Drilling string, threaded coupling, and rod adaptor for rotary drilling
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Solution Overview
Problem
Conventional drill strings for rotary drilling in underground mining are prone to high uncoupling torque, making it difficult and dangerous to disconnect extension rods, and existing solutions for improving thread coupling are not effective for rotary drilling.
Innovation Solution
The use of multi-start threads with increased thread lead and lead angle in drill strings and adaptors to minimize uncoupling torque, allowing for easy disconnection by hand, specifically by configuring male and female threads to have a thread lead greater than their diameter, such as double-start or triple-start threads with a lead angle exceeding 20°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional single-start threads are used in drill strings, then the thread coupling provides sufficient tightening capacity, but the uncoupling torque becomes excessively high making disconnection difficult and dangerous
Solution Approach 1:
The patent changes the fundamental parameter of thread configuration from single-start to multi-start (double-start or triple-start), which fundamentally alters the thread geometry and reduces the lead angle. This parameter change directly reduces the uncoupling torque while maintaining tightening capacity, enabling safe manual disconnection of drill strings.
Solution Approach 2:
Instead of increasing thread engagement to improve tightening (which would increase uncoupling torque), the patent inverts the approach by using multi-start threads with increased lead, which reduces the lead angle and consequently reduces the uncoupling torque. This inverted thinking solves the contradiction by achieving ease of disconnection through geometric inversion rather than increased engagement.
2Ease of operation
If multi-start threads with increased lead are used, then the uncoupling torque is minimized for easy disconnection, but the thread lead becomes greater than the diameter which is unconventional
Solution Approach 1:
The patent deliberately changes the conventional thread parameter relationships by making the lead greater than the diameter through multi-start configuration. This unconventional parameter change, while increasing geometric complexity, dramatically simplifies the operational complexity by enabling manual disconnection, thus trading manufacturing complexity for operational simplicity.
3Strength
If conventional threaded couplings are designed for high tightening capacity, then the threads are securely engaged during drilling, but the uncoupling torque increases making manual disconnection unsafe
Solution Approach 1:
The patent changes the thread geometry parameters (multi-start, increased lead, reduced lead angle) to decouple the relationship between tightening strength and uncoupling torque. This allows the threads to maintain secure engagement during drilling while reducing the uncoupling torque to safe levels for manual disconnection, eliminating the harmful effect to operators.
Data Source
AI summary
A drill string for rotary drilling of underground mining machines includes a first elongate drill string member and a second elongate drill string member. The first member has a main section and a male end, and the second member has a main section and a female end. The male and female ends each have respective threads to provide a thread coupling between the male and female ends, the thread coupling enabling the male end to be secured inside the female end such that the male and female ends overlap axially. A thread lead of the respective threads of the male and the female ends are greater than a diameter of the male end and the female end.