| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a head block is inadvertently rotated to break a safety switch, and in addition, to do away with breakage of a coupling part of the head block due to its stronger coupling intensity. SOLUTION: The head block 4 is composed of a switch mounting part 5 and an operation key movement receiving part 6, and it is so structured that an unintended rotation of the operation key movement receiving part 6 is prevented by firmly fixing a head case 6A constituting an outer shell of the operation key movement receiving part 6 to a head-case-mounting face 5a of the switch mounting part 5 to integrate the switch mounting part 5 with the operation key movement receiving part 6 and fixing the switch mounting part 5 to a fixing frame with mounting screw members 40. COPYRIGHT: (C)2008,JPO&INPIT
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