Extruded pipe coupling and method and apparatus for forming

Claim 1

The method of simultaneously forming a pair of back-to-back bells from a single piece of extruded pipe stock to thereby form a coupling, comprising: a. heating to plasticity an entire section of extruded thermoplastic pipe stock; b. enclosing the exterior of the entire pipe section in a mold having the shape of the finished coupling bells; c. simultaneously expanding two end portions of said stock by separating split mandrel elements inserted in both ends of said stock; and d. simultaneously thickening portions of said stock adjacent two ends thereof by axially compressing the entire section of pipe stock while confining it between said mold and said mandrel elements; thereby forming a coupling having a pair of bells opening outwardly on each end.

Claim 2

The method of simultaneously forming a pair of back-to-back bells from a single piece of extruded pipe stock to thereby form a coupling, comprising: a. heating to plasticity an entire section of extruded thermoplastic pipe stock; b. enclosing the exterior of the entire pipe section in a mold having the shape of the finished coupling bells; c. simultaneously expanding two end portions of said stock by separating split mandrel elements inserted in both ends of said stock; and d. simultaneously thickening portions of said stock adjacent two ends thereof by axially compressing the entire section of pipe stock while confining it between said mold and said mandrel elements; thereby forming a coupling having a pair of bells opening outwardly on each end.

Claim 5

A method for producing a plastic pipe coupling from relatively incompressible extruded thermoplastic pipe or tube stock wherein all the extruded thermoplastic pipe or tube stock is reshaped and its mass redistributed to simultaneously form two back-to-back socket portions joined near the middle of the coupling in a constriction of the inner and outer diameters with each said socket portion containing an annular groove with inside diameter greater than the inside diameter of the socket portions and outside diameter greater than the outside diameter of the socket portions, in such a manner that the wall thickness of any cross section along its length is maintained at a fixed ratio to the outside diameter of that cross section comprised of: a. heating to plasticity an entire piece of extruded thermoplastic stock; b. enclosing the entire piece of extruded thermoplastic stock in a mold; c. simultaneously expanding two end portions of said stock by separating split mandrel elements inserted in both ends of said stock; and d. simultaneously thickening said stock adjacent two ends thereof by axially compressing the entire section of pipe stock while confining it between said mold and said mandrel elements; thereby forming a coupling having a pair of bells opening outwardly on each end.

Claim 6

A method for producing a plastic pipe coupling from relatively incompressible extruded thermoplastic pipe or tube stock wherein all the extruded thermoplastic pipe or tube stock is reshaped and its mass redistributed to simultaneously form two back-to-back socket portions joined near the middle of the coupling in a constriction of the inner and outer diameters with each said socket portion containing an annular groove with inside diameter greater than the inside diameter of the socket portions and outside diameter greater than the outside diameter of the socket portions, in such a manner that the wall thickness of any cross section along its length is maintained at a fixed ratio to the outside diameter of that cross section comprised of: a. heating to plasticity an entire piece of extruded thermoplastic stock; b. enclosing the entire piece of extruded thermoplastic stock in a mold; c. simultaneously expanding two end portions of said stock by separating split mandrel elements inserted in both ends of said stock; and d. simultaneously thickening said stock adjacent two ends thereof by axially compressing the entire section of pipe stock while confining it between said mold and said mandrel elements; thereby forming a coupling having a pair of bells opening outwardly on each end.