Wedge Threaded Joint Geometry for Wider Sealing Torque Range
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Solution Overview
Problem
Existing threaded connections for oil well pipes face challenges in maintaining sealability when torque levels are outside a predetermined range, with high torque connections risking disengagement and low torque connections compromising seal performance.
Innovation Solution
The development of threaded connections featuring a combination of varying and constant thread widths, along with chamfered surfaces and strategically placed shoulders, allows for a wider torque range while ensuring sealability by adjusting thread engagement and interference torque levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a threaded connection is designed for high torque performance, then torque capacity is improved, but sealability deteriorates when torque exceeds the appropriate range
Solution Approach 1:
The patent modifies the thread geometry parameters by introducing a variable thread width along the thread length, with the thread width being smaller near the thread tip and larger near the thread root. This parameter change allows the thread to engage progressively from the root upward, maintaining sealability while accommodating high torque loads.
Solution Approach 2:
The patent applies different thread width characteristics to different portions of the thread. The thread width varies locally along the thread length, with specific regions having optimized widths to balance torque transmission and sealing functions. This local differentiation resolves the contradiction between high torque capacity and sealability.
2Power
If a threaded connection is designed for high torque, then torque performance is improved, but the connection becomes prone to disengagement
Solution Approach 1:
The variable thread width design creates a progressive engagement pattern where threads engage from the root upward. This parameter modification ensures that the thread connection remains stable and resistant to disengagement under high torque conditions, as the broader base provides mechanical stability.
Solution Approach 2:
The thread design ensures that the root portion of the thread engages first and provides preliminary mechanical interlocking before the full thread length is engaged. This preliminary action at the thread root establishes a stable foundation that prevents disengagement under high torque loads.
3Power
If a threaded connection is designed for high torque, then torque capacity is improved, but the connection requires precise torque control
Solution Approach 1:
The variable thread width creates a more gradual and predictable torque engagement curve. As the thread engages progressively from root to tip, the torque builds more smoothly, reducing the need for precise torque control during assembly while still achieving high torque capacity.
Data Source
Figure 1
Figure 2A~2D
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AI summary
An object of the present invention is to provide a threaded connection that has a wide range of torque at which a predetermined performance is achieved. The threaded connection according to the present invention includes a pin (1) including a wedge male thread (11) having a varying-thread-width portion (11A) and a box (3) including a wedge female thread (31) having a varying-thread-width portion (11A). The threaded connection is constructed such that, when both stab flanks (111) and load flanks (112) of the male thread (11) of the pin (1) contact the box (3), the shoulder (12) on the pin (1) is not in contact with the shoulder (22) on the pin (2), and, with a further rotation in the make-up direction, the shoulder (12) on the pin (1) is capable of contacting the shoulder (22) on the pin (2) before the threads (i.e. male and female threads (11) and (31)) yield.