JP2000175327A - Leading cable by high-pressure air flow and conduit tube therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lead in a cable smoothly by a high-pressure air flow and facilitate installing a conduit tube with flexibility like a corrugated tube. SOLUTION: This conduit tube is formed so that the external layer of a plastic corrugated tube 1 and the internal layer of a plastic straight tube 2 may be closely brought into contact with each other at the minimum inner diameter part of the corrugated tube 1, the ratio of L1/L2 of the length L1 whose corrugated tube 1 and straight tube 2 are in close contact with each other and the length L2 of which the corrugated tube 1 and the straight tube 2 are apart from each other may be determined as 0.25-0.45, L2 may be determined as equal to 12 mm or lower, and the thickness of the straight tube may be determined as 1.0-3.0 mm. The external layer of the corrugated tube 1 is formed out of high-density polyethylene, and the internal straight tube 2 is formed out of low-density polyethylene whose density is 0.900-0.940. The internal layer of the straight tube 2 is formed out of a mixture whose lubricant 0.5-5.0 weight part is mixed into a low-density polyethylene 100 weight part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting a cable to a conduit by high-pressure air flow, and a conduit suitable for the method.

[0002]

2. Description of the Related Art Generally, when an electric cable or an optical cable is laid underground or laid indoors, a cable conduit is first used in order to protect the cable and facilitate replacement of the cable later. A method of laying a cable and drawing a cable into the cable is widely used.

[0003] As the electric conduit used for this, those made of plastics such as polyethylene, polypropylene and polyvinyl chloride, and those made of cast iron and ceramics are known. Used. Plastic conduits include straight pipes and corrugated pipes. Corrugated pipes are particularly flexible and easy to construct because of their good flexibility, and they are not easily crushed even when external pressure is applied. .

On the other hand, as a method of drawing a cable into a conduit, a rope (or wire) is previously passed through the conduit, a cable is connected to the rope, and the rope is pulled by human power or a winch. Recently, a method of passing cables through a high-pressure air flow without using a pull-in rope (air jet method) has been put to practical use. This method, along with feeding the high pressure air of about 10 kgf / cm ² from one end into the conduit, by feeding the cable endless belt feeding machine, those that wire-passing put the cable into the high pressure air flow to the conduit It is. According to this method, even when the conduit is laid for about 1 km, for example, 30
It is possible to connect cables in a matter of minutes, and it is attracting attention.

[0005]

As described above, there are straight pipes and corrugated pipes as described above. However, when cables are passed by high-pressure air flow, it is most preferable to use straight pipes as the conduit. preferable. The reason is that the straight pipe has a smooth inner surface so that the air flow can be kept smooth. On the other hand, when a corrugated pipe is used, the air flow becomes unstable due to the unevenness of the inner surface, which makes it difficult for air sent from the inlet end to the outlet end to escape. Because the cable extends in the longitudinal direction and meanders, it becomes difficult to pass the cable over a long distance. For this reason, the corrugated pipe has been unsuitable for cable passage by high-pressure air flow.

[0006] As described above, it is preferable to use a straight pipe in order to route a cable using a high-pressure air flow, but if the straight pipe is made thick enough to withstand the earth pressure, for example, it becomes flexible. The installation work is troublesome because the installation is almost eliminated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cable routing method capable of smoothly passing a cable by a high-pressure air flow using a flexible conduit such as a corrugated tube, and a suitable conduit. Is to provide.

[0008]

In order to achieve this object, the present invention provides a method for passing a cable while feeding high pressure air having a pressure of 5 kgf / cm ² or more from one end into a conduit.
As the electric conduit, as shown in FIG. 1, an outer plastic corrugated pipe 1 and an inner plastic straight pipe 2 are connected to the corrugated pipe 1.
Characterized in that a double-walled conduit tube closely contacted at the minimum inner diameter portion is used (claim 1).

When such a double-walled conduit is used, the strength and flexibility of the conduit can be obtained by the corrugated tube of the outer layer, the high-pressure air can be smoothly flowed by the straight tube of the inner layer, and It is possible to prevent the extension of the attachment pipe.
Note that the straight pipe portion only needs to have enough strength to prevent the elongation of the corrugated pipe portion, and therefore may be thinner than the corrugated pipe.

More specifically, as shown in FIG. 1, the double-walled electric conduit according to the present invention comprises an outer plastic corrugated pipe 1 and an inner plastic straight pipe 2 having a minimum inner diameter portion of the corrugated pipe 1. And the ratio L ₁ / L ₂ of the length L _{1 of the} portion where the corrugated tube 1 and the straight tube 2 are in close contact and the length L _{2 of the} portion where the corrugated tube 1 and the straight tube 2 are separated from each other. It was used as a 0.25~0.45, L ₂ 1
2 mm or less, and the thickness of the straight pipe 2 is 3.0 mm or less and 1.0 m
The thickness is set to exceed m.

The plastic straight pipe 2 of the inner layer is integrated (closely adhered) to the minimum inner diameter portion of the plastic corrugated pipe 1 of the outer layer by means such as heat fusion. Therefore, this double wall conduit has
A portion (portion of the length L ₁₎ of corrugated tube 1 and the straight pipe 2 are in close contact, a portion where the corrugated tube 1 and the straight tube 2 apart (the length L
Part ₂ ). In the present invention, the ratio L ₁ / L ₂ of the length of these portions is set to 0.25 to 0.45 first.
Requirements. This is for the following reason. That is, L ₁
When / L ₂ is less than 0.25, when a cable is routed by a high-pressure air flow, a phenomenon in which the double-walled conduit extends in the longitudinal direction due to the high-pressure air is likely to occur. , It becomes difficult to route cables. The L ₁ / L
_{If 2} is greater than 0.45, the flexibility of the conduit will be impaired, for example, when the double-wall conduit is drawn from a narrow manhole into a large-diameter outer tube such as a concrete trough, locally high bending When stress is applied, buckling or bending is likely to occur, and the workability is impaired.

In the present invention, the second requirement is that the thickness of the portion of the straight pipe 2 be 3.0 mm or less and more than 1.0 mm. This is for the following reason. That is, when the thickness of the straight pipe 2 is 1.0 mm or less, the whole pipe is stretched in the longitudinal direction when high-pressure air flows,
If the thickness is more than 3.0 mm, the flexibility will be impaired, which will not only hinder the work of pulling in from the manhole to the concrete trough, etc. is there. The corrugated pipe 1 can be made thicker than the straight pipe 2.

Further, in the present invention, the length L ₂ of the part (part that is not in close contact) between the corrugated pipe 1 and the straight pipe 2 is determined.
The third condition is that it is 12 mm or less. This is because if a non-contact portion larger than 12 mm exists locally, when the high-pressure air flows, only the non-contact portion extends in the longitudinal direction and the conduit tends to meander, and as a result, cable This is because a trouble occurs.

With the conduit constructed as described above,
It is possible to simultaneously satisfy the cable passing performance by the high-pressure air flow and the flexibility required for constructing the conduit. In order to further improve these two performances, high-density polyethylene is used as a constituent material of the corrugated pipe of the outer layer, and a density of 0.900 to 0.940 is used as a constituent material of the straight pipe of the inner layer.
It is preferable to use polyethylene (claim 3).

The reason why high-density polyethylene is used as a constituent material of the corrugated pipe of the outer layer is to reduce the occurrence of damage when the pipe is laid. Density 0.940 for the material of the inner straight pipe
The following polyethylene is used for the following reasons. Polyethylene with a density of 0.940 or less is more flexible than high-density polyethylene, so it is difficult to bend even when a double-walled conduit is wound around a drum, and can be wound around a small-diameter drum. Therefore, the transportation efficiency is increased and the cost can be reduced. However, if polyethylene with a lower density of less than 0.900 is used, when high-pressure air is sent into a double-walled conduit,
A phenomenon in which a portion of the straight pipe that is not in close contact with the corrugated pipe expands in the radial direction due to the pressure of air appears, and as a result, the performance of the cable is reduced, which is not preferable.

Further, in the conduit of the present invention, a lubricant such as a silicone oil such as dimethylpolysiloxane, a graft silicone resin or an oleic amide is used as a material for the inner layer straight pipe in an amount of 0.5 to 5.0 parts by weight based on 100 parts by weight of polyethylene.
It is preferable to use a mixture of parts by weight (claim 4).

When a mixture containing 0.5 part by weight or more of a lubricant is used, the friction with the cable is reduced, and it is possible to extend the possible distance of the cable. However, even if a mixture containing more than 5 parts by weight of a lubricant is used, the effect corresponding thereto is not exhibited. Therefore, the range of 0.5 to 5.0 parts by weight is preferable in consideration of the balance between the cable passing performance and the cost.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The inner diameter is 50mm and the outer diameter is 65mm.
(Examples of the present invention) and double-walled conduit tubes shown in Table 2 (Reference Example) were produced, and the following performances (1) to (4) were evaluated. FIG. 2 shows dimensions of details other than Tables 1 and 2. The thickness of the corrugated pipe is 3 mm. The outer corrugated tube was made of high density polyethylene with a density of 0.955.

Cable Passage Test Using High-Pressure Air Flow One double-walled conduit having a length of 10 m was connected with an airtight pipe joint to lay a 1000 m-long conduit. This line has 200m, 350m, 500m, 650m and 800m from one end
At a point m, a curved part having a radius of curvature of 5 m and 90 ° was provided. 10kg from one end of the pipeline using a high pressure air passage device (trade name: Super Jet) manufactured by Plametage Co., Ltd.
While flowing high-pressure air of f / cm ^2, a wire test of a 100-core optical cable having an outer diameter of 14 mm was performed. The evaluation criteria are as follows. ☆: Available for 1000m or more ◎: Available for 800 to 1000m ○: Available for 300 to 800m ×: Available distance is less than 300m

[0020] Cable permeability when a drum-wound tube is laid. A double-walled conduit tube 1000m is drummed (body diameter 1700mm, width 1470mm).
, And the same test was carried out. The evaluation criterion is a value calculated by {(available distance when the drum is wound around the drum) / (a possible distance when the drum is not wound around the drum)} × 100, and is set as follows. ◎: 80 or more ○: 50-80 ×: 50 or less or drum winding not possible

Pullability from Manhole In order to check the ease of pulling in from the manhole when the double-walled conduit is laid, a bending test of the double-walled conduit was performed. The test method is to cut a double-walled conduit into a length of about 30 cm,
With both ends fixed, the central part is bent at a constant speed (150 mm · s ^-1 ) and the bending angle (the angle at which the two axes connecting the end of the tube and the central part intersect, before the test it is a straight line is 0 °) becomes 60 ° Was displaced.
The evaluation criteria were set as follows in the state of bending angle, pipe buckling and flatness. A: No buckling or flattening occurs in the pipe even when bent at 60 ° or more. ：: The pipe is bent by 60 ° or more, but the pipe is slightly flattened. ×: The tube buckled or significantly flattened before bending by 60 °.

[0022]

[Table 1]

[0023]

[Table 2]

Table 3 summarizes the results of the above trial production test.

[0025]

[Table 3]

According to the above test results, the double-walled conduit having the structure of the present invention has little influence of winding even after the drum is wound, has excellent pull-in ability from manholes, and has a high-pressure air flow. It can be seen that the lineability of the sample is also good. It is also clear that if low-density polyethylene with a density of 0.900 to 0.940 is used as the material of the straight pipe in the inner layer and a specified amount of lubricant is blended, a conduit with better workability and better permeability with high-pressure air flow can be obtained. .

[0027]

As described above, according to the first aspect of the present invention, a cable passage by high-pressure air flow is formed by using a flexible conduit similar to a conventional corrugated tube. It can be performed smoothly without causing stretching or meandering. According to the second aspect of the present invention, since a double-walled conduit having good flexibility and good cable passing properties can be obtained, both the installation work of the conduit and the cable passing work can be performed very efficiently. Can be.

[Brief description of the drawings]

FIG. 1 is a half-cut side view showing an embodiment of a double-walled conduit according to the present invention.

FIG. 2 is a sectional view showing the dimensions of details of a double-walled conduit subjected to a test.

[Explanation of symbols]

 1: Corrugated pipe of outer layer 2: Straight pipe of inner layer

Continued on the front page (72) Inventor Toshikazu Kajikawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Yutaka Furukawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Inside Electric Industry Co., Ltd.

Claims (5)

[Claims] When a cable is passed while high-pressure air having a pressure of 5 kgf / cm ² or more is sent from one end into an electric conduit, an outer plastic corrugated pipe and an inner plastic straight pipe are used as electric conduits. A method for passing a cable by high-pressure air flow, comprising using a double-walled electric wire tube closely contacted at a minimum inner diameter portion of a corrugated tube. 2. An outer layer plastic corrugated pipe and an inner layer plastic straight pipe are brought into close contact with each other at a minimum inner diameter portion of the corrugated pipe.
Ratio of the length L ₂ of the portion length of the portion corrugated tube and the straight tube is in close contact with L ₁ and corrugated tube and the straight tube is spaced L ₁ / L ₂
The 0.25 to 0.45, the L ₂ 12 mm or less, the cable communication line for conduits by high pressure air flow, characterized in that it has a thickness that there is 3.0 mm or less the wall thickness of the straight pipe exceeds 1.0 mm. 3. The conduit according to claim 2, wherein the outer layer corrugated pipe is made of high-density polyethylene, and the inner layer straight pipe is made of polyethylene having a density of 0.900 to 0.940. 4. The conduit according to claim 2, wherein the straight pipe of the inner layer comprises a mixture of 0.5 to 5.0 parts by weight of a lubricant with respect to 100 parts by weight of plastic. 5. The method according to claim 1, wherein the conduit according to claim 2, 3 or 4 is used.