Parallel Barrel Groups for Thin Watch Movement
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Solution Overview
Problem
Existing watch movements struggle to achieve a thin, flat design with a large power reserve and sufficient torque, as the central fixing of the rotor cannot overlap with the barrel, preventing the desired thickness and power reserve when the rotor is self-winding or manually wound.
Innovation Solution
The implementation of two groups of coaxial barrels mounted in parallel, each comprising two barrels in series, with a double barrel design featuring external toothing on input and output cages, allowing for a reduced diameter and increased power reserve without superimposing on the central bearing, enabling a thin movement with a power reserve of around forty-eight hours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the central bearing of the winding mass is superimposed on the barrel, then the movement can be made thinner, but the power reserve and torque become insufficient
Solution Approach 1:
The motor member is segmented into two groups of barrels (first group and second group), each group containing multiple barrels mounted in series. This segmentation allows the power reserve to be distributed across multiple springs while maintaining a compact layout that frees the central area for the winding mass bearing.
Solution Approach 2:
The barrels are arranged in a planar configuration rather than stacking them vertically. The two groups of barrels are positioned side-by-side in the radial direction, with each group's barrels arranged in series along a line. This dimensional rearrangement frees the central bearing area while maintaining sufficient power reserve through the series spring arrangement.
2Length of stationary object
If the barrel diameter is reduced and placed at the periphery to free central space, then the movement becomes thinner, but the torque and power reserve become insufficient
Solution Approach 1:
Two groups of barrels are merged into a single motor member assembly, with each group contributing to the total power reserve. The barrels within each group are connected in series, merging their spring capacities additively to achieve the required 48-hour power reserve while maintaining reduced individual barrel diameters.
Solution Approach 2:
The configuration changes from a single large-diameter barrel to multiple smaller-diameter barrels arranged in series. This parameter change allows the movement to achieve the same power reserve with reduced radial space requirements, enabling a thinner overall design while maintaining sufficient torque through the combined spring energy.
3Force
If two barrels are mounted in parallel to increase torque, then the power reserve improves, but the central space required increases
Solution Approach 1:
The two groups of barrels are positioned at different radial locations within the motor member, with each group occupying a specific sector. This local distribution allows the central area to remain free for the winding mass bearing while the barrels are positioned in the peripheral regions where they provide torque without interfering with the central bearing.
4Duration of action of moving object
If a single spring with many turns is used to increase power reserve, then the power reserve improves, but the spring becomes too long and complex to manufacture
Solution Approach 1:
The single long spring is segmented into multiple shorter springs, with each barrel containing a separate spring. Each spring requires only about twelve turns, which is much easier to manufacture than a single spring requiring forty-eight turns. The segmented springs are connected in series to achieve the total power reserve requirement.
Solution Approach 2:
Instead of using one spring with exactly the required number of turns, multiple springs with fewer turns each are used. Each spring provides partial action (about twelve turns), and the combination of multiple such springs exceeds the minimum requirement while being much more manufacturable.
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 configuration allows for a thin watch movement (typically 2.6 mm thick) with a comfortable power reserve and sufficient torque to maintain a 4 Hz oscillator frequency, while optimizing manufacturing by using identical barrels and freeing up central space for the automatic winding mechanism.
Implementation Method 1
A first spring housed in the input cage, the outer coil of which is connected to this input cage and the inner coil of which is fixed to the central shaft. A second spring housed in the output cage has its inner coil fixed to the central shaft and its outer coil fixed to the output cage.
Data Source
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AI summary
The timepiece movement includes a drive member and a finishing gear-train comprising a center mobile (23, 24, 25) that connects said drive member to an escapement controlled by a regulator. Said movement differs in that the drive member comprises two groups of barrels (1, 2) and in that each of said barrel groups comprises at least two coaxial barrels mounted in series. Both groups of barrels (1, 2) are mounted in parallel, the output frame (10) of each group of barrels (1, 2) engaging with a wheel (24) of the center mobile (23, 24, 25). No mobile from the finishing gear-train is even partially placed over one or the other of the groups of barrels (1, 2).