Patent ID: 6883401

Claim:
A power tool in combination with a fastener for fastening objects, comprising a tool part including a housing provided with a non-rotatable element; and a power drive in said housing and provided with a rotatable driving element; and a fastener part including a bolt having a thread and an axis and introducable into parts forming an object, a nut screwable on said bait and cooperating with said rotatable driving element, and a washer to be applied between said nut and the object and cooperating with said non-rotatable element, said washer having an axis and being provided with a first bearing face surface located at one axial side and adapted to cooperate with said nut and having a facial friction with said nut, a second bearing face surface located at an opposite axial side and adapted to cooperate with the object and having a facial friction with the object, and at least one third turning resistant surface located inside said washer and adapted to cooperate with said thread of said bolt and having a turning friction with the bolt, said washer including a radially inner part having a radially outer surface and bolt thread engaging means to connect with a thread of the bolt, and also including a radially outer part having a radially inner surface, said radially outer and inner surfaces of saidradially inner and radially outer parts of said washer cooperating with one another so that said radially inner part can not rotate freely inside said radially outer part during tightening but is displaceable axially relative to said radially outer part upon bolt elongation, so that when said driving element turns said nut with a given active force in one direction and said outer part of said washer is held stationarily by a reactive force applied by said non-rotatable element of said housing to absorb a reaction force corresponding to said given force and due to the facial friction of said washer with said nut, the facial friction of said was her with the object, and the turning friction of said washer with said bolt, only said nut turns to elongate said bolt, and said washer remains rotationally stationary while said bolt does not turn but elongates or relaxes in an axial direction.