EP2823493A1

EP2823493A1 - Method for producing a stranded inner conductor for coaxial cable, and coaxial cable

Info

Publication number: EP2823493A1
Application number: EP13707149.4A
Authority: EP
Inventors: Nikolaus Fichtner; Franz Manser
Original assignee: Huber and Suhner AG
Current assignee: Huber and Suhner AG
Priority date: 2012-03-05
Filing date: 2013-02-26
Publication date: 2015-01-14
Anticipated expiration: 2033-02-26
Also published as: US10056172B2; US20150096781A1; JP6195385B2; WO2013131779A1; CN104205251A; JP2015516644A; ES2601654T3; CN104205251B; CH706228A2; EP2823493B1

Abstract

The invention relates to a method for producing a stranded inner conductor (1), and to a coaxial cable (9). In a first step, a stranded inner conductor (2) is provided, which consists of several wires (3) twisted together. Then the stranded inner conductor (1) is rotary swaged by means of a rotary swaging device (10). In a further step, the rotary swaged stranded inner conductor (3) is enclosed with a dielectric (4). In a further step, the dielectric (4) is enclosed with an outer conductor (5) and a cable sheath (6).

Description

METHOD FOR THE PRODUCTION OF A HEADLINDER FOR COAXIAL CABLES, AND COAXIAL CABLES

The invention is in the field of inner conductor for a coaxial cable, respectively, the coaxial cable for Ü transmission of high frequency signals.

Coaxial cables for transmitting high frequency signals are known in the art. These cables have an inner conductor, which is surrounded by a dielectric and an outer conductor.

Rotary kneading machines have been known from the prior art since the beginning of the last century, by means of which ductile materials can be formed continuously or discontinuously. As a rule, these swaging machines have a forming tool consisting of two or four jaws arranged opposite each other in pairs. The jaws of the forming tool are deflected, for example, by rollers rotating in the outside in the radial direction inwards. At the same time, they move in the circumferential direction. The U mformwerkzeug has a central, usually continuous working opening, which has a tapered cross-section in the longitudinal direction. Workpieces to be machined can be introduced into the work opening of the mold and can be removed again by the same or, in the case of a continuous process, an opposite second opening. In the interior of the work opening, the workpiece is continuously formed by the jaws moving in the radial and in the circumferential direction. The working opening has a variable cross-section due to the movement of the jaws. Rotary kneading z. B. used in the manufacture of wire ropes or forgings in the auto industry. Out of the tentliteratur are several applications for rotary kneading known. Some selected examples are briefly described below.

US Pat. No. 6,644,444 B2 to Yazaki Corporation, issued Apr. 4, 2001, describes a structure and method for assembling an electrical cable and a cable end by means of rotary swaging. For this purpose, the insulation is replaced only at the cable end, so that the stranded conductor is exposed. This is then inserted into a hollow cylindrical sleeve. By means of rotary swaging, the sleeve is then compressed in the radial direction. Compression compresses the stranded conductor and thus lowers the electrical resistance.

US Pat. No. 7,746,333B2 to Yazaki Corporation, issued July 1, 2007, also describes a method for connecting an electrical cable to a cable end. For this purpose, an electrically conductive adhesive (for example a paste of epoxy and nickel powder) is introduced into a tubular end of a cable end piece. Subsequently, the previously stripped stranded conductor of the cable end is inserted into the bore. By means of rotary swaging, the tubular cable end piece is then radially compressed and brought into close contact with the stranded conductor. The nickel powder in the paste is intended as a conductive filler destroy possible oxide layers on the metal parts and increase the conductivity.

Japanese publication JP7226118A2 of Yazaki Corporation describes the use of a rotary swaging method to prevent uncontrolled deformation of a wire rope in a subsequent rolling process. The use of a multilayer stranded wire rope is provided. The rolling process serves to reduce the diameter, or to extend the wire rope. Japanese publication JP7249329A2 of Yazaki Corporation describes the production of a compacted concentric multi-layered wire rope and an apparatus for its production. In the method described, the rope is first stranded from several wires. Before winding, the rope is radially compacted and reshaped with a rotary swaging tool.

The Japanese patent JP3257388B2 Yazaki Corporation describes the geometry of meh erer different molds for the compression of multilayer, stranded wire strands by means of rotary swaging. Since relative rotations between the wire rope and the rotary swaging tool can lead to damage of the wire rope, at least at high densities, the kneading jaws in the closed state do not form a circular cross-section but a flattened cross-section at the back edges.

German laid-open specification DE1 9835901 A1 to River Seiko KK and Asahi Optical Co. Ltd. describes an endoscopic wire loop of corrosion resistant wire that can be used, for example, using high frequency electrical current for the surgical removal of polyps. Such loops are typically made from stranded wires according to DE'901. A common feature of corresponding slings is a strong U-shaped curve at its distal end, which is intended to allow a better withdrawal of the sling into the sleeve-shaped endoscopic guide instrument. However, the very small radius of curvature in the U-shaped part leads in practice to a loosening and irregular deformation of the wires of the strand, which leads to a disorderly spreading of the wires. Under heavy mechanical load or Joule heating this can lead to failure of the tool. The method used in DE '901 is based on a swaging operation in which a stranded wire is passed through a die whose bore has a (8-1.5%) smaller diameter than the strand. This leads to a radial compression of the strand. This leads to a deformation of the wires of the strand and disappearance of the gaps between the wires. The wires on the surface thus have a trapezoidal cross-section and the entire stranded wire a very smooth surface. The resulting stranded wire should retain this smooth surface, even in the case of strong curvature, or it should not be spliced into its wires. In addition, the wire according to the invention is certified as having a "quality appearance of higher quality", according to which a wire loop instrument made therefrom has a high commercial value.

GB79441 1 A of British Ropes Ltd. was published in 1 958 and claims a method, as well as a means for its execution, to treat ropes in such a way that their wires receive a cross-section deviating from the round shape under the influence of external radial forces. Characteristic of this method is a constant during the U molding in the area of the radial compressive forces acting axial prestressing of the rope. This axial force leads in cooperation with the radial force to an extension of the rope or the strand. The axial force is chosen so that the wire material begins to flow. Radial forces can be exerted by means of a rotating tool.

US6023026 of Nippon Cable Systems Inc. was published in 2000 and describes a new type of round kneaded forged steel cord which has both high mechanical flexibility / flexibility and high tensile strength. These improved properties result from an optimized construction of the individual cable strands as well as specified ratios of wire diameters and a measure of the compression during the forming process. DE1 943229 (or US365 1 243) from the company Western Electric Co. Inc. was first published in 1970 and deals with a coaxial cable with a stranded inner conductor. Unwanted peaks in return loss are reduced by variation in lay length during stranding.

An object of the invention is to provide a method for producing an improved Litzeninnen conductor, respectively, an improved coaxial cable for Ü transmission of high-frequency signals to show.

This object is achieved by the method defined in the claims.

Today's coaxial cable have inner conductor of a wire or strands inner conductor of meh eral wires. The inner wires, which consist of several wires, are usually stranded before they are installed in the cable. In the development of high-quality cables for the high-frequency range, it has been shown that the internal architecture as well as the surface quality of the stranded conductors used can have a significant influence on their mechanical and electrical properties. Compared to solid wire conductors, stranded conductors have increased mechanical flexibility and reduced susceptibility to breakage. However, there is the danger, among other things, that they spread apart at curvatures below a critical bending radius, that is, the dense arrangement of the wires loosens and separates them. This can lead to a deterioration of the transmission characteristics and thus problems with the use of the cable. In coaxial cables with inner strand conductors, the architecture of the inner conductor has two disadvantages compared to cables with inner conductors made of a single solid wire. On the one hand, the return loss (henceforth RL) has minima at certain frequencies and, on the other hand, an increased insertion loss (henceforth IL). Commercially available coaxial cable core conductors have a frequency-dependent return loss (RL), which has a negative effect on the transmission characteristics and is caused by defects in the cable. The return loss refers to a logarithmic measure of the ratio of injected signal energy to reflected signal energy at a fixed signal frequency. The return loss is usually indicated by the unit d B (for decibels). Since the reflected signal energy is always smaller than the injected signal energy, the return loss is always a positive quantity. In principle, coaxial cables must be designed so that the return loss is maximized and thus the maximum signal energy is transmitted. Typical values of the return loss are in the range from 20 d B to 30 d B, which corresponds to a reflected signal energy of 1% or of 0. 1% of the injected signal energy. In coaxial cables with inner strand conductors, the return loss often M inima at signal frequencies, which are given by the structural design of the Litzeninnenleiters. These minima will henceforth be referred to as RL peaks. It is known from the above-mentioned DE 1 943229 that RL tips can be reduced by varying the length of the litz wire along the strand. The length of the litz wire or short lay length is the length which a wire of the strand covers during a revolution along the strand. Due to design and manufacturing, the variation of the length of the litz wire can only be carried out between an upper and a lower limit, ie between a minimum and a maximum lay length. In general, the variation of the strand strike length between these extremes is not sufficient to eliminate all RL tips.

There are several approaches to reducing the I L value. A costly approach is to insulate isolated (painted) wires. One approach is the coating of strands z. As with silver or other material (precious metal), which improves the conductivity. By means of the method according to the invention, the problems described above can be reduced and the transmission properties of a coaxial cable produced according to the method according to the invention can be improved. By means of the method according to the invention, the electrical and at the same time mechanical properties of cables can be improved.

A method according to the invention for producing a coaxial cable generally has the following method steps:

(a) producing a stranded inner conductor by stranding a plurality of wires with a constant and / or a variable lay length;

(b) rotary kneading the strand inner conductor by means of a rotary swaging device;

(c) enveloping the strand inner conductor with a dielectric;

(d) enveloping the dielectric with an outer conductor;

(e) U enveloping the outer conductor with an outer jacket.

If necessary, the surface of the wires is coated prior to stranding and / or prior to swaging. Good results can be achieved with coatings of silver, gold or tin.

Advantages of a stranded and round-knit strand core conductor produced by the method according to the invention include the following: (a) The inner conductor of the invention has a homogeneous outer surface, which is comparable to the surface of a single wire.

(b) The inner strand conductor according to the invention has compacted and more homogeneous inner surfaces, which counteract a negative oxide formation.

(c) When swaging, damage to the coating of the individual wires can be avoided.

(d) The inner strand conductor according to the invention has a lower attenuation in the signal transmission, since more effective conductor surface is available.

(e) The inventive strand inner conductor has reduced RL tips. At the same time, the RL level is improved.

(f) The inner conductor of the invention tends less to splice under mechanical stress (bending, twisting, shaking), d. H. the wires remain in position and the round-knurled Litzenin nenleiter retains the shape even with very small bending radii.

(g) The strand inner conductor according to the invention has, after the swaging, a length of its cross section which remains constant along its length. This reduces the periodicity in the conductor structure. This leads to a reduction of the RL tips.

An embodiment of a method according to the invention for producing a stranded inner conductor for a coaxial cable, or a coaxial cable, has the following method steps: provision of a strand inner conductor which consists of several stranded wires; Rotary kneading of the strand inner conductor by means of a rotary swaging device, so that the cross-sections of the wires align with each other; Enveloping the strand inner conductor with a dielectric; U envelop the dielectric with an outer conductor. Advantageously, the wires are kneaded until they touch each other without gap. When stranding, a constant or a variable lay length can be used. Depending on the field of application, the outer conductor is constructed in one or more layers. He can z. B. made of a braid (mesh outer conductor) and / or formed as a foil outer conductor and / or Rohraussenleiter and / or Bandaussenleiter. The dielectric can be constructed in one or more layers and be by means of a device for applying the dielectric connected downstream of the rotary swaging device. Furthermore, a device for applying an external conductor to the dielectric may be connected downstream. If necessary, the surface of the wires can be coated before swaging. For example, the surface of the wires can be silver plated. If necessary, the outer conductor can be round-kneaded in several stages by means of several rotary kneaders connected in series. For example, it is possible to knead the individual layers round one after the other in a multilayer stranded inner conductor. Between the rotary swaging processes, some or more wires of the inner strand conductor may be subjected to a further process step.

A device for producing a strand inner conductor according to the invention, or coaxial cable, generally has one or more rotary kneading devices arranged successively from the process flow. Furthermore, the apparatus has a feed device for feeding one or more stranded stranded inner conductors to the rotary swaging device. Furthermore, the device has a Wegführeinrichtung, which serves to carry away the round kneaded Litzeninnenleiters. The feeder may be one or more (in particular with several strokes) meh rere consecutive stranding machine act. The feeder may also be act a supply roll, on which the Litzeninnenleiter or individual blows wound up. The routing device can be a machine for applying a dielectric to the round-knit strand inner conductor.

Further aspects of the invention will be explained in more detail with reference to the embodiment described in the following figures. Show it:

Fig. 1 shows a coaxial cable with periodic interference, shown symbolically by constrictions of the outer conductor

2 shows in a first diagram the frequency-dependent Rückflussdämpfungs- course of a coaxial cable according to Figure 1;

FIG. 3 shows in a second diagram the frequency-dependent return loss damping characteristic of a coaxial cable according to the invention;

4 shows schematically the production of an inventive inner conductor for a coaxial cable according to the invention;

Fig. 5 shows the arrangement shown in Figure 4 in a side view;

Fig. 6 (a) shows a micrograph of a stranded strand inner conductor and (b) the contours of the micrograph according to (a);

Fig. 7 (a) shows a micrograph of a strand inner conductor according to the invention; and (b) the contours of the micrograph according to (a);

Fig. 8 shows schematically the structure of a coaxial cable according to the invention. Figure 1 shows schematically and greatly simplified a known from the prior art conventional coaxial cable 1 00 with a stranded strand inner conductor. In the longitudinal direction (x-direction), this has periodically arranged defects 1 01 in the outer conductor (illustrated schematically as semicircles), which have a negative effect on the transmission and system behavior of the coaxial cable in a frequency-dependent manner. The defects 1 01 are arranged at a distance λ / 2, or in a multiple thereof (factor n). The defects cause 01 01, that at each defect 1 01 a proportion of 1 02 of the input input signal input 03 is reflected. Due to the periodicity of the defects 1 01, the backscattered signal components at the input of the coaxial cable in the same phase position and thus overlap constructively. This leads to an increase of the reflected signal component at a frequency or in a narrow frequency band.

FIG. 2 shows, in a first diagram, the frequency-dependent backflow damping behavior of a conventional coaxial cable with inner conductor according to FIG. 1. The abscissa (x-axis) shows the frequency (f) and the ordinate (y-axis) shows the return loss in d B. The permissible limits for the return loss are shown in the form of a horizontal line 1 05. The course of the return loss can be seen in the form of a strong ausschlagenden first curve 1 06. It can be seen that at two narrowband points 1 07 and 1 08 the return loss has pronounced minimums and the permissible limit values 1 05 are exceeded. These minima are called RL peaks.

FIG. 3 shows, in a second diagram, the return loss (ordinate) of a coaxial cable according to the invention with inner strand conductor according to FIG. 4 as a function of the frequency (abscissa) in the form of a second curve 1 09. The permissible limits for the return loss are again by means of a horizontally extending line 1 1 0 provides. As can be seen, the cable according to the invention does not have the cross-limit RL tips of the cable known from the prior art according to the diagram in FIG.

FIG. 4 shows, in a perspective view obliquely from the front and from above, a stranded inner strand conductor in the unprocessed state 1 and the same inner strand conductor in the processed state 2. FIG. 5 shows the arrangement according to FIG. 1 in a side view. FIG. 6 shows a sectional view through the inner strand conductor 1 along the cutting line EE according to FIG. 4. FIG. 7 shows a sectional view through the inner strand conductor 2 along the section line FF according to FIG. 4. FIG. 8 shows in a sectional view schematically a structure of a coaxial cable 9 with an inventive Stranded conductor 2.

In the method according to the invention, the inner strand conductor 1 is shaped into the processed inner strand conductor 2 by means of a rotary swaging device 10.

FIG. 6 a shows a photograph of a cross-section (micrograph) of a conventional stranded stranded inner conductor 1. FIG. 6b shows the same cross section in the drawing. FIG. 7 a shows a photograph of a cross section (micrograph) of a stranded inner conductor 2 kneaded in accordance with the invention. FIG. 7b shows the same cross section in the drawing.

6 and 7, it is noticeable that wires 3 are arranged comparatively loosely and with a great distance from each other before swaging (see FIGS. 6a and 6b) and do not necessarily abut one another. In addition, the Litzeninnenleiter 1 an irregular and furrowed Außenf surface 8. In contrast to this, in round-kneaded stranded inner conductor 2 according to FIG. 7a, resp. 7b the wires 3 are arranged close together and without gaps. They have seen in cross section a polygonal structure with usually four to six straight or slightly curved side walls 25, which pass over kinks 26 into each other.

The rotary swaging device 1 0 comprises in the embodiment shown a tool 1 1, which has four jaws 1 2 in the embodiment shown. The jaws 1 2 form in the center through a machining opening 1 3. The jaws 1 2 are driven in a deflected manner via external plungers 1 4 in the radial direction of a rotation axis 1 5 (compare arrow 22), while a working shaft 1 6, in which the jaws 1 2 and the outer plungers 1 4 are mounted in pockets 1 7, about the axis of rotation 1 5 rotates (see arrow 23). The outer tappets 1 4 have ramp-shaped elevations 1 8 mmenwirken with mating in an outer ring 1 9 and mounted in a cage 20 rollers 2 1 zusa. The outer ring 1 9 supports the rollers in the radial direction. By the rotation of the working shaft 1 6, the ramps 1 8 are moved over the co-rotating rollers 2 1 and thereby deflected inwards. This movement is the jaws 1 2 of the tool 1 1 transferred. Other drives are possible. The stranded stranded conductor 1 is moved in the direction of arrow 24 through the machining opening 1 3 of the tool 1 1. The wires 3 are compressed and deformed in cross section as shown in the following figures. The cross section of the stranded strand inner conductor is thereby reduced from a first diameter D 1 to a second diameter D 2. Depending on the field of application, the diameters D2 to D 1 are typically in a ratio of 0.5-0.9 to each other. U nterhalb of about 0.77 all intermediate areas between the wires 3 are filled and a stretching of the wires in the longitudinal direction can be achieved, which leads to an extension of the inner conductor 2. As can be seen in particular in Figure 7, the wires are 3 after the rotary kneading closely to each other and have a virtually seamless cross-section. In particular, the cross sections of the wires 3 are no longer round but polygonal. In the embodiment shown, the stranded conductor has a circular outer surface 8, which has a high constancy over the length of the stranded conductor. The inner surfaces 7 are partially meshed closely together. They are designed such that the wires 3 are still displaceable relative to each other in the longitudinal direction.

The coaxial cable 9 according to the invention, shown in FIG. 8, has a stranded inner strand conductor 2 which is stranded and kneaded round, which is surrounded by a dielectric 4. The dielectric 4 is in turn surrounded by an outer conductor 5 arranged concentrically with respect to the outer surface 8. The outer conductor 5 is enclosed here by a protective outer shell 6. Other outer conductor 5 are possible. For example, the inner conductor Litzen 2 and the dielectric 4 also from a solid outer conductor, respectively. Enclosed housing (not shown in detail). Good results are achieved with stranded conductors with a diameter of 0. 1 to 3 M illimeters. These have (depending on the field of application) usually 7, 1 9 or 37 individual wires. The diameter of the individual wires is in the range of 0.02 to 0.6 millimeters before the rotary swaging. The inventive Litzeninnenleiter offer for very high transmission frequencies of up to 1 1 0 G HZ.

reference numeral

1 stranded inner conductor (unprocessed) 26 kink (cross section wire)

2 internal strand conductors (machined) 100 cables

3 wire (single wire) 101 defect

5 4 dielectric 102 proportion (loss)

5 outer conductor 103 input signal

6 outer jacket 104 output signal

7 inner surface 105 limit value (damping)

8 Outer surface 106 First curve (damping) 10 9 Coaxial cable 107 Damping tip 1 (limit value)

10 Rotary swaging device 108 Damping tip 2 (limit value)

11 tool 109 second curve (damping)

12 jaw 110 limit value (damping)

13 machining opening

15 14 external tappets

15 rotation axis

16 working wave

17 bag

18 ramp (ramp-shaped increase)

20 19 outer ring

20 cage

21 rolls

22 arrow 1

23 arrow 2

25 24 arrow 3

25 width wall (cross section wire)

Claims

claims

1. A method for producing a coaxial cable (9) with the following method steps: a. Providing a strand inner conductor (1) consisting of a plurality of wires (3) stranded together; b. Rotary kneading of the strand inner conductor (1) by means of a rotary swaging device (10); c. Enveloping the round kneaded inner strand conductor (2) with a dielectric (4); d. Enveloping the dielectric (4) with an outer conductor (5).

2. The method according to claim 1, characterized in that the stranded strand inner conductor (1) has a constant and / or a variable lay length.

3. The method according to any one of the preceding claims, characterized in that the outer conductor (5) with an outer sheath (6) is enveloped.

4. The method according to any one of the preceding claims, characterized in that an outer conductor (5) as a mesh outer conductor and / or Rohraussen- conductor and / or Folienaussenleiter and / or Bandaussenleiter is produced.

5. The method according to any one of the preceding claims, characterized in that the dielectric (4) is constructed in multiple layers.

6. The method according to any one of the preceding claims, characterized in that the surface of the wires (3) is coated.

7. The method according to claim 6, characterized in that the surface of the wires (3) are coated with silver, gold or tin.

8. The method according to any one of the preceding claims, characterized in that the inner conductor (1) by means of a plurality of successively connected rotary swaging (10) is kneaded.

9. The method according to claim 8, characterized in that between the Rotknetvorgängen the Litzeninnenleiter (2) is subjected to a further process step.

10. Litzeninnenleiter (2) produced by the method of one of the preceding claims.

11. Coaxial cable (9) prepared according to a method of claims 1 to 9.

12. An apparatus for performing the method according to one of the claims 1 to 9 characterized by a rotary swaging device (10), a feeding device of a stranded strand inner conductor (1) for rotary swaging device, and a Wegführeinrichtung for carrying away the round knitted strand inner conductor (2).

1 3. A device according to claim 1 2, characterized in that the feed device comprises a stranding machine.

14. The device according to claim 1 2, characterized in that the feed device comprises a supply roll on which the stranded stranded inner conductor (1) is wound.

1 5. Device according to one of the claims 1 2 to 1 4, characterized in that the Wegführeinrichtung comprises a machine for applying a dielectric on the round knitted Litzeninnenleiter.