JP2012157124A - Cylindrical protection coated body and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an insulator layer which is further evenly packed with liquid insulating silicon rubber, relating to a cylindrical protection coated body and a method of manufacturing the same.SOLUTION: A cylindrical protection coated body 10 which protects a cable connection structure 1 includes a cylindrical external semiconductor layer 12 formed of conductive silicon rubber, an internal semiconductor layer 14 provided in the cylinder of the external semiconductor layer 12, a pair of cylindrical stress cones provided to both ends of the external semiconductor layer 12, and an insulator layer 20 formed by curing liquid insulating silicon rubber after packing it in the space surrounded by the external semiconductor layer 12, the internal semiconductor layer 14, the pair of stress cones 16 and 18, and a cable insert hole 28. At least one of the pair of stress cones 16 and 18 contains an injection hole 24 through which the liquid insulation silicon rubber is injected. At least one of the pair of stress cones 16 and 18 contains an exhaust hole 26 for exhausting the gas in the space.

Description

  The present invention relates to a cylindrical protective covering and a method for manufacturing the same, and more particularly to a cylindrical protective covering for protecting a cable connection structure in which power cables are connected to each other and a method for manufacturing the same.

  Since power cables are used in various installation locations and external environments, a wide variety of power cables with protective coatings having functions such as waterproofing and water shielding are manufactured according to the purpose of use. And also in the cable connection structure which connected electric power cables, according to the intended purpose, performing protection means, such as waterproofing and water shielding, is performed.

  The cable connection structure is generally covered and protected by a cylindrical protective covering formed in a cylindrical shape. Such a cylindrical protective covering includes, for example, a cylindrical external semiconductive layer, a cylindrical internal semiconductive layer provided in the external semiconductive layer, and stress provided at both ends of the external semiconductive layer. It is composed of a cone, and an insulating layer filled in a space surrounded by an outer semiconductive layer, an inner semiconductive layer, and a stress cone. The cylindrical protective covering is formed of a polymer rubber material such as EP rubber, silicone rubber, or butyl rubber, and is formed so that it can shrink at room temperature.

  In Patent Document 1, as a room temperature shrinkable rubber unit used for an insulation connection portion of a power cable such as a high-voltage CV cable, the diameter is supported on a diameter-expandable member that can be disassembled, and ethylene propylene rubber, silicone rubber, etc. An internal semiconductive layer formed mainly of a rubber material, a reinforcing insulating layer, an external semiconductive layer, and stress cone portions on both ends of the reinforcing insulating layer are provided. The internal semiconductive layer, the reinforcing insulating layer, and the external semiconductive layer are provided. It is described that the conductive layer and the stress cone portion are molded into a substantially cylindrical shape and formed into a one-piece.

JP 2006-223099 A

  By the way, as the cylindrical protective covering for covering and protecting the cable connection structure, a cylindrical protective covering formed of silicone rubber is used because of excellent stress relaxation characteristics. The insulating layer of the cylindrical protective covering is formed by, for example, setting an external semiconductive layer, an internal semiconductive layer, and a stress cone in a predetermined mold so that the axial direction of the external semiconductive layer is horizontal, In a space surrounded by the semiconductive layer, the internal semiconductive layer, and the stress cone, a liquid insulating silicone rubber is injected from an injection port provided substantially at the center in the axial direction of the external semiconductive layer.

  Since the liquid insulating silicone rubber is injected from the approximate center in the axial direction in the outer semiconductive layer in the direction orthogonal to the axial direction, liquid insulating properties are applied to both ends of the outer semiconductive layer in the axial direction. Silicone rubber may not be filled enough. In addition, since the liquid insulating silicone rubber is filled from substantially the center in the axial direction of the external semiconductive layer, the both ends in the axial direction of the external semiconductive layer enter the insulating layer by entrainment of gas such as air. Voids may occur.

  Therefore, an object of the present invention is to provide a cylindrical protective covering having an insulating layer formed by more uniformly filling an insulating silicone rubber and a method for manufacturing the same.

    The cylindrical protective covering according to the present invention is a cylindrical protective covering that protects a cable connection structure in which power cables are connected to each other, and has a cylindrical outer semiconductive layer formed of conductive silicone rubber, A cylinder provided in a cylinder of the outer semiconductive layer, formed of conductive silicone rubber, into which a conductor connecting portion connected by connecting an exposed conductor wire by peeling off the outer sheath of power cables in the cable connection structure is inserted. Internal semiconductive layer, a pair of cylindrical stress cones formed at both ends of the external semiconductive layer and formed of conductive silicone rubber, an inner peripheral surface of the external semiconductive layer, and the internal An outer sheath surface of the power cable of the cable connection structure communicating with the outer peripheral surface of the semiconductive layer, the pair of stress cones, the cylinder of the internal semiconductive layer, and the cylinders of the pair of stress cones Is inserted An insulating layer formed by curing a liquid insulating silicone rubber, and filling at least one of the pair of stress cones with the liquid insulating property. It has an injection port for injecting silicone rubber, and at least one of the pair of stress cones has an exhaust port for exhausting gas in the space.

  In the cylindrical protective covering according to the present invention, each of the pair of stress cones includes a stress cone main body, and the stress cone main body is inserted into one end portion of the external semiconductive layer, and the base of the stress cone main body is provided. A rising portion having a tapered hole that gradually increases in diameter from the end side to the tip side, wherein the inlet and the exhaust port are between the outer peripheral surface of the rising portion and the inner peripheral surface of the outer semiconductive layer. Preferably, they are formed in communication.

  In the cylindrical protective covering according to the present invention, the stress cone body is provided on a proximal end side of the stress cone body, and has a flange portion that protrudes outward in the radial direction, and the injection port The exhaust port is preferably provided in the flange portion.

  In the cylindrical protective covering according to the present invention, the inlet and the exhaust port are preferably provided in each of the pair of stress cones.

  In the cylindrical protective covering according to the present invention, it is preferable that the exhaust port has a smaller diameter than the injection port.

 In the cylindrical protective covering according to the present invention, the conductive silicone rubber forming the external semiconductive layer, the internal semiconductive layer, and the pair of stress cones is preferably a millable conductive silicone rubber. .

  A method for manufacturing a cylindrical protective covering according to the present invention is a method for manufacturing a cylindrical protective covering that protects a cable connection structure in which power cables are connected to each other, and is made of a conductive silicone rubber and has a cylindrical outer semiconductivity. An outer semiconductive layer forming step for forming a layer, and a cylindrical shape into which a conductive connecting portion connecting conductive wires exposed by peeling off the outer sheath of the power cables in the cable connection structure is inserted with conductive silicone rubber. An internal semiconductive layer forming step for forming an internal semiconductive layer, a stress cone forming step for forming a pair of stress cones in a cylindrical shape with conductive silicone rubber, and the internal semiconductive layer disposed in the external semiconductive layer The pair of stress cones are respectively disposed at both ends of the outer semiconductive layer, and the power cable of the cable connection structure is disposed in the cylinder of the inner semiconductive layer and the cylinder of the pair of stress cones. A cylindrical preform forming step of forming a cylindrical preform by inserting a core that forms a cable insertion hole through which the jacket covering portion of the bull is inserted; and an inner peripheral surface of the outer semiconductive layer; Insulating layer formation in which liquid insulating silicone rubber is injected into a space surrounded by the outer peripheral surface of the internal semiconductive layer, the pair of stress cones, and the core, and then cured to form an insulating layer And at least one of the pair of stress cones has an inlet for injecting the liquid insulating silicone rubber into the space, and at least one of the pair of stress cones is the space. It has an exhaust port for exhausting the gas inside.

  In the method for manufacturing a cylindrical protective covering according to the present invention, each of the pair of stress cones includes a stress cone body, and the stress cone body is inserted into one end of the external semiconductive layer, and the stress cone A rising portion having a tapered hole that gradually increases in diameter from the proximal end side to the distal end side of the main body, and the injection port and the exhaust port include an outer peripheral surface of the rising portion and an inner peripheral surface of the external semiconductive layer. Preferably, they are formed in communication with each other.

  In the manufacturing method of the cylindrical protective covering according to the present invention, the stress cone body is provided on the proximal end side of the stress cone body, and has a flange portion that protrudes outward in the radial direction, The injection port and the exhaust port are preferably provided in the flange portion.

  In the method for manufacturing the cylindrical protective covering according to the present invention, it is preferable that the inlet and the exhaust port are provided in each of the pair of stress cones.

  In the manufacturing method of the cylindrical protective covering according to the present invention, the cylindrical preform forming step includes the step of forming each of the pair of stress cones so that the injection port is vertically below the cylindrical preform. And it is preferable to arrange | position so that the said exhaust port may be located in the perpendicular direction upper side of the said cylindrical preform.

  In the manufacturing method of the cylindrical protective covering according to the present invention, it is preferable that the exhaust port has a smaller diameter than the injection port.

  In the method for manufacturing a cylindrical protective covering according to the present invention, the conductive silicone rubber forming the outer semiconductive layer, the inner semiconductive layer, and the pair of stress cones is a millable conductive silicone rubber. It is preferable.

  According to the cylindrical protective covering having the above-described configuration and the manufacturing method thereof, the injection port for injecting the liquid insulating silicone rubber into at least one of the pair of stress cones provided at both ends in the axial direction of the external semiconductive layer And at least one of the pair of stress cones is provided with an exhaust port for exhausting a gas such as air, so that the liquid insulating silicone rubber is on one end side along the axial direction of the outer semiconductive layer. From the injection port toward the other end, gas such as air is exhausted from the exhaust port, so that an insulating layer filled with insulating silicone rubber can be formed more uniformly.

In embodiment of this invention, it is sectional drawing which shows the structure of the cylindrical protective coating | covering body which protects a cable connection structure. In embodiment of this invention, it is sectional drawing which shows the structure of a cylindrical protective covering unit. In embodiment of this invention, it is sectional drawing which shows the state which mounted | wore the cable connection structure with the cylindrical protective coating | covering body. In embodiment of this invention, it is a flowchart which shows the manufacturing method of a cylindrical protective coating. In embodiment of this invention, it is sectional drawing which shows the structure of a stress cone. In embodiment of this invention, it is sectional drawing which shows the structure of another stress cone. In embodiment of this invention, it is sectional drawing which shows the structure of a cylindrical preform. In embodiment of this invention, it is sectional drawing which shows the other sealing method which seals the clearance gap between the outer peripheral surface of an external semiconductive layer, and the outer peripheral surface of a stress cone. In embodiment of this invention, it is sectional drawing which shows the structure of another cylindrical preforming body. In embodiment of this invention, it is sectional drawing which shows the state in which the insulating layer was formed. In embodiment of this invention, it is sectional drawing which shows another sealing method which seals the clearance gap between the outer peripheral surface of an external semiconductive layer, and the outer peripheral surface of a stress cone. In embodiment of this invention, it is a figure which shows an electrical property test result.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a cylindrical protective covering 10 that protects the cable connection structure 1. The cylindrical protective covering 10 is used to cover and protect the cable connection structure 1 in which ends of power cables such as CV cables are connected to each other. The cable connection structure 1 peels off the jackets 2a and 4a of the power cables 2 and 4 and the jackets of the power cables 2 and 4 to expose the conductor wires 2b and 4b. 4b is provided with a conductor connecting portion 8 that is compressed by a sleeve 6 and linearly connected.

  The cylindrical protective covering 10 includes an outer semiconductive layer 12, an inner semiconductive layer 14, a pair of stress cones 16 and 18, and an insulating layer 20.

  The outer semiconductive layer 12 is formed in a cylindrical shape such as a cylindrical shape. The outer semiconductive layer 12 is made of conductive silicone rubber to which a conductive material such as carbon black is added.

  The inner semiconductive layer 14 is provided in a cylinder of the outer semiconductive layer 12, and is formed in a cylindrical shape such as a cylindrical shape. The inner semiconductive layer 14 is provided with the outer semiconductive layer 12 aligned with the axis. The internal semiconductive layer 14 is provided, for example, in the approximate center in the axial direction of the external semiconductive layer 12.

  The inner semiconductive layer 14 is made of conductive silicone rubber. The conductive silicone rubber forming the internal semiconductive layer 14 is preferably the same conductive silicone rubber as the external semiconductive layer 12 from the viewpoint of improving productivity, but the conductive silicone forming the external semiconductive layer 12 is preferable. A conductive silicone rubber different from the rubber may be used.

  The conductor connection portion 8 of the cable connection structure 1 is inserted into the cylinder of the inner semiconductive layer 14. The one end side and the other end side in the axial direction of the internal semiconductive layer 14 are formed thicker than the central portion of the internal semiconductive layer 14 in the axial direction, and from the central portion to the one end side and the other end side. Each taper has a large diameter.

  The pair of stress cones 16 and 18 are formed in a cylindrical shape such as a cylindrical shape, and are provided at both ends of the outer semiconductive layer 12 in the axial direction. The stress cones 16 and 18 are provided so as to be aligned with the outer semiconductive layer 12 and the inner semiconductive layer 14. The power cables 2 and 4 of the cable connection structure 1 are inserted into the cylinders of the stress cones 16 and 18.

  The stress cones 16 and 18 are made of conductive silicone rubber. The conductive silicone rubber forming the stress cones 16 and 18 is preferably the same conductive silicone rubber as the external semiconductive layer 12 or the internal semiconductive layer 14 from the viewpoint of improving productivity. Alternatively, a conductive silicone rubber different from the inner semiconductive layer 14 may be used.

  Each of the pair of stress cones 16 and 18 includes stress cone main bodies 16a and 18a. The stress cone bodies 16a and 18a have rising portions 16b and 18b inserted into one end portions of the external semiconductive layer 12, and flange portions 16c and 18c.

  The rising portions 16b and 18b have tapered holes that gradually increase in diameter from the proximal end side to the distal end side of the stress cone main bodies 16a and 18a in order to alleviate the electric field. The rising portions 16 b and 18 b are formed with substantially the same outer diameter in the axial direction of the stress cones 16 and 18. An annular gap 22 is provided between the outer peripheral surfaces of the rising portions 16 b and 18 b and the inner peripheral surface of the outer semiconductive layer 12, and the gap 22 is filled with the insulating layer 20.

The flange portions 16c and 18c are formed to protrude outward in the radial direction (for example, the radial direction) on the base end side of the stress cone main bodies 16a and 18a. The flange portions 16 c and 18 c are formed with an outer diameter substantially the same as the outer diameter of the outer semiconductive layer 12.
The stress cone main bodies 16a and 18a are provided with cylindrical cable insertion ports 16d and 18d protruding from the base end side to the rear end side of the stress cone main bodies 16a and 18a in order to insert the power cables 2 and 4. Yes.

  At least one of the pair of stress cones 16 and 18 is provided with an injection port 24 for injecting a liquid insulating silicone rubber for forming the insulating layer 20. Further, at least one of the pair of stress cones 16 and 18 is provided with an exhaust port 26 for exhausting a gas such as air when liquid insulating silicone rubber is injected. The injection port 24 and the exhaust port 26 are formed, for example, in the flange portions 16c and 18c of the stress cones 16 and 18. Details of the inlet 24 and the outlet 26 will be described later.

  The insulating layer 20 includes an inner peripheral surface of the outer semiconductive layer 12, an outer peripheral surface of the inner semiconductive layer 14, a pair of stress cones 16, 18, a cylinder inside the inner semiconductive layer 14, and a pair of stress cones 16, 18 is filled with insulating silicone rubber in a space surrounded by the cable insertion hole 28 through which the jacket covering portions 2a and 4a of the power cables 2 and 4 in the cable connection structure 1 are inserted. Is formed. The insulating layer 20 is also filled in an annular gap 22 between the outer peripheral surface of the rising portions 16 b and 18 b and the inner peripheral surface of the outer semiconductive layer 12. The insulating layer 20 is formed by injecting a liquid insulating silicone rubber from the injection port 24 and then curing the liquid insulating silicone rubber.

  The outer peripheral surface of the stress cones 16 and 18 and the outer peripheral surface of the external semiconductive layer 12 are wound and electrically connected by a conductive tape 30 such as a metal mesh tape, for example. As described above, the cylindrical protective covering 10 is formed of a single piece (one piece) of silicone rubber and is formed so as to be shrinkable at room temperature.

  Next, the usage method of the cylindrical protective coating 10 is demonstrated.

  The cylindrical protective covering 10 is enlarged in diameter for mounting on the cable connection structure 1. In order to expand the diameter of the cylindrical protective covering 10, an inner core is inserted into the cylindrical protective covering 10 to form a cylindrical protective covering unit. FIG. 2 is a cross-sectional view showing the configuration of the cylindrical protective covering unit 32.

  The inner core 33 is formed in a cylindrical shape such as a cylindrical shape by winding a ribbon made of a resin material such as polyethylene or polypropylene in a spiral shape. The inner core 33 is provided with a spiral notch continuous along the circumference of the cylinder. The inner core 33 is formed so that the outer diameter of the cylinder is larger than the outer diameter of the cable connection structure 1. At one end portion of the inner core 33 in the axial direction, a knob portion 33a is provided so as to be freely drawn out. The inner core 33 is formed so that it can be disassembled sequentially from one end side to the other end side in the axial direction with a spiral notch as a boundary as the knob portion 33a is pulled out.

  FIG. 3 is a cross-sectional view showing a state where the tubular protective covering 10 is attached to the cable connection structure 1. The tubular protective covering 10 is attached to the cable connection structure 1 by the following method. One power cable 2, 4 is passed through the cylindrical protective covering unit 32, and the outer sheaths of both the power cables 2, 4 are peeled off to expose the conductor wires 2b, 4b. Next, after the end portions of both power cables 2 and 4 are arranged in a coaxial butted manner, the conductor wires 2b and 4b of both power cables 2 and 4 are compressed by the sleeve 6 and linearly connected. 8 is formed to constitute the cable connection structure 1. Thereafter, the cylindrical protective covering unit 32 is moved and arranged so as to cover the cable connection structure 1. Then, by pulling out the knob portion 33a of the inner core 33, the inner core 33 is sequentially disassembled and the tubular protective covering 10 is contracted, and the cable connection structure 1 is covered with the tubular protective covering 10. Protected. Thus, the mounting of the cylindrical protective covering 10 on the cable connection structure 1 is completed.

  Next, a method for manufacturing the cylindrical protective covering 10 will be described.

  FIG. 4 is a flowchart showing a method for manufacturing the cylindrical protective covering 10. The manufacturing method of the cylindrical protective covering 10 includes an external semiconductive layer forming step (S10), an internal semiconductive layer forming step (S12), a stress cone forming step (S14), and a cylindrical preform forming step ( S16) and an insulating layer forming step (S18).

  The external semiconductive layer forming step (S10) is a step of forming the cylindrical external semiconductive layer 12 with conductive silicone rubber.

  As the conductive silicone rubber, millable silicone rubber or liquid silicone rubber can be used. Millable silicone rubber is a type of silicone rubber that is cured by adding a crosslinking agent to a high-viscosity silicone polymer. As the crosslinking agent, for example, an organic peroxide such as dicumyl peroxide (DCP) is used. Liquid silicone rubber is a type of silicone rubber that is cured by adding a crosslinking agent or the like to a low viscosity silicone polymer. Examples of the liquid silicone rubber include an addition type liquid silicone rubber that cures by an addition reaction using a platinum compound as a catalyst, and a condensation type liquid silicone rubber that cures by reacting with moisture in the air. As a platinum compound, a platinum group metal simple substance and its compound are used, for example. Further, a conductive material is added to impart conductivity to the silicone rubber. For example, graphite or carbon black is used as the conductive material.

  The outer semiconductive layer 12 is preferably formed of a millable conductive silicone rubber because it can be easily molded. For example, HV4840U (manufactured by Dow Corning Toray) can be used as the conductive silicone rubber forming the external semiconductive layer 12.

  The outer semiconductive layer 12 is formed by a general rubber molding method such as extrusion molding or injection molding. The external semiconductive layer 12 is formed, for example, by inserting a core metal into the center of a cylindrical mold and injection-molding a silicone rubber composition in a cavity between the cylindrical mold and the core metal. When HV4840U (manufactured by Dow Corning Toray) is used as the conductive silicone rubber, the crosslinking conditions are a crosslinking temperature of 160 ° C. to 180 ° C. and a crosslinking time of 10 minutes to 20 minutes.

  The internal semiconductive layer forming step (S12) is a step of forming the cylindrical internal semiconductive layer 14 with conductive silicone rubber.

  As the conductive silicone rubber, the above-described millable silicone rubber or liquid silicone rubber can be used. The inner semiconductive layer 14 is preferably formed of a millable conductive silicone rubber because it is easy to mold. The conductive silicone rubber forming the inner semiconductive layer 14 is preferably the same conductive silicone rubber as the outer semiconductive layer 12 from the viewpoint of improving productivity. The inner semiconductive layer 14 is formed by a general rubber molding method such as extrusion molding or injection molding, like the outer semiconductive layer 12.

  The stress cone forming step (S14) is a step of forming a pair of cylindrical stress cones 16 and 18 with conductive silicone rubber.

  As the conductive silicone rubber, the above-described millable silicone rubber or liquid silicone rubber can be used. The stress cones 16 and 18 are preferably formed of a millable conductive silicone rubber because of easy molding. For the conductive silicone rubber forming the stress cones 16 and 18, it is preferable to use the same conductive silicone rubber as the outer semiconductive layer 12 and the inner semiconductive layer 14 from the viewpoint of improving productivity. Similar to the outer semiconductive layer 12 and the inner semiconductive layer 14, the stress cones 16 and 18 are molded by a general rubber molding method such as extrusion molding or injection molding.

  At least one of the pair of stress cones 16 and 18 is provided with an inlet 24 for injecting liquid insulating silicone rubber to form the insulating layer 20. Further, at least one of the pair of stress cones 16 and 18 is provided with an exhaust port 26 for exhausting a gas such as air when liquid insulating silicone rubber is injected.

  FIG. 5 is a cross-sectional view showing the configuration of the stress cones 16 and 18, and FIG. 5A is a cross-sectional view showing the configuration of the stress cone 16 provided with the inlet 24, and FIG. FIG. 5C is a cross-sectional view showing a configuration of the stress cone 18 provided with the exhaust port 26.

  As shown in FIG. 5A, the injection port 24 is preferably provided in the flange portion 16c of the stress cone. By providing the inlet 24 in the flange portions 16c and 18c, the liquid insulating silicone rubber is sufficiently applied to the narrow annular gap 22 between the outer peripheral surface of the rising portion 16b and the inner peripheral surface of the outer semiconductive layer 12. Can be filled. The inlet 24 is formed in a size that allows liquid insulating silicone rubber to be injected. For example, the injection port 24 is formed in a direction substantially parallel to the axial direction of the stress cone 16. The injection port 24 is formed by drilling with a drill or the like with a diameter of 8 mm to 12 mm, for example. In addition, the injection port 24 may be provided not only at one place but at a plurality of places.

  The exhaust port 26 is preferably provided in the flange portion 18c of the stress cone 18 as shown in FIG. By providing the exhaust port 26 in the flange portion 18c, gas such as air that tends to stay in the gap 22 between the outer peripheral surface of the rising portion 18b and the inner peripheral surface of the outer semiconductive layer 12 can be easily discharged. . The exhaust port 26 is formed in such a size that gas such as air can be exhausted and liquid insulating silicone rubber is difficult to leak. The exhaust port 26 is formed, for example, in a direction substantially parallel to the axial direction of the stress cone 18. The exhaust port 26 is preferably smaller than the diameter of the injection port 24, and is formed by drilling with a drill or the like with a diameter of 3 mm to 5 mm, for example.

  The exhaust port 26a may be provided so as to be inclined with respect to the axial direction of the stress cone 18 as shown in FIG. The exhaust port 26a is formed to be inclined so that the rising portion 18b side is closer to the axis of the stress cone 18 than the cable insertion port 18d side. By inclining in this inclination direction and forming the exhaust port 26a, the gas is less likely to stay in the exhaust port 26, so that the gas can be exhausted more efficiently. In addition, you may provide the exhaust ports 26 and 26a not only in one place but in multiple places.

  FIG. 6 is a cross-sectional view showing the configuration of another stress cone 50, 52. FIGS. 6 (a) and 6 (b) show the stress cone 50, 52 provided with both the inlet 24 and the exhaust port 26. FIG. It is sectional drawing which shows this structure.

  As shown in FIG. 6A and FIG. 6B, the stress cones 50 and 52 are provided with an inlet 24 and an outlet 26 one by one. For example, the injection port 24 and the exhaust port 26 are provided at intervals of 180 degrees in the circumferential direction of the stress cones 50 and 52. In the stress cone 50 shown in FIG. 6A, the shape of the inlet 24 is the same as that of the inlet 24 shown in FIG. 5A, and the shape of the exhaust port 26 is the exhaust shown in FIG. 5B. The shape of the mouth 26 is the same. In the stress cone 52 shown in FIG. 6B, the shape of the inlet 24 is the same as that of the inlet 24 shown in FIG. 5A, and the shape of the exhaust 26a is the exhaust shown in FIG. 5C. The shape of the mouth 26a is the same.

  When both the inlet 24 and the outlet 26 are provided in the stress cone, one inlet 24 and a plurality of outlets 26 may be provided, or a plurality of inlets 24 and one outlet 26 may be provided. A plurality of inlets 24 and a plurality of exhaust ports 26 may be provided.

  For example, one inlet 24 and three exhaust ports 26 may be formed at intervals of 90 degrees in the circumferential direction of the stress cone, and three inlets 24 and one exhaust port 26 may be formed in the circumferential direction of the stress cone. Alternatively, they may be formed at intervals of 90 degrees. Further, for example, the two inlets 24 and the two exhaust ports 26 may be formed at intervals of 90 degrees in the circumferential direction of the stress cone. The interval in the circumferential direction of the stress cone is not limited to 90 degrees, and may be another interval such as 45 degrees or 60 degrees, for example.

  As a combination of a pair of stress cones, (1) when one stress cone is provided with only the inlet 24 and the other stress cone is provided with only the exhaust port 26, (2) only one stress cone is provided with the inlet. When the other stress cone is not provided with the inlet 24 and the exhaust port 26, (3) one stress cone is provided with the inlet 24 and the exhaust port 26. In some cases, the other stress cone is also provided with an inlet 24 and an outlet 26. In order to inject liquid insulating silicone rubber efficiently without unevenness, it is preferable that an inlet 24 and an outlet 26 are provided in both stress cones.

  In the cylindrical preformed body forming step (S16), the inner semiconductive layer 14 is arranged in the cylinder of the outer semiconductive layer 12, and the stress cones are arranged on both sides of the outer semiconductive layer 12 to form a cylindrical preform. Is a step of forming. FIG. 7 is a cross-sectional view showing the configuration of the cylindrical preform 54.

  The cylindrical preform 54 is formed by setting the outer semiconductive layer 12, the inner semiconductive layer 14, and the pair of stress cones 16 and 18 in a predetermined shape mold (not shown). The external semiconductive layer 12 is set so that its axial direction is horizontal. The internal semiconductive layer 14 is provided in the cylinder of the external semiconductive layer 12 and is disposed, for example, at the approximate center in the axial direction of the external semiconductive layer 12. The inner semiconductive layer 14 is arranged with the outer semiconductive layer 12 aligned with the axis.

  The pair of stress cones 16 and 18 are disposed on both sides of the outer semiconductive layer 12 in the axial direction. The pair of stress cones 16 and 18 are arranged so that their axes are aligned with the outer semiconductive layer 12 and the inner semiconductive layer 14. The rising portions 16 b and 18 b of the stress cones 16 and 18 are inserted into the cylinder of the outer semiconductive layer 12. Between the outer peripheral surfaces of the rising portions 16b and 18b and the inner peripheral surface of the outer semiconductive layer 12, an annular gap 22 through which liquid insulating silicone rubber can be injected is provided.

  One stress cone 16 is provided with one injection port 24, and the other stress cone 18 is provided with one exhaust port 26. The stress cone 16 having the injection port 24 is filled with the liquid insulating silicone rubber from the lower side in the vertical direction of the cylindrical preform 54, so that the injection port 24 is located on the lower side in the vertical direction of the cylindrical preform 54. It is preferably set so as to be positioned. As the stress cone 18 having the exhaust port 26 is gradually filled with liquid insulating silicone rubber from the lower side in the vertical direction of the cylindrical preform 54, the air in the cylindrical preform 54, etc. It is preferable that the exhaust port 26 is set so as to be positioned on the upper side in the vertical direction of the cylindrical preform 54 so that the gas moves upward in the vertical direction in the cylindrical preform 54.

  The cylindrical preform 54 is provided with a core 56 which is inserted into the cylinder of the inner semiconductive layer 14 and the cylinders of the stress cones 16 and 18 in order to form the cable insertion hole 28. The core 56 is formed in, for example, an elongated cylindrical shape, and its surface is subjected to a mold release process.

  The gap between the outer peripheral surface of the outer semiconductive layer 12 and the outer peripheral surface of each of the stress cones 16 and 18 is wound and sealed with a sealing material 58 such as a release material so that the liquid insulating silicone rubber does not leak. Is done. After forming the insulating layer 20, the sealing material 58 is removed.

  FIG. 8 is a cross-sectional view showing another sealing method for sealing a gap between the outer peripheral surface of the outer semiconductive layer 12 and the outer peripheral surface of the stress cone 18. 8 shows the configuration on the stress cone 18 side, the configuration on the stress cone 16 side is the same configuration. Cylindrical protrusions 60 and 62 are provided on both ends in the axial direction of the external semiconductive layer 12 and the flange 18c of the stress cone 18, and abutting part 64 is formed by abutting these cylindrical protrusions 60 and 62. Then, a liquid insulating silicone rubber may be sealed. Note that, after the insulating layer 20 is formed, the butt portion 64 is removed by cutting or the like.

  FIG. 9 is a cross-sectional view showing the configuration of another cylindrical preform 70. The cylindrical preform 70 is different from the cylindrical preform 54 shown in FIG. 7 in the configuration of a pair of stress cones, and the other configurations are the same.

  In the cylindrical preform 70, both the stress cones 50 are provided with an injection port 24 and an exhaust port 26. One injection port 24 and one exhaust port 26 are provided at intervals of 180 degrees in the circumferential direction of each stress cone 50. Each stress cone 50 is preferably set so that the inlet 24 is positioned on the lower side in the vertical direction of the cylindrical preform 70 and the exhaust port 26 is positioned on the upper side in the vertical direction of the cylindrical preform 70. . According to the cylindrical preform 70, liquid insulating silicone rubber is injected from both axial ends of the cylindrical preform 70, and air or the like is injected from both axial ends of the cylindrical preform 70. Since the gas is exhausted, the liquid insulating silicone rubber can be filled more efficiently. In the cylindrical preform 70, the inlets 24 of both stress cones 50 are arranged to face each other (the axial directions of the inlets 24 coincide with each other). The 24 axial directions may be shifted.

  The insulating layer forming step (S18) is a step of forming the insulating layer 20 by injecting liquid insulating silicone rubber from at least one injection port 24 of the pair of stress cones 16 and 18.

  As the liquid insulating silicone rubber, it is preferable to use an addition type liquid silicone rubber that cures by an addition reaction using a platinum compound as a catalyst. This is because in the case of a condensation-type liquid silicone rubber that cures by reacting with moisture in the air, the curing time becomes long. For example, LSR2030J (Momentive Performance Materials Japan) is used as the liquid insulating silicone rubber.

The insulating layer 20 is injection-molded by injecting liquid insulating silicone rubber from the injection port 24 of the stress cone 16. For injection molding, a general injection molding apparatus of silicone rubber is used. The pressure at the time of injecting the liquid insulating silicone rubber is, for example, 6.86 MPa (70 kgf / cm ² ) to 8.82 MPa (90 kgf / cm ² ).

  Since the stress cone 16 is provided with the injection port 24, the liquid insulating silicone rubber extends from the axial end of the cylindrical preform 54 along the axial direction (parallel to the axial direction). Injected. Further, since the injection port 24 is located on the lower side in the vertical direction of the cylindrical preform 54, the liquid insulating silicone rubber is directed from the lower side in the vertical direction of the cylindrical preform 54 to the upper side in the vertical direction. Filled. Further, since the injection port 24 is provided in the flange 16c of the stress cone 16, the liquid insulating property is also provided in the annular gap 22 between the outer peripheral surface of the rising portion 16b and the inner peripheral surface of the outer semiconductive layer 12. Filled with silicone rubber.

  A gas such as air in the cylindrical preform 54 is exhausted from the exhaust port 26 of the stress cone 18. Since the exhaust port 26 is positioned on the upper side in the vertical direction of the cylindrical preform 54, the liquid insulating silicone rubber is filled from the lower side in the vertical direction to the upper side in the vertical direction of the cylindrical preform 54. Accordingly, gas such as air that has moved from the lower side in the vertical direction to the upper side in the vertical direction of the cylindrical preform 54 is efficiently exhausted. Further, since the exhaust port 26 is provided in the flange portion 18c of the stress cone, a gas such as air stays in the annular gap 22 between the outer peripheral surface of the rising portion 18b and the inner peripheral surface of the outer semiconductive layer 12. Is suppressed.

  After injecting and filling liquid insulating silicone rubber into the cylindrical preform 54, the cylindrical preform 54 is heated to crosslink and cure the liquid insulating silicone rubber. The crosslinking condition of the liquid insulating silicone rubber varies depending on the type of the insulating silicone rubber. For example, when LSR2030J (Momentive Performance Materials Japan) is used, the crosslinking temperature is 110 ° C. to 120 ° C., Crosslinking time is 20 to 25 minutes.

  After the liquid insulating silicone rubber injected into the cylindrical preform 54 is heat-cured, the core 56 is taken out. FIG. 10 is a cross-sectional view showing a state in which the insulating layer 20 is formed. Insulating layer 20 is formed in a space surrounded by the inner peripheral surface of outer semiconductive layer 12, the outer peripheral surface of inner semiconductive layer 14, a pair of stress cones 16 and 18, and core 56. A cable insertion hole 28 through which the jacket covering portions 2a and 4a of the cable connection structure 1 are inserted is formed at a portion where the core 56 is inserted. After forming the insulating layer 20, the sealing material 58 is removed. Then, since the sealing material 58 is removed, a conductive material such as a metal mesh tape is used to cover the insulating layer 20 exposed between the outer peripheral surface of the outer semiconductive layer 12 and the outer peripheral surfaces of the stress cones 16 and 18. Tape 30 is wound. Thus, the manufacture of the cylindrical protective covering 10 is completed.

  In order to seal the gap between the outer peripheral surface of the outer semiconductive layer 12 and the outer peripheral surface of the stress cone 18 during the injection of the liquid insulating silicone rubber, it is different from the sealing method shown in FIGS. A sealing method may be used. FIG. 11 is a cross-sectional view showing another sealing method for sealing a gap between the outer peripheral surface of the outer semiconductive layer and the outer peripheral surface of the stress cone. In addition, in FIG. 11, although the structure by the side of the stress cone 18 is shown, the structure by the side of the stress cone 16 is also the same structure.

  FIG. 11A is a cross-sectional view showing a state before injecting a liquid insulating silicone rubber. The cylindrical projection 60a of the stress cone 18 and the cylindrical projection 62a of the outer semiconductive layer 12 are arranged such that the insulating layer 20 is radiated from the outer peripheral surface of the outer semiconductive layer 12 and the outer peripheral surface of the stress cone 18 (for example, diameter (Direction) is provided so as to protrude outward. In order to seal the liquid insulating silicone rubber, the cylindrical protrusion 60a of the stress cone 18 and the cylindrical protrusion 62a of the outer semiconductive layer 12 are abutted to form an abutting portion 64a.

  FIG. 11B is a cross-sectional view showing a state in which liquid insulating silicone rubber is injected and cured. In an annular gap surrounded by the cylindrical projection 60a of the stress cone 18 and the cylindrical projection 62a of the external semiconductive layer 12, the insulating layer 20a is disposed on the outer peripheral surface of the external semiconductive layer 12 and the outer peripheral surface of the stress cone 18. And projecting from.

  In FIG. 11C, a part of the butting portion 64a is cut to expose the insulating layer 20a between the cylindrical projection 60a of the stress cone 18 and the cylindrical projection 62a of the external semiconductive layer 12. It is sectional drawing which shows a state. The method of cutting the abutting portion 64a is that the insulating layer 20a protrudes outward in the radial direction from the cylindrical projection 60a of the stress cone 18 and the cylindrical projection 62a of the outer semiconductive layer 12, and the like. Cut into shapes.

  FIG. 11 (d) is an enlarged view of the vicinity of the insulating layer 20 a when the cylindrical protective covering 10 is attached to the cable connection structure 1 with an enlarged diameter. When the butted portion 64a is cut in a direction parallel to the axial direction of the cylindrical protective covering 10 to expose the insulating layer, the cylindrical protective covering 10 is expanded in diameter to the cable connection structure 1. When attached, the insulating layer has a concave shape inward in the radial direction (for example, the radial direction) due to the difference in shrinkage between the conductive silicone rubber and the insulating silicone rubber. On the other hand, as shown in FIG. 11C, the insulating layer 20a is outward in the radial direction (for example, in the radial direction) from the cylindrical protrusion 60a of the stress cone 18 and the cylindrical protrusion 62a of the outer semiconductive layer 12. When the cylindrical protective covering 10 is expanded by being cut so as to protrude to the side, the cylindrical projection 60a of the stress cone 18 and the outer semiconductive layer 12 are formed as shown in FIG. Since the end surfaces of the cylindrical protrusion 62a and the insulating layer 20a are substantially horizontal and the same surface, the depression of the insulating layer 20a can be suppressed.

  In addition, the conductive silicone rubber that forms the outer semiconductive layer 12, the inner semiconductive layer 14, and the pair of stress cones 16 and 18 uses a conductive silicone rubber having an organic peroxide as a crosslinking agent, As the insulating silicone rubber forming the insulating layer 20, it is preferable to use an insulating silicone rubber having a platinum compound as a crosslinking agent. By molding the cylindrical protective covering 10 with a combination of this silicone rubber, the bonding strength between the outer semiconductive layer 12, the inner semiconductive layer 14, the pair of stress cones 16, 18 and the insulating layer 20 is as follows. It can be ensured sufficiently without using an adhesive or the like.

  According to the above configuration, since the injection port for injecting the liquid insulating silicone rubber into at least one of the pair of stress cones is provided, the liquid insulating silicone rubber is transferred from one end side to the other end of the cylindrical preform. It can be injected along the axial direction to the side. Further, since an exhaust port for exhausting gas such as air is provided in at least one of the pair of stress cones, gas such as air in the cylindrical preform is exhausted when the liquid insulating silicone rubber is injected. Therefore, it is not necessary to use a vacuum device or the like for exhausting the gas in the cylindrical preform. As described above, since the liquid insulating silicone rubber can be uniformly injected and filled into the cylindrical preform, the insulating layer of the cylindrical protective covering is more uniformly filled.

  According to the above configuration, since the injection port is provided in the flange portion of the stress cone, the liquid insulating silicone rubber is also provided in the annular gap between the outer peripheral surface of the rising portion and the inner peripheral surface of the external semiconductive layer. Is filled. In addition, since the exhaust port is provided in the flange portion of the stress cone, it is possible to suppress the retention of gas such as air in the annular gap between the outer peripheral surface of the rising portion and the inner peripheral surface of the outer semiconductive layer. The

  According to the above configuration, by disposing the stress cone so that the injection port is on the lower side in the vertical direction of the cylindrical preform, the liquid insulating silicone rubber is vertical from the lower side in the vertical direction of the cylindrical preform. Since the liquid is filled toward the upper side in the direction, the liquid silicone rubber can be uniformly injected into the cylindrical preform. Further, by disposing the stress cone so that the exhaust port is on the upper side in the vertical direction of the cylindrical preform, the liquid insulating silicone rubber is directed from the lower side in the vertical direction to the upper side in the vertical direction of the cylindrical preform. Along with filling, a gas such as air that has moved from the lower side in the vertical direction to the upper side in the vertical direction of the cylindrical preform can be more efficiently exhausted.

  The cylindrical protective covering 10 was manufactured by the manufacturing method having the above configuration.

  The outer semiconductive layer 12, the inner semiconductive layer 14, and the pair of stress cones 16 and 18 were molded from conductive silicone rubber. As the conductive silicone rubber, HV4840U (manufactured by Dow Corning Toray) was used. HV4840U (manufactured by Toray Dow Corning) is a millable conductive silicone rubber containing octamethylcyclotetrasiloxane, silica, and carbon black.

  The outer semiconductive layer 12, the inner semiconductive layer 14, and the pair of stress cones 16 and 18 were each injection molded using a mold having a predetermined shape. The molding conditions were such that the crosslinking temperature was 160 ° C. to 180 ° C. and the crosslinking time was 10 minutes to 20 minutes.

  The outer semiconductive layer 12, the inner semiconductive layer 14, and the pair of stress cones 16 and 18 were formed in substantially the same shape as shown in FIG. The outer semiconductive layer 12 was formed into a cylindrical shape having an outer diameter of 80 mm and a length of 500 mm. The inner semiconductive layer 14 was formed into a substantially cylindrical shape having an outer diameter of 30 mm and a length of 250 mm. Regarding the stress cone, the outer diameters of the rising portions 16b and 18b of the stress cone main bodies 16a and 18a were set to 60 mm, and the outer diameters of the flange portions 16c and 18c were set to 80 mm. The inlet 24 was formed in one stress cone, and the exhaust port 26 was formed in the other stress cone. The injection port 24 and the exhaust port 26 were formed by drilling in the stress cone flanges 16c and 18c so as to be parallel to the axial direction of the stress cone. The inlet 24 has a diameter of 10 mm, and the outlet 26 has a diameter of 4 mm.

  Next, the outer semiconductive layer 12, the inner semiconductive layer 14, and the pair of stress cones 16 and 18 were set in a predetermined shape in the same arrangement as shown in FIG. About the stress cone 16 in which the injection port 24 was formed, it arrange | positioned so that the injection port 24 may become a vertical direction lower side. About the stress cone 18 in which the exhaust port 26 was formed, it arrange | positioned so that the exhaust port 26 may become a vertical direction upper side. Further, the core 56 is inserted into the cylinder of the inner semiconductive layer 14 and the cylinders of the pair of stress cones 16 and 18 so that the insulating layer 20 is not formed at the portion where the core 56 is inserted. Further, the gap between the outer peripheral surface of the outer semiconductive layer 12 and the outer peripheral surfaces of the stress cones 16 and 18 was sealed with a sealing material 58.

Liquid insulating silicone rubber was injected from the inlet 24 of the stress cone 16 and surrounded by the outer semiconductive layer 12, the inner semiconductive layer 14, the pair of stress cones 16 and 18, and the core 56. An insulating layer 20 was formed in the space. LSR2030J (Momentive Performance Materials Japan) was used for the liquid insulating silicone rubber. LSR2030J includes polyalkylalkenylsiloxane, silica, and a platinum compound. Liquid insulating silicone rubber was injected from the injection port 24 at an injection pressure of 7.84 MPa (80 kgf / cm ² ). The curing conditions for the liquid insulating silicone rubber were a crosslinking temperature of 110 ° C. to 120 ° C. and a crosslinking time of 20 minutes to 25 minutes. After forming the insulating layer 20, the sealing material 58 was removed.

  Thus, the cylindrical protective covering 10 was manufactured. As a result of cutting and visually observing the manufactured cylindrical protective covering 10, the insulating layer 20 was formed to be uniformly filled, and no unfilled portion or the like was observed. In addition, no voids or the like were observed in the annular gap 22 between the outer peripheral surfaces of the rising portions 16b and 18b and the inner peripheral surface of the outer semiconductive layer 12.

  Next, an adhesion test was performed to evaluate the adhesion between the outer semiconductive layer 12, the inner semiconductive layer 14, the stress cones 16 and 18, and the insulating layer 20. The adhesion test was performed in accordance with JIS K6854-2 “Adhesive—Peeling peel strength test method—Part 2: 180 degree peel”.

  The test piece was prepared by cross-linking the conductive silicone rubber and then cross-linking the liquid conductive silicone rubber with the cross-linked conductive silicone rubber. As the conductive silicone rubber, HV4840U (manufactured by Dow Corning Toray), which is the same material as the material formed from the outer semiconductive layer 12, the inner semiconductive layer 14, and the stress cone, was used. As the insulating silicone rubber, LSR2030J (Momentive Performance Materials Japan), which is the same material as the material from which the insulating layer 20 was molded, was used. The curing conditions of HV4840U (manufactured by Toray Dow Corning) and LSR2030J (Momentive Performance Materials Japan) are the same as the above-described crosslinking temperature and crosslinking time. According to the adhesion test results, the adhesion was 3 kgf to 6 kgf and had sufficient adhesion.

  Next, an electrical property test was performed. The electrical property test was performed in accordance with JEC 3408 “Extra-high voltage (11 kV to 275 kV) cross-linked polyethylene cable and connection part high voltage test method”. The test piece was produced by the same molding method and molding conditions as those of the adhesion test described above. FIG. 12 is a diagram showing the electrical characteristic test results. All of the AC withstanding voltage test, the Imp withstanding voltage test, and the long-term charging test were acceptable.

DESCRIPTION OF SYMBOLS 1 Cable connection structure 2, 4 Electric power cable 2a, 4a Outer coating | cover part 2b, 4b Conductor wire 6 Sleeve 8 Conductor connection part 10 Cylindrical protective coating 12 External semiconductive layer 14 Internal semiconductive layer 16, 18 Stress cone 20 Insulating layer 16a, 18a Stress cone body 16b, 18b Rising part 16c, 18c ridge part 22 gap 16d, 18d Cable insertion port 24 Inlet 26 Exhaust port 28 Cable insertion hole 30 Conductive tape 32 Cylindrical protective covering unit 33 Inner core 33a Knob portion 26a Exhaust port 50, 52 Stress cone 54 Cylindrical preform 56 Core 58 Seal material 60, 62 Cylindrical projection 64 Butt portion 70 Cylindrical preform

Claims (13)

A cylindrical protective covering for protecting the cable connection structure connecting the power cables,
A cylindrical outer semiconductive layer formed of conductive silicone rubber;
A cylinder provided in a cylinder of the outer semiconductive layer, formed of conductive silicone rubber, into which a conductor connecting portion connected by connecting an exposed conductor wire by peeling off the outer sheath of power cables in the cable connection structure is inserted. An internal semiconductive layer,
A pair of cylindrical stress cones provided at both ends of the outer semiconductive layer, respectively, formed of conductive silicone rubber;
The inner surface of the outer semiconductive layer, the outer surface of the inner semiconductive layer, the pair of stress cones, the cylinder of the inner semiconductive layer, and the cylinders of the pair of stress cones communicate with each other. An insulating layer formed by curing a liquid insulating silicone rubber, filled in a space surrounded by a cable insertion hole through which an outer sheath portion of the power cable of the cable connection structure is inserted;
With
At least one of the pair of stress cones has an inlet for injecting the liquid insulating silicone rubber,
At least one of the pair of stress cones has an exhaust port for exhausting the gas in the space. The cylindrical protective covering according to claim 1,
Each of the pair of stress cones includes a stress cone body,
The stress cone body includes a rising portion that is inserted into one end portion of the outer semiconductive layer and has a tapered hole that gradually increases in diameter from the proximal end side to the distal end side of the stress cone body,
The cylindrical protective covering body, wherein the injection port and the exhaust port are formed in communication between an outer peripheral surface of the rising portion and an inner peripheral surface of the external semiconductive layer. The cylindrical protective covering according to claim 2,
The stress cone body is provided on the base end side of the stress cone body, and has a flange portion that is formed to protrude outward in the radial direction.
The cylindrical protective covering body, wherein the inlet and the exhaust port are provided in the flange portion. A cylindrical protective covering according to any one of claims 1 to 3,
Each of the pair of stress cones is provided with the injection port and the exhaust port. A cylindrical protective covering according to any one of claims 1 to 4,
The said exhaust port is a cylindrical protective coating body whose diameter is smaller than the said injection port. A cylindrical protective covering according to any one of claims 1 to 5,
The cylindrical protective covering, wherein the conductive silicone rubber forming the external semiconductive layer, the internal semiconductive layer, and the pair of stress cones is a millable conductive silicone rubber. A method of manufacturing a cylindrical protective covering for protecting a cable connection structure connecting power cables,
An external semiconductive layer forming step of forming a cylindrical external semiconductive layer with conductive silicone rubber;
Internal semiconductive layer formation for forming a cylindrical internal semiconductive layer into which a conductor connecting portion connecting conductive wires exposed by peeling the outer sheath of power cables in the cable connection structure is inserted with conductive silicone rubber Process,
A stress cone forming step of forming a pair of stress cones in a cylindrical shape with conductive silicone rubber;
The inner semiconductive layer is disposed in the outer semiconductive layer, the pair of stress cones are disposed at both ends of the outer semiconductive layer, and the inner semiconductive layer and the pair of stress cones are disposed. Inside, a cylindrical preform forming step of forming a cylindrical preform by inserting a core that forms a cable insertion hole through which the jacket covering portion of the power cable of the cable connection structure is inserted, and
After injecting liquid insulating silicone rubber into the space surrounded by the inner peripheral surface of the outer semiconductive layer, the outer peripheral surface of the inner semiconductive layer, the pair of stress cones, and the core, An insulating layer forming step of curing to form an insulating layer;
With
At least one of the pair of stress cones has an inlet for injecting the liquid insulating silicone rubber into the space,
At least one of the pair of stress cones has an exhaust port for exhausting the gas in the space. It is a manufacturing method of the cylindrical protective covering according to claim 7,
Each of the pair of stress cones includes a stress cone body,
The stress cone body includes a rising portion that is inserted into one end portion of the outer semiconductive layer and has a tapered hole that gradually increases in diameter from the proximal end side to the distal end side of the stress cone body,
The method for producing a cylindrical protective covering, wherein the inlet and the exhaust port are formed to communicate between an outer peripheral surface of the rising portion and an inner peripheral surface of the outer semiconductive layer. It is a manufacturing method of the cylindrical protective covering according to claim 8,
The stress cone body is provided on the base end side of the stress cone body, and has a flange portion that is formed to protrude outward in the radial direction.
The method for manufacturing a cylindrical protective covering, wherein the inlet and the exhaust port are provided in the flange portion. It is a manufacturing method of the cylindrical protective covering according to any one of claims 7 to 9,
Each of the pair of stress cones is provided with the injection port and the exhaust port. It is a manufacturing method of the cylindrical protection covering object according to any one of claims 7 to 10,
In the cylindrical preform forming step, each of the pair of stress cones is such that the injection port is positioned on the lower side in the vertical direction of the cylindrical preform, and the exhaust port is a vertical of the cylindrical preform. It arrange | positions so that it may be located in a direction upper side, The manufacturing method of the cylindrical protective coating body characterized by the above-mentioned. It is a manufacturing method of the cylindrical protection covering object according to any one of claims 7 to 11,
The method for manufacturing a cylindrical protective covering, wherein the exhaust port has a smaller diameter than the injection port. A method for producing the cylindrical protective covering according to any one of claims 7 to 12,
The method for producing a cylindrical protective covering, wherein the conductive silicone rubber forming the external semiconductive layer, the internal semiconductive layer, and the pair of stress cones is a millable conductive silicone rubber.

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