Combinational weighing is carried out firstly by calculating combinations of weight signals from a plurality of weighing devices each weighing a batch of objects to be packaged and selecting a combination having a total weight satisfying a specified criterion with respect to a target value, and secondly by re-checking the weight signals from the weighing devices of the selected combination before discharging the objects therefrom. The value of the difference between the total weights obtained at the time of the combinational calculations and at the re-checking time is stored cumulatively after each cycle of operation, and a new target value is calculated and set after each cycle from many stored difference values from previous cycles in order to improve the work efficiency and the yield at the same time. According to a preferred embodiment, the difference between the weight values obtained at these two times of measurement is cumulatively stored after each cycle for all weighing devices and a new target value is calculated by considering the distributions of past difference values corresponding to the individual weighing devices of the selected combination.
A batching of currently supplied articles with non-uniform weights into portions of a uniform target weight is effected by passing the articles through a weighing station (6, 8) to a distribution system (12), in which the articles (4) are selectively allocated to a plurality of receiver bins (14). It is known to improve the capacity of such a system by way of probability calculations based on the normal distribution of the articles in the supply flow, but it is better to base such calculations on a regularly updated recorded histogram (28) of the weight distribution of a relatively high number of newly weighed articles. Thereby the target calculations will rely on factual rather than just expected conditions, and a result is that it is possible to effect batching even when the article weights in the supply flow are not normally distributed.
A batching of currently supplied articles with non-uniform weights into portions of a uniform target weight is effected by passing the articles through a weighing station (6, 8) to a distribution system (12), in which the articles (4) are selectively allocated to a plurality of receiver bins (14). It is known to improve the capacity of such a system by way of probability calculations based on the normal distribution of the articles in the supply flow, but according to the invention it is still better to base such calculations on a regularly updated recorded histogram (28) of the weight distribution of a relatively high number of newly weighed articles. Thereby the target calculations will rely on factual rather than just expected conditions, and a very important result is that it is possible to effect relevant batching even when the article weights in the supply flow are not normally distributed.
An improved feeder control system is disclosed. The system implements an incremental metering process that incorporates the standard deviation of the material feeder. By intentionally initially under metering at a level corresponding the standard deviation of the feeder, and then subsequently metering a more accurate delivery of materials is achieved. Additionally, the system implements a system for correcting for metering errors caused by gate cycles delays. By incorporating offsets into a feed time when gate cycle time is larger than the feed time, error caused by significant gate cycle times is cured.
