| 摘要 |
PROBLEM TO BE SOLVED: To provide a supply and exhaust opening chamber having required strength and which can be manufactured conveniently and inexpensively. SOLUTION: A first plate 5 has a coupling flange part 5s formed by bending, and a hooked protrusion 20 provided at the coupling flange part, while being arranged in a specified direction. A second plate 7 is provided with an opening 30 at a position corresponding to the hooked protrusion and coupled with the first plate 5 by stopping the opening 30 fixedly at the hooked protrusion 20.
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