| 摘要 |
PURPOSE:To contrive to disuse nut and to abolish welding operation by forming a structure wherein a recessed seat, which has a spiral step for one pitch of thread and at the same time a thread engageable keyhole, is formed integrally on a bottom plate by pressing and the diametral dimension of the seat is made smaller than the outer diameter of a leg. CONSTITUTION:A keyhole part 8 has a spiral step for one pitch of thread so as to attach a leg 10 to a bottom plate 7 by screwing a threaded part 11 in the keyhole pat 8 for clamping. Because the diametral dimension A of a recessed seat 9 provided on the bottom plate 7 is made smaller than the outer diameter B of the leg 10, the incomplete fixing of the leg 10 to the bottom plate 7 and the grogginess of the leg due to the abutting of the incomplete thread of the threaded part 11 of the leg 10 against the keyhole part 8 are prevented from occurring. In addition, the seat 9 serves also as the reinforcement of the leg attaching part of the bottom plate 7.
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