Hannover, Germany - LZH, an international consortium composed of three research institutes, nine SMEs and one large enterprise, has developed prototypes of protective clothing that have been presented at different industrial fairs this year (e.g., Hannover Messe and Laser World of Photonics). Plans are being made for launching the products onto the market shortly.
Protective clothing is needed because, despite the wide use of lasers in industry and research, no suitable protective clothing has been developed. Only protective laser eyewear has been classified and certified when it comes to hazards from intensive laser radiation.
Safety clothing also protects the skin from the increasing number of cutting and welding applications with hand-guided laser systems. Operators are often directly next to the interaction zone between the laser beam and the materials to be processed, and often high-power lasers are in use. Under unfavorable conditions, for example, when highly reflective surfaces are being processed, the laser beam may be quickly deflected toward the user, causing severe skin burns. Also, near-infrared laser radiation may penetrate into deeper tissue and damage blood vessels and other biological tissue. Laser safety is an important consideration.
Therefore, the laser protective clothing developed within the framework of LZH's EU "PROSYS" project is pursuing two strategies. First, researchers have designed a passive system with multilayer technical textiles. The top layer has a special coating that diffusely reflects the laser radiation as much as possible. Radiation that may penetrate this first layer is then evenly spread out by the middle layer. Any residual heat, at least for a limited amount of time, which enters the energy barrier of the inner layer, may trigger a pain sensation.
"This [pain] is intentional. Users should notice that they are being exposed to hazardous radiation, so they have the chance to withdraw their hand or arm," explains Michael Hustedt, head of the Safety Group at LZH and coordinator of the PROSYS project. Normal reaction time is up to 4 sec, and the passive system can protect users for output densities up to 900 kW/m2, making this protective clothing 20 times more effective than what is available on the market.
The effectiveness of the protective clothing can be even further improved by integrating an active system, which uses sensors embedded in the different layers. If the sensors are damaged by radiation, they send an electrical signal to the laser in less than 100 msec, and the laser is automatically shut off. The operator's movement is not impaired since the active system uses a wireless communication system between the safety transmitter and the receiver for the laser. Since the complete shut-down of the laser may take approximately 80 msec, a combination of the active sensors and the passive protection layers makes sense. This system offers protection against output densities of up to 20 MW/m2.
Further developmental work will be, above all, concerned with improving the active systems, making them even more robust and flexible, without losing their protective functions. Practical tests in an industrial setting should provide further information for improving ergonomics and wearing comfort of the protective clothing, in order to achieve high user acceptance. The focus of this work is, for example, on reducing the weight of the material and improving the haptic characteristics of the gloves.
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Photo above: Prototype of passive protective gloves for working with lasers with high output power.