CA1245417A - Protection of cable splice - Google Patents
Protection of cable spliceInfo
- Publication number
- CA1245417A CA1245417A CA000457844A CA457844A CA1245417A CA 1245417 A CA1245417 A CA 1245417A CA 000457844 A CA000457844 A CA 000457844A CA 457844 A CA457844 A CA 457844A CA 1245417 A CA1245417 A CA 1245417A
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- CA
- Canada
- Prior art keywords
- reservoir
- liquid sealant
- splice
- pressure
- liner
- 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.)
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Abstract
ABSTRACT OF THE DISCLOSURE
A splice between at least two multi-wire electric cables is protected from ingress of water by forming a com-pressible reservoir about the splice, the reservoir being formed by a plastic film which is sufficiently strong to support the weight of the liquid sealant and capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant; and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir, filling the reservoir with a curable liquid sealant, compressing the reservoir to force the liquid sealant to penetrate into the interstices between the individual wires of the splice bundle and into the adjacent cable core and maintain-ing the reservoir under compression at least for a time suffi-cient for the sealant to cure.
A splice between at least two multi-wire electric cables is protected from ingress of water by forming a com-pressible reservoir about the splice, the reservoir being formed by a plastic film which is sufficiently strong to support the weight of the liquid sealant and capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant; and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir, filling the reservoir with a curable liquid sealant, compressing the reservoir to force the liquid sealant to penetrate into the interstices between the individual wires of the splice bundle and into the adjacent cable core and maintain-ing the reservoir under compression at least for a time suffi-cient for the sealant to cure.
Description
i2~ 7 The present invention relates -to protectin~ a splice in multi-wire electrical cables, in particular communications cables, from ingress of water into the splice.
Multi-wire electrical cables comprise a core containing a plurality of individual insulated wire conductors, surrounded by an outer sheath. The cable core can contain frcm a few pairs of conductors up to several thousand pairs. The outer sheath generally consists of an outer plastic jacket surrounding a metallic shield.
Additional inner polymeric layer or layers may be present.
To protect the conductors from water, the interstices between the individual wire conductors may be filled with a filling compound, usually a grease based or petroleum jelly. Cables that are so filled are generally referred to as "filled" cables and cables that are not filled are generally referred to as "air core" cables. Air core cables can be pressurized to prevent ingress of water.
When a splice is made in a cable, the outer sheath is removed from the end of the cable. At least some of the individual wire conductors in the core of the cable are joined to conductors of another cable or cables. After completion of the splice, the entire splice area, that is the area of the cables where the sheath has been removed, must be protected. Generally, an enclosure or splice case is placed over the area. A preferred enclosure is a dimensionally recoverable polymeric sleeve, preferably a heat-shrinkable polymeric sleeve.
~.
~2~S~7 An inner protective casing or lining may be pQsitioned about the splice before installation of the sleeve to provide additional mechanical protection. Molded plastic or lead splice cases are also used.
The splice case can be filled with a suitable filling compound to protect the individual wire conductors in the core of the splice (referred to herein as the splice bundle or splice core). Such filling compounds can be curable liquid polymer systems or grease-like materials, generally based on petroleum jelly. Curable liquid polymer systems are ùsed by pouring a curable liquid sealant into a splice case positioned about the splice and allowing it to cure. Particularly useful curable liquid sealants are two-part polyurethane systems comprising a prepolymer and a curing agent or hardener. When cured the filling compound solidifies, preferably to a gel-like consistency, forming a protective layer around the splice.
It has been found that this technique doesn't adequately protect the ~splice from ingress of water, particularly if one of the cables contains 400 pairs or more of wire conductors. Seepage of water into the splice eventually causes electrical failure of the joined conductors.
It has been discovered that a splice in multi-wire electric cables can be protectèd from water ingress if a curable liquid sealant is placed in a flexible reservoir surrounding the splice and subjected to compression ~24~
while it is in the liquid state and maintained under compression for a time sufficient to permit cure of the liquid sealant to its hardened state.
There has been proposed in a brochure of Pirelli General, entitle "Resinwrap Joints" of March, 1964, a procedure for providing synthetic joints for plastic and insulated sheath cables, particularly for joints hav:Lng a considerable free space internally, which is required to be filled with resin, wherein an aluminium polyethylene laminate sheet foil is formed around the joint in envelope fashion, the ends of the envelope are pressed on the sheath and secured with pvc tape, the top of the envelope is formed into a pouring hole, and a specified amount of resin is introduced. The envelope is then compacted by folding and mani-pulating, thus ~orcing the resin fully into the joint, and~inally, when the envelope has been folded down completely to the joint surface, it is taped overall with pvc tape, the pvc tape firstly being an adhesive pvc tape applied without tension, and the joint being compressed with the hands, and then a further layer of pvc tape being applled over the joint with maximum ten-sion. On particularly large joints it is desirable to apply one layer of cotton tape over the first layer of pvc tape very tightly to compress the joint, which is then left on and the final layer of pvc tape applied overall.
However, while such a procedure provides a flexible reservoir and sub~ects it to compression, such a procedure with the use of a reservoir formed from aluminium foil laminate, is subject to a number of disadvantages. In particular, the forma-tion and subsequent manipulation of the flexible reservoir iscumbersome and time consuming and is not readily usable by the craftsmen in the field. In particular, it requires a number of manipulative steps. Further, the aluminium foil on the envelope being compacted by folding and manipulating to force the resin into the joint by squeezing, and subsequently using wrapping tape under tension, particularly using thin film wrapping tape, tends ..
;.
~2~5~7 to wrinkle and form irregular shapes, and further, aluminium has high tensile strength, and thus the crushed and wrinkled alu-minium envelope will tend to puncture and cut the wrapping tape.
Further, the aluminium foil laminate sheet is a relatively expen-sive material.
It has now been found that the use of a plastic film informing the envelope, such as a nylon film, overcomes all the above disadvantages in that it is easy to manipulate, does not require a significant amount of manipulation, and therefore is readily usable by the craftsmen in the field, does not cut the wrapping tape, and is relatively inexpensive. However, it has been further found that a simple plastic film of desirable thick-ness for optimum flexibllity is not sufficiently strong to sup-port the weight of the liquid sealant in the reservoir, and thereservoir will tend to bulge during curing and wrapping, giving the joint an irregular shape which is undesirable, as it is in many cases desirable to enclose the wrapped taped joint in a con-ventional splice case of regular shape to protect it against mechanical damage. It has, however, further been found that this bulging can be avoided by providing a porous liner adhered to the inside surface of the reservoir, which liner does not interfere with the compression of the reservoir, such as a flexible polymeric open-celled foam sheet, or a corrugated rigid plastic sheet.
The present invention provides a method of protecting a splice connecting at least two multi-wire electrical cables from ingress of water, each of said cables having an outer sheath of at least two layers of material and an inner core comprising a plurality of individual insulated wire conductors having inter-stices therebetween, whlch comprises: (a) positioning a flexible reservoir about the splice, said reservoir having at least one opening therein and being sealed at each end thereof to the outer sheath of the cables adjacent said splice; (b) introducing a cur-able liquid sealant into said reservoir through said opening and ~i then closing said opening; (c) compressing said reservoir thereby forcing said liquid sealant to penetrate into the core of said splice and into the core of said cables adjacent said splice; and (d) maintaining said reservoir under compression for a period o~
time sufficient to permit said liqu:Ld sealant to cure thereby forming a water impenetrable seal said plastic film being suffi-ciently strong to support the weight of the liquid sealant and capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reser-voir to assume a smaller volume thereby applying pressure on theliquid sealant; and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir.
The present invention also provides a corrugated rigid sheet of plastic.
The present invention further provides a kit-of-parts comprising (a) a flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising a plastic film which is sufficiently strong to support the weight of the liquid sealant and is capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir; and (b) a splice case.
The present invention again provides an assembly com-prising: a cable splice; a flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising a plastic film which is sufficiently strong to support the weight of the liquid sealant and is capable of containing the liquid sealant 5~7 while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir; and (b) a splice case.
In the practice of this invention, a flexible reservoir formed by a plastic film is placed around a cable splice. The reservoir is positioned so that it completely surrounds the splice area. The ends of the reservoir are sealed to the adja-cent cables. The reservoir has at least one opening at the top thereof to permit filling the reservoir with a curable liquid sealant. Preferably, such opening is virtually coextensive with the reservoir permitting rapid filling of the reservoir. The reservoir is of a polymeric material and preferably is of a mate-rial which bonds or adheres to the sealant used to fill the reservoir. The reservoir is thus formed from a plastic film, just prior to filling with the sealant. The plastic film must be sufficiently strong to support the weight of the liquid sealant.
A preferred plastic film is of nylon, having a thickness of about 1 to about 2 mils. Film of various thicknesses can be used. The thickness of a particular film necessary to support the weight of the sealant depends on the material of the film.
Support means are provided in combination with the plastic film. Such support means is a porous liner adhered to the inside surface of the plastic film. The liner is preferably of a material which is compatible with the liquid sealant. The liner can be, for example, a flexible polymeric open-celled foam sheet of a thickness from about 0.1 inch to about 1.0 inch, preferably from about 0.2 to about 0.5 inch. A relatively inflexible llner such as a porous corrugated rigid sheet of plas-tic is preferably used. When such a liner is used, it should not prohibit or interfere with compression of the reservoir. For example, the si~e of the liner can be such that when the reser-- 6a -voir is positioned around the splice area, the edges of the liner do not meet. Compression of the reservoir then forces the edges of the liner together.
The liner is secured to the reservoir with an adhesive, preferably a pressure sensitive adhesive. The support means can be used alone or in conjunction with other support means. For example, plastic support rods adhered to the outer surface of the film may be used together with a flexible liner, if additional support is desired.
~ - 6b -r,' ~
3 ~ 2~ 7 The curable liquid sealant used can be any curable liquid system pourable at room temperature and hardening, preferably to a gel-like consistency within a relatively short period of time. Sealants of this type are well known in the art and many are commercially available. Liquid sealant systems used to encapsulate cable splices are generally two-part polyurethane or epoxy compositions. Typically, a polyurethane system comprising a prepolymer and a curing agent are supplied separately to be combined just prior to use.
In the practice of this invention, the curable liquid sealant is poured into the Flexible reservoir. Air trapped in the reservoir can be removed, if desired, by kneading or messaging the flexible reservoir. Air bubbles are forced to the top and can be pierced to allow air to escape. This kneading step can be accomplished by wrapping a first layer of tape, preferably transparent, around the reservoir while applying slight pressure to the tape.
The reservoir, filled with liquid sealant, is then compressed to apply pressure on the sealant. This is accomplished by applying pressure to the outer walls of the flexible reservoir forcing the 'reservoir to assume a smaller volume. Such pressure forces the liquid sealant into the interstices in the splice bundle and into the adjacent cable. The sealant penetrates the cable core and between the layers of the cable sheath. Compression is maintained while the sealant hardens, preferably to a gel-like consistency, Forming a water impenetrable seal surrounding and throughout the splice bundle and the adjacent cable.
The flexible reservoir can be compressed by any suitable means. A simple expedient is to pressure wrap the reservoir. This can be done by wrapping at least one layer oF tape to the outside of the reservoir. The tape is applied under tension and prefe;rably is of an elastomeric material. As the elastomeric tape is applied, it is stretched and elastic recovery forces continue to exert pressure on the reservuir after it has been applied. The tape used can be, for example, a vinyl tape, but is preferably "double rubber" tape, an elastomeric tape commercially available from Plymouth Rubber Co., Inc.
Other means of compressing the flexible reservoir can be used.
Compression of the reservoir exerts pressure on the liquid sealant in the reservoir. It is this pressure which forces the sealant to penetrate into the interstices of the space bundle and into the adjacent cable. The pressure applied can be from about 3 to about 12 pounds per square inch depending on the means used to compress the reservoir. Pressure of up to about 1û pounds per square inch will be adequate for most sealant/reservoir combinations.
Penetration of the sealant some distance along the cable core9 results in a highly desirable cable block protecting the splice from water migrating along the cable core or between the layers of the cable sheath. In the practice of this invention, this is accomplished by compressing the flexible reservoir filled with liquid sealant. To insure that adequate penetration of the cable core is obtained, the sheath of the cable can be ~2~ 7 slit or "tabbed" a short distance, generally a couple of inches, up from the splice area. A porous insert is then positioned under the slit cable sheath between the sheath and the cable core providing a pathway for sealant to flow from the reservoir up the cable. The porous insert can be, for example, a strip of net or foam, and in a preferred embodiment, is a porous corrugated rigid strip of plastic. Tabbing or slitting of the cable sheath in this manner also facilitates installation of a bond clamp for attaching a ground connector.
The present invention will be further illustrated by way of the accompanying drawings, in which:-Figure 1 illustrates a cable splice encompassed by a flexible reservoir for receiving curable liquid sealant;
Figure ~ is an end view of the cable of Figure 1 show-ing a reservoir formed from a plastic film supported by a pair of rods;
Figure 3 shows compressing the filled reservoir by tightly wrapping it with suitable tape; and Figure 4 shows the completed wrapped splice enclosed within a commercial splica case enclosure.
Figure 1 shows a splice between cables 1 and 2 which are multi-wire communication cables each containing 300 pairs or wire conductors. A flexible reservoir, 3, is formed from a plas-tic film, in this case a nylon film having a porous inner linerof a corrugated rigid sheet of plastic. The reservoir is formed by placing the nylon film around the splice area, 4, and taping the ends of the sheet to the adjacent cable sheath. The taped ends, 5, of the sheet form a fluid tight seal between the reser-voir and cable. The reservoir is supported by support rods oneach side thereof, adhered to the outer surface of the film.
~&2~5~7 Support rod, 6, on one side of the reservoir is shown in the Figure 1. The reservoir, 3, encompasses the entire splice area, 4, which contains the individual conductors, 7, shown here ~olned by modular connectors 8.
To more clearly illustrate formation of the reservoir, in Figure 2, a sheet of nylon film, 10, having a porous inner liner of a corrugated rigid sheet of plastic forms a reservoir, 3, around the splice bundle, 11, containing the individual con-ductors, 7. Support rodsr 6, are each coated with a pressuresensitive adhesive and adhered to the outer surface of the nylon film. The nylon film is - 9a -~;~4~i417 positioned and secured to the cable so thst a flap, 12, is created. The flap is folded over the opening of the reservoir after it has been filled with liquid sealant.
After filling and closing the reservoir, the filled reservoir is compressed, in accordance with this invention, to force the sealant into the splice bundle and adjacent cable core. This can be accomplished by compression wrapping the reservoir by one or more layers of tape.
In the preferred emdodiment a first layer of trans-parent polymeric tape is applied under light pressure. This tape provides a fluid tight seal around the reservoir.
Application of the tape with slight compression forces the liquid sealant to penetrate into at least the outer perimeter of the splice bundle and forces any entrapped displaced air to the surface of the liquid sealant. Such entrapped air can be removed by piercing the plastic film and tape to allow the air to escape. An additional wrap of the transparent tape seals any holes so made. In Figure 3 this first wrap of tape, 13, is over-wrapped with a second layer of tape, 14, which is applied under pressure to compress the sealant-containing reservoir. This second layer of tape is a commercially available tape made of butyl rubber and identified as "Double Rubber" tape. As the tape is applied under pressure it is stretched.
Since it is of an elastomeric material, it will continue to exert additional pressure on the compressed reservoir due to the elastic recovery forces of the stretched material. ~ther tapes, such as vinyl tape, can be used.
The compression wrapped tapedsplice is desirably protected against mechanical damage by enclosing the 5;4~7 splice in a conventional splice case or other enclosure. A pre-ferred enclosure is illustrated in Figure 4. In Figure 4, the splice, 20, joining cables, 21, and 22, is enclosed in a liner, 23. The liner can be, for example, a metal, e.g., aluminum can-ister or a thermoplastic sheet laminated to a foam layer such asthe liner disclosed in Canadian Patent No. 1,164,061. Over the liner, 23, is a heat recovered polymeric sleeve, 24. The poly-meric sleeve preferably is adhered to the cables, 21, and 22, by an adhesive, preferably a hot melt adhesive, forming an environ-mental seal around the splice. The heat-recoverable sleeve can be a tubular sleeve or wraparound sleeve of the type known in the art. For example a suitable wraparound heat recoverable sleeve is described in U.S. Patent No. 3,455,336, to Ellis. Dimension-ally recoverable sleeves which do not require heat for recovery, such as those described in U.S. Patents Nos. 4,070,746 and 4,135,553, for example, can also be used.
The techni~ue of protecting a splice in accordance with this invention can be used to protect splices between filled cables and/or unpressurized air core cables. It can also be used in a splice terminating a pressurized air core cable or connect-ing a pressurized cable to a non-pressurized one. In this case, the cable block prevents escape of pressurized air or other gas from the pressurized cable. The technique can be used to protect splices in multi-wire electric cables of any size but is particu-larly suitable for use with larger cables, i.e., those containing ~l ,. ..
~Z~54~'7 4DO pairs or more of individual wire conductors. The technique is particularly useful when at least one of the cables of the splice is filled with a grease-based filling composition.
Multi-wire electrical cables comprise a core containing a plurality of individual insulated wire conductors, surrounded by an outer sheath. The cable core can contain frcm a few pairs of conductors up to several thousand pairs. The outer sheath generally consists of an outer plastic jacket surrounding a metallic shield.
Additional inner polymeric layer or layers may be present.
To protect the conductors from water, the interstices between the individual wire conductors may be filled with a filling compound, usually a grease based or petroleum jelly. Cables that are so filled are generally referred to as "filled" cables and cables that are not filled are generally referred to as "air core" cables. Air core cables can be pressurized to prevent ingress of water.
When a splice is made in a cable, the outer sheath is removed from the end of the cable. At least some of the individual wire conductors in the core of the cable are joined to conductors of another cable or cables. After completion of the splice, the entire splice area, that is the area of the cables where the sheath has been removed, must be protected. Generally, an enclosure or splice case is placed over the area. A preferred enclosure is a dimensionally recoverable polymeric sleeve, preferably a heat-shrinkable polymeric sleeve.
~.
~2~S~7 An inner protective casing or lining may be pQsitioned about the splice before installation of the sleeve to provide additional mechanical protection. Molded plastic or lead splice cases are also used.
The splice case can be filled with a suitable filling compound to protect the individual wire conductors in the core of the splice (referred to herein as the splice bundle or splice core). Such filling compounds can be curable liquid polymer systems or grease-like materials, generally based on petroleum jelly. Curable liquid polymer systems are ùsed by pouring a curable liquid sealant into a splice case positioned about the splice and allowing it to cure. Particularly useful curable liquid sealants are two-part polyurethane systems comprising a prepolymer and a curing agent or hardener. When cured the filling compound solidifies, preferably to a gel-like consistency, forming a protective layer around the splice.
It has been found that this technique doesn't adequately protect the ~splice from ingress of water, particularly if one of the cables contains 400 pairs or more of wire conductors. Seepage of water into the splice eventually causes electrical failure of the joined conductors.
It has been discovered that a splice in multi-wire electric cables can be protectèd from water ingress if a curable liquid sealant is placed in a flexible reservoir surrounding the splice and subjected to compression ~24~
while it is in the liquid state and maintained under compression for a time sufficient to permit cure of the liquid sealant to its hardened state.
There has been proposed in a brochure of Pirelli General, entitle "Resinwrap Joints" of March, 1964, a procedure for providing synthetic joints for plastic and insulated sheath cables, particularly for joints hav:Lng a considerable free space internally, which is required to be filled with resin, wherein an aluminium polyethylene laminate sheet foil is formed around the joint in envelope fashion, the ends of the envelope are pressed on the sheath and secured with pvc tape, the top of the envelope is formed into a pouring hole, and a specified amount of resin is introduced. The envelope is then compacted by folding and mani-pulating, thus ~orcing the resin fully into the joint, and~inally, when the envelope has been folded down completely to the joint surface, it is taped overall with pvc tape, the pvc tape firstly being an adhesive pvc tape applied without tension, and the joint being compressed with the hands, and then a further layer of pvc tape being applled over the joint with maximum ten-sion. On particularly large joints it is desirable to apply one layer of cotton tape over the first layer of pvc tape very tightly to compress the joint, which is then left on and the final layer of pvc tape applied overall.
However, while such a procedure provides a flexible reservoir and sub~ects it to compression, such a procedure with the use of a reservoir formed from aluminium foil laminate, is subject to a number of disadvantages. In particular, the forma-tion and subsequent manipulation of the flexible reservoir iscumbersome and time consuming and is not readily usable by the craftsmen in the field. In particular, it requires a number of manipulative steps. Further, the aluminium foil on the envelope being compacted by folding and manipulating to force the resin into the joint by squeezing, and subsequently using wrapping tape under tension, particularly using thin film wrapping tape, tends ..
;.
~2~5~7 to wrinkle and form irregular shapes, and further, aluminium has high tensile strength, and thus the crushed and wrinkled alu-minium envelope will tend to puncture and cut the wrapping tape.
Further, the aluminium foil laminate sheet is a relatively expen-sive material.
It has now been found that the use of a plastic film informing the envelope, such as a nylon film, overcomes all the above disadvantages in that it is easy to manipulate, does not require a significant amount of manipulation, and therefore is readily usable by the craftsmen in the field, does not cut the wrapping tape, and is relatively inexpensive. However, it has been further found that a simple plastic film of desirable thick-ness for optimum flexibllity is not sufficiently strong to sup-port the weight of the liquid sealant in the reservoir, and thereservoir will tend to bulge during curing and wrapping, giving the joint an irregular shape which is undesirable, as it is in many cases desirable to enclose the wrapped taped joint in a con-ventional splice case of regular shape to protect it against mechanical damage. It has, however, further been found that this bulging can be avoided by providing a porous liner adhered to the inside surface of the reservoir, which liner does not interfere with the compression of the reservoir, such as a flexible polymeric open-celled foam sheet, or a corrugated rigid plastic sheet.
The present invention provides a method of protecting a splice connecting at least two multi-wire electrical cables from ingress of water, each of said cables having an outer sheath of at least two layers of material and an inner core comprising a plurality of individual insulated wire conductors having inter-stices therebetween, whlch comprises: (a) positioning a flexible reservoir about the splice, said reservoir having at least one opening therein and being sealed at each end thereof to the outer sheath of the cables adjacent said splice; (b) introducing a cur-able liquid sealant into said reservoir through said opening and ~i then closing said opening; (c) compressing said reservoir thereby forcing said liquid sealant to penetrate into the core of said splice and into the core of said cables adjacent said splice; and (d) maintaining said reservoir under compression for a period o~
time sufficient to permit said liqu:Ld sealant to cure thereby forming a water impenetrable seal said plastic film being suffi-ciently strong to support the weight of the liquid sealant and capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reser-voir to assume a smaller volume thereby applying pressure on theliquid sealant; and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir.
The present invention also provides a corrugated rigid sheet of plastic.
The present invention further provides a kit-of-parts comprising (a) a flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising a plastic film which is sufficiently strong to support the weight of the liquid sealant and is capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir; and (b) a splice case.
The present invention again provides an assembly com-prising: a cable splice; a flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising a plastic film which is sufficiently strong to support the weight of the liquid sealant and is capable of containing the liquid sealant 5~7 while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir; and (b) a splice case.
In the practice of this invention, a flexible reservoir formed by a plastic film is placed around a cable splice. The reservoir is positioned so that it completely surrounds the splice area. The ends of the reservoir are sealed to the adja-cent cables. The reservoir has at least one opening at the top thereof to permit filling the reservoir with a curable liquid sealant. Preferably, such opening is virtually coextensive with the reservoir permitting rapid filling of the reservoir. The reservoir is of a polymeric material and preferably is of a mate-rial which bonds or adheres to the sealant used to fill the reservoir. The reservoir is thus formed from a plastic film, just prior to filling with the sealant. The plastic film must be sufficiently strong to support the weight of the liquid sealant.
A preferred plastic film is of nylon, having a thickness of about 1 to about 2 mils. Film of various thicknesses can be used. The thickness of a particular film necessary to support the weight of the sealant depends on the material of the film.
Support means are provided in combination with the plastic film. Such support means is a porous liner adhered to the inside surface of the plastic film. The liner is preferably of a material which is compatible with the liquid sealant. The liner can be, for example, a flexible polymeric open-celled foam sheet of a thickness from about 0.1 inch to about 1.0 inch, preferably from about 0.2 to about 0.5 inch. A relatively inflexible llner such as a porous corrugated rigid sheet of plas-tic is preferably used. When such a liner is used, it should not prohibit or interfere with compression of the reservoir. For example, the si~e of the liner can be such that when the reser-- 6a -voir is positioned around the splice area, the edges of the liner do not meet. Compression of the reservoir then forces the edges of the liner together.
The liner is secured to the reservoir with an adhesive, preferably a pressure sensitive adhesive. The support means can be used alone or in conjunction with other support means. For example, plastic support rods adhered to the outer surface of the film may be used together with a flexible liner, if additional support is desired.
~ - 6b -r,' ~
3 ~ 2~ 7 The curable liquid sealant used can be any curable liquid system pourable at room temperature and hardening, preferably to a gel-like consistency within a relatively short period of time. Sealants of this type are well known in the art and many are commercially available. Liquid sealant systems used to encapsulate cable splices are generally two-part polyurethane or epoxy compositions. Typically, a polyurethane system comprising a prepolymer and a curing agent are supplied separately to be combined just prior to use.
In the practice of this invention, the curable liquid sealant is poured into the Flexible reservoir. Air trapped in the reservoir can be removed, if desired, by kneading or messaging the flexible reservoir. Air bubbles are forced to the top and can be pierced to allow air to escape. This kneading step can be accomplished by wrapping a first layer of tape, preferably transparent, around the reservoir while applying slight pressure to the tape.
The reservoir, filled with liquid sealant, is then compressed to apply pressure on the sealant. This is accomplished by applying pressure to the outer walls of the flexible reservoir forcing the 'reservoir to assume a smaller volume. Such pressure forces the liquid sealant into the interstices in the splice bundle and into the adjacent cable. The sealant penetrates the cable core and between the layers of the cable sheath. Compression is maintained while the sealant hardens, preferably to a gel-like consistency, Forming a water impenetrable seal surrounding and throughout the splice bundle and the adjacent cable.
The flexible reservoir can be compressed by any suitable means. A simple expedient is to pressure wrap the reservoir. This can be done by wrapping at least one layer oF tape to the outside of the reservoir. The tape is applied under tension and prefe;rably is of an elastomeric material. As the elastomeric tape is applied, it is stretched and elastic recovery forces continue to exert pressure on the reservuir after it has been applied. The tape used can be, for example, a vinyl tape, but is preferably "double rubber" tape, an elastomeric tape commercially available from Plymouth Rubber Co., Inc.
Other means of compressing the flexible reservoir can be used.
Compression of the reservoir exerts pressure on the liquid sealant in the reservoir. It is this pressure which forces the sealant to penetrate into the interstices of the space bundle and into the adjacent cable. The pressure applied can be from about 3 to about 12 pounds per square inch depending on the means used to compress the reservoir. Pressure of up to about 1û pounds per square inch will be adequate for most sealant/reservoir combinations.
Penetration of the sealant some distance along the cable core9 results in a highly desirable cable block protecting the splice from water migrating along the cable core or between the layers of the cable sheath. In the practice of this invention, this is accomplished by compressing the flexible reservoir filled with liquid sealant. To insure that adequate penetration of the cable core is obtained, the sheath of the cable can be ~2~ 7 slit or "tabbed" a short distance, generally a couple of inches, up from the splice area. A porous insert is then positioned under the slit cable sheath between the sheath and the cable core providing a pathway for sealant to flow from the reservoir up the cable. The porous insert can be, for example, a strip of net or foam, and in a preferred embodiment, is a porous corrugated rigid strip of plastic. Tabbing or slitting of the cable sheath in this manner also facilitates installation of a bond clamp for attaching a ground connector.
The present invention will be further illustrated by way of the accompanying drawings, in which:-Figure 1 illustrates a cable splice encompassed by a flexible reservoir for receiving curable liquid sealant;
Figure ~ is an end view of the cable of Figure 1 show-ing a reservoir formed from a plastic film supported by a pair of rods;
Figure 3 shows compressing the filled reservoir by tightly wrapping it with suitable tape; and Figure 4 shows the completed wrapped splice enclosed within a commercial splica case enclosure.
Figure 1 shows a splice between cables 1 and 2 which are multi-wire communication cables each containing 300 pairs or wire conductors. A flexible reservoir, 3, is formed from a plas-tic film, in this case a nylon film having a porous inner linerof a corrugated rigid sheet of plastic. The reservoir is formed by placing the nylon film around the splice area, 4, and taping the ends of the sheet to the adjacent cable sheath. The taped ends, 5, of the sheet form a fluid tight seal between the reser-voir and cable. The reservoir is supported by support rods oneach side thereof, adhered to the outer surface of the film.
~&2~5~7 Support rod, 6, on one side of the reservoir is shown in the Figure 1. The reservoir, 3, encompasses the entire splice area, 4, which contains the individual conductors, 7, shown here ~olned by modular connectors 8.
To more clearly illustrate formation of the reservoir, in Figure 2, a sheet of nylon film, 10, having a porous inner liner of a corrugated rigid sheet of plastic forms a reservoir, 3, around the splice bundle, 11, containing the individual con-ductors, 7. Support rodsr 6, are each coated with a pressuresensitive adhesive and adhered to the outer surface of the nylon film. The nylon film is - 9a -~;~4~i417 positioned and secured to the cable so thst a flap, 12, is created. The flap is folded over the opening of the reservoir after it has been filled with liquid sealant.
After filling and closing the reservoir, the filled reservoir is compressed, in accordance with this invention, to force the sealant into the splice bundle and adjacent cable core. This can be accomplished by compression wrapping the reservoir by one or more layers of tape.
In the preferred emdodiment a first layer of trans-parent polymeric tape is applied under light pressure. This tape provides a fluid tight seal around the reservoir.
Application of the tape with slight compression forces the liquid sealant to penetrate into at least the outer perimeter of the splice bundle and forces any entrapped displaced air to the surface of the liquid sealant. Such entrapped air can be removed by piercing the plastic film and tape to allow the air to escape. An additional wrap of the transparent tape seals any holes so made. In Figure 3 this first wrap of tape, 13, is over-wrapped with a second layer of tape, 14, which is applied under pressure to compress the sealant-containing reservoir. This second layer of tape is a commercially available tape made of butyl rubber and identified as "Double Rubber" tape. As the tape is applied under pressure it is stretched.
Since it is of an elastomeric material, it will continue to exert additional pressure on the compressed reservoir due to the elastic recovery forces of the stretched material. ~ther tapes, such as vinyl tape, can be used.
The compression wrapped tapedsplice is desirably protected against mechanical damage by enclosing the 5;4~7 splice in a conventional splice case or other enclosure. A pre-ferred enclosure is illustrated in Figure 4. In Figure 4, the splice, 20, joining cables, 21, and 22, is enclosed in a liner, 23. The liner can be, for example, a metal, e.g., aluminum can-ister or a thermoplastic sheet laminated to a foam layer such asthe liner disclosed in Canadian Patent No. 1,164,061. Over the liner, 23, is a heat recovered polymeric sleeve, 24. The poly-meric sleeve preferably is adhered to the cables, 21, and 22, by an adhesive, preferably a hot melt adhesive, forming an environ-mental seal around the splice. The heat-recoverable sleeve can be a tubular sleeve or wraparound sleeve of the type known in the art. For example a suitable wraparound heat recoverable sleeve is described in U.S. Patent No. 3,455,336, to Ellis. Dimension-ally recoverable sleeves which do not require heat for recovery, such as those described in U.S. Patents Nos. 4,070,746 and 4,135,553, for example, can also be used.
The techni~ue of protecting a splice in accordance with this invention can be used to protect splices between filled cables and/or unpressurized air core cables. It can also be used in a splice terminating a pressurized air core cable or connect-ing a pressurized cable to a non-pressurized one. In this case, the cable block prevents escape of pressurized air or other gas from the pressurized cable. The technique can be used to protect splices in multi-wire electric cables of any size but is particu-larly suitable for use with larger cables, i.e., those containing ~l ,. ..
~Z~54~'7 4DO pairs or more of individual wire conductors. The technique is particularly useful when at least one of the cables of the splice is filled with a grease-based filling composition.
Claims (28)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of protecting a splice connecting at least two multi-wire electrical cables from ingress of water, each of said cables having an outer sheath of at least two layers of material and an inner core comprising a plurality of individual insulated wire conductors having interstices therebetween, which comprises: (a) positioning a flexible reservoir about the splice, said reservoir comprising a plastic film and having at least one opening therein and being sealed at each end thereof to the outer sheath of the cables adjacent said splice; (b) introducing a cur-able liquid sealant into said reservoir through said opening and then closing said opening; (c) compressing said reservoir at a pressure which forces said liquid sealant to penetrate into said splice and into the interstices between the conductors in the core of said cables adjacent said splice; and (d) maintaining said reservoir under said pressure for a period of time suffi-cient to permit said liquid sealant to cure thereby forming a water impenetrable seal, said plastic film being sufficiently strong to support the weight of the liquid sealant and capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant;
and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir.
and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir.
2. A method according to claim 1 wherein said pressure is from about 3 pounds per square inch.
3. A method according to claim 1 wherein the said pressure is from about 3 to about 12 pounds per square inch.
4. A method in accordance with claim 1 wherein the step of compressing said reservoir comprises wrapping at least one layer of tape under pressure around said reservoir.
5. A method according to claim 4 wherein the step of compressing said reservoir includes wrapping a second layer of tape over said layer of tape whereby when the second layer of tape is applied under pressure it is stretched.
6. A method according to claim 1 wherein the plastic film has a thickness of about 1 to about 2 mils.
7. A method according to claim 6 wherein the plastic film is nylon.
8. A method according to claim 1 wherein the porous liner is a flexible polymeric open-celled foam sheet.
9. A method according to claim 1 wherein the porous liner is a corrugated rigid sheet of plastic.
10. A method according to claim 7 wherein the liner is adhered to the nylon film with a pressure sensitive adhesive.
11. A flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising: a plastic film which is sufficiently strong to support the weight of the liquid sealant and capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant; and a support means comprising a porous liner adhered to the inside surface of the reservoir while liner does not interfere with compression of the reservoir.
12. A reservoir according to claim 11 wherein the plas-tic film has a thickness of about 1 to about 2 mils.
13. A reservoir according to claim 12 wherein the plas-tic film is nylon.
14. A reservoir according to claim 11 wherein the porous liner is a flexible polymeric open-celled foam sheet.
15. A reservoir according to claim 11 wherein the porous liner is a corrugated rigid sheet of plastic.
16. A reservoir according to claim 13 wherein the liner is adhered to the nylon film with a pressure sensitive adhesive.
17. A kit-of-parts comprising (a) a flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising a plastic film which is sufficiently strong to support the weight of the liquid sealant and is capable of con-taining the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant and a sup-port means comprising a porous liner adhered to the inside sur-face of the reservoir which liner does not interfere with com-pression of the reservoir; and (b) a splice case.
18. An assembly comprising: a cable splice; a flexible reservoir adapted to surround a cable splice and to contain a liquid sealant while the liquid sealant is compressed into the cable splice comprising a plastic film which is sufficiently strong to support the weight of the liquid sealant and is capable of containing the liquid sealant while pressure is applied to the outer walls of the reservoir to force the reservoir to assume a smaller volume thereby applying pressure on the liquid sealant and a support means comprising a porous liner adhered to the inside surface of the reservoir which liner does not interfere with compression of the reservoir; and (b) a splice case.
19. A reservoir according to claim 10 wherein the porous liner has a plurality of apertures therein.
20. A method according to claim 8 in which the foam sheet has a thickness of 0.1 to 1.0 inches.
21. A method according to claim 8 in which the foam sheet has a thickness of 0.2 to 0.5 inches.
22. A reservoir according to claim 14 in which the foam sheet has a thickness of 0.1 to 1.0 inches.
23. A reservoir according to claim 14 in which the foam sheet has a thickness of 0.2 to 0.5 inches.
24. A method according to claim 1 or 5 further com-prising the Step (e) of placing a dimensionally recoverable sleeve over the flexible reservoir after Step (d).
25. A kit-of-parts according to claim 17, wherein the splice case is a dimensionally recoverable sleeve.
26. A kit-of-parts according to claim 25, wherein the dimensionally recoverable sleeve is a heat-recoverable tubular sleeve or a heat-recoverable wrap-around sleeve.
27. An assembly according to claim 18, wherein the splice case is a dimensionally recovered sleeve.
28. An assembly according to claim 27, wherein the dimensionally recovered sleeve is a heat-recovered tubular sleeve or a heat-recovered wrap-around sleeve.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57858384A | 1984-02-10 | 1984-02-10 | |
| US578,583 | 1984-02-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1245417A true CA1245417A (en) | 1988-11-29 |
Family
ID=24313479
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000457844A Expired CA1245417A (en) | 1984-02-10 | 1984-06-29 | Protection of cable splice |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1245417A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111962127A (en) * | 2020-07-31 | 2020-11-20 | 常州费曼生物科技有限公司 | Single-side sealing method of anodic aluminum oxide porous membrane |
-
1984
- 1984-06-29 CA CA000457844A patent/CA1245417A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111962127A (en) * | 2020-07-31 | 2020-11-20 | 常州费曼生物科技有限公司 | Single-side sealing method of anodic aluminum oxide porous membrane |
| CN111962127B (en) * | 2020-07-31 | 2022-06-07 | 常州费曼生物科技有限公司 | Single-side sealing method of anodic aluminum oxide porous membrane |
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