Low-attenuation coaxial cable and preparation method thereof

Abstract

The invention discloses a low-attenuation coaxial cable and a preparation method thereof. The cable insulation layer comprises a supporting framework and a foaming layer. The supporting framework is provided with ridges with the same height and a base band of a net structure; the ridges of the supporting framework are supported on the outer surface of the inner conductor, so that the base band forms an annular net concentric with the inner conductor, the foaming layer is attached to the annular net, and the outer surface of the foaming layer is concentric with the inner conductor; the outer conductor is coated with a foaming layer of the insulating layer and is concentric with the inner conductor; the outer sheath wraps the outer conductor. According to the low-attenuation coaxial cable provided by the invention, the foaming layer is extruded on the outer side of the supporting framework, and the thickness of the foaming layer is reduced compared with that of an insulating layer made of a full-foaming layer, so that a regular circular appearance can be formed more easily, and when the outer conductor acts on the insulating layer, the foaming layer can provide uniform and comprehensive support; therefore, the roundness of the outer conductor and the concentricity between the outer conductor and the inner conductor are improved, and the attenuation of the large-size coaxial cable is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and more specifically, relates to a low-attenuation coaxial cable and a preparation method thereof. Background Art

[0002] A coaxial cable is a communications cable consisting of two conductors, one inner and one outer. From the inside out, these are: an inner conductor, an insulating foam layer, an outer conductor, and an outer sheath. The inner and outer conductors are coaxially nested, forming a current loop. The insulation in a coaxial cable is the material between the center conductor and the outer conductive shielding layer, and it plays a crucial role in the coaxial cable.

[0003] The insulating medium separates the center conductor from the outer conductive shield, preventing electrical short circuits between the two. This ensures that current flows only along its intended path within the center conductor, thus ensuring proper signal transmission. Without good insulation, current can leak, causing signal distortion, attenuation, or even failure to transmit. Properties such as the dielectric constant of the insulating medium affect signal transmission speed and loss within the cable. A suitable insulating medium enables signal transmission through the cable at high speeds and with minimal attenuation, maintaining signal integrity and accuracy.

[0004] Therefore, the insulating medium for coaxial cables has two requirements: first, maintaining the coaxial position of the inner and outer conductors; second, having a low dielectric constant to minimize signal attenuation. Theoretically, a hollow space between the inner and outer conductors results in the lowest dielectric constant and optimal transmission performance. However, maintaining coaxial position between the inner and outer conductors is not feasible. Currently, expanded polyethylene (PE) is commonly used as the insulating medium. It has a low dielectric constant and high hardness, and the density can be further reduced by increasing the foaming ratio. Currently, the density of expanded polyethylene can reach over 80%, even 90%, and can be reduced to below 0.3 g / cm³. Further reduction in the dielectric constant by increasing the polyethylene foaming ratio and reducing the density is difficult. However, for large-diameter coaxial cables, the insulation foam layer increases in size, and excessively thick PE foam takes a long time to cool, which can cause deformation due to external forces, resulting in reduced concentricity. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides a low-attenuation coaxial cable and a preparation method, the purpose of which is to form an insulating layer with uniform support and a thinner foam layer by combining a support skeleton with a foam layer, thereby shortening the cooling time of the foam layer, improving the roundness of the insulating layer after molding and the concentricity with the inner conductor, providing the outer conductor with regular shape, isotropic uniform support, improving the concentricity of the outer conductor and the inner conductor and making it less prone to deformation, thereby reducing the attenuation of the coaxial cable and optimizing the electrical performance of the coaxial cable, thereby solving the technical problem of the prior art in that it is difficult to provide uniform and regular insulating layer support when manufacturing large-size coaxial cables, resulting in deterioration of concentricity and roundness and decreased electrical performance.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a low-attenuation coaxial cable comprising, from the inside out, an inner conductor, an insulating layer, an outer conductor, and an outer sheath;

[0007] The insulating layer includes a support frame and a foam layer; the support frame has a highly consistent ridge and a base tape with a mesh structure; the ridge of the support frame is supported on the outer surface of the inner conductor, so that the base tape forms an annular network concentric with the inner conductor, and the foam layer is attached to the annular network, and its outer surface is concentric with the inner conductor;

[0008] The outer conductor is covered with the foam layer of the insulating layer and is concentric with the inner conductor;

[0009] The outer sheath covers the outer conductor.

[0010] Preferably, the spine of the support frame of the low-attenuation coaxial cable has arc-shaped legs that match the outer diameter of the inner conductor, and the connection between the spine of the support frame and the baseband has side wings.

[0011] Preferably, the ridge of the support frame of the low-attenuation coaxial cable is arranged along the radial direction of the cable.

[0012] Preferably, the baseband of the low-attenuation coaxial cable has a three-dimensional annular mesh structure, the side connected to the ridge has a base surface, the ridge is combined with the base surface, and the other side is an open mesh.

[0013] Preferably, the support skeleton of the low-attenuation coaxial cable is unfolded into a long strip and spirally arranged around the inner conductor.

[0014] Preferably, the baseband width of the low-attenuation coaxial cable is satisfy:

[0015]

[0016] in, is the cross-sectional radius of the inner conductor, is the height of the ridge supporting the skeleton, is the wrapping inclination angle.

[0017] Preferably, in the low-attenuation coaxial cable, within a unit space between the inner conductor and the outer conductor, the average volume proportion of the support skeleton is less than or equal to 20%, and the foaming degree of the foaming layer is greater than or equal to 80%.

[0018] Preferably, the insulation layer thickness of the low-attenuation coaxial cable is greater than or equal to 6.5 mm.

[0019] According to another aspect of the present invention, there is provided a method for preparing the low-attenuation coaxial cable, comprising the following steps:

[0020] (1) Install a support frame outside the inner conductor so that the mesh structure base band of the support frame forms a ring network coaxial with the inner conductor;

[0021] (2) Extruding the molten insulating foam material onto the annular net and forming a foam layer with a preset outer diameter through the extruder outlet die;

[0022] (3) After the foamed layer is cooled and formed, an outer conductor is formed and an outer sheath is extruded to obtain the coaxial cable.

[0023] Preferably, the method for preparing the low-attenuation coaxial cable comprises the following steps (1):

[0024] Wrap the prefabricated support frame so that the ridge of the support frame is supported on the inner conductor, and the wrapping angle is ,in is the baseband width, is the cross-sectional radius of the inner conductor, is the height of the ridges that support the skeleton.

[0025] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0026] The low-attenuation coaxial cable provided by the present invention utilizes a foam layer extruded outside a support frame. Because the thickness of the foam layer is reduced compared to an insulation layer made of a fully foamed layer, it more easily forms a regular circular appearance. When the outer conductor acts on the insulation layer, the foam layer provides uniform and comprehensive support, rather than the partial support provided by the support frame. This improves the roundness of the outer conductor and the concentricity between the outer and inner conductors, effectively reducing the attenuation of large-sized coaxial cables. In a preferred embodiment, the support frame and the foam layer are combined to reduce the unit volume of the support frame, thereby reducing the average density of the insulation layer without further increasing the foaming degree of the foam layer, thereby reducing the dielectric constant of the insulation layer and further reducing the attenuation of the coaxial cable.

[0027] The method for preparing the low-attenuation coaxial cable provided by the present invention enables the foaming layer and the supporting skeleton to be tightly combined to produce a stable and regular insulating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the end face structure of a low-attenuation coaxial cable provided by an embodiment of the present invention;

[0029] Figure 2 1 is a schematic diagram of the cross-sectional structure of a low-attenuation coaxial cable provided by an embodiment of the present invention;

[0030] Figure 3 1 is a schematic structural diagram of a ridge of a low-attenuation coaxial cable support skeleton provided by an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the unfolded structure of a prefabricated support frame for a low-attenuation coaxial cable provided by an embodiment of the present invention;

[0032] Figure 5 It is a schematic diagram of a method for preparing a low-attenuation coaxial cable provided by an embodiment of the present invention.

[0033] In all the drawings, the same figure marks are used to represent the same elements or structures, where: 1 is the inner conductor, 2 is the insulating layer, 21 is the supporting frame, 211 is the ridge, 2111 is the arc-shaped support foot, 2112 is the side wing, 212 is the base tape, 2121 is the base surface, 2122 is the open mesh structure, 22 is the foaming layer, 3 is the outer conductor, 4 is the outer sheath, 01 is the wrapping head, 02 is the extruder head, and 021 is the extruder outlet die. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0035] The low-attenuation coaxial cable provided by the present invention comprises, from the inside out, an inner conductor, an insulating layer, an outer conductor and an outer sheath;

[0036] The inner conductor is generally a metal wire or a metal tube. Large-sized coaxial cables generally use metal tubes, such as copper tubes.

[0037] The insulating layer includes a supporting skeleton and a foaming layer; the supporting skeleton has a highly consistent ridge and a base strip with a mesh structure; the ridge of the supporting skeleton is supported on the outer surface of the inner conductor, so that the base strip forms an annular network concentric with the inner conductor, and the foaming layer is attached to the annular network, and its outer surface is concentric with the inner conductor.

[0038] The ridge of the support frame has an arc-shaped support foot that matches the outer diameter of the inner conductor. The ridge of the support frame is connected to the base belt with a side wing, so that the annular network formed by the base belt remains stable, and the supporting strength is guaranteed when the foaming layer is prepared, forming a foaming layer with a regular circular appearance. In the preferred embodiment, the ridge of the support frame is arranged radially along the cable. When the cable body is subjected to lateral pressure, the pressure is transmitted radially. The radially arranged ridge can better reduce deformation and provide the cable with good resistance to lateral pressure.

[0039] The base belt has a three-dimensional annular network structure, and the side connected to the ridge has a base surface. The ridge is combined with the base surface, and the other side is an open network structure, so that the molten extrudate forming the foaming layer can enter, thereby being tightly combined with the base belt into a whole. The base surface can effectively limit the position of the molten extrudate to form a uniform annular foaming layer.

[0040] The insulating layer of the composite structure needs to be supported on the inner conductor by a prefabricated support frame, and then the foam layer is extruded to form. Conveniently, the support frame is unfolded into a long strip and spirally arranged around the inner conductor. The base tape is wrapped to form a ring network concentric with the inner conductor. Therefore:

[0041] The baseband width satisfy:

[0042]

[0043] in, is the cross-sectional radius of the inner conductor, is the height of the ridge supporting the skeleton, is the wrapping inclination angle.

[0044] The supporting skeleton is preferably a non-polar material with good strength and bending modulus, such as high-density polyethylene; the foaming layer also needs to be made of a non-polar material, and the preferred solution has good compatibility with the material of the supporting skeleton. When the supporting skeleton is made of high-density polyethylene material, the foaming layer is preferably foamed polyethylene.

[0045] In large-sized coaxial cables, the support skeleton has the advantages of low average density, low dielectric constant, and no need for cooling and forming. However, the support performance of the support skeleton is uneven. When subjected to external forces during winding, transportation, installation, etc., the concentricity of the coaxial cable deteriorates, resulting in performance degradation of the coaxial cable. When foaming materials such as foamed polyethylene are used as the insulating layer, the foaming degree has reached 80% or even 90%, which is difficult to improve further. During the cooling and forming process of the thicker foam layer, the temperature distribution is uneven, and problems such as defoaming and deformation are prone to occur. The roundness and concentricity of the insulating layer deteriorate, resulting in degradation of the cable performance. The present invention combines the support skeleton and the foam layer as the insulating layer. The support skeleton is regular and not easily deformed. The foam layer makes the supporting structure uniform and stable, and the thinner foam layer has good molding stability. Combined with the above characteristics, the roundness and concentricity of the insulating layer are improved, thereby ensuring the electrical performance of the large-sized coaxial cable. A preferred solution uses a relatively sparse support skeleton to partially replace the uniformly foamed insulation layer. This reduces the average density of the insulation layer, thereby lowering the dielectric constant and optimizing the cable's overall performance, while preserving the foaming degree of the foamed insulation material. Within the unit space between the inner and outer conductors, the average volume of the support skeleton accounts for less than or equal to 20%, and the foaming degree of the foam layer is greater than or equal to 80%.

[0046] The outer conductor is covered with the foam layer of the insulating layer and is concentric with the inner conductor;

[0047] The outer sheath covers the outer conductor.

[0048] The thickness of the insulation layer is greater than or equal to 6.5 mm. This type of coaxial cable usually has a thick insulation layer, which causes defoaming and shape distortion during cooling and shaping of the foamed insulation, and deterioration of concentricity and roundness, such as 7 / 8" coaxial cable and 5 / 8" coaxial cable.

[0049] The method for preparing a low-attenuation coaxial cable provided by the present invention comprises the following steps:

[0050] (1) Install a support frame outside the inner conductor so that the mesh structure base band of the support frame forms a ring network coaxial with the inner conductor; the preferred solution is to use a prefabricated support frame to wrap around the ring network, and the specific steps are as follows:

[0051] Wrap the prefabricated support frame so that the ridge of the support frame is supported on the inner conductor, and the wrapping angle is ,in is the baseband width, is the cross-sectional radius of the inner conductor, is the height of the ridges that support the skeleton.

[0052] (2) Extruding the molten insulating foam material onto the annular net and forming a foam layer with a preset outer diameter through the extruder outlet die;

[0053] (3) After the foamed layer is cooled and formed, an outer conductor is formed and an outer sheath is extruded to obtain the coaxial cable.

[0054] The following are examples:

[0055] The low-attenuation coaxial cable provided in this embodiment is a 15 / 8" radio frequency coaxial cable with an end face structure as shown in FIG. Figure 1 As shown, the cross-sectional structure is Figure 2 As shown, from the inside out, it includes an inner conductor 1, an insulating layer 2, an outer conductor 3 and an outer sheath 4;

[0056] Inner conductor 1, a hollow copper tube;

[0057] The insulation layer 2 has a width of 12.3 mm on the cable end surface and includes a support frame 21 and a foam layer 22; the support frame 21, such as Figure 3 As shown, it has a ridge 211 with a height of 9 mm and a base band 212 with a mesh structure; the ridge 211 of the supporting skeleton is supported on the outer surface of the inner conductor 1, so that the base band 212 forms an annular network concentric with the inner conductor 1, and the foaming layer 22 is attached to the annular network, and its outer surface is concentric with the inner conductor 1.

[0058] The ridge 211 of the support frame 21 has a specific structure as follows Figure 3 As shown, it has an arc-shaped support foot 2111 that matches the outer diameter of the inner conductor 1. The connection between the ridge 211 of the support frame 21 and the base belt 212 has a side wing 2112, so that the annular network formed by the base belt 212 remains stable, and the supporting strength is guaranteed when preparing the foaming layer 22, forming a foaming layer 22 with a regular circular appearance. In this embodiment, the ridge 211 of the support frame 21 is arranged along the radial direction of the cable.

[0059] The base belt 212 has a three-dimensional annular network structure, and one side thereof connected to the ridge 211 has a base surface 2121. The ridge 211 is combined with the base surface 2121, and the other side thereof is an open network structure 2122, so that the molten extrusion material forming the foaming layer 22 can enter, thereby being tightly combined with the base belt 212 as a whole, and the base surface 2121 can effectively limit the position of the molten extrusion material to form a uniform annular foaming layer 22.

[0060] The insulating layer of the composite structure needs to be supported on the inner conductor 1 by a prefabricated support frame 21, and then the foam layer 22 is extruded to form. In this embodiment, the support frame 21 is unfolded into a long strip, such as Figure 4 As shown, the base tape 212 is spirally arranged around the inner conductor 1, and the base tape 212 is formed into a ring network concentric with the inner conductor 1 by wrapping. Therefore:

[0061] Baseband 1 width satisfy:

[0062]

[0063] in, is the cross-sectional radius of the inner conductor, is the height of the ridge supporting the skeleton, is the wrapping inclination angle.

[0064] The supporting frame 21 is made of high-density polyethylene, with an average volume share of 18%; the foaming layer 22 is made of foamed polyethylene, with a foaming degree of 85%.

[0065] The outer conductor 3 is a longitudinally wrapped threaded copper tube, covered with a foamed insulating layer, and is concentric with the inner conductor 1; the inner diameter is 42.5 mm;

[0066] The outer sheath 4 covers the outer conductor 3 and is a low-smoke zero-halogen sheath.

[0067] The present invention provides a method for preparing a low-attenuation coaxial cable, such as Figure 5 As shown, the following steps are included:

[0068] (1) Install the support frame outside the inner conductor. The specific steps are as follows:

[0069] The prefabricated support frame 21 is wrapped by a wrapping machine 01 so that the ridge 211 of the support frame 21 is supported on the inner conductor 1. The wrapping angle is ,in is the width of the baseband 212, is the cross-sectional radius of the inner conductor 1, is the height of the ridges that support the skeleton.

[0070] (2) Extruding molten foamed polyethylene onto the annular net through the basic die 02, and forming a foam layer 22 with a preset outer diameter through the extruder outlet die 021;

[0071] (3) After the foaming layer 22 is cooled and formed, the copper strip is longitudinally wrapped and rolled into a thread to form an outer conductor 3, and an outer sheath 4 is extruded outside the outer conductor 3 to obtain the coaxial cable.

[0072] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low-attenuation coaxial cable, characterized in that: From the inside out, it includes inner conductor, insulation layer, outer conductor and outer sheath; The insulating layer includes a support frame and a foam layer; the support frame has a highly consistent ridge and a base tape with a mesh structure; the ridge of the support frame is supported on the outer surface of the inner conductor, so that the base tape forms an annular network concentric with the inner conductor, and the foam layer is attached to the annular network, and its outer surface is concentric with the inner conductor; The outer conductor is covered with the foam layer of the insulating layer and is concentric with the inner conductor; The outer sheath covers the outer conductor.

2. The low-attenuation coaxial cable according to claim 1, wherein The ridge of the support frame has an arc-shaped support foot that matches the outer diameter of the inner conductor, and the connection between the ridge of the support frame and the base band is provided with a side wing.

3. The low-attenuation coaxial cable according to claim 1, wherein The ridges of the support frame are arranged along the radial direction of the cable.

4. The low-attenuation coaxial cable according to claim 1, wherein The base belt has a three-dimensional annular network structure, one side of which is connected to the ridges and has a base surface, the ridges are combined with the base surface, and the other side of the base belt is an open network.

5. The low-attenuation coaxial cable according to claim 1, wherein The support frame is unfolded into a long strip and is arranged spirally around the inner conductor.

6. The low-attenuation coaxial cable according to claim 5, wherein: The baseband width satisfy: in, is the cross-sectional radius of the inner conductor, is the height of the ridge supporting the skeleton, is the wrapping inclination angle.

7. The low-attenuation coaxial cable according to claim 5, wherein In a unit space between the inner conductor and the outer conductor, an average volume proportion of the support skeleton is less than or equal to 20%, and a foaming degree of the foaming layer is greater than or equal to 80%.

8. The low-attenuation coaxial cable according to claim 1, wherein The thickness of the insulating layer is greater than or equal to 6.5 mm.

9. The method for preparing a low-attenuation coaxial cable according to any one of claims 1 to 8, wherein: The following steps are involved: (1) Install a support frame outside the inner conductor so that the mesh structure base band of the support frame forms a ring network coaxial with the inner conductor; (2) Extruding the molten insulating foam material onto the annular net and forming a foam layer with a preset outer diameter through the extruder outlet die; (3) After the foamed layer is cooled and formed, an outer conductor is formed and an outer sheath is extruded to obtain the coaxial cable.

10. The method for preparing a low-attenuation coaxial cable according to claim 9, wherein: Step (1) is as follows: Wrap the prefabricated support frame so that the ridge of the support frame is supported on the inner conductor, and the wrapping angle is ,in is the baseband width, is the cross-sectional radius of the inner conductor, is the height of the ridges that support the skeleton.

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