TAMPER-RESISTANT FASTENER

摘要

A tamper-resistant fastener includes a non-circular drive recess optionally with a non-circular center post. Preferably the recess and center post are at least partially ellipsoidal cylinders that are concentric and aligned (i.e. they share a common major axis direction). This configuration forms a slot having preferably a substantially uniform width into which an authorized driver is inserted. The length of the major maximum dimension of the post is selected so that a circular arc tangent to the maximum radius of the post will pass closely to or intersect the minimum radial dimension of the recess.

主权项

1. A threaded fastener having tamper-resistant qualities, comprising:
a threaded portion defining a fastener axis; a head portion, said head portion having an upper surface with a recess formed therein, the recess having an inner wall comprising a first series of curvilinear surfaces joined together and lying along a first elliptical path generated from a centroid, the centroid being located a predetermined radial distance from the fastener axis, said first elliptical path having a major axis and a minor axis, the first series of curvilinear surfaces forming at least 240 degrees of an elliptical surface along the first elliptical path; the inner wall of the recess further comprising at least one indentation disposed between adjacent surfaces of the first series of curvilinear surfaces, said at least one indentation extending radially outward from the first elliptical path, the indentation comprising a curvilinear profile having a radius that is less than the smallest radius of the first series of curvilinear surfaces.