Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1992-12-16
1994-06-21
Nimmo, Morris H.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 77R, 174 84R, 174DIG8, H02G 1508
Patent
active
053229720
DESCRIPTION:
BRIEF SUMMARY
This invention relates to dimensionally recoverable articles and especially to the use of such articles for the insulation and/or protection of elongate objects such as cable harnesses.
Dimensionally recoverable articles, especially heat-shrinkable articles, are now widely used in many areas where insulation, sealing and encapsulation are required. 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 there 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 3,957,372. 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 performed dimensionally heat stable article is deformed to a dimensionally heat unstable form in a separate stage.
In other articles, as described, for example, in British Patent 1,440,524, and elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating, weakens and thus allows the elastomeric member to recover.
In certain circumstances it is necessary to enclose a branch in an electrical cable, in which case a clip may be employed to bifurcate the dimensionally recoverable article into two (or more) outlets for the cable, a number of such clips being described in UK patent specification No. 1,604,981. However, one problem that has been encountered with the use of clips in such arrangements is that, as the sleeve recovers, the clip can attempt to slide off the end of the sleeve due to the recovery forces in the sleeve, this phenomenon being referred to in the art as "milking off". Although a number of means have been provided according to the prior art for preventing the clip milking off in this way, they have been employed in arrangements designed for use with telecommunication cables and are not applicable for use with smaller cables and branch-offs, such as employed in electrical wiring harnesses, especially those intended for use in a high temperature sealed for environment, e.g. for military use. In contrast with branch-offs employed for telecommunications, these branch-offs are often subjected to prolonged periods in use during which the temperature rises above the recovery temperature of the sleeve so that the clip is therefore again subjected to the "milking off" forces, sometimes on a continual basis, and often in the presence of vibration.
According to one aspect, the present invention provides an arrangement for enclosing a branch-off between a pair of elongate bodies, which comprises a dimensionally recoverable sleeve which can surround the branch-off, and a clip having a pair of legs that can be positioned about opposed walls of the sleeve to divide the sleeve into channels for the bodies, the sleeve having a transversely extending rib in the region of an end thereof and the clip having a profile such that it can be pushed onto the end of the sleeve and be retained on the sleeve by engagement of the rib.
The clip may have any of a number of configurations. For example, in one type of clip in which it is of unitary form the legs are separated from one another along their length by spacing that increases in the region of the clip where the legs are joined together in order to accommodate the rib. For example, the spacing between the legs of the clip may have a substantially keyhole profile which has an enlarged circular region for accommodating the rib. The clip may be formed from wire or otherwise have a configuration in which the legs are of generally constant thickne
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Barrat Alan
Fitch Anthony R. L.
Miles Graham
Burkard Herbert G.
Nimmo Morris H.
Novack Sheri M.
Raychem Limited
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