JP7607259B2 - Protective body for buried objects - Google Patents

Description

The present invention relates to a protector for underground buried objects.

In recent years, there has been an increasing demand for the removal of utility poles at low cost. As a result, electric wires and other objects have begun to be buried shallow underground. On the other hand, to prevent accidents in which electric wires and other objects buried underground (hereinafter also referred to as "underground buried objects") are cut or damaged during subsequent pavement cutting work associated with road construction, it is common to cover and protect the underground buried objects with steel plates or the like.

For example, Patent Document 1 discloses a metal material for preventing cutting damage, which has excellent cut protection properties and is attached to or disposed outside underground buried objects in order to prevent cutting damage to underground buried objects that occurs during road cutting work in road construction and the like. Patent Document 2 also discloses a protective body that can reliably protect underground buried objects when cutting the road surface.

Japanese Patent Application Publication No. 8-338036 Japanese Patent Application Publication No. 10-9480

The cutting damage prevention material described in Patent Document 1 uses a metal material with a Brinell hardness of 100 or less, and therefore exhibits high cutting damage prevention performance. However, as a result of the inventors' research, it was found that there is room for further improvement in cutting resistance.

In addition, in the protective body for buried objects described in Patent Document 2, for example, the surface of high-hardness steel is coated with a material that deteriorates the cutter function, such as low-hardness steel, to improve cutting resistance. However, when low-hardness steel and high-hardness steel are layered on top of each other, an increase in weight is unavoidable, and there is a problem in that workability deteriorates.

The present invention was made to solve these problems, and aims to provide a protector for buried objects that is lightweight yet highly resistant to cutting.

The gist of the present invention is the following underground buried object protection device:

(1) a plate-like member having a surface on one side in a thickness direction and a back surface on the other side in the thickness direction;
a pair of L-shaped members fixed to the rear surface, extending in a first direction perpendicular to the thickness direction, and spaced apart from each other in a second direction perpendicular to the thickness direction and the first direction;
In a cross section perpendicular to the first direction, each of the L-shaped members has a first flat plate portion extending from the back surface to the other side in the thickness direction, and a second flat plate portion extending from an end of the first flat plate portion on the back surface side toward an outside of the plate-shaped member in the second direction,
The plate-shaped member is made of a metal material having a Brinell hardness of 100 or less,
The L-shaped member is made of a metal material having a Brinell hardness of more than 100.
A protective body for underground buried objects.

(2) The metal material constituting the plate-shaped member is steel, and the chemical composition of the steel is, in mass%,
C: 0.10% or less, and
Ceq defined by the following formula (i) is 0.10 or less;
A protector for underground buried objects as described in (1) above.
Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14...(i)
In the above formula, the element symbols represent the content (mass %) of each element.

(3) When viewed from the thickness direction,
the plate-like member has a pair of linear edges extending in the first direction, a first end edge connecting one end of the pair of edges in the first direction, and a second end edge connecting the other end of the pair of edges in the first direction,
At least one of the one end edge and the other end edge is curved in an arc shape.
A protector for underground buried objects according to (1) or (2) above.

(4) When viewed from the thickness direction,
The one end edge is curved in an arc shape so as to protrude outward, and the other end edge is parallel to the one end edge and curved in an arc shape so as to recess inward.
A protector for underground buried objects as described in (3) above.

The present invention makes it possible to obtain a protective body for buried objects that is lightweight yet highly resistant to cutting.

1 is a perspective view of a protector for an underground buried object according to an embodiment of the present invention. 1 is a cross-sectional view perpendicular to a first direction of a protector for an underground buried object according to an embodiment of the present invention. 6 is a cross-sectional view perpendicular to the first direction of a protector for an underground buried object according to another embodiment of the present invention. FIG. 10A and 10B are diagrams illustrating a state in which a protective body according to an embodiment of the present invention is cut. 13A to 13C are diagrams for explaining a method of joining an L-shaped member to a plate-shaped member. 1 is a view of a protector for an underground buried object according to an embodiment of the present invention as viewed from the thickness direction. 13 is a view of a protection body for an underground buried object according to another embodiment of the present invention as viewed from the thickness direction. FIG. 13 is a view of a protection body for an underground buried object according to another embodiment of the present invention as viewed from the thickness direction. FIG. 1A to 1C are diagrams illustrating examples of construction of a protection body for an underground buried object according to one embodiment of the present invention and other embodiments.

This article describes a protector for underground buried objects according to one embodiment of the present invention.

Figure 1 is a perspective view of a protector for underground buried objects according to one embodiment of the present invention. The protector 10 comprises a plate-shaped member 11 and a pair of L-shaped members 12. As shown in Figure 1, in this specification, the direction perpendicular to the thickness direction of the plate-shaped member 11 is referred to as the first direction, and the direction perpendicular to the thickness direction and the first direction is referred to as the second direction.

Figure 2 is a cross-sectional view perpendicular to the first direction of a protector for an underground buried object according to one embodiment of the present invention. As shown in Figure 2, the protector 10 according to this embodiment is intended to protect an underground buried object 20 that is buried in the ground so as to extend in the first direction.

The plate-like member 11 has a surface 11a on one side in the thickness direction (the upper side when buried, hereafter also referred to as the "upper side") and a back surface 11b on the other side in the thickness direction (the lower side when buried, hereafter also referred to as the "lower side"). That is, as shown in FIG. 2, the buried object 20 is buried on the back surface 11b side of the plate-like member 11.

As shown in Figs. 1 and 2, the pair of L-shaped members 12 are fixed to the back surface 11b of the plate-shaped member 11, extend in the first direction, and are spaced apart from each other in the second direction. The L-shaped members 12 have a first flat portion 12a and a second flat portion 12b. As shown in Fig. 2, in a cross section perpendicular to the first direction, the first flat portion 12a extends downward from the back surface 11b of the plate-shaped member 11. The second flat portion 12b extends from an end portion 12c on the back surface 11b side of the first flat portion 12a toward the outside of the plate-shaped member 11 in the second direction.

There is no particular restriction on the length of the second flat portion 12b in the second direction. As shown in FIG. 2, the outer end 12d of the plate-like member 11 in the second direction of the second flat portion 12b and the outer end 11c of the plate-like member 11 may coincide in the second direction, or, as shown in FIG. 3, the end 11c of the plate-like member 11 may protrude outward beyond the end 12d of the second flat portion 12b.

The plate-shaped member 11 is made of a metal material with a Brinell hardness of 100 or less. There are no particular limitations on the type of metal material, so long as it has a Brinell hardness of 100 or less, but for example, low carbon steel can be used.

Generally, the hardness of a steel material depends on the carbon equivalent. Therefore, the metal material constituting the plate-shaped member 11 is steel, and the chemical composition of the steel preferably contains, in mass %, C: 0.10% or less, and Ceq defined by the following formula (i) is 0.10 or less.
Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14...(i)
In the above formula, the element symbols represent the content (mass %) of each element.

C is an element that increases the hardness of the material and reduces its toughness, and it is preferable to keep it as low as possible. Therefore, the C content is preferably 0.10% or less, and more preferably 0.05% or less. In addition, Ceq is the amount of the effect of other alloying elements on hardness converted into carbon, and like C, it is preferable to keep it as low as possible. Therefore, Ceq is preferably 0.10 or less, and more preferably 0.05 or less.

There is no particular limit to the thickness of the plate-like member 11, but if it is too thin, there is a risk that the cut resistance will be insufficient, while if it is too thick, it will be difficult to reduce the weight. Therefore, the thickness of the plate-like member 11 is preferably 6 to 25 mm, more preferably 9 to 22 mm, and even more preferably 12 to 19 mm.

When producing the above low carbon steel material, there is no particular restriction on the manufacturing method, but for example, it can be produced by hot rolling a steel ingot or slab having the above chemical composition. In order to keep the hardness of the steel material low, it is desirable to set the heating temperature before hot rolling to 1100 to 1250°C and the rolling finish temperature to 700°C or higher. In addition, the steel material may be used as is after hot rolling, but it may also be tempered after hot rolling. Furthermore, after hot rolling, normalization at 910°C or higher may be performed in order to remove the residual strain introduced by the hot rolling.

On the other hand, the L-shaped member 12 is made of a metal material with a Brinell hardness exceeding 100. There is no need to set an upper limit on the Brinell hardness of the metal material that makes up the L-shaped member 12. However, if the hardness is increased excessively, it may become difficult to achieve low costs. For this reason, it is preferable that the Brinell hardness of the metal material that makes up the L-shaped member 12 is less than 300.

From the viewpoint of reducing costs, it is preferable to use, for example, SS400, a general structural rolled steel material as specified in JIS G 3101:2015, as a metal material having the above hardness.

There is no particular limit to the thickness of the L-shaped member 12, but if it is too thin, there is a risk that the cut resistance will be insufficient, while if it is too thick, it will be difficult to reduce the weight. Therefore, the thickness of the L-shaped member 12 is preferably 3 to 15 mm, and more preferably 4 to 8 mm.

The protective body 10 according to the present invention has the above-mentioned configuration, and therefore has high cut resistance even though it is lightweight. The reason for this will be explained. Figure 4 is a schematic diagram showing the state when the protective body according to one embodiment of the present invention is cut.

First, because the plate-shaped member 11 is made of a metal material with a Brinell hardness of 100 or less, the cut metal material adheres to the diamond on the cutting edge of the cutter used in the pavement cutting work, degrading the function of the cutter.

In addition, the L-shaped member 12 extending downward from the plate-like member 11 further improves the cutting resistance. As shown in FIG. 4, the blade 30, whose cutting ability has deteriorated due to cutting the relatively soft plate-like member 11, attempts to cut the relatively hard L-shaped member 12 after passing through the plate-like member 11. As a result of closely observing the cut marks of the L-shaped member 12, the inventors found that the width of the cut marks of the L-shaped member 12 is larger than the width of the cut marks of the plate-like member 11. In other words, it is presumed that the cutting ability has deteriorated significantly due to a slight distortion in the rotation of the blade 30.

Here, when fixing the L-shaped member 12 to the plate-shaped member 11, they are joined by providing welds 13a and 13b as shown in FIG. 5(a). However, when considering the ease of welding, it is common to fix the L-shaped member 12' to the plate-shaped member 11' in the orientation shown in FIG. 5(b).

However, in the orientation shown in FIG. 5(b), the blade 30, whose cutting ability has deteriorated due to cutting the plate-like member 11', immediately cuts the second flat plate portion 12'b of the L-shaped member 12' without bending. As a result, it is believed that the cutting ability of the blade 30 is restored by cutting the hard L-shaped member 12', and the blade 30 cuts the first flat plate portion 12'a in a straight line.

In contrast, in the protective body 10 according to the present invention, the second flat plate portion 12b extends outward from the plate-like member 11, so the blade 30, whose cutting ability has deteriorated as a result of cutting the plate-like member 11, cuts the first flat plate portion 12a directly. As a result, it is presumed that when the blade 30 enters the hard first flat plate portion 12a, the blade becomes distorted, causing a significant deterioration in its cutting ability.

Figure 6 is a view from the thickness direction of a protector for an underground buried object according to one embodiment of the present invention. Figures 7 and 8 are views from the thickness direction of a protector for an underground buried object according to other embodiments of the present invention.

There are no particular limitations on the shape of the plate-like member 11 when viewed from the thickness direction, and it may be rectangular, for example. It may also be shaped as shown in Figures 6 to 8. Specifically, when viewed from the thickness direction, the plate-like member 11 has a pair of linear edges 11d, 11e extending in a first direction, one edge 11f connecting one ends of the pair of edges 11d, 11e in the first direction, and another edge 11g connecting the other ends of the pair of edges 11d, 11e in the first direction.

In the shape shown in FIG. 6, only one edge 11f is curved in an arc so that it protrudes outward. In the shape shown in FIG. 7, only the other edge 11g is curved in an arc so that it recesses inward. In the shape shown in FIG. 8, one edge 11f is curved in an arc so that it protrudes outward, and the other edge 11g is parallel to the one edge 11f and curved in an arc so that it recesses inward.

Figure 9 is a schematic diagram showing an example of construction of a protective body for underground buried objects according to one embodiment (a) of the present invention and another embodiment (b).

When protecting a gently curved underground object, if the plate-like member 11 is rectangular, the protective body 10a will be installed as shown in FIG. 9(a). In contrast, as shown in FIG. 9(b), by combining protective body 10b with only one edge 11f curved, protective body 10c with only the other edge 11g curved, and protective body 10d with both one edge 11f and the other edge 11g curved, the cutting edge of the cutting machine can be reliably struck against the L-shaped member during pavement cutting work, and the function of protecting the underground object can be demonstrated. In addition, it is possible to minimize the amount of material used, thereby reducing costs.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

Two types of steels, A and B, were prepared, with the chemical composition and Brinell hardness shown in Table 1. Two types of protective bodies were prepared: a protective body consisting of only a plate-shaped member, and a protective body consisting of a plate-shaped member and an L-shaped member welded to it. In each type of protective body, steels A and B were used for the plate-shaped member, and steel A was used for the L-shaped member.

The plate-shaped member has a length of 300 mm in the first direction, a length of 200 mm in the second direction, and a thickness of 12 mm. The L-shaped member is a 6 mm thick steel plate bent into an L shape, with a length of 40 mm in the first direction, a length below the first flat plate portion of 50 mm, and a length of the second flat plate portion of 50 mm in the second direction.

Each protective body was then placed on a concrete surface with a groove 50 mm wide and 200 mm deep, and then subjected to a cutting test using a cutter equipped with a diamond blade. The cutting machine moved in the second direction, and for protective bodies equipped with an L-shaped member, cutting was performed from the side where the L-shaped member was fixed. The time until the entire plate-shaped member, which was 200 mm long in the second direction, was cut was measured. The cutting depth of the cutter was set to 100 mm from the concrete surface, and the settings for the running speed of the cutter and the rotation speed of the diamond blade were constant.

The results are shown in Table 2.

As is clear from Table 2, when a protective body that satisfies the provisions of the present invention and has a soft plate-shaped member and a hard L-shaped member is used, the time required for cutting is significantly longer than when a protective body that does not satisfy the provisions is used, and cut resistance is significantly increased.

As described above, the present invention makes it possible to obtain a protective body for underground buried objects that is lightweight yet has high cut resistance.

REFERENCE SIGNS LIST 10 Protective body 11 Plate-shaped member 11a Surface 11b Back surface 11c End 11d, 11e Pair of edges 11f One end edge 11g Other end edge 12 L-shaped member 12a First flat plate portion 12b Second flat plate portion 12c End portion of first flat plate portion 12d End portion of second flat plate portion 13a, 13b Welded portion 20 Buried object 30 Blade

Claims (6)

A plate-like member having a surface on one side in a thickness direction and a back surface on the other side in the thickness direction;
a pair of L-shaped members fixed to the rear surface, extending in a first direction perpendicular to the thickness direction, and spaced apart from each other in a second direction perpendicular to the thickness direction and the first direction;
In a cross section perpendicular to the first direction, each of the L-shaped members has a first flat plate portion extending from the back surface to the other side in the thickness direction, and a second flat plate portion extending from an end of the first flat plate portion on the back surface side toward an outside of the plate-shaped member in the second direction,
The plate-shaped member is made of a metal material having a Brinell hardness of 100 or less,
The L-shaped member is made of a metal material having a Brinell hardness of more than 100.
A protective body for underground buried objects. The metal material constituting the plate-shaped member is steel, and the chemical composition of the steel is, in mass%,
C: 0.10% or less, and
Ceq defined by the following formula (i) is 0.10 or less;
A protector for an underground buried object according to claim 1.
Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14...(i)
In the above formula, the element symbols represent the content (mass %) of each element. When viewed from the thickness direction,
the plate-like member has a pair of linear edges extending in the first direction, a first end edge connecting one end of the pair of edges in the first direction, and a second end edge connecting the other end of the pair of edges in the first direction,
At least one of the one end edge and the other end edge is curved in an arc shape.
A protector for an underground buried object according to claim 1 or 2. When viewed from the thickness direction,
The one end edge is curved in an arc shape so as to protrude outward, and the other end edge is parallel to the one end edge and curved in an arc shape so as to recess inward.
The protector for an underground buried object according to claim 3. The thickness of the plate-like member is 6 to 25 mm.
A protector for an underground buried object according to any one of claims 1 to 4. The thickness of the L-shaped member is 3 to 15 mm.
A protector for an underground buried object according to any one of claims 1 to 5.

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