| 摘要 |
PROBLEM TO BE SOLVED: To provide a keyhole closing device for a manhole cover, by which extraction from a keyhole for the manhole cover can be conducted surely. SOLUTION: The keyhole closing device 11 has a drum section 12 inserted into the keyhole 3 formed to the manhole cover 1 and a cover section 13 screwed to the drum section 12. A locking mechanism section 21 and a control unit section 51 are disposed into the keyhole closing device 11. The locking mechanism section 21 has a lock pin 22, a rocking shaft 23, a gear 24, a step-up gear row 31 and an electromagnetic solenoid. The lock pin 22 is disposed to a recessed section 14 formed to the drum section 12, and fixed onto the rocking shaft 23 axially supported to the drum section 12 through bearing sections 25, 25. The gear 24 formed in a fan shape is fixed at the end section of the rocking shaft 23. The step-up gear row 31 speeds up the rocking of the gear 24, and transmits the speed-up to the fourth gear pair 35. A pin 36 capable of being engaged with a rod for the electromagnetic solenoid is projected from the fourth gear pair 35.
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