GB1102063A - Apparatus for producing sheets and tubes of fibrous cement by winding a web of plastic mass of fibrous cement on to a sizing roll or a mandrel - Google Patents

Abstract

1,102,063. Manufacturing cement pipes. K. A. OESTERHELD. 10 Feb., 1965 [19 Feb., 1964], No. 5738/65. Heading F2P. In apparatus for producing sheets and tubes of fibrous cement wherein a web of fibrous cement conveyed by an endless felt belt 11 is wound, compressed and dewatered on a vertically movable mandrel carried on pivoted arms 4, a breast roller 6 is driven at a constant but variable speed by a first motor (not shown) and the mandrel is directly driven by second hydraulic or electric motor, the driving torque of which varies automatically as the being- formed tube wall thickness increases. Said torque produces a thrust on the mass of cement at the nip between the mandrel and the breast roller which is less, equal to or greater than that thrust exerted by the breast roller. As illustrated, the mandrel is driven by a D.C. motor 24 through worm gearing 32, 34 and a belt drive 35, 36, the motor itself being driven at a speed proportional to the breast roller by a generator (20), Fig. 2 (not shown), of a Ward- Leonard system whose field is energized by the rectified voltage of a tacho-generator 18 driven through a belt 17 by the driving motor (not shown) of the breast roller. In operation, as the wall thickness of the being-formed tube grows, the mandrel motor speed is reduced by the frictional contact between the mandrel and the cement until the peripheral velocities of the mandrel and breast roller are the same. This reduction in speed reduces the back e.m.f. of the mandrel motor and induces a correspondingly increased mandrel motor-driving torque. In an alternative system, Figs. 5, 6 and 7 (not shown), the motor is driven by an hydraulic motor (37) fed by a motor-driven swash-plate type pump (53) whose volume output is controlled through valves (55) and (50) by a centrifugal governor (43) driven by the mandrel. As the mandrel speed is decreased by the frictional interference between it and the breast roller on increasing wall thickness of the being-formed tube, valves (50) and (55) are operated to reduce the volume of fluid directed to the motor (37) by the pump thereby reducing the torque applied to the mandrel. This permits the outer layers of the formed pipe to be applied with a relative higher tension than the inner so that the compressive effect on the outer layers on opening out the pipe into sheet form is counteracted. In a modification of the latter system, Figs. 7-8 (not shown) the governor is replaced by a cam and cam follower (62) and (48) respectively. In a further modification, Fig. 9 (not shown), the control valve (50) is replaced by a continuously-operated motor-driven pump (65) actuated by a time control clock (63) said clock being started by a limit switch (68) and being switched off by a preset michro-switch (69) when the being- formed tube is completed. The output of the pump continuously acts to progressively reduce the fluid supply the mandrel motor thereby progressively reducing the drive torque applied to the mandrel.