| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable a screw to be fastened certainly with a predetermined axial force and check of its fastening to be certainly conducted visually as well. <P>SOLUTION: A fastening device includes a polygonal plain washer 2 bigger than the profile of the head 12 of the headed bolt 1, and a salient washer 3 having a convex part 3b on the surface side and a recessed part 3c on the back side corresponding to the convex part 3b and a relief groove 3d, which accommodates the paint having the visibility in the recessed part 3c, while the convex part 3b of a washer 3 is set up so that it is completely crushed by using an electric wrench 5 and caved-in by lower axial force than the yield point which should be searched for. A bolt 1 is rotated preventing the simultaneous rotation of the plain washer 2 by the electric wrench 5 when tightening. When the required axial force is obtained, it makes to stop the electric wrench 5 while the convex part 3b of the washer 3 is crushed and completes a cave-in and the paint 4 in the recessed part 3c and it oozes to the perimeter part of the washer 3 through the groove 4, the changing point of the motor current accompanying the completion of the convex part cave-in is caught electrically simultaneously. <P>COPYRIGHT: (C)2012,JPO&INPIT |
