JPH1193425A - Object drop preventive net material and manhole structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drop preventive net material for manhole lid and offer a manhole structure which will never damage electric cables and/or communication cables even in the event of falling-off of the lid of a manhole for an underground buried electric box, etc., as a heavy weight, being embodied in a lightweight construction and presenting excellent easiness in handling. SOLUTION: The object drop preventive net material 1 is to prevent an object such as manhole lid from dropping, being made of a fiber material whose tensile ruptural strength at least in one direction is between 5-50 tf/m upon conversion into the one-meter width value. The manhole structure is such that the netting 1 is fixed to a lid supporting frame of the manhole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a net material for preventing a fall of an object, more specifically, a net for preventing a fall of a manhole cover installed for the purpose of preventing a fall of a manhole cover such as an underground electric box. The present invention relates to materials and manhole structures.

[0002]

2. Description of the Related Art In recent years, electric poles have disappeared from the streets, and electric cables and communication cables have been laid in underground common trenches (underground buried electric boxes). Manholes where people can enter are installed in some places in the common gutter for maintenance. The lid of this manhole is rectangular instead of the conventional circular one, and the weight of the lid is as heavy as about 100 kg, so it may drop into the electric box when opening and closing the lid and damage the electric cable and communication cable. is there. Therefore, for the purpose of preventing the lid from falling, a fall prevention member is provided immediately below the lid.

[0003] As this fall prevention member, iron grating (lattice-shaped one) is conventionally used.

[0004]

However, the anti-fall material of the grating is heavy and requires a great deal of labor to open and close, and when the anti-fall material is dropped, an electric cable or communication cable is provided by the anti-fall material. There were problems such as damaging the cable.

[0005] The present invention provides a lightweight manhole which does not damage an electric cable or a communication cable even when a manhole cover such as an electric box buried underground which is heavy is dropped. The present invention provides a net material and a manhole structure for preventing the lid from falling. It is another object of the present invention to provide a light-weight and highly-handled fall-preventing net material for the purpose of preventing any object from falling, not limited to a manhole cover.

[0006]

The present invention employs the following means in order to solve the above problems. That is, the net material for preventing the object from falling according to the present invention is a net for preventing the object from falling, and the net has a tensile rupture strength in at least one direction converted to a width of 1 m, which is 5 tf.
/ M or more and 50 tf / m or less.

Further, the manhole structure of the present invention is characterized in that the net material for preventing the object from falling is attached to the manhole cover supporting frame.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has intensively studied a manhole structure which is excellent in handleability, a material for preventing a fall of a manhole cover or a damage of an electric cable or a communication cable due to a fall of the cover itself. However, the present inventors have sought to solve the above-mentioned problems at once by using a specific net, and have reached the present invention.

Here, the object referred to in the present invention refers to a manhole cover in the present invention, but is not particularly limited, and includes any object that requires a fall prevention measure. . Further, the net material of the present invention,
In other words, the fall-prevention material for the manhole cover as an object has a high strength that does not catch the cover and breaks even if the manhole cover such as an underground electric box falls, and the electric cable and communication cable located below. Low elongation is required at the same time. As the specific strength, as shown in FIG. 1, the both ends of the net having a length of 1 m are fixed and horizontally held, and a 200 cm-weight iron cube from a height of 20 cm from the surface of the net. When dropping so that the sides are not faces or vertices but down, the net does not break through the iron cube, and the vertical deflection of the net is required to be 200 mm or less, preferably Is 15
A deflection within a range of 0 mm or less, more preferably 120 mm or less is required.

At this time, the strength required for the net is such that the tensile breaking strength is 5 tf / m or more and 50 tf when converted to a 1 m width.
/ M or less. If it is less than 5 tf / m, the net cannot be tolerated by the impact of the dropping of the lid, and the net will be broken.
If it exceeds m, it will not break, but it will be over-spec and not economical.

[0011] Fiber materials required to exhibit these characteristics include metal fibers and natural fibers, polyamide fibers, polyester fibers, polyaramid fibers, carbon fibers, and the like.
Although synthetic fibers such as high-strength polyethylene fibers are used, polyaramide fibers, carbon fibers, high-strength polyethylene fibers, and the like are preferably used because light weight, high strength, and low elongation are desired. Among them, para-based polyaramid fibers are particularly preferably used.

Among these synthetic fiber materials, the tensile strength is a very important characteristic, and the tensile strength of a single yarn is 14 gf / d.
A synthetic fiber having a weight of 100 gf / d or more is preferably used. If it is less than 14 gf / d, the required yarn amount becomes extremely large, and it is not possible to secure a sufficient space to be described later. Further, although the tensile strength of the single yarn may be arbitrarily large, synthetic fibers exceeding 100 gf / d do not exist on a commercial basis and are not economical in view of development costs.

It has already been mentioned that these synthetic fiber materials are not only high in strength but require low elongation. In order to achieve this low elongation, a synthetic fiber material having a tensile elongation at break of 0.4% or more and 5% or less is preferably used. If it exceeds 5%, the deflection at the time of dropping the lid is large, and the lower electric cable and communication cable are damaged. Also,
The lower the tensile elongation at break, the better, but 0.4%
Synthetic fibers of less than do not exist on a commercial basis and are not economical in view of development costs.

Further, since this net is installed underground, rainwater enters and dust enters. Therefore, it is preferable to have excellent water permeability and air permeability, and a mesh fabric is preferably used. The size of the eye, which is the gap, is preferably 2 mm or more and 100 mm or less. If it is less than 2 mm, dust accumulates in the eyes, and if it exceeds 100 mm, the eyes are too large, and a sufficient capturing effect cannot be obtained against falling from the corner (apex) of the lid.

[0015] As these mesh fabrics, a woven structure of a tangled weave, a monsa weave, a basket weave, or a Russell knit structure is preferably used.

These woven fabrics are preferably subjected to resin processing for the purpose of preventing the surface from being scratched. The resin used here is preferably a resin containing no halogen, more preferably selected from polyolefin-based resins, polyester-based resins, polyamide-based resins, polyurethane-based resins, polyacryl-based resins, and polyvinyl acetate-based resins. At least one or a mixture thereof is used. It is also preferable to add at least one selected from a coloring agent, an ultraviolet absorber, an ultraviolet shielding agent, and a halogen-free flame retardant to the resin. The net is
It is preferable that it is flexible and has good handleability as compared with iron grating, etc., and JIS L 1096 6.
20 The softness according to the bending resilience method A (Gurley softness) is preferably 5000 mg or less.

The net of the present invention has a weight of 2 cm from a height of 20 cm above the surface of the net when the both ends of a 1 m long drop prevention material are fixed and held horizontally.
The iron cube of 00 kg does not break even when dropped so that the sides are not faces or vertices but the sides are down, and the vertical deflection of the net needs to be 200 mm or less, preferably 150 mm or less, more preferably 150 mm or less. It is preferable to have physical properties of 120 mm or less.

[0018] The excellent physical properties of such a net are 100%.
For use, it is preferable that the end of the net is folded back through a core material, and is used in the form of a reinforcing structure sandwiched and fixed by two plates having a width shorter than the folded length of the net. In other words, even if the net has a high strength and low elongation, it may be broken at a low strength at the fixing portion unless it is fixed to the frame of the manhole so that the tensile strength of the net is exhibited. is there. Therefore, as a fixing method, as shown in FIG. 2, the end of the net is folded by inserting a rope in the inside thereof, and two plates having a width shorter than the folded length are used in the length direction of the plate. It is preferable to use a fixing method in which one side is in contact with the swelling of the rope so as to be in contact with the upper and lower directions.

It is preferable that such a plate material has a corner portion of the plate material that is in contact with the core material and that a process for preventing cutting of the net has been performed. For example, the plate material is selected from a taper process, a round process, and a chamfer process. One that has been subjected to one type of processing is preferred. That is, by such processing, the net is prevented from being broken by the edge of the plate material at the portion between the rope and the edge of the plate material, which is the portion where the force is most exerted on the net. As the reinforcing structure, a frame-shaped structure is preferably used.

The net material for preventing the fall of the manhole cover is attached to the manhole cover support frame so as to be detachable so as to constitute a manhole structure. When such a manhole is formed of a rectangular lid and a rectangular support, the effect of preventing the net from dropping of the present invention is sufficiently exhibited.

[0021]

The present invention will be described in more detail with reference to the following examples. Example 1 Polyaramide fibers ("Kevlar" manufactured by Du Pont-Toray Co., Ltd.) were used for the warp yarns, and polyester fibers were used for the weft yarns.
A woven fabric having an entangled weave structure with an opening of mm was prototyped. The single yarn tensile strength of this polyaramid fiber was 22 gf / d, and the tensile elongation was 3.6%. The tensile strength in the warp direction of the woven fabric was 10.6 tf / m in terms of a 1 m width. This fabric was subjected to resin processing using an acrylic resin. The Gurley hardness was 28000 mg.

The woven fabric is folded back with the end of the net inserted in a rope, and has a width shorter than the folded length.
A sheet of material is sandwiched from both the top and bottom so that one side of the length of the sheet is in contact with the swelling of the rope. The sides of the plate material that are in contact with the swelling of the rope were previously smoothed at the corners by tapering. Next, both ends of the net having a length of 1 m are fixed and held horizontally, and a weight of 20 cm from a height of 20 cm from the surface of the net is obtained.
A 0 kg iron cube was dropped so that the side was down instead of the surface or vertex, and it was evaluated whether the net was torn or the vertical deflection of the net was 120 mm or less.
Further, ease of handling by weight was evaluated. Table 1 shows the obtained results.

Example 2 A woven fabric having an entangled weave structure with a space of 20 mm was produced using carbon fiber ("Torayca" manufactured by Toray) for the warp and polyester fiber for the weft. The single fiber tensile strength of this carbon fiber was 35 gf / d, and the tensile elongation was 1.2%. The tensile strength in the warp direction of the woven fabric is 16.3 tf in terms of 1 m width.
/ M. This fabric was subjected to resin processing using an acrylic resin. This fabric was fixed in the same manner as in Example 1 and an experiment was performed. Table 1 shows the obtained results.

Comparative Example 1 A woven fabric having an entangled woven structure with a space of 20 mm was produced using polyester fibers ("Tetron" manufactured by Toray) for the warp and polyester fibers for the weft. The single yarn tensile strength of the polyester fiber of this warp was 8 gf / d, and the tensile elongation was 14%. The tensile strength in the warp direction of the woven fabric was 4.6 tf / m in terms of 1 m width. This fabric was subjected to resin processing using an acrylic resin. Its Gurley hardness is 2
0000 mg. This fabric was fixed in the same manner as in Example 1 and an experiment was performed. Table 1 shows the obtained results.

COMPARATIVE EXAMPLE 2 A grid-like welded wire mesh was prepared by welding an iron rod having a diameter of 10 mm at a pitch of 30 mm vertically and horizontally. Its stiffness was too high to be measured. An experiment was carried out by fixing the end portions of the two plate members used in Example 1 by sandwiching them from above and below. Table 1 shows the obtained results.

[0026]

[Table 1]

[0027]

The net material for preventing the object from falling and the manhole structure according to the present invention can exhibit the following excellent effects.

(1) Even if the lid of the underground buried electric box is accidentally dropped, the breakage that penetrates the fall prevention net material does not occur. • The fall prevention net material does not bend more than necessary. It does not damage the electric cable and communication cable installed under the fall prevention material.

(2) Since it is lighter than iron grating, the fall prevention member can be removed or installed with less labor.

(3) Since it is lighter than iron grating, it is less likely that the fall prevention member is dropped on an electric cable or a communication cable by mistake.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a drop test of a fall prevention material of the present invention.

FIG. 2 is a schematic view of a method of fixing an end of a fall prevention member to a fixing portion according to the present invention.

[Explanation of symbols]

 1: Fall prevention material 2: Fixed part 3: Iron cube weighing 200 kg 4: Plate material 5: Rope 6: Edge with smooth corners

Claims (20)

[Claims] 1. A net for preventing falling of an object, wherein the net has a tensile breaking strength in at least one direction of 1
What is claimed is: 1. A net material for preventing falling of an object, comprising a fibrous material having a width of 5 tf / m or more and 50 tf / m or less in terms of m width. 2. The fiber material has a single yarn tensile strength of 14 gf /
2. The net material for preventing an object from falling according to claim 1, wherein the net material contains at least one kind of fiber having a value of d to 100 gf / d. 3. The net material according to claim 1, wherein the fiber material contains at least one fiber having a tensile elongation at break of 0.4% or more and 5% or less. 4. The net material for preventing falling of an object according to claim 1, wherein said fiber material contains at least one selected from polyaramid fiber, high-strength polyethylene fiber and carbon fiber. 5. The net material according to claim 4, wherein said polyaramid fiber is a para-based polyaramid fiber. 6. The net has an eye size of 2 mm or more and 10 mm or more.
The net material for preventing falling of an object according to claim 1, which is a woven fabric having a size of 0 mm or less. 7. The woven fabric has a structure of entangled weave, crested weave, or basket weave.
A net material for preventing falling of the described object. 8. The net has an eye size of 2 mm or more and 10 mm or more.
2. The net material for preventing falling of an object according to claim 1, wherein the net material is a Russell knitted fabric of 0 mm or less. 9. The net material for preventing an object from falling according to claim 1, wherein the net is formed by resin processing. 10. The net material according to claim 8, wherein the resin used for the resin processing does not contain halogen. 11. The resin used in the resin processing is at least one selected from a polyolefin resin, a polyester resin, a polyamide resin, a polyurethane resin, a polyacryl resin, and a polyvinyl acetate resin. The net material for preventing an object from falling according to claim 9. 12. The resin used in the resin processing, wherein at least one selected from a coloring agent, an ultraviolet absorber, an ultraviolet shielding agent, and a halogen-free flame retardant is added. A net material for preventing falling of the described object. 13. The JIS L 1096 of the net.
20. The softness according to the bending resilience A method (Gurley softness) is 5,000 mg or less.
A net material for preventing falling of the described object. 14. When the net is stretched in a state where both ends of a fall prevention material having a length of 1 m are fixed and held horizontally.
From the height of 20cm from the surface of the net, weight 200k
Even if the iron cube of g is dropped so that the side is not the surface or the vertex but the side is down, the iron cube does not break through, and the net has a physical property that the vertical deflection of the net is 200 mm or less. The net material for preventing an object from falling according to any one of claims 1, 2, 6 and 7. 15. The net is formed by folding an end portion of the net through a core material and having a width smaller than the folded length of the net.
15. The net material for preventing an object from falling according to any one of claims 1, 2, 6, 9 and 14, wherein the net material is a reinforcing structure sandwiched and fixed between two plate materials. 16. A net material for preventing falling of an object according to claim 15, wherein a corner portion of said plate material which is in contact with said core material is processed to prevent cutting of said net. 17. The method for preventing cutting of the net is selected from taper processing, round processing and chamfer processing.
17. The net material for preventing falling of an object according to claim 16, which is a seed. 18. The net material for preventing an object from falling according to claim 15, wherein the reinforcing structure is a frame-like structure. 19. A manhole structure, wherein the net material for preventing falling of an object according to any one of claims 1 to 18 is attached to a manhole cover supporting frame. 20. The manhole structure according to claim 19, wherein said manhole comprises a rectangular lid and a rectangular support.