JP2540313B2 - High frequency coaxial cable manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a high-frequency coaxial cable used for, for example, a television broadcast power supply line or a micro circuit power supply line.

(Prior art and its problems) When manufacturing a high-frequency coaxial cable in which an insulator made of foamed plastic or solid plastic is interposed in the gap between the inner conductor and the outer conductor, conventionally, the outer conductor is an aluminum or copper pipe. In the case of a smooth tube made of, etc., cover the insulator with a smooth tube having an inner diameter larger than the outer diameter of the insulator, and use interlocking sinking to drop the smooth tube to an inner diameter approximately equal to the outer diameter of the insulator to form an outer conductor. Or, prepare a smooth tube with an inner diameter larger than the outer diameter of the insulator in advance, and after inserting the insulator into it, make the inner diameter of the smooth tube approximately the same as the outer diameter of the insulator by sinking. Was configured.

When the outer conductor is a corrugated pipe made of aluminum or copper, etc., cover it with a smooth pipe with an inner diameter larger than the outer diameter of the insulator and corrugate it with a corrugator to correlate the inner diameter of the smooth pipe with an insulator. The outer diameter of the outer conductor was made substantially equal to or smaller than the outer diameter of the insulator, and the outer conductor was formed by biting into the insulator.

The high frequency coaxial cable thus manufactured by the conventional method is shown in FIGS. 9 and 10.

However, in the manufacturing method in which the outer diameter of the insulator 50 is matched with the inner diameter of the outer conductors 51 and 52 by sinking or the like as in the above-described conventional case, the variation in the outer diameter of the insulator 50 in the length direction and the wall thickness of the smooth tube are used. It was necessary to change the condition of sinking or corrugation due to the variation in the length direction. That is, when the inner diameter of the outer conductors 51, 52 becomes smaller than the outer diameter of the insulator 50 (too tight), the outer conductors 51, 52 are in a state of being excessively strained, and the outer conductors 51, 52 are not affected by temperature change or bending. The conductors 51, 52 may explode, and conversely the outer conductors 51, 52
If the outer diameter of 52 becomes too large, the insulation 50 and outer conductor 5
Since there is a gap between them and 1, 52 and they are not integrated, the insulator 50 may fall out or project during use, which causes a problem. Further, the inner diameters of the outer conductors 51 and 52 determine the electrical characteristics of the high-frequency coaxial cable, particularly the characteristic impedance, so they have certain designed optimum values, and significant changes are not allowed. In order to satisfy these conditions, strict dimensional control was required. Reference numeral 56 is an inner conductor.

In the high-frequency coaxial cable having the corrugated outer conductor 52 shown in FIG. 10, the outer conductor 52 is larger than the outer diameter of the insulator 50.
One of the purposes of making the inner diameter of the wire smaller and making it penetrate into the insulator 50 is to ensure water tightness in the cable axial direction. But the outer conductor
The valley portion 53 of 52 bites into the insulator 50, but the mountain portion 54 does not bite and the air 55 remains. Further, when the valley portion 53 is formed, it is hindered by the repulsive force of the insulator 50, and it is difficult to secure the wave shape, and the biting allowance is limited for stable manufacturing. Therefore, in order to have watertightness in the axial direction, the corrugated outer conductor 52 is used instead of the spiral shape, and the mountain portion 54 is formed.
55 parts of the air of each were independent. Under these circumstances, there has been a demand for the appearance of a high-frequency coaxial cable in which the outer conductor 52 can have not only a ring-shaped corrugation but also a spiral corrugation, and can further improve watertightness.

(Means for Solving the Problems) The present invention, when manufacturing a high-frequency coaxial cable in which an insulator is interposed in the gap between the inner conductor and the outer conductor, the inner peripheral surface of the outer conductor of the pipe and the inner conductor At least one of the inner peripheral surface of the outer conductor and the outer peripheral surface of the inner conductor is formed by facing an unfoamed cylindrical synthetic resin layer to at least one of the outer peripheral surfaces and then heat-foaming the synthetic resin layer. It is a method of manufacturing a high-frequency coaxial cable, which is characterized in that it is closely attached to one side.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is an explanatory view of a method for manufacturing a high frequency coaxial cable in one embodiment of the present invention, showing an upper half portion of a cross section along the cable axis direction. The outer peripheral surface of the inner conductor 1 made of, for example, an aluminum or copper tube is extruded and coated with a cylindrical synthetic resin layer 2 which is unfoamed or insufficiently foamed (referred to as unfoamed in the present invention). The material of this synthetic resin layer 2 is
For example, low density polyethylene, dicumyl peroxide (crosslinking agent) and azodicarbonamide (foaming agent) 100:
A mixture such as a mixture having a weight ratio of 0.5: 10 is used. High-density polyethylene can be used instead of low-density polyethylene. More specifically, azodicarbonamide or P, P'as a foaming agent is added to 100 parts by weight of low-density polyethylene or high-density polyethylene. It is possible to use a mixture of 1 to 50 parts by weight of oxybis (benzenesulfonyl hydrazide) and 0.1 to 2.0 parts by weight of dicumyl peroxide as a crosslinking agent. On the outer peripheral surface of the synthetic resin layer 2, outer conductors 3 made of a smooth tube made of, for example, an aluminum or copper tube are provided at intervals in the radial direction, and the synthetic resin layer 2 and the outer conductor 3 are provided. A space 4 is formed between and.

When the synthetic resin layer 2 and the outer conductor 3 are integrated in the manufacturing process of the high frequency coaxial cable, the synthetic resin layer 2 is formed on the outer peripheral surface of the inner conductor 1 fed from the feeding drum.
Is extrusion-coated, and while being fed in the length direction, a tape-shaped raw material of the outer conductor 3 is longitudinally formed around this outer periphery, and the seam of the tape is made larger than the outer diameter of the synthetic resin layer 2 by a method such as welding. The outer conductor 3 having a large predetermined inner diameter is formed and covered with the synthetic resin layer 2 so that the inner peripheral surface of the outer conductor 3 and the outer peripheral surface of the synthetic resin layer 2 face each other as shown in FIG. The synthetic resin layer 2 is continuously heated at a predetermined position while being fed in the direction. As a result, the synthetic resin layer 2 is foamed and adheres to the inner peripheral surface of the outer conductor 3 to become the insulator 5 as shown in FIG.

The high frequency coaxial cable thus obtained has the outer conductor 3
Since the synthetic resin layer 2 and the synthetic resin layer 2 are in close contact with each other, mechanical properties such as bending properties and drawing strength are improved. Further, since the outer diameter of the insulator 5 is determined by the inner diameter of the outer conductor 3, the outer diameter of the insulator 5 can be easily controlled. Further, when the synthetic resin layer 2 is covered with the outer conductor 3, a sufficient gap can be maintained between the synthetic resin layer 2 and the outer conductor 3, so that the synthetic resin layer 2 is not affected and
The outer conductor 3 having a stable shape is obtained, and from this, a high-frequency coaxial cable having stable electrical characteristics is obtained. Particularly, in the example of the present invention, since the synthetic resin layer 2 is foamed sequentially in the axial direction, it is easy for air to escape, and the synthetic resin layer 2
And the outer conductor 3 are completely adhered.

(Another embodiment) FIGS. 3 to 4 show the case where the corrugated outer conductor 6 made of the same material as the outer conductor 3 is used. Also in this case, a method similar to that of the above embodiment is used. Can be manufactured in. That is, when the synthetic resin layer 2 and the outer conductor 6 are integrated, the outer peripheral surface of the inner conductor 1 fed from the feeding drum is extrusion-coated with the synthetic resin layer 2, and the synthetic resin layer 2 is fed in the lengthwise direction.
A tape-shaped raw material of the outer conductor 6 is longitudinally formed on the outer periphery of the outer conductor 6, and the seam of the tape is formed into a smooth tube by a method such as welding, and the outer diameter of the synthetic resin layer 2 is smaller than the outer diameter of the synthetic resin layer 2 by a corrugator. An outer conductor 6 having a thick valley portion 7 with a predetermined inner diameter
While being formed on the synthetic resin layer 2, the outer conductor 6 and the outer peripheral surface of the outer conductor 6 are opposed to each other as shown in FIG. The synthetic resin layer 2 is continuously heated. As a result, the synthetic resin layer 2 foams and adheres to the inner peripheral surface of the outer conductor 6 to become the insulator 5 as shown in FIG. In this case, since the outer conductor 6 and the insulator 5 are in close contact with each other, air does not exist inside the crest portion 8 of the outer conductor 6, the watertightness in the axial direction is improved, and the outer conductor 6 is corrugated. Not only the ring shape but also the spiral wavy shape can be used. Regarding the dimensions of the outer conductor 6, the outer diameter of the crest portion 8 is 30 mm, the outer diameter of the trough portion 7 is 27.6 mm, and the pitch between the adjacent trough portions 7 or the neighboring crest portions 8 is 10 mm.

5 to 8 show still another embodiment, and the insulator 5 may have a multi-layer structure in this way. That is, the synthetic resin layer 9 is a completely foamed layer or a solid layer, and a synthetic resin layer 2 of unfoamed or incompletely foamed is formed on the outer peripheral surface of the cylindrical synthetic resin layer 9, The resin layer 2 may be heated and foamed to form the insulator 5 with the synthetic resin layer 9 and the synthetic resin layer 2.

In each of the above embodiments, the synthetic resin layer 2 was continuously heated while the synthetic resin layer 2 was covered with the outer conductor 3 or the outer conductor 6, but the synthetic resin layer 2 is covered with the outer conductor 3 or the outer conductor 6. It is also possible to make a cover with a predetermined length, wind this on a cable drum, and put it all together in a high-temperature kettle for heating.

Further, in each of the above-mentioned embodiments, the case where the synthetic resin layer 2 and the outer conductor 3 or the outer conductor 6 are brought into close contact with each other has been described. Can be used. That is, after the inner conductor 1 having an outer diameter smaller than the inner diameter of the synthetic resin layer 2 is drawn into the synthetic resin layer 2, the synthetic resin layer 2 is completely foamed to obtain an insulator 5 that is in close contact with the inner conductor 1. Of.

As described above, according to the present invention, the inner peripheral surface of the outer conductor and the outer peripheral surface of the synthetic resin layer or the outer peripheral surface of the inner conductor and the inner peripheral surface of the synthetic resin layer are opposed to each other. Since the synthetic resin layer is heated and foamed to obtain the insulator, the outer conductor or the inner conductor is completely adhered to the synthetic resin layer, so that the mechanical properties such as bending property and pulling strength are improved. Moreover, since the outer diameter of the insulator is determined by the inner diameter of the outer conductor, the outer diameter of the insulator can be easily controlled. Moreover, when the synthetic resin layer is covered with the outer conductor, a sufficient gap can be maintained between the synthetic resin and the outer conductor, so that the outer conductor having a stable shape can be obtained without being affected by the synthetic resin layer. From this, a high frequency coaxial cable with stable electrical characteristics can be obtained. When the outer conductor is a corrugated pipe, the outer conductor and the synthetic resin layer are in close contact with each other, so that the watertightness in the axial direction is improved, and not only the ring-shaped but also the spiral corrugated can be formed. Since the outer conductor is composed of a tube, when the outer conductor is covered with an unfoamed synthetic resin layer and then the synthetic resin layer is heated and foamed, the foamed synthetic resin layer firmly adheres to the inner surface of the outer conductor and bends. Not only the mechanical characteristics such as the characteristics are improved, but also the electrical characteristics are further improved.

[Brief description of drawings]

1 to 8 are explanatory views of a method for manufacturing a high frequency coaxial cable in an embodiment of the present invention, and FIGS. 9 to 10 are explanatory views of a conventional method for manufacturing a high frequency coaxial cable. 1 ... inner conductor, 2 ... synthetic resin layer, 3,6 ... outer conductor, 5 ... insulator

Claims (2)

(57) [Claims] 1. When manufacturing a high-frequency coaxial cable in which an insulator is interposed in a gap between an inner conductor and an outer conductor, at least one of an inner peripheral surface of the outer conductor and an outer peripheral surface of the inner conductor of the pipe is not covered. After the foamed cylindrical synthetic resin layers are opposed to each other, the synthetic resin layer is heated and foamed to be brought into close contact with at least one of the inner peripheral surface of the outer conductor and the outer peripheral surface of the inner conductor. High frequency coaxial cable manufacturing method. 2. When the synthetic resin layer is heated and foamed, an unfoamed cylindrical synthetic resin layer is formed to a predetermined length on the inner peripheral surface of the outer conductor or the outer peripheral surface of the inner conductor. The method for producing a high frequency coaxial cable according to claim 1, wherein the coil drum is wound around the cable drum and the whole is heated at once.