Rotary drive fastener

Claim 1

Rotary drive fastener providing integral construction which is preclusive of compromise, comprising: (A) fastening means having a central axis at extremes of which are driving and driven ends; (B) a driver engageable head on the driving end of the fastening means, said head having its central axis aligned with the central axis of the fastening means, the head in exterior configuration, forming a hemispherical dome; (B1) a tapered asymetric cavity located generally centrally within the dome of the head, said cavity defining a circular open outer end and a circular closed inner end, the inner end being of smaller dimension than the outer end, the center of the open outer end being coaxial with the central axis of the head and the center of the closed inner end being offset therefrom, the respective ends of the cavity being concentric to each other, said asymetric cavity comprising two portions interconnecting the open outer end and the closed inner end, one portion of the cavity being generated about a first axis which is parallel to said central axis and a second portion of the cavity being generated about a second axis which is at an acute angle relative to the central axis of the head and fastening means, the respective second axis of the cavity and central axis of the head and fastener intersecting at the top of the head whereby the cavity in said dome provides means for the engagement of a corresponding tool having a recessed head for the application of torsional force to the fastener, said fastener being, by reason of the positioning of the axis described above, subject to captivation, the bottom portion of the cavity serving as a repository for the transfer of torque from the driver tool by means of a driving pin.