Polygonal Pump Shaft Coupling for Easier Lubrication Assembly Machining
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Solution Overview
Problem
The manufacturing of spline couplings for rotary shafts in aircraft turbomachine lubrication assemblies is complex and prone to tool deformation due to their small size, making machining difficult.
Innovation Solution
The use of polygonal profile couplings, which can be machined by milling or turning, to mechanically couple the shafts of rotary pumps, allowing for easier production and accommodating misalignment between shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spline couplings are used to mechanically couple shafts, then reliable rotary drive transmission is achieved, but manufacturing complexity increases and tool deformation occurs due to small size
Solution Approach 1:
The invention changes the geometric parameters of the coupling profile from traditional splines to a polygonal profile with specific mathematical definitions (equations 1-3). This parameter change allows the coupling to be manufactured by conventional milling or turning operations rather than complex electro-erosion or broaching, thereby improving ease of manufacture while maintaining coupling reliability
Solution Approach 2:
Instead of machining complex internal splines that require small, deformable tools, the invention inverts the approach by using a polygonal profile that can be machined by larger, more stable tools. The male and female parts are designed with complementary polygonal profiles that engage through external geometry rather than internal keyways, reversing the traditional spline manufacturing challenge
2Reliability
If traditional spline machining methods are used, then shaft coupling is achieved, but manufacturing time and process complexity increase
Solution Approach 1:
By defining the coupling profile through simple mathematical equations (polygonal geometry with parameters Rm, e, and n) rather than complex spline tooth forms, the manufacturing process is simplified to conventional milling or turning operations, significantly reducing manufacturing time while maintaining reliable shaft coupling
Solution Approach 2:
The polygonal profile can be generated by copying the mathematical definition (equations 1-3) to create the male and female coupling parts, allowing for precise reproduction of the coupling geometry through standard machining operations rather than time-consuming manual or electro-erosion processes
3Manufacturing precision
If small tools are used to machine small splines, then coupling is achieved, but tool deformation makes machining almost impossible
Solution Approach 1:
The invention changes the coupling geometry from fine-pitched internal splines to a polygonal profile with larger, more robust features defined by equations (1-3). This parameter change allows the use of larger, stiffer cutting tools that do not deform, making machining feasible while maintaining the precision needed for reliable shaft coupling
Solution Approach 2:
Instead of machining small internal splines that require fragile small-diameter tools, the invention inverts to an external polygonal profile system that can be machined by larger, more stable tools, eliminating the tool deformation problem while achieving the same coupling function
Data Source
AI summary
A lubrication assembly includes two pumps whose shafts are coupled for rotation via at least one polygonal profile coupling.