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Quality Fabric Of The Month

Proactive Protection For Chainsaw Operators

HORST, a textile-based electronic active cut-prevention system developed by Hohenstein Institute and University of Bremen researchers, automatically turns off a chainsaw before its blade makes contact with the protective clothing worn by its operator.

Janet Bealer Rodie, Managing Editor

T he Hohenstein Institute for Textile Innovation e.V. and the University of Bremen, both based in Germany, have joined forces to develop an active cut-protection system for forestry workers and other chainsaw operators. Dubbed HORST — an acronym comprising letters from the German words "HOse," meaning "pants" or "trousers," and "fORST," meaning "forest" — the system comprises a conductive textile circuit board with magnetic field sensors, or reed switch contacts attached to it; a battery-operated radio transmitter; and multiple magnets installed on the guide rail of the chainsaw. The textile circuit board is incorporated into the protective clothing worn by the person operating the saw, and the magnets on the chainsaw's guide rail create a magnetic field that activates the sensors in the fabric when the chainsaw blade comes too close to the fabric. Via a radio signal, the activated sensors automatically and immediately turn off the saw before the blade makes contact with the protective clothing. The fabric can be incorporated into a garment using traditional sewing machinery and equipment, and it also can undergo numerous domestic launderings without affecting the protective function. The HORST technology won an Avantex Innovation Award at Techtextil 2011, which took place last month in Frankfurt.

The HORST active electronic cut-protection system involves interaction between the electronic magnetic sensor network on a conductive textile circuit board inside the protective pants worn by the chainsaw operator and the chainsaw's magnetic field.

Traditional protective clothing for chainsaw operators includes pants and chaps that generally have a nylon, polyester or denim outer fabric and inner inserts comprising layers of ballistic nylon or high-tenacity polyester fabric; or, in higher-quality clothing, layers of aramid fabric such as Kevlar® or ultra high molecular weight polyethylene such as Dyneema®. The cut-resistant protective layers provide passive protection to the wearer and are designed to jam the chainsaw drive sprocket, thereby stopping the saw before it can cut through the pants leg and cause injury. The less expensive, lower-quality styles have more layers of fabric and are heavier, bulkier and less breathable than the more expensive, higher-quality styles. However, because of the several-layer construction, even the higher-end styles may be uncomfortable in warm weather.

According to Dr. Jan Beringer, Hohenstein's head of research in the Function & Care department, the conductive textile developed for the HORST system would be placed between the outer fabric and the layers of protective cut-resistant fabric. The single HORST conductive textile layer could replace up to half of the cut-resistant fabric layers, thereby reducing weight and bulk and enhancing the wearing comfort of the pants while retaining a back-up level of mechanical safety. "You can remove some of the protective layers because you have more safety thanks to the conductive layer with the reed switches, and removing those layers makes it more comfortable," he said.

The reed switches, which measure 2.5 to 3 centimeters in length by 3 to 4 millimeters in diameter, are soldered onto the conductive textile. Beringer said the solder connections are the most vulnerable points in the fabric, and Hohenstein has applied a waterproof coating very locally on those points to protect them during laundering.

The magnetic sensors, or reed switch contacts, on the conductive textile circuit board inside the protective clothing are activated by the chainsaw's magnetic field and turn off the saw when it comes too close to the garment.

Beringer said that in testing, the system turned off the saw when the guide rail was between 5 and 10 centimeters from the pant leg more than 80 percent of the time. He also noted that the sensors can be tuned to sense a specific proximity of the saw blade. "Professional forest workers want a very close contact, while other users may want the saw to turn off at a greater distance," he said.

The radio transmitter is integrated into the pants. Beringer said that if the battery, which is a conventional 9-volt battery, has a low charge level or is dead, the saw won't turn on. "It's a fail-safe system," he said. "When the battery is dead or too many switches are broken, the electronics are turned off, and the chainsaw won't turn on."

The technology would allow other sensors, such as temperature or acceleration sensors, to be integrated into the system as well to provide a diagnostic function; and its applications could be expanded to include other industrial and workshop uses.

The reed switch contacts are soldered onto the conductive textile, and a waterproof coating is applied over them to protect them during laundering.

HORST is a prototype system, and the development project received funding from the German government via the Industry Research Alliance (AiF). Martin Rupp and Angela Mahr-Erhardt from Hohenstein provided the textile know-how for the project, and Christoph Breckenfelder and Dmitriy Boll from the University of Bremen provided the electronics expertise. The technology will be offered to private companies to develop it for commercialization. "The next step before bringing HORST to market is to work closely with chainsaw manufacturers to integrate the magnet in the blade's guide rail so the technology will work," Beringer said. "The chainsaw manufacturers have said that in principle, it is possible, and the first signals from the industry are positive. The system will depend on a partnership between the protective garment manufacturers and the chainsaw manufacturers. The next challenge will be to make the trousers and electronics compatible with a large number of chainsaw brands."

For more information about HORST, contact Jan Beringer +49-7143-271-714; j.beringer@hohenstein.de.

June 21, 2011