Abstract:
A blasting apparatus capable of increasing suction power to collect an abrasive without exerting any influence on processing of a work surface with the abrasive. The apparatus includes a blasting nozzle ( 2 ) blasting an abrasive ( 100 ) on a surface ( 200   a ) of work ( 200 ), a cover ( 10 ) including a surface ( 10   a ) for airflow alignment parallel to the work surface and a blast hole ( 10   b ) through which the abrasive from the nozzle passes, a nozzle case ( 9 ) including the cover and surrounding the nozzle, and a collecting case ( 11 ) covering an outer surface of the nozzle case and including a collecting passage ( 11   c ) disposed around the nozzle case, from the passage, the abrasive being collected by suction, wherein the apparatus collects the abrasive that is blasted from the nozzle and strikes the work surface from the passage through a clearance ( 13 ) provided between the airflow-alignment surface and the work surface.

Description:
TECHNICAL FIELD 
     The present invention relates to an apparatus and a method for processing a surface of work, and specifically relates to a blasting apparatus and a method for blast processing, with which processing is performed such that a depressed portion is formed on a surface of work such as a glass substrate by the use of a blast of an abrasive. 
     BACKGROUND ART 
     Conventionally, a glass substrate having a thickness of about 0.7 mm is generally used for a flat-screen display panel such as a liquid crystal display panel and a plasma display panel. The glass substrate of this type is desired to have a flat surface and an excellent light transmission property. 
     The glass substrate of this type could sometimes develop, during production, a defect such as a tiny flaw and a pore of air bubble on its surface, or a defect such as an air bubble and a foreign substance that are trapped inside of the glass substrate. If there exists such a defect, a problem that causes a scattering of light arises. In order to solve this problem, the portion where the defect exists is usually scraped off the glass substrate, and the depressed portion thus made is filled with a transparent resin and then planarized. 
     The defect is scraped off the glass substrate in a method using a blasting apparatus for processing the glass substrate, in which the glass substrate is struck with a high-speed blast of an abrasive (also referred to a shot or an abrasive grain) such as alumina powder, silicon carbide powder, glass beads and very small steel balls, together with fluid such as air, and the striking power causes minute destruction to the glass substrate to process the glass substrate. 
       FIG. 2  is a cross-sectional view showing a schematic configuration of a conventional blasting apparatus. A blasting apparatus  21  includes a blasting nozzle  22  arranged to blast an abrasive  100 , and a nozzle case  23  arranged to surround the blasting nozzle  22  as shown in  FIG. 2 . 
     A suction hose  24  is connected to a posterior portion of a side wall  23   a  of the nozzle case  23 . The suction hose  24  is arranged to collect the abrasive  100  that is blasted from the blasting nozzle  22  and used for blast processing in forming a depressed portion  200   b  on a surface  200   a  of a glass substrate  200 , and thus the abrasive  100  is prevented from shattering around. 
     The abrasive  100  is collected because, while shattering around, it worsens a working environment and exert a harmful influence such as health damage on workers. 
     In this case, an abrasive having a grain diameter of several micrometers is used as the abrasive  100  blasted from the blasting nozzle  22 . The depressed portion  200   b  that is formed by scraping a defect of the glass substrate  200  in blast processing is several millimeters in diameter, and several tens to several hundreds micrometers in depth. The prior art to the present invention is described in PTL 1. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP H08-216024 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, having the configuration to suck out air in the nozzle case  23  as described above, the blasting apparatus  21  is not capable of sufficiently sucking the abrasive  100  having the grain diameter of several micrometers, which is used for fine processing informing the depressed portion  200   b  that is several millimeters in diameter on the surface  200   a  of the glass substrate  200 , while the blasting apparatus  21  is capable of sufficiently sucking an abrasive having a grain diameter of several hundreds micrometers to several millimeters, which is used for sand blast processing in roughening the surface of stone, concrete or metal. 
     In order to solve this problem, the suction power is increased so that the abrasive  100  having the small grain diameter may be collected by suction. However, a problem is caused that the blast processing is not sufficiently performed because the striking power of strikes of the abrasive  100  on the surface  200   a  of the glass substrate  200  diminishes due to the configuration of the blasting apparatus  21  that the abrasive  100  is sucked in a direction opposite to a direction in which the abrasive  100  is blasted as shown in  FIG. 2 . 
     Increasing the blasting power of the blasting nozzle  22  to blast the abrasive  100  may counter the increased suction power; however, another problem is caused that processing accuracy is deteriorated. 
     The processing in a depth direction should be within an accuracy of several micrometers to several tens micrometers in forming the depressed portion  200   b  on the surface  200   a  of the glass substrate  200  having a thickness of about 0.7 mm by scraping a defect as described above of the glass substrate  200 . Thus, if the blasting power is increased in addition to the suction power, the processing accuracy in the depth direction cannot be obtained. 
     In order to overcome the problems described above, preferred embodiments of the present invention provide a blasting apparatus and a method for blast processing that are capable of increasing suction power to collect an abrasive, without exerting any influence on processing of a work surface with an abrasive. 
     Solution to Problem 
     Preferred embodiments of the present invention provide a blasting apparatus that includes a blasting nozzle arranged to blast an abrasive on a surface of work, a cover including a surface for airflow alignment that is parallel to the work surface and a blast hole through which the abrasive blasted from the blasting nozzle passes, a nozzle case that includes the cover and arranged to surround the blasting nozzle, and a collecting case that is arranged to cover an outer surface of the nozzle case, and includes a collecting passage disposed around the nozzle case, from the collecting passage, the abrasive being collected by suction, wherein the blasting apparatus is arranged to collect the abrasive, which is blasted from the blasting nozzle and strikes the work surface, from the collecting passage through a clearance provided between the surface for airflow alignment of the cover and the work surface. 
     In another aspect of the present invention, a method for blast processing a surface of work with an abrasive blasted from a blasting nozzle includes the steps of blasting the abrasive from the blasting nozzle on the work surface through a blast hole of a cover of a nozzle case that surrounds the blasting nozzle, striking the work surface with the abrasive, and collecting by suction the abrasive, which has passed through a clearance provided between a surface for airflow alignment that is provided to the cover and parallel to the work surface, and the work surface, from a collecting passage disposed around the nozzle case and provided to a collecting case that covers an outer surface of the nozzle case. 
     The blasting apparatus and the method for blast processing having the configurations described above are capable of more abating a scattering force of the abrasive (a force of the abrasive scattering around), which is blasted from the blasting nozzle, passes through the blast hole of the cover and strikes the work surface, that is, the abrasive used for blast processing the work surface, as the abrasive scatters around farther through the clearance provided between the surface for airflow alignment of the cover and the work surface, and capable of collecting by suction the abrasive from the collecting passage provided to the collecting case when the scattering force of the abrasive is abated. 
     To be specific, the configuration that a direction in which the abrasive used for blast processing the work surface is sucked is radial and perpendicular to a direction in which the abrasive is blasted prevents the suction power from influencing the striking power of strikes of the abrasive on the work surface even when the suction power from the collecting passage is increased so that the abrasive, even having a small grain diameter, maybe sufficiently sucked. Thus, the blasting apparatus and the method for blast processing are capable of maintaining blast processing accuracy, and collecting the abrasive while preventing the abrasive from scattering around. 
     It is preferable that the collecting case includes an open end that is flush with the surface for airflow alignment of the cover. This configuration allows the abrasive to be sufficiently sucked and collected from the collecting passage provided to the collecting case even when the surface for airflow alignment of the cover is brought closer to the work surface, that is, even when the clearance provided between the surface for airflow alignment of the cover and the work surface is narrowed. 
     It is preferable that the nozzle case has a conical shape such that a side wall of the nozzle case expands toward a direction in which the abrasive is blasted, and the collecting case has a conical shape such that a side wall of the collecting case expands toward the direction in which the abrasive is blasted. Allowing the surface for airflow alignment of the cover to obtain a size enough to abate the scattering force of the abrasive that is used for blast processing the work surface and scatters, the configuration contributes to a downsizing of the nozzle case and the collecting case. 
     It is preferable that the method for blast processing further includes the step of forming a depressed portion on the work surface by the use of the blast of the abrasive from the blasting nozzle. It is preferable that the work defines a glass substrate used for a display panel such as a liquid crystal display panel. These configurations allow the depressed portion to be formed easily with precision such that a defect such as a tiny flaw and a pore of air bubble on its surface or a defect such as an air bubble and a foreign substance that are trapped inside of the glass substrate can be scraped off the glass substrate, which improves a workability of repairing the defect of the glass substrate. 
     Advantageous Effects of Invention 
     According to the blasting apparatus and the method for blast processing according to the preferred embodiments of the present invention, a scattering force of the abrasive (a force of the abrasive scattering around) used for blast processing the work surface can be abated more as the abrasive scatters farther in the clearance provided between the surface for airflow alignment of the cover and the work surface, and the abrasive can be collected by suction from the collecting passage provided to the collecting case. Thus, the blasting apparatus and the method for blast processing are capable of preventing the suction power from influencing the striking power of strikes of the abrasive on the work surface even when the suction power from the collecting passage is increased so that the abrasive, even having a small grain diameter, may be sufficiently sucked. In addition, the blasting apparatus and the method for blast processing are capable of maintaining blast processing accuracy, and collecting the abrasive while preventing the abrasive from scattering around. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view showing a schematic configuration of a blasting apparatus according to a first preferred embodiment of the present invention. 
         FIG. 2  is a cross-sectional view showing a schematic configuration of a conventional blasting apparatus. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A detailed description of a blasting apparatus and a method for blast processing according to preferred embodiments of the present invention will now be provided with reference to the accompanying drawings. 
       FIG. 1  is a cross-sectional view showing a schematic configuration of a blasting apparatus  1  according to one of the preferred embodiments of the present invention. The blasting apparatus  1  includes a blasting nozzle  2 . The blasting nozzle  2  includes a nozzle body  3  that includes a port  3   a  for abrasive feeding and a chamber  3   b  for abrasive guiding that communicates with the port  3   a  and has the shape of a cylindrical container, where an abrasive  100  is guided to the chamber  3   b  via a hose  4  for abrasive supply from a tank for abrasive supply (not shown) as shown in  FIG. 1 . The chamber  3   b  includes a conical inner surface  3   c  disposed at the front end of the chamber  3   b.    
     The front end of a pipe  6  for air blasting that is inserted from behind the chamber  3   b  is disposed inside the conical inner surface  3   c . The pipe  6  communicates with a source for compressed-air supply (not shown) via a hose  7  for compressed-air supply. Compressed air at a relatively high pressure is sent to the pipe  6 , and airflow is blasted from the front end of the pipe  6 . 
     A nozzle  5  is provided to the front end of the nozzle body  3 , and disposed in front of the pipe  6  in the direction in which the pipe  6  blasts air. The nozzle  5  communicates with the chamber  3   b  through the conical inner surface  3   c , and is arranged to blast a flow of blasting abrasive from a port  5   a  for abrasive blast. 
     A nozzle holder  8  has a cylindrical shape, and includes a tapered portion on its inner surface. The tapered portion provided on the inner surface of the nozzle holder  8  is fitted onto a tapered portion provided on the outer surface of the nozzle  5 , and the nozzle  5  is fastened to the front end of the nozzle body  3  with a screw portion provided on the outer surface of the nozzle holder  8 , whereby the nozzle  5  is secured to the nozzle body  3 . 
     In the blasting nozzle  2  having this configuration, negative pressure builds up in the chamber  3   b  when the compressed air is blasted from the front end of the pipe  6  toward the nozzle  5 , so that the abrasive  100  in the tank for abrasive supply (not shown) is sucked into the chamber  3   b  via the hose  4 . 
     Then, the abrasive  100  in the chamber  3   b  is guided to a ring-shaped clearance between the conical inner surface  3   c  and the pipe  6 . Riding the airflow blasted from the pipe  6 , the abrasive  100  is blasted toward the outside from the port  5   a  at the front end of the nozzle  5  while scattering conically. 
     The outer surface of the blasting nozzle  2  having this configuration is surrounded with a nozzle case  9 . The nozzle case  9  has a conical shape such that a side wall  9   a  of the nozzle case  9  expands by degrees toward a direction in which the abrasive  100  is blasted. A posterior wall  9   b  of the nozzle case  9  is disposed so as to close a posterior portion of the nozzle case  9  and secured to the nozzle body  3 . 
     A cover  10  having a disk shape is disposed in front of the nozzle case  9  (on the side toward which the abrasive  100  is blasted) so as to close an opening portion of the nozzle case  9 . The cover  10  includes a surface  10   a  for airflow alignment having a circular shape on the side toward which the abrasive  100  is blasted. The cover  10  includes a blast hole  10   b  in its center, through which the abrasive  100  blasted from the nozzle  5  passes. 
     The surface  10   a  of the cover  10  has a configuration parallel to a surface  200   a  of a glass substrate  200  that is to be blast working as shown in  FIG. 1 , and is disposed apart from the surface  200   a  of the glass substrate  200  at a given distance during the blast processing. 
     The outer surface of the nozzle case  9  is surrounded with a collecting case  11 . The collecting case  11  has a conical shape such that a side wall  11   a  of the collecting case  11  expands by degrees toward a direction in which the abrasive  100  is blasted. A posterior wall  11   b  of the collecting case  11  is disposed so as to close a posterior portion of the collecting case  11  and secured to the nozzle body  3 . 
     The clearance between the inner surface of the side wall  11   a  of the collecting case  11  and the outer surface of the side wall  9   a  of the nozzle case  9  is defined as a collecting passage  11   c  arranged to collect the abrasive  100 . A collecting port  11   d  having a ring shape is provided at the front end of the collecting passage  11   c . In this configuration, an open end  11   e  that defines the front end of the collecting case  11  (i.e., the collecting port  11   d ) has a configuration substantially flush with the surface  10   a  of the cover  10 . 
     The collecting passage  11   c  communicates with a suction hose  12  via a suction port  11   f  that opens behind the side wall  11   a  of the collecting case  11 . The suction hose  12  is connected to a suction equipment (not shown), and arranged to suck the abrasive  100  in the collecting passage  11   c.    
     An abrasive having a grain diameter of several micrometers is used as the abrasive  100  blasted from the blasting nozzle  5 . A depressed portion  200   b  having a circular shape in a plan view is formed by scraping a defect (e.g., a tiny flaw and a pore of air bubble on the surface  200   a  or an air bubble and a foreign substance that are trapped inside of the glass substrate  200 ) of the glass substrate  200  in blast processing. Thus-formed depressed portion  200   b  is several millimeters in diameter, and several tens to several hundreds micrometers in depth. 
     In accordance with the size of the depressed portion  200   b , the blast hole  10   b  provided in the center of the cover  10  is made to have a size such that the blasted abrasive  100  is not brought into contact with the blast hole  10   b , which is several millimeters in diameter. A transparent glass substrate having a thickness of about 0.7 mm that is generally used for a flat-screen display panel such as a liquid crystal display panel and a plasma display panel is used as the glass substrate  200 . 
     As shown in  FIG. 1 , a scattering force of the abrasive  100  (a force of the abrasive  100  scattering around), which is blasted from the blasting nozzle  2 , passes through the blast hole  10   b  of the cover  10  and strikes the surface  200   a  of the glass substrate  200 , that is, the abrasive  100  used for blast processing in which the depressed portion  200   b  is formed by striking the surface  200   a  of the glass substrate  200  with the abrasive  100 , is abated more as the abrasive  100  farther scatters around radially from a position on the surface  200   a  of the glass substrate  20  where the abrasive  100  strikes through a clearance  13  provided between the surface  10   a  of the cover  10  and the surface  200   a  of the glass substrate  200 . 
     The suction from the ring-shaped collecting port  11   d  produces airflow, which radially spreads centering around the position on the glass substrate  200  where the abrasive  100  strikes, in the clearance  13  provided between the surface  10   a  of the cover  10  and the surface  200   a  of the glass substrate  200 . Thus, riding the airflow, the abrasive  100  that has struck is guided to the collecting port  11   d.    
     Consequently, the abrasive  100   a , of which the scattering force is abated by passing through the clearance  13  where the airflow is produced, can be easily collected by suction from the collecting port  11   d . During the collection, glass wastes (not shown) that are scraped off the glass substrates  200  by the strikes of the abrasive  100  are collected by suction together with the abrasive  100  from the collecting port  11   d.    
     According to the blasting apparatus  1  having this configuration, the suction power can be prevented from influencing the striking power of strikes of the abrasive  100  on the surface  200   a  of the glass substrate  200  even when the suction power from the collecting passage  11   c  is increased so that the abrasive  100 , even having a small grain diameter such as several micrometers, may be sufficiently sucked. 
     To be specific, the configuration that a direction in which the abrasive  100  used for blast processing the surface  200   a  of the glass substrate  200  is sucked is substantially perpendicular to a direction in which the abrasive  100  is blasted, and the direction in which the abrasive  100  is sucked is made radial by the clearance  13  prevents the suction power from influencing the striking power of strikes of the abrasive  100  on the surface  200   a  of the glass substrate  200  even when the suction power from the collecting passage  11   c  is increased so that the abrasive  100 , even having a small grain diameter, may be sufficiently sucked. 
     The conventional blasting apparatus  21  explained above in the Background Art referring to  FIG. 2  has the configuration that the abrasive  100  is sucked from behind the nozzle case  23 , that is, the configuration that the abrasive  100  is sucked in the direction opposite to the direction in which the abrasive  100  is blasted, so that if the suction power is increased, the striking power of strikes of the abrasive  100  on the surface  200   a  of the glass substrate  200  diminishes accordingly, which causes a problem that the blast processing is not sufficiently per formed. However, the blasting apparatus  1  according to the preferred embodiment of the present invention can solve this problem because it has the configuration that the abrasive  100  is sucked from behind the collecting case  11 , not from behind the nozzle case  23 . 
     Though the processing in a depth direction should be within an accuracy of several micrometers to several tens micrometers in forming the depressed portion  200   b  on the surface  200   a  of the glass substrate  200  having a thickness of about 0.7 mm by scraping a defect as described above off the glass substrate  200 , the blasting apparatus  1  according to the preferred embodiment of the present invention is capable of maintaining such blast processing accuracy, and collecting the abrasive  100  while preventing the abrasive  100  from scattering around. 
     It is to be noted that the depressed portion  200   b  formed by scraping a defect off the glass substrate  200  is repaired such that a transparent ultraviolet cure resin, for example, is charged in an uncured state into the depressed portion  200   b  and then ultraviolet cured, and the raised portion of the resin is scraped preferably with a scraper to be planarized. 
     According to the blasting apparatus  1  described above, the scattering force of the abrasive  100  (the force of the abrasive  100  scattering around), which is blasted from the blasting nozzle  2 , passes through the blast hole  10   b  of the cover  10  and strikes the surface  200   a  of the glass substrate  200 , that is, the abrasive  100  used for blast processing in which the depressed portion  200   b  is formed by striking the surface  200   a  of the glass substrate  200  with the abrasive  100 , is abated more as the abrasive  100  farther scatters around radially through the clearance  13  provided between the surface  10   a  of the cover  10  and the surface  200   a  of the glass substrate  200 , and then the abrasive  100  is collected by suction from the collecting port  11   d.    
     Therefore, the blasting apparatus  1  is capable of preventing the suction power from influencing the striking power of strikes of the abrasive  100  on the surface  200   a  of the glass substrate  200  even when the suction power from the collecting passage  11   c  is increased so that the abrasive  100 , even having a small grain diameter, may be sufficiently sucked. In addition, the blasting apparatus  1  is capable of maintaining the blast processing accuracy, and collecting the abrasive  100  while preventing the abrasive  100  from scattering around. 
     Having the configuration that the open end  11   e  of the collecting case  11  is flush with the surface  10   a  of the cover  10 , the blasting apparatus  1  allows the abrasive  100  to be sufficiently sucked and collected from the collecting passage  11   c  provided to the collecting case  11  even when the surface  10   a  of the cover  10  is brought closer to the surface  200   a  of the glass substrate  200 , that is, even when the clearance  13  provided between the surface  10   a  of the cover  10  and the surface  200   a  of the glass substrate  200  is narrowed. 
     Having the configuration that the nozzle case  9  has the conical shape such that the side wall  9   a  of the nozzle case  9  expands toward the direction in which the abrasive  100  is blasted, and the collecting case  11  has the conical shape such that the side wall  11   a  of the collecting case  11  expands toward the direction in which the abrasive  100  is blasted, the blasting apparatus  1  allows the surface  10   a  of the cover  10  to obtain a size enough to abate the scattering force of the abrasive  100  that is used for blast processing the surface  200   a  of the glass substrate  200  and scatters, and allows a downsizing of the nozzle case  9  and the collecting case  11 . 
     The foregoing descriptions of the preferred embodiments of the present invention have been presented for purposes of illustration and description with reference to the drawings. However, it is not intended to limit the present invention to the preferred embodiments, and modifications and variations are possible as long as they do not deviate from the principles of the present invention. 
     For example, though the blasting apparatus  1  described above has the configuration of a so-called suction blasting apparatus, the present invention is not limited to the embodiments described above and can be applied also to a pressure blasting apparatus or a centrifugal blasting apparatus. 
     Described above is the configuration that one suction port  11   f  is provided to the collecting case  11 ; however, two or more suction ports are preferably provided thereto in order to increase suction power to collect the abrasive  100 . 
     In addition, described above is the configuration that the depressed portion  200   b  is formed on the surface  200   a  of the glass substrate  200  in the blast processing; however, the present invention is not limited to the embodiments described above, and the blasting apparatus according to the present invention can be used also for forming a groove or a through-hole in the glass substrate  200 .