Concentric Coplanar Gear Teeth for Thin Watch Correction
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Solution Overview
Problem
Existing time indication correction devices in watchmaking are bulky and unsuitable for ultra-thin movements due to their thickness, primarily caused by the deflection wheel's two levels of teeth and the complexity of the corrector pinion, which limits their applicability in thin mechanical or electromechanical movements.
Innovation Solution
A correction device featuring a pinion with a secondary toothing of reduced pitch, mounted on a winding stem, and an intermediate wheel with a main toothing meshing with the display member, and a secondary toothing that is concentric and coplanar with the main toothing, reducing the overall thickness and size of the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a deflection wheel with two levels of teeth is used in the correction device, then the correction function is achieved, but the thickness of the device increases
Solution Approach 1:
The patent merges the two levels of teeth that were previously separated in space (one on the deflection wheel, one on the corrector pinion) into a single planar level on the intermediate wheel. The first toothing engages with the display member while the second toothing engages with the pinion, both at the same radial position, eliminating the need for axial stacking and reducing thickness.
Solution Approach 2:
The invention transitions from a three-dimensional arrangement (two axial levels of teeth) to a two-dimensional arrangement (concentric toothings on the same plane). By placing both toothings on the same radial level but with different pitch circles, the design eliminates axial thickness while maintaining functional separation between the two engagement interfaces.
2Ease of operation
If a pinion with two active levels is used to engage with both the deflection wheel and display member, then the correction mechanism functions, but the device complexity increases
Solution Approach 1:
The invention extracts the deflection function from the pinion by introducing an intermediate wheel. The pinion now only needs to engage with the intermediate wheel's second toothing, while the intermediate wheel handles the engagement with the display member through its first toothing. This separation simplifies the pinion structure to a single-level toothing.
Solution Approach 2:
The intermediate wheel acts as a mediator between the pinion and the display member. It receives rotational input from the pinion through its second toothing and transfers controlled rotational output to the display member through its first toothing, enabling the pinion to be simpler while maintaining the correction function.
3Ease of operation
If a pinion with large diameter is used to directly engage with a large display member, then the correction function is achieved, but the device thickness increases
Solution Approach 1:
The intermediate wheel serves as a mediator that allows a small-diameter pinion to control a large-diameter display member. The pinion engages with the intermediate wheel's second toothing (with pitch p), and the intermediate wheel's first toothing (with pitch P) engages with the display member, providing mechanical advantage and enabling size mismatched components to work together in a thin profile.
Data Source
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AI summary
The wheel has a toothing (40) defined by a pitch (P), head diameter and foot diameter. Teeth (42) are provided with a tip portion that forms another toothing i.e. saw-shaped toothing, which is coplanar and concentric to the toothing (40). The head diameter of the saw-shaped toothing is equal to head diameter of the toothing (40). The foot diameter of the saw-shaped toothing is greater than the foot diameter of the toothing (40), where the two toothings allow coupling in different direction of rotation. An independent claim is also included for a correction device for a timepiece display mechanism, comprising a display member that is fitted with a toothing.