Prosthetic Knee Joint Layout for Powered Extension Under Load
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Solution Overview
Problem
Prosthetic legs, such as those described in Patent Literature 1, can generate resistance for bending and stretching but lack the power necessary for smooth ascension, particularly when a load is applied, as they cannot effectively generate power for stretching the knee joint.
Innovation Solution
A joint device with a coupling portion that utilizes an expansion-contraction device, where one side of the device is mechanically connected to a first member and the other side to a second member, incorporating a motion conversion mechanism with a shaft member and cylindrical member, allowing the angles between the members to vary through expansion and contraction, with the expansion-contraction device disposed on the side of the minimum formed angle, enabling tensile force application as the second formed angle increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a hydraulic cylinder with a variable valve is used to adjust resistance, then resistance of bending and stretching can be generated, but power for bending and stretching cannot be generated
Solution Approach 1:
The joint device is divided into two independent functional systems: a hydraulic cylinder for generating resistance force, and an expansion-contraction device with a motor for generating power. This segmentation allows each subsystem to optimize its function without compromising the other, resolving the contradiction between resistance generation and power generation capabilities
Solution Approach 2:
The patent merges two previously separate functional systems (hydraulic resistance system and mechanical power system) into a single integrated joint device. The expansion-contriction device is combined with the hydraulic cylinder, allowing the joint to simultaneously provide both resistance control and active power generation for bending and stretching movements
2Ease of operation
If the expansion-contriction device is disposed on the side of the first formed angle, then the coupling portion can be stretched and bent effectively, but the arrangement of components becomes more complex
Solution Approach 1:
The expansion-contriction device is strategically positioned on the first formed angle side of the coupling portion, where it can most effectively influence the bending and stretching motion. This localized placement optimizes the mechanical advantage and operational effectiveness while minimizing unnecessary component distribution throughout the entire structure
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 the joint device to effectively stretch and bend, enhancing the ability to ascend steps with a load by generating necessary power through the expansion-contraction mechanism, preventing buckling deformation and optimizing the arrangement of components for efficient operation.
Implementation Method 1
the expansion-contraction device has a motion conversion mechanism including a shaft member and a cylindrical member that performs translational motion along an axis of the shaft member due to a rotation of the shaft member
Implementation Method 2
the expansion-contriction device is provided such that a tensile force acts on the shaft member as the second formed angle increases
Data Source
AI summary
An electric prosthetic leg includes a below-knee member, an above-knee member, a knee joint mechanism coupling the below-knee member and the above-knee member such that angles formed between the below-knee member and the above-knee member are variable, and an expansion-contraction device capable of varying the angles formed between the below-knee member and the above-knee member by expanding and contracting, in which one side of the expansion-contraction device in an extending direction is mechanically connected to the below-knee member, and the other side of the expansion-contraction device is mechanically connected to the above-knee member. Assuming that smaller one of minimum formed angles, of the angles formed between the below-knee member and the above-knee member centering on a pivoting portion of the knee joint mechanism, is defined as a second formed angle, the expansion-contraction device is partially disposed on a side of a first formed angle.