CA1242773A - Protection of cable splice - Google Patents

Protection of cable splice

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Publication number
CA1242773A
CA1242773A CA000490874A CA490874A CA1242773A CA 1242773 A CA1242773 A CA 1242773A CA 000490874 A CA000490874 A CA 000490874A CA 490874 A CA490874 A CA 490874A CA 1242773 A CA1242773 A CA 1242773A
Authority
CA
Canada
Prior art keywords
splice
closure
enclosed area
pressure
liquid sealant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000490874A
Other languages
French (fr)
Inventor
Stephen H. Diaz
Christian A.M. Debbaut
William H. Humphries
Alvah A. Lawrence
Gerald L. Shimirak
Glen W. Ragland
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raychem Corp
Original Assignee
Raychem Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Raychem Corp filed Critical Raychem Corp
Application granted granted Critical
Publication of CA1242773A publication Critical patent/CA1242773A/en
Expired legal-status Critical Current

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  • Processing Of Terminals (AREA)
  • Cable Accessories (AREA)

Abstract

S P E C I F I C A T I O N
PROTECTION OF CABLE SPLICE
Stephen H. Diaz Christian A. M. Debbaut William H. Humphries Alvah A. Lawrence Glen W. Ragland Gerald L. Shimirak Abstract A splice between two multiconductor cables is protected from ingress of water by a closure which is filled with a sealant which is pressurized by a bladder inside the closure to a pressure sufficient to force the sealant into the interstices of the splice and the interstices between the conductors in the cable, and the pressure is maintained by the bladder until the sealant cures or hardens.

Description

-2- MPO978-USl Background of the Invention This invention relates to protecting a splice of multiconductor electrical cables from the ingress of water.
Of particular interest are communication cables, such as telephone cables.

The multiconductor communications cables usually comprise a core containing a plurality of individually insulated wire conductors surrounded by an outer sheath.
The cable core may contain a few pairs of conductors up to several hundreds or even thousands of pairs of conductors.
The outer sheath of the cable usually is a plastic jacket surrounding a metal shield~ Additional inner polymeric layers may be present. The cables are usually referered to as "filled" cables because the cable is usually filled with a filling compound such as a grease or`petroleum jelly which helps prevent the ingress of water into the cable.

When two or more of the cables are spliced to~ether, the jacket and oth~r layers of the cable are removed near the end of the cable to expose the individual insulated conductors which are then individually connected to the conductors from the other cable or cables. After co~ple-tion of the splice the entire splice area must be protected from ingress of water. Various devices and methods have been used for protection of such splices such as U.S.
Patent 3,361,605 to Gilbert, U.S. Patent 3,895,180 to Plummer, and U.S. Patent 3,992,569 to Hankins et al.
Plummer and Hankins are typical examples of methods and apparatus used to protect cable splices of the type referred to above and are sometimes referred to as "buried splice closures." These types of cables are commonly used underground and the splices must be protected to prevent ingress of water when they are burisd underground.

, "

~2~ 3
-3- MPO978-USl It is generally recognized that one of the paths through which water may enter the splice area and da~age the individual spliced conductors by corrosion or short circuit is by migration through the interior of one or more of the cables spliced. 5ince such water migration occurs in the "filled" cables, it is necessary to provide splice protection method and apparatus to prevent water from entering the splice area from any path, including through the interior core of the cable. U.S. Patent 4,466,843 to Shimirak recognized the importance of applying pressure to the liquid sealant while the liquid sealant cures to form a water impenetrable seal.

The liquid sealants used to protect splices of the type referred to herein are generally curable liquid polymer systems which comprise a pre-polymer and a curing agent or hardener which can be mixed together and poured into the splice enclosure and allowed to cure.
Particularly uqeful curable liquid sealants are the two-part polyurethane system~. The sealants normally used solidify to a gel-like consistency, i.e., the solid cured sealant has considerable elasticity to allow the sealant to conform to changes in size or shape of the splice araa due to exQansion or extraction or other mechanical forces acting on the splice area. These sealants are also usually 2S reenterable.-Su~mary of the Invention This invention provides apparatus and methods forencapsulation and protection of a splice of multiconductor electric cable from the ingress of water which are simple in construction and operation. In addition, the efec-
-4- 26775-2~

tiveness of the splice protection provided by this invention is not significantly affected by installer skill.
The invention provides an apparatus for protecting a splice connecting at least two multi-conductor electrical cables from ingress of water which comprises:
(a) a closure for enclosing the splice and forming a seal to the cable jackets thereby forming an enclosed area for the splice and the cable ends; and (b) pressure means comprising a heat expandable material which can be activated by heat or electric current from outside the closure which pressure means i5 inside the enclosed area and capable of applying sufficient pressure -to a liquid sealant in the enclosed area to force the liquid sealant to penetrate into the splice and the interstices between the conductors in the cables.
The invention also provides an assembly comprising (a) a splice connecting at least two multi-conductor electrical cables;
(b) a closure capable of maintaining pressure enclosing the splice and forming a seal to the cable jackets thereby forming an enclosed area for the splice and the cable ends;
(c) sufficient hardenable liquid sealant in the enclosed area to essentially fill the enclosed area; and (d) pressure means positioned inside the enclosed area and capable of applying sufficient pressure to the liquid sealant in the enclosed area to force the liquid sealant to penetrate into J
-4a- 26775-24 the splice and the interstices between the conductors in the cables and capable of being activated and controlled from outside the closure; whereby the splice is protected from ingress of water.
The invention further provides a method of protecting a splice connecting at least two multiconductor electrical cables from ingress of water which comprises:
(a) positioning a closure about the splice and sealing the closure to the cable jackets to form an enclosed area for the splice and the cable ends wherein the closure has an opening for introducing sealant into the enclosed area and a pressure means in the enclosed area for applying pressure to the liquid sealant;
(b) introducing a hardenable liquid sealant into the enclosed area, thereby displacing the air from the enclosed area;
(c) closing the opening; and
-5- MPO978-USl (d) pressurizing the precsure means to a pressure suf-ficient to force the liquid sealant to penetrate into said splice and into the interstices between the conductors in the cable; and te) maintaining said pressure in the enclosed area for a period of time to permit the liquid sealant to harden.

The closure useful in the invention as described above may b,e any conventional closure for cable splices, which is capable of maintaining its structural inteqrity under the pressures generated. Examples of such closures which may be readily adapted for use in the apparatus and method of this invention are the closures in U.S. Patents 3,455,336 to Ellis, 4,135,587 to Diaz, 4,283,239 to Corke et al., 4,468,536 to Van Noten, and in the Hankins et al. U.S.
Patent No. 3,992,569 referred to above. It is generally preferred that the closure be a wraparound type closure, although a sleeve closure is equally effective, but is generally limited to new installations and is not practical in reentry situations. It is also generally preferred to use a heat-recoverable wraparound closure due to the ease of installation and the superior sealing and bonding the cable jackets obtained with the hot-melt adhesives. It may be particularly convenient to use a heat-recoverable wra-paround enclo~ure which is self-recovering through an integral electrical heater.

The pressure means inside the enclosed area may be any pressure means which will exert the required pressure on the liguid sealant inside the closure and which can be activated and controllsd from outside the closure. A pre-ferred method means is a bladder which is connected througha valve to the outside of the closure. The bladder can be ~2~
-6- 26775-24 an elastic or rubber bladder which can be inflated through the valve communicating outside the closure. Other pressure means may be used, such as an expandable foam which expands in response to heat, whereby the heat can be applied to the outside of the closure heating the expandable foam causing it to pressurize the sealant contained within the closure. Alternatively, the heat-expandable foam may have an internal electric heater which may be powered from outside the closure. From the description contained herein, numerous other means will be obvious to one skilled in the art~
The sealants useful in this invention are those sealants which are liquid for some period of time to enable the filling of the closure and the application of the necessary pressure to effect the desired sealing and penetration of the splice, connectors and interstices between the conductors in the cables. Then the sealant should harden by chemical curing or other phenomenon to form a solid. In addition to conventional curing sealants, a non-curable sealant may be used, for example a molten liquid wax which will solidify at normal service temperatures. In the solid form the sealant is preferably somewhat elastic so it will conform to any slight changes in shape of the closure, the splice or the cables through, for example, expansion and contraction by temperature change. Conventional sealants are well known in the art and dis-cussed in the background patents referred herein. The preferred sealants for use in this invention are the conventional two-package urethane sealants, which cure to a gel-like solid which is easily reenterable.
-7- MPO978-USl Brief Description of the Drawinq Figure l illustrate~ a cable splice closure containing a pressure means in accordance with this invention.

Detailed Description of the Invention Reference to Figure l will illustrate the apparatus and methods of this invention. In Fi~ure l cables l and 2 are spliced together and the splice is enclosed by closure 3, which is a conventional heat-recoverable wraparound closure such as disclosed in U.S. Patents 3,455,336 and 4,468,536 and as adapted to hold a pressure of about 20 psig. An opening in filler tube 4 is provided for intro-ducing the liquid sealant into closure 3 and for allowing the air to escape from the closure. A rubber bladder 5 is positioned inside closure 3 and connected through valve 6 to th~ outside of the closure. In reference to Figure 1 it can ~e seen that the cloqure 3 is filled with liquid sealant through opening 4, which is then closed after the closure is filled with the sealant and the air is removed.
Bladder 5 is then inflated through valve 6 by air or other fluid to pressurize the sealant within closure 3. A pre-ferred method for pressurizing the bladder 5 is through compressed alr on a regulator valve set at a preselected pres~ure such as 15 psig. In this manner, when there i~
any movement of the sealant within the cloqure, the regu-lated air pressure automatically compensates and con-sistently maintains the pressure inside the closure at the desired level.

,,i ., t73 -~- MP0978-USl Ex~mple : A sample was prepared for testing using a Western Electric type AFMW, 400 pair, "Flexgel" cable having 24 gauge conductors with PIC insulation. The splice was pre-pared with a 20-inch opening using Western Electric's 710-SBl-25 modular nonfilled connectors and a D-bond clamp tAT-8688 size 2) and a Raychem Type 6 bond bar. The connectors were arranged in two banks in a fold back arrangement. The closure used was an Xaga 2000 from Raychem Corporation~ The sealant used was a D-encapsulant, which is two-part ureth~ne curable sealant commercially available from Caschem Corporation and typically used in poured-in-place splice closures. The encapsulant was cooled to zero degrees centigrade in this test to assure sufficient time for filling the closure and removing the air before the encapsulant began to cure. After the clo-sure was filled and the air removed and the opening in the closure sealed, the bladder inside the closure, which was constructed from a rubber bicycle tube sealed at two ends and connected to the outside of the closure through a v~lve stem, was pressurized with compressed air under a regulator vaLve set at 15 psig. The pressure was held at 15 psig for two hours and the air supply was shut off. Two days later the pressure stood at 12 psig. The closure was then sub-jected to a waterhead test on the core of the cable. Table1 shows the result of this test in terms of the number of pairs of conductor failures out of the 400 pairs and the retained pressure inside the closure is also listed in the table~
~ rr~c.

~2~t~
-9- MP0978-USl Table I

. . Pairs of Time Pressure (psig)Conductors Failed . .._ _ before waterhead test 12.03 .

after 4 hours at 4-foot waterhead 12.32 O
, ater 3 day.s at 4-foot waterhead 11.63 O
. ... ~ ~
after 1 day at
8-foot waterhead 11.67 O
_ after 2 days at 8-foot waterhead 11.71 O
_ ... .___ ,~ .
ater 3 days at 8-foot waterhead 11.25

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for protecting a splice connecting at least two multi-conductor electrical cables from ingress of water which comprises: (a) a closure for enclosing the splice and forming a seal to the cable jackets thereby forming an enclosed area for the splice and the cable ends, and (b) pressure means comprising a heat expandable material which can be activated by heat or elec-tric current from outside the closure which pressure means is in-side the enclosed area and capable of applying sufficient pressure to a liquid sealant in the enclosed area to force the liquid sealant to penetrate into the splice and the interstices between the conductors in the cables.
2. An assembly comprising: (a) a splice connecting at least two multi-conductor electrical cables; (b) a closure capable of maintaining pressure enclosing the splice and forming a seal to the cable jackets thereby forming an enclosed area for the splice and the cable ends; (c) sufficient hardenable liquid sealant in the enclosed area to essentially fill the enclosed area; and (d) pressure means positioned inside the enclosed area and capable of applying sufficient pressure to the liquid sealant in the enclosed area to force the liquid sealant to penetrate into the splice and the interstices between the conductors in the cables and capable of being activated and controlled from outside the closure; whereby the splice is protected from ingress of water.
3. An assembly according to claim 2, wherein the pressure means is a heat expandable material which can be activated by heat or electric current from outside the closure.
4. An assembly according to claim 2 wherein -the pressure means is a flexible bladder which can be pressurized with a fluid from outside the closure.
5. A method for protecting a splice connecting at least two multi-conductor electrical cables from ingress of water which com-prises: (a) positioning a closure about the splice and sealing the closure to the cable jackets to form an enclosed area for the splice and the cable ends wherein the closure has an opening for introducing sealant into the enclosed area and a pressure means in the enclosed area for applying pressure to the liquid sealant; (b) introducing a hardenable liquid sealant into the enclosed area thereby displacing the air from the enclosed area; (c) closing the opening; and (d) pressurizing the pressure means to a pressure suf-ficient to force the liquid sealant to penetrate into said splice and into the interstices between the conductors in the cables; and (e) maintaining said pressure in the enclosed area for a period of time to permit the liquid sealant to harden.
CA000490874A 1984-09-18 1985-09-17 Protection of cable splice Expired CA1242773A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US65235984A 1984-09-18 1984-09-18
US652,359 1984-09-18

Publications (1)

Publication Number Publication Date
CA1242773A true CA1242773A (en) 1988-10-04

Family

ID=24616542

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000490874A Expired CA1242773A (en) 1984-09-18 1985-09-17 Protection of cable splice

Country Status (1)

Country Link
CA (1) CA1242773A (en)

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