US 5,328,210 AGranted

Polyolefin coupler for joining polyolefin pipes

AssigneeBritish Gas Corporation

InventorsTrevor G. Stafford, Lindsay Ewing

Life of this patent

Estimating the term…

Loading patent…

Abstract

A coupler 10 consists of a length of cross-linked polyethylene pipe having a spiral groove 16 cut in its outer surface and another spiral groove cut in its inner surface. A heating element 18 is wound in the groove. The coupler is expanded mechanically so as to have an easy fit over the ends of polyethylene pipes 12, 14. The heater element 18 is energized and the coupler shrinks and forms fusion welded joints between itself and the pipes. No preparation of the pipe ends is necessary because the serrated inner surface cuts through the oxidized skin and bonds to material beneath the skin. The coupler is especially advantageous in large sizes of 500 mm or above. Instead of an electric heater, radiant energy, e.g. infra red or light is used to heat the coupler. For example, an array of reflector lamps can be used circumferentially located around the coupler.

Claims7

Dependent claims

A coupler joining pipes of non-cross-linked polyolefin material comprising an open-ended hollow body of non-conductive cross-linked polyolefin material, said hollow body having an inner surface extending between the open ends and having a heat shrink memory capability which has been radially expanded so that before heating said coupler inner surface;

has a first least inner diameter which accommodates outer surfaces of said pipes with a clearance and after heating said coupler has shrunk and said inner surface has a second least inner diameter which is less than said first least inner diameter and which is less than an outer diameter of said pipes, and said inner surface which has said second least inner diameter has entered said outer surfaces of said pipes and has formed a welded joint with the polyolefin material of each said pipe underlying said outer surfaces and said outer surfaces exhibiting upset of said polyolefin material of said pipes.

Dependencies are inferred from the claim text.

Facts

Application: 07/873,270Filed 24 Apr 1992
Priority: GB 910912324 Apr 1991
Granted: 12 Jul 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification46 codes

B29C 66/7373
Characterised by the state of the material of the parts to be joined: joining soiled or oxidised materials
B29C 37/0082
Measures or configurations for obtaining anchoring effects in the contact areas between layers: mechanical anchoring
B29C 61/0608
Making preforms having internal stresses, e.g. plastic memory: characterised by the configuration or structure of the preforms
B29C 61/0625
Characterised by the configuration or structure of the preforms: preforms comprising incorporated or associated heating means