JPS62251075A - Method and device for blasting by coanda slit flow - Google Patents

Abstract

PURPOSE:To suppress wear of a pipeline and nozzle inner wall due to blasting particles by transporting the blasting particles to a slit-formed nozzle area by means of Coanda flow by air, and injecting the blasting particles from the nozzle at a high speed. CONSTITUTION:Pressurized air is sent into a pipe 2 from a slit 3 at a high speed. At the outlet from this slit 3, the air draws a stream line alpha inclined toward the pipeline 1 from the slit 2 by the Coanda effect. As a result, a negative pressure area is generated on the opposite side, and from outside, the air and blasting particles flow into this negative pressure area in the beta direction as shown by the arrow. The motion vector of the air stream from said slit 3 and the motion vector of air stream from the outside are composed to form an air stream which advances toward the pipeline 1 within the pipe. The section area of this air stream becomes smaller by an by, and the air stream is accelerated to form a dynamic boundary layer of high-speed stream in the neighborhood of the pipeline 1. The blasting particles are sent to a slit-shaped nozzle by this Coanda flow, and the blasting particles are jetted out of the nozzle outlet 22 at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface blasting treatment of metals, glass, ceramics, etc., and an apparatus therefor.

More specifically, the present invention relates to a high-efficiency, low-pollution blasting method using a Coanda spiral full type, which has excellent abrasion resistance of the nozzle part, and an apparatus therefor.

(Prior art and its problems) A common sandblasting method as conventional blasting uses a so-called high-speed ejector one-way method, in which air is sent into the pipe toward the nozzle outlet. Blast particles of inorganic materials, metals, etc. are fed into the high-speed flow from the side of the pipe and are ejected along with air from the nozzle outlet.

In this conventional method, since the high-speed air is in a turbulent state, the blast particles and air mix turbulently.

For this reason, the blast particles collide violently with the inner wall of the pipe before being ejected from the nozzle outlet, causing the inner wall to wear out. Wear makes it difficult to control the blasting process, reduces process accuracy, and even causes nozzle blockage.

In addition, since the particles ejected from the nozzle exit are in a state of turbulent mixing with air, they scatter over a wide range from the nozzle exit, making it difficult to concentrate them on the target area to be treated. For this reason, the efficiency of the blasting process is low, requiring masking for areas other than the target area, using a large amount of blast particles to increase production efficiency, and using pressurizing equipment to increase the velocity of high-speed air. It had to be made larger.

Furthermore, in the conventional method, violent collisions between blast particles and the inner surface of the tube, the use of a large amount of particles to increase productivity, and the increase in the size of the equipment all generate severe noise.
Moreover, it has a negative impact on the working and living environment by generating a large amount of dust.

For this reason, it has been strongly desired to realize a blasting method with high production efficiency, excellent economic efficiency, and extremely low pollution, and an apparatus therefor.

(Object of the Invention) The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a novel blasting method and apparatus that solve the problems of the conventional methods.

(Structure of the Invention) The blasting method of the present invention solves the problems of the conventional method and achieves a blasting process that is excellent in production efficiency and economical efficiency and is low in pollution. Instead of high-speed turbulent mixing, the Coanda flow one-way system is used for high-speed feeding.

To explain the method of this invention in more detail, this method:
Blast particles are flowed together with air into a negative pressure area generated by high-speed feeding of pressurized air, and the blast particles are transferred to a slit-shaped nozzle area by Coanda flow caused by air, and the blast particles are transferred from this slit-shaped nozzle. High-speed injection means high-speed feeding.

This funder flow and its industrial use were discovered for the first time by the inventor of this invention. It has been discovered that when a lateral vector is added to the fluid vector in the pipe direction, a boundary layer of fluid is formed near the inner wall of the pipe, and the fluid moves at high speed in the pipe direction. When solid particles are mixed into this Coanda flow, the particles move at high speed in the direction of the pipe, and contact between the particles and the inner wall of the pipe is suppressed.

This invention makes effective use of such a Coanda effect.

] In order to generate the antuff 0-, in the present invention, pressurized air is introduced at high speed in a direction transverse to the flow direction of the air flowing into the pipe line and the blast particles. The pressure of pressurized air in this case is 2 to 10 Kl/ci G.

More specifically, for example, pressurized air is introduced into the pipe through a slit formed in a pipe whose cross section is rectangular and whose cross section gradually becomes larger in the opposite direction of the connecting face. The pressurized air is caused to flow along the smoothly curved wall surface from the slit toward the conduit. In this way, the Coanda flow generated is used to realize high-speed movement of blast particles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The blasting method of the present invention and the essential parts of the apparatus therefor will be explained in more detail with reference to the attached drawings.

FIG. 1 shows the concept of the turbulent mixing process of the conventional sandblasting method. FIG. 2 shows an example of this invention.

In the conventional method shown in Fig. 1, the pipe line (
10) is fed with a high velocity air jet stream (11).

The blast particles (12) are introduced through an introduction pipe (13) provided diagonally along the pipe.

The particles are turbulently mixed with the jet stream and ejected from the nozzle. At this time, the particles violently collide with the inner wall of the pipe.

In the example of the invention shown in FIG. 2, a pipe (2) having the same cross-sectional shape and dimensions is connected to the end face of a pipe line (1) having a rectangular cross-section. The cross-sectional shape of the pipe (2) gradually becomes larger in a direction opposite to this connecting surface. Pipe (2
) has a slit (3) for feeding pressurized air from the side.
form.

Further, a smoothly curved wall surface (4) is provided from this narrow gap (3) toward the conduit. An inlet (5) for air and blast particles is provided on the end face of the pipe (2) opposite to the pipe line (1),
Appropriate supply means (6) such as a hopper for supplying particles and air to this inlet and means (7) for supplying pressurized air to the slits are provided.

On the side opposite to the wall surface (4) of the slit (3), there is an auxiliary cylinder (8).
The wall surface (9) may be bent by connecting the two. This slit (3) has a structure in which the interval can be adjusted.

The inclination angle θ of the tube (2) is preferably such that tan θ is approximately 1/4 to 1/8. In addition, the pipe and cylinder (2
) is preferably about 1/4 to 1/25. By doing this, the flow velocity in the air pipe is reduced to
2) The flow rate is increased to 4 to 25 times the flow rate in 2).

As the means (7) for supplying pressurized air to the slit (3), any suitable means can be adopted, but the distribution chamber (21) is provided so as to surround the pipe (2) or only on its long side, This distribution chamber can communicate with the slit (3).

In this structure, pressurized air (secondary fluid) is fed into the tube (2) through the slit (3) at high speed. At the exit of the slit (3), the air draws a streamline (arrow α in Figure 2) tilting from the pipe (2) toward the pipe (1) due to aerodynamic action (known as the Coanda effect). As a result, a negative pressure area is created on the opposite side. Air (secondary fluid) and blast particles flow into the negative pressure area from the outside (arrow β).

The motion vector of the airflow from the slit (3) and the motion vector of the airflow from the outside are combined to form an airflow that advances inside the pipe toward the pipe (1).

The airflow speeds up as the cross-sectional area becomes smaller and smaller. Also, at this time, a dynamic boundary layer of high-speed flow is formed near the pipe wall instead of a static boundary layer.

The blast particles and air stream are ejected at high speed through the slit-like nozzle (22).

Of course, the method and apparatus of the present invention are not limited to the above examples. It goes without saying that various structural variations are possible.

Regarding the means for transporting air and blast particles to the nozzle and the nozzle means, there are no particular structural limitations as long as the Coanda slit flow accompanied by the formation of a dynamic boundary layer is maintained. In addition, in this invention, since the air and particles are not mixed in turbulent flow, collisions with the inner wall of the pipe and the inner wall of the nozzle are suppressed, so there is extremely little wear on the pipe and nozzle, and the material of the inner wall is also It does not need to be hard. An elastic material such as a plastic tube or a rubber tube may be used.

The Coanda flow generation part and the nozzle part can be separated as appropriate. The flow rate of the air injected from the nozzle can be controlled by adjusting the pressure, amount, etc. of the pressurized air introduced from the slit (3). There is no particular limitation on the mixing ratio of blast particles. It can be selected depending on the processing purpose and processing target.

In the case of this invention, the air flow velocity at the nozzle outlet of the conventional method is not only 40 to 60 m/min but also 100 to 200 m/min.
Injection at high speeds of m/min is also possible. The device may suitably have various accessories and may be a stationary or hand-held device.

(Effects of the Invention) According to the method and apparatus of the present invention as described above, it is possible to suppress wear of the pipe line and the inner wall of the nozzle due to blast particles, and to significantly reduce noise caused by particle collision. It is possible to suppress the spread of the scattering range of blast particles from the nozzle outlet, greatly improving the efficiency of blast particles.

Since the amount of blast particles used is smaller than in conventional methods, the amount of dust generated is also small.

Moreover, the scattering of dust can also be made within a narrow range.

The effects of this invention, which is excellent in productivity, economy, and low pollution, are immeasurably great. Moreover, the range of its applications is wide-ranging, including polishing, grinding, deburring, drilling, and even cutting, making it extremely useful.

[Brief explanation of drawings]

FIG. 1 shows the concept of a part corresponding to a nozzle in a conventional blasting process. FIG. 2 shows an example of the method and apparatus of the present invention. The numbers in the figure indicate the following. 10... Pipe line 11... Air jet flow 12... Blast particles 13... Blast particle introduction pipe 14... Nozzle outlet 1... Pipe line 2... Cylindrical pipe 3... Thin Gap 4... Curved wall surface 5... Air and blast particle inlet 6... Air and blast particle supply means 7... Pressurized air supply means 8... Auxiliary tube 9... Auxiliary tube wall surface 21 ...Distribution chamber 22...Nozzle outlet

Claims (11)

[Claims] (1) Blast particles are flowed together with air into a negative pressure area generated by high-speed supply of pressurized air, and the blast particles are transferred to a slit-shaped nozzle by Coanda flow caused by air, and the blast particles are transferred from the nozzle at high speed. A blasting method using Coanda slit flow, which is characterized by injection and blasting. (2) The blasting method according to claim (1), wherein the blasting particles are inorganic particles or metal particles. (3) The blasting method according to claims (1) and (2), in which pressurized air is fed at high speed in a direction transverse to the flow direction of the air flowing into the pipe line and the blast particles. (4) Pressurized air is sent into the pipe through a slit formed in a pipe with a rectangular cross-section that is connected to the end face of a pipe with a rectangular cross-section and whose cross-sectional shape gradually becomes larger in the opposite direction of the connection face. Claims (1) to (3) in which the pressurized air flows along a smoothly curved wall surface from the slit toward the pipe line to generate a Coanda flow. Blasting method. (5) The blasting method according to claims (1) to (4), wherein the pressure of the pressurized air is 2 to 10 Kg/cm^2G. (6) The blasting method according to claims (1) to (5), wherein the object to be treated is metal, glass, or ceramics. (7) The blasting method according to claims (1) to (6), which comprises polishing, grinding, cutting, deburring, or drilling the surface of the object to be treated. (8) The blasting method according to claims (1) to (7), wherein the object to be treated is a wide plate or sheet. (9) Pressurized air is supplied to the pipe (2), which has a rectangular cross section and which is connected to the end face of the pipe line (1), which has a rectangular cross section, and whose cross section gradually becomes larger in the opposite direction to the connecting face. (2)
A slit (3) is formed for feeding into the slit (3).
A smoothly curved wall (4) is provided from the pipe (2) toward the pipe (1), and an inlet (5) for air and blast particles is provided at the end face of the pipe (2) on the opposite side from the pipe (1). ), and further includes means for supplying pressurized air to the slit (3) and means for supplying air and blast particles to the inlet (5); A blast processing apparatus using Coanda slit flow, characterized by comprising: a pipe transfer section that transfers blast particles to a slit-shaped nozzle through a pipe transfer section; and a slit-shaped nozzle section with a rectangular cross section that injects blast particles to a workpiece at high speed. . (10) Claim No. 9, which has attached means such as a means for conveying the processed material, a dust collector, and an air filter.
) The blast processing device described in item 2. (11) The blast processing apparatus according to claims (9) to (10), which is a stationary or hand-held device.