air nozzle

Abstract

SOLUTION: A shaft core part 20 is connected through a connection part 22 to a cylindrical part 12. The shaft core part is inserted through a small-diameter hole 16 provided at the tip of the cylindrical part, and projects from the tip of the cylindrical part. An annular air injection port 26 is formed by a gap existing between the wall surface of the small-diameter hole and the outer surface of the shaft core part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air nozzle that sprays air at high pressure. [Background technology]

[0002] Conventionally, air nozzles have been known that blow air onto workpieces in production lines to remove foreign matter such as dust, chips, and moisture adhering to the workpieces. When such air nozzles are used at high pressure, they generate noise.

[0003] Various technologies have been proposed to reduce noise generated in air nozzles. For example, Patent Document 1 describes a fluid nozzle in which a noise-reducing member made of a woven wire fabric is placed in the central hole of the nozzle and which has a passage connecting the central hole of the nozzle to the outer surface. In this fluid nozzle, back pressure is generated upstream of the noise-reducing member, creating a laminar airflow that flows along the outer surface of the nozzle. This laminar airflow attracts ambient air and merges with the airflow flowing through the central hole of the nozzle.

[0004] The above-described fluid nozzle provides some noise reduction because the airflow through the central bore of the nozzle passes through a noise-reducing member, and also because the ambient air, entrained by the laminar airflow, smoothly merges with the airflow through the central bore of the nozzle, providing some noise reduction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 58-24182 Summary of the Invention [Problem to be solved by the invention]

[0006] It is known that when high-pressure air is introduced into a convergent nozzle, the air becomes choked inside the nozzle, and the air is ejected from the convergent nozzle without fully expanding to atmospheric pressure. This under-expanded jet is accompanied by a shock cell structure in which shock waves and expansion waves appear alternately. The noise generated when high-pressure air is ejected from a convergent nozzle is closely related to the under-expanded jet. However, air nozzle technology that focuses on the under-expanded jet has not yet been fully developed. The technology in Patent Document 1 also does not take into account the under-expanded jet.

[0007] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide an air nozzle that ensures the necessary collision pressure while minimizing noise caused by an under-expanded jet. [Means for solving the problem]

[0008] The present invention is an air nozzle in which an axial core portion is connected to a cylindrical portion via a connecting portion, the axial core portion is inserted into a small diameter hole provided at the tip of the cylindrical portion, the axial core portion protrudes from the tip of the cylindrical portion, and an annular air injection port is formed by a gap existing between the wall surface of the small diameter hole and the outer surface of the axial core portion. [Effects of the Invention]

[0009] With the air nozzle according to the present invention, an annular air injection port is formed by the gap that exists between the wall surface of the small diameter hole in the cylindrical portion and the outer surface of the axial portion, and the axial portion protrudes from the tip of the cylindrical portion, so that noise can be reduced while ensuring the necessary collision pressure. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an air nozzle according to a first embodiment of the present invention, taken along a plane including the axis of the air nozzle. [Figure 2] FIG. 2 is a view of the air nozzle of FIG. 1 as seen from the direction along its axis. [Figure 3] FIG. 3 is a diagram showing a state in which the air nozzle of FIG. 1 is attached to a pipe. [Figure 4]FIG. 4A is an external view of a known single-hole nozzle, and FIG. 4B is an external view of a known silencer nozzle. [Figure 5] FIG. 5 is a graph comparing the noise level of an air nozzle of the present invention with a known single-hole nozzle and a known silencer nozzle. [Figure 6] FIG. 6 is a graph comparing the impact pressure of the air nozzle of the present invention with a known single-hole nozzle and a known silencer nozzle. [Figure 7] FIG. 7 is a graph showing the relationship between the axial length of the axial core portion of the air nozzle and the noise level. [Figure 8] FIG. 8 is a graph showing the relationship between the axial length of the axial core portion of the air nozzle and the collision pressure. [Figure 9] FIG. 9 is a cross-sectional view of an air nozzle according to a second embodiment of the present invention, taken along a plane including the axis of the air nozzle. [Figure 10] FIG. 10 is a cross-sectional view of an air nozzle according to a third embodiment of the present invention, taken along a plane including the axis of the air nozzle. [Figure 11] FIG. 11 is a view showing the air nozzle of FIG. 10 attached to a manifold by a one-touch joint. [Figure 12] FIG. 12 is a cross-sectional view of an air nozzle according to a fourth embodiment of the present invention, taken along a plane including the axis of the air nozzle. [Figure 13] FIG. 13 is a view of the air nozzle of FIG. 12 as seen from the direction along its axis. [Figure 14] FIG. 14 is an external view of an air nozzle according to a fifth embodiment of the present invention. [Figure 15] FIG. 15 is a cross-sectional view of the air nozzle of FIG. 14 taken along a plane including the axis of the nozzle. [Figure 16] FIG. 16 is a view of the air nozzle of FIG. 14 as seen from the direction along its axis. [Figure 17] FIG. 17 is a diagram showing an example in which the air nozzle of FIG. 1 is applied to a blow gun. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) An air nozzle 10 according to a first embodiment of the present invention will be described with reference to Figures 1 to 3. In the following description, when terms relating to up, down, left, and right directions are used, they refer to directions on the drawings for convenience and do not limit the actual arrangement.

[0012] As shown in FIG. 1, the air nozzle 10 is composed of a tubular portion 12, an axial portion 20, and a connecting portion 22. The axial portion 20 has a uniform outer diameter and is connected to the tubular portion 12 via the disk-shaped connecting portion 22. The tubular portion 12, the axial portion 20, and the connecting portion 22 are all made of metal. The connecting portion 22 is molded integrally with the axial portion 20. The cylindrical tubular portion 12 has an air inlet 14 at its left end and a small-diameter hole 16 at its right end (tip). The tubular portion 12 has a male thread portion 18 on its outer periphery.

[0013] The axial core portion 20 is inserted into the small diameter hole 16 of the tubular portion 12. A ring-shaped air injection port 26 is formed by a gap between the wall surface of the small diameter hole 16 of the tubular portion 12 and the outer surface of the axial core portion 20. The left end of the axial core portion 20 is connected to the center of the connecting portion 22. The axial core portion 20 protrudes a predetermined length outward from the right end (tip) of the tubular portion 12. The tip of the axial core portion 20 has a flat surface. The connecting portion 22 is fixed to the tubular portion 12 by being press-fitted into the tubular portion 12.

[0014] 1 and 2, the connecting portion 22 has a plurality of through holes 24 that serve as air flow paths. The plurality of through holes 24 are arranged at equal angular intervals around the axis X of the air nozzle 10. In this embodiment, a total of four through holes 24 are arranged, but the number of through holes 24 is arbitrary. As shown in FIG. 3, the air nozzle 10 is connected and fixed to a pipe 28 for guiding high-pressure air using a nut 27.

[0015] Air that flows into the air inlet 14 of the air nozzle 10 through the piping 28 passes through the multiple through-holes 24 in the connecting portion 22 and is then sprayed into the atmosphere from the annular air outlet 26. Air that flows in through the air inlet 14 at a pressure above a predetermined level is sprayed from the air outlet 26 without fully expanding to atmospheric pressure. In other words, air that flows in through the air inlet 14 at a pressure above a predetermined level becomes an under-expanded jet and is sprayed from the air outlet 26. This under-expanded jet is guided to the outer surface of the axial core portion 20 and flows around the axial core portion 20. This is thought to effectively dampen air vibrations and reduce noise.

[0016] The air flow path area in the connecting portion 22 (the total cross-sectional area of ​​the multiple through holes 24) is three times or more the area of ​​the air ejection port 26. This allows the flow rate of the air ejected from the air ejection port 26 to be sufficiently high. The length of the axial core portion 20 protruding outward from the right end of the tubular portion 12 (hereinafter referred to as the "axial length of the axial core portion 20") is preferably 3 mm or more and 15 mm or less. The reason for this will be described later.

[0017] Next, the noise level and impact pressure of the air nozzle 10 based on experimental results will be explained in comparison with a known single-hole nozzle 30 and a known silencer nozzle 32. The single-hole nozzle 30 used for comparison is a convergent nozzle with a single nozzle orifice 30a, as shown in Fig. 4A. The silencer nozzle 32 used for comparison is a nozzle with four nozzle orifices 32a, as shown in Fig. 4B, which are arranged at equal angles around the axis of the nozzle.

[0018] The outer diameter of the axial core portion 20 of the air nozzle 10 used was 3 mm. The inner diameter of the small diameter hole 16 of the cylindrical portion 12 of the air nozzle 10 used was approximately 3.6 mm. Therefore, the area of ​​the air injection port 26 of the air nozzle 10 was approximately 4 mm. 2The inner diameter of the injection port 30a of the single-hole nozzle 30 used was 2 mm. The inner diameter of each injection port 32a of the silencer nozzle 32 used was 1 mm. In other words, the area of ​​the injection port 30a of the single-hole nozzle 30 and the area of ​​the four injection ports 32a of the silencer nozzle 32 were set to be equal to the area of ​​the air injection port 26 of the air nozzle 10. Seven different axial lengths of the axial core portion 20 of the air nozzle 10 were prepared: 1 mm, 3 mm, 5 mm, 7.5 mm, 10 mm, 15 mm, and 20 mm.

[0019] Fig. 5 shows the noise levels measured for the air nozzle 10, the single-hole nozzle 30, and the silencer nozzle 32. The horizontal axis represents the air gauge pressure (unit: MPa) measured at the air inlet of the nozzle. The vertical axis represents the noise level (unit: dB) measured at a predetermined position at 45 degrees to the axis of the nozzle using the noise measurement method specified in JIS B8379. Hereinafter, the air gauge pressure measured at the air inlet of the nozzle will be referred to as the "immediate pressure."

[0020] As shown in Figure 5, the noise level of the air nozzle 10 increases as the immediate pressure increases from 0.1 MPa to 0.6 MPa. Except when the axial length of the axial core portion 20 is 1 mm, the noise level of the air nozzle 10 is generally 10 dB or more lower than the noise level of the single-hole nozzle 30 and can be evaluated to be about the same as the noise level of the silencer nozzle 32. It is believed that when the immediate pressure is 0.1 MPa or higher in the air nozzle 10, an under-expanded jet will occur.

[0021] FIG. 6 shows the impact pressures measured for the air nozzle 10, the single-hole nozzle 30, and the silencer nozzle 32. The horizontal axis represents the pressure immediately before the impact (unit: MPa). The vertical axis represents the impact pressure (unit: kPa) measured at a position a predetermined distance away from the nozzle orifice. When measuring the impact pressure, a plate (not shown) equipped with a pressure sensor was prepared and placed vertically below the nozzle orifice so that the distance from the nozzle orifice to the pressure sensor was 40 mm.

[0022] As shown in Figure 6, the collision pressure of the air nozzle 10 increases as the immediate pressure increases from 0.1 MPa to 0.6 MPa. The collision pressure of the air nozzle 10 is greatest when the axial length of the axial core portion 20 is 3 mm. The collision pressure of the air nozzle 10 can be evaluated as being sufficiently greater than the collision pressure of the silencer nozzle 32, except when the axial length of the axial core portion 20 is 20 mm.

[0023] According to the above experimental results, in order to reduce noise as much as possible while ensuring the necessary collision pressure, it is preferable that the axial length of the axial portion 20 of the air nozzle 10 be 3 mm or more and 15 mm or less. Figure 7 is a graph that clearly shows the relationship between the axial length of the axial portion 20 and the noise level, obtained by replacing the immediately preceding pressure with the axial length of the axial portion 20, in the experimental results of the air nozzle 10. Figure 8 is a graph that clearly shows the relationship between the axial length of the axial portion 20 and the collision pressure, obtained by replacing the immediately preceding pressure with the axial length of the axial portion 20, in the experimental results of the air nozzle 10.

[0024] In the above experiment, the outer diameter of the axial core portion 20 was set to 3 mm, and the inner diameter of the small diameter hole 16 of the tubular portion 12 was set to approximately 3.6 mm, but the outer diameter of the axial core portion 20 and the inner diameter of the small diameter hole 16 of the tubular portion 12 can be set to various dimensions. It is believed that as the outer diameter of the axial core portion 20 and the inner diameter of the small diameter hole 16 of the tubular portion 12 increase, the preferable numerical range for the axial length of the axial core portion 20 also increases.

[0025] The air nozzle 10 can be applied to a blow gun or various valves. An example of the air nozzle 10 applied to a blow gun 34 is shown in Figure 17. An operator can spray air from the air nozzle 10 toward the workpiece by grasping the handle 36 of the blow gun 34 and pulling the lever 38.

[0026] In the air nozzle 10 according to this embodiment, an annular air outlet 26 is formed by a gap between the wall surface of the small diameter hole 16 in the tubular portion 12 and the outer surface of the axial portion 20, and the axial portion 20 protrudes from the tip of the tubular portion 12. The under-expanded jet of air ejected from the annular air outlet 26 is configured to flow around the axial portion 20, thereby ensuring the collision pressure required for the air nozzle 10 while reducing noise.

[0027] (Second embodiment) Next, an air nozzle 40 according to a second embodiment of the present invention will be described with reference to Figure 9. In the air nozzle 40 according to the second embodiment, components that are the same as or equivalent to those in the air nozzle 10 described above are denoted by the same reference numerals.

[0028] The tubular portion 12 of the air nozzle 40 is composed of a first tubular portion 12a made of resin and a second tubular portion 12b made of metal. The cylindrical first tubular portion 12a is fixed to the cylindrical second tubular portion 12b by press fitting. The axial core portion 20 and the connecting portion 22 are molded from resin integrally with the first tubular portion 12a using, for example, a 3D printer.

[0029] The axial core portion 20 is connected to the first cylindrical portion 12a via a disk-shaped connecting portion 22. The second cylindrical portion 12b has an air inlet 14 at its left end, and the first cylindrical portion 12a has a small diameter hole 16 at its right end. The second cylindrical portion 12b has a male thread portion 18 on its outer periphery. The axial core portion 20 is inserted into the small diameter hole 16 of the first cylindrical portion 12a. A ring-shaped air ejection port 26 is formed by a gap between the wall surface of the small diameter hole 16 of the first cylindrical portion 12a and the outer surface of the axial core portion 20. The axial core portion 20 protrudes outward from the right end (tip) of the first cylindrical portion 12a.

[0030] The connecting portion 22 has a plurality of through holes 24 that serve as air flow paths. As in the first embodiment, the air flow path area in the connecting portion 22 (the total cross-sectional area of ​​the plurality of through holes 24) is three times or more the area of ​​the air ejection port 26. The preferred range of values ​​for the axial length of the axial core portion 20 is the same as in the first embodiment.

[0031] In the air nozzle 40 according to this embodiment, the gap between the wall surface of the small-diameter hole 16 in the first cylindrical portion 12a and the outer surface of the axial portion 20 defines an annular air outlet 26, and the axial portion 20 protrudes from the tip of the first cylindrical portion 12a. This reduces noise while ensuring the necessary collision pressure. Furthermore, because the axial portion 20 and the connecting portion 22 are resin-molded integrally with the first cylindrical portion 12a, the air flow path structure can be reproduced with greater precision than when the connecting portion 22 is a separate member from the cylindrical portion 12a.

[0032] (Third embodiment) Next, an air nozzle 50 according to a third embodiment of the present invention will be described with reference to Figures 10 and 11. In the air nozzle 50 according to the third embodiment, components that are the same as or equivalent to those in the air nozzle 10 described above are denoted by the same reference numerals.

[0033] The air nozzle 50 is composed of a cylindrical portion 12, an axial portion 20, and a connecting portion 22. The cylindrical portion 12, the axial portion 20, and the connecting portion 22 are integrally molded from resin using, for example, a 3D printer. A ring-shaped air ejection port 26 is formed by a gap between the wall surface of the small diameter hole 16 in the cylindrical portion 12 and the outer surface of the axial portion 20. The axial portion 20 protrudes outward from the right end (tip) of the cylindrical portion 12.

[0034] The connecting portion 22 has a plurality of through holes 24 that serve as air flow paths. As in the first embodiment, the air flow path area in the connecting portion 22 (the total cross-sectional area of ​​the plurality of through holes 24) is at least three times the area of ​​the air ejection port 26. The preferred range of values ​​for the axial length of the axial core portion 20 is the same as in the first embodiment. As shown in FIG. 11 , the air nozzle 50 is attached to a manifold 54 via a one-touch coupling 52, for example.

[0035] In the air nozzle 50 according to this embodiment, the gap between the wall surface of the small-diameter hole 16 in the tubular portion 12 and the outer surface of the axial portion 20 defines the annular air outlet 26, and the axial portion 20 protrudes from the tip of the tubular portion 12. This reduces noise while ensuring the necessary collision pressure. Furthermore, because the tubular portion 12, axial portion 20, and connecting portion 22 are integrally molded from resin, the air flow path structure can be reproduced with greater precision than when the connecting portion 22 is a separate member from the tubular portion 12.

[0036] (Fourth embodiment) Next, an air nozzle 60 according to a fourth embodiment of the present invention will be described with reference to Figures 12 and 13. In the air nozzle 60 according to the fourth embodiment, components that are the same as or equivalent to those in the air nozzle 10 described above are denoted by the same reference numerals.

[0037] The air nozzle 60 is composed of a tubular portion 12, an axial core portion 20, and a connecting portion 22. The tubular portion 12, the axial core portion 20, and the connecting portion 22 are all made of resin and are integrally molded using a 3D printer or injection molding. The connecting portion 22 is composed of a plurality of wing portions 62 that extend radially from the outer periphery of the axial core portion 20 to the inner periphery of the tubular portion 12. In this embodiment, a total of three wing portions 62 are arranged equiangularly around the axis X of the air nozzle 60. However, the number of wing portions 62 is arbitrary.

[0038] The axial core portion 20 has a uniform outer diameter and is connected to the tubular portion 12 via a plurality of wing portions 62. A circular air injection port 26 is formed by a gap between the wall surface of the small diameter hole 16 in the tubular portion 12 and the outer surface of the axial core portion 20. The axial core portion 20 protrudes outward from the right end (tip) of the tubular portion 12.

[0039] An air flow path 64 in the connecting portion 22 is defined by the inner surface of the tubular portion 12, the side surfaces of the wing portions 62, and the outer surface of the axial core portion 20 (see FIG. 13). As in the first embodiment, the area of ​​the air flow path in the connecting portion 22 is at least three times the area of ​​the air ejection port 26. The preferred range of values ​​for the axial length of the axial core portion 20 is the same as in the first embodiment.

[0040] In the air nozzle 60 according to this embodiment, the gap between the wall surface of the small-diameter hole 16 in the tubular portion 12 and the outer surface of the axial portion 20 defines the annular air ejection port 26, and the axial portion 20 protrudes from the tip of the tubular portion 12. This makes it possible to reduce noise while ensuring the necessary collision pressure. Furthermore, since the connecting portion 22 is defined by the blade portions 62 that extend radially from the outer periphery of the axial portion 20 to the inner periphery of the tubular portion 12, a large flow path area can be easily ensured in the connecting portion 22.

[0041] (Fifth embodiment) Next, an air nozzle 70 according to a fifth embodiment of the present invention will be described with reference to Figures 14 to 16. In the air nozzle 70 according to the fifth embodiment, components that are the same as or equivalent to those in the air nozzle 10 described above are denoted by the same reference numerals.

[0042] The air nozzle 70 is composed of a cylindrical portion 12, an axial core portion 20, a connecting portion 22, and a protective portion 74. The cylindrical portion 12, the axial core portion 20, the connecting portion 22, and the protective portion 74 are all made of resin and are integrally formed by injection molding. The connecting portion 22 is composed of a plurality of wing portions 72 that extend radially from the outer periphery of the axial core portion 20 to the inner periphery of the cylindrical portion 12. The width of the wing portions 72 (the length along the axis X of the air nozzle 70) is not constant, and is smaller in the vicinity of the axial core portion 20.

[0043] The axial core portion 20 is connected to the tubular portion 12 via a plurality of wing portions 72. A circular air injection port 26 is formed by a gap between the wall surface of the small diameter hole 16 in the tubular portion 12 and the outer surface of the axial core portion 20. The axial core portion 20 protrudes outward from the right end (tip) of the tubular portion 12. In this embodiment, two wing portions 72 extend in opposite directions from the axial core portion 20 (see FIG. 16). However, the number of wing portions 72 is arbitrary.

[0044] The protective portion 74 is composed of a flange portion 76 and multiple protruding pieces 78. The annular flange portion 76 extends outward from the outer periphery of the tubular portion 12. The protruding pieces 78 protrude to the right from the end face of the flange portion 76. The protruding pieces 78 are arranged around the axial core portion 20 protruding from the tubular portion 12 at a predetermined distance from the axial core portion 20. The protruding pieces 78 extend slightly to the right beyond the tip of the axial core portion 20 (see Figure 15). The multiple protruding pieces 78 are arranged at equal angular intervals around the axis X of the air nozzle 70.

[0045] The gaps between adjacent protruding pieces 78 are large enough that a human finger cannot fit through. By arranging multiple protruding pieces 78 around the axial core portion 20, the axial core portion 20 is prevented from coming into contact with the outside, eliminating the risk of damage to the axial core portion 20. Furthermore, when an operator uses a device to which the air nozzle 70 is applied, there is no risk of the operator coming into contact with the axial core portion 20, improving operator safety. In this embodiment, a total of four protruding pieces 78 are arranged, but the number of protruding pieces 78 may be three or more.

[0046] An air flow path 80 in the connecting portion 22 is defined by the inner surface of the tubular portion 12, the side surfaces of the wing portions 72, and the outer surface of the axial core portion 20 (see FIG. 16). As in the first embodiment, the area of ​​the air flow path in the connecting portion 22 is at least three times the area of ​​the air ejection port 26. The preferred range of values ​​for the axial length of the axial core portion 20 is the same as in the first embodiment.

[0047] In the air nozzle 70 according to this embodiment, the gap between the wall surface of the small-diameter hole 16 in the tubular portion 12 and the outer surface of the axial portion 20 defines the annular air outlet 26, and the axial portion 20 protrudes from the tip of the tubular portion 12. This reduces noise while ensuring the necessary collision pressure. Furthermore, the connecting portion 22 is defined by the wing portions 72 that extend radially from the outer periphery of the axial portion 20 to the inner periphery of the tubular portion 12, making it easy to ensure a large flow path area in the connecting portion 22. Furthermore, multiple protruding pieces 78 are arranged around the axial portion 20, protecting the axial portion 20 and ensuring the safety of the operator.

[0048] The air nozzle according to the present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0049] 10, 40, 50, 60, 70...Air nozzle 12...Cylinder part 12a...First cylinder part 12b...Second cylinder part 16...Small diameter hole 20...Shaft core part 22...Connection part 24...Through hole 26...Air injection port 62, 72... Wings 74... Protective part 76...Flange portion 78...Protruding piece

Claims

1. An air nozzle in which an axial core portion is integrally connected to a cylindrical portion via a connecting portion, the axial core portion is inserted into a small diameter hole provided at the tip of the cylindrical portion, the axial core portion protrudes from the tip of the cylindrical portion, and an annular air ejection port is formed by a gap existing between a wall surface of the small diameter hole and an outer surface of the axial core portion, The metal connecting portion is integrally formed with the metal axial core portion, and is fixedly connected to the metal cylindrical portion.

2. An air nozzle in which an axial core portion is integrally connected to a cylindrical portion via a connecting portion, the axial core portion is inserted into a small diameter hole provided at the tip of the cylindrical portion, the axial core portion protrudes from the tip of the cylindrical portion, and an annular air ejection port is formed by a gap existing between a wall surface of the small diameter hole and an outer surface of the axial core portion, The air nozzle has a cylindrical portion made of a first cylindrical portion made of resin and a second cylindrical portion made of metal, and the axial core portion and the connecting portion are molded from resin integrally with the first cylindrical portion.

3. An air nozzle in which an axial core portion is integrally connected to a cylindrical portion via a connecting portion, the axial core portion is inserted into a small diameter hole provided at the tip of the cylindrical portion, the axial core portion protrudes from the tip of the cylindrical portion, and an annular air ejection port is formed by a gap existing between a wall surface of the small diameter hole and an outer surface of the axial core portion, The air nozzle has the cylindrical portion, the axial core portion, and the connecting portion integrally molded from resin.

4. An air nozzle in which an axial core portion is integrally connected to a cylindrical portion via a connecting portion, the axial core portion is inserted into a small diameter hole provided at the tip of the cylindrical portion, the axial core portion protrudes from the tip of the cylindrical portion, and an annular air ejection port is formed by a gap existing between a wall surface of the small diameter hole and an outer surface of the axial core portion, The air nozzle is provided with a protective portion for preventing the axial core portion from coming into contact with the outside.

5. The air nozzle according to any one of claims 1 to 3, The disk-shaped connecting portion is an air nozzle having a plurality of through holes that serve as air flow paths.

6. The air nozzle according to any one of claims 1 to 4, The length of the axial core portion protruding from the tip of the cylindrical portion is 3 mm to 15 mm.

7. The air nozzle according to any one of claims 1 to 4, An air nozzle in which the area of ​​the air flow path at the connecting portion is three times or more the area of ​​the air ejection port.

8. The air nozzle according to claim 4, The connecting portion is composed of wing portions extending radially from the outer periphery of the axial core portion to the inner periphery of the tubular portion, and the air flow path in the connecting portion is defined by the inner surface of the tubular portion, the side surfaces of the wing portions, and the outer surface of the axial core portion.

9. The air nozzle according to claim 4, The protective portion is composed of a flange portion and a plurality of protruding pieces, the flange portion extending outward from the outer periphery of the cylindrical portion, the protruding pieces protruding from the flange portion, and the protruding pieces being arranged around the axial core portion protruding from the cylindrical portion at a predetermined distance from the axial core portion.

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