| 摘要 |
A method of detecting failure to tighten screws against works includes steps of detecting every screw tightening operation against a work after start of a screw tightening step, counting the number of times of the screw tightening operations detected in the previous step, detecting the completion of the screw tightening step, and comparing a counted value at the time of the completion of the screw tightening step with a predetermined value, thereby informing of a result of comparison. A device for carrying out this method includes a current relay responsive to a large load current during the tightening operation of an electric screwdriver in a screw tightening step, a presettable counter for counting the number of operations of the current relay for the purpose of counting the number of screw tightening operations, setting knobs operated for setting a desirable number of screws to be tightened, photoelectric switches for detecting completion of the screw tightening step for the work, and an alarming device for comparing a counted value obtained by the presettable counter and the value set by the knobs when a screw tightening work completion signal is generated by any one of the photoelectric switches. The alarming device includes a buzzer energized when counted value does not reach the preset value set at the presettable counter.
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