CA1054038A - Forming sealed seams in moisture barriers for cables - Google Patents

Abstract

FORMING SEALED SEAMS IN
MOISTURE BARRIERS FOR CABLES
Abstract of the Disclosure In the manufacture of a communications cable, a moisture barrier comprising a corrugated metallic tape is wrapped longitudinally about a cable core to form an over-lapped seam, with at least a portion of the moisture barrier which forms the seam being precoated with an adhesive mate-rial. Heat is applied to at least the portions of the moisture barrier which form the seam while the portions are maintained spaced apart to permit a stripe of adhesive material in molten form to be introduced into the seam.
Then the enclosed cable core is advanced between coacting rollers which apply forces to the moisture barrier to cause the spaced apart portions to engage each other with the stripe filling the spaces between associated corrugations to form a reliably sealed seam. A longitudinally extending mandrel supports the barrier during the application of the forces to preserve the configuration of the enclosed core and to prevent damage to the core or the moisture barrier.

Description

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ackc~round of tlle Invention . .
1. ~ield of the Invention This invention relates to forming sealed seams in moisture barriers for cables and, more particularly, to methods oE and apparatus for causing overlapping portions of a lonyitudinally formed moisture barrier wrapped about an a~vancing cable core to be bonded adhesively to Eoreclose the ingress of moisture into the cable core.

2. Description of the Prior ~rt It is well known that the diffusion of water vapor in a uni-directional manner through a cable jacket will result in undesirably high moisture levels in the cable which will have a detrimental effect on the transmission character-istics of the cable. It is also well known that a metallic tube surrounding the cable core provides an effective barrier r,-against moisture diffusion into the cable core.
The tube is generally made from a single strip or tape of metal wrapped longitudinally about the cable core to form an overlap seam. ~oreover, in order to impart greater flexibility to the cable, the moisture barrier may be corru-gated prior to being wrapped about the core.
The effectiveness of the tube as a moisture barrier is enhanced greatly if the resulting overlapping seam is sealed. The most effective seam seal is one in which a metal-to-metal bond exists, such as a welded or soldered seam.
Problems arise when attempting to weld or solder the seam. The materials which make up most communications cables are temperature-sensitive and easily damaged if over-heated. This temperature sensitivity renders impracticalthe use of metal-welding as a sealing technique because of ~, -- 1 -- ~
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Since most communications cables require an elec-trically conductive, metallic sheath, to shield against external electrical signals, it is usually desirable to incorporate the shielding function with the moisture barrier ~Ilnction in onc single la~er of metal. Good electrical corlductivity is a requisite of a shielding material, and the best overall compromise for a material to fit all needs of a metal layer has been found to be aluminum. Because of its highly reactive nature, the aluminum maintains almost consis-tently an oxide film which virtually precludes continuous soldering as a joining technique for the overlapped seam.
Einally, the strip or tape from which the moisture barrier is formed is extremely thin, e.g., on the order of four to six mils. The thinness of the barrier coupled with ; the corrugations typically formed therein render undesirable the use o~ welding or soldering for sealing the seam.
It has been found that a sealed moisture barrier seam can be obtained by adhesively joining the overlapped seam. This may be accomplished by using adhesive-copolymer aluminum laminates at least for those portions of the barrier ; which form the seam. The application of adhesive copolymers in laminates is discussed by B. Wargotz in an article ;
"Environmental Stability of Ethylene-Acrylic Acid Adhesive Copolymers Bonded to Metal Substrates" published in Vol. 12 of the Journal of Applied Pol~mer Science, pages 1873-188B ~- ;
(1968).
Adhesive copolymers can also be used to manufacture bonded cable sheaths in which thermoplastic jackets are 30 bonded to the surface of aluminum tapes which have been `
wrapped around the cable core. This is accomplished generally ` 2 -, ~
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~3~ 8 ~y Lirec~atinc~ an alu~inum tape with an adhcsive copolymer across its entire width before formincJ it in~o a tube around the cable. ~hen a polyethylene jacket is applied over such a precoated aluminum tape, the heat from the semi-molten polyethylene, being extruded around the precoated tape, causes a bonding reaction between the adhesive copolymer, the alumlnum, and the polyethylene ~acket. The heat imparted to the ~olyetllylene material is sufficiently high and the aluminum tape will become hot enough so that bonding will also occur between overlapped layers of tape at the seam.
At least one problem develops from the use of a fully-bonded sheath. Present splicing practices requires the removal of the jacekt from the tape at a splice location in order to develop electrical contact with the aluminum tape at the splice location to assure that the shielding function of the tape may occur. With the jacket bonded to the shield around the entire periphery thereof, it may be very difficult for an installer to strip the jacket ~rom `
the shield during a splicing operation.
The greate~t advantage of a bGnded cable sheath is - brought about by the sealing of the overlapped seam. sonding the polyethylene jacket to the metal tape around the entire outer surface of the metal tape produces only a secondary effect in enhancing the moisture barrier properties of the sheath. Thus, it is possible by restricting the precoating ~ `
of the metal to only an overlapped seam area to accomplish virtually all of the moisture diffusion prevention which might be required in a cable, while precluding the herein-before discussed disadvantage associated with the fully-bonded cable sheath.
The art abounds wlth patents r~lating to moisture :
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b~rriers or tube-makiilc~ with bonde~-ty~e longitudinally formed, overlapped seams. In U.S. Patent 3,574,016 issued to R.R. Wa}llberg, a moisture barrier is formed of a longi-tudinally applied metallic strip in which a resultant over-lapped seam is sealed with an acrylic acid ethylene copoly-mer which has been inserted into the seam in tape form and subsecluently heated by the extrusion of a thermoplastic jacket over the metallic strip. In an alternate embodiment in that patent, there is shown a oable sheath in which the inside surface of the metallic strip is precoated with an adhesive cGpolymer. A still further embodiment discloses the combining of a precoating of the shield with a film of adhesive copolymer on the inwardly facing major surface with the introduc-tion of a strip of adhesive material into the seam portion.
Another patent, U.S~ patent 3,703,605 issued to M.R. Dembiak and G.W. Webster, shows a moisture barrier coated across the entire transverse width on the outwardly facing surface and along an edge portion of the portion of the strip which forms the overlapped seam. The compositions of the coatings are different to permit a thin striping of -~
the inwardly facing surface in order to avoid specific manufacturing problems.
In F.F. Polizzano, Patents 3,504,102 and 3,575,748 an overlap seam of a double side coated moisture barrier is preferably reinforced by a longitudinally extending plastic . . .
metal laminated tape or bridging strip under the seam. The plastic coating on the confronting faces of the seam is ~
heat softened and pressed together to bond the edge portions ;
of the seam together.

O.G. Carner Patent 3,332,138 shows forming an `` adhesive coated metal strip into a tube with a longitudinal - ~ 4 ~

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' ~5~1~3~3 overla~ ed seam and heatiny the adhesive within the seam to bond the o~erlapped edges. See also U.S. Patent 3,260,636 issued to 1l. Witzenmann. U.S. Patent 3,409,734 issue~ to ~l. Devine et al. discloses a narrow band of adhesive applied to the inside sur~ace of an outer layer of a tape enclosing a metal stranc~ and bonded to the underlying tape sur~ace so as to lcave a fine strip of the tape adjacent to the edge free from adhesion.
A patent issued to A.K~ Turner (U.S. Patent

3,203,085) shows a ribbon of solder fed between the over-lapped edges of a shield wrapped about a conductor and melted with the edges clamped under pressure to form a continuous impenetrable seam. In U.S. Patent 3,471,350 `
issued to ~.V. O'Berry et al. there is shown making a carrier for wound packages by applying adhesive to a major portion of one surface and applying a ribbon of adhesive to a minor portion of the surface which forms a longitudinal overlapped seam. I.~I. Marantz Patent 3,558,378 shows a web wrapped about an armored cable and bonding material extruded into the nip between a marginal edge and an outer surface of the convolution of the web. Shigekazu Takeda Patent 3,597,292 discloses a nozzle distributing a molten resin in the longitudinal overlapped seam portion of synthetic resin fabrics.
The related art of pipe-making includes F.W. Yeager Patent 2,044,456 which shows the application of a hot asphalt to a longitudinal seam of pipe shield material. U.S. Patent 775,541, issued to J.A. McConnell, shows a mandrel projecting forward into the bite of cooperating rollers to support a tube against buckling during seam sealing. See also U.S. Patent 2,897,~75.

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Despite the numerous processes for forming a longitud-inal seam having integrity agalnst moisture diffusion, problems are yet experienced in obtaining consistently a reliably sealed seam in ca~le manufacture, especially when the metallic tape is corrugated. With the trend toward an increased number of cor-rugations per unit length, the mis-registration of corrugations at the overlapped seam causes excessively deep valleys. This causes the adhesion on the opposing faces to not engage each other, thereby providing undesirable gaps in the seam.
Summary of the Invention With these and other objects ln mind this invention relates to forming a tubular member having a sealed overlapped ?~
seam such as a moisture barrier for communications cables, in which an elongated strip is advanced along a path and is formed with longitudinal edge portions being adjacent each other. The strip has an inwardly facing surface and an outwardly facing surface with at least one of the major surfaces having an ad-` hesive material precoated along a longitudinal edge portion : : .
thereof which is to form an overlapped seam. ~
According to one aspect of the invention there is -~
provided a method of manufacturing a cable with a moisture barrier having a sealed overlapped seam, which includes the ` steps of: advancing a cable core along a path; applying a -metallic strip around the core with longitudinal edge portions of the strip being adjacent each other, the formed strip having outwardly and inwardly facing major surfaces, the inwardly facing surface facing the core, at least one of the major facing surfaces having an adhesive copolymer material precoated along ` a longitudinal edge portion thereof which is to form an over-lapped seam; flowing an adhesive copolymer material into engage-ment with at least one of the adjacent longitudinal edge portions ~-:
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of the major facing surfaces of the strip which is to form the overlapped seam; and causing relative movement of tha longi-tudinal edge portions to form the overlapped seam with the flowed and precoated adhesive copolymer materials bonding the over:Lapped portions to seal the seam.
Accor~ing to another aspect of the invention there is provided an apparatus for manufacturing a cable with a moisture barrier having a sealed overlapped seam, which includes: means for advancing a cable core along a path; means for applying a metallic strip around the core with longitudinal edge portions of the strip being adjacent each other, the formed strip havlng outwardly and inwardly facing ma~or surfaces, the inwardly facing surface facing the core, at least one of the ma~or facing surfaces having an adhesive copolymer material precoated along a longitudinal edge portion thereof which is to form an overlapped seam; means for flowing an adhesive copolymer material into engagement with at least one of the ad~acent longitudinal edge portions of the major facing surfaces .
of the strip which is to form the overlapped seam; and means for causing relative movement of the longitudinal edge portions to form the overlapped seam with the flowed and precoated ~:
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adhesive copolymer materials bonding the overlapping portions to seal the same. ~:
. More particularly, a cable core is advanced along a predetermined path, while a metallic corrugated tape having an adhesive copolymer material precoated along at least longitudinal : edge portions thereof is formed about the ... ~.
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.,. . . i advancing ca~le core in order to provide an overlapped seam with adhesive copolymer on the outwardly facing surface and the inwardly facing surface beiny opposed in order to provide an adhesive bond. ~s the cable core with the corru-gated ta~e is advanced along the manufacturing line, the portions of the tape forming the seam are separated slightly with heat applied thereto and a stripe of adhesive copolymex material is extruded into the seam yortion. Subsequently, the core and enclosing tape are ad~anced between a pair of opposing coactiny rollers with a mandrel being interposed between the core and the seam portion in order to provide support for forces applied by the pressure rollers. The use of the extruded stripe of adhesive copolymer cooperates with the adhesive copolymer precoated on the opposing faces at the overlapped seam in order to provide a consistently reliably sealed seam. Subsequently, the cable core with the corrugated tape having the sealed seam is advanced through a chilling station, is preheated and finally jacketed, after which the finished cable is taken up on a reel.
Brief Description of the Drawinys ; Other objects and features of the present -- invention will be more readily understood from the following detailed description of specified embodiments thereof when ; read in conjunction with the accompanying drawings in which:
FIG. 1 is a cross-sectional view of a cable core showing a moisture barrier wrapped about the core with an ~;
overlapped seam and in relation to a jacket and the core; ~ `
FIG. 2 is a simplified view in elevation showing .. ,. ~ .
- the manufacture of a communications cable as the cable core, comprised of a plurality of conductors, is advanced throuyh a plurality of stations along the manu~ac-turing line;

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FIG. 3 is an enlarged detailed view showing a portion of the overlapped seam of a moisture barrier, which includes a corrugated tape, just prior to the closing of the overlapping portions;
FIG. 4 is an enlarged perspective view o a portion of the m~nufacturing line whi.ch shows the portions of the line which are used to carry out the principles and the method of this invention to introduce a stripe of adhesive into the overlapped seam;
FIG. 5 is an enlarged detailed view of a mandrel which is used to support the overlapped seam during the application of forces by two forming rollers;
FIG. 6 is a detailed plan view of portions of facilities which are used to separate the o~erlapped seam to facilitate the introduction of the stripe of adhesive; and ; FIG. 7 is a sectional view of a portion of the facilities used to open the seam prior to the .introduction ; of the adhesive stripe and showing the portions of the tape ; which form the seam in relation to those facilities, and FIGS. 8A, 8B and 8C, which can be found on the same sheet of drawings as FIG. 1, are enlarged detail Yiews `- of the overlapped seam of several different moisture barrier: constructions with the stripe of adhesi~e extrusion-intro-. :
duced between opposing faces of the seam.
D tailed Descri tion of the Invention e P .
As is shown in FIG. 1, a cable, designated gener~
. ally by the numeral 10, includes a core, designated generally by the numeral 11, which includes a plurality of conduc~ors 12-12. The cable core 11 is enclosed by a moisture barrier, :
3Q designated generally by the numeral 13, which includes a metallic tape 14. The metallic tape 14, generally construc-ted of aluminum, has an inwardly facing surface 15, which ~':
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f~ces t~le core 1l, alld an outwardly facing surface 16. The inwardly and the outwardly facing sur~aces 15 and 1~, res-pectively, in this embodiment are covered with an adhesive r copolymer material layer 17 and 18, respectively, across the entire transverse widths thcreof. The adhesive layers 17 and 1~ are bonded together along the interface 19 thereof by an adhesive striue in accordance with the principl~s oE
this invention to Eorm a seam 20. Subsequent].y, the moisture barrier 13 has a jacket 21 extruded thereover.
The moisture barrier 13 may be manufactured during the cable-making operation or is available commercially as a separate item. For example, a four mil thick aluminum tape coated on each side thereof with a two mil thick adhesive copolymer layer is available from the Dow ~hemical Company under the designation "Zetabon" tTrade Mark). ~ ~;
A manufacturing apparatus 30, which may be employed to manufacture 'che cable 10, is shown in FIG. 2 and includes a supply reel 31 of a continuous length of the core 11. The core 11 is advanced along a predetermined path with a sepa-rate supply of the coated tape 14 being advanced through a corrugator, designated generally by the numeral 32. After being corrugated, the tape 14 is fed into a belt former, ;~
designated generally by the numeral 33, which wraps the tape longitudinally around the cable core 11. The enclosed cable core 11 is advanced through facilities, designated generalIy by the numeral 34, in which a stripe of adhesive is extruded between separated, opposing faces of the corrugated tape 14. --; : , After the extrusion of the stripe of adhesive, the overlapped seam 20 is reclosed, and the enclosed core advanced through chilling facilities, designated generally by the numeral 35, and, subsequently, through preheat facilities, designated '`~':: `

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generally by the numeral 35. Then the core 11 having a sealed seam moisture barrier 13 thereabout is advanced through an extruder 37, wherein the jacket 21 is extruded thereover. Then the communica-tions cable 10 is advanced through a caps~an 38 and is taken up on a reel 39.
~ eferrincJ now to FIG. 8, there is shown a cross-sectional view of portions of the overlapped longitudinally-formed seam 19 o~ the corrugated tape 14. It should be quite apparent that unless the corrugations are precisely formed and mated, portions thereof may not be in complete registration with associated portions at the overlap.
Moreover, in recent years there has been a trend toward increasing the number of corrugations per inch of tape length.
This makes it even more difficult to nest associated corru-gations at the overlapped portion of the tape 13.
Because of potential misregistration of associated corrugations, it becomes somewhat difficult to obtain the bonding of the adhesive copolymer layers which face each other on opposing portions of the tape seam 20. For example, in the portion of the seam designated by the numeral 41 (see FIG. 3), it can be seen that even though the opposing faces ~-of the seam are coated with adhesive copolymer, there may be a space unoccupied by either at the overlap simply because of the misregistration of the corrugations. Hence, a portion of the seam 20 will not be bonded and the integrity of the moisture barrier 13 against moisture diffusion is put in jeopardy.
In order to overcome these problems, the methods of this invention may be used to obtain a reliably sealed seam 20. Referring now to FIG. 4, there is shown in detail the apparatus 3~ for carrying out the principles of this ...: '.

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invention. The cable core 11 is shown being advanced out of the belt former 33 and then past a device 51 (see also FIG. 8) which extends transversely of the cable core Erom a support post 52. The device 51 is positioned so as to be interposed be-tween the over~apped seam portions.
The device 51 has a dual Punction. When the cable core 11 is advanced past the device 51, the device separates slightly the overlapping portions of -the moisture barrier 13 and causes them to be spaced apart for a short distance, 10 e.g., eight inches, alon~ the path of travel. Moreover, the ~
device 51 has a longitudinally extending mandrel 53 which ~;
extends in a downstream direction from the post 52. The mandrel 53 permits closing forces to be applied to the seam 20 without destroying the circular configuration of the core 11 or inflicting damage to the core. The separation of the opposing portions of the moisture barrier 13 which form the seam 20 permits the introduction therebetween of addi-tional adhesive material.
- Also shown in FIG. 4 is a device 54 for applying heat to at least those portions of ~he moisture barrier 13 which form the overlapped seam 20 just downstream o~ the seam separating device 51. The device 54 directs streams of heated air having a temperature of approximately ldOOF into engagement with the seam area, and portions contiguous thereto of the moisture barrier 13. This causes the temperature of -~
the aluminum tape to be elevated to approximately 200F. ~ -: :: .: :
In this way, the entire seam area is in a heated ~ ;
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condition, thereby enhancing the possibility for supplemental ., :
' adhesive copolymer to fill spaces such as ~1 shown in FIG. 3, and thereby increase the probability for obtaining a i~` reliably seale~3 seam between all the corrugations.

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rr}le sel~aration of the opposincJ faces of the moisture barrier 13 permits an extruder, designated generally by the numeral 56, to extrude a thin stripe or ribbon 57 (see FIG. 8A) of adhesive copolymer material into the seam betwoen overlap~inc3 opposing faces of the moisture barrier.
The extruder 56 includes a die 58, having a ten mil thick slot 59 (see FIG. 8).
The extrusion of the stripe 57 is performed to insure a sealing of the seam 20. Referring now to FIG. 6, 10 it can be seen that as the core 11 is advanced past the device 51, the external overlapping portion of the moisture barrier 13 rides up over the device 51j while the internal portion of the moisture barrier has an edge 60 moving in engagement with a downturned end 63 of the support 51. This causes the edge 60 to be moved out of line with its path of travel upstream and downstream of the apparatus 34 (see , FIG. 7).
In this way, the die 58 may be positioned to flow the stripe 57 of plasticized material on the barrier 13 20 prior to the edge 60 resuming its normal path of travel.
This avoids requiring the die 58 to be positioned vertically below the upper portion of the moisture barrier 13. Also, the die 58 is positioned so as to be spaced slightly above the peaks of the corrugations of the inner portion of the moisture barrier 13 along the seam. The positioning of the die 58 apparently causes the material to be moved out of the die onto the portion of the outwardly facing surface of the inner portion of the moisture barrier 13 which forms the seam.
The adhesive copolymer which is applied by the 30 extruder 56 into the seam 20 is accomplished to provide the stripe 57 as is shown in FIG. 8A with the stripe being j, ; :, ~ , , . . :. : ; : -:~ ~ , : , . ., . :. . . . .
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slightly less ill width than the seam width itself. For example, a minimum acceptable seam width is approximately 0.25 inch with the seam 20 generally being 0.375 -to 0.5 inch in width. The width of ~he extruded stripe 57 is generally 0.25 incll ancl has a thickness of approximately 0.10 inch.
It will be recalled that at the seam 20, at least those longitudinal portions of the metallic strip 1~ which face each other at -the seam have been precoated with the adhesive copolymer material. The stripe 57 of adhesive material is extruded longitudinally generally centered along the width of the seam (see FIG. 8A) so that when the seam is closed, the stripe will engage with the adhesive on the opposing faces of the precoated tape 14. In this way, when the overlapping portions are pressed together, the adhesive material of the stripe 57 tends to fill the portions between ;
the peaks and the valleys of the corrugations.
The composition of the material introduced by the ;
extruder 56 may be the same as that which had been precoated ~ ~.
on the tape 14. Specifically, the stripe 57 may be a polyethylene acrylic acid copolymer adhesive available in pellet form ~rom the Dow Chemical Company under the designation PZ449.
While the adhesive copolymer is generally the same material as that which is used to precoat the aluminum tape ~ 14, it is not without the ~ounds of this invention to precoat - the inwardly facing surface 15 o~ the tape 14 with a stripe ; of an adhesive copolymer having a higher melt index and acry~
lic acid content, for example, than on the outwardly facing surface. See, for example, U.S. Patent 3,703,605. The adhe-sive copolymer which is injected into the seam may be either the composition which has been precoated on the inwardly or on the outwardly facing surface.

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~ ubsecl~ently, the enclosed cable core 11 is ad~anced between a pair of cooperating, coacting rollers 61 and 62. The rollers 61 and 62 each have a curvature essen-tially equal to that of the enclosed cable core 11. The roller 61 is comprised on three segments with a middle seg-Me~nt 6~ beincJ an aluminum disc.
The rollers 61 and 62, which are opposed to each other, coact in applying forces to the enclosed core 11 in order to maintain the core in a circular configuration and to press together the overlapped portions of the moisture barrier 13 in order to obtain a reliably sealed seam 20.
The downstream end (see FIG. 4) of the mandrel 53 interposed between the core 11 and the moisture barrier 13, extends between the coacting rollers 61 and 62. E~ence, the mandrel 53 acts as an anvil for the forces applied by the rollers 61 and 62 to the enclosed cable core, thereby preventing damage thereto.
As the rollers 61 and 62 coact and apply compres-sion forces to the moisture barrier 13, the opposing faces of the corrugations tend to become contiguous. For those misregistered corrugations, the stripe 57 supplies the adhe~
sive connection between the adhesive material on the faces thereof and which would otherwise be spaced apart along some portions of the overlap, thereby presenting undesirably a path for moisture. A nozzle 65 (see FIG. 4) directs chilled air into engagement with the disc 64 to prevent adhesive from accumulating thereon.
~` The use of the above-described technique provides a ~; surprisingly uniformly sealed seam 20. The application of the forces to the seam 20 apparently causes the stripe 57 to become flattened and in engagement with the ~djacent heated surfaces `i - 14 -,,- ~' :

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~rminy the seam Any voids are filled by the supple~ental adhesive Elowing from the stripe 57.
Another problem relates to the amount of heat necessary to insure a seal at the overlapped seam 20. When the aluminum tape 14 is fully coated on its outer side with adhcsive co~olymer, that copolymer may act as an insulating barrier to the transfer of heat from the polyethylene jacket to the aluminum. In order to transfer the necessary heat through the insulating barrier in order to seal the seam when using conventionally the double-side-coated tape, certain precautions may have to be taken to avoid degrading the jacketing material.
It should be observed that although the tape 14 is precoated with an adhesive material r merely wrapping the moisture barrier 13 about the core 11 does not cause a sealing of the seam 20. The bonding temperature of the adhesive material to the metal tape 14 is such that the bonding occurs by the application of external heat or ~ during the extrusion of the jacket 21 thereover.
; 20 By practicing the methods of this invention, the hereinbefore-described problem is avoided. The sealing of the seam i= achieved prior to the jacketing operation. As a result, the temperature of the jacket extrudate need only be as high as required to jacket and not that required for the dual function of sealing the seam.
Examples In one example, a 600 pair, 20 gauge conductor - cable core approximately 2.55 inches in diameter was ` enclosed with a moisture barrier 13 which included a four mil thick aluminum tape having each major face thereof precoated with a two mil thick covering of adhesive copolymer. The . ` ~' . ~, '.' , . ` ' ` ' . .. . ` ~ , ~"' ` ` .- '. , ` ' ~ ' ~, ' ` ' ' '' ~ ~

~)5~03~3 core was advanced at a line speed of approximately 50 feet per minute through the belt former 33 and past the device 51 to open the overlapped seam. A stripe of adhesive copolymer was extrusion-introd~lced into the seam being subjected to air heated to a temperature of 1000F. The pressure rollers 61 an~ 62 applied Eorces to the barrier 13 to seal the seam.
In another example, a 27 pair, 22 gauge expanded `~
insulation cover conductor core having a diameter of au~roximately 0.82 inch was advanced at a line speed of ; 10 140 feet per minute. A moisture barrier of the same con-struction described in the foregoing example was wrapped about the core to form an overlapped seam which was sealed by the introduction of the stripe 57 of adhesive copolymer thereinto with the subsequent application of closing forces. ` `
Alternative Embodiments In the preferred embodiment described hereinbefore, the tape 14 is precoated with adhesive material along at least the edge portions of the inwardly and outwardly facing ~
major surfaces which form the overlapped seam. Also, as is ;
shown in FIGS. 1 and 8A, the coatings may extend across the ` entire transverse widths of those faces or as is not shown, ` may be restricted to the portions of the faces which form the seam.
It should be realized that the principles of this `~
invention may also be applied to seal the seam of a moisture barrier which includes a tape 1~ having at least a longitu-dinal edge portion which forms the seam precoated on only ;~
` one major face. The precoating may be on the outwardly `
,~ facing surface 16 as shown in FIG. 8C or may be on the inwardly facing surface 15 as shown in FIG. 8B.
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, 'L~he apparatus 30 may also include facilities for applying additional closing forces to the seam 20 subsequent to the passage through the chilling station 35 where the enclosecl core is subjected to an environmen~ having a temperature generally below 32F. As can be seen in FIG. 4, a second pair of coacting rollers 66 and 67 are positioned downstream of the chilling station 3S.
The roller 66 is formed with a larger radius of curvature than that of the enclosed core 11 to insure engagement thereof with the seam 20. The face of the roller 67, similar to the rollers 61 and 62, has a radius of curva-ture essentially equivalent to that of the enclosed core 11.
~ hile the use of the rollers 66 and 67 is optional, they offer additional assurance that the seam 20 is closed consistently along the length of the cable 10.
` In the preferred embodiment described hereinbefore, the device 54 directs heated air into engagement with the ~;~
seam 20. While this is preferred to cause a more uniform distribution of the extruded adhesive material, it may not be required in all cases. Its use depends, for example, on the type of adhesive material used and the quality tolerances desired for the finished product. Similarly, the use of the chilling facilities 35 may also be optional in specific ~ ~!
applications.
It is to be understood that the above-described arrangements are simply illustrative of the principles of the invention. Other arrangements may be devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof. ~ ~-,.~

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Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of manufacturing a cable with a moisture barrier having a sealed overlapped seam, which includes the steps of:
advancing a cable core along a path;
applying a metallic strip around the core with longitudinal edge portions of the strip being adjacent each other, the formed strip having outwardly and inwardly facing major surfaces, the inwardly facing surface facing the core, at least one of the major facing surfaces having an adhesive copolymer material precoated along a longitudinal edge portion thereof which is to form an overlapped seam;
flowing an adhesive copolymer material into engage-ment with at least one of the adjacent longitudinal edge portions of the major facing surfaces of the strip which is to form the overlapped seam; and causing relative movement of the longitudinal edge portions to form the overlapped seam with the flowed and pre coated adhesive copolymer materials bonding the overlapping portions to seal the seam.

2. The method of claim 1, wherein the applying of the metallic strip is accomplished to overlap the longitudinal edge portions and which also includes:
causing relative movement of the overlapped edge portions to space apart the overlapped edge portions; and the adhesive material is flowed into engagement with at least one of the spaced apart longitudinal edge portions of the strip which formed the seam and the relative movement subsequent to the flowing of the adhesive material reforms the longitudinal edge portions into an overlapped seam.

3. The method of claim 2, which also includes preheating the overlapped and spaced-apart edge portions.

4. The method of claim 2, wherein the adhesive intro-duced between overlapping spaced apart edge portions is extruded as a stripe therebetween.

5. The method of claim 2, wherein the causing relative movement of the overlapped edge portions to close the seam includes applying forces to the overlapped portions of the strip to laminate the overlapping portions with the flowed adhesive therebetween.

6. The method of claim 5, which also includes providing support for the overlapping edge portions during the application of forces thereto to avoid damage to the core and to the strip.

7. A method of manufacturing a cable, which includes the steps of:
advancing a cable core along a path;
applying a metallic strip at least partially precoated with an essentially non-metallic copolymer sealing material around the core with at least one overlapped seam, the strip, having inwardly and outwardly facing major surfaces, the inwardly facing surface facing the core, with the sealing material positioned at least between the adjacent, mating portions of the major surfaces of the metallic strip which face each other and form the overlapped seam, the sealing material being characterized by being capable of maintaining a definite form at ambient temperature and being capable of developing an adhesive bond with the metallic strip at a pre-determined temperature above ambient temperature;
spacing apart the overlapped edge portions;
extruding an essentially non-metallic copolymer sealing material into engagement with at least one of the portions of the mating surfaces which face each other and form the seam, the extruded sealing material capable of developing an adhesive bond at a predetermined temperature above ambient with the precoated adhesive on the adjacent mating portions of the strip which face each other;
maintaining a proper positional relationship between the adjacent mating portions of the major surfaces of the metallic strip which face each other at the overlapped seam to assure that the extruded sealing material contacts at least some parts of the mating portions of the mating surfaces while the extruded material is at the elevated temperature; and applying forces to the strip to reform the overlapped seam with the extruded and precoated adhesive materials sealing the seam.

8. The method of claim 7, which also includes applying heat to the strip having the overlapped seam during the intro-duction of the sealing material and providing support for the strip during the reforming the seam thereof to prevent damage to the core and to the strip.

9. An apparatus for manufacturing a cable with a moisture barrier having a sealed overlapped seam, which includes:
means for advancing a cable core along a path;
means for applying a metallic strip around the core with longitudinal edge portions of the strip being adjacent each other, the formed strip having outwardly and inwardly facing major surfaces, the inwardly facing surface facing the core, at least one of the major facing surfaces having an adhesive copolymer material precoated along a longitudinal edge portion thereof which is to form an overlapped seam;
means for flowing an adhesive copolymer material into engagement with at least one of the adjacent longitudinal edge portions of the major facing surfaces of the strip which is to form tile overlapped seam; and means for causing relative movement of the longitudinal edge portions to form the overlapped seam with the flowed and precoated adhesive copolymer materials bonding the overlapping portions to seal the seam.

10. The apparatus of claim 9, wherein the applying means forms the strip around the core with a longitudinally extending overlapped seam and which also includes:
means for spacing apart the overlapping longitudinal edge portions; and the flowing means flows the adhesive material into engagement with at least one of the spaced apart longitudinal edge portions which formed the overlapped seam and the means for causing relative movement reforms the longitudinal edge portions into an overlapped seam.

11. The apparatus of claim 10, which also includes means for preheating the overlapped and spaced-apart edge portions.

12. The apparatus of claim 10, wherein the means for ??lowing the adhesive material is an extruder and the extruded material is in the form of a stripe.

13. The apparatus of claim 10, wherein the means for causing relative movement of the overlapped edge portions to close the seam includes means for applying forces to the overlapped portions of the strip to laminate the overlapping portions with the flowed adhesive therebetween.

14. The apparatus of claim 13, which also includes means for providing support for the overlapping edge portions during the application of forces thereto to avoid damage to the core and to the strip.