Polishing method by blasting and nozzle structure for a blasting apparatus for use in the polishing method

Abstract

In a polishing performed by imparting kinetic energy to abrasive using a compressed gas flow, horizontal cutting force is obtained while vertical cutting force acting on a surface of a workpiece is inhibited. A compressed gas containing no abrasive is ejected from an accelerated flow generation nozzle 10 toward a surface of a workpiece W to generate an accelerated flow S along the surface of the workpiece W. Also, abrasive 30 is introduced into an abrasive introduction path 20 opening toward the surface of the workpiece W at an area where the accelerated flow S is generated, preferably together with a compressed gas to merge the abrasive 30 with the accelerated flow S and make the abrasive 30 slide along the surface of the workpiece W. Thus, horizontal cutting force is exerted on the surface.

1 . A polishing method by blasting, comprising the steps of:
 introducing a compressed gas containing no abrasive as an ejection fluid into an accelerated flow generation nozzle arranged to be pointed at a surface of a workpiece and ejecting the compressed gas to generate an accelerated flow along the surface of the workpiece, and   introducing abrasive into an abrasive introduction path opening toward the surface of the workpiece at an area where the accelerated flow is generated to merge the abrasive with the accelerated flow and make the abrasive slide along the surface of the workpiece.   
     
     
         2 . The polishing method by blasting according to  claim 1 , wherein the abrasive is mixed with a carrier fluid which is a compressed gas at a pressure lower than the pressure of the ejection fluid introduced into the accelerated flow generation nozzle, to be introduced into the abrasive introduction path. 
     
     
         3 . The polishing method by blasting according to  claim 2 , wherein a pressure of the carrier fluid is set to two-thirds or less of that of the ejection fluid. 
     
     
         4 . The polishing method by blasting according to  claim 1 , wherein a gap between an opening of the abrasive introduction path and the surface of the workpiece is larger than a gap between an ejection orifice of the accelerated flow generation nozzle and the surface of the workpiece. 
     
     
         5 . A nozzle structure for a blasting apparatus, comprising:
 an accelerated flow generation nozzle for ejecting a compressed gas containing no abrasive supplied as an ejection fluid from a compressed gas supply source toward a surface of a workpiece to generate an accelerated flow along the surface of the workpiece, and   an abrasive introduction path opening toward the surface of the workpiece at an area where the accelerated flow is generated and having abrasive from an abrasive supply source supplied thereto.   
     
     
         6 . The nozzle structure for a blasting apparatus according to  claim 5 , wherein the abrasive introduction path is made to communicate with the abrasive supply source for supplying the abrasive as a mixture fluid with a carrier fluid which is a compressed gas. 
     
     
         7 . The nozzle structure for a blasting apparatus according to  claim 5 , wherein an end portion of the accelerated flow generation nozzle on the ejection orifice side is arranged in the abrasive introduction path. 
     
     
         8 . The nozzle structure for a blasting apparatus according to  claim 5 , wherein an ejection orifice of the accelerated flow generation nozzle is formed into a form of a slit, and an opening of the abrasive introduction path is arranged parallel to the ejection orifice. 
     
     
         9 . The nozzle structure for a blasting apparatus according to  claim 8 , wherein the opening of the abrasive introduction path is arranged on each of opposite sides of the ejection orifice of the accelerated flow generation nozzle. 
     
     
         10 . The nozzle structure for a blasting apparatus according to  claim 5 , wherein a gap between an ejection orifice of the accelerated flow generation nozzle and the surface of the workpiece is set to 0.5 to 3.0 mm, and a gap between an opening of the abrasive introduction path and the surface of the workpiece is formed to be wider than the gap between the ejection orifice of the accelerated flow generation nozzle and the surface of the workpiece by 1.0 to 3.0 mm. 
     
     
         11 . The nozzle structure for a blasting apparatus according to  claim 10 , wherein the ejection orifice of the accelerated flow generation nozzle protrudes from the opening of the abrasive introduction path in an ejection direction by 1.0 to 3.0 mm.