Rotary Encoder Disc Springs for Self-Centering Shaft Mounting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotary encoders, particularly those with glass or metal discs, face challenges in providing a low-profile, high-performance solution with effective self-locating capabilities, especially when dealing with manufacturing tolerances and variations in shaft diameters, which affect repeatability and accuracy.
Innovation Solution
A rotary scale apparatus with cantilevered spring members around a planar disc, configured to engage with a cylindrical shaft, ensuring balanced and predictable self-locating performance by using identical spring forces and opposite orientations to counteract turning forces, thereby enhancing stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional attachment methods are used for glass or metal discs, then the encoder can be assembled, but the self-locating performance is poor and repeatability is affected by manufacturing tolerances and shaft diameter variations
Solution Approach 1:
The patent changes the physical state and mechanical properties of the attachment mechanism by using elastically deformable cantilevered spring members instead of rigid attachment methods. These spring members can flex and adapt to shaft diameter variations within a range, transforming the rigid connection into a compliant one that maintains consistent self-locating performance despite manufacturing tolerances in both the disc and shaft.
Solution Approach 2:
The cantilevered spring members are positioned asymmetrically around the periphery of the disc, with at least three springs arranged at different angular positions. This asymmetric distribution provides balanced radial locating forces while accommodating shaft diameter variations, improving repeatability without requiring high manufacturing precision.
2Length of moving object
If the disc profile is reduced to achieve a low-profile encoder, then the encoder becomes more compact, but the self-locating capability and stability are compromised
Solution Approach 1:
The patent moves the self-locating function from the axial dimension (thickness of the disc) to the radial dimension (peripheral spring members). The cantilevered springs extend radially outward from the disc periphery and engage with the shaft surface, providing stable self-locating capability without increasing the axial profile of the disc. This dimensional transition allows low-profile design while maintaining stability.
Solution Approach 2:
The cantilevered spring members act as intermediary elements between the disc and the shaft. These springs provide the necessary mechanical compliance and locating force while allowing the disc to maintain a thin profile. The springs absorb the mechanical stress and adaptation requirements, enabling the disc itself to remain thin without compromising self-locating stability.
3Measurement precision
If multiple spring members are added to improve self-locating performance, then the encoder achieves better centering accuracy, but the device complexity increases
Solution Approach 1:
The patent concentrates the self-locating function at the local periphery of the disc where the cantilevered spring members are attached. Instead of distributing complexity throughout the entire disc structure, the springs are localized at strategic peripheral positions, providing efficient centering accuracy with minimal additional components. The local quality of the spring members at the periphery delivers the required precision without global complexity.
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 configuration provides a compact, self-locating rotary encoder with improved repeatability and accuracy, capable of centering the disc relative to the shaft with less than 10µm eccentricity, even with varying shaft diameters, ensuring high metrological performance.
Implementation Method 1
comprising at least three cantilevered spring members which are provided substantially in plane with the planar disc and spaced around the edge of the hole, for engaging with, and radially locating (e.g. centring) the planar disc on, a cylindrical shaft inserted therethrough
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A rotary scale apparatus for an encoder apparatus comprising a planar disc on which at least one track comprising scale features is provided, in which the planar disc comprises a hole through its centre for receiving a cylindrical shaft, and in which the rotary scale member comprises at least three cantilevered spring members which are provided substantially in plane with the planar disc and spaced around the edge of the hole, for engaging with, and radially locating the disc on, a cylindrical shaft inserted therethrough.