Patent ID: 7758321
Filing Date: 2010-07-20
Classification: F04B

Abstract:
1. A pump apparatus comprising: a body, having a suction port for sucking a fluid and a discharge port for discharging said fluid, and wherein a pump chamber is formed in said body; a piston which is displaceable along a first chamber formed in said body under an action of a pilot pressure; an indirect medium composed of a non-compressive fluid, wherein said indirect medium is pressed by said piston when said fluid is discharged; and a diaphragm that is flexibly bendable in cooperation with said indirect medium, and which presses said fluid charged in said pump chamber, such that said fluid is discharged in an amount corresponding to a displacement amount of said piston, said pump chamber being defined by said diaphragm, an inclined surface formed in said body, and a flat surface formed in said body, wherein a second chamber is formed in said piston, and said indirect medium can be introduced into said second chamber, wherein a displacement amount of said diaphragm in an axial direction is set to be larger than said displacement amount of displacement of said piston in said axial direction, is set to be identical with a volume change which is caused by displacement of said diaphragm in said axial direction, wherein a displacement member, which is connected to said diaphragm, is disposed so as to be movable back and forth in said second chamber, said diaphragm including a thick-walled central section, a thin-walled circumferential edge section, which continues from said central section and is fixed to said body, and a connecting section, which protrudes from said central section in said axial direction and connects to said displacement member, wherein said indirect medium is charged into a space between said diaphragm and a flat end surface of said piston in said axial direction, and said indirect medium does not move outside of said space and said second chamber, and when said fluid contained in said pump chamber is completely discharged therefrom, said thick-walled central section abuts against said flat surface, and said thin-walled circumferential edge section abuts against said inclined surface, whereby a volume of said pump chamber is reduced substantially to zero.