Patent ID: 7393018

Claim:
A tube fitting for metal tubes, comprising: a) a body and nut that are joinable; said body having an interior bore that is adapted to receive a metal tube end along a central longitudinal axis of the fitting; said bore having a camming surface at one end of said bore; b) said nut having an interior shoulder that forms a drive surface; and c) a ferrule having a front end and a back end; and said back end engages said nut drive surface when the fitting is pulled up; said ferrule front end engaging said camming surface during pull-up to form a generally narrow line contact seal against said camming surface; said ferrule front end plastically deforming and having a front edge that indents into the tube end; said nut when joined to said body driving said ferrule against said camming surface; d) wherein said camming surface forms an included angle of at least thirty-five degrees to about sixty degrees with respect to said longitudinal axis and said ferrule front end is at least about 3.3 times as hard as the metal tube end on the Vickers scale; and e) wherein said ferrule plastically deforms with a radially compressive hinging action that produces a radial compression in a central portion of said ferrule against said tube end to collet said ferrule onto the tube end.