Prosthetic Hand Thumb Element Trajectory Switching
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Solution Overview
Problem
Prosthetic hands with movable thumb and finger elements lack the ability to intuitively and simply switch between different gripping modes, such as opposition and lateral grips, which are essential for handling various objects effectively.
Innovation Solution
The prosthetic hand design allows the thumb element to move along multiple trajectories based on control force limits, enabling seamless switching between gripping modes by exceeding predetermined force values, utilizing mechanical arrangements like springs and traction elements to achieve different end positions, and potentially incorporating actuators or centrifugal clutches for mode changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional spring-loaded thumb element is used, then the hand automatically returns to the closed position when control force is released, but the ability to switch between different gripping modes (opposition and lateral grips) is lost
Solution Approach 1:
The thumb element's movement trajectory is made dynamic and adaptable. By using a guide contour with multiple branches that the guide pin can switch between, the system allows the thumb to move along different paths (first trajectory for opposition grip, second trajectory for lateral grip) depending on the control force applied, enabling mode switching while maintaining automatic return to closed position
Solution Approach 2:
The system changes the parameter of control force magnitude to switch between gripping modes. When control force exceeds a predetermined limit value, the guide pin moves to a different branch of the guide contour, changing the thumb's movement trajectory. This parameter-based switching allows the same mechanical structure to provide multiple grip modes without complex control systems
2Adaptability or versatility
If motorized actuators are used to enable mode switching, then grip mode changes become precise and controllable, but the device becomes heavier, more complex, and more expensive
Solution Approach 1:
The system uses the user's own control force (applied through the traction element) to automatically trigger mode switching. When the user applies sufficient control force to exceed the predetermined limit, the guide pin automatically jumps to a different branch of the guide contour, initiating mode change without requiring external actuators or complex control electronics. The user's natural movement drives the system
Solution Approach 2:
The patent replaces motorized actuation with a purely mechanical solution. Instead of using motors, sensors, and electronic controls, the system uses a mechanical guide contour with multiple branches and a guide pin that responds to control force magnitude. This mechanical substitution eliminates motors, batteries, and electronic control systems while achieving the same mode switching function
3Device complexity
If the thumb element is constrained to a single fixed trajectory, then the mechanical structure is simple, but the hand cannot perform different gripping modes such as opposition grip and lateral grip
Solution Approach 1:
The guide contour is segmented into multiple distinct branches (first branch for opposition grip, second branch for lateral grip). The guide pin can be positioned on different branches, and each branch defines a specific movement trajectory for the thumb element. This segmentation allows a single guide contour structure to provide multiple gripping modes by dividing the contour into functionally distinct sections
Solution Approach 2:
The guide contour is designed as a multi-functional element that can guide the thumb element along different trajectories depending on which branch the guide pin is on. The same guide contour structure serves multiple purposes: it provides the first trajectory for opposition grip, the second trajectory for lateral grip, and maintains the automatic return to closed position function, making the system versatile without requiring separate mechanisms for each function
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
Enables easy and intuitive switching between gripping modes by applying varying control forces, enhancing the prosthetic hand's versatility in grasping different objects without the need for motorization, ensuring the hand returns to a closed position without control force.
Implementation Method 1
at least one force-applying element that applies a restoring force to the thumb element and preferably to the at least one finger element, acting in the opposite direction to the control force. Such a force-applying element can be a spring element, for example, a torsion spring, a constant-force spring, or a helical spring.
Data Source
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AI summary
The invention relates to a prosthetic hand, comprising a thumb element (2) and at least one finger element. The thumb element (2) can be moved relative to the at least one finger element by means of a control force (16). The thumb element (2) can be moved relative to the at least one finger element along a first trajectory in at least one first mode and along a second trajectory in at least one second mode and can be brought from the first mode into the second mode as a result of the control force (16) exceeding a first predefined limit value.