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Publication numberUS3569610 A
Publication typeGrant
Publication dateMar 9, 1971
Filing dateOct 15, 1969
Priority dateOct 15, 1969
Publication numberUS 3569610 A, US 3569610A, US-A-3569610, US3569610 A, US3569610A
InventorsLouis A Bopp, George S Eager Jr, Oscar G Garner
Original AssigneeGen Cable Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Ethylene-propylene rubber insulated cable with cross-linked polyethylene strand shielding
US 3569610 A
Abstract  available in
Images(1)
Previous page
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Claims  available in
Description  (OCR text may contain errors)

United States Patent [72] lnventors Oscar G. Garner Riverside, Conn.;

George S. Eager, Jr., Upper Montclair, N.J.; Louis A. Bopp, Fair Haven, NJ. 866,611

Oct. 15, 1969 Mar. 9, 1971 General Cable Corporation New York, N.Y.

[21 Appl. No. [22] Filed [45] Patented [73 Assignee [54] ETHYLENE-PROPYLENE RUBBER INSULATED CABLE WITH CROSS-LINKED POLYETHYLENE STRAND SHIELDING 10 Claims, 3 Drawing Figs.

[52] US. Cl 174/102, 174/107,174/110 [51] 1nt.Cl ..H01bll/06 [50] Field of Search 174/ 102,

102.2,105.1,l06.2,107,110.3,110.4, 110.44, 174 (Shield); 156/51; 264/174 [56] References Cited UNITED STATES PATENTS 2,304,210 12/1942 Scott et a1 3,100,136 8/1963 DAscoli et a1. 174/102x 3,187,071 6/1965 Radziejowski... 264/174 3,441,660 4/1969 Garner 174/102 3,446,883 5/1969 Garner 264/174 FOREIGN PATENTS 653,518 12/1962 Canada 174/102.2 703,930 2/1965 Canada 174/11044 1,150,690 4/1969 Great Britain 174/102.2

Primary Examiner-Laramie E. Askin Assistant Examiner-A. T. Grimley Attorney-Sandoe, Hopgood & Calimafde ABSTRACT: A high-tension cable is made with a strand shield of cross-linked, conductive polyethylene compound and with insulation that is a proprietary compound of ethylenepropylene rubber. The insulation is approximately 48 percent ethylene-propylene amorphous copolymer; approximately 12 percent crystalline polyethylene homopolymer; and reinforcing fillers to provide adequate physical properties. The shield and insulation are extruded and cured simultaneously to obtain void-free bonding.

PATENTEDHAR 9l97l 3,569,610

0!! INSULATION STRAND SHIELD E EXTRUDER EXTRUDER CURING 22 OVEN 30 E X T RUDE POLYETHYLENE CONDUCTOR SHIELDING LAYER COOL SHIELDING LAYER EXTRUDE INSULATION ETHYLENE'PROPYLENE COPOLYMER WITH POLYETHYLENE SIMULTANEOUS CURE SHIELDING 8- INSULATION INVENTORS M \N W ATTORNEYS.

.ETHYLENE-PROPYLENE RUBBER INSULATED CABLE WITH CROSS-LINKED POLYETHYLENE STRAND SHIELDING SUMMARY OF THE INVENTION This invention provides an improved electrical cable for high-voltage power transmission. The cable has improved resistance to ozone and corona discharge; excellent insulating characteristics and aging properties, and greater flexibility that permits bending through shorter radii. The invention also provides a construction in which the conductor shielding is not forced into the interstices of a stranded conductor and this aids splicing and terminating operations by leaving a clean,

free stripped conductor. The invention includes also a method of making the improved cable.

The two compounds are applied to a suitable conductor (i.e., copper stranded wire), preferably in a tandem extrusion operation, and are cured simultaneously. The ,strand shield of conductive chemically cross-linkable polyethylene is applied in the first stage of the tandem extrusion process, and provides a smooth outer surface upon which to apply the insulating compound. Being firm and of high green strength, and having a low coefficient of friction after a short period of air cooling following extrusion at elevated temperature, the strand shielding compound of conductive cross-linkable polyethylene may be passed through tt he guide tip of the second extruder, which applies the insulation compound, while still preserving the electrically desirable smooth outer surface of the strand shielding material. At this stage of the process, the lower processing temperature of the ethylene-propylene rubber compound, as opposed to the processing temperature of the cross-linked polyethylene shielding compound, plays an important part in maintaining the original smooth shape of the crosslinkable conductive polyethylene layer previously extruded.

Extruded strand shielding of chemically cross-linked polyethylene has numerous desirable features compared with an extruded rubber or rubber-like material such as an ethylene-propylene rubber conductive compound. The low coefficient of friction makes it unnecessary to use a lubricant in order to pass it through the guider tip of the second extruder. Such lubricant is commonly an oil such as dimethyl naphthalene or naphthenic petroleum oil having penetrating properties that can produce side effects such as gassing at the interface of the compounds during subsequent curing operations, or may promote an undesired softening of both compounds at the interface, and may also have a deleterious effect on physical, aging and electrical characteristics due to migration into the insulation compound. The advantages of an extruded shield in lieu of a semiconducting fabric tape are, of course, well known.

The ethylene-propylene rubber compound is advantageous because it is extremely resistant to ozone and corona discharge, and has excellent electrical insulating characteristics, and aging properties. It is flexible, and enables bending through much shorter radii than a similar cable utilizing cross-linked polyethylene as the insulation.

Unlike cross-linked polyethylene compounds which shrink considerably after curing, the ethylene-propylene rubber compound can be extruded through a die with a diameter equal to the desired diameter of the cured insulation. The lack of shrinkage of the ethylene-propylene rubber wall during and after cure, enables the concentricity and surface smoothness of the underlying strand shielding compounds to be maintained, and further does not force it into the interstices of the stranded conductor, thereby aiding in splicing and terminating operations associated with cable installations by leaving a clean, free stripped conductor.

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

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

FIG. 1 is a sectional view of a power cable made in accordance with this invention;

FIG. 2 is a diagrammatic illustration of apparatus for making the power cable of this invention; and

FIG. 3 is a flow diagram for the method of this invention.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 shows a powercable having a stranded conductor 10; a conductor shield I2; and insulation 14. This invention is concerned with the application of the shield 12 and the insulation 14 and with the combination of material used for the shield and insulation. The cable shown in FIG. I has insulation shielding I6 and an outer jacket 18 which may be conventional. The insulation shielding may be conducting crosslinked polyethylene, conducting polyethylene, conducting ethylene-propylene amorphous terpolymer of copolymer, conducting tapes, etc.

In the preferred method of making a cable in accordance with this invention, the conductor 10 is supplied to a strand shield extruder 22 (FIG. 2) in which the strand shield 12 is applied to the conductor 10 by an extrusion die 24.

The material used for the shield or shield layer 12 is a compound of conductive cross-linked polyethylene. This material is applied in a thin layer of between.

The strand shielding l2 cools rapidly because of its thin section and because of the heat sink effect of the conductor 10.

FIG. 2 shows a second extruder 26, arranged in tandem with the extruder 24, for extruding a layer of insulation over the shielded conductor which is indicated by the reference character 10. The shielded conductor 10 passes from the extruder 22 to a guide tip 28 of the second extruder 26.

The low coefficient of friction of the polyethylene shield on the shielded conductor 10' makes it unnecessary to use a lubricant in order to pass the shielded conductor through the guide tip 28, as previously explained.

The extruder 26 applies the insulation 14 to the shielded conductor 10' through an extruder die 30; and the insulated conductor is indicated bythe reference character I0".

The insulation applied by the extruder 26 is a particular formulation of an ethylene-propylene rubber compound having a higher-than-normal polymer content. Ordinarily, ethylenepropylene copolymer rubber compounds designed for highvoltage service, contain about 30 to 45 percent by weight of polymer. The compound used for this invention contains approximately 48 percent of ethylene-propylene copolymer, which is amorphous, and I2 percent polyethylene homopolymer which is crystalline. However, other compounds containing as little as 51 percent or as much as percent ethylene-propylene copolymer and as little as 0 percent, and as much as 49 percent polyethylene homopolymer may be used equally well for this invention. The total of polymer can be as high as percent and as low as 20 percent.

The amorphous ethylene-propylene copolymer requires reinforcing filler to provide adequate physical properties, while the addition of filler actually reduces the physical properties of the polyethylene component.

In the insulating compound of this invention, however, the polyethylene does provide reinforcement and raises the physical properties to a desired level while also enhancing the electrical properties of the compound. Thus, the necessary but electrically undesirable filler is kept to a minimum, while the polymer content can be maintained at a much higher level than is generally considered processable. The balance of processing properties, desired physical strength level, and extraordinarily good electrical properties is, therefore, achieved by this invention. The insulated conductor 10' passes from the extruder 26 to a curing oven 34 in which the shielding layer and insulating layer are cured simultaneously. By use of chemically cross-linked polyethylene as the conductor strand shield, and an ethylene propylene copolymer insulation which contains polyethylene, excellent adhesion of the shield and insulation is achieved. The lack of shrinkage of the ethylenepropylene rubber insulation during and after cure enables the concentricity and surface smoothness of the underlying strand shielding compound to be maintained and avoids forcing of the shielding compound into the interstices of stranded conductor, as previously explained.

The cocured layers of shield and insulation are chemically cross linked to one another in the oven 34 by formulating both compounds with a dicumyl peroxide curative system, or with an equivalent agent which causes both layers to cure at about the same rate. Any gasses which form at the interface of the shield and insulation as byproducts of the cure, are rapidly and readily absorbed by the ethylene-propylene rubber compound so as to produce a void-free interface. The higher-than-normal polymer content of the rubber insulation further provides for higher-than-normal reactive sites at the interface so that a strong, uniform degree of bonding is obtained along the full length of the cable.

The preferred embodiment of the invention has been illustrated and described and the invention is defined in the appended claims.

We claim:

I. An electrical cable comprising a conductor, semiconducting polydetin shield on the conductor, and insulation surrounding the shield and said insulation comprising an ethylene-propylene rubber compound containing also a polyolefin that fusion bonds to the shield.

2. The electrical cable described in claim 1 characterized by the shield being polyethylene and the ethylene-propylene rubber compound containing polyethylene that fusion bonds to the shield.

3. The electrical cable described in claim 2 characterized by the ethylene-propylene copolymer of the insulation compound being amorphous and the polyethylene of the insulation being crystalline.

4. The electrical cable described in claim 1 characterized by the conductor being stranded, the shield being a smooth coating on the conductor, and the ethylene-propylene rubber compound being cured and bonded to the shield but free of radial pressure sufficient to force the shield into the interstices of the stranded conductor. 7

5. The electrical cable described in claim 3 characterized by the ethylene-propylene rubber compound containing approximately 20 to percent by weight of ethylene-propylene copolymer and approximately 0 to 46 percent by weight of polyethylene, the balance being reinforcing and filler materials.

6. The electrical cable described in claim 5 characterized by the ethylene-propylene copolymer being approximately 48 percent of the insulation and the polyethylene being approximately 12 percent of the insulation.

7. The electrical cable described in claim 1 characterized by the conductor shield being a cross linked polyethylene having a higher softening point than that of the insulation before curing of the shield and insulation.

8. The electrical cable described in claim 1 characterized by both the shield and the insulation being circumferentially and longitudinally continuous layers extruded over the conductor and the shield, respectively.

9. The electrical cable described in claim 2 characterized by the materials for the shield and for the insulation being both formulated with a dicumyl peroxide curative system so that the shield and the insulation are cross linked to one another.

10. The electrical cable described in claim 2 characterized by an insulating shield of material from the group consisting of conducting cross linked polyethylene,.conducting ethylenepropylene, and rubber.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2304210 *Feb 28, 1940Dec 8, 1942Int Standard Electric CorpInsulated electric cable
US3100136 *Jun 18, 1959Aug 6, 1963Anaconda Wire & Cable CoMethod of making polyethylene-insulated power cables
US3187071 *Jul 18, 1962Jun 1, 1965Gen Cable CorpChemical bonding of rubber layers
US3441660 *Jul 12, 1966Apr 29, 1969Gen Cable CorpSolid aluminum conductor insulated with cross-linked polyethylene
US3446883 *Dec 20, 1965May 27, 1969Gen Cable CorpMethod and apparatus for producing conductors surrounded by three or more extruded layers
CA653518A *Dec 4, 1962Gen ElectricPolyethylene insulated electrical conductors
CA703930A *Feb 16, 1965Hercules Powder Co LtdInsulated electrical conductors
GB1150690A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3737557 *Jun 27, 1972Jun 5, 1973British Insulated CallendersElectric cables with ethylene-propylene insulation
US3792192 *Dec 29, 1972Feb 12, 1974Anaconda CoElectrical cable
US3832481 *Oct 4, 1973Aug 27, 1974Borg WarnerHigh temperature, high pressure oil well cable
US3865971 *Aug 7, 1973Feb 11, 1975Nippon Telegraph & TelephoneSubmarine coaxial cables
US3878319 *Jul 8, 1974Apr 15, 1975Gen ElectricCorona-resistant ethylene-propylene rubber insulated power cable
US4276251 *Sep 22, 1978Jun 30, 1981General Cable CorporationDielectric coating of blend of polyethylene and ethylene-propylene copolymer
US5109599 *Apr 15, 1991May 5, 1992Cooper Industries, Inc.Miniature coaxial cable by drawing
US5426264 *Jan 18, 1994Jun 20, 1995Baker Hughes IncorporatedCross-linked polyethylene cable insulation
US5515603 *Nov 28, 1994May 14, 1996Kabelmetal Electro GmbhMethod for manufacturing a coaxial cable
US5820014 *Jan 11, 1996Oct 13, 1998Form Factor, Inc.For forming solder joints between two electronic components
US5919565 *Mar 20, 1997Jul 6, 1999Union Carbide Chemicals & Plastics Technology CorporationTree resistant cable
US5994152 *Jan 24, 1997Nov 30, 1999Formfactor, Inc.Fabricating interconnects and tips using sacrificial substrates
US6274823Oct 21, 1996Aug 14, 2001Formfactor, Inc.Interconnection substrates with resilient contact structures on both sides
US6289581 *Jun 14, 1999Sep 18, 2001Flexco Microwave, Inc.Method of making flexible coaxial cable having locked compressible dielectric
US7601039Jul 11, 2006Oct 13, 2009Formfactor, Inc.Microelectronic contact structure and method of making same
US8033838Oct 12, 2009Oct 11, 2011Formfactor, Inc.Microelectronic contact structure
US8373428Aug 4, 2009Feb 12, 2013Formfactor, Inc.Probe card assembly and kit, and methods of making same
EP0539905A1 *Oct 26, 1992May 5, 1993Alcatel CableElectrical cable
EP0837476A2 *Oct 16, 1997Apr 22, 1998UNION CARBIDE CHEMICALS & PLASTICS TECHNOLOGY CORPORATIONTree resistant cable
WO1998041995A1 *Mar 18, 1998Sep 24, 1998Union Carbide Chem PlasticTree resistant cable
Classifications
U.S. Classification174/102.00R, 174/107, 174/110.0AR, 29/828
International ClassificationH01B3/44, B29C47/00, H01B7/02, H01B13/14, B29C47/06
Cooperative ClassificationH01B13/14, H01B13/141, B29K2301/10, B29C47/128, B29C47/0004, B29K2101/10, H01B7/02, B29K2105/20, H01B3/441, B29L2031/3462
European ClassificationB29C47/00B, B29C47/12E, H01B13/14, H01B13/14B, H01B7/02, H01B3/44B