Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1996-05-31
1998-08-11
Kincaid, Kristine L.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 93, 174138G, H02G 15013
Patent
active
057929912
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the formation of an environmental seal around objects such as telecommunications and other cables.
Splicing of cables requires removal of cable jackets in order to expose the underlying conductors for connection. Once the conductors have been connected some sort of seal must be built up across the splice, effectively replacing the removed jacket, in order to protect the otherwise exposed conductors from the environment. The resulting seal, known as a splice case, should have a life-time comparable to that of the cables themselves, commonly 20 or so years. In addition to protecting the conductors from moisture and other environmental contaminants, the splice case must provide some mechanical protection, such as axial pull strength, so that any stresses on the cables are not taken up by the conductor connections. Some cables are pressurized in order to prevent ingress of moisture or to provide a means for detecting and locating leaks, and splice cases joining such cables must, in general, be resistant to pressure-induced creep over their desired life-time. Splice cases must often be installed under unfavourable outdoor conditions and installation must therefore be simple and quick.
It can be seen from these requirements that design of a splice case is not a trivial matter. In recent years heat-shrinkable sleeves, internally coated with a hot melt adhesive, have become widely used for protecting cable splices. They are quick and easy to install and provide the desired environmental and mechanical protection. However, they generally require the use of an open-flame torch for installation which is discouraged in some locations and prohibited in others.
Alternative techniques for forming a seal around cables are disclosed in WO 92/19034 (Raychem), the disclosure of which is incorporated herein by reference. That patent application discloses a flexible hollow sealing member, or bladder, that can be inflated to seal the gap between first and second articles, such as a cable and a duct or splice case housing, and that has a hole directly through a wall or between walls thereof through which hole a tube can be inserted to introduce a pressurizing gas. When the tube is removed the hole is automatically sealed by an internal gel-coated flap. The bladder may be wrapped around the cable to be sealed and then slid along the cable into the duct or splice case housing, and then inflated.
Surprisingly, this technique has been found to be suitable for forming seals having the desired life-time. A difficulty can however arise where the housing, be it a duct or a splice case, is of the so-called wraparound type. This term is well known in the art and means simply that the housing can be installed around an intermediate portion of the cable without access to a free end of the cable. Such a housing will therefore be split, and may comprise two or more "half" shells. The problem arises because the split between the parts of the housing must be sealed if it is not to provide a leak path into the resulting splice case.
Such a split housing may comprise a split or wraparound sleeve that is supported at its ends by disc-shaped end plates. A seal must therefore be made circumferentially around each end plate to the overlying sleeve and also along the longitudinal split in the sleeve. Where these two seals meet is called a triple point and the problem of sealing it has been addressed in U.S. Pat. No. 4,845,314 (Siemens). That patent discloses a cable seal with a wraparound sleeve engaging a pair of split end plates having a sealing system including ring seals on the end plates and a longitudinal sealing element for the slit in the wraparound sleeve. The longitudinal edges of the sleeve have a groove receiving the seal with an inner wall of the groove in the region of the ring seals having a lateral opening or window through which a portion of the longitudinal sealing member can extend to contact the ring seals. Note, however, that no discussion is made of any seal between th
REFERENCES:
patent: 2740825 (1956-04-01), Rifenburg
patent: 3339011 (1967-08-01), Ewers, Jr. et al.
patent: 4245970 (1981-01-01), St. Onge
patent: 4332975 (1982-06-01), Dienes
patent: 5247974 (1993-09-01), Sargent et al.
Burkard Herbert G.
Kincaid Kristine L.
Machtinger Marc D.
N.V. Raychem S.A.
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