Tube coupling

Claim 1

In a tube coupling having a body defining a tubular insert adapted to be received in the end of a tube to be coupled for radially supporting the tube end in a made-up arrangement, said body further defining an annular camming surface circumjacent said insert, and a nut having an axially inner portion threaded to said body and an axially outer inturned flange defining an axially inwardly facing pressure surface, a sleeve comprising an annular member having a through bore for closely receiving said tube end in said made-up arrangement, an axially inner nose engaging said body camming surface, a reaction surface engaged by said nut pressure surface for urging the sleeve axially inwardly as a result of threaded advance of the nut on the body thereby to cause permanent inward radial constriction of said nose by said camming surface against the outer wall surface of said tube wall during make-up of the fitting thereby permanently locking said annular sleeve member to said tube end against relative axial movement therebetween, and thereby effectively preventing axial withdrawal of said tube end outwardly through said sleeve and forcing said tube end against said insert to provide a frictional retaining force between the tube end and said insert in said made-up arrangement, the axially outer end of said sleeve being flared to define means on said sleeve axially engageable by said nut flange for effectively precluding movement of said nut flange axially outwardly past said flared end, said flared end of the sleeve having a strength preselected to preclude constriction thereof to a diameter smaller than the inner diameter of said nut flange by a force applied thereto by said nut flange sufficient to overcome the frictional retaining force between the tube end and insert maintained by the constricted nose thereby to cause axial withdrawal away from said body of the tube end and the sleeve fixed thereon by a threaded withdrawal of the nut from the body.