US3662091A

US3662091A - Electrical conductor with paper insulation

Info

Publication number: US3662091A
Application number: US128763A
Authority: US
Inventors: Ludwik Jachimowicz; Edwin W Reasoner; Jerzy A Olszewski
Original assignee: General Cable Corp
Current assignee: General Cable Corp
Priority date: 1968-05-16
Filing date: 1971-03-29
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09

Abstract

This electrical conductor is insulated with paper formed by squeezing the water out of a ribbon of woodpulp applied to the conductor. The novel features include the offcenter location of the conductor in the ribbon so that the portion of the ribbon extending from one side of the conductor is long enough to wrap all the way around the conductor and over itself in a lap seam. A stream of water is applied to one surface of the paper to refloat some of the fibers that are in position to extend across the seam to lock the seam closed when the ribbon is wrapped around the conductor.

Description

United States Patent Jachimowicz et a1.

' [451 May 9, 1972 [54] ELECTRICAL CONDUCTOR WITH PAPER INSULATION [72] Inventors: Ludwik Jachimowicz, Elizabeth; Edwin W. Reasoner, Morristown; Jerzy A. Olszewski,

[21] Appl. No.: 128,763

Related US. Application Data [62] Division of Ser. No. 729,600, May 16, 1968, Pat. No.

[56] References Cited UNITED STATES PATENTS 1,800,411 4/1931 Selvig ..174/1 13 AS 3,409,734 11/1968 De Vine ..174/113 R Primary Examiner-E. A. Goldberg Attorney-Sandoe, Hopgood & Calimafde 5 7] ABSTRACT This electrical conductor is insulated with paper formed by squeezing the water out of a ribbon of woodpulp applied to the conductor. Thenovel features include the offcenter location of the conductor in the ribbon so that the portion of the ribbon extending from one side of the conductor is long enough to wrap all the way around the conductor and over itself in a lap seam. A stream of water is applied to one surface of the paper to refloat some of the fibers that are in position to extend across the seam to lock the seam closed when the ribbon is wrapped around the conductor.

8 Claims, 6 Drawing Figures PATENTEBMM 9 m2 3. 662,091

FIG. la.

If CLEANER I I TANK 2O FURNACE 80 DRYING FORMER TAKE- UP REELS INVENTORS LUDWIK JACHIMOWICZ JERZY A. OLSZEWSKI YEDWIN W. REASONER ATTORNEYS.

ELECTRICAL CONDUCTOR WITH PAPER INSULATION RELATED PATENTS BACKGROUND AND SUMMARY OF THE INVENTION In the manufacture of paper-insulated electrical conductors by passing a conductor through a tank of woodpulp and then squeezing the pulp to form a paper ribbon with the conductor imbedded therein, projecting edge portions of the ribbon on opposite sides of the conductor are wrapped around the conductor to form a cylindrical tube of paper insulation. If the edge portions of the ribbon were permanently affixed to the balance of the paper in the wrapping or polishing operation, the insulation would be a continuous homogenous tube. This does not occur, however, because wet paper ribbon does not bond to itself as woodpulp does. Use of glues, starches or other additives to secure the edge portions to the underlying paper in which the conductor is imbedded, is objectionable because it impairs the insulating qualities of the paper. It is necessary to squeeze the water out of the woodpulp-and form a paper prior to the wrapping or polishing operation because otherwise the wire and woodpulp will fall apart when lifted from the feltbelt on which drainingof water takes place.

In the subsequent operation of drying and wire handling, because the ribbon edge portions are not sealed to the underlying paper, the edge portions intermittentlyopen up and in some instances the bare wiresprings out of the paper in which it is imbedded. Since there has been no provision for sealing of the edge portions in acontinuous and positive-manner, the resulting product in the-prion art, because ofchange distribution andvarious degreesof edge portion adhesion, has been a non-uniform product.

In a strict sense the edge portions are ironed down in the forming and drying processes, butnot sealedrln the presence of moisture duringsplicing of cables athigh humidity and in handling of wire by. asplicer, the. edge portions tend to lift and open up. This becomes especially objectionable with automatic splicing machines. The sliding motion of the jaws gripping the wire tends to open the edge portions. The wire is bent at sharp angles and this also contributes to the opening of the edgeportions.

This invention is=based on the discovery that some of the woodpulp fibers forming the wet paper and predominantly aligned longitudinally parallel to the edges of the ribbon can be refloated from the surface of the wet paper and changed in alignment so as .to act as a,-binder by wrapping them around the outer surface of the insulated conductor in a manner similar to servingra cotton yarn around a conductor, as-is done on a magnet wire and the like.

In effect, the edge portion becomes as if stitched on the seam with the reoriented fibers occupyinga helical conformation across the edge portion seam. In addition, once the edge portion becomes fastened as described above, and the wet wire with the fastened edge portion is subsequently passed through a drying oven, an additional benefit isreali'zed. During the fast drying in the oven, the fibersof-the edge portion and the fibers of underlying layers of wet paper are kept in close contact by the fastening of the edge portions. When the drying commences in'the hot zone of thedrying oven, the fiber of the edge portions and the fiber of the underlying paper layers remain in contact; and in the process of shrinking and curling (due to drying) the fibers of the edge portions mesh to some extent with the fibers of the underlying .paper, resulting in a quasi-intermeshing of the paper which does not occur when wet edge portions are merely wrapped around the underlying paper and left free to shrink and lift slightly in the process of drying.

The liquid used for refloating of surface fibers can also be used as a vehicle for dye when it is desirable to color the outside of the insulation. Dye applied according to this invention is on the surface of the insulation and does not permeate all the way through. This maintains better insulating characteristics for the paper.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGS. la and 1b are diagrammatic side elevations of apparatus for making pulp-insulated electrical conductors in accordance with this invention;

FIG. 2 is a greatly enlarged sectional view of the line 22 of FIG. la, illustrating the way in which the woodpulp is molded around the electrical conductor with edge portions extending from both sides of the conductor;

FIG. 3 is a greatly enlarged sectional view taken on the line 33 of FIG. 1b and showing the change in cross section of the edge portion after the woodpulp has been squeezed or pressed to remove excess water and to produce a paper insulation, and showing also the application of water to refloat surface fibers near the edge of the longer edge portion;

FIG. 4 is a diagrammatic view showing the application of the water stream to the paper insulation; and

FIG. 5 is a fragmentary isometric view of the insulated conductor of this invention after forming and showing the way in which the refloated fibers of the longer edge portion extend across the lap seam.

DESCRIPTION OFTI-IE PREFERRED EMBODIMENT A bare wire electrical conductor 10 is withdrawn from a supply reel 12 at a conductor supply station 14. The wire passes over guide rolls 16 andthrough a wire cleaner 18, and thenpasses over other wire guides 19 and into a tank 20 containing a cylinder 22 which rotates on an axle 24. The apparatus actually h'as'a large number of parallel conductors, but to simplify the illustration and description, the invention will be described with only one conductor.

The'tank 20 contains woodpulp furnish 26 designated by stippling, and the conductor 10 passes around the underside of the cylinder 22and becomes imbedded in a mass or ribbon of woodpulp 30 which surrounds the entire circumference of the conductor 10 and whichis formed with projecting

edge portions

32 and 34. In accordance with one feature of the invention, the conductor 10 is located off center in the mass of woodpulp 30 so that the edge portion 34 is substantially longer than the edge portion 32.

The cylinder 22 extends above the surface of the pulp furnish 26 in the tank and at a location 38 the woodpulp 30 with the conductor 10 imbedded therein, is removed from the cylinder to a conveyor which preferably comprises a felt belt 40. This belt 40, passes around a guide roll 42 and across other guide rolls 44 to a squeeze station 46 where the woodpulp 30, with the conductor 10 imbedded therein, is squeezed between pressure rolls 48 to remove excess water from the woodpulp so that the woodpulp is changed into a wet paper ribbon. The squeeze station 46 is at a substantial distance from the guideroll 42 so that a substantial amount of water can drain from the woodpulp before the woodpulp reaches the pressure rolls 48.

At the discharge side of the pressure rolls 48, the paper insulation 30', with the conductor 10 imbedded therein, is removed from the conveyor belt 40, since the paper has sufficient strength to remain on the conductor after the excess water has been squeezed out by the pressure rolls 48. The belt 40, which is a continuous belt, passes around guide rolls 50 and back to the guide roll 42.

The apparatus thus far described is illustrated diagrammatically and is described broadly since it is conventional except for the feature by which the last wire guide 19 locates the conductor off center in the woodpulp mass 30.

The paper insulation 30, with the conductor 10 imbedded therein, passes around

guide rolls

52 and 53, and then passes to a former 56 in which the projecting

edge portions

32 and 34 are bent around the paper which covers the conductor 10, and wrapped so as to give the assembly a conductor, circular cross section, as shown in FIG. 4. A former for thus wrapping the projecting edge portions of a paper ribbon is well known and such a machine is disclosed in U.S. Pat. No. 1,615,416 issued Jan. 25, 1927. The construction of the former 56 of the present invention may be the same as that shown in FIGS. 3 and 4 ofU.S. Pat. No. 1,615,416.

When this invention is made with the offcenter feature, the conductor 10 is preferably located so that at least 70 percent of the width of the paper strip or ribbon, in which the conductor is imbedded, is on the side of the edge portion 34 and not more than 30 percent of the width of the insulation strip is on the other side of the conduction as shown in FIG. 3.

With this construction the edge portion 34 will wrap around substantially the entire circumference of the assembly, as shown in FIGS. 5. This leaves the paper insulation tube with only one seam 60 on the outside. It will be evident that the actual length of the edge portion 34, in order to obtain this result, depends upon the thickness of the edge portions, as well as upon their length, because the edge portion 34 has to cover the wrapped edge portion 32 and a greater length of the edge portion 34 is required if the

edge portions

32 and 34 are thicker and the radius around which the edge portion 34 must wrap is thereby increased.

Referring again to FIG. 1b, a stream of water is supplied to the continuously moving insulation strip 30 by a nozzle 64 at a location just ahead of the former 56. This stream of water, which also contains dye, if the insulation is to be colored, flows to the nozzle 64 through tubing 66 from a water and dye supply vessel 68. The rate of flow is controlled by the hydrostatic pressure from stable level of liquid in the supply tank. The details of maintaining constant level are conventional and are not shown.

When dye is used, it is desirable to limit the dye in the insulation so as to preserve the electrical characteristics of the insulation by applying the dye only to one surface of the flap on which the surface fibers are refloated.

When dye is applied to the insulation of the edge portion 34, the other insulation on the conductor is preferably left free of dye so as to maintain better electrical characteristics and to avoid impairing physical aging characteristics.

The nozzle 64 is located on one side of the long edge portion 34 and the stream of water is applied to the surface of the edge portion 34 which will be on the outside of the insulation.

after the forming operation. It is a feature of the invention that the water from the nozzle 64 is applied to the surface of the edge portion 34 immediately ahead (2 or 3 feet upstream) of the location at which the former 56 contacts with the edge portions to bend them circumferentially around the conductor 10 and the paper insulation which coats the conductor itself. FIG. 3 indicates the water from the nozzle 64 by the reference character 74 and the water is applied to the surface of the paper insulation so close to the former 56 that the water 74 does not have time to soak into the wet paper before the former contacts with the surface fibers which are refloated by the stream of water 74. These refloated fibers are thus reoriented from their longitudinally extending positions to a helical conformation which is a resultant of the longitudinal movement of the insulation 30' and the conductor 10 through the former and the relative movement of the former circumferentially with respect to the surface of the paper insulation.

In practice, this refloating operation requires a correlation of the amount of water 74, the distance from the nozzle 64 to the contact surfaces of the former, and the longitudinal speed of the conductor and insulation through the former.

I Experience has shown that from 2 to 5 percent of the surface fibers can be refloated and dislodged from their predominantly longitudinal alignment (parallel to the conductor 10) by former contact surfaces rotating at 6,000 revolutions per minute against paper insulation moving through the former at the rate of to feet per minute. These figures are given by way of illustration; but in the preferred construction the speed of the former is at least 5,000 revolutions per minute and the progress of the conductor and insulation through the former is at least 100 feet per minute. The paper insulation, as it passes through the former 56, has an approximate water content of 70 percent and a dry pulp content of 30 percent, neglecting the free floating water stream. Under such operating conditions, good results are obtained with the nozzle 64 2 to 3 feet upstream (ahead of) the location where the former first contacts with the

edge portions

32 and 34, to fold them. These values are given by way of illustration.

The nozzle 64 may be a hypodermic needle of size No. 20 or 22 and the necessary stream of water from this nozzle can be obtained with a static pressure of water column of 26 inches. The water stream 74 is prevented from spreading to the edge portion 32 by the hump in the insulation over the conductor 10, this hump serving as a barrier. When dye is included in the water 74, the outside surface of the edge portion 30 is colored an this colors the entire outside surface of the finished conductor when the edge portion 34 is long enough to extend around the entire circumference of the assembly as shown in FIG. 5. I

The refloated surface fibers, helically extending across the seam 60, are indicated diagrammatically by the reference character 78. These fibers hold the seam closed as it passes through a drying furnace 80 (FIG. 1b). By having the seam held closed there is an intermeshing of fibers of the interfaces of the edge portion 34 and the paper insulation over which it is wrapped, as previously explained. The insulation produced by this invention is substantially stronger than that produced by methods of the prior art, which do not include the refloating step for reorienting fibers along the seam edge prior to forming. It has also further mechanical and electrical implications. In pairing, stranding and cabling, the insulation of conductors is held rigidly around the wires due to sealing of edge portions to a greater extent than in the prior art. This results in higher inductance of pairs and lower mutual capacitance for a given cable cross section.

Beyond the drying furnace 80, the insulated conductor passes around a pulling capstan 82 and over guide rolls 84 to take-up reels 86 on which the wire is wrapped.

The preferred embodiments of the invention have been illustrated and described, but changes and modifications can be made and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. An electrical conductor including a wire conductor, a coating of insulating paper around the wire conductor, the coating having an edge portion extending from one side thereof, said edge portion having an inner end joined to and of one-piece construction with the rest of the coating, the edge portion projecting far enough beyond the other part of the coating to .provide a length as great as the circumference of the coating on the conductor other than the edge portion and said edge portion being wrapped around substantially the entire circumference of the coating on the wire conductor and with the outer end of the edge portion in contact with an underlying part of the coating to form a lap seam.

2. The electrical conductor described in claim 1 characterized by the paper being made of woodpulp and having surface fibers at the outer end of the edge portion extending across the lap seam to hold the seam closed.

3. The electrical conductor described in claim 2 characterized by the paper having two edge portions extending from the part of the coating on opposite sides of the conductor, the edge portion that wraps around substantially the entire circumference being longer than the other edge portion and completely covering it when the edge portions are wrapped to form an insulation tube of substantially circular cross section, and dye on the outside surface of at least longer edge portion and only on said outside surface.

4. The electrical conductor described in claim 1 characterized by the edge portion being of a width greater than the circumference of the coating on the conductor other than said edge portion and the outer end of said edge portion overlapping a portion of its own width that is near to its inner end to form a lap seam.

5. The electrical conductor described in claim 1 characterized by the paper being made of a mass of woodpulp applied to the wire conductor and with some of the woodpulp extending for a radial distance outward from the conductor further than the other pulp as the pulp is originally applied, and the paper being made of woodpulp from which water has been squeezed out after application of the woodpulp to the wire conductor, the outer surface of the edge portion adjacent to the lap seam having raised fibers of the paper extending across the lap seam and different from other fibers that are in their squeezed condition.

6. The electrical conductor described in claim 5 characterized by all of the paper, including the fibers that extend across the lap seam, being pressed down firmly with smooth circumferencial surface around the entire outside surface of the insulated conductor.

7. The electrical conductor described in claim 3 characterized by the longer edge portion being at least 70 percent of the combined width of the conductor plus the length of both edge portions.

8. The electrical conductor described in claim 3 characterized by the shorter edge portion being wrapped circumferentially around a part of the circumferential extent of the other paper insulation on the conductor and in the same direction as the longer edge portion is wrapped but not extending far enough to overlap any of the outside surface of the longer edge portion.

Claims

1. An electrical conductor including a wire conductor, a coating of insulating paper around the wire conductor, the coating having an edge portion extending from one side thereof, said edge portion having an inner end joined to and of one-piece construction with the rest of the coating, the edge portion projecting far enough beyond the other part of the coating to provide a length as great as the circumference of the coating on the conductor other than the edge portion and said edge portion being wrapped around substantially the entire circumference of the coating on the wire conductor and with the outer end of the edge portion in contact with an underlying part of the coating to form a lap seam.