A Compression on tube fittings 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 fungible web. Upon a partial pull-up the female 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 Compression tube fittings.

Flared tube endsare commonly encountered in use with plastic tubing and plastic Compression tube fittingss. The present invention is not primarily directed to plastic tubing or Compression tube fittingss because such fittings have significantly different challenges and material properties thataffect the ability of the fitting to both grip the tube and provide an adequate seal.

The most commonly used camming surfaces are frusto-conical such that the term "camming angle" refers to the cone angle of the camming surface relative to the tube endlongitudinal axis or outer surface. The tube end is axially inserted into the body bore and extends past the frusto-conical camming surface. The gripping device is slipped onto the tube end and the nut is partially threaded onto the body to the fingertight position such that the tube gripping device captured axially between the camming surface and the nut. The nut typically includes an inward shoulder that drives the tube gripping device into engagement with the angled camming surface on the body asthe nut and body components are threadably tightened together.

The bowing action helps direct the front end of the single ferrule into the tubeend. The bowing action is also used to cause the back end of the ferrule to likewise engage and grip the tube end. This is accomplished usually by provided an angled drive surface on the nut shoulder that engages the back end of the single ferrule soas to radially compress the back end of the ferrule into a gripping action on the tube end. In some single ferrule designs, the back end of the ferrule apparently is intended to bite into the tube end.

Especially inextreme environments and for sealing gas. This is because the front end of the single ferrule attempts to make the seal against the axially elongated camming surface. The radially outward bowing action causes a larger portion of the outer surface ofthe front end of the single ferrule to come into contact with the camming surface against which it is being driven. The result necessarily is a larger seal surface area between the outer surface of the single ferrule and the camming surface. Thisenlarged seal area causes an unwanted distribution of the sealing force between the single ferrule and the camming surface, and also creates a larger area for surface imperfections to allow leaks to occur.

Attempts have been made to design Compression on tube fittingss with a tube gripping element that separates during pull-up to function as a single element tube gripping device. Known designs place the breakaway element on the male threaded component. Additionally, the known designs either force the tube gripping element against a shallow camming surface angle or do not attempt to create a tube gripping bite into the tube wall. Thus the prior art designs suffer from the same limitations as the priorart single ferrule Compression on tube fittings designs.