Cable and method for stripping cable

Abstract

To provide a cable which contributes to improvement of work efficiency in cable construction, and to provide a method of stripping the cable.SOLUTION: A cable including a conductor, an insulator covering the conductor, and a sheath covering the insulator, the sheath including a first sheath layer covering the insulator and a second sheath layer covering the first sheath layer, the first sheath layer having a groove formed in a surface of the first sheath layer located on a side of the second sheath layer, the groove extending along a longitudinal direction of the cable, the first sheath layer having a void surrounded by the groove and the second sheath layer, the first sheath layer and the second sheath layer have the composition described in the specification of the present application.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cable and a method for stripping a cable. [Background technology]

[0002] Patent Document 1 discloses an invention relating to an electric cable having a plurality of electric wires such as power lines and signal lines, and in particular an electric cable with excellent flexibility. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-299558 Summary of the Invention [Problem to be solved by the invention]

[0004] Eco Cable, which does not emit harmful gases or dioxins during fire or incineration, uses a non-halogen flame-retardant polyolefin as its sheath material. This non-halogen flame-retardant polyolefin is much harder than the vinyl chloride resin used in conventional cables. This makes it difficult to strip the sheath during cable installation.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cable and a cable stripping method that contribute to improving work efficiency during cable installation. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the cable according to the present invention has the following features. A conductor; an insulator covering the conductor; a sheath covering the insulator; A cable comprising: the sheath includes a first sheath layer covering the insulator and a second sheath layer covering the first sheath layer, a groove extending along the longitudinal direction of the cable is formed on the surface of the first sheath layer facing the second sheath layer, and a gap is formed between the groove and the second sheath layer; the first sheath layer includes a resin composition A containing a base resin A and a flame retardant; The density of the base resin A is 0.900 to 0.955 g / cm 3 and The resin composition A has a gel fraction of 30% or more, In the resin composition A, the flame retardant is contained in an amount of 50 to 200 parts by mass relative to 100 parts by mass of the base resin A, the second sheath layer includes a resin composition B containing a base resin B, The base resin B has a type D durometer hardness (HDD) of 50 or more. A cable characterized by:

[0007] In order to achieve the above-mentioned object, the cable stripping method according to the present invention is characterized as follows. A cable stripping method for stripping the sheath from the cable, comprising: a first step of inserting a blade into the sheath; a second step of cutting the sheath by moving the blade inserted into the sheath along the longitudinal direction of the cable; a third step of peeling the sheath from the insulator by applying an external force to the cut portion of the sheath; a fourth step of cutting the portion of the sheath that has been stripped from the insulation from the remaining portion of the sheath that has not been stripped from the insulation; and In the second step, the blade, whose tip has penetrated the second sheath layer and reached the first sheath layer, moves through the first sheath layer and the second sheath layer while being guided by the groove, thereby cutting through the sheath. A method for stripping a cable.

[0008] According to the cable of the present invention, the formation of a gap inside the sheath reduces the load required to bend the cable compared to a cable without a gap in the sheath, thereby improving the efficiency of cable installation, i.e., making the cable easier to handle. Furthermore, the first sheath layer, which has grooves that create an uneven surface and an overall gear-shaped cross section, is covered by the second sheath layer, so the second sheath layer is exposed in the unstripped parts of the cable, maintaining the cable's smooth appearance.

[0009] Furthermore, according to the cable and the cable stripping method of the present invention, a gap is formed inside the sheath, and therefore the following actions and effects are achieved when the sheath is stripped. In other words, if the tip of the blade passes through the gap when inserting the blade into the sheath, the repulsive force from the sheath acting on the blade when inserting the blade into the sheath is reduced, making it easier to insert the blade into the sheath. Furthermore, when the blade is inserted into the sheath and cuts the sheath, the blade penetrates the second sheath layer, its tip reaching the first sheath layer, and moves in the longitudinal direction of the cable while being guided by the groove. If the blade is inserted into the sheath so that its tip passes through the gap, as described above, the blade will be guided by the groove and cut the sheath. On the other hand, even if the blade is inserted into the sheath so that its tip does not pass through the gap but instead enters the dense portion of the first sheath layer, the blade will reach the groove when it deviates from the longitudinal direction of the cable while cutting the dense portion of the first sheath layer (in other words, when the direction of blade movement is slightly tilted in a direction intersecting the longitudinal direction), and then the blade will be guided by the groove and cut the sheath. By moving the blade through the gap while being guided by the groove, the repulsive force from the sheath acting on the blade when cutting the sheath is reduced compared to when cutting a sheath without a gap. Furthermore, when an external force is applied circumferentially around the cut portion of the cable to peel the sheath from the insulation, the sheath's flexibility along the circumferential direction of the cable is increased compared to when the sheath does not have any gaps. This means that the sheath that has been lifted up from the insulation can be bent with less external force. For example, when peeling the sheath from the insulation with a human finger, the finger will grasp one end of the sheath that has been lifted up slightly from the cut portion. If the sheath gripped with the finger is flexible, the repulsive force that tries to return the sheath to its original shape is reduced, making it easier to maintain the grip of the sheath end with the finger. [Effects of the Invention]

[0010] The cable according to the present invention reduces the load required to bend the cable, improving work efficiency during cable installation, and particularly facilitating cable routing. In addition, the first sheath layer, which has a gear-shaped cross section as a whole, is not exposed in the unstripped portion, maintaining a smooth appearance of the cable.

[0011] Furthermore, with the cable and cable stripping method of the present invention, the repulsive force generated by the sheath is reduced when the blade is inserted into the sheath, when the sheath is cut with the blade inserted into the sheath, and when the sheath is stripped from the insulator, thereby improving work efficiency during cable installation, particularly work efficiency when stripping the sheath.

[0012] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view of a cable according to an embodiment of the present invention. [Figure 2]FIG. 2 is a perspective cross-sectional view of a cable according to an embodiment of the present invention with the second sheath layer removed. [Figure 3] FIG. 3 is a partial cross-sectional view of a cable according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a cross section of a cable according to an embodiment of the present invention in a state where a cutter knife is inserted into the cable. [Figure 5] FIG. 5 is a schematic diagram showing the path of movement of a cutter knife inserted into a cable according to an embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram showing another example of the path of movement of the cutter knife inserted into the cable according to the embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram showing a state in which a part of the sheath is peeled off from the insulator in the cable according to the embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Specific embodiments of the present invention will be described below with reference to the accompanying drawings. The "to" in a numerical range means that the range includes the numerical values ​​before and after it. For example, "0% by mass to 100% by mass" means a range of 0% by mass or more and 100% by mass or less.

[0015] Fig. 1 is a cross-sectional view of a cable according to an embodiment of the present invention. Fig. 2 is a perspective cross-sectional view of a cable according to an embodiment of the present invention from which the second sheath layer has been removed. Fig. 3 is a partial cross-sectional view of a cable according to an embodiment of the present invention. The configuration and structure of a cable according to an embodiment of the present invention will be described in detail below with reference to Figs. 1, 2 and 3.

[0016] [Basic configuration and structure of the cable according to the embodiment of the present invention] A cable 1 according to an embodiment of the present invention includes a conductor 11, an insulator 12, and a sheath 13. The cable 1 is, for example, an eco-cable that does not generate harmful gases or dioxins during fire or incineration. Such eco-cables use, for example, a non-halogen flame-retardant polyolefin coating. With the recent rise in environmental awareness, the installation of eco-cables has been increasing. Note that, although an eco-cable is used as an example of the cable 1 in this embodiment, the type of cable to which the structure of the sheath 13 described below is applied is not limited to eco-cables.

[0017] Conductor 11 is a metal member that serves as the core of cable 1. Because cable 1 is used to transmit electrical signals or transmit power, conductor 11 needs to be made of a highly conductive material. Copper or aluminum is generally used as conductor 11. While FIGS. 1 and 2 show conductor 11 as a single core, the present invention is also applicable to multi-core cables 1, and is not limited by the structure of conductor 11.

[0018] The insulator 12 is an insulating material that covers the conductor 11. The insulator 12 used in the cable 1 protects the conductor 11 and prevents external interference and short circuits. Commonly used materials for the insulator 12 include plastic, rubber, polyvinyl chloride, polyethylene, and chlorosulfonated polyethylene. The insulator 12 is covered by a sheath 13, which protects the conductor 11 from external physical damage and environmental factors, and the insulator 12 itself also protects the conductor 11. As will be described later, when the sheath 13 is stripped from the cable 1, the insulator 12 is exposed.

[0019] The sheath 13 is an outer covering that covers the insulator 12. The sheath 13 protects the entire cable 1 and protects the conductor 11 and insulator 12 from external physical damage and environmental factors. The sheath 13 is usually made of a durable material and improves the properties of the cable 1, such as heat resistance, durability, weather resistance, and abrasion resistance.

[0020] [Sheath structure of the cable according to the embodiment of the present invention] The sheath 13 according to the embodiment of the present invention includes a first sheath layer 13A that covers the insulator 12 and a second sheath layer 13B that covers the first sheath layer 13A. The structures of the first sheath layer 13A and the second sheath layer 13B will be described in detail below. Note that although the following describes a case where the sheath has a two-layer structure, it may also have a multi-layer structure of three or more layers.

[0021] As shown in FIGS. 1 and 2, the first sheath layer 13A has a shape in which grooves 131 extending along the longitudinal direction of the cable 1 are formed on the surface of the first sheath layer 13A located on the second sheath layer 13B side. In other words, the grooves 131 are formed as depressions in the surface of the first sheath layer 13A when viewing a cross section of the first sheath layer 13A, which is formed cylindrically as a whole. A plurality of grooves 131 are formed side by side in the circumferential direction of the first sheath layer 13A, which is formed cylindrically as a whole. In the cable 1 shown in FIG. 1, the plurality of grooves 131 are formed at regular intervals and spaced apart in the circumferential direction of the first sheath layer 13A. It can be said that the plurality of grooves 131 formed in the first sheath layer 13A are spaced apart in the circumferential direction, thereby forming a protrusion 132 sandwiched between two grooves 131. 1 and 2, the ridges 132 are protruding in the longitudinal direction of the cable 1, and are formed on the surface of the first sheath layer 13A in parallel with the grooves 131. In this way, the grooves 131 and the ridges 132 are alternately and multiplely formed in the first sheath layer 13A, so that the surface of the first sheath layer 13A has a shape with continuous projections and depressions in the circumferential direction, and the cross section thereof has an overall gear-like structure.

[0022] The second sheath layer 13B is formed to cover the first sheath layer 13A, whose surface has continuous recesses and projections in the circumferential direction. The second sheath layer 13B is formed so that the surface facing the first sheath layer 13A contacts the ridges 132 of the first sheath layer 13A and bridges the grooves 131. In other words, the portions of the second sheath layer 13B facing two adjacent ridges 132 and the grooves 131 sandwiched between those ridges 132 are formed to bridge the grooves while being supported by the two ridges 132. By covering the first sheath layer 13A with the second sheath layer 13B in this manner, a gap 133 is formed between the first sheath layer 13A and the second sheath layer 13B, surrounded by the surface of the groove 131 of the first sheath layer 13A and the surface of the second sheath layer 13B facing the groove 131. The gap 133 is formed along the longitudinal direction of the cable 1. Furthermore, a plurality of gaps 133 are formed at regular intervals in the circumferential direction of the first sheath layer 13A.

[0023] The width of the circumferential ridge 132 (also referred to herein as the "protrusion width") shown in Fig. 3 iii is preferably 1.0 mm to 2.5 mm, and more preferably 1.5 mm to 2.0 mm. When the protrusion width is within this range, the force required to cut the sheath can be reduced, and the sheath does not deform too much when heated, so the width tends to be an appropriate value. As shown in FIG. 3i, the thickness of the ridges 132 from the upper surface 134 of the ridges 132 facing the second sheath layer 13B to the surface of the insulator 12 (also referred to in this specification as the "projection thickness") is preferably 0.4 mm to 1.3 mm. 3 iv, the width of groove 131 along the circumferential direction (also referred to herein as "recess width") is preferably 1.0 mm to 2.5 mm, and more preferably 1.5 mm to 2.0 mm. When the recess width is within this range, the force required to cut the sheath can be reduced, and the sheath does not deform too much when heated, so that the width tends to be an appropriate value. As shown in FIG. 3 ii, the thickness of groove 131 from bottom surface 135 of groove 131 facing second sheath layer 13B to the surface of insulator 12 (also referred to in this specification as "recess thickness") is preferably 0.3 mm to 0.9 mm. Furthermore, the distance in gap 133 from the surface of second sheath layer 13B facing gap 133 to bottom surface 135 of groove 131 facing second sheath layer 13B, which is shown as the length obtained by subtracting ii from i in Fig. 3 (also referred to herein as "gap thickness"), is preferably 0.1 mm to 0.7 mm. When the gap thickness is within this range, the force required to tear the sheath can be reduced, and the sheath does not deform too much when heated, so that the gap thickness tends to be an appropriate value.

[0024] The thickness from the surface of the second sheath layer 13B to the surface of the first sheath layer 13A (also referred to herein as "second sheath layer thickness") shown in v of FIG. 3 is preferably 0.4 mm to 1.0 mm. Moreover, the thickness from the surface of the second sheath layer 13B to the surface of the insulator 12 (also referred to herein as "total sheath thickness"), as shown in vi of FIG. 3, is preferably 1.4 mm to 2.0 mm. The diameter of the conductor 11 and the thickness from the surface of the insulator 12 to the surface of the conductor 11 are not particularly limited. The nominal cross-sectional area of ​​the conductor 11 is preferably 2 to 325 mm 2 , more preferably 14 to 200 mm 2 The thickness from the surface of the insulator 12 to the surface of the conductor 11 is preferably 0.7 to 2.5 mm, and more preferably 0.9 to 2.3 mm.

[0025] [Composition of the sheath of the cable according to the embodiment of the present invention] In the sheath of the cable according to the embodiment of the present invention, the first sheath layer 13A contains a resin composition A containing a base resin A and a flame retardant, The density of the above base resin A is 0.900 to 0.955 g / cm 3 and The resin composition A has a gel fraction of 30% or more, In the resin composition A, the flame retardant is contained in an amount of 50 to 200 parts by mass relative to 100 parts by mass of the base resin A. The second sheath layer 13B includes a resin composition B containing a base resin B, The base resin B has a type D durometer hardness (HDD) of 50 or more.

[0026] <First sheath layer> (Base resin A) The density of base resin A is 0.900 to 0.955 g / cm 3 is. The density of base resin A is 0.900 g / cm 3 When the density of the base resin A is 0.955 g / cm or more, the first sheath layer has an appropriate hardness and exhibits good tensile strength. 3 When the hardness is not more than 100%, the first sheath layer does not become too hard and exhibits good tensile elongation. The density of the base resin A is a value measured in accordance with JIS K7112.

[0027] As the base resin A, from the viewpoint of environmental consideration, a halogen-free resin is preferable, such as a polyolefin resin, and at least one selected from the group consisting of polyethylene (PE), ethylene-ethyl acrylate resin (EEA), ethylene-vinyl acetate copolymer (EVA), and ethylene propylene diene rubber (EPDM) is preferable. Of these, PE is particularly preferable from the viewpoint of excellent thermal deformation and tensile properties.

[0028] The base resin A can be commercially available. For example, PE includes "Kernel (registered trademark) KS240T" and "Kernel (registered trademark) KF260T" manufactured by Japan Polyethylene Corporation, and "Nipolonhard (registered trademark) 5700" and "Nipolonhard (registered trademark) 6000" manufactured by Tosoh Corporation. EEA includes "Rexpearl (registered trademark) A1100" manufactured by Japan Polyethylene Corporation. EVA includes "VF115G" manufactured by Ube Maruzen Polyethylene Co., Ltd. and "Evaflex (registered trademark) EV550" manufactured by The Dow Chemical Company. EPDM includes "Mitsui EPT (registered trademark) 3045" manufactured by Mitsui Chemicals, Inc.

[0029] (gel fraction) The gel fraction of resin composition A is 30% or more. When the gel fraction of the resin composition A is 30% or more, the resin composition A does not deform too much even when heated, and the sheath consisting of the first sheath layer and the second sheath layer exhibits a good thermal deformation rate. The gel fraction of resin composition A can be measured as follows. First, the weight of resin composition A is measured. Next, resin composition A is immersed in a solvent and the remaining weight is measured. Heated xylene is preferably used as the solvent. Next, the gel fraction can be calculated using the following formula. Gel fraction (%) = {(remaining weight after immersion in hot xylene (g)) / (weight before immersion in hot xylene (g))} × 100

[0030] Here, the residual weight after immersion in hot xylene is a value calculated by the following procedure. 1. Prepare a small bag made of metal mesh fabric. 2. Place the sample cut into 1mm squares into a small mesh bag. 3. Measure the combined weight of the mesh sachet and sample. 4. The mesh pouch containing the sample is immersed in a solvent (xylene heated to 110°C) for 24 hours. 5. After 24 hours, remove the mesh pouch containing the sample and measure its weight. Calculate the remaining weight from the weight measured in 5. Because the mesh is made of metal, it does not dissolve in xylene, but non-crosslinked (non-gel fraction) resin does. Therefore, the sample remaining after immersion in hot xylene is the crosslinked sample, i.e., the sample with the gel fraction.

[0031] The cross-linking is preferably a covalent bond.

[0032] The gel fraction of the resin composition A can be adjusted to the above-mentioned preferred value by adjusting the amounts of the crosslinking agent, crosslinking catalyst, and coupling agent used in producing the resin composition A.

[0033] Examples of crosslinking agents include organic peroxides. Specific examples of crosslinking agents include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butylcumyl peroxide. These may be used alone or in combination of two or more.

[0034] As the crosslinking agent, commercially available products can be used, and examples thereof include "Dicumyl Peroxide" manufactured by Mitsui Fine Chemicals, Inc. and "Percumyl (registered trademark) D" manufactured by NOF Corporation.

[0035] Crosslinking catalysts include, but are not limited to, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctaate, dioctyltin compounds, stannous acetate, stannous caprylate, zinc caprylate, lead naphthenate, and cobalt naphthenate.

[0036] As the crosslinking catalyst, commercially available products can be used, for example, dibutyltin dilaurate "L-101" manufactured by Tokyo Fine Chemical Co., Ltd., "Neostan U-810" manufactured by Nitto Kasei Co., Ltd., and the like.

[0037] Examples of coupling agents include vinyl silane compounds such as vinyl trimethoxysilane, vinyl triethoxysilane, and vinyl tris(β-methoxyethoxy)silane; amino silane compounds such as γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane, N-β-(aminoethyl)γ-aminopropyl trimethoxysilane, β-(aminoethyl)γ-aminopropylmethyl dimethoxysilane, and N-phenyl-γ-aminopropyl trimethoxysilane; and β-(3,4 epoxycyclohexyl)ethyl trimethoxysilane. Examples of suitable silane coupling agents include epoxysilane compounds such as γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropylmethyldiethoxysilane, acrylic silane compounds such as γ-methacryloxypropyltrimethoxysilane, polysulfide silane compounds such as bis(3-(triethoxysilyl)propyl)disulfide and bis(3-(triethoxysilyl)propyl)tetrasulfide, and mercaptosilane compounds such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane. However, the silane coupling agent is not limited to these. These compounds may be used alone or in combination of two or more.

[0038] As the coupling agent, commercially available products can be used, for example, vinyltriethoxysilane "KBE-1003" manufactured by Shin-Etsu Chemical Co., Ltd.

[0039] (Flame retardant) In resin composition A, the amount of the flame retardant is 50 to 200 parts by mass per 100 parts by mass of base resin A. In resin composition A, the amount of the flame retardant is preferably 80 to 170 parts by mass, more preferably 100 to 150 parts by mass per 100 parts by mass of base resin A.

[0040] In resin composition A, when the content of the flame retardant is 50 parts by mass or more per 100 parts by mass of base resin A, resin composition A exhibits good flame retardancy, and when the content is 200 parts by mass or less, resin composition A exhibits good tearability.

[0041] Examples of the flame retardant that can be used include inorganic flame retardants, phosphorus-based flame retardants, and melamine-based flame retardants. Examples of the inorganic flame retardant include metal hydroxides and metal hydrates such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, basic magnesium carbonate, and hydrotalcites. Examples of the phosphorus-based flame retardant include polyphosphate compounds such as polyphosphoric acid and melamine polyphosphate, aromatic phosphate esters, and aromatic condensed phosphate esters. From the viewpoint of cost, inorganic flame retardants, particularly metal hydroxides such as magnesium hydroxide, are preferred as the flame retardant.

[0042] Commercially available flame retardants can be used. For example, inorganic flame retardants include "KISMA (registered trademark) 5B" manufactured by Kyowa Chemical Industry Co., Ltd. and "ECOPIREN 3.5" manufactured by Finetech Co., Ltd., which contain magnesium hydroxide. Phosphorus-based flame retardants include "ADEKA STAB FP-2100JC" manufactured by ADEKA Corporation. Melamine-based flame retardants include "MC-2010N" manufactured by Sakai Chemical Industry Co., Ltd.

[0043] (others) In addition to the above-mentioned components, resin composition A may contain resins other than base resin A, crosslinking agents, crosslinking catalysts, coupling agents, antioxidants, lubricants, etc. Examples of antioxidants include phenol-based antioxidants and sulfur-based antioxidants, and examples of lubricants include fatty acid-based lubricants and silicone-based lubricants.

[0044] <Second sheath layer> (Resin composition B) Resin composition B contains base resin B. The type D durometer hardness (HDD) of the base resin B is 50 or more. The type D durometer hardness (HDD) of the base resin B is preferably 51 or more, and more preferably 52 or more. When the type D durometer hardness (HDD) of the base resin B is 50 or more, the second sheath layer has an appropriate hardness, and the thermal deformation of the sheath consisting of the first sheath layer and the second sheath layer does not become too large and tends to show an appropriate value. The type D durometer hardness (HDD) of the base resin B is a value measured in accordance with JIS K7215.

[0045] As the base resin B, a non-halogen-based resin is preferred from the viewpoint of environmental consideration, such as a polyolefin-based resin, and at least one selected from the group consisting of polyethylene (PE), ethylene-ethyl acrylate resin (EEA), ethylene-vinyl acetate copolymer (EVA), and ethylene propylene diene rubber (EPDM) is preferred. Of these, PE is particularly preferred from the viewpoint of excellent thermal deformation and tensile properties.

[0046] Commercially available base resins can be used as the base resin B. For example, PE includes "Novatec (registered trademark) LL UF230" and "Novatec (registered trademark) LL UF960" manufactured by Japan Polyethylene Co., Ltd., and "UBE Polyethylene (LDPE) F120N" manufactured by Ube Maruzen Polyethylene Co., Ltd.

[0047] In addition to the above-mentioned components, resin composition B may contain a flame retardant, an antioxidant, a lubricant, etc. Specific examples of the flame retardant, the antioxidant, and the lubricant are the same as those exemplified as those that may be contained in resin composition A.

[0048] [Method for manufacturing a cable according to an embodiment of the present invention] The first sheath layer 13A and the second sheath layer 13B are manufactured by extrusion molding. Specifically, the conductor 11 and the insulator 12 are used as a core material, and the material for the first sheath layer 13A (the material for manufacturing resin composition A) is poured radially outward from the core material and molded and extruded. As shown in FIG. 2, the mold is designed so that a molded product having a gear-shaped cross section can be removed. In this way, a molded product consisting of the conductor 11, the insulator 12, and the first sheath layer 13A is manufactured. Next, the material for the second sheath layer 13B is poured radially outward from the core material and molded and extruded. The speeds at which the molded product is extruded and the speed at which the material for the second sheath layer 13B is poured are appropriately adjusted so that a gap 133 remains between the first sheath layer 13A and the second sheath layer 13B. In this way, the cable 1 is manufactured.

[0049] The material for producing the above-mentioned resin composition A is preferably a mixture of 50 to 200 parts by mass of a flame retardant, 0.03 to 0.30 parts by mass of a crosslinking agent, 0.03 to 0.30 parts by mass of a crosslinking catalyst, and 0.50 to 2.50 parts by mass of a coupling agent per 100 parts by mass of base resin A, and the content of the coupling agent is more preferably 1.0 to 2.0 parts by mass.

[0050] When preparing the material for producing resin composition A, first, a crosslinking agent is used to graft a coupling agent onto base resin A. Next, a crosslinked structure can be formed by kneading base resin A to which the coupling agent has been introduced with a crosslinking catalyst. When a silane coupling agent is used as the coupling agent, silane crosslinking can be formed. In this case, the flame retardant can be added either before or after the crosslinked structure is formed.

[0051] [Actions and Effects of the Cable of the Embodiment of the Present Invention] The following describes the functions and effects of the cable according to the embodiment of the present invention. According to the cable 1 shown in Figures 1 and 2, a void 133 is formed inside the sheath 13, which reduces the rigidity compared to a cable with the same outer diameter and thickness of the sheath but no void formed in the sheath. This reduces the load required to bend the cable 1, meaning that high flexibility is achieved. Because the cable 1 thus has high flexibility, it becomes easier to handle. As a result, the work efficiency during cable installation is improved.

[0052] Furthermore, in cable 1, first sheath layer 13A, which has a gear-shaped cross section as a whole, is not exposed in the unstripped portions. While a cable is usually required to have a smooth outer shape, in cable 1, second sheath layer 13B is exposed except for the stripped portions, and second sheath layer 13B maintains an overall cylindrical outer shape while covering groove 131. Therefore, the outer shape of cable 1 is maintained smooth, and the outer shape satisfies the standard cable specifications.

[0053] [Actions and Effects When Stripping the Cable of the Embodiment of the Present Invention] Next, the operation and effect of stripping a cable according to an embodiment of the present invention will be described with reference to Figs. 4 to 7. Fig. 4 is a schematic diagram showing a cross section of a cable according to an embodiment of the present invention in a state where a blade is inserted into the cable. Fig. 5 is a schematic diagram showing the path of movement of a blade inserted into a cable according to an embodiment of the present invention. Fig. 6 is a schematic diagram showing another example of the path of movement of a blade inserted into a cable according to an embodiment of the present invention. Fig. 7 is a schematic diagram showing a state in which a portion of the sheath has been stripped from the insulator in a cable according to an embodiment of the present invention.

[0054] The cable stripping method is carried out in the following manner. First step: Insert the blade into the sheath Second step: The blade inserted into the sheath moves along the length of the cable, cutting through the sheath. Third step: Applying external force to the cut in the sheath to peel the sheath away from the insulation. Step 4: Cut the portion of the sheath that has been stripped from the insulation away from the remaining portion of the sheath that has not been stripped from the insulation. Below, the process of stripping the cable 1 will be explained along these steps, and the actions that occur in each step and the effects that are obtained will be described.

[0055] First, in the first step, as shown in Fig. 4, a blade 2 such as a cutter knife is inserted into the sheath 13. Fig. 4 schematically illustrates a state in which the blade 21 provided on the blade 2 penetrates the second sheath layer 13B, passes through the gap 133, and penetrates a portion of the first sheath layer 13A located on the insulator 12 side of the gap 133, and the tip of the blade 21 reaches the vicinity of the boundary between the first sheath layer 13A and the insulator 12.

[0056] In this way, when inserting the blade 21 into the sheath 13, the tip of the blade 21 enters the sheath 13 so as to pass through the gap 133, thereby reducing the repulsive force from the sheath 13 that acts on the blade 21 when inserting the blade 21 into the sheath 13. This makes it easier to insert the blade 21 into the sheath 13. This means that, for example, in a situation where an operator holds the handle 22 of the blade 2 to perform the first step, the external force that the operator applies to the handle 22 can be reduced. In this way, in the step of inserting the blade 21 into the sheath 13 of the cable 1 according to the embodiment of the present invention, the external force that can be applied to the blade 21 can be reduced, thereby reducing the workload during cable installation.

[0057] Subsequently, in a second step, blade 21 inserted into sheath 13 in the first step cuts sheath 13 in the longitudinal direction of cable 1. In Figure 5, the trajectory V along which blade 21 moves while cutting sheath 13 is depicted by a dashed line. When cutting sheath 13 with blade 21 inserted into sheath 13, blade 21, whose tip has penetrated second sheath layer 13B and reached first sheath layer 13A (see Figure 4), moves in the longitudinal direction of cable 1 while being guided by groove 131. At this time, if blade 21 has entered sheath 13 so that the tip of blade 21 passes through gap 133 when inserted into sheath 13 as described above, blade 21 will cut sheath 13 while being guided by groove 131 without climbing over rib 132.

[0058] In this way, by moving blade 21 through gap 133 while being guided by groove 131, the repulsive force from sheath 13 acting on blade 21 when cutting sheath 13 is reduced compared to when cutting a sheath of the same outer diameter and thickness but without a gap. This means that, for example, in a situation where an operator holds handle 22 of blade 2 and performs the second step, the operator can apply less external force to handle 22. In this way, in the step of cutting sheath 13 of cable 1 according to the embodiment of the present invention, the external force applied to blade 21 can be reduced, thereby reducing the workload during cable installation.

[0059] Incidentally, in the first step, when blade 21 is inserted into sheath 13, the tip of blade 21 may penetrate the dense portion (rib 132) of first sheath layer 13A without passing through gap 133. Alternatively, a part of blade 21 inserted into sheath 13 may penetrate rib 132, while another part passes through gap 133. In such a case, a locus VI along which blade 21 moves while cutting through sheath 13 is depicted by a dashed line in Figure 6. Also, in Figure 6, locus VI is depicted as blade 21 moves from left to right in the drawing of cable 1.

[0060] When blade 21 moves along path VI, blade 21 first penetrates second sheath layer 13B and ribs 132 of first sheath layer 13A, and then moves in the longitudinal direction of cable 1 without being guided by groove 131. While blade 21 moves along ribs 132, the repulsive force acting on blade 21 from sheath 13 is not reduced. However, as blade 21 moves while cutting through ribs 132 of the first sheath, the direction of movement of blade 21 may be slightly tilted in a direction intersecting the longitudinal direction of cable 1. This is because blade 21 is moving without being guided. If blade 21 continues to move in this slightly tilted state, blade 21 enters groove 131 from ribs 132. When blade 21 reaches groove 131 in this manner, blade 21 is subsequently guided by groove 131 to cut through sheath 13.

[0061] Even when blade 21 inserted into sheath 13 cuts sheath 13 without being guided by groove 131, blade 21 enters groove 131 from ridge 132 as it moves. Since blade 21 moves through gap 133 while being guided by groove 131 from the middle of the second step, the repulsive force from sheath 13 acting on blade 21 when cutting sheath 13 is reduced compared to cutting a sheath with the same outer diameter and thickness but no gap formed. In this way, in the step of cutting sheath 13 of cable 1 according to the embodiment of the present invention, the external force applied to blade 21 can be reduced in the situations shown in FIGS. 5 and 6 , thereby reducing the workload during cable installation.

[0062] Next, in the third step, an external force is applied to the torn portion of the sheath 13, thereby peeling the sheath 13 from the insulator 12. Figure 6 schematically shows a state in which a portion of the sheath 13 has been peeled from the insulator 12. An external force is applied to the torn portion in the circumferential direction of the sheath 13, peeling the sheath 13 from the insulator 12. In this way, the insulator 12 is exposed from the cable 1. At this time, the sheath 13 is peeled off by the lengths of the conductor 11 and insulator 12 required in the subsequent process of the stripping process, exposing the insulator 12.

[0063] When the sheath 13 is peeled from the insulator 12, the presence of the gap 133 in the sheath 13 increases the flexibility of the sheath 13 in the circumferential direction compared to when the sheath 13 does not have the gap. This means that the sheath 13 rolled up from the insulator 12 can be bent with less external force. For example, when peeling the sheath 13 from the insulator 12 with a human finger, the finger grasps one end of the sheath 13 that is slightly rolled up from the cut portion. If the sheath 13 grasped with the finger is flexible, the repulsive force acting on the sheath 13 to return to its original shape is reduced, making it easier to maintain the grip of the one end of the sheath with the finger. In this way, in the step of peeling the sheath 13 of the cable 1 according to the embodiment of the present invention, the repulsive force acting on the sheath 13 to return to its original shape is reduced, thereby reducing the workload during cable installation.

[0064] Finally, in the fourth step, the portion of the sheath 13 that has been stripped from the insulator 12 is cut away from the remaining portion of the sheath that has not been stripped from the insulator 12. This completes the stripping process.

[0065] The cable and the cable stripping method according to the embodiment of the present invention have been described in detail above. Although the case where the sheath of the cable 1 has a two-layer structure has been described, the effects of the present invention can also be obtained in a configuration where the sheath has a multi-layer structure of three or more layers, one of which has a layer corresponding to the first sheath layer 13A formed therein. [Example]

[0066] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples.

[0067] The components used in the examples and comparative examples are as follows. <First sheath layer> (Base resin A) Polyethylene (PE), "Kernel (registered trademark) KS240T" (density 0.880 g / cm3 )···Abbreviation: "A1" Polyethylene (PE), "Kernel (registered trademark) KF260T" (density 0.901 g / cm 3 )...Abbreviation "A2" Polyethylene (PE), Tosoh Corporation's "Nipolon Hard (registered trademark) 5700" (density 0.954 g / cm 3 )···Abbreviation: "A3" Polyethylene (PE), Tosoh Corporation's "Nipolon Hard (registered trademark) 6000" (density 0.957 g / cm 3 )···Abbreviation: "A4" (Crosslinking agent) Organic peroxide, "Dicumyl peroxide (DCP)" manufactured by Mitsui Fine Chemicals, Inc., abbreviated as "B1" (Crosslinking catalyst) Dibutyltin dilaurate, "L-101" manufactured by Tokyo Fine Chemical Co., Ltd., abbreviated as "C1" (Silane coupling agent) Vinyltriethoxysilane, Shin-Etsu Chemical Co., Ltd., "KBE-1003"...Abbreviation "D1" (Flame retardant) Magnesium hydroxide, manufactured by Kyowa Chemical Industry Co., Ltd., "KISUMA (registered trademark) 5B"... abbreviated name "E1" <Second sheath layer> (Base resin B) Polyethylene (PE), "Novatec (registered trademark) LL UF240" manufactured by Japan Polyethylene Co., Ltd. (MFR 2.1 g / 10 min, Type D durometer hardness (HDD) 49)...Abbreviation "F1" Polyethylene (PE), "Novatec (registered trademark) LL UF230" manufactured by Japan Polyethylene Co., Ltd. (MFR 1.0 g / 10 min, Type D durometer hardness (HDD) 50)...Abbreviation "F2" Polyethylene (PE), "Novatec (registered trademark) LL UJ960" manufactured by Japan Polyethylene Co., Ltd. (MFR 5.0 g / 10 min, Type D durometer hardness (HDD) 56)...Abbreviation "F3"

[0068] Based on the materials and blending amounts shown in Tables 1 and 2 below, each component was kneaded in a kneader at a temperature of 110°C to prepare a first sheath layer material and a second sheath layer material. Furthermore, cables were manufactured using these materials.

[0069] <Cable> Cross-sectional area 38mm 2 A 1.1 mm thick insulator was formed on the stranded copper conductor. The first sheath layer material described above was then extruded around the insulator-coated stranded copper conductor using an extrusion molding machine to form the first sheath layer. The second sheath layer material described above was then extruded around the first sheath layer using the extrusion molding machine to form the second sheath layer. In this manner, a cable was manufactured. The structures of the first and second sheath layers were as shown in Tables 1 and 2, using molds designed to achieve the structures shown in Tables 1 and 2.

[0070] Only the sheath was stripped from the cable manufactured as described above, and the following items were measured for the sheath. [Tensile strength] The tensile strength was measured in accordance with JIS C 3005:2014. A value of 10 MPa or more was rated as pass (○), and a value of less than 10 MPa was rated as fail (×). The results are shown in Tables 3 and 4. [Tensile elongation] The tensile elongation was measured in accordance with JIS C 3005:2014. A value of 350% or more was rated as pass (○), and a value of less than 350% was rated as fail (×). The results are shown in Tables 3 and 4. [Thermal deformation] The heat distortion test (heat resistance characteristics) was measured in accordance with JIS C 3005:2014. A distortion of 10% or less was considered pass (○), and a distortion of more than 10% was considered fail (×). The results are shown in Tables 3 and 4. [Gel fraction] The gel fraction was measured as follows. First, the weight of resin composition A was measured. Next, resin composition A was immersed in a solvent and the remaining weight was measured using the method described above. Heated xylene was used as the solvent. Next, the gel fraction was calculated using the following formula. Gel fraction (%) = (remaining weight (g) after immersion in hot xylene) / (weight (g) before immersion in hot xylene) × 100 A gel fraction of 30% or more was rated as pass (◯), and a gel fraction of less than 30% was rated as fail (×). The results are shown in Tables 3 and 4. [Tearability] A rectangular sheath measuring 150 mm in the longitudinal direction and 300 mm in the transverse direction was prepared. The gap was aligned parallel to the longitudinal direction. A 50 mm incision was made in the longitudinal direction from the gap near the center of the short side along the gap. The blade of a fixed-position cutter knife ("Hyper M Thick Type" manufactured by Olfa Corporation) was placed against the incision, and the sheath was moved at a speed of 100 min / mm to cut the sheath. The maximum load at this time was measured using a "Strograph S" manufactured by Toyo Seiki Seisakusho Co., Ltd. A load of 10 N / mm or less was considered pass (○), and a load exceeding 10 N / mm was considered fail (×). The results are shown in Tables 3 and 4.

[0071] The flame retardancy of the produced cables was evaluated. [Flame retardant] To evaluate flame retardancy, a 60° tilt test was conducted in accordance with JIS C3005 (2014). In the 60° tilt test, samples in which the flame naturally extinguished within 60 seconds after ignition were rated "good," and samples in which the flame extinguished for more than 60 seconds were rated "NG." The results are shown in Tables 3 and 4.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] The results in Tables 3 and 4 show that the tensile strength, tensile elongation, heat deformation, gel fraction, and flame retardancy of all of Examples 1 to 12 were excellent. Furthermore, the excellent tear resistance of 10 N / mm was observed, indicating that the sheath of a cable having such a sheath can be easily peeled off.

[0077] Density is 0.900g / cm 3 In Comparative Example 1, in which a resin composition of less than 100% was used for the first sheath layer, the first sheath layer was too soft, resulting in an unsatisfactory sheath tensile strength. Density is 0.955g / cm 3 In Comparative Example 2, in which a resin composition having a larger value than the above was used for the first sheath layer, the first sheath layer was too hard, resulting in an unsatisfactory sheath tensile elongation. In Comparative Example 3, in which a resin composition having a hardness of less than 50 was used for the second sheath layer, the second sheath layer was too soft, resulting in unsatisfactory sheath thermal deformation. In Comparative Example 4, in which the degree of cross-linking of the first sheath layer was less than 30%, the thermal deformation was not satisfactory. In Comparative Example 5, in which the amount of flame retardant compounded in the first sheath layer was too small, the flame retardancy was unsatisfactory, and in Comparative Example 6, in which the amount was too large, the tearability was unsatisfactory. Comparative Example 7, in which there was no void in the first sheath layer, resulted in unsatisfactory tearability.

[0078] Here, the features of the embodiments of the cable and the cable stripping method according to the present invention described above will be briefly summarized and listed below in [1] and [3], respectively.

[0079] [1] A conductor (11), an insulator (12) covering the conductor (11); a sheath (13) covering the insulator (12); A cable (1) comprising: The sheath (13) has a first sheath layer (13A) that covers the insulator (12) and a second sheath layer (13B) that covers the first sheath layer (13A), In the first sheath layer (13A), a groove (131) along the longitudinal direction of the cable (1) is formed on the surface of the first sheath layer (13A) located on the side of the second sheath layer (13B), and a gap (133) surrounded by the groove (131) and the second sheath layer (13B) is formed; The first sheath layer (13A) contains a resin composition A containing a base resin A and a flame retardant, The density of the base resin A is 0.900 to 0.955 g / cm 3 and The resin composition A has a gel fraction of 30% or more, In the resin composition A, the flame retardant is contained in an amount of 50 to 200 parts by mass relative to 100 parts by mass of the base resin A, the second sheath layer (13B) contains a resin composition B containing a base resin B, The base resin B has a type D durometer hardness (HDD) of 50 or more. A cable (1) characterized by:

[0080] The cable having the above-mentioned configuration [1] improves the work efficiency during cable installation, that is, makes the cable easier to handle, and also keeps the cable appearance smooth.

[0081] [2] The first sheath layer (13A) has a plurality of the grooves (131) formed therein at intervals in the circumferential direction. 2. The cable (1) according to claim 1.

[0082] According to the cable having the configuration [2] above, the work efficiency during cable installation is further improved, that is, the cable can be more easily handled.

[0083] [3] A cable stripping method for stripping the sheath (13) from the cable (1) according to claim 1 or 2, comprising: a first step of inserting a blade (21) into the sheath (13); a second step of cutting the sheath (13) by moving the blade (21) inserted into the sheath (13) along the longitudinal direction of the cable (1); a third step of peeling the sheath (13) from the insulator (12) by applying an external force to the cut portion of the sheath (13); a fourth step of cutting the portion of the sheath (13) that has been stripped from the insulator (12) from the other portion of the sheath (13) that has not been stripped from the insulator (12); and In the second step, the blade (21), whose tip has penetrated the second sheath layer (13B) and reached the first sheath layer (13A), moves through the first sheath layer (13A) and the second sheath layer (13B) while being guided by the groove (131), thereby cutting through the sheath (13). A method for stripping a cable.

[0084] According to the cable stripping method having the configuration [3] above, the repulsive force generated by the sheath is reduced when the blade is inserted into the sheath, when the sheath is cut with the blade inserted into the sheath, and when the sheath is stripped from the insulator, thereby improving work efficiency during cable installation, especially work efficiency when stripping the sheath. [Explanation of symbols]

[0085] 1 cable 2. Knives 11 Conductor 12 Insulators 13 Sheath 13A First sheath layer 13B Second sheath layer 21 blades 22 Handle 131 Groove 132 Projection 133 void 134 Upper surface of ridge 135 Bottom of groove V trajectory VI trajectory

Claims

1. A conductor; an insulator covering the conductor; a sheath covering the insulator; A cable comprising: the sheath includes a first sheath layer covering the insulator and a second sheath layer covering the first sheath layer, a groove extending along the longitudinal direction of the cable is formed in the surface of the first sheath layer located on the second sheath layer side, and a gap is formed surrounded by the groove and the second sheath layer; the first sheath layer includes a resin composition A containing a base resin A and a flame retardant; The density of the base resin A is 0.900 to 0.955 g / cm ３ and The resin composition A has a gel fraction of 30% or more, In the resin composition A, the flame retardant is contained in an amount of 50 to 200 parts by mass relative to 100 parts by mass of the base resin A, the second sheath layer includes a resin composition B containing a base resin B, The base resin B has a type D durometer hardness (HDD) of 50 or more. A cable characterized by:

2. The first sheath layer has a plurality of grooves formed therein and spaced apart from one another in the circumferential direction.

2. The cable according to claim 1.

3. 3. A cable stripping method for stripping the sheath from the cable according to claim 1 or 2, comprising: a first step of inserting a blade into the sheath; a second step of cutting the sheath by moving the blade inserted into the sheath along the longitudinal direction of the cable; a third step of peeling the sheath from the insulator by applying an external force to the cut portion of the sheath; a fourth step of cutting the portion of the sheath that has been stripped from the insulation from the remaining portion of the sheath that has not been stripped from the insulation; and In the second step, the blade, whose tip has penetrated the second sheath layer and reached the first sheath layer, moves through the first sheath layer and the second sheath layer while being guided by the groove, thereby cutting through the sheath. A method for stripping a cable.

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