Compression coupling for service valve

Claim 1

A plastic pipe coupling comprising, a fitting having a plastic body portion with a bore for receiving a plastic pipe, said fitting terminating in an end portion and said fitting bore including an internally threaded portion, said fitting body portion having a recess adjacent said bore internally threaded portion to form an internal shoulder within said fitting, an elastic deformable member positioned in said recess in surrounding relation with the plastic pipe, a plastic nut having a plastic body portion with an internal bore including an internal wedge surface, said nut body portion having an externally threaded portion engageable with said fitting bore internally threaded portion and terminating in an end portion to form a shoulder extending radially outwardly on said nut body portion, said elastic deformable member including an annular gasket having one side abutting said fitting internal shoulder and an opposite side positioned to receive an axially directed force, said gasket being compressed axially between said fitting body portion internal shoulder on said one side and said nut end portion on said opposite side upon advancement of said nut into said fitting bore, said gasket being compressed on the pipe to effect a fluid tight seal around the pipe, a plastic pipe-gripping collar having an external wedge surface complementary to and cooperating with said nut internal wedge surface so that said collar is positioned within said nut internal bore and surrounding the plastic pipe, said collar having an internal wall with a roughened surface for frictionally gripping the plastic pipe, said collar external wedge surface being formed by an enlarged end portion and a reduced end portion, said nut surrounding said collar and said nut end portion extending beyond the end of said collar in said fitting bore, said nut end portion having a bearing surface for applying a compressive force which is transmitted to said gasket opposite side to compress said gasket one side against said fitting internal shoulder, said nut being threadedly advanced upon rotation to a stop point in said fitting bore where said nut body portion shoulder abuts said fitting end portion limiting the compression of said gasket to form a controlled seal around the pipe within said fitting, said nut extending into said fitting bore to said stop point where said nut body portion shoulder abuts said fitting end portion to externally indicate the position of said nut in said fitting to obtain a preselected degree of compression of said gasket by said nut where the degee of compression of the gasket is limited by the abutment of said nut body portion shoulder with said fitting end portion thereby preventing excessive compression of said gasket, said collar roughened surface being urged into frictional engagement with the pipe upon rotation of said nut to retain the pipe within said fitting, and said collar enlarged end portion being removed from compressive relation with said elastic deformable member when said nut is advanced to said stop point such that compressive forces are applied to said elastic deformable member only by said nut end portion.