JP2973281B2 - 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 plastic manhole cover reinforced by inserting a reinforcing material.

[0002]

2. Description of the Related Art At present, manhole covers are mainly made of cast iron, but some are made of plastic in order to reduce the weight and cost. However, plastics have much lower rigidity than cast iron. Therefore, a so-called reinforced plastic material reinforced with glass fiber is used, and the rigidity is increased by further increasing the wall thickness.

[0003] Reinforced plastic reinforced with glass fiber as described above is difficult to recycle when discarded, and glass fiber residue remains in incineration, making disposal difficult. Therefore, glass fiber reinforced plastic is not used as much as possible. You are moving in the direction.
In addition, there is a problem that increasing the thickness significantly reduces the cost advantage of using a plastic material.

[0004]

Therefore, taking advantage of the advantages of plastic RIM molding (reaction injection molding), a metal rod-like reinforcing material such as a metal pipe is inserted into a non-reinforced plastic containing no glass fiber. We tried to solve the above problem. However, if a reinforcing material such as a pipe is simply inserted into the thick part over the entire length, a large stress is applied between the plastic and the reinforcing material due to the molding shrinkage of the plastic, and the product is considerably warped. There is a problem.

[0005] The present invention has been made in view of the above points, and has as its object to provide a plastic manhole cover reinforced by a metal rod-like body which does not warp the product, eliminating the above problems. I do.

[0006]

According to the first aspect of the present invention, there is provided a plastic manhole cover reinforced by inserting a reinforcing material, wherein a metal rod is used as the reinforcing material. the metallic rod-shaped body with partially inserted into the rear surface side of the manhole cover, the insert part
When plastic shrinks around the periphery of the plastic, the plastic
Metal that absorbs the stress applied between the metal and the metal rod
Stress absorbing member made of tape or resin tape or lubricant
Is provided .

[0007]

[0008]

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are views showing the structure of a plastic manhole cover according to the present invention. FIG. 1A is a plan view, FIG. 1B is an AA section, and FIG. 1C is a BB section. . As shown in the figure, the manhole cover 1 is made of plastic formed by a RIM molding method, a lattice-shaped uneven pattern 2 is formed on the front side, and a plurality of (four in the figure) reinforcing ribs are arranged on the back side in the width direction. A metal rod (for example, SUS304 pipe) 4 is inserted through the reinforcing rib 3.

A metal tape 5 made of aluminum or the like is attached to an outer surface of a portion of the metal rod 4 penetrating the reinforcing rib 3. When the manhole cover 1 is formed by the RIM molding method by attaching the metal tape 5 to the outer surface of the portion of the metal rod 4 penetrating the reinforcing rib 3 as described above, the metal tape 5 has a smooth surface. Therefore, the stress generated between the plastic and the metal rod 4 due to the plastic shrinkage is absorbed, and the manhole cover 1 does not warp.

Next, a method of manufacturing a plastic manhole cover will be briefly described with reference to FIG. As shown in FIG. 2, a gap 103 having the same shape as the manhole cover 1, a gap 104 having the same shape as the rib 3, and a gap 105 for accommodating the metal rod 4 are integrally formed between the upper mold frame 101 and the lower mold frame 102. Is formed. As shown in FIG. 3, a metal rod 4 having a metal tape 5 attached to the outer surface of a portion penetrating the reinforcing rib 3 is accommodated in the gap 105, and, for example, two liquids are mixed in the gap 103 and the gap 104. By injecting the resin liquid, the two liquid resin liquids solidify by reaction, and a plastic manhole cover reinforced with the metal rod 4 is completed.

As described above, the reinforcing ribs 3 of the metal rod 4
The metal tape 5 is adhered to the outer surface of the portion penetrating the metal rod 5 so that the metal tape 5 has a smooth surface as described above, and when the resin liquid reacts and solidifies and contracts, the metal tape 5
A stress is generated between the metal rib 5 and the reinforcing rib 3, but the stress is absorbed by the smooth movement of the reinforcing rib 3 on the surface of the metal tape 5 due to the shrinkage, and the manhole cover 1 does not warp.

In the above example, the metal tape 5 is applied to all the locations (four locations in the figure) penetrating the reinforcing ribs 3. However, even if the metal tape 5 is applied to both ends, the warp is almost eliminated. It was confirmed that it did not occur. In addition, when the surface of the metal rod 4 is smooth, no warpage occurs even if the metal tape 5 is not provided. Further, even if a resin tape having a smooth surface is attached instead of the metal tape 5 or a lubricant such as silicon grease is applied, substantially the same operation and effect as in the case of the metal tape 5 can be obtained.

The manhole cover 1 reinforced with the metal rods 4 as described above was actually put over the manhole opening, and a passenger car was placed on the manhole cover 1 to examine the deformation state.
Only deformation within a range that did not pose a problem in practice could be observed.

In the above embodiment, an example is shown in which one metal rod 4 is used at the center of the back side of the manhole cover 1; however, the number of metal rods is not limited to one. Instead, a structure in which a plurality of metal rods are partially inserted may be used. In this case, a stress absorbing member such as a metal tape is provided on the outer peripheral surface of the insert portion.

[0016]

As described above, according to the first aspect of the present invention , a metal rod is used as a reinforcing material , and the metal rod is partially inserted into the back surface of the manhole cover.
At the same time, plastic is molded around the insert
When shrinking, it is hung between the plastic and the metal rod.
Metal or resin tape or lubrication to absorb such stress
Since the stress absorbing member made of a material is provided, an excellent effect of being able to provide a plastic manhole cover reinforced with a metal rod and having a small warpage can be obtained.

[0017]

[Brief description of the drawings]

FIGS. 1A and 1B are views showing the structure of a plastic manhole cover according to the present invention, wherein FIG. 1A is a plan view and FIG.
FIG. 1C is a cross section taken along line BB in FIG.

FIG. 2 is a view for explaining a method of manufacturing a plastic manhole cover according to the present invention.

FIG. 3 is a view showing a metal rod for reinforcement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Manhole cover 2 Lattice-like uneven pattern 3 Reinforcement rib 4 Metal rod 5 Metal tape

Claims (1)

(57) [Claims] 1. A reinforcing member a plastic manhole cover which is reinforced by inserts, using a metal rod-shaped member to the reinforcement, prior to the metal rod-shaped body
Co when partially inserted into the back side of the serial manhole cover
Plastic shrinks around the insert
When it hangs between the plastic and the metal rod
Metal or resin tape or lubricant that absorbs stress
A plastic manhole cover provided with a stress absorbing member .