Low-capacitance tandem digital coaxial cable and production method thereof

Abstract

The invention discloses a low-capacitance serial digital coaxial cable and a production method thereof, and the production method comprises the following steps: 1) drawing a copper wire to obtain an inner conductor; 2) cleaning the outer surface of the inner conductor by using a cleaning solution and ultrasonic waves, and then cleaning with clear water and drying; 3) coating an anti-oxidation lining layer on the outer surface of the inner conductor; (4) foaming PTFE belts are wound on the outer surface of the lining layer in sequence to form a plurality of foaming PTFE layers; (5) double-sided aluminum foil is wound on the outer side of the foaming PTFE layer on the outermost layer to form a shielding layer, and the lap joint rate of the double-sided aluminum foil is larger than or equal to 35%; 6) processing a metal braid layer on the outer side of the shielding layer; and 7) coating the outer side of the metal braid layer with a sheath layer. According to the method, the outer surface of the inner conductor is cleaned through the cleaning liquid and ultrasonic waves to effectively remove impurities of the inner conductor, then the inner conductor is cleaned and dried through clean water to obtain the dry and clean inner conductor, finally, after the inner conductor and the lining layer are combined, the mechanical property is better, and return loss is not prone to being increased.

Description

Technical Field

[0001] The invention relates to the field of cables, and in particular to a low-capacitance series digital coaxial cable and a production method thereof. Background Art

[0002] In the broadcasting and television system, digital format is applied to the production and broadcasting of television models. Signal loss occurs during normal signal transmission. In order to reduce signal link loss, low-capacitance coaxial cable is needed to reduce signal link loss. The inner conductor of the existing low-capacitance coaxial cable is easy to move relative to the cable after being stressed, and the movement of the conductor will cause the characteristic impedance to change, resulting in an increase in return loss. Summary of the invention

[0003] In view of the above problems, the present invention provides a low-capacitance series digital coaxial cable and a production method thereof.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for producing a low-capacitance serial digital coaxial cable comprises the following steps:

[0006] 1) The copper wire is drawn to a set size through a die to obtain an inner conductor;

[0007] 2) Clean the outer surface of the inner conductor with a cleaning liquid and ultrasonic waves, then clean the inner conductor with water and dry it;

[0008] 3) A layer of anti-oxidation lining is coated on the outer surface of the inner conductor;

[0009] 4) Winding the foamed PTFE tape on the outer surface of the inner lining layer in sequence to form a multi-layer foamed PTFE layer;

[0010] 5) Wrap double-sided aluminum foil around the outermost foamed PTFE layer to form a shielding layer, and the overlap rate of the double-sided aluminum foil is ≥35%;

[0011] 6) Processing a metal braided layer on the outside of the shielding layer;

[0012] 7) A sheath layer is covered on the outside of the metal braided layer.

[0013] The outer surface of the inner conductor obtained by processing will have copper powder and grease. If the inner lining layer is directly coated on the outer surface of the inner conductor, the connection between the inner conductor and the inner lining layer will be unreliable and the inner conductor will be easy to move. The present application uses a cleaning liquid and ultrasonic waves to clean the outer surface of the inner conductor to effectively remove impurities from the inner conductor, and then washes and dries with clean water to obtain a dry and clean inner conductor. Finally, the mechanical properties of the inner conductor and the inner lining layer are better after being combined, and it is not easy to cause an increase in return loss.

[0014] The inner conductor of this application is made of high-quality oxygen-free solid bare copper, which is of good material and not easy to oxidize. The solid conductor has a more stable characteristic impedance and return loss. Digital signal transmission includes low-frequency transmission along the center of the conductor and high-frequency transmission along the outer surface of the conductor due to the skin effect. The double-sided aluminum foil has the characteristics of high strength and low resistance, which ensures that electromagnetic interference and radio frequency interference are isolated and improves the anti-interference ability of the cable.

[0015] In one embodiment of the present invention, step 2) is implemented by a cleaning device, which includes an ultrasonic cleaning mechanism, a water spraying mechanism, and an air drying mechanism arranged in sequence, wherein the ultrasonic cleaning mechanism includes:

[0016] A cleaning container, wherein both ends of the cleaning container have openings corresponding to each other, the openings are used for the inner conductor to pass through, and the cleaning container is used to contain a cleaning liquid. When working, the liquid level of the cleaning liquid is higher than the inner conductor;

[0017] An ultrasonic generator is fixed on the side wall of the cleaning container;

[0018] The machine box has a cleaning liquid storage tank, the bottom end of the cleaning container is fixed on the cleaning liquid storage tank, and the cleaning liquid in the cleaning container flows into the cleaning liquid storage tank below through two openings;

[0019] An infusion tube, one end of which is connected to the cleaning liquid storage tank, and the other end of which is connected to the cleaning container;

[0020] A delivery pump is installed on the delivery tube and is used to deliver the cleaning liquid in the cleaning liquid storage tank to the cleaning container so that the liquid level of the cleaning container is always above the inner conductor.

[0021] During production, the inner conductor passes through the two openings in turn, and because the delivery pump continuously replenishes the cleaning liquid, it can ensure that the liquid level in the cleaning container is always above the inner conductor. The ultrasonic generator works and can efficiently clean the part of the inner conductor located in the cleaning liquid to remove impurities such as grease and copper powder.

[0022] In one embodiment of the present invention, the outer side of the opening further has a set of limiting rollers cooperating with the inner conductor.

[0023] In one embodiment of the present invention, the clean water spraying mechanism comprises:

[0024] A first shell having a water outlet at the bottom;

[0025] A plurality of water spray pipes arranged inside the first shell and spaced around the axis of the first shell;

[0026] The water receiving box is located below the first shell and is used to receive water from the water outlet.

[0027] The water spray pipe is used to spray clean water onto the inner conductor to remove the residual cleaning liquid on the inner conductor.

[0028] In one embodiment of the present invention, the air-drying mechanism comprises:

[0029] a second shell;

[0030] A plurality of air blowing pipes are arranged inside the second shell and spaced around the axis of the first shell.

[0031] The air blowing tube is used to spray dry gas to the inner conductor to remove the residual water on the inner conductor.

[0032] In one embodiment of the present invention, the inner lining layer is composed of low-density polyethylene and an antioxidant, and the mass ratio of the low-density polyethylene to the antioxidant is 100:3.

[0033] The inner conductor can be made resistant to oxidation by adding antioxidants. In addition, the adhesion between the inner conductor and the core wire is controlled at 50±5N to prevent the inner conductor from moving. Because the movement of the inner conductor will cause the change of characteristic impedance and increase the return loss, the inner lining layer added by this application ensures the stability of the return of the entire cable during link transmission and reduces the return loss.

[0034] In one embodiment of the present invention, the foamed PTFE layer has four layers, which are, from inside to outside, a first foamed PTFE layer, a second foamed PTFE layer, a third foamed PTFE layer, and a fourth foamed PTFE layer;

[0035] The first foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the left direction and has a thickness of 0.3 mm and a width of 5 mm, the second foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the right direction and has a thickness of 0.3 mm and a width of 10 mm, the third foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the left direction and has a thickness of 0.3 mm and a width of 15 mm, and the fourth foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the right direction and has a thickness of 0.3 mm and a width of 20 mm; the overlap rate of the foamed PTFE tape of each foamed PTFE layer is 50%.

[0036] Capacitance is proportional to dielectric constant. To achieve low capacitance and low loss while keeping the size unchanged, the dielectric constant of the material must be reduced. The dielectric constant of the foamed PTFE tape is 1.2, which is much lower than the 1.8 dielectric constant of conventional foamed PE. The low dielectric parameters ensure the low capacitance of the cable and achieve low attenuation of signal transmission.

[0037] In one embodiment of the present invention, the overlap rate of the double-sided aluminum foil is 50%; one side of one surface of the double-sided aluminum foil has a hot melt adhesive layer, and the width of the hot melt adhesive layer is half the width of the double-sided aluminum foil;

[0038] After the double-sided aluminum foil is wrapped, the hot melt adhesive layer is heated to make the double-sided aluminum foil adhere to the outermost foamed PTFE layer.

[0039] When the width of the hot melt adhesive layer is the same as the width of the double-sided aluminum foil, the overlap of the double-sided aluminum foil has a thin hot melt adhesive layer. However, the overlap rate of the double-sided aluminum foil in the present application is 50% and the width of the hot melt adhesive layer is half the width of the double-sided aluminum foil. This arrangement allows the double-sided aluminum foils at the overlap to be in direct contact with each other without a hot melt adhesive layer between the two, and the anti-interference of the shielding layer can be effectively enhanced.

[0040] In one embodiment of the present invention, the metal braided layer is processed by double helix braiding, and the braiding density of the metal braided layer is ≥90%;

[0041] The material of the sheath layer is chlorinated polyethylene.

[0042] The outer conductor is used to achieve lower outer conductor resistance, ensure low attenuation of the link loop, and quickly discharge the inductive current inside the cable out of the cable without affecting the normal operation of surrounding equipment; Chlorinated polyethylene (CPE) is non-toxic and odorless, has excellent ozone resistance, chemical resistance and aging resistance, and has good oil resistance, flame retardancy and coloring properties. Good toughness (still flexible at -30℃).

[0043] The present application also discloses a low-capacitance serial digital coaxial cable, which is prepared by the production method of the low-capacitance serial digital coaxial cable described above. The low-capacitance serial digital coaxial cable of the present application is suitable for cable television systems, satellite receiving systems, security monitoring systems, professional audio systems, home theater systems, computer networks, industrial automation control and other fields.

[0044] The beneficial effects of the present invention are as follows: the outer surface of the inner conductor obtained by processing will have copper powder and grease. If the inner lining layer is directly coated on the outer surface of the inner conductor, the connection between the inner conductor and the inner lining layer will be unreliable, and the inner conductor is easy to move. The present application uses a cleaning liquid and ultrasonic waves to clean the outer surface of the inner conductor to effectively remove impurities of the inner conductor, and then washes and dries with clean water to obtain a dry and clean inner conductor. Finally, the mechanical properties of the inner conductor and the inner lining layer are better after being combined, and it is not easy to cause an increase in return loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a cross-sectional view of a coaxial cable produced by the production method of the low-capacitance serial digital coaxial cable of the present application;

[0046] Figure 2 is a schematic diagram of a cleaning device;

[0047] Figure 3 yes Figure 2 The enlarged view of point A in the middle;

[0048] Figure 4 is a cross-sectional view of the clean water spray washing mechanism;

[0049] Figure 5 is a cross-sectional view of the air-drying mechanism;

[0050] Figure 6 is a schematic diagram of a double-sided aluminum foil with a hot melt adhesive layer.

[0051] The reference numerals in the figures are:

[0052] 1. Inner conductor; 2. Inner lining layer; 3. First foamed PTFE layer; 4. Second foamed PTFE layer; 5. Third foamed PTFE layer; 6. Fourth foamed PTFE layer; 7. Shielding layer; 71. Double-sided aluminum foil; 72. Hot melt adhesive layer; 8. Metal braided layer; 9. Sheath layer; 100. Ultrasonic cleaning mechanism; 11. Cleaning container; 111. Opening; 112. Limiting roller; 12. Ultrasonic generator; 13. Machine box; 131. Cleaning liquid storage tank; 14. Infusion tube; 15. Delivery pump; 200. Clean water spraying mechanism; 21. First shell; 211. Water outlet; 22. Water spraying pipe; 23. Water receiving box; 300. Air drying mechanism; 31. Second shell; 32. Air blowing pipe. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0054] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0055] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0056] The present invention is described in detail below in conjunction with the accompanying drawings.

[0057] like Figure 1 As shown, a method for producing a low-capacitance serial digital coaxial cable comprises the following steps:

[0058] 1) Drawing the copper wire to a set size through a die to obtain an inner conductor 1;

[0059] 2) Cleaning the outer surface of the inner conductor 1 with a cleaning liquid and ultrasonic waves, then cleaning the inner conductor 1 with clean water and drying it;

[0060] 3) A layer of anti-oxidation lining layer 2 is coated on the outer surface of the inner conductor 1;

[0061] 4) Wrapping the foamed PTFE tape on the outer surface of the inner lining layer 2 in sequence to form a multi-layer foamed PTFE layer; in this embodiment, the foamed PTFE layer has four layers, which are, from inside to outside, a first foamed PTFE layer 3, a second foamed PTFE layer 4, a third foamed PTFE layer 5, and a fourth foamed PTFE layer 6;

[0062] 5) Wrapping a double-sided aluminum foil 71 around the outermost foamed PTFE layer (i.e., the fourth foamed PTFE layer 6) to form a shielding layer 7, wherein the overlap rate of the double-sided aluminum foil 71 is ≥35%;

[0063] 6) Processing a metal braided layer 8 on the outer side of the shielding layer 7;

[0064] 7) The outer side of the metal braided layer 8 is covered with a sheath layer 9 .

[0065] The outer surface of the inner conductor 1 obtained by processing will have copper powder and grease. If the inner lining layer 2 is directly coated on the outer surface of the inner conductor 1, the connection between the inner conductor 1 and the inner lining layer 2 will be unreliable, and the inner conductor 1 will be easy to move. The present application uses a cleaning liquid and ultrasonic waves to clean the outer surface of the inner conductor 1 to effectively remove impurities in the inner conductor 1, and then washes and dries with clean water to obtain a dry and clean inner conductor 1. Finally, the mechanical properties of the inner conductor 1 and the inner lining layer 2 are better after being combined, and it is not easy to cause an increase in return loss.

[0066] The inner conductor 1 of the present application is made of high-quality oxygen-free solid bare copper, which is of good material and not easy to oxidize. The solid conductor has a more stable characteristic impedance and return loss. The digital signal transmission includes low-frequency transmission along the center of the conductor and high-frequency transmission along the outer surface of the conductor due to the skin effect. The double-sided aluminum foil 71 has the characteristics of high strength and low resistance, which ensures that electromagnetic interference and radio frequency interference are isolated and improves the anti-interference ability of the cable.

[0067] like Figure 2 and Figure 3 As shown, in this embodiment, step 2) is implemented by a cleaning device, which includes an ultrasonic cleaning mechanism 100, a clean water spraying mechanism 200 and an air drying mechanism 300 arranged in sequence, wherein the ultrasonic cleaning mechanism 100 includes:

[0068] A cleaning container 11, wherein both ends of the cleaning container 11 have openings 111 corresponding to each other, and the openings 111 are used for the inner conductor 1 to pass through. The cleaning container 11 is used to contain a cleaning liquid. When working, the liquid level of the cleaning liquid is higher than the inner conductor 1;

[0069] An ultrasonic generator 12 is fixed on the side wall of the cleaning container 11;

[0070] The machine box 13 has a cleaning liquid storage tank 131. The bottom end of the cleaning container 11 is fixed on the cleaning liquid storage tank 131. The cleaning liquid in the cleaning container 11 flows into the cleaning liquid storage tank 131 below through the two openings 111.

[0071] A liquid infusion tube 14, one end of which is connected to the cleaning liquid storage tank 131, and the other end of which is connected to the cleaning container 11;

[0072] The delivery pump 15 is installed on the infusion tube 14 and is used to deliver the cleaning liquid in the cleaning liquid storage tank 131 to the cleaning container 11 so that the liquid level of the cleaning container 11 is always above the inner conductor 1.

[0073] During production, the inner conductor 1 passes through the two openings 111 in sequence, and because the delivery pump 15 continuously replenishes the cleaning liquid, it can ensure that the liquid level of the cleaning container 11 is always above the inner conductor 1. The ultrasonic generator 12 works and can efficiently clean the part of the inner conductor 1 located in the cleaning liquid to remove impurities such as grease and copper powder.

[0074] like Figure 3 As shown, in this embodiment, the outer side of the opening 111 further has a set of limiting rollers 112 that cooperate with the inner conductor 1 .

[0075] like Figure 2 and Figure 4 As shown, in this embodiment, the clean water spraying mechanism 200 includes:

[0076] The first shell 21 has a water outlet 211 at the bottom;

[0077] A plurality of water spray pipes 22 disposed inside the first housing 21 and spaced apart around the axis of the first housing 21;

[0078] The water receiving box 23 is located below the first housing 21 and is used to receive water from the water outlet 211 .

[0079] The water spray pipe 22 is used to spray clean water toward the inner conductor 1 to remove the residual cleaning liquid on the inner conductor 1 .

[0080] like Figure 2 and Figure 5 As shown, in this embodiment, the air-drying mechanism 300 includes:

[0081] A second housing 31;

[0082] A plurality of air blowing pipes 32 are disposed inside the second shell 31 and spaced apart around the axis of the first shell 21 .

[0083] The air blowing tube 32 is used to spray dry gas toward the inner conductor 1 to remove residual water on the inner conductor 1 .

[0084] In this embodiment, the inner liner 2 is composed of low-density polyethylene and an antioxidant, and the mass ratio of the low-density polyethylene to the antioxidant is 100:3.

[0085] By adding an antioxidant, the inner conductor 1 can be made resistant to oxidation. In addition, the adhesion between the inner conductor 1 and the core wire is controlled at 50±5N, which can prevent the inner conductor 1 from moving. Because the movement of the inner conductor 1 will cause a change in the characteristic impedance, resulting in an increase in the return loss, the inner lining layer 2 is added by the present application to ensure the stability of the return of the entire cable during link transmission and reduce the return loss.

[0086] In this embodiment, the first foamed PTFE layer 3 is formed by winding a foamed PTFE tape which is wrapped in the left direction and has a thickness of 0.3 mm and a width of 5 mm, the second foamed PTFE layer 4 is formed by winding a foamed PTFE tape which is wrapped in the right direction and has a thickness of 0.3 mm and a width of 10 mm, the third foamed PTFE layer 5 is formed by winding a foamed PTFE tape which is wrapped in the left direction and has a thickness of 0.3 mm and a width of 15 mm, and the fourth foamed PTFE layer 6 is formed by winding a foamed PTFE tape which is wrapped in the right direction and has a thickness of 0.3 mm and a width of 20 mm; the overlap rate of the foamed PTFE tape of each foamed PTFE layer is 50%.

[0087] Capacitance is proportional to dielectric constant. To achieve low capacitance and low loss while keeping the size unchanged, the dielectric constant of the material must be reduced. The dielectric constant of the foamed PTFE tape is 1.2, which is much lower than the 1.8 dielectric constant of conventional foamed PE. The low dielectric parameters ensure the low capacitance of the cable and achieve low attenuation of signal transmission.

[0088] like Figure 6 As shown, in this embodiment, the overlap rate of the double-sided aluminum foil 71 is 50%; one side of one surface of the double-sided aluminum foil 71 has a hot melt adhesive layer 72, and the width of the hot melt adhesive layer 72 is half the width of the double-sided aluminum foil 71;

[0089] After the double-sided aluminum foil 71 is wound, the hot melt adhesive layer 72 is heated to make the double-sided aluminum foil 71 adhere to the outermost foamed PTFE layer.

[0090] When the width of the hot melt adhesive layer 72 is the same as the width of the double-sided aluminum foil 71, the overlap of the double-sided aluminum foil 71 has a thin hot melt adhesive layer 72. However, the overlap rate of the double-sided aluminum foil 71 of the present application is 50% and the width of the hot melt adhesive layer 72 is half the width of the double-sided aluminum foil 71. This arrangement allows the double-sided aluminum foils 71 at the overlap to be in direct contact with each other without the hot melt adhesive layer 72 between them, and the anti-interference of the shielding layer 7 can be effectively enhanced.

[0091] In this embodiment, the metal braided layer 8 is processed by double helix braiding, and the braiding density of the metal braided layer 8 is ≥90%;

[0092] The material of the sheath layer 9 is chlorinated polyethylene.

[0093] The outer conductor is used to achieve lower outer conductor resistance, ensure low attenuation of the link loop, and quickly discharge the inductive current inside the cable out of the cable without affecting the normal operation of surrounding equipment; Chlorinated polyethylene (CPE) is non-toxic and odorless, has excellent ozone resistance, chemical resistance and aging resistance, and has good oil resistance, flame retardancy and coloring properties. Good toughness (still flexible at -30℃).

[0094] like Figure 1 As shown, this embodiment also discloses a low-capacitance serial digital coaxial cable, which is prepared by the production method of the low-capacitance serial digital coaxial cable of this embodiment. The low-capacitance serial digital coaxial cable is suitable for cable television systems, satellite receiving systems, security monitoring systems, professional audio systems, home theater systems, computer networks, industrial automation control and other fields.

[0095] The above description is only a preferred embodiment of the present invention, and does not limit the patent protection scope of the present invention. Any equivalent structural transformation made by using the contents of the present invention and the drawings, directly or indirectly used in other related technical fields, is also included in the protection scope of the present invention.

Claims

1. A method for producing a low-capacitance serial digital coaxial cable, characterized in that: The following steps are involved: 1) The copper wire is drawn to a set size through a die to obtain an inner conductor; 2) Clean the outer surface of the inner conductor with a cleaning liquid and ultrasonic waves, then clean the inner conductor with water and dry it; 3) A layer of anti-oxidation lining is coated on the outer surface of the inner conductor; 4) Winding the foamed PTFE tape on the outer surface of the inner lining layer in sequence to form a multi-layer foamed PTFE layer; 5) Wrap double-sided aluminum foil around the outermost foamed PTFE layer to form a shielding layer, and the overlap rate of the double-sided aluminum foil is ≥35%; 6) Processing a metal braided layer on the outside of the shielding layer; 7) A sheath layer is covered on the outside of the metal braided layer.

2. The method for producing a low capacitance serial digital coaxial cable according to claim 1, characterized in that: The step 2) is implemented by a cleaning device, which includes an ultrasonic cleaning mechanism, a clean water spraying mechanism and an air drying mechanism arranged in sequence, wherein the ultrasonic cleaning mechanism includes: A cleaning container, wherein both ends of the cleaning container have openings corresponding to each other, the openings are used for the inner conductor to pass through, and the cleaning container is used to contain a cleaning liquid. When working, the liquid level of the cleaning liquid is higher than the inner conductor; An ultrasonic generator is fixed on the side wall of the cleaning container; The machine box has a cleaning liquid storage tank, the bottom end of the cleaning container is fixed on the cleaning liquid storage tank, and the cleaning liquid in the cleaning container flows into the cleaning liquid storage tank below through two openings; An infusion tube, one end of which is connected to the cleaning liquid storage tank, and the other end of which is connected to the cleaning container; A delivery pump is installed on the delivery tube and is used to deliver the cleaning liquid in the cleaning liquid storage tank to the cleaning container so that the liquid level of the cleaning container is always above the inner conductor.

3. The method for producing a low capacitance serial digital coaxial cable according to claim 2, characterized in that: The outer side of the opening is also provided with a group of limiting rollers matched with the inner conductor.

4. The method for producing a low capacitance serial digital coaxial cable according to claim 3, characterized in that: The clean water spraying mechanism comprises: A first shell having a water outlet at the bottom; A plurality of water spray pipes arranged inside the first shell and spaced around the axis of the first shell; The water receiving box is located below the first shell and is used to receive water from the water outlet.

5. The method for producing a low capacitance serial digital coaxial cable according to claim 4, characterized in that: The air-drying mechanism comprises: a second shell; A plurality of air blowing pipes are arranged inside the second shell and spaced around the axis of the first shell.

6. The method for producing a low capacitance serial digital coaxial cable according to claim 1, characterized in that: The inner lining layer is composed of low-density polyethylene and antioxidant, and the mass ratio of the low-density polyethylene to the antioxidant is 100:

3.

7. The method for producing a low capacitance serial digital coaxial cable according to claim 1, characterized in that: The foamed PTFE layer has four layers, which are the first foamed PTFE layer, the second foamed PTFE layer, the third foamed PTFE layer and the fourth foamed PTFE layer from the inside to the outside; The first foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the left direction and has a thickness of 0.3 mm and a width of 5 mm, the second foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the right direction and has a thickness of 0.3 mm and a width of 10 mm, the third foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the left direction and has a thickness of 0.3 mm and a width of 15 mm, and the fourth foamed PTFE layer is formed by winding a foamed PTFE tape which is wrapped in the right direction and has a thickness of 0.3 mm and a width of 20 mm; the overlap rate of the foamed PTFE tape of each foamed PTFE layer is 50%.

8. The method for producing a low capacitance serial digital coaxial cable according to claim 1, characterized in that: The overlap rate of the double-sided aluminum foil is 50%; one side of one surface of the double-sided aluminum foil has a hot melt adhesive layer, and the width of the hot melt adhesive layer is half the width of the double-sided aluminum foil; After the double-sided aluminum foil is wrapped, the hot melt adhesive layer is heated to make the double-sided aluminum foil adhere to the outermost foamed PTFE layer.

9. The method for producing a low capacitance serial digital coaxial cable according to claim 1, characterized in that: The metal braided layer is processed by double helix braiding, and the braiding density of the metal braided layer is ≥90%; The material of the sheath layer is chlorinated polyethylene.

10. A low capacitance serial digital coaxial cable, characterized in that: The low-capacitance series digital coaxial cable is prepared by the production method of any one of claims 1 to 9.

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