US 5,296,073 AGranted

Method of forming a welded joint between polyolefinic members

AssigneeBritish Gas Corporation

InventorsTrevor G. Stafford, Andrew Smart

Life of this patent

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Abstract

A polyethylene pipe 10 is joined by a welded joint to a cross-linked polyethylene coupler 14 which has been expanded to make the coupler heat recoverable. Radiant energy (eg light in the visible spectrum or infra-red light) illuminates the outer surface of the coupler 14 supplied by an array of 15OW reflector lamps 20. The coupler 14 shrinks and is forced into engagement with the pipe 10 and the pipe 12 to join the pipes. A fusion welded joint is formed between the coupler 14 and each pipe, 10, 12. In an alternative a pipe is drawn down and inserted in an aperture through the wall of another pipe. A lamp is inserted in the drawn down pipe and the radiant energy causes the pipe to expand into engagement with the edge of the aperture and to be joined to it by a welded joint (FIG. 2).

Claims6

Dependent claims

A method of making a fusion welded joint comprising the steps of:

providing a hollow first member of non-crosslinked polyolefin material wherein said first member has a wall including a through-aperture defined by an edge surface having an original internal diameter;
providing a hollow second member of cross-linked polyolefin material having an end portion which has been drawn down so that said second member is heat recoverable, inserting said end portion of said second member in said through-aperture in said first member wherein, before heating, said end portion of said second member has an outside diameter which is less than said original internal diameter of said through-aperture;
inserting a source of electromagnetic radiation into said end portion of said second member;
and
heating through said end portion with said source so that said end portion recovers outwardly into contact with said edge surface and so that polyolefin material of said fist member is upset at margins of said through-aperture, and while said end portion is recovering outwardly, said heating being of sufficient duration to ensure that a fusion welded joint is formed between said end portion of said second member and said first member.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/873,424Filed 24 Apr 1992
Priority: GB 91 08934.224 Apr 1991
Granted: 22 Mar 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification29 codes

B29C 66/91218
With special temperature measurement means or methods: using colour change, e.g. using separate colour indicators
B29C 65/14
By heating, with or without pressure: using wave energy , i.e. electromagnetic radiation, or particle radiation
B29C 65/1435
Characterised by the way of heating the interface: at least passing through one of the parts to be joined, i.e. transmission welding
B29C 65/1467
Making use of several radiators: at the same time, i.e. simultaneous welding