JP2000324651A - Wire box embedded in concrete wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount a coating width cover and a back plate on a box body easily without using screws, thereby increasing workability. SOLUTION: When a coating width cover 2 is placed on the lower end surface of a box body 1 which is of regular polygonal and cylindrical shape so that the centers of them may be met, and both of them are relatively rotated around the central axis, a portion between of the inward end-surfaces of the inward protrusions 13, 13 of engaging leg pieces 12, 12 facing each other of the coating width cover 2 is engaged with chamfers 8, 8 facing each other on the outer surface of the box body 1 via the elastic deformation of the engaging leg piece 12. However, when a back plate 3 is placed on the upper end surface of the box body 1 so that the centers of them are matched met, and both of them are rotated relatively around the center axis, a portion between the inward end-surface of inward protrusions 20, 20 of engaging leg pieces 19, 19 facing each other of the back plate 3 is engaged with chamfers 7, 7 which face each other on the outer surface of the box body 1 via the elastic deformation of the back plate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric wire box for embedding a concrete wall.

[0002]

2. Description of the Related Art In order to mount a wiring device such as a lighting device on a ceiling concrete wall surface of a building, an electric wire box for introducing electric wires into a ceiling concrete wall such as a PC board is buried in advance. As this electric wire box, for example, FIG.
As shown in FIG. 5, a box body 30 having a tubular shape, a coating cover 31 for closing a lower end opening of the box body 30, and a back plate 32 for closing an upper end opening of the box body 30
Some are provided with The coating cover 32 is formed in a dish-shaped cross-section, and has an open bottom plate 34 integrally provided inside a central concave portion 33 via a thin portion 35 so as to be separable. In order to embed this electric wire box in the ceiling concrete wall, as shown in FIG.
Prior to driving, concrete formwork (panel) 36
The opening bottom plate 34 is hit with a nail 38 at a predetermined position on the inner surface of the box, and the coating cover 31 is fixedly fixed. The box body 30 is fixed and fixed on the coating cover 31 with screws 39.
Then, the back plate 32 attached to the box body 30 with the screws 40 is once removed from the box body 30, an electric wire (not shown) is introduced and wired into the box body 30, and the back plate 32 is again attached to the box body 3.
Then, screw 0 is used to close the upper end opening of screw 0. Thus, as shown in FIG.
Pour concrete 37 into the inside. After the concrete 37 is solidified, the concrete form 36 is removed as shown in FIG. With the removal of the concrete formwork 36, the open bottom plate 34 is pulled in the removal direction to break the thin portion 35 and separate from the coating cover 31. By the separation of the opening bottom plate 34, a space is formed inside the coating cover 31 so that a wiring device can be attached.

[0003]

However, the work of fixing the coating margin cover 31 and the back plate 32 to the box body 1 with the screws 39 and 40 each time as described above is a major cause of a decrease in work efficiency. Was.

According to the present invention, concrete which can easily set both the coating cover and the back plate or either of them on the box body without using the above-mentioned screws to improve the work efficiency. An object of the present invention is to provide an electric wire box for wall embedding.

[0005]

The invention according to claim 1 of the present invention is an electric wire box embedded in a concrete wall as shown in FIG. 4, and is formed in a regular polygonal cylindrical shape having an open lower end. Plastic box body 1
And a plastic coating cover 2 for closing the lower opening end of the box body 1, and at least a pair of facing corners 6, 6 of the outer surface of the regular polygon of the box body 1.
6, a chamfered portion 8 is formed at a position near the lower end, and a locking step portion 10 is formed below the chamfered portion 8. At least the opposing outer peripheral edge of the inner surface of the coating cover 2 is opposed to the chamfered portion 8. An elastically deformable engaging leg piece 12 having an inward projection 13 that engages with the chamfered portion 8 at the distal end from each of a pair of locations is integrally and upwardly protruded outward from the main body box 1. Positioning step portions 11, 11 at both circumferential ends of at least one of the chamfered portions 8 for restricting circumferential movement of the inward projection 13 engaging with the chamfered portion 8.
(See FIG. 3), and the distance a between the inward end faces of the inward projections 13, 13 facing each other is equal to the distance b between the two opposite surfaces of the regular polygonal outer surface of the box body 1. 1 (see FIG. 1), and is narrower than the distance c between the opposing ridges 6, 6 on the outer surface of the regular polygon of the box body 1, and between the opposing chamfers 8, 8. The dimension is set to be substantially the same as the interval d, and the height e of the lower surface of the inward projection 13 from the inner surface 2a of the coating cover is:
The distance f between the locking step 10 and the lower end surface of the box body 1
The characteristic feature is that the dimensions are set to be substantially the same as those of the above.

As shown in FIG. 4, the invention according to claim 2 is an electric wire box embedded in a concrete wall, comprising a plastic box body 1 formed in a regular polygonal cylindrical shape having an open upper end. And a plastic back plate 3 for closing the upper open end of the box body 1, at least at a position near each upper end of a pair of opposing ridges 6, 6 on the outer surface of the regular polygon of the box body 1.
A chamfered portion 7 is formed and a locking step 9 is formed on the upper side of the chamfered portion 7. An elastically deformable engaging leg 19 having an inward projection 20 that engages with the chamfer 7 is integrally and downwardly protruded toward the outside of the main body box 1, and at least one of the chamfers 7 is provided. Positioning steps 11, 11 for regulating the circumferential movement of the inward projection 20 engaging with the chamfered portion 7 are provided at both circumferential ends in one chamfered portion 7. The distance a between the inward end faces of the direction projections 20 and 20 is wider than the distance b between two opposing surfaces of the regular polygonal outer surface of the box body 1 and the box body 1
Of the regular polygonal outer surface is smaller than the distance c between the opposing edge corners 6, 6 and the opposing chamfers 7, 7
The distance g is set to be substantially the same as the distance d between the two, and the height g of the upper surface of the inward projection 20 from the inner surface 3a of the back plate is set between the locking step 9 and the upper end surface of the box body 1. Is set to be substantially the same as the interval h.

The invention according to claim 3 is an electric wire box embedded in a concrete wall, as shown in FIG. 4, wherein the plastic box body 1 is formed in a regular polygonal cylindrical shape having upper and lower ends open. And a plastic coating cover 2 for closing the lower opening end of the box body 1 and a plastic back plate 3 for closing the upper opening end of the box body 1. Upper and lower chamfers 7, 8 are respectively formed at least near the upper and lower ends of the pair of opposing ridge corners 6, 6, and a locking step 9 is provided above the upper chamfer 7.
An engaging step portion 10 is formed below the lower chamfered portion 8, and the lower end portion is formed at a tip from at least a pair of opposing outer peripheral edges of the inner surface of the coating cover 2. An elastically deformable engaging leg piece 12 having an inward projection 13 that engages with the chamfered portion 8 is integrally formed so as to project upward toward the outside of the main body box 1. Inward projections 20 that engage with the upper chamfered portion 7 at the ends from at least a pair of opposing portions of the edge.
The elastically deformable engaging leg piece 19 having the
Of the upper chamfered portion 7 and at least one circumferential end in at least one chamfered portion 7 of the upper chamfered portion 7 and the lower chamfered portion 8 of the lower chamfered portion 8. Each of the chamfers 7, 8 is provided at both ends in the circumferential direction in at least one chamfer 8.
Positioning steps 11, 11 are provided for regulating the circumferential movement of the inward projections 20, 13 engaging with the inward projections. The inward end faces of the inward projections 20, 20, 13, 13 facing each other are provided. The interval a between them is wider than the interval b between two opposing surfaces of the regular polygonal outer surface of the box body 1 and between the opposing ridge corners 6, 6 of the regular polygonal outer surface of the box body 1. While making it smaller than the interval b,
The distance between the facing chamfers 7, 7, 8, 8 is set to be substantially the same as the distance c between each other, and the lower surface of the lower inward projection 13 from the inner surface 2a of the coating cover is removed. The height e is set to be substantially the same as the distance f between the lower locking step 10 and the lower end surface of the box body 1. The height g from 3a is characterized in that it is set to be substantially the same as the distance h between the upper locking step 9 and the upper end surface of the box body 1.

[0008]

According to the electric wire box for embedding a concrete wall according to the first and third aspects, when the lower opening end of the box body is closed with the paint cover, the inner surface of the paint cover and the lower end face of the opening of the box body are closed. When they are overlapped so that their centers match each other, and they are relatively rotated about the center axis,
Opposing chamfers on the outer surface of the box body are fitted between the inward end faces of the inward projections of the coating cover by elastic deformation of the engaging leg pieces. At the same time as this fitting, the lower surface of the inward projection of the coating cover engages with the lower locking step of the box main body, so that the box main body can be prevented from moving upward from the coating cover. At the same time, a certain inward projection temporarily climbs over one of the positioning steps on the chamfered portion and fits between the positioning step and the other positioning step. Rotation in the circumferential direction can be prevented.

According to the electric wire box for embedding a concrete wall according to the second and third aspects, when the upper opening end of the box body is closed by the back plate, the inner surface of the back plate and the upper end surface of the opening of the box body are closed. When they are overlapped so that their centers coincide with each other and they are relatively rotated about the central axis, the facing inward end faces of the facing inward projections of the back plate are engaged with the facing chamfers on the outer surface of the box body. Fitting is performed through elastic deformation of the joint pieces. At the same time as the fitting, the upper surface of the inward projection of the back plate is engaged with the locking step on the upper side of the box body, so that the back plate can be prevented from moving upward from the box body. At the same time, since a certain inward projection temporarily climbs over one of the positioning steps on the chamfered portion and fits between the positioning step and the other positioning step, the back plate moves in the rotational direction or the anti-rotation direction. Rotation in the circumferential direction can be prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electric wire box for embedding a concrete wall according to the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view of an electric wire box for embedding a concrete wall, FIG. 2 is a sectional view of a chamfered portion of a box body of the electric wire box, and FIG. 3 is a chamfered portion of the box main body with a positioning step. , FIG. 4 is a longitudinal sectional front view showing an assembled electric wire box, FIG. 5 is a cross-sectional view showing a state where the electric wire box is set on a concrete formwork and concrete is poured, and FIG. 6 is a state shown in FIG. It is sectional drawing which shows the state which removed the concrete formwork from.

As shown in FIG. 1, the electric wire box for embedding a concrete wall according to the present invention includes a box body 1, a coating cover 2 and a back plate 3. In these, the box body 1, the coating cover 2 and the back plate 3 are molded products of synthetic resin such as vinyl chloride resin, respectively.

As shown in FIG. 1, the box body 1 is formed in a cylindrical shape of a regular polygon (convex polygon) such as an octagon with open upper and lower ends, and each surface of the regular polygonal cylindrical wall 4 has A conduit insertion portion 5 that can be opened by being strongly pressed is formed.
Also, the upper and lower ends of a pair of opposing ridges on the outer surface of the regular polygonal cylindrical wall 4 of the box body (exposed corners where two adjacent surfaces of the regular polygonal cylindrical wall 4 meet). The upper and lower flat chamfers 7 and 8 are formed respectively, and a flat triangular locking step 9 is provided above the upper chamfer 7 and a flat lower chamfer 8 is provided below the lower chamfer 8. Each of the triangular locking steps 10 is formed (see FIG. 2). In the illustrated example, two pairs of opposing upper chamfers 7 and 7 are provided, and two pairs of opposing lower chamfers 8 and 8 are provided. You may. As shown in FIG. 3, at least one of the upper chamfers 7 is provided with an inward projection 2, which will be described later, that engages with the chamfers 7 at both ends in the circumferential direction.
Positioning steps 11, 11 for restricting the circumferential movement of 0 are provided. In addition, a positioning step portion that regulates a circumferential movement of an inward projection 13 described later that engages with the chamfered portion 8 at both circumferential ends of at least one of the lower chamfered portions 8. 11, 11 are provided.

As shown in FIG. 1, the coating cover 2 is formed in the same polygonal shape as the outer shape of the box main body 1 having a size capable of closing the lower opening end of the box main body 1 and has a dish-shaped cross section. At least a pair of elastically deformable engaging legs 12 are projected upward from at least a pair of opposing portions of the outer peripheral edge, and an inward projection 13 is formed at an end of each engaging leg 12 at a right angle inward. It is formed integrally. In addition, coating cover 2
As shown in FIG. 4, an open bottom plate 15 is provided integrally with the inside concave portion 14 of the inner surface 2 a so as to be separable via a thin portion 16. Further, between the engaging leg piece 12 and the central concave portion 14 on the inner surface 2a of the coating cover 2, a box body 1 is provided.
Is formed on the inner surface of the regular polygon.

The back plate 3 is, as shown in FIG.
The box body 1 is formed in the shape of a regular polygonal flat plate having the same size as the outer shape of the box body 1 so as to be able to close the upper opening end of the box body 1, and a conduit insertion portion 18 that can be opened by being strongly pressed is formed in several places. ing. The back plate 3, like the coating cover 2, has elastically deformable engaging leg pieces 1 at least from a pair of opposing outer peripheral edges of an inner surface 3 a thereof.
9 are protruded integrally downward, and an inward projection 20 is integrally formed at the tip of each engaging leg piece 19 at an inward right angle.

In FIG. 1 and FIG. 4, a space between the inwardly facing end faces of the inwardly facing projections 13 of the coating cover 2 is shown.
And opposing inward projections 20 and 2 of the back plate 3
The distance a between the inward end faces 0 is wider than the distance b between two opposing surfaces of the regular polygonal outer surface of the box body 1 and the opposing faces of the regular polygonal outer surface of the box body 1 face each other. The distance between the corners 6, 6 is made smaller than the distance c, and the distance d between the facing chamfers 7, 7 and between the chamfers 8, 8 is set to be substantially the same as the distance d. I have. The height e of the lower surface of the inward projection 13 of the coating cover 2 from the coating cover inner surface 2a is equal to the engagement step 10
The distance is set to be substantially the same as the distance f between the box body 1 and the lower end surface of the box body 1. The height g of the upper surface of the inward projection 20 of the back plate 3 from the inner surface 3a of the back plate.
Is set to be substantially the same as the distance h between the locking step 9 and the upper end surface of the box body 1.

In such a case, when the inner cover 2a of the coating cover 2 is overlapped with the lower end surface of the box main body 1 so that the center thereof coincides with each other and the two are relatively rotated about the central axis, the relative position of the coating cover 2 is reduced. The facing inward end faces of the facing inward projections 13, 13 are fitted to lower opposing chamfered portions 8, 8 on the outer surface of the box body 1 via elastic deformation of the engaging leg pieces 12, 12. By this fitting, the box main body 1 and the coating cover 2 are connected to each other without being detached from each other in the vertical direction. Further, the inward projection 13 is provided on one of the positioning step portions 1 for the chamfered portion 8 having the positioning step portions 11 and 11.
1 can be obtained in which the coating margin cover 2 is set in such a manner that the positioning is regulated so as not to move in the circumferential direction once between the positioning step 11 and the other positioning step 11 once over the step 1. .

When the inner surface 3a of the back plate 3 is superimposed on the upper end surface of the box body 1 so as to coincide with the center and the two are relatively rotated about the central axis, the inward projections 20 of the back plate 3 oppose each other. , 20 are fitted to the upper opposed chamfers 7, 7 on the outer surface of the box body 1 via the elastic deformation of the engaging leg pieces 19, 19, and this fitting causes 1 and the back plate 3 are connected to each other without being separated from each other in the vertical direction. Further, the chamfered portion 7 having the positioning step portions 11, 11
The positioning of the inward projection 20 is restricted such that the inward projection 20 does not once move over one positioning step 11 and rotate in the circumferential direction between the positioning step 11 and the other positioning step 11. , Can be obtained.

The positioning step 11 has a slight height dimension from the inner surfaces of the chamfers 7 and 8, so that the coating cover 2 and the back plate 3 are respectively set after setting. By rotating the box body 1 around the central axis with a strong rotational force, the inward projections 13 and 20 ride over one of the positioning steps 11 through the elastic deformation of the engaging leg pieces 12 and 19, so that the chamfers 8 and 7 can also be extracted.

Next, a procedure for embedding the above-structured electric wire box B integrally in a concrete wall will be described with reference to FIGS. First, as shown in FIG. 5, before the concrete is poured, the open bottom plate 15 is driven into the predetermined position on the inner surface of the concrete formwork (curtain plate) 25 with a nail 26 so as to cover the coating cover 2.
Is fixed in place. Next, the inner surface 2a of the coating cover 2
The lower ends of the openings of the box main body 1 are overlapped with each other so that the centers thereof coincide with each other, and the box main body 1 is rotated around the central axis. Then, the opposing chamfered portions 8 on the outer surface of the box body 1 cause the elastic deformation of the engaging leg pieces 12 between the inward end faces of the opposing inward projections 13 of the coating cover 2. Fit through. By this fitting, the lower surface of the inward projection 13 of the coating cover 2 engages with the locking step portion 10 of the box body 1, so that the box body 1 is
Does not move upward from At the same time, a certain inward projection 13 is positioned on the positioning step 11, 11 in the chamfer 8.
Since the box body 1 is interposed, the box body 1 does not rotate in the circumferential direction in the rotation direction or the anti-rotation direction.

Next, an electric wire (not shown) is introduced and wired into the box body 1 using the conduit tube insertion portion 5. After the wiring, the inner surface 3a of the back plate 3 is superimposed on the upper end surface of the opening of the box body 1 so that the centers thereof coincide with each other, and the back plate 3 is rotated around the central axis. Then, between the facing chamfered portions 7 on the outer surface of the box body 1 and the inward end faces of the facing inward projections 20 on the back plate 3, elastic deformation of the engaging leg pieces 19 is formed. Fit through. By this fitting, the upper surface of the inward projection 20 of the back plate 3 engages with the locking step 9 of the box body 1, so that the back plate 3 does not move upward from the box body 1. At the same time, a certain inward projection 2
Since 0 is located between the positioning steps 11 in the chamfered portion 7, the back plate 3 does not rotate in the circumferential direction in the rotation direction or the anti-rotation direction.

Thus, the concrete 27 is driven into the concrete form 25. After solidification of concrete 27,
As shown in FIG. 6, the concrete formwork 25 is removed.
With the removal of the concrete form 25, the open bottom plate 15 nailed to the concrete form 25 is pulled in the removing direction, breaking the thin portion 16 and separating from the coating cover 2. By the separation and removal of the open bottom plate 15, a state is obtained in which the central concave portion 14 of the coating cover 2 faces the outer surface of the concrete 27 in an open state. The wiring device can be attached to the central concave portion 14 so as to be connectable to the electric wire in the box body 1.

In the above embodiment, both the coating cover 2 and the back plate 3 are engaged with the chamfers 7, 8 and the engaging steps 9, 10 and the engaging legs 19, 12 with respect to the box body 1. Although it can be set through means, it is not limited to this, and only one of the coating cover 2 or the back plate 3 is chamfered 7 or 8, the locking step 9 or 10, and It can be set via engagement means with the engagement leg pieces 19 or 12, and the other back plate 3 or painting cover 2 may be set to the box body 1 by other coupling means. The box body 1 may be formed in a regular polygon such as a hexagon or a quadrangle, in addition to the octagon in the illustrated example.

[0024]

According to the present invention, a simple operation of superposing the coating cover and / or the back plate on the box main body and rotating the required angle by a required angle can be achieved without using screws. There is an advantage that the work can be easily set, and the work of embedding in the concrete wall can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an electric wire box for embedding a concrete wall.

FIG. 2 is a sectional view of a chamfered part of a box body of the electric wire box.

FIG. 3 is a cross-sectional view of a chamfer with a positioning step of the box body.

FIG. 4 is a longitudinal sectional front view showing a state where the electric wire box is assembled.

Fig. 5 Set the electric wire box on the concrete formwork,
It is sectional drawing which shows the state which poured concrete.

FIG. 6 is a cross-sectional view showing a state where a concrete form has been removed from the state of FIG. 5;

FIG. 7 is a vertical sectional front view of a conventional electric wire box.

8 is a sectional view showing a state where the electric wire box of FIG. 7 is set on a concrete formwork and concrete is poured.

FIG. 9 is a cross-sectional view showing a state in which a concrete form has been removed from the state of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Box main body 2 Filling cover 3 Back plate 6 Ridge corner 7 Upper chamfered part 8 Lower chamfered part 9 Upper locking step part 10 Lower locking step part 11 Positioning step part 12 Engagement leg piece 13 Inward projection of coating cover 19 Engagement leg piece of back plate 20 Inward projection of back plate

Claims (3)

[Claims] 1. An electric wire box embedded in a concrete wall, comprising: a plastic box body formed in a regular polygonal cylindrical shape having an open lower end; and a plastic coating member closing a lower opening end of the box body. A chamfered portion, and a chamfered portion is formed at a position near each lower end of at least a pair of opposing ridges on the outer surface of the regular polygon of the box body, and the chamfered portion is formed below the chamfered portion. An elastically deformable engaging leg piece having a step portion formed thereon, and having inward projections at its ends from at least a pair of opposing locations on the inner peripheral edge of the inner surface of the coating cover at the ends thereof. Are projected integrally upward toward the outside of the main body box, and the inward projections engaging with the chamfered portions at both circumferential ends in at least one of the chamfered portions. Around Moving and positioning step is provided for regulating a spacing between the inward end face each other in the inward protrusions opposed,
The distance between two opposing surfaces of the regular polygonal outer surface of the box body is wider than the distance between two opposing surfaces of the regular polygonal outer surface of the box body, and the distance between the opposing ridge corners of the regular polygonal outer surface of the box body is smaller than the distance between the opposing corners. The distance between the chamfers is set to be substantially the same as the distance between the chamfers, and the height of the lower surface of the inward projection from the inner surface of the coating cover is equal to the upper surface of the locking step and the lower end of the box body. An electric wire box for embedding in a concrete wall, wherein the electric wire box is set to have substantially the same size as an interval between the two. 2. An electric wire box embedded in a concrete wall, comprising: a plastic box body formed in a regular polygonal cylindrical shape having an open upper end; and a plastic bag closing an upper open end of the box body. And a plate, at a position near the upper end of each of at least a pair of opposing ridges on the outer surface of the regular polygon of the box body,
A chamfered portion is formed and a locking step is formed above the chamfered portion, and the chamfered portion is formed at a tip from at least a pair of opposing outer peripheral edges of the inner surface of the back plate. An elastically deformable engaging leg having an engaging inward projection is integrally and downwardly projected outwardly of the main body box, and a circumferential direction in at least one of the chamfered portions. At both ends, there are provided positioning steps for restricting the circumferential movement of the inward projection engaging with the chamfered portion, and the interval between the inward end faces of the opposed inward projections is
The distance between two opposing surfaces of the regular polygonal outer surface of the box body is wider than the distance between two opposing surfaces of the regular polygonal outer surface of the box body, and the distance between the opposing ridge corners of the regular polygonal outer surface of the box body is smaller than the distance between the opposing corners. The distance between the chamfers is set to be substantially the same as the distance between the chamfers. The height of the upper surface of the inward projection from the inner surface of the back plate is the height between the lower surface of the locking step and the upper end of the box body. An electric wire box for embedding in a concrete wall, wherein the size of the electric wire box is set to be substantially the same as the interval between the electric wires. 3. An electric wire box embedded in a concrete wall, comprising: a plastic box main body formed in a regular polygonal cylindrical shape having upper and lower ends open; and a plastic box main body closing a lower opening end of the box main body. A coating back cover, and a plastic back plate that closes an upper opening end of the box main body, respectively, at a position closer to upper and lower ends of each of at least a pair of opposing ridges of the regular polygonal outer surface of the box main body. , Upper and lower chamfers are formed, a locking step is formed above the upper chamfer, and a locking step is formed below the lower chamfer, respectively. An elastically deformable engaging leg having an inward projection engaging with the lower chamfer at the tip from at least a pair of opposing locations on the inner peripheral edge of the inner surface of the cover faces outward of the main body box. Elastically deformable having an inward projection which is engaged with the upper chamfered portion at each end from at least a pair of opposing edges of the inner peripheral edge of the inner surface of the back plate. A plurality of engaging leg pieces projecting downward toward the outside of the main body box, and both circumferential ends in at least one of the upper chamfers, and a lower chamfer. Positioning steps for restricting the circumferential movement of the inward projections engaging with the respective chamfers are provided at both ends in the circumferential direction in at least one of the chamfers. The interval between the inward end faces of the projections is wider than the interval between two opposing faces of the regular polygonal outer surface of the box body, and between the opposing ridge corners of the regular polygonal outer face of the box body. If it is smaller than the interval The height of the lower surface of the lower inward projection from the inner surface of the coating cover is set to be substantially the same as the distance between the chamfered portions facing each other. The distance between the upper surface of the stop portion and the lower end surface of the box body is set to be substantially the same size. The height of the upper surface of the upper inward projection from the inner surface of the back plate is set to the upper locking position. An electric wire box for embedding in a concrete wall, wherein a distance between the lower surface of the step portion and an upper end surface of the box body is set to be substantially the same as the distance between the step and the upper end surface of the box body.