JPH06150745A - Manufacture of coaxial cable - Google Patents

Abstract

PURPOSE:To prevent deterioration of the characteristic of a coaxial cable on which shielding layers are formed by overlapping tape ends. CONSTITUTION:A third shielding layer 5 made of a metal-plastic laminated tape is molded with the plastic tape in contact with a sheath 6, and after the sheath 6 is extruded to cover a coaxial cable, a certain annealing period 31 is initiated. Then the plastic tape of the third shielding layer 5 is softened and its boundary surface makes intime contact with the sheath 6; i.e., even if a plastic tape made of material different from that of the sheath 6 is used in the third shielding layer 5, both of them are firmly bonded to each other and are not easily peeled by bending, etc. Therefore, the overlapping ends of the third shielding layer are not disarranged by bending and thus characteristics of the coaxial cable are stabilized. A first shielding layer is formed in a similar way.

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 used for high frequency signal transmission.

[0002]

2. Description of the Related Art For example, in a system such as CATV, a coaxial cable is used to transmit a high frequency signal received by an antenna. FIG. 2 shows an exploded perspective view of a conventional coaxial cable of this type. As shown in the figure, this cable has a structure in which an outer periphery of a conductor 1 is covered with an insulator 2, a first shield layer 3, a second shield layer 4, a third shield layer 5 and an outer cover 6 in order. The conductor 1 is composed of twisted copper wires, and the insulator 2 is composed of foamed polyethylene or the like. Each of the first shielding layer 3 and the third shielding layer 5 is composed of a metal-plastic laminated tape in which a polyester tape and an aluminum tape are laminated. Further, the second shield layer is composed of a braided wire such as copper. The jacket 6 is made of vinyl chloride resin, polyethylene, or the like.

In the coaxial cable having the above-mentioned structure, the first shield layer 3, the second shield layer 4, and the third shield layer 5, in particular, form an outer conductor having a low transfer impedance for preventing radio interference. For this purpose, the plastic tape side of the first shielding layer 3 is brought into contact with the insulator 2 and the third shielding layer 5
The plastic tape surface of is formed so as to face the jacket 6.

FIG. 3 shows a schematic view of a manufacturing line for the above cable. As shown in the figure, this line supplies the conductor 1 from the supply drum 11 and the insulator extruder 12
The insulator 2 is extruded and covered with and cooled by the insulator cooling tank 13. The outer periphery of the insulator 2 is covered with the first shielding layer 3 in the first shielding layer molding portion 14. As shown in the upper part of the figure, the first shielding layer molding portion 14 includes a tape former 21 for cylindrically molding the first shielding layer 3 vertically attached to the outer periphery of the insulator 2, and a first shield after molding. A molding die 22 for narrowing the layer 3 to a constant outer diameter.

Then, the outer periphery of the first shielding layer 3 is covered with the second shielding layer 4 made of a braided wire by the second shielding layer molding portion 15. The outer periphery of the second shielding layer 4 is covered with the third shielding layer 5 in the third shielding layer molding portion 16. As shown in the lower part of the drawing, the third shielding layer molding portion 16 vertically attaches the third shielding layer 5 to the outer periphery of the second shielding layer 4, and the tape former 23 molds the third shielding layer into a tubular shape. Then, the molding die 24 is used to reduce the outer diameter to a predetermined value. The outer circumference of the third shielding layer 5 is extruded and covered with the outer cover extruder 17 and cooled by the outer cover cooling tank 18, and then wound on the winding drum 19.

[0006]

The conventional coaxial cable manufactured by the above method has the following problems to be solved. For example, this kind of cable is installed in a complicated route outdoors and indoors. Therefore, for example, as shown in FIG.
Can also be bent with a relatively small radius. However, when the cable 10 is bent in such a state, the shielding effect that normally functions in the AA cross section of the drawing becomes insufficient in the BB cross section of the drawing, and the characteristics as designed are obtained. There was a problem of not having.

FIG. 5 is an explanatory view of problems seen from the sectional structure of the conventional cable as described above. 5A is a cross-sectional view of the cable, FIG. 5B is a partial cross-sectional view of the first shielding layer or the third shielding layer, and FIG. 5C is a cross-sectional view of a main portion of the cable. As shown in the drawing, each shield layer 3, 4, 5 of the cable is covered on the outer periphery of the insulator 2 concentrically, as shown in the figure. In this case, as shown in (b), the first shielding layer 3 and the third shielding layer 5 are formed by laminating the metal tape 8 and the plastic tape 9, and the edges thereof are as shown in (c) of the figure. , So as to be overlapped with each other by a predetermined width. In this case, for example, the surface of the plastic tape 9 of the third shielding layer 5 is oriented so as to be in contact with the outer cover 6, and the metal tape 8 and the second shielding layer 4 are electrically contacted. .

In the above case, when the cable is bent at a steep angle, a part of the third shielding layer 5 is bent and lifted up, as shown by a dashed line in FIG.
There is a gap in the overlapping part. Such a phenomenon deteriorates the characteristics of the cable. The same tendency is seen in the first shielding layer 3.

The present invention has been made in view of the above points, and in a coaxial cable in which a shield layer is formed by stacking the ends of the tape as described above, a coaxial cable in which deterioration of characteristics due to bending is prevented. It is an object of the present invention to provide a manufacturing method of.

[0010]

According to a first aspect of the present invention, the outer periphery of an insulator of a cable is coated with a first shielding layer made of a metal-plastic laminate tape so that the plastic tape surface is in contact with the insulator. The metal-plastic laminate tape is covered with a second shielding layer made of a good electrical conductor, and the outer periphery of the second shielding layer is covered with a metal-
A third shielding layer made of plastic laminate tape,
When the plastic tape surface is covered on the outside and the outer circumference of the third shielding layer is extruded and covered with a plastic jacket, a slow cooling section is provided after the extruding of the jacket, and the cable insulator and the first shield are provided. The present invention relates to a method for manufacturing a coaxial cable, characterized in that the interface between the layer and the plastic tape and the interface between the third shielding layer and the outer cover are softened and brought into close contact.

A second aspect of the present invention is the first aspect of the present invention, which comprises a metal-plastic laminate tape on the outer circumference of the cable insulator.
A shielding layer is coated so that the surface of the plastic tape is in contact with the insulator, a second shielding layer made of a good electric conductor is coated on the outer periphery of the metal-plastic laminate tape, and a plastic jacket is extruded on the outermost periphery. The present invention relates to a method for manufacturing a coaxial cable, which is characterized in that, in the case of coating, a slow cooling section is provided after extruding a jacket, and the interface between the cable insulator and the plastic tape of the first shielding layer is softened and adhered.

In a third aspect of the present invention, the outer periphery of the cable insulator is covered with a second shielding layer made of a good electric conductor,
When the outer periphery of the shielding layer is covered with a third shielding layer made of a metal-plastic laminate tape with the plastic tape surface facing outward, and when the outer periphery of the third shielding layer is extruded and coated with a plastic outer cover, The present invention relates to a method for manufacturing a coaxial cable, characterized in that a slow cooling section is provided after extrusion and the interface between the third shielding layer and the outer cover is softened and adhered.

[0013]

In this manufacturing method, the third shielding layer made of, for example, a metal-plastic laminate tape is molded so that the plastic tape is in contact with the outer cover, and the outer cover is extruded and covered, and then a certain slow cooling section is formed. deep. As a result, the plastic tape of the third shielding layer is softened, and the interface with the outer cover adheres well. That is, even if a plastic tape made of a material different from that of the outer cover is used for the third shielding layer, the both adhere strongly to each other and are not easily peeled off by bending or the like. Therefore, the overlapping portion at the end of the third shielding layer is not disturbed by bending, and the characteristics are stable. The same applies to the first shielding layer.

[0014]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a schematic view of a production line in which the method for producing a coaxial cable of the present invention is carried out. The schematic part of this manufacturing line is the same as the conventional manufacturing line already described in FIG. Therefore, the overlapping description of the overlapping portions will be appropriately omitted. In the production line, that is, the conductor 1 supplied from the supply drum 11 is covered with the insulator 2 by the insulator extruder 12, cooled in the insulator cooling tank 13, and then the first shield layer molding unit 14 1. Form the shielding layer 3. After that, the second shielding layer 4 is formed in the second shielding layer molding portion 15, and the third shielding layer 5 is covered by the third shielding layer molding portion 16. Further, after the jacket 6 is extruded and covered by the jacket extruder 17, it is cooled in the jacket cooling tank 32, and the winding drum 1
It is configured to be wound around 9.

Here, in the method of the present invention, the jacket extruder 1 is used.
A constant slow cooling section 31 is provided at the rear of 7, and a jacket cooling tank 32 is disposed behind it. That is, the conventional jacket extruder 1
In No. 7, the jacket 6 was cooled in the jacket cooling tank 18 immediately after the jacket 6 was extruded. However,
In the present invention, the jacket 6 immediately after extrusion is gradually cooled in the air in the slow cooling section 31 for a certain period of time, and then cooling is started.

As a result, the plastic tape and the insulator 2 of the first shielding layer 3 and the third shielding layer 5 which form the cable are formed.
The outer surface and the like are softened and their interfaces are sufficiently adhered to each other. For example, the insulator 2 and the jacket 6 are polyethylene, and the first
When the plastic tape forming the shielding layer 3 and the third shielding layer 5 is polyester, both do not fuse even if heated. However, when both are subjected to a high pressure by the jacket extruder 17 and are slowly cooled in the slow cooling section 31 while maintaining a high temperature to some extent, these interfaces are softened and closely adhere to each other without a gap, and are separated by some force. Will not do.

FIG. 6 shows a cross-sectional view of the main parts of a coaxial cable manufactured by the method of the present invention. (A) of the figure is a cross-sectional view showing an interface state between the third shielding layer 5 and the outer cover 6, and (b) shows the first state.
4 is a cross-sectional view showing an interface state between the shield layer 3 and the insulator 2. FIG.
For example, the plastic tape 9 and the jacket 6 of the third shielding layer 5
When and are sufficiently adhered by the above-mentioned processing, even when they are bent, the overlapping portions do not open. Further, when the insulator 2 and the plastic tape 9 of the first shielding layer 3 are sufficiently adhered to each other, stable characteristics are obtained without peeling even when bent.

FIG. 7 is an explanatory view showing the manufacturing conditions in the above manufacturing line. As shown in the figure, for example, in a 5C type cable with an outer diameter of 5 mm of an insulator made of vinyl chloride, the die temperature is 155 ° C and the head temperature is 155 ° C.
When extrusion coating of the jacket is performed at a temperature of 46 ° C. and a linear velocity of 46 m / min, a slow cooling section by air cooling is provided for 5 m, and then water cooling is performed.
The above-mentioned results were obtained by conducting the test in a section of 5 m.
In the case of using a polyethylene jacket, the die temperature is 190 ° C, the head temperature is 190 ° C, the linear velocity is 20m / min, and the slow cooling section is set to 1.8m for the same insulator outer diameter. Then, after cooling with 0.5 m of water, a 3.5 m slow cooling section was further provided, followed by cooling with 5.6 m of water. As a result, it was possible to manufacture a cable having a shielding layer having a similar high adhesion property.

The present invention is not limited to the above embodiments. In the embodiment of the first invention, the first shielding layer 3 and the third shielding layer 5
Although both are made of a metal-plastic laminate tape, the same effect can be obtained even if only one of them is a metal-plastic laminate tape. Further, the insulating material, the metal-plastic laminate tape, or the insulating material used for the outer cover may be freely changed to the conventionally well-known materials other than the above. Further, the configuration of the second shielding layer 4 may be freely changed.

[0020]

According to the method of manufacturing a coaxial cable of the present invention described above, when a metal-plastic laminate tape is used for the shielding layer of the cable, the plastic surface is molded so as to be in contact with the insulator or the jacket. Since the outer cover is extruded and covered, a certain slow cooling section is provided, so that the outer cover and the insulator and the plastic tape of the shielding layer are softened and adhered to each other and are not easily separated. As a result, when the cable is bent, a gap is not formed in the overlapping portion of the ends of the shielding layer, and the shielding characteristic is not deteriorated. Even if the above treatment is performed, if the outer cover and the plastic tape of the shielding layer, or the insulator and the plastic tape of the shielding layer are made of different materials, these will not be fused, Terminal processing and the like can be easily performed as before.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing line showing an embodiment of a method for manufacturing a coaxial cable according to the present invention.

FIG. 2 is an exploded perspective view of a coaxial cable to be manufactured by the method of the present invention.

FIG. 3 is a schematic view showing a conventional coaxial cable manufacturing line.

FIG. 4 is a side view when a cable is bent.

5A and 5B are explanatory views showing problems when the cable is bent, in which FIG. 5A is a cross-sectional view of the cable, FIG. 5B is a partial cross-sectional view of the shielding layer, and FIG. It is a side view.

FIG. 6 is a cross-sectional view of a main part of a cable manufactured by the method of the present invention.

FIG. 7 is an explanatory diagram illustrating manufacturing conditions according to the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 conductor 2 insulator 3 1st shielding layer 4 2nd shielding layer 5 3rd shielding layer 6 jacket 11 supply drum 12 insulator extruding machine 13 insulator cooling tank 14 1st shielding layer molding part 15 2nd shielding layer molding part 16 Third Shielding Layer Molding Section 17 Envelope Extruder 31 Slow Cooling Section 32 Enclosure Cooling Tank

Claims (3)

[Claims] 1. A first shielding layer made of a metal-plastic laminate tape is coated on the outer circumference of the cable insulator so that the plastic tape surface contacts the insulator, and the outer circumference of the metal-plastic laminate tape is electrically insulated. A second shielding layer made of a good conductor is coated, and a third shielding layer made of a metal-plastic laminate tape is coated on the outer periphery of the second shielding layer with the plastic tape surface facing outward, In the case of extruding and covering a plastic jacket on the outer periphery, a slow cooling section is provided after extruding the jacket, and the interface between the cable insulator and the plastic tape of the first shielding layer and the third shielding layer and the casing are provided. A method for manufacturing a coaxial cable, characterized in that the interface of the is softened and adhered. 2. The outer periphery of the cable insulator is covered with a first shielding layer made of metal-plastic laminate tape so that the plastic tape surface is in contact with the insulator, and the outer periphery of the metal-plastic laminate tape is a good electrical conductor. When a plastic jacket is extruded and covered on the outermost periphery, a slow cooling section is provided after the jacket is extruded, and the cable insulator and the plastic tape of the first shielding layer are provided. A method for manufacturing a coaxial cable, characterized in that the interface of the is softened and adhered. 3. A cable insulating material has an outer periphery covered with a second shielding layer made of a good electric conductor, and an outer periphery of the second shielding layer is covered with a third shielding layer made of a metal-plastic laminate tape, and the plastic tape surface is provided. When the plastic jacket is extruded and coated on the outer circumference of the third shielding layer, a slow cooling section is provided after extrusion of the outer jacket to soften and adhere the interface between the third shielding layer and the outer jacket. A method of manufacturing a coaxial cable, characterized by: