US3351706A

US3351706A - Spaced helically wound cable

Info

Publication number: US3351706A
Application number: US450231A
Authority: US
Inventors: Gnerre C Gerald; Dinunzio Ralph
Original assignee: Simplex Wire and Cable Co
Current assignee: SubCom Cable Systems LLC
Priority date: 1965-03-18
Filing date: 1965-03-18
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07
Also published as: GB1143226A

Description

, .-No v. 7,- 1967 c. GNERRE T 3,351,706

SPACED HELICALLY WOUND CABLE Filed March 18, 7 196 5 Z-Sheets-Sheet 1 v INVENTORS.

C. Gerald Gnerre Ralph DiNunzio v. BY Cm,Wn -42 amt! ATTORNEYS United States Patent-O 3,351,706 SPACED HELICALLY WOUND CABLE C. Gerald Grierre, Belmont, and Ralph Diuunzio, Lexington, Mass, assignors to Simplex Wire and Cable Company, Cambridge, Mass., a corporation of Massachusetts Filed Mar. 18, 1965, Ser. No. 450,231 1 16 Claims. (Cl. 174-105) I This invention relates to a method for applying spaced helical wire servings to oblong objects, such as electrical conductors.

It is often desirable to provide wire servings about oblong objects, such as tubes and electrical conductors, for the purpose of adding strength and armor protection to the finished product and in some cases for the purpose of providing an additional conductor to the overall composite. Moreover, it is often economical to apply such servings in spaced relationship to each other in instances where partial coverage is satisfactory.

Helical wire servings have, however, been generally avoided where less than about 90% surface coverage is used becauseof the difiiculty in applying the individual wire strands in uniformly spaced relationship to each other and alsobe'cause of the difficulty in holding such spaced wire in place during subsequent handling and use.

It is, therefore, an object of this invention to provide a method for applying spaced helical wire to oblong objects, such as electrical conductors and tubes, and for holding such wire in place during subsequent handling and use. These and other objects are accomplished by helically applying wire strands in equally spaced relationship to each other about a ribbed core. Preforming the wire is frequently desirable to reduce its tendency to change position on the core and to facilitate application of the wire strands in uniformly spaced relationship with respect to each other. Preforming also reduces the tendency of the wrapping to pop out of place when the conductor is put under stress and increases the flexibility of the product.

The ribs on the 'core, which are incorporated in the core at its formation oraddedin the form of, a tape,

that of the wire to be applied over them. The size of the can be straight or they can be helical with a lay opposite ribs will vary with the diameter of he wires to be used and the hardness .of the core. Generally the radial height of the ribs ranges from one-third to two-thirds ofthe diame ter of the overlying helical wire. The presence of the ribs on the core greatly aids in maintaining the spacing of the overlying wire during application of the wires and during subsequent handling and processing, and increases the permissable angle of lay of the wire, therefore, providing further economies.

A particularly advantageous application of this invention is in the manufacture of small armored submarine cable for deep water service. In such instances using polyolefin insulation it is often possible to realize a good cable modulus with less armor wire than would be required to cover the entire surface of the cable. By the method of this invention such conductors can b provided with spaced helical armor wires, covering 50% or less of the conductor core, which wire provides a high strength, light weight cover having sufiicient external protection in the circumstances and greater flexibility than has been heretofore realized in such cable. Further, such cables can be made with greater ease and uniformity than has heretofore been supposed possible.

In the usual case the ribs are incorporated with the core during the extrusion of the polyolefin insulation and can be formed easily by using slotted extrusion dies. The size and shape of the ribs are controlled by the size of the slots, which in turn is afunction of the extrusion technique used, and the material characteristics of the extrudate. The shape of the outer surface of each rib can be of semi-circular cross-section, pointed, flat or of any other desired configuration, and, as stated above, the radial height of each rib generally ranges from one-third -to two-thirds the diameter of wire used. The number of ribs used varies depending on the relative diameters of the core and overlying wire and on the severity of service anticipated.'Generally between 2 and 5 ribs are sufficient, although a greater or lesser number can be used," but in the usual case the number willv not be so large that the overlying wire is supported solely by the ribs without touching the core between adjacent ribs. It is anticipated that the overlying wire will be applied about theribs and core under sufficient tension to cause depression of the ribs, locking the ribs and wire securely together. For this reason the width of the ribs should be quite small, each one to three degrees of the circumference covering about of the core. a

As suggested above, the overlying wire, particularly when it is to serveas mechanical protection for the overlying core, is preferably preformed. Preformed armor Wire has been previously used, for example, in well logging cables. In that application armor wire is applied in a layer covering generally 94to of the external surface of the cable. Preforming of the overlying wire is preferably carried out in the same manufacturing line in which the wire is applied to the cable core by passing each strand, as it is served about the core, over a set of rollers which are spaced and oifset to give the desired pitch diameter and lay. In this manner each strand of wire is permanently shaped into a predetermined helix which hugs the core and has no tendency to pop out of position when the cable is under stress. Tension applied to preformed armored cable is thus evenly distributed among the individual wire strands.

After application of the'overlying wire to the cable, an external layer of plastic or rubbery material can be applied to hold the wire even more firmly in place against dislodging forces which may be encountered during subsequent use. Alternatively the cable can be drawn through a reducing die in which the overlying wire is pressed deeply into the ribs and, if desired, into the core to make a form-fitting depression which locks and holds the'wire preventing subsequent wire displacement and eliminating the need of any form of external binding. It will be understood, however, that the choice of such post application Cable 1 Cable 2 A ngle ofLay. deg l7 5 Breaking Strength, p.s.i 4, 500 4, 600 Percent Elongation a Break N 0. turns under 500?! Load l9 1 2 1 Per 200 ft.

As noted above the application of overlying wire about a ribbed core enables the use of longer lay than has heretofore been deemed possible without noticeable displacement of the wire during use. For a further description of the present invention reference is made to the attached drawings in which:

FIGURE 1 is a perspective view of a submarine coaxial cable constructed according to this invention with each layer broken away successively to show the details of the cable construction;

FIGURE 2 is a section taken along lines 22 in FIGURE 1;

FIGURE 3 is a perspective view of an underground residential power distribution cable constructed according to the present invention, with each layer broken away successively to show the details of the cable construction;

FIGURE 4 is a section taken along lines 44 in FIG- URE 3;

FIGURE 5 is a schematic plan view of an arrangement suitable for applying spaced helical wire to cables and tubes according to the present invention;

FIGURE 6 is a sectional view taken along line 6-6 in FIGURE 5;

FIGURE 7 is a sectional view taken along line 7-7 in FIGURE 5; and

FIGURE 8 is a sectional view taken along line 88 in FIGURE 5.

Referring more particularly to FIGURE 1 a submarine coaxial cable 29 is shown consisting of a central metallic conductor 30 embedded in a layer 32 of dielectric material and with a braided conductor 34 of wire strands located between an inner layer 32 of solid dielectric and an outer layer 36 of solid dielectric. Outer layer 36 includes four integral, longitudinal ribs 38 spaced at equal arcuate intervals about its exterior. A layer 39 of twelve, equally spaced, preformed helical armor wire strands 40 partially covers dielectric layer 36 and is in turn encased in an external insulating jacket 42 with strands 40 actually embedded in jacket 42. Both central conductor 30 and braided conductor 34 are copper or other highly conductive material and

dielectric layers

32 and 36 are preferably of a polyolefinic material, such as polyethylene. Jacket 42 can, for example, be made of a polyolefinic material or of rubber. Armor wire strands 40 normally are steel.

As will be noted especially with reference to FIG- URE 2, each rib 38 extends radially from jacket 36 a distance equal to slightly more than one-half the diameter of each armor wire strand 40 and is relatively narrow, covering only two or three degrees of the circumference of dielectric layer 36. As noted above each strand 40 of armor wire is preformed immediately prior to its application about dielectric layer 36 and is applied under sufficient tension to make depressions in ribs 38 at all points of intersection of armor wire strands 40 and ribs 38. Each strand 40 is in contact with outer dielectric layer 36 in the space between adjacent ribs 38. V Referring to FIGURE 3 an underground residential power distribution cable is shown having a central conductor 12. A thick layer 14 of solid dielectric is extruded about conductor 12, while a relatively thin, exteriorly ribbed layer 16 of semi-conducting material is extruded about dielectric layer 14, and a layer 17 of spaced drain wire 18 is served helically about layer 16.

Layers

14 and 16 can be polyethylene or other extrudable substance.

As will be seen from FIGURE 4 semi-conducting layer 16 includes three longitudinal ribs 20, equally spaced about layer 16. Ribs 20 extend radially outward from the general cylindrical contour of layer 16, a distance equal to about one-half the diameter of drain wires 18, their width covering no more than two or three degrees of the circumference of layer 16.

In the cable shown in FIGURE 3, layer 17 of drain wires 18 is intended to act as a conductor and preferably tin-coated copper is used. Each drain wire 18 is applied under sufficient tension to cause a depression of ribs 20 and cable 10 is then pulled through a reducing die to deepen these depressions and also to cause some depression to be made in the surface of layer 16 between ribs 20 by drain wires 18.

In FIGURE 5 a schematic representation of a manufacturing arrangement suitable for practicing the method of the present invention is shown consisting of an extruder 50, a stranding machine 52 and a post-winding station 54. At extruder a layer 56 of polyolefin insulation is extruded about a central conductor 57 as it passes through a slotted die 59 which produces longitudinal ribs 62 on insulation 56. Alternately, extruder 50 can be replaced by a taping machine in which longitudinally ribbed insulating tape is applied to a core with a straight or helical lay of the ribs opposite the lay of the wire to be applied over it.

Conductor 57 having insulating layer 56 applied to it then passes to stranding machine 52 in which wire servings 60 are helically applied. Where wire servings 60 are of a relatively hard material such as steel, stranding ma chine 52 preferably includes a preforming head 58 in which each wire strand is passed over a set of rollers which are spaced and offset to give the desired pitch di ameter and lay to the wire prior to its application to the ribbed core. The wire servings 60 are applied to ribbed insulation 56 under sufficient tension to cause indentation of ribs 62 at points of intersection of wire 60 and ribs 62. Each strand of wire 60 is also in contact with layer 56 between adjacent pairs of ribs 62. As will be seen from FIGURE 7 wire 60 is evenly distributed about the circumference of ribbed insulation 56.

Post-winding station 54 which is not necessary in all cases, can be a reducing die wherein wires 60 are more firmly pressed into ribs 62, or, as illustrated, it can include an extruder for applying an external jacket 64 of a polymeric or rubbery substance over wire 60 whereby wires 60 are even more firmly held in place and protected from the environment.

Although the examples illustrated in the drawings are of insulated conductors and cables, the practice of this invention, it will be readily apparent, extends to the formation of wire reinforced tubes which can serve as conduits. It will thus be noted that many modifications and variations of the examples are within the scope of the invention resulting in products which vary from conductors with exposed external wire to reinforced tubes with encapsulated wire. It will also be noted from the description of the conductor shown in FIGURES 3 and 4 that, in instances when the wire servings are made of soft material such'as copper, the wire can be applied directly to the ribbed insulation while preforming is preferred when steel wire is used.

We claim:

1. The method for applying wire servings in spaced relationship to each other about oblong objects which includes forming a core having a plurality of radially extending ribs disposed longitudinally thereon at intervals about its circumference, and helically applying a plurality of wire strands about said ribbed overlying said ribs, in spaced relationship to each other, said wire strands having been permanently shaped into a predetermined helix prior to application about said ribbed core.

2. The method according to claim 1 wherein said helical wire strands are applied under sufficient tension to cause indentation of said ribs.

3. The method according to claim 1 wherein said wire strands contact said core between adjacent pairs of ribs.

4. The method according to claim 3 wherein said core includes between two and five said ribs, said ribs having a height above said core equal to one-third to two-thirds the diameter of said wires.

5. The method of applying wire servings in spaced relationship to each other about an electrical conductor which includes forming a layer of a solid dielectric about said conductor, said layer having a plurality of longitudinal ribs extending radially outward therefrom, said ribs being disposed about the external surface of said layer of solid dielectric, and applying a plurality of wire strands in spaced relationship to each other helically about said layer of solid overlying said ribs under suiticient tension to cause indentation of said ribs at points of intersection of said ribs and said wire strands, said wire strands having been permanently shaped into a predetermined helix prior to application about said layer of solid dielectric.

6. The method according to.claim which further includes applying an external coating about said Wire servlngs.

7. The method according to claim 5 which further includes drawing said conductor with said wire servings thereon through a reducing die.

8. A cable which includes a central electrical conductor, a layer of solid dielectric surrounding said conductor, said layer of solid dielectric having longitudinal ribs extending outward therefrom, and spaced wire servings permanently shaped into a predetermined helix and helically applied about said layer of solid dielectric overlying said ribs.

9. The cable according to claim 8 which further includes an external covering surrounding said wire servrugs.

10. The cable according to claim 8 wherein said wire servings are partially impressed into said layer of solid dielectric.

11. A coaxial cable which includes a central metallic conductor, a first layer of solid dieletcric surrounding said central metallic conductor, an outer metallic conductor surounding said first layer of solid dielectric, a second layer of solid dielectric surrounding said outer metallic conductor, said second layer of solid dielectric having longitudinal ribs extending outward therefrom, and spaced wire servings permanently shaped into a pre- 7 layer of solid dielectric overlying said ribs.

12. The cable according to claim 11 which further includes an external covering surrounding said wire servings.

13. An underground residential power distribution cable which includes a core consisting of a central metallic conductor and a layer of solid dielectric surrounding said central metallic conductor, longitudinal ribs extending outward from said core and spaced Wire servings permanently shaped into a predetermined helix and helically applied about said core overlying said ribs.

14. The cable according to claim 13 wherein said core further includes a second layer of material surrounding said layer of solid dielectric which second layer includes said longitudinal ribs.

15. The cable according to claim 14 wherein said second layer of material is semiconductive.

16. The cable according to claim 13 wherein said wire servings are electrically conductive and are partially impressed into said cor References Cited UNITED STATES PATENTS 3,106,815 10/1963 Nance et al. 3,180,926 4/1965 Trill 174 107 3,259,684 7/1966 Wakefield 174 X FOREIGN PATENTS 506,948 6/1939 Great Britain.

LARAMIE E. ASKIN, Primary Examiner. H. HUBERFELD, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,351,706 November 7, 1967 C. Gerald Gnerre et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 44, for "he" read H the column 4, line 55, after "ribbed" insert core column 5, line 1, after "solid" insert dielectric Signed and sealed this 7th day of January 1969.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer