Rolling Diaphragm Capstan Transmission for Low-Friction High Torque
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Solution Overview
Problem
Existing rotary motion transmission systems face challenges in achieving high torque with low inertia, friction, mass, and backlash, particularly in extreme environments such as subsea applications where seals introduce high friction and large magnetic fields preclude standard electric motors.
Innovation Solution
A linear to rotary motion converter using rolling diaphragm linear actuators and a capstan mechanism with pretensioned cables that translate linear motion into rotational motion, minimizing friction and allowing for high torque transmission with low bearing loads and no direct loading on rotary bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If standard electric motors are used in large magnetic fields, then motor function is lost due to magnetic field interference, but the patent eliminates motors entirely by using cable-driven hydraulic actuators with rolling diaphragms that convert linear motion to rotary motion through a capstan mechanism
Solution Approach 1:
The patent extracts and eliminates the electric motor from the system entirely, replacing it with a cable-driven hydraulic actuation system that operates independently of magnetic fields. The rolling diaphragm linear actuators convert hydraulic pressure to linear motion, which is then transformed to rotary motion by the capstan, completely removing the source of magnetic field vulnerability.
Solution Approach 2:
The patent replaces the electromagnetic actuation system with a purely mechanical transmission system. The rolling diaphragm actuators use hydraulic pressure to drive linear motion, and the capstan converts this to rotary motion through mechanical cable tension, eliminating reliance on electromagnetic fields that are susceptible to magnetic interference.
2Reliability
If seals are used in subsea applications to prevent water ingress, then reliability is improved, but friction increases significantly
Solution Approach 1:
The patent extracts and eliminates traditional rotary seals from the system by using a cable-driven mechanism. The rolling diaphragm actuators and capstan system transmit power through cables rather than requiring rotary seals, thereby maintaining subsea reliability while dramatically reducing friction losses associated with sealed rotary joints.
Solution Approach 2:
The patent introduces cables as an intermediary medium to transmit mechanical power from the linear actuators to the capstan. This intermediary approach allows power transmission without requiring direct mechanical contact or rotary seals, thereby maintaining sealing integrity while minimizing friction.
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 solution enables efficient, low-friction, and high-torque transmission suitable for dynamic and accurate robot systems, including subsea and magnetically sensitive environments, with reduced component size and cost, and improved reliability in maintaining motion under varying loads.
Implementation Method 1
rolling diaphragm linear actuators... cause linear displacement of the rigid body
Implementation Method 2
linear motion of the rigid body caused by actuation of the rolling diaphragm linear actuators is translated to rotational motion of the capstan
Data Source
AI summary
A linear to rotary motion converter includes a rigid body having first and second opposing end plates interconnected by at least one rigid crossmember. Each of the end plates is adapted to receive a rolling diaphragm linear actuator to thereby cause linear displacement of the rigid body in an axial direction upon actuation of the rolling diaphragm linear actuators. The linear to rotary motion converter also includes a capstan operably coupled to and located between the end plates such that linear motion of the rigid body caused by actuation of the rolling diaphragm linear actuators is translated to rotational motion of the capstan.