Cable shielding

Abstract

The invention relates to a cable screen and to an electrical conductor having such a cable screen. The cable screen has a first wire winding and a second wire winding. The first wire winding has a plurality of turns. The first wire winding is wound in a first direction with a first pitch about a longitudinal axis. The second wire winding has a plurality of turns. The second wire winding is wound in a second direction different from the first direction with a second pitch about the longitudinal axis. Turns of the plurality of turns of the first wire winding and corresponding turns of the plurality of turns of the second wire winding cross each other at first crossing points, respectively, such that a plurality of the first crossing points of the first wire winding and the second wire winding lies in the direction of the longitudinal axis. The plurality of the first crossing points extends at least approximately helically in the direction of the longitudinal axis.

Description

TECHNICAL FIELD

[0001] The present invention relates to a cable shield and to a power cable having such a cable shield. BACKGROUND

[0002] A shield is an electrically conductive protective sheath which surrounds a device, a space or a transmission medium, for example a cable. For the sake of distinction, a shield of a device is often referred to as a device shield, a shield of a space is referred to as a space shield and a shield of a transmission medium is referred to as a cable shield.

[0003] A cable shield is used for a transmission medium, for example a cable. An electrical conductor conducts electrical power for various purposes. The current in an electrical conductor always produces a magnetic field along with the flow of the current. It is generally desirable to reduce the influence of such a magnetic field on other devices and equipment, as it can lead to undesired malfunctions of electrically or electronically operated devices. This is often summarized under the term electromagnetic compatibility (EMC). A shield reduces electromagnetic interference on the signal transmission conductor or in the device on the one hand. On the other hand, a shield also reduces the leakage from the cable or the device into the environment.

[0004] In cable shields, a distinction is made between foil shields and braided shields and combinations of both. Foil shields are more effective at high frequencies, while braided shields are more effective at low frequencies. Foil shields and braided shields can also be combined and, for example, placed in layers alternately. The quality of a shield depends on the coverage, which is expressed as shield attenuation or shield effectiveness. It directly enters the coupling resistance, also called shield coupling impedance or transmission impedance. The transmission impedance is the ratio of the high-frequency (HF) interference voltage induced on the data line to the resulting HF interference current flowing through the shield. The smaller the transmission impedance, the better the shielding effect. In addition to the mentioned cable shields, there are also special cables in which the shield is a copper tube. These cables are distinguished by a very high shield effectiveness.

[0005] In addition to the stresses related to its electrical and / or magnetic properties, a cable shield is also subjected to mechanical stresses. In a braided shield, the braided wires subjected to movement experience a movement relative to one another and are accompanied by friction. In addition, these wires are also subjected to traction and thrust loads. This leads to a limited service life of the wires and thus to a limited service life of the braided wires. Shields with reverse wire wrapping (Drahtumspinnung) have a higher mechanical service life. However, the shield can move here and locally produce, for example, nesting and / or holes. As mentioned above, this has a negative effect on the electrical properties.

[0006] There is therefore a need to improve cable shields. In particular, there is a need for cable shields which have a greater resistance to mechanical stresses and thus have more stable electrical properties. SUMMARY

[0007] According to a first aspect of the present application, a cable shield is presented. The cable shield has a first wire winding and a second wire winding. The first wire winding has a plurality of turns. The first wire winding is wound in a first direction around a longitudinal axis with a first pitch. The second wire winding has a plurality of turns. The second wire winding is wound in a second direction different from the first direction around the longitudinal axis with a second pitch. Turns of the plurality of turns of the first wire winding and corresponding turns of the plurality of turns of the second wire winding cross each other at first crossing points, respectively. Turns of the plurality of turns of the first wire winding and corresponding turns of the plurality of turns of the second wire winding cross each other at first crossing points, respectively, such that a plurality of the first crossing points of the first wire winding and the second wire winding lies in the direction of the longitudinal axis. The plurality of the first crossing points extends at least approximately helically in the direction of the longitudinal axis.

[0008] The helical extension can also be described as a solenoid, a vortex or a coiled coil extension. The helical extension of the first crossing points (which can also be described as overlapping points ) ensures a good / increased stability against pulling, twisting and alternating bending movements. The longitudinal axis can be a longitudinal axis of the cable shield (braid shield). The cable shield can be at least approximately cylindrical. The crossing points can thus extend helically along the cable shield (braid shield).

[0009] The first wire winding can have at least one first wire. The at least one first wire can be wound around the longitudinal axis such that the winding of the first wire around the longitudinal axis extends helically. The second wire winding can have at least one second wire. The at least one second wire can be wound around the longitudinal axis such that the winding of the second wire around the longitudinal axis extends helically (solenoid / vortex / coiled coil).

[0010] In the cable shield, due to the fact that the wires are interwoven at least once per turn, the arrangement of the first wire winding and the second wire winding relative to each other can be seen as a combination of wire wrapping and braiding, where both wire windings are interwoven with themselves at least at one point per turn. In this regard, the cable shield can be described as a two-layer wire wrapping with the crossing points extending helically / intersections extending helically.

[0011] A turn of the first second wire winding can be understood as a complete rotation in the circumferential direction from a starting position to an end position. In this case, the starting position and the end position do not have to coincide in the longitudinal axis direction, taking into account the first pitch. The starting position and the end position must only coincide in the circumferential direction around the longitudinal axis in order to form a turn. If the first pitch is not equal to 0, the starting position and the end position will differ from each other in the longitudinal axis direction. A turn of the second wire winding can be understood as a complete rotation in the circumferential direction from a starting position to an end position. In this case, the starting position and the end position do not have to coincide in the longitudinal axis direction, taking into account the second pitch. The starting position and the end position must only coincide in the circumferential direction around the longitudinal axis in order to form a turn. If the second pitch is not equal to 0, the starting position and the end position will differ from each other in the longitudinal axis direction.

[0012] Correspondingly, a "corresponding turn" can be understood as a turn of the first wire winding and a turn of the second wire winding, which respectively correspond when they at least almost coincide in their position, for example at least almost coincide such that they can cross in their normal extension in the case of counter- winding.

[0013] A turn of the plurality of turns of the first wire winding and a corresponding turn of the plurality of turns of the second wire winding can respectively cross at a second crossing point. A turn of the plurality of turns of the first wire winding and a corresponding turn of the plurality of turns of the second wire winding can respectively cross at a second crossing point, such that a plurality of second crossing points of the first wire winding and the second wire winding lies in the longitudinal axis direction. The plurality of second crossing points can respectively extend at least approximately helically in the longitudinal axis direction.

[0014] The extension of the plurality of first crossing points in the longitudinal axis direction and the extension of the plurality of second crossing points in the longitudinal axis direction can be at least almost parallel to each other. Thereby two at least almost parallel helical lines (spiral / vortex / coil) of crossing points can be generated.

[0015] A turn of the plurality of turns of the first wire winding and a corresponding turn of the plurality of turns of the second wire winding can respectively cross at a number of crossing points. A turn of the plurality of turns of the first wire winding and a corresponding turn of the plurality of turns of the second wire winding can respectively cross at a number of crossing points, such that a plurality of the number of crossing points of the first wire winding and the second wire winding lies in the longitudinal axis direction. The plurality of the number of crossing points can respectively extend at least approximately helically in the longitudinal axis direction. The plurality of the number of crossing points can respectively extend at least approximately parallel to each other in the longitudinal axis direction.

[0016] Multiple of the intersections may extend at least approximately parallel to each other in the longitudinal direction. Alternatively, the spiral extensions of the multiple first intersections may be parallel to the spiral extensions of the multiple second intersections, and, if applicable, to the spiral extensions of the multiple third intersections, etc.

[0017] The first pitch and the second pitch can have the same value. The first direction of the first conductor winding and the second direction of the second conductor winding are different from each other. The first direction and the second direction can be at least nearly opposite to each other. In this respect, the first conductor winding and the second conductor winding can be described as conductor windings with opposite directions. The first conductor winding and the second conductor winding can extend in opposite directions and with the same pitch, respectively.

[0018] The first and second conductor windings can typically cross at their intersection point so that they interweave with each other at the intersection point. This can provide a braid with opposite directions, that is, a braid of two conductor windings extending in opposite directions.

[0019] For example, the first and second conductor windings can extend symmetrically about a plane passing through the longitudinal axis of the cable shield. Viewed in cross-section of the cable shield, the first and second conductor windings can be arranged symmetrically to each other, for example, symmetrical about the longitudinal axis of the cable shield. The first conductor winding can have one or more first conductors, or be composed of one or more first conductors. The second conductor winding can have one or more second conductors, or be composed of one or more second conductors. Alternatively, a single first conductor or a bundle of first conductors can form the first conductor winding, and a single second conductor or a bundle of second conductors can form the second conductor winding.

[0020] The intersections / overlaps of the spiral extension increase the stability of the cable shield against dragging, torsion, and / or alternating bending movements. Therefore, by using cable shielding according to the first aspect, the service life of the cable shield under mechanical stress conditions can be increased in two or three dimensions. Over the service life of the cable shield, this is accompanied by better electrical performance (i.e., better electrical characteristics, such as EMC, leakage current, etc.).

[0021] According to a second aspect, a power cable is proposed. The power cable has at least one electrical conductor and a cable shield arranged around the electrical conductor according to the first aspect.

[0022] Due to the shielding, the measurable magnetic field of the electrical conductor is significantly reduced compared to a known conductor without shielding. Furthermore, the cable shielding is mechanically stable. Additionally, the cable sheath / outer sheath can be arranged around the cable shielding.

[0023] Even if some of the above aspects and details are described in relation to a cable shield according to the first aspect, these aspects can be implemented in a corresponding manner in a cable according to the second aspect as well. BRIEF DESCRIPTION OF DRAWINGS

[0024] The application will be further explained below with reference to the drawings. These drawings show schematically:

[0025] Figure 1a Cable shield according to examples;

[0026] Figure 1b Cable shield according to possible embodiments of the application. DETAILED DESCRIPTION

[0027] In the following, specific details are set forth in connection with the application to provide a thorough understanding of the application. However, it will be apparent to those skilled in the art that the application can be practiced in other exemplary embodiments that depart from these specific details.

[0028] Figure 1a A cable shield, more precisely a braided shield 1 for a cable, is schematically shown. The braided shield 1 has a first wire winding 2 which extends helically in the direction of a longitudinal axis 1a of the braided shield 1 with a first pitch in a first rotational direction. Expressed in another way, seen from a lower end of the braided shield 1, i.e. the arrow direction of the longitudinal axis 1a, the first wire winding 2 is wound upwards in a counter clockwise direction with the first pitch. The braided shield 1 has a second wire winding 3 which extends helically in the direction of the longitudinal axis 1a of the braided shield 1 with a second pitch in a second rotational direction. Expressed in another way, seen from the lower end of the braided shield 1, i.e. the arrow direction of the longitudinal axis 1a, the second wire winding 3 is wound upwards in a clockwise direction with the second pitch. In Figure 1a In examples of the application, the first pitch corresponds to the second pitch.

[0029] As Figure 1a shown, a turn of the first wire winding 2 and a turn of the second wire winding 3 overlap at a point. This point is described as a crossing point 4 or an overlap point. In Figure 1a In examples of the application, the two wire windings 2, 3 interweave each other at the crossing point 4. Since each of the windings 2, 3 has a number of turns in the direction of the longitudinal axis 1a, there are a number of such crossing points in the direction of the longitudinal axis 1a, even if there is one crossing point per turn. In Figure 1a In examples of the application, it can be seen that these crossing points are located on a straight line 5 which is parallel to the direction of the longitudinal axis 1a. It can be said that due to the interweaving, the two windings 2, 3 form two layers, and thus can also be described as two layers of wire wrapping, and due to the crossing points being parallel to the longitudinal axis 1a, can be described as two layers of wire wrapping with axially extending intersections.

[0030] Figure 1aThe wires / wire windings 2, 3 of the braided / braided shield 1 in the motion exposed to, experience a movement relative to each other and with friction. In addition, these wires / wire windings 2, 3 experience traction and thrust loads. This leads to a limited service life of the wires / wire windings 2, 3 and thus to a limited service life of the braided / braided shield 1.

[0031] Although Figure 1a The braided shield 1 with oppositely directed wire packings has a relatively high mechanical service life and a higher mechanical service life than conventional braiding (for example with wires of the same direction), but the braided shield 1 can move, or more precisely the wires of the braided shield 1 can move and form for example nests and holes. This has a negative effect on the electrical performance of the braided shield 1.

[0032] Figure 1b A cable shield according to exemplary embodiments, more precisely a braided shield 10 for a cable, is schematically shown in Figure 1a The braided shield 10 has a first wire winding 20 which extends helically in the direction of the longitudinal axis 10a of the braided shield 10 with a first pitch in a first rotational direction. Expressed in another way, seen from the lower end of the braided shield 10, i.e. in the direction of the arrow of the longitudinal axis 10a, the first wire winding 20 is wound upwards in a counterclockwise direction with the first pitch. The braided shield 10 has a second wire winding 30 which extends helically in the direction of the longitudinal axis 10a of the braided shield 10 with a second pitch in a second rotational direction. Expressed in another way, seen from the lower end of the braided shield 10, i.e. in the direction of the arrow of the longitudinal axis 10a, the second wire winding 30 is wound upwards in a clockwise direction with the second pitch. In Figure 1b In the example shown, the first pitch corresponds to the second pitch, i.e. each individual complete turn of the wire windings 20, 30 runs back in the direction of the longitudinal axis 10a the same path W. A turn is described herein as one complete rotation of the wires of the respective winding 20, 30.

[0033] As shown in Figure 1b The turns of the first wire winding 20 and the turns of the second wire winding 30 each overlap at one point. This point is described as a crossing point 40 or overlap point. In Figure 1b In the example shown, the two wire windings 20, 30 are also interwoven at the crossing point 40. Since each of the wire windings 20, 30 has a plurality of turns in the direction of the longitudinal axis 10a, there are a plurality of such crossing points 40 in the direction of the longitudinal axis 10a, even in the case of one crossing point per turn. In Figure 1bIn the example of Fig. 1, it can be seen that the crossing points 40 extend in the form of helical lines 50, or spirals, i.e. do not form any straight lines extending in the direction of the longitudinal axis 10a. Due to the interweaving, the two wire windings 20, 30 form two layers, and can thus also be described as two-layer wire wrapping, and due to the spiral extension 50 of the crossing points 40, as two-layer wire wrapping with spirally extending crossing points.

[0034] For simplicity and clarity, in Figure 1b Fig. 1 only one crossing point 40 per turn is shown, more precisely one crossing point per turn of the wire winding 20 and the respective wire winding 30. However, the turns of the wire winding 20 and the respective turns of the wire winding 30 can cross at more than one point, i.e. at several points, respectively, at which they interweave with each other. For example, the wire winding 20 and the wire winding 30 interweave with each other at one or more of their turns, for example not only once but twice or, if applicable, several times per turn, thus having a first crossing point 40, a second crossing point and, if applicable, a further crossing point per turn. In this case, there are multiple first crossing points 40, multiple second crossing points and, if applicable, further multiple crossing points in the direction of the longitudinal axis 10a. The multiple first crossing points 40 can be described by a first helical line / spiral 50 in the direction of the longitudinal axis 10a. The multiple second crossing points can be described by a second helical line / spiral in the direction of the longitudinal axis 10a parallel to the first helical line / spiral. The further multiple crossing points can be described by a further helical line / spiral in the direction of the longitudinal axis 10a parallel to the first helical line / spiral 50 and the second helical line / spiral.

[0035] In contrast to the Figure 1a braid shield 1 described with axially extending overlapping points 4, Figure 1b The braid shield 10 described with axially extending crossing points 40 is more stable against pulling, twisting and alternating bending movements. The shield provided by the braid shield 10 as a combination of wire wrapping and braiding is only intertwined with itself per turn at one point of the circumference or at several points of the circumference, one pair per turn. The points of interweaving extend / helically extend along the longitudinal axis 10a, e.g. the product axis, of the braid shield 10. This increases the service life of the cable's shield 10 under two- or three-dimensional mechanical stress situations. This way, better electrical performance, i.e. better electrical properties, are additionally obtained over the service life, e.g. in terms of EMC, leakage current, etc.

Claims

1. A cable shield, having: a first wire winding having a plurality of turns, wherein the first wire winding is wound in a first direction around a longitudinal axis at a first pitch; a second wire winding having a plurality of turns, wherein the second wire winding is wound in a second direction different from the first direction around the longitudinal axis at a second pitch; wherein turns of the plurality of turns of the first wire winding and corresponding turns of the plurality of turns of the second wire winding cross each other and interweave with each other at first crossing points, respectively, such that a plurality of the first crossing points of the first wire winding and the second wire winding are located in the longitudinal axis direction and the plurality of the first crossing points extend approximately helically in the longitudinal axis direction.

2. The cable shield of claim 1, wherein, turns of the plurality of turns of the first wire winding and corresponding turns of the plurality of turns of the second wire winding cross each other and interweave with each other at second crossing points, respectively, such that a plurality of the second crossing points of the first wire winding and the second wire winding are located in the longitudinal axis direction and the plurality of the second crossing points extend approximately helically in the longitudinal axis direction.

3. The cable shield of claim 1 or 2, wherein, turns of the plurality of turns of the first wire winding and corresponding turns of the plurality of turns of the second wire winding cross each other and interweave with each other at a number of crossing points, respectively, such that a plurality of the number of crossing points of the first wire winding and the second wire winding are located in the longitudinal axis direction and the plurality of the number of crossing points extend approximately helically in the longitudinal axis direction, respectively.

4. The cable shield of claim 3, wherein, the plurality of the number of crossing points extend approximately parallel to each other in the longitudinal axis direction, respectively.

5. The cable shield of claim 1, wherein, the first pitch and the second pitch have the same value.

6. The cable shield of claim 1, wherein, the first direction and the second direction are almost opposite to each other.

7. A power cable, having: at least one electrical conductor; and a cable shield according to any one of claims 1 to 6 arranged around the electrical conductor.

Images