JPH0750111A - Manufacture of coaxial cable - Google Patents

Abstract

PURPOSE:To manufacture a coaxial cable which has an external conductor excellent in elongation. CONSTITUTION:A cable core 1 is continuously supplied to a conforming extruder 3 and, at the same time, an aluminum rod 2 is supplied to the extruder 3 to extrude an aluminum pipe 6 apart from the outside of the cable core 1. Then, after warming it by a drive roller 21, it is cooled down by a cooling water tank 4 and them warmed again by a drive roller 23 and cold machined with a round die 5a to coat the outer periphery with the aluminum pipe. The drive rollers 21, 23 are such that sets of rolls formed with a pair of vertical drive rolls to give circular working and a pair of lateral non-drive rolls to give oval working are arranged in multiple steps. An external conductor molded in such a way is excellent in elongation and bending property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a coaxial cable, and more particularly to an improvement of a method of manufacturing a coaxial cable which can improve the mechanical properties of an outer conductor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for broadband cables that transmit broadband signals such as high-speed data and television images in addition to voice communication. A cable for CATV is used for.

In this CATV cable, generally, an annealed copper single wire is used as an inner conductor, an insulating material made of expanded polyethylene or highly expanded polyethylene is coated on the outer side thereof, and an outer conductor made of an aluminum pipe and a polyethylene sheath are sequentially arranged on the outer side thereof. CATV coaxial cables having the arranged structure are often used.

The outer conductor of such a coaxial cable is formed by extruding an aluminum pipe on the outer side of a cable core in which an outer conductor is covered with an insulator so as to be separated from the insulator, or by coating an aluminum tape on the outer side of the insulator. Are separated from the insulator and arranged in a pipe shape and welded, and then the aluminum pipe is subjected to a forming process.

The method of forming the outer conductor is excellent in the extrusion method from the viewpoint of the stability of the quality and the productivity, and the aluminum pipe after the extrusion is coated on the outside of the insulator by the expansion process using a die. .

FIG. 4 shows a method of forming an outer conductor by such a conventional extrusion method and a tube-expanding method using a die. Therefore, 1 is a cable core in which the outer surface of the inner conductor is covered with an insulator, and 2 is aluminum. A rod, 3 is an extruder, 4 is a cooling water tank, and 5 is a round die. The extruder 3 is a conform extruder (Japanese Patent Publication No. Sho-
No. 38316), and this apparatus is also called a rotary wheel type continuous extruder or a friction drive type extruder. Figure 5
As shown in FIG. 1, the extruder 3 includes a rotating wheel 10 having a groove 10 a formed on the outer peripheral surface thereof, a fixed shoe block 11 engaging with a part of the outer periphery of the rotating wheel, and a die 1.
2 and a nipple 13 are mainly configured,
The aluminum rod 2 supplied into the groove 10a of the rotating wheel 10 generates frictional heat due to the rotation of the rotating wheel 10 and is applied with high pressure to continuously supply the aluminum core 2 from the die 12 into the nipple 13. The pipe is extruded in a pipe shape while being separated from the outside.

After being extruded, the aluminum pipe 6 is cooled in the cooling water tank 4, guided to the round die 5 via the dancer roll 7, and given a pulling force by the pulling machine 8, as shown in FIG. The outer circumference of the cable core 1 is covered with an aluminum pipe 6a. Such a conventional extrusion method and a method using a die-expanding method have an advantage that an outer conductor having excellent roundness and dimensional accuracy of the pipe can be formed.

[0008]

However, the outer conductor formed by the above-described extrusion method and the tube-expanding method using a die has the following problems.
There is a problem that it is difficult to bend because the mechanical properties, especially the elongation property, are inferior to the outer conductor produced by the welding method, and cracks are likely to occur in the outer conductor when subjected to bending with a small curvature during cable construction.

For example, while the elongation of the outer conductor by the welding method is about 20%, the elongation of the outer conductor by the extruding method and the tube-expanding method using a die is only about 5%.

The reason for this is that in the case of the extrusion method, in order to prevent the aluminum pipe extruded by heat from damaging the internal insulator, the aluminum pipe is pushed away from the insulator with a predetermined distance. Therefore, reduction (drawing rate; when the outer diameters before and after processing are A and B, respectively, in the tube expansion process using a die during the forming process of the aluminum pipe (AB))
It is expressed by × 100 / A (%). same as below. ) Is large and the work is hardened by the tension applied to the aluminum pipe at the time of working.

The reduction at the time of tube expansion by the above die cannot be made small for the above-mentioned reasons as long as the extrusion method is adopted, and in order to improve the elongation characteristics of the outer conductor, the aluminum after extrusion is improved. There is nothing but to improve the method of forming pipes.

The present invention has been made in order to solve the above problems, and provides a method for manufacturing a coaxial cable in which an outer conductor of the coaxial cable is formed by an extrusion method and the mechanical characteristics thereof can be improved. Is its purpose.

[0013]

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a coaxial cable in which an insulator, an outer conductor and a protective coating layer are sequentially arranged outside an inner conductor. A cable core coated with an insulator on the outside is continuously supplied to an extruder, an aluminum pipe is extruded on the outside while being separated from the insulator, and then the aluminum pipe is sequentially subjected to warm working and cold working. Thus, the outer conductor is formed on the outer circumference of the insulator.

The extrusion of the aluminum pipe in the present invention can be performed by the above-mentioned conform extruder.

In the present invention, the extruded aluminum pipe is sequentially subjected to warm working and cold working. This is done by subjecting the extruded aluminum pipe to warm working and then cooling it. , And then cold working.

The above warm working is preferably carried out by using a driving roll device in which a set of vertical rolls and horizontal rolls are arranged in multiple stages. In this case, it is preferable in view of the structure of the apparatus that the group roll is configured by using a pair of drive vertical rolls for performing circular processing and a pair of non-driving horizontal rolls for performing oval processing. In this warm working, it is necessary to set the reduction so that the aluminum pipe does not contact the cable core.

The cold working can be carried out by any of the method using the above driving roll device, the method using a combination of this driving roll device and a round die, or the method using only a round die.

[0018]

With the above construction, in the method of manufacturing a coaxial cable of the present invention, since the extruded aluminum pipe is sequentially subjected to warm working and cold working, the reduction applied to the extruded aluminum pipe as a whole is reduced. Without this, the tension applied to the aluminum pipe during processing can be reduced, and as a result, work hardening can be reduced, so that the elongation characteristics of the aluminum pipe after molding are improved.

[0019]

EXAMPLE An example of the present invention will be described below.

FIG. 1 shows an outline of an apparatus 20 for manufacturing a coaxial cable used in such a method of the present invention. Reference numeral 1 is a cable core in which an outer side of an inner conductor is covered with an insulator, and 2 is an aluminum rod. 3 is a conform extruder, 4 is a cooling water tank, 5a is a round die, and 21 and 23 are drive roll devices. The same parts as those in FIG. 4 are designated by the same reference numerals.

The cable core 1 is continuously supplied into the nipple 13 of the conform extruder 3, and at the same time, the aluminum rod 2 supplied into the groove 10a of the rotary wheel 10 of the extruder 3 is rotated by the rotation of the rotary wheel 10. The die 12 is heated by frictional heat and high pressure is applied.
It is extruded in a pipe shape while being separated from the nipple 13 to the outside of the cable core 1.

The extruded aluminum pipe 6 is warm-worked by the drive roll device 21 with a predetermined reduction, then cooled in the cooling water tank 4, and then passed through the dancer roll 7 to the drive roll device 23 and the round die 5a. The aluminum pipe 6 is fed to the outer periphery of the cable core 1 by being drawn and given a drawing force by the take-up machine 8 to perform cold working.
a is coated.

The drive roll devices 21 and 23 are, as shown in FIG. 2, a pair of drive vertical rolls 21 for circular processing.
a and a pair of non-driving horizontal rolls 21b for performing the oval processing are arranged in multiple stages. Reduction between the pair of rolls (reduction between vertical rolls) is, for example, a reduction in the order of reduction. It has such a roll shape. FIG. 3 shows an example of the aluminum pipe molded in this way, and FIG.
(B) shows the cross-sectional shape of the aluminum pipe after circular processing and after oval processing, respectively.

Specific Example One specific example of the present invention will be described below.

Using the coaxial cable manufacturing apparatus 20 shown in FIG. 1, a CATV coaxial cable was manufactured by the following method.

A cable core 1 having an outer diameter of 8.3 mm, which is obtained by extruding high-foam polyethylene on the outside of an inner conductor having an outer diameter of 2.1 mm, is used. The cable 1 is supplied to the extruder 3 and aluminum is supplied to the extruder 3. A rod (3N) 2 was supplied, and an aluminum pipe 6 having an outer diameter of 13.4 mm and a thickness of 0.6 mm was extruded on the outside thereof.

This aluminum pipe is molded by a driving roll device 21 consisting of five stages of rolls, cooled in a cooling water tank 4, and then driven by a driving roll device 23 consisting of five stages of roll rolls.
Was molded to an outer diameter of 9.8 mm.

At this time, the reduction by the drive roll devices 21 and 23 was 24.6%. Next, a round die 5a was used to perform a reduction treatment of 2% to coat the outer circumference of the cable core 1 with an aluminum pipe 6a. A CATV coaxial cable was manufactured by coating polyethylene on the outside of the aluminum pipe 6a according to a usual process.

The total reduction between the aluminum pipe 6 and the outer conductor (aluminum pipe 6a) was 28.4%.

The results of measuring the mechanical characteristics of the outer conductor of the coaxial cable manufactured in this way are shown in Table 1.
Shown in.

[0031]

[Table 1] Also, the external conductor had a smooth surface condition.

Comparative Example Using the apparatus shown in FIG. 4, an aluminum pipe 6 was extruded to the outside of the cable core 1 in the same manner as in the specific example, the aluminum pipe was cooled in a cooling water tank 4, and then the cable core was rounded with a round die 5. The outer circumference of No. 1 was coated with an aluminum pipe 6a, and the outside of the aluminum pipe 6a was coated with polyethylene according to a normal process to manufacture a CATV coaxial cable.

The total reduction between the aluminum pipe 6 and the outer conductor (aluminum pipe 6a) was 28.4%.

The results of measuring the mechanical characteristics of the outer conductor of the coaxial cable manufactured in this way are shown in Table 1.
At the same time.

In addition, the appearance of the outer conductor was found to be rough on the surface as compared with the examples.

[0036]

As described above, according to the method of manufacturing a coaxial cable of the present invention, the tension and work hardening applied to the aluminum pipe during the molding of the outer conductor can be reduced, and therefore the elongation and bending characteristics are excellent. A coaxial cable with an outer conductor can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an apparatus for manufacturing a coaxial cable used in the method of the present invention.

FIG. 2 is a schematic view showing an embodiment of the drive roll device of FIG.

FIG. 3 is a cross-sectional view of an aluminum pipe formed by the set roll of FIG.

FIG. 4 is a schematic view showing a conventional coaxial cable manufacturing apparatus.

FIG. 5 is a schematic sectional view of a conform extruder.

6 is a cross-sectional view showing a pulled-out state by the die of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cable core 2 ... Aluminum rod 3 ... Conform extruder 4 ... Cooling water tank 5a ... Round die 6 ... Aluminum pipe 6a ... Outer conductor 20 ... Coaxial cable manufacturing device 21, 23 ... Drive roll device 21a ... Drive vertical roll 21b … Non-driving side rolls 22… Group rolls

Front page continuation (72) Inventor Taisuke Ito 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Showa Electric Wire & Cable Co., Ltd. (72) Norio Shirahata 2-chome Oda, Kawasaki-ku, Kanagawa Prefecture No. 1 Showa Electric Cable Co., Ltd.

Claims (4)

[Claims] 1. A method for manufacturing a coaxial cable in which an insulator, an outer conductor and a protective coating layer are sequentially arranged on the outer side of an inner conductor, wherein a cable core coated with the insulator on the outer side of the inner conductor is continuously extruded. The aluminum pipe is supplied to the machine, and an aluminum pipe is extruded on the outer side of the aluminum pipe while being separated from the insulator, and then the aluminum pipe is sequentially subjected to warm working and cold working to form the outer conductor on the outer periphery of the insulator. A method of manufacturing a coaxial cable, characterized in that 2. The method of manufacturing a coaxial cable according to claim 1, wherein the warm working is performed by using a drive roll device in which a set roll including a vertical roll and a horizontal roll is arranged in multiple stages. 3. The method of manufacturing a coaxial cable according to claim 1, wherein the cold working is performed by using a driving roll device and / or a round die in which a set roll including a vertical roll and a horizontal roll is arranged in multiple stages. 4. The method of manufacturing a coaxial cable according to claim 2, wherein the pair of rolls comprises a pair of driving vertical rolls for performing circular processing and a pair of non-driving horizontal rolls for performing oval processing.