US 3312775 A
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Description (OCR text may contain errors)
April 4, 1937 LAMBERT 3,312,775
ELECTRI CAL CABLE Filed Dec. 15, 1 965 zi /7 am INVENTOR, HENRY LAMBERT,-
United States Patent 3,312,775 ELECTRICAL CABLE Henry Lambert, 1026 Central Ave., Pawtucket, RI. 02863 Filed Dec. 13, 1965, Ser. No. 513,298 Claims. (Cl. 174120) The present invention relates generally to the electrical art and is more particularly concerned with the provision of a novel and improved protective sheath for insulated electrical conductors.
It is well known in the art to provide an outer protective sheath for insulated electric wires, and, in providing such a sheath, many requirements and standards must be met. For example, the resultant cable must meet certain requirements for tensile strength and elongation, as well as meeting certain minimum requirements for resistance to impact and crushing. In addition, tests for flexibility, dielectric strength, impregnation, moisture absorption, and dripping and flaking must also be met. Also of importance are its flame-retardant properties and its capacity to carry current overload.
In order to meet the many and varied tests listed above, the cable, in addition to having the necessary insulation for the electric conductors per se, must also have a suitable protective outer sheath. It is with such an outer sheath that the instant invention is concerned, it being understood that the function of such an outer sheath is not an insulation function, but rather is a protective function enabling the cable to meet many of the aforelisted tests.
In providing a protective outer sheath of the character above described, it has been conventional in the art to first cover the insulated conductors with an inner covering, such as paper, and then to cover the paper with an extruded vinyl. Although from a functional standpoint a protective sheath embodying the paper inner layer with the extruded vinyl outer covering has proven to be satisfactory, it has been found that the application of such a protective sheath to insulated conductors is relatively costly. Not only are separate operations required for first covering the insulated conductors with a layer of paper or the like, but, in addition, the equipment required for extruding a Vinyl sheath over the paper-coveredinsulated conductors is complicated and costly.
It is therefore a primary object of the instant invention to provide a protective outer sheath for insulated condoctors that is capable of meeting all of the aforelisted requirements for sheaths of this type but which nevertheless is easier and less expensive to apply to the insulated electrical conductors.
Another object is the provision of a protective outer sheath for electric conductors that may be applied to the conductors by using conventional and existing equipment, thus eliminating the expense of designing and providing special equipment for this purpose.
A further object is the provision of a protectivesheath of the character described wherein the sheath is in the form of an elongated laminated tape whereby only one operation is required to properly encase the insulated conductors so as to meet the aforestated requirements.
Still a further object is the provision of a protective sheath of the character described wherein that part of the inner surface of the sheath that comes in contact with the conductors is free of adhesive, or at least substantially so, thus facilitating free stripping of the sheath from the conductors.
Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.
In the drawings which illustrate the best mode presently contemplated for carrying out the instant invention:
FIG. 1 is a fragmentary perspective view showing my novel and improved protective sheath being applied to cover a plurality of insulated electrical conductors;
FIG. 2 is a fragmentary perspective view of a modified form of tape that may be used in making a protective sheath in accordance with the instant invention;
FIG. 3 is a further modification of the tape shown in FIG. 2; and
FIG. 4 is another modified form of tape.
Referring now to the drawings and more particularly to FIG. 1 thereof, there is shown generally at 10 a length of cable comprising a plurality of electrical conductors 12 and 14, each covered by its own suitable insulation 16 and 18, which insulation may be of any suitable material, such as vinyl. Located between the wires 12 and 14 is a ground conductor 20 also covered with its own insulation 22 which may be of any suitable material, such as paper. It will be understood that although FIG. 1 illustrates two insulated electrical conductors with an insulated ground conductor therebetween, the instant invention is applicable to a cable having one or any number of insulated conductors.
A protective outer sheath 24 is spirally wrapped around the insulated conductors so as to completely encase and protect the latter in order that the resultant cable 10 may meet the various types of requirements and standards hereinbefore enumerated. As illustrated, the outer protective sheath 24 comprises three separate elongated tapes 26, although it will be understood that an equally effective sheath could be provided utilizing one or two tapes as well. It has been found that the use of three separate ends enables existing equipment to be used for spirally wrapping the sheath 24 around the inner conductors, and hence the use of three ends is preferred, even though it is not essential.
Each of the tapes 26 is of identical construction and comprises a vinyl outer layer 28 to which there is laminated an inner backing 30 of a suitable material, preferably paper. It will be understood that the backing 30 imparts to the tape 26 certain desired characteristics, such as resistance to elongation, etc., and hence a critical feature of the inner backing 30 is that it be greatly resistant to elongation, this beinga feature which is obviously lacking in vinyl. As Will be noted, the inner backing 30 extends longitudinally for the length of the tape 26, but does not cover its entire Width. More specifically, a portion 3-2 of the inner surface of the vinyl layer 28 is left exposed, and preferably this exposed inner surface portion is covered with a pressure sensitive adhesive. Likewise, it is. preferred to cover a portion of the outer surface of the vinyl layer 26 with a pressure sensitive adhesive, as illustrated at 34. It will now be seen that when the tapes 26 are spirally wound around the inner conductors, the unbacked portions 32 will overlap the portion 34 of the adjacent spiral wrap covered with pressure sensitive adhesive, whereupon the adhesive on portions 32 and 34 will' securely bind and integrate the sheath 24 in a manner thought to be apparent. Although it is preferred to utilize pressure sensitive adhesive at both the areas 32 and 34, it will be obvious that adhesive may be applied to only one of these areas with satisfactory results. It will be equally. obvious that the proportion of tape 26 that is backed, and hence the proportion that is exposed, may be varied. The important thing is that when the tapes 26 are spirally Wrapped to form the sheath 24, the inner surface of the sheath in engagement with the insulated conductors 12, 14 and 20 will be completely hacked or, at least, substantially so. This is an important consideration in meeting certain of the 6 requirements and standards for protective sheaths of the type with which the instant invention is concerned.
In some cases, no pressure sensitive adhesive may be used, but rather the overlapping portions of the tape may be bound by fusion, such as by-application of heat or a suitable solvent. Where used, however, this technique must be employed with caution, since the application of too much heat might well result in deleterious effects to the vinyl inner insulations 1 4 and 16.
Referring now to FIG. 2, a slightly modified form of tape is shown. Specifically, the tape 36 comprises a vinyl outer layer 38 having an inner backing made up of a plurality of longitudinally extending strands 40 of Fiberglas or the like in side-by-side relation. Thus, the Fiberglas strands 40 function to complement the vinyl layer 38 in the same manner that the paper backing 30 complements the vinyl layer 28 shown and described heretofore. It will again be noted that the Fiberglas backing 40 does not cover the entire width of the layer 38, thus leaving a portion 42 exposed, which portion may be covered with a pressure sensitive adhesive as discussed hereinbefore. It will be understood that the tape 36 is applied to provide a protective sheath in exactly the same manner as hereinbefore described in connection with the tapes 26. It will also be understood that other materials having generally the same binding effect as Fiberglas could be alternatively used for the backing. Examples of acceptable alternative materials would be nylon and cotton yarn.
The tape 44 shown in FIG. 3 is very similar to the tape 36, the only difference being that the Fiberglas backing 46 comprises strands that instead of being in sideby-side relation are slightly spaced from each other. In addition, the overall tape is strengthened by having a few widely spaced strands of Fiberglas 48 secured to the unbacked portion 50 of the vinyl layer 52. Here again, a pressure sensitive adhesive may be applied to the unbacked portion 50 for effecting integration of the sheath during spiral winding of the tape 44.
In FIG. 4, another form of m yinvention is shown, wherein by making the vinyl tape 54 of suflicient thickness the desired protective characteristics are achieved without the necessity of providing a backing. Once again, however, a portion of the inner surface of the tape 54 is preferably covered with a pressure sensitive adhesive, as at 56, and the outer surface of the tape 54 (not shown) may have a similar edge portion covered with a pres sure sensitive adhesive in the same manner that the'p'ortion 34 of tape 26 is so covered.
While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.
What is claimed is:
1. A cable comprising an insulated conductor, a spiral Wrap in contact with said insulated conductor consisting of at least one elongated tape, said tape comprising a vinyl outer layer, an inner backing laminated to the inside surface thereof, said backing extending for the length of said tape but covering only a portion of the Width thereof, said backing being of a material characterized by substantially greater resistance to elongation than said vinyl, the unbacked portion of said tape overlapping the outer surface of the next-adjacent spiral wrap whereby the inner surface of said sheath in engagement with said conductor is substantially completely hacked, and means securing said overlapping portions of said tape to each other to integrate said sheath.
2. The cable of claim 1 further characterized in that said inner backing is paper.
3. The cable of claim 1 further characterized in that said inner backing comprises longitudinally extending strands of a material having substantially the binding characteristics of glass fibers.
4. The cable of claim 1 further characterized in that saidsecuring means comprises a pressure sensitive adhesive.
5. The cable of claim 1 further characterized in that said securing means comprises fusion of said overlapping portions.
6. The cable of claim 3 further characterized in that said strands are in side-by-side engagement.
7. The cable of claim 3 further characterized in that said strands are slightly spaced from each other.
8. The cable of claim 3 further characterized in that said unbacked portion of said vinyl layer has a few widely spaced longitudinally extending strands of the same material adhered thereto.
9. The cable of claim 4 further characterized in that said pressure sensitive adhesive is applied to the unbacked portion of said vinyl layer.
10. The cable of claim 9 further characterized in that said pressure sensitive adhesive is also applied to the outer overlapped surface of said tape.
References Cited by the Examiner UNITED STATES PATENTS LEWIS H. MYERS, Primary Examiner. E. GOLDBERG, Assistant Examiner.