Joint-free dynamic and static combined submarine cable and preparation method thereof

Abstract

The invention provides a jointless dynamic and static combined submarine cable and a preparation method thereof, and the cable comprises a dynamic transmission assembly which comprises a first armor layer and a second armor layer; the transition transmission assembly comprises a third armor layer and an outer coating layer, the third armor layer is connected to the first armor layer, and the outer coating layer is connected to the second armor layer; and the static transmission assembly comprises a fourth armor layer. According to the invention, all the advantages of a dynamic cable and a static cable can be integrated, and an additional connection box and other structures are not needed, so that the production cost can be greatly reduced in the actual use process, the installation operation process is simplified, the connection strength between the dynamic cable and the static cable is greatly improved, and the service life of the cable is prolonged. Therefore, the joint-free dynamic and static combined submarine cable can be suitable for more scenes. Compared with the conventional technology at the present stage, the method has the advantages of being low in cost, high in connection strength, wide in adaptability, high in mechanical performance, convenient to operate, stable, environmentally friendly and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and in particular to a jointless dynamic-static combined submarine cable and a preparation method thereof. Background Art

[0002] Under the current background of global climate governance, carbon peak and carbon neutrality have become important strategic goals to promote the transformation of the global energy structure. In response to this goal, the development of electric energy is gradually moving towards low-carbon or even zero-carbon. Wind energy, as a clean and renewable energy source, has increased its share in global energy consumption year by year. Especially in my country, the development and utilization of wind energy has become a key link in achieving the low-carbon transformation of electric energy. In recent years, the development of offshore fixed wind power platforms has reached saturation. According to statistics, about 80% of offshore wind energy resources are located in waters with a depth of more than 60 meters, which has prompted the focus of wind energy development to gradually shift to deep waters.

[0003] In this context, floating offshore wind power platforms have emerged as an important system for obtaining wind energy in deep waters. Compared with traditional fixed wind power platforms, floating platforms can better capture high-quality wind energy resources in deep waters and are considered an inevitable trend in the development of offshore wind power in the future. However, with the continuous advancement of offshore wind power technology, the supporting submarine cable system is also facing new challenges.

[0004] At the same time, the long-term operation of fixed offshore oil platforms has led to a shortage of originally reserved submarine cable routing resources, which cannot meet the demand for the use of new submarine cables. The newly built routing pipe rack has certain limitations in achieving static laying of submarine cables, which makes the application of dynamic submarine cables on offshore oil platforms increasingly important. Dynamic submarine cables can adapt to changes in submarine topography, maintain the flexibility and safety of cables, and effectively reduce the failure rate of submarine cable systems.

[0005] At present, the dynamic submarine cables used by floating offshore wind power platforms and offshore oil platforms need to be transmitted to land or other marine engineering equipment through static cables on the seabed. In this process, the conversion equipment between dynamic submarine cables and static submarine cables, namely the dynamic-static cable conversion joint box, plays a vital role. However, the existing dynamic-static cable conversion joint boxes have problems such as high cost and complex on-site installation, which to some extent limit their wide application. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems of high cost and complicated installation of the dynamic-static cable conversion joint box in the prior art, and to provide a jointless dynamic-static combined submarine cable and a preparation method thereof.

[0007] In order to solve the above technical problems, the present invention provides a jointless dynamic-static combined submarine cable, which comprises: a dynamic transmission component, the dynamic transmission component comprises a first armor layer and a second armor layer, the second armor layer is covered and connected to the outer surface of the first armor layer; a transition transmission component, one end of the transition transmission component is connected to the dynamic transmission component, which comprises a third armor layer and an outer layer, the outer layer is covered and connected to the outer surface of the third armor layer, wherein the third armor layer is connected to the first armor layer, and the outer layer is connected to the second armor layer; a static transmission component, the static transmission component is connected to the other end of the transition transmission component, and comprises a fourth armor layer, the fourth armor layer is connected to the third armor layer, the first armor layer, the second armor layer, the third armor layer and the fourth armor layer all comprise a plurality of metal wires arranged in the same direction, and the outer layer comprises a plurality of insulating wires arranged in the same direction; at least one cable core, at least one of the cable cores is sequentially passed through the center of the first armor layer, the center of the third armor layer and the center of the fourth armor layer.

[0008] In one embodiment of the present invention, the cross-sectional diameter of the dynamic transmission component is greater than the cross-sectional diameter of the static transmission component, and the cross-sectional diameter of the transition transmission component transitions uniformly from the dynamic transmission component to the static transmission component.

[0009] In one embodiment of the present invention, the dynamic transmission component includes a first filler, the transition transmission component includes a second filler, and the static transmission component includes a third filler. The first filler, the second filler and the third filler are all covered and connected to at least one surface of the cable core.

[0010] In one embodiment of the present invention, the dynamic transmission component, the transition transmission component and the static transmission component all include optical cable detection units, and the optical cable detection units are respectively embedded in the first filling piece, the second filling piece and the third filling piece.

[0011] In one embodiment of the present invention, the dynamic transmission component also includes a first protective layer, the transition transmission component also includes a second protective layer, and the static transmission component also includes a third protective layer. The first protective layer is connected to the inner surface of the first armor layer, the second protective layer is connected to the inner surface of the third armor layer, and the third protective layer is connected to the inner surface of the fourth armor layer.

[0012] In one embodiment of the present invention, the dynamic transmission component also includes a first insulation layer, the transition transmission component also includes a second insulation layer, and the static transmission component also includes a third insulation layer. The first insulation layer is connected to the outer surface of the second armor layer, the second insulation layer is connected to the outer surface of the outer layer, and the third insulation layer is connected to the outer surface of the fourth armor layer.

[0013] In one embodiment of the present invention, the cable core includes a conductor and a conductor shielding layer, and the conductor shielding layer is coated and connected to the outer surface of the conductor.

[0014] In one embodiment of the present invention, the cable core also includes an insulating layer, an insulating shielding layer, a first water-blocking layer, a metal shielding layer, a second water-blocking layer and a sheath arranged in sequence from the inside to the outside, wherein the insulating layer is covered and connected to the outer surface of the conductor shielding layer.

[0015] The present invention also provides a method for preparing a jointless dynamic-static combined submarine cable, which is used to prepare the above-mentioned jointless dynamic-static combined submarine cable, and comprises the following steps: step S1, sequentially passing a cable core through a dynamic transmission component, a transition transmission component and a static transmission component; step S2, docking the two ends of the transition transmission component with the dynamic transmission component and the static transmission component respectively, so that a plurality of metal wires in the third armor layer are docked one by one with a plurality of metal wires in the first armor layer, and at the same time, a plurality of insulating wires in the outer layer are docked one by one with a plurality of metal wires in the second armor layer and a plurality of metal wires in the fourth armor layer; step S3, connecting the two ends of the insulating wire with the metal wires in contact with them respectively, so as to replace the metal wires one by one in the length direction of the cable, and after connecting the dynamic transmission component and the static transmission component, wrapping and fixing them on the outer surface of the transition transmission component to obtain the target jointless dynamic-static combined submarine cable.

[0016] In one embodiment of the present invention, in step S2, each insulating wire and insulating wire needs to be gently cut to increase the contact area between the metal wires; in step S3, the joints between the insulating wires and the metal wires are successively wrapped with hot-melt tape, tightened, shaped, and surface-finished.

[0017] The above technical solution of the present invention has the following advantages compared with the prior art: The jointless dynamic-static combined submarine cable and its preparation method described in the present invention realize a uniform transition connection between the dynamic transmission component and the static transmission component through the transition transmission component. The processed jointless dynamic-static combined submarine cable not only has all the advantages of the dynamic cable and the static cable, but also does not need to set up additional connection boxes and other structures. Therefore, in actual use, the production cost can be greatly reduced, the installation operation process can be simplified, and the connection strength between the dynamic cable and the static cable can be greatly improved, so that the jointless dynamic-static combined submarine cable can be applied to more scenarios. Compared with the conventional technology at this stage, the present application has the advantages of low cost, high connection strength, wide adaptability, high mechanical performance, easy operation, and stable and environmental protection, and has broad prospects for use in this industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0019] Figure 1 It is a schematic diagram of the connection structure of a jointless dynamic and static combined submarine cable in a preferred embodiment of the present invention; Figure 2 yes Figure 1 The schematic diagram of the cross-sectional structure of the cable core in the jointless dynamic and static combined submarine cable is shown; Figure 3 yes Figure 1 The schematic diagram of the cross-sectional structure of the dynamic transmission component in the jointless dynamic-static combined submarine cable is shown; Figure 4 yes Figure 1 The schematic diagram of the cross-sectional structure of the transition transmission component in the jointless dynamic and static combined submarine cable is shown; Figure 5 yes Figure 1 The cross-sectional structure diagram of the static transmission component in the jointless dynamic-static combined submarine cable is shown.

[0020] Explanation of the reference numerals in the specification: 100, cable core; 110, conductor; 120, conductor shielding layer; 130, insulating layer; 140, insulating shielding layer; 150, first water-blocking layer; 160, metal shielding layer; 170, second water-blocking layer; 180, sheath; 200, dynamic transmission component; 210, first filling piece; 220, first protective layer; 230, first armor layer; 240, second armor layer; 250, first insulating layer; 300, transition transmission component; 310, second filling piece; 320, second protective layer; 330, third armor layer; 340, outer layer; 350, second insulating layer; 400, static transmission component; 410, third filling piece; 420, third protective layer; 430, fourth armor layer; 440, third insulating layer. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0022] See also Figure 1 As shown, this embodiment provides a jointless dynamic-static combined submarine cable, which includes: a dynamic transmission component 200, the dynamic transmission component 200 includes a first armor layer 230 and a second armor layer 240, the second armor layer 240 is coated and connected to the outer surface of the first armor layer 230; a transition transmission component 300, one end of the transition transmission component 300 is connected to the dynamic transmission component 200, and includes a third armor layer 330 and an outer layer 340, the outer layer 340 is coated and connected to the outer surface of the third armor layer 330, wherein the third armor layer 330 is connected to the first armor layer 230, and the outer layer 340 is connected to the third armor layer 330. Two armor layers 240; a static transmission component 400, the static transmission component 400 is connected to the other end of the transition transmission component 300, and includes a fourth armor layer 430, the fourth armor layer 430 is connected to the third armor layer 330, the first armor layer 230, the second armor layer 240, the third armor layer 330 and the fourth armor layer 430 all include a plurality of metal wires arranged in the same direction, and the outer layer 340 includes a plurality of insulating wires arranged in the same direction; at least one cable core 100, at least one cable core 100 is sequentially passed through the center of the first armor layer 230, the center of the third armor layer 330 and the center of the fourth armor layer 430.

[0023] The jointless dynamic and static combined submarine cable described in the present invention realizes a uniform transition connection between the dynamic transmission component 200 and the static transmission component 400 through the transition transmission component 300. The processed jointless dynamic and static combined submarine cable not only has all the advantages of dynamic cables and static cables, but also does not need to set up additional connection boxes and other structures. Therefore, in actual use, it can greatly reduce production costs and simplify the installation operation process. At the same time, it greatly improves the connection strength between the dynamic cable and the static cable, thereby making the jointless dynamic and static combined submarine cable applicable to more scenarios. Compared with the current conventional technology, the present application has the advantages of low cost, high connection strength, wide adaptability, high mechanical performance, easy operation, and stable and environmental protection, and has broad prospects for use in this industry.

[0024] See also Figure 1As shown, the dynamic transmission component 200 has more layer structures than the static transmission component 400, so the cross-sectional diameter of the dynamic transmission component 200 in this embodiment is larger than the cross-sectional diameter of the static transmission component 400. In order to reduce the impact on the connection between the two during actual use, the transition transmission component 300 needs to be cut so that its cross-sectional diameter is uniformly transitioned from the dynamic transmission component 200 to the static transmission component 400.

[0025] See also Figure 2 As shown, in this embodiment, in order to improve the electrical conductivity of the cable, three cable cores 100 are arranged inside the dynamic transmission component 200, the transition transmission component 300 and the static transmission component 400, and the three cable cores 100 are mutually abutted to form a triangular support structure in the cross-sectional direction. Further, the cable core 100 in this embodiment includes a conductor 110 and a conductor shielding layer 120, and the conductor shielding layer 120 is coated and connected to the outer surface of the conductor 110, wherein the conductor 110 is preferably a second-class copper conductor, and a circular longitudinal glue-coated water-blocking structure is provided on its surface or other materials that meet the water-blocking requirements can be tightly coated. In other embodiments, the conductor 110 can also be set to other conductor materials that meet the application requirements, and the present invention does not make specific restrictions on this. Furthermore, the conductor shielding layer 120 in this embodiment adopts a semi-conductive cross-linked material or other semi-conductive polymer, which is used to solve the problem of excessive local voltage field.

[0026] Specifically, the cable core 100 also includes an insulating layer 130 , an insulating shielding layer 140 , a first water-blocking layer 150 , a metal shielding layer 160 , a second water-blocking layer 170 and a sheath 180 which are arranged in sequence from the inside to the outside, wherein the insulating layer 130 is covered and connected to the outer surface of the conductor shielding layer 120 . The insulating layer 130 in this embodiment is preferably an XLPE insulating material that is resistant to water treeing, which can provide electrical insulation to prevent current leakage; the insulating shielding layer 140 uses a semi-conductive cross-linked material or other semi-conductive polymer, which is used to further uniformize the electric field, especially at the cable terminal or joint; the first water-blocking layer 150 uses a semi-conductive water-resistant tape or other tape that meets the requirements to prevent moisture from penetrating into the cable, thereby protecting the insulating layer 130; the metal shielding layer 160 is composed of a copper tape or copper wire, which is coated on the outside of the water-blocking layer to shield external electromagnetic interference and serve as a return path to carry large current in the event of a short circuit; the second water-blocking layer 170 also uses a semi-conductive water-resistant tape or other tape that meets the requirements to provide additional waterproof protection; the sheath 180 uses a semi-conductive polyethylene (PE) material to protect the cable from mechanical damage and environmental factors. In other embodiments, it can also be configured as other materials with protective effects.

[0027] See also Figure 3As shown, the dynamic transmission component 200 in this embodiment includes a first filler 210, the transition transmission component 300 includes a second filler 310, and the static transmission component 400 includes a third filler 410. The first filler 210, the second filler 310 and the third filler 410 are all covered and connected to the surface of at least one of the cable cores 100.

[0028] The operating environment of the dynamic transmission component 200 in this embodiment is relatively complex, and it needs to withstand multiple loads such as tension, bending, and torsion at the same time. Therefore, a first filler 210 and an optical cable detection unit are set in its structure. The first filler 210 is coated and connected to the surface of at least one of the cable cores 100, and the optical cable detection unit is embedded and connected to the first filler 210. The main function of the first filler 210 is to protect the cable core 100 and reduce the risk of damage under complex mechanical loads. It can absorb part of the external force, reduce the pressure on the cable core 100, and provide a certain structural stability. The optical cable detection unit is used to monitor the performance of the optical cable, such as signal transmission quality, optical fiber integrity, etc. It can provide timely feedback when the optical cable fails or the performance deteriorates, so as to facilitate maintenance or replacement.

[0029] Correspondingly, see Figure 4 and Figure 5 As shown, the transition transmission component 300 includes a second filler 310, and the static transmission component 400 includes a third filler 410, and the second filler 310 and the third filler 410 are both covered and connected to the surface of at least one of the cable cores 100. The transition transmission component 300 and the static transmission component 400 also include an optical cable detection unit, and the optical cable detection unit is respectively embedded in the second filler 310 and the third filler 410.

[0030] See also Figures 3 to 5 As shown, the dynamic transmission component 200 in this embodiment also includes a first protective layer 220, the transition transmission component 300 also includes a second protective layer 320, and the static transmission component 400 also includes a third protective layer 420. The first protective layer 220 is connected to the inner surface of the first armor layer 230, the second protective layer 320 is connected to the inner surface of the third armor layer 330, and the third protective layer 420 is connected to the inner surface of the fourth armor layer 430. The first protective layer 220, the second protective layer 320 and the third protective layer 420 are all made of medium-density polyethylene (MDPE) material to achieve all-round protection of the cable core 100.

[0031] In this embodiment, the first armor layer 230, the second armor layer 240, the third armor layer 330 and the fourth armor layer 430 are all made of two layers of galvanized steel wire, which can support and protect the internal battery cells and achieve electromagnetic shielding effect. This application sets different armor layer structures in the corresponding structures according to the differences in the action scenarios and use scopes of the dynamic transmission component 200 and the static transmission component 400. Furthermore, it is precisely because of the differences in the armor layers that it is necessary to achieve uniform transition and connection between the dynamic transmission component 200 and the static transmission component 400. Furthermore, the insulating wire in this embodiment is preferably a plastic structural element with the same diameter as the metal wire in the second armor layer 240, thereby achieving uniform transition from the dynamic transmission component 200 to the static transmission component 400 by replacing the second armor layer 240 one by one.

[0032] In addition, the dynamic transmission component 200 in this embodiment further includes a first insulating layer 250, the transition transmission component 300 further includes a second insulating layer 350, and the static transmission component 400 further includes a third insulating layer 440. The first insulating layer 250 is connected to the outer surface of the second armor layer 240, the second insulating layer 350 is connected to the outer surface of the outer layer 340, and the third insulating layer 440 is connected to the outer surface of the fourth armor layer 430. In this embodiment, the first insulating layer 250, the second insulating layer 350, and the third insulating layer 440 are preferably made of high-density polyethylene (HDPE) material so that they have the effects of high elasticity, high strength, and waterproof insulation. Embodiment 2

[0033] This embodiment provides a method for preparing a jointless dynamic-static combined submarine cable, which is used to prepare the jointless dynamic-static combined submarine cable described in Example 1, and comprises the following steps: Step S1, the cable core 100 is sequentially passed through the dynamic transmission component 200, the transition transmission component 300 and the static transmission component 400. Further, in this embodiment, three cable cores 100 are provided, and the three cable cores 100 are mutually abutted to form a stable triangular support structure.

[0034] Step S2, docking the two ends of the transition transmission component 300 with the dynamic transmission component 200 and the static transmission component 400 respectively, so that the multiple metal wires in the third armor layer 330 are docked one by one with the multiple metal wires in the first armor layer 230, and the multiple insulating wires in the outer layer 340 are docked one by one with the multiple metal wires in the second armor layer 240 and the multiple metal wires in the fourth armor layer 430 respectively; further, in this embodiment, in step S2, each insulating wire and insulating wire needs to be gently cut to increase the contact area between the metal wires and the insulating wires; Step S3, respectively connect the two ends of the insulating wire to the metal wire in contact with it, so as to replace the metal wires one by one in the length direction of the cable, connect the dynamic transmission component 200 and the static transmission component 400, and then wrap and fix them on the outer surface of the transition transmission component 300 to obtain the target jointless dynamic and static combined submarine cable. Furthermore, in this embodiment, the joints between the insulating wire and the metal wire are sequentially wound with hot melt tape, tightened, shaped, and surface finished.

[0035] In summary, the jointless dynamic-static combined submarine cable and its preparation method described in the present invention realizes a uniform transition connection between the dynamic transmission component 200 and the static transmission component 400 through the transition transmission component 300. The processed jointless dynamic-static combined submarine cable not only has all the advantages of dynamic cables and static cables, but also does not need to set up additional connection boxes and other structures. Therefore, in actual use, it can greatly reduce production costs and simplify the installation operation process. At the same time, it greatly improves the connection strength between the dynamic cable and the static cable, thereby making the jointless dynamic-static combined submarine cable applicable to more scenarios. Compared with the current conventional technology, the present application has the advantages of low cost, high connection strength, wide adaptability, high mechanical performance, easy operation, and stable and environmental protection, and has broad prospects for use in this industry.

[0036] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A jointless dynamic and static combined submarine cable, characterized in that: include: A dynamic transmission component, the dynamic transmission component comprising a first armor layer and a second armor layer, wherein the second armor layer is coated and connected to an outer surface of the first armor layer; A transition transmission component, one end of which is connected to the dynamic transmission component, comprising a third armor layer and an outer layer, wherein the outer layer is coated and connected to the outer surface of the third armor layer, wherein the third armor layer is connected to the first armor layer, and the outer layer is connected to the second armor layer; A static transmission component, the static transmission component is connected to the other end of the transition transmission component, and comprises a fourth armor layer, the fourth armor layer is connected to the third armor layer, the first armor layer, the second armor layer, the third armor layer and the fourth armor layer all comprise a plurality of metal wires arranged in the same direction, and the outer layer comprises a plurality of insulating wires arranged in the same direction; At least one cable core, at least one of the cable cores is sequentially passed through the center of the first armor layer, the center of the third armor layer, and the center of the fourth armor layer.

2. The jointless dynamic-static combined submarine cable according to claim 1 is characterized in that: The cross-sectional diameter of the dynamic transmission component is greater than the cross-sectional diameter of the static transmission component, and the cross-sectional diameter of the transition transmission component transitions uniformly from the dynamic transmission component to the static transmission component.

3. The jointless dynamic-static combined submarine cable according to claim 1 is characterized in that: The dynamic transmission component includes a first filling piece, the transition transmission component includes a second filling piece, and the static transmission component includes a third filling piece. The first filling piece, the second filling piece and the third filling piece are all covered and connected to at least one surface of the cable core.

4. The jointless dynamic-static combined submarine cable according to claim 3 is characterized in that: The dynamic transmission component, the transition transmission component and the static transmission component all include an optical cable detection unit, and the optical cable detection unit is respectively embedded in the first filling piece, the second filling piece and the third filling piece.

5. The jointless dynamic-static combined submarine cable according to claim 1, characterized in that: The dynamic transmission component also includes a first protective layer, the transition transmission component also includes a second protective layer, and the static transmission component also includes a third protective layer. The first protective layer is connected to the inner surface of the first armor layer, the second protective layer is connected to the inner surface of the third armor layer, and the third protective layer is connected to the inner surface of the fourth armor layer.

6. The jointless dynamic-static combined submarine cable according to claim 1, characterized in that: The dynamic transmission component also includes a first insulation layer, the transition transmission component also includes a second insulation layer, and the static transmission component also includes a third insulation layer. The first insulation layer is connected to the outer surface of the second armor layer, the second insulation layer is connected to the outer surface of the outer layer, and the third insulation layer is connected to the outer surface of the fourth armor layer.

7. The jointless dynamic-static combined submarine cable according to claim 1, characterized in that: The cable core comprises a conductor and a conductor shielding layer, and the conductor shielding layer is covered and connected to the outer surface of the conductor.

8. The jointless dynamic-static combined submarine cable according to claim 7, characterized in that: The cable core also includes an insulating layer, an insulating shielding layer, a first water-blocking layer, a metal shielding layer, a second water-blocking layer and a sheath which are sequentially arranged from the inside to the outside, wherein the insulating layer is coated and connected to the outer surface of the conductor shielding layer.

9. A method for preparing a jointless dynamic and static combined submarine cable, characterized in that: The method for preparing the jointless dynamic-static combined submarine cable according to any one of claims 1 to 8 comprises the following steps: Step S1, sequentially pass the cable core through the dynamic transmission component, the transition transmission component and the static transmission component; Step S2, docking the two ends of the transition transmission component with the dynamic transmission component and the static transmission component respectively, so that the multiple metal wires in the third armor layer are docked one by one with the multiple metal wires in the first armor layer, and at the same time, the multiple insulating wires in the outer layer are docked one by one with the multiple metal wires in the second armor layer and the multiple metal wires in the fourth armor layer respectively; Step S3, respectively connecting the two ends of the insulating wire to the metal wires in contact with them, so as to replace the metal wires one by one in the length direction of the cable, and after connecting the dynamic transmission component and the static transmission component, wrapping and fixing them on the outer surface of the transition transmission component to obtain the target jointless dynamic-static combined submarine cable.

10. The method for preparing a jointless dynamic-static combined submarine cable according to claim 9, characterized in that: In step S2, each insulating wire and insulating wire needs to be gently cut to increase the contact area between the metal wires; in step S3, the joints between the insulating wires and the metal wires are successively wrapped with hot-melt tape, tightened, shaped, and surface-finished.

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