CPM Device Worm Wheel Torsion Spring Dynamic Force
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Solution Overview
Problem
Current Continuous Passive Motion (CPM) devices do not effectively provide a dynamically loaded force and static progressive force to joints, which are essential for comprehensive motion therapy and rehabilitation, particularly in post-operative care to prevent immobilization disease and promote joint nutrition and remodeling.
Innovation Solution
A CPM device comprising a wrist drive unit with a worm wheel, torsion springs, and a rotatable frame that applies dynamically loaded force and static progressive force to joints through a combination of spring loading pins and pin stop blocks, allowing for controlled flexion and extension of joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional CPM devices are used to provide passive motion to joints, then joint mobility is improved, but the devices fail to provide dynamically loaded force and static progressive force necessary for comprehensive rehabilitation
Solution Approach 1:
The patent applies dynamics by replacing static force application with dynamic force delivery through a cam mechanism that varies force magnitude throughout the range of motion. The cam profile is specifically designed to provide different force levels at different joint angles, creating a dynamically loaded force that adapts to the joint's position and rehabilitation needs.
Solution Approach 2:
The patent implements parameter changes by modifying the force application parameters through the cam mechanism. The cam profile changes the force parameter dynamically during motion, transitioning from constant force to variable force. Additionally, the spring mechanism introduces progressive force parameters that change with compression distance, enabling static progressive force application.
2Reliability
If a cam mechanism is added to provide dynamically loaded force, then rehabilitation effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by combining the cam mechanism with the existing spring mechanism into a single integrated force application system. The cam and spring work together synergistically, where the cam provides the dynamic force profile and the spring provides the progressive force element, eliminating the need for separate complex mechanisms for each function.
Solution Approach 2:
The patent implements multi-functionality by designing the cam mechanism to simultaneously achieve multiple objectives: controlling force magnitude, defining range of motion, and providing mechanical advantage. The single cam component performs what would otherwise require multiple separate mechanisms, reducing overall device complexity while maintaining comprehensive force application capabilities.
3Reliability
If spring mechanisms are used to provide static progressive force, then joint remodeling is promoted, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies this principle by using standard, off-the-shelf spring components rather than custom-engineered complex mechanisms. The springs are conventional mechanical elements that are inexpensive, readily available, and easy to manufacture or replace, making the static progressive force function achievable without significant manufacturing complexity.
4Productivity
If the device provides comprehensive motion therapy with dynamic and static forces, then rehabilitation outcomes are improved, but the device becomes more complex and harder to operate
Solution Approach 1:
The patent implements self-service through the self-adjusting nature of the cam and spring mechanism. The system automatically provides the appropriate force profile based on joint position without requiring user intervention or adjustment. The cam profile inherently delivers the correct dynamic force pattern, and the spring automatically provides progressive force as the joint moves through its range, eliminating the need for complex controls or user programming.
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 device enhances joint rehabilitation by providing a comprehensive range of motion, reducing the need for pain medication, promoting joint nutrition, and aiding in the remodeling of joint surfaces, thereby improving recovery outcomes.
Implementation Method 1
at least one torsion spring located either between the first hinge housing and the worm wheel or between the worm wheel and the second hinge housing, the at least one torsion spring located adjacent to the worm wheel, the spring loading pin of the worm wheel configured to engage the at least one torsion spring, the at least one torsion spring configured to engage the spring loading pin and the pin stop block of the second hinge housing
Data Source
AI summary
A method and a continuous passive motion device for providing a dynamically loaded force and a static progressive force to a joint of a patient.