A Compliant Two-Port Bistable Mechanism with Application to Easy-Chair Design

10.6567/IFToMM.14TH.WC.OS8.008

Darshan S；T. J. Lassche；J. L. Herder；G. K. Ananthasuresh

Kinetoelastic bistable model ； static balancing ； geriatric sit-to-stand chair

Proceedings of the 14th IFToMM World Congress

14th-4（2015 / 11 / 04）

227 - 236

英文

A click-clack tin-lid mechanism analyzed in this paper has the feature to be switched between its two stable states by applying forces along different lines of action, generally at two different points, called ports here. A mechanism such as this has an inherent mechanical advantage because the magnitude of the actuation force at one port is different from that at the other port. The 3D circular click-clack tin-lid mechanism is modified to design a planar fully-compliant two-port bistable mechanism. An analytical kinetoelastic model and finite element analysis are used to explain the energy behavior of the mechanism and gain insights in using it in practice. The mechanism is implemented to design a sit-to-stand easy chair where a small force applied on the armrest can gently propel and ease the occupant rising from it. Further, a static balancing spring is combined with the two-port bistable mechanism to enable adjustment for different weights of the occupant.