Importance

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Abstract

A hydraulic percussion apparatus has an elongated housing having a front nose piece and forming a chamber extending along an axis, a tool projecting axially backward through the nose piece into the housing and having in the nose piece an axially forwardly directed shoulder, and a piston axially reciprocal in the chamber and axially forwardly engageable with the tool. A high-pressure line, a low-pressure line, and a control valve can axially oppositely pressurize the piston and thereby hammer the piston against the tool. A sleeve surrounding the tool in the nose piece is displaceable axially in the nose piece between a full-forward end position axially forwardly abutting the housing and a full-rear end position axially abutting the housing and through an intermediate position between the end positions. This sleeve is formed with a radially outwardly open groove defining in the nose piece a damping compartment. A damping conduit in the housing has one end connected to the high-pressure line and an opposite end opening in the nose piece at a location opening into the groove only in and between the full-forward and intermediate positions of the sleeve. Thus this opposite end is blocked by the sleeve between the intermediate and full-rear positions of the sleeve.

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First Claim