Apparatus for making self-locking fasteners with a pressure rolled thermoplastic patch

Claim 1

Apparatus for making a self-locking, externally threaded fastener of the type having a resilient, deformable patch of thermoplastic resin material fusion bonded to the thread surface, comprising: means for supporting said fastener in a position with its longitudinal axis approximately horizontal; means for heating said external thread surface to a temperature at least equal to the melting temperature of said thermoplastic resin material; means for depositing said thermoplastic resin material in powder form on said heated external thread surface over a preselected circumferential extent less than 180° in an amount sufficient that the resin material extends above some portion of the fastener thread crests whereby said thermoplastic resin material is fusion bonded to said external thread surface; and means for applying rolling pressure to said thermoplastic resin material to form said patch and to displace the excess resin material above the thread crests into the root areas of the threads to control and limit the radial height of the patch above the thread crests within the normal envelope of the basic major diameter of the fastener thread, including a pair of rollers each having a circumferential surface juxtaposed one from the other, whereby the fastener is passed between said rollers and the thermoplastic material is rollingly contacted on the external surface thereof by one of said circumferential surfaces.