Downhole Torque Tool Cable Coupling
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Solution Overview
Problem
Conventional torque limiting tools in drilling operations are sensitive to lower torque levels, providing inadequate axial movement at higher torque levels, leading to inefficient protection of drill string components and potential stalling of mud motors.
Innovation Solution
A downhole tool with a coupling mechanism using longitudinally elongate cables that allow relative rotational movement between inner and outer mandrels, providing differential reactions to tension and compression, and a biasing device like belleville springs to absorb shock and vibration, enabling telescoping movement without rotation, thus offering enhanced torque control and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional screw threaded torque limiting tools are used, then torque control is provided, but the tools are sensitive to lower torque levels and provide insufficient axial movement at higher torque levels
Solution Approach 1:
The coupling mechanism is divided into multiple cable elements (typically 3-6 cables) arranged radially around the tool axis. Each cable independently carries tensile load, and collectively they provide the force to stroke the inner mandrel. This segmentation allows the system to handle higher torque levels effectively while maintaining proportional axial movement.
Solution Approach 2:
The cables are arranged in a radial pattern around the tool axis, converting rotational torque into axial movement through a three-dimensional force distribution. The cables extend from the outer mandrel through guide elements to the inner mandrel, creating a spatial force system that efficiently translates torque differential into linear stroke motion.
2Force
If screw threaded connections are used in torque limiting tools, then torque transmission is achieved, but unwanted rotation of the bit occurs when weight is applied
Solution Approach 1:
The lead screw mechanism that converts axial motion to rotation is completely removed from the system. Instead, the cables directly transmit tensile force from the outer mandrel to the inner mandrel, eliminating the intermediate rotational conversion step that causes unwanted bit rotation when weight is applied.
Solution Approach 2:
The traditional screw-threaded mechanical coupling is replaced with a cable-tension-based mechanical system. The cables maintain torque control through tensile force while allowing the inner mandrel to stroke axially without inducing rotational motion, thereby preventing unwanted bit rotation during weight application.
3Reliability
If conventional torque limiting tools are used, then torque limitation is provided, but separate shock absorber tools are needed
Solution Approach 1:
The shock absorption function is integrated into the torque limiting tool by incorporating a shock absorber mechanism within the inner mandrel structure. The shock absorber uses a spring-loaded piston system that absorbs axial shock loads, combining two functions (torque limitation and shock absorption) into a single tool assembly, thereby reducing the need for separate tools.
4Adaptability or versatility
If cable-based coupling mechanism is used, then differential reaction to tension and compression is achieved, but cable arrangement complexity increases
Solution Approach 1:
The cable arrangement exploits the asymmetric mechanical properties of cables (strong in tension, weak in compression) by positioning cables to carry tensile loads during torque limiting operation. The cables are anchored to the outer mandrel and pass through guide elements on the inner mandrel, creating a configuration where cable tension directly controls inner mandrel positioning while cable compression is minimized or ignored.
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 tool provides greater axial movement at higher torque levels, effectively protecting drill string components and preventing mud motor stalling, while also acting as a shock and vibration absorber, reducing the need for separate tools.
Implementation Method 1
a biasing device acting between the inner and outer mandrel, wherein the biasing device is a separate component from the plurality of cables
Implementation Method 2
the plurality of cables are substantially fixed in their longitudinal length when tension is applied to one end relative to another but substantially do not resist relative compressive longitudinal movement occurring between the inner and outer mandrels
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A downhole tool (30) particularly for controlling torque and torsion and also for absorbing/dampening vibration in a downhole string is provided and comprises an inner mandrel (1, 7, 11, 15) and an outer mandrel (14, 13, 12, 19) and a coupling mechanism (8) to couple the inner and the outer mandrel, the coupling mechanism comprising one or more longitudinally elongate members (8) acting between the inner and outer mandrel, wherein the one or more longitudinally elongate members are substantially fixed in their longitudinal length but substantially do not resist relative compressive longitudinal movement occurring between the inner and outer mandrels. The coupling mechanism is arranged such that compression of the inner and outer mandrels results in compression of the one or more longitudinally elongate members without necessarily resulting in relative rotation of the inner and outer mandrels.