Mechanical Oscillator Tunable Isochronism Defect
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Solution Overview
Problem
Mechanical oscillators in horology suffer from non-linearity of the elastic restoring force, leading to isochronism defects due to amplitude-dependent stiffness, which existing solutions like fusée mechanisms, constant force devices, and isochronism correctors either complicate or fail to maintain constant amplitude, causing inefficiencies in timekeeping precision.
Innovation Solution
A mechanical oscillator design featuring a compensation spring pivotably linked to an inertial mass via a rigid connecting bar, applying a compensating force that varies with displacement to maintain linear effective stiffness, allowing for tuning of isochronism without altering the nominal frequency, using a slider and adjustable pre-stress to manage the compensating force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional hairspring or flexure pivot system is used to provide the restoring force, then the oscillator can be compact and simple in structure, but the coefficient of stiffness becomes non-linear with amplitude, causing isochronism defects
Solution Approach 1:
The patent introduces a compensation spring whose stiffness parameter is specifically designed to counteract the amplitude-dependent stiffness variations of the main restoring spring. By carefully selecting the compensation spring's elasticity coefficient and pre-load, the system maintains effectively constant total stiffness across the operating range, eliminating isochronism defects while preserving the simplicity of the overall oscillator structure.
Solution Approach 2:
The compensation spring acts as an intermediary element between the main restoring spring and the inertial mass. It mediates the non-linearity of the restoring force by applying an opposing non-linear force that cancels out the stiffness variations, thereby maintaining constant frequency without requiring complex mechanical adjustments.
2Reliability
If a fusée mechanism is used to compensate for mainspring torque variations, then isochronism can be improved, but the device becomes bulky and complex
Solution Approach 1:
The patent extracts the essential function of the fusée mechanism (compensating for spring torque variations) and implements it through a much simpler compensation spring system. Instead of using a complex chain mechanism with varying radius, the invention uses a spring-based approach that achieves the same torque compensation effect with minimal mechanical complexity, thereby maintaining compactness.
Solution Approach 2:
The patent replaces the mechanical fusée chain mechanism with a spring-based compensation system. The compensation spring uses elastic deformation to provide the necessary torque variation compensation, substituting the complex mechanical geometry changes of the fusée with a simpler spring elasticity-based solution that is more compact and easier to manufacture.
3Reliability
If a constant force device with an intermediate spring is used, then torque to the escape wheel remains substantially constant, but the mechanism becomes complex and difficult to adjust
Solution Approach 1:
The compensation spring serves multiple functions simultaneously: it provides the restoring force for the oscillator, compensates for amplitude-dependent stiffness variations, and maintains substantially constant torque delivery to the escape wheel throughout the mainspring unwinding process. This multi-functionality eliminates the need for separate constant force mechanisms, reducing overall complexity while achieving the desired constant torque characteristic.
4Reliability
If a blade spring is used to compensate for elastic non-linearity, then isochronism can be corrected, but discontinuities appear in the restoring force curve causing rebounds and friction effects
Solution Approach 1:
The patent uses a compensation spring with specifically engineered elasticity parameters that provide smooth, continuous force compensation without abrupt changes. By carefully selecting the spring constant and pre-load, the system achieves continuous cancellation of non-linearity throughout the oscillation range, avoiding the discontinuities and contact issues that arise with blade spring mechanisms.
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
This design effectively reduces and eliminates isochronism defects by maintaining a linear restoring force over the full working range, ensuring constant frequency and improved timekeeping precision without the complexity of existing solutions.
Implementation Method 1
a compensation spring pivotably linked to said inertial mass by means of a substantially rigid first connecting bar so as to apply a compensating force to said inertial mass in such a manner that said compensating force varies in function of displacement of said inertial mass from its neutral position
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
Mechanical oscillator (1) for a timepiece comprising an inertial mass (3) arranged to oscillate about a neutral position under the effect of a restoring force provided by at least one elastic element (5), characterised in that said mechanical oscillator (1) further comprises a compensation spring (11) pivotably linked to said inertial mass (3) by means of a substantially rigid first connecting bar (15), said compensation spring (11) and said first connecting bar (15) being arranged so as to apply a compensating force to said inertial mass (3) which varies in function of displacement of said inertial mass (3) from its neutral position. This arrangement permits tuning of the isochronism and thus reduction and/or elimination of the isochronism defect of the oscillator typically caused by nonliearity of the restoring force provided by the elastic element (55)