PURPOSE: To detect accurately the melting-down of a plug, by measuring a motor current at the time when a shell is separated by retreating a thrust block, and comparing the current with a motor current in a normal state.
CONSTITUTION: When a shell 5 is separated with the aid of a stripper 6 by retreating a thrust block 7 to retreat the shell 5, plug 1, and a plug holder 3, an electric current at the part (b) while the part (b) is being separated indicates an approximately fixed value in a motor current of the block 7. When anything unusual occurs in the plug 1, a part corresponding to a part (b') indicates an abnormal electric current pattern such as (b'). Thus an abnormal state of the plug 1 is detected by comparing a current taken out from an operating motor of the block 7 with an electric current at the normal state.
ONOHARA HARUO
TSUDA TAKAO