Virtually every large letter delivered by mail in Germany passes through a sorting facility that contains inventions created by Dr. Wolf-Stephan Wilke (49). The letter sorting machines developed by Wilke are much faster than conventional units. That's why Germany’s Deutsche Post operates them in each of its 82 letter sorting centers. The postal services in Sweden and Austria also use these machines.

The secret behind the success of Wilke’s sorting machines lies in their architecture. At around 50 by 20 meters, they are exactly the same size as conventional units but are nevertheless able to process many more large letters in the same period of time. Sorting machines normally operate with a pocket carousel — a type of chain equipped with pockets that are arranged one after the other. The carousel moves above a row of stationary containers into which the large letters are sorted by address. Once the carousel reaches the right container, the corresponding pocket opens and the letter is dropped inside. Wilke’s innovation was to mount the containers onto a moving chain that runs counter to the carousel. The advantage of this approach is that it allows the number of carousels, and thus letter throughput, to be increased many times over. Siemens has built sorting facilities for Deutsche Post that contain two carousels and containers that rotate under them. “When I started thinking about how we could raise the throughput, I realized that if we moved the containers as well as the carousels, we could ensure that they would always pass under all the pockets,” Wilke explains.

Deutsche Post uses these machines as incoming and outgoing sorters at all of its 82 letter sorting centers. Large letters that arrive at a postal center are sorted into containers for delivery to the other 81 centers. A new electronically stored sorting plan is selected, and then the machines begin sorting the letters going to the addresses in each of the centers. “The new machines not only collect all of the letters for a particular postal center, as previous systems did; they also put them in the right order for the delivery route, according to streets and house numbers,” says Wilke.

It took ten years to get from Wilke’s original idea to a finished product. After Wilke developed the basic concept for the machine architecture, his colleagues began developing everything from software to component arrangements for the sorting facilities. “That was a great feat of teamwork,” says Wilke, who for this reason views his Inventor of the Year Award as an honor that actually belongs to everyone involved in the project. In his capacity as a product manager, Wilke was responsible for overseeing another innovation that’s also used at the new Deutsche Post sorting facilities: an image recognition system that identifies large letters and therefore eliminates the need for barcodes or stickers.

Wilke has been working at Siemens for 11 years. After studying mechanical engineering in Karlsruhe, he earned a Ph.D. with a dissertation on solar architecture that he wrote while working at the Fraunhofer Institute for Solar Energy Systems in Freiburg. “Back then, we thought about using building walls as solar collectors, but the idea never really got off the ground,” says Wilke, who later began working with conventional energy technologies at a Swiss company. Wilke started working for Siemens in Konstanz in 2000. He was initially assigned to the Industry Sector, where he helped develop new logistics solutions for postal applications. “Since that time I’ve been very inventive as well,” he explains. Indeed, during his 11 years at Siemens, Wilke has registered 53 inventions, which have led to 72 individual patents and 42 patent families.

Wilke likes to sail in his free time — and he and his wife have also put to good use the rooms his grown children used to occupy. For example, he has resumed his childhood hobby of playing with model trains — but even here, Wilke has taken an unconventional and inventive approach, as he’s now building a digitally controlled model train track. “It’s going to take me a while to finish it,” he says. “But that’s fine, because I enjoy working on it just as much as I’ll enjoy playing with it later.”

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