Spring Perfectly Statically Balanced 1-DOF Mechanisms Using Slider-Crank

Spring static balance method is widely used in the mechanical field. There are many different types of linkages for 1-DOF balancer. However, in 1-DOF balancer with gear slider-crank, which is not reached perfect static balance. This paper presented a novel arrangement of spring for linkage with gear slider-crank to make it achieve perfect static balance. Spring installed in a slider-crank, the elongation of spring is relative to the rotation of link. The elastic potential energy of spring can be expressed as quadratic term which is the function of rotation angle of link. By double angle formula, the elastic potential energy of spring can be reduced to single power term, and can be compatible to gravitational potential energy. Based on the compatibility between gravitational and elastic potential energy, the requirement of spring installation can be obtained. Through the arrangement of spring to reach zero-free-length, the linkage can achieve perfect static balance. In practical, the spring can be installed in ground link or rotatory link, and the spring can be tension spring or compression spring. Applying this method to multiple degree-of-freedom serial link is expected as future work.