JPH0198706A - Looseness detector for bolt - Google Patents

Abstract

PURPOSE: To detect bolt looseness in a simple, easy and correct way by pivoting a hammer member having a weight on a body having a fix member for engaging a nut or the head of a bolt, and arranging a drive member and a force or acceleration sensor between the hammer member and the body. CONSTITUTION: A switch 30 arranged in the root portion of a handle 1 is manipulated to energize a solenoid coil to drive a movable iron core 18 into a drive member 9. In this way, a hammer member 8 is pulled against the spring force of a return spring, and the flat portion f of a nut 4 is stricken by a weight 10. The force exerted by the strike is detected by a sensor 7, and the signal thereof is introduced to a comparing section or calculating section or the like arranged in the handle 1 to detect the abnormality of a bolt 3. In this way, the structure is simple and detection can be conducted very easily. There exist no individual differences between the people using the detecting device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a bolt loosening detection device for detecting loosening of bolts in steel structures such as bridges.

[Prior art]

For example, steel structures such as bridges are assembled using a large number of bolts. Therefore,
It is necessary to confirm the safety of this steel structure by inspecting the loosening of bolts when it is assembled or completed, or after a certain period of time has elapsed.

A common method for testing bolt looseness is to lightly hit the head of the bolt in the shearing direction with a hammer.
A method is used in which humans judge based on the blow at this time. However, this method is highly dependent on people's "feelings", and as a result there are large individual differences, and not only can accurate judgment be made only by experienced people, but there is also the problem that even highly skilled people will make different judgments when the degree of loosening is small. Ta.

Additionally, when a relatively large number of bolts are arranged in a relatively narrow area, the spacing between the bolts inevitably becomes small, which makes it difficult to accurately strike the bolts with a hammer in the shearing direction. There was a problem.

[Purpose of the invention]

The present invention has been made in order to solve the various problems as described above. This is a device that detects acceleration and uses this detection signal to detect loosening of bolts.The purpose is to use a lightweight and simple device.
The purpose is to simply, easily, and accurately detect the loosening of bolts.

[Summary of the invention]

To achieve the above object, the present invention includes a main body having a fixing part that engages with the head of a nut or bolt, and a hammer part having a weight pivoted thereon, and a hammer part having a weight between the hammer part and the main body. This is a bolt loosening detection device that is provided with a drive unit that applies a blow, and a sensor that detects the force or acceleration caused by the blow force.

A solenoid coil is most easily used as a power source for the drive unit, but a pneumatic actuator can be used to instantaneously generate a large force.

The force sensor is a load detector using a piezoelectric element, a strain gauge, or the like, and is attached to the weight. On the other hand, the acceleration sensor is attached to the weight or the fixed part, and detects subtle shifts and vibrations when the bolt is struck.

To detect this, it is possible to check the left and right asymmetry of the pulse waveform around the peak value, and to issue an alarm depending on the degree of the asymmetry.

In addition, when an acceleration sensor and a force sensor are used together, bolts that are fastened with a predetermined tension and bolts that are outside the tension can be recognized by the ratio of both signals and mathematical processing using both signals as variables. can do.

The direction in which the hammer hits the nut is the shearing direction of the bolt,
That is, by being in the vertical direction, it is possible to obtain accurate signals. For this purpose, it is preferable that the line connecting the impact point and the pivot point of the hammer portion be parallel to the axis of the bolt.

The hammer part is equipped with a weight to increase the mass and strike in a stable state, but in order to avoid the influence of other bolts and produce a large striking force with a small stroke, the weight is increased. , it is preferable to use a U-shaped cross section with a gentle curve.

It is necessary to easily and accurately attach the detection device according to the present invention to a NAND screwed onto a bolt. For this purpose, it is best to provide a fixing part with a rectangular fitting surface that fits into the head of a nut or bolt at the tip of the main body.In this way, the detection device can be attached and detached from the bolt accurately and easily. be able to.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view of a bolt loosening detection device H of the present invention, and FIG. 2 is a plan view thereof, which has a handle portion 1 at one end and a napht 2 or a head portion 2 of a bolt 3 at the other end. It is composed of a main body 5 having a fixing part 4 that engages with the angle, and a hammer part 8 having one end pivoted to the main body 5 by a pin 6 and having a sensor 7. In order to generate a predetermined impact force on the hammer portion 8, a driving portion 9 is provided between the hammer portion 8 and the main body 5.

Specifically, as shown in FIG. 3, the fixing part 4 attached to the main body 5 is configured so that the - side is open along three sides of the nut 2, and moves in the axial direction of the bolt 3. By doing so, it can be inserted into and removed from the throat 2 or the head 2 of the bolt 3.

A weight 10 is attached to the tip of the hammer portion 8, and a load detector (force sensor) such as a piezoelectric element or a strain gauge is attached to the weight 10 as a sensor 7. The weight 10 is formed wide and is designed to have a large mass as the weight moves between the gaps 2 between the bolts 3.

In order to further increase the mass of the weight 10, the cross section may be formed into a gently curved arc shape as shown in FIG.

The weight 10 has a recess 11 formed in its lower surface as shown in FIG. This sensor 7 may be an acceleration sensor if necessary.

The driving part 9, whose one end is attached to the intermediate part of the main body 5 by a pin 13, has an outer shell 14, a receiving part 15 and a guide part 16 disposed within the outer shell 14, as shown in FIG. A solenoid coil 1 is installed in this guide portion 16.
Due to the action of 7, the movable iron core 18 is fitted so as to be slidable in the vertical direction.

At the end of this movable iron core 18 is a connecting portion 19 having a U-shaped cross section.
is provided, and is attached to the hammer part 8 by a pin 21 whose end is fitted into a hole 20 drilled therein. In addition, 2
Reference numeral 5 denotes an arm portion whose one end is attached to the hammer portion 8 as shown in FIG. 7, and the other end of this arm portion 25 and the drive portion 9
A return spring 26 is provided between the hammer portion 8 and the hammer portion 8 to provide a restoring force to the hammer portion 8.

Furthermore, instead of the solenoid coil 17, the drive unit 12 may use, for example, an air actuator.

In addition to the method of attaching the sensor 7 to the weight 10, for example, as shown in FIG. 8, an acceleration detector 28 can be inserted into a hole 27 provided in the weight 10 and used as a sensor. Furthermore, this acceleration detector 28 can also be used alone.

Then, when the switch 30 provided at the base of the handle portion 1 is operated and the solenoid coil 17 is energized, the movable iron core 18
In other words, the hammer part 8 is pulled (downward) against the spring force of the return spring 26, and the flat part f of the napft 4 is struck by the weight 10. The force or acceleration caused by this impact is detected by the sensor 7 (or 28), and this signal is sent to a comparison section or calculation section provided in the handle section 1 to detect an abnormality in the bolt.

This comparison section or calculation section 34 amplifies the signal 32 from the sensor 7 with an amplification section 33, as shown in FIG. 9, for example.
The comparison unit 34 compares the value with a reference value input in advance, and if the reference value deviates from the allowable range, the sound generator 35 can issue an alarm. The signal 32 from the sensor 7 has a pulse waveform, pulse width, etc., for example, and can be led to the calculation unit 34 to determine an abnormality.

The inventor of the present invention discovered that there is a close relationship between the looseness of the bolt and the pulse waveform. Specifically, the inventor discovered that when the tightening force of the bolt decreases, the pulse waveform becomes asymmetric around the peak value. We previously proposed a method to detect abnormalities in bolt fasteners by detecting pulse waveforms.

By the way, what about the bolt loosening detection bag shown in the above example? &H
According to , since the drive unit 9 is struck by a tensile force using a solenoid coil 17, it may not be possible to obtain a good pulse waveform simply by striking.

Therefore, as shown in FIG. 1θ, a connecting portion 19a having an elongated hole 20a is provided at one end of the movable core 18, and a pin 21a attached to the hammer portion 8 is provided within the elongated hole 20a.
The head of the figure is inlaid.

Then, the line B connecting the striking surface f of the nut 2 and the pin 6 that attaches the hammer part 8 to the main body 5 is made parallel to the axis C of the bolt l, and the lower end 18a of the movable core 18 is As shown in FIG. 6, the receiver comes into contact with the part 15,
The engagement between the pin 21a and the connecting portion 19a is released.

With this configuration, the hammer part 8 is released from the drive part 9 at the time of impact, and as a result, the pulse waveform obtained by the sensor 7 provided on the weight 10 is due to the pure impact force of the hammer part 8. Therefore, it can be detected as being good.

〔Effect of the invention〕

As is clear from the above description, the bolt loosening detection device according to the present invention includes a main body having a fixing portion that engages with the head of a nut or bolt, and a hammer portion having a weight pivoted thereon. A drive section for applying a striking force to the hammer section is provided between the hammer section and the main body, and a sensor is provided for detecting the force or acceleration caused by the striking force, and the following effects can be achieved.

It has a simple structure consisting of a main body with a fixed part that fits and fixes bolts, and a swingable hammer part on this main body, so even if the bolts are fastened at relatively narrow intervals, this The bolt can be struck with a constant force in a direction perpendicular to the axis of the bolt, that is, in the shearing direction, and the striking force can be detected by a sensor to detect loosening of the bolt.

Therefore, this detection work is extremely simple and can be performed easily, and the results do not vary among individuals who use this detection device.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, in which Fig. 1 is a side view of a bolt loosening detection device according to the first embodiment of the invention, Fig. 2 is a plan view thereof, and Fig. 3 is a hammer. 4 is a sectional view showing another shape of the weight, FIG. 5 is a sectional view showing the fixing part of the sensor, and FIG. 6 is a sectional view of the drive part. FIG. 7 is a diagram showing the mounting structure of the return spring, FIG. 8 is a sectional view of the sensor mounting portion of the weight, and FIG. 9 is a block diagram of the signal processing section. FIG. 10 is a side view of a detection device according to a second embodiment of the present invention. H... Bolt looseness detection device, 1... Handle part,
2... Natsu, 2゛... Head, 3... Bolt, 4
... Fixed part, 5... Main body, 6... Pin, 7...
Sensor, 8... Hammer section, 9... Drive section, 10
... Weight, 11 ... Recess, 12 ... Lid, 13.
...Pin, 14...Outer shell, 15...Bake part, 32.
... Signal, 33... Amplification section, 34... Comparison or calculation section, 35... Sound generator. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] A hammer part having a weight is pivotally supported on a main body having a fixed part that engages with the head of a nut or bolt, and a driving part is provided between the hammer part and the main body to apply a striking force to the hammer part, A bolt loosening detection device characterized by further comprising a sensor for detecting force or acceleration caused by the impact force.