JPH0570004B2 - - Google Patents

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 check the safety of the bolts by inspecting the loosening of the bolts when the steel structure is assembled or completed, or after a certain period of time has elapsed.

A general method for inspecting bolt looseness is to use a hammer to lightly strike the head of the bolt in the shearing direction, and then make a human judgment based on the strike. However, this method relies heavily on people's "intuition," and as a result, there are large individual differences, and not only does it require an experienced person to make an accurate judgment, but there is also the problem that even highly skilled people will make different judgments when there is little slack. Ta.

By the way, when detecting the loosening of a structure having a fastening part, a method of extracting the impact force as a signal from a sensor and comparing it with a reference value to detect the loosening is disclosed in, for example, Japanese Patent Laid-Open No. 60-29660. Are known.

As a result of intensive studies to apply this loosening detection method to detecting loosening of bolts, the inventor attached a hammer section with a weight to a main body having a fixed section that engages with the head of a nut or bolt, and the hammer A driving part that applies a striking force to the hammer part is provided between the part and the main body, and a sensor that detects force or acceleration is provided in at least one of the hammer part or the fixed part, and the signal from this sensor is compared with a reference value. He invented and separately proposed a bolt-looseness detection device that detects loosening of bolts.

However, in such a bolt loosening detector, the signal obtained by the impact force is not necessarily satisfactory. That is, when the head of a nut or bolt is struck by the hammer part, the striking force of the hammer by the driving part influences the force or acceleration. In other words, the impact force of the drive part is added to the momentum of the hammer part alone,
As a result, there is a problem that a good signal cannot be obtained. In particular, when this signal is extracted as a pulse waveform, the pulse waveform changes rapidly.

[Object of the Invention] The present invention has been made in order to solve the various problems as described above. This system detects force or acceleration acting on a fixed part, and uses this detection signal to detect loosening of bolts.The purpose is to obtain a particularly good detection signal to reduce weight. The object is to easily and accurately detect bolt loosening using a large and simple device.

[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 a bolt, and a hammer part having a weight that is pivoted between the hammer part and the main body. A driving section is provided for applying a hammer blow, and a sensor is provided for detecting the force or acceleration caused by the striking force, and the signal from the sensor is compared with a reference value, and the striking force of the hammer by the driving section is The bolt loosening detection device is configured to release the bolt immediately before the hammer part hits the nut or the head of the bolt.

A solenoid coil is the easiest to use as a power source for the drive unit, but in order to instantaneously generate a large force, a pneumatic actuator, a spring, etc. can be used.

The force sensor is a load detector using, for example, a voltage element or a strain gauge, 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 around the peak value of the pulse waveform, and to issue a warning depending on the degree of the asymmetry. Also,
When an acceleration sensor and a force sensor are used together, it is possible to check which bolts are fastened with a predetermined tension and which bolts are outside the tension using the ratio of both signals and mathematical processing using both signals as variables. I can do it.

An accurate signal can be obtained by ensuring that the direction in which the hammer strikes the nut is in the shearing direction of the bolt, ie in the vertical direction. 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 nut screwed onto a bolt. For this purpose, it is preferable to provide a fixing part having 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 to and detached from the bolt accurately and easily.

As a means of releasing the impact force of the hammer section by the drive section immediately before the hammer section hits the head of the nut or bolt, it is possible to release the connection between the drive section and the hammer section and free the hammer section. The head of the nut or bolt is struck with only the hammer part. Specifically, just before the hammer part hits the head of the nut or bolt, the connection between the drive part and the hammer part is cut off, and the impact is made by free hitting only with the hammer part.

〔Example〕

Next, embodiments will be described with reference to the drawings.

FIG. 1 is a side view of the bolt loosening detection device H of the present invention, and FIG. 2 is a plan view thereof.

A fixing part 4 having the handle part 1 at one end and engaging the head 2' of the nut 2 or bolt 3 at the other end.
The hammer part 8 has one end pivoted to the main body 5 by a pin 6 and has a sensor 7. In order to generate a predetermined impact force on the hammer section 8, a drive section 9 is provided between the hammer section 8 and the main body 5.

Specifically, the fixed part 4 attached to the main body 5
As shown in FIG. 3, the nut 2 is arranged so that one side is open along the five sides, and is fitted onto the head 2' of the nut 2 or bolt 3 by moving it in the axial direction of the bolt 3. It has become possible to escape.

A weight 10 is attached to the tip of the hammer portion 8, and a load detector (force sensor) made of a piezoelectric element, a strain gauge, etc. 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 a weight that moves between the gaps P 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. 4.

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 drive 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 movable core 18 is fitted into the guide portion 16 so as to be slidable in the vertical direction by the action of a solenoid coil 17. A connecting portion 19 having a U-shaped cross section is provided at the end of the movable core 18, and a long hole 20 is formed in the connecting portion 19.
It is attached to the hammer part 8 by a pin 21 whose end is inserted into the hammer part 8.
Only the player can move forward and be in a state of ``free batting''.

In addition, 25 is an arm part whose one end is attached to the hammer part 8 as shown in FIG. 7, and a return spring 26 is provided between the other end of this arm part 25 and the drive part 9, It is designed to provide restoring force to the portion 8.

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 the bolt 3.
The lower end 18a of the movable iron core 18 is made to be parallel to the axis C of the pin 21 and the connecting part 1 during impact, as shown in FIG.
The engagement with 9 is released.

Furthermore, instead of the solenoid coil 17, the drive unit 9 may be replaced with an air actuator, for example.

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, by operating the switch 30 provided at the base of the handle part 1 and energizing the solenoid coil 17, the movable core 18 is drawn into the drive part 9, that is, the hammer part 8 is moved against the spring force of the return spring 26 ( downward) and strike the flat part f of the nut 2 with the weight 10. Detected by the force or acceleration sensor 7 (or 28) due to this impact,
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. If the value deviates from the allowable range, the sound generator 3
An alarm can be issued from 5. This sensor 7
The signal 32 from the sensor is, for example, a pulse waveform, pulse width, etc., and is led to the calculation unit 34 where it is subjected to mathematical processing and compared with a reference value to determine an abnormality.

With this configuration, the hammer part 8 is disengaged from the drive part 9 during impact, resulting in a "free impact".
As a result, the signal obtained by the sensor 7 provided on the weight 10 is due to the pure striking force of the hammer portion 8, and can be detected as a good one.

〔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. and the main body, a drive unit that applies a striking force to the hammer part is provided, and a sensor that detects the force or acceleration caused by the striking force is provided, and the signal from the sensor is compared with a reference value, The impact force of the hammer part by the driving part is released immediately before the hammer hits the head of the nut or bolt, and the following effects can be achieved.

It has a simple structure consisting of a main body with a fixing part that fits and fixes bolts, and a swingable hammer part on this main body, and even if the bolts are fastened at relatively narrow intervals, It is possible to strike with a constant force in the direction perpendicular to the axis of the bolt, that is, in the shearing direction, and when the hammer part strikes the nut or bolt, it enters a "free striking" state in which the striking force of the drive part does not act, and the sensor Since a good signal can be extracted from the sensor, it is possible to accurately detect loosening of bolts.

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 drawings]

The figure shows an embodiment of the present invention.
The figure is a side view of the bolt loosening detection device according to the first embodiment of the present invention, FIG. Cross-sectional view showing another shape of the weight, No. 5
The figure is a cross-sectional view showing the fixed part of the sensor, Figure 6 is a cross-sectional view of the drive part, Figure 7 is a diagram showing the return spring mounting structure, Figure 8 is a cross-sectional view of the sensor mounting part of the weight, and Figure 9 is a cross-sectional view of the sensor mounting part. The figure is a block diagram of the signal processing section. H...Bolt looseness detection device, 1...Handle part,
2... Nut, 2'... Head, 3... Bolt, 4... Fixed part, 5... Body, 6... Pin, 7... Sensor, 8... Hammer part, 9... Drive part, 10... Weight, 11... Recessed part, 12...Lid body, 13...Pin, 14...Outer shell, 15
...Receiving section, 32... Signal, 33... Amplifying section, 34... Comparison or calculation section, 35... Sound generator.

Claims (1)

[Claims] 1 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. , and a sensor for detecting the force or acceleration caused by the impact force is provided, and the signal from the sensor is compared with a reference value, and the hammer part applies the impact force of the hammer by the drive part to the nut or bolt. A bolt loosening detection device characterized in that the bolt is released immediately before hitting the head of the bolt.