JPH068325Y2 - Breakaway bolt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a breakaway bolt for preventing transient tightening by breaking a tightening rotary head when a predetermined tightening torque is exceeded.

[Prior Art] When the bolts of various devices are tightened manually by the worker using a bolt turning tool such as a wrench or a spanner, etc., and depending on the worker's manual adjustment, the operator's manual adjustment is required. Torque is not constant when tightened by tightening. Therefore, in order to ensure that the torque is always fixed without being affected by the amount of work done by the operator, see
As disclosed in Japanese Patent No. 772, a reduced diameter neck portion that breaks when the tightening torque exceeds a certain value is provided between the base end head portion and the tip end head portion of the bolt head, and the tip end head portion rotates the bolt. When the worker fits the tool and rotates, and the torque exceeds a certain level, the diameter-reducing neck portion breaks so that further tightening torque does not reach the bolt side.

Also, like the constant torque tightening member of Japanese Utility Model Laid-Open No. 58-50305, a small-diameter shaft portion that breaks and separates at a predetermined torque is provided on the head of a non-magnetic material bolt, and the separation portion above it. A piece of magnetic material smaller than the diameter of the top surface is fixed to the top surface,
It is known that the separated portion that has been broken and separated is attracted to the tightening spanner by the magnetic force of the magnetic material piece to prevent the separated portion from falling off.

Also, in a box-type tool for turning a nut, such as the box-type nut turning with a fall prevention ring in Japanese Utility Model Publication No. 51-113899, an O-shaped elastic is provided by providing an annular groove on the inner peripheral surface of the box for housing the nut. A nut turning tool is known in which a body is fitted and a nut is placed inside the O-type elastic body to prevent the nut from falling off.

[Problems to be Solved by the Invention] Just by providing a breaking separation head like the conventional bolt, when a bolt turning tool is fitted to the tip head of the bolt and the bolt is rotated to break the reduced diameter neck, Since the tip head part fitted into the turning tool comes out, there is a risk that the tip head part coming out of the turning tool may fall when working at a high place.

Also, the reduced diameter neck part provided in the middle part of the bolt head must be formed so that it breaks at a constant tightening torque, so high accuracy is required and it is not suitable for mass production, and it is formed into a concentric circle shape by lathe processing. Since it was not made into a simple fracture surface shape, it was a factor of high cost.

Furthermore, since the tip part that breaks and separates has the same shape as the base part that remains on the bolt side, there is a large amount of material separation loss, which increases the cost, and the bolt head becomes large and its mass becomes large, so carry many. However, when the bolt becomes thicker, a large rotating tool that fits on the head of the large-diameter bolt is required, resulting in a problem that work efficiency deteriorates.

Also, like the constant torque tightening member disclosed in the Utility Model,
Ordinary bolts other than non-magnetic material bolts cannot be used with a structure in which a magnetic material piece smaller than the surface diameter of the non-magnetic material bolts is fixed to the top surface of the separation part and magnetically attracted to the tightening wrench. In addition, since the magnetic material piece is fixed to the top surface of the separation portion of the non-magnetic material, there is a problem that it becomes expensive.

Further, unlike the box-type nut turning tool with a fall prevention ring disclosed in the above-mentioned utility model, the configuration in which the O-type elastic body is fitted in the annular groove on the inner peripheral surface of the box cannot be applied to the bolt.

The present invention prevents the breaking separation part fitted in the turning tool from falling when the bolt turning tool is turned to exceed the predetermined torque and the narrow neck part is broken, and the cost is low and work efficiency is high. It is intended to provide an improved breakaway bolt.

[Means for Solving the Problems] In order to solve the above problems and achieve the object, the breakaway bolt of the present invention has a thin neck portion 3 which is broken at a predetermined tightening torque at the center of the top surface of the bolt head 2. A tightening and turning head 4 having a diameter smaller than that of the bolt head 2 is provided at the tip of the thin neck portion 3, and a cap for preventing falling is provided so as to project from the peripheral edge of the top surface of the tightening and turning head 4. The configuration is such that the rim 5 is provided.

[Operation] When the turning tool for tightening the bolt is fitted into the tightening turning head 4, the drop-out preventing protruding edge portion 5 is also fitted into the turning tool, and the tightening turning head 4 is rotated by the turning tool. When the bolt is moved, the bolt is tightened, and when the tightening torque reaches a predetermined tightening torque, the thin neck portion 3 breaks to prevent a further transient tightening torque from being applied to the bolt. Since the fall-out preventing protruding edge portion 5 fitted in the rotating tool is locked in the rotating tool, the thin neck portion 3 is broken and the tightening rotating head portion 4 is separated from the bolt head portion 2. Even then, the remaining drop in the rotary tool is prevented.

Overhanging edge portion 5 provided on the top surface of the head 4 for tightening and turning to prevent falling off.
Since it is not a magnetic material, it is not particularly limited to bolts made of non-magnetic material such as known constant torque tightening members, and can be applied using ordinary bolts.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show one embodiment of the breakaway bolt of the present invention, FIG. 3 is a view for explaining the operation thereof, and FIGS. 4 to 8 show other embodiments.

In the embodiment shown in the front view of FIG. 1 and the second top view, 1 is a male screw portion, 2 is its bolt head, and this bolt head 2 corresponds to the male screw portion 1 as nominally specified by JIS. To standard size.

Reference numeral 3 denotes a thin neck portion provided upright at the center of the top surface of the bolt head 2. The thickness of the neck portion is such that it breaks when a predetermined tightening torque is exceeded, and its cross-sectional shape is concentric or other suitable shape. Then, it is formed by lathe processing, forging, pressing or the like.

On the upper end of the thin neck portion 3, a tightening / rotating head 4 having a diameter smaller than that of the bolt head 2 is provided. This small diameter tightening head 4
Is formed to have a nominal size which is one to two ranks lower than the bolt head 2, and is formed into a hexagonal shape having the same shape as the bolt head 2 or an appropriate square head.

On the top surface of the small-diameter tightening / rotating head 4, a drop-out preventing protruding edge portion 5 is provided so as to project from the peripheral edge of the top surface. The fall-out preventing overhanging edge portion 5 is formed of rubber, plastic, or the same material as the tightening / rotating head 4 or a soft material, and is attached to the top surface of the tightening / rotating head 4.

The breakaway bolt of the embodiment shown in FIGS. 1 and 2 according to the present invention is constructed as described above. To tighten the breakaway bolt with a turning tool, as shown in FIG. For example, if the box portion 11 such as an L-shaped wrench 10 is fitted into the tightening / rotating head portion 4 and the drop-out preventing protruding edge portion 5 of the top surface thereof is also fitted into the box portion 11, the tightening / rotating head portion 4 is tightened. The protruding edge portion 5 protruding from the peripheral edge of the top surface of the head portion 4 is pushed into the inside of the box portion 11 and locked. This L-shaped wrench
If the male screw portion 1 is screwed into the mating female screw by turning 10 and tightened, when the tightening exceeds a predetermined tightening torque, the thin neck portion 3 is broken and the bolt is tightened and screwed with the predetermined torque.

As described above, when the thin neck portion 3 is broken, the tightening / rotating head portion 4 fitted in the box portion 11 is separated from the bolt head portion 2, but the fall-preventing projecting edge portion 5 is also fitted and engaged. Since it is stopped, the tightening / rotating head 4 separated from the bolt head 2 remains in the box portion 11. Therefore, even if the tightening and turning head 4 is separated from the bolt head 2, it does not drop and danger is prevented. In order to take out the tightening / rotating head 4 remaining in the box portion 11, the handle portion of the L-shaped wrench 10 can be tapped out easily.

The embodiment shown in FIG. 4 is an example in which the present invention is applied to a conventional breakaway bolt, and the same reference numerals as those in FIG. 1 indicate the same parts. Reference numeral 6 is a locking portion provided on the lower edge of the tightening and turning head 4, and the tightening and turning head 4 is provided with a box 11 such as a wrench.
When the bolt is fitted, the bolt head 2 is stopped from being fitted.

The embodiment shown in the front view of FIG. 5 and the top view of FIG. 6 shows an example in which the cross-sectional shape of the thin neck portion 3 is modified, and the same reference numerals as those in FIG. 1 denote the same parts. In this embodiment, the thin neck portion 3 is formed in a square shape such as a hexagonal shape, and a notch is formed in the middle portion thereof by a press or the like to form a cut portion 7 having a substantially square cross section. 7 is designed to be broken when the tightening torque reaches a predetermined value. By forming the broken portion in this manner, it is possible to perform work-molding rapidly with uniform accuracy and mass production becomes possible.

The embodiment shown in the front view of FIG. 7 and the top view of FIG. 8 shows an example in which the thin neck portion 3 is formed so that it can be molded by forging, and the fall-preventing protruding edge portion is modified. The same reference numerals indicate the same parts. Since the groove width of the reduced neck portion of the conventional breakaway bolt is about 3 to 4 mm, it can be processed only by lathe processing, but in this embodiment, the length of the thin neck portion 3 is extended. Since it can be manufactured only by forging without a processing step, the cost can be reduced. The fall-out preventing overhanging edge portion 8 is formed by providing a slit or a concave portion on the side surface of the tightening / rotating head portion 4 and embedding or adhering a plastic piece or a soft elastic material piece into this. It is formed so as to slightly project from the side surface of the tightening / rotating head 4 and to be caught by a box portion such as a wrench.

As described above, in any of the embodiments, even if the thin neck portion 3 is broken by the predetermined tightening torque, the tightening turning head 4 remains in the box portion 11 of the turning tool and does not drop.

[Effects of the Invention] As described above, the breakaway bolt of the present invention has the protrusion-preventing protrusion edge portion protruding from the peripheral edge of the top surface of the tightening and rotation head, so that the rotation tool is rotated to a predetermined position. When the tightening torque breaks the narrow neck and the head for tightening rotation separates from the head of the bolt, the overhanging edge for prevention of falling is locked in the turning tool and the head for tightening rotation is Since the remaining drop in the rotating tool is prevented, it is possible to safely perform work in high places, and the broken and separated tightening rotating head does not drop and is lost. It is possible to prevent mistakes in construction by forgetting to tighten the bolts by checking the numbers.

Also, since the head for tightening rotation has a small diameter, the amount of material loss is small,
In addition, the thin neck can be manufactured by forging or pressing without the need for lathe processing, so the cost can be reduced.Because the tightening and turning head is small, it is lightweight, and the turning tool is also small and lightweight, making it easy to carry. Will be easier and work efficiency will be improved.

Furthermore, since the fall-out preventing protruding edge portion provided on the top surface of the tightening / rotating head is not made of a magnetic material as is known, it is not limited to a non-magnetic material bolt, and an ordinary bolt is used. And can be applied.

[Brief description of drawings]

FIG. 1 is a front view of one embodiment of the present invention, FIG. 2 is a top view thereof, FIG. 3 is an operation explanatory view, FIG. 4 is a front view of another embodiment, and FIG. An example front view, FIG. 6 is a fifth view
FIG. 7 is a sectional view taken along line XX of FIG.
FIG. 8 is a top view thereof. 2: Head of bolt, 3: Neck neck 4: Head for tightening rotation, 5: Overhanging edge to prevent falling

Claims (1)

[Scope of utility model registration request] 1. A head portion for bolting which is broken at a predetermined tightening torque is erected on a top surface of a bolt head, and a head portion for tightening and turning having a small diameter is provided at a tip of the thin neck portion. Breakaway bolt that has a protruding edge to prevent it from protruding from the top edge of the part.