Hübner GmbH, a leading international systems provider for the manufacturers of rail vehicles has entered a new business area and now also offers door systems for rail vehicles and buses. The opening mechanism of these doors is highly stressed in operation. In these harsh applications, energy chains and also plain bearings from igus® prove their worth. In the long-term test under practical conditions, the energy chains have already completed 2 million movement cycles and the iglidur® plain bearings around 1.7 million double strokes.
A push of the button - and the door opens: this process repeats itself in the case of sliding and hinged doors on suburban trains and local passenger trains in minute cycles, over the years, in humid and hot conditions as well as below zero temperatures. And hardly any user will ever be concerned that the door mechanisms and the moving components of the doors are highly stressed.
As leading international provider of systems for rail vehicles, Hübner GmbH, headquartered in Kassel, has a wealth of experience in this field. The "rails" product group of the company develops and manufactures among other things driver workstations, windshield and side window systems and - based on bellows and gangway bellows - flexible transfer systems and vehicle joint systems. Streetcars, subways and urban trains are also currently operating with components and systems from Hübner, as also regional, long-distance and high-speed trains.
Around one and a half years ago, the company decided to supplement the business area product portfolio with an important addition the door systems. A logical step to take when you possess a strong position in the market for rail and transfer systems, but still a challenge as the doors are highly stressed.
This applies in particular to the first concrete order that Hübner acquired in this area: A door system should be made for a southern European regional train. This meant very high opening frequency and a wide temperature range across the year, in which the system must be able to function faultlessly over many years.
During this process, Hübner designers could of course fall back on their experience in rail vehicle technology - and they have advanced systematically.
Engineer Uwe Krug, construction manager for window and door systems of the Rails department at Hübner: "We have developed many of the components ourselves, for example, the complete drive. In the case of purchased parts, we basically use standard components, which are subjected to a comprehensive range of tests. " This also applies to the energy chain, which is mounted above the sliding door. It guarantees that the moving energy supply reaches the button with which the passengers open the door and to the closing edges safeguard with anti-trap protection, which is also manufactured by Hübner. Whether an energy chain is required for this purpose was out of the question. Engineer Oliver Rang, Door Systems Construction: "As a result of our investigations on drive development, we know that when cables are not guided it can quickly lead to wearing of the cable jacket." We know this problem from bus joints and entry systems where we also use energy chains. “
Collaboration partners in this area were established well in advance. Uwe Krug: "From the start we have been planning with igus®. " On the basis of specifications and by means of an initial model of the sliding door, igus® selected an energy chain and with it also delivered a sample of the top-quality, flexible chainflex® cable. Part of the selection parameters dictate that the chain and cable must be able to function at temperatures of down to -40 °C. And the intelligent mechanical construction means that one energy chain is sufficient, although on opening the sliding door two counter-directional movements are executed. The type 06 chain, which is delivered by igus® as a pre-mounted readychain® with cable, one-sided plug, cable marker and connecting angle, is proving its worth not only in laboratory tests, for example in the climatic chamber and in shock and vibration tests, but meanwhile also through practical experience. Regional trains have already been operating since fall 2005 with the new door systems from Hübner - and there have been no problems or complaints so far. In view of the high strains and complex kinematics with the sliding door and entry system, this cannot be taken for granted - and it shows that Hübner engineers, due to the wealth of experience gained in this application area, best adjust their developments according to the usage conditions of rail vehicles.
Admittedly the positive experiences of clients have not resulted in overall satisfaction. Markus Hühn, in charge of electronic development in the rails division of Hübner GmbH: "On the company's premises, we have constructed a door system which under real weathering conditions continually opens and closes in long-term tests. " This trial has been running for 22 months now and the counter reading has got to 2 million. Oliver Rang: "After around 1.8 million strokes we examined chain and cable and detected no appreciable signs of wear."
While Hübner collaborated from the outset with igus® on the selection of the energy chain, only in the second stage were the igus® plain bearings made from the self-lubricating high-performance plastic used. Oliver Rang: "In the kinematics of the sliding doors, we first used metallic bearings, however they soon started showing signs of corrosion and also noticeable wearing. "
Only after these experiences did we decide on plastic instead of metal and asked igus® to propose an extremely wear-resistant material with in-built lubricant and very good low-temperature properties, and to supply corresponding plain bearings. They did this successfully, as the long-term test shows. The iglidur® plain bearings have in the meantime completed 1.7 million double strokes and are proving to be just as long-lasting as the energy chains.