Patent ID: 7367595

Claim:
A tube fitting comprising: a fitting body having a cylindrical bore for receiving a tube end and including a tapered mouth at one end of said bore; a drive member having a threaded engagement with said body and having a ferrule drive surface; a first ferrule having a tapered first end that is insertable into said tapered mouth of the fitting body and having a second end with a tapered recess that axially extends toward said first end; and a second ferrule having a continuous cylindrical interior wall that closely surrounds the tube end when installed thereon, a tapered nose portion that is insertable into said tapered recess of said first ferrule, and a driven surface on a back end thereof that engages said ferrule drive surface during pull-up of the fitting; and wherein said second ferrule is case hardened about its entire surface, and said second ferrule has a configuration such that after complete pull-up of the fitting: said second ferrule will deform to cause a forward edge of said tapered nose portion to penetrate an outer surface of the tube end; a rear portion of said cylindrical interior wall is radially spaced from said tube end outer surface; said second ferrule will also deform to form a convex portion of said cylindrical interior wall in longitudinal section, said convex portion having at least a portion thereof which is axially spaced from said forward edge; and a swaged region is produced by said cylindrical interior wall on said tube end outer surface.