GB1175366A - Method and Apparatus for use in making Asbestos-Cement Shapes. - Google Patents

Abstract

1,175,366. Extruding asbestos-cement; removing moulded products. CERTAIN-TEED PRODUCTS CORP. 6 Dec., 1966 [6 Dec., 1965], No. 54619/66. Heading B5A. [Also in Divisions B2 and C1] Asbestos-cement boards or pipes are made using a combined mulling, mixing and extrusion machine, the dry ingredients being intermixed by mulling wheels 28 in a muller crib 18 to which mixture water is subsequently added, the mulling being continued thereafter only until all the ingredients have been wetted. From crib 18 the wet mix is transferred on opening a gate (21), Fig. 6 (not shown), to a pug mill 8 and a further transference occurs on rotation of pug-screw 15 to an extruder 9 via vacuum chamber 10. The mix is comminuted by choppers 16 before entrainment by screw impeller 12. As shown, extrusion nozzle 13 has a rectangular orifice and the extrudate is supported by a table 60, which is preferable at least twice the length of the board length required. The extrudate is cut by transversely operating saws 69 and/or (71), Fig. lb (not shown). On table 60 is placed a carrier board (66), Fig. 2 (not shown), and to facilitate movement of the extrudate a sheet 68 of material having a low coefficient of friction, e.g. waxed paper, is used which moves therewith. Table 60 is tiltable by a mechanism 61, 62, 65, to straighten the extrudate which is sufficiently plastic to be aligned by a " straight edge "(70), Fig. 2 (not shown). To ensure that mulling may be terminated at the required instant after addition of the water to the mix, mulling wheels 28, Fig. 4, are supported on pivoted brackets 30 moved to render the wheels operative or inoperative by piston and cylinder arrangements 35, 37, fixed to rotatable hub 32. The downwards travel of wheels 28 is limited by adjustable screws 51 which abut face 52. Also provided are scraper blades (54, 57 and 58), Fig. 5 (not shown). A suitable fluid-pressure control system is described, Fig. 7 (not shown). Figs. 8-13 (not reproduced), show a sequence of operations in a delivery system where carrier boards (66a) are moved on roller ways (74) to extrusion nozzle 13 and thence to positions alternately upstream and downstream thereof where the extrudate is straightened. The preferred proportions of the mix are 18-48 parts by weight of asbestos, e.g. chrysotile slip fibres, for each 100 parts of cement, and between 23 and 28 parts by weight of water for 100 parts of the dry ingredients. As optional additives, up to 100, but preferably not more than 66À7 parts by weight of silica for each 100 parts of cement may be used and from 0À2 to 0À5% by weight of lubricants such as high molecular weight water-soluble polymers of ethylene oxide.