JPH05335813A - Cable - Google Patents

Abstract

PURPOSE:To obtain a cable having an extruded sheath formed to have a thickness almost uniform in the lengthwise direction and a little fluctuation in outer diameter. CONSTITUTION:An inner conductor 7, an insulator 8, an outer conductor 9 and an outer sheath 10 are provided on a ferrite core 6 in this order, and the insulator 8 consists of a skin layer 81 and an outer sheath 82 provided thereon. Thus, the fluctuation in the outer diameter of the insulator in the lengthwise direction is less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable having an extruded coating on the outer circumference of a conductor, and more particularly to a cable having an extruded coating having a uniform outer diameter.

[0002]

2. Description of the Related Art In general, the insulator of a cable, including the insulator of a coaxial cable, is formed by extrusion of rubber / plastic one layer.

FIG. 2 shows an example of a spiral leaky coaxial cable known as one of coaxial cables, in which an inner conductor 2, an insulator 3, an outer conductor 4 and a jacket 5 are provided on a ferrite core 1. It has a structure provided in order. Then, in this cable, the insulator 3 is usually formed by extruding a single layer of polyethylene.

[0004]

However, in such an insulator formed by one-layer extrusion, when the coating diameter is thin or the coating thickness is thin, the outer diameter does not fluctuate relatively and the thickness is almost uniform in the longitudinal direction. However, if the outer diameter exceeds 8 to 10 mm or the thickness exceeds 1.5 to 2 mm, the coating amount increases, and the temperature of the extruder and Since it is difficult to adjust the extrusion conditions such as the extrusion speed, there is a problem that the fluctuation of the outer diameter becomes large.

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a cable having an extruded coating formed in a substantially uniform thickness in the longitudinal direction with less variation in outer diameter. .

[0006]

The cable of the present invention is a cable having an extrusion coating on the outer periphery of a conductor, wherein the extrusion coating is composed of a plurality of layers, and at least the innermost layer thereof is a skin layer. Is characterized by.

The thickness of the skin layer constituting the innermost layer is preferably about 0.5 to 1.0 mm. By providing such a skin layer, it is possible to smoothly extrude from the second layer, suppress fluctuation in the outer diameter in the longitudinal direction, and form an extruded coating having a uniform thickness. ..

In the present invention, each layer constituting the extrusion coating may be formed by coextrusion of a plurality of layers including a skin layer, and each layer may be formed by extruding each layer individually. You can

[0009]

In the cable of the present invention, since the extruded coating on the outer circumference of the conductor is composed of a plurality of layers, the extruded amount per one time is small, and further, the skin layer is provided as the first layer. Layers, or even the third and fourth layers ...
The extrusion of …… will be performed smoothly. Therefore, even if the extrusion coating has a large outer diameter or a thick coating thickness, it is possible to form a coating having a uniform variation in outer diameter variation in the longitudinal direction.

[0010]

EXAMPLES Examples of the present invention will be described below.

0.2mmφ on 6.5mmφ ferrite core
80 annealed copper wires were horizontally wound to form an inner conductor having an outer diameter of 6.9 mm. Next, in order to provide an insulator with a thickness of 2.8 mm on the inner conductor by extruding polyethylene, first, polyethylene is extruded with a target thickness of 0.6 mm to form an insulator skin layer, and then polyethylene is extruded on this. The thickness is 2.2mm
Was extruded to form an outer layer of an insulator. Here, when measuring the outer diameter of the insulator at intervals in the longitudinal direction, 12.5
It was formed in the range of ± 0.2 mm.

Thereafter, a laminated Al tape having slots for radio wave leakage formed therein is vertically coated on the outer layer of the insulator to form an outer conductor, and polyethylene is extruded on the outer conductor to cover the outer sheath. Was installed to manufacture a spiral leaky coaxial cable with an outer diameter of 16 mm.

FIG. 1 is a perspective view showing a spiral leaky coaxial cable obtained in this way, in which 6 is a ferrite core,
Reference numeral 7 is an inner conductor, 8 is an insulator composed of a skin layer 81 and an outer layer 82, 9 is an outer conductor, and 10 is a jacket.

Next, for comparison, when the insulator 8 was not formed into a two-layer structure and polyethylene was extruded at once to a thickness of 2.8 mm to form the insulator 8, the outer diameter of the insulator 8 was 1
The variation range of the outer diameter was 2.5 ± 1 mm, which was larger than that of the above examples.

As described above, in the above-mentioned embodiment, since the fluctuation range of the outer diameter of the insulator in the lengthwise direction is small, it has good and stable insulating characteristics and high reliability can be obtained.

In this embodiment, only the insulator 8 has a predetermined two-layer structure, but the outer cover 10 may have a similar structure. That is, the first
A skin layer may be provided as the first layer, and the second layer, or the third layer, the fourth layer, and so on may be extrusion-coated in that order on the skin layer. As a result, the outer diameter variation range of the jacket 10 can also be reduced.

The above embodiment is an example in which the present invention is applied to a spiral leaky coaxial cable, but the present invention is not limited to such a cable, and any coaxial cable having an extrusion coating can be used. Not limited to the above, it can be applied to various power cables and communication cables, and in the case of a cable having an extrusion coating as the outermost layer, variation in outer diameter is reduced, so that a cable with good aesthetics can be provided. ..

[0018]

As described above, according to the present invention,
Since the extruded coating on the outer circumference of the conductor is composed of a plurality of layers and at least the innermost layer thereof is the skin layer, it is possible to form an extruded coating having a substantially uniform thickness in the longitudinal direction with less variation in outer diameter. A cable having a good aesthetic appearance can be obtained with the cable having the outermost layer of the coating.

[Brief description of drawings]

FIG. 1 is a perspective view showing a spiral leaky coaxial cable according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional spiral leaky coaxial cable.

[Explanation of symbols]

 7 ... Inner conductor 8 Insulator having a two-layer structure 81 Insulator skin layer 82 Insulator outer layer 9 Outer conductor 10 Outer sheath

Claims (1)

[Claims] 1. A cable having an extruded coating on the outer periphery of a conductor, wherein the extruded coating is composed of a plurality of layers, and at least the innermost layer thereof is a skin layer.