US 1746390 A
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Description (OCR text may contain errors)
Feb. 11, 1930.
o. A. FREDERlcKsoN 1,746,390
ELECTR I CAL CABLE Filed May 29. 1926 Patented Feb. 11, 1930 UNiTan stares PATENT OFFICE OTTO A. FREDERICKSON, OF 'WETHERSFIELD, CONNECTICUT, ASSIGNOR TO THE WIRE- MOLD COMPANY, OF HARTFORD, CONNECTICUT, A CORPORATION OF CONNECTICUT ELECTRICAL CABLE Application led May 29,
This invention relates to electrical cables formed of two or more covered electrical conductors, and more particularly to fillers adapted to be laid in the valleys between the conductors.
When electrical cables are made up of two or more covered conductors which are enclosed and united by an outer jacket it is desirable to lay fillers in the valleys between the 1a covered conductors to form a smooth surface over which the outer jacket is laid, and to exclude air spaces between the conductors and jacket.
Heretofore it has been customary to form these fillers of jute or other materials the fibres of which are spun or twisted together to produce strings or cords of the desired di ameter. The jute fillers employed heretofore are open to the objection that the fibres of the jute tend to form lumps or bunches within the covered cable, thus producing rough place in the finished cables.
If it is attempted to prevent the formation of lumps within the cable by giving a harder twist to the jute fibres, or by forming the fillers of cotton or other fibres that are capable of producing relatively strong strings or cords, difficulty is experienced in spreading out a filler and working the parts thereof into the various portions of the valley of a cable so that the air spaces'within the valleys are completely filled up.`
Having the foregoing in mind the present invention relates to a novel type of filler which overcomes the objections above mentioned, and the filler of the present invention is formed of a multiplicity of individual strands which are laid side by side in general longitudinal relation to each other so that the strands are free to move laterally relatively to each other, and as a result they may readily be worked into the various parts of the valleys to completely lill-the same.
The individual strands of the filler are preferably formed of twisted paper, as it is found that twisted paper strands will not form lumps or rough places in the cable jacket under the action of the dles `employed to work the iillers into the valleys. Furthermore, the paper strands do not cling to each 1926. Seal No. 112,506.
other to the same extent as do soft strands of spun ibres and the separate paper strands are therefore readily worked away from each pther into the diiferent portions of the valeys.
A filler constructed in accordance with the present invention and consisting of a multiplicity of individual strands that are free to move laterally relatively to each other,- cannotbe readily handled unless the strands are bound together, and in accordance with a further feature of the present invention the individual strands are held together by a binder or holding strand that is preferably wound spirally about the group of filler strands. This .binder strand however should be of low tensile strength in order that it will readily break after the filler has been incorporated in the cable. This is desirable in order that the iller strands may be released after they are laid in the valleys so that they are free to pread out into the various parts of the val- The various features of the invention will be best understood from the following description when read in connection with the drawings, wherein Fig. 1 is a perspective view of a short portion of a cablehaving two electrical conductors, and provided with llers constructed in accordance with the present invention;
Fig. 2 is a transverse sectional view through the cable of Fig. l;
Fig. 3 is a perspective view of a cable having three electrical conductors, and providedv with fillers constructed in accordance with the present invention;
Fig. 4 is a transverse sectional view through the cable of Fig. 3;
Fig. 5 is a perspective view of one type of filler constructed in accordance with the present invention; and p l Fig. 6 is a perspective view of a diii'erent type of filler.
The fller-forming the subject matter of the present invention may be used in connection with cables formed of two or more covered electrical conductors, and is well adapte'd for use in cables that vary extensively in size and construction.
In the construction shown in Figs. 1 and 2 the filler forming the subject matter of the present invention is employed in the construction of a two conductor cable such as is adapted for use in wiring a building for electric light current. This cable is shown as formed of the metallic electrical conductors 10 each of which is covered with rubber or other insulating material 11. A' braided jacket 12 is placed over the covering 11, and the jacket 12 is shown as protected by a spiral wrapper formed of cords or strands 13. The two covered conductors just described are enclosed in the outer jacket 14 which may be braided or otherwise constructed.
As above stated it is customary to place fillers in the valleys between the covered conductors to fill up the valleys to exclude air spaces and to form a smooth surface over which -the outer covering is laid, and it is highly desirable that the filler be so constructed that the parts thereof may be worked into the various portions of the valley to completely fill up the same.
The present invention therefore contemplates the use of fillers 15 that are formed of a multiplicity of relatively small cords or strands 16 (see Figs. 1, 2 and 6) which are laid side by side in substantially longitudinal relation so that when they are placed in a valley of a cable the individual strands may spread out and be forced into all portions of the space between the covered conductors and outer jacket 14, as best shown in Fig. 2.
The individual cords or strands 16 are preferably formed of twisted paper, as will be apparent from Fig. 6 where one of the strands 16 is shown. as having its end .untwisted The use of paper strands is desirable because twisted paper strands` a're extremely tough and durable, and they are also light in weight and inexpensive to manufacture, and may be readily worked into the various crevices of' a valley.
Cables of the type shown and described are frequently exposed to moisture and it is therefore desirable to treat the strands 16 with a moisture proofing substance. This treatment is preferably effected before the paper of the strands is twisted in order that a thorough treatment of all portions of the paper forming a twisted strand may be insured. A wax-like substance such as parafne which will serve as a lubricant between thestrands in preferably vemployed as the moisture-proofing substance, because the lubricating nature of such material will facilitate relative movementbetween the individual strands 16, and this will enable the strands to be more readily worked into the various portions of the valleys.
As above stated it is desirable to provide a readily ruptured holding or binding strand .about the filler strands 16 to hold them together until after they are laid in the valley of a cable. This binding strand may comprise a small relatively weak cord or thread 17 formed of cotton or other spun fibres as shown in Fig. 6, or it may be formed of twisted or untwisted paper or any other suitable material, and the binding or holding strand 17 is preferably wound spirally about the filler strands 16. The construction of the fillers 15 should be such that the individual strands 16 are held together as shown in Fig. 6 until the filler is incorporated in the cable, but the strength of the binder strands 17 should be sutliciently low to cause them to rupture readily under the action of the dies employed in manufacturing the cables to force the fillers into the valleys. This will be apparent from Fig. 1 of the drawing .wherein the fillers 15 are shown as having a v v vshape to conform to the valleys and some' of the binder strands are shown as broken.
In Figs. 3 and 4 of the drawings the filler of the present invention is shown as employed in constructing a cable having three electrical conductors 18 each of which covered with the insulating and protecting jackets 19, 20 and 21 of any suitable construction, and the three covered conductors are enclosed in the outer jackets 22 and 23 of any preferred construction. The conductors 18 are shown as larger in diameter than the conductors 10 and as provided with relatively thick protecting jackets. The val'leys between theconductors 18 are therefore relatively larger, and fillers of increased size are. required to till the valleys between the cables. The relatively large filler 24 shown in Fig. 5 may be formed of a central core 25 of substantial diameter 'The valley formed at the centre of thel cable of Fig. 3 between the three conductors .l
may contain a filler 28 such as shown in Fig. 6, and it will be noted that the binding strands 27 are shown ruptured in Fig. 3, as the binder strands are broken by the spreading movement of the strands forming the llers 24.
By forming the fillers in accordance with the present invention of a multiplicity of separate strands that are free to move relatively to each other and which are held together only by a readily ruptured binder strand, it will be seen that after the fillers are incorporated in a cable they may be spread out as shown so that they completely lill up the valley in which they are placed and form a smooth surface over which the outer jacket vention in the construction of a cable increases the flexibility of the cable since the individual filler strands are free to move to accommodate themselves .to a bend in the cable.
After the outer acket of a cable is applied and the lillers have been worked into the valleys between the conductors, it is desirable to treat the jacket with a moisture and fire repellant substance such as stearin pitch. This moisture and fire repellant substance is usually heated to a relatively high temperature to increase its penetration into the jacket, and the cable to be treated is passed through a bath of the heated coating substance. The heating of the coating substance not only increases its penetrating qualities, but serves also to melt the paraffine with which the paper strands forming the fillers are treated, with the results that the heated parafline will fill up the small air spaces that might occur between the strands of the fillers. The melting of the parafline serves also to secure the various strands of the fillers in their final position in the cable while at the Sametime the adhesvie properties of the parafline are not reat enough to prevent relative movement between the strands when they are subjected to a substantial strain.
What is claimed is 1. An electrical cable comprising, in combination, covered conductors laid side by side,
an outer jacket that encloses and `unites the conductors, and fillers for filling up the valleys between the conductors, each comprising la multiplicit of separate strands laid side by side longitu inally, a rupturable binder for maintaining the separate strands of a filler in assembled relation for handling and introduction into the space between the covered conductors, and which will readily break to free the separate strands of the filler when the filler is subjected to pressure that the individual strands thereof may be permitted to spread into and conform with the valley.
2. An electrical cable comprising, in combination, covered conductors laid side by side, an outer jacket that surrounds and unites the conductors, and llers for filling up the valleys between the conductors, each comprising a multiplicity of small separate strands of twisted paper laid side by side longitudinally in an unintertwined condition, a rupturable binder for maintaining the separate strands of a filler in assembled relation for introduction into the space between the covered conductors, and adapted to break readily to free the separate strands of the filler when the filler is subjected to pressure that the individual strands'thereof may move laterally into different portions of the valley.
3. As an article of manufacture, a filler for filling a valley between covered electrical conductors that are enclosed in an outer sheath, and formed of many individual twisted strips of paper laid side by side in a straight unintertwined condition so that the individual strands may move freely relatively to each other and held together by a binding strand of low tensile strength placed about the group of strands but which will readily break to release the strands.
5. As an article of manufacture, a filler for filling a valley between electrical conductors that are enclosed in an outer sheath, and formed of many individual strands of twisted paper having smooth rounded outer surfaces and laid side by side in a straightened unintertwined condition so that the individual strands may move freely relatively to each other into all portions of the valley to completely fill the valley, and means of low tensile strength for holding the strands of a filler in assembled relation for handling and introduction into a valley between conductors.
6. As an article of manufacture, a filler for filling a valley between electrical conductors that are enclosed in an outer sheath, and formed of many individual strands of insulating material having smooth rounded outer surfaces and laid side by side in a straightened unintertwined condition so that the individual strands may move freely relatively to each other into all portions of the valley to completely lill the valley, and means of low tensile strength for holding the strands of a filler in assembled relation for handling and introduction into a valley between conductors.
In testimony whereof, I have signed my name to this specification.
OTTO A. FREDERICKSON.