Hydraulic Friction-Fit Hub Joint for High Torque Without Shaft Damage
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Solution Overview
Problem
Current low moment hub joint assemblies in turbomachinery face limitations in interference limit between the hub and shaft, leading to potential damage during assembly and reduced machine capacity due to adherence issues, necessitating a solution to increase interference while preventing shaft damage.
Innovation Solution
A hub joint assembly comprising a coupling hub and a clamp ring with conical surfaces and anti-adhesion coatings, utilizing hydraulic fluid pressure to incrementally increase interference pressure, allowing for a higher torque friction fit without damaging the shaft, and featuring a clamp ring design that reduces radial strain on the coupling hub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hydraulic interference fit is used to connect hub and shaft, then torque transmission capability is improved, but shaft surface damage and adhesion occur during assembly and disassembly
Solution Approach 1:
A protective coating is applied to the shaft surface to serve as an intermediary layer between the hub and shaft. This coating prevents direct metal-to-metal contact and adhesion during assembly and disassembly, while still allowing the hydraulic interference fit to transmit torque effectively. The coating acts as a sacrificial element that protects the shaft surface from damage.
Solution Approach 2:
The patent replaces pure mechanical interference fit with a hydraulic interference fit system. Instead of relying solely on mechanical forcing of the hub onto the shaft, hydraulic pressure is used to control the interference fit process. This substitution allows for more controlled application of interference forces, reducing the risk of surface damage while maintaining torque transmission capability.
2Power
If interference limit is increased to improve machine capacity, then power density is improved, but shaft damage and adhesion problems worsen
Solution Approach 1:
The protective coating on the shaft is designed as a sacrificial, disposable element. It is applied to the shaft surface before hub installation and is intended to be consumed or damaged during the assembly process. This disposable coating protects the expensive, critical shaft from damage, allowing the use of higher interference limits for improved power density without compromising long-term reliability.
Solution Approach 2:
The patent changes the surface properties of the shaft by applying a protective coating with different material characteristics than the base shaft material. This parameter change in surface properties allows for higher interference pressures to be applied without causing adhesion or damage to the underlying shaft, enabling increased machine capacity while maintaining reliability.
3Strength
If high pressure friction connection is used to connect hubs, then torque capacity is improved, but radial strain on coupling hub increases
Solution Approach 1:
The patent employs conical surfaces with specific curvature profiles in the hub and clamp ring design. The curved, conical geometry distributes the radial strain more uniformly across the contact surfaces, reducing stress concentration points. This curvature-based design allows high pressure friction connections to achieve high torque capacity while minimizing peak radial strain on the coupling hub.
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 solution enhances the interference limit, reduces shaft damage during assembly, and improves both capacity and service reliability by maintaining a uniform pressure distribution and minimizing radial strain, thereby increasing power density and durability.
Implementation Method 1
a hub joint assembly for a low moment coupling that is used to frictionally connect a shaft of a machine to a connector
Implementation Method 2
utilizing hydraulic fluid pressure to incrementally increase interference pressure
Implementation Method 3
A protective anti-adhesion coating may be provided on at least a portion of the inner surface 176
Data Source
AI summary
A hub joint assembly for connecting a shaft to a connector comprises a coupling hub including a collar portion and a flange portion. The collar portion includes a bore having an inner surface configured to be positioned adjacent to an outer surface of the shaft, which may include a keyway for receiving a key defined in the shaft. The collar portion further includes an outer surface. The flange portion extends from the collar portion and is configured to be coupled with the connector. The assembly further includes a clamp ring including an inner surface. The inner surface is configured to mate with the outer surface of the coupling hub. A passage is defined in the clamp ring and may extend from an outer or face surface of the clamp ring to the inner surface of the clamp ring. The coupling hub may be formed as a two-piece sub-assembly.