Philippe Leray (57) has optimized the overhead conductors of the railroad tracks for high-speed trains with a new design. Leray, who was born in France and works in Siemens’ Infrastructures & Cities Sector, has developed a patented system for ensuring that the electrical conductors are constantly retensioned. As a result, the trains, which travel at speeds of up to 400 kilometers per hour, can operate without any risk of an interruption in the power supply. These tension wheel assemblies are also maintenance free.

Catenaries for high-speed rail vehicles require constant retensioning in order to ensure that the train’s pantographs do not loose contact with the overhead conductor. The tension wheel assemblies compensate for temperature-induced expansion of the conductors. Trams, which tend to travel slowly, can cope with the slight sagging of the conductors that results from a higher conductor temperature. However, things are different when it comes to systems such as the ICE trainsets. The pantograph of a rail vehicle traveling at a speed of 160 kilometers per hour or higher can very quickly loose contact with a conductor that varies greatly in height. For this reason, it is necessary to retension the overhead line with a force of at least 10 kilonewtons. This task is carried out using the tension wheel assemblies. Such an assembly consists of the tension wheel, which rolls up the cable; the swing lever; the hoop; the latching plate; and a weight. A conventional tension wheel has coarse teeth that engage with the latching plate if a conductor snaps — for example due to an external cause. In this way, the design prevents the weight from falling down and further damaging the overhead conductor.

“The teeth are damaged due to the severity with which the tensioning wheel engages with the latching plate,” says Leray. The engineer began thinking about ways of preventing such damage. He asked himself how the tension wheel could still lock immediately in the event of a conductor break, yet brake the retensioning weight more gently. He changed the profile of the tension wheel and replaced the teeth with a rippled rim, which acts to amplify the braking force. As a result, the wheel falls into the V-shaped latching plate and is held there. This protects the assembly and makes it possible to produce higher retensioning forces — and therefore higher train speeds.

Leray’s invention was transformed into a product within a few months. This tension wheel system has been used in the construction of overhead conductors for high-speed trains in many countries since 2000. “I remember how people used to say that developing a high-speed train was easy, whereas developing the catenary system needed to power it certainly wasn’t,” he says, obviously satisfied with what he has helped to achieve. And with good reason. After all, the pantograph of a high-speed train travels at up to 90 meters per second, so the conductor always needs to be very rigidly tensioned.

Leray is a native of Brittany. He studied engineering in Metz and moved to Germany to live with his German-born wife directly after his graduation, 25 years ago. He has specialized in catenary system components right from the start. The triumphant advance of high-speed trains systems has posed totally new challenges for Leray and his colleagues. The components he has developed are also attracting interest from Siemens’ competitors. “That’s when you start to realize just how good your invention is,” Leray says, with a grin. Leray has registered a total of 16 inventions. These are the basis of 127 individual patents in 20 families of patent rights.

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