US3602636A

US3602636A - Wrapped service entrance cable

Info

Publication number: US3602636A
Application number: US874466A
Authority: US
Inventors: Raymond D Evans
Original assignee: Reynolds Metals Co
Current assignee: Reynolds Metals Co
Priority date: 1969-11-06
Filing date: 1969-11-06
Publication date: 1971-08-31
Anticipated expiration: 1988-08-31
Also published as: CA922395A

Abstract

A plurality of conductors are helically wrapped with at least one layer of moisture and thermal barrier tape made of open weave glass cloth partly embedded in a layer of fire retardant synthetic plastic electrical insulation material. An outer sheath of synthetic plastic material is preferably extruded onto the cable and bonds to the synthetic plastic material of the barrier tape.

Description

United States Patent [72] Inventor Raymond D. Evans [56] I References Cited 7 I West Chester, Pa. UNITED STATES PATENTS P 2,658,014 11/1953 Morrison 174/121 x [22] 2 718544 9/1955 Shep 174/113 {451 Patented Aug, 1971 p [73] Assignee Reynolds Metals Company P ma y E.mminerE. A. Goldberg Richmond, Va. Attorney-Glenn, Palmer, Lyne, Gibbs and Thompson [54] n zig fggxg g CABLE ABSTRACT: A plurality of conductors are helically wrapped 8 I with at least one layer of moisture and thermal barrier tape [52] US. Cl 174/115, made of open weave glass cloth partly embedded in a layer of 174/121 SR fire retardant synthetic plastic electrical insulation material. [51] Int. Cl 1101b 3/00 An outer sheath of synthetic plastic material is preferably ex- [50] Field of Search 174/1 15, truded onto the cable and bonds to the synthetic plastic material of the barrier tape.

PATENTEUAUB31 m1 1 3.602.636

COMPDS/ TAP OPE/VW I E GLASS CLOTH PARTLY EMBEDDED //V A LAYER 0F UNCURED, FLA RES/STANT SYN E 776 RUBBER BY fzzW/x; 7 41/1/52, L n flaasvr/lmmsav v ATTORNEYS 22 g 14-: INVENTOR 1 WRAPPED'SERVICE ENTIIANCECABLE BACKGROUND oETII -INv'ENTIoN drops, meter boxes or load centers.

In many localities, one prerequisite to the use of cables'o'f new or modified design is'that approval of the design be 65-- tained from Underwriters Laboratories, Inc. Approval requires subjection of the cables to standard'tests'by the test} ing agency. One suchte'st for 'servieeentrance'cables is entitled Overload Of UninsulatdConductor in Type'SE Cable. This test, commonly called the 300 amp. test, consistsof the following:

A Type SE Cable withor'wi't'hout the t ti 'lialtapet'tl elttidned in paragraphs 32-33 but containing either (i) two'iri'su lated No. 6 A.w.g. cdpper'coiiductor and a No. '6A.w.g. copper uninsulated conductonor (2-)"twoinsulated'No. 4 A.w.g. aluminum conductors and a N6. 4" A;w.g-. aluminum uninsulatedconduc'tor shall'not warp excessively, flame, or rupture while a current of 300 ainperesis flow ing through the uninsula ted' conductor and the metal tape, if atape is used, for one hour as described in paragraph I04. This requirement applies to cable with an uninsulated conductor regardless'of how the conductor is assembled-into the cable-cabled in one of several sec; tions, laid straight, or distributedhe'lically.

One 11-foot specimen of 'finishedcable is to be laid in a straight, open, 90", V-shaped trough that 'is lined with asbestos. At each end of the specimen, connection is to be made between a source of alternating'or'directcurrent and (I) the uninsulated conductor or (2) the uninsula'ted conductor and metal tape in parallel, if both are used. A currentof 300 amperes is tobe'rnaintainedin the'uninsu lated conductor for'one hour. Any cable from which a specimen warps excessively, flames, o'rrup'tures' during the hour is not acceptable."

In one conventional, approved design-of service entrance cable in widespread use, the insulated, and uhirisiilated conductors are wrapped with a layer of Mylar polyethylene terephthalate film (which may be coated with an adhesive waterproofing agent), which layer is in tum'surro ndedby a braided in si'tu glass,'rayon cotton, or combination fiber sheath impregnated and covered with an asphaltic material and lacquered on the outside, usually with a gray colored lacqueri The terephthalate film layers serves to hold the insiila'ted and noninsulate'd" conductors and ropes of paper filler together while the sheathbraiding is being done.

The braiding'process is relatively slow and therefore expensive. All glass-fiber, although theoretically permissible in co ventional, approved service entrance cable, has not been satisfactory because of the'poor adherence of asphalt to glass fiber. In addition, all-glass fiber insuch braidedconstructions tends to fare badly on abrasiont'e'sts, suchas the standard joist pull-through test. The slowness of the braiding operation, 'th'e'desire to use allglass fiber and the desire to produc'ecables of more flame or fire resistant or retardant materialshas led to attempts at inhovation in the design of'service entrancecable.

However, even those s'killediri the art encounter much difficulty in successfully designing-modified service entrance cables, in view of the need for suclicables to successfully pass stringent tests, exemplified by the 300 amp. test described above. 1

For instance, the inventor herein is personally fairiiliar with an-attempt to provide anfaccep'table modification, wherein the asphalt lacquer finish of glass-cotton or' all-glass'fibe'r braid" fthe conventional service entrance cable as described "above" was replaced with a layer of extruded PVC resin. Thecab'le sd' modified fails to pass the 300 amp; test although the knowledgeable people who constructed it thought it would pass the test. Although the reasons'for failure are not known, it is now speculated that'the glass fiber braid and PVC coverin'gfu'sed and sparkedduring the test, thus igniting the gaseous products'evolving from thermallyde'graded cable insulation.

SUMMARY OF THE INVENTION A-service entrance cable is provided which can be made more rapidly, since in situ sheath braiding is'obviated;'all-glass fibermay be incorporated therein, as may other flame retardirig materials; and the cable successfully'passes the Un- ,derw'rit rs'Laboratories, Inc. 300 amp. test.

About the normal grouping of insulated (and in some constructioris' neutral uninsula'ted) conductors; and filler, there is spirally wound at least one layer of tapernade of open-weave glass fiber having a skim coating of flame retarding unvulcaniz'ed polychloroprene (Neoprene) in turn covered by an extruded in place adherent tubular layer of polyvinylchloride (polychloropr'enecan be used for this layer, but is more expensive The principles of theinvention will be further hereinafter discussed with reference to the drawing wherein preferred embodinients are shown. The specifics illustrated in the drawing are'interi'dedto'exernplify, rather than limit, aspects of the inversion asdefined In the claims.

BRIEF DESCRIPTION OF THE DRAWING Inth'e Drawing: FIG. 1 is'a transversecToss-sectional view of a preferred embodinie'nt of the service entrance cable of-the invention;

FIG. 2 is a top-plan view of a short piece of open weave glass fiber cloth skim coated with flame retarding" polychloroprene and used as the helical tape wrap'of the FIG.

l cable; I

FIG. 3 is a fragmentary longitudinal'sectional view of the lappingof'the helical wrap of tape on the cable of FIG. I; and

FIG. 4 is a view similar to FIG. 3, showing an alternative forth of lapping using two such tapes to produce a complete double thickness layer of tape. I

usually used to fill spaces between conductors exteriorly or interiorly of the grouped conductors. Sometimes the configuration'of conductors is such that they produce acceptably round cable with little or no'addition of filler. In the embodiment'depieced, the service'entrance cable 10 comprises three insulated conductors I2, anunirisulated neutral conductor 14 and filler of nonconducting material 16, usually paper, the number and placem'entpf these conductors and filler shown and so far described is exemplary and these elements will be collectively referred to hereinafter,generically, as grouped conductors" rm'The insulated conductors ma be insulated with any of the accepted insulating coatings or coverings 13 such as chemically cross-linked polyethylene; SB-R, EPDM', EPM or IIR rubbers. V

The grouped conductors 18 are provided with at least one coriiplete layer of helically wrapped tape 20 which is an open weave glass fiber cloth 22 provided with a' skim coating 24 of unvulcaiiized, flame retardant polychloroprene (Neoprene). In the presently preferred, illustrated embodiment the glass fiber cloth consists o'f about 20"bundles of approximately 204 filaments of l'l/0 glass fibers per inch along the length (warp) or the tape and about 10 bundles of approximately 204 of 75-1/0 glass filaments per inch along the width (woof) of the tape. The presently preferred glass fiber cloth 22has a weight of 1.6 to 1.9 ounces per square yard and preferably about 1.6 ounces per square yard including up to 10 weight percent of binderand a for strength of at least about 70 pounds per lineal inch, both widthwise and lengthwise of the tape. For the all-glass fiber preferred composition there may be substituted a blended fiber cloth made of an open weave of blended glass and asbestos fibers with an epoxy or silicone binder. One such binder is aminopropyltriethoxysilane. A typical such cloth has the following composition:

Constituent Weight Percent Glass fiber 50-70 Asbestos fiber 25-40 Binder 5-10 The presently preferred skim coating 24 consist of fame retarding unvulcanized Neoprene (polychloroprene-compound), a presently preferred commercially available formulation being:

The coating 24 is applied to produce a layer of about 67 mils in which the glass fiber cloth 22 is partly embedded to firmly mechanically connect the cloth 22 and the coating 24.

The composite tape 20 preferablyfl has a finished weight of about 35-40 pounds per 100 squa e yards. The tape 20 is preferably made in wide widths of for instance 60 inches wide and slit to desired width and stored in convolute wound condition on rolls. A typical finished width is 1.75 inches.

In certain instances the skim coatihg may be discontinuous in the sense of leaving the composit tape reticulated, or the coating may be constituted by the glass-cloth binder or sizing itself.

In contrast to the need to braid in situ the conductor grouping covering for conventional service entrance cables, the tape 20 is preferably completely manufactured prior in time to the point of its use and may in fact be manufactured by another entity or at another location than the cable manufacturing plant. l

It should be noticed that the glass fiber cloth 22 is woven in the sense that longitudinally directdd strands pass over and under alternating ones of encountered transversely directed strands and vice versa. Weaving is believed necessary for dimensional stability of the cloth durihg calendering thereto of the coating 24, and during subsequent slitting and application to the cable core of grouped conduct rs. In addition, since the Neoprene coating 24 is thin and unvulcanized, it adds no appreciable strength to the product. The weave imparts tensile strength longitudinally and transversely, permitting the composite tape 20 to be helically applied without edge fraying or tearing. This is especially important when the tape is applied with overlaps (FIG. 3) under tension? When wrapping the grouped conductors of the cable core with a single tape 20 (FIG. 3), the tape is overlapped by at least onefourth inch. When wrapping the cable core with two

tapes

20, 20" (FIG. 4) the adjacent edges of each tape are preferably butted and the outer tape 20" placed with its center over the edge butt line 30 of the inner tape 20". A double thickness of tapes can also be obtained by intercalating two tapes.

The decision whether to place the glass'fiber cloth side of the tape 20 faceup or facedown with respect to the cable core is not based on consideration for successful operability of the cable, since both orientations result in highly acceptable cables. Rather the decision is based on a consideration of trouble-free manufacture. It has been found that the glass fiber cloth in a face-upward position helps in production, as adjacent layers on reels of partly completed cable would tend to stick together were the vulcanized Neoprene coating 24 facing outwardly. Accordingly, in the FIG. 3 construction the tape 20 is preferably applied so that its cloth side faces outwardly and in the FIG. 4 construction, the two

tapes

20, 20 are preferably applied with coatings 24 thereof face to face.

The cable 10 is completed by extrusion thereonto by nowconventional techniques, of a jacket 32 of flame retarding thermoplastic material, preferably polyvinylchloride for instance 0.031 to 0.080 inch thick. As aforementioned, other electrically insulating, extrudible, flexible thermoplastics such as flame retarding Neoprene chloroprene could be used, but PVC is preferred because of its low cost.

The heat in the polyvinylchloride as it is extruded onto the tape-wrapped cable core causes the layer 24 to become firmly bonded to the jacket 32.

The mechanical strength of the new service entrance cable 10 is not significantly different from that of the conventional service entrance cables as described above.

The new service entrance cable 10 is susceptible of some modification from the preferred designs just described. For instance, should it be desired, a layer of helically wrapped Mylar polyethylene terephthalate tape with or without adhesive, waterproofing coating may be installed about the cable core prior to wrapping the tape 20 thereupon, should such a layer be desired. Preferably, in order to obtain all of :the manufacturing and economic advantages of the invention, the extra layer just described is not provided.

As outlined hereinabove, the core of the service entrance cable need not be as depicted, in order to take advantage of the wrap of the present invention. For instance, the core may consist of two insulated conductive stands surrounded by multiple bare neutral wires, this core having been wrapped by the composite tape 20 (or 20", 20") and provided with an extruded iii place jacket 32.

In the preferred service entrance cable according to the invention, the Mylar and lacquered, asphalt-coated in situ glass cotton fiber braid layers of conventional service entrance cable are replaced with a helically wound wrapping of composite barrier tape made of an open weave of glass fiber cloth partly embedded in a skim coating of uncured fire resistant plastic material such as Neoprene or I-I-ypalon synthetic rubber. An outer sheath of PVC or the like is extruded onto the tape wrap and the heat of the extruded material fuses the plastic material of the sheath to the plastic material of the tape wrap (where exposed between glass fiber bundles) thereby forming an impervious covering around the grouped conductors of the cable. The service entrance cable 10 has a good appearance. Its jacket can be cut away conveniently to expose the inner wrap 20, which, in turn, can be pulled away conveniently to expose the conductor strands for cable termination in the field.

It should now be apparent that the wrapped service entrance cable as described hereinabove possesses each of the attributes set forth in the specification under the heading Summary of the Invention" hereinbefore. Because the wrapped service entrance cable of the invention can be modified to some extent without departing form the principles of the invention as they have been outlined and explained in this specification, the present invention should be understood as encompassing all such modifications as are within the spirit and scope of the following claims.

Iclaim:

. A service entrance cable comprising:

rep-

2. The service entrance cable of claim 1 wherein said flame resistant synthetic rubber coating is a skim coating of polychloroprene.

3. The service entrance cable of claim 1 wherein said glass fiber cloth essentially consists of woven glass fibers and is free of cotton and rayon fibers.

4. The service entrance cable of claim 1 wherein the glass fiber cloth consists of about 20 bundles of glass fibers per inch widthwise of the composite tape and about l bundles of glass fibers per inch lengthwise of the composite tape; and wherein said glass fiber cloth has a weight of about 1.6 ounces per square yard and a tensile strength of about 70 pounds per lineal inch both widthwise and lengthwise of the composite tape.

5. The service entrance cable of claim 4 wherein said coating of uncured, flameresistant synthetic rubber comprises a skin coating of polychloroprene having a thickness of about 6-7 mils and wherein said composite tape has a finished weight of about 35-40 pounds per 100 yards.

6. The service entrance cable of claim wherein glass fiber cloth of said composite tape faces outwardly of said cable core.

7. A service entrance cable comprising:

a. a plurality of electrically insulated electrical conductor strands and a neutral conductor, grouped to constitute a cable core;

b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open weave glass fiber cloth partly embedded in a coating of uncured, flame resistant synthetic rubber; the glass fiber cloth consisting of about 20 bundles of glass fibers per inch widthwise of the composite tape and about 10 bundles of glass fibers per inch lengthwise of the composite tape; said glass fiber cloth having a weight of about 1.6 ounces per square yard and a tensile strength of about 70 pounds per lineal inch both widthwise and lengthwise of the composite tape; said glass fiber cloth of said composite tape facing outwardly of said cable core; said coating of uncured, flame resistant synthetic rubber comprising a skim coating of a plurality of electrically insulated electrical conductor I polychloroprene having a thickness of about 6-7 mils; said composite tape having a finished weight of about 35-40 pounds per square yards; and

c. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto;

said jacket comprising a layer of polyvinylchloride fused to said polychloroprene among the fiber bundles of said open weave glass fiber cloth.

8. A service entrance cable comprising:

b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open weave glass fiber cloth partly embedded in a coating of uncured, flame resistant synthetic rubber; said complete barrier layer comprising two complete helical wraps of said composite tape, applied one over the other, with lateral edges in each wrap abutting to form butt joints, the butt joint of the outer of said wraps of composite tape being centered upon the inner of said wraps of composite tape; and

c. a jacket of electrical material extruded in place about said barrier layer and being fused thereto. 9. The service entrance cable of claim 8 wherein the said coating of the two wraps of composite tape face one another.

10. A service entrance cable comprising: i

b. a complete barrier layer about said cable core, said barrier layer being at least on helical wrap of a composite tape of open weave glass fiber cloth partly embedded in a coating of uncure, flame resistant synthetic rubber; said complete barrier layer comprising two complete helical wraps of said composite tape, applied with intercalation each with the other; and

c. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto.

l l. A service entrance cable comprising:

b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open wave glass fiber cloth having an adherent coating thereon which closes the open spaces of the glass fiber cloth and is fusible with the following defined jacket; and

. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto.

Claims

1. A service entrance cable comprising: a. a plurality of electrically insulated electrical conductor strands and a neutral conductor, grouped to constitute a cable core; b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open weave glass fiber cloth partly embodied in a coating of uncured, flame resistant synthetic rubber which closes the open spaces of the glass fiber cloth; and c. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto.

4. The service entrance cable of claim 1 wherein the glass fiber cloth consists of about 20 bundles of glass fibers per inch widthwise of the composite tape and about 10 bundles of glass fibers per inch lengthwise of the composite tape; and wherein said glass fiber cloth has a weight of about 1.6 ounces per square yard and a tensile strength of about 70 pounds per lineal inch both widthwise and lengthwise of the composite tape.

5. The service entrance cable of claim 4 wherein said coating of uncured, flame-resistant synthetic rubber comprises a skin coating of polychloroprene having a thickness of about 6-7 mils and wherein said composite tape has a finished weight of about 35-40 pounds per 100 yards.

6. The service entrance cable of claim 5 wherein glass fiber cloth of said composite tape faces outwardly of said cable core.

7. A service entrance cable comprising: a. a plurality of electrically insulated electrical conductor strands and a neutral conductor, grouped to constitute a cable core; b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open weave glass fiber cloth partly embedded in a coating of uncured, flame resistant synthetic rubber; the glass fiber cloth consisting of about 20 bundles of glass fibers per inch widthwise of the composite tape and about 10 bundles of glass fibers per inch lengthwise of the composite tape; said glass fiber cloth having a weight of about 1.6 ounces per square yard and a tensile strength of about 70 pounds per lineal inch both widthwise and lengthwise of the composite tape; said glass fiber cloth of said composite tape facing outwardly of said cable core; said coating of uncured, flame resistant synthetic rubber comprising a skim coating of polychloroprene having a thickness of about 6-7 mils; said composite tape having a finished weight of about 35-40 pounds per 100 square yards; and c. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto; said jacket comprising a layer of polyvinylchloride fused to said polychloroprene among the fiber bundles of said open weave glass fiber cloth.

8. A service entrance cable comprising: a. a plurality of electrically insulated electrical conductor strands and a neutral conductor, grouped to constitute a cable core; b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open weave glass fiber cloth partly embedded in a coating of uncured, flame resistant synthetic rubber; said complete barrier layer comprising two complete helical wraps of said composite tape, applied one over the other, with lateral edges in each wrap abutting to form butt joints, the butt joint of the outer of said wraps of composite tape being centered upon the inner of said wraps of composite tape; and c. a jacket of electrical material extruded in place about said barrier layer and being fused thereto.

9. The service entrance cable of claim 8 wherein the said coating of the two wraps of composite tape face one another.

10. A service entrance cable comprising: a. a plurality of electrically insulated electrical conductor strands and a neutral conductor, grouped to constitute a cable core; b. a complete barrier layer about said cable core, said barrier layer being at least on helical wrap of a composite tape of open weave glass fiber cloth partly embedded in a coating of uncure, flame resistant synthetic rubber; said complete barrier layer comprising two complete helical wraps of said composite tape, applied with intercalation each with the other; and c. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto.

11. A service entrance cable comprising: a. a plurality of electrically insulated electrical conductor strands and a neutral conductor, grouped to constitute a cable core; b. a complete barrier layer about said cable core, said barrier layer being at least one helical wrap of a composite tape of open wave glass fiber cloth having an adherent coating thereon which closes the open spaces of the glass fiber cloth and is fusible with the following defined jacket; and c. a jacket of electrical insulation material extruded in place about said barrier layer and being fused thereto.