Composite thread coupling for reinforced pipe

摘要

A pipe joint is provided wherein mating female and male threads are ground or scribed into the ends of the pipes to be joined. At least one of the scribed threads has a paste thread contact molded onto it so that the valley of the contact molded thread is below the crest of the scribed thread. Upon mating of the coupled pipe ends, the contact molded thread surface provides a smooth finish and a relatively low, consistent engagement and disengagement torque. The overlapped crests of the scribed male and female threads provide for mechanical interlock and correspondingly enhanced tensile strength in the joint. The invention is particularly suited to pipes made of resin reinforced with wound filaments, where the scribed threads can be cut shallowly to retain the strength of the body of the pipe and minimize cutting of the wound filaments. In that application, use of the same resin in the pipe material and the contact molded threads eliminates problems with differential thermal expansion in response to temperature changes.