JPH0510500Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is a synthetic resin wiring box (hereinafter simply referred to as box) in which the box is pulled inside the formwork and fixed using a fixture. ).

[Conventional technology and its problems]

Figure 8 shows a conventional box of the type described above.
An example of B' is shown.

In order to bury this box B' in the wall of a concrete structure, the formwork 2 in which the concrete will be poured must be
Fix box B′ inside.

To fix box B' to formwork 2,
A threaded rod 6 is inserted into the threaded rod shape 4 provided in the formwork 2 from the outside of the box.
Screwed into the threaded part 10 provided on the bottom wall 8 of B',
After that, the nut 12 is screwed onto the threaded rod 6 protruding from the formwork 2, and by screwing the threaded rod 6 and the nut 12 together, the box B' is drawn to the inside of the formwork 2 and fixed in place. are doing.

When the threaded rod 6 and the nut 12 are screwed together and the box B' is strongly pulled toward the formwork 2 so that the open end surface of the box B' and the formwork 2 come into close contact, the box B The bottom wall 8 of ' is bent inward or cracks occur in the bottom wall 8.

Therefore, the tension rod 1 is attached to the bottom wall 8 near the threaded portion 10.
4 are integrally provided, and when the box B' is drawn into the formwork 2, the tension rods 14 are brought into contact with the formwork 2, thereby preventing the bottom wall 8 from being bent or cracked.

After pouring concrete between the formwork 2, the formwork 2 is removed, and then the specified wiring work is carried out in box B', but the tension rods 14 are an obstacle to the wiring work, so they must be broken off. There must be.

Since the tension rod 14 is integrally provided on the bottom wall 8, there is no need to attach the tension rod to the bottom wall 8, compared to a structure in which a separate tension rod is screwed into the bottom wall 8. On the other hand, the tension rod 14 provided integrally with the bottom wall 8 cannot be broken off without applying force many times, which reduces work efficiency.

The present invention is designed to prevent the bottom wall from bending or cracking when the box is pulled into the formwork and brought into close contact with the formwork, without reducing the tension force of the tension rods that are integrally provided on the bottom wall. This was designed to allow the tension rod to be easily broken with a small amount of force.

[Means for solving problems]

The means adopted by the present invention to achieve the above object is that a tension rod is provided on the bottom wall facing the box opening, and when the box is pulled into the inside of the formwork by a fixing device and fixed tightly, In a synthetic resin wiring box in which the tension rod is brought into contact with the inside of the formwork to prevent the bottom wall from bending, there is a gap between the base end of the tension rod and the base end to an extent that does not reduce the tension force. A recessed portion for reducing the breaking force of the tension rod is provided on the outer surface of the bottom wall so as to face the vicinity of the base end of the tension rod, leaving the connection portion intact.

[Effect of invention]

A connecting portion between the tension rod and the bottom wall that is integrated by providing a concave portion on the outer surface of the bottom wall facing the base end of the tension rod to facilitate breaking off the tension rod. As the cross-sectional area of the area becomes smaller, the section modulus of that part becomes smaller. Therefore, the permissible shearing stress of the part becomes small, and the tension rod can be easily broken off with a small force.

〔Example〕

The present invention will be explained in more detail with reference to Examples below. Note that the same reference numerals are used to describe parts that are the same as or equivalent to those described in the above-mentioned "Prior art and problems thereof" section.

1 to 4, a bulge 16 is provided at the center of the inside of the bottom wall 8 of box B, and a nut 18 is embedded in this bulge 16. A pair of tension rods 14 are integrally provided on the bottom wall 8 near the bulge 16 with the bulge 16 in between. The length of the tension rod 14 is made slightly shorter than the depth of the box B, so that when the box B is brought into close contact with the formwork 2, the opening end surface of the box B is brought into close contact with the formwork 2. It is set as.

As shown in detail in FIGS. 5 and 6, a recess 20 having a circular cross section is provided in the outer portion of the bottom wall 8 where the tension rod 14 is provided.
faces the base end of the tension rod 14. Therefore, the cross-sectional area of the connecting portion between the tension rod 14 and the bottom wall 8, which are integrated, becomes small, and the section modulus of this portion becomes small. Note that there is a recess 20 in the bottom wall 8 of box B.
Even if the tension rod 14 is provided, a predetermined connection portion remains between the tension rod 14 and the proximal end thereof, so that the tension force of the tension rod 14 does not decrease.

As shown in FIG. 3, the threaded rod hole 4 of the formwork 2
The threaded rod 6 inserted into the bulge 16 of box B
When the box B is pulled into the formwork 2 by screwing it into the nut 18 embedded in the box B and then by screwing the threaded rod 6 protruding from the formwork 2 into the nut 12, the tension rod 14 Since the box B comes into contact with the formwork 2, the bottom wall 8 does not bend and the box B comes into contact with the formwork 2.
closely adhere to. Note that the force applied to the tension rod 14 when the box B is brought into close contact with the formwork 2 is only the axial force, so by providing the recess 20, the connection portion between the tension rod 14 and the bottom wall 8 is reduced. Even if the cross-sectional area becomes smaller, the function of the tension rod 14 is not affected at all.

After pouring concrete C between the formwork 2, when the formwork 2 is removed and force is applied to the free end of the tension rod 14 in the direction perpendicular to the axis, shearing force is applied to the base end of the tension rod 14. . A recess 20 is formed on the outside of the bottom wall 8 by the tension rod 1.
4, the section modulus of the base end of the tension rod 14 is smaller than that in the case where the tension rod 14 is solid. It can be easily broken off. Note that when the diameter of the tension rod 14 is small, it is easier to break it off by applying force to its base end.

Furthermore, by changing the shape of the recess 20' provided on the outside of the bottom wall 8 as shown in FIG. , the tension rod 14 can be broken off even more easily.

In addition, in the above embodiment, as a fixture for drawing and fixing the box to the inside of the formwork,
Although a threaded rod is used, hook bolts can also be used as other fixing devices.The hook bolt is used to hook the hook attached to the bottom wall of the box, and the box is pulled inside the formwork and fixed. It may be something.

[Effect of idea]

In this invention, a tension rod is provided on the bottom wall toward the opening of the box, and when the box is pulled to the inside of the formwork using a fixing device and tightly fixed, the tension rod is brought into contact with the inside of the formwork. In a synthetic resin wiring box that prevents the bottom wall from bending, a connection portion is left between the base end of the tension rod and the tension rod to the extent that the tension rod is not reduced. By providing a concave portion on the outer surface of the bottom wall facing the base end of the tension rod, the cross-sectional area of the connecting portion between the tension rod and the bottom wall can be reduced. Therefore, the tension rods can be easily broken off with a small amount of force after the formwork is removed.

Therefore, it is no longer necessary to break off the tension rod by applying force many times as in the conventional method, so that work efficiency is improved.

In addition, since the force applied to the tension rod when the box is brought into close contact with the formwork is only the axial force, by providing the recess, the cross-sectional area of the connection between the tension rod and the bottom wall is reduced. This does not affect the function of the tension rod at all.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the box B according to the present invention, FIG. 2 is a perspective view of the box B with the bottom wall 8 facing upward, and FIG. 3 is a perspective view of the box B fixed to the formwork 2. FIG. 4 is a vertical cross-sectional view of the tension rod 14 broken off after removing the formwork 2, and FIG. 5 is a perspective cross-sectional view of the tension rod 14 along its length. 6A is an enlarged vertical sectional view of the recess 20, FIG. 6 is a bottom view of the same portion, FIG. 7A is an enlarged longitudinal sectional view of the recess 20',
The bottom view of the similar part, Figure 8, shows the conventional box.
FIG. 3 is a vertical cross-sectional view of B' fixed to the formwork 2;
The explanation of the symbols of the main parts is as follows. B... Box, 2... Formwork, 6... Threaded rod (fixing tool), 8... Bottom wall of box, 14... Tension rod, 20, 20'... Recess.

Claims (1)

[Scope of utility model registration request] A tension rod is provided on the bottom wall facing the opening of the box, and when the box is drawn to the inside of the formwork by the fixing device and tightly fixed, the tension rod is brought into contact with the inside of the formwork and the bottom In a synthetic resin wiring box designed to prevent the wall from bending, the tension rod is broken off while leaving a connecting part between the tension rod and the base end to the extent that the tension rod is not reduced. 1. A synthetic resin wiring box characterized in that a recess for reducing force is provided on the outer surface of the bottom wall facing near the base end of the tension rod.