A Fully Compliant Force Balanced Oscillator

Weeke, Sybren L.; Tolou, N.; Semon, Guy; Herder, Just L.

doi:10.1115/detc2016-59247

Cited by 7 publications

(9 citation statements)

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“…The effectiveness of these techniques was demonstrated on watch-scale silicon prototypes, which, due to the numerous other advantages in comparison to the traditional balance-hairspring oscillator [4][5][6], paves the way to their becoming the new standard in mechanical watchmaking. The two types of flexure-pivot oscillator architectures presented here correspond to the main categories observed in commercial and patented prototypes, namely, exhibiting either an axis of symmetry like the co-RCC [2,[29][30][31][32] or a ternary rotational symmetry like the TRIVOT [11,[33][34][35]. Therefore, it can be assumed that the design approaches presented here apply to these architectures and provide a way of compensating gravity effects in numerous flexure-pivot oscillators.…”

Section: Discussionmentioning

confidence: 99%

Gravity-Compensation Design Approaches for Flexure-Pivot Time Bases

Thalmann¹,

Gubler²,

Henein³

2022

Machines

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

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Section: Discussionmentioning

confidence: 99%

Gravity-Compensation Design Approaches for Flexure-Pivot Time Bases

Thalmann¹,

Gubler²,

Henein³

2022

Machines

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“…Passive balancing is considered to be achieved either (1) when the springs, magnets, masses, inertia, etc. of a mechanism are added or redistributed [3][4][5] or (2) when the initial mechanism kinematics is complexified (e.g., by adding new links to make it symmetric) as long as the initial number of DoF of the mechanism remains unchanged [6][7][8]. On the other hand, active balancing, although not the focus of this article, is considered to be achieved (1) when separate active units are used to actively cancel shaking forces and moments exported to the frame of the mechanism [9,10], or (2) when the trajectory of the mechanism is planned to follow a reactionless path [11,12].…”

Section: Literature Review Of Mechanism Balancing Classificationsmentioning

confidence: 99%

Mechanism Balancing Taxonomy

Schneegans¹,

JONG²,

COSANDIER³

et al. 2023

Preprint

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“…2. There also exists other designs of flexure pivot oscillators which do not discuss isochronism [17].…”

Section: Isochronismmentioning

confidence: 99%

Flexure Pivot Oscillator With Intrinsically Tuned Isochronism

Thalmann

Kahrobaiyan

Vardi

et al. 2019

Journal of Mechanical Design

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The most important property for accurate mechanical time bases is isochronism: the independence of period from oscillation amplitude. This paper develops a new concept in isochronism adjustment for flexure-based watch oscillators. Flexure pivot oscillators, which would advantageously replace the traditional balance wheel-spiral spring oscillator used in mechanical watches due to their significantly lower friction, exhibit nonlinear elastic properties that introduce an isochronism defect. Rather than minimizing this defect, we are interested in controlling it to compensate for external defects such as the one introduced by escapements. We show that this can be done by deriving a formula that expresses the change of frequency of the oscillator with amplitude, i.e., isochronism defect, caused by elastic nonlinearity. To adjust the isochronism, we present a new method that takes advantage of the second-order parasitic motion of flexures and embody it in a new architecture we call the co-RCC flexure pivot oscillator. In this realization, the isochronism defect of the oscillator is controlled by adjusting the stiffness of parallel flexures before fabrication through their length Lp, which has no effect on any other crucial property, including nominal frequency. We show that this method is also compatible with post-fabrication tuning by laser ablation. The advantage of our design is that isochronism tuning is an intrinsic part of the oscillator, whereas previous isochronism correctors were mechanisms added to the oscillator. The results of our previous research are also implemented in this mechanism to achieve gravity insensitivity, which is an essential property for mechanical watch time bases. We derive analytical models for the isochronism and gravity sensitivity of the oscillator and validate them by finite element simulation. We give an example of dimensioning this oscillator to reach typical practical watch specifications and show that we can tune the isochronism defect with a resolution of 1 s/day within an operating range of 10% of amplitude. We present a mock-up of the oscillator serving as a preliminary proof-of-concept.

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A Fully Compliant Force Balanced Oscillator

Cited by 7 publications

References 0 publications

Gravity-Compensation Design Approaches for Flexure-Pivot Time Bases

Gravity-Compensation Design Approaches for Flexure-Pivot Time Bases

Mechanism Balancing Taxonomy

Flexure Pivot Oscillator With Intrinsically Tuned Isochronism

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