Gravity-Compensation Design Approaches for Flexure-Pivot Time Bases

While flexure time bases have gained significant traction in the watchmaking industry thanks to their high quality factor and monolithic design, maintaining a stable frequency varying orientations of wrist watches with respect gravity remains challenge. This results from fact that flexures play two roles simultaneously: guiding oscillating mass along one-degree-of-freedom pivotal motion, providing oscillator’s elastic restoring force. Indeed, stress-stiffening effects induced by direction weight affect pivot angular stiffness, which impacts its frequency. In order address this issue, design approaches are presented which, when combined, allow reach strict chronometric standards mechanical watches. Firstly, differences for all vertical positions (i.e., orthogonal rotation axis) mitigated designing architectures reduced parasitic center shift, or offsetting (COM) axis symmetry, both. Secondly, between horizontal parallel COM axis. The implementation effectiveness these demonstrated numeric simulations, as well experimental measurements performed on watch-scale silicon etched prototypes.