Harmonic Drive Assembly for Downhole Rotary Motion Without Elastomers
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Solution Overview
Problem
Existing downhole drilling systems face challenges with high maintenance requirements, limited temperature range, and lateral vibration issues due to the use of elastomers and ball transfers in fluid-powered linear motors, which restrict their application in high-temperature and directional drilling environments.
Innovation Solution
The implementation of a harmonic drive assembly with a recirculating ball transfer mechanism that converts harmonic, cycloidal, or polynomial motion into rotary motion, reducing friction and abrasive wear by using rolling motion instead of sliding contact, and incorporating rotary pistons to allow drilling fluid flow, thereby minimizing particulate settlement and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If elastomers are used in fluid-powered linear motors, then the motors can operate in downhole drilling applications, but the temperature range is limited and maintenance requirements increase
Solution Approach 1:
The patent removes elastomers from the motor system entirely, replacing them with a harmonic drive mechanism that uses metal components and rolling contact. This extraction of the temperature-limiting component (elastomers) allows the motor to operate in high-temperature downhole environments while maintaining versatility through the harmonic drive's ability to convert reciprocating motion to rotary motion
Solution Approach 2:
The patent replaces the elastomer-based sealing and motion conversion mechanism with a harmonic drive system using metal components, rolling contact bearings, and precise mechanical geometry. This substitution eliminates the temperature constraints imposed by elastomers while maintaining the motor's functional versatility
2Ease of operation
If ball transfers with sliding contact are used, then motion conversion is achieved, but friction and abrasive wear increase leading to high maintenance requirements
Solution Approach 1:
The patent employs spherical ball transfers that roll between curved surfaces rather than sliding on flat surfaces. The harmonic drive mechanism uses balls that roll along curved track grooves, converting reciprocating linear motion to rotary motion through rolling contact. This spherical/curved geometry reduces friction and abrasive wear compared to traditional sliding ball transfers
Solution Approach 2:
The patent substitutes sliding contact mechanics with rolling contact mechanics in the ball transfer system. By using rolling balls within the harmonic drive mechanism instead of sliding ball transfers, the system achieves motion conversion with significantly reduced friction and wear, thereby lowering maintenance requirements
3Power
If multi-lobed helical rotor is used to generate rotation, then rotational energy is produced, but significant lateral vibration is introduced detrimental to hardware life
Solution Approach 1:
Instead of using a multi-lobed helical rotor that generates lateral vibration during rotation, the patent inverts the approach by using a harmonic drive where the reciprocating ring moves linearly and the balls convert this linear motion to smooth rotary motion. This inversion of the motion generation mechanism eliminates the nutation and lateral vibration inherent in helical rotor systems
Solution Approach 2:
The patent converts the reciprocating linear motion (which could be considered harmful due to its back-and-forth nature) into beneficial smooth rotary motion through the harmonic drive mechanism. The reciprocating ring's linear reciprocation is transformed by the rolling balls into continuous rotation without lateral vibration, turning a potentially harmful motion type into a beneficial output
4Power
If rigid drill pipe rotation system is used, then rotational energy transfer is achieved, but the system has limited applications in directional drilling due to additional torque from drill string curvature
Solution Approach 1:
The patent creates a dynamic downhole motor system that generates rotation locally at the drill bit rather than rotating the entire drill string from the surface. The harmonic drive mechanism dynamically converts reciprocating motion to rotary motion in situ, allowing the drill bit to rotate independently of drill string curvature and reducing the torque constraints associated with rigid drill pipe rotation systems
Solution Approach 2:
The patent segments the rotation generation function from the drill string, placing a compact downhole motor at the drill bit that independently generates rotational energy. This segmentation allows the drill bit to receive rotational power without requiring the entire drill string to rotate, thereby enabling directional drilling applications where the drill string curvature would otherwise create excessive torque
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
This solution enhances torque characteristics, reduces maintenance needs, operates effectively at high temperatures, and eliminates lateral vibration, improving efficiency and performance in drilling applications.
Implementation Method 1
converting harmonic, cycloidal or polynomial motion in the harmonic drive reciprocating ring to rotary motion... by using rolling motion instead of sliding contact
Implementation Method 2
harmonic drive reciprocating ring to convert harmonic, cycloidal or polynomial motion in the harmonic drive reciprocating ring to rotary motion
Implementation Method 3
incorporating rotary pistons to allow drilling fluid flow, thereby minimizing particulate settlement and vibration
Implementation Method 4
reducing friction and abrasive wear by using rolling motion instead of sliding contact
Data Source
AI summary
A harmonic drive assembly and fluid-powered linear motors with both axial pistons are rotary piston arrangements incorporating the harmonic drive assembly are disclosed. The motors may be used in downhole drilling applications, but the drive assembly and/or motors may be used in other applications. The assembly, motors and methods use advanced harmonic drives, advanced helical drives, and combinations thereof with 1) motors with axial pistons and reciprocating linear rings to convert reciprocative axial motion to continuous rotary motion, and 2) motors with rotary pistons and reciprocating linear rings to rectify reciprocative rotary motion to continual rotary motion to improve performance over prior configurations.