Threaded Pipe Joint Structure for High Torque and Faster Machining
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Solution Overview
Problem
Existing threaded connections for steel pipes require extensive machining time due to varying thread-groove widths and are prone to shear fractures under tensile loads, while maintaining high torque is a challenge.
Innovation Solution
A threaded connection design featuring constant and varying thread-width portions with dove-tailed tapered threads, including chamfered surfaces, to reduce machining time and prevent shear fractures, while ensuring high torque through controlled thread-groove and thread-ridge widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the thread-groove width varies over the entire thread length to achieve high torque, then the torque increases, but the machining time increases significantly due to the large difference between minimum and maximum thread-groove widths
Solution Approach 1:
The thread is divided into two distinct segments: a first thread portion with a constant thread-groove width and a second thread portion with a varying thread-groove width. This segmentation allows the machining process to use a fixed cutting tool width for the first portion (reducing machining time) while still achieving high torque through the varying width portion. The constant width portion provides a reference dimension that simplifies manufacturing.
Solution Approach 2:
Different portions of the thread are given different geometric properties tailored to their specific functions. The first thread portion has a constant thread-groove width optimized for efficient machining, while the second thread portion has a varying thread-groove width optimized for torque generation. This local differentiation allows each portion to excel at its intended function without compromising the other.
2Force
If the thread-ridge width varies along the entire thread length to achieve high torque, then the torque increases, but the thread-ridge width at the endmost portion becomes very small, making the thread prone to shear fracture under tensile load
Solution Approach 1:
The thread structure is segmented into two portions with different width characteristics. The first thread portion maintains a constant thread-ridge width that is sufficient to resist shear fracture, while the second thread portion allows the thread-ridge width to vary to optimize torque. This ensures that the critical load-bearing portion has adequate strength.
Solution Approach 2:
The thread-ridge width is locally optimized for different functions: in the first thread portion, the constant width provides structural strength and fracture resistance, while in the second thread portion, the varying width provides torque optimization. The constant width portion acts as a structural anchor that prevents catastrophic failure.
3Strength
If the thread-ridge width is made constant to prevent shear fracture, then the strength increases, but the torque decreases
Solution Approach 1:
The thread is divided into two functional segments: the first segment with constant dimensions provides structural strength and fracture resistance, while the second segment with varying dimensions provides torque optimization. This segmentation allows both strength and torque requirements to be satisfied by different portions of the same thread structure.
Solution Approach 2:
The invention merges two previously separate thread designs into a single integrated thread structure. The constant-width portion contributes strength and structural integrity, while the varying-width portion contributes torque generation. Together, they form a unified thread that achieves both strength and high torque in a single component.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An object of the present invention is to provide a threaded connection that has high torque and still requires reduced machining time for the thread. A threaded connection (1) connects a pair of pipes. The threaded connection (1) includes a pin (10) and a box (20). The pin (10) has a male thread (11) on its outer diameter. The box (20) has a female thread (21) on its inner diameter, the female thread corresponding to the male thread (11). The box (20) and the pin (10) are made up. The male thread (11) includes a constant-thread-width portion (111) and a varying-thread-width portion (112). The constant-thread-width portion (111) has a constant thread-groove width. The varying-thread-width portion (112) has a thread-groove width equal to or larger than the groove width of the constant-thread-width portion (111) and gradually increasing, going from the constant-thread-width portion (111) toward the tip of the pin (10). The female thread (21) includes a constant-thread-width portion (211) and a varying-thread-width portion (212). The constant-thread-width portion (211) has a constant thread-ridge width. The varying-thread-width portion (212) has a thread-ridge width equal to or larger than the thread-ridge width of the constant-thread-width portion (211) and gradually increasing, going from the constant-thread-width portion (211) toward the center of the box (20).