Thermoformable Elastomer Prosthetic Sleeve Uniform Thickness
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Solution Overview
Problem
Current methods for manufacturing custom-made prosthetic sleeves for amputees result in irregular thickness and securing properties that are difficult to control, leading to issues with adherence, durability, and circulation issues for the residual limb.
Innovation Solution
A method involving a reduced positive mould and a thermoformable elastomer preform with a hardness greater than 40 Shore A, heated to shape the sleeve precisely, ensuring uniform thickness and secure fit, combined with a polyurethane coating for ease of use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If impregnation of fabric by polymer material or casting between positive and negative moulds is used, then custom-made sleeves can be manufactured, but the thickness becomes irregular and difficult to control
Solution Approach 1:
The patent applies preliminary action by pre-forming the polymer material into a tubular preform with controlled thickness before the casting process. This preform serves as a prepared substrate that ensures uniform thickness from the outset, eliminating the irregularity problem that occurs when polymer is directly cast or impregnated during the manufacturing process.
Solution Approach 2:
The patent utilizes parameter changes by controlling the hardness of the polymer material to be between 20 and 40 Shore A, and by precisely controlling the thickness of the tubular preform before casting. These parameter specifications ensure that the final sleeve achieves both manufacturability and uniform thickness, resolving the contradiction between ease of manufacture and manufacturing precision.
2Ease of operation
If gel type elastomer is used for thermoformable preform, then the sleeve becomes flexible and conformable, but it becomes sticky and creates adherences with socket walls
Solution Approach 1:
The patent resolves the stickiness issue by changing the material parameter - using a copolymer of styrene-ethylene-butylene-styrene (SEBS) instead of gel type elastomer. The SEBS copolymer maintains the desired flexibility and conformability while eliminating the sticky property that causes unwanted adherences with socket walls. The hardness is specifically controlled between 20 and 40 Shore A to achieve the right balance of flexibility and non-stickiness.
3Adaptability or versatility
If SEBS copolymer with hardness of 5 to 40 Shore A is used, then the sleeve becomes thermoformable and adaptable, but it becomes malleable and greatly deformable
Solution Approach 1:
The patent optimizes the hardness parameter of the SEBS copolymer to be between 20 and 40 Shore A, which is higher than the previously cited range. This parameter adjustment reduces excessive malleability while preserving thermoformability. The controlled hardness ensures the sleeve maintains its shaped form after thermal forming rather than remaining greatly deformable.
Solution Approach 2:
The patent applies preliminary action by using a tubular preform with predetermined thickness and shape before the thermoforming process. This pre-formed structure provides initial shape stability that prevents excessive deformation during and after forming, while still allowing the material to be thermoformed to match the patient's anatomy.
4Reliability
If the sleeve is made to follow the shape of the stump precisely, then adherence is improved, but friction between stump and sleeve increases
Solution Approach 1:
The patent applies local quality by creating a surface treatment or coating on the inner surface of the sleeve that provides localized adherence properties. This allows the sleeve to adhere sufficiently to prevent slipping while reducing friction in the contact zones. The solution may involve specific surface treatments or material compositions applied to the inner surface to optimize the adherence-friction balance.
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 method provides a durable, comfortable, and precisely fitting prosthetic sleeve with improved adherence and circulation, ensuring uniform securing force and extended lifespan, while being cost-effective and easy to implement.
Implementation Method 1
shaping the preform by heating the preform/mould assembly to a temperature comprised between 60° C. and 150° C.
Implementation Method 2
moulding said tubular preform by heating
Data Source
AI summary
The method for manufacturing a made-to-measure prosthetic sleeve from a thermoformable preform includes: providing a reduced positive mold corresponding to the copy of the shape of the stump of the residual limb reduced by 3 to 5% of all of the circumferences of the shape of the stump; providing a preform made from a thermoformable elastomer base, the preform presenting an open proximal end, a closed distal end, a uniform wall thickness and a hardness of more than 40 Shore A; placing the preform on the reduced positive mold to form a preform/mold assembly; shaping the preform by heating the preform/mold assembly to a temperature between 60° C. and 150° C.