Patent ID: 7478648

Claim:
A hydraulic pressure peak absorbing accumulator for a hydraulic impact mechanism, comprising: an inner chamber wall and an outer chamber wall defining an expansion chamber, a flexible membrane dividing the expansion chamber into a pressure fluid compartment and a gas cushion compartment adapted to be pre-pressurized, at least one pressure fluid communication passage extending through said inner chamber wall into said pressure fluid compartment, and a movable membrane support member comprising a membrane engaging head located in said pressure fluid compartment which contacts and supports said membrane, and a stem portion movably guided in a bore in said inner chamber wall, wherein said membrane engaging head covers said at least one fluid communication passage at low fluid pressure levels, and at high fluid pressure levels fluid enters said pressure fluid compartment and pushes said membrane in a direction from said inner chamber wall toward said outer chamber wall with said membrane engaging head in contact with said membrane, wherein an abutment portion is provided on said outer chamber wall and arranged such that at high fluid pressure levels when said fluid enters the pressure fluid compartment and pushes said membrane in the direction from said inner chamber wall toward said outer chamber wall with said membrane engaging head in contact with said membrane, said abutment portion limits the outward movement of said membrane support member, and wherein said abutment portion comprises a bulge shaped projection formed on said outer chamber wall and located opposite and co-axially with said membrane support member in order to limit a length of the stem portion.