Power hand tool

Abstract

A power hand tool includes a housing, a motor mounted inside the housing, a transmission member coupled to the motor, a driven member, which has grooves on one side thereof facing the transmission member, a plurality of steel balls respectively mounted in the grooves of the driven member, a plurality of spring members respectively mounted in the transmission member and stopped at the steel balls for enabling the driven member to be rotated by the transmission member upon operation of the motor, and a tool bit adaptor fastened to the driven member. When the driven member receives a heavy reaction force through the tool bit adaptor, the steel balls can be disengaged from the grooves, thereby causing disconnection of the transmission member from the driven member so that the power hand tool runs idle to prevent

1 . A power hand tool comprising:
 a housing having an accommodation chamber therein;   a motor mounted in said accommodation chamber;   a transmission member mounted in said accommodation chamber and coupled to and rotatable by said motor;   a driven member mounted in said accommodation chamber, said driven member having at least one groove at one side thereof facing said transmission member;   at least one steel ball mounted in said at least one groove of said driven member; and   at least one spring member mounted in said transmission member and stopped at said at least one steel ball to force the steel ball to stop against a wall of said at least one groove of said driven member, thereby enabling said driven member to be rotated by said transmission member.   
   
   
       2 . The power hand tool as claimed in  claim 1 , further comprising a tool bit adaptor fastened to and rotatable by said driven member. 
   
   
       3 . The power hand tool as claimed in  claim 1 , wherein said transmission member comprises a transmission gear having at least one spring hole and a cover plate attached to said transmission gear; wherein said at least one spring member is mounted in said at least one spring hole with two distal ends thereof stopped against said at least one steel ball and said cover plate. 
   
   
       4 . The power hand tool as claimed in  claim 3 , wherein said driven member comprises a driven wheel having said at least one groove, a driving shaft having an end fastened to said tool bit adaptor and the other end inserted through said driven wheel, said transmission gear and said cover plate and coupled with a retainer. 
   
   
       5 . The power hand tool as claimed in  claim 4 , further comprising a cushion ring mounted onto said driving shaft and sandwiched between said cover plate and said retainer. 
   
   
       6 . The power hand tool as claimed in  claim 4 , wherein the driven wheel has a plurality of arched said grooves equiangularly spaced around a center thereof.