Threaded Joint for Coupling Rods with Interference Fit
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Solution Overview
Problem
Existing threaded joints for drill strings in the mineral exploration industry face challenges in withstanding significant tension and torque loads, fatigue, and maintaining a watertight seal, especially when subjected to alternating forces and repeated use, while preventing inward or outward flaring that could compromise drilling efficiency and core sample extraction.
Innovation Solution
A threaded joint design featuring primary and secondary geometries with frustoconical surfaces and differing angles for box and pin threads, creating an interference fit and optimized thread profiles to enhance axial and torsional loading capacities, prevent galling, and maintain a sealed connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional threaded joints are used in thin-walled drill rods, then the joint can be assembled and disassembled for repeated use, but the joint cannot withstand significant tension and torque loads without failing due to fatigue stress
Solution Approach 1:
The patent modifies the thread geometry parameters including the thread profile shape, flank angles, and pitch to optimize the distribution of tensile and torsional stresses. The modified parameters enable the thin-walled rod to withstand higher loads without fatigue failure while maintaining the ability to be assembled and disassembled multiple times
Solution Approach 2:
The joint design combines the threaded connection structure with the thin-walled rod material properties to create a composite system that leverages both the mechanical advantage of threading and the structural efficiency of thin-walled construction, achieving high strength-to-weight ratio and fatigue resistance
2Shape
If conventional threaded joints are used, then the joint can be made up with proper torque, but the joint becomes inwardly flared or outwardly flared during use, compromising drilling efficiency
Solution Approach 1:
The thread geometry parameters are specifically optimized to prevent flaring during make-up and breakout operations. The modified thread profile and flank angles distribute contact stresses more evenly, preventing the inward or outward flaring that would otherwise occur during repeated assembly and disassembly, thereby maintaining drilling efficiency
3Ease of operation
If conventional threaded joints are used, then the joint can be assembled quickly, but the joint does not maintain a watertight seal, causing drilling fluid to bleed off
Solution Approach 1:
The thread geometry is modified to include features that promote sealing, such as optimized flank angles and profile shapes that enhance contact between mating threads. These parameter changes allow the joint to maintain a watertight seal preventing drilling fluid leakage while still enabling quick assembly and disassembly operations
4Length of moving object
If thinner walled tubes are used for mineral exploration, then core extraction tools can pass through the drill string, but the joint requires additional strength to prevent failure due to alternating forces
Solution Approach 1:
The thread geometry parameters are optimized to compensate for the reduced wall thickness. The modified thread profile and flank angles distribute alternating stresses more effectively, providing the additional joint strength needed to prevent failure under the alternating forces experienced during drilling operations with thin-walled tubes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The joint effectively transfers forces with high efficiency, reduces wear and leakage, and maintains structural integrity under varying drilling conditions, ensuring reliable and efficient drilling operations.
Implementation Method 1
The secondary geometries differ between the box and pin threads to generate an interference fit when threaded together
Implementation Method 2
The primary geometry includes a pressure flank configuration that imparts axial and torsional loading capacities of the joint
Data Source
AI summary
The application relates to a threaded cylindrical member, which may be used for a segmented drilling tube. The member has opposing first and second ends and a central axis between the ends. The first end is threaded with a pin thread including a pressure flank, a crest and a root. The second end is threaded with a box thread including a pressure flank, a root, wherein the pin and box threads are configured whereby when threaded together a portion of the root of the pin thread is out of contact with the crest of the box thread to leave gap therebetween. The secondary geometries of the pin and box threads are configured to generate an interference fit between the pin and box threads. The roots and crests of the pin and box threads define parallel tapering conical frustrums that differ from each other in their taper angles.