Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1993-12-03
1995-10-03
Nimmo, Morris H.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 77R, 174 92, H02G 1504
Patent
active
054553911
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a cable seal, and in particular to a telecommunications cable splice case.
Cable splice cases have the following function. Where a cable splice is to be made, cable jackets have to be stripped back from the cable ends in order to connect the internal conductors. Once the conductors have been connected, the environmental protection previously provided by the cable jacket has to be made good across the splice in order to prevent corrosion or other damage of the conductors and connectors. This is done by building a so-called splice case across the splice from intact cable jacket of the incoming cable to intact cable jacket of the outgoing cable.
For many years now such cable splice cases have been made by positioning a heat-shrinkable sleeve, internally-coated with a hot-melt adhesive, around the splice, and heating it. Heat causes the adhesive to become activated and the sleeve to shrink into tight engagement around the incoming and outgoing cables.
A disadvantage of heat-shrinkable sleeves, however, is that an open-flame torch is generally needed to install them and they can be difficult to re-enter (by which is meant removal of the splice case to gain access to the splice without damaging the splice). Effort has recently been directed towards designing a splice case that avoids the need either to heat-shrink a sleeve or to heat-activate an adhesive. Proposals have been made for splice cases etc. that employ gels that can be installed at room temperature.
Where a seal is to be made using a gel or other suitable sealing material some force, generally compression of the sealing material, must be applied to keep the material against the substrate to be sealed. The force should be great enough to overcome any forces, such as a head of water, or mere capillary forces, tending to separate the material from the substrate.
The requirement for a force on a sealing material was recognized in U.S. Pat. No. 4,600,261 (Raychem) which discloses an apparatus and method for protection of electrical contacts. The protection apparatus includes a gel, first means to contain the gel, second means to retain the gel within the first means, and a force means which acts on the first means so that the gel is maintained in compressive contact with the electrical contacts and substantially encapsulates a conductive portion of them. That apparatus is of particular use in sealing a telecommunications terminal block.
Various specific devices for sealing using a gel under compression, within the general idea of U.S. Pat. No. 4,600,261, have been proposed. One such specific idea is disclosed in WO90/05401 (Raychem). In that specification, sealing is provided, at least in some embodiments, by a gel having an elongation of at least 100% and a compression set of 70.degree. C. of less than 30%. The gel is put under compression to seal an annular gap between the cables to be sealed and a surrounding housing. The gel is trapped between two end pieces that form a structural member, one such structural member being provided at each end of a cable splice. A central housing is provided spanning the splice from one of the structural members to the other. The two end pieces (of each member) are forced together to deform the gel between them. The gel is displaced radially to seal between the cables and the structural members, and also between the structural members, and the surrounding housing. The end pieces are forced together by means of a nut and bolt, the bolt carrying a coil compression spring driven by the nut. The force on the end pieces is thus spring loaded. Some displacement of the gel over time can thus occur, with the compressive force being maintained.
Other prior art disclosure of force being applied to a sealing material is made in U.S. Pat. No. 4,859,809 (Raychem), U.S. Pat. No. 4,610,738 (Raychem) and U.S. Pat. No. 4,736,071 (ATT and Bell Laboratories).
A problem may, however, arise with such prior art means for pressurizing a sealing material. In some instances the force applied by a spring and the d
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Demesmaeker Marc
Van Noten Lodewijk C. M.
Vandeputte Filip
Burkard Herbert G.
N.V. Raychem S.A.
Nimmo Morris H.
Zahrt II William D.
Zavell A. Stephen
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