Patent GB-756222-A (GB)
Title: Process and apparatus for the grinding and polishing of glass
IPC: B24B7/24
Filed: 1952-05-23
Abstract: 756,222. Grinding and polishing flat glass. SOC. ANON. DES MANUFACTURES DES GLACES ET PRODUITS CHIMIQUES DE ST-GOBAIN, CHAUNY & CIREY. May 23, 1952 [May 24, 1951], No. 13194/52. Class 60 Apparatus for grinding and polishing the surface of a glass sheet 1 fed continuously with respect to abrasive members is provided with at least one abrasive member 2. Fig. 2, actuated with a periodic movement of translation having an amplitude between 1mm. and several cms. and arranged to sweep an area of the sheet having a constant dimension in the direction of displacement of the glass. In grinding, the amplitude of movement of successive tools is decreased with decreasing size of abrasive grain while the frequency of the movement, which varies from one hundred to several thousand per minute, is increased. In polishing, the amplitude and frequency are increased together so that the ridges produced by the nogs of the polishing tools are attenuated. The abrasive member consists of a shoe of duralumin covered with felt or semi-hard rubber and provided with jets through which 'an aqueous suspension of rouge is fed under pressure. The rubbing surface of the shoe has a length slightly less than the width of the glass sheet so that it never crosses the edges of the latter and undue wear is thereby avoided. The shoe is supported by springs 3, 4 from a cross member 5 and is slidably engaged at its ends by synchronous motors 6, 7 which are connected to eccentric discs 8, 9 so that the shoe is moved in a circular path. In a further construction, one motor 10 supported by the framework of the apparatus is used. This motor drives, through gears 12, 13 and shafts 15, flexible shafts 16 journalled in the shoe 19 and connected to eccentric masses 20 which deflect the shafts 16 and hence impart a circular movement to the shoe. Pressure is adjustably applied to the latter by pneumatically loaded pistons 21, ball thrust bearings 24 being interposed between the piston rods and the shafts 15 which are slidably keyed to the gears 13. Alternatively, the circular movement may be derived from the eccentrics fitted to the shafts 15. The abrasive element may also be moved in an ellipse or a straight line, and if electro-magnets are used to actuate it, it may be moved according to a Lissajou figure the axes of which vary in orientation and dimension. To prevent the formation of a "combed" surface on the glass, a slow alternating movement, in addition to the periodic movement, is imparted to the abrasive elements which may then project over the edges of the glass sheet. In this arrangement, the abrasive element may consist of a slowly moving endless belt driven by worm gears from the ends of the shafts producing the periodic movement. Two belts travelling in opposite directions may be provided at each abrasive element or, alternatively, the belts of adjacent elements may run in opposite directions. The belt which may consist of coated glass threads or reinforced rubber covered with a layer of felt or resin, is scraped or cleaned on its upper run which is not in contact with the glass.