Watch Bridge Positioning with Dihedral Pin and Backlash Compensation
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Solution Overview
Problem
Traditional bridge positioning methods in watch mechanisms suffer from inaccuracies due to dimension chain tolerances and play between pins and bores, leading to insufficient repeatability, which affects the chronometric stability of escapement mechanisms.
Innovation Solution
A removable bridge assembly with internal backlash compensation means, utilizing a first centering pin with a dihedral female implantation and a second alignment pin, ensures precise positioning and reproducible alignment by exerting forces on distinct parts of the pin's peripheral surface and alignment socket, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a clearance is provided between pins and bores to allow assembly and disassembly, then ease of operation is improved, but positioning precision deteriorates due to play causing position variation
Solution Approach 1:
The pin is segmented into two distinct parts: a first part that contacts the facets for centering, and a second part that is distinct from the first part. This segmentation allows the pin to fulfill multiple functions - maintaining precise positioning through facet contact while allowing controlled movement for assembly and disassembly operations.
Solution Approach 2:
Different parts of the pin have different functional qualities. The first part is designed to rest on the two facets for precise centering, while the second part is distinct and serves a different purpose. This local differentiation enables the pin to provide both positioning accuracy and assembly flexibility simultaneously.
2Device complexity
If traditional positioning methods are used with dimension chain tolerances, then device complexity is reduced, but positioning repeatability deteriorates
Solution Approach 1:
The female centering implantation features an asymmetric dihedral angle configuration rather than a symmetric circular bore. This asymmetric geometry with two facets at specific angles provides unique positioning characteristics that eliminate play while maintaining structural simplicity, achieving both low complexity and high repeatability.
3Adaptability or versatility
If multiple assembly/disassembly operations are performed for adjustments, then adaptability is improved, but positioning repeatability deteriorates due to insufficient repeatability
Solution Approach 1:
The pin-facet connection is designed with preliminary action characteristics where the first part of the pin is pre-configured to rest on the two facets in a predetermined manner. This preliminary configuration ensures that each assembly operation automatically achieves the same precise position, enabling repeatable adjustments without requiring complex repositioning procedures.
Data Source
Figure 1~4
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AI summary
A detachable watch assembly (1) comprising a bridge (2) positioned on a plate (3) by a first centering pin (6) and a second alignment pin (11), cooperating with both said plate (3) and said bridge (2). Said plate (3) or said bridge (2) comprises, for their relative centering, a female centering recess (4) receiving said first pin (6) bearing on two facets (5) forming a dihedral angle (50), and backlash compensation means (20) arranged to exert a direct or indirect force on said first pin (6). An escapement mechanism comprising such a detachable assembly. A watch movement comprising such an escapement mechanism. A watch component comprising such a movement.