Rieter

Classification

Index

Since, as already discussed, the blowroom line is a sequence of individual machines, each machine must always receive an exact quantity of material per unit of time from the preceding machine, and must pass on the same quantity per unit of time to the next. To ensure an adequate flow of material, the machines are adapted to each other so that each machine can produce a little more than the succeeding machine requires. Since each machine has excess capacity, a control system must be provided to ensure the correct delivery quantities. Two basic principles are used: batch operation and continuous operation.

In a hopper feeder, for example, the conveyor (1, Fig. 70) places material into the hopper until sensing lever (a) is pushed so far to the right that a contact is made to switch off the drive of conveyor belt (1). In exactly the same way, during filling of the reserve hopper (R), the pressure exerted by the column of material eventually becomes so great that sensing lever (b) is depressed; this causes the preceding machine to be switched off . When the column of material has again been largely removed by conveyor (1), the sensing lever rises, the preceding machine is switched on and the reserve chute is refilled. Unfortunately, in practice the individual machines actually produce during a period that is often only 50% of operating time and are unproductive during the remainder of the operating time. On the other hand, in continuous operation created by changing the speeds of the machines, the machines’ production rates are much more closely adapted to each other. They operate almost continuously and without stops. A fine control device serves to maintain material throughput by adjusting the production speeds of the individual machines. Batch operation has the advantage that the machines always run at the same speed and with the same production rate when they are in operation. The treatment of the material remains uniform all the time. That means that the raw material is always processed under the same conditions, since there are only two treatment levels – full on or off . In continuous operation, however, there are continual slowdowns and accelerations, with possibly varying intensities of treatment of the raw material. Data provided by Trützschler indicate that there are no negative effects, provided variations in production rates do not exceed ± 20%. The disadvantage of batch operation lies in the incorrect handling of the material throughput. As machines often do not operate during 50% of the time, in their productive periods they are not working at, e.g., 300 kg/h as calculated by the spinner; instead they are actually processing material at a rate of 600 kg/h. The loading of the machine is high, and that might lead to a correspondingly poor cleaning effect. In the mill, therefore – and this is very important – an attempt should be made to regulate the installation so that the productive time of the individual machines is very high, and only few non-productive periods occur.

Fig. 70 – Regulated feed of material in the hopper feeder