a method of regulation of the charging of the feed hopper of an extruder with plastic granules , where it is necessary to supply the material in an amount such that the average level in the container or hopper remains constant with the least possible fluctuation despite the continual , and as a rule , uninterrupted removal of material from the container in the case of which , despite uninterrupted removal of material , the average level in the hopper or other container is maintained and is subject to the least possible fluctuation .