JPH041515A - Peripheral length measuring instrument - Google Patents

Abstract

PURPOSE:To simplify a peripheral length calculating process by housing and fixing a transmission vibrator and a reception vibrator in a container so that the incoming position of an output ultrasonic wave on an outer peripheral surface is coincident with the detection position of a surface wave. CONSTITUTION:In this peripheral length measuring instrument by making an ultrasonic wave incident from one place on the periphery of the outer peripheral surface of an object to be measured and detecting the surface wave which makes one round of the outer peripheral surface to calculate the peripheral length of the object from the propagation time required by the surface to make one round of the outer peripheral surface of the object and the propagation speed of the surface wave, a pulse ultrasonic wave 17 outputted by the vibrator 15 for transmission which is housed in the container 13 of a measurement head 12 is made incident on a steel pipe 11 at the incidence position 11b to become a surface wave 18 and after making one round of the outer peripheral surface 11a, is made incident on the vibrator 16 for reception from the incidence position 11b. Thus, the incidence position 11b of the vibrator 15 for transmission is coincident on the detection position of the vibrator 16 for reception in the measurement head 12 to eliminate the need to correct the calculated peripheral length, and the peripheral length calculating process is therefore simplified.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a bureau measuring device that uses ultrasonic waves to measure the burr of a measuring object having a cylindrical or columnar shape. The present invention relates to a circumference measuring device in which a receiving transducer and a receiving transducer are incorporated into one measurement bed.

[Prior art] For example, when measuring the outer diameter of large-diameter steel pipes or rolls,
If workers measure the circumference manually using a diameter tape with a scale divided by pi, the efficiency of the measurement process will decrease and high measurement accuracy cannot be obtained. A measuring device has been proposed (Japanese Patent Laid-Open No. 55-11
Publication No. 7905).

That is, as shown in FIGS. 9(a) and 9(b), air cylinders 2 are installed at three locations on the outer peripheral surface 18 of the steel pipe 1 as the object to be measured.
A measuring head 4 is attached to the outer surface 1a of the steel pipe with the piston rod 3 of
The transmitting transducer 5 and the receiving transducer 6 are housed in the measuring head 4. Furthermore, the measuring head 4 is formed into a substantially sealed structure, and a couplant such as water or oil is placed inside. The liquid is supplied via a supply vibrator (not shown). Further, the surface of the measuring head 4 that comes into contact with the outer circumferential surface 1a of the steel pipe 1 is formed into a curved surface having a curvature equal to this outer circumferential surface 111.

Further, as shown in FIG. 9(b), in the measuring head 4, the angle of incidence of the transmitting vibrator 5 with respect to the outer circumferential surface 1a is set to be equal to or greater than the critical angle.

Note that if the ultrasonic wave is incident on the outer peripheral surface 1a at an angle less than the critical angle, the incident ultrasonic wave will propagate within the steel pipe 1, but if the ultrasonic wave is incident at an angle greater than or equal to the critical angle, the incident ultrasonic wave will propagate within the steel pipe 1. Most of the waves 10 propagate along the outer circumferential surface 1a of the steel pipe 1 as surface waves 10 without being propagated inside the steel pipe 1.

Similarly, the attitude angle of the receiving transducer 6 is also set to be equal to or greater than the critical angle. By setting the critical angle or more in this way, the surface wave 1 propagated along the outer peripheral surface 1a
Only 0 can be detected reliably.

That is, the ultrasonic waves propagated within the steel pipe 1 are hardly incident on the receiving transducer 6. In the measuring head 4, the incident position of the transmitting transducer 5 and the receiving transducer 6 are
The transmitting transducers 5 and the receiving transducers 6 in each measuring bed 4, which are separated by a distance g from the detection position, are electrically controlled by an iIi control device 8. Further, the rotation of the steel pipe 1 is controlled by a pair of rollers 9m and 9b.

In such a circumference measuring device, when a pulse signal is applied from the control device 8 to each transmitting transducer 5 of each measuring head 4, a pulsed ultrasonic wave is output from each transmitting transducer 5. The ultrasonic waves output from each transmitting transducer 5 are transmitted to the outer peripheral surface 1.
Since it is incident on fi at an incident angle greater than the critical angle, it becomes a surface wave 10 and propagates in one circumferential direction determined by the inclination direction of the transmitting vibrator 5. The surface wave 10 propagating along the outer circumferential surface 1g is detected by the receiving transducer 6 in the next measuring head 4 in the propagation direction.

Therefore, each propagation time Tr, T2 from the sending time of the pulse signal to each transmitting transducer 5 to the receiving time of the surface wave 10 in each receiving transducer 6.

When determining T3, each distance Ll between each measurement head 4,
L2. lx is easily calculated using the propagation velocity V at which the ultrasonic surface wave 10 propagates within the steel pipe 1. Therefore, steel [
The circumferential length of 1 is the value obtained by adding the distance 1 within the radius 4 to each measurement to the above-mentioned distances.

L-(TI +T2 +Ts)V+347...
(1) Note that the propagation velocity V is a value determined by the material of the object to be measured, so it can be measured in advance.

[Problems to be Solved by the Invention] However, even in the circumference measuring device configured as shown in FIG. 9, the following problems still remain to be solved.

That is, in the measuring head 4 shown in FIG. 9(b), the transmitting transducer 5 and the receiving transducer 6 are arranged back to back to each other so that the transmitted and received ultrasonic waves do not interfere with each other. has been done. Therefore, a distance g exists between the incident position by the transmitting vibrator 5 and the detection position of the receiving vibrator 6 on the outer peripheral surface la. Therefore, (1
), it is necessary to correct this distance g when calculating the accurate circumference, which makes the calculation complicated.

In addition, in the circumference measuring device shown in Figure $9, it is necessary to bring the measuring rod 4 into contact with the outer circumferential surface 1a of the steel pipe 1 with a constant contact pressure. Proceed to measurement - Press and fix the throat 4 using the air cylinder 2 and piston rod 3. Therefore, when the diameter of the steel pipe 1 to be measured changes significantly, or when the steel pipe 1 is transferred and sent after measurement, it is necessary to evacuate the entire apparatus to the rear. Furthermore, when the aperture changes, it is necessary to move the vertical position of the entire device. Therefore, the changeover work when changing the measurement position or measurement object becomes complicated.

In addition, since it is necessary to measure the propagation velocity of the object to be measured in advance, it is necessary to measure the propagation velocity using a different test device each time the circumference of a measurement object made of a new type of material is measured. . Furthermore, if the material of the object to be measured is unknown, it is necessary to measure the propagation velocity each time using another test device as described above. Therefore, a great deal of time and effort is required to prepare for actually measuring the circumference of the object to be measured.

The present invention was made in view of these circumstances, and
By attaching the measurement head to only one location on the outer circumference of the object to be measured, it can be easily attached to and removed from the object to be measured.
In addition, by matching the incident position and the detection position within the measurement head, the circumference calculation process can be simplified, thereby improving operability and making the entire device smaller and lighter. The purpose is to provide

Furthermore, by using a sub-receiving transducer in addition to the receiving transducer, the propagation velocity of the ultrasonic wave inside the object is automatically measured, and the circumference is automatically corrected without the need to separately measure the propagation velocity. It is an object of the present invention to provide a circumference measuring device that can measure circumferences and greatly improve measurement work efficiency.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides ultrasonic waves that are incident on the outer circumferential surface of an object to be measured from one point on the circumference at an incident angle equal to or greater than a critical angle. It has a transmitting transducer that generates a surface wave that propagates in one circumferential direction, and a receiving transducer that detects the surface wave that has made one circuit around the outer circumferential surface of the measured object. A circumference measurement device that calculates the circumference of a measured object from the propagation time required to go around the outer circumferential surface and the propagation velocity of a surface wave. A transmitting transducer and a receiving transducer are housed and fixed as a measurement head in one container so that the incident position coincides with the surface wave detection position on the receiving transducer.

Further, in another invention, in addition to the above-mentioned means, a sub-receiving transducer that is housed in a sub-measuring head connected to the measuring head and receives surface waves, and a sub-receiving transducer and a receiving vibrator are provided. and a propagation velocity calculation means for calculating the propagation velocity from the detection time difference of the surface waves between the receiving transducer and the receiving transducer and the mutual distance between the detection positions of the receiving transducers.

In still another invention, in addition to the means of the previous invention, there is provided mutual distance correction means for correcting the mutual distance to a length along the outer circumferential surface of the object to be measured according to the curvature of the outer circumferential surface of the object. ing.

Moreover, water is interposed as a couplant between each vibrator and the outer peripheral surface of the object to be measured.

[Function] In the circumferential length measuring device configured as described above, a measuring head housing a transmitting vibrator and a receiving vibrator is attached to only one location on the outer circumferential surface of the object to be measured. The surface waves of the ultrasonic waves sent out from the transmitting transducer go around the outer peripheral surface of the object to be measured and are detected by the receiving transducer housed in the same measurement head. Therefore, the circumference is calculated from the propagation time and, for example, the propagation velocity input from the outside. Furthermore, since the incident position of the transmitting transducer and the detection position of the receiving transducer coincide within the measurement head, there is no need to correct the calculated circumference.

In another invention, if the distance between the sub-receiving transducer in the sub-measuring head and the receiving transducer in the measuring head is defined, the surface waves between the receiving transducers can be Since the propagation speed can be calculated from the detection time difference and the mutual distance,
The correct circumference is automatically calculated without inputting the propagation velocity separately from the outside.

Furthermore, the above-mentioned mutual distance used to calculate the propagation velocity is strictly speaking the length along the outer circumferential surface of the object to be measured, but the length along the outer circumferential surface depends on the curvature of the outer circumferential surface. changes slightly. Therefore, since the mutual distance is corrected according to the curvature, the accuracy of the calculated circumference can be further improved.

Further, since water is interposed as a couplant between each vibrator and the outer peripheral surface of the object to be measured, a good contact state is maintained by continuously supplying this water during the measurement period. Therefore, for example, it is only necessary to place the measurement head on the upper surface of the outer peripheral surface of the object to be measured, and there is no need for a complicated device for press-contacting the measurement head to the outer peripheral surface of the object to be measured.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic cross-sectional view showing a state in which the circumference measuring device of the embodiment is attached to a steel pipe as an object to be measured.

A measuring head 12 is attached to an upper position on an outer circumferential surface 11a of a steel pipe 11 having a cylindrical cross section using a simple attachment device (not shown).

This measurement head 12 is composed of one split-type probe in which a transmitting transducer and a receiving transducer are housed in one container. As shown in FIG. 1, a transmitting transducer 15 and a receiving transducer 16 are arranged symmetrically within the container 13 with the acoustic dividing plane 14 as the center. The ultrasonic wave 17 output from the transmitting transducer 15 is incident on the outer circumferential surface 11a of the steel pipe 11 at an incident angle θ larger than the critical incident angle. The transmitting vibrator 15 is positioned so that the incident position 11b is at the center of the container 13.

Therefore, the pulsed ultrasonic wave 17 output from the transmitting transducer 15 enters the steel pipe 11 at the incident position 11b, but the incident ultrasonic wave 17 is not propagated inside the steel pipe 11 and is a surface wave. 18, and propagates along the surface of the outer peripheral surface 11a in one direction determined by the arrangement direction of the transmitting vibrator 15. Further, a part of the ultrasonic wave 17 output from the transmitting transducer 15 is transmitted to the incident position 11b on the outer circumferential surface 11a.
The signal is reflected by the receiver and directly enters the receiving transducer 16.

On the other hand, the surface wave 18 inputted from the incident position 11b and propagated along the surface of the outer circumferential surface 11a goes around the outer circumferential surface 11g of this steel pipe 11 once, and then a part of the surface wave 18 is transmitted to the incident position 11b1, that is, Receiving transducer 1 from the detection position
6.

Note that since the angle θ between the reception transducer 16 and the outer circumferential surface 11a with respect to the perpendicular line is set to be larger than the critical incident angle, almost all ultrasonic components other than the surface wave 18 output from the steel pipe 11 are received. Not done.

Transmission and reception to and from each vibrator 15 and 16 constituting the measurement head 12, which is a split type probe, is controlled by the control device 20 via signal lines 19g and 19b.

FIG. 3 is a block diagram showing a schematic configuration of the control device 20. As shown in FIG. A clock signal having a reference frequency fc outputted from the clock signal oscillation circuit 21 is frequency-divided by a frequency divider 22 to a repetition frequency Fo, and then input to the transmitting circuit 23. The transmitting circuit 23 applies a pulse signal having a predetermined width at intervals of the input repetition frequency F0 to the transmitting vibrator 15 in the measuring head 12 via the signal line 19a. Further, a clock signal of frequency fc outputted from the clock oscillation circuit 21 is inputted to a tally terminal CP of a counter 24 that measures the propagation time T.

The received signal of the receiving transducer 16 of the measuring head 12 is amplified by the receiving circuit 25 and then set to a certain threshold voltage v.
Only signal components having a value of 5H or more are detected and input to the control terminal G of the counter 24. Every time a pulse signal is input from the receiving circuit 25 to the control terminal G, the counter 24 outputs the currently counted value, clears this counted value to O, and restarts the counting operation from the beginning. The circumference calculation section 26 calculates (2) from the propagation time T sent out from the counter 24 and the propagation velocity V outputted from the parameter setting section 27.
The circumferential length of the steel pipe 11 is calculated according to the formula.

L-V-L...(2
) The calculated circumference is displayed on the display section 28.

Note that the parameter setting section 27 sets a repetition frequency F indicating an output time interval of the ultrasonic waves 17 output from the transmitting transducer 15 to the frequency divider 22. It also has a function of setting a threshold voltage VSH for the receiving circuit 25 to remove noise components contained in the received signal. Further, the parameter setting section 27 sets the propagation velocity V set by the operator using, for example, a keyboard or the like to the circumference calculation section 26, and outputs a circumference calculation timing signal to the circumference calculation section 26.

In the circumference measuring device configured as described above, the measuring head 12 consisting of a split type probe is set on the outer circumferential surface 11a of the steel pipe 11 as the object to be measured, as shown in FIG.
Activate the control device 20.

Then, a pulse signal is applied from the transmitting circuit 23 to the transmitting vibrator 15 at a constant repetition frequency Fo. As a result, the ultrasonic wave 17 is output from the transmitting transducer 15.

When the ultrasonic wave 17 is output from the transmitting transducer 15, the received signal output from the receiving transducer 16 contains many components caused by the ultrasonic wave, but the noise component of the received signal is below the threshold. The output signal of the receiving circuit 25 removed by POL VS)l includes a plurality of peak waveforms P1 to P4 as shown in FIG.

Zunawaji, the peak waveform P1 at time t is the peak waveform of the direct wave due to the direct reception of the ultrasonic wave 17 output from the transmitted (Hj4J transducer 16), and the peak waveform P2 at time t2 is at the incident position 1fllb. The peak waveform P at time t, which is the peak waveform of the reflected wave that was bitten, is the first layer detected from the detection position (incident position) 11b after the surface wave 18 has made one revolution around the outer peripheral surface of the steel pipe 11. The peak waveform P4 at time t4 is the peak waveform of the surface wave of the second layer when the same surface wave 18 goes around the outer peripheral surface of the steel pipe]1 one more time.

Therefore, at the counter 24, the time 1. =t2+
i2~t3+ Each time T between i3~t4.

T2. T3 is detected. Then, in synchronization with the timing at which the second time T2 is output, a circumference calculation command is sent to the circumference calculation section 26. Then, the circumferential length calculation unit 26 regards the second time T2 as the propagation time T required for the surface wave 18 to go around the outer circumferential surface 11a, and calculates the circumferential length using equation (2). The calculated circumference is displayed on the display section 28.

With the circumferential length measuring device configured in this way, one measurement head 1 is installed at one location on the circumference of the outer circumferential surface 11a of the object to be measured 11.
You only need to install 2. Further, the measurement head 12 is mounted at an upper position on the outer peripheral surface 11a of the steel pipe 11, so that it is only necessary to place the measuring head 12 on the upper surface of the outer peripheral surface 11a and fix it to the extent that it does not fall off to both sides. That is, it is sufficient that only the incident position 11b of the measurement head 12, where the ultrasonic waves 17 are input and output, is in contact with each other through, for example, oil or water.

Therefore, compared to the conventional device shown in FIG. 9, which required the use of an air cylinder 2 and a piston rod 3 in order to maintain close contact between the measuring head 4 and the outer circumferential surface 1a of the steel pipe 1 with a constant area. This greatly simplifies the configuration. For example, this circumference measuring device can be miniaturized to the extent that it can be carried.

Therefore, the work of attaching and detaching the apparatus to the object to be measured can be greatly simplified. Furthermore, manufacturing costs can be significantly reduced.

In addition, since the incident position 11b of the transmitting transducer 15 and the detection position of the receiving transducer 16 are made to match in the measurement head 12, the surface wave 18 remains at the time T2 measured in FIG. Since it corresponds to the propagation time T for going around the surface 11a, as in the conventional device shown in FIG.
There is no need to further correct the calculated distance using the distance g within the measuring head 4. Therefore, the calculation process of the circumference calculation section 26 is simplified.

FIG. 5 is a schematic cross-sectional view showing a state in which a circumferential length measuring device according to another embodiment of the present invention is attached to the outer circumferential surface 11a of a steel pipe 11 as an object to be measured.

This embodiment device includes a measuring head 12g incorporating a transmitting probe 15a and a receiving probe 16a;
A sub-measuring head 31 incorporating a sub-receiving probe 33 rotatably connected to the measuring head 12a by a connecting member 32 is used.

Each of the probes 15a, 16a, and 33 is a vertical probe having one transducer for both transmission and reception. The transmitting probe 15a uses one transducer exclusively for transmitting, and each of the receiving probes 16a, 3
3 uses one vibrator only for reception.

The transmitting probe 15a and the receiving probe 16a incorporated in the measurement head 12a are arranged in the same direction as the transmitting transducer 15 and the receiving transducer 16 shown in FIG. ing. Further, the sub-receiving probe 33 incorporated in the sub-measuring head 31 is disposed in the same direction as the receiving probe 16g.

A plurality of support rollers 34a are provided on the lower surface of each measuring head 12a, 31 to support each measuring head 12a, 31 so as to be movable in the axial direction of the steel pipe 11.

34b, 34e, and 34d are attached.

Therefore, each measuring head 12a, 31 and the outer peripheral surface 11a
There is a certain gap between them. And in this gap,
As shown in FIG. 5, pressurized water 35 is constantly supplied through a water supply pipe. As a result, each measurement head 12a, 31 is also filled with this water 35. Therefore, this water has probes 15g and 16a.

33 and the outer circumferential surface 11a.

Note that when the measuring head 12a and the sub-measuring head 31 are placed on a flat surface, the mutual distance between the detection position 11b of the receiving probe 16a and the detecting position 11C of the sub-receiving probe 33 is LS. It is.

The reception signal output from the sub-reception probe 33 of the sub-measurement head 31 is transmitted to the measurement head 1 through the signal line 19c.
Each signal line 19a from 2g.

It is input to the control section 20g together with the signal 19b.

The control device section 20a is configured as shown in FIG. In this control device 20a, the control device 20 shown in FIG. 3 includes a receiving circuit 36 that amplifies the received signal output from the sub-receiving probe 33 and extracts a peak waveform signal having a threshold voltage v5□ or higher; A counter 37 that counts the detection time difference ΔT between the receiving probe 16a and the sub-receiving probe 33 in the surface wave 18, and the detection time difference ΔT and the mutual distance after correction set from the parameter setting unit 27. A velocity calculation unit 26 is added that calculates the propagation velocity V of the surface wave 17 from the LC. Then, the speed V calculated by the speed calculation section 38 is input to the circumference calculation section 26. The peak waveform signal output from the receiving circuit 25 is input to both counters 24 and 37.

Further, the parameter setting unit 27 stores a correction table for correcting the mutual distance L5 in FIG. 6 to the mutual distance LC along the outer circumferential surface 11a in accordance with the curvature of the outer circumferential surface 11g of the steel pipe 11.

That is, when the diameter of the steel pipe 11 as the object to be measured becomes smaller, it bends significantly at the position of the connecting member that connects the sub-measuring head 31 and the measuring head 12a. Since this connecting member does not bend into a curved surface, when the curvature of the outer circumferential surface 11a increases, the mutual distance LS corresponds to the length of a string, and the outer circumferential surface 11a, through which the surface waves 18 actually propagate, corresponds to an arc. As a result, the correct mutual distance LC along the outer peripheral surface 11a becomes longer than the initial mutual distance LS. This lengthening rate is determined by the curvature of the external phase surface 11a, that is, the diameter of the steel pipe 11. Therefore, in correspondence to each diameter of the steel pipe 11 as the object to be measured, the corrected mutual distance LC for the corresponding diameter is stored. Then, when the diameter of the steel pipe 11 to be measured is entered manually, the corrected mutual opening M L c is set from the parameter setting section 27 to the speed calculation section 38 .

In the circumference measurement device having such a configuration, the control section f[2
When 0a is activated, the repetition frequency is F. A pulse signal is applied to the transmitting probe 15a at a time interval determined by , and a pulsed ultrasonic wave 17 is output from the transmitting probe 15a. As a result, the receiving probe 16 inside the measuring head 12a
The peak waveform signal outputted from a and from which unnecessary components such as noise have been removed by the receiving circuit 25 is as shown in FIG. 8(a).
The waveform is the same as in FIG. 4.

On the other hand, the ultrasonic wave 17 output from the transmitting probe 15a becomes a surface wave 18 along the outer peripheral surface 11a, and the distance between them is t,
After propagating by c, a part of it reaches the sub-receiving probe 3.
Received on 3rd. Therefore, as shown in FIG. 8(b), the peak waveform signal output from the sub-receiving probe 33 and from which unnecessary components such as noise are removed by the receiving circuit 36 is the peak of the receiving probe 16a. The waveform is delayed by 61 hours from the waveform signal.

The counter 37 has a function of starting counting when a pulse signal is input to the control terminal G1, and stopping the counting operation when a pulse signal is input to the control terminal G2. Therefore,
This counter 37 measures the 61 hours, that is, the detection time difference ΔT between both receiving probes 16a and 33. Therefore, the velocity calculation unit 38 calculates the correct propagation velocity V based on equation (3).

v-L, /ΔT (3) As a result, the correct circumference is calculated by the circumference calculating section 26.

With the circumferential length measuring device configured in this way, the outer circumferential surface 11 of the object to be measured. The propagation velocity (2) of the surface wave 18 propagating along a is measured simultaneously with the circumference measurement using the object to be measured itself. Therefore, it is possible to always calculate the correct circumference without giving equivalent consideration to the material of the object to be measured.

Therefore, there is no need to measure the propagation velocity V for each material using a separate dedicated measuring device. As a result, there is no need to prepare a measuring device exclusively for measuring the propagation velocity, and work efficiency in measuring the circumference can be greatly improved.

Furthermore, since the mutual opening M L s is corrected according to the curvature of the outer circumferential surface to be measured, the measurement accuracy of the propagation velocity V can be further improved, and in turn, the circumference measurement accuracy of this circumference measuring device can be improved. You can improve even more.

Note that the present invention is not limited to the embodiments described above. In the embodiment, the mutual distance L5 was corrected using a correction table, but for example, a worker may actually measure the corrected mutual distance LC using a tape measure or the like, and the measurement result may be displayed on a keyboard, etc. You may also input using .

Furthermore, inside the measuring head 12a of the embodiment shown in FIG.
Two vertical probes were installed as transmitting and receiving transducers, each having a transducer for transmitting and receiving, but as in Figure 1, there is a transducer exclusively for transmitting and a transducer exclusively for receiving. It is also possible to incorporate a single segmented probe having a child.

[Effects of the Invention] As explained above, according to the circumferential length measuring device of the present invention, the measuring head is attached to only one location on the circumference of the outer circumferential surface of the object to be measured. Therefore, it can be easily attached to and detached from the object to be measured.

Furthermore, since the incident position and the detection position within the measurement head are matched, the circumferential length calculation process can be simplified. As a result, it is possible to improve operability and make the entire device smaller and lighter.

Furthermore, in addition to the receiving transducer, a sub-receiving transducer is used,
The propagation velocity of ultrasonic waves inside the measured body is automatically measured. Therefore, the correct circumference is automatically measured without separately measuring the propagation velocity, and the efficiency of measurement work can be greatly improved.

[Brief explanation of the drawing]

1 to 4 show a circumference measuring device according to an embodiment of the present invention, in which FIG. 1 is a schematic cross-sectional view showing the measuring head, FIG. 2 is a cross-sectional view showing the entire device, and FIG. FIG. 3 is a block diagram showing a control device, FIG. 4 is a peak waveform signal, and FIGS. 5 to 8 show circumference measuring devices according to other embodiments of the present invention. is a cross-sectional view showing the entire device, FIG. 6 is a schematic cross-sectional view showing the measuring head and sub-measuring head, FIG. 7 is a block diagram showing the control device, FIG. 8 is a peak waveform signal, and FIG. ) is a cross-sectional view showing a conventional circumference measuring device, and FIG. 3(b) is an enlarged cross-sectional view showing a measuring head of the conventional device. 11...Steel pipe, lla...Outer peripheral surface, 12.12a.
...Measuring head, 15...Transmission vibrator, 15a...
・Transmission probe, 16... Receiving transducer, 16a...
- Receiving probe, 17...Ultrasonic wave, 18...Surface wave, 20.20a...Control device, 24.37...Counter, 26...Outer circumference calculation unit, 1... Sub-measuring helad, 3... Sub-receiving probe, 38... Speed calculation unit.

Claims (3)

[Claims] (1) For transmission in which an ultrasonic wave is incident on the outer circumferential surface of the object to be measured from one point on the circumference at an incident angle greater than a critical angle to generate a surface wave that propagates in one circumferential direction on the outer circumferential surface. a receiving transducer for detecting the surface wave that has made one round around the outer circumferential surface of the object to be measured; A circumferential length measuring device that calculates the circumferential length of the object to be measured from the propagation velocity of a surface wave, the incident position of the ultrasonic wave output from the transmitting transducer on the outer circumferential surface and the receiving transducer's incident position on the outer circumferential surface. A circumference measuring device characterized in that the transmitting vibrator and the receiving vibrator are housed and fixed as a measurement head in one container so that the detection positions of the surface waves coincide. (2) A sub-receiving transducer that is housed in a sub-measuring head connected to the measuring head and receives the surface waves, and a sub-receiving transducer that receives the surface waves between the sub-receiving transducer and the receiving transducer. 2. The circumferential length measuring device according to claim 1, further comprising a propagation velocity calculating means for calculating the propagation velocity from a detection time difference and a distance between detection positions of each receiving transducer. (3) The measuring device further comprises mutual distance correction means for correcting the mutual distance to a length along the outer circumferential surface of the object to be measured according to the curvature of the outer circumferential surface of the object to be measured. Perimeter measurement device. (4) The circumferential length measuring device according to claim 2, characterized in that water is interposed as a couplant between each of the vibrators and the outer peripheral surface of the object to be measured.