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US 4,049,762 AGranted
Method of forming a pipe coupling
AssigneeHarsco Corporation
InventorsPaul D. Martino, Norris H. Barbre
Life of this patent
Estimating the term…
Abstract
A process for making a heavy walled pipe coupling wherein pre-formed thermoplastic pipe stock is heated to a soft pliable condition and blow-molded into a desired configuration. The molding step is accomplished in a mold cavity having openings in opposite ends thereof to receive retractable pistons which expand and seal ends of the pipe before blow air is injected. The coupling produced has an inside diameter which is greater than the outside diameter of the pipe stock blank, has a central stop element, and has spaced receptacles for receiving self-energizing seals to provide increased sealing capability as pressure is increased.
Claims7
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.
4 more elements
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.
2 more elements
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.
2 more elements
Dependencies are inferred from the claim text.