Plastic coated ferrule for a tube coupling

Claim 1

In a fitting for a high-pressure tubing including a body member having an opening for receiving an end of a length of tubing, a closure member surrounding the tubing and adapted to be threadably secured to the body member, each of said body and closure members being provided with opposed substantially frustoconical flared surfaces, the improvement comprising a metallic ferrule means, having a bore therethrough and sealing surfaces, one at each end for mating with said flared surfaces of the body and closure member and surrounding the tubing between the opposed flared surfaces, adapted to be compressed between the members upon threadably tightening the closure into the body member, whereby tightening of the closure into the body member advances the ferrule along the tubing to force the sealing surfaces into face-to-face engagement with the flared surfaces, said engagement causing a portion of a sealing surface to bite into the tubing to effect a fluid seal through the fitting, a plastic coating being bonded to the ferrule means on its exterior surface and extending at least a short distance into each end of the bore, said plastic coating being characterized by high lubricity and substantial inertness to its environment.