| 摘要 |
A first rotating body, which is rotated integrally with an operating knob, holds driving bodies and compression coil springs in recesses, and makes the driving bodies come into elastic contact with cam surfaces formed on the inner peripheral surface of a second rotating body. When current is not applied to an electromagnetic brake, the first and second rotating bodies are rotated integrally. When a user further rotates the operating knob against a sensation of resistance while the electromagnetic brake magnetically attracts a friction plate and a braking force is applied, the first rotating body is rotated relative to the second rotating body while the driving bodies slide on the cam surfaces. This relative rotation is allowed until stopper portions provided near the recesses come into contact with restricting wall portions provided near the cam surfaces.
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