US1739012A - Telephone plug cord - Google Patents

Description

Dec. 10,1929. w. 1. MIDDLETON TELEPHONE PLUG CORD Filed July 25, 1928' lNVENTOR Wash/yin l l/Md/efon ATTO'RNEYS Patented Dec. 10, 1929 UNITED STATES PATENT OFFICE SIMPLEX WIRE AND CABLE COMPANY, TION OF MASSACHUSETTS TELEPHONE Application filed July 25,

T his invention relates to improvementsin multi-conductor cables used to connect pairs of jack plugs in the conventional telephone switchboard. These cables are commonly designated telephone plug cords. The conventional cable now used for this purpose consists of three conducting elements each made up of a number of strands of tinsel on a cotton core enclosed within a silk wind and a braided jacket, the three conducting elements together with suitable fillers being enclosed within a common outer braided jacket. This conventional cable has two serious disadvantages; it is expensive and itis .of relaf tively short useful life. Replacement of such cable is frequently necessary as often as ten or twelve-times a year on busy switchboards. In such service the saving in operating expense possible by reducing the number of such re- 2 placements exceeds any saving possible in reducing the cost-of the cable; The improved telephone plug cord of the present invention islessexpensive than the conventional type of cord and it has the important advantage of 25 having a useful life exceeding fourfold or more the usual life of the conventional type of cord. 1

Cables embodying the invention are illustrated in the accompanyi g drawings and 30 the invention will be described in detail in connection therewith. In the accompanying drawings Fig. 1 is a fragment of one form of cable embodying the invention with parts broken away and Fig. 2 is a section of the cable shown in Fig. 1, and

Fig. 3 is. fragment of. another form of cable embodying the invention with parts broken away and Fig. 4 is a section of the cable shown in Fig. 3.

Referring to Figs. 1 and 2, the cable comprises three conducting elements 5, 6 and 7 three filler elements 8, 9 and 10, a binder 11 and ajacket 12. Each of the conducting elements 5, 6 and 7 comprises a non-conducting core 13 of soft fibrous material, a,plurality of conducting wires 14, small in diameter with respect to the core 13, wound about the core in a short spiral, 8 to 10 turns per inch for example, a non-conducting winding 15 OF BOSTON, MASSACHUSETTS, A CORPORA- PLUG CORD 1928. Serial No. 295,331.

elastic vulcanized rubber compounded to afford a maximum of physical strength and re-. sistance to abrasion. I Compounds of the type used as automobile tire tread stocks are useful in this connection. 'A suitable rubber compound, for example, may consist of the following:

Parts Rubber -(smoked-sheets) 63 Zincoxide -Q 9 Carbon black a 24 Ozokerite 2 Ethylidene-aniline -1 Di-phenyl-guanidine 'Sulphur 3 This compound may be vulcanized at 270 F. for 30 minutes. The rubber jacket 12 .'for example, may be of 0.022"0.'034"- in thickness.

Thesecables arefinished to an outer diameter Referring to Figs. 3 and 4, the cable is of construction identical with that illustrated in Figs. 1 and 2 except in that a braided jacket 17 is inter osed between the outer rubber jacket and t e bound group. of conducting elements and filler elements. This interposed jacket.17 may be a 40/2 soft cotton braid, for example. This interposed braidedjacket further improves the flexibility of the complete cable. I

In each of the cables just described in detail the conducting elements and the filler ele-' ments, the latter being small with respect to the former, are s'piralled together and bound to form a strong yet flexible composite. The conducting elements and filler elements are bound together independently of the encasing rubber acket. Within this composite the construction of the individual conducting elements provides the requisite flexibility. The conducting wires are wound on the core 5 in a short spiral and, with-advantage, are

arranged in a spiralled group with successive turns of the group spaced from the preceding turns. This particular construction makes possible the use of wire as the conducting element instead of the usual tinsel. This composite, then, encased within the outer elastic vulcanized rubber jacket is protected against mechanical disturbance and, with the added strength of a rubber jacket of the 5 type specified, provides a complete cable of unusual lifeyet having all of the other properties requisite to this class of service and at the same time relatively inexpensive. I claim: 1. An improved telephone plug cord, consisting of a pluralit of conducting elements and a plurality of Her elements small'with respect to the conducting elements spiralled together and encased in an outer jacket of r 5 elastic vulcanized rubber, said spiralled conduct-ing elements and filler elements being boundtogether independently of the encasing jacket, said conducting elements each consisting of a non-conducting core, a plurality of conducting wires small with respect to the core wound thereon in a short spiral, a winding of non-conducting material thereover and an encasing braided acket.

2. An improved telephone plug cord, con- 5 sisting of a plurality of conducting elements and a plurality of filler elements small with respect to the conducting elements spiralled together and encased in an outer'jacketof elastic vulcanized rubber, said spiralled con- 40 i ducting elements and filler elements being bound together independently of'the encasing jacket, said conducting elementsv each consisting of a non-conducting core, a plurality of conducting wires sma l with re ect ;to the core wound thereon in a short spiral,

a winding of non-conducting material thereover and an encasing braided jacket, said plurality of conducting wires arranged in a group with successive turns of the group spaced from preceding turns.

In testimony whereof I afiix my signature WASHINGTON IRVING MIDDLETON;

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