Patent GB-675713-A (GB)
Title: Improvements relating to the manufacture of fibrous cement sheets
IPC: B28B1/52
Filed: 1951-01-19
Abstract: 675,713. Making fibrous cement sheets. MAGNANI, A., and SMIDTH & CO., AKTIESELSKAB, F. L. Jan. 19, 1951, No. 1551/51. Class 87(ii) The object of the invention is to improve the manufacture of fibrous cement sheets from a pasty aqueous mass by simultaneously calendering them and compressing them, whereby the desired compression of the sheets is obtained and the water necessary to ensure effective calendering is forced to the surface. An endless water-permeable belt 4 overlies and is supported by a continuous moving chain of suction boxes 1, hinged together, and is associated with means 13 for feeding and distributing fibrous cement material over the belt and forming it into a sheet thereon, and a calendering and compressing element 25 is mounted and arranged for simultaneous movement parallel with the direction of movement of the chain of suction boxes and towards and away from the chain. The chain is carried over wheels 2, with adjustably mounted bearings, and its upper length moves over and is supported by hollow guides 8 which communicate through pipes 10, 10' with a vacuum pump. The endless belt 4, of water-permeable fabric, passes around rollers 5, between discs 7 and at a point 6 is removed from contact with the formed fibrous cement sheet 42 in a perpendicular direction. The discs 7 corrugate the belt to conform to the shape of the sheet to be manufactured, and the belt is washed at 11. 13 denotes the end walls of a bottomless trough, of which the two side walls are constituted by rollers 12. Wheels 14 on the roller shaft run on rails 15, one set of wheels being driven from a motor 16 through gearing 17 which causes a reciprocating movement. The material in the form of a pasty mass, is fed to the trough by a movable pipe 17<SP>1</SP> which, as the trough reciprocates, is moved laterally to and fro by an obliquely disposed guide 18, resulting in thin overlapping layers of material on the fabric belt. The compressing element 25 is a roller rotatably mounted on a shaft 38, Fig. 4, and fixed to a pulley 34 belt-driven from a motor 28 through reduction gearing 27. The shaft 38 has an eccentric hubbing 39 which runs in a bearing 40<SP>1</SP> and the shaft is rotated by a belt drive from the reduction gearing 27 to a pulley 33 mounted on it. The roller 25 therefore rotates on an axis which has a small circular movement and alternately presses on and eases from the surface of the formed sheet 42, thus achieving the object of simultaneous calendering and compressing. The rollers 25 and their associated mechanisms can be multiplied and there may be in addition a compressing roller 19 on a truck 20 reciprocated on rails 24. A partition 8<SP>11</SP> in the hollow guide 8 enables a different vacuum to be maintained beneath the rollers 25, through the pipe 10<SP>1</SP>, or suction to be cut off entirely, whereby the amount of excess water removed may be controlled. The belt 4 may be supported below the roller 25 on a table instead of a hollow guide and then no excess water is removed at that point, although before it reaches the table the belt may pass over a suction roller. The table may be replaced by a roller or other movable support, suction or otherwise. In a modification of the means to give the calendering roller the required simultaneous compressing movement, Fig. 5, the roller 25 is rotatable on a shaft 45 on which is keyed an eccentric 53 supported in a bearing 52. The free end of the shaft is driven from a driving mechanism (not shown) and owing to the eccentric mounting its axis moves in a circular path. The roller 25 is driven from the shaft 45 through gear wheels 51, 50, 47, the shaft 48 to which the gear wheels 50, 47 are fixed being rotatable in the ends of arms 49 pivoted on the shaft 45, so that the roller and gearing can follow the eccentric movement of the shaft. In a further modification, Fig. 7, the roller 60 is rotatably mounted at the lower ends of rods 61, the upper ends of which are pivoted on a shaft 62 which is urged downwards by springs 63. The roller is belt-driven from a pulley 66 which is also a crank disc from which connecting rods 65 oscillate the rods 61 and causes the roller 60 to follow a pendulum movement. The pressure may be adjusted by altering the springs 63. Specification 656,846 is referred to.