Insulator

Abstract

To provide an insulator capable of preventing deterioration of an insulator body due to liquid remaining in an insertion hole.SOLUTION: The insulator 1 according to the present disclosure includes: a synthetic resin insulator body 2 provided with an insertion hole 23; and a tubular member 3 coaxially inserted into the insertion hole 23. The insulator body 2 is characterized in that drainage paths 25 are provided therein for discharging the liquid outside the insulator body 2 from the insertion hole 23. Thereby, even if the liquid enters the insertion hole 23 or is generated in an internal space of the insertion hole 23, The liquid is discharged out of the insulator body 2 through the drainage paths 25. Therefore, the liquid hardly remains in the insertion hole 23. Accordingly, deterioration of the insulator body 2 due to the liquid remaining in the insertion hole 23 can be prevented.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to insulators. [Background technology]

[0002] Patent Document 1 describes an insulator that covers a connection portion between an electric wire and a rod-shaped terminal fitting. This insulator comprises a porcelain insulator body with a through-hole-like hollow portion, a metal nut (cylindrical member) inserted into the hollow portion, and a cement adhesive layer interposed between the outer peripheral surface of the nut and the inner peripheral surface of the hollow portion.

[0003] The tip of the terminal fitting is provided with a hollow portion for receiving the electric wire and a male screw that screws into the female screw of the nut. One end of the electric wire is connected to the tip of the terminal fitting by being inserted into the hollow portion of the terminal fitting. With the electric wire and the terminal fitting connected, the male screw of the terminal fitting screws into the female screw of the nut. As a result, the connection portion between the electric wire and the terminal fitting can be covered with the insulator body, which is an insulator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-147166 A Summary of the Invention [Problem to be solved by the invention]

[0005] The hollow portion of the insulator body of the insulator described in Patent Document 1 is in the form of a through hole. However, if the insulator body is provided with a non-through hole-shaped hollow portion (insertion hole), there is a concern that liquid such as rainwater or night dew may accumulate in the insertion hole. If a large amount of liquid accumulates in the insertion hole, a large external force caused by expansion when the liquid freezes is applied to the insulator body, which may deteriorate the insulator body.

[0006] An object of the present disclosure is to provide an insulator that can prevent deterioration of the insulator body caused by liquid remaining in an insertion hole. [Means for solving the problem]

[0007] The insulator according to the present disclosure comprises an insulator body made of synthetic resin having an insertion hole provided therein, and a tubular member inserted coaxially into the insertion hole, and is characterized in that the insulator body is provided with a drainage path for discharging liquid from the insertion hole to the outside of the insulator body.

[0008] In the present disclosure, an insertion hole is provided in an insulator body made of synthetic resin, and a tubular member is coaxially inserted into the insertion hole. The insulator body is provided with a drainage path. Even if liquid seeps into the insertion hole or is generated in the internal space of the insertion hole, it is discharged to the outside of the insulator body through the drainage path. Therefore, liquid is unlikely to accumulate in the insertion hole. Therefore, deterioration of the insulator body caused by liquid accumulating in the insertion hole can be prevented.

[0009] The insulator according to the present disclosure is characterized in that the drainage path is bent or curved.

[0010] In the present disclosure, the drainage path is bent or curved. The insulator is provided in a transformer, a switch, etc. When a transformer, a switch, etc. is used, a conductor through which a current flows (hereinafter, referred to as a live part) exists in the internal space of the insertion hole. Since the drainage path is bent or curved, even if a thin conductor (hereinafter referred to as a wire) is inserted into the drainage path from the outside of the insulator body, the wire can be prevented from entering the internal space of the insertion hole from the drainage path and coming into contact with the live part. Similarly, it is possible to prevent living things (such as small insects) from entering the internal space of the insertion hole through the drainage path and coming into contact with the live part.

[0011] The insulator according to the present disclosure is characterized in that a drainage hole is provided on the outer surface of the insulator body along the axial length direction of the insertion hole, the drainage hole has a drainage outlet on its inner surface, the drainage path includes an internal space of the drainage hole and has an opening on each of both ends, one of the openings of the drainage path is connected to the drainage outlet, and the other opening of the drainage path is an opening of the drainage hole.

[0012] In the present disclosure, a drain hole is provided on the outer surface of the insulator body. The drain hole extends in a direction along the axial length of the insertion hole. A drain port is provided on the inner peripheral surface of the drain hole. The drainage path includes an internal space of the drain hole. The drainage path has an opening at each end. One opening of the drainage path communicates with the drain outlet of the drain hole. The other opening of the drainage path is an opening of the drain hole. The liquid flows from the internal space of the insertion hole through one opening of the liquid drainage path into the liquid drainage path, and flows out from the liquid drainage path through the other opening of the liquid drainage path to the outside of the insulator body.

[0013] When a wire is inserted into the drainage passage from the outside of the insulator body through the other opening of the drainage passage, the tip of the wire faces the bottom side of the drainage passage along the axial direction of the insertion hole. Since the inner peripheral surface of the drainage hole is oriented along the axial direction of the insertion hole, in order for the wire inserted into the drainage passage to pass through the drainage opening provided on the inner peripheral surface of the drainage hole, the wire must be bent or curved in a direction intersecting the axial direction of the insertion hole. Therefore, it is possible to prevent the wire inserted into the drainage passage from entering the internal space of the insertion hole and coming into contact with the live part. Similarly, it is possible to prevent living things from entering the internal space of the insertion hole through the drainage passage and coming into contact with the live part.

[0014] The insulator of the present disclosure is characterized in that the outer peripheral surface of the tubular member is joined to a first portion of the inner peripheral surface of the insertion hole close to the opening of the insertion hole, the drainage path has an opening at each end, and one of the openings of the drainage path is located in a second portion of the inner peripheral surface of the insertion hole far from the opening of the insertion hole, and when the distance between the inner bottom surface of the insertion hole and the end face opposite the inner bottom surface of the tubular member in the axial direction of the insertion hole is L1 and the inside dimension of one of the openings of the drainage path in the axial direction is L2, L2 / L1≦0.2 holds.

[0015] In the present disclosure, the outer circumferential surface of the tubular member is joined to a first portion of the inner circumferential surface of the insertion hole that is closer to the opening of the insertion hole, i.e., the tubular member is spaced apart from a second portion of the inner circumferential surface of the insertion hole that is farther from the opening of the insertion hole. The drainage passage has an opening at each end. One opening of the drainage passage is located on the second portion of the inner circumferential surface of the insertion hole and is therefore spaced apart from the tubular member.

[0016] Furthermore, if the distance between the inner bottom surface of the insertion hole and the end surface of the cylindrical member facing the inner bottom surface of the insertion hole in the axial direction of the insertion hole is L1, and the inside dimension of one opening of the drainage path in the axial direction of the insertion hole is L2, then L2 / L1≦0.2 holds. In other words, the inner diameter of one opening of the drainage path is sufficiently small. Therefore, it is difficult for wires or living things to pass through one opening of the drainage path. As a result of the above, even if a wire is inserted into the drainage passage from outside the insulator body and the tip of the wire reaches one of the openings of the drainage passage, the wire can be prevented from coming into contact with the live part. Similarly, a living thing that passes through the drainage passage and reaches one of the openings of the drainage passage can be prevented from coming into contact with the live part.

[0017] The insulator according to the present disclosure is characterized in that a plurality of the drainage paths are arranged side by side in a direction along the circumferential direction of the insertion hole.

[0018] In the present disclosure, multiple drainage paths are arranged side by side in a direction along the circumferential direction of the insertion hole, so that liquid can be drained from the insertion hole through at least one of the multiple drainage paths regardless of the circumferential orientation of the insulator body. Effect of the Invention

[0019] According to the insulator of the present disclosure, deterioration of the insulator body caused by liquid remaining in the insertion hole can be prevented. [Brief description of the drawings]

[0020] [Figure 1] 1 is an external view of an insulator according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing the configuration of an insulator. [Diagram 3] FIG. 2 is a cross-sectional view of a bushing with an insulator. [Figure 4] FIG. 2 is an enlarged cross-sectional view of the vicinity of the drainage path. [Diagram 5] FIG. 11 is an enlarged cross-sectional view showing a modified example of the drainage path. [Figure 6] FIG. 11 is a cross-sectional view of an insulator according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the present disclosure will be described.

[0022] Embodiment 1. FIG. 1 is an external view of the insulator according to the first embodiment. In the drawings, reference numeral 1 denotes an insulator, FIG. 1A is a front view of the insulator 1, and FIG. 1B is a view taken along line II in FIG. 1A. The insulator 1 comprises an insulator body 2 and a tubular member 3 . The insulator body 2 is an insulator made of synthetic resin (thermoplastic resin or thermosetting resin). The thermoplastic resin constituting the insulator body 2 is, for example, polybutylene terephthalate.

[0023] Fig. 2 is a diagram showing the configuration of the insulator 1. Fig. 2A is a view taken along line II-II in Fig. 1A, and Fig. 2B is a cross-sectional view taken along line III-III in Fig. 2A. As shown in Fig. 1 and Fig. 2, the insulator body 2 integrally has a large-diameter, bottomed, cylindrical knob portion 21 and a small-diameter, columnar protruding portion 22. The knob portion 21 and the protruding portion 22 are coaxial with each other. Fig. 1A and Fig. 2B show the insulator 1 with the bottom wall / opening of the knob portion 21 located on the left / right side as viewed from the front, and with the axial length direction of the knob portion 21 facing left / right. In the following description, the left / right sides as viewed from the front and back of Fig. 1A and Fig. 2B are taken as the left / right sides of the insulator 1.

[0024] The peripheral wall of knob portion 21 is inclined in a direction in which the diameter increases from the bottom wall side of knob portion 21 toward the opening side of knob portion 21 (from the left side to the right side). An anti-slip portion 211 is provided on the outer circumferential surface of knob portion 21. In the present embodiment, anti-slip portion 211 is configured such that recessed portions 21a and protruding portions 21b are alternately connected in the circumferential direction of knob portion 21, but is not limited thereto.

[0025] The protrusion 22 protrudes rightward from the inner surface of the bottom wall of the knob portion 21 (hereinafter, referred to as the inner bottom surface 21c). The amount of protrusion of protrusion 22 (the axial distance from inner bottom surface 21c to the tip of protrusion 22) is greater than the amount of protrusion of the peripheral wall of knob portion 21 (the axial distance from inner bottom surface 21c to the tip of the peripheral wall). For example, a portion of protrusion 22 from the tip to about 20% to 40% of the total length protrudes from the opening of knob portion 21 to the outside of knob portion 21.

[0026] 1B and 2B, an insertion hole 23 is provided on the tip surface of the protruding portion 22. The insertion hole 23 is a non-through hole. The insertion hole 23 has a circular cross section and is coaxial with the protruding portion 22. The insertion hole 23 extends over the entire length of the protruding portion 22. Note that the insertion hole 23 may be shallower than the entire length of the protruding portion 22. The inner bottom surface 23a of the insertion hole 23 is perpendicular to the axial direction of the insertion hole 23 and is parallel to the outer surface (hereinafter referred to as the outer bottom surface 21d) of the bottom wall of the knob portion 21. The inner peripheral surface of the insertion hole 23 is parallel to the axial direction of the insertion hole 23. Note that the outer bottom surface 21d of the knob portion 21 (or the inner bottom surface 23a of the insertion hole 23) may be appropriately inclined with respect to the axial direction of the insertion hole 23.

[0027] The cylindrical member 3 is an insert nut. The cylindrical member 3 is made of, for example, metal, but is not limited to this. The cylindrical member 3 is inserted coaxially into the insertion hole 23 such that one end face (left end face) in the axial direction faces the inner bottom surface 23a of the insertion hole 23 and the other end face (right end face) in the axial direction is flush with the tip face of the protruding portion 22. The right end face of the cylindrical member 3 may be located to the right of the tip face of the protruding portion 22.

[0028] The outer peripheral surface of the tubular member 3 is directly joined to the inner peripheral surface of the insertion hole 23. More specifically, the outer peripheral surface of the tubular member 3 is directly joined to a portion (first portion) of the inner peripheral surface of the insertion hole 23 that is close to the opening of the insertion hole 23. The length in the axial direction of the portion of the tubular member 3 inserted into the insertion hole 23 is smaller than the depth of the insertion hole 23, and is approximately half the depth of the insertion hole 23. The tubular member 3 is separated from a portion (second portion) of the inner peripheral surface of the insertion hole 23 that is far from the opening of the insertion hole 23, and from the inner bottom surface 23a of the insertion hole 23.

[0029] The insulator 1 constitutes a bushing 4, which will be described next. FIG. 3 is a cross-sectional view of a bushing 4 equipped with an insulator 1. As shown in FIG. In addition to the insulator 1, the bushing 4 includes a porcelain tube 41 and a terminal fitting . The porcelain tube 41 is made of an insulating material and has, for example, a cylindrical shape. Fig. 3 shows the vicinity of one end 41a of the porcelain tube 41 in the axial direction. The outer diameter of one end 41a of the porcelain tube 41 is approximately the same as the maximum outer diameter of the knob portion 21 of the insulator body 2. The inner diameter of one end 41a of the porcelain tube 41 is larger than the outer diameter of the protruding portion 22 of the insulator body 2. A notch 411 is provided in the peripheral wall of one end 41a of the porcelain tube 41.

[0030] The bushing 4 is provided in a transformer, a switch, or the like (not shown). The porcelain tube 41 penetrates a side wall of a case provided in the transformer, the switch, or the like. One end 41a of the porcelain tube 41 is located outside the case. The porcelain tube 41 is attached to the case, for example, with the notch 411 facing downward and the axial direction horizontal.

[0031] The terminal fitting 42 is made of a conductor, for example, metal. The terminal fitting 42 is rod-shaped and coaxially penetrates the porcelain tube 41. At one end portion on the one end portion 41a side of the terminal fitting 42, a large-diameter disk portion 420, a small-diameter cylindrical first shaft portion 421, a large-diameter cylindrical bolt portion 422, a small-diameter cylindrical second shaft portion 423, and a large-diameter cylindrical connecting portion 424 are coaxially connected in this order from the one end side to the other end side.

[0032] The disk portion 420 and the first shaft portion 421 are located outside the porcelain tube 41. The bolt portion 422 passes through an opening in one end portion 41a of the porcelain tube 41 and extends from the inside to the outside of the porcelain tube 41. The second shaft portion 423 and the connection portion 424 are located inside the porcelain tube 41. An external thread is provided on the outer circumferential surface of the bolt portion 422, and this external thread corresponds to the female thread of the tubular member 3. The second shaft portion 423 is provided with a through hole 425 perpendicular to the axial length direction. A circumferential portion of the inner circumferential surface of the through hole 425 is generally flush with one end face of the connection portion 424 over the entire length of the through hole 425. One opening of the through hole 425 faces the notch 411 of the porcelain tube 41.

[0033] An electric wire 5 is connected to the terminal fitting 42. The electric wire 5 is a covered electric wire in which a conductor 51 is covered with an insulator. The conductor 51 is exposed at one end of the electric wire 5. The electric wire 5 passes through the cutout 411 and extends from the inside to the outside of the porcelain tube 41. The conductor 51 passes through the through hole 425.

[0034] The disk portion 420 and the first shaft portion 421 are coaxially inserted into the internal space of the insertion hole 23 through the inside of the cylindrical member 3, and the male thread of the bolt portion 422 is screwed into the female thread of the cylindrical member 3. As a result, the terminal fitting 42 penetrates the cylindrical member 3. The conductor 51 is sandwiched between the right end face (the end face facing the connection portion 424) of the cylindrical member 3, the inner circumferential surface of the through hole 425, and one end face of the connection portion 424. As a result, the conductor 51 contacts the second shaft portion 423 and the connection portion 424, so that the terminal fitting 42 and the electric wire 5 are electrically connected to each other.

[0035] It is desirable that a spring washer 43 and a flat washer 44 (refer to the two-dot chain lines in the figure) are interposed between the cylindrical member 3 and the conductor 51. The flat washer 44 is interposed between the spring washer 43 and the conductor 51, and the spring washer 43 biases the conductor 51 via the flat washer 44 so as to press the conductor 51 against the connection portion 424. For ease of viewing, the cylindrical member 3, the terminal fitting 42, the spring washer 43, the flat washer 44, and the conductor 51 are shown in FIG. 3 as being spaced apart from one another. Hereinafter, the axial direction of the insertion hole 23 will be simply referred to as the axial direction.

[0036] The axial length of the portion of terminal fitting 42 inserted into insertion hole 23 is smaller than the depth of insertion hole 23. Neither tubular member 3 nor terminal fitting 42 is present in the portion of the internal space of insertion hole 23 closer to inner bottom surface 23a of insertion hole 23. In this embodiment, approximately 40% of the internal space of insertion hole 23 is void, which contributes to reducing the weight of insulator 1.

[0037] The insulator 1 is detachable from the terminal fitting 42. The insulator 1 can be easily attached and detached manually by an operator pinching the knob portion 21 and rotating the insulator 1 in the circumferential direction of the knob portion 21. The knob portion 21 and the tubular member 3 are coaxial with each other, and a non-slip surface 211 is provided on the outer circumferential surface of the knob portion 21. Therefore, it is easy to pinch the knob portion 21 and rotate the tubular member 3 accurately in the circumferential direction to attach and detach the terminal fitting 42 to and from the bolt portion 422.

[0038] When screwing the tubular member 3 and the bolt portion 422 together, the worker rotates the knob portion 21 and tightens it with a load according to the screw diameter. At this time, the protrusion 22 is inserted coaxially into the inside of the porcelain tube 41 from the opening of one end 41a of the porcelain tube 41. The peripheral edge of the opening of one end 41a of the porcelain tube 41 and the peripheral edge of the opening of the knob portion 21 face each other in the axial direction with a small gap therebetween. Since the connection portion between the terminal fitting 42 and the electric wire 5 is covered by the peripheral wall of the porcelain tube 41 and the insulator body 2 of the insulator 1, the connection portion between the terminal fitting 42 and the electric wire 5 can be protected from collision with foreign objects or electrical connection, etc.

[0039] According to the insulator 1 as described above, the outer peripheral surface of the tubular member 3 is directly joined to the inner peripheral surface of the insertion hole 23. Therefore, the tubular member 3 can be fixed to the insulator body 2 without the need for an adhesive layer made of a material different from the material constituting the insulator body 2 and the material constituting the tubular member 3 between the insulator body 2 and the tubular member 3. In other words, the number of types of materials constituting the insulator 1 can be reduced. This facilitates the procurement of materials and the work of recycling or disposing of the insulator 1 after use. In particular, when the insulator body 2 is made of a thermoplastic resin, the insulator body 2 can be softened or melted by heating during recycling or disposal, allowing the insulator 1 to be easily disassembled.

[0040] The synthetic resin insulator body 2 is lighter than a porcelain insulator body with a cement adhesive layer attached. Moreover, the knob portion 21 is cylindrical with a bottom, and a gap is formed in the protruding portion 22 where nothing is placed. In other words, the insulator body 2 has a configuration in which both the knob portion 21 and the protruding portion 22 are hollowed out. As a result of the above, the weight of the insulator 1 can be reduced. Therefore, the insulator 1 can be easily transported and attached / detached to / from the terminal fitting 42.

[0041] The insulator body 2 has a reinforcing portion 24. The reinforcing portion 24 has a protruding tube 241 and eight ribs 242, 243. Note that the configuration of the reinforcing portion 24 is not limited to this, and it may be configured to reinforce at least one of the knob portion 21 and the protruding portion 22. The protruding tube 241 is provided integrally with the knob portion 21. The protruding tube 241 is cylindrical and protrudes rightward and coaxially from the inner bottom surface 21c of the knob portion 21. The protruding portion 22 is disposed inside the protruding tube 241. The protruding tube 241 can reinforce the bottom wall of the knob portion 21 over the entire circumferential direction. The protruding amount of the protruding tube 241 (the distance from the inner bottom surface 21c of the knob portion 21 to the tip of the protruding tube 241) is equal to the protruding amount of the protruding portion 22.

[0042] The eight ribs 242 and the eight ribs 243 are spaced apart at equal intervals in the circumferential direction of the knob portion 21. Each rib 242 is provided integrally with the inner surface of the knob portion 21 and the outer circumferential surface of the protruding tube 241, and is located inside the opening of the knob portion 21. The ribs 242 can reinforce the knob portion 21 and the protruding tube 241. Each rib 243 is in contact with the inner bottom surface 21c of the knob portion 21, the outer peripheral surface of the protruding portion 22, and the inner peripheral surface of the protruding tube 241, and is located inside the tip opening of the protruding tube 241. The ribs 243 can reinforce the knob portion 21, the protruding portion 22, and the protruding tube 241.

[0043] The cylindrical member 3 and the terminal fitting 42 are made of metal and are therefore prone to condensation. Therefore, there is concern that water droplets will form in the internal space of the insertion hole 23. There is also concern that rainwater will enter the internal space of the cylindrical member 3 through the inside of the cylindrical member 3 (or through a gap that has occurred between the outer circumferential surface of the cylindrical member 3 and the inner circumferential surface of the insertion hole 23 due to some defect). Since the insulator 1 is not used so that the opening of the insertion hole 23 faces downward or obliquely downward, there is a concern that liquid may accumulate in the insertion hole 23 (particularly, the space surrounded by the second portion of the inner circumferential surface and the inner bottom surface 23a of the insertion hole 23 and the left end surface of the tubular member 3). If a large amount of liquid accumulates in the insertion hole 23, a large external force caused by expansion when the liquid freezes is applied to the insulator body 2, which may deteriorate the insulator body 2.

[0044] 2 and 3, the insulator body 2 is provided with a drainage path 25. The drainage path 25 is for discharging liquid from the insertion hole 23 to the outside of the insulator body 2, and therefore each end of the drainage path 25 has two openings, an inner opening 25a (one opening of the drainage path) and an outer opening 25b (the other opening of the drainage path). The inner opening 25a is located on the inner surface of the insertion hole 23. The outer opening 25b is located on the outer surface of the insulator body 2. Each of the inner opening 25a and the outer opening 25b has, for example, a rectangular shape.

[0045] Even if liquid seeps into the insertion hole 23 or liquid is generated inside the insertion hole 23, the liquid is naturally discharged to the outside of the insulator body 2 through the drainage path 25. Therefore, liquid is unlikely to accumulate in the insertion hole 23. Therefore, deterioration of the insulator body 2 caused by liquid accumulating in the insertion hole 23 can be prevented.

[0046] 2A, in this embodiment, three drainage paths 25 are arranged in parallel at equal intervals in the circumferential direction of the insertion hole 23. Therefore, regardless of the circumferential direction of the insulator body 2, liquid can be drained from the insertion hole 23 through at least one of the three drainage paths 25. The number of drainage paths 25 is not limited to three. A plurality of drainage paths 25 may be arranged side by side at unequal intervals in the circumferential direction of the insertion hole .

[0047] Next, the configuration of the drainage path 25 will be described in detail. FIG. 4 is an enlarged cross-sectional view of the vicinity of the drainage channel 25, and is an enlarged view of the area surrounded by the two-dot chain line shown in FIG. 2B. The drainage path 25 includes an internal space of a drainage hole 251. The drainage hole 251 is provided in the outer bottom surface 21d of the knob portion 21 (the outer surface facing the left of the insulator body 2). The drainage hole 251 extends along the axial direction (for example, parallel to the axial direction) and has an inner circumferential surface and an inner bottom surface. The internal space of the drainage hole 251 is located outside a portion of the knob portion 21 that faces the inner bottom surface 23a in the axial direction.

[0048] The outer opening 25b of the drainage path 25 is an opening of the drainage hole 251. The outer opening 25b directly communicates with the space outside the insulator body 2. The inner opening 25a of the drainage path 25 is located in a second portion of the inner circumferential surface of the insertion hole 23. The inner opening 25a directly communicates with a space surrounded by the second portion of the inner circumferential surface of the insertion hole 23, the inner bottom surface 23a, and the left end surface of the cylindrical member 3 (i.e., a space where liquid is likely to stagnate).

[0049] A drainage outlet is provided on the inner circumferential surface of drainage hole 251, and this drainage outlet is inner opening 25a. In other words, inner opening 25a is located on the inner circumferential surface of insertion hole 23, and is connected to the drainage outlet provided in drainage hole 251. A part of the periphery of inner opening 25a is located on the inner bottom surface 23a of insertion hole 23. The other part of the periphery of inner opening 25a is located on the inner bottom surface of drainage hole 251. It is preferable that the terminal fitting 42 is disposed at a position closer to the opening of the insertion hole 23 than the inner opening 25a in the axial direction (see FIG. 3).

[0050] If the axial distance between the inner bottom surface 23a of the insertion hole 23 and the left end surface of the tubular member 3 is L1 (see FIG. 2B) and the inner dimension of the inner opening 25a in the axial direction is L2, the following formula (1) holds. L2 / L1≦0.2 … (1) Preferably, L2 / L1≦0.1. There is no limitation on the minimum value of the inside dimension L2 of the inner opening 25a. The inside dimension L2 of the inner opening 25a may be large enough to satisfy the above formula (1) and not to impede drainage from the insertion hole 23. A specific example of the inside dimension L2 is 1 mm.

[0051] An example of the flow of the drained liquid is indicated by dashed arrows in Fig. 4. The liquid flows from the internal space of the insertion hole 23 through the inner opening 25a (which also serves as the drainage port of the drainage hole 251) into the drainage path 25 (the internal space of the drainage hole 251), and then flows out of the insulator body 2 from the drainage path 25 through the outer opening 25b.

[0052] In this embodiment, the inner opening 25a of at least one of the three drainage paths 25 is located at the lower part of the inner surface of the insertion hole 23 (below the axis of the insertion hole 23), so there is no risk of the insertion hole 23 being filled with liquid. When inner opening 25a of one drainage path 25 is located at the lowermost portion of the inner circumferential surface of insertion hole 23, liquid can be efficiently drained from insertion hole 23 through drainage path 25.

[0053] The inner peripheral surface of the drainage hole 251 (and the inner peripheral surface of the insertion hole 23) where the inner opening 25a is located is aligned along the axial direction. The outer bottom surface 21d of the knob portion 21 where the outer opening 25b is located intersects with the axial direction. The extension direction of the drainage hole 251 is aligned along the axial direction. The drainage path 25 has the inner opening 25a and the outer opening 25b at both ends, and includes the internal space of the insertion hole 23. As a result of the above, the drainage path 25 is bent or curved.

[0054] When a transformer, a switch, or the like including the insulator 1 as described above is used, a current flows through the tubular member 3, the terminal fitting 42, and the conductor 51. In other words, a live part exists in the internal space of the insertion hole 23. If only a linear drainage path was provided from the inner surface of insertion hole 23 to the outer surface of knob portion 21, a wire inserted into the drainage path from the outside of insulator body 2 would easily come into contact with the live part. Also, there is a risk that living things could easily enter the internal space of insertion hole 23 through the drainage path and come into contact with the live part.

[0055] On the other hand, in the case of drainage path 25, the tip of the wire that enters drainage path 25 through outer opening 25b moves along the axial direction toward the bottom of drainage hole 251. In order for the tip of the wire that has reached the bottom of drainage hole 251 to pass through inner opening 25a, the wire must be bent or curved in a direction that intersects with the axial direction. In this way, because drainage path 25 is bent or curved, it is possible to prevent the wire inserted into drainage path 25 from entering the internal space of insertion hole 23 and coming into contact with the charging part. Similarly, it is possible to prevent living things from entering the internal space of insertion hole 23 through drainage path 25 and coming into contact with the charging part.

[0056] Moreover, since the inner opening 25a, whose inner dimension L2 satisfies the above formula (1), is sufficiently small, it is difficult for wires, living things, etc. to pass through the inner opening 25a. In addition, since the sufficiently small inner opening 25a is located in a position that contacts the inner bottom surface 23a of the insertion hole 23, the inner opening 25a is sufficiently spaced from the charging part. Furthermore, the inner opening 25a does not face the charging part. As a result of the above, even if a very thin wire or a very small living thing passes through the inner opening 25a, it is possible to prevent the wire or the living thing from coming into contact with the charging part.

[0057] The drainage hole 251 may be expanded in diameter from the inner opening 25a side toward the outer opening 25b side. When the lower part of the inner peripheral surface of the drainage hole 251 is inclined downward from the inner opening 25a side toward the outer opening 25b side due to such expansion, the inner peripheral surface of the drainage hole 251 effectively functions as a guide surface that guides the liquid in the internal space of the drainage hole 251 toward the outer opening 25b.

[0058] When manufacturing the insulator 1 as described above, for example, an operator sets the tubular member 3 in a metal mold for molding the insulator body 2, then injects synthetic resin into the metal mold and hardens it. As a result, the outer peripheral surface of the tubular member 3 can be directly joined to the inner peripheral surface of the insertion hole 23. Alternatively, an operator may push the tubular member 3 into the portion of the synthetic resin that is to become the insertion hole 23 before the synthetic resin injected into the metal mold hardens, and harden the synthetic resin. When a thermoplastic resin is used, an operator may soften the insulator body 2 formed using a metal mold or a 3D printer by heating, and before the softened thermoplastic resin hardens, push the tubular member 3 into the portion of the thermoplastic resin that is to become the insertion hole 23, and harden the thermoplastic resin.

[0059] The drainage path 25 may be formed simultaneously when the insulator body 2 is formed, or may be formed separately after the insulator body 2 is formed. When the drainage path 25 is formed simultaneously with the formation of the insulator body 2, for example, a mold for molding the insulator body 2 is provided with a portion corresponding to the insertion hole 23 and a portion corresponding to the drainage hole 251 so that they are partially adjacent to each other.

[0060] FIG. 5 is an enlarged cross-sectional view showing a modified example of the drain passage 25. In the configuration shown in FIGS. 2 to 4, there is no opening in the inner bottom surface 23a of the insertion hole 23 that communicates with the drain passage 25. However, as shown in FIG. 5A, an inner bottom opening 23b continuous with the inner opening 25a may be formed in the inner bottom surface 23a of the insertion hole 23. The drain outlet of the drain hole 251 extends over the inner peripheral surface and the inner bottom surface of the drain hole 251 and communicates with the inner opening 25a and the inner bottom opening 23b. In the case of the configuration shown in FIG. 5A, it is not necessary to strictly form the insertion hole 23 and the drain passage 25 so that the inner bottom opening 23b is not formed. Therefore, the manufacturing of the insulator 1 is easy. It is desirable that the inner diameter L3 of the inner bottom opening 23b satisfies L3 < L2.

[0061] In the configuration shown in FIGS. 2 to 4, the inner opening 25a on the inner peripheral surface of the insertion hole 23 also serves as the drain outlet on the inner peripheral surface of the drain hole 251. However, as shown in FIG. 5B, a drain outlet 25c may be provided on the inner peripheral surface of the drain hole 251, and the inner opening 25a may communicate with the drain outlet 25c via a relay hole 250. The relay hole 250 extends in a direction intersecting the axial length direction and is provided in the protruding portion 22 so as to have the inner opening 25a and the drain outlet 25c at both ends.

[0062] Also in this case, the liquid flows from the internal space of the insertion hole 23 through the inner opening 25a into the drain passage 25 and flows out of the insulator main body 2 through the outer opening 25b from the drain passage 25. More specifically, the liquid flows from the internal space of the insertion hole 23 through the inner opening 25a into the relay hole 250, and flows from the relay hole 250 into the drain hole 251 through the drain outlet 25c. Then, the liquid flows out of the insulator main body 2 through the outer opening 25b from the drain hole 251.

[0063] The outer periphery of the inner opening 25a may be separated from the inner bottom surface 23a of the insertion hole 23 over the entire circumference. In other words, there is a high degree of freedom in the arrangement of the inner opening 25a. If the extending direction of the relay hole 250 and the extending direction of the drainage hole 251 intersect with each other, the drainage path 25 is bent or curved, so there is a high degree of freedom in the arrangement or orientation, etc. of each of the relay hole 250 and the drainage hole 251.

[0064] The outer peripheral surface of the tubular member 3 and the inner peripheral surface of the insertion hole 23 may be joined to each other via an adhesive layer, a seal, or the like. The insulator body 2 does not necessarily have to include the reinforcing portion 24 . The knob portion 21 is not limited to a bottomed cylindrical shape, and may be, for example, a columnar shape. In this case, the protruding portion 22 protrudes from one end face of the knob portion 21. Even in this case, the insertion hole 23 is a blind hole. However, the insertion hole 23 may extend to the inside of the knob portion 21 by penetrating the protruding portion 22.

[0065] The number and shape of the drainage passages provided in the insulator body 2 are not limited. The number of drainage passages may be one. The drainage passages may be bent, for example, in an L-shape or a V-shape, or may be curved in an arc or a U-shape. The inner opening of the drainage passage is not limited to being arranged on the inner peripheral surface of the insertion hole 23, and may be arranged on the inner bottom surface 23a of the insertion hole 23. The outer opening of the drainage passage is not limited to being arranged on the outer bottom surface 21d of the knob portion 21, and may be arranged on the outer peripheral surface of the knob portion 21, for example. When a linear drainage passage is provided in the insulator body 2, it is desirable to arrange a member (such as an insulating filter or water absorbent) in the inner space of the drainage passage or the insertion hole 23 to prevent wires or living things from contacting the live part.

[0066] Embodiment 2. The insulator 1 of the present embodiment is substantially similar to the insulator 1 of the first embodiment, except that the drainage hole 251 is not provided in the outer bottom surface 21d of the gripping portion 21. Below, the differences from the first embodiment will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals and their description will be omitted.

[0067] FIG. 6 is a cross-sectional view of the insulator 1 according to the second embodiment. In this embodiment, a space surrounded by the inner surface of the protruding tube 241, the outer peripheral surface of the protruding portion 22, and two ribs 243 adjacent to each other in the circumferential direction of the protruding portion 22 functions as an internal space of the liquid drainage hole 252. The opening of the liquid drainage hole 252 is a part of the tip opening of the protruding tube 241. That is, the liquid drainage hole 252 is provided on the right-facing outer surface of the insulator body 2 along the axial length direction.

[0068] The outer circumferential surface of the protruding portion 22 (part of the inner circumferential surface of the drain hole 252) is provided with a drain port 25c. The inner opening 25a of the drainage path 25 communicates with the drainage port 25c via a relay hole 253. The relay hole 253 extends in a direction intersecting the axial length direction and is provided in the protruding portion 22 so as to have the inner opening 25a and the drainage port 25c at both ends. The outer opening 25 b of the drainage path 25 is the opening of the drainage hole 252 .

[0069] In Fig. 6, an example of the flow of the discharged liquid is indicated by dashed arrows. The liquid flows from the internal space of the insertion hole 23 through the inner opening 25a into the liquid drainage path 25, and flows from the liquid drainage path 25 through the outer opening 25b to the outside of the insulator body 2. More specifically, the liquid flows from the internal space of the insertion hole 23 through the inner opening 25a into the relay hole 253, and flows from the relay hole 253 through the liquid drainage port 25c into the liquid drainage hole 252. The liquid then flows from the liquid drainage hole 252 to the outside of the insulator body 2 through the outer opening 25b.

[0070] Since the drainage hole 252 and the relay hole 253 intersect with each other, the drainage path 25 is bent or curved. Moreover, since the tip of the protruding tube 241 is inserted into the porcelain tube 41 (see FIG. 3), it is difficult to reach the outer opening 25b from outside the bushing 4. As a result of the above, it is possible to reliably prevent wires, living things, etc. from entering the internal space of the insertion hole 23 through the drainage path 25.

[0071] As shown in the figure, the entire outer periphery of the inner opening 25a may be separated from the inner bottom surface 23a of the insertion hole 23. The inner dimension L2 of the inner opening 25a may satisfy the above formula (1), or L2 / L1>0.2. As a result of the above, the design freedom of the inner opening 25a is high. It is desirable that the inner diameter of the protruding tube 241 expands toward the tip side. It is desirable that both sides of the rib 243 are inclined so as to approach each other toward the tip opening of the protruding tube 241. In this case, the inner peripheral surface of the protruding tube 241 or one surface of the rib 243 effectively functions as a guide surface that guides the liquid toward the tip opening of the protruding tube 241.

[0072] In this embodiment as well, it is desirable that a plurality of drainage paths 25 are arranged side by side in the circumferential direction of the insertion hole 23. For this purpose, a plurality of relay holes 253 are arranged side by side in the circumferential direction of the insertion hole 23. If the rib 243 is not present, the different relay holes 253 communicate with a common drainage hole 252. If the protruding tube 241 is not present, the space surrounded by the inner surface of the knob portion 21 and the outer circumferential surface of the protruding portion 22 functions as the internal space of the liquid drainage hole 252 .

[0073] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is intended to include not only the above-mentioned meaning, but also the meaning equivalent to the claims and all modifications within the scope of the claims. The constituent elements (technical features) disclosed in each embodiment can be combined with each other, and new technical features can be formed by combination. In addition, the independent claims and dependent claims described in the claims can be combined with each other in any and all combinations regardless of the citation format. Furthermore, the claims use a format in which a claim cites two or more other claims (multiple claim format), but this is not limited to this. The claims may also be written in a format in which a multiple claim cites at least one other multiple claim (multi-multi claim). [Explanation of symbols]

[0074] 1 insulator; 2 insulator body; 23 insertion hole; 23a inner bottom surface; 25 drainage path; 25a inner opening (one opening of drainage path, drain outlet); 25b outer opening (the other opening of drainage path, drain hole opening); 25c drain outlet; 251, 252 drainage holes; 3 tubular member

Claims

1. an insulator body made of synthetic resin and having an insertion hole; a cylindrical member that is coaxially inserted into the insertion hole; Equipped with The insulator is characterized in that the insulator body is provided with a drainage path for discharging liquid from the insertion hole to the outside of the insulator body.

2. 2. The insulator according to claim 1, wherein the drainage path is bent or curved.

3. A drain hole is provided on an outer surface of the insulator body along an axial direction of the insertion hole, The drain hole has a drain port on an inner peripheral surface, The drainage path is The drain hole includes an internal space, It has an opening at each end, One of the openings of the drainage path is in communication with the drainage port, 3. The insulator according to claim 1, wherein the other opening of the drainage path is an opening of the drainage hole.

4. an outer circumferential surface of the tubular member is joined to a first portion of an inner circumferential surface of the insertion hole that is close to an opening of the insertion hole; The drainage passage has an opening at each end, The opening of one of the drainage paths is located in a second portion of the inner circumferential surface of the insertion hole, the second portion being far from the opening of the insertion hole, A distance between an inner bottom surface of the insertion hole and an end surface of the tubular member facing the inner bottom surface in an axial direction of the insertion hole is L1, If the inner dimension of one of the openings of the drainage path in the axial direction is L2, L2 / L1≦0.2 3. The insulator according to claim 1, wherein the following holds true:

5. 3. The insulator according to claim 1, wherein a plurality of the drainage paths are arranged in parallel in a circumferential direction of the insertion hole.

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