Design of a Compliant Monolithic Internally Statically Balanced Four-Bar Mechanism

Instigated by the need to statically balance compliant mechanisms, this paper presents a compliant internally static balanced monolithic four-bar linkage which can be used as generic building block in any compliant mechanism. The pivots of the four-bar are made compliant by the use of initially curved leaf springs. The balancing energy is provided by two pre-loaded opposing cantilever leaf springs that follow a circular path imposed by the input link in a range of forty degrees. The monolithic four-bar and its balancing mechanism are dimensioned by means of an analytical model (decoupled segments), optimized with a FE-analysis (coupled), and validated with a prototype and accompanying experiment. FEA shows a peak moment reduction of 95% (elastic material, working range: 40°), and the experiment of a lasercut 10 mm thick PMMA (visco-elastic material) prototype shows a peak moment reduction of 63% (working range: 36°) up to 88% (working range: 20°).