EP0007473A1 - Device for SZ stranding power current cable cores with a sector-shaped conductor cross-section - Google Patents

Abstract

For SZ stranding of non-pre-twisted high-voltage cable cores (2) with a sector-shaped conductor cross-section, two stranding heads (6,8)) are used, which are arranged behind or in front of a stranding nipple (5,9) and rotate synchronously with changing rotary movement. Before the first stranding point, a positive guide (4) is arranged for each cable core. The positive guides (4) and the stranding heads are arranged with the shortest possible distance (a, b) to the stranding points (5,9). In this way, an exact stranding geometry of the stranding assembly (7) is obtained in the area of the reversal points of the twist direction.

Description

The invention is in the field of manufacturing technology for electrical cables and deals with the SZ stranding of high-voltage cable cores with a sector-shaped conductor cross-section, with special attention to the mechanical forces that occur.

To make better use of the cable cross-section, it is common for multi-core power cables in the low and lower medium-voltage range (≤ 10 kV) to use cable cores with a sector-shaped conductor cross-section. These are stranded together with the same twist direction to form the cable core. Sector wires with and without pre-twist can be used. Sector cores without pre-twist are stranded together without reverse twist, whereby strong torsional stresses act on the sector cores during the stranding process. Sector wires with pre-twist are twisted together with reverse twist; here the torsional stresses are relative low ("Cable and wire production", combine VEB Kabelwerk Oberspree, VEB-Verlag Technik Berlin, 1976, page 200). When stranding sector cores, it is customary to arrange a positive guide for each core in front of the stranding nipple in order to fix the spatial position required for the stranding. Such positive guidance can consist of several profiled rollers arranged in a straight line one behind the other, between which the respective wire runs (DE-OS 22 11 111).

In addition to the usual stranding of the sector cores with a constant twist direction, a type of stranding is also known in which the sector cores are stranded with a twist direction that changes at intervals. Such a type of stranding has found its way into the manufacture of telecommunication cables and power lines under the name "SZ stranding" in recent years, but the SZ stranding machines developed for this purpose cannot be used for stranding sector wires without appropriate further development, since stranding large mechanical forces can be mastered by sector cores due to the large conductor cross-sections (Ξ 35 mm ² ).

In a known device for SZ stranding of sector wires without pre-twist, an oscillating stranding disk arranged in front of a stranding nipple is provided as the actual stranding tool, which is coupled to positive guides for the sector wires. With such a stranding device, of course, only one to two twist strands per stranding direction can be generated (DE-OS 25 14 033). Furthermore, it has already been proposed that the sector wires directed in front of the stranding nipple with a stranding device arranged between the first and a second stranding nipple to strand. This rotates in sections with alternating directions of rotation, so that the sector wires are stranded in the same direction in the first stranding nipple for the first time and in the second stranding nipple for the second time. The stranding device consists of one or two chuck pull-offs arranged one behind the other. If necessary, non-rotating collet deductions can be arranged between the stranding points and the stranding device, in order to ensure the same distances between the fixed and rotating parts of the stranding device which are decisive for the stranding in order to achieve a constant lay length. The direction of rotation of the stranding device is changed at intervals which are matched in a known manner to the storage capacity of the device (DE-OS 27 42 662).

For SZ stranding of round cable cores with a larger conductor cross-section, an SZ stranding machine is known which contains two stranding tools, namely an oscillating perforated disc and an oscillating stranding head in the form of a caterpillar take-off or a three-roller device. While the perforated disc is arranged in front of a first stranding nipple, the stranding head is located between the first and a second stranding nipple (DE-OS 24 12 199).

Furthermore, a stranding method is known for SZ stranding of wires for communication cables, in which the stranding elements are stranded with the aid of an elongated memory with alternating rotational movement. The stretched memory consists of two stranding heads arranged between two stranding nipples. The direction of rotation or the speed of the stranding heads is changed at intervals that correspond to the length of the stretched Memory are coordinated (FR-PS 14 47 458, DE-OS 22 30 972). For such stranding purposes it is also possible to use stranding heads which are designed in the manner of a caterpillar take-off (DE-OS 17 90 249) or consist of a deflecting roller which is once wrapped around by the stranded material and arranged tangentially to the stranding axis (DE-OS 17 65 452).

The invention has for its object to improve the already proposed stranding device for SZ stranding of non-pre-twisted power cable cores with a sector-shaped conductor cross section in such a way that the stranded material in the region of the reversal points of the twist direction has an accurate stranding geometry and that these reversal points are as short as possible.

The invention accordingly proceeds from a device for SZ stranding of high-voltage cable cores with a sector-shaped conductor cross-section, which consists of fixedly arranged core supplies, a first stranding nipple and, in front of it, a fixed guidance for each cable core and a second stranding nipple (stranding point), two between the stranding nipples arranged and assigned to the two stranding nipples, rotating synchronously with changing rotary motion (twisting heads) and consists of a take-off and winding device and in which the distance between the first stranding nipple and the first point of application of the first twisting device is the same or approximately the same as the distance between the last point of attack of the second twisting device and the second stranding nipple. According to the invention it is provided that the twisting devices and the positive guides immediately behind or in front of the respective stranding nipple or stranding point are arranged and that the distance between the last point of application of each positive guide on a cable core and the first point of application of the first twisting device to the stranded material is less than or equal to the lay length of the stranded material given by the take-off speed and the rotational speed or speeds of the stranding device , preferably less than or at most equal to half the length of the lay.

With a device designed in this way, the sector wires are effectively stranded together in a short way, the lengths of the torsion change points in the individual cable wires being matched to the length of the twist change points of the cable wires stranded together. In this regard, the invention is based, inter alia, on the consideration that the second twist of the stranding assembly in the region of the second stranding nipple proceeds without disruption when the first twisting in the region of the first stranding nipple has led to a precise stranding geometry. The prerequisite here is that the change in the rotational movement of the stranding heads is precisely matched to the distance between the two stranding nipples and stranding heads, that is to say to the storage length of the elongated memory formed by the stranding nipples and stranding heads.

The most accurate stranding geometry of the cable cores can be obtained if the torsion of the non-twisted cable cores and the formation of the torsion change points as well as the twist change points take place as short as possible and the forces required for this not only on the outer surface of the cable cores combined into one strand, but also on the individual cable cores themselves, as long as these are still stranded, attack. The path that is kept as short as possible should in no case be greater than a lay length of the stranded cable cores. In view of the lay lengths of around 150 cm customary in sector conductor cables, this means that the distance between the positive guides and the stranding device is as much as 60 to 100 cm.

To optimize the spacing depending on the type of sector wires to be stranded, it is advisable to arrange the positive guides and / or the stranding heads in their local position in relation to the stranding nipples so that they can be changed or adjusted independently of one another.

To form a clean stranding geometry, the first rotating stranding head and the positive guides for the cable cores should, as already mentioned, be spatially closely adjacent to one another. In this case, the flow of force from the rotating stranding head runs through the _V erseilgut to the positive guides on spatially relatively narrowly defined paths. The individual machine elements must be carefully dimensioned so that no wire damage occurs here. In order to be able to arrange the positive guides as close as possible to the stranding nipple, a configuration in ForD of several profiled guide rollers is recommended, which are each arranged along a corrugated line on the inside of the corrugated line. Some of the guide rollers arranged on both sides of the wavy line can face each other in pairs or in a gap, in particular in an area in which the wavy line changes its curvature. With such a configuration of the positive guidance, the longitudinal forces acting during the withdrawal movement of the cable cores are converted into transverse forces.

Particularly large forces can be taken up by a positive guide, if this consists of two deflection pulleys arranged one behind another, on which the respective cable core rests with a wrap angle of at least 90 ^0th Such deflection disks provided with a profile groove permit particularly gentle treatment of the sector-shaped cable cores. In order to avoid a too large distance between the last deflection plate and the stranding nipple, this distance can be bridged by one or more profiled guide rollers; these guide rollers are expediently arranged along a curved line, so that the respective cable core is pressed against these profile rollers by converting longitudinal forces into transverse forces.

The stranding heads arranged behind or in front of the stranding nipples must also be designed with regard to the transmission of the greatest possible forces and with regard to the arrangement as close as possible to the stranding nipples. Caterpillar belt arrangements or clamping jaw or collet devices are suitable for this. The use of a single-disc twister, in which the stranding head consists of a deflecting disc which is once wrapped around by stranded material and is arranged approximately symmetrically with respect to the stranding axis, is also advantageous with regard to gentle handling of the stranded material. Since the stranded material is deflected from the stranding axis in this case, very large torsional forces can be transmitted to the stranded material by using the leverage effect. In order to move the point of application of such a stranding head as close as possible to the stranding nipple, it is necessary to assign one or more guide rollers to each of the deflection sheaves for feeding and removing the stranded material. Exemplary embodiments of the new SZ stranding device are shown in FIGS. 1 to 4.

The devices shown schematically in the figures essentially consist of construction elements as are known to the person skilled in the art, such as a spool, perforated disc, deflection roller, positive guidance, stranding nipple, stranding head, caterpillar belt or jaw extraction, extruder, water cooling section, extraction and winding device. A constructive representation of these components is therefore omitted.

The device shown in FIG. 1 is used for stranding three high-voltage cable wires 2 to form a stranding assembly 7. The plastic-insulated cable wires 2 have a sector-shaped conductor cross section and are not pre-twisted. They run from fixedly arranged core supplies 1 and are fed to the stranding nipple 5 via deflection rollers 3 and positive guides 4.

Behind the stranding nipple 5 and in front of the take-off device 9, which forms a stranding point, a stranding head 6 or 8 rotating with an alternating rotational movement is arranged, which non-positively embraces the cable wires brought together in the stranding nipple 5 from outside and twists or strands together. Each stranding head consists of a caterpillar belt arrangement or an arrangement in the manner of a clamping jaw trigger. The crawler belts or clamping jaws are driven in the direction of the stranding axis by the stranding material passing through at a constant take-off speed v, but can also be driven from the outside and move the stranding material in the longitudinal direction of the stranding axis. The rotary movement, ie the speed or the direction of rotation, of the stranding heads 6 and 8 is changed synchronously at intervals which are in be are known to be matched to the running time of a longitudinal element of the stranded material from the first to the second stranding nipple or from the first to the second stranding head. Behind the stranding head 8, the stranded material is gripped by the take-off device 9 and wound onto the winding device 10.

In the area between the stranding heads 6 and 8, with changing direction of rotation of the stranding heads, the reversal points of the twisting direction of the stranded material cannot be expected to rope up under the influence of tensile stresses, since the cable wires 2 are plastically deformed in the region of the reversal points and thus ensure a stable stranding geometry . If necessary, however, special guide elements for the stranded material can be arranged between the stranding heads 6 and 8. In addition, the take-off device 9 can be omitted if one or both alternating rotating twisting heads take over their function. A deflection pulley or the like is then to be provided as the second stranding point.

The effective distance of the stranding head 6 from the stranding nipple 5 is denoted by b, the effective distance of the constraint 4 from the stranding nipple 5 by a. The sum of the distances a and b and thus also the length c between the stranding head 8 and the stranding point formed by the take-off 9 should be less than a lay length of the verscil material.

In the device shown in FIG. 1, the positive guides 4 consist of pairs of opposing roller groups, the individual rollers being profiled and these profiles being precisely adapted to the cross-sectional shape of the sector wires 2. The profiling and the contact pressure between the roller groups prevent that the sector wires 2 rotate in the area of the positive guides 4. The longitudinal movement of the sector veins is not hindered.

In Fig. 2 positive guides 11 are shown, which also consist of profiled deflection rollers 12. However, these deflection rollers are arranged on a wavy line, in particular an S-shaped curved line, so that the deflection of the cable cores which is achieved in this way results in the effective longitudinal as a result of the withdrawal movement. forces are converted into lateral forces. A special pressing of the profile rollers 12 on the cable cores is therefore not necessary. In the area of the change in curvature of the wavy line, deflecting rollers face each other in pairs or at a gap. The advantage of such an arrangement can be seen in the fact that a particularly small distance between the last guide roller of a forced guide 11 and the stranding nipple 5 can be achieved.

Fig. 3 shows a positive guide 13, which can absorb particularly large forces. For this purpose, two relatively large, profiled guide pulleys 14 and 15 are respectively provided, which are arranged one behind the other and are wrapped around a cable core over an angle of approximately 180 ^0th The distance between the outlet point of a cable core on the second deflection disk 15 and the stranding nipple 5 is expediently bridged using one or more profiled guide rollers 16. It is advisable to arrange the guide roller 16 in such a way that the cable core is guided on a curved line on the way from the deflection disk 15 to the stranding nipple 5.

Fig. 3 shows an advantageous embodiment of a Ver arranged behind the stranding nipple 5 Rope head 17. This is constructed in the manner of a single-disk twister and consists of the deflection disk 18, once wrapped by the stranded material 7, to which two guide rollers 19 are assigned in each case for the supply and removal of the stranded material. Such a stranding head requires relatively large transverse dimensions depending on the diameter of the stranded material, but with regard to the lay length of approximately 1.5 m provided for cable cores with a conductor cross section of, for example, 150 mm ² , this results at a take-off speed of, for example, 40 to 75 m / min Speeds of the stranding head in the order of 10 to 60 U / min. The inertial forces of such a stranding head that occur during stranding are, however, significantly smaller than in the case of conventional stranding with rotating coils.

The profile of the deflection disk 18, which can optionally also be designed as a pull-off disk, is slightly conical. The center of gravity of the deflection disk 18 is preferably somewhat outside the stranding axis.

FIG. 4 shows a device in which the stranding of the cable cores 2 to form a stranding association 7 is linked to an extrusion process for applying a cable sheath and with which a complete cable 25 can therefore be produced from cable cores 2. For this purpose, the stranding part, which essentially corresponds to the devices shown in FIGS. 1 and 3 and contains the two stranding heads 17 and 20, is followed by an extrusion line formed from the extruder 23 and the water cooling channel 24, which runs parallel to the stranding path and the stranding bandage 7 is fed via the deflection disks 21 and 22. In a modification of this embodiment there is also Possibility to connect the stranding of the cable cores 2 with the extrusion of the core insulation by allowing conductor ropes 1 to run off from the storage drums, which are then immediately wrapped using an extruder and a water cooling section, as described in patent application P 28 33 702.2.

When SZ stranding of sector wires by means of a stranding device, the stranding heads of which only change the speed but not the rotational movement, the take-off speed and speeds can be coordinated so that the lay length of the stranded material in the area of the stranding device, for example, alternately + 66 cm and + 200 cm, so that there is a lay length of + 100 cm in the finished stranded material. If the lay direction remains the same within the stranding device, it is ensured that large shear forces can be transferred from the stranding heads to the stranded material without the stranding elements (sector cores) lying parallel in one plane in the area of the twist change points.

Claims (7)

1.Device for SZ stranding of high-voltage cable cores with a sector-shaped conductor cross-section, consisting of fixed core wires, a first stranding nipple and prior to that a fixed guide for each cable core and a second stranding nipple (stranding point), two between the stranding nipples and the two stranding nipples each assigned rotating devices (twisting heads) rotating synchronously with changing rotary motion and from a take-off and winding device in which the distance between the first twisting nipple and the first point of application of the first twisting device is equal to or approximately the same as the distance between the last point of application of the second twisting device and the second stranding point,
characterized in that the twisting devices (6, 8) and the positive guides (4) are arranged immediately behind or in front of the respective stranding nipple (5,9) and in that the distance (a + b) between the last point of application of each positive guide (4th ) on a cable core and the first point of application of the first twisting device (6) to the stranded material is less than or at most equal to the lay length of the stranded material given by the take-off speed and the rotational speed or speeds, preferably less than or equal to half the lay length. 2. Device according to claim 1, characterized
characterized in that the distance (a) between each positive guide (4) and the stranding point (5) and the distances (b, c) between the stranding points (5,9) and the stranding devices (6,8) are independently adjustable. 3. Device according to claim 1 or 2, characterized
characterized in that each positive guide (11) consists of a plurality of profiled guide rollers (12) which are each arranged along a corrugated line on the inside of the corrugated line. 4. The device according to claim 3, characterized
characterized in that some of the guide rollers (12) arranged on both sides of the shaft line face each other in pairs or at a gap. 5. The device according to claim 1 or 2, characterized
in that each positive guide (13) consists of two guide pulleys (14,15) on which the respective cable core (2) rests with a wrap angle of at least 90 ^0th 6. The device according to claim 5, characterized
characterized in that one or more profiled guide rollers (16) are arranged between the second deflection disc (15) and the stranding nipple (5). 7. Device according to one of claims 1 to 6,
characterized in that each twisting device (17, 20) consists of a deflecting disc (18) once wrapped around by the stranded material (7) and arranged approximately symmetrically with respect to the stranding axis, each of which has one or more guide rollers (19) for supplying and removing the stranded material (7) ) assigned.

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