JP2004027562A - Thermoplastic resin cover body for underground structure, underground structure having this cover body and method of manufacturing its cover body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight thermoplastic resin cover body for an underground structure having high withstand load performance. <P>SOLUTION: This thermoplastic resin cover body for the underground structure blocks up an opening part of the underground structure for forming the opening part in the vicinity of the ground surface so as to be openable-closable, and has an almost rectangular cover plate part, a first rib group extending in parallel between the opposed long sides of the reverse of this cover plate part and a second rib group extending in parallel between the opposed long sides of the reverse of the cover plate part, and satisfies the requirements for a breaking load of at least 2 tons in a static load test. The first rib group and the second rib group incline the direction of respective ribs by 45 to 80 degrees to the corresponding long sides. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermoplastic resin lid for an underground structure, an underground structure provided with the same, and a method for manufacturing the lid, and more particularly, to a water-resistant box such as a water meter box or a digestion plug box. The present invention relates to a thermoplastic resin lid for underground structures requiring loadability, an underground structure provided with the same, and a method of manufacturing the lid.
[0002]
[Prior art]
A representative example of this kind of underground structure is, for example, a water meter box, which is composed of a box body having an opening on the ground surface and a lid that closes the opening of the box body so that it can be opened and closed. In other words, the entire box is buried in a road, and a water meter is housed therein, so that the amount of water consumption can be measured through an opening as appropriate. Therefore, a large load is applied to the box, especially its lid.
Correspondingly, the lid of this water meter box has conventionally been made of casting or concrete to withstand a large load, but recently it has been reduced in weight, water resistance or rust prevention, cost reduction, etc. In recent years, synthetic resins such as ABS resin, FRP resin, and polyvinyl chloride resin, or those obtained by laminating a metal plate to these resins for further reinforcement are increasing.
[0003]
[Problems to be solved by the invention]
Therefore, there are cases where the lid made of the synthetic resin cannot withstand a large load depending on its thickness or rib structure.
Specifically, a general synthetic resin lid has a substantially rectangular lid plate, a first rib group extending at right angles to a long side of the back surface of the lid plate, and a right angle formed integrally with the first rib group. And a second rib group extending at right angles to the short side of the back surface of the cover plate portion (see, for example, JP-A-53-145347).
[0004]
Although the synthetic resin lid is reinforced by the rib structure as described above, the lid may crack when subjected to a large load, for example, about 800 kg. Particularly in recent years, it is necessary to assume the passage of large trucks on ordinary roads, so it is necessary to withstand a load of at least 2 tons without destroying them (for example, by adding a 2 ton truck). Assumed static and impact loads).
[0005]
On the other hand, thermoplastic resins are light-weight, have high strength, are excellent in water resistance, chemical resistance, and electrical insulation, and are easily produced in a large amount because they are easy to mold and process. In particular, polyethylene terephthalate, which is usually abbreviated as PET (pet), is light-weight, strong, durable, and excellent in transparency, and is therefore produced in large quantities as beverage bottles (PET bottles). Recently, the Containers and Packaging Recycling Law has been enacted, and measures to shift to a recycling society for plastics are being advanced. In particular, recycling of PET bottles is desired, and this is a worldwide trend.
[0006]
In response to such social demands, various recycling (recycled) PET resins have been proposed for recycling PET bottles. However, these recycled PET resins have problems such as deterioration of physical properties, and have been considered to be difficult to apply to water meter box lids that require high strength for a long period of time.
[0007]
Therefore, one of the main objects of the present invention is to provide a heat treatment for underground structures that can significantly increase high load resistance by structural improvement without increasing the amount of resin used (total resin amount). An object of the present invention is to provide a lid made of a plastic resin.
Another main object of the present invention is for underground structures which can obtain sufficient strength only by adding pigments or glass fibers at most to a resin without attaching a metal plate for reinforcement. An object of the present invention is to provide a lid made of a thermoplastic resin.
Yet another primary object of the present invention is to provide a thermoplastic lid for underground structures that allows the use of recycled PET resin.
[0008]
[Means for Solving the Problems]
The present invention is a thermoplastic resin lid for an underground structure for opening and closing the opening of an underground structure having an opening formed in the vicinity of the ground, the cover having a substantially rectangular shape, A first rib group extending in parallel between opposed long sides of the back surface of the cover plate portion, and a first rib group intersecting with the first rib group and extending in parallel between opposed long sides of the back surface of the cover plate portion. And a group of two ribs, and satisfying a breaking load requirement of at least 2 tons in a static load test,
A lid made of a thermoplastic resin for underground structures, wherein the first rib group and the second rib group are formed by inclining the direction of each rib by 45 to 80 degrees with respect to the corresponding long side.
[0009]
That is, the present invention includes a first rib group and another second rib group that intersects the first rib group and extend in parallel between the opposing long sides of the substantially rectangular cover plate back surface. The amount of the thermoplastic resin used is almost increased by inclining the direction of each of these ribs at 45 to 80 degrees with respect to the long side of the back surface of the lid plate portion, instead of the conventional right angle (90 degrees). It is possible to withstand a breaking load of at least 2 tons only by adding a pigment or a glass fiber to the resin at most without attaching a metal plate for reinforcement. In particular, since the section modulus of a section perpendicular to the long side and the short side of the cover plate portion can be prevented from changing largely in any section, the strength of the entire cover body can be increased.
[0010]
Here, the first rib group and the second rib group incline the direction of each rib at 45 to 80 degrees with respect to the long side of the back surface of the cover plate portion. In order to make it higher, it can be set to 50 to 75 degrees, more preferably to 58 to 68 degrees, and more specifically to 61, 62, 63, 64 or 65 degrees.
[0011]
The thermoplastic resin lid for underground structures according to the present invention is made of a thermoplastic resin such as polyethylene terephthalate resin (PET resin), acrylonitrile / butadiene / styrene resin (ABS resin), polypropylene resin, polyvinyl chloride resin, or the like. Resins can be used, and in particular, recycled polyethylene terephthalate resin (recycled PET resin) or recycled acrylonitrile / butadiene / styrene resin (recycled ABS resin) has been adapted to the modern society's demand for transition to a recycling society. Therefore, it is more preferable. Further, these thermoplastic resins can be reinforced (reinforced) with fibers such as glass fibers and metal fibers. In addition, pigments can be added to these thermoplastic resins, either prescribed or as desired.
[0012]
The thermoplastic resin lid for underground structures according to the present invention is an underground structure having an opening formed in the vicinity of the surface of the ground, for example, a water meter box, a fire hydrant box, and a manhole for opening and closing the opening. This is a lid made of a thermoplastic resin, and is particularly suitable for a lid for a water meter box which is generally used in a generally rectangular shape.
According to another aspect of the present invention, there is provided an underground structure body having an opening on the ground surface, and an underground structure attached to the vicinity of the opening of the underground structure body so as to openably close the opening. And a lid made of thermoplastic resin for
The thermoplastic resin cover is formed of a substantially rectangular cover plate, a first rib group extending linearly and in parallel between opposing long sides on the back surface of the cover plate, and an integral part of the first rib group. A second rib group that intersects and extends linearly and in parallel between the opposing long sides of the back surface of the lid plate portion, and satisfies a requirement of a breaking load of at least 2 tons in a static load test,
The first rib group and the second rib group can provide an underground structure in which the direction of each rib is inclined by 45 to 80 degrees with respect to the corresponding long side.
[0013]
According to still another aspect of the present invention, there is provided a method of manufacturing a thermoplastic resin lid for an underground structure for opening and closing the opening of an underground structure having an opening formed near the ground surface. hand,
A cover made of a thermoplastic resin is formed of a substantially rectangular cover plate, a first rib group extending linearly and in parallel between opposed long sides of the back surface of the cover plate, and the first rib group. A second rib group that intersects and extends linearly and in parallel between opposing long sides of the back surface of the lid plate portion. When the thermoplastic resin lid is manufactured by an injection molding method, heat generated in a molten state is generated. A plastic resin is injected near the center corresponding portion of the surface of the lid plate portion in the mold, and the direction of each rib of the first rib group and the second rib group is inclined by 45 to 80 degrees with respect to the corresponding long side. A method for producing a thermoplastic resin lid for underground structures characterized by the above feature can be provided.
[0014]
In the method for producing a thermoplastic resin lid for underground structures according to the present invention, a normal injection molding method can be adopted as the injection molding method. In the present invention, in particular, the lid is formed of a substantially rectangular lid plate portion and a first rib group and a second rib group that intersect integrally on the back surface of the lid plate portion, and the direction of each rib is Instead of the conventional right angle (90 degrees) with respect to the long side of the back surface of the cover plate, the thermoplastic resin in a molten state is inclined at 45 to 80 degrees and the molten resin is applied to the center corresponding portion of the surface of the cover plate in the mold. By injecting the resin into the vicinity (for example, the temperature of the resin: 260 ° C., the pressure: 800 kg / cm ² ), the resin first flows through the entire lid plate portion, and then flows into each rib (the lid plate). The thickness of the ribs is preferably kept below a certain value, so that each rib has a weld line (the boundary where the resin finally collides when the resin flows in the mold. Without cracking) As a result, it is possible to prevent the strength from being reduced by the weld line and to prevent the occurrence of sink marks, and to improve the structural mechanics by a specific inclination of each rib with respect to the long side of the lid plate portion, thereby improving the deformation including high strength and warpage. The object of the present invention is to provide a highly synthetic resin that can be prevented, and to obtain a thermoplastic resin lid for underground structures suitable for the situation where high load resistance is required.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the cover plate is formed in a substantially rectangular shape, and the ratio of the long side to the short side is preferably about 1: 0.6 (golden ratio).
In the first and second rib groups, the height of each rib is 1 to 10 with the thickness of the cover plate portion being 1, the thickness is T ₁ : 0.5 to 2 at the base, and T _{1 is at} the tip. ₂ : Assuming that 0.1 × T _{1 to} 0.8 × T ₁ (see FIGS. 3A and 3B for T ₁ and T ₂ ), the thermoplastic resin to be injected into the mold in a molten state by pressing is firstly covered with a lid plate portion. The entire part is formed at once, and then the whole rib forming part is simultaneously and smoothly transferred, and the resin spreads all over the lid while preventing the formation of a weld line, and is generally more uniform and high. This is preferable because a lid having strength can be obtained.
Further, the first rib group and the second rib group are such that when the length of the long side of the lid plate portion is L and the span S of each rib is set to L / 40 to L / 4 (see FIG. 2), it is preferable because the ribs can be efficiently utilized to increase the strength of the cover plate (high strength can be obtained with a small amount of resin).
[0016]
Embodiment 1
FIG. 1 is a schematic structural explanatory view showing Embodiment 1 of an underground structure provided with a synthetic resin lid according to the present invention, and FIG. 2 is a view of the synthetic resin underground structure lid of FIG. FIG. 3 is a schematic configuration explanatory sectional view showing a sectional configuration of the rib.
[0017]
First, in FIG. 1, a water meter box 1 as an embodiment 1 (Example 1) of an underground structure has a box body 3 having an opening 2 at an upper part and a bottom plate (not shown) at a lower part, respectively. The box 1 is attached to the vicinity of the opening 2 of the box body 3 and mainly includes a lid 4 for closing the opening 2 so that it can be opened and closed. The entire box 1 is made of polyethylene terephthalate resin (PET resin) for recycling. The opening 2 is embedded so as to be located near the ground surface.
The box body 3 has a substantially trapezoidal shape, in which a water meter can be installed, and the meter for measuring the amount of water used can be measured through an opening 2 formed in the upper part thereof.
[0018]
Next, in FIGS. 2 and 3, the cover 4 for the underground structure includes a substantially rectangular cover plate portion 5, a frame portion 6 extending at a substantially right angle from a peripheral edge of the back surface of the cover plate portion, and a cover plate portion 5. The first rib groups 7, 7,... Extending linearly and integrally along the back surface to the frame portion 6, and linearly and integrally extending along the back surface of the lid plate portion 5 to form the frame portion. The second rib groups 8, 8, ..., and the first rib groups 7, 7, ... are integrally formed at a specific angle. Intersect. 9 and 10 are long sides and 11 and 12 are short sides. Reference numeral 13 denotes a hole into which the administrative ward is fitted, and corresponds to a position of the injection port (in the vicinity of the center of the surface of the cover plate portion 5) into which the molten resin is injected at the time of molding.
The ribs of the first rib group 7, 7, ... and the second rib group 8, 8, ... cross each other at 54 degrees (a large intersection angle is 126 degrees), and It is inclined to α: β: about 63 degrees (a large angle is about 117 degrees) with respect to the long side 9 or 10.
[0019]
The rib 7 has a height of H: 19.5 mm, a thickness of T ₁ : 3.6 mm at the base, and a thickness of T ₂ : 2.2 mm at the tip. The rib 8 is the same as the rib 7, and the span S of both ribs is 20 mm. The cover plate 5 has a length L of the long sides 9 and 10 of 356 mm, a length of the short sides 11 and 12 of 214 mm, and a thickness T _{3 of} 4.0 mm. The frame 6 is one of the ribs, and has a height of 19.5 mm and a thickness of mm. The molded article weight (total resin amount) is 1100 kg.
[0020]
Here, a brief description will be given of a method of manufacturing the lid 4 for an underground structure having the above configuration. First, a mold is set in an injection molding machine, and a molten thermoplastic resin (polyethylene terephthalate resin for recycling; A pigment may be added as appropriate in order to express the color defined by the administrative district) from the mold, that is, from the vicinity of the center of the cavity cover plate corresponding to the center (corresponding to the hole 13 into which the administrative district badge is fitted). Inject (for example, resin temperature: 260 degrees, pressure: 800 kg / cm ² ).
[0021]
Thus, in the underground structure cover 4, each of the first rib groups 7, 7,... And the other second rib groups 8, 8,. Is inclined at 45 to 80 degrees with respect to the long side 9 or 10 of the back surface of the lid plate portion 5 instead of the conventional right angle (90 degrees), and as described above, the molten thermoplastic resin is Since the pressure is injected into the vicinity of the central portion of the surface of the lid plate portion in the mold, even if the lid plate portion 5 is substantially rectangular, the resin uniformly spreads radially from the center of the mold to the entire corner. Therefore, it is possible to prevent the formation of weld lines, prevent warpage and sink marks, and have higher strength against bending and torsion. A suitable lid 4 of the water meter box 1 can be obtained.
[0022]
According to the static load test, the lid 4 of the water meter box 1 having the above configuration was found to withstand a load of 2800 kg. The method of the static load test is such that a rectangular rubber plate (125 mm × 200 mm, t: 6 mm) and an iron plate (125 mm × 200 mm, t: 50 mm) are placed at the center of the surface of the lid 4. It is placed so as to be parallel to that of the body 4, and the load is gradually applied through the iron plate and the rubber plate, and the load at the time when an abnormality occurs or the amount of deflection reaches 15.0 mm is measured as a breaking load. It is.
[0023]
Comparative Example 1
4 is a diagram corresponding to FIG. 2 showing Comparative Example 1, and FIG. 5 is a diagram corresponding to FIG. 3 showing Comparative Example 1. 4 and 5, a lid 24 for an underground structure made of PET resin has a substantially rectangular cover plate portion 25, a frame portion 26 extending substantially perpendicularly from a peripheral portion of the back surface of the cover plate portion, and a cover plate portion 25. The first rib groups 27, 27... Extending linearly and integrally along the back surface and reaching the frame portion 26, and linearly and integrally extending along the back surface of the lid plate portion 25 to form the frame portion. ., And the first rib groups 27, 27,... And the second rib groups 28, 28,.
[0024]
However, the intersection angle of each rib of both rib groups and the relationship angle between each rib and the frame 26 are different from the first embodiment (Example 1) shown in FIG.
That is, the ribs of each group intersect at a right angle (90 degrees), and the ribs 27, 27,. Are perpendicular (90 degrees) to the short side 31 or 32 of the cover plate 25, respectively.
The rib 27 has a height h: 15 mm, a thickness t ₁ : 5.0 mm at the base, and a thickness t ₂ : 4.0 mm at the tip. The rib 28 is the same as the rib 27, and the span S of both ribs is 25 mm. The length of the long sides 29 and 30 of the cover plate part 25 is 356 mm, the length of the short sides 31 and 32 is 208.5 mm, and the thickness thereof is t ₃ : 3.5 mm. The molded article weight (total resin amount) is 1000 kg. Then, according to the static load test, it was found that the lid 24 of the water meter box 21 could not withstand a load of 800 kg (breaking load: 720 kg, cracked at a weld line).
[0025]
Other Examples and Comparative Examples The same static load test results as those of Embodiment 1 described above were obtained under the same conditions except that the crossing angle of each rib, the relation angle with the long side, and the total volume were changed. Obtained.
(1) Example 2
Relationship angle between each rib and long side: 55 degrees (intersection angle of each rib: 90 degrees)
Molded product weight (total resin amount): 1100 kg
Breaking load: 2400kg
(2) Comparative example 2
Relationship angle between each rib and long side: 30 degrees (intersection angle of each rib: 60 degrees)
Molded product weight (total resin amount): 1100 kg
Breaking load: 1700kg
(3) Comparative example 3
Relationship angle between each rib and long side: 90 degrees (intersection angle of each rib: 90 degrees)
Molded product weight (total resin amount): 1100 kg
Breaking load: 1900kg
[0026]
【The invention's effect】
According to the present invention, a first rib group and another second rib integrally intersecting with the first rib group extend linearly and in parallel between opposing long sides on the back surface of the substantially rectangular cover plate portion. Group, and the direction of each of these ribs is inclined at 45 to 80 degrees with respect to the long side of the back surface of the lid plate portion, instead of the conventional right angle (90 degrees), so that the amount of thermoplastic resin used is To withstand a breaking load of at least 2 tons with little increase in In particular, the section modulus of the section perpendicular to the long side and the short side of the cover plate portion can be prevented from largely changing along each side, so that the strength of the entire cover body can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic structural explanatory view showing Embodiment 1 of an underground structure provided with a cover for a synthetic resin underground structure according to the present invention.
FIG. 2 is a perspective view of the synthetic resin underground structure lid of FIG. 1 as viewed from the back side.
FIG. 3 is a schematic configuration explanatory cross-sectional view showing a cross-sectional configuration of a rib in FIG. 2;
FIG. 4 is a diagram corresponding to FIG. 2, showing Comparative Example 1.
FIG. 5 is a diagram corresponding to FIG. 3, showing Comparative Example 1.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Water meter box 2 Opening 3 Box body 4 Lid 5 Lid plate 6 Frame 7 First rib group 8 Second rib group 9, 10 Long sides 11, 12 Short sides

Claims (14)

A lid made of a thermoplastic resin for an underground structure for opening and closing the opening of an underground structure having an opening formed in the vicinity of the ground, comprising a substantially rectangular cover plate and a back surface of the cover plate. A first rib group extending in parallel between the opposed long sides of the first rib group, and a second rib group intersecting with the first rib group and extending in parallel between the opposed long sides on the back surface of the cover plate portion. And meet the requirements of a breaking load of at least 2 tons in a static load test,
A lid made of a thermoplastic resin for underground structures, wherein the first rib group and the second rib group are formed by inclining the direction of each rib by 45 to 80 degrees with respect to the corresponding long side. The thermoplastic resin lid for underground structures according to claim 1, wherein the inclination of the first rib group and the second rib group with respect to the long sides facing each other is 50 to 75 degrees. 3. The thermoplastic resin lid for underground structures according to claim 1, wherein the lid plate has a ratio of a long side to a short side of about 1: 0.6. The first rib group and the second rib group each have a height of 1 to 10 and a thickness of T ₁ : 0.5 to 2 at the base and T ₂ : 0.1 × _T 1 to 0.8 underground construction thermoplastic resin lid according to any one of claims 1 to 3 comprising a × _{T 1.} The lid according to any one of claims 1 to 4, wherein the lid is molded by a thermoplastic resin injection molding method, and the injection port of the molten thermoplastic resin at the time of the molding is located near the center of the lid plate surface. Cover made of thermoplastic resin for underground structures. The first rib group and the second rib group each have a length of a long side of the lid plate portion as L and a span S of each rib as L / 40 to L / 4. 4. A lid made of a thermoplastic resin for an underground structure according to item 1. The synthetic resin lid for underground structures according to any one of claims 1 to 6, wherein the thermoplastic resin is a recycled polyethylene terephthalate resin or an ABS resin. The synthetic resin lid for an underground structure according to any one of claims 1 to 7, wherein the thermoplastic resin is a glass fiber reinforced thermoplastic resin. The lid made of a thermoplastic resin for underground structures according to any one of claims 1 to 8, which is a lid for a water meter box. An underground structure main body having an opening on the ground surface, and near the opening of the underground structure main body, a thermoplastic resin lid for an underground structure attached to close the opening so that it can be opened and closed,
The thermoplastic resin cover is formed of a substantially rectangular cover plate, a first rib group extending linearly and in parallel between opposing long sides on the back surface of the cover plate, and an integral part of the first rib group. A second rib group that intersects and extends linearly and in parallel between the opposing long sides of the back surface of the lid plate portion, and satisfies a requirement of a breaking load of at least 2 tons in a static load test,
An underground structure, wherein the first rib group and the second rib group are formed by inclining the direction of each rib by 45 to 80 degrees with respect to the corresponding long side. A method for manufacturing a thermoplastic resin lid for an underground structure for opening and closing the opening of an underground structure having an opening formed near the ground surface,
A cover made of a thermoplastic resin is formed of a substantially rectangular cover plate, a first rib group extending linearly and in parallel between opposed long sides of the back surface of the cover plate, and the first rib group. A second rib group that intersects and extends linearly and in parallel between opposing long sides of the back surface of the lid plate portion,
When manufacturing the thermoplastic resin lid by an injection molding method, a molten thermoplastic resin is injected near the center corresponding portion of the surface of the lid plate portion of the mold, and the first rib group and the second rib group. Wherein the direction of each of the ribs is inclined by 45 to 80 degrees with respect to the corresponding long side. The method for producing a thermoplastic resin lid for underground structures according to claim 11, wherein the inclination of the first rib group and the second rib group with respect to the long sides facing each other is 50 to 75 degrees. The method for producing a thermoplastic resin lid for underground structures according to claim 11 or 12, wherein the lid plate has a ratio of a long side to a short side of about 1: 0.6. The first rib group and the second rib group each have a height of 1 to 10 and a thickness of T ₁ : 0.5 to 2 at the base and T ₂ : 0.1 × _T 1 ~0.8 × manufacturing method of underground structures thermoplastic resin lid according to any one of claims 11 to 13 comprising a _{T 1.}

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