US 3921381 A
An improved method of twisting cables, particularly communications cables, made up of a plurality of cable units so as to maintain a high manufacturing rate while minimizing electrical coupling between cable units in which the process parameters, controlling a known SZ reversing twisting devices which twist the cable units, are randomly varied to cause the sums and differences of the twist, d and the number of reversals per unit length, a, to be continuously and alternatly increased and decreased by at least 0.5 percent about a mean value and so that one of the sum (d+a) and the difference (d-a) of each unit differs from that of at least one other unit by less than 10 percent.
Description (OCR text may contain errors)
United States Patent [191 Vogelsberg METHOD OF MANUFACTURING A CABLE USING SZ TWISTING DEVICES  Inventor:
 Assignee: Siemens Aktiengesellschaft, Munich,
Germany  Filed: Mar. 15, 1973  Appl. No.: 341,773
Dieter Vogelsberg, Berlin, Germany  Foreign Application Priority Data Mar. 17, 1972 Germany 2213693  References Cited UNITED STATES PATENTS 8/1938 Hall 57/34 AT 1/1959 Lilly 57/34 AT 1 Nov. 25, 1975 3,664,108 5/1972 Strelow et al. 57/34 AT 3,715,877 2/1973 AkaChl M 57/34 AT X FOREIGN PATENTS OR APPLICATIONS 1,468,382 2/1967 France 1,801,055 4/1970 Germany 57/34 AT Primary Examiner.lohn W. Huckert Assistant ExaminerCharles Gorenstein Attorney, Agent, or Firm-Keny0n & Kenyon Reilly Carr & Chapin  ABSTRACT An improved method of twisting cables. particularly communications cables, made up of a plurality of cable units so as to maintain a high manufacturing rate while minimizing electrical coupling between cable units in which the process parameters, controlling a known 82 reversing twisting devices which twist the cable units, are randomly varied to cause the sums and differences of the twist, d and the number of reversals per unit length, a, to be continuously and alternatly 2 924,930 2/19 0 Crosley et aL 7 3 AT increased and decreased by at least 0.5 percent about 2,956,102 10/1960 Lil1y..'.; 174/34 a mean value and so that one of the sum (d+a) and 3.0 7.450 1/1962 Cr0sley et a1. 57/34 AT the difference (d-a) of each unit differs from that of 3,140,577 7/1964 ASh 57/34 AT at least one other unit less than percent 3,491,525 l/l970 Sugi 57/34 AT 3,507,108 4/1970 Yoshimura et al. 57/34 AT 8 Claims, 4 Drawing Figures METHOD OF MANUFACTURING A CABLE USING SZ TWISTING DEVICES BACKGROUND oF' THE INVENTION This invention relates to electrical cables in general and more particularly to a method of twistingcommunication cables in an optimum manner so as to avoid electrical coupling between the individual wires in the cable.
Recently there have been developed a number of procedures and devices by which individual, cable elements can be twisted alternately in a left and then in a right twist. Thus, a cable can be manufactured in which successive lengths of the cable will alternate between having a right twist and a left twist. The left twist is commonly referred to as a S-twist and the right twist commonly referred to as a Z-twist. In general, this type of twisting is referred to as SZ-twisting. I
Each of the devices which perform this type of twisting have the advantage that the elements to be twisted can be unwound from stationary unwinding frames and that parallel operation in which a plurality of individual wires can be twisted to form cable units and the units then combined and twisted to form a complete cable. Most devices of this type accomplish the SZ-twisting using a rotating twisting device which contains an intermediate accumulator. A length wire or cable units to be twisted are accumulated within the accumulator and twisted therein in the successive lengths of right and left twists with the twisting apparatus reversing for each length. Generally, these accumulators are of a fixed length. A device which has an accumulator of fixed length and which changes the speed or direction of rotation from section to section while the feeding velocity of the cable elements is kept constant is shown in U.S. Pat. No. 3,169,360. It is also possible to have a fixed storage accumulator which is rotated at a constant speed and direction while the feeding velocity is changed from section to section. Such a system is shown in French Pat. No. 1,468,382.
It is further possible to increase and decrease the storage content of the intermediate accumulator while keeping the rotation constant. A system of this nature is shown in German Pat. No. l,66 5,831.;NTZ, 1970. Vol. 9, pp. 472-480, The SZ-Twisting of Communication Cables. Another type of winder uses a stationary intermediate storage unit witha flying twisting yoke. This system is disclosed in German Pat. No. 1,665,536.
In each of the above twisters, an attempt is being made to reduce coupling between the wires within a cable unit or cable units within acomplete cable. In each of the methods described above. one or more of the parameters of the process i.e. the speed of rotation, the velocity of feeding or pulling off the cable elements or the rate of change of the storage content of the accumulator, is changed or reversed at fixed intervals.
In the above described SZ-twisting methods, two successive twisting steps which were formerly carried out separately are combined into a single operation. That is, a number of groups of wires may be twisted into cable elements and the cable elements then twisted together to form the finished cable. An example would be the twisting of conductors to form spiral quads and then the twisting of several spiral quads to form a basic cable group. The second twisting step can be accomplished using a rotating unwinding and takeup device. However, it is frequently desired to perform SZ-twist- 2 ing in the second twisting step so that it is possible to work with a stationary unwinding and takeup device.
When parallel operation in two stage twisting is performed. it is a common practice to vary the length of lay of the twisted cable units used to form the finished cable. The lay length which is designated by the letter s is equivalent to the pitch dimension in a screw. Very often the reciprocal of the length of lay designated by the letter cl and called twist is used in describing this parameter. This quantity will indicate the number of lays per unit length of the cable unit. In addition. it is best that the points of reversal of direction i.e. from S to Z or Z to S are not at the same place on cable units which are twisted together to form the finished cable.
One way to accomplish these variations is to make the separation of the points of reversal of the direction of twists as large a dimension as possible. This dimension is designated by the letter T and its reciprocal is designated as 2a. As with the lay.-the reciprocal of the length T will indicate the number. of points of reversal per unit length of the cable. Thus. to minimize coupling it is desired to make a as small as possible and T as large as possible. To have a large T requires a large accumulator for use in the SZ-twisting. Obviously. this would make the accumulator quite large and increase its cost. For efficient operation there is arequirement that the output velocity of the finished cable be as high as possible. This requires a small accumulator. Thus the requirements ofa large accumulator to minimize cou-' pling and a small accumulator to increase output are factors which must be balanced and heretofore a compromise was required. Thus. it can be seen that there is a need for a method of operating SZ-twisting devices such that output is maximized and coupling between conductors is minimized.
SUMMARY OF THE INVENTION The present invention provides a method for manufacturing SZ-twisted cables which provides both a high output rate and low coupling between conductors. The method of the present invention is used with a twisting device having an intermediate accumulator in which the twists are reversed at intervals of T= l/Za; where T is the length between reversal points and 2a is the number of points of reversal per unit length. One or more of the process parameters which determine the values of the quantity d and/or the quantity a are continuously altered so that the sum d+a and the, difference d-a are continually increased and decreased (preferably in a random fashion) about a mean value with the amount of increase and decrease being at least 0.5 percent. In addition, the process parameters are chosen so that the mean value of the sum d+a and/or the difference d-a of each SZ-twisted cable unit used in making up the final cable differs from that of the other SZ-cable units used in that cable by less than IO percent. An additional method of accomplishing the same result, in which either before or after passing through the intermediate accumulators an additional twist or torsion in varying amount is superimposed on the SZ-twist. is also possible.
By continuously varying the separation of the points of reversal of the direction of twist of the SZ-twisted cable units and/or their length of lay it is possible to obtain good decoupling using SZ-twisted cable units in which the separation of the points of reversal of direction of twist is relatively small, e.g. less than 5 meters. Thus, small accumulators can be used permitting ligh- 3 ter and lower cost machinery to be used and a higher output rate to be maintained. Since the cable units making up the finished cable each vary about essentially the same mean values for length of lay. manufacturing speed can be maintained. [As opposed to previous methods. where to obtain good decoupling grossly different lengths of lay were used and this different amounts of. wire used causing one unit to have to wait for another before being formed into the finished cable].
DESCRIPTION OF THE DRAWINGS FIG. 1 shows the alternately twisted cable with pertinent dimensions;
FIGS. 2-3 show distributions of the lay numbers of the individual twists of which the sz twisting is comprised.
FIG. 4 illustrates in block diagram form a typical type of system in which the method of the present invention can be used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As noted above. it is possible to obtain the desired results by varying either the separation distance of the points or reversal maintaining a constant lay dimension or by keeping the points of reversal constant and varying the lay dimension with the cable units forming the final cable. Because of the parallel operation which will normally be used. it is more practical to form the twisted cable units with a length of lay which is equal from unit to unit and to change the quantity u i.e. the reciprocal of the distance between points of reversal. between cable units.
The basis of the invention lies in the fact that the SZ- twisting of a cable unit can analytically be replaced by a Fourier series of many [rigoriously speaking infinitly many] constant twists. As noted above. the length of a lay is designated by the letter S and its reciprocal i.e. the number of lays per meter by the letter d. These dimensions are shown in FIG. 1 wherein a cable 1 with both left and right twists is shown in schematic form with the dimensions S and T indicated thereon. Also, as defined above, the dimension T is the distance between the points of reversal and its reciprocal i.e. the number of changes of direction per unit length is designated 2a. In the Fourier analysis of the cable, a series of constant twists having lay numbers (diam). where n 1,2,5 to infinity. may be used to represent the cable. In such a series, the amplitude of the twists decreases with increasing n. Thus. the lay numbers of the individual twists of which the SZ-twisting is assumed to be comprised will have a distribution resembling a discrete frequency spectrum where the separation of the spectral lines is given by the separation of the points of reversal of direction of twists of the SZ-twisted cable units. This is illustrated by FIG. 2.
This analysis will apply to all SZ-cable units which are twisted together to form a complete cable. If two neighboring cable units in the finished cable have spectral lines which coincide or show a small separation. i.e. two component twists. in the Fourier sense. are present with equal or almost equal number of lays per meter,
coupling between these adjacent cable units which is undesirably high and which increases linerally with length is indicated.
The modulation of the quantities D and/or 21 however will result in a Fourier spectrum of component twists 4 for each SZ-twisted cable unit with exhibits a more evenly distributed amplitude spectrum as shown on FIG. 3. This modulation avoids the single spectral lines which have particularly high amplitudes and appear at the values di'u. di3a. diSu. which. if the same polarities were present. could produce large coupling components distributed over the length of the cable. Instead of these large components as shown in FIG. 2, there are a multiplicity of spectral lines of smaller amplitude. particularly in the vacinity of zl zna. where n equals 184.108.40.206 to infinity. The result is that only very small degrees of coupling occur. and further. that the components tend to cancel each other.
A spectrum such as that shown on FIG. 3 can be achieved if the modulation of the quantities (1 and/or a is made random. i.e. for example when the separation of the points of reversal of direction of twist fluctuations statistically about a mean value within the established minimum amplitude of fluctuation.
FIG. 4 illustrates in block diagram form a typical type of system in which the method of the'present invention can be used. Individual wires indicated collectively by ll, 13 and 15 are provided respectively to twisting devices 17. 19 and 21 wherein they are SZ-twisted in the manner described above. These machines may be any of the types listed above when discussing the background of the invention. The twisted cable being units output from devices 17, 19 and 2I are indicated respectively by the lines 23. 25 and 27 and are provided to a final cable twisting device 29 where they are twisted together to form the final cable output indicated by line 31. Each of the twisting devices l7, 19, 21 and 29 will have associated with it a control block. The control block for twisting device 29 is indicated by the numeral 33, that for the device 17 by the numeral 35, that for the device 19 by the numeral 37, and that for the device 21 by the numeral 39. Each of these controls will have a plurality of outputs to control their associated devices. Three typical control parameters are shown coming from control 33. They include as discussed above, accumulator length, feed velocity and rotational speed. The controls 35, 37 and 39 will have similar outputs which are indicated collectively by the single line couping them to their respective twisting devices. There is shown as an input to each of the controls 35. 37, and 39 a random function generator 41. Random function generator 41 will be designed to output random functions which will regulate the control block outputs to result in the process parameters which vary randomly within the limits to be described below. The outputs from the control blocks are used in a conventional manner to continuously change the control outputs being provided from the controls to the twisting devices so as to continually change one or more of the parameters in a random fashion to achieve the type of Fourier spectrum described above in connection with FIG. 3. The speed of rotation may be varied, as may the pulling off speed or. in the case of a flying twisting yoke, the speed of revolution of the yoke about the storage unit. From a practical standpoint. however, increasing and decreasing the storage content of the accumulator is'most useful. In such a case the modulation of thequantities d anda iseasily accomplished through a continuous change of the time of changing from an increase to a decrease of the storage content or through the modulation of the rate ofchange of the storage coritent.
Alternately, if the invention is to be carried by adding an additional twist a twisting head of the type wellknown in the art which positively grips the cable units and rotates it in a circumferial direction can be placed at the output of the twisting devices 17, 19 and 21. These twisting heads are shown as dotted blocks indicated by the numeral 43. An example ofa type of twisting head which can be used is that shown in German Pat. Nos. 1,765,452 and 1,928,591. 1f the additional twist method of modulating the cables is used, then the random function generators 41 will provide outputs to the twisting heads 43 as indicated by dotted lines 45 rather than providing inputs to the control blocks.
It is significant to note that the decoupling effect resulting from the modulation of the quantities d and a is independent of the magnitude of these quantities. Thus, SZ-twisted cable units which'have a relatively large value of a, that is the points of reversal of twist direction are relatively close together, can still be effectively decoupled from each other. This can be better shownby the numerical example below.
Assume that it is desired to assembly a communication cable of five spiral quads V through V for which the lengths of lay s, 100; s 95.2; 90.9; 5 87; s 83.3 (mm) are provided. These quads have the following twists:
Such lengths of lay or twists can be obtained, for example, with pulling-off speed v m/min and speeds of rotation n 250 to 300 rpm, in a device where the SZ- twisting is accomplished by rotating intermediate accumulators with fixed storage content and sectionally alternating the direction of rotation. In the manufacture of SZ-twisted cable units using a device wherein rotating intermediate accumulators in which the storage content is alternately increased and decreased at intervals, such twists may be obtained with pulling-off speed of v 50 m/min and speeds of rotation of n 1000 to 1200 rpm.
Assume that the mean lengths of the sections of different twist directions is equal, and that the separation of the points of reversal of the direction of twist is 2.50 in. Then a /2T 0.2 m for all spiral quads. This gives the following values for the quantities (d+a) and OOIQ Here the process parameters determining the quantities d and a, such as speed of rotation of the twisting device, pulling-off speed, storage content, and/or, possibly, rate of change of storage content, are so chosen that the quantities (d-l-a) and (da) of at least one of the SZ- twisted spiral quads differ from the quantities (d+a) and (d-a) of at least one of the other SZ-twisted sprial quads by less than 10 percent.
The modulation which will assure the decoupling of the sprial quads can now be accomplished, for example, by keeping the twists d constant, while the quantity a for all the quads is caused to vary by 50 percent about a mean value, i.e. a 0.1 0.3m, corresponding to a variation of the separation of the points of reversal of the direction of twist of between 1.66 and 5 m.
(d+ 1().2 $0.1 (for 1'.) 12.2 :01 (l'or1' (lll l 9.X i 0.1 (for V.)
tm") Here the relative variation of the quantities (d+a) and (d-a) is greater than i 0.8 percent.
As a further example assume that the separation of the points of reversal of the direction of twist, i.e. a. is kept constant while the twists (I, through d of the five spiral quads are modulated by 2 percent about their mean value. These variations should occur for each spiral quad independently of the others.
For the quantities (d+a) and (da) the following is obtained:
(d+a)= 10.: 10.20 (for 1'.)
(ll-ll) 9.8 i020 (for I") 11.8 10.24 (for 1' Here the relative variation of the quantities (a'+a) and (d-u) amounts to i 2 percent.
In the preceding example it was assumed that the lengths ofthe successive sections of differing directions of twist are all equal. But. the new procedure can also be used with SZ-twistcd cable units in which the successive sections of different directions of twist are of unequal lengths. In that case there will be a quantity d as well as a quantity a,,.,, for those sections with a left twist, and a quantity (I as well as a quantity a for those sections with a right twist. In that case. the modulations corresponding to the sections with a left twist and those corresponding to others with a right twist have to be considered separately.
Thus an improved method of SZ-cable twisting using known twisting devices which permits optimizing decoupling while maintaining a high output rate has been shown. Although specific examples ofthe method have been described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.
What is claimed is:
.1. A method of manufacturing a communication cable so as to minimize coupling between cable units making up a finished cable, in which a plurality of SZ- twisting devices each having intermediate accumulators which reverse the twist direction at intervals of T 1/2a are used to twist insulated conductors to a plurality of cable units such as pairs or quads which are then twisted to form a cable group or a finished cable comprising:
a. operating the plurality of SZ-twisting devices with one of different pulling off speeds, speeds of rotation and storage contents, to result in a plurality of cable units in which one of the sum and difference between the twist d and number of reversals per unit length, a. of each unit differs from that of at least one other unit in the cable group of the finished cable by less than 10 percent; and
b. continuously varying one of the speed of rotation of the twisting device, pulling off speed, storage content and rate of change of storage content in an alternatively increased and decreasing manner about a mean value so that the quantities d-l-a and d-a are continuously and alternatively increased and decreased at least 0.5 percent about a mean value.
2. The invention according to claim 1 wherein said continuous variation is done in a random fashion.
3. A method according to claim 1 wherein the step of operating is carried out so as to maintain the length of 11.8 10.1 (for V 7 lay constant in each individual cable unit but with one of different pulling off speeds. speeds of rotation and storage contents which differ from cable unit to cable unit so that the length lay S differs from cable unit to cable unit and wherein the step of continuously varying is carried out such that the same degree of variation occurs in all units.
4. The method according to claim 1 wherein said step of operating is carried out so that the length of lay S is maintained constant for all cable units and wherein said step of continuously varying is carried out in such a manner that the variation is different in each cable unit.
5. The invention according to claim 3 wherein said continuous variation is done in a random fashion.
6. The invention according to claim 4 wherein said continuous variation is done in a random fashion. v
7. A method of manufacturing a communication cable so as to minimize coupling between cable units making up a finished cable in which a plurality of S2- twisting devices each having intermediate accumulators which reverse the twist direction at intervals of T=ll2a are used to twist insulated conductors to form a plurality of cable units such as pairs or quads which are then twisted to form a cable group or finished cable comprising:
a. applying an additional twist to each of the units with the additional twist varying so as to cause the quantities d-l-a) and (da) where a is the number of reversals for unit of length and d is the twist, to vary by at least 5 percent about a mean value; and
b. operating the plurality of SZ-twisting devices with one of different pulling off speeds. speeds of rotation and storage contents. to result in a plurality of cable units in which one of the sum and difference between the twist d and the number of reversals per unit length. a. of each unit deffers from that of at least one other unit in the cable group of the fin ished cable by less than 10 percent.
8. The invention according to claim 7 wherein said continuous variation is done in a random fashion.