Threaded Coupling Locking Assembly for Low-Weight Compact Joints
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Solution Overview
Problem
Traditional threaded couplings in weight-sensitive applications, such as the aerospace industry, are bulky and increase the length of mechanical systems, making them undesirable due to additional weight and length considerations.
Innovation Solution
A threaded coupling design featuring a lock pin and lock nut assembly with a cylindrical portion and externally threaded member, allowing for secure locking with reduced material usage and space efficiency, enabling adjustments in timing and length by fractions of a turn, and incorporating secondary locking mechanisms for vibration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional locking assembly with lock washer and keyway is used, then secure locking is achieved, but weight and length increase significantly
Solution Approach 1:
The lock pin integrates multiple functions into a single component: it provides locking engagement through the key cavity, positioning through the rim projection, and radial constraint via engagement surfaces. This merges what would traditionally require separate lock washer, keyway, and retention features into one unified element, reducing weight while maintaining locking security.
Solution Approach 2:
The lock pin serves multiple purposes simultaneously: it acts as a locking key by engaging the key cavity, a positioning element by contacting the rim projection, and a retention feature through its engagement surfaces with the lock nut or rim. This multi-functionality eliminates the need for separate specialized components, addressing the weight concern while preserving reliable locking.
2Reliability
If a traditional locking assembly with lock washer and keyway is used, then secure locking is achieved, but the length of the threaded coupling increases
Solution Approach 1:
The lock pin is received within the key cavity of the externally threaded member, nesting the locking feature inside the existing component geometry rather than adding external protrusions. The lock nut then secures the pin axially, creating a compact nested arrangement that minimizes the overall length of the threaded coupling while maintaining secure locking.
Solution Approach 2:
The locking mechanism transitions from a traditional lateral keyway engagement to a primarily axial arrangement where the lock pin extends axially through the key cavity and is retained by the lock nut. The radial engagement surfaces provide lateral constraint, but the overall structure is optimized in the axial dimension, reducing coupling length.
3Weight of moving object
If material is reduced for weight savings, then weight decreases, but manufacturing precision requirements increase
Solution Approach 1:
The critical precision requirements are extracted and concentrated on the engagement surfaces of the lock pin and lock nut, rather than distributing precision requirements across multiple components. By taking out the locking function and implementing it through precisely machined engagement surfaces on fewer parts, the design achieves weight reduction while focusing manufacturing precision where it is most critical for functional reliability.
Data Source
AI summary
A threaded coupling is provided that comprises a first coupling member, comprising a cylindrical portion which is internally threaded around an axis of rotational symmetry of the cylindrical portion and comprises an open end that defines an opening having an annular rim; a second coupling member comprising an externally threaded portion and at least one key cavity; and a locking assembly. The locking assembly comprises a lock pin and a lock nut. The externally threaded portion is arranged to be received through the opening to be threadedly engaged with the internally threaded cylindrical portion to couple the first coupling member to the second coupling member. The rim comprises at least one projection that projects in a generally axial direction parallel to the axis of rotational symmetry of the cylindrical portion.