DETECTION OF LOOSENING OF BOLT AND APPARATUS THEREFOR

PURPOSE:To accurately discriminate the loosening of a bolt/nut by a method wherein a patch material is made to abut against the flat surface of the hexagonal part of the bolt/nut to be struck in the shearing direction of the bolt/nut from above and the force and acceleration due to striking force are detected. CONSTITUTION:When the loosening of a bolt is detected, the hexagonal part of a bolt/nut 19 is fitted in a fixing part 3 opened in a hexahedral surface shape. Next, when a motor 6 is operated and a cam 7 is revolved in the direction shown by an arrow (e), the press material 9 mounted to an arm 2 is pushed up against the spring force of a spring 10 and detached from the corner part of the cam and the arm 2 is instantaneously drawn up by the spring force of the spring 10 and the projection 24 of a patch material 25 is struck by the hammer 17 mounted at the leading end of the arm. At this time, the force and acceleration due to striking force are taken out as pulse signals by a force sensor 33 and an acceleration sensor 22 and these pulse signals are amplified and converted by an A/D converter to be displayed on a printer as waveforms. The change of the pulse waveforms is compared with a predetermined value to detect the loosening of the bolt.