Encoder Hub Conical Snap-Fit for Disc Alignment
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Solution Overview
Problem
Existing rotary encoder manufacturing technologies face challenges in achieving precise concentricity and rigidity between the code wheel disc and hub, leading to inaccuracies and signal attenuation due to gap-related moire patterns and the need for complex alignment and bonding processes.
Innovation Solution
A mechanical mechanism using a biaxially-oriented polyethylene terephthalate (boPET) polyester film, such as Mylar, is attached to an aluminum hub via a conical surface with an undercut groove, allowing for snap fit alignment and deformation to achieve optimal reflectivity and concentricity without additional assembly mechanisms, promoting a positive retaining mechanism and preventing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex alignment and bonding processes are used to attach the code wheel disc to the hub, then manufacturing precision and concentricity are improved, but device complexity and manufacturing time increase
Solution Approach 1:
The attachment mechanism is segmented into distinct functional elements: the conical surface for alignment and the undercut groove for retention. This segmentation allows each element to perform its specific function independently, achieving precise concentricity through the conical surface while the undercut groove provides automatic retention without requiring complex bonding processes.
Solution Approach 2:
The snap-fit mechanism with the undercut groove enables the code wheel disc to self-align and self-retain on the hub. When the disc is inserted, the conical surface automatically guides it into the correct concentric position, and the undercut groove automatically retains it, eliminating the need for external alignment tools or bonding operations.
2Manufacturing precision
If complex alignment and bonding processes are used to attach the code wheel disc to the hub, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The hub is pre-formed with the conical surface and undercut groove during manufacturing. This preliminary preparation ensures that when the code wheel disc is installed, the alignment and retention functions are already in place, eliminating the need for time-consuming bonding processes during final assembly and significantly improving productivity.
Solution Approach 2:
The snap-fit mechanism enables rapid assembly by allowing the code wheel disc to be quickly inserted and automatically retained without requiring bonding operations. The conical surface provides immediate alignment, and the undercut groove provides automatic retention, reducing assembly time while maintaining precision.
3Reliability
If intermediate materials are used to attach the code wheel disc to the hub, then adhesion is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for intermediate bonding materials by using a pure mechanical attachment mechanism. The conical surface and undercut groove work together to provide secure retention of the code wheel disc without requiring adhesives, epoxies, or other intermediate materials, thereby reducing device complexity and eliminating potential failure points associated with bonding.
Solution Approach 2:
The conical surface acts as an intermediary geometric feature that enables direct mechanical attachment between the hub and code wheel disc. Instead of using chemical bonding intermediaries, the conical geometry provides the necessary alignment and force distribution to achieve reliable attachment through purely mechanical means.
4Ease of manufacture
If the code wheel disc is not securely retained to the hub, then assembly simplicity is maintained, but measurement precision and signal quality deteriorate due to gap-related moire patterns
Solution Approach 1:
The undercut groove is strategically positioned at the critical interface between the hub and code wheel disc to provide localized retention. This local geometric feature ensures secure attachment at the specific location where the code wheel disc contacts the hub, preventing gaps that would cause moire patterns, while maintaining overall assembly simplicity through the snap-fit mechanism.
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 method ensures nearly perfect concentricity and adhesion, preventing signal attenuation and ensuring longevity by maintaining the reflective system's integrity and accuracy, while simplifying the assembly process and eliminating the need for intermediate materials.
Implementation Method 1
The difference in size of the conical surface on the hub and the bore of the mylar disk promotes a deflection of the mylar which forces the mylar to conform to a tapered reflective surface on the hub
Implementation Method 2
Beneath the conical surface of the hub lies an undercut groove into which the interior edge of the mylar code wheel disc snaps. Concurrently, the deflection and snap fit of the mylar into the undercut notch on the hub provides a positive retaining mechanism both in the radial and axial orientations of the assembly
Implementation Method 3
The style of encoder discussed herein is a third type referred to an optical encoder, which is a device that utilizes a lighting source, a code wheel disc and a sensor to decipher the interruptions of the lighting source that are established during its interaction with the code wheel disc. Another common type of optical encoder is that of the reflective code-wheel disc optical encoder, which employs a code-wheel disc which has a series of reflective and non-reflective patterns on its surface. Opposite that surface are both the light source and the sensor, arranged in a way in which the light source focuses on the surface of the code wheel disc in a fashion that reflects back toward the sensor
Data Source
AI summary
An annular having a central bore includes a conical surface concentric with the bore such that the conical surface has a peak, an inner trough and an outer lip and the inner trough is adjacent to the central bore. A retention groove located under the outer lip has an outside diameter that is less than the lip outside diameter. A tapered reflective face extends outward from the retention groove. When a code wheel disc having an inside diameter that is smaller than said lip outside diameter is pressed onto the conical surface, the difference in size of the lip outside diameter and the disc inside diameter promotes a deflection of the disc which forces it to conform to the tapered reflective surface.