Elliptical Thread Root Geometry for Drilling Connection Stress Reduction
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Solution Overview
Problem
Existing threaded connections in earth drilling devices suffer from high stress concentration and geometric notches, leading to reduced service life and difficulty in forming and releasing connections.
Innovation Solution
The geometry of the threaded bushing is modified to include adjacent flanks formed as sections of offset identical ellipses, reducing stress concentration and improving sliding properties during screwing, while maintaining a conical thread design for efficient force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded connections are used in earth drilling devices, then the connection can be formed and released, but high stress concentration and geometric notches reduce service life
Solution Approach 1:
The thread root is designed with a curved transition instead of a sharp corner, using a fillet radius that connects the thread root to the flank. This curvature eliminates the geometric notch effect and distributes stress more uniformly across the thread root area, significantly reducing stress concentration and extending service life of the threaded connection
Solution Approach 2:
The invention modifies the geometric parameters of the thread profile, specifically the flank angle and thread root radius, to optimize stress distribution. By changing these parameters, the connection achieves better mechanical properties and reduced stress concentration while maintaining functional requirements
2Ease of operation
If conventional threaded connections are used, then connection can be formed, but precise handling is required for formation and release
Solution Approach 1:
The thread flanks are designed with asymmetric angles where the load-bearing flank has a different angle than the non-load-bearing flank. This asymmetry creates favorable self-aligning properties during connection formation, allowing the threaded connection to be assembled and disassembled more easily without requiring precise manual handling or alignment
3Strength
If threaded connections with small diameter are used, then connection can be formed, but they represent the greatest weak points in the rod assembly
Solution Approach 1:
The curved thread root design eliminates stress concentration points, allowing the threaded connection to achieve higher strength despite the small diameter. This geometric optimization enables the use of smaller diameter threads without compromising strength, as the curved transition distributes loads more effectively than conventional sharp-cornered threads
Data Source
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AI summary
The invention relates to a threaded bushing on an elongated body for a threaded connection with a threaded plug, wherein the threaded bushing has a conical internal thread in which adjacent flanks of the internal thread are formed as sections of two offset identical ellipses.