| 摘要 |
PURPOSE:To secure airtight sealability around a bolt hole of a booster shell by bending an installed part of both inner and outer edges in peripheral area of the bolt hole formed in the sheet metal booster shell clearly with the outer circumferential edge of a ring step part, and making it closely attachable with high surface pressure. CONSTITUTION:A thread forming part 33 of a connecting bolt 29 is inserted into a bolt hole 38 formed in a rear shell half-body 1b from an inner part of this half-body 1b, and successively a base end 34 provided with plural pieces of projection strips 39 extending in the axial direction is pressed in the circumferential surface. With this press-in, peripheral range R of the bolt hole 38 is bent in a section V-shaped form, while an inner edge Ra of the peripheral edge area R is situated at the side of a ringlike step part 35 and an outer edge part Rb in a ringlike groove 36, respectively. Next, the base end 34 is caulked from one end of the side of the thread forming part 33, thereby forming pressure flange 40, and the inner edge Ra is pressed in between by the inner circumferential part 40 of the pressure flange 40 and the ringlike step part 35, while the outer edge Rb is thrust in the ringlike groove 36 by the outer circumferential part 40b, thus airtight sealability around the bolt hole. |
