Forestry cut-protection clothing developed
Researchers at the Hohenstein Institute in Bönnigheim, Germany and the University of Bremen, Germany have developed an innovative sensor system for cut-protection clothing, to make forestry work safer.
The principle of the system, named “Horst” (from Hose meaning ‘trousers’ and ‘Forst’ meaning ‘forest’) by the project team, is simple, yet effective: if the power saw comes too close to the trousers, the machine is switched off before it touches the fabric. The system was awarded the 2011 Innovation Prize at the specialist trade fair Techtextil in Frankfurt (24-27 May, 2011).
Special cut-protection clothing has been part of the legally-prescribed personal protection equipment (PPE) for foresters for many years now. In Germany, about 25,000 people work professionally in forestry, about half of them in privately-owned woodland. However, conventional cut-protection clothing only provides its wearer with passive protection: the trousers and jacket incorporate cut-protection inserts consisting of several layers of special material made of ultra-strong fibres. If the chain of the saw comes in contact with the textile, it becomes caught in the fabric and therefore stops before the wearer is affected. However, the multi-layered material results in greater thermal insulation which puts additional physiological stress on the wearer, especially during warmer times of year.
In contrast, with the electronic protection system Horst, there is no contact at all, and the system kicks in before there is any risk of the outer textile layer being damaged. The aim of the development work was to reduce the ‘passive’ cut-protection layers to an absolute minimum and increase the ‘active’ protection, so that the clothing feels lighter and has less of an insulating effect.
“What was important for us was to improve the protection from cutting injuries while at the same time making the clothes as comfortable as possible to wear,” said Angela Mahr-Erhardt, project leader in the Clothing Technology section of the Function and Care department of the Hohenstein Institute.
Magnets on the guide bar of the chainsaw and highly sensitive magnetic field sensors (reed switch contacts) incorporated in the textile fabric create a protective electronic field for the forester. If the saw comes too close, the contacts in the trousers close due to the magnetic field from the chainsaw and a radio signal is sent which stops the saw immediately.
Following trials, a minimum distance of 5 to 10 centimetres between the saw and the trousers was judged to be appropriate and practical. As the saw comes closer, it is detected accurately and quickly. This means that, in real life, both the forester and his clothing would remain untouched.
The switch contacts incorporated in the cut-protection trousers operate with zero quiescent current. Only the radio transmitter that is built into the trousers uses a battery. If its level of charge falls below a certain level, the power saw is switched off for safety reasons.
Practical tests at the Hohenstein Institute have shown that the innovative protective function is stable and reliable even during heavy physical work. The trousers can be washed many times without impairing the protective function.
Another advantage of Horst technology is that it does not restrict the cutting or manufacture of the garments. This means that in the future, manufacturers will be able to use this textile for all types of protective clothing, both trousers and jackets.
