Noncircular planetary gears applied to scissors

Abstract

The article presents the calculus of a noncircular planetary gear applied to scissors for cutting hard materials (metal plates, branches). The advantage of using the presented mechanism consists in the reduction of the necessary effort for cutting and the equal distribution of the effort during cutting. We have in view that for different openings of a person’s arms, the capacity to develop force is not constant and that in cutting the resisting moment is modified by alteration of the size of the cut section and its position to the edge articulations. Starting from the zero order transmission function, the centrodes are calculated as well as the conjugate curves of the gears. The limits of nonundercuttings are also highlighted. For the calculus and representation of the gears AutoLISP programs were written, with graphic representation in AutoCAD.