| 摘要 |
PROBLEM TO BE SOLVED: To provide an expansion screw that can be attached firmly to a wall body of solid or hollow. SOLUTION: It provides a bolt and a sleeve and a nut is provided in a front edge of the sleeve, and an expansion step is formed so that a hollow groove arranged annularly in the middle of the sleeve has one or more steps. Two or more reverse U-shaped grooves are arranged annularly to the sleeve between the expansion step and the nut and there is an expansion superposed piece in each reverse U-shaped groove and a longitudinal connecting piece between each reverse U-shaped groove forms a bending step. When the nut on the front edge of the sleeve is pressed inward by turning the bolt, the expansion superposed piece is opened and expanded outward and overlaps with the ring on the front edge of the sleeve and the longitudinal connecting piece presses outward by the bending step and forms a firm connection that is pressed double opened and expanded with an inside step of the hole of the wall body. The failure rate of installation is decreased to the minimum because it is applied to the firm connection to the wall body of hollow or solid by multi stage expansion step construction. COPYRIGHT: (C)2004,JPO
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