Controled filling and emptying of granulate hoppers for feeding extruder involves filling storage hopper with part of hourly material requirement which is completely emptied into weighing hopper before refilling

摘要

The hopper system comprises a storage hopper(7) and a weighing hopper(4) with computer controled output to an extruder below. The amount(8) of granulate material in the storage hopper forms a fraction of the hourly usage for each component. At each filling stage the fraction in the storage hopper is completely emptied into the weighing hopper and a further similar fraction is then delivered to the empty storage hopper. Amounts(8) of granulate in the storage hopper can be freely chosen and are programmable. The percentage of granules in the storage hopper relative to the hourly throughput in an extrusion plant is almost the same for each component. At the start of a particular production run the amount added to the storage hopper can be relatively large, but decreases towards the end of the run. Determination of individual amounts added to the storage hopper can be made by calculating the filled level(10) in the hopper and controling with an ultrasonic sensor(9) on the hopper. For determination of material weight added to the storage hopper the latter is mounted on a weighing cell which allows the filling level to be measured. Filling ends when the correct weight is reached. Alternatively the level of material during filling can be determined by a level sensor. Sensor positions can be set as required by a servomotor and height setter. After setting the filling amount all further stages are automatically controled by a computer.