Planetary Gearbox with Switchable Freewheel for Orthopedic Devices
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Solution Overview
Problem
Existing change-speed gearboxes for orthopedic devices face challenges in providing efficient, noise-free, and low-loss transmission with rapid gear changes, especially in limited space and weight constraints.
Innovation Solution
A change-speed gearbox with a planetary gearbox configuration, featuring a pivotably mounted ring gear coupled to a ring gear carrier via a switchable freewheel, allowing for automatic torque-dependent gear switching between high and low gear ratios without electronic control or sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a planetary gearbox with switchable freewheel is used, then gear changing speed and reliability are improved, but device complexity increases
Solution Approach 1:
The freewheel mechanism automatically switches between high gear and low gear based on the direction of torque flow, without requiring external actuators or electronic control. The mechanism self-regulates by utilizing the inherent properties of the freewheel to engage or disengage based on whether torque is applied to the sun gear or the ring gear, thereby achieving rapid gear changes without adding complex control systems
Solution Approach 2:
The invention extracts the switching function from the traditional clutch mechanism and implements it through the freewheel's inherent one-way locking capability. By removing the need for active clutch actuators and electronic control systems, the design simplifies the overall structure while maintaining the ability to switch between different gear ratios rapidly and reliably
2Device complexity
If electronic control systems are eliminated, then device complexity and weight are reduced, but control precision may worsen
Solution Approach 1:
The invention replaces electronic control systems with a purely mechanical freewheel-based switching mechanism. The gear ratio selection is determined by the direction of torque application rather than electronic signals, achieving precise gear switching through mechanical principles alone. This substitution eliminates sensors, microprocessors, and actuators while maintaining deterministic and precise gear ratio selection
Solution Approach 2:
The system automatically determines the appropriate gear ratio based on the direction of torque flow without requiring external control inputs. The freewheel mechanism self-regulates by engaging or disengaging based on whether torque is applied to the sun gear (high gear) or the ring gear (low gear), achieving precise control through passive mechanical response to load conditions
3Ease of operation
If torque-dependent automatic switching is implemented, then ease of operation is improved, but reliability under variable loads may worsen
Solution Approach 1:
The gearbox dynamically adapts its gear ratio based on the direction and magnitude of applied torque. The system automatically transitions between high gear (sun gear drive) and low gear (ring gear drive) depending on whether the load requires high speed/low torque or low speed/high torque conditions. This dynamic response ensures optimal performance across varying operational phases such as swing phase versus stance phase in orthopedic applications
Solution Approach 2:
The invention changes the transmission ratio parameter based on the direction of torque application. By utilizing the freewheel's ability to lock or free based on torque direction, the system automatically adjusts the gear ratio to match operational requirements, ensuring reliable performance under variable loads without requiring external control
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 gearbox achieves efficient and reliable gear changes with minimal noise and loss, enabling high rotational speeds with low torques and high torques at low rotational speeds, suitable for various phases of orthopedic device operation.
Implementation Method 1
The ring gear is pivotably mounted in a ring gear carrier and is coupled to the ring gear carrier via a switchable freewheel
Implementation Method 2
a planetary gearbox with at least one planet stage having a central sun gear, having a plurality of planet gears rotatably mounted on a planet carrier, which come into engagement with the sun gear, and having a ring gear which meshes with the planet gears
Data Source
AI summary
A change-speed gearbox for orthopedic devices has a planetary gearbox with at least one planet stage having a central sun gear, a plurality of planet gears rotatably mounted on a planet carrier which come into engagement with the sun gear, and has a ring gear which meshes with the planet gears. The sun gear can be coupled to a drive. The planet carrier is coupled to an output element. The ring gear is pivotably mounted in a ring gear carrier and is coupled to the ring gear carrier via a switchable freewheel.