Process and apparatus for the application of fluoropolymer coating to threaded fasteners

摘要

A process and apparatus are provided for the application of a fluoropolymer coating to the threads of an internally threaded fastener. The fastener has a body and a threaded bore extending to opposing ends of the body to define opposing first and second openings in the fastener. The fastener is moved on a conveyor along a path of travel with its threaded bore in a predetermined orientation. As the fastener moves along its path of travel, the first opening is closed by means of an obstructing member, while an air stream carrying entrained fluoropolymer powder is directed from a nozzle through the second opening and into the threaded bore. The nozzle is stationary and is located at an axially displaced position relative to the second opening of the fastener and immediately adjacent the conveyor. Preferably, the nozzle includes a diffuser which directs the air stream and entrained fluoropolymer powder into the fastener bore in a diverging pattern. After the fluoropolymer powder is deposited onto the threads of the fastener, the conveyor moves the fastener through a heating station where the fluoropolymer powder is raised to its melting temperature causing it to melt and fuse into a generally continuous film covering the fastener's threads.