| 摘要 |
750,619. Abrasive articles. M. & M. RESEARCH & DEVELOPMENT CO. June 23, 1953 [Oct. 10, 1952], No. 17427/53. Class 60. The firmly bonded abrasive material constituting the main body of an abrasive article has dispersed therein loosely bonded abrasive material of a hardness and fracture resistance comparable to that of the firmly bonded abrasive material so as to be capable of being bodily dislodged from the firmly bonded material by the action of engagement of the abrasive article with a workpiece, so as to self-dress the working surface of the firmly bonded material by the mechanical action of the dislodged loosely bonded abrasive material disposed between the surface and the workpiece. The firmly bonded abrasive material may be crystalline oxides, natural or synthetic such as alpha-corundum, beta-corundum, naxos-emery, spinel etc.; carbides such as silicon carbide, boron carbide; or a combination of such materials. The bond may be vitrified, resinoid, shellac, rubber, silicate, magnesium oxychloride or metallic. The loosely bonded abrasive may be of the same material or combination of materials as the firmly bonded abrasive. The loosely bonded doxosive may be in the form of grains coated with a refractory' oxide, e.g. magnesia, alumina or silica, to inhibit bonding by the bond for the firmly bonded grains. Alternatively, preformed pellets may be used comprising grains bonded by a bond weaker than that used for the firmly bonded grains; polyvinyl alcohol, dextrine solutions, methyl cellulose, urea resins, melamine resins, casein, starch, gum tragacanth, gum, acacic, alginates and blends thereof may be used. |
