Claim:
A pump apparatus comprising: a rotary driving source driven and rotated by an electric signal; a body provided with a seat section and fluid passages for communicating with a first port for sucking a fluid and a second port for discharging said fluid; a bonnet connected to said body and having a pump chamber defined therein; a piston provided in said pump chamber displaceably in an axial direction of said body under a rotary driving action of said driving source, said piston having a tapered surface on an outer circumference with diameters gradually reduced toward said fluid passages; and a valve plug membrane connected to said piston and provided with a shaft section which is screw-fitted into said piston, a thick-walled main valve body section formed adjacent to said shaft section, and a flexible thin skirt section extending radially outwardly from a surface of said main valve body section and from said piston, wherein said valve plug membrane has a circumferential edge which is interposed between said body and said bonnet, and said valve plug membrane is displaceable in said axial direction while being retained in a state in which said valve plug membrane is bent convexly in one of displacement directions of said piston, and wherein said main valve body section of said valve plug membrane abuts against said seat section when said piston is displaced by operation of said rotary driving source.