Corrugated tube fitting
A fitting for an end of a length of corrugated tubing forms a gas-tight metal-to-metal seal by rolling and folding an endmost corrugation into a axially extending annular groove in the fitting body. A ridged retainer grips the tubing corrugations above the endmost corrugation and is axially advanced into the fitting body by a nut. The cut end at the endmost corrugation of the tubing encounters the axially facing end of a tubular stub inside the fitting body and folds over itself and into the annular groove between the stub and the inside surface of the fitting body. A seal member is thus formed with a pair of substantially parallel sealing surfaces, and resides between the retainer and the outside surface of the tubular stub. The seal member forms a metal/metal seal with the tubular stub.
1. A fitting for an end of a length of tubing having corrugations ranging between a maximum and a minimum diameter for terminating the tubing at an end section, said fitting comprising:
a retainer having at least one ridge sized to extend inwardly to a radius between said maximum and minimum diameters for gripping said tubing axially above an endmost corrugation of said tubing and an axially oriented inwardly facing surface to seal against the tubing;
a body having a threaded surface and a hollow cylindrical part sized to admit said retainer;
a nut having thread complementary with said threaded surface of said body, said nut having a cap part configured to engage said retainer for urging said retainer axially toward said body with threaded advance of said nut relative to said body; and,
said body having an annular groove therein, said annular groove bounded inwardly by a tubular stub with an axially oriented outwardly facing sealing surface, and wherein said advance of said nut on said body folds said end section of the corrugated tubing over itself and forms said end section into a seal body by sliding the folded said end section between the retainer and the tubular stub, the seal body comprising a pair of substantially parallel axially disposed sealing surfaces between said axially oriented inwardly facing surface of the retainer and said axially oriented outwardly facing sealing surface of the tubular stub.
2. The fitting of claim 1 , wherein said end section is an endmost corrugation.
3. The fitting of claim 1 , wherein said tubular stub has an axially facing wall and an outer edge having a diameter greater than said minimum diameter and smaller than the maximum diameter whereby, upon said advance of said nut on said body, an end of said length of tubing is positioned on said axially facing wall.
4. The fitting of claim 3 , wherein said outer edge comprises an intersection of said axially facing wall and said outwardly facing sealing surface.
5. The fitting of claim 1 , wherein said retainer further comprises a terminal end having an axially oriented inwardly facing surface disposed below said at least one ridge, wherein said advance of nut on said body urges said terminal end past the axially facing wall, with a clearance between the terminal end and the axially facing wall occupied by said end section.
6. The fitting of claim 1 , wherein said seal body is substantially in contact with said outwardly facing sealing surface of the tubular stub.
7. The fitting of claim 1 , wherein said nut includes a leading edge wherein said end section of said tubing gets caught between said leading edge and said axially facing wall of said tubular stub during said advance of said nut to form said sealing member.
8. The fitting of claim 1 , wherein said body further includes a further surface for bearing a complementary means to connect to other hardware.
9. The fitting of claim 1 , wherein said retainer is circumferentially split along at least part of a length of the retainer, to enable engagement over said maximum diameter.
10. A method for forming a coupling between a fitting and an end of a length of tubing, comprising:
providing a length of tubing having corrugations ranging between a maximum diameter and a minimum diameter and including an endmost section and a cut end;
providing a fitting comprising a retainer with a ridge, the fitting further comprising a body and a nut;
engaging said tubing in said retainer so that the ridge is disposed axially behind at least an endmost corrugation of said tubing;
urging said cut end axially against an axially facing wall of said body, said axially facing wall peripherally surrounded by an annular groove around a tubular stub, and having an outer edge, said outer edge having a diameter greater than said minimum diameter;
advancing said nut on said body, thereby folding said endmost section over itself and over said outer edge to form a pair of substantially parallel axially extending sealing surfaces between said retainer and said tubular stub; and,
sliding the folded said endmost section between the retainer and the tubular stub by further advancing said nut, whereby the substantially parallel axially disposed sealing surfaces between said axially oriented inwardly facing surface of the retainer and said axially oriented outwardly facing sealing surface of the tubular stub, seal the coupling between the fitting and the tubing.
11. The method of claim 10 , wherein said annular groove is formed in said body having an radially extending surfaces, the method further comprising engaging said retainer in said nut having an axially leading edge, and wherein said urging is accomplished by advancing said nut relative to said body until said axially leading edge contacts said radially extending surfaces.
12. The method of claim 10 , wherein said annular groove is formed in said body having a first threaded surface, the method further comprising engaging said retainer in said nut having a second threaded surface, and wherein said urging is accomplished by engaging said threaded surfaces of the body and the nut and threading the nut causing said nut and said retainer to advance axially relative to said body.
13. The method of claim 10 , wherein said endmost section comprises said endmost corrugation, said retainer comprises a terminal flange with an end surface having an inward edge and an axially oriented inwardly facing surface, and said body comprises a tubular stub having an outer edge and an outwardly facing sealing surface, wherein said urging causes crimping said endmost corrugation between said inward edge and said outer edge of said tubular stub and further urging causes said folding of said endmost section over itself and said pair of substantially parallel axially oriented sealing surfaces are formed between said axially oriented inwardly facing surface of the retainer and said axially oriented outwardly facing sealing surface of the tubular stub.