Shaft-Expanding Frustoconical Lock for Backlash-Free Torque Transmission
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Solution Overview
Problem
Existing methods for connecting a shaft to a hub, wheel, or crank often introduce backlash, require tight tolerances, or are not durable, and lack efficiency in transmitting torque under various load conditions.
Innovation Solution
A shaft-expanding cone lock with a frustoconical component that tightens axially into the shaft, expanding it outward to create a strong friction fit with the mating piece, allowing torque transmission without backlash and supporting overhung loads and axial forces, while being compact and lightweight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a tight press fit is used to connect shaft to mating piece, then connection strength is improved, but manufacturing complexity increases due to tight tolerance control requirements
Solution Approach 1:
The invention changes the physical state of the shaft material through controlled thermal expansion (heating) to increase its diameter, enabling a interference fit connection. By temporarily altering the thermal parameter of the shaft, the connection achieves high strength without requiring tight manufacturing tolerances on the cold-fit dimensions.
2Strength
If thermal expansion method is used to join shaft to mating piece, then connection strength is improved, but difficulty of separation increases
Solution Approach 1:
The invention applies preliminary thermal expansion to the shaft before assembly, creating the interference fit condition only during the assembly process. After cooling, the shaft returns to its original dimensions, maintaining the strong connection during operation but allowing for potential disassembly by reapplying heat, thus preserving ease of repair while achieving strong connection.
3Ease of manufacture
If conventional locking methods are used, then ease of manufacture is improved, but backlash is introduced into the connection
Solution Approach 1:
The invention uses thermal expansion to create a precise interference fit that eliminates backlash. By temporarily increasing the shaft diameter through heating, the connection achieves zero-clearance engagement with the mating piece, removing backlash without requiring complex mechanical locking mechanisms.
4Strength
If cryogenic cooling is used to slip-fit shaft into interference hole, then connection strength is improved, but device complexity increases
Solution Approach 1:
Instead of cooling the shaft to shrink it for assembly (cryogenic method), the invention inverts the approach by heating the shaft to expand it for assembly. This reversed thermal approach achieves the same interference fit effect but with simpler equipment requirements, as heating can be accomplished with conventional ovens or induction heaters rather than complex cryogenic systems.
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 shaft-expanding cone lock provides a reliable, backlash-free connection that supports torque transmission and axial forces, is compact, and can be easily removed, making it suitable for space-constrained applications with reduced material usage and weight compared to other methods.
Implementation Method 1
tightening the connector by drawing the rings together in axial direction. As the rings are drawn together, the inner ring clamps against the shaft and the outer ring against an inner surface of the hub
Implementation Method 2
The shaft-expanding cone lock comprises a cone piece having a first frustoconical surface; and a shaft having: an end face defining an opening of a hole in the shaft; a wall around said hole; a second frustoconical surface that defines an inner surface of the wall, the second frustoconical surface configured to engage with the first frustoconical surface
Data Source
AI summary
A cone piece is tightened into a compatibly shaped hole in the end of a shaft. As the cone piece is tightened, it forces the shaft to expand outwards. As the shaft expands, it creates or increases pressure against a hub, wheel, crank or other mating piece that is positioned on the shaft, locking it into place.