Welded sleeve fitting

Abstract

A fitting for use with metal tubes adapted for critical applications such as involving high pressure and/or elevated temperatures for heavy external loads. The fitting includes a sleeve which is sealingly welded to the tube end and defines an improved cooperative nut and sleeve structure whereby the nut may be threadedly withdrawn from the body notwithstanding the projection of the sealing weld sufficiently from the tube to prevent complete withdrawal of the nut from the sleeve.

I claim: 
     
       1. A tube coupling structure comprising: a body having a port and a threaded portion coaxially of said port; a tubular sleeve having an inner end adapted to sealingly engage the body, an annular radially outer, axially outwardly facing shoulder, and a tubular outer end extending axially outwardly of said shoulder and terminating in a distal end; an annular nut having a threaded portion threadedly connected to the body threaded portion, said nut coaxially encircling said sleeve and having an inturned flange disposed axially outwardly of said sleeve shoulder for engaging said shoulder to urge said sleeve into sealing engagement with said body as an incident of threaded advance of said nut toward said body; a tube end extending coaxially inwardly into said sleeve; and an annular weld between said sleeve distal end and said tube sealingly connecting the sleeve to the tube end, said weld and said shoulder having a radial outer dimension greater than the corresponding radial inner dimension of said nut flange whereby said nut flange is captured axially movably between said sleeve shoulder and said weld in the made-up arrangement of the tube coupling, the length of said sleeve outer end outwardly of said shoulder being preselected to permit withdrawal of the nut axially outwardly of the axially inner end of the sleeve thereby to permit separation of said sleeve and nut from said body with said nut flange maintained radially outwardly of said sleeve outer end. 
     
     
       2. The tube coupling structure of claim 1 wherein said sleeve defines an internal tube stop shoulder axially outwardly of said radially outer shoulder limiting the axially inward positioning of the tube end in said sleeve outer end. 
     
     
       3. The tube coupling structure of claim 1 wherein said nut flange is annular. 
     
     
       4. The tube coupling structure of claim 1 wherein the axial length of said nut is no greater than the axial length of said sleeve. 
     
     
       5. The tube coupling structure of claim 1 wherein the axial length of said nut is less than the axial length of said sleeve. 
     
     
       6. The tube coupling structure of claim 1 wherein the length of said sleeve outer end outwardly of said shoulder is sufficient to permit said nut to be spaced outwardly from said body with said sleeve inner end engaging said body. 
     
     
       7. The tube coupling structure of claim 1 wherein said nut has an axial length no greater than the axial length of said sleeve outer end. 
     
     
       8. The tube coupling structure of claim 1 wherein said nut flange has an inner diameter only slightly greater than the outer diameter of said sleeve outer end. 
     
     
       9. The tube coupling structure of claim 1 wherein said body threaded portion defines a male thread. 
     
     
       10. The tube coupling structure of claim 1 wherein said inner end of the sleeve defines a convex seating surface and said body defines a complementary concave seating surface with said sleeve seating surface projecting into said body to sealingly engage said body seating surface in the make-up arrangement of the fitting. .Iadd. 11. The tube coupling structure of claim 1 wherein said sleeve outer end defines an annular, axially outwardly facing surface, said tube end being retained in abutment therewith by said weld. .Iaddend..Iadd. 12. The tube coupling structure of claim 1 wherein said sleeve outer end is defined by a stepped annular end surface including an axially outwardly facing outer planar portion, a cylindrical intermediate portion, and an axially outwardly facing inner planar portion, said tube end axially abutting said end surface. .Iaddend.