Down Hole Motor CV Joint Stress Distribution
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Solution Overview
Problem
Existing down hole motor CV joints in drilling operations are prone to failure under high torque, strain, and weight, necessitating frequent drill string removal for maintenance and repair, which disrupts deep and horizontal well drilling processes.
Innovation Solution
A CV joint design featuring a center rod with connected prongs and protuberances, a transmission adapter, and a bearing adapter with internal and external threads, along with a spherical member system, which distributes stress and increases load-carrying capacity by connecting the bases of the lobes, reducing the likelihood of breakage and allowing continuous drilling even if one protuberance fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional CV joint design is used in down hole motors, then the structure is simpler and easier to manufacture, but the joint is prone to failure under high torque, strain, and weight conditions
Solution Approach 1:
The CV joint is divided into multiple independent components including a cross-shaped center rod with four separate lobes, two distinct adapters (transmission adapter and bearing adapter), and multiple spherical members. This segmentation allows each component to be optimized independently for strength and reliability while distributing stress across multiple elements rather than concentrating it in a single structure.
Solution Approach 2:
The patent combines multiple functional elements into an integrated CV joint assembly where the center rod with lobes, adapters, and spherical members work together as a unified torque transmission system. The material bridges connect the lobes to the center rod, merging the rotational and axial functions into a single robust assembly that handles both torque and thrust loads.
2Strength
If the CV joint is designed to withstand high torque and strain, then the load-carrying capacity increases, but the complexity of the joint structure increases
Solution Approach 1:
The CV joint employs composite construction where spherical members interface between the transmission adapter and bearing adapter, creating a multi-material system that combines the advantages of different materials to handle both radial and axial loads effectively, thereby increasing overall strength and load-carrying capacity.
Solution Approach 2:
The design adds dimensional complexity by incorporating spherical members that provide rotational freedom in multiple directions, allowing the joint to accommodate angular misalignments and distribute loads across three-dimensional space, thereby enhancing strength without simply increasing the size of individual components.
3Ease of repair
If the drill string is pulled for maintenance when CV joint fails, then proper repair can be performed, but drilling operations must be ceased and downtime increases
Solution Approach 1:
The CV joint is designed as a modular assembly with distinct components (center rod, adapters, spherical members) that can be independently inspected and replaced. This segmentation enables targeted maintenance where only the failed component needs to be addressed, potentially avoiding complete drill string retrieval and reducing downtime.
Solution Approach 2:
The robust design with multiple spherical members and material bridges provides built-in redundancy and stress distribution that prevents sudden catastrophic failures. The gradual wear characteristics and multiple load paths allow for predictive maintenance scheduling before failure occurs, avoiding unplanned downtime.
Data Source
AI summary
An apparatus for transmitting torque to a down hole motor in a down hole drilling assembly. The apparatus includes a center rod having a distal protuberance and a proximal protuberance, a transmission adapter having a first end connected to the down hole motor, and a transmission socket formed within a second end of the transmission adapter and configured to receive the proximal protuberance. A material bridge may be provided for the protuberances. The apparatus may also include a bearing adapter operatively connected to the center rod, with the bearing adapter having a bearing socket therein, and wherein the transmission adapter is configured to connect to an output of the down hole motor and the bearing adapter is configured to connect to an input of a bearing assembly in the down hole assembly for drilling the well. The adapters may contain external threads and the caps may contain cooperating internal threads. A method of drilling a well is also disclosed.