US3643411A

US3643411A - Method and apparatus including a rotating intermediate storer for sz twisting of elements of a cable

Info

Publication number: US3643411A
Application number: US6663A
Authority: US
Inventors: Dieter Vogelsberg
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1969-02-07
Filing date: 1970-01-29
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22
Also published as: DE1906997B2; JPS4827613B1; GB1255372A; DE1906997C3; FR2033312B1; DE1906997A1; NL7001755A; AT292093B; FR2033312A1; SE352190B

Abstract

The elements are pretwisted prior to the supply of such elements to a rotating intermediate storer and independently of the rotary movement of the storer. An additional twist is superimposed on the section of elements withdrawn from the intermediate storer independently of the rotary movement of the storer.

Description

United States Patent Vogelsberg 1 Feb. 22, 1972 [54] METHOD AND APPARATUS [56] References Cited INCLUDING A ROTATING UNITED STATES PATENTS INTERMEDIATE STORER FOR SZ 2 869 316 H1959 L 5 I T I [N F EMENTS OF A CABLE 1 y 7 34A Tw ST G 0 EL 3,169,360 2/1965 Corra11eta1..... ..57/34 [72] inventor: Dieter Vogelsberg, Berlin, Germany 3,426,519 2/1969 Unger et a1 ..57/34 AT 3,455,098 7/1969 Klebl et a1 ....57/34 X [73] Assngnee: Siemens Aktiengesellschait Berhn and M v G y I 3,481,127 12/1969 Vogelsberg ..57/34 [22] Filed; Jan, 29, 1970 Primary Examiner-Stanley N. Gilreath Assistant Examiner-Wemer H. Schroeder 1 PP 6,663 AttorneyCurt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel .1. Tick [30] Foreign Application Priority Data 57] ABSTRACT Feb. 7, 1969 Germany ..P 19 06 997.7 The elements are pretwisted prior to the supply of such ments to a rotating intermediate storer and independently of [52] U.S.Cl. ..57/34 AT, 57/58.52,5577/l9546, the rotary movement of the storer. An additional twist is perimposed on the section of elements withdrawn from the in- [51] Int. Cl. ..H0lb 13/04 termediate store: independent), of the rotary movement of [58] Field oi Search ..S7/34, 34 AT, 58.3, 58.38, the Storen 15a 17a 18a 7 11 Claims, 2 Drawing Figures 14 11b10b3b 3 PAIENTEumzz m2 3.643.411

8 100 110 g 15 j; 5 14 11b 10b 9b 3 METHOD AND AlPllAlRATlUS llNCLlUDllNG A ROTATING liN'lllEllili/lllElDllA'llE STOREN IFON SZ TWlSTllNG 01F ELEMENTS Oll" A CABLE DESCRIPTION OF THE INVENTION The invention relates to a method and apparatus for SZ twisting of elements of a cable, More particularly, the invention relates to a method and apparatus including a rotating intermediate storer for S2 twisting of elements of a cable.

The technical development of the manufacture of communication cables has recently been directed toward combining several twisting operations which were previously effected separately. An example of such direction of development is the combination of the twisting of spiral quads and basic bunches or bundles into a single-operational step, in order to improve the economy of operation, This requires twisting processes in which the twisted units, which are stranded of a plurality of elements, are stranded in sequential longitudinal sections which comprise alternating left-hand, or S-twisted, and a right-hand, or Z-twisted elements. All twisting operations of this type, which are known as SZ-twisting processes, provide the advantage that the elements are supplied from stationary supply structures and that the processing of the SZ- twisted units, which are twisted from said elements, may follow during the same operational step.

it is known, from US. Pat. No. 3,169,360, for example, to undertake the S2 twisting process with a twisting device provided with a rotating longitudinal storer of constant length. The longitudinal storer is known as an intermediate storer and performs a double function. Thus, the intermediate storer simultaneously functions as a receiving drum for the longitudinal section of the twisted unit being fed in, as well as a takeup drum for the withdrawn longitudinal section. The direction of twisting is changed periodically, at intervals which depend upon the length contained in the intermediate storer. The twisting direction is changed in accordance with a change in speed or a change in the direction of rotation of the inter mediate storer.

ln known SZ-twisting operations and apparatus, the mag nitude and direction of twisting of the longitudinal section of the elements stored in the rotating intermediate storer depend solely on the direction of rotation and the number of revolutions of said intermediate storer, at a constant rate at which said elements pass through said intermediate storer. ln twisting apparatus comprising an intermediate storer having a plurality of guide rollers whose direction of rotation is changed in accordance with the stored length, the aforedescribed fact results in the occurrence of reversal points in the strands within said intermediate storer; The strands may thus easily become twisted on the guide rollers during their passage through the intermediate storer.

The principal object of the invention is to provide a new and improved method and apparatus for S2 twisting of elements of a cable into a twisted unit.

An object of the invention is to provide a method of S2 twisting of elements of a cable into a twisted unit at increased speed.

An object of the invention is to provide a method and ap-. paratus for SZ twisting of elements of a cable into a twisted unit at a speed which is three times faster than. that of known units, for the same magnitude of the final strand, alternating in sections, and the same number of rotations executed by the twisting apparatus.

An object of the invention is to provide a method and apparatus for SZ twisting of elements of a cable into a twisted unit at a speed of manufacture which is 1% times the speed of manufacture of known apparatus.

An object of the invention is to provide a method and apparatus for S2 twisting of elements of a cable into a twisted unit which prevent reversal points in the twists in the intermediate storer.

An object of the invention is to provide a method and apparatus for S2 twisting of elements of a cable into a twisted unit which prevent twisting of reversal points in the strands in the intermediate storer without the necessity for special measures.

My invention provides a considerable improvement over the known SZ twisting methods and apparatus, In accordance with the invention, ina method for S2 twisting of elements for communication cables into a single-twisted unit with a twisting direction which alternates by sections, the elements are twisted while being fed into a rotating intermediate storer. The elements are withdrawn from the intermediate storer after the direction of rotation or the number rotations or speed of the intermediate storer have been changed. The withdrawn section of the elements is superimposed by a second or additional, whereby a periodic change in the direction of rotation or the speed of the intermediate storer produces two sequential sections formed in different twisting directions.

ln accordance with my invention, the elements are fed to the intermediate storer, which intermediate storer rotates in alternating directions or speeds, with a superimposed pretwisting which is independent of the rotary movement of said intermediate storer. The section of the elements withdrawn from the intermediate storer is superimposed with another or additional twist, independently of the rotary movement of said storer.

The method of the invention permits the selection of the magnitude and the direction of twisting of the longitudinal section of the elements stored in the intermediate storer, independently from the twisting which is provided solely due to the sectional change in the direction of rotation or the speed of said intermediate storer.

ln accordance with the invention, the pretwisting and the superimposition of the strand are effected in the same direction as that in which the elements are twisted while being fed to the intermediate storer and while being withdrawn therefrom. This augments the twisting produced by the alter nation by sections of the speed or the rotary direction of the intermediate storer. The speed of production of the SZ- twisted elements may therefore be increased at the provided upper speed limit for the twisting apparatus and at the provided twisting, as compared to known SZ-twisting methods.

The elements are prestranded in constant direction. Simultaneously with the pretwisting of the elements, an additional twist is superimposed in constant direction on the section of elements withdrawn from the intermediate storer. In this manner, the level of the twist in the intermediate storer, that is, the average value of the two twists which result from the change in speed of the various sections or from the alternation of the rotary direction of said intermediate storer, is shifted in either one or the other direction. The shift or change in the level due to the pretwisting may be compensated'or cancelled out by the superimposition of an additional twist which over laps the section of elements withdrawn from the intermediate storer. In this event, the pretwisting serves only as an auxiliary magnitude or quantity during the SZ twisting of the elements.

It is particularly expedient that the pretwisting of the elements fed into the intermediate storer and the superimposing of the twist on the section of elements withdrawn from said intermediate storer be in opposite directions, but of equal magnitude. It is further expedient that the magnitudes be at least equal to the magnitude of the twisting provided during the feed in to or the withdrawal from the intermediate storer. This insures that the twist in the intermediate storer always has the same direction of twist independently of the speed or direction of rotation of the storer. This prevents the occurrence of reversal points in the intermediate storer and prevents the twisting of such reversal points in the twist without the access ity for special measures.

ln accordance with the invention, the twisting apparatus includes an intermediate storer which rotates in a direction or at a speed which changes alternately by sections. The inter mediate storer is encircled by two tightly interconnected rotating or flying twisting brackets or stirrups. One of the twisting brackets feeds or supplies the twisted elements to the intermediate storer. The other of the twisting brackets withdraws or removes the elements from the intermediate storer.

SZ-twisting apparatus in which the elements are supplied to an intermediate storer by a bracket and are withdrawn from the storer by a bracket is disclosed in Austrian Pat. No. 262,408. In the SZ-twisting apparatus disclosed in the Austrian patent, the elements are supplied to a stationary intermediate storer. Thus, the twisting is not effected by the rotary motion of the intermediate storer, but rather by the rotary motion of the twisting brackets which rotate around said intermediate storer. The number of revolutions or rotations or the direction of rotation of the twisting brackets is changed by the twisted sections in accordance with the length contained in the intermediate storer.

In contrast with the apparatus disclosed in the Austrian patent, twisting is effected by the apparatus of my invention essentially by the rotary movement of the intermediate storer. The twisting brackets rotate around the intermediate storer and affect the magnitude and/or the direction of the twisting of the section stored in said intermediate storer.

In the twisting apparatus of the invention, which includes an intermediate storer which alternately changes its direction by sections, it is particularly advantageous that the rotary direction of the twisting brackets be opposite to the direction of rotation of the intermediate storer. This augments the twisting produced by the intermediate storer.

If the intermediate storer and the twisting brackets rotate at the same speed, the elements passing through the twisting apparatus are twisted in a sextuple lay. A first single lay is produced upon the supply of the elements to the twisting bracket which feeds said elements to the intermediate storer. A first double lay is produced during the passage of the elements from the twisting bracket to the intermediate storer and a second double lay is produced during the passage of said elements from said intermediate storer to the twisting bracket which withdraws or removes said elements from said intermediate storer. A second single lay is produced when the elements are withdrawn from the twisting bracket.

Compared to known SZ-twisting apparatus, in which the intermediate storers change their direction of rotation by sections, the apparatus of the invention produces twists three times faster, providing the same magnitude or quantity for the final twist, alternating in sections, and with the same number of rotations completed by the twisting apparatus. Compared to known twisting apparatus, where the elements are fed via twisting brackets, which rotate with changing speed or direction of rotation, around a stationary intermediate storer, which has a total of four lays, the apparatus of the invention operates at an increase of manufacturing speed which is one and one half times the speed of operation of the known apparatus.

As previously indicated, the occurrence of reversal points in the twist results in twisting at such points. A reversal point is a point at which the direction of the twisting reverses itself repeatedly. It is thus advantageous to prevent the occurrence of reversal points. Reversal points may be reliably prevented by utilizing, in accordance with the invention, twisting apparatus whose twisting brackets rotate about the intermediate storer at constant speed and in constant rotary direction. The twisting produced by the twisting bracket which feeds or supplies the elements to the intermediate storer is compensated for or cancelled by the twisting which is produced by the twisting bracket which withdraws or removes said elements from said intermediate storer.

The pretwisting and superimposition of the twisted elements while they are respectively fed into and withdrawn from the intermediate storer, function as auxiliary magnitudes or quantities in order to produce a shift or change in the level of the strand located in said intermediate storer. The elements are thus provided, prior to being fed into the intermediate storer, with constant pretwisting, which is superimposed by the twist occurring in alternately changing directions, in accordance with the sections of elements.

In order to prevent points of reversal from occurring in the twist located in the intermediate storer, despite the sectional alternation or changing of the rotary direction of said intermediate storer, the twisting produced during the feed in of the elements to the twisting bracket must be of the same or greater magnitude than the twisting produced during the transfer of said elements from the twisting bracket to said intermediate storer. This means that the twisting brackets must rotate at a speed which is equal to or greater than half the speed of the intermediate storer.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein:

FIG. 1 is a schematic diagram of an embodiment of the twisting apparatus of the invention utilized to perform the method of the invention; and

FIG. 2 is a block diagram of an embodiment of the twisting apparatus of the invention for twisting a communication cable.

In the FIGS., the same components are indicated by the same reference numerals.

Elements 1, which may comprise, for example, four wires, are twisted by twisting apparatus 2. Elements comprising many wires such as, for example, pairs or fours, may be twisted into a single bunch. The twisting apparatus 2 produces a twisted unit or group 3 such as, for example, a spiral quad. The twisting apparatus 2 essentially comprises an intermediate storer 4. The direction of rotation of the intermediate storer 4 changes alternately by sections, depending upon the length of the twisted unit contained in said storer.

The twisting apparatus 2 further comprises twisting brackets or

stirrups

5 and 6 which are tightly coupled to each other. The intermediate storer 4 is pivotally mounted in a frame 19 having

frame parts

18a and 18b. The intermediate storer 4 is driven by an electric motor 7 mounted on the frame part 18a. The

interconnected twisting brackets

5 and 6 are pivotally mounted in the frame 19 via the

frame parts

18a and 18b, and are driven by a motor 21 through a gear train 20, 22.

The elements 1 are fed are supplied to the twisting apparatus 2 from the left via a twisting nipple 8 and are transferred through a hollow shaft 9 having a shaft portion 9a and a shaft portion 9b, a pair of

deflection rollers

10a and 11a and through the twisting bracket 5, which is hollow, to the intermediate storer 4. The elements 1 are thus fed to the intermediate storer 4 from the right, via deflection rollers llb and 10b.

The intermediate storer 4 comprises a frame 12. Two groups of

rollers

13a and 13b are mounted in the frame 12 at a specific distance from each other. The two groups of

rollers

13a and 13b are mounted on parallel shafts. The elements 1 are fed or supplied to the intermediate storer via the

aforedescribed components

8, 9, 10a, 11a, 5, 11b and 10b, and a deflection roller 14.

The elements 1 are withdrawn or removed from the intermediate storer 4 via a deflection roller 5 and are withdrawn from the twisting apparatus, toward the right, via a deflection roller 16a, a deflection roller 17a, the twisting bracket 6, which is hollow, a deflection roller 17b and a deflection roller 16b.

The number of rotations or revolutions, or speed, and the direction of rotation of the intermediate storer 4 and the twisting

brackets

5 and 6 may be selected so that they are difierent from each other, with regard to their ratio.

The elements 1 are twisted together while being fed into the intermediate storer 4. A section of the elements 1 having the same twisting direction and the same twist is located in the intermediate storer 4 and subsequently removed therefrom, via the deflection roller 15, in a different direction of rotation.

During the withdrawal of the elements from the intermediate storer 4, an additional twist is superimposed on the elements in the same direction as said elements. Simultaneously, a new section is supplied to the intermediate storer 4 and is twisted in the opposite direction. When the intermediate storer 4 is filled with the new section, the direction of rotation is again reversed, so that the new section is provided with an additional twist in the same direction, while being withdrawn from said intermediate storer, which additional twist subsequently becomes superimposed upon the initial twist.

it is essential that the rotating movement of the intermediate storer 4 be changed periodically in direction and that the period of constant rotation correspond to the passage of a section of elements 1 through the intermediate storer 4. The periodic change of the direction of rotation results in the twisted elements 1 being alternately, by sections, with an S- twist, followed by a Z-twist, followed by an S-twist, followed by a Z-twist, and so on.

in order to augment the S2 twisting of the twisted unit 3, caused by the sectional change of the direction of rotation, that is, in order to increase the number of twisted lays per lon gitudinal unit of said twisted unit, the direction of rotation of the twisting

brackets

5 and 6 is also periodically changed in accordance with the length of elements in the intermediate storer 4.

The direction of rotation of the twisting

brackets

5 and 6 is so selected that it is opposite to the direction of rotation of the intermediate storer 4. As a result, the elements 1 may be fed or supplied to the intermediate storer 4 in triple lay and are withdrawn or removed from said storer in triple lay and the twists of the twisted unit, which are produced during the passing of the elements through the twisting

brackets

5 and 6 and said storer 4 are all in the same direction. This results in the elements 1 which pass through the twisting apparatus 2 being twisted together in sextuple lay.

Twisting apparatus of the type of the invention may thus produce SZ-twisted units at a maximum twisting at a considerably higher speed of manufacture than twisting apparatus which produce SZ twisting which changes by sections, only with the assistance of an intermediate storer which alternately changes its direction of rotation by sections.

During the twisting of the elements 1 by the intermediate storer 4, the direction of rotation of which changes in sections, the sections of said elements stored in said storer alternately comprise an S-twist and a Z-twist. As a. result, reversal points occur in the twist which may become twisted during their passage through the intermediate storer 4. In order to prevent the occurrence of the reversal points, and thereby prevent the twisting of the reversal points in the twist, the twisting

brackets

5 and 6 are preferably driven via a gear arrangement, not shown in the FlGS., coupled to the motor 7, which gear arrangement rotates said twisting brackets at constant speed and in a constant direction of rotation.

The elements are thereby fed or supplied to the intermediate storer 4 with constant prestranding. An additional constant strand is superimposed on the elements withdrawn from the intermediate storer 4, with the assistance of the twisting

brackets

5 and 6. Since the twisting

brackets

5 and 6 rotate in a constant direction of rotation and at constant rotational speed, the additional twists produced with the assistance of said twisting brackets are opposed and of equal magnitude, so that they cancel each other.

ln order to prevent the occurrence of die reversal points in the twist within the intermediate storer 4, the speed of said storer and of the twisting

brackets

5 and 6 must be selected in a manner whereby the twisting which occurs during the feeding of the elements into the twisting bracket 5 is always greater than the twisting of said elements when they are being fed into the intermediate storer 4. Since the twisting bracket 5 and the intermediate storer 4 rotate, at times, in the same direction, the speed of the twisting

brackets

5 and 6 must be greater than half the speed of said intermediate storer.

When the speed of the twisting brackets 55 and 6 equals half the speed of the intermediate storer 4, the elements are always supplied to said storer in the same direction, while some sections are either not twisted or are provided with a twist. if, on the other hand, the speed of rotation of the twisting

brackets

5 and 6 is greater than half the speed of the intermediate storer 4, the elements 1 are fed into said storer in a manner whereby they are so twisted that they always have the same twisting direction, but some sections have a different twisting.

In selecting the number of rotations or revolutions for the intermediate storer 4 and for the twisting brackets 55 and 6, care must be taken, first, that there will be no occurrence of excessive torsion stresses in the elements twisted together. Care must be taken, secondly, that during the passage of the elements 1 through the intermediate storer 4 no undesirable changes in location will occur, that is, that there will be no overriding of the elements. When the foregoing requirements are taken into consideration, it is preferable to permit the intermediate storer 4 and the twisting

brackets

5 and 6 to rotate at the same speed, whereby said storer changes its direction of rotation by sections.

As hereinbefore mentioned, the SZ-twisting processes are necessary in order to combine several twisting processes, which were previously undertaken separately, into a singleoperating step. Twisting processes which were previously undertaken separately are, for example, the twisting of wires or elements into spiral quads and the subsequent twisting of the spiral quads into a basic bundle or bunch.

The twisting of elements into SZ-twisted units in a single process step, as well as the subsequent twisting of the twisted units into a singletwisted group, is illustrated in FIG. 2. 1n P16. 2, each four elements or

wires

10, 1b, 1n are fed at a constant speed into a corresponding one of a plurality of twisting

apparatus

2a, 2b, 2n The twisting

apparatus

2a, 2b, 2n operate in parallel and each comprises the apparatus of the invention disclosed in FIG. 1.

The elements 1a are twisted into a twisted unit 3a, the elements 1b are twisted into a twisted unit 312, and so on. Each of the

twisted units

3a, 3b, 3n is twisted into, for example, a spiral squad. Each twisting

apparatus

2a, 2b, 2n comprises, identically with the twisting apparatus 2 of FIG. 1, an intermediate storer 4 which changes its direction of rotation in sections, and two twisting

brackets

5 and 6 which rotate around said storer at constant speed and in constant direction of rotation. The speeds of rotation of the twisting apparatus 2a, 2b, ..l 2n may be selected so that they vary.

In the apparatus of FIG. 2, the SZ-twisted

units

3a, 3b, 3n are twisted during the same process step into a twisted group 21, which may comprise, for example, a basic bunch or bundle. The twisted group 21 is provided by a twisting apparatus 211 which rotates at constant speed and in a constant direction of rotation. The twisted group 21 is finally wound on a takeup drum 22 which rotates at constant speed and in constant direction of rotation.

While the invention has been described by means of a specific example and in a specific embodiment, 1 do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

1 claim:

1. A method of SZ twisting of elements of a cable into a twisted unit in a twisting direction which alternates by sec tions, in which method the twisted units are first twisted while being fed into a rotating intermediate storer from which they are withdrawn after a change in the rotary direction of the storer or after a change in the rotary speedof the storer, a second twist is superimposed on the withdrawn section of ele ments, and the direction or speed of the storer is periodically the rotary movement of said storer. 2. A method of SZ twisting of elements ofa cable as claimed in claim 1, wherein the pretwisting and superimposing are efv fected in the same direction in which the twisted elements are twisted while being fed into or withdrawn from the storer.

3. A method ofSZ twisting of'elements of a cable as claimed in claim 1, wherein each of the,;pretwisting and superimposing is effected in constant direction;

4. A method of S2 twisting of elements of a cable as claimed in claim 1, wherein the pretwisting and superimposing are effected in opposite directions at the same magnitude.

' 5. A method of S2 twisting of elements of a cable as claimed in claim 1, wherein the pretwisting and superimposing are effected in opposite directions at the same magnitude which is at least equal to the magnitude of the twisting during the feed into and the withdrawal from said storer.

6. Apparatus for S2 twisting of elements of a cable into a twisted unit in a twisting direction which alternates by sections, including means for twisting twisted units during feeding into a rotating intermediate storer from which they are withdrawn after a change in the rotary direction of the storer or after a change in the rotary speed of the storer, means for superimposing a second twist on the withdrawn section of twisted elements, and means for periodically changing the direction or speed of the storer to provide two successive sections of different stranding direction, said apparatus comprising an intermediate storer;

driving means coupled to said intermediate storer for rotating said storer at a speed and direction of rotation which changes by sections; and

a pair of twisting brackets rotatably mounted for rotation around said intermediate storer and tightly coupled to each other, one of said twisting brackets supplying the twisted elements to said storer and the other of said twisting brackets withdrawing the twisted elements from said storer.

7. Apparatus as claimed in claim 6, wherein said twisting brackets are coupled to said driving means and said driving means rotates said twisting brackets in a direction of rotation opposite the direction of rotation of the intermediate storer.

8. Apparatus as claimed in claim 6, wherein said twisting brackets are coupled to said driving means and said driving means rotates said twisting brackets at a constant direction of rotation and a constant speed of rotation.

9. Apparatus as claimed in claim 6, wherein said twisting brackets are coupled to said driving means and said driving means rotates said twisting brackets at a constant direction of rotation and a constant speed of rotation at least equal to half the speed of the intermediate storer.

10. Apparatus as claimed in claim 6, wherein said apparatus comprises a plurality of parallel operating systems each of said systems comprising an intermediate storer, driving means cou-' pled to said intermediate storer for rotating said storer at a speed and direction of rotation which changes by sections, and a pair of twisting brackets rotatably mounted for rotation around the intermediate storer and tightly coupled to each other, one of said twisting brackets supplying the elements to the storer and the other of said twisting brackets withdrawing the twisted elements from said storer, said apparatus further comprising additional twisting apparatus connected in common with said plurality of systems for twisting the twisted units provided by said systems into a twisted group in a singleoperating step.

11. Apparatus as claimed in claim 10, wherein the twisted units provided by said systems are twisted in constant twisting direction.

Claims

1. A method of SZ twisting of elements of a cable into a twisted unit in a twisting direction which alternates by sections, in which method the twisted units are first twisted while being fed into a rotating intermediate storer from which they are withdrawn after a change in the rotary direction of the storer or after a change in the rotary speed of the storer, a second twist is superimposed on the withdrawn section of elements, and the direction or speed of the storer is periodically changed to provide two successive sections of different twisting direction, said method comprising the steps of pretwisting the elements prior to the supply of said elements to the intermediate storer and independently of the rotary movement of said storer; and superimposing an additional twist on the section of elements withdrawn from the intermediate storer independently of the rotary movement of said storer.

2. A method of SZ twisting of elements of a cable as claimed in claim 1, wherein the pretwisting and superimposing are effected in the same direction in which the twisted elements are twisted while being fed into or withdrawn from the storer.

3. A method of SZ twisting of elements of a cable as claimed in claim 1, wherein each of the pretwisting and superimposing is effected in constant direction.

4. A method of SZ twisting of elements of a cable as claimed in claim 1, wherein the pretwisting and superimposing are effected in opposite directions at the same magnitude.

5. A method of SZ twisting of elements of a cable as claimed in claim 1, wherein the pretwisting and superimposing are effected in opposite directions at the same magnitude which is at least equal to the magnitude of the twisting during the feed into and the withdrawal from said storer.

6. Apparatus for SZ twisting of elements of a cable into a twisted unit in a twisting direction which alternates by sections, including means for twisting twisted units during feeding into a rotating intermediate storer from which they are withdrawn after a change in the rotary direction of the storer or after a change in the rotary speed of the storer, means for superimposing a second twist on the withdrawn section of twisted elements, and means for periodically changing the direction or speed of the storer to provide two successive sections of different stranding direction, said apparatus comprising an intermediate storer; driving means coupled to said intermediate storer for rotating said storer at a speed and direction of rOtation which changes by sections; and a pair of twisting brackets rotatably mounted for rotation around said intermediate storer and tightly coupled to each other, one of said twisting brackets supplying the twisted elements to said storer and the other of said twisting brackets withdrawing the twisted elements from said storer.

10. Apparatus as claimed in claim 6, wherein said apparatus comprises a plurality of parallel operating systems each of said systems comprising an intermediate storer, driving means coupled to said intermediate storer for rotating said storer at a speed and direction of rotation which changes by sections, and a pair of twisting brackets rotatably mounted for rotation around the intermediate storer and tightly coupled to each other, one of said twisting brackets supplying the elements to the storer and the other of said twisting brackets withdrawing the twisted elements from said storer, said apparatus further comprising additional twisting apparatus connected in common with said plurality of systems for twisting the twisted units provided by said systems into a twisted group in a single-operating step.