JP3025451B2 - Reinforced plastic manhole cover - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manhole cover for a drainage pipe for sewerage and the like which has become indispensable for public roads such as general roads and sidewalks and other public facilities.

[0002]

2. Description of the Related Art Sewerage facilities, mainly in urban areas, are being laid continuously year after year as a major item in urban planning.
It is a major goal of local governments to build a pipeline network that covers almost all urban areas by the first century. On the other hand, simplified sewage treatment facilities for small-scale settlements have been developed in each region in the agricultural and fishing villages, and the laying of sewage pipes has been progressing at a rapid pace throughout the country to build a comfortable living environment. Inside.

[0003] For inspection, repair, and maintenance of drainage pipes such as sewers, it is also necessary to provide openings appropriately communicating the pipes buried underground with the ground, and to carry out regular maintenance without fail. Based on the criteria set by each local government, human holes are provided at regular intervals so that the inspector can infiltrate into the pipeline. However, as it is well known, if this manhole is left open on public roads or amusement parks, it is extremely dangerous, so the manhole cover is usually fitted to cut off communication between the outside world and the pipeline. It is. Manhole covers are standardized by JIS and local governments. At present, a disc made of rattan cast iron with a diameter of about 600 mm is fitted into the opening for general road use. In some sewage treatment plants and simple sewage treatment plants in settlements, manhole covers made of reinforced plastic may be used instead of cast iron. In terms of strength, varieties of reinforced plastic materials that have already been reinforced to a level comparable to rattan cast iron have been developed, and are lightweight and much more resistant in corrosive atmospheres,
Almost no deterioration in quality due to discoloration, rusting, etc. is recognized, so it is easy to handle in laying work and daily inspection, etc., lightweight and durable, superior to cast iron in all respects. There is great expectation that the range of application will be generalized and occupy the mainstream of manhole covers.

[0004] The idea of applying a reinforced plastic material to a manhole cover and replacing it with a cast iron material of the prior art has been pursued in step with the development and progress of the reinforced plastic material itself. It is well known that reinforced plastics are used in many fields such as interior and exterior parts of automobiles, acoustic components, etc. In addition to weight reduction, corrosion resistance, It is no surprise that high-strength development approaching metal materials has attracted the attention of the industry. Reinforced plastic material is also known as FRP (Fiber Glass)
Reinforc-ed Plastics) is interpreted as a synonym, broadly encompasses all thermosetting resins and thermoplastic resins, and refers to a material reinforced by adding and adding all kinds of fibrous materials such as metals, plants, and minerals. In a narrow sense, an unsaturated polyester resin reinforced with glass fiber (epoxy resin, phenol resin as a special case) is a representative example. The tensile strength of glass fiber is 150-300Kgf /
Because of its very large size of mm ² , there is no question that this is the largest requirement that directly contributes to the strengthening of reinforced plastics.

FIG. 4 shows an example of a procedure for using a compound molding material as a recent example of a method of molding a reinforced plastic material. The molding method using the compound material is a bulk molding compound (BMC),
The sheet molding compound (SMC) method is mainly used. For example, as for the bulk molding compound, an unsaturated polyester resin, a curing agent, a pigment and other additives are charged into a mixer as shown in FIG. And then transferred to a kneading machine, mixed with a glass chop (short glass fiber), kneaded uniformly, and mixed with BMC (Bulk Molding Compo).
After und), the usual method is to calculate the weight of the material accurately, put it into a mold, heat, pressurize and cure and mold. According to this method, the quality uniformity and mass productivity are clearly superior to the conventional lay-up molding method, which has been regarded as a molding method that mainly uses a reinforced plastic material, and a flat surface such as a manhole cover is obtained. It has been evaluated to be the most suitable method for the production of mass-produced products in which uniform strength must be guaranteed in all directions in a typical shape.

On the other hand, a sheet molding compound (SMC) also represents another mainstay of the compounding method, in which a polyester resin, a filler, an internal mold release material, a hardening material, etc. are compounded and mixed, and immediately mixed. It is applied to a glass fiber substrate such as a roving cloth or glass fiber strand mat, immediately covered on both sides with a film, and formed by winding a cloth impregnated with the admixture into the glass fiber substrate by appropriate pressure. . FIG. 5 is a cross-sectional view showing a conventional technique of a reinforced plastic manhole cover after formation. The cross-sectional shape naturally depends on designation from each local government or the like, but the basic components are the upper surface and the lower surface of the manhole cover. Means a reinforced plastic material 1a, 1b such as the sheet molding compound (SMC), and a resin mortar layer 2 as an intermediate layer sandwiched between upper and lower portions.
What is formed by sandwiching and pressing in a sandwich manner in a is usually used. Resin mortar is a molded product obtained by compounding an unsaturated polyester resin with silica sand, which is an aggregate, and simultaneously pressing and heating it together with a reinforced plastic layer (sheet molding compound) on both sides to integrally cure it. The sheet molding compound with excellent material strength bears the bending stress applied to the manhole cover,
The intermediate resin mortar layer plays the role of transmitting the shearing force while maintaining the surface layer at a constant distance, and the three layers together have the breaking strength against external pressure (resistance including anti-pressure, impact resistance, etc.) It is configured to exhibit

[0007] There is relatively little information on manhole covers made of reinforced plastic disclosed as prior art, and in Japanese Utility Model Application Laid-Open No. 61-159487, as shown in FIGS. The gist of the invention is indicated by the expression of the claim, which is a groove lid made of glass fiber reinforced polyester, which is a product, but press molding is possible because the material is a resin system, and molding such as protruding stripes on the surface is possible. It is said that it will be possible to prevent slippage, and the figure of the manhole cover of the applied product will be shown in Fig. (C), and it will be possible to apply it to a product like a conventional iron manhole cover by press molding and commercialize it Just to explain. In addition, as a few examples in which a resin product was presented as a manhole cover, see
-47853, as shown in FIGS. 7A and 7B, a synthetic resin or a glass fiber reinforced synthetic resin or the like is formed under a metal manhole formed of a cover plate 101 and a receiving frame 102 by molding with cast iron or the like. And the cover plate 103 is fixed to the receiving frame 104 with bolts and nuts.
4 is provided with a double-shaped manhole formed by attaching a dish-shaped synthetic resin manhole having a flange 107 formed around the periphery of the vehicle. It has to be seen that it is still a manhole cover and is not the main purpose of replacing iron with reinforced plastic.

[0008]

As described above, while the development of drainage pipes such as sewers and the promotion of networking are being promoted nationwide, the development of traffic vehicles is remarkable, and the vehicle is driven on roads. The number and total weight of vehicles have increased remarkably, and the static pressure and dynamic pressure applied to manhole covers installed on roads and the like are steadily increasing. Needless to say, the manhole cover located on the road on which the vehicle travels must withstand the load of the total weight of the passing vehicle with a margin. The total weight of a 12-ton truck is 20.0 tons, and a 5 ton truck has a weight of 9.5 tons.
There are 1.8 tons for ordinary passenger cars. The wheel load of the rear one-wheeler is 12-ton normal truck, and each value is finely specified from 64.7 kN to 4.8 kN of ordinary passenger car. Conventionally, the strength is enough for ordinary passenger car to pass safely. It was considered to be suitable as a manhole cover to be installed on general roads if it had a breaking load of 2,000 kgf as a standard, but as the size of recent recreational vehicle (RV) vehicles and the like has become larger, The development of a high-strength manhole cover with a breaking load exceeding 4,000 kgf has emerged as an urgent issue as one of the requirements to be adopted for road surfaces such as roads.

The present invention regards the increase in the weight of a passing vehicle as described above as a trend of the times, and further develops a technique for improving the strength of a resin-based manhole cover that has been conventionally accumulated.
Prototypes and field tests were repeated in search of the assembly of a high-strength material configuration, and the conventional concept was fundamentally changed to provide a reinforced plastic manhole cover with numerous advantages that can no longer be expected with cast iron base. Aim.

[0010]

The manhole cover made of a reinforced plastic according to the present invention is made of a synthetic resin such as an unsaturated polyester resin as a base material, silica sand, calcium carbonate, pigment,
A resin-based manhole cover formed by heating, pressing, and molding a resin concrete layer 1 uniformly mixed and kneaded by adding a curing agent or the like as appropriate is used as a base, and in particular, a large number of short glass fibers are compacted in a non-directional manner. A glass fiber strand mat 11 molded and bound is laid in a resin concrete layer near the entire upper and lower surfaces of the manhole cover, and the glass fiber strand mat 1 on both surfaces or at least the lower surface thereof is provided.
At least two glass fiber roving cloths 12 reinforced in a specific direction are superimposed on the inner surface side of each of them in a phase orthogonal to the above direction, and the outer surfaces of the respective glass fibers are impregnated with a resin liquid to be integrated. This is a structural feature. Alternatively, bulk molding in which a synthetic resin such as an unsaturated polyester resin is used as a base material instead of the resin concrete layer 1 serving as a base, and short glass fibers, calcium carbonate, a pigment, a curing agent, and the like are appropriately added and uniformly kneaded. -It may be compound 1A.

In the structure of the present invention, the glass fiber strand mat 11 is laid along the upper surface and the lower surface of the manhole cover. The glass fiber strand mat is a large number of glass fibers (glass strands) 50 to 10.
It is a mat in the form of being cut to a length of 0 mm, deposited in a random sheet shape, weakly adhered to each other by a secondary binder dissolved in the styrene monomer, and wound up in a roll shape to a weight of 30 to 100 kg. Since the fiber materials with extremely high tensile strength are entangled with each other and do not interweave, they are free and only the mutual contact points are bound with a special adhesive. The feature is that it is persistent.

Next, the glass fiber roving cloth 12 to be laid on the inner side of the manhole cover is formed by bundling a large number of glass fibers into a cloth with a small number of fibers without twisting, as described above. Since the tensile strength of glass fiber alone is at a remarkable level that far surpasses metal, it has a strength that can not follow other in the fiber direction, but has strength in a direction different from the fiber direction. The rapid decline is unavoidable based on physical principles. So overwhelmingly many fibers are arranged in the horizontal direction,
The method of weaving with the smallest longitudinal fibers so that the fibers are aligned in the same direction is referred to as a (bridging) glass fiber roving cloth. The greatest feature is that it has outstanding strength in a specific direction from its background. Therefore, when targeting an unspecified load in a direction as in the present invention, at least two glass fiber roving cloths are specified. Lay them so that the directions are orthogonal to each other and lay them so that they can withstand a high breaking load in any direction.

In the present invention, in addition to the reinforcing layers on the front and back surfaces of the lid made of the glass fiber strand mat and the glass fiber roving cloth, an improvement measure has been disclosed in order to realize an even higher level of a super-reinforced layer. In other words, as the road conditions change and the need to further strengthen the manhole cover has become a necessity in today's era, to further improve the strength, simply consider the number of laid glass fiber strand mats and glass fiber roving cloths. It can be interpreted that it is only necessary to increase the compounding density of the strong glass fiber by overlapping, but it is necessary to change the diameter and thickness of the manhole cover itself no matter how strong the strength is required. This is a problem and should be considered to be almost unacceptable, given the compatibility with existing manhole equipment. For example, even if the number of glass fiber roving cloths is increased more than this, deviations occur in the woven portion between the longitudinal fibers and the weft fibers of the glass fiber roving cloth during heating, pressing, and molding, resulting in uneven density or weaving. There is also a possibility that "fraying" peculiar to the product occurs, the direction of the weft fibers is lost, and the strength level as expected is lost.

As described above, a large limit is imposed on the strength improvement due to an increase in size or an increase in size, an increase in mass, a failure in consistency of systematic strength, and the like. It was experimentally proved that it was directly linked to soaring unit prices, and that it was at all difficult to endure. In the present invention, as a further trumpet of the reinforced plastic manhole cover of the first and second embodiments,
A glass fiber strand mat 11 laid near the entire surface of the manhole cover of the resin concrete layer 1 or the bulk molding compound 1A, and a further inner surface of a glass fiber roving cloth 12 laid on the inner side of the glass fiber strand mat 11. A glass fiber non-woven net 13 bonded to each other with an adhesive without woven by combining glass long fibers in a lattice form, and impregnating with a resin liquid to form a layer integrally to provide the best configuration. Finally, the third embodiment has been reached.

The glass fiber non-woven mesh is characterized by arranging long glass fibers in a special lattice in the vertical and horizontal directions and firmly fixing the intersecting eyes with an alkali-resistant binder.
Compared to the chopped form of short glass fiber, it has a much higher crack-preventing and crack-preventing function, and a remarkable progress has been made in improving the impact resistance especially when combined with the resin liquid impregnated between the lattices. It is characterized by the fact that the intersection is glued only with an adhesive instead of a woven cloth, so there is no "thread loosening" caused by misalignment between fibers or weaving, which is a characteristic of glass fiber non-woven nets. Excellent flexibility, good compatibility with other materials such as glass fiber strand mat, glass fiber roving cloth, etc. as a reinforcing material.In addition, it is suitable for molding manhole lids in various points such as defoaming property and mold conformability. It has the properties as a strong reinforcement.

The greatest advantage of this glass fiber non-woven net is that the increase in mass is suppressed lower than the reinforcing effect obtained, and simultaneously satisfies the two conflicting propositions of improving strength and maintaining the current state of shape. For this reason, a significant improvement in the breaking strength was realized by adding a minimum amount of reinforcing material, and the ability to renew the existing manhole cover very easily was provided.

[0017]

1A and 1B are a plan view showing a first embodiment of the present invention and a sectional view taken along line MM of FIG. 1A. The manhole cover 10 is attached to the inner periphery of the receiving frame 2 placed on the ground level G so as to be removably attached to the edge of the opening of the sewage treatment tank (not shown),
Normally, vehicles and passers-by pass through the upper surface of the manhole cover 10 without any trouble, and at the time of necessary inspection based on regulations, or in the case of emergency, a person such as a local government grasps the hand-held handle 21 and lifts and removes it. The ground and the inside of the underground sewer pipe etc. are communicated.

The embodiment shown in FIG. 1 is based on resin concrete among the manhole covers made of reinforced plastic, and is filled with a mold of a predetermined shape to integrally heat, pressurize,
It is molded. The resin concrete layer 1 is made of unsaturated polyester resin as a base material, silica sand, calcium carbonate,
The main raw material is a mixture obtained by adding a toner (pigment), a curing agent, and the like and kneading the mixture so as to be uniformly dispersed. A glass fiber strand mat 11 is placed in the filling layer near the surface, and a glass fiber roving cloth 12 is And a single glass short fiber is impregnated with a resin liquid for each outer peripheral surface to integrally reinforce the glass fiber.

The embodiment shown in FIG. 2 shows a BMC (bulk molding) among reinforced plastic manhole covers.
(A) and M-M of a compound) manhole cover
It is a sectional view (B), and the bulk molding compound 1A is made of an unsaturated polyester resin as a base material, to which a short glass fiber, calcium carbonate, a toner (pigment), a curing agent, and other additives are added. The main material is kneaded so as to be dispersed, and the upper and lower surfaces of the manhole cover near the surface are made of glass fiber strand mat 1 as in the previous embodiment.
1 and a glass fiber roving cloth 12 intensively reinforced.

FIG. 3 is a plan view (A) and a sectional view taken along line MM (B).
In the third embodiment, the base of the reinforced plastic is not limited to the resin concrete or the BMC, but the resin concrete layer 1 or the bulk molding compound 1A is made of the glass fiber strand mat 11, the glass fiber A feature is that a glass fiber non-woven net 13 is laid on the roving cloth 12 and further on the inner surface side. Although this addition only slightly increased the content of the glass fiber as a whole, a unique result was obtained in which the breaking strength was improved at a much higher rate than expected.

For example, as a third embodiment, a glass fiber having a tensile strength of 60 kgf / mm ² is simply used as the non-woven glass fiber mesh with the same composition as the reinforced plastic manhole cover of the BMC system according to the second embodiment. As a raw material strand, an intersection of about 5 mm grid spacing and about 5 mm grid spacing without weaving each other is bonded with an alkali-resistant adhesive to form a non-woven mesh having a thickness of about 0.45 mm and a nominal diameter of 600 m.
m, a reinforced plastic manhole cover with a total thickness of 14 mm was manufactured under the same conditions except that a glass fiber non-woven net was not included. Table 1 shows a comparison with the manhole cover.

[0022]

As described above, according to the present invention, the manhole cover is made of a reinforced plastic in which the weight and durability of the manhole cover are remarkably improved, but the fracture strength and the resistance to metal are higher than those of a metal represented by a cast iron material. Material characteristics that can respond to the increase in size and weight of vehicles traveling on the road with an impact load can be provided, and the cost increase associated with strengthening is very small, assuming excessive mass Since there is no need to place it, it is possible to achieve the fruit of reinforcement simply by replacing it with the existing manhole cover, which has the effect of attracting attention as an ideal product that satisfies the long-awaited requirements of the public and private sectors. In particular, the ultra-strengthened product according to the third embodiment is endowed with qualifications that directly meet the needs of the times, and it is highly expected that there are immeasurable effects obtained with the implementation.

[Brief description of the drawings]

FIG. 1A is a plan view (A) of a first embodiment of the present invention, and FIG.

FIG. 2 is a plan view (A) of a second embodiment of the present invention and a cross-sectional view (B) of FIG.

3A is a plan view of a third embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along line MM of FIG.

FIG. 4 is an explanatory view showing a procedure for adjusting a compound molding material (bulk molding compound) among reinforced plastic materials.

FIG. 5 is a longitudinal sectional front view showing a conventional technique of a reinforced plastic manhole cover (sheet molding compound).

FIG. 6 is a vertical sectional front view (A) of another prior art, a perspective view (B) of an embodiment, and a perspective view (C) of another embodiment.

FIG. 7 is a vertical sectional front view (A) and a partially enlarged view (B) of a main part of still another conventional technique.

[Explanation of symbols]

 1 Resin concrete layer 1A Bulk molding compound 2 Receiving frame 10 Manhole cover 11 Glass fiber strand mat 12 Glass fiber roving cloth 13 Glass fiber non-woven net G Ground level

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E02D 29/14 E03F 5/02-5/06

Claims (3)

(57) [Claims] 1. A resin concrete layer 1 made of a synthetic resin such as an unsaturated polyester resin as a base material, and appropriately kneaded by appropriately adding silica sand, calcium carbonate, a pigment, a curing agent and the like.
The manhole cover 10 is heated, pressurized and formed into a predetermined shape by using
, A glass fiber strand mat 11 in which glass short fibers are compacted in a non-direction and bound together is laid along the entire upper and lower surfaces of the manhole cover, and at least a lower surface of the glass fiber strand mat 11 on the inner surface side. Characterized in that at least two glass fiber roving cloths 12 reinforced in a specific direction are overlapped with each other in a phase orthogonal to the above direction, and the outer peripheral surfaces of the respective glass fibers are respectively impregnated with a resin liquid and integrated. Plastic manhole cover. 2. The method according to claim 1, wherein a synthetic resin such as an unsaturated polyester resin is used as a base material in place of the resin concrete layer 1, and short glass fibers, calcium carbonate, a pigment, a curing agent and the like are appropriately added and uniformly added. A reinforced plastic manhole cover characterized by using a kneaded bulk molding compound (BMC) 1A as a base material. 3. The glass fiber strand mat 11 according to claim 1, which is laid near the entire surface of the manhole cover of the resin concrete layer 1 or the bulk molding compound 1A, and the inner side of the glass fiber strand mat 11. A glass fiber non-woven net 13 in which glass long fibers are combined in a lattice and bonded to each other by an adhesive without being woven is laid and further impregnated with a resin liquid on the inner surface side of the glass fiber roving cloth 12 laid. Manhole cover made of reinforced plastic, characterized by integrally forming layers.