Heat recoverable coupling for tubing

DETAILED DESCRIPTION The present invention is designed to eliminate relative motion at the ends of heat recoverable metal couplings as a means for preventing chafing, fretting or galling of the tubing associated therewith to avoid eventual tube failures.
To accomplish this end, a heat recoverable metallic coupling is here disclosed which includes a body having a generally cylindrical section and stress distribution sections extending from the generally cylindrical section to rigid collars.
The entire structure is of a heat recoverable nature and usually is of unitary construction, although a composite construction using a liner of another metal or material is feasible and would be desirable in certain applications, as, for instance, where a substance corrosive to the heat recoverable metal is to be contained in the tubing.
The stress distribution sections provide a transition from the thick-walled cylindrical section to thin-walled ends of the stress distribution sections.
At the generally cylindrical section, the body is in most instances more rigid than the tubing with which the coupling is to be employed.
At the ouher ends of the stress distribution sections, the walls of the coupling are thin and the coupling is at least as flexible as the tubing.
Thus, each end of the coupling provides an area of increasing strength such that the tubes extending into the coupling will experience stress loading from flexure of the tubing over a broad area rather than concentrated at a rigid edge of an untapered coupling.
The stress distribution sections further provide a strength gradient with respect to tensile and compressive loading.
Again, the tensile and compressive strengths of the coupling decrease from the comparatively rigid cylindrical sections to the thin-walled ends.
At the thin-walled ends, the compressive and tensile strengths of the coupling are less than those of the tubing with which the coupling is to be employed.
The collars located outwardly of the stress distribution sections have a transverse wall thickness which is substantially greater than the thin-walled ends adjacent thereto