Many innovations for rail vehicles aim to reduce energy consumption in order to make mass transportation systems less costly and more environmentally friendly. This is also the objective that Toni Schiffers (48) an engineer from Erlangen, pursues by means of his inventions. A brake specialist by trade, Schiffers has developed a self-energizing hydraulic brake system for rail vehicles. The brake not only saves a lot of weight but also sets the required braking energy with great precision.

Technical systems for rail vehicles have extremely long service lives. “In principle, the compressed-air brake that George Westinghouse developed back in 1869 is still the standard solution for trains,” explains Schiffers, who works at the Rail Systems Group of Siemens’ Infrastructures & Cities Sector. Schiffers had already specialized in hydraulics while studying mechanical engineering at university level. He subsequently worked for all of the major brake system manufacturers before joining Siemens in Erlangen in 2004. “At that time, the company had just started to gain further brake system know-how of its own,” he says.

His first task at Siemens was to investigate whether the wedge brake that had just been developed for automobiles would also be suitable for rail vehicles. In cooperation with RWTH Aachen, Schiffers conducted a number of studies which showed that electronic wedge brakes were inappropriate for rail vehicles because most of the components had been developed for automobiles and as a result could not be installed into trains. “There just weren’t enough synergies,” he explains. The brake systems that are installed underneath the bogies of trains have to be extremely robust so that they can operate reliably in spite of exposure to strong vibrations, blows, temperature fluctuations, and moisture. Although the rather delicate nature of the wedge brake’s precision mechanics makes them unsuited for use in rail vehicles, Schiffers continues to work on energy-saving brakes for trains.

From the very start, Schiffers focused on creating a decentralized, self-energizing hydraulic system with controlled retarding force. “Compared to today’s compressed-air brake, it would allow us to adjust the braking force in rail vehicles much more precisely and also increase the precision of the braking distance,” explains Schiffers, who cooperated very closely with RWTH Aachen on this project as well. The self-energizing hydraulic brake generates the pressure and thus the braking force itself because it is connected to the chassis via an intermediate hydraulic cylinder. Whereas in conventional brake systems the higher-level pneumatic brake control unit sets the pressure on the brake liners, the decentralized hydraulic brake controls the target braking force itself in the form of the retarding force. “Because hydraulic pressure can be measured with great precision, we can calculate the retarding force and brake with pinpoint accuracy,” explains Schiffers. The first systems to greatly benefit from his invention are railcars and subway trains. Because valve panels, tubing, and compressor modules are no longer needed, the weight can be greatly reduced — up to several hundred kilograms per car for some types of rail vehicles. What’s more, the decentralized hydraulic brake saves space and can be very easily installed. “All you have to do is screw it on and stick in the plug, and you’re done,” says Schiffers. “The number of interfaces is kept to a minimum, and the brake can be very easily parameterized to meet project-specific needs. It has neither pneumatic nor hydraulic interfaces connecting it to the vehicle!“

Schiffers showed a lot of perseverance during the system’s long development process. “Because Siemens tends to focus on electronics, it was initially unclear whether a hydraulic system would find acceptance,” he says. But Schiffers’ arguments eventually carried the day. The hydraulic system would not only take less time to develop than a fully electronic brake, but also have more robust technology and cost less. Schiffers and his team initially made a prototype version of the hydraulic brake. The first trials are scheduled to take place in a subway train in early 2014. Schiffers developed a non-self-energizing system for these trials to simplify the safety approval procedures, since the approval processes for rail vehicle safety are becoming increasingly complex, especially when new technologies are being introduced.

Schiffers is delighted about the inventor award and hopes that his flash of inspiration will one day find a commercial application involving the installation of decentralized, self-energizing hydraulic systems with controlled retarding force in rail vehicles. “Not until then will my invention also become an innovation,” he says. The development is already paying off for Siemens, however, because the expertise that the team of brake specialists has gained in recent years will make the company less dependent on suppliers. “Because we know what the systems have to be capable of and what they are allowed to cost, we can intensify competition among the brake manufacturers,” explains Schiffers. Schiffers’ inventions for Siemens are protected by 14 individual patents grouped in 13 patent families. “Registering good ideas as inventions is very easy at Siemens. Once you’ve done that, you just have to be very patient,” Schiffers advises his younger colleagues. Whenever Schiffers has the time, he relaxes by playing soccer for his club as an offensive midfielder. The rest of his spare time he spends with his wife and daughter.

​

​