Design for a kind of combined mechanisms based on gear pairs

Basic element of a kind of scaling mechanisms is constituted by two links which are connected by two small gears on the end of the links and one idler meshed with the two gears. With the constant instant transmission gear ratio, the two links move along a fixed path when driving the middle idler rotating. So the angle of the two links changes according to the certain rules. Using this principle, if a certain number of basic elements are connected by a certain way, a series of over-constrained scaling mechanisms with one degree of freedom are constructed. In this paper, some scaling mechanisms with gear´s kinematic pairs are designed. The DOFs of the proposed mechanisms are calculated as one. The scaling mechanisms designed with gear´s kinematic pairs reduce the number of the components than the scaling mechanisms constructed by parallelogram linkages.