Through-Shaft Assembly for Approximate Hole Alignment
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Solution Overview
Problem
The assembly of mechanical connections between aircraft propellants and support masts is complicated by the need for precise alignment of orifices, which is challenging due to the lack of play and congestion of parts, especially in aeronautical applications where the alignment must be perfect to avoid mechanical interference and facilitate stress transmission.
Innovation Solution
A mechanical connection using a shaft with a constant section and an outer surface featuring two diametrically opposite arcs of extra thickness, allowing the shaft to adopt two angular positions to facilitate alignment and assembly, with orifices designed to accommodate these thickness variations for easy alignment and secure bonding without play.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a shaft is used to connect parts requiring perfect alignment, then the mechanical connection strength is improved, but the assembly difficulty increases due to alignment constraints
Solution Approach 1:
The shaft features non-uniform thickness distribution with thicker sections (arcs) at specific locations and thinner sections elsewhere. This local variation in geometry allows the shaft to accommodate misalignment during assembly while maintaining strong mechanical connection when properly positioned, resolving the contradiction between connection strength and assembly ease.
Solution Approach 2:
The shaft's cross-sectional parameters are changed along its circumference, creating zones of different thickness. This parameter variation enables the shaft to adapt to alignment tolerances by allowing peripheral gaps in misaligned positions while providing full contact in aligned positions, thus improving both assembly ease and connection strength.
2Ease of manufacture
If the shaft has uniform thickness, then the manufacturing is simplified, but the alignment tolerance is reduced
Solution Approach 1:
Instead of uniform thickness, the shaft implements local quality variations with thicker arcs at specific angular positions. This allows the manufacturing process to focus precision on critical thick sections while tolerating variations in other areas, effectively balancing manufacturing simplicity with alignment precision requirements.
3Ease of operation
If the orifices are perfectly aligned, then the shaft can be inserted easily, but the assembly time increases due to precise positioning requirements
Solution Approach 1:
The shaft's variable thickness profile creates a geometric feature that guides alignment during insertion. The thicker arcs engage with corresponding orifice features to automatically indicate and achieve proper alignment, reducing the time required for precise positioning while maintaining easy insertion capability.
Data Source
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AI summary
The invention relates to an assembly of parts joined together by a shaft (5) passing through holes formed in said parts. The shaft (5) has two diameters in cross-section, namely a base diameter (DB) and a thickened diameter (DE) on diametrically opposed arcs (11) of its cross-section. The holes are aligned with each other and each has a circumference having a first diameter (D1) on diametrically opposed first portions (13), the first diameter (D1) corresponding to the thickened diameter (DE), and a second diameter (D2) larger than the first diameter (D1) on second portions (14) of the circumference. This allows for easy assembly of the shaft even in the case of approximate alignment of the holes, and also facilitates its disassembly. Aeronautical assemblies, for example of an aircraft propulsion unit on a support mast, constitute a preferred application of the invention.