US3379821A - Shielded electrical cable - Google Patents
Shielded electrical cable Download PDFInfo
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- US3379821A US3379821A US427435A US42743565A US3379821A US 3379821 A US3379821 A US 3379821A US 427435 A US427435 A US 427435A US 42743565 A US42743565 A US 42743565A US 3379821 A US3379821 A US 3379821A
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- strip
- jacket
- polyethylene
- cable
- shielding layer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/06—Insulating conductors or cables
- H01B13/14—Insulating conductors or cables by extrusion
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B11/00—Communication cables or conductors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/22—Sheathing; Armouring; Screening; Applying other protective layers
- H01B13/26—Sheathing; Armouring; Screening; Applying other protective layers by winding, braiding or longitudinal lapping
- H01B13/2613—Sheathing; Armouring; Screening; Applying other protective layers by winding, braiding or longitudinal lapping by longitudinal lapping
- H01B13/2686—Pretreatment
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
- H01B9/022—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients composed of longitudinal lapped tape-conductors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49194—Assembling elongated conductors, e.g., splicing, etc.
Definitions
- This invention relates to improvements in shielded and jacketed electrical cables. More particularly the invention relates to such cables in which the shield comprises a metallic strip, coextensive in length with the cable core, which is folded about the core into the form of a tube, and in which there is an outer jacket of polyethylene extruded over the tubular shield so formed.
- the metallic strip conventionally is corrugated transversely prior to being folded about the cable core in order to give greater flexibility to the cable and to permit bending of the completed cable without wrinkling or rupture of the shielding layer,
- the longitudinal edges of the folded metallic strip overlap each other slightly to insure complete coverage of the enclosed cable core.
- the polyethylene jacket is extruded over the tubular shield at an elevated temperature, for example in the range of 400-450 F. for high molecular weight polyethylene and for extrusion speeds of 50 feet per minute, and up. As the extruded polyethylene jacket cools the polyethylene contracts and tends to squeeze the tubular shield down firmly onto the cable core.
- Telephone cable of this construction is known as alpeth cable and is described more fully in the F. W. Horn and R. B. Ramsey paper, Bell System Cable Sheath Problems and Designs, in AIEE Proceedings, 1951, volume 70.
- the cooling proceeds from the outer surface of the jacket inwardly and the resulting shrinkage of the jacket forces the polyethylene into close engagement with the corrugated surface of the folded strip and then causes the tubular shield to be partially collapsed by the sliding of the overlapping edges of the strip relative to each other.
- This collapse of the tubular shield is halted when the contracting tube becomes supported by the enclosed cable core.
- the outer overlapping edge of the folded strip presses outwardly into the plastic jacket, making the jacket thinner along the strip edge.
- Such thinning is undesirable. It has been proposed in the L. Iachimowicz Patent 3,087,007, Apr. 23, 1963, to reduce such thinning by the use of a longitudinal bridging tape over the overlapped edges of the strip.
- the bridging tape is effective in minimizing or preventing localized thinning of the polyethylene jacket at the overlapping edges of the folded metallic strip, it does not provide a hermetic seal at the overlapped edges. In the event of damage to the jacket by lightning or by mechanical action moisture may penetrate into the cable core between the overlapped edges.
- a special adhesive polyethylene film may be applied to cover one or both sides of the metallic strip.
- Such an adhesive polyethylene film is disclosed in the L. Jachimowicz Patent No. 3,233,036, assigned to the owner of the present application.
- the polyethylene used for this film contains reactive carboxyl groups which have the ability to develop firm adhesion to the metallic strip and also to the overlying polyethylene jacket.
- Aluminum strip protected by the adhesive polyethylene film is highly resistant to corrosion.
- use of the adhesive polyethylene film improves telephone cables by inhibiting penetration of moisture into the cable core.
- This improved resistance to moisture penetration results in part from the sealing of the seam at the overlapping edges of the polyethylene coated shielding strip, thereby forming a tight tube or pipe around the core of the cable.
- the resistance of this cable structure against the penetration of moisture is further improved by reason of the sealing of the outer polyethylene jacket to the adhesive polyethylene coated shielding tape resulting from the use of sufficiently high extruding temperature and pressure to achieve optimum bonding.
- An added advantage resulting from use of the shielding strip with the sealed seam is the better mechanical strength of the cable structure and improved life under repeated bending.
- My new construction utilizes the aluminum or other metal shielding strip precoated with special adhesive polyethylene, preferably on both sides, with the outer polyethylene jacket extruded under such temperature and pressure conditions as to obtain firm adhesion over a portion only of the interface between the extruded jacket and the coated shielding layer.
- firm adhesion is restricted to the area of the interface over and adjoining the sealed seam of the folded metallic strip, while leaving the balance of the area between the extruded jacket and the precoated folded shielding strip easily strippable.
- This spatially limited adhesion between the extruded jacket and the shielding layer may be accomplished by a number of the methods which will be described hereinafter.
- FIGURE 1 is a perspective view of a short length of shielded and jacketed cable made according to the present invention, the jacket being cut back to show the construction better;
- FIGURE 2 is a transverse cross section, to enlarged scale as compared to FIGURE 1, through a coated metallic strip suitable for use to form the shielding layer in the cable;
- FIGURE 3 is a transverse cross section through the cable of FIGURE 1, substantially on line 3-3, and to somewhat enlarged scale;
- FIGURE 4 is a diagrammatic view showing how metallic shielding strip coated with highly adhesive polyethylene may be treated to selectively control the adhesion during manufacture of the cable;
- FIGURE 5 is a fragmentary transverse section through a cable sheath illustrating another way of selectively controlling the adhesion of the polyethylene jacket to the shielding layer;
- FIGURE 6 is a diagrammatic view showing one way of making the construction of FIGURE 5.
- the cable core 11 comprises a plurality of insulated conductors, for example plastic insulated wires arranged in pairs.
- the shield 12 Enclosing the cable core is the shield 12 comprising a transversely corrugated metallic strip coextensive in length with the cable core and folded about the core into a tube with the longitudinal edges of the strip overlapping each other a short distance, as shown.
- an extruded jacket 13 of polyethylene Over the tubular shielding layer is an extruded jacket 13 of polyethylene.
- the metallic strip 12 Prior to being folded about the cable core the metallic strip 12 was precoated, preferably on both sides, with a film of an adhesive polyethylene containing reactive carboxyl groups.
- This coating material has the ability to develop a firm adhesive bond to the metallic strip and also to the polyethylene jacket 13 extruded over the shielding layer. Details of the coated metallic strip 12 are disclosed in other figures of the drawings. Extrusion of the polyethylene, hot and under pressure, over the folded shielding strip produces a hermetic seal between the overlapping edges of the coated strip and a firm adhesion of the polyethylene jacket to the shield in the area over and adjoining the sealed seam.
- This area extending between the longitudinal marks A and B shown in FIGURE 1, preferably is limited to less than one-half the periphery or circumference at the interface. In the illustrative embodiment the peripheral extent of the firm adhesion is shown as about one-fourth the periphery.
- FIGURE 2 is a transverse section to enlarged scale through a coated metallic strip suitable for use in forming the shielding layer.
- the metallic strip 21 is coated on both surfaces with films of polyethylene material.
- the thickness of the metallic strip and the coating layers are exaggerated.
- an aluminum shielding strip might be from 5 to 10 mils thick and the film coating layer might be from 1 to 3 mils thick.
- This coating material 22 along both edges of the strip, in the limited areas designated 23 and 24, is polyethylene containing a reactive carboxyl group which has the ability to develop firm adhesion to the metallic strip, to itself at the overlapped edges of the strip, and also to the polyethylene jacket when it is extruded thereover.
- the coating material 25 along the center portion 26 of the strip has a controlled lesser ability to develop firm adhesion to the metallic strip and to the polyethylene jacket which will be extruded over the shielding layer.
- FIGURE 3 is a cross section taken transversely through the cable of FIGURE 1, the thickness of the metallic shielding strip and the coating layers thereon being exaggerated for purposes of illustration.
- the film coating along the edges of the metallic strip has the ability to develop firm adhesion between the overlapping edges of the folded strip, and to the polyethylene jacket in the region over the seam and for a limited peripheral distance on both sides thereof. This results in a hermetic seal along the longitudinal seam of the folded shielding strip.
- the film coating along the center portion of the metallic strip has a controlled lesser ability to develop adhesion to the polyethylene jacket around the peripheral extent 15 of the tubular shield.
- the precoated metallic strip illustrated in FIGURE 2 may be formed by extruding the polyethylene films onto the strip. During such extrusion polyethylene of limited adhesive characteristic may be extruded over the center part of the strip and highly adhesive polyethylene over the two edge portions of the strip.
- highly adhesive polyethylene may be extruded over the entire Width of the metallic strip and the center portion of the strip then treated to selectively reduce its adhesive ability.
- a suitable release agent for example a pigment such as talc, or an oil such as a silicone oil, to limit the area of firm adhesion between the sealed shield and the polyethylene jacket extruded over it.
- a suitable release agent for example a pigment such as talc, or an oil such as a silicone oil, to limit the area of firm adhesion between the sealed shield and the polyethylene jacket extruded over it. If the cable core with its enclosing longitudinally folded metallic strip coated with polyethylene containing reactive carboxyl groups is fed into the extruder with the seam of the shield in the top position, as shown in FIG- URE 6, talc or other release agent may be dusted or wiped around the lower half or three-quarter of the cable core circumference just before the core enters the extruder for application of the outer polyethylene jacket.
- This cable construction is illustrated in the fragmentary cross section of FIGURE 5, where 31 is the overlapping film coated metallic strip which encloses the cable core, 13 is the extruded polyethylene jacket, and 32 represents the thin coating of release agent.
- the release agent shown of exaggerated thickness merely for purposes of illustration, does not extend over the top approximately one-quarter of the tubular shielding layer, thus insuring firm adhesion of the polyethylene jacket 13 to the shielding layer at the longitudinal seam and for a limited peripheral distance on both sides thereof.
- Silicone oil, silicone oil emulsion in water, or a tale dispersion in an oil may be applied in similar manner as release agent to achieve the same results.
- the release agent could be applied by dusting, brushing or wiping to the center portion of that surface of the film coated metallic strip which will form the exterior of the tubular shielding layer prior to folding the strip about the cable core.
- a shielded electrical cable comprising at least one insulated conductor of indefinite length, a metallic strip which is coextensive in length with the conductor and which is folded about the insulated conductor with its edges overlapping each other to provide a tubular metallic shielding layer completely enclosing the insulated conductor, an outer jacket of plastic insulating material surrounding and closely enclosing the tubular shielding layer, the plastic jacket being firmly adhered to the shielding layer along its overlapping edges and for a limited peripheral distance on both sides thereof to seal the overlap, the plastic jacket having a controlled lesser adhesion to the shielding layer around the rest of its periphery to facilitate stripping the plastic from the shielding layer in a region removed from the sealed overlapped region.
- an electrical cable according to claim 1 in which the outer jacket is polyethylene and the metallic shielding strip is an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, and in which a release agent is interposed between the tubular metallic shielding layer and the polyethylene jacket for a limited peripheral extent opposite the overlapped edges of the shielding strip.
- an enclosing tubular metallic shielding layer formed from an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, and an outer jacket of polyethylene
- the method which comprises treating the center portion only of the coated aluminum strip to reduce the adhesion characteristics of the coating material along the center of the strip without affecting the high adhesion characteristics of the coating material along the edge portions of the strip, folding the coated aluminum strip longitudinally around the insulated conductor with its edges overlapping each other to enclose the insulated conductor completely, and extruding the outer jacket of polyethylene over the folded strip with resulting high adhesion of the jacket to the shielding layer along the overlapped portion and lesser adhesion of the jacket to the shielding layer opposite the overlapped portion.
- an enclosing tubular metallic shielding layer formed from an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, and an outer jacket of polyethylene
- the method of controlling the adhesion of the jacket to the shielding layer which comprises heating the center portion only of the coated aluminum strip to reduce the adhesion characteristics of the coating material along the center of the strip without affecting the high adhesion characteristics of the coating material along the edge portions of the strip, folding the coated aluminum strip longitudinally around the insulated conductor with its edges overlapping each other to enclose the insulated conductor completely, and extruding the outer jacket of polyethylene over the folded strip with resulting high adhesion of the jacket to the shielding layer along the overlapped portion and lesser adhesion of the jacket to the shielding layer opposite the overlapped portion.
- an enclosing tubular metallic shielding layer formed from an aluminum strip having bonded to its outer surface a coating of a copolyrner of ethylene with monomers containing carboxyl groups, and an outer jacket of polyethylene
- the method of controlling the adhesion of the jacket to the shielding layer which comprises folding the coated aluminum strip longitudinally around the insulated conductor with its edges overlapping each other to enclose the insulated conductor completely, applying a release agent to a peripheral portion only of the shielding layer opposite the overlapped edges to reduce the adhesion characteristics of such portion of the coating material without affecting the high adhesion characteristics of the coating material along the overlapped edges, and extruding the outer jacket of polyethylene over the folded strip with resulting high adhesion of the jacket to the shielding layer along the overlapped portion and lesser adhesion of the jacket to the shielding layer opposite the overlapped portion.
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Description
April 1968 0. cs. GARNER 3,379,821
SHIELDED ELECTRICAL CABLE Filed Jan. 22, 1965 AREA OF CONTROLLED POLYE'THYLENE F 2 LEssER ADHESION (MATERIAL 0 0A L E 113531-233? 2 L1 METALLIC V 25 STRIP 24 POLYETHYLENE HAVING ADHESIVE 4 52 LESSER ADHESIVE ABILITY AREA METALLIC STRIP EXTRUDED A CABLE CORE APPARATUS SHIELDING FOR FOLDING STRIP Q SHIELDING STRIP EXTRUDER ABOUT CABLE CORE OXIDIZING FLAME OF SHIELDING STRIP CABLE com:
\ APPARATUS RELEASE FOR FOLDING SHIELDING STRIP I I XTR ABOUT CABLE APPL'C L 7 CORE L.
I INVENTOR T P?P F 6 OSCAR e. GARNER 5% QMM,MQM
ATTORNEYS.
United States Patent 3,379,821 SHIELDED ELECTRICAL CABLE Oscar G. Garner, Westlicld, Ni, assiguor to General Cable Corporation, New York, N.Y., a corporation of New Jersey Filed Ian. 22, 1965, Ser. No. 427,435 12 Claims. (Cl. 174-46) This invention relates to improvements in shielded and jacketed electrical cables. More particularly the invention relates to such cables in which the shield comprises a metallic strip, coextensive in length with the cable core, which is folded about the core into the form of a tube, and in which there is an outer jacket of polyethylene extruded over the tubular shield so formed. The metallic strip conventionally is corrugated transversely prior to being folded about the cable core in order to give greater flexibility to the cable and to permit bending of the completed cable without wrinkling or rupture of the shielding layer, In the cable to be described herein the longitudinal edges of the folded metallic strip overlap each other slightly to insure complete coverage of the enclosed cable core. The polyethylene jacket is extruded over the tubular shield at an elevated temperature, for example in the range of 400-450 F. for high molecular weight polyethylene and for extrusion speeds of 50 feet per minute, and up. As the extruded polyethylene jacket cools the polyethylene contracts and tends to squeeze the tubular shield down firmly onto the cable core. Telephone cable of this construction is known as alpeth cable and is described more fully in the F. W. Horn and R. B. Ramsey paper, Bell System Cable Sheath Problems and Designs, in AIEE Proceedings, 1951, volume 70.
In conventional plastic telephone cables, that is in cables in which the insulation on the conductors is a plastic material such as polyethylene, aluminum strip has been used for many years as the shielding material, for example a transversely corrugated aluminum strip of 8 mils in thickness, over which is extruded a polyethylene packet of the order of 80 mils in thickness, When the polyethylene is extruded onto the tubular shield formed by the folded aluminum strip there is no adhesion of the polyethylene to the aluminum. As the polyethylene cools from 400 F. to 80 F. it contracts 21% in volume. The cooling proceeds from the outer surface of the jacket inwardly and the resulting shrinkage of the jacket forces the polyethylene into close engagement with the corrugated surface of the folded strip and then causes the tubular shield to be partially collapsed by the sliding of the overlapping edges of the strip relative to each other. This collapse of the tubular shield is halted when the contracting tube becomes supported by the enclosed cable core. In this shrinking process the outer overlapping edge of the folded strip presses outwardly into the plastic jacket, making the jacket thinner along the strip edge. Such thinning is undesirable. It has been proposed in the L. Iachimowicz Patent 3,087,007, Apr. 23, 1963, to reduce such thinning by the use of a longitudinal bridging tape over the overlapped edges of the strip.
While the bridging tape is effective in minimizing or preventing localized thinning of the polyethylene jacket at the overlapping edges of the folded metallic strip, it does not provide a hermetic seal at the overlapped edges. In the event of damage to the jacket by lightning or by mechanical action moisture may penetrate into the cable core between the overlapped edges.
3,370,$2l Patented Apr. 23, 1968 To improve the corrosion resistance of the shield a special adhesive polyethylene film may be applied to cover one or both sides of the metallic strip. Such an adhesive polyethylene film is disclosed in the L. Jachimowicz Patent No. 3,233,036, assigned to the owner of the present application. The polyethylene used for this film contains reactive carboxyl groups which have the ability to develop firm adhesion to the metallic strip and also to the overlying polyethylene jacket. Aluminum strip protected by the adhesive polyethylene film is highly resistant to corrosion. In addition, use of the adhesive polyethylene film improves telephone cables by inhibiting penetration of moisture into the cable core. This improved resistance to moisture penetration results in part from the sealing of the seam at the overlapping edges of the polyethylene coated shielding strip, thereby forming a tight tube or pipe around the core of the cable. The resistance of this cable structure against the penetration of moisture is further improved by reason of the sealing of the outer polyethylene jacket to the adhesive polyethylene coated shielding tape resulting from the use of sufficiently high extruding temperature and pressure to achieve optimum bonding. An added advantage resulting from use of the shielding strip with the sealed seam is the better mechanical strength of the cable structure and improved life under repeated bending.
In the cable structure just described there is an intimate bond between the outer polyethylene jacket and the shielding tape over their entire interface. The firm adhesion between the extruded polyethylene jacket and the shielding layer poses a problem for cable termination which requires the grounding of the metallic shielding strip. The same is true when two lengths of cable are to be spliced together. It is cumbersome and difficult to separate the jacket from the metallic shielding layer for the purpose of making electrical connection to the shield. Manufacture of the cable with something less than an intimate bond between the jacket and the shield will make easier grounding at terminations and easier splicing of cables while still providing excellent corrosion protection for the aluminum shielding tape. However, reduction in the bonding over the interface will be at the sacrifice of absolute resistance to moisture penetration which can be obtained only if the seam of the folded shielding strip is sealed and if the overlying polyethylene jacket is firmly bonded to the shielding layer, particularly at the sealed seam of the shielding layer.
The somewhat contradictory requirements of absolute resistance to moisture penetration and, at the same time, comparative ease of grounding for the shielding layer are achieved by the improved construction and method of the present invention. My new construction utilizes the aluminum or other metal shielding strip precoated with special adhesive polyethylene, preferably on both sides, with the outer polyethylene jacket extruded under such temperature and pressure conditions as to obtain firm adhesion over a portion only of the interface between the extruded jacket and the coated shielding layer. According to the present invention firm adhesion is restricted to the area of the interface over and adjoining the sealed seam of the folded metallic strip, while leaving the balance of the area between the extruded jacket and the precoated folded shielding strip easily strippable. This spatially limited adhesion between the extruded jacket and the shielding layer may be accomplished by a number of the methods which will be described hereinafter.
It is an object of this invention to provide an improved shielded and jacketed cable construction and method of manufacture. It is a further object of the invention to provide shielded and jacketed cable in which the shield, formed from a metallic strip folded about the cable core with overlapping edges, is hermetically sealed and is firmly bonded to the overlying jacket at the overlap and for a limited peripheral distance on both sides thereof, While having a controlled lesser bond to the jacket around the rest of the periphery.
The drawing forming a part hereof show preferred embodiments of the invention selected for illustrative purposes only. The legends on the drawings are not limitations on the invention, which is defined by the claims, but are merely for convenience in the consideration of the illustrative embodiments of the invention. In the drawings:
FIGURE 1 is a perspective view of a short length of shielded and jacketed cable made according to the present invention, the jacket being cut back to show the construction better;
FIGURE 2 is a transverse cross section, to enlarged scale as compared to FIGURE 1, through a coated metallic strip suitable for use to form the shielding layer in the cable;
FIGURE 3 is a transverse cross section through the cable of FIGURE 1, substantially on line 3-3, and to somewhat enlarged scale;
FIGURE 4 is a diagrammatic view showing how metallic shielding strip coated with highly adhesive polyethylene may be treated to selectively control the adhesion during manufacture of the cable;
FIGURE 5 is a fragmentary transverse section through a cable sheath illustrating another way of selectively controlling the adhesion of the polyethylene jacket to the shielding layer; and
FIGURE 6 is a diagrammatic view showing one way of making the construction of FIGURE 5.
Referring first to FIGURE 1, the cable core 11 comprises a plurality of insulated conductors, for example plastic insulated wires arranged in pairs. The precise nature of the cable core is not material to the present invention and further description is unnecessary to an understanding of this invention. Enclosing the cable core is the shield 12 comprising a transversely corrugated metallic strip coextensive in length with the cable core and folded about the core into a tube with the longitudinal edges of the strip overlapping each other a short distance, as shown. Over the tubular shielding layer is an extruded jacket 13 of polyethylene. Prior to being folded about the cable core the metallic strip 12 was precoated, preferably on both sides, with a film of an adhesive polyethylene containing reactive carboxyl groups. This coating material has the ability to develop a firm adhesive bond to the metallic strip and also to the polyethylene jacket 13 extruded over the shielding layer. Details of the coated metallic strip 12 are disclosed in other figures of the drawings. Extrusion of the polyethylene, hot and under pressure, over the folded shielding strip produces a hermetic seal between the overlapping edges of the coated strip and a firm adhesion of the polyethylene jacket to the shield in the area over and adjoining the sealed seam. This area, extending between the longitudinal marks A and B shown in FIGURE 1, preferably is limited to less than one-half the periphery or circumference at the interface. In the illustrative embodiment the peripheral extent of the firm adhesion is shown as about one-fourth the periphery.
By treatment in the manner hereinafter described a controlled lesser adhesion is obtained between the extruded jacket and the metallic shield at the interface around the rest of the periphery, this area being indicated by the arrow 15 in FIGURE 1. The result is a cable construction in which the seam at the overlapping edges of the shielding strip is hermetically sealed and in which the enclosed polyethylene jacket is firmly adhered to the shield over the seam and for a limited peripheral dis- CJI tance on both sides thereof. Around the rest of the periphery the polyethylene jacket is adhered to the shielding layer less firmly, thus facilitating removal of the jacket in this area to expose the metallic strip for making an electrical connection thereto.
FIGURE 2 is a transverse section to enlarged scale through a coated metallic strip suitable for use in forming the shielding layer. In FIGURE 2 the metallic strip 21 is coated on both surfaces with films of polyethylene material. For purposes of illustration the thickness of the metallic strip and the coating layers are exaggerated. In practice, an aluminum shielding strip might be from 5 to 10 mils thick and the film coating layer might be from 1 to 3 mils thick. This coating material 22 along both edges of the strip, in the limited areas designated 23 and 24, is polyethylene containing a reactive carboxyl group which has the ability to develop firm adhesion to the metallic strip, to itself at the overlapped edges of the strip, and also to the polyethylene jacket when it is extruded thereover. The coating material 25 along the center portion 26 of the strip has a controlled lesser ability to develop firm adhesion to the metallic strip and to the polyethylene jacket which will be extruded over the shielding layer.
FIGURE 3 is a cross section taken transversely through the cable of FIGURE 1, the thickness of the metallic shielding strip and the coating layers thereon being exaggerated for purposes of illustration. As explained hereinabove, the film coating along the edges of the metallic strip has the ability to develop firm adhesion between the overlapping edges of the folded strip, and to the polyethylene jacket in the region over the seam and for a limited peripheral distance on both sides thereof. This results in a hermetic seal along the longitudinal seam of the folded shielding strip. The film coating along the center portion of the metallic strip has a controlled lesser ability to develop adhesion to the polyethylene jacket around the peripheral extent 15 of the tubular shield. Thus, while there preferably is adherence of the film coating to the metallic strip and to the overlying jacket in this region it is less than along the seam of the shielding layer. As a result, removal of the polyethylene from the center portion of the metallic strip to permit electrical connection thereto is facilitated with little danger of stripping the polyethylene from the metallic strip along the seam at its overlapping edges.
The precoated metallic strip illustrated in FIGURE 2 may be formed by extruding the polyethylene films onto the strip. During such extrusion polyethylene of limited adhesive characteristic may be extruded over the center part of the strip and highly adhesive polyethylene over the two edge portions of the strip.
Alternatively, highly adhesive polyethylene may be extruded over the entire Width of the metallic strip and the center portion of the strip then treated to selectively reduce its adhesive ability. I have found that the adhesiveness of a coating of polyethylene containing reactive carboxyl groups on the metallic shielding strip is greatly reduced by an oxidizing flame treatment. Apparently the ability of the carboxyl groups required to develop high adhesive properties is made less effective by such treatment. By treating the center part of an aluminum strip coated with polyethylene containing reactive carboxyl groups coated with an oxidizing flame and then using this strip as a cable shielding tape it is possible to obtain excellent sealing in the seam to itself, and to the polyethylene jacket extruded over the shielding layer, and yet prevent such firm adhesion between the jacket and that part of the shielding tape which has been flame treated. For example, with a three inch wide polyethylene protected aluminum strip it is possible to flame treat the center part of the strip and leave the edges on either side of the strip with the original ability of the film to adhere to the aluminum and to itself, as well as to the outer polyethylene jacket. Flame treatment of the center part of the film coated metallic strip may take place as the strip enters the apparatus for folding the strip about the cable core, as illustrated in FIGURE 4. Alternatively, the strip could be pretreated to limit the adhesive ability of the center portion of the strip, if desired.
It also is possible by the use of a suitable release agent, for example a pigment such as talc, or an oil such as a silicone oil, to limit the area of firm adhesion between the sealed shield and the polyethylene jacket extruded over it. If the cable core with its enclosing longitudinally folded metallic strip coated with polyethylene containing reactive carboxyl groups is fed into the extruder with the seam of the shield in the top position, as shown in FIG- URE 6, talc or other release agent may be dusted or wiped around the lower half or three-quarter of the cable core circumference just before the core enters the extruder for application of the outer polyethylene jacket. This will result, under proper temperature and pressure conditions, in a sealing of the seam and a firm bond on the top half or top quarter of the core circumference at the interface between the shield and the jacket, with comparatively easy stripping of the bottom half or three-quarters of the jacket. This cable construction is illustrated in the fragmentary cross section of FIGURE 5, where 31 is the overlapping film coated metallic strip which encloses the cable core, 13 is the extruded polyethylene jacket, and 32 represents the thin coating of release agent. The release agent, shown of exaggerated thickness merely for purposes of illustration, does not extend over the top approximately one-quarter of the tubular shielding layer, thus insuring firm adhesion of the polyethylene jacket 13 to the shielding layer at the longitudinal seam and for a limited peripheral distance on both sides thereof. Silicone oil, silicone oil emulsion in water, or a tale dispersion in an oil may be applied in similar manner as release agent to achieve the same results. Of course, the release agent could be applied by dusting, brushing or wiping to the center portion of that surface of the film coated metallic strip which will form the exterior of the tubular shielding layer prior to folding the strip about the cable core.
Preferred embodiments of the invention have been illustrated and described, but changes and modifications can be made without departing from the invention as defined in the claims.
I claim:
1. A shielded electrical cable comprising at least one insulated conductor of indefinite length, a metallic strip which is coextensive in length with the conductor and which is folded about the insulated conductor with its edges overlapping each other to provide a tubular metallic shielding layer completely enclosing the insulated conductor, an outer jacket of plastic insulating material surrounding and closely enclosing the tubular shielding layer, the plastic jacket being firmly adhered to the shielding layer along its overlapping edges and for a limited peripheral distance on both sides thereof to seal the overlap, the plastic jacket having a controlled lesser adhesion to the shielding layer around the rest of its periphery to facilitate stripping the plastic from the shielding layer in a region removed from the sealed overlapped region.
2. An electrical cable according to claim 1 in which the outer jacket is polyethylene and the metallic shielding strip is an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, and in which a release agent is interposed between the tubular metallic shielding layer and the polyethylene jacket for a limited peripheral extent opposite the overlapped edges of the shielding strip.
3. An electrical cable according to claim 2 in which the release agent comprises a silicone oil.
4. An electrical cable according to claim 3 in which the release agent comprises a silicone oil emulsion in Water.
5. An electrical cable according to claim 2 in which the release agent comprises talc.
6. An electrical cable according to claim 5 in which the release agent comprises a talc dispersion in oil.
7. An electrical cable according to claim 1 in which the outer jacket is polyethylene and the metallic shielding strip is an aluminum strip having bonded to both surfaces thereof coatings of a copolymer of ethylene with monomers containing carboxyl groups.
8. An electrical cable according to claim 1 in which the outer jacket is polyethylene and the metallic shielding strip is an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, the aluminum strip being coated along its overlapped edge portions with such material having high adhesive characteristics and along its center portion opposite the overlap with such material having relatively lesser adhesive characteristics.
9. In the manufacture of electrical cable having at least one insulated conductor, an enclosing tubular metallic shielding layer formed from an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, and an outer jacket of polyethylene, the method which comprises treating the center portion only of the coated aluminum strip to reduce the adhesion characteristics of the coating material along the center of the strip without affecting the high adhesion characteristics of the coating material along the edge portions of the strip, folding the coated aluminum strip longitudinally around the insulated conductor with its edges overlapping each other to enclose the insulated conductor completely, and extruding the outer jacket of polyethylene over the folded strip with resulting high adhesion of the jacket to the shielding layer along the overlapped portion and lesser adhesion of the jacket to the shielding layer opposite the overlapped portion.
10. In the manufacture of electrical cable having at least one insulated conductor, an enclosing tubular metallic shielding layer formed from an aluminum strip having bonded to its outer surface a coating of a copolymer of ethylene with monomers containing carboxyl groups, and an outer jacket of polyethylene, the method of controlling the adhesion of the jacket to the shielding layer which comprises heating the center portion only of the coated aluminum strip to reduce the adhesion characteristics of the coating material along the center of the strip without affecting the high adhesion characteristics of the coating material along the edge portions of the strip, folding the coated aluminum strip longitudinally around the insulated conductor with its edges overlapping each other to enclose the insulated conductor completely, and extruding the outer jacket of polyethylene over the folded strip with resulting high adhesion of the jacket to the shielding layer along the overlapped portion and lesser adhesion of the jacket to the shielding layer opposite the overlapped portion.
11. The method of claim 10 which comprises heating the center portion of the coated aluminum strip by subjectin g it to an oxidizing flame.
12. In the manufacture of electrical cable having at least one insulated conductor, an enclosing tubular metallic shielding layer formed from an aluminum strip having bonded to its outer surface a coating of a copolyrner of ethylene with monomers containing carboxyl groups, and an outer jacket of polyethylene, the method of controlling the adhesion of the jacket to the shielding layer which comprises folding the coated aluminum strip longitudinally around the insulated conductor with its edges overlapping each other to enclose the insulated conductor completely, applying a release agent to a peripheral portion only of the shielding layer opposite the overlapped edges to reduce the adhesion characteristics of such portion of the coating material without affecting the high adhesion characteristics of the coating material along the overlapped edges, and extruding the outer jacket of polyethylene over the folded strip with resulting high adhesion of the jacket to the shielding layer along the overlapped portion and lesser adhesion of the jacket to the shielding layer opposite the overlapped portion.
References Cited UNITED STATES PATENTS 3,233,036 2/1966 Jachimowicz 17436X 8 FOREIGN PATENTS 942,730 11/1963 Great Britain. 968,061 8/1964 Great Britain.
5 DARRELL L. CLAY, Primary Examiner.
A. T. GRIMLEY, Assistant Examiner.
Claims (1)
1. A SHIELDED ELECTRICAL CABLE COMPRISING AT LEAST ONE INSULATED CONDUCTOR OF INDEFINITE LENGTH, A METALLIC STRIP WHICH IS COEXTENSIVE IN LENGTH WITH THE CONDUCTOR AND WHICH IS FOLDED ABOUT THE INSULATED CONDUCTOR WITH ITS EDGES OVERLAPPING EACH OTHER TO PROVIDE A TUBULAR METALLIC SHIELDING LAYER COMPLETELY ENCLOSING THE INSULATED CONDUCTOR, AN OUTER JACKET OF PLASTIC INSULATING MATERIAL SURROUNDING AND CLOSELY ENCLOSING THE TUBULAR SHIELDING LAYER, THE PLASTIC JACKET BEING FIRMLY ADHERED TO THE SHIELDING LAY-
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US427435A US3379821A (en) | 1965-01-22 | 1965-01-22 | Shielded electrical cable |
FR37751A FR1453587A (en) | 1965-01-22 | 1965-11-09 | Shielded electric cable |
GB48391/65A GB1133603A (en) | 1965-01-22 | 1965-11-15 | Shielded electrical cable |
DE1690782A DE1690782C3 (en) | 1965-01-22 | 1966-01-14 | Shielded electrical cable and process for its manufacture |
ES0321953A ES321953A1 (en) | 1965-01-22 | 1966-01-19 | A method to produce an armed electrical cable. (Machine-translation by Google Translate, not legally binding) |
CH81366A CH444248A (en) | 1965-01-22 | 1966-01-21 | Shielded electrical cable and its method of manufacture |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US427435A US3379821A (en) | 1965-01-22 | 1965-01-22 | Shielded electrical cable |
Publications (1)
Publication Number | Publication Date |
---|---|
US3379821A true US3379821A (en) | 1968-04-23 |
Family
ID=23694865
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US427435A Expired - Lifetime US3379821A (en) | 1965-01-22 | 1965-01-22 | Shielded electrical cable |
Country Status (6)
Country | Link |
---|---|
US (1) | US3379821A (en) |
CH (1) | CH444248A (en) |
DE (1) | DE1690782C3 (en) |
ES (1) | ES321953A1 (en) |
FR (1) | FR1453587A (en) |
GB (1) | GB1133603A (en) |
Cited By (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3485689A (en) * | 1966-12-06 | 1969-12-23 | Gen Cable Corp | Method and apparatus for making cable |
US3489844A (en) * | 1968-03-25 | 1970-01-13 | Dynatronic Cable Eng Corp | Multiple-pair digital data transmission cable |
US3532783A (en) * | 1968-02-28 | 1970-10-06 | Superior Continental Corp | Method of molding bonded messenger cable |
US3534149A (en) * | 1966-12-06 | 1970-10-13 | Bell Telephone Labor Inc | Communication cable systems |
US3564110A (en) * | 1966-12-06 | 1971-02-16 | Bell Telephone Labor Inc | Electrical cables |
US3607614A (en) * | 1969-03-04 | 1971-09-21 | British Non Ferrous Metals Res | Adhesives |
US3651244A (en) * | 1969-10-15 | 1972-03-21 | Gen Cable Corp | Power cable with corrugated or smooth longitudinally folded metallic shielding tape |
US3654027A (en) * | 1969-09-24 | 1972-04-04 | Pre Stress Concrete | Apparatus for manufacturing a sheathed cable for use in post-tensioning concrete structures |
US3703605A (en) * | 1971-03-17 | 1972-11-21 | Matthew R Dembiak | Communications cables with sealed metallic moisture barriers |
US3823747A (en) * | 1971-03-17 | 1974-07-16 | Western Electric Co | Tubular member having a sealed longitudinal seam |
US3891791A (en) * | 1974-05-10 | 1975-06-24 | Gen Cable Corp | Communication cable with improved coated shield |
US4157452A (en) * | 1976-08-30 | 1979-06-05 | Industrie Pirelli Societa Per Azioni | Electric power cable with improved screen and method of manufacture thereof |
USRE30228E (en) * | 1973-02-23 | 1980-03-11 | General Cable Corporation | Power cable with corrugated or smooth longitudinally folded metallic shielding tape |
US4327248A (en) * | 1980-10-06 | 1982-04-27 | Eaton Corporation | Shielded electrical cable |
US4698457A (en) * | 1985-09-25 | 1987-10-06 | Thomas & Betts Corporation | Strippable shielded electrical cable assembly |
US4758455A (en) * | 1985-07-10 | 1988-07-19 | Handy & Harman Automotive Group Inc. | Composite fuel and vapor tube having increased heat resistance |
US4859534A (en) * | 1984-11-19 | 1989-08-22 | Chemical Vulcanising Systems (Proprietary) Limited | Method and apparatus for repairing a cable |
US5077449A (en) * | 1989-11-13 | 1991-12-31 | Northern Telecom Limited | Electrical cable with corrugated metal shield |
US5486649A (en) * | 1994-03-17 | 1996-01-23 | Belden Wire & Cable Company | Shielded cable |
US5683778A (en) * | 1992-12-09 | 1997-11-04 | Crosier; Robert A. | Braided graphite-foil and method of production |
US20070251715A1 (en) * | 2004-08-12 | 2007-11-01 | Dalaine Jean C | Method for Protecting a Cable or a Pipe |
US9969907B2 (en) | 2011-09-30 | 2018-05-15 | Dow Global Technologies Llc | Controlled peel laminate adhesive films |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3551586A (en) * | 1969-03-24 | 1970-12-29 | Western Electric Co | Shielded electrical cable |
CN114933761A (en) * | 2022-03-24 | 2022-08-23 | 东台市海通金属制品有限公司 | Method for processing multi-core tube with shielding layer and sheath |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB942730A (en) * | 1962-07-30 | 1963-11-27 | Standard Telephones Cables Ltd | Electric cables |
GB968061A (en) * | 1963-01-02 | 1964-08-26 | Pirelli General Cable Works | Improvements in or relating to screened insulated electric conductors |
US3233036A (en) * | 1963-11-01 | 1966-02-01 | Gen Cable Corp | Corrosion proof shielding tape for shielding telephone cables |
-
1965
- 1965-01-22 US US427435A patent/US3379821A/en not_active Expired - Lifetime
- 1965-11-09 FR FR37751A patent/FR1453587A/en not_active Expired
- 1965-11-15 GB GB48391/65A patent/GB1133603A/en not_active Expired
-
1966
- 1966-01-14 DE DE1690782A patent/DE1690782C3/en not_active Expired
- 1966-01-19 ES ES0321953A patent/ES321953A1/en not_active Expired
- 1966-01-21 CH CH81366A patent/CH444248A/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB942730A (en) * | 1962-07-30 | 1963-11-27 | Standard Telephones Cables Ltd | Electric cables |
GB968061A (en) * | 1963-01-02 | 1964-08-26 | Pirelli General Cable Works | Improvements in or relating to screened insulated electric conductors |
US3233036A (en) * | 1963-11-01 | 1966-02-01 | Gen Cable Corp | Corrosion proof shielding tape for shielding telephone cables |
Cited By (23)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3534149A (en) * | 1966-12-06 | 1970-10-13 | Bell Telephone Labor Inc | Communication cable systems |
US3564110A (en) * | 1966-12-06 | 1971-02-16 | Bell Telephone Labor Inc | Electrical cables |
US3485689A (en) * | 1966-12-06 | 1969-12-23 | Gen Cable Corp | Method and apparatus for making cable |
US3532783A (en) * | 1968-02-28 | 1970-10-06 | Superior Continental Corp | Method of molding bonded messenger cable |
US3489844A (en) * | 1968-03-25 | 1970-01-13 | Dynatronic Cable Eng Corp | Multiple-pair digital data transmission cable |
US3607614A (en) * | 1969-03-04 | 1971-09-21 | British Non Ferrous Metals Res | Adhesives |
US3654027A (en) * | 1969-09-24 | 1972-04-04 | Pre Stress Concrete | Apparatus for manufacturing a sheathed cable for use in post-tensioning concrete structures |
US3651244A (en) * | 1969-10-15 | 1972-03-21 | Gen Cable Corp | Power cable with corrugated or smooth longitudinally folded metallic shielding tape |
US3703605A (en) * | 1971-03-17 | 1972-11-21 | Matthew R Dembiak | Communications cables with sealed metallic moisture barriers |
US3823747A (en) * | 1971-03-17 | 1974-07-16 | Western Electric Co | Tubular member having a sealed longitudinal seam |
USRE30228E (en) * | 1973-02-23 | 1980-03-11 | General Cable Corporation | Power cable with corrugated or smooth longitudinally folded metallic shielding tape |
US3891791A (en) * | 1974-05-10 | 1975-06-24 | Gen Cable Corp | Communication cable with improved coated shield |
US4157452A (en) * | 1976-08-30 | 1979-06-05 | Industrie Pirelli Societa Per Azioni | Electric power cable with improved screen and method of manufacture thereof |
US4327248A (en) * | 1980-10-06 | 1982-04-27 | Eaton Corporation | Shielded electrical cable |
US4859534A (en) * | 1984-11-19 | 1989-08-22 | Chemical Vulcanising Systems (Proprietary) Limited | Method and apparatus for repairing a cable |
US4758455A (en) * | 1985-07-10 | 1988-07-19 | Handy & Harman Automotive Group Inc. | Composite fuel and vapor tube having increased heat resistance |
US4698457A (en) * | 1985-09-25 | 1987-10-06 | Thomas & Betts Corporation | Strippable shielded electrical cable assembly |
US5077449A (en) * | 1989-11-13 | 1991-12-31 | Northern Telecom Limited | Electrical cable with corrugated metal shield |
US5683778A (en) * | 1992-12-09 | 1997-11-04 | Crosier; Robert A. | Braided graphite-foil and method of production |
US5486649A (en) * | 1994-03-17 | 1996-01-23 | Belden Wire & Cable Company | Shielded cable |
US20070251715A1 (en) * | 2004-08-12 | 2007-11-01 | Dalaine Jean C | Method for Protecting a Cable or a Pipe |
US7838771B2 (en) * | 2004-08-12 | 2010-11-23 | Jean-Charles Dalaine | Method for protecting a cable or a pipe |
US9969907B2 (en) | 2011-09-30 | 2018-05-15 | Dow Global Technologies Llc | Controlled peel laminate adhesive films |
Also Published As
Publication number | Publication date |
---|---|
GB1133603A (en) | 1968-11-13 |
CH444248A (en) | 1967-09-30 |
DE1690782C3 (en) | 1975-04-10 |
ES321953A1 (en) | 1966-11-01 |
DE1690782B2 (en) | 1974-08-15 |
FR1453587A (en) | 1966-06-03 |
DE1690782A1 (en) | 1971-06-16 |
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