Drill Rod Coupler With Offset Cross Aperture For Torque And Fluid Flow
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Solution Overview
Problem
Dual rod drilling systems face challenges in retaining couplers on inner rods while maximizing drilling fluid flow and ensuring adequate torque and fatigue life for longitudinal forces transmission.
Innovation Solution
A coupler design featuring a non-circular inner bore with a cross aperture perpendicular to the longitudinal axis, incorporating retention pins and notches for secure engagement, and fluid flow openings to optimize fluid flow between inner and outer rods, with stress-reducing cross apertures located in a non-torque-transferring portion to enhance fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coupler includes retention features (pins, notches) to secure the coupler to the inner rod, then the reliability of coupler retention is improved, but the structural complexity and stress concentration increase
Solution Approach 1:
The coupler body is segmented into distinct functional zones: a torque-transferring portion with non-circular inner bore for torque transmission, and a non-torque-transferring portion for housing retention features. This segmentation allows retention pins and notches to be located in a dedicated retention portion without interfering with the torque-transferring portion, thus improving reliability while managing structural complexity through functional separation.
Solution Approach 2:
Different portions of the coupler are given different functional qualities: the torque-transferring portion has a non-circular profile optimized for torque transmission, while the retention portion is specifically designed to house pins and notches. This local differentiation allows each portion to be optimized for its specific function, improving overall reliability without unnecessarily complicating the entire structure.
2Productivity
If the coupler outer peripheral surface is minimized to maximize fluid flow area, then the fluid flow is improved, but the structural strength and fatigue life may be reduced
Solution Approach 1:
The coupler is divided into a torque-transferring portion with minimal outer peripheral surface for strength, and a non-torque-transferring retention portion that can accommodate larger dimensions for fluid flow. By locating retention features in the non-torque-transferring portion, the design maximizes fluid flow area while maintaining structural strength in the critical torque-transmitting regions.
Solution Approach 2:
The retention features (pins, notches) are positioned in a different spatial dimension (the non-torque-transferring portion) rather than in the torque-transferring portion. This dimensional separation allows the torque-transferring portion to maintain minimal outer peripheral surface for strength while the retention portion provides the necessary structural features, and fluid can flow through openings in the retention portion.
3Productivity
If cross apertures are positioned to maximize fluid flow, then fluid flow is improved, but stress risers increase reducing fatigue life
Solution Approach 1:
The coupler is segmented into a torque-transferring portion and a non-torque-transferring retention portion. Cross apertures for fluid flow are positioned in the non-torque-transferring portion where they do not create stress risers in the critical torque-transmitting path. This segmentation allows fluid flow optimization without compromising fatigue life in the torque-transferring portion.
Solution Approach 2:
The non-torque-transferring retention portion acts as an intermediary zone that houses cross apertures for fluid flow while being isolated from the critical torque-transferring path. This intermediary portion allows fluid to pass through without creating stress risers in the torque-transferring portion, thus improving fluid flow while maintaining fatigue life.
Data Source
AI summary
A coupler for a drill rod includes a body defining an inner bore extending along a longitudinal axis, at least a portion of the inner bore defining a non-circular profile having a plurality of flats including a first pair of adjacent flats defining a vertex therebetween. A cross aperture of the body has a central axis that is perpendicular to and offset from the longitudinal axis. A radially-innermost portion of the cross aperture extends perpendicular to a reference line extending from the longitudinal axis to the vertex.