Tolerance Ring Plastic Phase Operation for Stable Retention
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Solution Overview
Problem
Conventional tolerance rings for delicate assemblies, such as hard disk drive pivot mounts, are sensitive to variations in compression force and exhibit unstable resonant frequencies due to their operation in the elastic phase, leading to potential damage from resonance and instability in assembly forces.
Innovation Solution
The tolerance ring is configured to operate in its plastic phase by making the projections 'softer' through increased circumferential width and blending of edges, allowing it to exhibit more stable retention and assembly forces, and control over resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tolerance ring operates in the elastic phase (conventional configuration), then it provides resilient force accommodation, but the retention force and resonant frequency become unstable and sensitive to compression force variations
Solution Approach 1:
The patent changes the material parameters of the tolerance ring by selecting a material with specific plastic properties (yield strength, elongation at break) and configuring the projections with specific geometric parameters (height, width, spacing) to enable operation in the plastic phase. This parameter change transforms the force-compression relationship from elastic (unstable) to plastic (stable), resolving the contradiction between resilience and stability.
Solution Approach 2:
The patent introduces a dynamic transition mechanism where the tolerance ring can switch between elastic and plastic phases depending on the compression force level. During normal operation, the ring operates in the plastic phase for stable retention, while still maintaining the ability to deform elastically within safe limits to accommodate minor variations without damage.
2Productivity
If the tolerance ring is made with stiffer projections, then the assembly force increases, but the control over resonant frequency becomes tighter and component damage is reduced
Solution Approach 1:
The patent optimizes the projection geometry parameters (height h, width w, spacing s) to achieve a balance where the projections are sufficiently stiff to control resonant frequency and limit assembly force magnitude, yet configured to yield plastically at controlled levels to prevent component damage. The specific parameter ranges are selected to resolve the contradiction between assembly force control and magnitude limitation.
3Reliability
If the tolerance ring projections are made softer with increased circumferential width, then the retention force stability improves, but the assembly requires more compression force
Solution Approach 1:
The patent carefully balances the projection circumferential width parameter to achieve optimal performance. Increased width improves retention force stability and resonant frequency control, but the width is limited to prevent excessive compression force requirements. The optimal width parameter is selected to resolve the contradiction between stability improvement and compression force increase.
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 results in a more stable retention force and assembly force, reducing the range of compressive forces and allowing tighter control over resonant frequency, making the assembly process more efficient and reducing the risk of component damage.
Implementation Method 1
The tolerance ring is configured to operate in its plastic phase by making the projections 'softer' through increased circumferential width and blending of edges, allowing it to exhibit more stable retention and assembly forces
Implementation Method 2
Each projection acts as a spring and exerts a radial force against the components, providing an interference fit between them
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A mounting assembly comprising mating inner and outer components (36, 38) mounted together using a tolerance (20) is disclosed. The tolerance ring (20) has radially extending projections (28) that are configured to cause the tolerance ring (20) to operate into the plastic phase of its compression force/retention force characteristic. This can be achieved by using softer projections than those found in conventional tolerance rings. The force required to mount the tolerance ring and a range of retention forces exhibited by it for a given variance in sizes of mating components is thereby stabilised.