US3733225A

US3733225A - Method of applying a waterproofing jelly-like compound to an elongated strand and forming a sheath about the strand

Info

Publication number: US3733225A
Application number: US00069837A
Authority: US
Inventors: L Moody
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1970-09-04
Filing date: 1970-09-04
Publication date: 1973-05-15
Anticipated expiration: 1990-05-15
Also published as: CA947484A; CH533889A; ES395250A1; GB1364856A; SE382713B; FR2105272A1; AU3286271A; DE2143920A1; BE772161A; JPS475981A; FR2105272B1

Abstract

AN ELONGATED STRAND, SUCH AS CABLE CORE ASSEMBLY, IS ADVANCED LONGITUDINALLY THROUGH A FORMING TUBE OF APPARATUS FOR FORMING A SHEATH ABOUT TO STRAND WITH EDGE PORTIONS OF THE SHEATH OVERLAPPED TO FORM A LONGITUDINALLY EXTENDING SEAM. AS THE STRAND PASSES THROUGH THE FORMING TUBE A WATERPROOFING JELLY-LIKE COMPOUND IS INTRODUCED INTO THE FORMING TUBE AT A POINT SPACED FROM ITS ENTRANCE END AND UNDER RELATIVELY HIGH PRESSURE SUCH THAT THE COMPOUND COMPLETELY FILLS A CIRCUMFERENTIALLY EXTENDING PORTION OF THE SPACE BETWEEN THE STRAND AND THE FORMING TUBE TO PRODUCE A WATERPROOF LAYER OF THE COMPOUND WHICH ENCIRCLES THE STRAND AND WHICH PROVIDES A SMOOTH CYLINDRICAL SUPPORT SURFACE ABOUT WHICH THE SHEATH CAN BE FORMED IN TIGHT-FITTING RELATIONSHIP AND WITH A TIGHT SEAM AS THE STRAND EXITS FROM THE FORMING TUBE. THE PRESSURE AT WHICH THE WATERPROOFING JELLY-LIKE COMPOUND IS INTRODUCED INTO THE FOMING TUBE ALSO IN SUCH THAT THE WATERPROOFING COMPOUND FLOWS BETWEEN THE OVERLAPPED EDGE PORTIONS OF THE SHEATH TO SEAL AND WATERPROOF THE SEAM FORMED BY THE EDGE PORTIONS.

Description

L. D. MOODY 3,733,225

*LIKE CUMPOUND TO AN A SHEATH ABOUT THE STRAND May l5, 1973 STRAND ANI) FOHMNG 2 Sheets-Sheet 1 l-ilud Sept. l, 1970 dmfum@ m. mw

lNVENTOR L D. MOODY ,bwm

ATTORNEY MOODY METHOD Ol" APILYING A WATEHPnOOFING JELLY-LIKE COMPOUND TO AN 2 Sheets-Sheet 2 May 15, 1973 {,'ILONGATED STRAND AND FORM'LNG A SHEATH ABOUT THE STRAND Fi 10d Sept. 4 1970 Patented May 15., 1973 METHOD OF APPLYING A WATERPROOFING .IELLY-LIKE COMPOUND TO AN ELONGATED STRAND AND FORMING A SHEATH ABOUT IHE STRAND Larry D. Moody, Ralston, Nebr., assignor to Western Electric Company, Incorporated, New York, N.Y. Filed Sept. 4, 1970, Ser. No. 69,837

' Int. Cl. H01b 13/16, 13/26 U.S. Cl. 156-48 ABSTRACT F THE DISCLOSURE An elongated strand, such as cable core assembly, is advanced longitudinally through a forming tube of apparatus for forming a sheath about the strand with edge portions of the sheath overlapped to form a longitudinally extending seam. As the strand passes through the forming tube a waterproofing jelly-like compound is introduced into the forming tube at a point spaced from its entrance end and under relatively high pressure such that the compound completely fills a circumferentially extending portion of the space between the strand and the forming tube to produce a waterproof layer of the compound which encircles the strand and which provides a smooth cylindrical support surface about which the sheath can 2 Claims be formed in tight-fitting relationship and with a tightY seam as the strand exits from the forming tube. The pressure at which the waterproofing jelly-like compound is introduced into the forming tube also is such that the waterproofing compound flows between the overlapped edge portions of the sheath to seal and waterproof the seam formed by the edge portions.

BACKGROUND OF THE INVENTION l (1) Field of the invention This invention relates to a method of applying a waterproofing jelly-like compound to an elongated strand and then forming a sheath about the strand, and more particularly to a method of applying a waterproofing jellylike compound to a cable core assembly having an irregular peripheral contour and then enclosing the cable core assembly in a tight-fitting metal sheath.

(2) Description of the prior art The manufacture of a recently developed type of waterproof communication cable, having a cable core made up of a plurality of electrical conductor wires and enclosed in suitable protective sheathing, involves the filling of the air voids in the cable core and between the various protective layers of sheathing with a waterproofing jellylike compound. In this type of cable, if the sheathing should become punctured or otherwise damaged after the cable has been installed in the field, the entrance of water into the cable is limited to the area in the vicinity of the damage since the waterproofing compound precludes the water from owing along the length of the cable internally thereof. Accordingly, the adverse effects of the water from the standpoint of the disruption of communication facilities is substantially reduced and repair of the cable is greatly facilitated.

In the manufacture of this waterproof cable, a plurality of electrical conducto-r wires are stranded into a cable core, during which the air voids between the conductor wires are filled with the waterproofing jelly-like compound in a series of liooding operations. Subsequently, as the filled cable core is being advanced longitudinally, a protective tape or core wrap is formed about the cable core and bound in place. A coating of the waterproofing jelly-like compound then is applied to the bound core wrap, and the cable core and the core wrap are enclosed in a corrugated aluminum sheath which provides lightning protection for the finished cable when it is installed in the field. The aluminum sheath then is bound in place and fiooded with the waterproofing jelly-like compound, and finally enclosed in an outer plastic jacket.

Heretofore, after the core wrap had been applied to the advancing cable core and had been bound in place, the cable core and the bound core wrap passed through a fiooding tank containing the waterproofing compound, with excess material being wiped from the core wrap by a suitable wiping die as it exited from the tank. The fiooded cable core and core wrap then traveled through an elongated forming tube of apparatus for forming the corrugated aluminum sheath about the fiooded core wrap.

This system has proven undesirable, however, because as the flooded cable core and core wrap are advanced longitudinally, being flexible in nature, they tend to sag by their own weight and also are subject to a certain amount of lateral oscillation. Thus, as they enter the forming tube, the forming tube tends to scrape the waterproofing compound therefrom. This condition becomes further aggravated as they continue on through the forming tube. Further, since the cable core, even when enclosed in the flooded core wrap, has an irregular peripheral contour, it is difficult to form the aluminum sheath in tight fitting relationship about the cable core and the core Wrap and with a tight seam. As a result the finished cable frequently does not contain a sufficient amount of waterproofing compound to make it completely mpervious to water and is not of the desired waterproof construction. In addition, the scraping of the compound from the core wrap by the forming tube creates a housekeeping problem in the vicinity of the sheath forming apparatus, particularly adjacent the entrance to the forming tube.

SUMMARY OF THE INVENTION An object of this invention is to provide a new and improved method of applying a waterproofing jelly-like compound to an elongated strand and then forming a sheath about the strand.

A further object of this invention is to provide a new and improved method of applying a waterproofing compound to an elongated cable core assembly having an irregular peripheral contour and then forming a tight-fitting sheath having a tight waterproof seam about the strand.

Another object of this invention is to provide a new and improved method of providing a waterproof cable construction.

In accordance with the invention, in a method in which an elongated strand is advanced longitudinally through an elongated tubular passageway and in which a sheath is formed about the strand as it exits from the passageway, a waterproofing jelly-like compound is introduced into the passageway at a point spaced from its entrance end and under relatively high pressure such that the compound completely fills a circumferentially extending portion of the space between the strand and the passageway. The compound thus produces a waterproof layer of the compound which encircles the strand and which provides a smooth support surface about which the sheath can be formed in tight-fitting relationship as the strand exits from the passageway.

More specifically, in a method in which a cable core assembly having an irregular peripheral contour is advanced longitudinally through an elongated forming tube, and in which a sheath is formed about the forming tube and edge portions of the sheath are overlapped to form a longitudinally extending seam so as to envelope the cable core assembly as it exits from the forming tube, a waterproofing jelly-like compound is introduced into the j fj 3,733,225

forming tube at a point spaced from its entrance end and under relatively high pressure so as to produce a water' BRIEF DESCRIPTION OF THE DRAWINGS i FIG. 1 is an elevational view of apparatus for use in practicing the method of the invention;

' FIG. 2 is an enlarged cross-sectional view of the apparatus shown in FIG. 1, taken substantially along the line 2-2;

FIG. 3 is a further enlarged cross-sectional view of a portion of the apparatus shown in FIG. 1;

FIG. 4 is a transverse cross-sectional view of a communication cable which may be manufactured by the method of the invention; and

FIG. 5 is a partial cross-sectional view of a longitudinally extending section of the cable, taken along the line 5-5 in FIG. 4.

DETAILED DESCRIPTION Referring to FIGS. 4 and 5, it is seen that the illustrated embodiment of the invention relates to the manufacture of a waterproof type communication cable 11. The communication cable 11 includes a cable core assembly 12 comprising a cable core 13 in the form of a plurality of insulated electrical conductors having the air voids therebetween filled with a waterproofing jelly-like compound 14, such as a mixture of 85% petroleum jelly and 15% polyethylene. The filled cable core 13 is wrapped in an elongated tape or core wrap 16 which has overlapped edge portions and which is held in place by a helical binder ribbon 17 (FIG. 5). The thus formed cable core assembly 12 is coated with a layer 18 of the waterproofing compound and is enclosed in an elongated aluminum sheath 19 having overlapped edge portions 19a (FIG. 4) which form a longitudinally extending continuous seam 21, and having transverse corrugations (FIG. 5) which form a series of elevations 19h and depressions 19C. The aluminum sheath 19, which is held in place by a helical binder ribbon 22 (FIG. 5), also is coated with a layer 23 of the waterproofing compound and is further enclosed in an outer extruded plastic jacket 24.

Referring to FIG. 1, in accordance with this invention the uncoated cable core assembly 12 is advanced from left to right, as viewed in this ligure, through an aluminum sheath forming apparatus 26, by a suitable advancing mechanism, such as a tractor-type capstan 27. More specifically, as the cable core assembly 12 travels through a passageway defined by an elongated forming tube 28 of the sheath forming apparatus 26, the waterproofing compound is introduced into the forming tube under relatively high pressure to coat the cable core assembly with the waterproofing layer 18. In this connection, the internal diameter of the forming tube 28 need only be slightly larger than the external diameter of the cable core assembly 12 to achieve satisfactory coating results, and preferably is kept as small as possible. Subsequently, as the coated cable core assembly 12 exits from the forming tube 28, it is substantially enveloped by an aluminum tape 19T for forming the sheath 19; The coated cable core assembly 12 and the tape 19T then pass sequentially through a set of preliminary rounding and finishing rolls 29, a lapping die 31 which squeezes the tape radially inward about the coated cable core assembly and which overlaps the edge portions 19a to form the seam 21, and a final set of rounding and finishing rolls 32. The cable core assembly 12 and the formed sheath 19 then pass through apparatus, not shown, for applying the helical binder ribbon 22 about the sheath, for flooding the bound sheath to provide theY layer 23 vof waterproofing compound, and for extruding the outer plastic jacket 24 about the iiooded sheath, with the finished cable 11 finally being Wound upon a reel by a suitable take-up.

In the illustrated embodiment of the invention, the waterproofing compound is introduced into the forming tube 28 from a heated Isupply 33 by a mechanism 34 which includes a pump 36 and a regulating valve 37 which is set to maintain the pressure in the system at a preselected constant value and to by-pass excess compound back to the heated supply. The compound is fed by the pump 36 through a manually adjustable flow control valve 38 to a metering pump 39 having an output which is directly proportional to its speed and which is driven by an electric motor 41. The speed of the motor 41, and thus of the metering pump 39, is controlled so that the pressure in the forming tube 28 also is maintained at substantially the above-mentioned constant value, with the volume of the waterproofing compound delivered to the `forming tube varying as a direct function of cable line speed. This is accomplished by a motor controller 42 of any suitable type capable of comparing signals received from a pair of tachometers 43 driven by the cable advancing capstan 27 and the metering pump drive motor 41, respectively, and then providing a feedback signal to the metering pump drive motor to maintain it at a speed corresponding to the speed of the capstan. As is best shown in FIGS. 1 and 2, the waterproofing compound is introduced into the forming tube 28 at an intermediate point of the tube, and this arrangement, taken with the pumping action of the advancing cable core assembly 12, which forces the waterproofing compound toward the open exit end of the tube, precludes the waterproofing compound from traveling rearward in the tube and flowing out of its entrance end.

The volume of the waterproofing compound delivered to the forming tube 28 and the pressure of the compound in the formingtube is such that at least the portion of the tube adjacent its exit end, and preferably a substantial portion of the tube in advance of its exit end, is completely filled with the compound at all times, whereby the alu- .minum sheath .19 can be formed about the coated cable core assembly 12 in tight-fitting mating engagement therewith. In addition, the amount of the Waterproofing compound delivered to the forming tube 28 and the pressure in the tube preferably is such that, as the aluminum sheath 19 is being formed about the coated cable core assembly 12 by the lapping die 31, a small portion of the waterproofing compound flows between the overlapped edge portions 19a of the sheath to seal and waterproof the seam 21 formed thereby. In this regard, the amount of the waterproofing compound and the internal pressure created within the sheath 19 during the forming thereof must be such as to insure firm circumferential engagement of the lapping die 3:1 and the final rounding and finishing rolls 32 with the sheath as it passes therethrough, without causing outward bulging of the sheath which would interfere with the passage of the sheath and the cable core assembly 12 through subsequent processing operations. By way of illustration, utilizing a waterproofing compound of petroleum jelly and 15 polyethylene at a temperature of 250 F., favorable results have been achieved with a pressure in the forming tube 28 on the order of 50 p.s.i.

With the waterproofing compound being introduced into the forming tube 28 as above described, the waterproofing compound is forced beneath the cable core assembly 12 in the forming tube to counteract the weight thereof, whereby the cable core assembly tends to lioat in the compound. At the same time the waterproofing compound functions to dampen out any tendency for the cable core assembly 12 to oscillate laterally in the forming tube. Thus, the cable core assembly 12 travels through the forming tube 28 substantially concentric therewith, particu larly adjacent its exit end, and exits from the forming tube substantially concentric 'therewith and completely surrounded by the waterproofing compound. Accordingly, while the uncoated cable core assembly 12 has an irregular peripheral contour, since the waterproofing compound assumes a circular shape corresponding to the interior of the forming tube 28, as the coated cable core assembly 12 exits from the forming tube the waterproofing compound provides a smooth cylindrical support surface 18a (FIG. 2) about which the corrugated aluminum sheath 19 can be formed in tight-fittingrelationship and with itsV seam 21 of relatively tight-fitting construction. In this regard, it is apparent thatI asl the sheath 19' is formed about the coated cable core assembly 12 the waterproong compound will flow to accommodate itself to the corrugations in the sheath. As a net result, the portion ofthe cable 11 between the cable core assembly 12 and the aluminum sheath 19 is completely lilled with Waterproofing compound and free of air voids, and the seam 21 of the sheath is sealed with the waterproofing compound, to provide a substantially Waterproof construction.

The sheath forming apparatus 26, with the exception of the modified forming tube 28, may be of any suitable type, and in the illustrated embodiment of the invention includes a plurality of forming stations 44, one of which is shown in detail in FIG. 2, and a pair of horizontally spaced continuous forming belts 46 which pass through each forming station and about suitable sheaves 47 at entrance and exit ends of the apparatus. As the tape l19T, which initially is pulled from a supply roll (not shown) in flat sheet form by a power driven corrugating. `device 48, passes through the sheath forming apparatus 26, it is formed by the belts 46 into an arcuate shape, and ultimately into a substantially cylindrical configuration about the forming tube 28 adjacent its exit end.

As is best shown in BIG. 2, at each forming station 44 the forming tube 28 extendsthrough an upstanding vertical frame plate 49 and each forming belt 46 rides over a sheave 51 rotatably mounted adjacent one end of an.

elongated rod assembly 52 which extends radially with respect to the forming tube andwhich is adjustable longitudinally. Each rod assembly 52 also is slidably mounted between suitable guideways fixed to the frame plate 49 and includes a stud 53 which projects laterally therefrom into a camming slot in a rotatable, ring-shaped cam plate 54. In addition, a tape support roller 56 and a forming tube hold down roller 57 are mounted on respective rod assemblies 52, and forming belt return sheaves 58 are suitably mounted on the frame plate 49. As is well known to those skilled in the art, at successive ones of the forming stations 44 as shown in FIG. 2, the positions of the belt support sheaves 51 progressively change in upward and inward directions with respect to the forming tube 28, to accomplish forming of the aluminum tape 19T, as above described. Further, adjacent the left-hand or entrance end of the sheath forming apparatus 26, as viewed in FIG. 1, the forming tube 28 is resiliently mounted on a frame member of the forming apparatus by means of a vertically adjustable, ilexible hanger assembly 9, while at the forming stations 44 adjacent the righthand or exit end of the forming apparatus, the forming tube is supported by the aluminum tape 19T as shown in FIG. 2.

The rotatable, ring-shaped cam plate 54 at each of the forming stations 44 encircles the forming tube 28, the forming belts 46, and the aluminum tape 19T, as is best shown in FIG. 2, and is supported for rotation on a plurality of rollers mounted on the stations vertical frame plate 49 in spaced relationship with respect to the frame plate. The cam plate 54 has an arcuate gear rack secured thereto and engaged with a gear 61 on a horizontally disposed and longitudinally extending shaft 62, which is journalled for rotation in the vertical frame plates 49. The shaft 62 is rotatable by an adjusting crank 63 which is meshed with the gear 61 at one of the forming stations 44 so that the cam plates 54 at the forming stations can be rotated in unison to move the sheaves 5.1 and the rollers 5-6 and 57 radially outward and inward for positioning of the aluminum tape 19T in the apparatus at the beginning of a cable run.

SUMMARY In preparing for a cable run the forming tube 28 is preset vertically so that the cable core assembly 12 is as nearly concentric as possible to the forming tube. At the entrance end of the forming tube 28 this adjustment is accomplished by the vertically adjustable hanger assembly 59, while at the exit end of the forming tube this is accomplished by adjusting the rod assemblies 52 and thus the positions of the sheaves 51 and the rollers 56 and 57. The crank 63 then is operated to rotate the cam plates v54 at the forming stations 44 in unison so that the studs 53 andv their respective camming slots in the cam plates cause radially outward movement of the sheaves 51 and the rollers 56 and 57, whereby the aluminum tape 19T can be inserted in the sheath forming apparatus 26. The sheaves 51 and the rollers 56 and 57 then are moved radially inward to their operating positions by rotation of the crank 63.

During the cable run the cable core assembly 12 is advanced by the capstan 27 from left to right in FIG. 1 and through the forming tube 28', in which the coating 18 of waterproofing compound is applied to the cable core assembly. At the same time the aluminum tape 19T is formed about the forming tube 28 by the forming belts 46 so that as the coated cable core assembly 11-2 exists from the forming tube it is substantially enveloped by the tape. The coated cable core assembly 12 and the tape 19T then pass sequentially through the preliminary rounding and nishing rollers 29,r the lapping die 31 which squeezes the tape radially inward about the cable core assembly and which overlaps the edge portions 19a to form the seam 21, and the final rounding and nishing rollers 32. The now sheathed cable core assembly -12 then passes through additional processing operations for applying the helical binder ribbon 22, the layer 23- of the waterprooiing compound and the outer plastic jacket 24, to produce the nished cable 11.

lAs the cable core assembly 12 travels through the forming tube 28 the waterproofing compound is withdrawn from the heated supply 33 by the pump 36 of the mechanism 34 and is introduced into the forming tube under relatively high pressure. In this connection, the flow of the waterproofing compound and the pressure in the forming tube 28 is controlled, by means of the constant pressure bypass valve 37, the ow-control valve 3'8 and the controller 42 for the drive motor 41 of the metering pump 39, to cause at least the portion of the forming tube adjacent its exit end, and preferably a substantial portion of the tube in advance of its exit end, to be completely filled with the waterproofing compound at all times, and such that as the sheath 19 is formed about the coated cable core assembly 12 by the lapping die 31, a portion of the waterproofing compound flows between the overlapped portions 19a of the sheath to seal and waterproof the seam 21.

[With the above described arrangement the waterproofing compound in the forming tube 28 is forced beneath the cable core assembly 12 so as to counterbalance its weight, whereby the cable core assembly tends to float in the compound, and the waterproong compound also functions to dampen out any tendency for the cable core assembly to oscillate laterally. Thus, the cable core assembly 12 travels through at least the portion of the forming tube 28 adjacent its exit end substantially concentric therewith and exits from the forming tube completely surrounded by the waterproofing compound. Accordingly, while the uncoated cable core assembly 12 has an irregular peripheral contour, the Waterproofing compound assumes a circular shape corresponding to the interior of the forming tube 28 to provide the smooth cylindrical support surface 18a (FIGS.v 2 and 4) about which the corrugated sheath 19 can be formed inl tightiitting relationship, with the compound. owing toaccommodate itself to the corrugationsrin the sheath. As a net result, the portion of the cable 11 between the cable core assembly 12 and the aluminum sheath 19 is completely lled with waterproofing compound andv free of air voids and the seam 21 of the sheath is sealed to provide a substantially waterproof construction. What is claimed is:

`1.l The method of sheathing an elongated, assembly, which comprises:

introducing waterproong jelly-like compoundv into an elongated, open-ended sheath forming tube at a point spaced from its entrance end andunder relatively high pressure such that the waterproofing compound completely encircles the cable core `assembly adjacent the open exit end of the forming tube;

advancingthe cable core assembly into the openentrance end of the sheath forming tube and through the tube at a speed of such magnitude as to force the waterproong jelly-like compound toward the open exit end of the tube Without any discharge of compound from the open entrance end of the tube; and

forming a sheath about the tube so as to confine the waterproofing jelly-like compound which has been introduced into the tube, about the cable core assembly and within the sheath as the cable core assembly exits from the forming tube.

2. The method of sheathing an elongated exble cable core assembly having an irregular peripheral contour in a longitudinally extending tight-fitting sheath having corrugations which form a series of elevations and depressions therein, which comprises:

introducing waterproong jelly-like compound into an elongated, open-ended sheath forming tube at a point spaced from its entrance end and under relatively high pressure such that the waterproofing comcable core pound completely ills a lcircumferentially extending portion of the space between the irregular peripheral contour of the cable core assembly and the forming tube adjacent its open exit end, to form a waterproof layer of the compound which encircles y the cable core assembly and which provides a smooth cylindrical support surface about which the sheath .can be formed in tight-tting relationship and with arelatively tight seam as the cable core assembly exits from the forming tube;l

. vadvancing the cable `core assembly into the open en trance end of the sheathvforming tube and through the tube at a speed of such magnitude as to force the Waterproofing jelly-like compound ltoward the open A exit end of the tube without any discharge of comi pound from the open entrance end of the tube; and forming the sheath about the tube so as to conne thewaterprooing jelly-like compound which has been introduced `into the tube, about the cable core assembly and within the` sheath as the cable core Yassembly exits. from the forming tube, withV the smooth-surfaced layer of compound formed about the cable core assembly owing to accommodate itself to said elevations and depressions in the sheath.

References Cited UNITED STATES PATENTS 3,085,388 4/1963 Ansell et al. 156--51 X 2,494,050 l/1950 Loucks 156-54 3,394,400 7/1968l Lamons f 156--54 X 3,607,487 9/1971 Biskeborn et al. `156--47 3,071,809 l/ 19-63 Lerch 264174 X .3,340,112 9/1967 Davis et al. 156-47 3,601,967 8/1971 Wardley 156,48

WILLIAM A. POWELL, Primary Examiner L. T. KENDELL, Assistant Examiner U.S. Cl. X.R.