An ultra-fine low-capacitance foamed cable and a method for manufacturing the same

Abstract

The present application belongs to the technical field of special cable for medical imaging equipment, in particular to a super-fine low-capacitance foamed cable and a preparation method thereof.The cable of the present application comprises an internal conductor and a foamed insulation sleeve co-extruded with the conductor, without a lobe structure, so that the special cable can be more efficiently applied to medical imaging equipment.In addition, the present application also provides a preparation method of the cable, which comprises the following steps: first, preparing a molten material, then co-extruding to obtain a molten state cable, and finally water-cooling and solidifying to form a final low-capacitance foamed cable product.The entire preparation method is relatively stable, efficient and reliable.

Description

Technical Field

[0001] This invention belongs to the field of special cables for medical imaging equipment, and particularly relates to an ultra-fine, low-capacitance foamed cable and its preparation method. Background Technology

[0002] Common medical imaging equipment includes CT, CR, DR, MRI, and DSA. On the other hand, with the rapid development of medical imaging detection technology, we have increasingly higher requirements for the clarity and color accuracy of the detection image results. However, the biggest limitation of the original dedicated cables for medical imaging equipment is that the capacitance is too high, which ultimately leads to insufficient clarity of the transmitted image signal.

[0003] Therefore, many low-capacitance cables for medical imaging equipment have emerged. The principle is to add air with an extremely low dielectric constant to the insulation layer of the cable. The method is to use a perforated mold to extrude the cable, resulting in a perforated cable similar to a lotus root. This can indeed significantly reduce the capacitance of the cable. However, the most fatal drawback is that its structure is very unstable. When it encounters a slightly stronger external force, the insulation layer is prone to collapse, which leads to changes in performance.

[0004] For example, Chinese invention patent with publication number CN104319027A and publication date of January 28, 2015, discloses a method for extruding high-temperature ultra-fine wire foamed Teflon in a lotus root shape. The high-temperature ultra-fine wire consists of a conductor, a lotus root-shaped foamed fluoroplastic insulator, and a protective layer from the inside out. The conductor wire diameter is 28AWG~42AWG. The lotus root-shaped foamed fluoroplastic insulator is tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polytetrafluoroethylene (ETFE).

[0005] The high-temperature ultra-fine wire in this invention patent has a "hole 203" structure that is easily deformed under pressure, causing the entire lotus root-shaped insulator to collapse and greatly affecting its effective service life.

[0006] Therefore, in summary, there is an urgent need for a dedicated cable for medical imaging equipment that is low in capacitance, high in structural strength, and sufficiently thin. Summary of the Invention

[0007] This invention provides an ultra-fine, low-capacitance foamed cable, the structure of which includes an internal conductor and a foamed insulating sleeve co-extruded with the conductor. Without the need for a truncated joint structure, this dedicated cable can be applied more efficiently to medical imaging equipment.

[0008] In addition, the present invention also provides a method for preparing the cable, the steps of which are as follows: first, a molten material is prepared, then a molten cable is obtained by co-extrusion, and finally, the cable is solidified by water cooling to obtain the final low-capacitance foamed cable product. The entire preparation method is relatively stable, efficient and reliable.

[0009] The technical solution adopted by the present invention to solve the above problems is: an ultra-fine low-capacitance foamed cable, the structure of which includes an internal conductor and a foamed insulating sleeve co-extruded with the conductor. The raw material of the foamed insulating sleeve is tetrafluoroethylene polymer and foaming gas. The material of the foamed insulating sleeve is an open-cell foamed material with an open cell ratio of 50-55% and a pore size of 0.012-0.018mm. The wire diameter of the cable is 40-48AWG.

[0010] In this invention, the tetrafluoroethylene polymer refers to any one of polytetrafluoroethylene (Teflon), tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP).

[0011] If the opening ratio of the foamed insulating sleeve is less than 50%, the effect of reducing the capacitance of the cable is not obvious. If the opening ratio is greater than 55%, the structural strength of the foamed insulating sleeve is also insufficient, and it will also bring great challenges to the air-filling foaming method, such as the airtightness of the air-filling equipment, and the excessive air volume can easily cause the conductor to deviate from the center inside the foamed insulating sleeve.

[0012] Finally, if the foaming gas is not used, the tetrafluoroethylene polymer can only form a solid insulating sleeve structure.

[0013] A further preferred technical solution is that the conductor is made of any one of the following: a silver-copper alloy with silver plating, a tin-copper alloy with silver plating, or a tin-copper alloy with tin plating, and the conductor has a wire diameter of 40-48 AWG.

[0014] In this invention, the low-capacitance foamed cable comes in five specifications: 40AWG, 42AWG, 44AWG, 46AWG, and 48AWG. Specifically, the 40AWG cable has a conductor diameter of 0.090mm and an insulation sheath diameter of 0.38mm; the 42AWG cable has a conductor diameter of 0.075mm and an insulation sheath diameter of 0.28mm; the 44AWG cable has a conductor diameter of 0.060mm and an insulation sheath diameter of 0.26mm; the 46AWG cable has a conductor diameter of 0.048mm and an insulation sheath diameter of 0.21mm; and the 48AWG cable has a conductor diameter of 0.036mm and an insulation sheath diameter of 0.16mm.

[0015] More importantly, the capacitance values ​​of the five different cable products mentioned above all meet at least the national standard, truly achieving the effect of "thin wire and low capacitance". In other words, existing medical imaging equipment cables need to be thicker than the above cable specifications to achieve this low capacitance effect. Thicker cables are not only inconvenient to use, but also have higher production costs.

[0016] A further preferred technical solution is that the gas used for foaming is high-purity nitrogen with a purity of ≥99.999%.

[0017] In this invention, the primary requirement for the gas used for foaming is to ensure its inertness; therefore, high-purity nitrogen is a sufficient and relatively economical choice.

[0018] A further preferred technical solution is that the capacitance of the cable is 48-55pF and it is used for image transmission operations of medical imaging equipment.

[0019] In this invention, the capacitance value of the cable conforms to the national standard: 50±5pF. This is not the most important factor, as medical imaging equipment cables with equivalent capacitance levels already exist on the market. However, the most crucial point is that existing cables have a much larger diameter than the cable of this invention, and their insulation layer structure is also weaker.

[0020] A method for preparing an ultrafine, low-capacitance foamed cable includes the following steps:

[0021] S1. Install a die head on the screw barrel of the Teflon extruder, wherein the screw barrel and the die head are perpendicular to each other, and install an outer mold and an inner mold inside the die head;

[0022] S2. Heat the screw barrel, inject tetrafluoroethylene polymer into the rubber material inlet, inject foaming gas into the gas inlet, and finally obtain molten material at the discharge outlet;

[0023] S3. The conductor passes through the inner mold and the outer mold in sequence, and the molten material enters between the inner mold and the outer mold, finally obtaining a molten cable at the outlet of the outer mold;

[0024] S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

[0025] In this invention, the final low-capacitance foamed cable product is subjected to further online high-voltage electric spark testing. The result shows that it passes the 700V non-breakdown test, which is at an upstream level in the industry.

[0026] Furthermore, the extruded foamed core wire is a low-capacitance foamed cable.

[0027] A further preferred technical solution is that: in S2, the heating temperature inside the screw barrel is 300-320℃, the structure of the die head also includes a feed port connected to the discharge port, and the amount of foaming gas injected for heating 1kg of tetrafluoroethylene polymer is 1.5-1.8L.

[0028] A further preferred technical solution is that, in S3, the angle between the inner inclined side of the outer mold cross-section and the conductor is 30°.

[0029] A further preferred technical solution is that, in S2, the injection rate of the foaming gas at the gas inlet is 8-10 ml / min.

[0030] A further preferred technical solution is that, in S3, the temperature of the inner mold and the outer mold is 350-360℃.

[0031] A further preferred technical solution is that, in S3, the speed at which the molten cable leaves the outer mold outlet is 40-120 m / min.

[0032] In this invention, the direction in which the molten material enters the feed inlet is perpendicular to the direction in which the conductor is pulled.

[0033] The present invention has the following advantages.

[0034] First, compared with existing coiled cables, the low capacitance effect is at least equivalent, but the wire diameter is smaller, the insulation layer structure is stronger, and the effective service life of the cable is longer.

[0035] Secondly, the gas injection foaming method is used instead of the perforated mold, and the "large and numerous" perforations are used instead of the "lotus root holes". This ensures that the comprehensive advantages of low capacitance, smaller wire diameter and greater insulation layer structure strength are effectively realized. The entire gas injection foaming and extrusion molding preparation method is stable, precise and reliable.

[0036] Third, the foamed insulation sleeve has sufficient adhesion strength to the conductor and is not easy to fall off during transportation and storage.

[0037] Fourth, the final cable product can pass the 700V online spark voltage test.

[0038] Fifth, during the cable manufacturing process, the structure, shape, and angle of the screw barrel, die head, outer mold, and inner mold used are appropriate to ensure a smooth and stable molten material extrusion molding effect. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the low-capacitance foamed cable in this invention.

[0040] Figure 2 This is a photograph of the foamed insulating sleeve of the cable in Embodiment 1 of the present invention.

[0041] Figure 3 This is a table showing the parameter performance test results of eight different cables in five embodiments and three comparative examples of the present invention.

[0042] Figure 4 This is a schematic diagram illustrating the installation and use of the screw barrel, die head, outer mold, and inner mold in this invention.

[0043] In the attached diagram, the components represented by each number are as follows: conductor a, foamed insulating sleeve b, screw barrel 1, die head 2, outer mold 3, inner mold 4, rubber inlet 1a, air inlet 1b, discharge outlet 1c, and feed inlet 2a. Detailed Implementation

[0044] The following description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention.

[0045] Example 1

[0046] An ultrafine, low-capacitance foamed cable, comprising an internal conductor a and a foamed insulating sleeve b co-extruded with said conductor a.

[0047] The conductor a is made of silver-copper alloy with silver plating on the surface, and the wire diameter of the conductor a is 40AWG, or 0.090mm.

[0048] The raw materials for the foamed insulating sleeve b are polytetrafluoroethylene Teflon and high-purity nitrogen with a purity of ≥99.999%. The material of the foamed insulating sleeve b is open-cell foam material with an open cell ratio of 52% and a pore size of 0.013-0.018mm. The wire diameter of the cable is 40AWG, which is 0.38mm.

[0049] Finally, the capacitance of the cable was measured to be 48pF, and it was used for image transmission in medical imaging equipment to ensure higher image transmission quality, finer wire diameter, and greater cable structural strength.

[0050] The method for preparing this ultrafine, low-capacitance foamed cable includes the following steps:

[0051] S1. Install a die head 2 on the screw barrel 1 of the Teflon extruder. The screw barrel 1 and the die head 2 are perpendicular to each other. Install an outer mold 3 and an inner mold 4 inside the die head 2.

[0052] S2. Heat the screw barrel 1, inject tetrafluoroethylene polymer into the rubber material port 1a, inject foaming gas into the gas inlet 1b, and finally obtain molten material at the discharge port 1c.

[0053] S3, conductor a passes through the inner mold 4 and outer mold 3 in sequence, the molten material enters between the inner mold 4 and outer mold 3, and finally a molten cable is obtained at the outlet of the outer mold 3;

[0054] S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

[0055] In S2, the heating temperature inside the screw barrel 1 is 300°C, and the structure of the die head 2 also includes a feed port 2a connected to the discharge port 1c. The amount of foaming gas that needs to be injected to heat 1 kg of tetrafluoroethylene polymer is 1.5 L.

[0056] In S3, the angle between the inner inclined side of the cross-sectional shape of the outer mold 3 and the conductor a is 30°.

[0057] In S2, the injection rate of the foaming gas into the gas inlet 1b is 8 ml / min.

[0058] In S3, the temperature of the inner mold 4 and the outer mold 3 is 350°C.

[0059] In S3, the molten cable leaves the outlet of the outer mold 3 at a speed of 40 m / min.

[0060] In S4, the water temperature in the tank is 20°C, and the molten cable stays in the tank for more than 5 minutes to obtain the final low-capacitance foamed cable.

[0061] Example 2

[0062] An ultrafine, low-capacitance foamed cable, comprising an internal conductor a and a foamed insulating sleeve b co-extruded with said conductor a.

[0063] The conductor a is made of silver-copper alloy with silver plating on the surface, and the wire diameter of the conductor a is 42AWG, or 0.075mm.

[0064] The raw materials for the foamed insulating sleeve b are polytetrafluoroethylene Teflon and high-purity nitrogen with a purity of ≥99.999%. The material of the foamed insulating sleeve b is open-cell foam material with an open cell ratio of 53% and a pore size of 0.012-0.017mm. The wire diameter of the cable is 42AWG, which is 0.28mm.

[0065] Finally, the capacitance of the cable was measured to be 49pF, and it was used for image transmission in medical imaging equipment to ensure higher image transmission quality, finer wire diameter, and greater cable structural strength.

[0066] The method for preparing this ultrafine, low-capacitance foamed cable includes the following steps:

[0067] S1. Install a die head 2 on the screw barrel 1 of the Teflon extruder. The screw barrel 1 and the die head 2 are perpendicular to each other. Install an outer mold 3 and an inner mold 4 inside the die head 2.

[0068] S2. Heat the screw barrel 1, inject tetrafluoroethylene polymer into the rubber material port 1a, inject foaming gas into the gas inlet 1b, and finally obtain molten material at the discharge port 1c.

[0069] S3, conductor a passes through the inner mold 4 and outer mold 3 in sequence, the molten material enters between the inner mold 4 and outer mold 3, and finally a molten cable is obtained at the outlet of the outer mold 3;

[0070] S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

[0071] In S2, the heating temperature inside the screw barrel 1 is 310°C, and the structure of the die head 2 also includes a feed port 2a connected to the discharge port 1c. The amount of foaming gas that needs to be injected to heat 1 kg of tetrafluoroethylene polymer is 1.6 L.

[0072] In S3, the angle between the inner inclined side of the cross-sectional shape of the outer mold 3 and the conductor a is 30°.

[0073] In S2, the injection rate of the foaming gas into the gas inlet 1b is 9 ml / min.

[0074] In S3, the temperature of the inner mold 4 and the outer mold 3 is 360°C.

[0075] In S3, the molten cable leaves the outlet of the outer mold 3 at a speed of 60 m / min.

[0076] In S4, the water temperature in the tank is 20°C, and the molten cable stays in the tank for more than 5 minutes to obtain the extruded foamed core wire.

[0077] Example 3

[0078] An ultrafine, low-capacitance foamed cable, comprising an internal conductor a and a foamed insulating sleeve b co-extruded with said conductor a.

[0079] The conductor a is made of silver-plated tin-copper alloy, and the wire diameter of the conductor a is 44AWG, or 0.060mm.

[0080] The raw materials for the foamed insulating sleeve b are polytetrafluoroethylene Teflon and high-purity nitrogen with a purity of ≥99.999%. The material of the foamed insulating sleeve b is open-cell foamed material with an open cell ratio of 55% and a pore size of 0.012-0.018mm. The wire diameter of the cable is 44AWG, which is 0.26mm.

[0081] Finally, the capacitance of the cable was measured to be 50pF, and it was used for image transmission in medical imaging equipment to ensure higher image transmission quality, finer wire diameter, and greater cable structural strength.

[0082] The method for preparing this ultrafine, low-capacitance foamed cable includes the following steps:

[0083] S1. Install a die head 2 on the screw barrel 1 of the Teflon extruder. The screw barrel 1 and the die head 2 are perpendicular to each other. Install an outer mold 3 and an inner mold 4 inside the die head 2.

[0084] S2. Heat the screw barrel 1, inject tetrafluoroethylene polymer into the rubber material port 1a, inject foaming gas into the gas inlet 1b, and finally obtain molten material at the discharge port 1c.

[0085] S3, conductor a passes through the inner mold 4 and outer mold 3 in sequence, the molten material enters between the inner mold 4 and outer mold 3, and finally a molten cable is obtained at the outlet of the outer mold 3;

[0086] S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

[0087] In S2, the heating temperature inside the screw barrel 1 is 315°C, and the structure of the die head 2 also includes a feed port 2a connected to the discharge port 1c. The amount of foaming gas that needs to be injected to heat 1 kg of tetrafluoroethylene polymer is 1.7 L.

[0088] In S3, the angle between the inner inclined side of the cross-sectional shape of the outer mold 3 and the conductor a is 30°.

[0089] In S2, the injection rate of the foaming gas into the gas inlet 1b is 9.5 ml / min.

[0090] In S3, the temperature of the inner mold 4 and the outer mold 3 is 360°C.

[0091] In S3, the molten cable leaves the outlet of the outer mold 3 at a speed of 80 m / min.

[0092] In S4, the water temperature in the tank is 20°C, and the molten cable stays in the tank for more than 5 minutes to obtain the final low-capacitance foamed cable.

[0093] Example 4

[0094] An ultrafine, low-capacitance foamed cable, comprising an internal conductor a and a foamed insulating sleeve b co-extruded with said conductor a.

[0095] The conductor a is made of silver-plated tin-copper alloy, and the wire diameter of the conductor a is 46AWG, or 0.048mm.

[0096] The raw materials for the foamed insulating sleeve b are polytetrafluoroethylene Teflon and high-purity nitrogen gas with a purity of ≥99.999%. The material of the foamed insulating sleeve b is open-cell foamed material with an open cell ratio of 54% and a pore size of 0.013-0.018mm. The wire diameter of the cable is 46AWG, which is 0.21mm.

[0097] Finally, the capacitance of the cable was measured to be 51pF, and it was used for image transmission in medical imaging equipment to ensure higher image transmission quality, finer wire diameter, and greater cable structural strength.

[0098] The method for preparing this ultrafine, low-capacitance foamed cable includes the following steps:

[0099] S1. Install a die head 2 on the screw barrel 1 of the Teflon extruder. The screw barrel 1 and the die head 2 are perpendicular to each other. Install an outer mold 3 and an inner mold 4 inside the die head 2.

[0100] S2. Heat the screw barrel 1, inject tetrafluoroethylene polymer into the rubber material port 1a, inject foaming gas into the gas inlet 1b, and finally obtain molten material at the discharge port 1c.

[0101] S3, conductor a passes through the inner mold 4 and outer mold 3 in sequence, the molten material enters between the inner mold 4 and outer mold 3, and finally a molten cable is obtained at the outlet of the outer mold 3;

[0102] S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

[0103] In S2, the heating temperature inside the screw barrel 1 is 320°C, and the structure of the die head 2 also includes a feed port 2a connected to the discharge port 1c. The amount of foaming gas that needs to be injected to heat 1 kg of tetrafluoroethylene polymer is 1.8 L.

[0104] In S3, the angle between the inner inclined side of the cross-sectional shape of the outer mold 3 and the conductor a is 30°.

[0105] In S2, the injection rate of the foaming gas into the gas inlet 1b is 10 ml / min.

[0106] In S3, the temperature of the inner mold 4 and the outer mold 3 is 360°C.

[0107] In S3, the molten cable leaves the outlet of the outer mold 3 at a speed of 100 m / min.

[0108] In S4, the water temperature in the tank is 20°C, and the molten cable stays in the tank for more than 5 minutes to obtain the final low-capacitance foamed cable.

[0109] Example 5

[0110] An ultrafine, low-capacitance foamed cable, comprising an internal conductor a and a foamed insulating sleeve b co-extruded with said conductor a.

[0111] The conductor a is made of tin-copper alloy with tin plating on the surface, and the wire diameter of the conductor a is 48AWG, or 0.036mm.

[0112] The raw materials for the foamed insulating sleeve b are polytetrafluoroethylene Teflon and high-purity nitrogen with a purity of ≥99.999%. The material of the foamed insulating sleeve b is open-cell foamed material with an open cell ratio of 54% and a pore size of 0.012-0.016mm. The wire diameter of the cable is 48AWG, which is 0.16mm.

[0113] Finally, the capacitance of the cable was measured to be 52pF, and it was used for image transmission in medical imaging equipment to ensure higher image transmission quality, finer wire diameter, and greater cable structural strength.

[0114] The method for preparing this ultrafine, low-capacitance foamed cable includes the following steps:

[0115] S1. Install a die head 2 on the screw barrel 1 of the Teflon extruder. The screw barrel 1 and the die head 2 are perpendicular to each other. Install an outer mold 3 and an inner mold 4 inside the die head 2.

[0116] S2. Heat the screw barrel 1, inject tetrafluoroethylene polymer into the rubber material port 1a, inject foaming gas into the gas inlet 1b, and finally obtain molten material at the discharge port 1c.

[0117] S3, conductor a passes through the inner mold 4 and outer mold 3 in sequence, the molten material enters between the inner mold 4 and outer mold 3, and finally a molten cable is obtained at the outlet of the outer mold 3;

[0118] S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

[0119] In S2, the heating temperature inside the screw barrel 1 is 320°C, and the structure of the die head 2 also includes a feed port 2a connected to the discharge port 1c. The amount of foaming gas that needs to be injected to heat 1 kg of tetrafluoroethylene polymer is 1.6 L.

[0120] In S3, the angle between the inner inclined side of the cross-sectional shape of the outer mold 3 and the conductor a is 30°.

[0121] In S2, the injection rate of the foaming gas into the gas inlet 1b is 9 ml / min.

[0122] In S3, the temperature of the inner mold 4 and the outer mold 3 is 350°C.

[0123] In S3, the molten cable leaves the outlet of the outer mold 3 at a speed of 110 m / min.

[0124] In S4, the water temperature in the tank is 20°C, and the molten cable stays in the tank for more than 5 minutes to obtain the final low-capacitance foamed cable.

[0125] Comparative Example 1

[0126] The low-capacitance foamed cable and its preparation method in this comparative example differ from those in Example 1 in only one aspect.

[0127] In the conductor of this comparative example, in step S2 of its preparation method, no foaming gas is injected at the gas inlet 1b.

[0128] The final measured capacitance of the cable was 59pF, and the opening rate of the insulating sleeve was 0%. Compared with Example 1, it is easier to fall off and easily separate from the conductor during storage and transportation.

[0129] Comparative Example 2

[0130] The low-capacitance foamed cable and its preparation method in this comparative example differ from those in Example 2 in only one aspect.

[0131] In the conductor of this comparative example, in step S2 of its preparation method, no foaming gas is injected at the gas inlet 1b.

[0132] The final measured capacitance of the cable was 62pF, and the opening rate of the insulating sleeve was 0%. Compared with Example 1, it is easier to fall off and easily separate from the conductor during storage and transportation.

[0133] Comparative Example 3

[0134] The low-capacitance foamed cable and its preparation method in this comparative example differ from those in Example 3 in only one aspect.

[0135] In the conductor of this comparative example, in step S2 of its preparation method, no foaming gas is injected at the gas inlet 1b.

[0136] The final measured capacitance of the cable was 58pF, and the opening rate of the insulating sleeve was 0%. Compared with Example 1, it is easier to fall off and easily separate from the conductor during storage and transportation.

[0137] Finally, for the above eight different low-capacitance foamed cable products, seven items were tested: conductor wire diameter, insulation sheath wire diameter, hole diameter, cable capacitance, insulation sheath opening ratio, insulation sheath adhesion degree, and online spark voltage breakdown. The final results are shown in the attached figure. Figure 3 The table data shown.

[0138] From the data in the table above, we can draw the following conclusions.

[0139] First, a capacitance range of 48-55pF is sufficient to ensure efficient image signal transmission. However, the cable products in comparison samples 1-3 fail in this aspect. The reason for this is that high-purity nitrogen was not injected simultaneously in the S2 step of the manufacturing process.

[0140] Secondly, correspondingly, if high-purity nitrogen is not injected simultaneously into S2 in the preparation method, the opening rate of the insulating sleeve will be completely eliminated, resulting in a solid structure. The harmful effect is that the insulating sleeve is prone to separation from the conductor during storage and transportation.

[0141] Third, regarding the adhesion of the insulation sleeve, it is required that the adhesion be firm, but it should also be easy to peel off, since the cable will be used in practice by partially peeling off the insulation sleeve.

[0142] Finally, the cable products in the five embodiments have many advantages, including low capacitance, ultra-fine size, high overall structural strength, and relative safety. All eight cable products showed a safe performance of not breaking down in the 700V online spark voltage breakdown test.

[0143] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various modifications can be made without departing from the spirit of the present invention. These are non-inventive modifications and are protected by patent law as long as they fall within the scope of the claims of the present invention.

Claims

1. A type of ultrafine, low-capacitance foamed cable, characterized in that: The structure comprises an internal conductor (a) and a foamed insulating sleeve (b) co-extruded with the conductor (a). The raw material for the foamed insulating sleeve (b) is tetrafluoroethylene polymer and foaming gas. The material of the foamed insulating sleeve (b) is an open-cell foam material with an open-cell ratio of 50-55% and a pore size of 0.012-0.018 mm. The wire diameter of the cable is 40-48 AWG. The conductor (a) is made of any one of the following: a silver-copper alloy with a silver-plated surface, a tin-copper alloy with a silver-plated surface, or a tin-copper alloy with a tin-plated surface. The wire diameter of the conductor (a) is 40-48 AWG. The cable has a capacitance of 48-55pF and is used for image transmission operations in medical imaging equipment.

2. The ultrafine, low-capacitance foamed cable according to claim 1, characterized in that: The gas used for foaming is high-purity nitrogen with a purity of ≥99.999%.

3. A method for preparing an ultrafine, low-capacitance foamed cable as described in claim 1, characterized in that... The steps are as follows: S1. Install a die head (2) on the screw (1) of the Teflon extruder, wherein the screw (1) and the die head (2) are perpendicular to each other, and install an outer mold (3) and an inner mold (4) inside the die head (2). S2. Heat the screw barrel (1), inject tetrafluoroethylene polymer into the rubber material port (1a), inject foaming gas into the gas inlet (1b), and finally obtain molten material at the discharge port (1c); S3. The conductor (a) passes through the inner mold (4) and the outer mold (3) in sequence. The molten material enters between the inner mold (4) and the outer mold (3) and finally obtains a molten cable at the outlet of the outer mold (3). S4. The molten cable enters the water tank at a constant speed, cools and solidifies to form the extruded foamed core wire.

4. The method for preparing an ultrafine, low-capacitance foamed cable according to claim 3, characterized in that: In S2, the heating temperature inside the screw barrel (1) is 300-320℃, and the structure of the head (2) also includes a feed port (2a) that is connected to the discharge port (1c). The amount of foaming gas that needs to be injected to heat 1 kg of tetrafluoroethylene polymer is 1.5-1.8L.

5. The method for preparing an ultrafine, low-capacitance foamed cable according to claim 3, characterized in that: In S3, the angle between the inner inclined side of the cross-sectional shape of the outer mold (3) and the conductor (a) is 30°.

6. The method for preparing an ultrafine, low-capacitance foamed cable according to claim 5, characterized in that: In S2, the injection rate of the foaming gas into the gas inlet (1b) is 8-10 ml / min.

7. The method for preparing an ultrafine, low-capacitance foamed cable according to claim 3, characterized in that: In S3, the temperature of the inner mold (4) and the outer mold (3) is 350-360℃.

8. The method for preparing an ultrafine, low-capacitance foamed cable according to claim 3, characterized in that: In S3, the speed at which the molten cable leaves the outlet of the outer mold (3) is 40-120 m / min.

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