Helical Involute Teeth Coupling for Torque Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mechanical couplings in electrophotographic devices, such as copiers and laser printers, face issues with high stress concentrations, wear, and maintenance costs due to point contact and uneven engagement between the driving and driven mechanisms, leading to reduced printing accuracy and increased maintenance needs.
Innovation Solution
The use of a plurality of helical involute teeth that engage with a twisted recess, distributing compression forces over a greater surface area and reducing shear stress, allowing for more torque transmission while maintaining coaxial alignment and minimizing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a triangular coupling block with point contact is used to engage the drive shaft, then the device complexity is reduced, but the stress concentration increases and wear accelerates
Solution Approach 1:
The coupling block is segmented into multiple teeth (typically three or more) instead of a single triangular block. Each tooth distributes the load separately, transforming the concentrated point contact into multiple distributed contact points, thereby reducing stress concentration while maintaining structural simplicity
Solution Approach 2:
The contact surfaces of the teeth are designed with specific geometric profiles (such as involute or helical surfaces) that optimize the local stress distribution. This local quality enhancement ensures that stress is evenly distributed across the contact area rather than concentrated at vertices or edges
2Stress or pressure
If beveling the triangular tips is done to increase contact area, then the stress distribution improves, but the manufacturing precision requirements increase
Solution Approach 1:
Instead of using flat beveled surfaces, the patent employs curved surfaces such as helical or involute profiles on the teeth. These curved surfaces naturally distribute stress more effectively and are more tolerant to manufacturing variations, as the continuous curvature provides gradual contact rather than sharp edges that require high precision
3Ease of manufacture
If point contact coupling is used, then the ease of manufacture is improved, but the wear rate increases and reliability decreases
Solution Approach 1:
The coupling block is divided into multiple teeth that distribute the mechanical load across several contact points instead of one. This segmentation reduces wear at each individual contact point while maintaining the overall simplicity of the coupling structure, thereby improving reliability without significantly complicating manufacturing
Solution Approach 2:
The teeth are designed with helical or inclined surfaces that provide dynamic engagement during rotation. This dynamic contact pattern ensures continuous surface contact rather than static point contact, distributing wear over time and across the surface area, thereby extending the coupling life and maintaining print accuracy
4Device complexity
If a twisted triangular recess with point contact is used, then the device complexity is minimized, but the torque transmission capability is reduced due to high stress
Solution Approach 1:
The coupling recess is segmented into multiple tooth profiles instead of a single triangular void. This segmentation allows the torque to be distributed across multiple contact surfaces, increasing the total contact area and enabling higher torque transmission while keeping the overall coupling mechanism simple and straightforward
Data Source
AI summary
A rotatable coupling is used with a replaceable developer cartridge and electrostatographic image devices. The coupling has a driven portion and a driving portion. The driven portion has a shaft with a connecting portion that has a plurality of helical involute teeth extending outwardly. The driving portion has an end with a gear shaft and a twisted recess in the gear shaft. The sides of the recess are engageable with the helical involute teeth so that the driving portion drives the driven portion and transmit torque.