Fan Hub Blade Pivot Locking to Eliminate Radial Clearance Wear
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Solution Overview
Problem
The radial retention systems in turbojets with high bypass ratios face issues such as residual mounting clearance leading to contact wear and uneven force distribution due to centrifugal forces, which can cause critical loads on unsized parts.
Innovation Solution
A blade pivot with adjustable orientation featuring a stud, rolling bearing, radial retention ring, and clamping parts with a tightening nut system that eliminates mounting clearances by ensuring forces pass through a consistent path, using keystone-type tightening to maintain radial retention and prevent wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a segmented retention ring is used to retain the pivot in the groove, then the pivot can be retained radially, but residual mounting clearance causes the pivot to fall back when stopped, creating contact wear
Solution Approach 1:
The invention extracts the retention function from a passive segmented ring and implements it through an active locking mechanism using a retention ball and groove system that positively engages to eliminate clearance and prevent wear
Solution Approach 2:
The retention ball is positioned in advance in a groove to preemptively prevent pivot fallback before it occurs, eliminating wear by pre-establishing the correct radial position rather than reacting to clearance issues
2Ease of manufacture
If mounting tolerances are accommodated by making the groove wider than the retention ring, then assembly is easier, but the entire pivot falls back and consumes residual mounting clearance, creating wear
Solution Approach 1:
The retention ball acts as an intermediary element between the pivot and the retention ring, mediating the connection by positively engaging with the groove to eliminate clearance while maintaining ease of assembly through the segmented ring design
3Ease of manufacture
If the retention ring is housed in a groove wider than itself to accommodate tolerances, then assembly is facilitated, but forces pass through unintended paths before centrifugal force engages the retention ring
Solution Approach 1:
The retention ball is pre-positioned in the groove to establish the correct force path before centrifugal forces act on the system, ensuring that loads are immediately transmitted through the intended retention path rather than alternative routes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides stable radial retention of the stud both during operation and when stopped, preventing wear on pivot parts and ensuring consistent force distribution, thus enhancing the structural integrity and longevity of the turbojet components.
Implementation Method 1
a tightening nut screwed onto an external thread of the stud to come into conical support against the clamping parts so that said tightening parts ensure tightening of the internal ring of the rolling bearing on the stud
Implementation Method 2
a rolling bearing for absorbing centrifugal forces having an internal ring mounted in transverse support against an external radial part of the stud
Implementation Method 3
When tightening the clamping nut, it will cause the clamping parts to slide radially outwards until they come into contact with the internal ring of the rolling bearing
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The invention relates to a blade pivot (2) with adjustable orientation for a turbomachine fan hub, comprising a stud (4) having means (10) for retaining a fan blade root and coupling means for transmitting a torque, a roller bearing (14) for taking up centrifugal forces having an inner ring (16) mounted to bear transversely against a radial outer portion of the stud, a radial retaining ring (24) for retaining the stud with respect to the roller bearing housed in an annular groove (22) formed in the stud, a plurality of clamping parts (26) each mounted to bear transversely against the retaining ring and to bear radially against the inner ring of the roller bearing, and a clamping nut (28) screwed onto an external thread (30) of the stud to bear conically against the clamping parts so that said clamping parts clamp the inner ring of the roller bearing on the stud and clamp the retaining ring in the groove.