Method for manufacturing rodent-proof communication cables

Abstract

To provide a method for producing a rodent-proof communication cable, capable of achieving such a rodent-proof communication cable that has superior electric characteristics and a small cable outer diameter.SOLUTION: The present invention provides a method for producing a rodent-proof communication cable 1 that includes a cable core 3 with a plurality of signal lines 2, and a rodent-proof layer 7 that is provided so as to encase the cable core 3 and consists of braided strands of steel wire. The tension of the steel wire when forming the rodent-proof layer 7 is less than 9.80 N.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a rat-proof communication cable.

Background Art

[0002] As a communication cable wired in a station building or the like, a rat-proof communication cable capable of suppressing damage by rats is known.

[0003] As a conventional rat-proof communication cable, one in which a component of red pepper is kneaded into a sheath is known. However, a cable with a red pepper component kneaded into the sheath has a problem that the effect of preventing damage by rats deteriorates over time, and protective clothing, gloves, etc. are required during construction due to the pungent odor.

[0004] Also, for preventing damage by rats, a rat-proof layer in which a metal tape made of stainless steel or the like is wound around the periphery of a cable core is known. However, when using a metal tape, there is a problem that the flexibility is not sufficient and the wiring work is not easy.

[0005] Therefore, in Patent Document 1, in order to improve flexibility, it is proposed to use a stainless steel braid instead of a stainless steel tape for the rat-proof layer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when the rodent-proof layer is made of braided material or metal tape, there is a problem in that the rodent-proof layer constricts the cable core, degrading its electrical properties. For example, to suppress the deterioration of electrical properties, it is conceivable to use a cushioning layer made of plastic sheath or plastic tape in the inner layer of the rodent-proof layer, but in this case, the outer diameter of the cable becomes larger.

[0008] Therefore, the present invention aims to provide a method for manufacturing a rodent-proof communication cable that has good electrical characteristics and a small cable outer diameter. [Means for solving the problem]

[0009] The present invention aims to solve the above problems and provides a method for manufacturing a rodent-proof communication cable comprising a cable core having a plurality of signal lines and a rodent-proof layer provided so as to cover the periphery of the cable core and consisting of a braid made of steel wires, wherein the tension of the steel wires when forming the rodent-proof layer is less than 9.80 N. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for manufacturing a rodent-proof communication cable that has good electrical characteristics and a small outer diameter. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of a rodent-proof communication cable according to one embodiment of the present invention. [Figure 2] This diagram illustrates the rodent-proof layer of the rodent-proof communication cable shown in Figure 1. [Figure 3] This is a flowchart of a method for manufacturing a rodent-proof communication cable according to one embodiment of the present invention. [Figure 4] (a) and (b) are graphs showing the measurement results of insertion loss. [Figure 5] (a) and (b) are photographs showing the results of the rodent control test. [Modes for carrying out the invention]

[0012] [Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0013] (Rodent-proof communication cable 1) First, let's describe the rodent-proof communication cable 1 manufactured according to this embodiment. Figure 1 is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of the rodent-proof communication cable 1 according to this embodiment.

[0014] As shown in Figure 1, the rodent-proof communication cable 1 comprises a cable core 3 having multiple signal lines 2, a retaining tape 4 spirally wrapped around the cable core 3, a shield layer 5 covering the retaining tape 4, an internal sheath 6 covering the shield layer 5, a rodent-proof layer 7 covering the internal sheath 6, and an external sheath 8 covering the rodent-proof layer 7. The rodent-proof communication cable 1 is a so-called LAN (Local Area Network) cable and is used as a communication cable wired, for example, in a train station. Furthermore, the rodent-proof communication cable 1 according to this embodiment conforms to at least Category 5e (CAT.5e) of the LAN cable standard.

[0015] The signal wire 2 has a conductor 21 and an insulator 22 that surrounds the conductor 21. In this embodiment, a single-wire conductor was used as the conductor 21. In this embodiment, four stranded wires 23, each consisting of two signal wires 2 twisted together, were twisted together to form a cable core 3. The retaining tape 4 wrapped around the cable core 3 is made of, for example, resin tape, non-woven fabric tape, or paper tape. Alternatively, an internal sheath may be provided by tube extrusion molding or the like instead of the retaining tape 4.

[0016] In this embodiment, the shield layer 5 consists of a first shield layer 51 formed by spirally winding a metal tape, and a second shield layer 52 provided to cover the periphery of the first shield layer 51 and consisting of a braid made of woven metal wires. As the metal tape constituting the first shield layer 51, for example, an AL / PET tape can be used, which has a metal layer made of aluminum on one side of a PET (polyethylene terephthalate) layer. When winding the metal tape, the metal layer should be on the outside, and it should be wound spirally so that a portion of the metal tape in the width direction overlaps. As the metal wires used in the braid of the second shield layer 52, copper or a copper alloy can be used. The second shield layer 52 is in contact with the metal layer of the first shield layer 51 and is electrically connected to it. Note that, for example, if only a braid is used for the shield layer 5, the shielding effect, especially for high frequencies, will be reduced due to the effect of the gaps between the metal wires. Furthermore, if only metal tape is used for the shielding layer 5, the amount of metal will be insufficient, reducing the shielding effect against low-frequency signals, and there is a risk of a phenomenon called "suck-out" occurring, in which the signal attenuation increases at a certain frequency. By using both a braided layer and metal tape for the shielding layer 5, as in this embodiment, the shielding effect can be enhanced for signals across a wide bandwidth, and suck-out can also be suppressed.

[0017] The inner sheath 6 surrounding the shield layer 5 is made of, for example, polyvinyl chloride resin (PVC). The inner sheath 6 is formed by tube extrusion molding to prevent resin from seeping into the braids of the second shield layer 52 during molding.

[0018] The rodent-proof layer 7 is provided so as to cover at least the perimeter of the cable core 3 and consists of a braid made of strands of steel wire. Stainless steel wire can be used as the steel wire for the rodent-proof layer 7. It is preferable to use stainless steel wire with an outer diameter of 0.1 mm or more. If the outer diameter is too thin, less than 0.1 mm, the stainless steel wire may break easily, which may reduce its rodent-proof properties. Note that rodent-proof properties here refer to resistance to damage caused by rodents biting.

[0019] More specifically, as shown in FIG. 2, the rat-proof layer 7 is formed by intertwining a plurality of first strand groups 71a obtained by bundling a plurality of stainless steel wires and inclined at a predetermined inclination angle θ with respect to the longitudinal direction of the cable, and a plurality of second strand groups 71b obtained by inclining at the same inclination angle θ as the first strand group 71a in the direction opposite to the first strand group 71a with respect to the longitudinal direction of the cable. The number of strands (stainless steel wires) constituting the strand group 71 is preferably 3 or more and 11 or less. In the present embodiment, the number of strands of the strand group 71 is 24.

[0020] The outer sheath 8 is made of, for example, vinyl chloride resin (PVC). The outer sheath 8 is preferably formed by tube extrusion molding so that resin does not enter between the strands of the rat-proof layer 7 during molding.

[0021] (Manufacturing method of rat-proof communication cable) FIG. 3 is a flowchart of a manufacturing method of the rat-proof communication cable according to the present embodiment. As shown in FIG. 3, when manufacturing the rat-proof communication cable 1, first, in step S1, a cable core forming process is performed. In the cable core forming process, four pairs of twisted wires 23 are twisted together to form a cable core 3, and a holding tape 4 is wound around the periphery thereof. Then, in step S2, a shield layer forming process is performed. In the shield layer forming process, an AL / PET tape is spirally wound around the holding tape 4 to form a first shield layer 51, and then a metal strand made of copper or a copper alloy is braided around the first shield layer 51 to form a second shield layer 52 which is a braided shield, and the shield layer 5 is obtained.

[0022] Thereafter, in step S3, an inner sheath coating process for forming the inner sheath 6 by tube extrusion molding is performed, and then in step S4, a rat-proof layer forming process for forming the rat-proof layer 7 is performed. Thereafter, in step S5, an outer sheath coating process for forming the outer sheath 8 by tube extrusion molding is performed, whereby the rat-proof communication cable 1 of FIG. 1 is obtained.

[0023] (Regarding the tension applied to the steel wire in the rat-proof layer forming process) In step S4, the rodent-proof layer formation process, braiding is performed while applying tension to the steel wire (in this case, stainless steel wire). Our investigations revealed that if the tension applied to the steel wire is too high, the force pressing down on the cable core 3 increases, degrading the electrical characteristics of the communication cable. Conversely, if the tension applied to the steel wire is too low, the rodent-proof performance decreases.

[0024] Therefore, in this embodiment, in order to suppress the deterioration of electrical properties, the tension of the steel wire when forming the rodent-proof layer 7 was set to less than 9.80 N (1 kgf), more preferably 4.90 N (500 gf) or less. Furthermore, it was found that in order to ensure rodent-proof performance, it is desirable that the tension of the steel wire when forming the rodent-proof layer 7 be 2.94 N (300 gf) or more. Thus, in order to reliably suppress the deterioration of electrical properties and ensure rodent-proof performance, the tension of the steel wire when forming the rodent-proof layer 7 should be between 2.94 N (300 gf) and 4.90 N (500 gf) N. The basis for these numerical limitations will be explained below.

[0025] (Electrical characteristics test) First, to investigate the effect on electrical characteristics, electrical characteristic tests were conducted on a comparative example in which the tension of the steel wire used to form the rodent-proof layer 7 was 9.80 N (1 kgf), and on Example 1 in which the tension was 4.90 N (500 gf). In the electrical characteristic tests, a test was considered successful if it satisfied the characteristics of Category 5e. The measurement results of insertion loss, which are part of the test results, are shown in Figures 4(a) and (b).

[0026] As shown in Figures 4(a) and 4(b), the comparative example failed because the insertion loss exceeded the standard value around 20-40 MHz. In contrast, the example satisfied the standard value at all frequencies from 1 to 100 MHz and passed the test. Although not shown in the figures, in addition to insertion loss, the comparative example also failed in terms of electrical characteristics such as near-end crosstalk (NEXT), input impedance, and return loss. In contrast, in the example, all electrical characteristics satisfied the Category 5e standard value and passed the test.

[0027] From these results, it can be seen that in order to obtain electrical characteristics that satisfy the Category 5e standard, the tension of the steel wires used to form the rodent-proof layer 7 must be less than 9.80 N (1 kgf). Furthermore, by setting the tension of the steel wires used to form the rodent-proof layer 7 to 4.90 N (500 gf) or less, it can be said that electrical characteristics that satisfy the Category 5e standard can be obtained more reliably.

[0028] (Rat-proofing test) A rat-proofing test was conducted on the rat-proofing communication cable 1 of Example 1, in which the tension of the steel wire when forming the rat-proofing layer 7 was 4.90 N (500 gf), and on the rat-proofing communication cable 1 of Example 2, in which the tension was 2.94 N (300 gf). In the rat-proofing test, a case containing food (in this case, a concrete block was used) was placed inside a cage containing rats, and the rat-proofing communication cables 1 of Examples 1 and 2 were placed in the passage leading to the food storage area of ​​the case, so that the rats could not reach the food storage area unless they gnawed through the rat-proofing communication cable 1. This was left for 3 days, and then the rat-proofing communication cable 1 was removed and its condition was observed.

[0029] The test results for Example 1 are shown in Figure 5(a), and the test results for Example 2 are shown in Figure 5(b). As shown in Figures 5(a) and (b), no bite marks were observed on the inner sheath 6 in either Example 1 or 2, confirming that sufficient rodent-proof performance was achieved. However, in the rodent-proof communication cable 1 of Example 2, there was disorder in the braiding of the rodent-proof layer 7, indicating that if the tension of the steel wire used to form the rodent-proof layer 7 is less than 2.94 N (300 gf), there is a possibility that rodent-proof performance may be affected. Therefore, from the viewpoint of rodent-proof performance, it is desirable to set the tension of the steel wire used to form the rodent-proof layer 7 to 2.94 N (300 gf) or higher.

[0030] (Operation and Effects of the Embodiment) As described above, in the method for manufacturing a rodent-proof communication cable according to this embodiment, the tension of the steel wire when forming the rodent-proof layer 7 is set to less than 9.80 N. This makes it possible to improve the electrical characteristics without providing a cushion layer or the like in the inner layer of the rodent-proof layer 7, and realizes a rodent-proof communication cable 1 with good electrical characteristics and a small outer diameter. By reducing the outer diameter of the rodent-proof communication cable 1, the allowable bending radius during installation work can be reduced, improving the freedom of wiring layout and improving the workability of installation work.

[0031] (modified version) In the above embodiment, stainless steel wire was used as the steel wire for the rodent-proof layer 7, but other types of steel wire may also be used. Furthermore, a cushioning layer may be provided on the inner layer of the rodent-proof layer 7 by wrapping rubber tape around it.

[0032] (Summary of the embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0033] [1] A method for manufacturing a rodent-proof communication cable (1), comprising a cable core (3) having a plurality of signal lines (2), and a rodent-proof layer (7) provided to cover the periphery of the cable core (3) and consisting of a braid made of strands of steel wire, wherein the tension of the steel wire when forming the rodent-proof layer (7) is less than 9.80 N.

[0034] [2] The method for manufacturing a rodent-proof communication cable according to [1], wherein the tension of the steel wire when forming the rodent-proof layer (7) is 4.90 N or less.

[0035] [3] The method for manufacturing a rodent-proof communication cable according to [1], wherein the tension of the steel wire when forming the rodent-proof layer (7) is 2.94 N or more.

[0036] [4] The method for manufacturing a rodent-proof communication cable according to [1], wherein the steel wire is a stainless steel wire with an outer diameter of 0.1 mm or more.

[0037] (Note) Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. In addition, the present invention can be implemented with appropriate modifications without departing from its spirit. [Explanation of symbols]

[0038] 1…Rodent-proof communication cable 2… Signal line 3… Cable core 4…Securing tape 5...Shield layer 6…Internal sheath 7…Ant-rat layer 8…External sheath

Claims

1. A cable core with multiple signal lines, A shield layer is provided to cover the periphery of the cable core and consists of a braid made of interwoven metal wires, A method for manufacturing a rodent-proof communication cable, comprising a rodent-proof layer provided so as to cover the periphery of the shield layer and consisting of a braid made of strands of steel wire, The tension of the steel wire when forming the rodent-proof layer is 2.94 N or more and 4.90 N or less. A method for manufacturing rodent-proof communication cables.

2. As the steel wire, a stainless steel wire with an outer diameter of 0.1 mm or more is used. A method for manufacturing a rodent-proof communication cable according to claim 1.

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