GB1292127A - Method and apparatus for drying tobacco - Google Patents

Abstract

1292127 Automatic control of tobacco HAUNI-WERKE KÍRBER & CO K G 18 Dec 1969 [15 Jan 1969] 61733/69 Heading G3R A substantially constant flow of tobacco is dried by two sources of heat in succession, the first being automatically controlled by the moisture content of the tobacco before it reaches that source, and the second being automatically controlled by the moisture content of the tobacco after it has passed that source. In Fig.4, tobacco is fed from a supply 201 to a store 230 by a pin belt 252 driven at one or other of two speeds by a pole-changing asynchronous motor 247. When the tobacco in store 230 rises to the level of a photo-electric detector 233, a relay 246 is operated to run the motor at a low speed, and when the level falls to a photo-electric detector 232 the motor runs at a high speed to tend to maintain the level between the detectors. Tobacco from store 230 is transported by belt conveyers 211, 216, 22, and mass flow is maintained constant by comparing a signal 213, dependent on the weight of tobacco on conveyer 216, with a desired weight determined by the setting of a potentiometer 219 so that any difference controls, through a magnetic or thyristor amplifier 224, the speed of a motor 212 driving conveyer 211. Delay units 239, 241 prevent relay operation by the effect of tobacco falling past the detectors. In a modification, store 230 is fed directly from supply 201 by means of a carding roll the speed of which is automatically controlled to keep the level between the detectors. Conveyer belt 22 supplies the tobacco via a vibratory feeder 16, Fig. 1, into a rotating drying drum 11. A condenser 19, influenced by the tobacco on feeder 16 and forming part of an oscillatory circuit associated with a wobbulator 43 and peak voltmeter 47, produces a signal representative of moisture content which is compared with a reference value from a potentiometer 49 so that any difference is effective to set the datum of a system which automatically controls the temperature of air electrically heated at 63 and supplied by a fan 64 through a duct 54 to drum 11. This system controls the setting of a flap valve 61 mixing hot and cold air in response to the temperature of the mixed air at 53. Dried tobacco from drum 11 is transported by belt conveyers 24, 32 and a vibratory conveyer 27. A condenser 29 influenced by the tobacco on feeder 27 produces a signal representative of moisture content, in a manner similar to condenser 19, to vary the datum of a system automatically controlling the supply of steam from a source 8 to heaters 12 within the drum. This system controls the setting of a steam valve 86 in response to the pressure of steam applied to the drum at 77. In a modification, the steam heating is uncontrolled and moisture content of the tobacco leaving the drum is corrected by automatically controlling the datum of a temperature control system associated with a hot air supply to the outlet end of the drum.