Manufacturing method of fire-resistant electric wire

Abstract

To provide a fireproof wire capable of preventing insulation resistance deterioration of a folding part which is an overlapping part of a fireproof tape, and thereby improving fire resistance efficiency.SOLUTION: A fireproof wire 1 includes a conductor 10, a fireproof tape 20 attached vertically to the outer periphery of the conductor 10, and insulator layers 31, 32 applied to the outer periphery of the fireproof tape 20. The fireproof tape 20 is folded at both-side ends, and folding parts 23A, 24A are piled up so as to sandwich the end mutually by folding pieces thereof 23a, 24a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fire-resistant electric wire that can withstand long-term use even when exposed to high temperatures and flames due to a fire or the like, and a method for manufacturing the fire-resistant electric wire. [Background technology]

[0002] An example of this type of fire-resistant electric wire is disclosed in Patent Document 1. The fire-resistant electric wire disclosed in Patent Document 1 includes a conductor, a fire-resistant tape that is wrapped around the outer periphery of the conductor in a longitudinal manner and has one end folded back and the other end overlapped thereon, a pressing thread that presses the outer periphery of the fire-resistant tape, and an insulating layer that covers the outer periphery of the fire-resistant tape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-57589 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional fire-resistant electric wire, one end of the fire-resistant tape is folded over and overlapped with the other end. In the event of a fire, the insulating layer will burn, the holding thread will come off and the fire-resistant tape will open, resulting in a loss of insulation resistance, exposing the conductor and causing a cut-off in the flow of electricity.

[0005] The present invention has been made in view of the problems inherent in the conventional techniques, and an object of the present invention is to provide a fire-resistant electric wire capable of preventing a decrease in insulation resistance at the folded-back portion, which is the overlapping portion of the fire-resistant tape, and thus improving fire resistance. [Means for solving the problem]

[0006] A fire-resistant electric wire according to one embodiment of the present invention comprises a conductor, a fire-resistant tape attached longitudinally to the outer periphery of the conductor, and an insulating layer applied to the outer periphery of the fire-resistant tape, and the fire-resistant tape is folded back at both side ends, with the folded back portions overlapping each other so that the ends are sandwiched between the folded back pieces.

[0007] It is preferable that a pressing yarn is wound around the outer periphery of the fire-resistant tape.

[0008] The fire resistant tape preferably has an adhesive within the folded portion.

[0009] The fire-resistant tape has a film-like substrate made of resin or glass cloth, and a fire-resistant layer laminated on the film-like substrate, and it is preferable that, at one of the folded portions, the film-like substrate is laminated on the outer circumferential side and the fire-resistant layer is laminated on the conductor side.

[0010] A manufacturing method of a fire-resistant electric wire according to another aspect of the present invention is a manufacturing method of a fire-resistant electric wire in which a fire-resistant tape is vertically attached to the outer circumference of a conductor using a tape vertical attachment jig having a tubular portion and a curved tubular portion with a folded portion on the exit side, in which the conductor is inserted into the tubular portion and the fire-resistant tape is inserted into the curved tubular portion, and then the conductor is pulled out one after another from the tubular portion and the fire-resistant tape is pulled out one after another from the folded portion on the exit side of the curved tubular portion while folding back both side ends of the fire-resistant tape at the folded portion of the curved tubular portion to overlap so that the ends are sandwiched between each other. Effect of the Invention

[0011] According to the present invention, it is possible to prevent a decrease in insulation resistance at the folded-back portion, which is the overlapping portion of the fire-resistant tape, and to provide a fire-resistant wire having improved fire resistance. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an example of a fire-resistant electric wire according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing a main portion of a fire-resistant tape in the fire-resistant wire. [Figure 4] 1A is a cross-sectional view of the middle part of a vertical tape application jig that applies the fire-resistant tape vertically to the outer circumference of a conductor, and FIG. 1B is a cross-sectional view of the outlet side of the same vertical tape application jig. [Diagram 5] 1A is a cross-sectional view of the middle part of the tape vertical application jig when the fire-resistant tape is applied vertically, and FIG. 1B is a cross-sectional view of the outlet side of the tape vertical application jig when the fire-resistant tape is applied vertically. [Figure 6] 5(a) to 5(c) are enlarged cross-sectional views of the main part, showing how the folded-back portion of the fire-resistant tape is opened. [Figure 7] FIG. 4 is an enlarged cross-sectional view showing a main part of a fire-resistant tape in a fire-resistant electric wire according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a fire-resistant electric wire according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] FIG. 1 is a perspective view showing an example of a fire-resistant electric wire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is an enlarged cross-sectional view showing a main part of a fire-resistant tape in a fire-resistant electric wire. FIG. 4(a) is a cross-sectional view of a middle part of a vertical tape application jig for vertically applying a fire-resistant tape to the outer periphery of a conductor. FIG. 4(b) is a cross-sectional view of the outlet side of the vertical tape application jig. FIG. 5(a) is a cross-sectional view of a middle part of the vertical tape application jig when the fire-resistant tape is applied vertically. FIG. 5(b) is a cross-sectional view of the outlet side of the vertical tape application jig when the fire-resistant tape is applied vertically. FIGS. 6(a) to (c) are enlarged cross-sectional views of a main part showing how to open a folded-back part of the fire-resistant tape.

[0015] As shown in FIG. 1, the fire-resistant wire 1 includes a conductor 10, a fire-resistant tape 20 attached longitudinally to the outer periphery of the conductor 10, a holding yarn 30 wound around the outer periphery of the fire-resistant tape 20, and an insulating coating 31 and a sheath 32 as insulating layers applied to the outer periphery of the fire-resistant tape 20.

[0016] 1 and 2, the conductor 10 is a single-core conductor having a circular cross section. The conductor 10 is made of a copper material, a copper alloy material, an aluminum material, or the like.

[0017] As shown in Fig. 3, the fire-resistant tape 20 that is attached vertically to the outer periphery of the conductor 10 is composed of a film-like substrate 21 made of, for example, polyethylene (PE) or glass cloth, and a mica layer (fire-resistant layer) 22 laminated on the film-like substrate 21. As shown in Figs. 2 and 3, the fire-resistant tape 20 is folded back at both side ends 23, 24, and the folded back portions 23A, 24A are overlapped so that the folded back pieces 23a, 24a sandwich the ends 23, 24. As shown in Fig. 3, the folded back pieces 23a, 24a of the folded back portions 23A, 24A are overlapped with the film-like substrate 21 on the outer periphery side and the mica layer 22 on the conductor 10 side.

[0018] 1, the pressing yarn 30 wound around the outer periphery of the fire-resistant tape 20 is made of, for example, glass yarn, silica yarn, alumina yarn, etc. Then, by wrapping the pressing yarn 30 around the both side ends 23, 24 of the fire-resistant tape 20 in a state where the both side ends 23, 24 are sandwiched between the folded pieces 23a, 24a of the folded parts 23A, 24A, the both side ends 23, 24 are overlapped and fixed in close contact with each other. On the fire-resistant tape 20 in this state, an insulating coating 31 made of, for example, polyethylene is extruded and molded, and the insulating coating 31 is further coated with a sheath 32 to form the fire-resistant electric wire 1.

[0019] 4(a) and (b) is used to manufacture the fire-resistant electric wire 1. The tape-laying jig 40 includes a tubular portion 41 and a curved tubular portion 42 having a bent portion 43 in the middle and a folded-back portion 44 on the outlet side.

[0020] Next, a method for manufacturing the fire-resistant wire 1, specifically, a method for vertically attaching the fire-resistant tape 20 to the outer periphery of the conductor 10 using a tape vertical attachment jig 40 will be described in order with reference to Figs.

[0021] First, as shown in FIG. 5( a ), the conductor 10 is inserted into the tubular portion 41 of the tape-vertical application jig 40 , and the fire-resistant tape 20 is inserted into the curved tubular portion 42 of the tape-vertical application jig 40 .

[0022] Next, as shown in Fig. 5(b), the conductor 10 is pulled out one after another from the tubular portion 41, and the fire-resistant tape 20 is pulled out one after another from the folded-back portion 44 on the outlet side of the curved tubular portion 42. By this pulling out, both side ends 23, 24 of the fire-resistant tape 20 are folded back at the folded-back portion 44 of the curved tubular portion 42, and the ends 23, 24 are overlapped in a tight contact state so as to be sandwiched between the folded-back pieces 23a, 24a. By overlapping the folded-back pieces 23a, 24a, the fire-resistant tape 20 is vertically attached to the outer periphery of the conductor 10. Next, the pressing yarn 30 is wound around the outer periphery of the fire-resistant tape 20, and then the outer periphery is covered with the insulating coating 31 and the sheath 32, thereby completing the fire-resistant electric wire 1.

[0023] According to the fire-resistant wire 1 of the first embodiment, even if the pressing yarn 30 comes off the fire-resistant tape 20 due to combustion of the insulating coating 31 and the sheath 32, the fire-resistant tape 20 is less likely to open than in the conventional product, and the insulation resistance is less likely to be lost in the event of a fire. This results in a fire-resistant wire 1 with higher fire resistance. In other words, it is possible to prevent a decrease in the insulation resistance of the folded-back parts 23A and 24A, which are the overlapping parts of the fire-resistant tape 20, and the fire resistance of the fire-resistant wire 1 can be further improved.

[0024] Specifically, as shown in Fig. 6(a) to (c), even if the pressing yarn 30 comes off the fire-resistant tape 20 and the fire-resistant tape 20 moves in the opening direction, the both ends 23, 24 are hindered by the folded back parts 23A, 24A, so that the fire-resistant tape 20 is difficult to open. This reduces the chance of the conductor 10 being exposed to the fire direction, and the insulation resistance is difficult to be lost. In addition, the winding angle of the pressing yarn 30 is widened, so that the gap between the both ends 23, 24 of the fire-resistant tape 20 is widened, and even if the molten insulating coating 31 flows into the gap, the molten insulating coating 31 that has flowed in is blocked by the folded back parts 23A, 24A of the fire-resistant tape 20 and does not reach the conductor 10. This makes it difficult to lose the insulation resistance. Since the insulation resistance is difficult to be lost, the possibility of the current being interrupted is reduced.

[0025] FIG. 7 is an enlarged cross-sectional view showing a main part of a fire-resistant tape in a fire-resistant electric wire according to a second embodiment of the present invention.

[0026] The fire-resistant tape 20 in the fire-resistant electric wire 1 of the second embodiment is different from that of the first embodiment in that an adhesive 25 is provided in the folded portion 23A (between the fire-resistant tape 20 and the folded piece 23a) of one end portion 23. Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0027] The fire-resistant tape 20 in the fire-resistant electric wire 1 of the second embodiment has higher fire resistance than that of the first embodiment by applying the adhesive 25 inside the folded-back portion 23A of the end portion 23. In addition, the possibility of the adhesive 25 adhering to the conductor 10, the holding yarn 30, the insulating coating 31, etc. can be reduced, and the possibility of deterioration, etc. can be reduced.

[0028] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

[0029] That is, in the above embodiment, the insulating coating is made of polyethylene, but the insulating coating may be made of a resin material other than polyethylene. [Explanation of symbols]

[0030] 1 Fireproof wire 10 Conductors 20 Fireproof Tape 21 Film-like substrate 22 Mica layer (fireproof layer) 23,24 End 23A, 24A Folded part 23a, 24a Folding piece 25 Adhesive 30 Presser yarn 31 Insulating coating (insulating layer) 32 Sheath (insulating layer) 40 Tape vertical attachment jig 41 Cylinder part 42 Curved tube section 43 Bending section 44 Folded part

Claims

[Claim 1] A method for manufacturing a fire-resistant electric wire, comprising: applying a fire-resistant tape to an outer periphery of a conductor using a tape applying tool having a cylindrical portion and a curved cylindrical portion having a folded portion on an outlet side; The conductor is inserted into the cylindrical portion, and the fire-resistant tape is inserted into the curved cylindrical portion; Next, the conductors are successively pulled out from the tubular portion, and the fire-resistant tape is successively pulled out from the folded-back portion on the outlet side of the curved tubular portion, while both side ends of the fire-resistant tape are folded back at the folded-back portion of the curved tubular portion to overlap so as to sandwich the ends of each other.

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