Arcuate Tab Lock Bolt Collar Swaging Breakage
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Solution Overview
Problem
Existing lock bolt collars often experience premature tab breakage during swaging, leading to misalignment and reduced strength of the fastener due to inadequate engagement with the pin member's lock grooves.
Innovation Solution
A lock bolt collar design featuring a radial tab with an arcuate top surface, positioned intermediate the ends, which maximizes cross-sectional area and volume to securely engage with helical lock grooves, preventing strip-off or break-off during swaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tab is made smaller or thinner to allow easier swaging, then the swaging process becomes easier, but the tab strength decreases and premature breakage occurs
Solution Approach 1:
The tab is designed with an arcuate top surface that conforms to the curvature of the pin member, distributing stress more effectively and preventing stress concentration at sharp edges. This curved geometry maintains tab strength while allowing the tab to flex during swaging without breaking.
Solution Approach 2:
The tab dimensions are optimized to specific parameter ranges - the height is approximately 0.020-0.040 inches and the width is approximately 0.060-0.120 inches, with a controlled thickness. These parameter changes balance the competing requirements of being thin enough for easy swaging while maintaining sufficient cross-sectional area to prevent breakage during the swaging process.
2Strength
If the tab is made larger with more cross-sectional area, then the engagement strength with lock grooves increases, but the tab may interfere with proper fit within the lock grooves
Solution Approach 1:
The arcuate top surface of the tab is designed to match the curvature radius of the pin member and lock groove geometry. This allows the tab to engage deeply into the helical lock grooves with maximum contact area for strength, while the curved profile ensures the tab can be freely spun onto and fit within the grooves without interference.
Solution Approach 2:
The tab cross-sectional dimensions are precisely controlled - with height, width, and thickness parameters optimized to maximize engagement area while maintaining compatibility with standard lock groove dimensions. The tab width is sized to provide adequate contact area approximately 20-40% larger than conventional tabs, while the thickness is controlled to ensure proper fit within the grooves.
3Device complexity
If conventional tabs are used, then the collar assembly is simple, but misalignment occurs during swaging leading to installation failure
Solution Approach 1:
The arcuate top surface of the tab provides inherent alignment guidance by conforming to the curved profile of the pin member and lock grooves. This self-aligning geometry ensures the tab engages properly with the lock grooves during assembly and maintains alignment throughout the swaging process, preventing misalignment failures without adding complex alignment mechanisms to the collar assembly.
Solution Approach 2:
The tab features an asymmetric cross-sectional profile with the arcuate top surface facing outward and a relatively flat bottom surface. This asymmetric geometry is specifically designed to engage with the asymmetric lock groove profile, providing directional stability and preventing rotational misalignment during swaging while maintaining simple collar assembly construction.
Data Source
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AI summary
A lockbolt collar having a shank including a first end, a second end opposite the first end, a through-bore extending from the first end to the second end, an inner wall extending from the first end to the second end, and a tab extending radially and outwardly from the inner wall, the tab including a top surface having an arcuate shape, the arcuate shape of the tab being sized and shaped to mate with at least one lock groove of a threaded portion of a pin member.