Multi-stage piston type compressor

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).