Lead Thread Geometry for False-Threading-Resistant Fasteners
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing threaded fasteners often experience false threading due to manufacturing variations, leading to misalignment and structural damage during assembly, as a result of inconsistent lead thread profiles and helix angles, which cause the external lead thread to engage grooves in internal threads instead of the thread root.
Innovation Solution
An anti-false threading fastener system featuring a male lead thread with a curved profile that maintains a constant height and width, anchored to the root of adjacent threads, preventing engagement with grooves in internal threads and ensuring proper alignment and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lead threads with variable profiles are used, then manufacturing is easier and more adaptable, but false threading occurs due to engagement with grooves in internal threads
Solution Approach 1:
The patent applies parameter changes by standardizing the lead thread profile with constant height and width parameters. This transformation from variable to fixed parameters eliminates the engagement with internal thread grooves, preventing false threading while maintaining manufacturing feasibility through consistent geometric definitions.
Solution Approach 2:
The patent utilizes curvature by defining the lead thread peak with a rounded profile rather than a sharp or variable contour. This curved geometry allows the lead thread to smoothly bridge over grooves in the internal thread without engaging them, eliminating false threading while preserving ease of manufacture.
2Ease of manufacture
If lead threads with inconsistent helix angles are used, then manufacturing flexibility is improved, but misalignment and structural damage occur during assembly
Solution Approach 1:
The patent applies parameter changes by fixing the helix angle as a constant parameter throughout the lead thread section. This standardization ensures consistent alignment between external and internal threads during assembly, preventing misalignment and structural damage while maintaining manufacturing capability through well-defined geometric parameters.
3Ease of manufacture
If pointed lead thread profiles are used, then manufacturing is simpler, but false threading is more likely due to groove engagement
Solution Approach 1:
The patent applies curvature by replacing the pointed lead thread profile with a rounded peak geometry. This curved profile maintains manufacturing simplicity while eliminating the tendency to engage with grooves in internal threads, thereby preventing false threading and improving engagement reliability.
4Length of moving object
If short lead threads are used, then fastener length is reduced, but false threading increases due to insufficient alignment capability
Solution Approach 1:
The patent applies parameter changes by optimizing the lead thread section to provide sufficient length for proper alignment function. By carefully selecting the minimum required length parameters, the patent achieves false threading prevention while minimizing overall fastener length, balancing compactness with alignment reliability.
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4E
AI summary
An anti-false threading fastener system comprising: a female fastener member (30) comprising: 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); a male fastener member (10) comprising: a shank (12) that has a lead end (14) for insertion into the interior of the female fastener member (30); at least one male fastening thread (11) formed on the exterior of the shank (12) as a plurality of thread windings (15) adapted to mate with the female fastening thread; at least one male lead thread (17) formed on the exterior of the shank (12) at the lead end (14) that is at least a half winding around the shank (12) and comprises a curved profile defined by an arc having a radius (R) 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 (11) and below the pitch line of the at least one male fastening thread (11).