Public transport must be safe in all circumstances. There must be no interruptions in the running of operations. The focus is often on the doors. In this example, a cable used in a moving energy supply system ensures smooth opening and closing. Improved conductors and jacket materials make it possible that no more failures occur despite high continuous stresses.
The collaboration with igus® started over two years ago. The first step was to introduce the chainflex® CF98 cable, especially developed for such applications, into the existing igus® energy supply system in electric swinging-sliding doors on the low-floor tram as part of due maintenance work. This family of cable is designed for very fast applications with a very high number of cycles combined with small bending radii and tight installation space. After over two years of daily practical testing, it was confirmed what has already been standard for years in other public transport services in Germany. That the cables work totally untroubled and hence open and close the doors reliably. “It withstood all adverse conditions and did not fail under either heat, cold, snow or ice!” says Hans Bennerscheid succinctly.
The control cable is responsible first and foremost for opening and closing the doors in a controlled manner. This involves a part relevant to safety, which is sure to receive plenty of attention during all inspections. “To keep the costs as low as possible, we strive to only replace wearing parts with high quality, state of the art components,” explains Ernst Baerhausen. “And the longer the operating time of the cable, the more the maintenance intervals are reduced and thus our cost expenditure,” adds Hans Bennerscheid.
“The main difference to comparable cables lies in the conductor,” explains Rainer Rössel, Development and Marketing Manager for chainflex® and readychain® at igus®, in the interview. “Copper ages and becomes brittle over time. The CF98 cable is no longer purely copper, but instead a special alloy that is designed for a much higher mechanical stress. “
Trials lasting years have been able to demonstrate no wear to the conductors even with radii of <3xd and over 60 million strokes. “For over two and a half years we have conducted elaborate material research in our laboratory in Cologne in order to be able to offer users of very small energy supply chains and the tight bending radii usually associated with them, along with a high number of strokes, a suitable cable,” reports Rainer Rössel. “And in the end there was the classic solution. When it comes to minimal installation space and tight bending radii, in this case 18 mm, we are able to provide a reliable series of cables with the CF98/CF99. “
It features only a slightly lower conductivity compared to pure copper, which was compensated for by somewhat larger cross-sections – approximately 10 % bigger outer diameter compared to a comparable type. In view of the much higher demands of the last few years, it is certain, however, that such high quality solutions will be needed more frequently so that they can guarantee operational safety in the critical area of very small cross-sections. It enables new applications in energy supply systems – for example in the automation industry, the packaging industry, the mounting and semiconductor industry as well as the automotive and banking sector.
“Although we come from machinery and plant construction, our cables can show their strengths in many safety-relevant parts such as automatic doors in buses and trains,” Rainer Rössel points out. “Especially in the public transport sector, for example, we have been able to come up with solutions in some cases with very high tensile loads, which ultimately led to greater passenger safety, a higher availability and hence more cost efficiency. ” In the meantime, very many train doors have been fitted with our cables to ensure much higher reliability. As there is also no minimum order quantity or surcharge, follow-up costs are also reduced. Over 750 types of cable can be supplied from stock worldwide.
Out of the 24 low-floor trams in Bonn, 21 are permanently in operation. “We can't afford any failures,” says Alexander Wingen bringing the requirements to the point. “The technical and hence also the economic benefits of the CF98/CF99 cables convinced us from the very start. ” And his colleague Oliver Walbröhl adds: “We have united to form a city alliance with Dresden, Erfurt, Mülheim and Brandenburg among others. Not only is the same vehicle series used here, but spare parts are also ordered jointly. At the regular meetings, the focus is not only on operating costs, there is also a brisk exchange of experiences. We are happy to pass on our experiences with the control cables for reliably working doors. “