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Screw anchor

  • US 4,828,439 A
  • Filed: 05/15/1987
  • Issued: 05/09/1989
  • Est. Priority Date: 05/15/1987
  • Status: Expired due to Fees
First Claim
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1. A screw anchor for holding a fixture or other object against the outer surface of a hollow wall and constituted by a compressible anchor molded of synthetic plastic material and a screw cooperating with the anchor, said anchor comprising:

  • A. a four-legged shank whose normal shape is diamond-like, said shank having a pair of front legs joined together by a front apex living hinge having a hole therein, and a pair of rear legs joined by side living hinges to the front legs, the rear legs terminating in feed forming the rear apex of the shank, said feed being relatively inflexible and having substantially flat soles which when the shape of the shank is diamond-like define an inverted V-inlet;

    B. a socket having a bore therein which lies in axial registration with the front apex hole; and

    C. a pair of normally outstretched resilient webs securing said socket to the respective rear legs of the shank at a point thereon outward of said feet, whereby when the shank is manually compressed at the side hinges, the shank is collapsed to form a tongue which is insertable through a hole drilled in the wall until the socket is seated therein and the shank which is then behind the wall recovers its diamond-like shape, the screw when thereafter inserted in the socket bore and as it is turned in it advances toward the apex hole, in the course of which advance its tip is intercepted by the inlet to initiate triangulation of the shank, the inlet then being dilated to admit the advancing screw whose crests then engage the soles of the feet to force the rear legs apart and compel the shank to now assume a triangular shape in which the soles of the feet are in substantially parallel relation and abut the screw, each sole having a length sufficient to straddle adjacent crests of the screw whereby the soles engaging the crests are spaced from the root of the screw, the tip of the screw at the conclusion of its advance being threadably received in the front apex hole to create behind the wall a triangular truss in which the screw forms a central strut.

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