Low vibration hand-held tools for occupational safety and health.
NIOSH 1995 Jul; :1-34
White finger disease is very prevalent in foundry workers using chipping tools for cleaning burrs in large castings. The research reported here established feasibility of low vibration hand-held tools that do not cause vibration related injuries. The project included development and design of inherently low vibration tool concepts, and engineering designs for fabrication of an actual working prototype. The oscillator dynamics of a pneumatic percussive tool was modeled and design parameters were optimized through computer simulation. Based on Charles Leavell's Vibration-less Principle, and introducing innovative features, a practical low vibration tool body (casing) was devised. The casing, on which handles were attached, is a primary vibration transmission mechanism to the tool operator. An improved chisel attachment containing elastomeric material can isolate secondary vibration transmitted back from the chisel and the work piece resonance. At beginning of the project, it was anticipated that special vibration absorbing materials would be needed, but better than expected success of the oscillator design provided the required vibration reduction without special damping materials. Two prototypes were designed, one with and another without a valve. The valved unit had some leakage problems, meanwhile the valveless unit performed with great success. This result veered us toward the valveless design. However, for larger tools valved units may offer some advantages. Vibration measurements were made on the low vibration prototype and a conventional tool unit under comparable performance. The acceleration level on the valveless prototype was 2.5 g, which was low enough to prevent vibration induced injuries. In comparison, the conventional tool measured 110 g, which is a high level typical of such tools. The results of the feasibility studies were quite gratifying and the PI is anxious to apply this findings to design and build few field prototypes for trials by foundry workers. A phase II proposal for further research would be submitted for the December 1995 round. Meanwhile work will continue with modest in-house resources to generate more data. The findings of the research would be readily applicable to other percussive tools, such as larger Jackhammers and paving breakers.
Vibration-disease; Vibration-effects; Occupational-health; Safety-measures; Tools; Hand-tools; Hand-injuries; Foundry-workers; Foundries
Analytic Engineering Co., 483 Sinclair Frontage Road, Milpitas, CA 95035
Final Grant Report
National Institute for Occupational Safety and Health
Analytic Engineering Company, Sunnyvale, California