Patent ID: 6923269

Claim:
A demolition hammer and/or hammer drill for working a material, comprising: a tool having a tool shaft which is movable over a limited axial path; a percussion generating device having an axially reciprocatable percussion piston; and a percussion changing device, the percussion changing device including: a force detection device configured to detect a pulling force which acts upon the tool when the tool is jammed in the material being worked and which is generated by pulling on the demolition hammer and/or hammer drill, and a switching device which is responsive to operation of the force detection device to switch over the percussion piston from a main percussion state to a free percussion state when the force detection device detects that the pulling force exceeds a threshold value, wherein, in the main percussion state the percussion piston influences the tool shaft of the tool directly or via an intermediate element in a main percussion direction, and wherein, in the free percussion state, the percussion piston influences the tool indirectly in a free percussion direction which is opposite to the main percussion direction.