Patent ID: 6988563
Filing Date: 2006-01-24
Classification: B25D

Abstract:
1. A hammer drill for applying rotational forces and percussive forces to a drill bit, comprising: a motor; a percussive force converter mechanism driven rotationally by said motor for modifying percussive forces of said hammer drill by changing a rotational speed ratio of said motor and a connector shaft; a connector shaft driven rotationally by said percussive force converter mechanism; a spindle capable of holding said drill bit, wherein a rotational force through said connector shaft is propagated; a motion converter mechanism for converting the rotational force of said connector shaft to a reciprocating force in an axial direction in said spindle; and a percussive member for applying a percussive force in an axial direction to the drill bit held in said spindle based on the reciprocating force converted by said motion converter mechanism, wherein said percussive force converter mechanism comprises a plurality of gears with mutually differing numbers of gear teeth, wherein the plurality of gears can move freely in an axial direction of said connector shaft, wherein a shifting switch selects a gear from the plurality of gears and the selected gear meshes, by a force of a spring, to gear teeth equipped on said connector shaft, and wherein mating teeth of a gear that mates with the gear teeth of said connector shaft side are provided with sidewalls on one side in an axial direction thereof.