| abstract |
Screws 4 are inserted from a bottom surface of a ceiling plate 32 and screwed to a base plate 31 , and the ceiling plate 32 and the base plate 31 are press-connected to each other by an elastic restoring force of an elastic member 51 interposed between a head of the screw 4 and the ceiling plate 32 . A gap is formed between the head and the ceiling plate 32 . Further, a periphery of the head is covered with a cover via a ring-shaped elastic member 52 . In another embodiment, a periphery of a base plate 31 is protruded from a periphery of a ceiling plate 32 , and the protruded portion of the base plate 31 and a ring-shaped clamp positioned at an outer side of the ceiling plate 32 are joined by screws. Here, an elastic member is interposed between the clamp and the ceiling plate 32. |