JP2701144B2 - Bolt with torque limit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bolt provided with torque limit means for cutting at a predetermined tightening torque.

[0002]

2. Description of the Related Art Conventionally, a bolt with a torque limit has a double head consisting of a lower head and an upper head as shown in Japanese Utility Model Publication No. 55-5772, for example. , Forming a reduced diameter neck portion which is divided by the tightening torque.

Therefore, when a predetermined tightening torque is reached when a tool such as a wrench is engaged with the upper head portion to tighten the bolt, the reduced diameter neck portion is cut off and the transmission of the torque is interrupted.

[0004]

In the prior art, a reduced diameter neck portion is provided between both heads in order to cut off torque by separating the upper head from the lower head. When the neck is cut off, there is a problem that the segment left on the lower head is exposed on the top surface of the lower head. At this time, since the reduced diameter neck is made of metal integral with the bolt, there is a danger that the finger or the like may be injured if the fragment appears as so-called burrs or burrs due to a metal piece. When such bolts are used for connecting conductors of wiring equipment,
There is a risk of causing an accident such as a short circuit.

[0005]

SUMMARY OF THE INVENTION The present invention is secure,
Moreover, it is intended to provide a bolt with a torque limit excellent in electrical insulation. As a first means, the lower part of the metal shank and the upper part made of synthetic resin are attached to the base end of the metal shank. A head shaft arranged with the head overlapped, and a lower shaft portion embedded in the lower head portion and an upper core portion embedded in the upper head portion extending from the base end portion of the shank. The core shaft is formed between a lower core portion and an upper core portion with a dividing shaft portion reduced in diameter so as to be divided by a predetermined tightening torque, and is formed by the dividing shaft portion. Also, a large-diameter concave portion forming shaft portion is formed between the dividing shaft portion and the upper core portion, and the dividing shaft portion is embedded in the lower head, and the concave portion forming shaft portion is formed. The point is that it is embedded from the top of the lower head toward the inside.

Further, the present invention is configured as a second means in that a metal bolt body having a core shaft connected between a head and a shank surrounds the core shaft and is made of a synthetic resin head. Forming an upper portion, a metal upper portion and a synthetic resin lower portion are superimposed on each other, and the core shaft has a diameter reduced so as to be separated by a predetermined tightening torque. A shaft portion is formed, and a concave portion forming shaft portion having a larger diameter than the dividing shaft portion is formed between the dividing shaft portion and the upper head, and the dividing shaft portion is formed inside the lower head. And the recess-forming shaft portion is embedded from the top surface of the lower head portion toward the inside.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) In a first embodiment shown in FIG. 1, a metal bolt body 1 has a core shaft 4 extending from a base end of a shank 3 having a thread 2. I have.
On the upper part of the bolt body 1, a lower head 5 and an upper head 6 made of synthetic resin formed by embedding the core shaft 4 are arranged so as to overlap each other, forming a so-called double head. ing.

Each of the heads 5 and 6 has an outer peripheral portion formed in a polygonal shape such as a hexagon so that a tool such as a wrench or a spanner can be engaged. The upper head 6 is formed small, so that a tool sized to be engaged with the upper head 6 is not engaged with the lower head 5.

The core shaft 4 has a lower core 7 embedded in the lower head 5 and an upper core 8 embedded in the upper head 6 connected to each other. Forming a dividing shaft portion 9 whose diameter is reduced so as to be divided by a predetermined tightening torque between 7, 8;
The dividing shaft 9 is embedded in the lower head 5.

The lower core 7 has a large-diameter flange 10 embedded in the lower head 5, and forms a reduced-diameter portion 11 that gradually decreases in diameter from the flange 10 toward the base of the shank 3. The lower head 5 has a holding portion 12 for holding the lower surface of the flange 10 via the reduced diameter portion 11. The flange 10
It is preferable that the diameter-reduced portion 11 has a peripheral surface formed into a rough surface having irregularities, or a peripheral surface formed into a polygon.

The upper core 8 is provided with an engaging portion 13 formed of irregularities such as serrations which are coupled to the upper head 6 so as not to rotate relatively.
And a concave portion forming shaft portion 14 is formed between the upper core portion 8 and the dividing shaft portion 9. The concave portion forming shaft portion 14 forms a tapered portion 15 whose diameter gradually decreases toward the upper core portion 8. The tapered portion 15 is embedded in the upper head portion 6 while the concave portion forming shaft portion 14 is formed. The lower head 5
It is embedded from the top to the inside.

The lower head 5 and the upper head 6 are insert-molded by inserting the core shaft 4 into an injection mold, but are each formed by injection molding twice. That is, by molding the lower head 5 by primary molding, and then molding the upper head 6 by secondary molding,
The two heads 5, 6 are formed as superposed double heads.

According to the first embodiment, when a tool is engaged with the upper head 6 to perform a fastening operation while rotating the bolt,
When a predetermined tightening torque is reached after the bolt is tightened, the cutting shaft 9 is broken and cut. That is, the dividing shaft portion 9 which is the minimum diameter portion of the core shaft 4 reduced in diameter between the flange 10 and the concave portion forming shaft portion 14 is broken, and the upper head portion 6 is connected to the lower head portion 5.
, Thereby interrupting the transmission of torque.

At this time, as shown in FIG. 1 (C), the recess forming shaft 14 is integrally separated from the upper core 8 embedded in the upper head 6 and separated therefrom. On the other hand, the lower head 5 in which the lower core 7 is embedded remains and is fixedly secured to the bolt body 1 that has been fastened, and a cutting shaft is mounted on a flange 10 of the lower core 7. A fraction 9a of part 9 results. However, when the concave portion forming shaft portion 14 is removed from the lower head portion 5, a concave portion 14a is formed on the top surface of the lower head portion 5, so that the segment 9a is positioned below the concave portion 14a. I do. For this reason, the segment 9a does not protrude from the top surface of the lower head 5 or is exposed near the top surface.

(Second Embodiment) In a second embodiment shown in FIG. 2, the upper head 6 is formed to be the same size as the lower head 5, and a flange 6a is provided below the upper head 6. . Other configurations are the same as those of the first embodiment described with reference to FIG.
Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and the above description is referred to.

According to the first embodiment, when the fastening operation is performed by turning the bolt, the tool engaged with the upper head 6 moves downward and moves downward because the flange 6a constitutes a stopper. It is not engaged with the head 5. On the other hand, after tightening the bolt, after the upper head 6 is separated due to the separation of the separating shaft 9, if it becomes necessary to loosen the bolt or the like, the tool used at the time of tightening is directly attached to the lower head 5. Can be engaged.

(Third Embodiment) In a third embodiment shown in FIG. 3, the upper core portion 8 and the concave portion forming shaft portion 14 are formed to have substantially the same diameter, and the concave portion forming shaft portion 14 is It is embedded toward the lower head 5. Other configurations are the same as those of the first embodiment described with reference to FIG. 1 and the second embodiment described with reference to FIG. 2. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals and described above. Invite explanation.

As in the third embodiment, the concave portion forming shaft portion 14 only needs to have a larger diameter than the dividing shaft portion 9, and need not have a different diameter from the upper core portion 8. In other words, the present invention reduces the diameter of the cutting shaft 9 between the recess forming shaft 14 and the lower core 7, and forms the cutting shaft 9 so that it can be cut with a predetermined tightening torque. In addition, it is only necessary that the recess 14 a as the above-described safety area be formed on the top surface of the lower head 5 by the recess forming shaft 14.

(Fourth Embodiment) In the fourth embodiment shown in FIG. 4, the upper head 6X is formed integrally with the core shaft 4 of the metal bolt body 1, and surrounds the core shaft 4. By forming the lower head 5 made of synthetic resin, a double head in which the lower head 5 made of synthetic resin and the upper head 6X made of metal are overlapped. At this time, both the heads 5 and 6 are formed to have a hexagonal outer peripheral portion so that a tool such as a wrench or a spanner can be engaged.
The upper head 6 may be formed smaller than the lower head 5,
Alternatively, as shown by a chain line in the figure, the upper head 6 and the lower head 5 may be formed in the same size, and a flange 6a may be provided below the upper head 6.

The core shaft 4 has a large-diameter flange 10 embedded in the lower head 5, and forms a reduced-diameter portion 11 that gradually decreases in diameter from the flange 10 toward the base of the shank 3. The lower head 5 has a holding portion 12 for holding the lower surface of the flange 10 via the reduced diameter portion 11.
A dividing shaft 9 having a diameter reduced so as to be divided by a predetermined tightening torque is formed between the upper part 6 and the upper part 6. still,
It is preferable that the flange 10 and / or the reduced-diameter portion 11 have a peripheral surface formed into a rough surface with irregularities or a polygonal peripheral surface.

Between the metal upper head 6 and the dividing shaft 9, the concave forming shaft 1 having a diameter larger than that of the dividing shaft 9.
The recess forming shaft 14 is embedded from the top surface of the lower head 5 toward the inside.

The lower head 5 made of synthetic resin is insert-molded by inserting the core shaft 4 together with the upper head 6 into an injection mold, and a double head in which both heads 5 and 6 are overlapped. To form

Also in the fourth embodiment, when a predetermined tightening torque is reached after the bolt is tightened, the dividing shaft 9
Is destroyed, and the upper head 6 is separated from the lower head 5,
As a result, transmission of torque is cut off. Since the recessed shaft 14 is integrally connected to the separated upper head 6, a recess 14 a is formed on the top surface of the lower head 5. Therefore, the segment 9a of the cutting shaft 9 remaining on the flange 10 is located below the concave portion 14a formed in the lower head 5, and projects from the top surface of the lower head 5 or There is no exposure near the surface.

[0025]

According to the present invention, the lower head 5 and the upper head 6 are arranged one on top of the other, and the cutting shaft 9 whose diameter of the core shaft 4 is reduced by a predetermined tightening torque. Accordingly, in a bolt having a torque limit function for separating the two heads 5 and 6, at least the lower head 5 is formed of a synthetic resin, and the dividing shaft 9 is embedded in the lower head 5. At the same time, a large-diameter recess forming shaft 14 is connected to the dividing shaft 9 and the recess forming shaft 14 is embedded from the top surface of the lower head 5 toward the inside. Therefore, there is an effect that it is possible to provide a bolt with torque limit which is safe and excellent in electrical insulation.

That is, when the torque limit is executed by the division of the dividing shaft 9, the divided pieces 9 a of the dividing shaft 9 appear as so-called burrs or burrs made of metal. Not only is the segment 9a located inside the lower head 5 made of synthetic resin, but also between the segment 9a and the top surface of the lower head 5, a safety area corresponding to the shaft 14 for forming a recess. Is formed, there is no possibility that the segment 9a protrudes from the top surface of the lower head 5 or is exposed near the top surface. There is no danger, and there is no danger of causing an accident such as a short circuit when connecting the conductors of the wiring device, and it is safe.

[Brief description of the drawings]

FIGS. 1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a side view, FIG. 1B is a longitudinal sectional view, and FIG.

FIGS. 2A and 2B show a second embodiment of the present invention, wherein FIG. 2A is a side view, FIG. 2B is a longitudinal sectional view, and FIG.

3A and 3B show a third embodiment of the present invention, wherein FIG. 3A is a side view, FIG. 3B is a longitudinal sectional view, and FIG. 3C is a longitudinal sectional view during operation.

4A and 4B show a fourth embodiment of the present invention, in which FIG. 4A is a side view, FIG. 4B is a longitudinal sectional view, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bolt main body 3 Shank 4 Core shaft 5 Lower head made of synthetic resin 6 Upper head made of synthetic resin 6X Upper head made of metal 7 Lower core 8 Upper core 9 Cutting shaft 9a Segment 10 Flange 14 Shaft for forming recess 14a Recess

Claims (2)

(57) [Claims] 1. A synthetic resin lower head and an upper head are superposed on a base end of a metal shank, and a lower core and an upper head are embedded in the lower head. A core shaft having a continuous upper core portion embedded in the shank is extended from a base end of the shank, and the core shaft has a diameter reduced so as to be separated by a predetermined tightening torque. A shaft portion is formed between the lower core portion and the upper core portion, and a concave portion forming shaft portion having a larger diameter than the dividing shaft portion is formed between the dividing shaft portion and the upper core portion, A bolt with a torque limit, wherein the dividing shaft is embedded in the lower head, and the recess forming shaft is embedded from the top surface of the lower head toward the inside. . 2. A metal bolt body having a core shaft connected between a head and a shank surrounds the core shaft to form a synthetic resin head, and is combined with a metal upper head. The lower shaft made of resin is arranged in an overlapping manner, and the core shaft forms a dividing shaft portion reduced in diameter so as to be divided by a predetermined tightening torque, and is formed by the dividing shaft portion. Also, a large-diameter recess forming shaft is formed between the dividing shaft and the upper head, and the dividing shaft is embedded in the lower head, and the recess forming shaft is formed. A torque-limited bolt characterized by being embedded from the top surface of the lower head toward the inside.