Truncated Conical Spiral Spring for Watch Pointer Stability
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Solution Overview
Problem
Existing pointer devices for wristwatches face instability in pointer rotation due to fluctuating frictional resistance from plate springs, leading to unintended rotation of the spring with the pointer wheel, causing rotation angle fluctuations.
Innovation Solution
A pointer device incorporating a spiral spring with a truncated conical shape is arranged between the pointer wheel and the wheel train holding member, providing a stable spring force and frictional resistance to regulate the rotation angle, preventing the spring from rotating with the wheel and ensuring smooth operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plate spring is used to regulate pointer wheel rotation, then the pointer rotation can be controlled, but the frictional resistance fluctuates causing instability and unintended rotation
Solution Approach 1:
The patent changes the geometric parameters of the spring from a conventional plate shape to a truncated conical shape with specific dimensions (large diameter 1.5-2.5mm, small diameter 0.5-1.5mm, height 0.3-0.8mm). This parameter change optimizes the spring's mechanical properties to provide stable frictional resistance that prevents rotation angle fluctuations while maintaining reliable pointer rotation control.
Solution Approach 2:
The truncated conical shape creates local quality variations in the spring structure, with different diameters at different locations. This allows the spring to have varying stiffness and friction characteristics along its length, with the larger diameter base providing stable anchoring and the smaller diameter top providing controlled interaction with the pointer wheel, thereby achieving both stability and reliability.
2Device complexity
If a plate spring is arranged between pointer wheel and wheel train holding member, then the structure can be compact, but the spring rotates with the pointer wheel causing rotation angle fluctuations
Solution Approach 1:
The truncated conical spring is inherently asymmetric with a larger diameter base and smaller diameter top. This asymmetry is strategically oriented with the larger base attached to the wheel train holding member and the smaller top interacting with the pointer wheel. The asymmetric geometry prevents the spring from rotating with the wheel while maintaining a simple compact structure, thereby resolving the contradiction between structural simplicity and rotation angle precision.
3Reliability
If the spring force is increased to stabilize rotation, then the frictional resistance becomes too high causing operation difficulty
Solution Approach 1:
The truncated conical spring provides dynamic frictional resistance that adapts to operational conditions. The varying diameter along the spring length creates a progressive spring force that is sufficient to prevent rotation angle fluctuations during normal operation, yet allows smooth operation when force is applied. This dynamic characteristic resolves the contradiction between rotation stability and ease of operation.
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 spiral spring design stabilizes the rotation of the pointer wheel by generating consistent frictional resistance, suppressing rotation angle fluctuations and ensuring precise movement of the pointers.
Implementation Method 1
a spiral spring which has a substantially truncated conical shape and is arranged between the rotation body and the base member
Implementation Method 2
the rotation angle of the pointer wheel is regulated by a load being applied to the pointer wheel by the spring force of the plate spring
Data Source
AI summary
A pointer device including a rotation body, a pointer shaft provided on the rotation body, a base member which rotatably supports the pointer shaft, and a spiral spring which has a substantially truncated conical shape and is arranged between the rotation body and the base member.