METHOD AND DEVICE FOR DAMPING REPULSIVE POWER OF IMPACT TOOL

A percussion tool comprising a housing; a tool bit movably supported by the housing for alternatingly executing forward and recoil strokes; a hammer piston supported in the housing and arranged for delivering consecutive blows at least indirectly to the tool bit for effecting the forward strokes thereof; a dampening chamber in the housing; an arrangement for introducing fluid into the dampening chamber for generating a dampening force therein; and a dampening piston supported in the housing and bounding the dampening chamber. The tool bit is connected with the dampening piston for effecting an axial displacement of the dampening piston into the dampening chamber by the tool bit during the recoil strokes thereof. There is further provided a control arrangement carried by the dampening piston for varying the dampening force of the fluid in the dampening chamber as function of a relative axial displacement between the dampening piston and the housing.