Connection structure between double-wall rectangular conduit and hand hole

Abstract

To provide a pipe line or the like, of double-wall corner type wiring pipe, capable of preventing damages due to a pressure at a time of an expansion of a water expansion nonwoven fabric while securing a high cut-off performance with a simple structure.SOLUTION: An inner connector 1a includes: a cylinder part 3a which is made of, for example, a resin, and has a helical crest part 7a; and a flange part 5a expanded substantially perpendicularly from a pipe end part of the cylinder part 3a to one end part of the cylinder part 3a. A cross sectional shape of the helical crest part 7a in a direction parallel to a pipe shaft direction of the cylinder part 3a is formed by two faced crest parts 11a so as to be separated from each other by a predetermined distance. A separation wall 9a substantially in parallel to the pipe shaft direction, connecting between the crest parts 11a so as to block a groove 13a formed between the faced crest parts 11a is formed in a predetermined interval, and is formed over an upper part of the groove by connecting both of the crest parts in which a water expansion nonwoven fabric 17a provided to the cylinder part 3a is faced.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a double-wall rectangular conduit in which a double-wall rectangular conduit is connected to a handhole. and hand hole connection structure Regarding. [Background technology]

[0002] Conventionally, when connecting an electric conduit to a handhole, for example, a connector that is provided with measures to prevent it from coming loose and to stop water from entering is used.

[0003] For example, Patent Document 1 proposes a pipe connection structure that enables simple and reliable assembly of various components for preventing the cable protection tube from coming loose and for preventing water from entering when connecting the cable protection tube to a pipe entrance component buried in a wall, such as a handhole or manhole.

[0004] In the pipe connection structure of Patent Document 1, one end of a pipe joint is connected to a pipe port member, and a cable protection tube is connected to the other end of the pipe joint via a functional member for preventing slipping out and for water blocking. That is, the functional member is fitted to the end of the cable protection tube. The functional member has a fitting tubular portion that is fitted to the other end of the pipe joint when the cable protection tube is connected. The functional member also includes a slip-out prevention member that is integrally formed with the fitting tubular portion and prevents the cable protection tube from slipping out of the pipe joint when the cable protection tube is connected, and a water blocking member that is provided on the fitting tubular portion and blocks water from entering the connection when the cable protection tube is connected.

[0005] Moreover, Patent Documents 2 and 3 propose a pipe connection structure that includes a waterproofing material that seals the connection portion when a cable protection pipe is connected.

[0006] The pipe joint of Patent Document 2 has a joint portion that is joined to the outer peripheral surface of the pipe body, and has an abutment surface that abuts against the periphery of the through hole of the connection target. The bell mouth has a joint portion that is joined to the inner peripheral surface of the pipe body, and has an abutment surface that abuts against the periphery of the through hole of the connection target. At this time, a protrusion that enters the through hole is formed in a portion of the pipe joint that is on the inner peripheral side of the abutment surface and on the outer peripheral side of the joint portion. In this way, by forming a cylindrical protrusion that fits into the through hole on the pipe joint, Patent Document 2 makes it possible to prevent the abutment surface of the pipe joint from being displaced in a direction away from the periphery of the through hole.

[0007] Similarly to Patent Document 2, the pipe fitting of Patent Document 3 has an internal thread on its inner circumferential surface that screws into the external circumferential surface of a pipe, and comprises an outer tubular portion that fits into the external circumferential surface of the pipe, and an external flange portion that protrudes outwardly at one axial end of the outer tubular portion and has an abutment surface that abuts against the periphery of the through hole that is the connection target. The bell mouth has an internal tubular portion that has an external thread on its outer circumferential surface that screws into the inner circumferential surface of the pipe, and comprises an inner flange portion that is inserted into the pipe, and has an abutment surface that protrudes outwardly at one axial end of the inner tubular portion and abuts against the periphery of the through hole.

[0008] Furthermore, in Patent Document 3, an outer pipe water expansion portion that expands upon absorbing moisture is formed on the inner peripheral surface of the outer cylindrical portion of the pipe joint, and an inner pipe water expansion portion that expands upon absorbing moisture is formed on the outer peripheral surface of the inner cylindrical portion of the bell mouth. By forming water expansion portions in this way, a connection structure can be obtained that provides sufficient water stoppage while facilitating connection work. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2009-159742 A [Patent Document 2] JP 2014-207752 A [Patent Document 3] JP 2018-031412 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the pipe connection structure of Patent Document 1, the shape of the opening of the pipe port member into which the pipe joint is inserted is complex, making it difficult to process the pipe port member.

[0011] On the other hand, the structure of Patent Document 2 is simpler overall than that of Patent Document 1, and in order to ensure watertightness, water-swellable nonwoven fabrics are provided on the inner peripheral portion and the back surface of the outer flange of the outer peripheral pipe joint, and on the outer peripheral portion and the surface of the inner flange of the inner cylindrical portion of the bell mouth. However, the structure of Patent Document 2 is also complex because the outer peripheral pipe joint has a protrusion that enters the through hole, and there is a problem that the through hole must be made larger by the amount of the protrusion that enters the through hole.

[0012] Also, Patent Document 3 has a similar structure to Patent Document 2, but since there is no protrusion that enters the through hole, the structure is simple and the diameter of the through hole does not need to be unnecessarily large. However, in such a pipe connection structure, the pipe, etc. may be deformed due to the earth pressure when backfilling with soil after construction of the bell mouth, and as a result, the water-stopping ability may decrease and groundwater may infiltrate into the electric conduit, etc. This problem is particularly noticeable when the pipe has a large diameter.

[0013] 15(a) and 15(b) are schematic diagrams showing a conventional connection structure. A through hole 124 is formed in a wall 125 of a hand hole 123. The tip of a spiral conduit 121 is inserted into the through hole 124. At this time, outside the hand hole 123, an outer connector 101b is attached to the outer periphery of the spiral conduit 121.

[0014] The outer connector 101b has an expanded flange portion at one end (hand hole 123 side). Also, a spiral shape is formed on the inner surface of the outer connector 101b to screw with the spiral shape of the outer peripheral surface of the spiral conduit 121, and the outer connector 101b screws with the outer surface of the spiral conduit 121. At this time, a water-swellable nonwoven fabric is arranged on the inner surface of the outer connector 101b, and the outer connector 101b and the spiral conduit 121 screw with each other via the water-swellable nonwoven fabric.

[0015] On the other hand, the inner connector 101a has an expanded flange portion at one end side (hand hole 123 side). The inner connector 101a also has a spiral shape on its outer circumferential surface that screws together with the spiral shape on the inner surface of the spiral electric conduit 121. A water-swellable nonwoven fabric is disposed on the outer circumferential surface of the inner connector 101a (the drawing shows a perspective view of the water-swellable nonwoven fabric).

[0016] First, as shown in Fig. 15(a), the inner connector 101a is screwed and inserted into the tip of the spiral conduit 121 inserted into the through hole 124 (arrow P in the figure). Next, as shown in Fig. 15(b), the outer connector 101b is tightened (arrow Q in the figure) so that the wall portion 125 of the hand hole 123 can be sandwiched between the flange portion of the inner connector 101a and the flange portion of the outer connector 101b. In this way, the spiral conduit 121 is connected to the hand hole 123.

[0017] 16 is a cross-sectional view of a connection structure between a helical conduit 121 and a hand hole 123. As described above, the helical ridge portion 107a on the outer surface of the inner connector 101a screws into the helical shape of the helical conduit 121 inside the helical conduit 121. Also, the helical ridge portion 107b on the inner surface of the outer connector 101b screws into the helical shape of the helical conduit 121 outside the helical conduit 121.

[0018] FIG. 17(a) is an enlarged view of the R portion of FIG. 16, and FIG. 17(b) is an enlarged view of the S portion of FIG. 16. As shown in FIG. 17(a), a water-swellable nonwoven fabric 117a is disposed on the outer peripheral surface of the inner connector 101a. As shown in FIG. 17(b), a water-swellable nonwoven fabric 117b is disposed on the inner peripheral surface of the outer connector 101b. Therefore, when water infiltrates from the periphery into the gap between the outer connector 101b and the spiral electric conduit 121, the water-swellable nonwoven fabric 117b expands, thereby ensuring water-stopping properties. Furthermore, when water infiltrates into the gap between the inner connector 101a and the spiral electric conduit 121, the water-swellable nonwoven fabric 117a expands, thereby ensuring water-stopping properties.

[0019] In this state, soil is backfilled around the handhole 123, and the spiral conduit 121 is buried. For example, the spiral conduit 121 is buried at a depth ranging from about 30 cm to 5 m from the ground (usually, it is often about 30 cm to 2 m), depending on the application site.

[0020] In this case, as shown in Fig. 18, when the spiral conduit 121 is laid and then backfilled with soil, the spiral conduit 121 may be subjected to earth pressure when the soil is backfilled with soil and a load when trucks or the like pass above (arrow T in the figure). When such earth pressure or the like is applied, the spiral conduit 121 may be deformed, etc., and the gap between the spiral conduit 121 and the inner connector 101a and the outer connector 101b may become large. Here, if the burial depth is shallow, the earth pressure is low, but the pressure when vehicles such as trucks pass is high. Conversely, if the burial depth is deep, the earth pressure is high, but the pressure when vehicles pass is reduced by being dispersed to the surrounding ground.

[0021] As described above, the water-swellable nonwoven fabrics 117a and 117b are disposed between the helical conduit 121 and the inner connector 101a and the outer connector 101b. However, when the gap becomes large due to deformation of the helical conduit 121, etc., it becomes difficult to completely ensure watertightness by the expansion of the water-swellable nonwoven fabrics 117a and 117b. This reduces the watertightness, and there is a risk that groundwater may infiltrate into the hand hole 123 or the inside of the helical conduit 121. This tendency becomes more pronounced for helical conduits 121 with a larger diameter.

[0022] As a countermeasure to this, there is a method of designing the clearance between the spiral conduit 121 and the inner connector 101a and the outer connector 101b to be small in advance. However, if the clearance between the spiral conduit 121 and the inner connector 101a and the outer connector 101b is too small, there is a risk that the pressure caused by the expansion of the water-swellable nonwoven fabrics 117a and 117b will become too large.

[0023] For example, as shown in Fig. 17(a), if the clearance between the spiral conduit 121 and the inner connector 101a is too small, the pressure (U in the figure) generated when the water-swellable nonwoven fabric 117a expands may damage the inner connector 101a and the spiral conduit 121. Similarly, as shown in Fig. 17(b), if the clearance between the spiral conduit 121 and the outer connector 101b is too small, the pressure (V in the figure) generated when the water-swellable nonwoven fabric 117b expands may damage the outer connector 101b and the spiral conduit 121, and may actually cause damage.

[0024] In this way, if the clearance between the spiral conduit 121 and the inner and outer connectors 101a and 101b is reduced in order to prevent deterioration of the watertightness due to the influence of earth pressure, etc., there is a risk of damage to both. For this reason, a connection structure or the like that can suppress damage to the spiral conduit 121, the inner and outer connectors 101a and 101b due to the pressure when the water-swellable nonwoven fabrics 117a and 117b expand and that also has excellent watertightness is required.

[0025] The present invention has been made in consideration of such problems, and provides a partition wall on the crests of the screwing part of the connector, and also provides grooves between the crests as movement space to allow deformation and movement of the water-swellable nonwoven fabric that has absorbed water, swelled, and gelled, thereby making it possible to ensure high water stoppage with a simple structure and prevent damage caused by pressure when the water-swellable nonwoven fabric expands. Using inner and outer adapters Conversion adapter By Double wall rectangular conduit For hand holes Connected double wall rectangular conduit and hand hole connection structure The purpose is to provide. [Means for solving the problem]

[0026] In order to achieve the above object, the first invention provides a double-wall rectangular conduit. and hand hole connection structure And, a double-walled rectangular conduit, a hand hole, a conversion adapter connected to the double-walled rectangular conduit, and an inner connector and an outer connector for connecting the conversion adapter to the hand hole, the double-walled rectangular conduit being composed of an outer tube and a straight inner tube disposed inside the outer tube, the outer tube being composed of a large diameter portion and a small diameter portion, and the outer surface of the inner tube being fused to the inner surface of the outer tube and the small diameter portion of the outer tube, The double-wall rectangular conduit is The above Through a conversion adapter The above The conversion adapter is connected to a hand hole. The above Inner connector and The above From a helix that is attached to the hand hole with an outer connector The double wall The conversion adapter can be converted into a joint portion of a rectangular electric conduit, and the conversion adapter has the spiral portion formed on one side and the spiral portion formed on the other side. The double wall a joint portion for connecting with a rectangular electric conduit, the inner connector and the outer connector both having a substantially T-shaped cross section, a tubular portion having a helical ridge portion, and a flange portion at one end of the tubular portion which expands in diameter at a substantially right angle from the tube end portion of the tubular portion, a water-swellable nonwoven fabric is provided on the outer peripheral surface of the tubular portion of the inner connector, a rubber packing and a water-swellable nonwoven fabric are attached in this order to the inner surface of the flange portion of the inner connector, a water-swellable nonwoven fabric is provided on the inner peripheral surface of the tubular portion of the outer connector, and a rubber packing and a water-swellable nonwoven fabric are attached in this order to the outer surface of the flange portion of the outer connector, and the inner connector is screwed onto the inner peripheral surface of the end of the helical portion, The above the water-swellable nonwoven fabric on the inner surface of the flange portion of the inner connector abuts against an inner wall surface of a hand hole, and the outer connector is screwed onto an outer peripheral surface of the spiral portion, The above The water-swellable nonwoven fabric on the outer surface of the flange portion of the outer connector is in contact with the outer wall surface of the hand hole, and the flange portion of the inner connector and the flange portion of the outer connector are in contact with each other. The above a wall portion of a handhole is sandwiched between the cylindrical portion of at least one of the inner connector and the outer connector, the cross-sectional shape of the helical ridge portion of the cylindrical portion of at least one of the inner connector and the outer connector in a direction parallel to the pipe axis direction is composed of two ridge portions opposed to each other at a predetermined distance from each other, partition walls connecting the ridge portions and extending approximately parallel to the pipe axis direction are formed at predetermined intervals so as to close a groove formed between the opposed ridge portions, the water-swellable nonwoven fabric provided on the cylindrical portion is formed so as to straddle and cover an upper portion of the groove formed between the ridge portions, and the double-wall rectangular conduit is connected to the joint portion of the conversion adapter. and hand hole connection structure It is. Here, the double-wall rectangular conduit and hand hole connection structure In the double-walled rectangular conduit connected to the joint of the conversion adapter, it is preferable that the outer tube and the inner tube are at least partially fused together. In the present invention, in all the following inventions, the definition of handhole includes not only handholes, but also small branch manholes having substantially the same structure as handholes, or is interpreted as being synonymous with handholes. In the present invention, the description of rubber packing is given as a representative example of an elastic body used for rubber packing, and rubber or elastomers can be suitably used. As the elastomer, both thermosetting elastomers and thermoplastic elastomers can be used.

[0027] The double-walled rectangular conduit is composed of a male joint and a female joint formed at both ends of the outer tube, respectively, and a main body connecting the male joint and the female joint. The main body is formed by alternatingly repeating a substantially cylindrical small diameter portion and a substantially rectangular large diameter portion larger than the male joint. Furthermore, the straight inner tube is substantially cylindrical in shape. There is Good too.

[0028] In the male joint portion, the inner tube is either housed and covered inside the male joint portion, or is integrated with the inner surface near the tip of the male joint portion, and in the female joint portion, it may be cut so as not to interfere with the connection with the male joint portion.

[0029] The double wall rectangular conduit and hand hole connection structure In the present invention, the cross-sectional shapes of the helical ridge portions of the tubular portions of the inner connector and the outer connector in a direction parallel to the pipe axis direction may each consist of two ridge portions facing each other at a predetermined distance from each other, and partition walls connecting the ridge portions and extending approximately parallel to the pipe axis direction may be formed at predetermined intervals so as to close the grooves formed between the opposing ridge portions, and the water-swellable nonwoven fabric provided on the tubular portions may be formed so as to straddle and cover the upper parts of the grooves formed between the ridge portions.

[0030] The double wall rectangular conduit and hand hole connection structure In the present invention, it is preferable that partition walls parallel to the pipe axis direction connecting the helical ridges of the inner connector and the outer connector are provided at predetermined intervals of 30° to 90° in the circumferential direction of the helical ridges. By providing the partition walls at predetermined intervals of 30° to 90° in the circumferential direction from the start position or end position of the ridges, sufficient water stopping properties and rigidity of the ridges can be ensured.

[0031] The double wall rectangular conduit and hand hole connection structure In the double-wall rectangular conduit, it is preferable that the partition walls, which are parallel to the pipe axis direction and connect the helical ridges of the inner connector and the outer connector, are formed substantially parallel to the pipe axis direction at predetermined intervals in a direction perpendicular to the pipe axis direction and to a predetermined center line. If the partition walls are formed vertically to the pipe axis direction and at predetermined intervals in the range of 1 / 2 to 1 / 5 of the radius above and below the center, sufficient watertightness and rigidity of the ridges can be ensured. The partition walls are and hand hole connection structure The present invention can be applied not only to the above but also to a single-wall rectangular conduit having no inner tube.

[0032] The double wall rectangular conduit and hand hole connection structureIn the above, the joint portion of the conversion adapter is composed of a female joint portion of a rectangular electric conduit, and the female joint portion may be fitted with a male joint portion composed of a substantially C-shaped or annular anti-slip ring attached to a predetermined position and an annular rubber gasket.

[0033] The double wall rectangular conduit and hand hole connection structure In the above, the joint portion of the conversion adapter is composed of a male joint portion of a rectangular electric conduit, and the male joint portion may be composed of a substantially C-shaped or annular anti-slip ring and an annular rubber packing attached to a predetermined position of the male joint portion.

[0034] The conversion adaptor may have an extra length for adjusting the length of the conversion adaptor.

[0035] According to the first invention, a double-wall rectangular conduit and hand hole connection structure In the above, the part connected to the hand hole is a conversion adapter for converting the shape of the spiral part to the shape of the joint part with the double-wall rectangular conduit, so and hand hole connection structure It has good water-stopping properties and can suppress deformation of the spiral portion, inner connector, or outer connector due to earth pressure, etc., and damage due to water absorption. As a result, by using a conversion adapter for converting the shape of the joint part with the double-wall rectangular electric conduit, it is possible to have a connection structure with a handhole that has excellent effective water-stopping properties for the double-wall rectangular electric conduit.

[0036] In addition, in a cross section parallel to the pipe axial direction, the cross-sectional shape of the helical ridge of at least one of the inner connector or the outer connector is composed of two ridges that face each other at a predetermined distance from each other, and a groove is formed between the ridges. Therefore, when the water-swellable nonwoven fabric absorbs water and swells, the excess expansion of the water-swellable nonwoven fabric can be released into the groove. As a result, the excess stress caused by the swollen and gelled water-swellable nonwoven fabric can be alleviated between the helical portion and the inner connector or the outer connector, and damage to the member can be suppressed.

[0037] In addition, between the opposing crests, partition walls connecting the crests are formed at a predetermined interval so as to close the grooves in parallel with the pipe axis direction, so that the grooves can be prevented from becoming a path for water infiltration. Furthermore, by providing a partition wall connecting the two crests, the rigidity of the two crests can be increased. In this way, by using an inner connector or an outer connector in which the cross-sectional shape of the helical crests is composed of two crests that face each other at a predetermined distance from each other, it is possible to obtain both the effect of ensuring water blocking and the effect of preventing damage to the inner connector or the outer connector due to an increase in stress caused by water absorption and swelling. As a result, even in the case of a large-diameter double-walled rectangular electric conduit, damage to each member can be suppressed and groundwater can be prevented from flowing into the double-walled rectangular electric conduit, etc.

[0038] In addition, at the tip of the male joint, the inner surface near the tip of the male joint is integrated with the inner tube, or the inner tube is covered by the male joint, making manufacturing easy and also facilitating the connection of double-walled rectangular electric conduits to each other.

[0039] In addition, by cutting out the inner tube on the inner surface of the female joint, it is possible to prevent interference between the male joint and the inner tube inside the female joint when it is fitted with the male joint. As described above, in the case of a male joint, it is not always necessary to cut out the inner tube, but in the case of a female joint, it is necessary to cut out the male joint because it becomes an obstacle to the insertion of the male joint when connecting with the male joint.

[0040] In addition, double wall rectangular conduit and hand hole connection structure In the above, the cross-sectional shape of the spiral ridge portion of both the inner connector and the outer connector in a direction parallel to the pipe axis direction is made into two opposing ridge portions spaced a predetermined distance from each other, and a partition wall is formed connecting the ridge portions so as to block the groove formed between the opposing ridge portions, thereby making it possible to more reliably obtain the above-mentioned effects.

[0041] Furthermore, the partition walls are arranged to connect the peaks of the spiral ridge portion and are arranged at predetermined intervals of 30° to 90° circumferentially from the start or end position of the ridge portion, thereby ensuring sufficient water stopping properties and rigidity of the ridge portion.

[0042] Furthermore, if the partition walls are provided to connect the ridges of the spiral ridges and are formed in a plurality of approximately parallel rows at a predetermined interval between 1 / 2 and 1 / 5 of the radius above and below the center line position, sufficient water-stopping properties and rigidity of the ridges can be ensured. Here, the partition walls formed in a plurality of approximately parallel rows may or may not be formed at the center line position, but it is preferable to form them at the center line position because the partition walls are formed at equal intervals overall.

[0043] In addition, the joint portion of the conversion adapter is composed of a female joint portion of a square electric conduit, and if the female joint portion can be connected to a male joint portion composed of a roughly C-shaped or annular anti-slip ring and an annular rubber gasket attached to a predetermined position, it can be easily connected to the female joint portion of the square electric conduit, and the anti-slip properties and watertightness of the connection portion can be ensured.

[0044] Furthermore, if the joint portion of the conversion adapter is composed of a male joint portion of a rectangular electrical conduit, and the male joint portion is composed of a roughly C-shaped or annular anti-slip ring and an annular rubber packing, it can be easily connected to the female joint portion of the rectangular electrical conduit, and the anti-slip properties and watertightness of the connection portion can be ensured.

[0045] In addition, if the conversion adapter has an extra length for adjusting the length of the spiral portion, the length of the conversion adapter can be adjusted according to the length of the rectangular conduit to be connected. By cutting the spiral part of the conversion adapter This allows for adjustment. The above Double wall square conduit In the connection structure between the hand hole and the handrail, the connection structure is adjusted to a desired length. This is particularly useful for fine adjustment of the length in front of the junction box.

[0046] In addition, the cross-sectional shape of the helical ridge of the cylindrical part of both the inner connector and the outer connector in the direction parallel to the pipe axis direction is formed into two opposing ridges spaced apart by a predetermined distance, and a partition wall connecting the ridges is formed at a predetermined interval between the opposing ridges parallel to the pipe axis direction to block the groove, thereby preventing the groove from becoming a path for water infiltration. Furthermore, by providing a partition wall connecting the two ridges, the rigidity of the two ridges can be increased. In this way, by using an inner connector or an outer connector in which the cross-sectional shape of the helical ridge is made up of two ridges spaced apart from each other by a predetermined distance, it is possible to obtain both the effects of ensuring watertightness and preventing damage due to increased stress caused by swelling due to water absorption. This makes it possible to use a large-diameter conversion adapter and Double wall square conduit of To the hand hole The connection structure prevents damage to each component and is a double-walled rectangular wire. To the tube This can prevent groundwater from flowing in. Effect of the Invention

[0047] According to the present invention, it is possible to ensure high water stopping performance with a simple structure and prevent damage to the water-swellable nonwoven fabric due to the pressure during expansion. Double wall rectangular wire and Hand hole connection structure Construction can be provided. [Brief description of the drawings]

[0048] [Figure 1] 1A is a side view of the inner connector 1a, and FIG. 1B is a front view of the inner connector 1a (a perspective view of the helical ridge portion 7a). [Diagram 2] 6A is a cross-sectional view of the helical ridge portion 7a, FIG. 6B is a cross-sectional view of the helical ridge portion 7a in a partition wall 9a, and FIG. 6C is a cross-sectional view of another form of the helical ridge portion 7a. [Diagram 3] 1A is a side view of the inner connector 1aa, and FIG. 1B is a front view of the inner connector 1aa (a perspective view of the helical ridge portion 7a). [Figure 4] FIG. 2 is a side view of the inner connector 1a to which the water-swellable nonwoven fabric 17a and the like are attached. [Diagram 5]1A is a cross-sectional view of the outer connector 1b, and FIG. 1B is a front view of the outer connector 1b (a perspective view of the helical ridge portion 7b). [Figure 6] FIG. 2 is a side view of the outer connector 1b to which the water-swellable nonwoven fabric 17b and the like are attached. [Figure 7] 4A is a side view showing a double-walled rectangular conduit 40, and FIG. 4B is a cross-sectional view of FIG. [Figure 8] 4A is a cross-sectional view showing the connection structure between a male joint portion 41 and a female joint portion 43 of a double-wall rectangular electric conduit, and FIG. 4B is an enlarged view of portion AA of FIG. [Figure 9] FIG. 1A is a diagram showing a conversion adaptor 60a, and FIG. 1B is a diagram showing a conversion adaptor 60b. [Figure 10] 1 is a cross-sectional view showing a connection structure 20a in which a hand hole and a conversion adapter 60a are connected. [Figure 11] 4A and 4B are diagrams showing the shape of a water-swellable nonwoven fabric 17a in a helical ridge portion 7a when it is expanded, where (a) is a cross-sectional view parallel to the tube axis direction, and (b) is a cross-sectional view perpendicular to the tube axis direction. [Figure 12] 13(a) and (b) are diagrams showing a process for constructing a connection structure 30b between a double-wall rectangular conduit and a handhole. [Figure 13] 13(a) and (b) are diagrams showing a process for constructing a connection structure 30c between a double-wall rectangular conduit and a handhole. [Figure 14] 13 is a diagram showing a method of adjusting the length using an extra length portion 65 of a conversion adaptor 60a to connect to a double-wall rectangular conduit 40. FIG. [Figure 15] 10(a) and 10(b) are diagrams illustrating a process of connecting a spiral conduit to a hand hole 123 using a conventional inner connector 101a and an outer connector 101b. [Figure 16] FIG. 1 is a cross-sectional view of a spiral conduit connected to a hand hole 123 using a conventional inner connector 101a and an outer connector 101b. [Figure 17] 16A is an enlarged view of part R in FIG. 16, and FIG. 16B is an enlarged view of part S in FIG. [Figure 18] FIG. 13 is a diagram showing a state in which earth pressure is applied from above to the spiral conduit 121. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] (Inner Connector) Hereinafter, the members used in the embodiment of the present invention will be described with reference to the drawings. Fig. 1(a) is a side view of the inner connector 1a, and Fig. 1(b) is a view taken along the arrow W in Fig. 1(a), showing a perspective view of the helical ridge portion 7a. The inner connector 1a is a member used when connecting a helical conduit as shown in Fig. 15 or a helical portion of a conversion adapter (Fig. 9) to be described later to a handhole, and is used together with the outer connector to be described later.

[0050] The inner connector 1a is made of, for example, resin, and has a cylindrical portion 3a having a helical ridge portion 7a, and a flange portion 5a at one end of the cylindrical portion 3a, which expands in diameter at a substantially right angle from the tube end of the cylindrical portion 3a. That is, the inner connector 1a is a member having a substantially T-shaped cross section. The helical ridge portion 7a in the inner connector 1a is a portion that protrudes from the outer surface of the cylindrical portion 3a, and is formed on the outer surface of the cylindrical portion 3a of the inner connector 1a to screw into a helical portion of a conversion adapter or the like.

[0051] Fig. 2(a) is an enlarged cross-sectional view of the helical ridge portion 7a. The cross-sectional shape of the helical ridge portion 7a in the direction parallel to the tube axis direction of the cylindrical portion 3a is composed of two ridge portions 11a that face each other at a predetermined distance. As shown in Figs. 1(b) and 2(b), partition walls 9a that connect the ridge portions 11a and are approximately parallel to the tube axis direction are formed at predetermined intervals so as to close the grooves 13a formed between the opposing ridge portions 11a. The more partition walls 9a there are, the more reliably the water-stopping effect and the rigidity-improving effect can be obtained, but if the partition walls 9a are increased too much, the effect of mitigating the pressure during expansion of the water-swellable nonwoven fabric decreases.

[0052] The circumferential spacing θa of the partition walls 9a (see FIG. 1(b)) is preferably 30° to 90° in order to obtain a good balance between the water-stopping effect, the effect of improving rigidity, and the effect of preventing damage caused by the pressure when the water-swelling nonwoven fabric expands due to water absorption, but it can be in the range of 20° to 90° at maximum. As will be described later, the arrangement direction of the partition walls 9a does not necessarily have to face toward the center. For example, it may be parallel to the partition line of the mold or the same direction as the separation direction of the mold used during molding.

[0053] More specifically, the partition walls 9a are desirably formed at a distance in a predetermined range of 30° to 90° in the circumferential direction from the start or end position of the helical ridge portion 7a, starting from the start or end point, respectively. However, in order to prevent water from entering the grooves 13a between the ridge portions 11a and to increase the rigidity of the ends of the ridge portions 11a, it is desirably that the first and last partition walls 9a are provided near the start or end position of the helical ridge portion 7a.

[0054] 2(a), in a cross section parallel to the tube axis direction of each of the two peaks 11a, the angle θo of the outer ridge of each peak 11a with respect to the tube axis direction is smaller than the angle θi of the inner ridge. Also, the length Y of the outer support part of the base of each peak 11a divided by a line O that passes through the apex of each peak 11a and is perpendicular to the tube axis direction is longer than the length Z of the inner support part.

[0055] The cross-sectional shape of the peak 11a is not limited to the illustrated example. For example, in the illustrated example, both the outer ridgeline and the inner ridgeline of the peak 11a are curved, but one of them may be straight. For example, the tip of the outer ridgeline may be curved, and the inner ridgeline may be a straight peak.

[0056] In the example shown in FIG. 2(a), the crest 11a has a solid cross section of a protruding crest shape, but is not limited thereto. For example, as shown in FIG. 2(c), the cross section may be such that both the outer and inner surfaces of the crest 11a are formed in a protruding wave shape, and the inner surface has a recessed portion. Here, it is preferable that the cross section of the protruding crest shape of the crest 11a is solid. This is because the rigidity of the cylindrical portion 3a of the inner connector 1a is improved when the cross section of the protruding crest shape is solid. As a result, the effect of preventing deformation of the cross section of the cylindrical portion 3a of the inner connector 1a is improved to prevent water leakage from the handhole 23, and the effect of preventing creep deformation when subjected to earth pressure for a long period of time is excellent, and dimensional stability during molding of the connector is excellent. In the following description, the case where the crest 11a is solid will be described.

[0057] Fig. 3(a) is a side view of the inner connector 1aa, and Fig. 3(b) is a view taken along the line AB in Fig. 3(a) with the helical ridge portion 7a seen through. The inner connector 1aa has a similar configuration to the inner connector 1a, but the shape of the partition wall 9a is different. Unlike the inner connector 1a, the inner connector 1aa does not have the partition wall 9a formed radially from the center, but has partition walls formed substantially parallel to the center line (diameter) at a predetermined interval in a direction substantially perpendicular to a predetermined position in a cross section perpendicular to the pipe axis direction.

[0058] Here, instead of forming the partition walls 9a evenly in the circumferential direction as in the inner connector 1a, the partition walls 9a are formed substantially parallel to a predetermined interval in a direction substantially perpendicular to a predetermined center line (diameter), because this makes it possible to manufacture the inner connector using two molds symmetrical with respect to the predetermined center line, rather than dividing the mold for molding this product into multiple parts in the circumferential direction. In other words, by making the center line at a predetermined position the partition line of the mold, the partition walls 9a can be provided in a direction perpendicular to the partition line of the mold for molding the inner connector 1aa (i.e., toward the separation direction of the mold used during molding).

[0059] The partition walls 9a may be arranged, for example, at the center line in the left-right direction (center line AC dividing the wall into left and right in FIG. 3(b)), or may not be arranged at the position. In either case, the partition walls 9a are arranged symmetrically with respect to the center line, and a predetermined number of them are arranged substantially parallel to each other at a predetermined interval in the vertical direction. Here, the length of each partition wall 9a arranged side by side in the vertical direction increases with distance from the center line in the vertical direction (center line AD dividing the wall into top and bottom in FIG. 3(b)), and the partition wall 9a furthest from the center line AD is the longest. Usually, the partition walls 9a are arranged to connect the inner and outer spiral ridge portions 7a, but the partition wall 9a furthest from the center line AD may be arranged to connect the outer spiral ridge portions 7a together, as shown in FIG. 3(b).

[0060] In the illustrated example, 12 partition walls 9a are formed symmetrically above and below the center line AD of the vertical direction. The partition wall 9a located farthest from the center line AD is arranged so as to connect the outer spiral ridges 7a. In addition, another partition wall 9a that is approximately perpendicular to the center line AD is provided in the center of the partition wall 9a located farthest from the center line AD. Although this perpendicular partition wall 9a cannot be provided at an arbitrary position, the position at which this perpendicular partition wall 9a is formed corresponds to the position at which the partition line of the mold is formed, so that it does not hinder the division of the mold.

[0061] The partition walls 9a formed in a plurality of substantially parallel rows at a predetermined interval in the vertical direction may be formed at a predetermined interval. For example, the partition walls 9a may be formed at a predetermined interval between 1 / 2 to 1 / 5 of the radius, i.e., 1 / 4 to 1 / 10 of the diameter, on both sides of the center line AD, which divides the vertical direction into two. Alternatively, the partition walls 9a formed in a plurality of substantially parallel rows at a predetermined interval may be formed at a predetermined interval between the center line AD position and 1 / 3 to 1 / 5 of the radius, i.e., 1 / 6 to 1 / 10 of the diameter, on both sides of the center line AD. Here, the interval at which the partition walls are provided must be within a predetermined range in order to obtain a water-stopping effect and a rigidity-improving effect for suppressing deformation of the spiral crest portion. Therefore, since it is necessary to provide many partition walls as the product size increases, it is desirable to make the ratio of the formation interval to the diameter or radius of the partition walls small while satisfying the above-mentioned set range. In the following description, an example using the inner connector 1a will be described, but the inner connector 1aa can also obtain the same effect.

[0062] Fig. 4 is a view showing the inner connector 1a in use, showing a part of the water-swellable nonwoven fabric 17a in a see-through view. As shown in the enlarged cross-sectional view of part D in Fig. 4, the water-swellable nonwoven fabric 17a is provided on the outer peripheral surface of the tubular portion 3a of the inner connector 1a. In this case, the water-swellable nonwoven fabric 17a provided on the tubular portion 3a is attached so as to straddle a pair of peaks 11a and to straddle and cover the upper portion of the groove 13a formed between the peaks 11a. Therefore, a gap corresponding to the groove 13a is formed between the water-swellable nonwoven fabric 17a and the outer surface of the inner connector 1a.

[0063] The water-swellable nonwoven fabric 17a is preferably a nonwoven fabric containing, for example, polyester fibers, sodium polyacrylate fibers, and a binder resin. In this way, by using the binder resin, a nonwoven fabric in which some of the fibers of the nonwoven fabric are bonded by the binder resin and the fibers are connected to each other is obtained. In this case, the ratio of the polyester fibers and the sodium polyacrylate is 30% by mass to 70% by mass, and more preferably 50% by mass to 70% by mass, when the total of the two is 100% by mass. In addition, the water-swellable nonwoven fabric 17a preferably contains a binder resin in the range of 1 to 10% by mass, and more preferably 1 to 5% by mass, relative to the total of the polyester fibers and the sodium polyacrylate fibers. The water-swellable nonwoven fabric 17a is preferably formed by, for example, a needle punch method. Here, a representative example of polyester resin is PET resin, and therefore, in many cases, PET fibers are used as the polyester fibers used in the nonwoven fabric. The polyester resin is synthesized by dehydration condensation of polyalcohol and polycarboxylic acid, thereby polymerizing the polyalcohol and polycarboxylic acid in an alternating arrangement.

[0064] The water-absorbing property of the water-swellable nonwoven fabric 17a is provided by sodium polyacrylate. Since polymers of acrylic acid have many carboxyl groups, they are highly hydrophilic. When cross-linked into a mesh structure and converted into the sodium salt form, they become a highly absorbent gel, exhibiting excellent water-absorbing properties.

[0065] Here, the side of the tubular portion 3a of the flange portion 5a of the inner connector 1a (arrow B in the figure) is the inner surface side of the flange portion 5a, and the side of the flange portion 5a opposite to the tubular portion 3a (arrow A in the figure) is the outer surface side of the flange portion 5a. As shown in the enlarged cross-sectional view of part C in Fig. 3, a rubber packing 15a and a water-swellable nonwoven fabric 17a are attached in this order as elastic members to the inner surface of the flange portion 5a of the inner connector 1a. That is, the water-swellable nonwoven fabric 17a is provided on the rubber packing 15a provided on the inner surface of the flange portion 5a.

[0066] (Outer Connector) Next, the outer connector 1b will be described as a member used in the embodiment of the present invention. FIG. 5(a) is a side view of the outer connector 1b, and FIG. 5(b) is a view taken along the X arrow in FIG. 5(a), showing the helical ridge 7b. The outer connector 1b is made of, for example, resin, and has a cylindrical portion 3b having the helical ridge 7b, and a flange portion 5b at one end of the cylindrical portion 3b, which expands in diameter at a substantially right angle from the tube end of the cylindrical portion 3b. That is, both the outer connector 1b and the inner connector 1a are members having a substantially T-shaped cross section. The helical ridge 7b in the outer connector 1b is a portion that protrudes toward the center on the inner surface of the cylindrical portion 3b, and is formed on the inner surface of the cylindrical portion 3b of the outer connector 1b to screw into a helical portion of a conversion adapter or the like.

[0067] A helical ridge portion 7b is provided on the inner surface of the cylindrical portion 3b, and the cross-sectional shape of the helical ridge portion 7b in a direction parallel to the pipe axis direction is composed of two ridge portions 11b that face each other at a predetermined distance. The shape of the ridge portion 11b is substantially the same as that of the ridge portion 11a. Note that, like the helical ridge portion 7a of the inner connector 1a described above, the ridge portion 11b may be solid in cross section, or may have a shape in which the outer and inner surfaces of the ridge portion 11b have the same wave shape in cross section and have a recess on the inner side.

[0068] Similarly to the helical ridges 7a of the inner connector 1a, partition walls 9b are formed at predetermined intervals between the ridges 11b and are substantially parallel to the pipe axis direction so as to close the grooves 13b formed between the opposing ridges 11b. The more partition walls 9b there are, the more reliable the water-stopping effect and the rigidity-improving effect can be. However, if there are too many partition walls 9b, the effect of mitigating deformation caused by the pressure of the water-swellable nonwoven fabric when it expands decreases. Therefore, the circumferential arrangement interval θb (see FIG. 5(b)) of the partition walls 9b needs to be set in the range of 20° to 90° in order to obtain a good balance between the water-stopping effect, the rigidity-improving effect, and the effect of mitigating deformation caused by the pressure of the water-swellable nonwoven fabric when it expands, but it is preferable to set it in the range of 30° to 90°.

[0069] In addition, as in the above-described inner connector 1aa, the outer connector 1b may also be provided with partition walls 9b parallel to each other. That is, the partition walls 9a, 9b formed parallel to the pipe axis direction so as to connect between the crests 11a, 11b of the helical crests 7a, 7b of the inner connector and the outer connector may be formed in a plurality of parts at predetermined intervals in a direction substantially perpendicular to the center line at a predetermined position in a cross section perpendicular to the pipe axis direction. In this way, the inner connector and the outer connector formed in a plurality of parts at predetermined intervals in a direction substantially perpendicular to the center line at a predetermined position in a cross section perpendicular to the pipe axis direction can be applied not only to double-walled electric conduits but also to rectangular electric conduits without a normal inner tube.

[0070] 6 is a partial cross-sectional view showing the outer connector 1b in use. A water-swellable nonwoven fabric 17b is provided on the inner circumferential surface of the tubular portion 3b of the outer connector 1b. The water-swellable nonwoven fabric 17b can be the same as the water-swellable nonwoven fabric 17a. The water-swellable nonwoven fabric 17b provided on the tubular portion 3b is attached so as to straddle a pair of peaks 11b and to straddle and cover the upper portion of the groove 13b formed between the peaks 11b. Therefore, a gap corresponding to the groove 13b is formed between the water-swellable nonwoven fabric 17b and the inner surface of the outer connector 1b.

[0071] As with the inner connector 1a, the cylindrical portion 3b side of the flange portion 5b of the outer connector 1b (arrow B in the figure) is the inner surface side of the flange portion 5b, and the opposite side of the flange portion 5b from the cylindrical portion 3b (arrow A in the figure) is the outer surface side of the flange portion 5b. As shown in the enlarged cross-sectional view of part E in Fig. 5, a rubber packing 15b and a water-swellable nonwoven fabric 17b are attached in this order to the outer surface of the flange portion 5b of the outer connector 1b. That is, the water-swellable nonwoven fabric 17b attached to the inner surface of the flange portion 5b is provided on the rubber packing 15b provided on the outer surface of the flange portion 5b.

[0072] The inner connector 1a and the outer connector 1b may be collectively referred to simply as a connector. That is, the connectors to be connected to a conversion adapter or the like each have a substantially T-shaped cross section, cylindrical portions 3a, 3b having helical ridges 7a, 7b, and flange portions 5a, 5b at one end of the cylindrical portions 3a, 3b, which expand in diameter at a substantially right angle from the tube end of the cylindrical portions 3a, 3b.

[0073] In this case, in the case of the inner connector 1a, a water-swellable nonwoven fabric 17a is attached to the outer peripheral surface of the tubular portion 3a and the inner surface of the flange portion 5a, and in the case of the outer connector 1b, a water-swellable nonwoven fabric 17b is attached to the inner peripheral surface of the tubular portion 3b and the outer surface of the flange portion 5b. In either case, the cross-sectional shape of the helical ridge portions 7a, 7b of the tubular portions 3a, 3b in a direction parallel to the pipe axis direction is composed of two ridge portions 11a, 11b opposed to each other at a predetermined distance, and partition walls 9a, 9b are formed at a predetermined interval between the ridge portions 11a, 11b and approximately parallel to the pipe axis direction to close the grooves 13a, 13b formed between the opposed ridge portions 11a, 11b.

[0074] (Structure of double-wall rectangular conduit and rectangular conduit) Next, a double-walled rectangular conduit 40 will be described as a member used in the embodiment of the present invention. Fig. 7(a) is a side view showing the double-walled rectangular conduit 40, and Fig. 7(b) is a cross-sectional view of the double-walled rectangular conduit 40 in the tube axis direction.

[0075] The double-walled rectangular conduit 40 is mainly composed of an inner tube 59, an outer tube 57, a male joint portion 41, a female joint portion 43, etc. The double-walled rectangular conduit 40 is made of a synthetic resin such as polyolefin resin. The double-walled rectangular conduit 40 is composed of an outer tube 57 and an inner tube 59 disposed inside the outer tube 57. The inner tube 59 is substantially cylindrical, and the outer surface of the inner tube 59 is integrated with the inner surface of the outer tube 57 at a position corresponding to the small diameter portion 49 by fusion.

[0076] Moreover, a male joint 41 is provided at one end of an outer tube 57 of the double-walled rectangular electric conduit 40, and a female joint 43 is provided at the other end. That is, a male joint 41 and a female joint 43 are formed at both ends of the outer tube 57, respectively. The male joint 41 and the female joint 43 are connection parts with other double-walled rectangular electric conduits 40, etc. That is, the double-walled rectangular electric conduit 40 is composed of the male joint 41 and the female joint 43 formed at both ends of the outer tube 57, respectively, and a main body connecting the male joint 41 and the female joint 43. In the main body connecting the male joint 41 and the female joint 43, a substantially cylindrical small diameter part 49 and a substantially rectangular large diameter part 51 having a larger diameter than the male joint 41 are alternately and repeatedly formed. The diameter (length of one side) of the large diameter portion 51 is larger than the outer diameter of the small diameter portion 49. Although not shown, the structure of the rectangular conduit will be described below. The rectangular conduit is obtained by removing the inner tube 59 from the double-wall rectangular conduit 40, and since there is no inner tube, there is no fused portion. The rectangular conduit is composed of only the outer tube 57, which is composed of the male joint portion 41, the female joint portion 43, and a main body portion connecting the two. The structures of the male fitting portion, the female fitting portion, and the main body portion of the outer tube are completely the same as those of the double-wall rectangular conduit 40, and the main body portion is formed by alternating and repeating substantially cylindrical small diameter portions and large diameter portions of substantially rectangular shape.

[0077] (Fitting of double wall rectangular conduit) Next, the male joint part 41 and the female joint part 43 will be described. The male joint part 41 and the female joint part 43 can be fitted together. In other words, the double-walled rectangular electric conduits 40 can be connected to each other. Fig. 8(a) is a cross-sectional view showing the connection structure between the male joint part 41 and the female joint part 43, and Fig. 8(b) is an enlarged view of part AA in Fig. 8(a).

[0078] A retaining ring 47 and a rubber packing 45 are disposed at a predetermined position on the end of the male joint portion 41. The retaining ring 47 is an approximately C-shaped member with a part in the circumferential direction cut at a cut portion. The retaining ring 47 has claw portions 46 and slide guides 48 alternately formed with slits in the circumferential direction. The retaining ring 47 can be made of, for example, ABS resin, PP resin, hard polyvinyl chloride, a mixed resin of any of these with PC resin, or a polymer alloy. Although not shown in particular, the retaining ring 47 does not necessarily have to be approximately C-shaped, and can have connection portions such as sawtooth grooves, a large number of minute protrusions, an adhesive layer with release paper, or locking protrusions and locking slits at both ends of the ring, and can be made into an annular ring by connecting the respective connection portions to each other. As described above, in the present invention, an annular ring can be used instead of an approximately C-shaped ring. That is, either an approximately C-shaped ring or an annular ring can be used.

[0079] An annular rubber packing 45 is provided on the base side of the retaining ring 47. The rubber packing 45 is made of, for example, EP rubber, SBR, CR, NBR, ACM rubber, or a dynamically crosslinked elastomer such as EPDM / PP.

[0080] 8(b), one end of the retaining ring 47 is a reduced diameter portion whose outer diameter is smaller than the other portions, and a plurality of claws 46 are provided so as to expand in diameter toward the other end. The retaining ring 47 can be reduced in diameter by the elastic deformation of each of the claws 46.

[0081] A slide guide 48 is provided between the claws 46 in the circumferential direction of the retaining ring 47 via a slit. The slide guide 48 is formed from the reduced diameter portion in a manner substantially parallel to the axial direction of the retaining ring 47. The retaining ring 47 is disposed between a pair of restricting portions 50 in the male joint portion 41. The restricting portions 50 are portions having an outer diameter larger than the portion where the retaining ring 47 is disposed. The retaining ring 47 is capable of sliding in the axial direction between the restricting portions 50. At this time, the slide guide 48 prevents the retaining ring 47 from tilting with respect to the axial direction of the male joint portion 41 when the retaining ring 47 slides. This allows the retaining ring 47 to slide smoothly.

[0082] The outer shape of the male joint 41 is formed by the outer tube 57. The inner tube 59 is housed and covered inside the male joint 41. In the male joint 41, the inner tube 59 is integrated with the inner surface of the tip of the male joint 41, for example. The inner surface of the male joint 41 and the inner tube 59 may not be integrated, and the inner tube 59 and the male joint 41 may be separated. That is, the male joint 41 does not necessarily need to be in contact with and fixed to the inner tube 59 as long as the inner surface near the tip of the male joint 41 is integrated with the inner tube 59, or the inner tube 59 is covered on the outer periphery without protruding from the tip of the male joint 41, but it is preferable that they are integrated.

[0083] Next, the female joint part 43 will be described. The female joint part 43 fits with the male joint part 41 described above. The female joint part 43 has, in order from the tip side (opening side), a cylindrical part 54, a sloped part 52 whose inner diameter gradually decreases from the cylindrical part 54, and a ring fitting part 53 whose diameter increases from the minimum inner diameter part of the sloped part 52. At least a part of the inner surface of the female joint part 43 has an inner tube 59 cut out so as not to impede the fitting with the male joint part 41.

[0084] As shown in Fig. 8(a), when the male joint part 41 is pushed into the female joint part 43, the inclined surface 52 of the female joint part 43 comes into contact with the retaining ring 47, causing the claw part 46 to deform and the retaining ring 47 to contract in diameter. At this time, since the retaining ring 47 is slidable between the restricting parts 50, the insertion resistance can be reduced by the contraction in diameter and sliding of the retaining ring 47 when the male joint part 41 is inserted. In addition, the slide guide 48 can suppress the inclination of the retaining ring 47 when it slides.

[0085] When the male joint part 41 is further pressed in, the end of the claw part 46 passes through the inclined surface part 52 of the female joint part 43, and the elastically deformed claw part 46 returns to its original diameter and expands in diameter. This causes the claw part 46 of the retaining ring 47 to fit into the ring fitting part 53 of the female joint part 43. This connects the female joint part 43 and the male joint part 41.

[0086] In this state, the outer peripheral surface of the rubber packing 45 is in close contact with the inner surface of the tubular portion 54 of the female joint portion 43, and can fill the gap between the female joint portion 43 and the male joint portion 41. This makes it possible to prevent moisture from entering between the female joint portion 43 and the male joint portion 41 from the outside.

[0087] (Conversion adapter) Next, a conversion adapter as a member used in the embodiment of the present invention will be described. Fig. 9(a) is a diagram showing a conversion adapter 60a. The conversion adapter 60a has a spiral portion 63 formed on one side and a female joint portion 61a formed on the other side. The female joint portion 61a is a joint portion with the double-wall rectangular electric conduit 40 described above.

[0088] The spiral portion 63 has the same shape as the spiral conduit 121 described above. Therefore, the inner connector 1a and the outer connector 1b can be screwed into the spiral portion 63. The female joint portion 61a has the same shape as the female joint portion 43 described above. Therefore, the male joint portion 41 of the double-wall rectangular conduit 40 can be connected to the female joint portion 61a. That is, the conversion adapter 60a can convert the spiral portion 63, in which the inner connector 1a and the outer connector 1b can be arranged, into the female joint portion 61a, which is a joint portion with the double-wall rectangular conduit 40.

[0089] (Connection structure of conversion adapter to hand hole) Next, a connection structure of a conversion adapter 60a to a handhole using an inner connector 1a and an outer connector 1b will be described. Fig. 10 is a cross-sectional view showing a connection structure 20a in which the spiral part 63 of the conversion adapter 60a is connected to a handhole 23 using the inner connector 1a and the outer connector 1b. The inner connector 1a and the outer connector 1b can be used in the same procedure as the conventional inner connector 101a and the outer connector 101b, as shown in Fig. 16. Therefore, in the following description, some overlapping explanations will be omitted.

[0090] A through hole 24 is formed in a wall 25 of the hand hole 23. Outside the hand hole 23, the outer connector 1b is disposed on the outer peripheral surface of the spiral portion 63 of the conversion adapter 60a. The outer connector 1b is screwed onto the outer peripheral surface of the spiral portion 63 of the conversion adapter 60a. At this time, the outer connector 1b is disposed with the flange portion 5b facing the end side of the spiral portion 63 of the conversion adapter 60a. In addition, the amount of protrusion of the spiral portion 63 of the conversion adapter 60a from the flange portion 5b side of the outer connector 1b is set to be slightly larger than the thickness of the wall 25 of the hand hole 23.

[0091] In this state, one end of the spiral portion 63 of the conversion adapter 60a is inserted into the through hole 24. Also, the inner connector 1a is disposed by being screwed onto the inner circumferential surface of one end of the spiral portion 63 of the conversion adapter 60a from the inside of the hand hole 23. The inner connector 1a is screwed onto the conversion adapter 60a until the flange portion 5a (water-swellable nonwoven fabric 17a) and the end of the spiral portion 63 of the conversion adapter 60a come into contact with each other and the tubular portion 3a is completely inserted into the conversion adapter 60a.

[0092] In this state, by tightening the outer connector 1b into the conversion adapter 60a, the flange portion 5a of the inner connector 1a and the flange portion 5b of the outer connector 1b can sandwich the wall portion 25 of the handhole 23. At this time, the water-swellable nonwoven fabric 17a on the inner surface of the flange portion 5a of the inner connector 1a abuts against the inner wall surface of the handhole 23, and the water-swellable nonwoven fabric 17b on the outer surface of the flange portion 5b of the outer connector 1b abuts against the outer wall surface of the handhole 23.

[0093] Here, as described above, the double-wall rectangular conduit using the conversion adapter 60a and hand hole connection structure The conversion adaptor 60a is used after being backfilled with soil. At this time, there is a risk of water seeping in through the gap between the conversion adaptor 60a and the inner connector 1a or the outer connector 1b. To prevent this, water-swellable nonwoven fabrics 17a, 17b are placed in the gap between the spiral part 63 of the conversion adaptor 60a and the inner connector 1a and the outer connector 1b.

[0094] (Water-stopping mechanism between conversion adapter and connector using water-swellable nonwoven fabric) 11(a) and 11(b) are conceptual diagrams showing the swelling of the water-swellable nonwoven fabric 17a in the helical ridge portion 7a, where FIG. 11(a) is a cross-sectional view parallel to the pipe axis direction, and FIG. 11(b) is a cross-sectional view perpendicular to the pipe axis direction at the partition wall 9a. Note that, although FIG. 11(a) and FIG. 11(b) show the helical ridge portion 7a in the inner connector 1a, the helical ridge portion 7b in the outer connector 1b also exhibits the same behavior. Therefore, hereinafter, the helical ridge portion 7a in the inner connector 1a will be described, and the description of the helical ridge portion 7b in the outer connector 1b will be omitted.

[0095] 11(a), when moisture penetrates between the spiral portion 63 and the spiral ridge portion 7a of the conversion adaptor 60a, the water-swellable nonwoven fabric 17a swells (arrow G in the figure). At this time, in the area other than the groove 13a, the water-swellable nonwoven fabric 17a swells and gels, thereby reliably ensuring watertightness between the inner surface of the spiral portion 63 of the conversion adaptor 60a and the outer surface of the tubular portion 3a of the inner connector 1a.

[0096] On the other hand, the swelling of the water-swellable nonwoven fabric 17a increases the pressure between the spiral portion 63 and the spiral ridge portion 7a of the conversion adaptor 60a. However, the groove 13a functions as a relief portion for the excessively swollen water-swellable nonwoven fabric 17a. This prevents the pressure between the spiral portion 63 and the spiral ridge portion 7a from increasing excessively, thereby preventing damage to the conversion adaptor 60a and the inner connector 1a.

[0097] On the other hand, as shown in FIG. 11(b), the groove 13a has partition walls 9a formed at a predetermined interval. In the area directly above the partition wall 9a, the water-swellable nonwoven fabric 17a abuts against the upper surface of the partition wall 9a and cannot escape into the groove 13a, but as shown in the figure, the partition wall 9a is thin and the water-swellable nonwoven fabric has moderate deformability, so the water-swellable nonwoven fabric 17a can escape into the space before and after the partition wall 9a. At this time, the upper part of the partition wall 9a is blocked by the water-swellable nonwoven fabric 17a, so that the water that permeates through the groove 13a can be stopped at the position of the partition wall 9a. At this time, the water-swellable nonwoven fabric 17a that has absorbed water and gelled is in a material form intermediate between solid and liquid, and has moderate viscosity and deformability, so it is easy to move and deform. Therefore, the water-swellable nonwoven fabric 17a that has absorbed water and gelled can easily deform and move into the space formed by the grooves 13a at the front and rear of the partition wall 9a. Furthermore, the water-swellable nonwoven fabric 17a that has absorbed water and gelled shrinks and returns to its pre-swelled state when it dries. Furthermore, because some of the fibers that make up the water-swellable nonwoven fabric 17a are bonded to each other by a binder resin, it easily returns to its original state when it dries.

[0098] Here, the ridges 11a are pressed toward the grooves 13a due to swelling of the water-swellable nonwoven fabric 17a arranged on the outer periphery of the ridges 11a. Therefore, the ridges 11a receive a force in a direction in which they collapse. However, because the partition walls 9a are arranged at a predetermined interval, the partition walls 9a increase the rigidity of the ridges 11a, and the collapse of the ridges 11a can be suppressed. In addition, the excessively swollen and gelled water-swellable nonwoven fabric 17a is deformed and moved to the grooves 13a between the ridges 11a, and the water-swellable nonwoven fabric 17a that has moved to the grooves 13a is deformed by the stress of the water-swellable nonwoven fabric 17a arranged on the outer periphery of the ridges 11a, thereby alleviating the stress caused by the swelling of the water-swellable nonwoven fabric 17a arranged on the outer periphery of the ridges 11a.

[0099] In particular, as shown in FIG. 2(a), in the cross section of the two peaks 11a, the angle θo of the outer ridge of each peak 11a with respect to the tube axis direction is smaller than the angle θi of the inner ridge. Also, the length Y of the outer support part of the base of each peak 11a divided by a line O that passes through the apex of each peak 11a and is perpendicular to the tube axis direction is longer than the length Z of the inner support part. Therefore, the peaks 11a are easily deformed inward by the force from the outer periphery of the peaks 11a. However, this deformation can be suppressed by the partition wall 9a. Also, since the tip of the inner ridge is curved, the swollen and gelled water-swellable nonwoven fabric 17a is easily inserted between the peaks 11a.

[0100] (Double-wall rectangular conduit Connection structure for hand hole via conversion adapter (Construction process) Figures 12(a) and 12(b) show double-wall rectangular conduits. and hand hole connection structure 12(a), a conversion adapter 60a is attached to the handhole 23 using the inner connector 1a and the outer connector 1b. At this time, since the spiral part 63 of the conversion adapter 60a has the same structure as the spiral conduit 121, the conversion adapter 60a can be connected to the handhole 23 in the same procedure as the spiral conduit 121. Therefore, a connection structure 20a in which the conversion adapter 60a and the handhole 23 are connected can be obtained.

[0101] From this state, as shown in Fig. 12(a), the male joint portion 41 of the double-walled rectangular conduit 40 is inserted into the female joint portion 61a of the conversion adaptor 60a (arrow J in the figure). As described above, the male joint portion 41 and the female joint portion 61a are connectable. Therefore, as shown in Fig. 12(b), the double-walled rectangular conduit 40 is connected to the joint portion of the conversion adaptor 60a, and the double-walled rectangular conduit 40 is connected to the hand hole 23 via the conversion adaptor 60a. and hand hole connection structure That is, according to the connection structure 20a, the spiral part 63 attached to the handhole 23 using the inner connector 1a and the outer connector 1b can be converted into a joint part with the double-wall rectangular electric conduit 40, and the double-wall rectangular electric conduit 40 can be connected.

[0102] 9(b) is a diagram showing a conversion adaptor 60b. The conversion adaptor 60b has a spiral portion 63 formed on one side and a male joint portion 61b formed on the other side as a joint portion with the double-walled rectangular electric conduit 40. It differs from FIG. 9(a) in that the joint portion is changed from the female joint portion 61a to the male joint portion 61b.

[0103] As with the conversion adapter 60a, the inner connector 1a and the outer connector 1b can be screwed into the spiral portion 63 of the conversion adapter 60b. The male joint portion 61b has the same form as the male joint portion 41 of the double-wall rectangular electric conduit 40 described above. Therefore, the male joint portion 61b of the conversion adapter 60b is composed of a retaining ring 47 and a rubber packing 45 attached at a predetermined position. The female joint portion 43 of the double-wall rectangular electric conduit 40 can be connected to the male joint portion 61b. That is, the conversion adapter 60b can also be converted from the spiral portion 63 in which the inner connector 1a and the outer connector 1b can be arranged to the male joint portion 61b, which is a joint portion with the double-wall rectangular electric conduit 40.

[0104] 13(a) and 13(b) show a double-wall rectangular conduit using a conversion adapter 60b. and hand hole connection structure 13(a) is a diagram showing the construction process of the above-mentioned. First, in the same procedure as described above, the conversion adapter 60b is attached to the hand hole 23 using the inner connector 1a and the outer connector 1b, as shown in FIG. 13(a). By the above, a connection structure 20b in which the conversion adapter 60b and the hand hole 23 are connected can be obtained.

[0105] From this state, as shown in Fig. 13(a), the male joint part 61b of the conversion adaptor 60b is inserted into the female joint part 43 of the double-walled rectangular electric conduit 40 (arrow K in the figure). As described above, the female joint part 43 and the male joint part 61b are connectable. Therefore, as shown in Fig. 13(b), the double-walled rectangular electric conduit 40 is connected to the hand hole 23 via the conversion adaptor 60b. and hand hole connection structureIn this way, by using the connection structures 20a, 20b between the conversion adapters 60a, 60b and the hand hole 23 at least in part, it is possible to obtain a double-walled rectangular conduit 30c in which the double-walled rectangular conduit 40 is connected to the joints of the conversion adapters 60a, 60b by fitting thereto. and hand hole connection structure In this way, the conversion adapter may have the spiral portion 63 on one side and either the male joint portion 41 or the female joint portion 43 on the other side.

[0106] The connection structure between the conversion adaptors 60a, 60b and the hand hole 23 is not limited to the above example. For example, a structure in which another spiral electric conduit or other electric conduit such as a steel pipe or a PVC pipe is connected by a pipe joint to the end of the conversion adaptors 60a, 60b opposite to the connection part with the hand hole 23 may be used.

[0107] (Double wall square conduit and hand hole connection structure Length adjustment method) When the length of the double-walled rectangular conduit 40 is short, as shown in the upper right of FIG. 14 (arrow L in the figure), this conversion adapter 60a is used as is, and the spiral portion 63 is positioned so as to protrude from the outer connector 1b, and the double-walled rectangular conduit 40 is connected to the female joint portion 61a at a position protruding largely from the handhole 23.

[0108] On the other hand, if the double-walled rectangular conduit 40 is long, the excess length 65 of the spiral portion 63 is cut off as shown in the lower left of Fig. 14 (arrow M in the figure). Then, as shown in the lower right of Fig. 14 (arrow N in the figure), the conversion adapter 60a after cutting is connected to the outer surface of the wall portion 25 of the handhole 23 so that most of the spiral portion 63 is hidden by the outer connector 1b. In this way, the double-walled rectangular conduit Adjust the length of the connection structure between the hand hole and the This can be done by cutting off the excess length 65 of the conversion adaptor 60a.

[0109] The length of the spiral portion 63 of the conversion adapter 60a must be at least the sum of the thickness of the wall portion 25 of the hand hole 23 and the length of the tubular portion 3b of the outer connector 1b (and the tightening margin of the tubular portion 3b of the outer connector 1b). Here, the tightening margin is usually sufficient if it is 1 / 4 of the circumference of the spiral ridge portion. Also, since the inner connector 1a is simply screwed into the end of the conversion adapter 60a, the tightening margin is not necessary. Therefore, the minimum length required for the conversion adapter can be considered as the excess length, which is the length of the portion that exceeds the total length of the wall thickness of the hand hole 23, the length of the outer connector 1b in the pipe axis direction, and the tightening margin of the outer connector 1b. On the other hand, the length of the spiral portion 63 of the conversion adapter 60a is the minimum required length of the spiral portion 63 plus the excess portion 65 for length adjustment when connecting to the double-wall rectangular electric conduit 40 described above.

[0110] As described above, according to this embodiment, the cross-sectional shapes of the helical ridges 7a, 7b of the inner connector 1a and the outer connector 1b in the direction parallel to the pipe axis direction are each composed of two ridges 11a, 11b that face each other at a predetermined distance, and grooves 13a, 13b are formed between the facing ridges 11a, 11b. Therefore, when the water-swellable nonwoven fabrics 17a, 17b arranged to cover the helical ridges 7a, 7b swell, the swollen and gelled water-swellable nonwoven fabric can be released into the grooves 13a, 13b. Therefore, excessive stress between the conversion adapters 60a, 60b and each connector can be relieved, and damage to the members can be suppressed.

[0111] Here, the water-swellable nonwoven fabric absorbs water, swells, and gels. In polymer chemistry, gels are defined as polymers with a three-dimensional network structure that are insoluble in solvents, and their swollen bodies. Crosslinked polymers with a three-dimensional network structure swell due to their interaction with the solvent, but because they have a crosslinked structure, they exhibit limited swelling. The degree of swelling depends on the crosslink density, and the higher the crosslink density, the smaller the swelling. In addition, a swollen gel is a substance form between a liquid and a solid, and by controlling its chemical composition and various factors, it can be changed from a viscous liquid to a state close to a solid, to a state with viscosity and moderate deformability. Therefore, by swelling the water-swellable nonwoven fabric to gel, it is possible to ensure water-stopping properties and release excess stress at the same time. Here, gelation is brought about by a crosslinked structure, but the generation of the crosslinked structure does not necessarily have to be caused by a crosslinked structure, and it can also be caused by a secondary bonding force between specific units of different molecular chains, such as hydrogen bonds. Furthermore, a cross-linked polymer having a swollen and gelled three-dimensional network structure can shrink and return to its original state when dried.

[0112] In addition, partition walls 9a, 9b that connect the ridges 11a, 11b and are substantially parallel to the tube axis direction are formed at a predetermined interval so as to close the grooves 13a, 13b. This makes it possible to prevent the grooves 13a, 13b from becoming an infiltration path. Furthermore, by providing the partition walls 9a, 9b that connect the two ridges 11a, 11b, the rigidity of the two ridges 11a, 11b can be increased, and deformation of the ridges 11a, 11b so as to fall toward the grooves 13a, 13b can be prevented.

[0113] In particular, the partition walls 9a, 9b are arranged at intervals of 30° to 90° in the circumferential direction, so that the water-stopping effect and the rigidity-improving effect can be obtained more reliably. Here, the partition walls 9a, 9b are arranged at intervals of 30° to 90° because if the intervals are greater than 90°, it is difficult to obtain a uniform rigidity-improving effect in the circumferential direction, and the intervals are set to 30° or more because if the intervals are smaller than this, the rigidity-improving effect becomes excessive. In this way, by using the inner connector 1a and the outer connector 1b, it is possible to obtain the connection structures 20a, 20b that can ensure the water-stopping effect and suppress damage even in the case of the conversion adapters 60a, 60b with large diameters. Furthermore, it is possible to obtain a double-walled rectangular electric conduit using the connection structures 20a, 20b that can obtain the same effect. and hand hole connection structure 30b and 30c can be obtained.

[0114] In this embodiment, an example using both the inner connector 1a and the outer connector 1b is shown, but at least one of them may be used. That is, the inner connector 1a or the outer connector 1b may be used as one connector, and the conventional inner connector 101a or the outer connector 101b may be used as the other connector, and these may be used in combination. For example, even if the inner connector 1a and the outer connector 101b are used in combination, the final route of water intrusion into the hand hole 23 or the conversion adapters 60a and 60b can be reliably stopped, and damage to the inner connector 1a and the conversion adapters 60a and 60b screwed thereto can be prevented. In this way, by using at least one of the inner connector 1a or the outer connector 1b, the effect of this embodiment can be obtained in the connection part between the inner connector 1a or the outer connector 1b and the conversion adapters 60a and 60b.

[0115] In addition, by connecting conversion adapters 60 a and 60 b to the handhole 23 , the double-walled rectangular conduit 40 can be connected to the handhole 23 .

[0116] In this case, by forming an extra length 65 in advance on the spiral portion 63 of the conversion adapters 60a and 60b, and hand hole connection structureThe length can be easily adjusted.

[0117] Although the embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention is not limited to the above-described embodiment. It is clear that a person skilled in the art can think of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0118] 1a, 1aa...Inner connector 1b: Outer connector 3a, 3b……Cylindrical part 5a, 5b...Flange portion 7a, 7b....Spiral mountain portion 9a, 9b………Partition wall 11a, 11b………Yamabe 13a, 13b……Groove 15a, 15b………Rubber packing 17a, 17b……Water-swellable nonwoven fabric 20, 20a, 20b... Connection structure 23………Hand hole (branch manhole) 24...Through hole 25……Wall part 30b, 30c...Double wall square conduit and hand hole connection structure 40……Double wall square conduit 41... Male joint 43………Female joint part 45………Rubber packing 46……Claw part 47………Prevention ring 48...Slide guide 49……Small diameter part 50...Regulatory department 51...Large diameter section 52...Slope section 53: Ring fitting 54... Cylindrical section 57……Outer pipe 59……Inner tube 60a, 60b... Conversion adapter 61a………Male joint part 61b...Female joint part 63……Spiral part 65……Extra length 101a………Inner connector 101b: Outer connector 107a, 107b... Spiral mountain portion 117a, 117b……Water-swellable nonwoven fabric 121……Spiral conduit 123………Hand hole 124...Through hole 125……Wall part

Claims

1. A connection structure between a double-wall rectangular conduit and a hand hole, Double-wall rectangular conduit; Hand holes and A conversion adapter to be connected to the double-wall rectangular conduit; an inner connector and an outer connector for connecting the conversion adapter to the hand hole; having The double-wall rectangular conduit is composed of an outer tube and a straight inner tube disposed inside the outer tube, In the double-wall rectangular conduit, the outer tube is composed of a large diameter portion and a small diameter portion, and the outer surface of the inner tube is fused to the inner surface of the outer tube and the small diameter portion, The double-wall rectangular conduit is connected to the hand hole via the conversion adapter, the conversion adapter is capable of converting a spiral portion attached to the handhole into a joint portion of the double-wall rectangular conduit using the inner connector and the outer connector; the conversion adapter is composed of the spiral portion formed on one side and a joint portion formed on the other side with the double-wall rectangular conduit, The inner connector and the outer connector each have a generally T-shaped cross section, and each have a cylindrical portion having a helical ridge portion, and a flange portion at one end of the cylindrical portion, the flange portion expanding in diameter at a generally right angle from a tube end of the cylindrical portion, a water-swellable nonwoven fabric is provided on an outer peripheral surface of the tubular portion of the inner connector, and a rubber packing and a water-swellable nonwoven fabric are attached in this order to an inner surface of the flange portion of the inner connector; a water-swellable nonwoven fabric is provided on an inner peripheral surface of the tubular portion of the outer connector, and a rubber packing and a water-swellable nonwoven fabric are attached in this order to an outer surface of the flange portion of the outer connector; the inner connector is screwed onto an inner circumferential surface of the end of the spiral portion, and the water-swellable nonwoven fabric on the inner surface of the flange portion of the inner connector abuts against an inner wall surface of the hand hole; the outer connector is screwed onto the outer peripheral surface of the spiral portion, and the water-swellable nonwoven fabric on the outer surface of the flange portion of the outer connector abuts against the outer wall surface of the hand hole; a wall portion of the hand hole is sandwiched between the flange portion of the inner connector and the flange portion of the outer connector, a cross-sectional shape of the spiral ridge portion of the cylindrical portion of at least one of the inner connector or the outer connector in a direction parallel to the pipe axis direction consists of two opposing ridges spaced a predetermined distance from each other, partition walls connecting the ridges and extending approximately parallel to the pipe axis direction are formed at predetermined intervals so as to close the grooves formed between the opposing ridges, the water-swellable nonwoven fabric provided on the cylindrical portion is formed so as to straddle and cover an upper portion of the grooves formed between the ridges, and the double-walled rectangular conduit is connected to the joint portion of the conversion adapter.

2. 2. The connection structure between a double-walled rectangular conduit and a handhole according to claim 1, characterized in that the double-walled rectangular conduit comprises a male joint portion and a female joint portion formed at both ends of the outer tube, respectively, and a main body portion connecting the male joint portion and the female joint portion, the main body portion being formed by alternatingly repeating the small diameter portion having a substantially cylindrical shape and the large diameter portion having a substantially rectangular shape larger than the small diameter portion, and the straight inner tube is substantially cylindrical in shape.

3. 3. The connection structure between a double-walled rectangular conduit and a handhole as described in claim 2, characterized in that, in the male joint portion, the inner tube is either housed and covered inside the male joint portion or is integrated with the inner surface near the tip of the male joint portion, and in the female joint portion, the inner tube is cut so as not to impede connection with the male joint portion.

4. 4. The connection structure between a double-walled rectangular conduit and a handhole according to claim 1, wherein the cross-sectional shape of the helical ridge portion of the tubular portion of the inner connector and the outer connector in a direction parallel to the pipe axis direction is composed of two ridge portions opposed to each other at a predetermined distance from each other, partition walls connecting the ridge portions and extending approximately parallel to the pipe axis direction are formed at predetermined intervals so as to close the grooves formed between the opposing ridge portions, and the water-swellable nonwoven fabric provided on the tubular portion is formed so as to straddle and cover the upper part of the grooves formed between the ridge portions.

5. The connection structure between a double-walled rectangular electric conduit and a handhole according to any one of claims 1 to 4, characterized in that the partition walls parallel to the pipe axis direction connecting the helical ridges of the inner connector and the outer connector are provided at predetermined intervals of 30° to 90° in the circumferential direction of the helical ridges.

6. 5. The connection structure between a double-walled rectangular conduit and a handhole according to claim 1, wherein the partition walls parallel to the pipe axis direction connecting the ridges of the spiral ridges of the inner connector and the outer connector are formed in a plurality of substantially parallel positions at predetermined intervals in a direction perpendicular to the pipe axis direction and substantially perpendicular to a center line at a predetermined position.

7. A connection structure between a double-walled rectangular conduit and a handhole as described in claim 6, characterized in that the partition walls formed in a plurality of approximately parallel rows at the predetermined intervals on the inner connector and the outer connector are formed in a direction perpendicular to the pipe axial direction at a predetermined interval between 1 / 2 to 1 / 5 of the radius above and below the center line position.

8. The joint portion of the conversion adapter is composed of a female joint portion of a rectangular electric conduit, 8. A connection structure between a double-walled rectangular electric conduit and a handhole as described in any one of claims 1 to 7, characterized in that the female joint portion is fitted with a male joint portion consisting of a substantially C-shaped or annular anti-slip ring attached at a predetermined position and an annular rubber packing.

9. The joint portion of the conversion adapter is composed of a male joint portion of a rectangular electric conduit, The connection structure between a double-walled rectangular electric conduit and a handhole as described in any one of claims 1 to 7, characterized in that the male joint portion is composed of an approximately C-shaped or annular anti-slip ring attached to a predetermined position of the male joint portion and an annular rubber packing.

10. 10. The connection structure between a double-walled rectangular conduit and a handhole as described in any one of claims 1 to 9, wherein the conversion adapter has an excess length in the spiral portion of the conversion adapter for adjusting the length of the conversion adapter.

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