| 摘要 |
PROBLEM TO BE SOLVED: To materialize a compact contact structure while guaranteeing big current density by providing a pressing member to push a contact in the radial direction so as to press it onto the outer surface of an internal cylinder part or the inner surface of an external cylinder part, and a means of energizing to energize the pressing member or to release it. SOLUTION: A pressing board 52 extending in its peripheral direction to press a contact 22 onto the inner surface of an internal cylinder part 12 or an external cylindrical part 14 by stroking it in the radial direction is provided, and the pressing board 52 is pressed by moving it in the radial direction by the piston 62 of an air cylinder 60. When a grounding end 20 is energized at a designated position, air is introduced into a bellows to press the contact 22 onto the peripheral surface 14 of the internal cylinder part 12 or to its inner peripheral surface through the piston 62 and the pressing plate 52. When the grounding end 20 is moved, if the air supplied into the bellows is interrupted, the piston 62 is pulled back by the action of a coil spring and the contact 22 is opened. Thereby, a reliable pressing force can be secured for a long time.
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