At every sorting office of Deutsche Post AG, the systems carry out two key tasks. First, they sort all the shipments to be dispatched according to their destinations. This is known as outward sorting. Then, systems at the destinations put the letters in the order that the postal delivery workers’ rounds are made, so that the mail carriers don’t have to rifle through the pile of mail every time they stop at a mailbox.

At the moment, postal services are starting to introduce this sorting process according to rounds not just for standard letters, but also for larger envelopes, which are known in the industry as "flats." In this context, it is highly advantageous if the volume of flats for the individual delivery points can first be brought together separately within the system, i.e. not yet forming a single pile for the postman. "It was from this perspective in particular that I thought about how a single system for flats could master these two tasks," says Dr. Berdelle-Hilge.

The starting point was two system concepts with very different topologies. Each topology was optimized for one of the two tasks. With the Open Mail Handling System, a sorting system from Siemens that Deutsche Post AG is currently using in a pilot study, two carousels lie on top of each other, turning in opposite directions. The top one, which first picks up the unsorted flats in individual bags, drops a letter at exactly the moment when the bag is above the relevant container on the lower carousel. The top carousel is only half as long as the bottom one, which has an individual container for each sorting point, e.g. a delivery center. The Integrated Flats Processor, on the other hand, works the other way round. Here, the bottom carousel is only half as long as the top one although the rest of the architecture is similar.

In order to be able to nevertheless combine the two systems, Dr. Berdelle-Hilge designed a new architecture in which the two carousels were of the same length. Through a special arrangement and the use of several loading and unloading points in both carousels, along with different carousel speeds for the two sorting tasks, the inventor succeeded in enabling one and the same system to be used in sequence both for outward sorting and for the special round sorting of flats.

The system’s topology also brings a second important benefit. Because the volumes of flats at the individual delivery points are still separate within the system, a loading device for each delivery point can add the associated letters that were previously placed in the same round sequence by a different system. "So far, this has not been possible through automated means, which is why the postman always has to check two piles of mail in order to remove everything for that particular mailbox," explains Dr. Berdelle-Hilge.

This optimization is leading to noticeable time savings when it comes to mail delivery. On the approximately 237,000 postal routes in the U.S. – which, with around 50 percent of the world’s mail volume, represents the biggest market – around 130 million mailboxes have mail delivered to them every single working day. If only a few seconds are saved each time, the total time saved rapidly amounts to several tens of thousands of hours a day. And so the good old postal service has once again become just a little bit faster.