Hydraulic Fitting Key-Shaped Cross Section Anti-Rotation
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Solution Overview
Problem
Hydraulic fittings tend to rotate during installation through bulkheads, making it difficult to maintain proper orientation, especially in tight and hard-to-reach locations, which complicates the assembly of hydraulic systems in machines like wheel loaders.
Innovation Solution
The hydraulic fitting features a long set of external threads with a split flat surface, creating a key shape that matches a key-shaped mounting bore in the bulkhead, preventing rotation by interacting with the bore, and a short set of external threads oriented at an elbow angle, allowing for secure clamping without the need for a wrench, using a power tool for nut tightening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a circular hydraulic fitting is used in a circular mounting bore, then the fitting can be easily manufactured and installed, but the fitting rotates during installation making it difficult to maintain proper orientation
Solution Approach 1:
The patent applies asymmetry by changing the circular cross-section of the hydraulic fitting to a key-shaped cross-section with flat surfaces and rounded corners. This asymmetric geometry engages with a corresponding key-shaped mounting bore, preventing rotation during installation and ensuring proper orientation without requiring additional orientation features or complex installation procedures
2Manufacturing precision
If a wrench is used to hold the fitting orientation during nut tightening, then proper orientation can be maintained, but the installation becomes difficult in tight and hard-to-reach locations
Solution Approach 1:
The key-shaped cross-section with flat surfaces provides inherent anti-rotation capability that eliminates the need for a wrench to hold orientation during installation. The asymmetric geometry engages with the mounting bore to prevent rotation automatically, allowing installation in tight and hard-to-reach locations without requiring wrench access
Solution Approach 2:
The fitting's key-shaped geometry performs the orientation-maintaining function automatically during installation. The flat surfaces engage with the mounting bore to prevent rotation as the nut is tightened, making the system self-orienting without requiring external tools or additional operations
3Stability of the object's composition
If the flat surface width to thread outer diameter ratio is increased, then rotation prevention is improved, but face seal leakage may occur
Solution Approach 1:
The patent optimizes the ratio of flat surface width to thread outer diameter to balance two competing requirements: a wider flat surface provides better anti-rotation stability, while a narrower flat surface maintains face seal reliability. The specific ratio is selected to prevent rotation during installation while preserving sufficient face seal surface area to prevent leakage
Solution Approach 2:
The key-shaped cross-section distributes the anti-rotation function to specific localized flat surfaces while preserving the circular symmetry of the overall fitting body and face seal areas. This local asymmetry provides rotation prevention without compromising the global sealing surfaces
Data Source
AI summary
A hydraulic fitting is used to fluidly connect hydraulic hoses on opposite sides of a bulkhead of a machine. The bulkhead is clamped between a flange of the hydraulic fitting and a nut. One set of threads of the hydraulic fitting is split by a flat surface to create a cross section with a key shape that is received in only one orientation through a matched key shaped mounting bore in the bulkhead. The key shape interaction prevents the hydraulic fitting from rotating when installed in the bulkhead.