Articulated PDM Transmission With Ball Torque Transfer Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotary power transmission assemblies for bottom hole assemblies (BHAs) face challenges in maintaining stable torque transfer due to misaligned rotations, leading to high stress concentrations and wear on contact surfaces.
Innovation Solution
The design incorporates a ball and recessed torque transfer element (TTE) configuration, similar to a constant velocity (CV) joint, where the TTE is free to rotate and tilt about the ball, maintaining contact and reducing stress during misaligned rotations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Woodruff key designs are used to provide large TTEs, then torque transfer capability is improved, but stability during misaligned rotation deteriorates leading to TTE unseating and high stress concentrations
Solution Approach 1:
The patent employs spherical balls instead of traditional Woodruff key TTEs. These balls are received in spherical recesses in the shaft and housing, allowing them to maintain stable contact during misaligned rotation. The spherical geometry enables the TTE to articulate smoothly through angular deviations without unseating, while still transferring torque effectively through the ball-shaft and ball-housing contact interfaces.
Solution Approach 2:
The patent makes the TTE configuration dynamic by allowing the ball to rotate and tilt relative to the shaft and housing during misaligned rotation. The ball is free to articulate within the spherical recesses, adapting its orientation to maintain contact as the shaft rotates at angles up to 3.0 degrees relative to the housing. This dynamic adjustment prevents unseating and distributes stress evenly throughout the torque transfer cycle.
2Stability of the object's composition
If bridge designs are used to provide TTE stability, then TTE stability is improved, but torque transfer angle efficiency deteriorates limiting mechanical advantage
Solution Approach 1:
The spherical ball TTE maintains stability through its geometry and the spherical recesses that receive it, eliminating the need for bridge-like stabilizing structures. The ball naturally centers itself in the spherical recess during rotation, providing inherent stability without compromising the torque transfer angle. This allows the shaft to articulate through the full range of misalignment while maintaining optimal mechanical advantage.
3Manufacturing precision
If sliding TTE constrained by radial groove is used, then TTE positioning is improved, but ball engagement stability deteriorates causing physical disengagement during misaligned rotation
Solution Approach 1:
The patent replaces the radial groove constraint with spherical recesses in both the shaft and housing. The ball is received in a spherical recess in the shaft and articulates within a spherical recess in the housing. This dual spherical configuration allows the ball to maintain engagement throughout the misalignment cycle without being constrained by grooves that would force disengagement. The spherical geometry provides positioning precision while accommodating the necessary articulation motion.
4Power
If Foote ball design with sliding TTE in radial groove is used, then torque transfer is achieved, but torque transfer angle efficiency deteriorates and TTE disengagement occurs
Solution Approach 1:
The patent improves upon the Foote design by using spherical recesses instead of a radial groove to receive the sliding TTE. The TTE (ball) is received in a spherical recess in the shaft and articulates within a spherical recess in the housing, allowing it to maintain optimal torque transfer angle throughout the misalignment cycle. This eliminates the disengagement problem inherent in radial groove designs while preserving effective torque transfer.
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 configuration allows for smooth and predictable torque transfer, reducing wear and stress on the components, and enabling the transmission to handle higher torque loads while maintaining engagement throughout misaligned rotations.
Implementation Method 1
The TTE bearing surface opposes the housing bearing surface, and the shaft backlash surface opposes the housing backlash surface... maintaining contact and reducing stress during misaligned rotations
Implementation Method 2
The ball, at least in theory, provides additional freedom to allow the shaft head to 'tilt' with respect to shaft head during misaligned rotation... optimize the torque capability of the TTEs
Data Source
AI summary
A ball-CV style transmission suitable for use in a Positive Displacement Motor (PDM). A shaft provides shaft wings received into housing receptacles on a housing. A Unitary Torque Transfer Element (UTTE) is interposed between each shaft wing and housing within each housing receptacle, with a spherical surface on the UTTE received into a recess preferably on the housing. The UTTEs float within their corresponding housing receptacles so as to maintain torque transfer contact between all thrust surfaces during articulated rotation of the shaft with respect to the housing. The UTTEs preferably float generally radially towards the shaft centerline as angular deflection increases during articulated rotation.