Coupling Nut Head Geometry to Prevent Seal-Deforming Wrench Loads
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Solution Overview
Problem
Existing coupling nuts in gas turbine engines face issues with efficient sealing due to deformation caused by traditional open-ended wrenches, leading to non-uniform force distribution and potential leakage, as they can plastically deform and alter the sealing interface between the ferrule and nipple.
Innovation Solution
Designing coupling nuts with specific torque-transmitting face patterns, such as double-hexagonal, triple-square, and spline shapes, that prevent the use of open-ended wrenches, ensuring torque is transmitted through edges rather than faces, thereby reducing deformation and enhancing load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional open-ended wrenches are used to tighten coupling nuts, then the tightening operation can be performed, but the coupling nut and ferrule undergo plastic deformation leading to non-uniform force distribution and potential leakage
Solution Approach 1:
The coupling nut head is segmented into multiple flat faces (e.g., hexagonal with 6 faces, or double-hexagonal with 12 faces) instead of a traditional single hexagonal shape. This segmentation allows the wrench to contact multiple distributed points, spreading the applied force uniformly across the coupling nut and preventing localized plastic deformation that would occur with traditional single-face contact.
Solution Approach 2:
The patent introduces asymmetric face configurations such as the double-hexagonal shape where inner and outer hexagons are rotated relative to each other, creating non-uniform face orientations. This asymmetry ensures that wrench contacts occur at optimally distributed angles, preventing the coupling nut from rotating or shifting during tightening, thereby maintaining uniform force distribution and preventing deformation.
2Ease of manufacture
If traditional hexagonal coupling nuts are used, then the design is simple and easy to manufacture, but the force distribution during tightening is non-uniform causing deformation
Solution Approach 1:
The coupling nut head is divided into multiple flat faces (6 or 12 faces) around the circumference. This segmentation allows the wrench to apply force at multiple distributed contact points rather than concentrating force on a single face, resulting in uniform radial force distribution that prevents plastic deformation of the coupling nut and ferrule, thereby maintaining sealing reliability.
Solution Approach 2:
Different regions of the coupling nut head have different geometric properties - the multiple flat faces are positioned at specific angular intervals to optimize force distribution, while the shank and threading regions maintain their structural integrity. This local optimization of face placement and geometry ensures uniform force application exactly where needed at the sealing interface, preventing deformation and ensuring reliable sealing.
3Manufacturing precision
If multiple torque-transmitting faces are used in the coupling nut, then force distribution becomes uniform preventing deformation, but the head geometry becomes more complex
Solution Approach 1:
The multi-faced coupling nut head serves multiple functions simultaneously: it provides uniform force distribution through multiple contact faces, maintains structural integrity through the integrated shank and threading, and enables wrench engagement through the geometric configuration. The double-hexagonal or multi-faced design is manufactured as a single integrated component, combining what could be separate elements into one universal part that achieves both simplified manufacturing and improved force distribution.
Data Source
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AI summary
A coupling nut (120) for sealingly engaging a ferrule (18) of a fluid line (7) to a component of a hydraulic system (6), has: a shank (20s) extending along a central axis (A) and having threads (20a) to engage a nipple (16), the threads (20a) extending circumferentially around the central axis (A), the shank (20s) defining an inner passage (20p) extending along the central axis (A) and sized to receive the fluid line (7); and a head (120c) extending from the shank (20c) circumferentially around the inner passage (20p) relative to the central axis (A), the head (120c): defining faces (120d) circumferentially distributed about the central axis (A) and edges (120e) at junctions between the faces (120d), the faces (120d) including torque-transmitting faces (120f) each facing a direction (D) having a circumferential component relative to the central axis (A), and having a cross-section in a plane normal to the central axis (A), the cross-section defining a plurality of symmetry planes (P1) containing the central axis (A), the torque-transmitting faces (120f) free of intersection with the plurality of symmetry planes (P1).