JP2002165322A - Small duct sleeve - Google Patents

Abstract

(57) [Problem] To provide a small-sized duct sleeve capable of reducing the number of types of duct sleeves by half and improving the insertability of an underground pipe into the duct sleeve. A small duct sleeve (10) for connecting an underground pipe (2) to a special part (1) such as a handhole or a manhole in an electric wire joint groove or the like, which is buried and fixed to the end wall (2) of the special part (1). A fixed portion 11 extending from the fixed portion 11 to the outside of the special portion 1 and having a telescopic guide portion 12 in which an underground pipe 2 is internally fitted so as to be movable in the pipe axis direction. A substantially trumpet-shaped guide surface 14 is formed on an inner surface of the base 11 on the inner side of the special portion 1 of the portion 11, and the thickness of the inner surface of the extendable guide 12 is partially reduced.
An annular groove 19 for mounting the seal ring was formed at an angle with respect to the plane perpendicular to the axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized duct sleeve for connecting a special part such as a handhole or a manhole to an underground pipe in an electric wire joint groove or the like.

[0002]

2. Description of the Related Art An electric wire joint groove (CCBox) is for realizing underground burying of electric wires such as electric power cables, communication cables, and cables for road managers.
Special parts (connecting parts, branching parts), pipes, and ground equipment are categorized and defined. Its features are: [1] Compared to the conventional cab (cable box) method, [1] Change from concrete U-shaped grooves to multi-story pipes, [2] Compactness with narrower spacing between pipes The aim is to reduce the price (about 1/3 of the cab method) by using such methods as burying in a shallow layer, and [3] putting the electric wires together underground.

As a duct sleeve for connecting the above-mentioned special part and the underground pipe, for example, a duct sleeve having a structure as shown in FIG. 6 is widely used. This duct sleeve 10
Numeral 0 denotes a substantially cylindrical shape formed by the first cylindrical portion 101 and the second cylindrical portion 102, and the second cylindrical portion 102 is configured to have a larger diameter than the first cylindrical portion 101. The base end portion of the first cylindrical portion 101 is fixed to the end wall portion 111 of the special portion 110 so as to penetrate therethrough.
An end of an underground pipe 112 is fitted inside the cylinder 102 so as to be movable in the pipe axis direction, and a substantially trumpet-shaped guide surface 103 is formed at one end of the first cylinder 101. Various cables (not shown) mounted on the guide surface 112
3 is guided into the special part 110 so as not to be damaged. A large-diameter portion 104 bulging outward with almost no change in wall thickness is formed at an intermediate portion of the second cylindrical portion 102, and a seal ring 113 is formed on the inner surface side of the large-diameter portion 104.
Is installed, and the underground pipe 1 is inserted through the seal ring 113.
12 and the special part 110
Intrusion of rainwater etc. into the inside is prevented.

A plurality of underground pipes 112 are usually connected to the special part 110. The center of adjacent duct sleeves 100 is arranged so that the plurality of underground pipes 112 are compactly arranged. The distance L is set to 175 mm in the Kanto Regional Construction Bureau of the Ministry of Construction. However, power pipes used in the Kanto region mainly consist of φ130
(Inner diameter 130mm, outer diameter 148mm) are used,
Such a power pipe is connected to the existing duct sleeve 1 shown in FIG.
00, the seal ring 113 to be mounted
Including the thickness of the large diameter portion 104, the outer diameter D2 of the large diameter portion 104 is 183 m.
m, and the large-diameter portions 104 interfere with each other, so that there is a problem that the duct sleeve 100 cannot be arranged adjacently. Therefore, usually, as shown in FIG. 6, two types of duct sleeves 100 in which the position of the large-diameter portion 104 is shifted in the pipe axis direction are used.
By arranging 00 alternately, the large-diameter portions 104 of the adjacent duct sleeves 100 are configured not to interfere with each other.

However, when two types of short and long duct sleeves are used, [1] the production cost of the duct sleeve is relatively high, [2] the inventory management is complicated, and [3] special. There is a problem that the arrangement of a plurality of duct sleeves to be attached to a part is easily mistaken. Also,
[4] The positioning of the duct sleeve is performed by measuring the dimensions, but the work is complicated and there is a possibility of measurement error, etc. [5] Because the length of the duct sleeve is different, Since all duct sleeves to be installed on special parts cannot be held together and are currently generally fixed individually with bolts and nuts for each duct sleeve,
There are also problems such as the complicated construction work and the increase in the number of work steps.

Accordingly, the present applicant has disclosed in Japanese Patent Laid-Open No. 2000-50
As described in Japanese Patent Publication No. 480, a bell mouth buried and fixed in a penetrating portion of a special wall, and a telescopic sleeve fixed inside the bell mouth and fixed inside the end of an underground pipe. Proposed an assembled duct sleeve consisting of two parts, a telescopic sleeve that movably accommodates the part, and having a thinner wall and an annular groove for mounting a seal ring on the inner surface near the tip of the telescopic sleeve. .

[0007]

In the assembled duct sleeve described in the above publication, one kind of duct sleeve can be used by setting the outer diameter of the duct sleeve to be smaller than the duct sleeve installation interval (175 mm). Can be solved. However, also in this assembled duct sleeve, as in the case of the conventional assembled duct sleeve, the annular groove for mounting the seal ring is arranged orthogonally to the axis of the duct sleeve, so that the underground of the duct sleeve is When the buried pipe is inserted, it is necessary to insert the end of the buried pipe at the same time around the entire circumference of the seal ring, and there is a problem that the insertion resistance is significantly increased.

Further, in the assembled duct sleeve described in the above publication, since the duct sleeve is composed of two parts, a bell mouth and a telescopic sleeve, at least two molds are required to manufacture them. There have been problems such as an increase in the equipment economic burden and an increase in the manufacturing cost, and the necessity of bonding the bell mouth and the telescopic sleeve at the site, which complicates the operation.

An object of the present invention is to provide a small-sized duct sleeve capable of reducing the number of types of duct sleeves by half and improving the insertability of an underground pipe into the duct sleeve.

[0010]

SUMMARY OF THE INVENTION A small duct sleeve according to the present invention is a small duct sleeve for connecting an underground pipe to a special part such as a handhole or a manhole in an electric wire joint groove or the like. A fixed portion that is embedded and fixed in the wall portion in a penetrating manner, and a telescopic guide portion that extends from the fixed portion to the outside of the special portion, and into which an underground pipe is internally fitted movably in the pipe axis direction. Having a substantially trumpet-shaped guide surface extending outward on the base end inner surface of the special portion inside the fixed portion, and partially reducing the thickness of the inner surface portion of the telescopic guide portion,
An annular groove for mounting a seal ring is formed at an angle to a plane orthogonal to the axis of the telescopic guide.

In this small-sized duct sleeve, an annular groove for mounting the seal ring is formed by partially reducing the thickness of the inner surface of the expansion and contraction guide portion. There is no need to increase the outer diameter. That is, since it is not necessary to set the outer diameter of the mounting portion of the seal ring having the largest outer diameter of the duct sleeve to be large, even when one type of small duct sleeve having the same shape and the same size is used, It is possible to provide a plurality of these adjacent to the special wall.
In addition, the strength of the telescopic guide portion is slightly reduced in the portion where the annular groove is formed, but this annular groove may be formed near the tip of the telescopic guide portion where a large bending load hardly acts. Since the middle buried pipe is fitted inside,
Even if the strength is slightly reduced, there is no adverse effect such as breakage. In addition, since the annular groove for mounting the seal ring is provided at an angle with respect to the plane perpendicular to the axis of the telescopic guide, when inserting the underground pipe into the duct sleeve, sealing is performed at the tip of the underground pipe. While gradually expanding the ring, the underground pipe can be inserted into the seal ring, and the insertion resistance of the underground pipe into the duct sleeve can be reduced without lowering the sealing performance.

Here, it is preferable that the inclination angle α of the annular groove with respect to the plane orthogonal to the axis of the telescopic guide is set to 0 ° <α <60 °. In this case, the insertability of the underground pipe into the seal ring can be improved while preventing the annular groove from becoming large in the pipe axis direction.

Further, an insertion guide surface may be formed on the inner peripheral portion of the distal end of the telescopic guide portion, the diameter of the insertion guide surface increasing with increasing distance toward the distal end. In this case, when inserting the underground pipe into the duct sleeve, the tip of the underground pipe can be guided into the duct sleeve via the insertion guide surface, so that the underground pipe relative to the duct sleeve can be guided. The insertability can be improved.

Further, the duct sleeve may be constituted by a substantially cylindrical one-piece part. In this case, it is possible to mold the duct sleeve with one type of mold, so that the equipment economic load can be reduced and the manufacturing cost can be reduced. In addition, since it is a single component, there is no need to assemble it using an adhesive or the like at the site, so that the construction work at the site can be reduced, and the storage and transportability can be improved.

In order to increase the mounting strength of the duct sleeve to the special part, at least one rotation restricting part for restricting the rotation of the duct sleeve with respect to the special part is formed on the outer surface of the fixing part, or the outer diameter of the fixing part is reduced. Is preferably partially reduced in diameter to form a movement restricting portion for restricting the movement of the duct sleeve relative to the special portion in the pipe axis direction.

In addition, it is preferable to form a positioning projection for setting the interval between the adjacently disposed duct sleeves at the base end of the fixed portion so that the duct sleeve can be easily installed at an appropriate position of the special portion.

Furthermore, the duct sleeve is made as short as possible while ensuring sufficient length of expansion and contraction of the underground pipe, and the length of protrusion from the special part is made as short as possible. It is preferable that the tip of the middle buried pipe is configured to be insertable.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of an electric wire common groove. In a special part 1 such as a manhole or a handhole, a plurality (two in the figure) of underground pipes in which a plurality of power transmission and distribution cables and the like are bundled and installed. 2 is connected via a small duct sleeve 10 fixed to the special portion 1 so as to be movable in the tube axis direction.

As shown in FIGS. 1 and 2, the duct sleeve 10 is made up of one part, and has a substantially cylindrical fixing portion 11 penetratingly fixed to the end wall portion 3 of the special portion 1, and a fixing portion. And a substantially cylindrical expansion / contraction guide portion 12 extending outward from the base member 11 and integrally formed using a synthetic resin material, a metal material, or the like.
The duct sleeve 10 of this embodiment is integrally formed by injection molding using a synthetic resin material.

A square hole-shaped through hole 4 is formed in the wall 3 of the special part 1.
The mortar 5 is filled in the through-hole 4 with the required number of duct sleeves 10 positioned and set in the through-hole 4, and the fixing portion 11 is embedded in the end wall portion 3, so that a special It is fixed to the section 1. The underground pipe 2 is connected to the special part 1 by fitting its end inside the telescopic guide 12 movably in the pipe axis direction.

A bell mouth portion 13 having a substantially trumpet-shaped guide surface 14 extending outward toward the base end is formed at the base end of the fixed portion 11 (the end on the inner side of the special portion 1). The inner diameter d1 on the distal end side of the guide surface 14 is set to be substantially the same as the inner diameter d2 of the underground pipe 2, and the power transmission / distribution cables and the like in the underground pipe 2 are smoothly introduced into the special part 1 via the guide surface 14. It is configured to be introduced into. The inside diameter d3 of the portion of the duct sleeve 10 other than the bell mouth portion 13 is set to be substantially the same over the entire length, and the outside diameter D1 of the underground pipe 2 is set.
The bell mouth portion 13 is formed with a step portion 15 at the tip end side thereof, and the underground pipe 2 is fixed to the duct sleeve 10 until the tip end portion thereof is engaged with the step portion 15. It is configured so that it can be inserted into. In this way, by configuring the underground pipe 2 to be insertable into the fixing portion 11, the overall length of the duct sleeve 10 is set short while ensuring a sufficient length of expansion and contraction of the underground pipe 2. Thus, the projecting length of the duct sleeve 10 from the special part 1 is shortened, so that the transportability and storage property of the special part 1 and handleability during construction can be improved. For example, as shown in FIG. 1, the duct sleeve 10 is protruded to the outside by a length excluding the length of the fixed portion 11 embedded in the end wall portion 3. In addition, since the step portion 15 is provided in a direction substantially orthogonal to the pipe axis of the duct sleeve 10, when the underground pipe 2 is inserted into the duct sleeve 10, a fixed length Is inserted in a state where the spacing setting tool (not shown) is arranged, and the spacing setting tool is sandwiched between the step portion 15 and the tip of the underground pipe 2 so that the insertion length of the underground pipe 2 is properly adjusted. And the insertion length of the underground pipe 2 can be easily set, and the workability can be improved. As the interval setting tool, a strip-shaped or rod-shaped member that can abut on the step portion 15 and the tip end of the underground pipe 2, a member having an arc-shaped cross section along the inner surface of the fixed portion 11, or the like can be used. is there. Further, such an interval setting tool is removed from the duct sleeve 10 after the insertion of the underground pipe 2. It can also be used for the next construction.

A movement restricting portion 16 having a small outer diameter and a small thickness is formed at an intermediate portion of the fixed portion 11, and the movement restricting portion 16 is embedded in the end wall portion 3, so that the special portion 1 is formed. The movement of the duct sleeve 10 in the pipe axis direction with respect to the direction is restricted. Further, by forming such a movement restricting portion 16, a sufficient amount of mortar 5 can be filled between the fixing portions 11 of the adjacent duct sleeves 10, and
Since it is possible to arrange reinforcing bars between the fixing portions 11, it is preferable to increase the mounting strength of the duct sleeve 10 to the rear wall portion 3. However, as long as the movement restricting portion 16 is disposed so as to be buried in the rear wall portion 3, its shape, size, number, arrangement position, and the like can be arbitrarily set. For example, it is possible to form at regular intervals in the circumferential direction, arbitrarily set the width in the tube axis direction, and arbitrarily set the position in the tube axis direction.

A rotation restricting portion 17 is provided on the outer peripheral portion in the vicinity of the front end of the fixed portion 11 at four equally-circumferential positions. Have been. In the present embodiment, the rotation restricting portion 17 is formed in the movement restricting portion 16 so that the outer end of the rotation restricting portion 17 does not protrude outward. However, the shape, size, number, arrangement position, and the like of the rotation regulating portion 17 can be arbitrarily set as long as the portion is buried in the rear wall portion 3.

A large diameter portion 1 is provided at the tip of the duct sleeve 10.
8 is formed, and one annular groove 19 is formed on the inner surface side of the large-diameter portion 18 by partially reducing the wall thickness. In both annular grooves 19, a seal which presses against the outer surface of the underground pipe 2 is formed. Each of the rings 6 is mounted. And the large-diameter portion 18
The annular groove 19 is formed by partially reducing the thickness on the inner surface side of
The outer diameter D2 of the large-diameter portion 18 having the largest outer diameter dimension in the duct sleeve 10 is configured to be smaller than the center distance L of the duct sleeve 10 specified by the Kanto Regional Construction Bureau of the Ministry of Construction, so that it is adjacent. The same shape and the same size as the duct sleeve 10 can be adopted to reduce the production cost of the duct sleeve 10 and simplify inventory management, and different types of duct sleeves are erroneously attached to the special part 1. Such a problem can be reliably prevented.

In order to improve the insertability of the underground pipe 2 into the duct sleeve 10, an insertion guide surface 22 is formed at the distal end of the telescopic guide portion 12, the diameter of which increases toward the distal end. , Annular groove 19 is telescopic guide 1
2 with respect to the plane perpendicular to the axis. When the inclination angle α of the annular groove 19 is 60 ° or more, the duct sleeve 10 becomes large in the pipe axis direction.
0 ° <α <60 °, and more preferably 1 ° ≦ α ≦ 30 °. By providing the insertion guide surface 22, the tip of the underground pipe 2 is guided into the duct sleeve 10, and by providing the inclination angle α, the underground pipe 2 is inserted when the underground pipe 2 is inserted. Are simultaneously abutted against the seal ring 6 to prevent an increase in insertion resistance.

The number of the annular groove 19 and the number of the seal rings 6 provided in the large diameter portion 18 can be set to any number according to the use conditions such as the outer diameter of the underground pipe 2. In addition, the large diameter portion 18
Can be set at an arbitrary position in the pipe axis direction of the telescopic guide portion 12, but since the portion where the annular groove 19 is formed becomes thinner and the strength decreases, the It is preferable that the large-diameter portion 18 be disposed on the distal end side of the duct sleeve 10 so that a large bending moment does not act.

The seal ring 6 is composed of a general-purpose O-ring, and has an inner diameter slightly smaller than that of the underground pipe 2. In order to facilitate the insertion of the underground pipe 2 into the seal ring 6, the end of the underground pipe 2 is chamfered or rounded, and the end of the underground pipe 2 and its end are provided. It is preferable to apply a lubricant to the vicinity and the seal ring 6.

The outer shape of the base end of the duct sleeve 10 may be substantially circular when viewed from the front. For example, as in a duct sleeve 10A shown in FIG. 3, positioning protrusions projecting outward at four locations in the circumferential direction. 4A, the positioning projections 20 of the adjacent duct sleeves 10A are formed as shown in FIG.
Abutting the adjacent duct sleeves 10
If the center distance L between A is set to an appropriate value,
The work of assembling the duct sleeve 10A to the special part 1 can be remarkably simplified. However, the shape of the positioning projection 20 can be set arbitrarily. For example, as in a duct sleeve 10B shown in FIG. 4B, an octagonal positioning projection 21 may be formed at the base end so as to protrude. Alternatively, the base portion may be formed so as to protrude so as to have a square shape. Further, a configuration may be adopted in which a part of the positioning protrusion of the adjacent duct sleeve is fitted into the concave and convex portions.

In this embodiment, the duct sleeve in which the fixing portion 11 and the extension / contraction guide portion 12 are formed as an integral member has been described. However, as shown in FIG. 5, the fixing portion 11C and the extension / contraction guide portion 12C are separately provided. Duct sleeve 10C composed of members
The present invention can be similarly applied to In this case,
There is no need to handle the long assembling duct sleeve as it is on the special part, and the telescopic guide part 12C is removed until just before the special part 1 is constructed on the site. Since it can be handled in the attached state, contact between the fixed portion 11C and another object can be avoided as much as possible, and even if it comes into contact with another object, it is possible to prevent a large rotational moment from acting on the base end portion of the fixed portion 11C. . For this reason, when assembling the fixing portion 11C to the special portion 1, the displacement of the fixing portion 11C due to contact with other objects can be prevented before the mortar solidifies, and the fixing portion can be fixed by small fixing means. 11C can be firmly fixed. Further, when transporting or installing the special part 1 to which the fixing part 11C is assembled, damage to the fixing part 11C and falling off from the special part 1 due to contact with other objects can be effectively prevented, and compactness can be achieved. Can be stored or transported.

Next, a performance test of the duct sleeve 10 will be described. An underground pipe having an outer diameter of 148 mm is used, and a seal ring 6 having a thickness of 7 mm is used.
A rubber ring having an inner diameter of about 144 mm at the time of installation was used. Then, the inclination angle α of the annular groove 19 with respect to the plane orthogonal to the axis of the duct sleeve 10 is 0 °, 1.9 °, 3.9 °,
For the case of 5.8 °, the insertion resistance was measured for the case where the lubricant was applied and for the case where the lubricant was not applied,
The results as shown in Table 1 were obtained.

[0031]

[Table 1]

As can be seen from Table 1, when the lubricating material is used, the insertion load is reduced by about 6 to 10 times as compared with the case where the lubricating material is not used, and the insertability is remarkably improved. I understand. In addition, it can be seen that the larger the inclination angle α is set, the smaller the insertion load becomes. In particular, when using a sliding material, α = 1.9 ° to 3.9 °
, The insertion load greatly decreases, and if α exceeds 3.9 °, the amount of decrease in the insertion load becomes small, so that the inclination angle α
Is preferably set to about 4 °.

[0033]

According to the small duct sleeve of the present invention, the seal ring has a simple structure in which the thickness of the expansion and contraction guide portion is partially reduced to form an annular groove for mounting the seal ring. It is possible to prevent the outer diameter of the duct sleeve from increasing in the mounting portion, and it is not necessary to use two types of duct sleeves even when the duct sleeve is disposed adjacent to the special portion. For this reason, the same shape and the same size can be used as the multiple duct sleeves to be assembled to the special part, reducing the production cost of the duct sleeve, simplifying the inventory management, and making It is also possible to reliably prevent an installation error in which the duct sleeves are installed in a different arrangement. In addition, when the duct sleeve is applied to the end wall of the duct sleeve, a plurality of duct sleeves can be collectively installed, so that the work for temporarily fixing the positioning can be greatly simplified.

Even if the seal ring is changed from a conventional rubber ring to an O-ring, sufficient sealing performance can be ensured. In addition, the strength of the telescopic guide portion is slightly reduced in the portion where the annular groove is formed, but this annular groove may be formed near the tip of the telescopic guide portion where a large bending load hardly acts. Since the middle buried pipe is fitted inside,
Even if the strength is slightly reduced, there is no adverse effect such as breakage.

Further, since the annular groove for mounting the seal ring is provided at an angle with respect to the plane perpendicular to the axis of the telescopic guide, the tip of the underground pipe is inserted when the underground pipe is inserted into the duct sleeve. It is possible to insert the underground pipe into the seal ring while gradually expanding the seal ring at the part, and the insertability of the underground pipe can be remarkably improved.

When the inclination angle α of the annular groove with respect to the plane perpendicular to the axis of the telescopic guide is set to 0 ° <α <60 °, the annular groove is prevented from becoming large in the pipe axis direction, and the ground relative to the seal ring is prevented. The insertability of the middle buried pipe can be improved.

When an insertion guide surface whose diameter increases toward the distal end is formed on the inner peripheral portion of the distal end of the telescopic guide portion, the insertion of the underground pipe into the duct sleeve can be improved.

When the duct sleeve is formed of one substantially cylindrical part, it becomes possible to mold the duct sleeve with one type of mold, and it is possible to reduce the economical burden on equipment and
Production costs can be reduced. In addition, since it is a single component, there is no need to assemble it using an adhesive or the like at the site, so that the construction work at the site can be reduced, and the storage and transportability can be improved.

At least one rotation restricting portion for restricting the rotation of the duct sleeve with respect to the special portion is formed on the outer surface of the fixed portion, or the outer diameter of the fixed portion is partially reduced to reduce the diameter of the duct sleeve with respect to the special portion. By forming a movement restricting portion for restricting the movement in the pipe axis direction, the mounting strength of the duct sleeve to the special portion can be improved.

Further, when a positioning projection for setting the interval between the adjacently arranged duct sleeves is formed at the base end of the fixed portion, the duct sleeve can be easily positioned at an appropriate position of the special portion when the duct sleeve is applied to the special portion. Temporary fixing becomes possible, and the work for temporarily fixing the duct sleeve can be remarkably reduced.

Furthermore, if the tip of the underground pipe is configured to be insertable into the fixed part, the duct sleeve can be made as short as possible while ensuring a sufficient length of expansion and contraction of the underground pipe so that the special part can be removed. The length of the protrusion can be set as short as possible, and the transportability and storage performance of the special part to which the duct sleeve is assembled, and the ease of handling during construction can be improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a main part of a special part using a small duct sleeve of the present invention.

2A is a front view of a duct sleeve, and FIG. 2B is a longitudinal sectional view of the duct sleeve.

FIG. 3 is a diagram corresponding to FIG. 2 of a duct sleeve having another configuration.

FIG. 4A is an explanatory view of an arrangement of the duct sleeve,
(B) is an explanatory view of an arrangement of a duct sleeve having another configuration.

FIG. 5 is a diagram corresponding to FIG. 1 of a duct sleeve having another configuration.

FIG. 6 is a longitudinal sectional view of a main part of a special part using a conventional duct sleeve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Special part 2 Underground pipe 3 Wife wall 4 Through hole 5 Mortar 6 Seal ring 10 Duct sleeve 11 Fixed part 12 Telescopic guide part 13 Bell mouth part 14 Guide surface 15 Step part 16 Movement regulation part 17 Rotation regulation part 18 Large Diameter part 19 Annular groove 10A Duct sleeve 20 Positioning projection 10B Duct sleeve 21 Positioning projection 22 Insertion guide surface 10C Duct sleeve 11C Fixed part 12C Telescopic guide part

Claims (8)

[Claims] 1. A small-sized duct sleeve for connecting an underground pipe to a special part such as a handhole or a manhole in an electric wire common groove or the like, and a fixed part buried and fixed in a penetrating shape to a special wall of the special part. A telescopic guide portion extending from the fixed portion to the outside of the special portion and having an underground pipe internally fitted therein so as to be movable in the pipe axis direction, and a base inside the special portion of the fixed portion. A substantially trumpet-shaped guide surface is formed on the inner surface of the end, and the thickness of the inner surface of the telescopic guide is partially reduced, and an angle is formed with respect to the plane perpendicular to the axis of the telescopic guide. A small duct sleeve having an annular groove for mounting a seal ring. 2. The small duct sleeve according to claim 1, wherein the inclination angle α of the annular groove with respect to the plane perpendicular to the axis of the telescopic guide is set to 0 ° <α <60 °. 3. An insertion guide surface whose diameter increases toward the distal end side is formed on an inner peripheral portion of the distal end of the telescopic guide portion.
Small duct sleeve as described. 4. The apparatus according to claim 1, wherein said part is formed of a substantially cylindrical part.
4. The small duct sleeve according to any one of claims 3 to 3. 5. The small duct sleeve according to claim 1, wherein at least one rotation restricting portion for restricting rotation of the duct sleeve with respect to the special portion is formed on an outer surface of the fixed portion. 6. A movement restricting portion for restricting a movement of a duct sleeve with respect to a special portion in a pipe axis direction by partially reducing an outer diameter of the fixing portion. Small duct sleeve according to the item. 7. The small-sized duct sleeve according to claim 1, wherein a positioning protrusion for setting an interval between adjacently arranged duct sleeves is formed at a base end of the fixed portion. 8. The small-sized duct sleeve according to claim 1, wherein a tip portion of an underground pipe is inserted into said fixed portion.