Development of a Fully Automated Circulating Letter Sorting Machine

We have developed a machine that can sequence 2 000 letters into a specified order in 15 minutes. It singles out a letter from a stack of letters supplied into the feeder, transports it to a bar code reader that reads the address information, and stacks it in a bin according to the address. To increase the throughput, we have developed downward feeder, instead of upward feeder and switchback mechanism. As sorting algorithm, we have applied the radix sorting method, because of the higher throughput and simple arrangement. To sequence letters based on the method, it is necessary to repeat the sorting. After all letters have been stacked into bins, the letters are transferred from the bins to the feeder automatically. An interchanging bin / feeder mechanism makes circulating possible.