GB1569796A - Multiple coaxial cable - Google Patents

Description

(54) MULTIPLE COAXIAL CABLE (71) We, AEG - TELEFIJNKEN KABELWERKE AKTIENGESELL SCHAFT, RHEYDT, of 405 Monchengladbach, D433 Mulheim/Ruhr 13, Federal Republic of Germany, a German body corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a high-frequency cable formed from coaxial tubes stranded together.

Multiple coaxial cables with standardised tubes may be utilized in the present-day state of the art up to 60 MHz. Furthermore, periodic disruptions affects the structural return loss to an impermissible extent. This disruption is chiefly determined by successive deformations of the tubes at the seams of the outer conductor, wherein the spacing of the deformations is equal to the length of twist of the layers.

In this case the frequency ranges of poor return flow damping correspond to the length of twist of the layers.

When manufacturing the outer conductor of the tube, a metal, preferably copper, strip has previously been formed into a pipe so as to pass lengthwise, wherein the non-welded open junction provides a line in the tube of the coaxial conductor which is parallel to the axis. In order to shield and hold together the junction, the coaxial conductor thus formed is wound about by strips, preferably steel strips.

The previously mentioned periodic disruptions result from the fact that the coaxial tubes must be stranded free of twisting, i.e.

with 1000,0,, or nearly 100% untwisting. This means that the longitudinal seam of the outer conductor always points in the same direction i.e. the seam follows a swung sleeve line. As a result, the seam, which is sensitive to pressure, touches the stranding die or matrix and the stranding core once per twisting length.

Moreover, with this type of stranding, it is not possible to prevent the seams of the tubes from coming into contact with the stranding machine parts under pressure and thus for example with the offtake wheel and branching ring of the offtake wheel, with the guide matrices of the strips winders, with the traverse fork, the wind-up reel and with the next layer od the cable on the wind-up reel.

Until now attempts have been made to meet the disruptions by varying the lengths of twisting of the layers, so that the periodic effect was wiped out. However this variation had a disadvantageous effect on manufacture.

The invention seeks to prevent periodic twisting length deformation of tube seam in a simple and economic manner without intervention being necessary in manufacture.

According to the invention, there is provided a high frequency cable comprising coaxial tubes stranded together, the outer conductor of each coaxial tube having a helical joint therein whose pitch corresponds to the twisting length of the cable.

The outer conductor of the tubes may be formed by a helically coiled metal band the pitch of the coil corresponding to the layer twisting length during stranding.

In an advantageous refinement of the subject of the invention the position of the joint is always selected to be in the direction of a cable filler at the commencement of stranding.

In this way the seams are not subjected to any pressure during stranding and during further processing.

Moreover the tubes having helical outer conductors are less sensitive to lateral flexure and are capable of processing with smaller bending radii.

The invention will now be described in greater detail, by way of example, with reference to the drawings in which: - Figure 1 shows a conventional embodiment of a high-frequency cable in schematic crosssection, and Figure 2 shows a cross-section through a high-frequency cable constructed in accordance with the invention.

Figure 1 shows a stranded core 4 about which the coaxial tubes 5 are formed, only the outer conductor 2 of which is shown comprising lengthwise passing metal strips formed into pipes. Each outer conductor 2 is formed with a junction 3 respectively. As a result of the 100% untwisting during stranding of the tubes the pressure sensitive junction 3 points, once per twisting length, to the stranding die or matrix as is shown at A and once to the stranding core 4, as is shown at B.

The cable in accordance with the invention, as Figure 2 shows, has a different arrangement of the coaxial tubes in contrast thereto.

Even with this coaxial cable 1, the coaxial tubes are stranded about a stranded core 4, which may comprise a core 10 for example made of leads stranded together and a wrapping 9. In contrast to the conventional arrangement the coaxial tubes S in accordance with the invention are however arranged so that their junction 3 always points to the filler area lying between the adjacent coaxial tube and the stranded core 4. This is achieved by the inner conductor 8 being surrounded by the metal band forming the outer conductor 2 of the coaxial tube not, as in the conventional tubes, in parallel to the axis but helically. Thus the position of the junction 3 is determined by its starting position and because of the helical pitch of the junction 3 over the layer twisting length it always remains unchanged with respect to the axis of the cable.Thus the periodic disruptions, which affect the structural return loss in the cable 1 shown in Figure 1 are eliminated.

In the embodiment shown in Figure 2 of a cable 1 in accordance with the invention the outer conductor 2 of the coaxial tubes 5 are additionally surrounded by an iron band 6.

The core of the cable formed by the stranded core 4 and the position of coaxial tubes 5 is surrounded by a winding 7 for example made of absorbent paper and a cable sleeve known per se, which is not shown in the drawing for the purpose of simplification.

WHAT WE CLAIM IS: 1. A high-frequency cable comprising c axial tubes stranded together, the outer conductor of each coaxial tube having a helical joint therein whose pitch corresponds to the twisting length of the cable.

2. A high-frequency cable according to claim 1, wherein the outer conductor of the tubes is formed by a helically coiled metal band, the pitch of the coil corresponding to the layer twisting length during stranding.

3. A high-frequency cable according to claim 1 or 2, wherein the position of the joint is always selected to be in the direction of a cable filler at the commencement of stranding.

4. A high-frequency cable substantially as described herein with reference to figure 2 of the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. Figure 1 shows a stranded core 4 about which the coaxial tubes 5 are formed, only the outer conductor 2 of which is shown comprising lengthwise passing metal strips formed into pipes. Each outer conductor 2 is formed with a junction 3 respectively. As a result of the 100% untwisting during stranding of the tubes the pressure sensitive junction 3 points, once per twisting length, to the stranding die or matrix as is shown at A and once to the stranding core 4, as is shown at B. The cable in accordance with the invention, as Figure 2 shows, has a different arrangement of the coaxial tubes in contrast thereto. Even with this coaxial cable 1, the coaxial tubes are stranded about a stranded core 4, which may comprise a core 10 for example made of leads stranded together and a wrapping 9. In contrast to the conventional arrangement the coaxial tubes S in accordance with the invention are however arranged so that their junction 3 always points to the filler area lying between the adjacent coaxial tube and the stranded core 4. This is achieved by the inner conductor 8 being surrounded by the metal band forming the outer conductor 2 of the coaxial tube not, as in the conventional tubes, in parallel to the axis but helically. Thus the position of the junction 3 is determined by its starting position and because of the helical pitch of the junction 3 over the layer twisting length it always remains unchanged with respect to the axis of the cable.Thus the periodic disruptions, which affect the structural return loss in the cable 1 shown in Figure 1 are eliminated. In the embodiment shown in Figure 2 of a cable 1 in accordance with the invention the outer conductor 2 of the coaxial tubes 5 are additionally surrounded by an iron band 6. The core of the cable formed by the stranded core 4 and the position of coaxial tubes 5 is surrounded by a winding 7 for example made of absorbent paper and a cable sleeve known per se, which is not shown in the drawing for the purpose of simplification. WHAT WE CLAIM IS:

1. A high-frequency cable comprising c axial tubes stranded together, the outer conductor of each coaxial tube having a helical joint therein whose pitch corresponds to the twisting length of the cable.

2. A high-frequency cable according to claim 1, wherein the outer conductor of the tubes is formed by a helically coiled metal band, the pitch of the coil corresponding to the layer twisting length during stranding.

3. A high-frequency cable according to claim 1 or 2, wherein the position of the joint is always selected to be in the direction of a cable filler at the commencement of stranding.

4. A high-frequency cable substantially as described herein with reference to figure 2 of the drawings.