Electricity: conductors and insulators – With fluids or vacuum – With fluid stops
Patent
1988-02-12
1990-11-20
Nimmo, Morris H.
Electricity: conductors and insulators
With fluids or vacuum
With fluid stops
174 77R, 174DIG8, H02G 15013
Patent
active
049720422
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to blocking cables, that is to say, to the provision of a quantity of sealant in a cable in order to prevent the transmission of fluids along the cable.
There are many circumstances in which it is necessary to provide a fluid block in a cable, for example to prevent transmission of water or water vapour along the cable or, in the case of pressurised cables, to limit the extent of depressurisation in the event of damage to the cable. Such cables include electrical cables and harnesses, optical fibre cables and hybrid cables and harnesses that contain both electrical wires and optical fibres (the term "wire" used herein including optical fibres and the term "cable" including harnesses).
A number of cable blocking systems have been proposed. For example a heat-shrinkable sleeve provided with a thick layer of hot-melt adhesive may be used to provide a block for cables having a small number of wires, for example up to 2 wires, but in the case of larger cables having three or more wires the wires are often pushed together during recovery of the sleeve and act as a barrier to prevent the adhesive flowing into the central interstice or interstices in the cable. In addition, in the case of larger cables it is not possible reliably to heat the centre of the cable without damaging the surface of the cable because of the relatively low heat conductivity of the insulating and water blocking materials. Although systems for forming water blocks in larger telecommunication cables exist, such systems are all very expensive and are time consuming to install taking often one half to three quarters of an hour for full installation. In certain instances, however, there is a need to provide a reliable fluid block in cables and harnesses of moderate size where the cost of the block and the time taken to form it are at a premium. One example of such an instance is in the manufacture of electrical harnesses for motor vehicles.
SUMMARY OF THE INVENTION
According to the present invention there is provided a generally flat blocking array for forming a block in a cable against transmission of fluid along the cable, the array having a plurality of passageways extending from one end thereof to the other end thereof for receiving wires and each passageway being capable of receiving one or more wires by insertion of the wires from the side of the passageway, the array being formed from a hot-melt or thermosetting adhesive that has a melting point of not more than 120.degree. C.
A cable or harness may be blocked in a simple manner according to the invention by:
(a) positioning wires of the cable in passageways that extend along a substantially flat blocking array, the blocking array being formed from a fusible polymeric sealant;
(b) positioning a heat-shrinkable covering about the blocking array; and blocking array, recovery of the covering causing the configuration of the assembly to change from one that is substantially flat to one that is generally cylindrical.
Although it is possible to conduct the method according to the invention by inserting the wires into the open ends of the passageways in the blocking array, the passageways are preferably capable of receiving the wire or wires by insertion of the wire or wires from the side of the passageway.
The blocking array according to the invention enables the rapid formation of a fluid block in a cable or harness having three or more wires, especially one having more than 10 wires, for example at least 20 wires, and usually up to about 60 wires. Because the blocking array has a substantially flat configuration, no parts of the array or wires are remote from the surface of the arrangement before recovery of the heatshrinkable covering, with the result that the entire quantity of fusible sealant and all the wire insulation can be heated to the required degree to form an effective seal even though the sealant in the central region of the completed cable block can be a considerable distance from the surface of the cable. It is possible for
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Bradley Paul A.
Hill Alistair F.
Seabourne Judith L.
Burkard Herbert G.
Nimmo Morris H.
Raychem Limited
Rice Edith
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