US1475139A - Telephone cable - Google Patents

Description

Nov. 20 1923.

G. c PEARSON TELEPHQNE CAB Filed March 5f), 1920 Patented Nov. 20, 1923. p t I UNITED IPA TENT OFFICE.

eiioaen o. PEAR-SUN, or Lonnon; ENGLAND.

TELEPHONE CABLE.

Application filed March so, 1920. Serial No. 369,969.

To all whom it may concern:

Be it known that 1, GEORGE CHARLES PnARsoN, a subject of the King of Great Britain,residing in London, England, have invented certain new and useful Improvements Relating to Telephone Cables, of which the following is a. specification.

The invention relates to telephone cables of the multiple twin type. in which two elements are twisted together to form a pair, and two pairs are twisted together to form two pair cores, thesetwo twisted together to'form a cable.

In these cables and particularly in those in which a-phantom circuit is superimposed on two side circuits, it is a mostimportant condition for satisfactory working, that working currents circulatingin one circuit shall not electrically disturb the working of any other circuit in the cable.

To ensure this condition being obtained, it is necessary that any electrical unbalancing between the side circuits, between the phantom and side circuits and between the side circuits and earth shall be reduced to a minimum. This is also necessary in the case in which there is a further superimposition of phantom circuit on phantom circuit. i

In order to obtain the minimum unbalancing it is necessary that the elements in any combination of pairs forming a circuit should not be in parallel dispositions, that r they should be as nearly as possible equal in length and uniformly distant from one another and in as nearly as possible correct relative positions to one another when the combinations of pairs are stranded together to form a cable.

According to a known method for reducing the disturbance, the elements forming a pair are twisted together with a variable twist, the pairs being transposed with reference to each other at certain intervals in the cable length; such transposition, however, is not practicable in the case of cables composed of quads, multiple twin or quadded cores, as the crossing of the quads or combinations of pairs would tend to increase the diameter of the cable at these points and as each layer is added there would be considerable crushing of the cores which would be detrimental.

In two pair cores comprising two pairs twisted together, the elements of which are twisted together, in known manner at a difpairs belng B of a pair in relation to the central axis ferent pitch or at different degrees at alter nate sections and so combined into a'cable that parallelism between the two wires or any .two different pairs is avoided elements of the two pairs must frequently cross in the same axial plane and the four elements will then he in a straight line, and a little later the elements of each pair .will lie side by side in planes at right angles to the for iner plane, the width of the two pair cores varying considerably throughout its length.

In laying these two pair cores together to form a cable, the elements at the wide portions are displaced from their correct posi tions by contact with the adjacent two pair cores and are subject to a much greater pressure than at other parts.

Fig. 1 of the accompanying drawings shows the positions of two conductors A and C at different angular Fig. 2 shows laid together at twists.

Fig. 3 shows a method of winding two phases of the lay. a two pair core as usually two difi'erent points of the pair cores according to the invention; and

Figs. 4- and 5 are sections of these cores showing positions occupied by the conductors according to the invention.

According to the invention the pitch of the twists in all adjacent parts of the pairs is different, but the total numberof twists is substantially the same in each pair, thereby ensuring the same length of conductors and the same electric resistance. For example there may be a series of 20 inch pitches succeeded by a series of 10 inch pitches, the center part of the shorter twists of one pair being opposite the center part 01. the longer twists of the other pair.

Also, the actual lengths of the twists in adjacent combinations of pairs are, preferably, different; for instance, in one combination a series of 20 inch pitches may be succeeded by a series of 10 inch pitches, and in an adjacent combination a series of 18 inch pitches maybe succeeded by a series of 12 inch pitches, the total number of twists being the same in each combination. 7

The arrangement is illustrated in Fig. 3, where the distances between 10 and 11, 11 and 12 represent the long twists and the distances between 12 and l3, l3 and 14, 14 and 15, 15 and 16 represent the short twists.

In the other pair of the two pair cores (shown separated in the diagram) the short twists, viz: between 10' and 11, 11' and 12, 12 and 13', 13' and 14: are opposite the long twists of the first pair and similarly the long twists between 14: and 15, 15 and 16 are opposite the short twists of the first pair.

Also, according to the invention, the two pairs are so relatively disposed that the four elements of the pairs cannot come into the same plane simultaneously at any part of the length of the cable. This condition is fulfilled under the arrangement described, in which the center portions of the shorter twists of one pair are opposite the center portions of the longer twists of the other pair, it the pairs are laid together so that the four conductors at any part of the length of the cable assume the positions shown in Fig. 5, viz: The tour conductors lie in two parallel planes; this disposition is obviously easily arranged at the commencement of the operation of laying the two pairs togther. Under these conditions the four elements cannot assume the positions shown in Fig. 2 and the resultant conformation of the two pair cores at their largest diameter is shown in Fig. 4.

In cables of this type it is obvious that the pairing and building up of the combinations of pairsmay be done in separate operations, but combinations consisting of two pairs twisted together forming two pair cores may be made in one operation. The latter method tends more to ensure the correct relative positions of the twists in the pairs throughout the whole length of the combinations.

Having thus described the nature of the said invention and the best means I know of carrying the same into practical effect, I claim In telephone cables for duplex and phantom circuit working, two pair cores comprising two pairs of elements twisted together in which the pairs for a manufactured length are formed with a series of long twists followed by a series of shorter twists, the eenter portion of the shorter twists in one pair being placed opposite the center portion of the longer twists of the other pair, the elements of the two pairs at these points being in parallel planes, the elements of one pair being always in a different plane from the elements of the other pair, and the relative positions of these planes being the same at corresponding cross sections of the complete twists throughout the length.

In testimony whereof I have signed my name to this specification.

GEORGE C. PEARSON.

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