JPH1130548A - Dustproof hood for ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dustproof hood that prevents a powder from sticking to an ultrasonic transmitting-receiving face and by which a measurement can be performed continuously without obstructing ultrasonic waves by jetting a purge gas from the inside of the hood having a double structure, and forming an air curtain immediately before the ultrasonic transmitting-receiving face. SOLUTION: The hood 1 is formed as a double structure, which is composed of an outside tube 2 and an inside tube. The cross section of the outside tube 2 as a cylindrical body is U-shaped, and a mounting hole 2-1 for an ultrasonic sensor 8 is formed in the center of a horizontal plane 2a . In the inside tube, a windown hole 3-1 whose diameter is larger than that of the sensor mounting hole 2-1 is formed in the center of a horizontal plane 3a . The outside tube 2 and the inside tube are arranged concentrically, and a ring-shaped gap 5 which surrounds the sensor mounting hole 2-1 is formed between the horizontal plane 2a and the horizontal plane 3a . In addition, the outside end part of the inside tube and the inner circumferential face of the outer tube 2 are airtightly fixed and bonded by a ring-shaped seal plate 6, and a space 4 which communicates with the gap 5 is formed. Then, a purge gas from a purge-gas pipe 7 is introduced into the space 4, the purge gas is jetted toward the center of the sensor mounting hole 2-1 in parallel with the horizontal planes 2a , 3a from the gap 5. An air curtain is formed in an opening part, i.e., an ultrasonic transmitting-receiving face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dustproof hood for an ultrasonic sensor for dustproofing a transmitting / receiving surface of an ultrasonic sensor such as an ultrasonic level meter used for measuring a granular material level with a purge gas.

[0002]

2. Description of the Related Art Conventionally, as a method for continuously measuring the level of a granular material in a granular material storage tank and the bulk of a sintering raw material of a sintering machine, measurement using an ultrasonic level meter is generally known. . However, in equipment such as various types of powder storage tanks and sintering machines that are forced to generate dust, the dust may adhere to the transmitting and receiving surfaces of the ultrasonic level meter, resulting in measurement errors and measurement failure. In particular, powdery particles having high hygroscopicity, such as quicklime and soda ash, have severe adhesion problems, and stable level measurement is difficult.

As a countermeasure, a method of dustproofing the transmitting and receiving surfaces of an ultrasonic level meter with a purge gas has been used. For example, in Japanese Patent Application Laid-Open No. Hei 4-220532, a purge gas nozzle is arranged in proximity to an ultrasonic level meter attached to the upper end of a granular material storage tank, and purge gas is supplied to an ultrasonic detection unit (transmission / reception surface) at predetermined intervals. There has been proposed a method of removing adhered powder particles by spraying for a certain period of time.

[0004] However, the method of removing the powder particles adhered to the ultrasonic transmitting / receiving surface by using a purge gas nozzle arranged close to the ultrasonic level meter does not prevent the powder particles from adhering to the ultrasonic transmitting / receiving surface. Since it is a method of removing the powder particles once adhered to the ultrasonic transmitting and receiving surface, for example, particularly in the case of powder particles having a high hygroscopic property such as quicklime or soda ash,
Even if a purge gas is sprayed on the ultrasonic transmitting / receiving surface with the purge gas nozzle, the ultrasonic transmitting / receiving surface is not easily removed, and the ultrasonic transmitting / receiving surface cannot be sufficiently cleaned. Further, in this method, since the purge gas is directly blown onto the ultrasonic transmission / reception surface, the level cannot be measured during the purge, and the level in the powder storage tank cannot be measured continuously.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and by forming an air curtain in close proximity to the ultrasonic transmitting / receiving surface of a sensor, It is an object of the present invention to provide a dustproof hood for an ultrasonic sensor which prevents adhesion of a granular material to an ultrasonic transmitting / receiving surface of a sensor and enables continuous measurement without disturbing ultrasonic waves.

[0006]

The dustproof hood for an ultrasonic sensor according to the present invention has a double structure of a cylindrical hood integrally attached to the ultrasonic sensor, and ejects a purge gas from the inside to superpose the sensor. An air curtain is formed just before the sound wave transmission / reception surface to prevent dust from entering the ultrasonic wave transmission / reception surface. The gist of the air curtain is that the cross section is concave and the sensor is located at the center of the horizontal plane. An outer cylinder formed of a cylindrical body provided with a mounting hole, and an inner cylinder formed of a cylindrical body having the same size as the outer cylinder and having a window having a larger diameter than the sensor mounting hole in the center of a horizontal plane having a concave cross-sectional shape. The outer cylinder and the inner cylinder are concentrically arranged so that an annular gap surrounding the sensor mounting hole is formed between the outer cylinder and each horizontal surface of the inner cylinder. Part and inner surface of outer cylinder Between the outer cylinder and the inner cylinder to form an annular space that communicates with the annular gap. The outer cylinder of the dual-structure hood has the annular structure. A purge gas pipe for introducing a purge gas into the space is connected, and the purge gas introduced from the purge gas pipe into the annular space is uniformly distributed in the center direction substantially parallel to the opening surface of the sensor mounting hole from the annular space to the opening surface of the sensor mounting hole. To form an air curtain covering the opening surface of the sensor mounting hole. In addition, one or more purge gas pipes are connected in the tangential direction of the outer peripheral surface of the hood having a double structure, and the annular gap surrounding the sensor mounting hole is provided with the purge gas uniformly at the center of the sensor mounting hole. A plurality of partition members for jetting are arranged in the circumferential direction.

The size of the cylindrical hood according to the present invention is set in consideration of the angle of spread of ultrasonic waves of an ultrasonic sensor used for an ultrasonic level meter or the like. That is, since ultrasonic waves are originally spread at a certain angle (approximately 10 degrees), when a hood having a concave cross-sectional shape is used, a space where ultrasonic waves propagating at the spread angle do not cause reflection in the hood is created. It should be a size that can be secured.

In addition, a cylindrical hood integrally attached to the ultrasonic sensor has a double structure, and a purge gas is uniformly jetted from the inside of the hood toward the center so that an air curtain is provided immediately before the ultrasonic transmitting / receiving surface of the sensor. The reason is that in the case of an air curtain, since the penetration of dust to the ultrasonic transmitting and receiving surface can be prevented without attenuating or blowing out the ultrasonic wave, continuous and stable measurement can be performed. It is.

The reason why the purge gas pipe is provided in the tangential direction of the outer peripheral surface of the hood having a double structure is that the purge gas ejected toward the center from the space surrounding the sensor mounting hole of the hood, that is, the nozzle hole, is more uniform. It is to be. However, in this state, the purge gas introduced into the annular space formed between the inner cylinder and the outer cylinder is swirled, and there is a possibility that external air may be sucked. A plurality of partition members are arranged in the circumferential direction in the portion (nozzle hole).

[0010]

FIG. 1 is a longitudinal sectional front view showing an example of a dustproof hood according to the present invention, FIG. 2 is a perspective view showing a part of the hood, and FIG. 3 is another structural example of the present invention. 1 is a hood of a double structure, 2 is an outer cylinder,
1 is a sensor mounting hole, 3 is an inner cylinder, 3-1 is a window hole, 4 is an annular space, 5 is an annular space (nozzle hole), 6 is a seal plate, 7 is a purge gas pipe, 8 is an ultrasonic sensor, 9 is a partition member.

The dustproof hood of the present invention shown in FIG.
And a window hole 3-1 having a concave cross-sectional shape and a larger diameter than the sensor mounting hole 2-1 at the center of the horizontal plane 3a, and is smaller than the outer cylinder 2 The inner cylinder 3 is formed of a cylindrical body having a size, and the outer cylinder 2 and the inner cylinder 3 are disposed between the horizontal surfaces 2a, 3a.
-1 are formed concentrically so as to form annular gaps 5 surrounding the inner cylinder 1, and the space between the outer end of the inner cylinder 3 and the inner peripheral surface of the outer cylinder 2 is hermetically sealed with a ring-shaped seal plate 6. And a hood 1 having a double structure in which an annular space 4 communicating with the annular space 5 is formed between the inner peripheral surface of the outer cylinder 2 and the outer peripheral surface of the inner cylinder 3. Horizontal surface 3a of outer cylinder 2
The ultrasonic sensor 8 is inserted in the sensor mounting hole 2-1 provided in the center.
A purge gas is introduced into the annular space 4 from a purge gas pipe 7 connected to the outer peripheral surface of the outer cylinder 2 and provided between the outer cylinder 2 and each of the horizontal surfaces 2a, 3a of the inner cylinder 3. Purge gas is ejected from the annular space 5 toward the center of the sensor mounting hole 2-1 in parallel with the horizontal plane, and an air curtain is formed at the opening of the sensor mounting hole 2-1. .

The outer cylinder 2 and the inner cylinder 3 constituting the hood of the double structure are provided with a sensor mounting hole 2-1 formed in the outer cylinder 2.
In consideration of the spread angle of the ultrasonic wave of the ultrasonic sensor 8 attached to the hood, the size of the hood is such that a space space in which the ultrasonic wave does not reflect is formed. The ultrasonic sensor 8 is fixed to the horizontal surface 2a of the outer cylinder 2 with bolts or the like.

That is, in the case of the dustproof hood having the above structure, as shown in FIG. 1, a space for preventing reflection of the ultrasonic waves is secured according to the spread angle of the ultrasonic waves from the ultrasonic sensor 8, The ultrasonic wave from the ultrasonic sensor 8 does not impinge on the inner peripheral surface of the hood and cause reflection.

In this dustproof hood, the purge gas introduced from the purge gas pipe 7 into the annular space 5 formed between the inner peripheral surface of the outer cylinder 2 and the outer peripheral surface of the inner cylinder 3 passes through the annular cavity 5 and is used as a sensor. Since the gas is uniformly ejected from the annular gap 5 surrounding the mounting hole 2-1 toward the center of the sensor mounting hole, an air curtain parallel to the horizontal plane of the hood is formed immediately before the ultrasonic transmitting / receiving surface of the ultrasonic sensor 8. The air transmitting / receiving surface of the ultrasonic sensor 8 is completely covered with the air curtain. Therefore, the dust that has entered the hood is blocked by the air curtain immediately before the ultrasonic transmitting / receiving surface, so that the dust does not adhere to the ultrasonic transmitting / receiving surface.
In the case of an air curtain, since the ultrasonic waves are not attenuated or blown off, the measurement can be continuously and stably performed.

The dustproof hood shown in FIG. 3 is an example in which a purge gas pipe 7 is provided in the tangential direction of the outer peripheral surface of a hood having a double structure. In this case, the purge gas pipe 7 is formed between the outer cylinder 2 and the inner cylinder 3. In order to prevent the purge gas introduced into the annular space 4 from being swirled and sucking external air, a plurality of partition members 9 are arranged in the circumferential direction in the annular gap (nozzle hole) 5 which is a purge gas ejection hole. Things. In the case of this dust-proof hood, the purge gas pipe 7 is provided in the tangential direction of the outer peripheral surface of the hood, and the partition member 9 is disposed in the annular gap 5, so that the purge gas ejected from the annular gap 5 toward the center is formed. It becomes more uniform and a good air curtain is formed.

[0016]

As described above, the dust hood for an ultrasonic sensor according to the present invention has a double structure of a cylindrical hood integrally attached to the ultrasonic sensor, and purge gas is supplied from the inside to the center of the hood. Since an air curtain is formed immediately before the ultrasonic transmission / reception surface of the sensor by being continuously ejected, there is an effect that dust can be prevented from entering the ultrasonic transmission / reception surface without attenuating or blowing off the ultrasonic wave even during purge. Therefore, even in equipment such as various kinds of powder storage tanks and sintering machines that are forced to generate dust, the dust does not adhere to the transmitting and receiving surfaces of the ultrasonic level meter, causing no measurement error or measurement failure, and in particular, Even if the powdery material has high hygroscopicity, for example, quicklime or soda ash, an excellent effect of continuously and stably measuring the level can be obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing an example of a dustproof hood according to the present invention.

FIG. 2 is a perspective view showing a part of the hood in a cutaway manner.

FIG. 3 is a plan view showing another structural example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hood of double structure 2 Outer cylinder 2-1 Sensor mounting hole 3 Inner cylinder 3-1 Window hole 4 Annular space 5 Annular space (nozzle hole) 6 Seal plate 7 Purge gas pipe 8 Ultrasonic sensor 9 Partition member

Claims (2)

[Claims] 1. A dustproof hood for an ultrasonic sensor for dustproofing a transmission / reception surface of an ultrasonic sensor with a purge gas, comprising a cylindrical body having a concave cross section and a sensor mounting hole provided in the center of a horizontal plane. A cylindrical body having a window having a larger diameter than the sensor mounting hole at the center of the horizontal plane, and having an inner diameter of a cylindrical body smaller than the outer cylinder. The outer cylinder and the inner cylinder are arranged concentrically so that an annular gap surrounding the sensor mounting hole is formed between each horizontal surface of the cylinder and the outer cylinder and the inner peripheral surface of the outer cylinder. And a hood having a double structure in which an annular space communicating with the annular gap is formed between the outer cylinder and the inner cylinder, and the annular space is formed in the outer cylinder of the hood having the double structure. A purge gas pipe for introducing a purge gas is connected to the A structure in which a purge gas introduced from the pipe into the annular space is uniformly jetted from the annular gap substantially in the center direction substantially parallel to the opening surface of the sensor mounting hole to form an air curtain covering the opening surface of the sensor mounting hole. A dust hood for ultrasonic sensors, characterized by the following. 2. The method according to claim 1, wherein one or more of the purge gas pipes are connected in a tangential direction to an outer peripheral surface of the hood having a double structure, and an annular gap surrounding the sensor mounting hole is uniformly formed at the center of the sensor mounting hole. 2. A plurality of partition members for ejecting a purge gas in a circumferential direction are arranged.
Dust hood for an ultrasonic sensor as described.