Patent ID: 7351044

Claim:
A multistage piston compressor comprising a valve casing ( 4 ) and a shiftable valve piston ( 9 ) formed as a single piece and driven linearly oscillating by a drive motor ( 2 ), wherein the valve piston ( 9 ) is furnished with a low pressure piston ( 10 ) and with a high pressure piston ( 12 ), wherein the low pressure piston ( 10 ) and the high pressure piston ( 11 ) form at least one volume changeable low-pressure chamber ( 5 ) with the intake check valve ( 15 ) and with at least one volume changeable high-pressure chamber ( 6 ) with the discharge check valve ( 30 ), and wherein the low-pressure chamber ( 5 ) and the high-pressure chamber ( 6 ) are connected to each other through an overflow duct ( 19 ), wherein an overflow check valve ( 20 ) opening in the direction toward the high-pressure chamber ( 6 ) is inserted in the overflow duct ( 19 ), wherein the overflow check valve ( 20 ) is equipped with a sealing disc, wherein the overflow duct ( 19 ) joins at least two passage bore holes ( 26 , 27 ), wherein the sealing disc of the overflow check valve ( 20 ) is formed as a loosely guided and stroke limited sealing membrane ( 28 ), wherein the passage bore holes ( 26 , 27 ) of the overflow duct ( 19 ) exhibit different diameters and wherein the passage bore holes ( 26 , 27 ) are disposed at an identical radial distance to the axis of the sealing membrane ( 28 ) and wherein the passage bore holes ( 26 , 27 ) are completely covered by the sealing membrane ( 28 ).