Composite Sealing Gasket and Process for Belling Plastic Pipe

Abstract

An sealing gasket is shown for use in forming joints of plastic pipe. The gasket is formed as a composite elastomeric body with a leading region formed of a thermoplastic elastomer material and with a trailing region formed of a synthetic plastic material. The gasket body has an outer circumferential region provided with a series of recessed pocket which give it a scallop-like appearance. The relatively harder plastic region of the gasket body deforms the associated pipe socket end during manufacture of the pipe end, whereby the gasket is integrally locked within an internal pipe groove in the pipe socket end upon completion of the pipe belling operation.

1 . A pipe sealing gasket designed for receipt within a groove provided within a socket end of a thermoplastic pipe for sealing engagement and forming a pipe joint with a mating male pipe having an exterior pipe surface, the gasket comprising:
 a ring shaped composite elastomeric body which, when viewed in cross section, has a leading region formed of a thermoplastic elastomer material and which has a trailing region formed of a synthetic plastic material, the leading region having an outer surface and an inner primary sealing surface which forms a seal with the exterior surface of the mating male pipe when the mating male pipe is inserted within the socket end of the thermoplastic pipe to form a pipe joint; and   wherein the trailing body region of the gasket has a series of recessed pockets formed therein which provide a scallop-like pattern on the outer surface of the trailing region of the gasket body, the recessed pockets being located at evenly spaced locations about an outer circumferential region of the gasket body, and wherein the outer circumferential region of the gasket body contacts the groove provided within the socket end of a thermoplastic pipe during pipe belling operations as the socket end is heated to thereby deform the socket end and integrally lock the gasket body within the socket end during the belling operation.   
   
   
       2 . The gasket of  claim 1 , wherein the contact between the gasket body and the socket end of the thermoplastic pipe during the belling operation structurally integrates the gasket body with the pipe socket end so that the trailing region of the gasket body is no longer required to act as a discrete structural member in the resulting pipe joint. 
   
   
       3 . The gasket of  claim 1 , wherein the thermoplastic elastomer material is selected from the group consisting of TPE's and TPV's. 
   
   
       4 . The gasket of  claim 1 , wherein the synthetic plastic material is a polyolefin material. 
   
   
       5 . The gasket of  claim 1 , wherein the leading region of the ring shaped composite elastomeric body has an outer surface and an inner primary compression sealing surface which forms a compression seal with the exterior surface of the mating male pipe when the mating male pipe is inserted within the socket end of the thermoplastic pipe to form a pipe joint. 
   
   
       6 . A method of forming a pipe joint using a pipe sealing gasket designed for receipt within a groove provided within a female socket end of a first section of pipe for forming a seal between an internal surface of the female socket end and a male spigot end of a mating second pipe section, the method comprising the steps of:
 installing a sealing gasket within the groove provided within the female socket end of the first pipe section, the sealing gasket being formed as a ring shaped composite elastomeric body which, when viewed in cross section, has a leading region formed of a thermoplastic elastomer material and which has a trailing region formed of a synthetic plastic material, the leading region having an outer surface and an inner primary compression sealing surface which forms a compression seal with the exterior surface of the mating male pipe when the mating male pipe is inserted within the socket end of the thermoplastic pipe to form a pipe joint;   wherein the trailing body region of the gasket has a series of recessed pockets formed therein which provide a scallop-like pattern on the outer surface of the trailing region of the gasket body, and wherein the outer circumferential region of the gasket body contacts the groove provided within the socket end of a thermoplastic pipe during pipe belling operations as the socket end is heated to thereby deform the socket end and integrally lock the gasket body within the socket end during the belling operation, wherein the contact between the gasket body and the socket end of the thermoplastic pipe during the belling operation structurally integrates the gasket body with the pipe socket end so that the trailing region of the gasket body is no longer required to act as a discrete structural member in the resulting pipe joint;   installing the spigot end of one thermoplastic pipe section within the socket end of a second pipe section to form a pipe joint.   
   
   
       7 . The method of  claim 6 , wherein the thermoplastic elastomer material is selected from the group consisting of TPE's and TPV's. 
   
   
       8 . The method of  claim 7 , wherein the synthetic plastic material is a polyolefin material. 
   
   
       9 . A method of installing a gasket in a socket end of a thermoplastic pipe which is used to form a pipe joint, the method comprising the steps of:
 providing a mandrel with an inner end and an outer end and having an outer working surface;   installing a gasket at a first circumferential position on the outer working surface;   heating a socket end of the thermoplastic pipe; forcing the heated socket end of the thermoplastic pipe over the working surface of the mandrel and over the gasket and backup collar, whereby the heated socket end of the thermoplastic pipe flows over the gasket to form a retention groove for retaining the gasket;   cooling the heated socket end of the thermoplastic pipe;   retracting the cooled socket end of the thermoplastic pipe and the retained gasket from the working surface of the mandrel;   the sealing gasket being formed as a ring shaped composite elastomeric body which, when viewed in cross section, has a leading region formed of a thermoplastic elastomer material and which has a trailing region formed of a synthetic plastic material, the leading region having an outer surface and an inner primary compression sealing surface which forms a compression seal with the exterior surface of the mating male pipe when the mating male pipe is inserted within the socket end of the thermoplastic pipe to form a pipe joint;   wherein the first circumferential region provided on the working surface of the mandrel comprises a circumferential groove having opposing sidewalls, and wherein the gasket body is seated within the circumferential groove so that the thermoplastic pipe is forced over the trailing region of the gasket body and then over the leading region thereof, contact with the trailing region of the gasket body acting to deform the bell pipe end and integrally lock the gasket body within the subsequently formed retention groove in the pipe socket end.   
   
   
       10 . The method of  claim 9 , further comprising the steps of:
 providing a backup collar at a second circumferential location on the mandrel, the backup collar having an exposed lip portion which initially abuts the gasket;   wherein the backup collar is retracted once the heated thermoplastic pipe end is forced over the forming mandrel and the gasket.   
   
   
       11 . The method of  claim 10 , further comprising the step of applying a vacuum or positive external pressure to the heated, socket end of the thermoplastic pipe after the pipe has been forced over the working surface of the gasket and mandrel to thereby force the heated, socket end to contract about the mandrel and gasket. 
   
   
       12 . The method of  claim 11 , wherein the heated thermoplastic pipe is cooled by water or air after the mandrel is retracted.