WO2008074179A1

WO2008074179A1 - A coaxial cable and its manufacturing approach

Info

Publication number: WO2008074179A1
Application number: PCT/CN2006/003259
Authority: WO
Inventors: Zijü REN; Baijiang Song
Original assignee: Zte Corporation
Priority date: 2006-12-04
Filing date: 2006-12-04
Publication date: 2008-06-26

Abstract

A coaxial cable consists of a inner conductor (31), a insulator (32, 33), a shield (34) and a sheath (35) from the inner to the outer, the insulator (32, 33) contains a foaming insulator(32) inside and a solid insulator (33) outside. A manufacturing approach of a coaxial cable, is that the first step is to supply a inner conductor (31), the Second step is to extrude a foaming insulator (32), the third Step is to extrude a solid insulator (33), the forth Step is to braid a shield (34) and the last step is to extrude a sheath (35).The invention has solved the prior cable' defects, such as large cable diameter, large attenuation, difficulty in machining cable subassembly and peeling head, and high cost.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial cable, such as a 75 ohm coaxial cable for a 2M interface in the field of communication. The invention also relates to a method of manufacturing such a coaxial cable. BACKGROUND OF THE INVENTION In the field of communications, coaxial cables are often used to carry electrical signals, such as 2M interfaces for transmission equipment and switching equipment. One: a 75 ohm coaxial cable is used to transmit 2 Mbps signals, and CDMA and WCDMA equipment are used for RF signals. It is also transmitted by coaxial cable. Common coaxial cables have characteristic impedances of 50 ohms and 75 ohms. The characteristic impedance of the local coaxial cable for communication is 75 ohms, and cables of different wire diameters can be used depending on the transmission distance of the signal and the requirements for attenuation. For the coaxial cable used for the 2M interface, each device manufacturer selects coaxial cables of different wire diameters according to the requirements of the wiring density of the device. For the local coaxial cable in the field of communication, in the early years, equipment manufacturers generally chose a coaxial cable with a cable outer diameter of 3.2 mm ~ 5.0 mm. The structure of this cable is shown in Figure 1. The cable 1 includes: an inner conductor 11, an insulating layer 12, a screen layer 13, and a sheath 14. The cable 1 is characterized in that: the insulating layer 12 is a solid polyolefin material, and the outer diameter of the cable 1 is relatively large, and the attenuation is small, and it is required to occupy more wiring space in the device, so that the outlet density of the device is not high. In recent years, in order to increase the outlet density of equipment, equipment manufacturers mostly use coaxial cable 2 with a wire diameter of 1.6 mm to 3.0 mm. The structure of the cable 2 is as shown in Fig. 2, wherein the diameter of the inner conductor 21 The thickness of the solid bonding layer 22 of the polyethylene material is 0.05 ± 0.01 mm, the thickness of the insulating layer 23 of the foamed structure of the polyethylene material is 1.2 ± 0.05 mm, and the outer diameter of the outer conductor shielding layer is 1.8. The outer diameter of the mm, and the low-smoke, halogen-free sheath 25 is 2.2 ± 0.1 mm. A cable of this construction is disclosed in Chinese Utility Model Patent ZL 200420120974.5. Although in order to reduce the cable diameter and not increase the cable attenuation too much, the insulating layer of the cable 2 is made of a physically foamed polyolefin material, and in order to ensure the adhesion between the inner conductor and the insulating layer of the cable 2, the inner conductor A bonding layer of polyolefin is disposed between the 21 and the insulating layer 23, but the cable 2 is easily wetted by water due to its foamed structure, resulting in a corresponding change in distributed capacitance and inductance, forming its characteristic resistance, resulting in relatively large attenuation. In addition, because of the addition of the bonding layer 22, the cost is higher, and in the cable assembly During the processing, when the adhesive layer 22 in the insulating layer 23 is peeled off, the inner conductor 21 is easily damaged, causing a quality hazard. SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a coaxial cable that solves the problems of large cable diameter, large attenuation, difficulty in processing and stripping of cable assemblies, and high cost. In order to solve the above technical problem, the present invention provides a coaxial cable comprising, in order from the inside to the outside, an inner conductor, an insulating layer, a shielding layer, and a sheath, wherein the insulating layer includes a foamed insulating layer on the inner side. And a solid insulation layer on the outside. Preferably, the inner conductor is made of tinned copper wire. Preferably, the foamed insulating layer, the solid insulating layer and/or the sheath are made of a polyolefin material. Preferably, the shielding layer is made of woven copper wire of φ 0.08 mm. Preferably, the sheath is made of a low-smoke, halogen-free material. Preferably, the foamed insulating layer has a thickness of from 0.35 to 0.55 mm, preferably 0.45 mm. Preferably, the solid insulating layer has a thickness of 0.04 to 0.06 mm, preferably 0.05 mm. Preferably, the jacket has a diameter of 2.0 ± 0.1 mm. Preferably, the inner conductor has a diameter of 0.247 ~ 0.257 mm, the foamed insulating layer has a thickness of 0.45 mm, the solid insulating layer has a thickness of 0.04-0.06 mm, and the solid insulating layer has an outer diameter of 1.26 ± 0.05 mm, and the outer conductor shield layer The diameter of the sheath is 1.8 mm and the outer diameter of the sheath is 2.0 ± 0.1 mm. According to another aspect of the present invention, a method for manufacturing a coaxial cable is provided, comprising: step one, providing an inner conductor; step two, extruding a foamed insulating layer forming a foamed structure; , extruding a solid insulating layer forming a solid skin structure; step four, weaving the shielding layer; and step five, extruding to form a sheath. Preferably, in the first step, the inner conductor is further preheated. Further, the bridge pressure can be appropriately increased. Preferably, in the second step, the foamed insulating layer is made of a foamed polyethylene material, and the extruded thickness is 0.35-0.55 mm, preferably 0,45 mm. Preferably, in step three, the solid insulating layer (33) is made of a polyethylene cerium material having an extruded thickness of 0.04 to 0.06 mm, preferably 0.05 mm. Preferably, step 3 is performed while performing step two, and a solid insulating layer (32) forming a solid sheath structure is directly extruded on the foamed insulating layer (32) of the foamed structure formed by extrusion. The invention has the following advantages: Since the insulating layer comprises a foamed insulating layer on the inner side and a solid insulating layer on the outer side, the surface of the insulating layer is smooth and flat, and the hooking property is good compared with the prior art. Since the outer solid insulating layer can prevent moisture from penetrating into the foamed insulating layer, it can function as a moisture barrier and thus reduce the attenuation of the cable. And since the attenuation of the cable can be reduced, the diameter of the cable can be further reduced if the attenuation allows. Since the bonding layer previously disposed between the inner conductor and the insulating layer is eliminated, it is possible to avoid damage to the inner conductor when the cable assembly is subjected to stripping, thereby reducing the reject rate and improving the quality of the cable assembly. Correspondingly, the process of previously forming an adhesive layer on the inner conductor is eliminated, which simplifies the processing and reduces the cost. Since the inner conductor is preheated during the processing, and then the foamed insulating layer is extruded on the inner conductor, the inner conductor and the inner conductor can be increased although the bonding layer previously provided between the inner conductor and the insulating layer is eliminated. The adhesion of the foamed insulating layer and the adhesion of the foamed insulating layer to the inner conductor. At the same time, since the foamed insulating layer in direct contact with the inner conductor has a large thickness with respect to the original bonding layer, the adhesion and adhesion between the inner insulating conductor and the inner conductor does not affect the peelability, that is, the cable assembly The insulating layer of the present invention facilitates stripping during processing. The above and other features and advantages of the present invention will become more apparent from the embodiments of the invention. For the sake of clarity, the dimensions in the figure may have been enlarged. In the drawings: FIG. 1 is a transverse cross-sectional view showing a coaxial cable of a larger wire diameter commonly used by existing communication device manufacturers; FIG. 2 is a view showing a commonly used communication device manufacturer in recent years. Coaxial cable with bonding layer Transverse cross-sectional view; Fig. 3 is a transverse cross-sectional view showing a coaxial cable having a foamed insulating layer in an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a coaxial cable 3 having a foamed insulating layer 32 of an exemplary embodiment of the present invention will be described more fully and fully with reference to the accompanying drawings, wherein Referring to FIG. 3, a coaxial cable 3 having a foamed insulating layer 32 according to an embodiment of the present invention includes, in order from the inside to the outside, an inner conductor 31, insulating layers 32 and 33, an outer conductor shield layer 34, and a sheath 35. Among them, the insulating layers 32 and 33 are composed of a foamed insulating layer 32 and a solid insulating layer 33. In terms of materials, the inner conductor 31 of the coaxial cable 3 having the foamed insulating layer 32 according to an exemplary embodiment of the present invention is made of a φ 0.26 mm high quality tinned copper wire produced by Shanghai Zhenxiong Copper Co., Ltd. The outer conductor shielding layer 34 is made of a tinned copper wire of φ 0.08 mm, and the foamed insulating layer 32, the solid insulating layer 33 and the sheath 35 can be made of a polyolefin material. The material of the foamed insulating layer 32 of the foamed structure may be DGDA3485 foamed polyethylene of Dow Company of the United States, and the solid insulating layer 33 of the solid skin structure may be made of solid polyethylene of HDPE5305E of Mitsui, Japan. The material used for the sheath 35 is a low-smoke halogen-free material. For example, the AFR/15 sheath material of the Italian Pandner Company can be used, which meets the ROHS environmental protection requirements. Further, in terms of structural parameters, the inner conductor 31 of the coaxial cable 3 having the foamed insulating layer 32 according to the exemplary embodiment of the present invention has a diameter of 0.247 to 0.257 mm, and foam insulation of the polyethylene material. The thickness of layer 32 is 0.35-0.55 mm, preferably 0.45 mm, the thickness of solid insulating layer 33 of polyethylene material is 0.04-0.06 mm, preferably 0.05 mm, and the outer diameter of solid insulating layer 33 is 1.26 ± 0.05 mm, shielding of outer conductor The outer diameter of the layer 34 is 1.8 mm, and the outer diameter of the jacket 35 of the 4-inch smoke-free material is 2.0 ± 0.1 mm. In an exemplary embodiment of the present invention, the insulation is a foamed structure formed of a foamed polyethylene material, and extruded on the outer layer to form a 0.05 mm polyethylene solid skin layer. This insulating structure can be called Insulate PE foam. A method of manufacturing the coaxial cable 3 having the foamed insulating layer 32 according to an exemplary embodiment of the present invention will be described below. The manufacturing method includes preheating and extruding the tinned inner conductor 31 having a diameter of 0.247 to 0.257 mm to form insulating layers 32 and 33, a braided outer conductor shield layer 34, and extruding to form a sheath 35. Specifically, in the method of manufacturing the coaxial cable 3 having the foamed insulating layer 32 according to an exemplary embodiment of the present invention, the tin-plated inner conductor 31 having a diameter of 0.247 to 0.257 mm is first preheated, which can be increased. The adhesion of the conductor 1 and the foamed insulating layer 32 improves the adhesion of the inner conductor 31 and the foamed insulating layer 32. Then, the polyethylene material is extruded to form a foamed insulating layer 32. Among them, the foamed insulating layer 32 is made of expanded polyethylene. In the process, the extrusion pressure is appropriately increased in accordance with the structural parameters and the process parameters, etc., to further secure the inner conductor after the elimination of the bonding layer 22 between the inner conductor 31 and the foamed insulating layer 32 in the prior art. The adhesion between 31 and the foamed insulating layer 32 is not lowered. Then, solid polyethylene was extruded outside the foamed insulating layer 32 to form a 0.05 mm solid insulating layer 33. The surface of the insulating layer is smooth and uniform, and at the same time, it has a moisture-proof effect. Then, the outer conductor shield layer 34 is woven. Finally, a polyethylene material is extruded over the shield layer 34 to form a jacket 35. Among them, it is preferable that the solid insulating layer 32 of the solid skin structure is directly extruded on the foamed insulating layer 32 while extruding the foamed insulating layer 32 of the foamed structure. The cable 2 (SFYE-75-2-1 χ 8 ) shown in Fig. 2 and the coaxial cable 3 (SYFE - 75 - 2) having the foamed insulating layer 32 according to an exemplary embodiment of the present invention shown in Fig. 3 - 1 X 8 ) The amount of attenuation is compared and the results are shown in the following table:

As can be seen from the above table, the coaxial with the foamed insulating layer 32 according to an exemplary embodiment of the present invention The attenuation of cable 3 (SYFE-75-2-1 x 8 ) is relatively low. In addition, the material used for the bonding layer 22 of the cable 2 shown in Fig. 2 is different from the material used for the solid insulating layer 33 of the cable 3 shown in Fig. 3. If the two materials are the same, the difference in attenuation will be larger. . The attenuation result is a test according to GB/17737.1-2000. As can be seen, in the case where the outer diameter of the coaxial cable 3 having the foamed insulating layer 32 according to the exemplary embodiment of the present invention is reduced, not only the attenuation of the cable is not increased, but the attenuation of the cable is reduced. In addition, the material used for the foamed insulating layer 32 has a large number of via holes therein, which are channels through which water permeates in the foamed insulating layer 32. The present invention passes through the outside of the foamed insulating layer 32. The layer is a solid insulating layer 33 formed of a solid polyolefin which is capable of preventing moisture from penetrating into the foamed insulating layer 32, thereby reducing the attenuation of the cable. Thus, with this configuration, the diameter of the cable can be further reduced with the aid of the attenuation. In addition, by modifying the processing process, the bonding layer 22 previously disposed between the inner conductor 31 and the insulating layer 32 is eliminated, thereby avoiding damage to the inner conductor 31 during the processing of the cable assembly, which reduces the reject rate and improves the cable assembly. The amount of shield, and the elimination of the need to extrude the adhesive layer 22 on the inner conductor 31, simplifies the processing and reduces the cost. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalents, improvements, etc., made within the spirit and scope of the invention are intended to be included within the scope of the appended claims.

Claims

The invention relates to a coaxial cable comprising, in order from the inside to the outside, an inner conductor (31), an insulating layer (32, 33), a shielding layer (34), and a sheath (35), characterized in that the insulating layer (32, 33) includes a foamed insulating layer (32) on the inner side and a solid insulating layer (33) on the outer side. The coaxial cable according to claim 1, characterized in that the inner conductor (31) is made of tinned copper wire. The coaxial cable according to claim 1, wherein the foamed insulating layer (32), the solid insulating layer (33) and/or the sheath (35) are made of a polyolefin material . The coaxial cable according to claim 1, wherein said shield layer (34) is woven from a tinned copper wire of φ 0.08 mm. The coaxial cable according to claim 1, characterized in that the sheath (35) is made of a low-smoke halogen-free material.

The coaxial cable according to any one of claims 1 to 5, wherein the foamed insulating layer (32) has a thickness of 0.35 to 0.55 mm, preferably 0.45 mm.

The coaxial cable according to any one of claims 1 to 5, characterized in that the solid insulating layer (33) has a thickness of 0.04 - 0.06 mm, preferably 0.05 mm.

The coaxial cable according to any one of claims 1 to 5, wherein the sheath

The outer diameter of ( 35 ) is 2.0 ± 0.1 mm.

The coaxial cable according to any one of claims 1 to 5, wherein the inner conductor (31) has a diameter of 0.247 - 0.257 mm, and the foamed insulating layer (32) has a thickness of 0.45 Mm, the solid insulating layer (33) has a thickness of 0.04-0.06 mm, the solid insulating layer (33) has an outer diameter of 1.26 ± 0.05 mm, and the outer conductor shielding layer (34) has an outer diameter of 1.8 mm. The outer diameter of the sheath (35) is 2.0 ± 0.1 mm.

A method of manufacturing a coaxial cable, comprising:

Step one, providing an inner conductor (31);

Step two, extruding a foamed insulating layer (32) forming a foamed structure;

Step three, extruding a solid insulating layer (33) forming a solid skin structure;

Step four, braiding the shielding layer (34);

In step five, extrusion forms a sheath (35).

The method of manufacturing a coaxial cable according to claim 10, wherein in the step 1, the step of preheating the inner conductor (31).

The method of manufacturing a coaxial cable according to claim 11, wherein in the second step, the extrusion pressure is increased.

The method of manufacturing a coaxial cable according to any one of claims 10 to 11, wherein in the second step, the foamed insulating layer (32) is made of a foamed polyethylene material, The thickness of the extrusion is from 0.35 to 0.55 mm, preferably 0.45 mm.

The method for manufacturing a coaxial cable according to any one of claims 10 to 11, wherein in the third step, the solid insulating layer (33) is made of a polyethylene material, and the thickness thereof is extruded. It is 0.04-0.06 mm, preferably 0.05 mm.

The method of manufacturing a coaxial cable according to any one of claims 10 to 11, wherein the step 3 is performed while the step 2 is performed, and the foamed structure is formed by extrusion. On the bubble insulating house (32), a solid insulating layer (32) of a solid skin structure is directly extruded.