Filter Cartridge Thread Geometry for Rip-Out Resistance
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Solution Overview
Problem
Threaded connections in filter cartridges, particularly in commercial vehicle applications, are prone to damage due to ripping out forces caused by pressure forces, leading to early cracks and potential thread failure.
Innovation Solution
A threaded device with a thread configuration where the load flank and stab flank are oriented rearward with respect to the screwing direction, and a transition portion between the crest and the load flank is formed such that at least two tangents of the transition portion are inclined with respect to each other, reducing bending torque and increasing contact surface for better stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flat portion is provided on the crest to allow clearance between threads, then the thread connection allows easier assembly and clearance, but material stress in the sharp corners increases leading to early cracks
Solution Approach 1:
The invention replaces the flat portion with a rounded transition area that has a radius of curvature. This curvature eliminates the sharp corners that cause stress concentration while still providing the necessary clearance between the male and female threads during assembly and operation.
Solution Approach 2:
The transition area is designed with different geometric properties at different locations: it provides clearance where needed between threads while maintaining structural integrity at the corners. The localized rounding approach allows each region of the thread to have the quality needed for its specific function.
2Force
If the load flank is oriented rearward to increase cohesion force against ripping out force, then the thread connection resistance to ripping out force improves, but the transition area between crest and load flank becomes a stress concentration point
Solution Approach 1:
The transition area is designed with a rounded profile having a specific radius of curvature that eliminates sharp corners. This curvature distributes stress more evenly across the transition zone while maintaining the rearward orientation of the load flank necessary for resisting ripping out forces.
Solution Approach 2:
The rounded transition area acts as a stress-distributing feature that preemptively cushions the stress concentrations that would otherwise occur at sharp corners. This design anticipates and prevents crack initiation before it can occur under loading conditions.
3Ease of manufacture
If a conventional thread design is used, then manufacturing is simple, but the thread connection is prone to damage from ripping out forces in harsh environments
Solution Approach 1:
The rounded transition area can be manufactured using standard machining or forming processes. The curvature is defined by a specific radius that can be achieved through conventional manufacturing methods, maintaining ease of production while significantly improving reliability in harsh environments.
Solution Approach 2:
The invention modifies the geometric parameters of the thread, specifically the transition area radius and flank angles, to optimize performance. These parameter changes are implemented within standard manufacturing capabilities to achieve both improved reliability and maintained manufacturability.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to a threaded device (1, 2) comprising a thread formed by a load flank (11, 21), a crest (12, 22), a stab flank (14, 24) and a root (15, 25), wherein the load flank (11) and the stab flank (14) are oriented rearward with respect to a screwing direction (S1, S2) to screw the threaded device (1, 2) in or on a mating thread, wherein the threaded device (1, 2) further comprises a transition portion (13, 13', 13", 23) as a transition area between the load flank (11, 21) and the crest (12, 22), and wherein the transition portion (13, 13', 13", 23) is formed such that at least two tangents (T1, T2) of the transition portion (13, 13', 13", 23) are inclined with respect to each other.