Patent ID: 8709318

Claim:
A method of installing a gasket in a socket end of a thermoplastic pipe during a pipe belling operation where the pipe has a female socket end and a outer circumferential lip region, 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; providing an unheated backup collar at a second circumferential location on the mandrel, the unheated backup collar having an exposed lip portion which abuts the gasket and an outer circumferential contact surface which contacts and supports the outer circumferential lip region of the thermoplastic pipe being belled; 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 unheated backup collar, whereby the heated socket end of the thermoplastic pipe flows over the gasket to form a retention groove for retaining the gasket; retracting the unheated backup collar; 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; wherein the outer contact surface of the unheated backup collar is provided with an undulating shape which reduces the surface area of the interface between the outer circumferential lip region of the pipe female socket end and the contact surface area of the unheated backup collar, thereby reducing the coefficient of friction between the unheated backup collar and the outer circumferential lip region of the pipe female socket end and consequently eliminating the tendency of the pipe socket end to buckle or stick to the unheated backup collar.