Balance Spring Attachment Using Complementary Support Surfaces
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Solution Overview
Problem
Existing methods for securing the outer end of a spiral spring in a timepiece movement fail to maintain the three-dimensional integrity of the spring and ensure precise perpendicularity and concentric development with respect to the balance wheel axis, especially when using fragile materials like silicon, due to induced deformation during attachment.
Innovation Solution
The use of complementary support surfaces with significant angular extent and precise manufacturing, including multiple positioning and fixing elements, to securely attach the spiral spring without plastic deformation, ensuring the initial shape is retained and precise positioning is maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fixing methods (pin, adhesive, screw) are used to attach the outer end of the balance spring to a stud, then the spring can be secured to the frame, but the fixing process induces deformation of the balance spring and compromises its three-dimensional integrity and perpendicularity
Solution Approach 1:
The outer end of the balance spring is pre-formed with a connecting element (integration seat) that has a bearing surface precisely shaped to receive a complementary bearing surface from the frame or angular positioning member. This preliminary formation of the connecting element with precise geometric features eliminates the need for post-attachment deformation correction, as the spring is designed from manufacture to interface precisely with the fixing structure.
Solution Approach 2:
The patent introduces bearing surfaces as an intermediary interface between the balance spring's connecting element and the frame or angular positioning member. These bearing surfaces act as a precise mechanical interface that transmits positioning information without inducing deformation, replacing the direct contact of traditional pin or screw fixings that cause stress and shape changes.
2Manufacturing precision
If the outer end of the balance spring is fixed using a stud with tight manufacturing tolerances and robust assembly, then perpendicularity between the stud axis and the spring plane can be maintained, but the assembly process itself induces changes in the spring's orientation and three-dimensional shape
Solution Approach 1:
The connecting element is pre-formed with a bearing surface whose geometry is precisely defined during manufacturing of the balance spring. This preliminary action ensures that when the complementary bearing surface from the frame is brought into contact, the spring's orientation and shape are determined by the pre-formed geometry rather than being imposed during assembly, preventing assembly-induced deformation.
3Manufacturing precision
If plastic deformation adjustment is used to correct deviations from the ideal three-dimensional shape of metal alloy balance springs, then the spring can be aligned perpendicular to the balance staff, but this delicate operation requires significant skill and is unsuitable for fragile materials like silicon
Solution Approach 1:
The balance spring is manufactured with the connecting element and bearing surfaces already precisely formed to the correct geometry and orientation. This preliminary formation eliminates the need for post-manufacturing plastic deformation adjustment, making the process suitable for fragile materials like silicon that cannot be plastically deformed. The precision is achieved through manufacturing processes such as micromachining or precision molding rather than mechanical adjustment.
4Ease of manufacture
If the outer end of the balance spring is left unadjusted after fixing, then the attachment process is simplified, but traditional fixing methods cannot guarantee that the spring retains its three-dimensional integrity or maintains concentric development during oscillation
Solution Approach 1:
The connecting element is pre-formed with a bearing surface that has precise geometric features including a specific orientation and position relative to the spring's axis. This preliminary formation ensures that when assembled with the complementary bearing surface, the spring automatically achieves correct concentric development and perpendicularity without requiring post-attachment adjustment, simplifying the manufacturing process while maintaining precision.
Data Source
Figure 1~4
Figure 5~8
Figure 9~10
AI summary
The member has a hairspring comprising a blade located in a plane, where an internal end of the hairspring is fixed to a pivot shaft. An external end of the hairspring is manufactured with an annular connecting member to a frame i.e. balance bridge (9) or to an angular positioning member (6) of the regulator member to the bridge. The connecting member and the bridge or the angular positioning member provide support surfaces partially complementary and parallel to a plane of the hairspring. A fixing unit assembles the complementary support surfaces.