Method of forming a pipe coupling

Claim 1

A method of forming a thermoplastic pipe coupling comprising the steps of: heating a prefabricated thermoplastic tubular member to a soft pliable state; positioning the pliable tubular member in a mold cavity having walls maintained at a temperature to quickly harden a surface of the tubular member moved into contact therewith, the tubular member being positioned such that opposite ends of the tubular member extend beyond ends of the mold cavity; engaging only outer surfaces of the tubular member adjacent ends of the tubular member with mold portions to space walls of the tubular member from a major portion of the surface of walls of the mold cavity; moving seal members into engagement with opposite ends of the tubular member such that force is exerted on surfaces inside the ends of the tubular member to deform outer surfaces of the tubular member into sealing engagement with surfaces adjacent opposite ends of the mold cavity; urging the seal members into sealing engagement with inner surfaces of the tubular member; delivering pressurized fluid to a pressure actuated cylinder connected to the seal members to maintain constant pressure on said seal members to urge the seal members inwardly and to maintain a constant seal with the ends of the tubular members to compensate for the tendency of the wall of the tubular member to contract in length and thickness due to expansion of the diameter of the tubular member and cooling of the wall of the tubular member; and injecting pressurized fluid into the tubular member to urge walls of said tubular member into conformity with surfaces of the mold cavity.

Claim 2

A method of forming a thermoplastic pipe coupling comprising the steps of: heating a prefabricated thermoplastic tubular member to a soft pliable state; positioning the pliable tubular member in a mold cavity having walls maintained at a temperature to quickly harden a surface of the tubular member moved into contact therewith, the tubular member being positioned such that opposite ends of the tubular member extend beyond ends of the mold cavity; engaging only outer surfaces of the tubular member adjacent ends of the tubular member with mold portions to space walls of the tubular member from a major portion of the surface of walls of the mold cavity; moving seal members into engagement with opposite ends of the tubular member such that force is exerted on surfaces inside the ends of the tubular member to deform outer surfaces of the tubular member into sealing engagement with surfaces adjacent opposite ends of the mold cavity; urging the seal members into sealing engagement with inner surfaces of the tubular member; delivering pressurized fluid to a pressure actuated cylinder connected to the seal members to maintain constant pressure on said seal members to urge the seal members inwardly and to maintain a constant seal with the ends of the tubular members to compensate for the tendency of the wall of the tubular member to contract in length and thickness due to expansion of the diameter of the tubular member and cooling of the wall of the tubular member; and injecting pressurized fluid into the tubular member to urge walls of said tubular member into conformity with surfaces of the mold cavity.

Claim 7

A method of forming a thermoplastic pipe coupling comprising the steps of: heating a prefabricated thermoplastic tubular member to a soft pliable state; positioning said tubular member in a mold cavity having walls maintained at a temperature to quickly harden the surface of the tubular member moved into contact therewith; engaging outer surfaces of the tubular member only adjacent ends thereof with mold portions to space a major portion of walls of the tubular member adjacent opposite ends of the mold cavity from walls of the mold cavity; delivering pressurized fluid to a pressure actuated cylinder having a piston rod connected to a pair of seal members such that the seal members are moved into engagement with opposite ends of the tubular member to deform outer surfaces of the tubular member into sealing engagement with surfaces adjacent opposite ends of the mold cavity, such that the seal members are urged into sealing engagement with inner surfaces of the tubular member, and such that constant force is exerted by the pressure actuated cylinder on said seal members to maintain the seal members in a sealing relationship with the ends of the tubular member to compensate for the tendency of the wall of the tubular member to contract in length and thickness due to expansion of the diameter of the tubular member and cooling of the wall thereof; and injecting pressurized fluid into the tubular member into conformity with surfaces of the mold cavity.

Claim 8

A method of forming a thermoplastic pipe coupling comprising the steps of: heating a prefabricated thermoplastic tubular member to a soft pliable state; positioning said tubular member in a mold cavity having walls maintained at a temperature to quickly harden the surface of the tubular member moved into contact therewith; engaging outer surfaces of the tubular member only adjacent ends thereof with mold portions to space a major portion of walls of the tubular member adjacent opposite ends of the mold cavity from walls of the mold cavity; delivering pressurized fluid to a pressure actuated cylinder having a piston rod connected to a pair of seal members such that the seal members are moved into engagement with opposite ends of the tubular member to deform outer surfaces of the tubular member into sealing engagement with surfaces adjacent opposite ends of the mold cavity, such that the seal members are urged into sealing engagement with inner surfaces of the tubular member, and such that constant force is exerted by the pressure actuated cylinder on said seal members to maintain the seal members in a sealing relationship with the ends of the tubular member to compensate for the tendency of the wall of the tubular member to contract in length and thickness due to expansion of the diameter of the tubular member and cooling of the wall thereof; and injecting pressurized fluid into the tubular member into conformity with surfaces of the mold cavity.

Claim 9

A method of forming a pipe coupling comprising the steps of: inserting a preheated thermoplastic tubular member into a mold cavity, the mold cavity having a wall maintained at a temperature below the solidification temperature of the thermoplastic material during the inserting step; supporting the preheated tubular member only adjacent opposite ends of the tubular member and in spaced relation from a major portion of the wall of the mold cavity; moving seal members into engagement with opposite ends of the tubular member such that surfaces on the tubular member are sealingly compressed between the seal members and surfaces adjacent opposite ends of the mold cavity; delivering pressurized fluid through at least one of the seal members to urge walls of the tubular member into engagement with the wall of the mold cavity such that upon conforming to the shape of the wall of the mold cavity the wall of the tubular member is cooled to its solidification temperature; and applying constant fluid pressure to maintain the seal members in sealing engagement with opposite ends of the tubular member while the tubular member is being conformed to the shape of the mold cavity and while the wall of the tubular member is cooling.

Claim 10

A method of forming a pipe coupling comprising the steps of: inserting a preheated thermoplastic tubular member into a mold cavity, the mold cavity having a wall maintained at a temperature below the solidification temperature of the thermoplastic material during the inserting step; supporting the preheated tubular member only adjacent opposite ends of the tubular member and in spaced relation from a major portion of the wall of the mold cavity; moving seal members into engagement with opposite ends of the tubular member such that surfaces on the tubular member are sealingly compressed between the seal members and surfaces adjacent opposite ends of the mold cavity; delivering pressurized fluid through at least one of the seal members to urge walls of the tubular member into engagement with the wall of the mold cavity such that upon conforming to the shape of the wall of the mold cavity the wall of the tubular member is cooled to its solidification temperature; and applying constant fluid pressure to maintain the seal members in sealing engagement with opposite ends of the tubular member while the tubular member is being conformed to the shape of the mold cavity and while the wall of the tubular member is cooling.