JPH07308016A - Electrical insulation support - Google Patents

Abstract

PURPOSE:To provide an electrical insulation support made of a fiber reinforced composite material in which mechanical strength is enhanced at the joint of the support and a metal. CONSTITUTION:Metals 3 are coupled to the opposite ends of a pipe 2 made of a composite material reinforced with insulating fibers, e.g. glass rovings, produced by filament winding. The metal 3 comprises a first metal 4 embedded in the inner periphery at each end of the pipe 2, a second metal 5 fitted over the pipe 2 at each end, and a third metal 6 being screwed with the first metal 4 to press the second metal 5 against the end face of the pipe 2. When the pipe 2 is molded, the first metal 4 is embedded in the inner periphery of the pipe 2 at each end. The first metal 4 is tapered (m) toward the pipe end in order to prevent removal from the pipe 2. The first and second metals 4, 5 reinforces the end parts of the pipe 2 and a light weight electric insulation insulator 1 useful for an insulator requiring high mechanical strength can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating support material used for insulating and supporting electric wires such as distribution lines and power transmission lines on a steel tower or for securing a distance between the electric wires.

[0002]

2. Description of the Related Art Conventionally, porcelain insulators have been widely used as an electrically insulating support material for insulatingly supporting transmission lines and the like. This porcelain insulator has line post insulators, tension insulators, interphase spacer insulators, station post insulators, etc., and has high reliability in insulation under high voltage. However, the porcelain insulator is heavy to obtain the necessary withstand load. Also, the fracture mode is brittle. That is, it is heavy and brittle.

Therefore, in recent years, FRP (fiber) has been used as an electrically insulating support material which is lighter in weight than porcelain insulators and is superior in mechanical strength.
Fiber reinforced composite material insulators using r-reinforced plastics are being investigated. This FRP insulator generally has a structure in which mounting brackets are joined to both ends of a FRP rod that is formed by drawing a round bar, and is lighter in weight and easier to handle than a porcelain insulator, and has excellent mechanical strength. It has been known.

[0004]

The connection between the FRP rod of the FRP insulator and the mounting member is secondarily performed by adhesion with an ordinary adhesive, caulking connection, pin connection, or screw connection. In the FRP insulator, the following (a) is added to the structure of the connection between the FRP rod and the mounting bracket and the structure of the FRP rod itself.
There was a problem of (f).

(A) When a fitting is bonded to the end of the pultruded FRP rod with an adhesive, the bonding strength between the FRP rod and the fitting is determined by the bonding area between the FRP rod and the fitting and the material of the adhesive. Will depend on
It is difficult to maintain high strength. Therefore, the strength possessed by the FRP rod cannot be fully utilized, and the mounting metal fitting may come off before the FRP rod breaks, making it difficult to apply it to a tensile strength insulator or the like that requires high tensile strength.

(B) When the mounting member is caulked to the end portion of the FRP rod, the coupling strength between the FRP rod and the mounting member depends on the caulking force of the mounting member to the FRP rod, which is high. It is difficult to maintain the strength, and in this case as well, it is difficult to apply to tensile insulators and the like that require high tensile strength.

(C) When the fitting is pin-connected or screw-connected to the end portion of the FRP rod, the pin-connected portion and the screw portion of the FRP rod receive stress concentration and are easily broken.
It becomes difficult to fully exert the strength of the reinforcing fibers of the FRP rod. Also in this case, it is difficult to maintain high strength between the FRP rod and the mounting fitting.

(D) It is difficult to increase the section modulus of the FRP rod in manufacturing, and the bending strength and the compressive strength are low, and its use is limited.

(E) The pultruded FRP rod is
Since the strengthening is unidirectional, the anisotropy is strong, and shear failure in the longitudinal direction of the rod is likely to occur when bending or compressive load is applied, resulting in lack of reliability.

(F) The compressive withstand load when a load is applied axially to the connecting portion of the FRP rod and the mounting bracket can be set to be sufficiently high by the sectional shape and elastic modulus of the FRP rod, but the tensile withstand load is Since there is a gap between the FRP rod and the mounting bracket, it must be lowered.

The present invention has been made in view of the above problems, and an object thereof is to provide an electric insulation made of a fiber reinforced composite material such as an FRP insulator in which the mechanical strength of a connecting portion with an end fitting is improved. It is to provide a support material.

[0012]

In order to achieve the above object, the present invention has a structure in which fittings are connected to both ends of a fiber reinforced composite material pipe formed by a filament winding method. The mounting metal fittings include a first metal fitting that is embedded and fixed on the inner circumference of both ends of the pipe and has a threaded portion on the exposed surface, a second metal fitting that is fitted and fixed on the outer circumference and the end surface of both ends of the pipe, and a screw portion of the first metal fitting. A third metal fitting or the like that is mounted to press and fix the second metal fitting to the end surface of the pipe is provided.

Further, according to the present invention, the first metal fitting is integrally formed with the pipe during filament winding molding of the pipe, and the outer peripheral surface of the first metal fitting has a tapered surface axially reduced toward the end of the pipe. It features the structure provided.

Further, according to the present invention, the outer circumference of the pipe may be covered with a resin cover having a plurality of projecting edge-shaped cap portions on the outer circumference.

[0015]

[Function] A fiber-reinforced composite material pipe or FRP pipe formed by the filament winding method is a mandrel that becomes a pipe core at the time of molding. Direction and the diagonal direction that intersects them at a predetermined angle, it can be formed into various shapes such as circular pipes and square pipes. A shape that enhances the bonding strength can be easily formed. Since such a FRP pipe is hollow, the section modulus can be set high, and the bending strength and compressive strength of the pipe itself can be increased by not biasing the directionality of the reinforcing fibers, and shear fracture is difficult to occur. Therefore, various mechanical strengths can be set high.

Further, the first metal fittings, which are embedded and fixed on the inner circumferences of both ends of the FRP pipe, are integrally formed with the FRP pipe at the time of filament winding molding of the pipe.
The man-hours for attaching the metal fitting to the FRP pipe are omitted, and the first metal fitting can be firmly fixed to the FRP pipe. Further, by providing the outer peripheral surface of the first metal fitting with a taper surface that reduces in diameter in the axial direction toward the end of the pipe, even if a tensile load is applied to the first metal fitting in the axial direction of the pipe, the tapered surface is The first metal fitting is prevented from coming out of the FRP pipe by engaging with the inner peripheral surface.

Further, the second metal fitting is fitted and fixed to the outer circumference and the end surface of both ends of the FRP pipe, and the third metal fitting is screwed to the screw portion of the first metal fitting which is previously fixed to the FRP pipe. When the second fitting is pressed and fixed to the end surface of the FRP pipe, the second fitting and the third fitting are firmly fixed to the FRP pipe, and the end of the FRP pipe is held between the first fitting and the second fitting. FRP pipe end damage is prevented and FR
The mounting strength of the mounting metal fitting to the P pipe is maintained at still higher strength, and a highly reliable composite insulator type electrical insulating support material that sufficiently withstands high stress concentration is realized.

[0018]

EXAMPLE An electrically insulating support material 1 of the example shown in FIGS. 1 (a) and 1 (b) is a fiber reinforced composite material pipe formed by a filament winding method (hereinafter referred to as FW method), that is, an FRP pipe. 2, the metal fitting 3 is connected to both ends. The mounting bracket 3 is a metal product that has been rust-proofed by galvanizing or the like for connecting the FRP pipe 2 to an external component such as an electric wire, and is, for example, a first bracket embedded on the inner circumference of both ends of the FRP pipe 2. 4 and FRP
The second metal fitting 5 fitted on the outer circumference of both ends of the pipe 2;
A third metal fitting 6 screwed onto the metal fitting 4 is provided.

The FRP pipe 2 is, for example, a hollow pipe having a large section modulus. FRP pipe 2
When FW is formed, the first metal fitting 4 is integrally embedded and fixed to the inner circumference of both ends of the FRP pipe 2. The first metal fitting 4 is, for example, a nut metal fitting having a threaded portion 4a on the inner circumference, and has an outer peripheral surface having a taper surface m whose diameter decreases toward the pipe end. First
The FW molding of the FRP pipe 2 integrally molded with the metal fitting 4 is
For example, it is performed as shown in FIG.

A pair of first metal fittings 4 are inserted into a mandrel 10 having a round bar shape shown in FIG. 5 at predetermined intervals, and continuous reinforcing fibers 11 such as glass roving are wound around the mandrel 10 including the outer circumference of the first metal fitting 4. To wear. The continuous reinforcing fiber 11 is an insulating reinforcing fiber such as glass fiber, aramid fiber, high-density polyethylene fiber, polyamide fiber, polyester fiber, etc., and passes through the eye 14 while impregnated with the resin 13 in the resin bath 12 to pass through the mandrel 10. Wrapped around. The resin 13 is a thermosetting resin such as an epoxy resin, which firmly adheres and fixes the fibers to each other. The mandrel 10 rotates in the circumferential direction, and the eye 14
Moves reciprocally in the axial direction of the mandrel 10, and by selecting these two relative movements variously, the continuous reinforcing fibers 11 in the mandrel 10 have a desired thickness in multiple layers, the axial direction and the circumferential direction of the mandrel 10, and It is wound diagonally.

When the reinforcing fiber 11 is wound around the mandrel 10, the mandrel 10 is heat-treated at 60 to 120 ° C. in a high temperature furnace to be FRP.
Primary hardening of the impregnating resin of the pipe 2 is performed. After the primary curing, the mandrel 10 is pulled out from the FRP pipe 2 (demolding), and the first metal fitting 4 remains in both ends of the FRP pipe 2. Next, after the final secondary hardening process of the FRP pipe 2, the end face machining for grinding the end face of the FRP pipe 2 into a predetermined shape is performed.

The wall thickness of the end portion of the FRP pipe 2 is set sufficiently larger than the maximum wall thickness of the first metal fitting 4, as shown in FIGS. Securely bury it in place. The directionality of the reinforcing fibers wound in multiple layers constituting the FRP pipe 2 is arbitrary, and for example, as shown in FIG. 4, from the inner circumference of the FRP pipe 2 to the first to sixth layers S1 to S2.
The first layer S1, the third layer S3, and the sixth layer S6 are wound in the circumferential direction, the second layer S2 is wound in an oblique direction such as 45 ° with respect to the circumferential direction, and the fourth layer S4 is The fifth layer S5 is wound in the circumferential direction and the axial direction alternately, and the fifth layer S5 is wound in the axial direction. The reinforcing fiber wound around the outer periphery of the first metal fitting 4 conforms to the fourth layer S4. By selecting the winding direction of the reinforcing fiber of the FRP pipe 2 in this way, various mechanical strengths of the FRP pipe 2 become appropriate for the insulator for supporting electric wires and the like. It is a characteristic of FW molding that the fiber orientation can be arbitrarily selected in this way, and in particular, by orienting the reinforcing fibers in the 90 ° direction,
It is possible to suppress shear fracture during bending and compression and obtain a large strain energy.

Further, as shown in FIG. 1B, if a flat surface n for preventing rotation is partially formed on the outer periphery of the thick end portion of the first metal fitting 4, the FRP pipe 2 can be provided with a flat surface n. The first metal fitting 4 is prevented from being rotationally displaced, and the mounting strength of the second metal fitting 5 and the third metal fitting 6 is stabilized.

The second metal fitting 5 is the FRP pipe 2 shown in FIG.
It is fitted to the outer circumference and the end surface of the end and fixed by the adhesive 7, and has a circular flange portion 5a integrally on the outer circumference of the tip. In the claims, "fitting and fixing" naturally includes not only the case of fitting, but also the case of putting the adhesive 7 on the fitting surface in the technical scope. Flange part 5a
Has a circular shape as shown in FIG. 2 and has a plurality of mounting holes 8 at equal intervals. After attaching the second metal fitting 5 to the FRP pipe 2, the screw portion 6a of the third metal fitting 6 is screwed onto the first metal fitting 4 after being coated with an adhesive. The third metal fitting 6 is a bolt metal fitting corresponding to the first metal fitting 4, and as shown in FIG.
A is fastened and attached to the threaded portion 4a on the inner circumference of the first metal fitting 4. Head 6b of third metal fitting 6 screwed onto first metal fitting 4
Thus, the second metal fitting 5 is pressed against the end surface of the FRP pipe 2, and in this state, the attachment of the second metal fitting 5 to the FRP pipe 2 is completed.

In the electrical insulation support member 1 of FIG. 1, the flange portion 5a of the second metal fitting 5 is connected to an external electric wire support metal fitting (not shown) or the like by using bolts and nuts, etc. Used as etc. The load applied to the second metal fitting 5 is
It directly joins the FRP pipe 2, and also joins the FRP pipe 2 through the third metal fitting 6 and the first metal fitting 4. Since the FRP pipe 2 is a pipe, such an electrically insulating support material 1 can have a large section modulus, a high bending strength and a high compression strength. The shear fracture strength can also be set high.

The compressive load of the second metal fitting 5 is FRP.
The compressive strength of the pipe 2 in the axial direction can be set high enough,
The tensile load resistance of the second metal fitting 5 is the third metal fitting 6 and the first metal fitting 4,
The first fitting 4 and the FRP pipe 2 have a strong connection structure, which can be set sufficiently high. That is, when a large tensile load is applied to the first metal fitting 4, the tapered surface m of the first metal fitting 4 engages with the inner surface of the end portion of the FRP pipe 2 in contact therewith, and the tapered surface m
Even if the reinforcing fiber on the inner surface of the end portion of the FRP pipe 2 that comes into contact with is slightly broken, the first metal fitting 4 itself does not come out. Further, when a tensile load is applied, a force that radially expands is applied to the end of the FRP pipe 2 by the tapered surface m of the first metal fitting 4, but this expansion is caused by the reinforcing fibers and the FRP pipe oriented in the circumferential direction. It is blocked by the second metal fitting 5 fixed to the outer periphery of the end portion of 2. Therefore, the end of the FRP pipe 2 is completely broken before the first fitting 4 is pulled out by the tensile load. This means that the tensile load resistance of the electrically insulating support material 1 is
This means that it is possible to set a large value up to the limit of the breaking load in the axial direction of.

The mechanical strength of the end portion of the FRP pipe 2 to which the compressive load and the tensile load are concentrated in the electric insulating support material 1 can be set sufficiently high by utilizing the strength peculiar to the members of the FRP pipe 2. Further, when a larger mechanical strength is required at the end of the FRP pipe 2, it becomes possible by changing the cross-sectional shape by partially increasing the wall thickness of this end. The change in shape is easy because the FRP pipe 2 is FW molded.

Next, another embodiment of the present invention will be described.

The electrically insulating support 1'shown in FIG.
The outer periphery of the RP pipe 2 is covered with an insulating cover 9. The cover 9 is a polymer molded product such as heat-shrinkable silicone rubber, and integrally has a plurality of flange-shaped cap portions 9a on the outer periphery.
The electric insulating support material 1 ′ having such a cover 9 is suitable for outdoor electric wire insulating support such as line post insulators for transmission lines and insulators for interphase spacers.

A step portion 19 for fitting the end of the cover 9 is formed on the inner peripheral surface of the end portion of the second metal fitting 5.

The electrically insulating support material 1 shown in FIG.
Tapered surfaces m, m are formed in two steps in the axial direction on the outer circumference of the first metal fitting 4 buried in the inner circumference of the end of the P pipe 2. By increasing the tapered surfaces m, m of the first metal fitting 4 in two steps in this way, the coupling force between the first metal fitting 4 and the FRP pipe 2 in the axial direction increases. Further, by increasing the taper angle (inclination angle with respect to the pipe center line) of each taper surface m, the coupling force with the FRP pipe 2 is increased. First metal fitting 4
The taper surfaces m, m can be appropriately increased to a desired number of steps, such as three steps, depending on the use of the electrical insulating support material 1.

The electrically insulating support material 1 shown in FIG.
The shape of the first metal fitting 4, which is a nut metal fitting embedded in the inner circumference of the end of the P pipe 2, is changed. The first metal fitting 4 has a thick portion 4b that is a rear end portion, an intermediate portion 4c that extends forward from the thick portion 4b and has an outer periphery that is a tapered surface m, and an intermediate portion 4
There is a thin portion 4d extending from c to the front end with a substantially equal thickness, and a screw portion 4a is formed on the inner periphery of each of them. Screw part 4a
The inner diameter of the FRP pipe 2 is made smaller than the inner diameter of the FRP pipe 2, and the wall thickness of the end portion of the FRP pipe 2 formed on the thin portion 4d is positively increased. By embedding the first metal fitting 4 in the thick-walled portion of the FRP pipe 2 in this manner, the mechanical strength of the end portion of the FRP pipe 2 which is the stress concentration portion increases, and the fitting strength of the mounting metal fitting increases.

The electrically insulating support material 1 shown in FIG.
A bolt fitting is used for the first fitting 4 embedded in the inner circumference of the end portion of the P pipe 2, and a nut fitting is used for the third fitting 6 corresponding to the bolt fitting. The first metal fitting 4 of the bolt fitting is F
The RP pipe 2 has a base end portion 4e embedded in the opening end portion and a screw rod portion 4f integrally protruding from the base end portion 4e, and a tapered surface m is formed on the outer periphery of the base end portion 4e. . Proximal end 4
The FRP pipe 2 is integrally FW-molded in e, and the threaded rod portion 4f projects from the end surface of the FRP pipe 2.

The second metal fitting 5 is inserted into the outer circumference of the end portion of the FRP pipe 2 shown in FIG. 9, and the adhesive 7 is applied to the outer peripheral surface of the end portion of the FRP pipe 2 and / or the inner peripheral surface of the second metal fitting 5 in advance. After bonding, the third metal fitting 6 of the nut metal fitting is screwed onto the threaded portion 4g on the outer periphery of the screw rod portion 4f of the first metal fitting 4 protruding from the second metal fitting 5. The third metal fitting 6 connects the second metal fitting 5 to the FRP pipe 2
Press the end face of the to fix it.

10 and 11 show an example in which the electrically insulating support material 1'with a cover shown in FIG. 6 is used as an insulator for insulating support of the power transmission line 15. FIG. 10 shows a line post insulator that insulates and supports the power transmission line 15 on the steel tower 16 with a pair of electrically insulating support materials 1 ′ with a cover. This line post insulator can be one, three, four, or the like of the electrically insulating support material 1'with a cover. FIG. 11 shows a tension insulator that insulates and supports the power transmission line 15 on the steel tower 16 with one of the electric insulating support materials 1 ′ with a cover.

Another example used as an insulator for supporting the insulation of the power transmission line 15 is shown in FIGS. FIG. 12 (A) shows a structure in which four cover-equipped electrically-insulating support materials 1'are assembled in a yagura,
FIG. 12 (B) also shows four electric insulating support materials 1 ′ with a cover, which are assembled in a kettle. The scaffolds of the electric insulating support material 1 ′ with a cover are located at four points of the rhombus.
(C) is an assembly of three electric insulating support materials 1 ′ with a cover, which are assembled in a tower. In addition, FIG. 13 shows a two-story truss shape using a total of nine long and short electrically insulating support materials 1'with a cover, and FIG. Then, the transmission line 15 is supported through the plate 20 at the tip, and FIG. 15A shows the two electrically insulating support members 1 ′ with a cover linearly connected.
FIG. 15 (B) shows a conical electrical insulating support 1'with a cover, and FIG. 15 (C) shows an electrical insulating support 1'with a cover as an insulator for an interphase spacer for maintaining a distance between the transmission lines 15,15. FIG. 15 (D) shows a self-supporting station post insulator in which the base end portion of the electrically insulating support material 1 ′ with a cover is rigidly connected to the steel tower 16.

The cover-equipped electrically insulating support material 1'can be effectively applied to a high voltage insulator of a distribution line.

The number and shape of the metal fittings 3 connected to the end of the FRP pipe 2 are not limited to those in the above embodiment, and can be selected or changed according to the use of the electrically insulating support material.
Further, although the FRP pipe 2 is described as a circular pipe, it may be formed into a square pipe shape or the like by changing the shape of the mandrel for FW molding.

[0039]

According to the present invention, the FRP pipe of the fiber reinforced composite material pipe formed by the filament winding method has various end portions to which the fittings are joined to increase the joining strength with the fittings. The cross-sectional shape can be easily made, and since the FRP pipe is hollow, the cross-section coefficient can be set high, and the pipe itself has high bending strength and compressive strength, making it difficult to shear and fracture, and the overall mechanical strength is high. It is possible to provide an electrically insulating support material having high strength, which is suitable for insulators for power transmission lines and the like.

Further, the first metal fittings are provided on the inner circumferences of both ends of the FRP pipe so that the F
By integrally molding with the RP pipe, the joint strength between the FRP pipe and the metal fitting can be increased and the number of assembling steps can be reduced. Further, by providing a taper surface on the outer peripheral surface of the first metal fitting, the diameter of which decreases in the axial direction toward the pipe end, even if a tensile load is applied to the first metal fitting in the axial direction of the pipe, the taper surface is engaged with the inner peripheral surface of the pipe. As a result, the first metal fitting will no longer come out of the FRP pipe,
The metal fitting strength can be maintained high, and the reliability of the insulator etc. is improved.

Further, the second metal fittings are fitted and fixed on the outer circumferences and the end faces of both ends of the FRP pipe, and the third metal fittings are screwed on the threaded portions of the first metal fittings previously fixed to the FRP pipe. When the second metal fitting is pressed and fixed to the end face of the FRP pipe, the metal fittings reinforce each other to increase the metal fitting attachment strength, and the end portion of the FRP pipe is held between the first metal fitting and the second metal fitting, and the FRP pipe is held. It is possible to provide an electrically insulating support material having a high tensile load resistance and a compressive load resistance, since the destruction of the end portions of the FRP pipe is prevented and the fitting strength of the metal fitting to the FRP pipe is maintained at a still higher strength.

[Brief description of drawings]

1A is a front view including a partial cross-section of a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA of FIG.

FIG. 2 is a side view of the electrically insulating support material of FIG.

3 is a partially exploded cross-sectional view of the electrically insulating support material of FIG.

FIG. 4 is a partially enlarged cross-sectional view of the electrically insulating support material of FIG.

5 is a perspective view of a main part of a molding machine when filament-winding molding a pipe in the electric insulating support material of FIG. 1. FIG.

FIG. 6 is a front view including a partial cross section of a second embodiment of the present invention.

FIG. 7 is a partial front view including a partial cross section of a third embodiment of the present invention.

FIG. 8 is a partial sectional view of a fourth embodiment of the present invention.

FIG. 9 is a partial sectional view of a fifth embodiment of the present invention.

FIG. 10 is a perspective view showing an application example of the electrically insulating support material of FIG.

FIG. 11 is a perspective view showing another application example of the electrically insulating support material of FIG.

12 (A), (B) and (C) are perspective views showing other examples of use of the electrical insulating support material of FIG. 6, respectively.

13 is a perspective view showing another application example of the electrical insulating support material of FIG.

14 is a perspective view showing another example of application of the electrically insulating support material of FIG.

15 (A), (B), (C), and (D) are perspective views showing other uses of the electrically insulating support material of FIG. 6, respectively.

[Explanation of symbols] 1 electrical insulating support material 1'electrical insulating support material 2 FRP pipe (fiber reinforced composite material pipe) 3 mounting metal fitting 4 first metal fitting 4a screw part m taper surface 5 second metal fitting 6 third metal fitting 9 cover 9a Kasabe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Annaka 5-10-11 Wakatakecho, Kusatsu City, Shiga Prefecture (72) Inventor Yasuhiko Iwasaki 2-7-403 Uenomachi, Yokaichi City, Shiga Prefecture (72) Inventor Hiroyuki Kondo 297 Takebe Kitamachi, Yokaichi City, Shiga Prefecture

Claims (7)

[Claims] 1. An electrically insulating support material comprising fitting pipes connected to both ends of a fiber-reinforced composite material pipe formed by a filament winding method. 2. The electrically insulating support material according to claim 1, wherein the fitting includes a first fitting that is embedded and fixed in the inner circumference of both ends of the pipe and has a threaded portion on the exposed surface. 3. The first metal fitting, which is embedded and fixed in the inner circumference of both ends of the pipe and has a threaded portion on the exposed surface,
The second metal fitting, which is fitted and fixed to the outer circumference and the end surface of both ends of the pipe, and the third metal fitting, which is screwed to the screw portion of the first metal fitting and presses and fixes the second metal fitting to the end surface of the pipe. Electrical insulation support material. 4. The pipe according to claim 2, wherein the first fitting is integrally formed with the pipe during filament winding of the pipe.
The electrically insulating support material described. 5. The electrically insulating support material according to claim 2, wherein the first metal fitting has an outer peripheral surface having a tapered surface that reduces in diameter in the axial direction toward the end of the pipe. 6. The electrically insulating support material according to claim 5, wherein the tapered surface of the outer peripheral surface of the first metal fitting is formed in a plurality of steps in the axial direction. 7. The electrically insulating support material according to claim 1, wherein the outer circumference of the pipe is covered with a resin cover having a plurality of projection-shaped cap portions on the outer circumference.