JPH0938926A - Cementitious cable pipe and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce a long cementitious cable pipe having a cabler of every kind and having a cable insertion hole of which the inner peripheral surface is made smooth by subjecting a cementitious kneaded mixture containing a cementitious raw material in a specific compounding ratio to extrusion molding. SOLUTION: The large hole of a cable pipe 1 becomes a cable insertion hole 2 and the small hole thereof becomes a PC steel rod insertion hole 3 permitting a PC steel rod to pass in order to connect the cable pipe. Since a molding material is extruded while rubbing the side surface of a core, the inner surfaces of the holes 2, 3 keep glossy smoothness and, when the holes 2, 3 are used as the cable pipe 1 later, friction is small even when a cable is drawn around and the cable is not damaged. The molded product of this cable pipe 1 is cut into predetermined length and cured in a next ageing process. The compounding ratio of a cementitious raw material is consist of 20-50 pts. of cement, 10-40 cut % of silica sand, 5-15wt.% of wallastonite, 2-4 pts.wt. of pulp and 0.3-1 pts.wt. of a thickener.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric pipe and a method for manufacturing an electric pipe used for underground laying of electric wires. More specifically, cement is a main raw material, and if necessary, inorganic and organic materials are added. The present invention relates to an electric tube formed by kneading a blended raw material with water and extrusion molding, and a method for manufacturing the electric tube.

[0002]

2. Description of the Related Art In recent years, in the underground burial work of electric wires in urban areas, it has become possible to carry out compact construction by using an electric pipe having a plurality of electric wire insertion holes.

The electric tubes currently on the market are roughly classified into ceramic tubes and concrete tubes, both of which have a considerable track record of use. Generally, the physical properties required for an electric tube are compressive strength, bending strength, impact resistance, electrical resistance, incombustibility, water impermeability, bulk specific gravity, etc., but both ceramic and concrete electric tubes are made of materials. There is no problem with that.

[0004] Ceramic perforated porcelain tubes are produced by molding porcelain clay with a friction press, and drying, calcination, glazeing, and main-baking processes to finish the product. The perforated porcelain tube produced by this method has a limit in length because the porcelain tube is made to stand by itself at the time of firing, and the standard length is 60 cm.
It has become. In the connection work for connecting the perforated porcelain pipes in the ground, since the groundwater infiltrates from the joint part of the perforated porcelain pipes, the perforated porcelain pipes are extended one by one while sandwiching the rubber packing and tightening with the connecting metal fittings.

Concrete perforated pipes include cement, sand,
It is manufactured by an instant demolding method, in which a concrete is mixed by adding a small amount of water to gravel and kneaded (zero fluidity) and packed in a formwork with a vibrator. This immediate demolding method has high productivity among the methods for manufacturing concrete products, but has a problem that the surface of the product becomes rougher than that of ordinary concrete. As a result, the inner surface of the hole of the perforated pipe is also rough, so when laying the cable,
There is a risk of damaging the cable coating, and the meaning of modifying the inner diameter of the insertion hole.Therefore, it is necessary to grind the inner surface of the hole with a grinder to provide smoothness, which is a heavy burden on manufacturing. It has become. Regarding the length of the perforated concrete pipe, the standard product has a length of 1 m, and it is difficult to manufacture a product longer than this due to the manufacturing process.

The type of the electric tube is indicated by the diameter of the insertion hole, the number of holes, and the length. For ceramic perforated porcelain tubes, the diameters are 54mm, 75mm, 90mm, 100mm, 1
There are products with large and small diameters of 25 mm, 150 mm, and 200 mm, and the number of holes can be 9 holes, 6 holes, 4 holes, and 2 holes depending on the diameter, and various products can be manufactured. On the other hand, there are only two types of concrete perforated pipes, with two types of diameters of 125 mm and 200 mm, and the number of holes is only four and two, which is less than the types of perforated porcelain pipes.

By the way, since the electric tube is for passing electric wires through the hollow portion, the state of the hole is very important. The size of the hole diameter depends on the diameter of the cable passed through it,
Various sizes from 50 mm to 200 mm are available. In any case, the shape of the hole is a perfect circle, and there are strict requirements regarding the accuracy of the hole diameter dimension and the smoothness of the inner peripheral surface of the hole. However, since the weight per unit bottom area of the electric tube is very large, the molded body is likely to undergo plastic deformation, and the dimensional accuracy of the hole diameter is likely to deteriorate. That is, the cement in the forming raw material reacts with water and gradually hardens, but is in a plastic state for about 30 minutes to 1 hour, and gradually deforms during this period. In order to prevent this plastic deformation, strengthen the cross-sectional structure of the product (thicken the support), reduce the kneading water amount and knead hard to strengthen the shape retention of the material, or the fibrous raw material. Is taken to increase the bridge effect.

[0008]

[Problems to be Solved by the Invention]

(Correspondence to long electric tube) The length of the electric tube currently on the market is 60 cm for a ceramic porous ceramic tube and 1 m for a concrete porous tube. As mentioned above, in the underground burial work for electric pipes, rubber packing is used at the joints between pipes, and special metal fittings are used for connecting pipes. This does not depend on the length of the electric tube and is a necessary cost for each end face of the tube. Therefore, if a long electric tube can be used, the cost will be reduced and the work efficiency will be improved. The cost can be reduced significantly.

(Correspondence to various diameter products) In the recent underground burial work of electric wires in the urban area, the electric wires of a relatively small diameter such as an optical fiber cable and a cable for cable broadcasting are assumed for the purpose of the future mass media era. Due to the increasing demand for electric pipes, the use of electric pipes with a small diameter and a large number of holes is increasing.

Unlike the concrete casting method, the current concrete porous tube is one in which hard concrete without fluidity is packed in a mold and compacted by a vibrator to form a complex cross-sectional shape. It is unsuitable for manufacturing electric pipes with small diameter and large number of holes.

(Improvement of inner surface of wire insertion hole) The inner surface of the insertion hole of the electric tube must be in a smooth state in order to protect the coating of the cable to be laid. Therefore, in the ceramic porcelain tube, glaze is applied to the inner surface of the hole and fired to make the inner surface of the hole smooth. On the other hand, in the case of a concrete perforated pipe, the inner surface of the hole is ground by a grinder to provide a smooth surface, which requires a great deal of time and effort to manufacture.

(Improvement of Pore Diameter Dimensional Accuracy) A conventional cement extruded board (building material panel) is a mixture of cement and silica powder with fibers such as pulp and wollastonite and fibrous minerals.
Methyl cellulose, which is a thickening agent, is further added, and the mixture is kneaded into a plastic form with a relatively small amount of water, and this is supplied to an extrusion molding machine.Since the molding raw material is in such a plastic state, immediately after discharging from the die During the period from the hardening of the cement in the raw material to the hardening of the raw material, the molded product will be deformed if it receives a large amount of gravity or vibration. The shapes of the electric pipe and the building material panel are so-called “stubby type” and “flat type”. When comparing the weight per unit area of the bottom surface, the electric pipe is 3 to 4 times larger. Therefore, if an electric tube is manufactured with the same raw material composition as the building material panel,
By the time the cement hardens, it may not be able to support its own weight and may undergo significant deformation.

In particular, in an electric tube having a large number of holes, the deformation is concentrated in the lowermost hole, and it is difficult to manufacture a product which can clear the standard. Reinforcing the cross-sectional structure to prevent deformation of the electric tube molding increases unit weight and cost, and strengthening the shape retention property increases the friction resistance of the molding raw material and deteriorates the extrusion moldability. Therefore, there are limitations such as the inability to inject the raw material, and the deformation cannot be completely prevented.

[0014]

The cement-based electric tube of the present invention is obtained by extruding a cement-based kneaded product.

The method for producing a cement-based electric tube according to the present invention comprises:
By extrusion-molding a cement-based raw material, a method for manufacturing an electric tube having a hole having a regular circular cross-sectional shape, wherein a core having a non-circular circular cross-section is used as the core of the extrusion device. It is characterized in that the cross-section of the deformed hole is made substantially circular by plastic deformation of the molded body after extrusion molding.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the mixing ratio of the cement-based raw material is 20 to 55 parts by weight of cement and 0 of silica powder.
-30 parts by weight, silica sand 10-40 parts by weight, wollastonite 5-15 parts by weight, pulp 2-4 parts by weight, polypropylene fibers 0-1.0 parts by weight, metal fibers 0-10 parts by weight, thickener ( For example, methyl cellulose or ethyl cellulose)
3 to 1.0 parts by weight is preferable. Furthermore, one or both of 3.0 parts by weight or less of a wax-based emulsion and 10 parts by weight or less of mica may be added.

From 20 parts by weight of water to 100 parts by weight of this blended raw material
When 30 parts by weight is added and kneaded, the raw material is kneaded into a hard dumpling. This forming raw material is continuously supplied into the extruder. By rotating the auger screw in the extruder, the molding raw material is pushed into the die. A die for molding an electric tube is attached to the tip of this die, and when the molding raw material passes through the die part, a molded product having a desired shape is formed.

This raw material mixture maintains weak plasticity when a small amount of water is added and kneaded during extrusion molding of an electric tube,
Moreover, it can withstand a large weight. With this formulation,
A large amount of silica sand is used as an aggregate, which prevents deformation of the molded product and reduces shrinkage that occurs during the hardening process of cement.

Silica powder is effective in developing strength when used in autoclave curing as a secondary curing in the production of electric tubes.

The wollastonite also serves to improve shape retention and also as a reinforcing fiber. Since this wollastonite has high heat resistance, it does not deteriorate at all even when the green shaped product is steam-cured.

Further, wollastonite has a good affinity with a hydraulic substance such as cement, and is also effective in this respect. If the added amount of wollastonite is too small, the effect of improving the performance such as bending strength is not sufficient, and if it is too large, the extrusion resistance during extrusion molding increases and the extrusion speed decreases, which is not preferable in production. Therefore, the compounding amount of wollastonite is 5 to 1
5 parts by weight.

Pulp also functions as a reinforcing fiber. The amount of pulp is 2 to 4 parts by weight for the same reason as in the case of wollastonite.

The organic fiber has a function of enhancing the shape retention of the formed product. Since the extrusion resistance increases if the amount of polypropylene added is too large, it is preferable that the compounding amount be 1 part by weight or less as claimed in claim 3. As the organic fiber, polypropylene fiber, vinylon fiber and the like are preferable, but polypropylene fiber is particularly preferable.

Metal fibers such as steel fibers can also be used as reinforcing fibers. The addition amount of the metal fibers is preferably 10 parts by weight or less, more preferably 3 to 5 parts by weight.

As the thickener, water-soluble polymer substances such as cellulose derivatives such as methyl cellulose and ethyl cellulose can be used. If the blending amount of the thickener is too small, the water retention ability to maintain the fluidity necessary for molding is insufficient,
If the amount is too much, the water retention will not change, but rather the molded product will become soft and the shape and dimensional accuracy of the product will decrease.
1 part by weight.

In order to prevent the fluidity of the molding raw material in the extruder from decreasing due to the addition of a large amount of silica sand, the method according to claim 5
It is preferable to add a wax emulsion and / or mica as described above. These have the effect of increasing the fluidity of the kneaded product. If the amount added is too large, the molded product becomes too soft. Therefore, the content of the wax emulsion is 3 parts by weight or less, especially 0.5 to 3 parts by weight, and the amount of mica added is 10 parts by weight or less, especially 1. It is preferably 10 to 10 parts by weight.

FIG. 1 is a front view of an end surface of an electric tube 1 having six insertion holes. The large hole of the electric tube serves as the cable insertion hole 2, and the small hole serves as the PC steel rod insertion hole 3 through which the PC steel rod for connecting the electric tubes is inserted.

Since the molding raw material is extruded while rubbing the side surface of the core, the inner surfaces of the holes 2 and 3 maintain a glossy smoothness, and even when the cable is pulled around when it is later used as an electric tube, friction is generated. Is small and will not damage the cable.

The molded product of the electric tube is cut into a predetermined length and cured in the next curing step. Steam curing is suitable as this curing method. Curing conditions are 40-80 ° C
3-24Hr is preferable.

Unlike the existing products manufactured by the formwork, the electric pipes manufactured by the cement-based raw material extrusion molding machine are continuously molded, so that the handling in each manufacturing process following the molding is allowed. As long as the length of the product can be freely cut, as long as practically, 3 m or less is appropriate. The electric tube of the present invention molded by an extrusion molding machine,
It is possible to make the product 3 to 5 times as long as the existing product, and therefore the effect of reducing the burial cost is extremely large.

Next, a preferred form of the core of the method of claim 6 will be described.

Plastic deformation of holes is inevitably caused when an electric tube is produced from a cement-based raw material by an extruder, but the tendency of deformation is substantially uniform depending on the position of the holes.

This deformation tendency will be described by taking the nine-hole electric tube shown in FIG. 2 as an example. The code for the hole position is I from the top
If the rows A, B, and C are arranged in rows from the left to the rows II, III, and the holes in the center row B are deformed like crushing a circle, The holes of rows A and C at both ends are deformed in an asymmetrical manner with respect to a perpendicular line passing through the axis of the holes. The semi-circle near the row B of the hole is similar to the deformation of the row B hole, and the semi-circle on the opposite side is accompanied by the deformation of the side edges,
It deforms as if it were protruding diagonally downward. The holes in the same row are deformed with the same tendency, but the degree of deformation (magnitude of deformation) is small in the I-th stage and increases in the II-th and III-th stages. Further, the holes in the rows A and C at both ends are deformed into a shape that is almost symmetrical.

Thus, based on the deformed state of the perforated pipe using the same circular core, plastic deformation is alleviated, and
In order to develop a core in which the cross-section of the deformed hole becomes a practical circle, first replace the three cores in the third stage with an oval core with a vertically long section. went. The design of the oval core is as follows.

Let D be the diameter of the target hole, D _{v be} the average of the longitudinal diameters of the deformed holes, and D _{H be} the average of the transverse diameters of the deformed holes. Set according to.

The vertical size of the elliptical core = D + k (D-D V) transverse diameter of the elliptical core = D + k (D-D H) However, k =
0.7-1.0 As a result, a large improvement was observed in the deformation of the holes, especially III-
The hole of B is practically seen as a perfect circle (D ± 1.5 m
Strictly speaking, the upper half circle and the lower half circle are slightly different. With respect to the holes of III-A and III-C, there is an overall improvement effect, but the deformation near the edge portions on both sides remains, and the limit of the perfect circle is still exceeded. From this result, it was found that it is not possible to unify all the cores with the same elliptical shape, and it is necessary to develop a core suitable for the deformation of each hole. Therefore, we developed a non-sex circular core by the following method.

A cross section of a perforated tube produced using the same core of a perfect circle is copied on paper. For example, the shape of the core suitable for III-A will be described with reference to FIG.
Line 8 and aliquoted into equal angles around the axis 0 of the A hole, and the point of intersection with the periphery of the hole, respectively _{P 1, P 2, P 3} , and _{··· P 8, OP 1, OP} 2, OP ₃ ... R of OP ₈ length
₁ , R ₂ , R ₃ ... R ₈ . Also, assuming that the radius of the core of the perfect circle is R, the length R ′ ₁ from the center O of the perfect circle is
R _'2, R' _3, the · · · · R _'8 is calculated according to the following equation.

R ′ _i = R + k _i (R−R _i ) i = 1,2,3,4,5,6,7,8 K _i = 0.7 to 1.0 Returning to the original copy paper, axis Plot T ₁ at the point of R ′ ₁ from the heart O, T ₂ at the point of R ′ ₂ and T ₃ at the point of R ′ ₃ ...
・ Plot T ₈ at each point of R ′ ₈
The non-circular circle of the curve passing through ₁ , T ₂ , T ₃ , ... T ₈ serves as a reference for the cross-sectional shape of the core, and the shape of the hole of the product is checked to make a minor correction with the numerical value of k _i . By using the core manufactured in this way, it is possible to manufacture a perforated tube in which all the holes are practically seen as a perfect circle.

[0039]

EXAMPLES First, examples and comparative examples of the invention of claims 1 to 5 will be described.

The raw materials used in the following examples and comparative examples are as follows.

Cement: Ordinary Portland cement (manufactured by Mitsubishi Materials Corp.) Quartz sand: River sand from Kashima, Ibaraki Prefecture Coarse grain ratio 1.2 Silica powder: Specific surface area 4500 cm ² / g Wollastonite: Apparent specific gravity 0.4 to 0 .5 (JIS K
51-101 method) Pulp fiber: Average fiber length 1 mm Product name "PK # 1" (manufactured by Tachibana Shoten) Polypropylene fiber: Average fiber length 3 mm Product name "PZL" (manufactured by Daiwabo Co., Ltd.) Methyl cellulose: Product name "Metroose 90SH" -15
000 ”(manufactured by Shin-Etsu Chemical Co., Ltd.) Wax emulsion: trade name“ Cerosol M ”(manufactured by Chukyo Yushi Co., Ltd.) Mica: trade name“ Clarite mica ”(manufactured by Kuraray Co., Ltd.) The ingredients were blended in the proportions shown in Table 1, and the amounts of water shown in Table 1 were added and kneaded. This kneaded product was supplied to an extruder (V-40E type manufactured by Ishikawa Toki Kogyo Co., Ltd.) to extrude the molded product shown in FIG.

The dimensions of the molded product are shown in FIG.

[0043]

[Table 1]

After the length of the green molded product was cut at 5.2 m and 3.2 m, it was cured at 60 ° C. for 8 hours in a steam curing cabinet, and after the cement was hardened, these were 5.0 m, 3.0 m,
It cut | disconnected to the length of 1.5 m and 0.75 m. As a result of investigating the compression strength, bending strength, linearity in the tube axis direction, etc. of each prototype, it was a good long product as an electric tube. The measurement results of the compressive strength are shown in Table 1.

Next, these electric tubes are packed with rubber,
It was connected using a PC steel rod, a metal fitting for connection, etc., a new cable was inserted into the pipe line, and repeated insertion and withdrawal tests were repeated, but only a slight rubbing mark remained on the cable coating, No problematic scratches were found.

(Embodiment of the Invention of Claim 6) Next, an embodiment of the invention of Claim 6 will be described.

FIG. 4 shows that, in order to manufacture an electric tube having nine holes each having a diameter of 80 mm, a regular circular core was used for molding, and the holes of III-A after the plastic deformation of the product were enlarged. It was done. R _i (i = 1 to 8) is calculated from this figure and Table 2
Filled out. R ′ _i is calculated by setting R = 40 mm. Repeat this measurement twice with another sample.
The design value of the I-A core was determined. The [R _i after remodeling] Table 2, after fabricating a non-positive-circular core is obtained by measuring the III -A the pores of the porous tube prepared by extrusion molding machine using the core . Even when compared with the first R _i , it is considerably improved and practically reaches the range of a perfect circle.

[0048]

[Table 2]

[0049]

As described above, since the cement-based electric tubular tube of the present invention is made of an extruded product, it can be easily provided with a long size and various diameters. Therefore, the construction period and the construction cost can be reduced. Also, the inner peripheral surface of the cable insertion hole is extremely smooth, and surface treatment such as grinding is unnecessary. Therefore, the cement-based electric tube of the present invention is easy to manufacture and the manufacturing cost is low.

According to the method of the present invention, it is possible to efficiently manufacture a cement-based electric tube having a circular hole with a high roundness by extrusion molding.

[Brief description of drawings]

FIG. 1 is a front view of an end surface of a cement-based electric tube according to an example.

FIG. 2 is a front view of a 9-hole cement-based electric tube.

FIG. 3 is a dimensional drawing of a hole.

FIG. 4 is a dimensional drawing of a hole and a non-regular circular core.

[Explanation of symbols]

 1 Cement-based electric tube 2 Cable insertion hole 3 PC steel rod insertion hole

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C04B 16:02 16:06 24:38 24:08) 103: 30 103: 44 111: 56 (72 ) Inventor Takeyuki Ideyama 2-3-10 Shinjuku, Shinjuku-ku, Tokyo Inside Mitsubishi Material Construction Materials Co., Ltd.

Claims (6)

[Claims] 1. A cement-based electric tube produced by extrusion-molding a cement-based kneaded product. 2. The cement-based kneaded material according to claim 1, wherein the cement-based kneaded material is 20 to 55 parts by weight of cement, 10 to 40 parts by weight of silica sand, 5 to 15 parts by weight of wollastonite, 2 to 4 parts by weight of pulp, and a thickener. A cement-based electric tube containing 0.3 to 1 part by weight. 3. The cement-based electric tube according to claim 2, wherein the cement-based kneaded material further contains 1 part by weight or less of organic fibers and / or 10 parts by weight or less of metal fibers. 4. The cement-based electric tube according to claim 2, wherein the cement-based kneaded material further contains 30 parts by weight or less of silica powder. 5. The cement-based electric tube according to claim 2, wherein the cement-based kneaded material further contains 3 parts by weight or less of a wax-based emulsion and / or 10 parts by weight or less of mica. 6. A method for manufacturing an electric tube having a hole having a regular circular cross-section by extrusion-molding a cement-based raw material, wherein the cross-section is a non-round circular medium as a core of a die of an extrusion molding apparatus. A method for producing a cement-based electric tube, characterized in that a cross section of the deformed hole is substantially circular by plastic deformation of a molded body after extrusion molding using a child.