Polymeric Prosthetic Liner with Asymmetric Stretch Control
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Solution Overview
Problem
Polymeric prosthetic liners exhibit excessive longitudinal stretch, which can hinder knee flexion in below-knee amputees and cause discomfort, as existing techniques to limit stretch either restrict radial stretch or fail to effectively control longitudinal elasticity.
Innovation Solution
A fabric-covered polymeric prosthetic liner with a specially designed fabric exterior that controls longitudinal stretch by using stretch-controlling fabrics with asymmetric elasticity, combined with a polymeric material that is less stretchable through reduced mineral oil content and added reinforcing materials like KEVLAR, allowing for adequate radial stretch and knee flexion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polymeric gel materials are used to provide cushioning and comfort, then comfort and cushioning are improved, but longitudinal stretch becomes excessive
Solution Approach 1:
The patent combines polymeric gel material with fabric material to create a composite liner structure. The fabric material is integrated with the polymeric material to form a unified structure that provides both cushioning comfort and longitudinal stretch control, resolving the contradiction between comfort and excessive stretch.
Solution Approach 2:
The fabric material is selectively positioned at specific locations on the liner, particularly at the closed end and along portions of the liner body, to provide localized stretch control where needed while maintaining comfort in other areas. This allows different regions of the liner to have different functional properties.
2Length of moving object
If techniques are employed to limit longitudinal stretch, then longitudinal stretch is reduced, but radial stretch is restricted
Solution Approach 1:
The fabric material exhibits asymmetric elastic properties with different stretch characteristics in longitudinal versus radial directions. The fabric is engineered to have lower elasticity in the longitudinal direction (parallel to liner axis) while maintaining higher elasticity in the radial direction (perpendicular to liner axis), allowing directional control of stretch.
Solution Approach 2:
The patent modifies the elastic parameters of the liner by introducing fabric material with specific elasticity characteristics. The fabric material changes the stretch parameters of the overall liner structure, reducing longitudinal elasticity while preserving radial elasticity through its anisotropic properties.
3Length of moving object
If fabric material with limited longitudinal stretch is used, then longitudinal stretch is controlled, but adaptability to different limb sizes is reduced
Solution Approach 1:
The fabric material is strategically positioned at specific locations (closed end and selected portions of the liner body) rather than uniformly throughout, allowing the liner to maintain controlled longitudinal stretch in critical areas while preserving adaptability in other regions through the polymeric material's inherent elasticity.
Solution Approach 2:
The composite structure of fabric and polymeric gel materials creates a synergistic effect where the fabric provides longitudinal stability and the polymeric material provides radial adaptability, allowing the liner to accommodate different limb sizes while controlling excessive longitudinal stretch.
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 solution effectively limits longitudinal stretch while maintaining sufficient radial elasticity and comfort, accommodating various residual limb sizes and shapes without causing discomfort or restricting movement.
Implementation Method 1
The fabric material is comprised of a material that is less stretchable than the polymeric material forming the covering... acts to reduce stretching and/or movement of the covering
Implementation Method 2
polymeric gel materials provide amputees with a great deal of cushioning and comfort
Implementation Method 3
The reinforcing material is comprised of a material that is less stretchable than the polymeric material forming the covering, and acts to reduce stretching and/or movement of the covering
Data Source
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AI summary
A control I?d-stretch prosthetic liner comprising a polymeric material covered with at least a stretch-controlling fabric. Certain liner types, such as below knee (BK) liners, may also include a panel of more stretchable fabric so as to prevent any interference with knee flexion. The polymeric material of the liner may also be used to control liner stretch, such as by adding Kevlar pulp or other materials that increase the strength and reduce the elasticity of the polymeric material and/or by reducing the amount of plasticizer(s) present therein. The stretch-controlling fabric, possibly in conjunction with the polymeric material, acts to limit the longitudinal stretch of the liner while not adversely affecting the radial stretch thereof.