US3282040A - Method of making cable and cable valley filler - Google Patents

Description

Nov. 1, 1966 F. HlRscH 3,282,040

METHOD 0F MAKING CABLE AND CABLE VALLEY FILLER Original Filed June 15, 1964 ATTORNEYS.

United States Patent O l 4 Claims. (Cl. 57-165) This application is a division of the application filed June 15, 1964, Serial No. 375,235.

This invention relates to improvements in electric cables and more particularly to the method of making l-ow voltage cables that have water repellent paper fillers in the valleys between insulated conductors and to the method of making the valley lillers.

Multiple conductor electric cables commonly have the valleys between the insulated conductors filled with paper, jute, or other material to provide a round contour over which the outer covering or sheath of the cable is applied. It is important, however, to prevent the paper, jute or other filler material from acting as a wick and conveying moisture longitudinally of the cable. Where paper has been used as the filler it has been conventional practice to prevent such wick action by using a relatively hard paper which is immersed in wax prior to being twisted into a filler strand or cord.

Such twisted paper filler strands are hard and have a limited deformability, and in order to provide a substantially round contour for the cable it often is necessary to use a number of them. It has been necessary to have a number of different sizes of fillers for different sizes of cables, and for cables having different numbers of conductors and resulting differences in the shapes and sizes of their valleys.

It is an object of this invention to provide an improved method of making cable of the type having a paper filler in the valleys, and an improved method of making the valley filler for such cable.

Contrary to the usual practice, this invention uses creped paper for the valley filler instead of kraft paper. Creped paper has been considered unsuitable for such use in cables where wick action must be avoided. In fact, creped paper has been use in the past as a valley filler only in oil-filled cables where the wick action was desirable, as in the Branthwaite Patent 1,886,786, November 8, 1932, where it is explained that with creped paper the oil becomes more quickly distributed through the cable. In cables that are filled with insulating oil or other fluid insulation it is known to provide a channel in the cable to facilitate the flow of the oil or other fiuid lengthwise through the cable.

The cable with which this invention is concerned involves just the opposite considerations. Travel of moisture or -other liquid, if it gets into the cable, must be prevented or limited. The valley fillers must be constructed of material which will not operate with a wick action to distribute moisture lengthwise within the cable. Creped paper cannot be immersed in wax and then gathered to form valley llers in the way in which hard kraft papers are treated because the creped paper will take up an excessive amount of wax and it is of too low tensile strength to be formed into a suitable cord or strand for use in a valley of an electric cable.

This invention involves the novel concept of using creped paper which is much lighter, more flexible, and more resilient than ordinary kraft paper as a valley ller and imparting the necessary water repellent quality to the creped paper by applying wax which is sprayed onto the paper instead of immersing the paper in Wax. By this method the amount of Wax on the paper is limited and 3282,04@ Patented Nov. 1, 1966 rice there is no lling of the small crepe valleys of the creped paper with wax. However, the wax sprayed onto the surface of the paper covers the entire surface and after the paper has been gathered and twisted into a filler strand lor cord the wax penetrates the paper and is present in suicient quantity to prevent wick action. It has been found that the wax can be m-ost easily applied in the necessary small quantity by spraying it onto the creped paper in the form of a water dispersion before the paper is folded or gathered. In the preferred embodiment of the invention the amount of wax applied is approximately three to four percent of the weight of the paper with the wax on it, after the water has evaporated.

The invention has several important advantages. One is that the creped paper had added volume and that a 16 lb. creped paper can be used in place of 30 to 40 lb. kraft paper fillers which are not creped. Another advantage is that the amount of wax used lon the creped paper is much less than that used on the kraft paper which has been immersed in a wax bath prior to twisting it int-o a cord or strand. This results in a `substantial saving in material which makes the cable less expensive to manu facture and which also makes the cable lighter in weight. For example, one cable valley filler made in accordance with this invention weighs 5 lbs. per thousand linear feet as compared with 9.6 lbs. per thousand linear feet for comparable conventional kraft paper valley filler.

In addition to the advantages of being less expensive and lighter in weight, the electric cable made in accordance with this invention actually is better cable. The valley fillers made of the creped paper are soft and more formable than the valley fillers made of the hard kraft paper immersed in a wax bath. Because of this softer and more formable characteristic the assembly of insulated conductors and valley llers takes the desired round shape more easily and forms a smoother and better final product.

Other objects, features and advantages of the invention willdappear or will be pointed out as the description procee s.

In the drawings, forming a part hereof, in which like views:

FIGURE l is a diagrammatic View showing a multiconductor electric cable with the outside sheath removed for part of the length and with the conductors and valley fillers separated to show the various parts of the assembly;

FIGURE 2 is an enlarged sectional view taken on the line 2 2 of FIGURE l; and

FIGURE 3 is a diagrammatic view showing the way in which the filler material is made in accordance with this invention.

In the illustrative embodiment of this invention an electric cable indicated generally by the reference character 10 includes three electrical conductors 11, 12 and 13 surrounded by individual walls of suitable electrical insulation 15 and enclosed within an outer sheath 17 of electrically insulating material. The outer sheath 17 may be moistureproof or waterproof for use in underground installation. The insulated conductors 11, 12 and 13 are located adjacent to one another and preferably touch one another along lines of adjacency designated by the reference characters 21.

There are several valley fillers 23 located in each of the valleys between the insulated conductors and outwardly of the lines of adjacency. These valley fillers 23, originally round or oval in shape, are distorted as necessary to fill the valleys and make the assembly of the insulated conductors and the valley fillers substantially circular, so as to fill the space within the sheath 17.

While it is desirable that the valley fillers distort and compress to the exact cross section of each valley, it is not essential that they ll the valley all the way to the line of adjacency 21 because the fillers pressing against each other and against the sides of insulated conductors will form a barrier to the entrance of any water into the interior of the assembly even though they do not reach all t-he way to the vertex lof the angle formed by the insulated conductors at the points lof adjacency. However, it is desirable that the llers should reach into the vertex of these angles at frequent locations so as not to leave an unobstructed passage lengthwise of the cable for the trave-1 of any moisture which may enter at the end of the cable. The actual cross section of each of the valley fillers 23, in the completed assembly, will vary somewhat at different locations along the length of the cable depending upon how they are pressed into the valleys and their relation to one another at the time of distortion into the space which they are to till.

The valley llers 23 are originally round or oval in cross section and since there are limits to which the shape can be distorted it is usual to employ a plurality of fillers in a valley so as to ll the valley with less distortion of the shapes of the individual fillers. With conventional fillers it has been the practice to employ nine different sizes of fillers for various valleys on different sizes of cable, but with this invention it is sufficient to have only three sizes of fillers. This saving is because of the `greater softness and compressibility of the creped paper fillers.

Comparative tests have been conducted on the lightly waxed, creped paper filler of the present invention and heavily waxed kraft paper ller widely used in cable manufacture. The following table lists data obtained using a Randall Stickney gage with a ya in. diameter pressure foot at room temperature and measuring the deformation l seconds after the application of the load:

Creped, .23 x .10.

The above data indicates that the lightly waxed creped paper filler deforms 4about twice as much as the more heavily waxed kraft paper ller.

FIGURE 3 is a diagrammatic showing of the way in which one of t-he fillers 23 is manufactured. A strip of creped paper 28, for example inches wide is sprayed with a water dispersion of wax from a spray nozzle 30. The dispersion is preferably applied as a ne mist or fog and it is, of course, desirable to apply as little wax as necessary for adequate water repellancy.

An anionic dispersion of parat-'tin wax such as is available from Nopco Chemical Company is suitable, for example. The wax itself may be the same as the wax used in treating kraft paper by the immersion procedure. The temperature at which the dispersion is sprayed onto the creped ypaper -should be such as to prevent the parain from solidifying and separating. This temperature may be room temperature, but it has been found that a temperature of about degrees F. gives very satisfactory results. As previously explained, it has been found that wax applied by a fine spray to the surface of the creped paper is in suioient quantity if the weight orf wax is between three and four percent of the weight of the combined wax and paper after the water of the dispersion has evaporated. The dispersion partially penetrates the paper as it is sprayed on. This does not leave the paper covered with a continuous coating of wax and substantial quantities of the interstices of the creped paper are not filled with Wax. The paper is gathered and twisted while wet to form a cord 32, as indicated in FIGURE 3. The amount of twist may vary, but about six turns per foot gives a satisfactory product. This causes further penetration and distribution of the wax into the paper and over its surface. The contact between wax covered areas of the gathers and adjacent areas form barriers which effectively close off against moisture transfer any longitudinally extending open space-s which may exist within the twisted cord 32.

The creped valley llers of the present invention may be made from 16 pound ream weight paper as compared with 30 to 40 pound kraft papers required for impregnated fillers. It has been found that valley fillers made as herein described are adequately water repellant and will not permit Water to travel along their length by wick action. More wax can be used, but it is unnecessary and adds both cost and weight. In the creped paper iiller of this invention the wax comprises 3 to 4% of the weight of the ller, whereas in the wax impregnated kraft paper the wax comprises 15 to 20% of the weight of the ller. Because of the lower weight and the greater compressibility of the creped paper filler t-he weight of the ller per foot of cable is substantially reduced, for example from 9.6 pounds to 5 pounds per y1000 feet in one cable.

This invention may be variously .modified and embodied within the scope of the subjoined claims.

What is claimed is:

1. The method of making a multi-conductor electric cable which comprises locating insulated conductors adjacent to one another with valleys beyond their lines of adjacency, making lightweight water repellant cable valley llers by spraying creped paper with wax to apply a quantity of wax to the surface but limiting the application of wax so as to leave at least a substantial quantity of the interstices of the creped paper free of wax, and gathering the paper transversely of its length to the cross section of a cord with a diameter that leaves the gathers loosely packed against one another and the cord capable of distortion and compression to conform to space within a val- Iley between conductors of the electric cable, placing the fillers in valleys between said conductors, shaping the assembled conductors and llers to a rounded cross section, and enclosing the assembly in an outer sheath.

2. The method described in claim 1 characterized by twisting each paper strip to confine the gathers to a given diameter.

3. The method described in claim 2 characterized by spraying the wax on the creped paper in a water dispersion and with the wax approximately three to four percent of the weight of the creped paper with the wax thereon after the water has evaporated.

4. The method of making a water repellant, light weight cable valley filler which comprises the steps of spraying creped paper with a wax in water dispersion at a temperature which prevents the wax from solidifying and separating, gathering and twisting the paper transversely of its length to a cord, limiting `the application of the wax in water dispersion so as to leave the creped paper with a discontinuous coating of wax and a substantial quantity of the interstices of the creped paper unfilled With Wax, and drying the cord to evaporate the water.

(References on following page) 5 6 References Cited bythe Examiner 2,388,745 11/ 1945 Katz 57-165 X 2,407,926 9/1946 Hamilton 57-32 X UNITED STATES PATENTS 2,787,045 4/1957 Crawfond 57-165 X 448,174 3/1891 Williams et a1 57-154 2,981,052 4/1961 McHenry 57-165X 604,350 5/1898 claviez 57-32 5 3,023,267 2/1962 Rubinstein er a1. 174-116 X 1,169,949 2/191-6 Gares 174-116 1,837,795 12/19311 schneider 174-116 FRANK J. COHEN, Primary Examiner.

Claims (1)

1. 4. THE METHOD OF MAKING A WATER REPELLANT, LIGHT WEIGHT CABLE VALLEY FILLER WHICH COMPRISES THE STEPS OF SPRAYING CREPED PAPER WITH A WAX IN WATER DISPERSION AT A TEMPERATURE WHICH PREVENTS THE WAX FROM SOLIDIFYING AND SEPARATING, GATHERING AND TWISTING THE PAPER TRANSVERSELY OF ITS LENGTH TO A CORD, LIMITING THE APPLICATION OF THE WAX IN WATER DISPERSION SO AS TO LEAVE THE CREPED PAPER WITH A DISCONTINUOUS COATING OF WAX AND A SUBSTANTIAL

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