JP2012135852A - Dustproof device for abrasive blasting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dustproof device for abrasive blasting capable of properly discharging the dust of abrasive blasting treatment having a width in particulate size distribution to the outside of the a hood, being lightweight, having superior handling properties.SOLUTION: The dustproof device 1 for the abrasive blasting surrounding a blasting surface 41 and preventing the dust including blasting materials or blasting chips from scattering has a casing body shape hood 11 having an opening 12 formed in the surface facing a blasting surface 41 and an inserting opening 13 into which a blasting material jetting nozzle 2 is inserted, a seal means 21 for hermetically sealing the gap of the surrounding of the opening of the hood 11 and the blasting surface, and the bottom discharging pipe 14 connected to the bottom of the hood 11, and further has the first dust discharging the means for discharging the dust while dropping the dust from the bottom discharging pipe, an upper part discharging pipe 16 connecting upward from the bottom of the hood, and a negative pressure generating means for making the inside space of hood negative pressure, and further has the second dust discharging means for discharging air including the dust within the hood from the upper discharging pipe 16 by the negative pressure.

Description

  The present invention relates to a dust proofing device for blasting that prevents dust generated by blasting from being scattered around.

  2. Description of the Related Art Conventionally, a blasting process has been widely used in which a jet stream mixed with a polishing material is sprayed onto a blast surface to remove rust, scale, coating film, and the like. For example, in blasting work performed at a repair ship dock, rust on the painted surface is removed by causing the abrasive to collide with the painted surface at high speed using air pressure outdoors or in the ship. As shown in FIG. 9, when the blast surface 57 is located at a high place, an operator 53 gets on the work table 52 movable by the crane 51 and operates the blast gun 55 to sharpen the blast surface 57 of the hull 56. Sweeper was sprayed. Since such a blasting work has a wide working range, conventionally, the blasting gun 55 has been used with the outside exposed.

  In the blasting process, dust containing abrasives sprayed from a blast gun or abrasive scraps scraped by the abrasives is scattered, which may cause dust damage to the surrounding area when working outdoors. is there. In addition, when working indoors, dust is filled indoors. On the other hand, a polishing material containing liquid has been commercialized from the viewpoint of preventing dust scattering, but when this liquid contains water, moisture remains on the painted surface after blasting and rusting occurs again. There was a problem of doing. In addition, when a chemical other than water is used for the liquid, there is a problem in that the chemical is scattered to leave a problem in safety and increase the cost.

  Thus, as a measure for preventing dust scattering in the blasting process, an apparatus in which the blast surface is covered with a hood has been proposed. For example, Patent Document 1 (Japanese Patent Laid-Open No. 61-103777) discloses a hull side plate cleaning apparatus. This device has a dust-proof hood provided with an opening that can be brought into close contact with the hull-side plate surface, an abrasive recovery hopper attached to the bottom of the dust-proof hood, and an abrasive nozzle, and the hull-side plate surface. It has a drive mechanism so that the forward movement can be performed.

  As a related technique, a hood type blast processing apparatus is disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2003-1563). This device has a blast nozzle and a hood that is partially open and into which the blast nozzle is inserted from one end. Further, the hood is inclined toward the discharge port formed on the lower surface thereof, whereby the dust moves toward the discharge port and is naturally discharged.

JP 61-103777 A JP 2003-1563 A

  However, in Patent Document 1 and Patent Document 2 described above, dust accumulated on the bottom of the hood due to gravity can be discharged to the outside through the discharge port, but dust staying in the air cannot be discharged. Dust generated by blasting includes abrasive scraps such as rust, scales, and coating films in addition to abrasives, but these abrasive scraps are refined by being cracked or crushed by the impact of the abrasive. There is also. The refined dust floats in the hood space without falling by gravity. When this floating dust accumulates, it becomes difficult to visually recognize the blast surface, and the work becomes difficult. Thus, since the blasting dust has a wide particle size distribution, an apparatus capable of smoothly discharging such dust is required.

Moreover, in the case where the hood is provided with a moving mechanism, conventionally, the hood has the following problems.
The device of Patent Document 1 has a drive mechanism such as a hydraulic cylinder in order to move the hood, and the size and weight of the device cannot be avoided. On the other hand, the apparatus of Patent Document 2 is configured to include a roller that abuts on the blast surface and a magnet that attracts the hood to the wall surface as a hood moving mechanism. Since a gap is provided between them, a powerful magnet is required, which increases the cost. In addition, it is difficult to stably support the hood, and a configuration in which the hood is suspended with a wire from the top to stabilize the hood has been disclosed.
Therefore, in view of the problems of the prior art, the present invention provides a blasting dustproof device that can appropriately discharge blasting dust having a wide particle size distribution to the outside of the hood, and is lightweight and excellent in handling properties The purpose is to do.

  In order to solve the above-described problems, a dust blasting apparatus according to the present invention surrounds a blast surface and removes abrasives ejected from an abrasive jet nozzle or abrasive scraps scraped by the abrasive. In the dust proofing device for blasting to prevent scattering of the dust containing, a housing-like hood having an opening formed in a surface facing the blast surface, and an insertion port into which the blast material spray nozzle is inserted, A sealing means for sealing a gap between the periphery of the opening of the hood and the blast surface; and a bottom discharge pipe connected to the bottom of the hood. The first discharges the dust by dropping from the bottom discharge pipe. Dust discharge means, an upper discharge pipe connected above the bottom of the hood, and negative pressure generation means for making the internal space of the hood a negative pressure, and negative air containing dust in the hood Pressure from the upper discharge pipe Characterized in that it comprises a second dust discharge means.

According to the present invention, since the blast surface is surrounded by the hood and the internal space of the hood is sealed by the sealing means, dust generated by the blasting process can be prevented from being scattered around.
In addition to this, in the first dust discharging means, the first dust discharging means mainly discharges the dust having a large particle size or a large specific gravity by dropping from the bottom discharge pipe by gravity, and the second dust discharging means, Since dust floating in the internal space of the hood is mainly discharged from the upper discharge pipe, blasting dust having a wide particle size distribution can be appropriately discharged to the outside of the hood.
Further, since the dust floating in the internal space of the hood is discharged by the second dust discharging means, it is possible to clearly see the blast surface from the viewing window.

The negative pressure generating means includes a high-pressure air pipe connected to a side surface of the upper discharge pipe and introducing high-pressure air into the upper discharge pipe. The high-pressure air causes the upper discharge pipe to move outward from the hood side. It is preferable that the air flow is generated to create a negative pressure in the internal space of the hood.
As described above, by introducing the high-pressure air into the upper discharge pipe and generating the air flow from the hood side to the outside, the air in the hood can be sucked. At this time, since the internal space of the hood can be set to a negative pressure only by connecting the high-pressure air pipe, it is possible to reduce the size and weight of the device, and further to make the device excellent in handling properties.

In addition, the hood has a moving mechanism that slides along the blast surface, and the moving mechanism is detachably provided on the blast surface and has a rail formed on the upper surface thereof, and an upper portion of the hood. And a roller that rolls on the rail, and the hood is suspended on the rail via the roller, and the hood is supported on the blast surface.
Thus, by having the rail provided on the blast surface and the roller attached to the hood, the moving mechanism of the hood can be simplified. Moreover, handling property can be improved more because a rail is detachable from a blast surface. Further, since the hood is suspended from the rail via the roller, it is not necessary to hold and hold the hood by hand, thereby improving workability. Furthermore, since the moving mechanism also serves as a support mechanism for the hood, the apparatus can be simplified and reduced in weight compared to the case where a support mechanism is newly added.

The sealing means includes a rubber member that comes into contact with the blast surface, a spring member interposed between the rubber member and the periphery of the opening of the hood, and an opening of the rubber member and the hood. It is preferable to include a stretchable cover member that seals a gap with the surroundings.
Thus, since it was set as the structure which presses a rubber member with a spring member, the adhesiveness to a blast surface can be made high and a sealing performance can be improved further. Furthermore, since the gap between the rubber member and the periphery of the opening of the hood is sealed with an extendable cover member, the cover member can follow the spring member and reliably seal the gap.

Furthermore, it has a viewing window provided in the hood, and a transparent or translucent protective partition plate that partitions between the viewing window and the internal space of the hood, and the protective partition plate is configured to be replaceable. Preferably it is.
As described above, since the protective partition plate is interposed between the observation window and the internal space of the hood, damage to the observation window due to dust can be prevented, and the blast surface can be clearly seen. Further, since the protective partition plate can be replaced, the visibility of the blast surface can be recovered by replacing the protective partition plate even when the protective partition plate is damaged.

As described above, according to the present invention, the blast surface is surrounded by the hood and the internal space of the hood is sealed by the sealing means, so that dust generated by the blasting process can be prevented from being scattered around.
In addition to this, in the first dust discharging means, the first dust discharging means mainly discharges the dust having a large particle size or a large specific gravity by dropping from the bottom discharge pipe by gravity, and the second dust discharging means, Since dust floating in the internal space of the hood is mainly discharged from the upper discharge pipe, blasting dust having a wide particle size distribution can be appropriately discharged to the outside of the hood.
Further, since the dust floating in the internal space of the hood is discharged by the second dust discharging means, it is possible to clearly see the blast surface from the viewing window.

It is a figure explaining the blasting process using the dustproof apparatus for blasting which concerns on this embodiment. It is a figure which shows the dustproof apparatus for blasting which concerns on this embodiment, (A) is the front view seen from the blast surface side, (B) is AA sectional drawing. It is a sectional side view which shows the 2nd dust discharge | emission means in this embodiment. It is a figure which shows the modification of the 2nd dust discharge | emission means shown in FIG. 3, (A) is a sectional side view, (B) is a figure which shows a fan. It is a rear view which shows the dustproof apparatus for blast which has a moving mechanism in this embodiment. It is sectional drawing of the dustproof apparatus for blast shown in FIG. 5, (A) is BB sectional drawing, (B) is CC sectional drawing. It is a figure which shows the other structural example of the dust-proof apparatus for blasting which concerns on this embodiment, (A) is the front view seen from the blast surface side, (B) is DD sectional drawing, (C) is E It is -E sectional drawing. It is a figure which shows the observation window structure in this embodiment, (A) is a rear view, (B) is a sectional side view. It is a figure explaining the conventional blast process.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  First, with reference to FIG.1 and FIG.2, the whole structure of the dustproof apparatus for blast which concerns on embodiment of this invention is demonstrated. FIG. 1 is a view for explaining blasting using the blast dustproof device according to the present embodiment, FIG. 2 is a diagram showing the blast dustproof device according to the present embodiment, and FIG. It is the front view seen, (B) is AA sectional drawing.

  The dust-proof device 1 for blasting according to the present embodiment is a device that prevents the scattering of dust mainly including the abrasive material ejected from the abrasive material spray nozzle 2 or the abrasive scraps scraped by the abrasive material. Here, the blasting device is a blasting machine for injecting an abrasive material, a hose 3 connected to the injection nozzle 2, and a blasting machine for supplying the abrasive material to the injection nozzle 2 through the hose 3. 4. The blast machine 4 pumps the abrasive to the injection nozzle 2 by air pressure, and an injection flow mixed with the abrasive is injected from the injection nozzle 2 at a high speed. The jet stream collides with the blast surface 41 of the processing target 40 at a high speed to remove rust, scale, coating film, and the like. The injection nozzle 2 is operated by, for example, a worker 7 on a work table 6 that can be moved by a crane 5.

The blast dustproof device 1 mainly includes a hood 11, a sealing means 21, a first dust discharging means, and a second dust discharging means.
The hood 11 surrounds the blast surface 41 to prevent dust from being scattered, and is formed in a casing shape. Here, a rectangular shape is shown, but the shape is not limited. The material of the hood 11 is a material that has a strength that does not cause damage when the polishing material collides with the hood 11, and is lightweight from the viewpoint of portability, such as reinforced resin fiber, rubber, metal fiber, A lightweight metal material or the like is used.

The hood 11 has an opening 12 formed on a surface facing the blast surface 41 and an insertion port 13 into which the scouring material spray nozzle 11 is inserted. The opening 12 may be formed on the entire surface facing the blast surface 41 or may be partially formed. The insertion port 13 is preferably provided with a radially cut rubber sheet (not shown), and it is preferable that no gap be formed around the nozzle when the abrasive spray nozzle 2 is inserted.
Further, the hood 11 is provided with an inspection window 36 for visually recognizing the blast surface 41. A specific configuration of the observation window 36 will be described later.

The sealing means 21 seals a gap between the periphery of the opening 12 of the hood 11 and the blast surface 41. For example, a rubber member is used for the sealing means 21. A specific configuration example of the sealing means 21 will be described later.
The first dust discharge means has a bottom discharge pipe 14 connected to the bottom of the hood 11, and drops dust collected on the bottom of the hood from the bottom discharge pipe 14 and discharges it. The bottom of the hood is preferably inclined downward toward the bottom discharge pipe 14 so that dust collects in the bottom discharge pipe 14. A dust storage tank 15 is connected to the lower end of the bottom discharge pipe 14. Dust falling from the bottom discharge pipe 14 is stored in the dust storage tank 15.

The second dust discharging means has an upper discharge pipe 16 connected to the upper side from the bottom of the hood 11 and negative pressure generating means for making the internal space of the hood 11 into a negative pressure. The contained air is forcibly exhausted from the upper discharge pipe 16 by a negative pressure.
FIG. 3 shows a side sectional view of the second dust discharging means. As shown in the figure, the second dust discharge means has an upper discharge pipe 16 and a high-pressure air pipe 17 as a negative pressure generating means. The high-pressure air pipe 17 introduces high-pressure air into the upper discharge pipe 16 and is inclined and connected to the upper discharge pipe 16. At this time, the hood-side inclination angle θ of the axis of the high-pressure air pipe 17 with respect to the axis of the upper discharge pipe 16 is set to an acute angle. Then, the high-pressure air introduced from the high-pressure air pipe 17 generates an air flow from the hood side to the outside (in the direction of the broken arrow in the figure) in the upper discharge pipe 16 to make the internal space of the hood 11 have a negative pressure. The dust-containing air sucked from the internal space of the hood 11 due to the negative pressure is exhausted through a filter (not shown). The dust collected by the filter is stored in the dust storage tank. This dust storage tank is preferably the same as the dust storage tank 15 connected to the lower discharge pipe 14, and thus the size of the apparatus can be reduced.

  FIGS. 4A and 4B are views showing a modification of the second dust discharging means shown in FIG. 3, wherein FIG. 4A is a side sectional view and FIG. 4B is a view showing a fan. As shown in the figure, a fan 18 may be provided inside the upper discharge pipe 16 in addition to the high-pressure air pipe 17. The fan 18 is supported by a support 19 that is fixed to the inner wall of the upper discharge pipe 16. The fan 18 is installed at a position where high-pressure air introduced from the high-pressure air pipe 17 passes, and is rotated by the high-pressure air. By providing the fan 18, the generation of negative pressure inside the hood 11 is promoted.

As described above, according to the present embodiment, the blast surface 41 is surrounded by the hood 11, and the internal space of the hood 11 is sealed by the sealing means 21, so that dust generated by the blasting process is scattered around. Can be prevented.
In addition to this, in the present embodiment, the first dust discharging means mainly discharges the dust having a large particle diameter or a large specific gravity by dropping from the bottom discharge pipe 14 while being discharged to the second dust discharging means. In addition, since dust floating in the internal space of the hood 11 is mainly discharged from the upper discharge pipe 16, blasting dust having a wide particle size distribution can be appropriately discharged to the outside of the hood.
Furthermore, since the dust floating in the internal space of the hood 11 is discharged by the second dust discharging means, it is possible to clearly see the blast surface 41 from the viewing window 36.

  Further, in the second dust discharge means, the negative pressure generating means includes a high pressure air pipe 17 connected to a side surface of the upper discharge pipe 16 to introduce high pressure air into the upper discharge pipe 16, and the upper discharge pipe 16 has a high pressure. By introducing high-pressure air from the air pipe 17 and generating an air flow from the hood 11 side to the outside, the air in the hood can be sucked. At this time, since the internal space of the hood 11 can be set to a negative pressure only by connecting the high-pressure air pipe 17, the apparatus can be reduced in size and weight, and the apparatus can be excellent in handling properties.

Moreover, as shown in FIG. 5, it is preferable that the dustproof apparatus 1 for blasting concerning this embodiment has a moving mechanism. FIG. 5 is a rear view of the blast dustproof device having the moving mechanism in the present embodiment.
The moving mechanism slides the hood 11 along the blast surface 41. The moving mechanism includes a rail 28 that is detachably provided on the blast surface 41 and has a traveling path formed on the upper surface, and a plurality of rollers 25 that are attached to the upper portion of the hood 11 and roll on the rail 28. The rail 28 is preferably detachably provided on the blast surface 41 by a plurality of magnets 29 attached at predetermined intervals. A magnet base is preferably used for the magnet 29. Since the magnet base can instantaneously apply and remove magnetic force, the rail 28 can be easily attached and detached.
Further, this moving mechanism also has a function of suspending and supporting the hood 11. The hood 11 is suspended from the rail 28 via the roller 25, and the hood 11 is supported on the blast surface 41.

6 is a cross-sectional view of the blast dustproof device shown in FIG. 5, (A) is a BB cross-sectional view, and (B) is a CC cross-sectional view.
In this blast dustproof device 1, a hood frame 27 such as an L-shaped angle is provided around the opening 12 of the hood 11, and a roller shaft 26 on which a roller 25 is mounted is fixed to the hood frame 27. . At this time, the roller shaft 26 is fixed to the hood frame 27 so as to be perpendicular to the blast surface 41, and the roller 25 is configured to rotate in a plane parallel to the blast surface 41. On the other hand, the rail 28 is formed in a U-shaped cross section, and the hood 11 is suspended and supported so that the hood 11 is not separated from the blast surface 41 by accommodating the lower portion of the roller 25 in the recess of the rail 28. Yes. The hood 11 is slid horizontally in the horizontal direction while spraying the abrasive with the spray nozzle 2 (see FIG. 1).

  Thus, by having the rail 28 provided on the blast surface 41 and the roller 25 attached to the hood 11, the moving mechanism of the hood 11 can be made simple. Further, since the rail 28 is detachably attached to the blast surface 41, handling properties can be further improved. Further, since the hood 11 is suspended from the rail 28 via the roller 25, it is not necessary to hold and hold the hood 11 by hand, thereby improving workability. Furthermore, since the moving mechanism also serves as a support mechanism for the hood 11, the apparatus can be simplified and reduced in weight compared to the case where a support mechanism is newly added.

FIG. 6 also shows a specific configuration example of the sealing means.
The sealing means includes a rubber member 31 that contacts the blast surface 41, a spring member 32 interposed between the rubber member 31 and the periphery of the opening 12 of the hood 11, and an opening of the rubber member 31 and the hood 11. 12 and a stretchable cover member 33 that seals the gap with the periphery.

The rubber member 31 is formed in an annular shape and is disposed around the opening 12 of the hood 11.
The spring member 32 is disposed so as to be elastically deformed in a direction perpendicular to the blast surface 41, and is configured to contract a predetermined length when the roller 25 is installed on the rail 28. A plurality of spring members 32 are provided around the opening 12 of the hood 11 at predetermined intervals. As the spring member 32, for example, a coil spring (spring) or a leaf spring is used.
The cover member 33 is formed in a cylindrical shape, expands and contracts following the elastic deformation of the spring member 32, and always seals the gap between the rubber member 31 and the periphery of the opening 12 of the hood 11. For example, a bellows-shaped sheet member is used for the cover member 33.

In the sealing means having the above configuration, when the roller 25 is installed on the rail 28, the rubber member 31 is pressed by the hood frame 27 and the spring member 32, and the rubber member 31 is in close contact with the blast surface 41. At this time, the cover member 33 expands and contracts following the spring member 32 and seals the gap between the rubber member 31 and the hood frame 27, so that the internal space of the hood 11 is maintained in a substantially airtight state.
Thus, since it was set as the structure which presses the rubber member 31 with the spring member 32, the adhesiveness to the blast surface 41 can be made high and a sealing performance can be improved further. Further, since the gap between the rubber member 31 and the periphery of the opening 12 of the hood 11 is sealed with the extendable cover member 33, the cover member 33 can follow the spring member 32 and reliably seal the gap. It becomes possible.

FIG. 7 is a view showing another configuration example of the blast dustproof device according to the present embodiment, (A) is a front view seen from the blast surface side, (B) is a DD sectional view, C) is a cross-sectional view taken along line EE.
This blast dustproof device 1 ′ has a hood 11 ′ having an opening 12 ′ and an insertion port 13 ′, and a sealing means having a rubber member 31 ′ and a spring member 32 ′, as in the configuration shown in FIG. And a first dust discharge means having a bottom discharge pipe 14 'and a second dust discharge means having an upper discharge pipe 16' and a high-pressure air pipe 17 '. In the figure, the cover member of the sealing means is omitted. Further, the hood 11 'shown in the figure is formed in a circular shape.

Furthermore, the dust-proof device 1 for blasting according to the present embodiment may have a viewing window structure shown in FIG. FIGS. 8A and 8B are views showing a viewing window structure in the present embodiment, in which FIG. 8A is a rear view and FIG. 8B is a side sectional view.
This peep window structure is configured such that a peep window 36 and a protective partition plate 37 are fitted into a window frame 35 provided in the hood 11. The protective partition plate 37 is disposed so as to partition the view window 36 and the internal space of the hood 11. The protective partition plate 37 is configured to be replaceable. Furthermore, the protective partition plate 37 is transparent or translucent, and the material thereof can be selected according to the use situation such as a form in which tempered glass or a plastic film is attached to the tempered glass.

  In this way, by adopting a configuration in which the protective partition plate 37 is interposed between the observation window 36 and the internal space of the hood 11, damage to the observation window 36 due to dust can be prevented, and the blast surface 41 can be clearly seen. To do. Further, since the protective partition plate 37 can be replaced, the visibility of the blast surface 41 can be recovered by replacing the protective partition plate 37 even when the protective partition plate 37 is damaged.

DESCRIPTION OF SYMBOLS 1, 1 'Dust-proof device for blasting 2 Abrasive material injection nozzle 11, 11' Hood 12, 12 'Opening part 13, 13' Insertion port 14, 14 'Bottom discharge pipe 15 Dust storage tank 16, 16' Upper discharge pipe 17 17 'High-pressure air piping 18 Fan 19 Strut 21 Sealing means 25 Roller 27 Hood frame 28 Rail 29 Magnet 31, 31' Rubber member 32, 32 'Spring member 33 Cover member 36 Peep window 27 Protective partition plate 41 Blast surface

Claims (5)

In the dust proofing device for blasting that surrounds the blast surface and prevents the scattering of the dust containing the scouring material sprayed from the scouring material spray nozzle or the scouring scraps cut by the scouring material,
A housing-shaped hood having an opening formed in a surface facing the blast surface, and an insertion port into which the abrasive spray nozzle is inserted;
Sealing means for sealing a gap between the periphery of the opening of the hood and the blast surface;
A first dust discharge means having a bottom discharge pipe connected to the bottom of the hood, and dropping and discharging the dust from the bottom discharge pipe;
An upper discharge pipe connected above the bottom of the hood; and a negative pressure generating means for making the internal space of the hood a negative pressure. A dustproof device for blasting, comprising: a second dust discharging means for exhausting air from the dust.   The negative pressure generating means includes a high-pressure air pipe that is connected to a side surface of the upper discharge pipe and introduces high-pressure air into the upper discharge pipe, and an air flow that flows outward from the hood side into the upper discharge pipe by the high-pressure air. The dust-proof device for blasting according to claim 1, wherein a negative pressure is generated in the internal space of the hood. The hood has a moving mechanism that slides along the blast surface;
The moving mechanism includes a rail that is detachably provided on the blast surface and has a traveling path formed on an upper surface thereof, and a roller that is attached to an upper portion of the hood and rolls on the rail.
The dust proofing device for blasting according to claim 1 or 2, wherein the hood is suspended from the rail via the roller, and the hood is supported on the blast surface.   The sealing means includes a rubber member that comes into contact with the blast surface, a spring member interposed between the rubber member and the periphery of the opening of the hood, and the rubber member and the periphery of the opening of the hood. A dustproof device for blasting according to any one of claims 1 to 3, further comprising an extendable cover member that seals the gap. It has a peep window provided in the hood, a transparent or translucent protective partition plate that partitions between the peep window and the internal space of the hood, and the protective partition plate is configured to be replaceable. The dustproof device for blasting according to any one of claims 1 to 4, wherein the dustproof device is for blasting.

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