US2284370A - Cable bushing - Google Patents

Description

x May 26, 1942. CARLSQN 2,284,370

' CABLEIBUSHI'NG Original Filed Aug. 25, 1958 Fig.2.

Inventor: George Carlson,

yy 63 bg His Attorney.

r Patented May 26, 1-942 STATES PA E T-lorries 2,284,370 7 CABLE BUSHING George Carlson, Bridgeport, Conn, assignor to General ElectricCompany, a. corporation of New York Original application August 23, 1938,'Serial No.

226,265. Divided and this application February'l, 1941, Serial No. 377,043 v 2 Claims. (o1. 174-83) This inventionjrelates toa bushing for armored cables of the typeemploying a paperwrap in combination with a spiral metallic armor. This application is a division of my copending application Serial No. 226,265; filed'August 23, 1938 for Armored cable construction, now Patent No. 2,246,124; dated 'June 17; 1941, and assigned to the same assignee as the instant app ca im, A," Q

' It is an object of the invention to provide .an improved form of bushing which maybe easily inserted beneath the armor of the cable to protect the underlying conductors and which is so" constructed and arranged as to furnish an addi tional insulating medium between the conductors. V v In the accompanying drawing Fig. 1 is a View of the bushing in assembled position on an ;ar--

mored cable; Fig. 2 is a sectional view through such a cable employing two-conductors showing the manner of applying the insulating paper wrap; Fig. 3 is a sectional view/{through a modification of the cable employing three conductors; Fig. 4 is a sectionalview through another modification of the cable'employing four 'conductors; Fig. 5 is a'perspective'view' of theim-f proved form of bushing, and Fig. 6 is a'diagrammatic view of the twisted conductors'and paper wrap of the cable.

' Referring to the drawing the numeral I 0 refers to the improved form of armored cable shown most clearly by Fig. 1, the cable forming conductors. Inasmuch as the strip of paper [4' is .fed into the twisting machine longitudinally and the'conductors are twisted about the paper wrap, it will be apparent that the paper'wrap constitutes in effect a longitudinal wrap running lengthwise of I the cable and having a length equal to the length of the cable. It will be seen that with the improved construction just described a considerable saving in paper is effected over those constructions in which the paper is wrapped spirally about the twisted conductors due to the fact that a single strip of paper is disposed'longitudinally of the cable ratherthan a plurality of spiral wraps. The strip 14 is cut of suflicient width to encircle completely the individual conductors when in the final twisted form. I

Immediately after twisting together of the I conductors and paper wrap the assembly is rethe subject matter of the aforementioned 'co-' pending application Serial No. 226,265. In the form of the invention illustrated by Figs. land 2 the cable employs two insulated conductors having conducting wires H, each being insulated with a rubber compound 12 and an'overall saturated braid l3. In the manufacturebfthe'cable the individual insulated .condu'ctors'are run through a twisting machine, together with a longitudinal strip of waxed paper 14, commonly known to the trade as kraft paper. Upon entering the twisting'mac'hine' the individual conductors are twisted together about the longitudinal paper as an .axis so that the paper is wrapped about the individual conductors in an S-form, as 1 7 shown by Fig. 2; Inthis form a central portion of the paper wrap remains placed between each" of the insulated conductors, as shownat l 5, while the edges [6 of the paper wrap encirclethe entire periphery of the insulated conductors and completely cover them. As shown diagrammati-' cally by Fig. 6, the edges of the S-shaped paper wrap appear twisted as they cover the twisted moved from the twisting machine and fed into an armoring machine which applies an inter-.

locked spiral metallic armor l"! upon' the assembly in overlapping convolutions such asv shown at I8. Due to-the fact that the longitudinal wrap l4 closely grips the periphery of each of the insulated conductors a twisted assembly of conductors is formed having a minimum uniform diameter because only a' single layer of the paper. l4 surrounds the insulation on each of the conductors. This makes it possible for the armoring machine to applyan armor of minimum diameter evenly over the entire length of cable, without variations; in the tightness of arinor on the conductor assembly. At the same 7 time the edges of the paper wrap encircling the conductors adequately protect them from damage during the ar'moring operation. Inasmuch as the diameter of the 'armorl'is reduced to a minimum by the reduced overall diameter of the twisted conductors and paper wrap a substantial saving is effected in the quantity of metallic armor used. I V

It will be apparent from an examination of Fig. 2 that the layer of paper I4 is disposed at all times. between the individual. conductors. Should the conductors inadvertently become crushed together during the armoring operations, thereby damaging the insulation on the individual conductors, the layer of paper will provide an additional insulating medium between the conductors. capable of withstanding approximately GQO volts. It has been found that the provision of this additional insulating means between the conductors reduces by a substantial amount the number of rejects to be had in the V el'thegrnodification Fig 4 shown having four conductors --22,;-213,:- 2 4 and'25.

1 lengths 1 commie I g g H ,7 oficables employedj'withvoltages of 110 to 600 re testedj by placing a; potentialpf 1500' volts and-betw en ach ndu' 1 i stantiallyvcylindrioal and'p'rovided' with a $10 21 a'pei wrapeons the 3 oondllctqrs Y 1 cant I inipyiindribalj for g By' using thes shaped wrap it I manufacti r cablemwhich"; W111-W1 V bending iwl'thent injury to ulating and protective" layer of paper nsulated conductors themselyesa easil stripped by pullin tionsiof armor'slide easily overt-theplain longi nd inaily" dispose This To ns true-v me in installing soj ags implermatter er the I spiral metallici armor that it is" possible to secure a an improved form of ai mored cableihavinguthe dy tages'abovedescribed; These'a'dva'ntages v r better electric 1' eharacteifistics of the t of maniif actnre; v a I 'ng of time'in the use, of the cable'by skilledlelectricians. v

a 'onnec on with a two'qenductor c aple it Whatthe cqnstruction mayb h I employing a plural uall vas'welle l aper st-rin so thatfth S.-'shaped f 0rmation bout the tviiojconductoi's I 9 and 2fl togetherandaibbHt the singIe Iemainin conductor" 21!. Cables havingthree"conductors5= 1 a frequently have one of the condlictors grouncled V r or at a 'ne itral potential. suchsituatigns the longitudinal papex stripis disposed; between the conductorspf'high'potential toIprovideadditionalinsulation; for example, inthe construction of new: the conductors- 19 0122 ma co hehi "damagin the insulation on he indlvl 'u c ahleg'whlch 1n the-ease I V g ductors, an; improved 7 form of bushing -han'd an mse ted;

ongitudinally 'ofthe cable because the coli'irolilg V them fromeach other icabl e quickly f nstruction has been-described V 7 potential e xist "n cond ctor and the (Sable is.

I the end f the armorm'smn gzs. I i and. is slightlyit pere'd e is g s V e'rthe insulated conductqrs' wh may p ssfthro r lt f equently happens that; careiess iwofldn inise'vering the spiral armor prepaiatory'tois 1p ping a length of the; cable, willthroug hithe layers of insulati congiuctorsi Whenjthishappen t 7 :steel sliverso fi nb's incident armorf will' be surrounding the; 'Iidifidlial conductors, ahd t causea shorteircuit to develop between the 1n 'div'idual conduotors ofthe armored cable;

' those cases" where the insulation on the individ a1 conductorsfhasbeen damage of the metalliciarmpr the d Vents anyipossibility of a short bircuit' roecurring tweenfthe indiwdual eon in efiect a complementary compartments 4 f or I the reception of the insulated conductors asgsaiq member is disposed gbetw'een said conductorsand said armor, js'aid member having a bead; extendinganound he periphe 'th ere'of for engagin-g t .Isaid cable;

armor comprising an a 'etricalfldividingwall separatingi said nto two compartments each compartment -bei adapted to receive on'e of theilis'illatedcbndll t ors asi'sai d. membef is slipbeqover the'condu ors V to a" pgsition beneath. argsevered I end; ofj't .sai me'mbe-r having a beadenga ng' and vjer "lyin the-severed enni'of'theaimor.

, GEGRGE CAR o The bushing may m as sheet hekcompai'tmerits 29 y. he severing I? n; plate pre-V

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