Flexure Pivot Oscillator Gravity Insensitivity
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Solution Overview
Problem
Mechanical watch oscillators using flexure pivots face limitations such as sensitivity to gravity, non-linear restoring torque, parasitic shift, limited stroke, and difficulty in fitting a 3D structure into a wristwatch, which affect chronometric performance and usability.
Innovation Solution
Design of gravity-insensitive flexure pivots with a 2D or 2.5D structure, featuring co-struts with elastic elements providing rotational and translational mobility, ensuring linear restoring torque and minimizing the impact of gravity, suitable for small-scale fabrication in watches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a 3D structure is used to minimize gravity effect, then gravity insensitivity is improved, but device complexity and manufacturing difficulty worsen
Solution Approach 1:
The patent transitions from a 3D structure to a 2D planar structure by arranging elastic elements in specific geometric patterns (crossing at right angles) within a single plane. This dimensional simplification maintains gravity insensitivity while reducing manufacturing complexity and enabling small-scale fabrication for wristwatches.
Solution Approach 2:
The patent employs asymmetric arrangement of elastic elements where pairs of elements are positioned at different orientations (e.g., one pair at 0 degrees, another pair at 90 degrees). This asymmetric geometric configuration creates gravitational insensitivity through compensating stiffness effects while maintaining a simple 2D structure.
2Length of moving object
If flexure pivot beams are made longer to increase stroke, then angular stroke is improved, but gravity sensitivity worsens
Solution Approach 1:
The patent uses asymmetric geometric arrangement where elastic elements of different lengths are positioned at specific angles (0 and 90 degrees). This asymmetric configuration allows the longer elements to provide increased stroke while the angular arrangement compensates for gravity effects, maintaining insensitivity.
Solution Approach 2:
The patent applies different geometric configurations and material properties to different regions of the flexure pivot. By varying the orientation, length, and cross-section of elastic elements at different locations, the design achieves both long stroke and gravity insensitivity through localized optimization of mechanical properties.
3Ease of manufacture
If a 2D structure is used to simplify manufacturing, then ease of manufacture is improved, but gravity insensitivity worsens
Solution Approach 1:
The patent achieves gravity insensitivity in a 2D structure by employing asymmetric geometric patterns of elastic elements arranged at specific angles (0 and 90 degrees). This planar asymmetric configuration provides the necessary gravitational compensation while maintaining manufacturing simplicity and enabling small-scale fabrication.
4Force
If flexure pivot elements are made more flexible to reduce friction, then friction is reduced, but restoring torque linearity worsens
Solution Approach 1:
The patent compensates for non-linearity in flexible elements by using asymmetric geometric arrangements and pre-stressing the elastic elements. The asymmetric configuration of elements at different angles, combined with controlled pre-stress, linearizes the restoring torque while maintaining the flexibility needed to reduce friction.
Solution Approach 2:
The patent adjusts parameters such as pre-stress level, element cross-section, and geometric dimensions to optimize the balance between flexibility and linearity. By carefully controlling these parameters, the design achieves low friction through flexibility while maintaining linear restoring torque through parameter optimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves significant improvements in chronometric performance by reducing gravity sensitivity, maintaining a long angular stroke, and enabling linear restoring torque, making the oscillators more suitable for portable timekeepers like wristwatches.
Implementation Method 1
a first pair of elements providing rotational guidance, the elements of said first pair being elastically substantially identical to each other
Implementation Method 2
flexure pivots which are insensitive to gravity, i.e. perform similarly independent of their orientation
Implementation Method 3
Spring stiffness can be affected by the orientation of gravity
Data Source
Figure 1(a)~2
Figure 3~4
Figure 5~6
AI summary
The mechanical oscillator according to the invention comprises an oscillating body (601), at least one rigid intermediate body (602) and a support (600). Each rigid intermediate body is connected to the support by a pair of elements (610, 611) providing rotational guidance. The elements of each pair are elastically substantially identical to each other and extend along respective axes which, in orthogonal projection onto a plane parallel to the oscillation plane of the oscillating body, cross at a point (G) and are symmetric to each other with respect to a line (x) passing between the points of junction of the first pair of elements to the rigid intermediate body. The rigid intermediate body is connected to the oscillating body by at least one further element (604, 605) providing relative guided mobility between the oscillating body and the rigid intermediate body in a direction substantially parallel to the line (x) during regular functioning of the mechanical oscillator. In a variant the pair of elements connect the rigid intermediate body to the oscillating body and the at least one first further element connects the rigid intermediate body to the support.