Aircraft Engine Fastener Ball-and-Socket Joint Design
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Solution Overview
Problem
The existing engine fastener systems for aircraft, particularly the ball-and-socket joints, are prone to deformation and radial jamming when screws are over-tightened, and the cramped location makes it difficult to increase screw diameter for thread repair.
Innovation Solution
An engine fastener with a one-piece ball forming a spherical portion that fits over a cylindrical extension, accompanied by fixing and joining means such as cages and threaded rods, which eliminates stress on the ball during tightening and reduces the risk of jamming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If screws are used to fix the ball-and-socket joint, then the joint can be assembled and secured, but the ball deforms and jams when screws are over-tightened
Solution Approach 1:
The joint is divided into separate components: a spherical element and a socket element with independent fixing mechanisms. The spherical element is secured by a retaining ring on the cylindrical extension, while the socket is fixed to the paddle separately, eliminating stress concentration on a single ball component during tightening
Solution Approach 2:
The fixing function is extracted from the ball itself and applied to the surrounding structure. The retaining ring captures the spherical element without requiring screws to directly fasten the ball, thereby preventing deformation and jamming while maintaining secure fixation
2Strength
If screw diameter is increased for thread repair, then thread strength is improved, but the cramped location prevents screw access
Solution Approach 1:
The fixing function is extracted from the ball itself and applied to the surrounding structure. The retaining ring captures the spherical element without requiring screws to directly fasten the ball, thereby preventing deformation and jamming while maintaining secure fixation
Solution Approach 2:
The fixation approach moves from a two-dimensional screw-from-side approach to a three-dimensional solution where the retaining ring engages the spherical element radially, allowing access from directions that avoid the cramped location constraints
3Reliability
If a one-piece ball is used, then deformation and jamming risks are reduced, but assembly complexity increases
Solution Approach 1:
The joint is divided into separate components: a spherical element and a socket element with independent fixing mechanisms. The spherical element is secured by a retaining ring on the cylindrical extension, while the socket is fixed to the paddle separately, eliminating stress concentration on a single ball component during tightening
Solution Approach 2:
The spherical element's own geometry (its spherical shape and central bore) is utilized for fixation. The central bore receives the cylindrical extension for positioning, while the spherical outer surface engages with the socket, making the ball's form itself part of the fixing mechanism and simplifying the overall assembly process
Data Source
AI summary
An engine fastener for an aircraft, to secure an engine to a pylon and comprising a fastener body fixed to the pylon and having a cylindrical extension, and a fixing assembly comprising a paddle fixed to the engine and a connection arrangement joined to the paddle and arranged on the cylindrical extension to form a ball-and-socket joint between the cylindrical extension and the paddle. The connection arrangement comprises a ball, formed in one piece, having a central bore in which the cylindrical extension fits, and of which the outer surface is a spherical portion, a fixing element fixing the ball on the cylindrical extension, and two cages, each having an inner surface assuming the form of a spherical portion. The two inner surfaces are arranged opposite one another to house the ball, and for each cage, a joining element joins the cage to the paddle.