| 摘要 |
1,270,773. Grinding. JOHNS-MANVILLE CORP. 24 April, 1970 [5 May, 1969], No. 19676/70. Heading B3D. [Also in Division B6] A stone-like textured surface is produced on a cementitious sheet such as an asbestos-cement sheet by texturing the sheet surface before cure so as to have high and low surface areas, curing the sheet to a hardened state with the sheet having a bloom deposition on the textured surface, buffing the textured surface with a resilient and compressible abrasive material so that the high and low areas are contacted but with varying pressure such that the bloom is removed from high portions and left on the low portions of the textured surface. The term " bloom " is defined as meaning either a deposit of water-insoluble calcium silicate hydrate produced by precipitation on the surface of a cementitious composition during a steam curing operation or a deposit of water insoluble calcium carbonate produced by precipitation of such material on the surface of a cementitious composition during a normal curing operation or by exposure of the composition to a carbon dioxide atmosphere under pressure in the presence of moisture. The abrasive material may comprise a resilient, compressible matrix of fibrous material having a fine abrasive bonded thereto. The abrasive material may be in the form of a belt, or a wheel comprising ring-like pads made of a nylon web with aluminium oxide, silicon carbide or flint particles bonded to the fibres in the matrix. Alternatively the abrasive material may be steel wool. A textured asbestoscement sheet may be formed from an asbestoscement aqueous slurry which is introduced into the cavity of a textured die plate press. As shown in Fig. 3, textured sheet 10 covered with bloom is carried along by conveyer 22 above which is mounted for rotation above the conveyer a shaft 28 carrying ring-like abrasive pads 30. |
