Three ZHAW institutes optimize sliding windows with pneumatic sealing system
With its "air-lux" system, Krapf AG is one of the leading suppliers of sliding windows in glass facades. Now the company is working with the ZHAW School of Engineering on the further development of its product. Innosuisse is funding the project.
If you google "sliding windows with pneumatic sealing system", you can't avoid the name "air-lux". Thanks to a patent, the system from Krapf AG is the only one on the market that has a fully integrated air-assisted sealing system.
How the "air-lux" windows work
"air-lux" is a sliding window system from the company Krapf AG in Engelburg SG. It was developed in 2004 and patented in Switzerland in 2010. The special feature of "air-lux" is the air-assisted sealing system: when a slider is closed, air is pumped into the sealing rings. Once closed, the "air-lux" sliders are extremely tight. Before opening, the air escapes – this enables frictionless movement of the sliders.
"So far, we have developed according to the trial-and-error principle," says Roman Büchler, member of the management board of Krapf AG. Working with trial-and-error is suitable for SMEs in order to develop quickly and cost-effectively, he says. But: "We have reached a point where we can no longer get anywhere with trial-and-error. What we need now is in-depth knowledge."
The company wants to break out of the familiar mansion segment and move into the construction of high-rise residential buildings. This further increases the demand on the already high-quality "air-lux" system. That is why Krapf AG is collaborating with the ZHAW School of Engineering.
The sliders should be tight, safe and long-lasting
Funded by Innosuisse, three ZHAW institutes are working on the further development of the "air-lux" system. The Institute of Materials and Process Engineering (IMPE) is leading the work and conducting research into material technology and coatings. The Institute of Energy Systems and Fluid Engineering (IEFE) is concentrating on the complete air system which makes the sliders tight. Furthermore, the Institute of Computational Physics (ICP) supports its colleagues with simulations.
"The three institutes work on different focal points and at the same time in an interdisciplinary way," says Martin Winkler. He is the laboratory manager for polymer coatings at the IMPE and is leading the project on the ZHAW side. "We want to improve the system in terms of opening times, safety and durability."
The Innosuisse project started in February 2020 and is expected to run until the end of 2022. Winkler says: "It is about understanding the product in order to then generate approaches to solutions."
In order to find these approaches, IEFE has set up a test bench. It essentially consists of a single "air-lux" slider. Its proud dimensions: three by six meters. "For Krapf AG, this is a small slider. It only weighs about 400 kilos. The biggest ones weigh up to 1.8 tons," explains Martin Schneider. He is project manager of the IEFE research group Fluid Engineering and thus responsible for the air system.
For IEFE's work, the "small" version is sufficient, says Schneider. "We measure the actual state, incorporate improvements and test them." The test bench provides figures on sound, pressure, volume flows and opening times. Especially the latter are important, says Schneider. "For customers, it cannot be fast enough until the sliding window is open."
The scientific approach proves its worth
Roman Büchler of Krapf AG is almost as impatient as the customers: "The scientific approach is more elaborate than we thought." Nevertheless, Büchler is satisfied: "Without the ZHAW, we would have taken shortcuts to speed up the project. But the collection of reliable data by the ZHAW is the right approach."
After one year on the project, the work is beginning to bear fruit. "The reason for the adhesion effect of our pneumatic sealing system has most likely been found and a solution approach exists," says Büchler. The task now, he says, is to find an economical remedy for the problem – the sealing and the slider should stick to each other as little as possible in the future.
The three ZHAW institutes and Krapf AG still have two years to achieve all the predefined project goals. If Roman Büchler has his way, the collaboration with the ZHAW could even bring another advantage: "Ideally, we can have one of the implemented solutions protected by a patent."
At a glance
The Project 41619.1 IP-ENG entitled "New development of air-lux sliding windows for the targeted development of a new expansive market" can be found on Aramis, the federal administration's research database.
The institutes involved in the project are
- the Institute of Materials and Process Engineering (IMPE),
- the Institute of Energy Systems and Fluid Engineering (IEFE)
- and the Institute of Computational Physics (ICP).
Project duration: 2020 - 2022