Clockwork Barrel Segmentation for Composite Spring Stress Reduction
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Solution Overview
Problem
Conventional drive members for clock movements face challenges in reducing bending stresses and achieving a reduced volume while maintaining the storage of mechanical energy, particularly with composite materials that have lower elasticity and elastic limits compared to steel.
Innovation Solution
A motor member design featuring superposed barrels with a common shaft, where the springs work in series and are connected via a kinematic link, utilizing composite materials with a pivoting flange to minimize bending stresses and tangential forces, and a disengageable crown to control torque during winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If composite materials are used for springs, then fatigue resistance and service life are improved, but bending stresses increase due to lower elasticity and yield strength
Solution Approach 1:
The motor element is divided into two separate barrels (first barrel and second barrel) with two separate springs working in series. This segmentation allows each spring to operate independently with optimized geometry, reducing the bending stresses on each individual spring while maintaining the total energy storage capacity. The series configuration means the torque is distributed across both springs, further reducing stress on each composite material spring.
Solution Approach 2:
The invention changes the geometric parameters of the springs, specifically the radius of the barrels. By increasing the barrel radius, the bending moment on the springs is reduced for the same torque, which directly reduces bending stresses. The patent specifies that the barrels have a radius between 0.8mm and 1.2mm, optimized for composite material springs with lower elastic properties.
2Stress or pressure
If barrel radius is increased, then bending stresses on springs are reduced, but volume of the motor element increases
Solution Approach 1:
By segmenting the motor element into two barrels arranged in series, each barrel can have a smaller radius than a single barrel would require. The series configuration allows the torque to be distributed across both springs, enabling the use of smaller radius barrels that reduce volume while still maintaining acceptable bending stress levels through the combined effect of both springs.
Solution Approach 2:
The two barrels are arranged in series along the axial dimension rather than side-by-side, utilizing the axial space efficiently. This dimensional arrangement allows the motor element to achieve reduced volume by stacking the barrels along the shaft axis, accommodating the larger effective radius needed for stress reduction without proportionally increasing the overall volume.
3Power
If two barrels are superimposed on a common shaft, then torque transmission efficiency is improved, but height of the drive unit increases
Solution Approach 1:
The two barrels are nested concentrically on a common shaft, with one barrel positioned inside or alongside the other along the axial direction. This nesting arrangement allows both barrels to share the same radial space while transmitting torque through the common shaft, thereby maintaining high torque transmission efficiency without significantly increasing the overall height of the drive unit.
Solution Approach 2:
The common shaft serves multiple functions: it supports both barrels, transmits torque from both springs, and provides a unified rotational axis for the entire motor element. This multi-functionality allows the height to be minimized by consolidating support structures, as the single shaft replaces what would otherwise require separate support mechanisms for each barrel.
4Quantity of substance
If blade thickness of composite springs is increased, then stored energy and maximum torque are improved, but manufacturing precision becomes more difficult
Solution Approach 1:
The segmentation into two barrels with two springs allows each spring to have optimized, thicker blade dimensions that are easier to manufacture with composite materials. Each spring can be manufactured with sufficient thickness to achieve the required energy storage and torque, while the series configuration ensures that the total energy capacity meets the design requirements without requiring excessively thin or precision-critical single-spring dimensions.
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 reduces bending stresses and allows for a compact motor member that stores the same amount of mechanical energy as conventional designs, with composite springs experiencing less degradation and a longer lifespan, while maintaining chronometric performance.
Implementation Method 1
a unidirectional glass fiber reinforced polymer has a modulus of elasticity approximately four times lower than that of steel
Implementation Method 2
The use of composite materials, such as glass fiber reinforced polymers or others, for manufacturing engine springs results in springs that are less susceptible to fatigue fractures than conventional metal springs
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Drive member (1) for clock movement comprising: a barrel (2, 2') comprising a drum (6, 6') mounted on an arbor (3) so that it can rotate with the abrbor (3) about an axis (4) when the drive member (1) is wound up; a main spring (8, 11) wound inside the barrel (2) and able to be wound up around the arbor (3) when the drive member (1) is wound up, and a core (17, 17') coaxial with and pivoting on the arbor (3); the exterior end (9, 13) of the spring (8, 11) being coupled to the drum (6, 6') and the interior end (10, 12) of the spring (8, 11) being coupled to the core (17, 17'); the exterior end (9, 13) of the spring (8, 11) is coupled to the drum (6, 6') by a first clamp (18) that is pivot mounted in the drum (6, 6') so that when the spring (8, 11)is unwound, the first clamp (18) pivots in such a way as to hold the exterior tuen of the first spring (8, 11) against the drum (6, 6') and when the spring (8, 11) is wound up, the first clamp (18) pivots towards the centre of the barrel (2) to follow the exterior turn of the spring (8, 11). The bending stresses in the spring are reduced.