Service Tube Locking Assembly for Vibration-Resistant Threaded Joints
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Solution Overview
Problem
Threaded connections in aircraft engines are prone to loosening due to vibrations, impacts, and thermal loads, leading to potential oil leakage and instability in service tube assemblies.
Innovation Solution
A service tube assembly with a frustoconical shoulder and seat face configuration, combined with a locking member and mechanical fastener, creates a frustoconical-to-frustoconical contact surface to securely lock the service tube against rotation, using a threaded fastener to compress the locking member against both the shoulder and seat face, enhancing friction and preventing loosening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If threaded connections are used between service tubes and engine components, then assembly is simplified and components can be easily installed, but the connections are susceptible to loosening due to vibrations, impacts, and thermal loads
Solution Approach 1:
The connection system is divided into multiple functional segments: the threaded connection provides basic assembly, the frustoconical shoulder provides positioning and initial loading, the locking member provides friction-based anti-loosening, and the mechanical fastener provides final securing. This segmentation allows each component to perform its specific function optimally while working together to solve both ease of assembly and connection stability requirements.
Solution Approach 2:
The solution employs a composite connection structure combining different mechanical principles: threaded engagement (screw mechanism), frustoconical friction surfaces (friction-based locking), and mechanical fastening. This composite approach integrates multiple locking mechanisms into a single assembly system, achieving both ease of installation and high reliability under vibrational and thermal stresses.
2Reliability
If a locking mechanism is added to prevent loosening of threaded connections, then connection stability is improved, but device complexity increases
Solution Approach 1:
The locking member integrates multiple functions into a single component: it provides frictional engagement with the frustoconical shoulder for anti-loosening, receives the mechanical fastener for securing, and maintains axial positioning of the service tube. This merging reduces the number of separate parts needed while achieving comprehensive connection stability.
Solution Approach 2:
The frustoconical shoulder acts as an intermediary element between the threaded connection and the locking member. It translates the axial compression force from the mechanical fastener into radial friction force on the service tube, providing a mechanical advantage that enhances locking effectiveness while simplifying the overall structure.
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 effectively prevents the loosening of service tubes, ensuring secure fluid routing and reducing the risk of oil leakage by maximizing frictional engagement between the frustoconical surfaces, thereby maintaining the integrity of the threaded connection under operational stresses.
Implementation Method 1
the frustoconical shoulder face and the frustoconical inner face are configured to create a frustoconical-to-frustoconical contact surface between the locking member and the outer shoulder of the service tube
Implementation Method 2
a mechanical fastener releasably holding the locking member in abutment against both of the outer shoulder of the service tube and the mating part
Data Source
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AI summary
A service tube assembly has a service tube (26) having a threaded end portion (26A) and an outer shoulder (26B) adjacent to the threaded end portion (26A), the outer shoulder (26B) having a frustoconical shoulder face (26C) converging towards the tube axis (T) and away from the threaded end portion (26A); a mating part (28) threadingly engaged by the threaded end portion (26A), the mating part (28) having a seat face (28A) converging towards the service tube (26) and towards the threaded end portion (26A); a locking member (32) extending from a first end to a second end, the first end including a notch receiving the outer shoulder (26B), the notch circumscribed by a frustoconical notch face (32E) abutting the frustoconical shoulder face (26C) to create a frustoconical-to-frustoconical contact surface between the locking member (32) and the outer shoulder (26B), the second end in abutment against the seat face (28A); and a mechanical fastener (34) releasably holding the locking member (32) in abutment against both of the outer shoulder (26B) and the mating part (28).