BigPatents India

A tube fitting for a tube end has a female threaded member that cooperates with a male threaded member. The female member includes a tube gripping device in the form of a gripping ring or ferrule that is attached to the female member by a frangible web. Upon a partial pull-up the ferrule engages a camming surface on the male threaded member and breaks off or separates from the female threaded member to become a separate piece so that the fitting then functions as a single ferrule tube fitting. Additional features include a steep camming angle on the camming surface to cause the ferrule to grip the tube end with a bite-type action and to form a primary seal between the camming surface and a front end of the separated ferrule. The ferrule front end, and optionally the entire female threaded member including the initially integral tube gripping device, are hardened to have a hardness ratio that is at least about 3.3 times the hardness of the material of the tube end on the Vickers scale.