Four-Channel Worm Gear Hand Prosthesis Mechanism
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Solution Overview
Problem
Existing upper limb prostheses, particularly hand prostheses, face challenges in achieving a balance between speed and torque in finger opening and closing movements, often requiring high energy consumption and compromising on strength or speed, which is crucial for effectively grasping and lifting objects.
Innovation Solution
The mechanism employs a unique four-channel worm gear system coupled with a DC motor and a displacement mobile, allowing for a faster and stronger finger movement without excessive energy consumption, by adjusting the number of screw channels to optimize speed and torque based on patient needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional worm gear systems are used in hand prostheses, then the structure is simple, but the finger opening and closing speed is slow and torque is insufficient
Solution Approach 1:
The worm gear is divided into four separate channels instead of a single channel, allowing each channel to contribute independently to the linear displacement. This segmentation enables the system to achieve higher speed and torque by combining the output of multiple channels while maintaining a relatively simple overall structure.
Solution Approach 2:
The four channels of the worm gear are positioned asymmetrically around the central axis, with each channel angled at 45 degrees to the vertical axis. This asymmetric arrangement optimizes the distribution of forces and allows for more efficient conversion of rotational motion to linear displacement, improving both speed and torque characteristics.
2Force
If more torque is provided for stronger grasping, then the grasping strength is improved, but the energy consumption increases
Solution Approach 1:
The system dynamically adjusts the engagement of the four worm gear channels based on the required torque. When high grasping force is needed, all four channels engage to provide maximum torque. When lower force is sufficient, the system can operate with reduced engagement, thereby lowering energy consumption while maintaining the capability for high-force grasping when needed.
Solution Approach 2:
The system changes the operational parameters of the worm gear by varying the number of active channels and their engagement depth. This allows the prosthesis to operate in different torque modes, optimizing the balance between grasping force and energy consumption based on the specific task requirements.
3Productivity
If faster finger movement is achieved, then the productivity is improved, but the torque and strength are compromised
Solution Approach 1:
By segmenting the worm gear into four channels, the system can distribute the torque requirements across multiple pathways. This allows for faster rotational-to-linear conversion in each channel while maintaining sufficient total torque output, achieving both high speed and adequate strength simultaneously.
Solution Approach 2:
The invention transitions from a single-dimensional linear displacement approach to a multi-dimensional approach by utilizing four spatially distributed channels. This dimensional expansion allows the system to achieve faster movement through optimized kinematic paths while maintaining torque through the combined effect of all channels.
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 enables the prosthesis to achieve a four to five times greater forward movement speed compared to conventional systems, providing both high torque and speed while minimizing electric power consumption, thus enhancing the prosthesis's ability to grasp and lift objects with precision and control.
Implementation Method 1
A fourth view is a partial perspective view of the longitudinal section of the support plate wherein the worm gear with the four channels and the bearing are shown; A fifth view is a perspective view of the displacement mobile wherein the guides for the mobile within the support plate and the connection with the worm gear are shown
Implementation Method 2
The internal walls of the support plate have a pair of guides that support a safety plate. A second pair of displacement guides receive a displacement mobile that glides with a linear movement along the guides
Data Source
AI summary
A functional prosthesis for a hand comprises an opening and closing mechanism for articulated fingers. A worm gear coupled to a DC actuator-motor provides linear movement to a displacement mobile which is coupled to articulated fingers of the artificial hand. When the actuator rotates in one direction, the displacement mobile moves in one direction, causing the fingers to open or close, depending upon the direction of rotation. Rotation of the actuator in the opposite direction will cause the fingers to move in the opposite direction.