US2939907A - Coaxial cable wound on a drum and process of winding - Google Patents

Description

June 7, 1960 COAXIAL CABLE WOUND ON A DRUM AND PROCESS w. G. HILL 2,939,907

OF WINDING Original Filed Feb. 19, 1951 FIG.

Inventor W/LUAM (i. HILL U i e Sm ace COAXIAL CABLE WOUND ON A DRUM AN D PROCESS OF WINDING Claims. cl. 174-113 This invention relates to coaxial conductor cables and.

more particularly to such cables in which the outer conductor is formed by the longitudinal folding of a metal tape into a tube with the edges of the tape abuttedto, form a seam.

This application is acontinuation of application Ser. No. 211,621, filed February 19, 1951, and abandoned March 29, 1956. v H I In the manufacture of such cables it is the usual prac tice to form a coaxial conductorby passing a conductor having spaced insulating means thereon, horizontally into and through a die, into and through whichis also passed a'metal tape which is folded longitudinally .into fa tt'lbe fitting over the insulating'menlbers. "The metaltapeis passed intothe die as a fiat-horizontal strip and after magnetic screening tapes and/ or binding means have been applied the finished coaxial conductor is taken up on a drum rotating about a horizontal axis, with possibly a take up capstan interposed. The result is that all points of the seam in the outer conductor lie on radial lines of the take up drum and capstan, the seam facing towards from the axis. In all subsequent operations in making up the cable from a coaxial conductor or conductors and other conductors, the seam remains in the same relation to the axes of the various capstans and drums and is thus in the position in which maximum stretching and contracting forces are exerted upon the outer conductor tube whenever the coaxial core is flexed on or off the capstan or drum. Similar forces are exerted along a line of the outer conductor tube which lies nearest to the surface, of the capstan or drum. The seam is the weakest part of the tube and thus the usual process of manufacture suffers from disadvantages.

It has also been found that the outer tubular conductor was liable to kink during the subsequent manufacturing operation, involving bending of the coaxial pair, with consequent deterioration of both the uniformity of characteristic impedance and in the dielectric strength.

These disadvantages are removed by the present invention.

In accordance with an aspect of the invention, the tubular outer conductor of a coaxial cable is formed in such way that the abutting edges of the tubular outer conductor always lie on that diameter of the tubular conductor which is parallel to the axis of the take up drum so that the seam is in a neutral plane where neither compression nor tension is applied to the tube.

The seam remains in the same position relative to the axis about which the conductor pair is bent or flexed throughout all the processes up to the finished cable, which may contain several coaxial conductor pairs, wound on a drum ready for installation. Consequently throughout all these processes a coaxial conductor pair according to the invention retains the seam of the outer conductor in the neutral plane.

Experience has confirmed that the side-seam tube is 2 less liable to distortion during the subsequent operations than the. tubes produced by the known processes. The adoption of the process accordingto this invention has led to the production of coaxial conductor pairs which will withstand flexing to a greater extent than the previously constructed tubes. Tests have shown that the same amount of flexing which reduces the breakdown voltage of a top-seam tube by two thirds and almost completely disrupts the tube, causes only slight kinking of the sideseam tube and no appreciable diminution of breakdown voltage.

According to a feature of the present invention, there is provided a process of manufacturing a coaxial conductor cable which comprises the step of folding a metal tape longitudinally into a tube with the edges of the tape abutted together to form a seam, characterized in that the folding is performed in such relation to the take-up of the folded tube that the said seam is positioned substantially on the neutral axis of the tube as it is wound on the take'=up capstan or drum.

According to another feature of the invention there is provided1 a process of manufacturing a coaxial conductor electric cable which comprises passing a conductor having spaced insulating members thereon and a metal tape into and through a die to fold the said tape longitudinally into .a tube fitting over said spacers with and taking up the coaxial conductors on a take-up drum rotating about an axis substantially perpendicular to the planein which the-tape passes into said die.

The invention will be better understood from the following description of one embodiment thereof taken in conjunction with the accompanying drawings in which:

Fig. 1 is an elevation and Fig. 2 a plan of the relevant part of a machine for manufacturing a coaxial core;

Fig. 3 is a cross-section of the coaxial core on the line --a of Fig. 1;

Fig. 4 is a cross section of a cable comprising four coaxial cores.

Referring to the drawings, a central conductor 1 having thereon spaced insulating discs 2 of polythene is traversed from right to left as seen in the drawings. A metal tape 3 is drawn from a pad 4, over a guide roller 5 and passes through a tool 6 in which the edges of the tape are formed with corrugations in the manner described in British Patent No. 668,950, filed February 21, 1950, published July 16, 1952. The tape 3 is then drawn over a guide roller 7 and turned so that its plane is rotated through into a plane parallel to the plane of the paper. The conductor 1 with the discs 2 thereon and the tape 3 are then passed through a forming tool 8 which folds the tape 3 in known manner to form the outer conductor in the form of a tube 9 with the seam 10 formed by the abutting edges of the tape at the side of the core as seen in elevation in Fig. 1. The tube 9 is then traversed past a wrapping head (not shown) by which helical magnetic screening tapes are applied thereto and is then wound on a take up drum 11 rotated about an axis 12 perpendicular to the plane of Fig. 1 by means not shown. Fig. 3 shows a cross section of the coaxial conductor pair consisting of the central conductor '1 and the outer tube 9 and it will be seen that the seam 10 lies along the neutral axis of the tube 9 with respect to any flexing as it is wound or unwound from the drum 11.

The process above described possesses the further advantage that dross or dirt on the tape 3 will tend to fall away from the tape as the latter is turned into a vertical plane. If desired an air blast may be positioned to blow on the tape just before it enters the tool 8.

In any subsequent winding of the coaxial core around a drum during the processes of making up a cable from the coaxial core the seam 10 will substantially maintain Patented June 7, 1960 its relation with respect to the axis about which the core is flexed, since such cores are usually laid up by being drawn off floating bobbins and the seam accordingly remains substantially parallelto the central conductor and in. a' constant relative position inallithe. cores. Fig. 4 shows. a cross section of. a finished. cable. in which; four coaxial cores 9 are. laid up.together. andwi'th additional:

conductor groups 13 within. an outer leadslieatlitl lland it will be seen that all the. seams preserve thesame re.-.-

lationwith the reel- 15 on.which the,:cable.is wound...

. While the principles of the invention have. been described above. in, connection. with. specific embodiments, and particular. modificationsthereof, it is to .-be. clearly. understood that this description is made only by way of example. and. not: as. a limitation on. the scopeofi the invention.

I claimz. 1.. Anzelectric conductor cable woundonatdrum, com.- prising a plurality of coaxial conductors, the outeri con'-- ductor of each of said coaxial conductors being; in the-- form of. a longitudinally folded tape'with edgeslabuttingi; to. form asearn', the'seam of each ofasaidouter;conductors. being positioned in the neutral axis oftheouter conductor:

asitliesonthe drum. 2. The cable. according tocIaim. 1i and rounding. said group: ofi'conductorsfon maintaining said relationship; whereby the: conductors are held-firmly within said jacket withrtheirrneutral axes fixediin position; 3-. Inxthe processof:manufacturingacoaxial conductor cable: which comprisesfolding ametaltape longitudinally into a tube withthe'sedges of'the. tape abutting'to form a.

further. prising means-.for gro'upingsaidplurality. ofconductors'zin a" predetermined relationship, andjacketing: means: sur

abutting together to. form a. seam: and taking up.- the:-

coaxi'allcondilctors on-altal'ce up drum, the. step of'orienting andmaintaining said tube so. that thegseam is. positioned substantially on the neutral axis of the tube as it. is'wound on-thedrum: I

5: A process of winding'arr electric cable on. a. drum, the cable comprising a plurality of coaxial conductors rigidly pnsitioned within a cable; jacket, and the-outer conductor of each coaxial conductor being in the form of a longitudinally" folded tape with edges abutting to form a seam, the process comprising positioning the coaxial conductors so that the seams thereof are oriented in' the same direction; andwinding the conductors on said. drum" so that" the seams of the respective conductors lie on the'neutral' axesthereofi References-Cited in the file of this patent UNITED STATES PATENTS 1,975,045 Kossowslrituut Sept. 25 1934 1 2.1215942. Barrett. June::28,l938? OIH-ER REFERENCES Iolinsons Materials oi Construction) Sthledition, re

written-by. MLQQ Whithey; and. James Aston, John'Wiley" and-;Sons, .Inc.,.19 18. BirgeaM-Zfirelied upom

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