Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1994-02-28
1995-03-21
Nimmo, Morris H.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 35C, 174 36, 174 74R, 174DIG8, 439610, H02G 1504
Patent
active
053998081
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the termination of screened electrical cables to electrical connectors, in particular to terminations which are enclosed by means of dimensionally recoverable articles, and especially by means of dimensionally heat-recoverable articles.
A heat-recoverable article is an article 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 by 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 and 3,086,242. 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.
Dimensionally recoverable moulded articles have been widely employed for enclosing the termination of screened electrical cables to electrical connectors for example as part of an electrical harness. If the cable is screened against electromagnetic interference it may be desirable to employ a recoverable article that includes an electrical screen in order to provide continuity of screening between the connector and the screen of the cable. One such article is described in British Patent Specification No. 2,113,022 A, although other forms of recoverable articles that include screens are available. Recently it has been proposed to supply arrangements in which the recoverable articles are partially recovered onto a coupling element, for example a spin-coupling adaptor, of the electrical connector so that one end of the arrangement can be engaged with the connector by screwing, and only at the other end must an adhesive bond be formed by the customer, with the result that the screening performance of the terminated is improved. Typically the connector and the coupling element will be formed from a metal, for example aluminium that has a different metal coating thereon, eg. cadmium or a zinc-cobalt alloy, followed by a conductive passivate layer, for example a chromate passivate layer formed by immersing the coupling element in a chromate passivating agent. In the case of cadmium plated articles this chromate passivate layer gives the articles a characteristic "olive drab" appearance.
Although such arrangement perform well in practice, we have found that extended storage of the arrangements particularly at elevated temperatures can cause the resistance of the bond between the screen of the dimensionally recoverable article and the coupling member to increase. This increase in resistance can cause problems in determining the quality of the adhesive bond between recoverable article and the coupling member during manufacture or between the recoverable article and the cable screen during termination of the cable because this is normally tested electrically by measuring the dc resistance across the adhesive bond, and any drift of the resistance value removes any reference value against which the quality of the bond can be judged.
According to the present invention, there is provided an arrangement for enclosing the termination of a screened electrical cable to an electrical connector, which comprises a coupling element that is intended to engage the electrical connector and which is formed from a metal having a conductive passivate layer thereon, and a dimensionally recoverable article for enclosing the termination after recovery onto the cable, which article includes an electrical screen and is partially recovered into
REFERENCES:
patent: 4433206 (1984-02-01), Lewis
patent: 4467002 (1984-08-01), Crofts
patent: 4766267 (1988-08-01), Gray et al.
patent: 4896000 (1990-01-01), Procter et al.
patent: 5098753 (1992-03-01), Gregory et al.
Carter Richard
Collett Derrick S.
Grover Adam C. S.
Burkard Herbert G.
Nimmo Morris H.
Novack Sheri M.
Raychem Limited
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