Conical Threaded Plug Geometry for Lower Root Stress in Drilling Joints
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Solution Overview
Problem
Existing threaded connections in earth drilling devices are prone to failure due to high notch effects and stress concentrations, leading to reduced service life and increased risk of damage during operation.
Innovation Solution
The design of threaded connections for earth drilling devices is modified by extending the flank geometry beyond the thread base, with a section of the flank having an angle greater than 45° to the cone, reducing stress concentrations and improving force transmission and sliding characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If traditional threaded connections are used in earth drilling devices, then the structure is simple and easy to manufacture, but the service life is reduced due to high stress concentrations and notch effects
Solution Approach 1:
The patent applies curvature to the flank section of the thread by defining it as a section of a function with curvature, where the tangential element forms an angle greater than 45° with the cone. This curved geometry replaces traditional straight or elliptical flanks, distributing stress more evenly along the thread contact surface and reducing stress concentrations at the thread root, thereby extending the service life of the threaded connection in earth drilling devices.
2Duration of action of moving object
If the flank is designed with a section having an angle greater than 45° to the cone, then stress concentrations are reduced and service life is extended, but the manufacturing complexity increases
Solution Approach 1:
The patent defines the flank section through specific geometric parameters: a function with curvature where the tangential element forms an angle greater than 45° with the cone over a defined section of the flank. This parametric definition allows for standardized manufacturing processes while achieving the stress distribution benefits of curved geometry. The angle parameter (>45°) serves as a key design variable that balances stress reduction with manufacturability.
3Force
If the threaded connection design is modified with a curved flank section, then force transmission and sliding characteristics are improved, but the geometric complexity of the thread form increases
Solution Approach 1:
The patent applies the curved flank section (function with curvature and angle >45°) specifically to the load-bearing portion of the thread where force transmission and sliding occur. This localized geometric modification targets the critical contact zone between mating threads, optimizing force distribution and sliding characteristics precisely where needed, while leaving other portions of the thread structure relatively simple for ease of manufacture.
Data Source
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AI summary
The invention relates to a threaded plug on an elongated body for a threaded connection with a threaded bushing, wherein the threaded plug has a conical external thread, in which a section of a flank of the external thread can be represented as a section of a function having a curvature, wherein the section of the function has an angle to a connecting line of adjacent thread roots or thread crests over a height of at least 0.3 times the thread height, which is greater than 45°.