Lead Thread Profile for Misalignment-Resistant Fastener Engagement
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Solution Overview
Problem
Existing threaded fasteners often experience false threading due to manufacturing variations, misalignment, and inconsistent lead thread profiles, leading to structural damage and assembly failures.
Innovation Solution
A male fastener with a lead thread that has a curved profile, anchored to the anti-cross thread, and maintains a consistent height and width, designed to prevent engagement with grooves in the internal thread, ensuring proper alignment and preventing false threading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional lead threads with variable profiles are used, then manufacturing is easier and cost is reduced, but false threading occurs due to engagement with grooves in internal threads
Solution Approach 1:
The patent applies parameter changes by modifying the lead thread profile from a traditional variable cross-section to a constant cross-section with fixed width and height. This consistent geometry prevents the thread from engaging with grooves in the internal thread crest, eliminating false threading while maintaining manufacturability through standard threading processes
Solution Approach 2:
The patent employs curvature by rounding the peak of the lead thread to a radius of approximately 0.002 to 0.005 times the nominal fastener diameter. This curved profile allows the lead thread to bridge over grooves in the internal thread rather than engaging them, preventing false threading while preserving ease of manufacture
2Ease of operation
If lead threads with pointed peaks are used, then initial engagement is facilitated, but false threading is caused by engagement with crests of internal threads
Solution Approach 1:
The patent replaces the pointed peak with a rounded profile having a radius of 0.002 to 0.005 times the nominal fastener diameter. This curved configuration maintains ease of initial engagement by allowing smooth insertion while preventing the peak from catching on grooves in the internal thread, thereby eliminating false threading
Solution Approach 2:
The patent applies local quality by creating a differentiated lead thread profile where the peak is rounded with a specific radius while the body of the thread maintains its standard geometry. This localized modification at the critical engagement point prevents false threading without affecting the overall thread function or requiring changes to the entire fastener design
3Productivity
If manufacturing variations and misalignment are present, then production efficiency is maintained, but cross threading and false threading occur leading to structural damage
Solution Approach 1:
The patent implements beforehand cushioning by designing a lead thread with a rounded peak and constant cross-section that anticipates and prevents misalignment issues before they occur. This profile allows the thread to bridge over grooves and accommodate minor manufacturing variations, preventing cross threading and false threading that would otherwise cause structural damage
Solution Approach 2:
The patent uses parameter changes by establishing a constant cross-section for the lead thread with fixed width and height parameters, rather than the traditional variable profile. This consistent geometry provides tolerance to misalignment and manufacturing variations, preventing harmful engagement effects while maintaining production efficiency
Data Source
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Figure 3A~3B
Figure 4A~4E
AI summary
A method for correcting translational misalignment between male (10) and female (30) fastener members to prevent false threading, the method comprising: inserting a lead end (14) of a male fastener member (10) into a female fastener member (30), wherein the female fastener member (30) comprises: at least one female fastening thread formed in an interior of the female fastener member (30), at least one female lead thread (31) formed in the interior of the female fastener member (30), the at least one female lead thread (31) having a groove (32) in the crest, and wherein the male fastener member (10) comprises: a shank that has a lead end for insertion into the interior of the female fastener member (30); at least one male fastening thread formed on the exterior of the shank as a plurality of thread windings adapted to mate with the at least one female fastening thread; at least one male lead thread (17) formed on the exterior of the shank at the lead end (14) that is at least a half winding around the shank and comprises a curved profile defined by an arc having a radius approximately equal to a radius of an arc that is tangent to both flanks of a thread profile of the at least one male fastening thread and below the pitch line of the at least one male fastening thread; and rotating the fastener members (10,30) relative to each other while the at least one male lead thread (17) of the male fastener member (10) passes over and does not thread into the groove (32) in the crest of the at least one female lead thread (31) of the female fastener member (30).