JPH10299954A - Composite rigid pipe and its transfer method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long size pipe with an excellent crash resistance and rigidity, which can be transferred by a normal ground transfer means such as a truck, and provide its transfer method. SOLUTION: This composite rigid pipe consists of a rigid plastic layer P2 and a crash reinforcing metal layer P1, and its bending rigidity is 3×10<6> to 5×10<7> kg.mm<2> . This compound rigid pipe can be transferred by a vehicle, by winding it on a drum at the bending diameter 40 to 100 times of the pipe outer diameter, for example. This pipe is very useful to insert a subduct, by inserting it in a cable duct.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite rigid pipe and a method for transferring the same, and more particularly, to a long composite rigid pipe that can be transferred by ordinary land-based transfer means such as a truck and a method for transferring the same.

[0002]

2. Description of the Related Art At present, there is an increasing demand for various kinds of long rigid pipes such as telecommunication cables such as telecommunication cables and optical fiber communication cables, pipes for laying underground power cables, and pipes for fluid transport. . An example is introduced below. FIG. 9 is a side sectional view schematically showing a state of laying underground cables such as power cables, and FIG.
11 is a sectional view taken along line XX in FIG.
0 is a partially enlarged view of FIG. 9 to 11, G is a road surface of a paved road, M is a manhole provided on the road surface G,
S is a work space dug under each manhole, D is a cable duct, and C is a cable group laid in the cable duct D and exposed in the work space S. As an example is shown in FIG. 10, the cable duct D is composed of nine cable laying ducts (pipes). Of the nine cable ducts, eight of them D2 to D9 are used for laying power cables, and only one remaining D1 is used for laying communication cables. The nine cable laying ducts are buried in the ground and open at the side wall of the work space S, and the cables laid in each cable duct are exposed in the work space S.

[0003] With the advent of the information communication society in recent years, communication cables, especially optical fiber communication cables, have been rapidly increasing, and cable ducts D1 for laying communication cables in cable ducts D in various parts of Japan have already become communication cables. , And the demand for laying additional communication cables continues. Excavating the surface G of a paved road to add cable ducts is practically impossible from the viewpoints of construction costs, construction period, and paralysis of urban functions due to the construction because the amount of existing cable ducts is enormous. It is. In view of the fact that a space remains in each of the power cable laying ducts D2 to D9 in FIG. 10, it has been proposed to use the space for laying a communication cable, and some of the methods will be implemented. Has reached. FIG. 11 shows the state of the duct D7, for example.
CT is 6 kv composed of three cores, CT1 to CT3, most often laid in a cable duct for laying power cables.
A power cable (triplex), and SD is a sub duct laid in the remaining space RS of the duct D7.
In the sub duct SD, there is an optical fiber communication cable OFC
Is laid.

[0004] The installation interval of the manhole M, that is, the section length of the cable duct D is usually 30 to 250 m,
The sub duct S is installed in the existing long cable duct D.
D needs to be inserted. The insertion work is performed by pushing a pipe serving as a sub duct SD from one end of each cable duct D opening on a side wall of a work space S provided below each manhole M. In addition, pipe insertion work,
It can also be performed by connecting one end of a pipe serving as a sub duct SD to the tip of a guide wire previously inserted into the cable duct D, and pulling the other end of the guide wire. However, in this method, even if a relatively large traction resistance is generated during the traction, the pipe is often forced to be pulled against the resistance, and this forced retraction causes the existing power cable CT in the cable duct D to be pulled. Risk of damage to the product. On the other hand, in the method of pushing a pipe, if a pushing resistance is generated, it is difficult to push even if the resistance is slight. When sensing this resistance,
The insertion is performed without damaging the existing power cable CT by, for example, changing the pressing direction or angle without forcibly pressing. For this reason, the pushing method is recommended.

[0005] The method of pushing a pipe has the above-mentioned advantages. On the other hand, in the case of a flexible plastic pipe, even a small pushing resistance can be used, for example.
Buckling is also impossible due to contact resistance between the surface of T and the inner wall surface of the cable duct D. For this purpose, rigid plastic pipes, especially pipes made of rigid polyvinyl chloride, have conventionally been employed. However, the conventional rigid plastic pipe has the following serious drawbacks for the sub duct SD.

[0006] Rigid plastic pipes such as rigid polyvinyl chloride pipes are extremely rigid and cannot be bent. Therefore, conventional commercial products are of a length that can be transported by ordinary land transport means such as trucks. That is, 4m
It is limited to the following short objects. Even in the continuous production of rigid plastic pipes, a method is employed in which a continuously extruded pipe is cut into short pieces of 4 m or less immediately after extrusion. Therefore, in order to form a subduct SD over the entire length in a cable duct D of, for example, 150 m using such a short rigid polyvinyl chloride pipe,
37 pipe connections are required for each cable duct, which requires a large amount of construction cost and construction time. In addition, there is also a problem that unevenness of the pipe surface generated each time the pipe is connected hinders smooth pushing of the pipe. Further, rigid plastic pipes such as hard polyvinyl chloride pipes generally have poor pressure crush resistance, and have a weak point that they are damaged if they are stepped on by mistake.

In general, metal pipes have crush resistance, but are difficult to bend. As a long flexible metal pipe, there is a corrugated pipe made of aluminum, copper, SUS or the like, but since a corrugated pipe is generally too flexible, a sub duct is inserted by a pushing method using the corrugated pipe. If it is to be installed, it will buckle even with a slight pushing resistance, as in the case of the above-mentioned flexible plastic pipe, and will not be able to be pushed.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a long pipe which is excellent in crush resistance and rigidity and which can be transferred by ordinary land transfer means such as a truck, and a transfer method therefor. With the goal.

[0009]

The present invention has the following features. (1) Consists of a rigid plastic layer and a crushed reinforcing metal layer,
The bending rigidity of the pipe is 3 × 10 ^{6 to} 5 × 10 ⁷ kg · mm
² is a composite rigid pipe. (2) The bending rigidity of the pipe is 5 × 10 ⁶ to 2 × 10 ⁷ kg.
mm ² and the rigid plastic layer is made of a plastic having a breaking elongation of at least 25%.
(1) The composite rigid pipe according to (1). (3) The above (2) wherein the plastic is rigid polyvinyl chloride
A composite rigid pipe as described. (4) The inner diameter and wall thickness of the pipe are each 20 to 40 m
m, the composite rigid pipe according to any one of the above (1) to (3), which is for a subduct installed in a cable duct. (5) The crushing reinforcing metal layer is a metal spiral pipe, and the metal spiral pipe has a rigid plastic layer thereon (1) to
(4) The composite rigid pipe according to any of (4). (6) A composite rigidity characterized in that the composite rigid pipe according to any one of the above (1) to (5) is wound at a bending diameter of 40 to 100 times the outer diameter of the pipe and transferred by a vehicle. Pipe transfer method. (7) The method for transferring a composite rigid pipe according to the above (6), wherein the composite rigid pipe is wound on an inner winding portion of a winding means having an outermost diameter of 3 m or less.

[0010]

[Function] A composite layer of a rigid plastic layer and a crushed reinforcing metal layer, and the pipe has a bending rigidity of 3 × 10 ⁶ kg · mm.
By setting the ratio to ² or more, a pipe having both excellent crush resistance and rigidity can be obtained, and the bending rigidity of the pipe is 5 × 10 ^7.
By setting the weight to not more than kg · mm ² , it is possible to obtain a long pipe having a length of several tens to several hundreds of meters, which can be wound by a drum and can be transported by ordinary land transport means such as a truck.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the crushed reinforcing metal layer in the composite rigid pipe has the function of mainly improving the crush resistance of the pipe as the name implies, while the rigid plastic layer reduces the rigidity of the pipe. It mainly acts to improve. Therefore, as long as the above-mentioned problem of the present invention can be solved, there is no particular limitation on the mutual positional relationship between the rigid plastic layer and the crushed reinforcing metal layer, and various composite structures in which both layers are combined in various modes. Included in the present invention. For example, a structure having a rigid plastic layer on the inner crushed reinforcing metal layer, a structure having a crushed reinforcing metal layer on the inner rigid plastic layer, a structure having a rigid plastic layer above and below the crushed reinforcing metal layer, a rigid plastic For example, a structure having a crushed reinforcing metal layer above and below the layer. The composite rigid pipe of the present invention, like many ordinary pipes, is generally preferable except for special cases, in which the presence of edge-shaped or projection-shaped irregularities is aside from smooth irregularities on its outer surface. Absent. In particular, when the present invention is used for a sub duct installed in a cable duct described later, it is particularly necessary that the outer surface thereof be smooth so that the above-described push-in insertion becomes as easy as possible. Become. However, even in this case, smooth irregularities on the outer surface do not pose any particular problem.

The crush reinforcing metal layer is made of a metal having high mechanical strength, which is generally called a structural material, especially a general-purpose metal such as aluminum, copper, iron, or an alloy thereof such as brass or SUS. Sex structure. Examples of the flexible structure include a corrugated pipe and a spirally wound metal tape. Examples of the corrugated pipe include a corrugated pipe in which the surface irregularities are helical in the longitudinal direction of the pipe, and a corrugated concave and convex section having concentric cross sections alternately exist in the longitudinal direction of the pipe. As a spiral wound body of metal tape,
Spiral-wound metal tapes with a gap between their side walls, spirally-wound metal tapes with their side walls abutting against each other, as shown later in the drawing, contact portions between metal tapes And those mechanically connected to each other by caulking both ends.

The material for forming the rigid plastic layer is not particularly limited, and various rigid plastics can be used. However, it is preferred that the fracture surface elongation be at least 25%, especially at least 35%. Examples of such rigid plastics include general-purpose rigid plastics such as hard polyvinyl chloride, polyethylene, polystyrene, and acrylic resin, and engineering plastics such as fluororesin, polyamide, polyacetal, polyamideimide, and polyimide.

In general, the rigidity of plastics can be increased by compounding additives, especially fillers and fibers. Examples of fillers effective for improving rigidity include talc, clay, carbon black, silica, glass powder, and mica.Examples of fibers include ceramic fibers, rock wool, glass fibers, carbon fibers, and silicon carbide. These are inorganic or organic fibers such as whiskers such as alumina, polyamide fibers, and aramid fibers. Even if the rigidity of the plastic alone is insufficient, there are some plastics that can be used as the constituent material of the rigid plastic layer in the present invention by forming a composition containing the above compounding agents.

A particularly preferred material for forming the rigid plastic layer in the present invention is rigid polyvinyl chloride. In this case, as the hard polyvinyl chloride, polyvinyl chloride used in the production of various hard polyvinyl chloride products and the above-mentioned filler 2 per 100 parts by weight thereof are used.
A substantially plasticizer-free polyvinyl chloride composition comprising from 0 to 70 parts by weight, in particular from 30 to 60 parts by weight, wherein the composition has an elongation at break of at least 25%, in particular at least 35%. .

The bending rigidity of the composite rigid pipe of the present invention is 3 × 10 ^{6 to} 5 × 10 ⁷ kg · mm ² . If this bending rigidity is small, the rigidity of the pipe will be poor,
For example, when it is used for forming a sub duct by the above-described pushing, it becomes difficult to push. On the other hand, when the bending stiffness is increased, the rigidity of the pipe is increased, and it becomes difficult to wind the drum. When the drum is forcibly wound, the pipe may be cracked. Thus, a composite rigid pipe having a bending rigidity of 5 × 10 ⁶ to 2 × 10 ⁷ kg · mm ² is particularly preferable.

In the present invention, the bending rigidity (kg ·
mm ² ) is measured by the following method. [Method of measuring pipe bending stiffness] The distance between fulcrums is L (m)
On each of the two fulcrums, a test pipe piece cut and sampled to a length of 2L is placed on the fulcrum such that the fulcrum comes to a position of L / 2 from each of both ends thereof, and from the center, that is, both ends of the test pipe piece The amount of deflection δ (m) of the pipe piece to be measured that occurs when a load F (kg) is applied to a position at a distance of L is measured. At this time, the size of L is set in a range of 0.45 m to 0.55 m. In addition, the deflection amount δ of the pipe piece to be inspected is obtained by changing the deflection amount δ with respect to 10 loads in 1 kg steps from 1 kg to 10 kg.
Is measured, and the average value [δ] is calculated. The load [F] that can generate the average value [δ] is read by interpolation from a load F-bending amount δ graph created based on the above-mentioned ten data points. The bending stiffness of the pipe (E
I) is calculated by the following equation. EI = L ³ × [F] / 48 [δ]

The composite rigid pipe having the pipe bending rigidity described above has a total average thickness of the composite rigid pipe of 4 to 8 m.
In the range of m, the average thickness of the rigid plastic layer is about 85 to 95% of the total average thickness, and the thickness of the crushed reinforcing metal layer (the thickness or the average thickness of the flat plate portion or the portion occupying the largest area) is 5 to 5%. It can be obtained by setting it to about 15%.

1 to 6 are sectional views of an embodiment of the present invention, wherein P1 is a crushing reinforcing metal layer, and P2 is a rigid plastic layer. In FIG. 1, the crushed reinforcing metal layer P
1 is a metal tape spiral wound body having a gap P12 between the side walls of the spirally wound metal tape P11. In FIG. 2, the crushing reinforcing metal layer P1 is formed by the side wall of the spirally wound metal tape P11. A spirally wound metal tape is used. In the embodiments shown in FIGS. 3 to 5, the crushing reinforcing metal layer P1 is made of a metal tape P.
One that is mechanically connected to each other by caulking both end portions of the contact portions 11 is used. FIG. 3 shows what is referred to as close contact, in which a rigid plastic layer P2 is used.
Has a flat outer surface that fills the valleys with surface irregularities caused by mutual caulking between the two ends of the crushing reinforcing metal layer P1. FIG. 4 shows what is referred to as unevenness, and the rigid plastic layer P2 has an outer surface that is uneven according to the surface unevenness generated by mutual caulking between the both ends of the crushed reinforcing metal layer P1. FIG. 5 shows what is called a puffing. The rigid plastic layer P2 is formed in such a manner that the gap P13 is left without filling the valleys of the surface irregularities generated by mutual caulking of the both ends of the crushed reinforcing metal layer P1. It has a uniform thickness and a flat outer surface formed on the convex top surface of the irregularities.
In FIG. 6, a helical corrugated pipe is used for the crushing reinforcing metal layer P1, and the rigid plastic layer P2 has an outer surface that is uneven according to the surface unevenness of the corrugated pipe.

The composite rigid pipe of the present invention may be of a suitable size depending on the intended use. For example, when the composite rigid pipe is used for forming a sub duct by pushing as described above, the inner diameter is about 20 to 40 mm. , Wall thickness is 4-8mm
Degree, especially inner diameter about 25-34mm, wall thickness 5-7m
m is preferable. In this case, the composite rigid pipe has a generally circular cross-section, but may have an elliptical or pseudo-elliptical cross-section slightly deviating from the circular shape.

The composite rigid pipe of the present invention can be bent if the bending diameter is about 40 times the outer diameter of the pipe. Therefore, it can be wound around a drum that can be wound with at least such a bending diameter, and can be transported together with the drum on a vehicle such as a truck. Increasing the bending diameter of the pipe makes it easier to bend the pipe, but on the other hand, requires an expensive large drum, which is inconvenient for transporting the vehicle. Therefore, it is preferable to wind it around a drum with a bending diameter of 40 to 100 times the outer diameter of the pipe, preferably 50 to 90 times the outer diameter of the pipe, and transfer it by vehicle. Further, the inner diameter of the composite rigid pipe of the present invention is about 20 to 40 mm, the wall thickness is about 4 to 8 mm, so as to be within the upper limit height (3.8 m) that allows undelivered transfer according to the Road Traffic Law. In particular, the inner diameter is about 25 to 34 mm and the wall thickness is about 5 to 7 mm.
In consideration of (before and after), it is recommended that the material be transported by being wound around a drum having an outermost diameter of 3 m or less.

The composite rigid pipe may be wound and transported on a drum, reel or other suitable winding means. For example, an ordinary drum having a disk-shaped flange at both ends of a cylindrical or columnar winding core may be used, and a composite rigid pipe may be wound around the core and transferred. However, although the composite rigid pipe of the present invention can be wound, it retains an extremely strong repulsive force due to internal stress due to bending in the wound state, so that the pipe is taken out of the drum in the drum wound state. It is necessary to pay attention to the possibility of an accident due to this strong repulsion. On the other hand, if an inner winding drum is used as an example of the winding means described below with reference to the drawings, the above-described problem unique to the normal drum is solved.

FIG. 7 is a front view of the inner winding drum A in the process of winding the composite rigid pipe, and FIG. 8 is a side view of FIG. 7 and 8, reference numeral 1 denotes a pipe winding portion;
Is an inner frame, 3 is a short connecting portion for concentrically fixing the pipe winding portion 1 and the inner frame 2 concentrically, and 4 is a concentrically fixing connection between the pipe winding portion 1 and the inner frame 2 and a rotating shaft. Reference numeral 8 denotes a long connecting portion, 5 denotes a substrate, 6 denotes a supporting member that supports the rotating shaft 8, 7 denotes a support that supports the supporting member 6, and P denotes a composite rigid pipe. The pipe winding part 1 includes a pair of ring bodies 11, 1
1 ′ and a total of eight horizontal bars 12 (five of them are shown in FIG. 8) connecting the ring bodies 11 and 11 ′. Each horizontal bar 12 is welded to the ring bodies 11, 11 'and the short connecting part 3 or the long connecting part 4. The pipe winding section 1 is capable of winding the pipe substantially in the presence of the eight horizontal bars 12, and the composite rigid pipe P is wound inside the horizontal bar 12 by a method described later. Has been turned. The inner frame 2 includes a pair of ring bodies 21 and 21 ′ (however,
1 ′ overlaps 21 in FIG. 7). The rotating shaft 8 is supported by a disk-shaped bearing plate 41 and a support member 6 formed at the intersection of the two long connecting portions 4, and the inner winding drum A is rotated around the rotating shaft 8. It is rotatable. In addition, the long connecting part 4 is the ring body 1.
It does not exist on the side where 1 'to 21' exist.

For example, a composite rigid pipe P produced by continuously forming a rigid plastic layer on a crushed reinforcing metal layer by an extruder (not shown) rotates in synchronization with the line speed of the pipe P. The inner winding drum A is wound around the inside of the pipe winding portion 1 as shown in FIG. At this time, two stages, three stages, as necessary,
It is also possible to superimpose a step, and so on. By this overlapping step winding, it is possible to wind an ultra-long composite rigid pipe P of about 400 to 800 m.

The inwardly wound composite rigid pipe P tends to repel the internal stress caused by bending so as to be straightened by relaxing the internal stress. This repulsion is caused by the composite rigid pipe P
It acts in the direction of pressing itself against the inside of the pipe winding part 1, in other words, once it is wound, it always acts in the direction of maintaining the wound state, without causing the pipe unraveling phenomenon. The composite rigid pipe P can be wound very easily and stably. After the necessary length has been wound, the pipe P can be transported together with the inner winding drum A while the winding end of the pipe P remains free. The required length of the pipe P can be easily taken out of the drum A without requiring a large force and without fear of collapse of the wound state due to the repulsive force that returns straight.

[0026]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

Example 1 As a crushing reinforcing metal layer, a SUS tape having a thickness of 0.3 mm and a width of 10 mm is mechanically connected to each other by caulking both ends of a contact portion between the metal tapes.
The spirally wound metal tape (the inner diameter of the flat portion was 25.5 mm) used in FIG. 5 was used. On the other hand, a polyvinyl chloride composition pellet (trade name: KDV9982Y, elongation at break: 150%) manufactured by Riken Vinyl Co., Ltd. was used as a material for forming the rigid plastic layer, and this was extruded onto the above spiral wound metal tape. 5, a composite rigid pipe having a puffing structure shown in FIG. 5 having a thickness of a polyvinyl chloride composition layer of 1.2 mm and an outer diameter of 31.5 mm was continuously produced. The bending rigidity of the pipe was 4.1 × 10 ⁶ kg · mm ² .

Example 2 Instead of the polyvinyl chloride composition pellets used in Example 1, a polyvinyl chloride composition pellet (trade name: ASTERON CAL222, elongation at break: 40) manufactured by Kureha Chemical Co., Ltd.
%), A composite rigid pipe having the same structure and dimensions was continuously manufactured in the same manner as in Example 1. The bending rigidity of the pipe was 8.5 × 10 ⁶ kg · mm ² .

Example 3 As a crush reinforcing metal layer, it is used in FIGS. 3 to 5 which are mechanically connected to each other by crimping both ends of a contact portion between SUS tapes having a thickness of 0.3 mm and a width of 10 mm. Spiral winding of metal tape (25.5 inner diameter of flat part)
mm), and as a material for forming the rigid plastic layer, a polyvinyl chloride composition pellet (trade name: ASTERON CAL222, elongation at break: 40) manufactured by Kureha Chemical Co., Ltd.
%)It was used. This was extruded on a spirally wound SUS tape, and the thickness of the polyvinyl chloride composition layer was 2.0 m.
m, and a composite rigid pipe having an outer diameter of 33.0 mm and having a squirt structure shown in FIG. 5 was continuously manufactured. The bending rigidity of the pipe was 2.1 × 10 ⁷ kg · mm ² .

Example 4 As a crushing reinforcing metal layer, it is used in FIGS. 3 to 5 in which both ends of a contact portion of a SUS tape having a thickness of 0.3 mm and a width of 10 mm are mechanically connected to each other by caulking at both ends. Spiral winding of metal tape (inner diameter of flat part 31.8)
mm), and as a material for forming the rigid plastic layer, a polyvinyl chloride composition pellet (trade name: ASTERON CAL222, elongation at break: 40) manufactured by Kureha Chemical Co., Ltd.
%)It was used. This was extruded on a spirally wound SUS tape, and the thickness of the polyvinyl chloride composition layer was 1.2 m.
m, and a composite rigid pipe having an outer diameter of 38.5 mm and having a structure shown in FIG. The bending rigidity of the pipe was 3.8 × 10 ⁷ kg · mm ² .

Comparative Example 1 A polyvinyl chloride composition pellet (trade name: ASTERONE CAL273, elongation at break: 20%) manufactured by Kureha Chemical Co., Ltd. was used.
Extrusion molding, water cooling, inner diameter 29.0mm, outer diameter 34.0m
m (thickness: 2.5 mm) hard PVC pipes were continuously manufactured. The bending rigidity of the pipe is 5.3 × 10
^{It was 7} kg · mm ² .

Comparative Example 2 Soft polyvinyl chloride composition pellets manufactured by Riken Vinyl (trade name: PTD7298S, elongation at break: 250%)
Was extruded and water-cooled to obtain an inner diameter of 25.0 mm and an outer diameter of 27.
8 mm (thickness: 1.4 mm) soft rigid polyvinyl chloride pipe was continuously manufactured. The bending rigidity of the pipe is 2.
It was 8 × 10 ⁶ kg · mm ² .

Examples 5 to 8 When the composite rigid pipes of Examples 1 to 4 were continuously manufactured, they were wound four steps inside the pipe winding portion of the inner winding drum shown in FIGS. The inside diameter of the pipe winding portion was 2.5 m, and the pipe was continuously and smoothly wound. The winding length of the composite rigid pipe was about 400 m.

Comparative Examples 3 and 4 When the polyvinyl chloride pipes of Comparative Examples 1 and 2 were continuously manufactured, they were wound on the same inner drum as in Examples 5 to 8. In Comparative Example 4 in which the bending rigidity of the pipe was small, in Comparative Example 4, the pipe could be continuously and smoothly wound, but in Comparative Example 1 in which the bending rigidity of the pipe was excessive. In No. 3, continuous winding of the pipe was quite impossible.

The inner winding drum wound around each of the pipes obtained in Examples 5 to 8 and Comparative Examples 3 to 4 has a loading height of 0.
It is mounted on an 8m truck and transported 50km, and then the following test method is used to check whether there is any abnormality in each hard polyvinyl chloride layer.
The crush resistance of the pipe and the pushability into the cable duct were examined. As a result, in Examples 5 to 8 and Comparative Example 4, there was no abnormality in each polyvinyl chloride layer, but the polyvinyl chloride pipe of Comparative Example 3 had cracks. On the other hand, each of the pipes obtained from Examples 5 to 8 and Comparative Example 3 could easily be pushed into a 150 m cable duct, but the pipe obtained from Comparative Example 4 was buckled and had a length of 20 m or more. Pushing was not possible. Regarding the crush resistance, all the pipes from Examples 5 to 8 passed, but the pipes from Comparative Examples 3 and 4 failed the crush test.

[Method of Inspecting Hard Polyvinyl Chloride Layer] The pipe is taken out of the inner winding drum and the entire surface thereof is visually inspected for cracks. [Pressure crush test] A test pipe piece having a length of 100 mm was measured for a diameter of 1
It is sandwiched between two iron plates having a thickness of 50 mm and a thickness of 20 mm, and a load of 2 kN is applied between the iron plates to check for cracks in the pipe piece to be tested. If cracks do not occur, the test is passed, and if cracks occur, the test is rejected. [Pushability into Cable Duct] For a straight electric conduit having an inner diameter of 125 mm and having an existing power cable (6 kV-CVT: 325 mm ² , height about 85 mm), a pipe is pushed into the gap from one end of the pipe. .

[0037]

In order to insert a sub duct by pushing it into a 150 m cable duct using a conventional 4 m short rigid pipe, the time required for connecting the pipes and the pushing due to the unevenness of the pipe connection portion are reduced. Combined with the difficulty, it took an average of about 40 hours per cable duct. On the other hand, when the long composite rigid pipe of the present invention is used, it is not necessary to connect the pipes, and the pipe has a smooth surface over its entire length, so that it can be easily pushed in, and as a result, it takes only about 30 minutes on average. Complete. Therefore, the effect of the present invention is industrially enormous in view of the demand for subduct insertion, which will increase in proportion to the demand for optical fiber communication cables, which is expected to increase in the future. Furthermore, the long composite rigid pipe of the present invention
Because of its excellent crush testability, it has the advantage of high flexibility in handling and laying pipes, and is very useful for various uses other than subducts.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of another embodiment of the present invention.

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a sectional view of another embodiment of the present invention.

FIG. 5 is a sectional view of another embodiment of the present invention.

FIG. 6 is a cross-sectional view of another embodiment of the present invention.

FIG. 7 is a front view of the inner winding drum in the course of winding the composite rigid pipe.

FIG. 8 is a side view of FIG. 7;

FIG. 9 is a side cross-sectional view schematically showing a state of laying underground cables.

FIG. 10 is a sectional view taken along line XX in FIG. 9;

FIG. 11 is a partially enlarged view of FIG. 10;

[Explanation of symbols]

 P1 Crushed reinforcing metal layer P2 Rigid plastic layer P11 Metal tape

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hirokazu Katsura 8 Nishinocho, Higashimukaijima, Amagasaki City, Hyogo Prefecture Inside Mitsubishi Electric Wire Industry Co., Ltd.

Claims (7)

[Claims] The pipe comprises a rigid plastic layer and a crushed reinforcing metal layer, and has a bending rigidity of 3 × 10 ^{6 to} 5 × 10 ^7.
Composite rigid pipe of kg · mm ² . 2. The pipe has a bending rigidity of 5 × 10 ⁶ to 2 × 1.
0 ⁷ a kg · mm ^2, and stiff composite rigid pipes of plastic layer according to claim 1, wherein the elongation at break, which are composed of at least 25% of the plastic. 3. The composite rigid pipe according to claim 2, wherein the plastic is rigid polyvinyl chloride. 4. An inner diameter and a wall thickness of a pipe are each 2
The composite rigid pipe according to any one of claims 1 to 3, which has a length of 0 to 40 mm and 4 to 8 mm, and is used for a sub duct installed in a cable duct. 5. The composite rigid pipe according to claim 1, wherein the crushing reinforcing metal layer is a metal spiral pipe, and a rigid plastic layer is provided on the metal spiral pipe. 6. A composite rigid pipe according to claim 1, wherein the composite rigid pipe is wound at a bending diameter of 40 to 100 times the outer diameter of the pipe and transferred by a vehicle. Transportation method. 7. The method for transferring a composite rigid pipe according to claim 6, wherein the composite rigid pipe is wound on an inner winding portion of a winding means having an outermost diameter of 3 m or less.