Electric percussion drilling machine

摘要

The electric percussion drilling machine comprises a rotatably mounted drill holder (20), a drive member (58) to which a reciprocating movement is imparted, and an electric motor (2) which simultaneously sets the drill holder (20) in rotation and applies the reciprocating movement to the drive member (58). Arranged at an axial distance from the drive member (58) is a percussion hammer (60) which transmits blows to the drill holder (20) when the latter rotates in the one direction. A helical spring (59) is arranged between the percussion hammer (60) and the drive member (58) in such a way that it is expanded and compressed in accordance with the reciprocating movement of the drive member (58) and thus produces a prestress which presses the percussion hammer (60) in the direction of the percussion movement. Accordingly, the helical spring (59) transmits the energy of the reciprocating drive member (58) to the percussion hammer (60) and the drill (23) without an additional connecting medium, such as, for instance, an air cushion. In this way, the efficiency of transmission is improved and a powerful percussion action with low power consumption is obtained. <IMAGE>