Toothed-Rack Balance Return Component with Dual Elastic Strips
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Solution Overview
Problem
Existing mechanical watch escapements, particularly in portable watches, face challenges with spiral springs that are delicate to manufacture, suffer from vertical position variations, and exhibit torque fluctuations, leading to energy losses and inefficiencies due to asymmetry and friction, making them unsuitable for conventional wristwatch sizes.
Innovation Solution
A return member comprising a rack with a toothed sector and two independent elastic blades, which pivot between extreme positions, compensates for friction and asymmetry by storing and releasing energy symmetrically, allowing for a balanced operation regardless of the balance wheel's direction of rotation, and is compact enough for wristwatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spiral spring is used as a balance return member, then the balance can be returned to its neutral position, but the spiral spring is delicate to manufacture and suffers from torque variations between contraction and relaxation
Solution Approach 1:
The patent extracts the spiral spring from the system and replaces it with a balance return member consisting of a fork and two independent springs. This removes the problematic component while retaining the essential function of returning the balance to its neutral position, thereby improving reliability without manufacturing complexity
Solution Approach 2:
The single spiral spring is segmented into two independent springs that act on opposite sides of the balance fork. This segmentation eliminates the torque variation problem because each spring operates independently, providing consistent force in both contraction and relaxation phases, thus improving timekeeping precision
2Duration of action of moving object
If a spiral spring is used as a balance return member, then the balance can oscillate, but the torque varies between ascending and descending angles causing energy losses
Solution Approach 1:
The patent introduces asymmetry in the arrangement of the two springs relative to the balance fork, with one spring acting on the left side and the other on the right side. This asymmetric configuration ensures that torque is consistently applied in both directions of oscillation, eliminating the energy losses associated with torque variation and maintaining stable oscillation duration
3Device complexity
If a rack with elastic blade is used to replace the spiral spring, then the return member can be simpler, but the elastic blade must be sufficiently stiff to store energy yet flexible enough to allow large angular displacement
Solution Approach 1:
The single elastic blade is segmented into two separate springs that act on opposite sides of the balance fork. This segmentation allows each spring to be optimized for its specific function, providing sufficient stiffness for energy storage while maintaining the flexibility needed for large angular displacement through the coordinated action of both springs
Solution Approach 2:
The balance fork acts as an intermediary between the two springs and the balance wheel. This intermediary component allows the springs to apply force indirectly, enabling large angular displacement of the balance while the springs themselves remain relatively stiff for efficient energy storage, thus resolving the contradiction between stiffness and flexibility
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 provides a balanced and efficient energy transfer without significant friction, enabling smooth operation and precise timekeeping in portable watches, overcoming the limitations of spiral springs by reducing stiffness and size constraints.
Implementation Method 1
The elastic blade must be capable of storing energy when it is deformed by the movement of the rack. It must then release this energy to move the rack in the opposite direction
Data Source
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AI summary
The invention particularly relates to a return component of a balance (10) of a timepiece, replacing a spiral spring. This return component comprises a rack (21) provided with a toothed sector (22) arranged to engage with a balance pinion (20). The rack (21) comprises an axis of rotation (24) allowing it to move between two end positions, called work positions, separated by a rest position. The return component also comprises two springs (26) arranged to urge the rack (21) towards its rest position. Each spring (26) is formed by a resilient strip (27) arranged to store energy, then restore it to the rack. Each resilient strip works alternately such that they never work simultaneously. The invention also relates to an escapement comprising such a return component, a timepiece movement comprising this return component and a timepiece comprising such a movement.