One aspect of the present invention relates to a protective cover for a cable connecting portion and a method for protecting the cable portion.

RELATED ART

Conventionally, using a cylindrical protective cover that covers a cable connecting portion is known for ensuring the insulation and waterproofing of a cable connecting portion of a transmission line or the like. For example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2001-320823), a protective cover is described provided with a linear outer tube and an inner tube disposed on both ends of the outer tube, wherein a ring shaped ridge is provided on an inner periphery face of the inner tube.

BACKGROUND DOCUMENTS

Patent Documents

Patent Document 1 : Japanese Unexamined Patent Application Publication No.

2001-320823

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

Here, with the conventional protective cover described above, the ridge on the inner periphery face of the inner tube may get caught on a connection sleeve or the like when the cable connecting portion is passed through. The cable connecting operation of a transmission line or the like may be performed suspended in air, and improvement for easily covering the cable connecting portion with the protective cover is in demand.

Here, an object of the present invention is to provide a protective cover for a cable connecting portion that can easily cover the cable connecting portion and improve the workability of the cover installation and a method for protecting the cable connecting portion.

SUMMARY OF THE INVENTION

The present invention, in one aspect, is a protective cover for a cable connecting portion provided with a main body tube made of resin having insulating properties and a pair of contractible end tubes provided respectively on both ends of the main body tube, the main body tube being curved so that a central axis of the main body tube forms an arc- shape, and a curvature of the central axis is 2.0 x 10 ^~3 [l/m] or greater and 40.0 x 10 ^"3 [l/m] or less.

Because the main body tube is curved to make an arc shape with the curvature of the central axis 2.0 x 10 ^"3 [l/m] or greater and 40.0 x 10 ^"3 [l/m] or less, it can be easily covered by passing through while twisting so that it orients to match the cable connecting portion curved in a similar arc shape. In other words, during the cable connection of an overhead cable of a transmission line or the like, a pressure bonding is performed that flattens the sleeve in the radial direction with a tool with conductors of a pair of cables each inserted from both sides of the connection sleeve. At this time, the sleeve cannot maintain a straight line shape and bending deformation occurs by the pressure bonding. More pressure bondings are performed by the tool the longer the sleeve, and the effects of bending deformation also increase. Because of this, the cable connecting portion is often slightly curved. On the other hand, because the main body tube is curved so as to have a fixed curvature, this protective cover can cover the cable connecting portion, and work ability of the cover installation can also be improved. Furthermore, this protective cover has contractible end tubes provided on both ends of the main body tube, and by contracting the end tubes and causing them to contact the cable, the waterproofing of the cable connecting portion can be easily ensured.

In another aspect, in a cross-section perpendicular to the central axis of the main body tube, a thickness of an inner side of a curve on the main body tube may be larger compared to a thickness of an outer side of the curve on the main body tube.

In another further aspect, the cross-section perpendicular to the central axis of the main body tube is annular, and the gap between center points of the outer periphery and inner periphery that form the cross-section may be 0.05 mm or greater and 0.35 mm or less.

Further, in another aspect, a length of the main body tube may be 450 mm or greater and 700 mm or less.

Furthermore, in another aspect, lubricant may be applied to one portion or all of the inner periphery of the main body tube.

The present invention, in one aspect, is a method for producing a cable connecting portion that uses a main body tube made of resin having insulating properties and a pair of contractible end tubes provided respectively on both ends of the main body tube, the main body tube being curved so that a central axis of the main body tube forms an arc-shape, and a curvature of the central axis is 2.0 x 10 ^"3 [l/m] or greater and 40.0 x 10 ^"3 [l/m] or less, the method including a process that passes the sleeve cover through the cable connecting portion by a holder with the pair of end tubes each in an expanded state and a process that contracts the pair of end tubes and covers the cable by removing the holder.

EFFECT OF THE INVENTION

According to the present invention, a protective cover of a cable connecting portion that can easily cover the cable connecting portion and improve the workability of the cover installation and a method for protecting the cable connecting portion can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a sleeve cover according to the present

embodiment.

FIG. 2 is a diagram illustrating a cable connecting portion.

FIG. 3 is a cross-sectional view along a III-III line of FIG. 1.

FIG. 4 is an enlarged view of one end of the sleeve cover.

FIG. 5A is a diagram illustrating a core member, and FIG. 5B is a diagram illustrating the disassembly of the core member.

FIG. 6 is a diagram illustrating a sleeve cover covering the cable connecting portion. FIG. 7 is a diagram illustrating a sleeve cover installed on the cable connecting portion after contracting an end tube.

DETAILED DESCRIPTION

The following is a detailed explanation of the preferred embodiments of the present invention, with reference to the drawings. Note that the dimensional ratios and curvature in each drawing do not necessarily coincide with actual dimensional ratios.

A sleeve cover 10 illustrated in FIG. 1 is, for example, a cylindrical protective cover used for protecting a cable connecting portion of an overhead cable of a

transmission line. The sleeve cover 10 covers, for example, the cable connecting portion of the transmission line and ensures the insulation and waterproofing of the cable connecting portion.

(Structure of the Cable Connecting Portion)

First, a cable connecting portion 20 will be described referring to FIG. 2. Here, a cable connecting portion 20 is described that connects outdoor cross linked polyethylene (OC) lines that have aluminum as the conductor.

As illustrated in FIG. 2, the cable connecting portion 20 is a part that connects a pair of cables 21 and 22. The cable connecting portion 20 includes a conductor 21a that is exposed from the cable 21, a conductor 22a that is exposed from the cable 22, and a sleeve 23.

The sleeve 23 is a cylindrical member used for connecting cables, and is, for example, formed with a tinned copper tube. This sleeve 23 has sufficient length (for example, 38 cm) for connecting OC lines that have aluminum as the conductor. Note that with OC lines that have aluminum as the conductor, longer sleeves are used compared to OC lines that have copper as the conductor from the viewpoint of power loss.

The conductor 21a of the cable 21 and the conductor 22a of the cable 22 are respectively inserted into both ends of the sleeve 23. With the conductors 21a and 22a respectively inserted into both ends of the sleeve 23 in this manner, cables 21 and 22 are connected by crimping that flattens the sleeve in the radial direction by a tool such as tongs. A plurality of crimping marks are formed on the surface of the sleeve 23. The crimping operation of this type of sleeve 23 is often performed suspended in air with, for example, an overhead cable of a transmission line.

In this crimping operation, the sleeve 23 cannot maintain a straight line shape when the sleeve 23 is flattened in the radial direction by a tool, and bending deformation occurs. Because of this, it is normal for the cable connecting portion 20 to be formed slightly curved. Note that an example was described with a cable connecting portion 20 of OC lines that have aluminum as the conductor, but a cable connecting portion connecting conductors of copper or the like may also be used. Furthermore, the cables 21 and 22 do not necessarily need to be OC lines.

(Structure of the Sleeve Cover)

Next, the structure of the sleeve cover 10 will be described. As illustrated in FIG.

1, the sleeve cover 10 includes a main body tube 11 made of resin, a pair of end tubes 12 and 13 provided on both ends of the main body tube 11, and core members 14 and 15 disposed in each of the end tubes 12 and 13.

The main body tube 11 is a cylindrical member formed from resin having insulating properties. As materials for the main body tube 11 , a resin having insulating properties and flame retardance, for example, flame retardant polyethylene, flame retardant polypropylene, and the like are given. Sufficient rigidity to endure the contracting force of the end tubes 12 and 13 provided on both ends is required in the main body tube 11. As a resin material that can obtain sufficient rigidity, for example, a resin material can be used where the measured value of the yield point of the tensile strength is 1.68 kg/mm by JISK6301. This type of main body tube 11 is formed by, for example, extrusion molding.

The main body tube 11 is formed curved so a central axis C forms a cylindrical shape. The central axis C of the main body tube 11 is a curved line included in a single plane and curved in one direction. The central axis C has a fixed curvature p. FIG. 1 illustrates a center point P and a curvature radius r of a curvature circle including the central axis C. The curvature radius r is equal to the reciprocal value of the curvature p.

The curvature p of the central axis C is 2.0 x 10 ^"3 [l/m] or greater and 40.0 x 10 ^{" 3} [l/m] or less. To make it easier to pass through the cable connecting portion 20 which is curved in an arc shape, it is preferable for the curvature p of the central axis C to be 2.0 x 10 ^"3 [l/m] or greater. Furthermore, it is preferable for the curvature p of the central axis C to be 40.0 x 10 ^"3 [l/m] or less to maintain favorable appearance and ease of handling. Note that the curvature p of the central axis C may be 6.0 x 10 ^_1 [l/m] or greater and 16.0 x 10 ^{" 3} [l/m] or less.

The curvature p of the central axis C can be obtained by formula (1) below via the curvature radius r described above when a length of the main body tube 11 (the distance between one end of the main body tube 11 to the other end on the central axis C) is defined as LI, and a warp of the main body tube 11 is defined as L2.

Equation 1

p = l/r = (2 x L2) /Ll ² · ' · ( 1 )

Note that in formula (1) described above, the length LI of the main body tube 11 is assumed to be a linear distance. Further, the warp L2 of the main body tube 11, within a plane including the central axis C, is obtained as the shortest distance between the connection contacting the outer periphery face of one end of the main body tube 11 from the outer side of the curve of the main body tube 11 , and a point on the outer side of the curve configuring the outer periphery face of the other end.

Note that the curvature p of the central axis C does not necessarily need to be fixed, and may vary within the range described above.

The length of the main body tube 11 is selected corresponding to the length of the sleeve 23 and the like. In the present embodiment, the length of the main body tube 11 used in the cable connecting portion 20 of OC lines having aluminum as the conductor is, for example, 450 mm or greater and 700 mm or less. The length of the main body tube 11 can be selected from, for example, about 480 mm, about 485 mm, about 515 mm, about 560 mm, and about 615 mm.

FIG. 3 is a schematic cross-sectional view along a III-III line of FIG. 1. In FIG 3, a cross-section perpendicular to the central axis C of the main body tube 11 is illustrated. As illustrated in FIG. 3, the cross-section of the main body tube 11 forms an annular shape. The cross-section of the annular shape is formed so that a thickness Tin on the inner side of the curve on the main body tube 11 is larger compared to a thickness TOU _T on the outer side of the curve on the main body tube 11. Note that the ratio of the thicknesses TOU _T and Tin illustrated in FIG. 3 is only one example, and the ratio of the actual product is not limited to this.

Specifically, the annular cross-section on the main body tube 1 1 forms an outer circumference N and an inner circumference M. The outer circumference N is equivalent to an edge of an outer periphery face Fa of the main body tube 1 1 , and the inner circumference M is equivalent to an edge of an inner periphery face Fb of the main body tube 1 1. On this cross-section, a center point Cn of the outer periphery N and a center point Cm of the inner periphery M do not match. That is to say that the cross-section of the main body tube 1 1 is formed so that the inner periphery M is eccentric relative to the outer periphery N.

The center point Cm of the inner periphery M is positioned more on the outer side of the curve of the main body tube 1 1 compared to the center point Cn of the outer periphery N, and the gap between the center point Cm and the center point Cn is 0.05 mm or greater and 0.35 mm or less. A thick walled part and a thin walled part described hereafter can be clearly formed by the gap between the center point Cm and the center point Cn being 0.05 mm or greater. Further, it is also preferable for the gap between the center point Cm and the center point Cn to be 0.35 mm or less from the viewpoint of the yield of material.

The main body tube 1 1 having this type of annular cross-section can be produced by, for example, disposing a collet on the extrusion molder. Note that the central axis C of the main body tube 1 1 in the present embodiment is equivalent to an axis passing through the center point Cn of the outer periphery N.

With the main body tube 1 1 made of resin extrusion molded to have this type of annular cross-section, the thin walled part of thickness TOUT and the thick walled part of thickness Tin are formed on the annular cross-section. Afterwards, this main body tube 1 1 is curved so that the thin walled part becomes the outer side and the thick walled part becomes the inner side because of the difference in thermal shrinkage of the thin walled part and the thick walled part. In this manner, the main body tube 1 1 having the curvature p described above can be easily produced. Note that the cross-section of the main body tube 1 1 does not necessarily need to be annular. The shape of the cross-section of the main body tube 1 1 may be a rectangular or polygonal cross-section shape having an opening in the center, and may be a cross-sectional shape with one part of a circle replaced with a linear part.

Further, a lubricant is applied to one part or all of the inner periphery face Fb of the main body tube 1 1 to make the sleeve cover 10 easily pass through the cable connecting portion 20. Fluorine grease, fluorine oil, silicon grease, silicon oil, and the like can be used as the lubricant from the viewpoint of insulating properties and weather resistance. Furthermore, oil can be used instead of grease from the viewpoint of controlling the reduction of the coating amount and the dripping of the lubricant. Here, those with viscosity over 10,000 cp will be taken as grease and those with a viscosity of 10,000 cp or less will be taken as oil. In this manner, by using an oil with low viscosity as a lubricant, the coating amount can be greatly reduced, and processing price can be cut compared to grease. Furthermore, reducing the coating amount of the lubricant allows the lubricant to drip and enter the gap between the end tubes 12, 13 and the main body tube 1 1 , thereby enabling the end tubes 12 and 13 to be removed easily and avoiding contamination by the lubricant adhering to the cable or the like.

Next, the end tubes 12 and 13 will be described. The pair of end tubes 12 and 13 are cylindrical rubber members provided on both ends of the sleeve cover 10, have insulating properties and contractility, and have excellent elastic properties. Ethylene- propylene rubber, acrylic rubber, silicone rubber, and the like are given as the material for the end tubes 12 and 13. Silicone rubber can be used as the material of the end tubes 12 and 13 in terms of water resistance and weather resistance.

The core members 14 and 15 rolled in a cylindrical shape are disposed respectively on the inner portions of the pair of end tubes 12 and 13. The end tubes 12 and 13 are held in an elongated and expanded state by the core members 14 and 15.

Here, FIG. 4 is an enlarged diagram illustrating one end of the sleeve cover 10. FIG. 5A is a diagram illustrating the core member 14. FIG. 5B is a diagram for describing the disassembly of the core member. Below, the core member 14 is described referring to FIGS. 4 and 5. Note that details regarding the core member 15 having the same configuration as the core member 14 are omitted.

As illustrated in FIGS. 4 and 5 A, the core member 14 is a cylindrical member formed by rolling one core ribbon. The core member 14 functions as a holder that holds the expanded state of the end tube 12. The core member 14 has a wound body 14a that enters the end tube 12 and an annular portion 14b formed on the end portion of the core ribbon that extends from the wound body 14a. Note that the annular portion 14b of the core member 14 is normally stored in the inner portion of the wound body 14a of the core member 14 and the main body tube 1 1 (refer to FIG. 1).

As illustrated in FIG. 5B, the core member 14 is taken out from the outer side of the end tube 12 by a worker placing a finger on the annular portion 14b and withdrawing it in the direction of the arrow A. In this manner, the opposite side of the main body tube 1 1 in the end tube 12 contracts in the radial direction and adheres to the cable 21.

(Method for Protecting the Cable Connecting Portion)

Below, a method for protecting the cable connecting portion 20 that uses the sleeve cover 10 will be described.

Here, FIG. 6 is a diagram illustrating the sleeve cover 10 in a state covering the cable connecting portion 20. FIG. 7 is a diagram illustrating the sleeve cover 10 installed on the cable connecting portion 20 after contracting the end tubes 12 and 13.

First, the annular portions 14b and 15b of the core members 14 and 15 are withdrawn from both ends of the main body tube 1 1 from the state shown in FIG. 1 with the sleeve cover 10. In this state, the sleeve cover 10 passes to the vicinity of the cable connecting portion 20 via the cables 21 and 22 illustrated in FIG. 2. Then, the sleeve cover 10 passes while twisting so that it orients to match the curved cable connecting portion 20, which is in a bent state, and covers the outer periphery of the cable connecting portion 20 as illustrated in FIG. 6.

Afterwards, by taking out the annular portions 14b and 15a of the core members 14 and 15 from both ends of the sleeve cover 10, the core members 14 and 15 are

disassembled and removed from inside the end tubes 12 and 13. As illustrated in FIG. 7, the end tubes 12 and 13 with the core members 14 and 15 removed cover the cables 21 and 22 by the end portions in an expanded state contracting. In this manner, the sleeve cover 10 is installed on the cable connecting portion 20, and the cover installation of the cable connecting portion 20 is completed.

Next, the operation and effect of the sleeve cover 10 and the protection method of the cable connecting portion according to the present embodiment will be described. According to this sleeve cover 10 and the protection method, because the main body tube 11 is curved so the curvature of the central axis C is an arc shape that is 2.0 x 10 ^"3 [l/m] or greater, it can be easily covered by passing through while twisting so that it orients to match the curved cable connecting portion 20 curved in a similar arc shape. In other words, because the main body tube 11 is curved so that it has a fixed curvature, this sleeve cover 10 can easily cover the cable connecting portion 20 and can raise the efficiency of the cover installation of the cable connecting portion 20 compared to when the main body tube is linear. Furthermore, because this sleeve cover 10 can easily cover the cable connecting portion 20 curved in an arc shape, the possibility of adding force and causing damage to the sleeve cover 10 can be reduced. Further, because the curvature of the central axis C is 40.0 x 10 ^"3 [l/m] or less, handling of this sleeve cover 10 is simple without being bulky, and the installation operation can be easily performed even while suspended in air, compared to when the curvature is large.

The present invention is not limited to the above described embodiments, but includes modifications which do not depart from the spirit of the present invention.

For example, with the sleeve cover described above, there is not necessarily a need to use a core member to hold the expanded state of the end tube, and the end tube may be expanded using an exclusive jig (holder) or the like when passing the cable. Further, the production method of the main body tube is not limited to extrusion molding, and may be produced by blow molding or the like.

(Explanation of Reference Numerals)

10 Sleeve cover

11 Main body tube

12, 13 End tube

14 Core member

14a Wound body

15a Annular portion

20 Cable connecting portion

21, 22 Cable

21a, 22a Conductor

23 Sleeve C center axis

Cm Center point of the inner periphery Cn Center point of the outer periphery Fa Outer periphery face

Fb Inner periphery face

M Inner periphery

N Outer periphery

P Center point of curvature circle r Curvature radius