Patent ID: 7100949

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 extends 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, said second ferrule is case hardened over its entire surface; a tapered nose that extends into said tapered recess of said first ferrule, and a driven surface on a back end thereof that engages said drive member ferrule drive surface; said second ferrule driven surface having a convex contour; said second ferrule having a forward edge that penetrates an outer surface of the tube end caused by radial inward compression of said forward edge as said second ferrule tapered nose slides against said first ferrule tapered recess during pull-up; said second ferrule back end being radially spaced from the tube end upon pull up of the fitting; said second ferrule also hinges between said back end and said forward edge to produce a swaged region near said forward edge which in longitudinal cross-section upon pull up is a convex portion of said interior cylindrical wall; said swaged region having high gripping pressure and frictional engagement with the tube end.