Tubing coupling

Claim 1

A coupling for sealingly connecting a fluid passage to a section of tubing having a smooth cylindrical external surface without distorting said tubing or marring said cylindrical external surface comprising: a. a rigid housing having 1. a cylindrical fluid passage formed therein, 2. an enlarged cylindrical chamber coaxial with said fluid passage and formed to receive an annular piston, 3. a frusto-conical internal surface coaxial with, and extending from, said enlarged cylindrical chamber toward the tubing receiving end of said housing; b. an annular piston positioned within said cylindrical chamber in sliding sealing relation to the cylindrical surface of said chamber; c. an annular initial seal formed of deformable material and having an internal surface in the relaxed position having a diameter smaller than the outside diameter of the tubing to be connected by said coupling to thereby form an interference fit when said tubing is inserted into said housing, said annular initial seal being sealingly fixed axially to said annular piston; d. an annular secondary seal having a frusto-conical outer surface, a smooth cylindrical inner surface and being formed of a deformable material, said annular secondary seal being positioned within said housing frusto-conical inner surface in abutting relation to saiD annular piston; said initial seal, upon insertion of said tubing into said housing, creating a fluid tight seal between said initial seal and said tubing whereby line fluid pressure forces said piston against said secondary seal in a manner that said secondary seal is forced toward said housing and deformed against said housing frusto-conical surface to cause said secondary seal to tightly grip said tubing external surface.