Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1992-09-18
1994-05-03
Nimmo, Morris H.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 84R, 174DIG8, H01R 422
Patent
active
053089243
DESCRIPTION:
BRIEF SUMMARY
This invention relates to devices for forming solder connections between electrical conductors, and, in particular, relates to such devices that are dimen-sionally heat-recoverable.
BACKGROUND OF THE INVENTION
Heat-recoverable articles are articles the dimensional configuration of which may be made substantially to change when subjected to heat treatment.
Usually these articles recover, on heating, towards an original shape from which they have previously been deformed but the term "heat-recoverable", as used herein, also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.
In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in U.S. Pat. Nos. 2,027,962; 3,086,242 and 3,597,372. As is made clear in, for example, U.S. Pat. No. 2,027,962, the original dimensionally heat-stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in other applications, a preformed dimensionally heat-stable article is deformed to a dimensionally heat-unstable form in a separate stage.
In the production of heat-recoverable articles, the polymeric material may be cross-linked at any stage in the production of the article that will enhance the desired dimensional recoverability. One manner of producing a heat-recoverable article comprises shaping the polymeric material into the desired heat-stable form, subsequently cross-linking the polymeric material, heating the article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, deforming the article and cooling the article whilst in the deformed state so that the deformed state of the article is retained. In use, since the deformed state of the article is heat-unstable, application of heat will cause the article to assume its original heat-stable shape.
Heat-recoverable articles have become widely used for forming solder connections between electrical conductors in view of the ease of forming the connection and the quality of the connection so formed.
For such applications the article, usually in the form of a sleeve, contains a quantity of solder for forming the electrical connection and a pair of fusible inserts for sealing the connection. These articles are described for example in U.S. Pat. Nos. 3,243,211, 4,282,396 and 4,283,596, the disclosures of which are incorporated herein by reference, and are sold by Raychem Corporation, Menlo Park, Calif. under the trade mark "SOLDER SLEEVE".
Such heat-recoverable articles may be used for forming a stub splice, between a pair of wires, in which case both wires are inserted into one end of the sleeve, and the sleeve is then recovered. The devices are usually manufactured with a fusible polymeric sealing ring in the region of each end of the sleeve to provide a seal when the sleeve is recovered about the conductors. Some devices, for example, as described in European Patent Application No. 159,945 are provided with a cylindrical insert in one end of the device which will act as a seal. We have found, however, that the articles employed in the prior art suffer from a number of disadvantages. For example, when the article contains a ring-shaped seal, the seal must be completely melted during recovery of the article so that it will act as a plug. Such a degree of heating is not only time consuming when large quantities of articles are to be installed but also runs risk that the article will be overheated which may cause the article itself or electrical insulation of the conductors to be damaged, or may cause the formation of a poor joint due to migration of the solder. In addition, when the insert is fused it will tend to flow along the sleeve, both towards the centre of the sleeve and out of the end of the sleeve. This fusion of the insert prevents the insert
REFERENCES:
patent: 3396460 (1968-08-01), Wetmore
patent: 4304959 (1981-12-01), Vidakovits et al.
patent: 4504699 (1985-03-01), Dones et al.
patent: 4654473 (1987-03-01), Roux et al.
patent: 4687280 (1987-08-01), Toy et al.
patent: 4722471 (1988-02-01), Gray et al.
patent: 4806402 (1989-02-01), Vidakovits
Burkard Herbert G.
Nimmo Morris H.
Novack Sheri M.
Raychem SA
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