A multi-impactor mechanism for passive force amplification in hand tools: Design, modelling, and validation

This study presents the Spring-Loaded Multi-Impactor Shovel (SLMIS), a non-electric hand tool that integrates multiple spring-loaded impact mechanisms between the shaft and blade to convert operator input into amplified impulsive loading. The system stores elastic energy during loading and releases it instantaneously upon reaching a triggering threshold.</p> <p>The work contributes at three levels.

At the theoretical level, a closed-form trigger-efficiency function is derived showing that the fraction of stored spring energy converted to impact force depends only on the ratio of triggering displacement to total compression, providing a generalizable design guideline for spring-loaded impact mechanisms. At the component level, stiffness and peak impact force are characterized using theoretical modeling, compression testing, and Brinell hardness back-calculation, yielding <i>K_i</i> = 4823.55 N/m and <i>K_r</i> = 1217.25 N/m with strong agreement across methods.