Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1996-12-27
1999-03-30
Ball, Michael W.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156188, 1562722, 1563099, B29D 2300, B28B 2164
Patent
active
058883312
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to methods of joining bodies of thermoplastic material.
PRIOR ART
British patent specification No.GB-A-1147477 discloses a method of causing a heat-recoverable article to recover, the article comprising a tubular sleeve of a material having the property of elastic memory and a fusible insert positioned within the sleeve, which comprises irradiating the sleeve and the insert with light energy, the material and the wavelength band of the energy being such that the material absorbs a fraction of the energy and transmits the remainder to the insert, the transmitted energy being sufficient to raise the insert to its fusing temperature and the fraction absorbed by the material being sufficient to raise the material to its recovery temperature.
The fusible insert is a solder insert composed of 63% tin and 37% lead and the sleeve was cross-linked polymeric material having elastic memory. On heating, the sleeve recovered and shrank and firmly gripped the electrical connectors which the sleeve encircled while the solder melted and flowed and formed a soldered connection between the electrical conductors.
The specification states that: " . . . where the - - - sleeve itself is transparent to infra-red radiation, an absorber can be added to it, for example, carbon black . . . can be added to polyethylene".
The specification was not concerned to join two bodies together by a fusion weld.
The aim of the method described in GB-A-1147477, apart from melting the solder insert, was to cause the sleeve to absorb a sufficiently large fraction of the radiation to raise the material to its recovery temperature. The specification states that the sleeve was heated for 0.75 seconds and reached its recovery temperature of 347.degree. F. (175.degree. C.).
SUMMARY OF THE INVENTION
The aim of the present invention is to join bodies of thermoplastic material, by means of fusion welding using radiation in the near infra-red region.
The invention is particularly, though not exclusively, concerned with joining layers of reinforcement to a pipe. Reinforced thermoplastic pipe can be manufactured by applying layers of fibre reinforced thermoplastic tape or film onto the pipe. The tapes are wound on the pipe in pairs, the two tapes in a pair being of opposite hand to balance the torsional forces when the pipe is conveying a product subjected to pressure. Each tape is wound under tension and the applied tension holds the tape and the pipe together in order to ensure that a fusion welded joint is established between them when they are subsequently heated by irradiation. It will be understood that the first tape will be applied directly to the pipe. The second tape will be applied on top of the first tape and the tension in the second tape will provide the force required to urge the second tape, and the underlying first tape, together in order to effect a fusion welded joint between them.
If necessary, a second pair of tapes can be wound on top of the first pair of tapes and, if necessary, further pairs of tapes can be wound on top of those.
Typically, each tape is composed of polyethylene and contains a number of reinforcing fibres extending lengthwise of the tape, the fibres being distributed across the width of the tape. Each fibre may be composed of a large number of fine filaments, for example, of aramid material.
In another application, the invention is used to join a tape or tapes containing reinforcement to a pipe, the tape and reinforcement extending longitudinally along the pipe. In this application, the reinforcement is not reinforcing the pipe in the radial sense, to resist internal pressure, but instead is reinforcing the pipe to resist longitudinal forces which may be exerted upon the pipe. For example, if a very long length of thermoplastic pipe is required to be pulled into a host metallic pipe in order to provide resistance to corrosion, for example, very great tensile forces would arise in the thermoplastic pipe, which may cause it to deform and/or break.
The invention is not l
REFERENCES:
patent: 2723705 (1955-11-01), Collins
patent: 4010054 (1977-03-01), Bradt
patent: 4419304 (1983-12-01), Ficke et al.
patent: 4898637 (1990-02-01), Starlinger-Huemer
patent: 5177340 (1993-01-01), Zaffiro
Ball Michael W.
BG plc
Yao Sam Chuan
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