Sheet metal nut

Claim 1

A one-piece sheet metal nut member for clampingly securing a thermoplastic workpiece to a primary workpiece, wherein the properties of the thermoplastic workpiece are such that it exhibits cold flow under load, said nut comprising a tubular, radially inner body portion extending downwardly a first predetermined axial distance from an upper wall surface, the inner periphery of said inner body portion having a first predetermined inner diameter and including a plurality of thread convolutions in a central through bore; a generally tubular, radially outer body portion surrounding said inner body portion and extending downwardly a second predetermined axial distance from the upper wall surface, the second axial distance being greater than the first axial distance so that the lowermost extremity of the outer body is spaced downwardly from the lowermost extremity of the inner body; the upper wall surface integrally connecting the uppermost extremities of the inner and outer body portions; the outer body portion comprising an upper and a lower section, the lower section being a downwardly and inwardly tapered frustoconical load bearing surface terminating at a circular aperture having a center substantially on the longitudinal axis of the tubular, threaded inner body portion; the diameter of said aperture being a second predetermined diameter greater than said first diameter of the threaded inner body portion, the upper section being generally concentric with the inner body portion and including torque accepting surfaces on its outer periphery, the upper section of the outer body and the upper wall surface incorporating axially compressible spring means for permitting the inner body to move axially relative to the outer body without disturbing the broad surface contact between the frustoconical lower outer body section and a bearing surface of the thermoplastic workpiece; wherein the frustoconical load bearing surface of said nut is adapted to matingly engage a frustoconical recess surrounding a through bore in the thermoplastic workpiece so that the nut, with an associated threaded stud extending through the bore in the thermoplastic workpiece, can compressingly clamp said thermoplastic workpiece and distribute the clamping force over the workpiece in a manner which minimizes the cold flow effect in the clamped joint and remain in clamping engagement inspite of said cold flow.