Inflatable Prosthetic Liner for Easy Application and Secure Fit

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Solution Overview

Problem

Existing prosthetic liners and bandages struggle with stretching difficulties, particularly for patients with physical limitations, making application and fit adjustment challenging.

Innovation Solution

A casing with an enclosed volume and fluid connection that expands or contracts based on pressure, featuring elastic walls and cavities, allowing easy application and customizable fit by adjusting internal pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the prosthetic liner is made with a smaller inner diameter to ensure a tight fit, then the fit security is improved, but the material must stretch significantly during application which creates difficulty for patients with physical limitations

Engineering Contradiction:
Improvefit securityVSAvoidapplication ease
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The prosthetic liner incorporates an inflatable chamber that allows the circumference to dynamically change. During application, the chamber is inflated to expand the liner's inner circumference, making it easier to put on. After application, the chamber is deflated to reduce the inner circumference, ensuring a secure tight fit. This dynamic adjustment resolves the contradiction between fit security and application ease.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The liner uses pressure as a controllable parameter to change its physical state. By adjusting the internal pressure of the inflatable chamber, the liner's circumference can be changed from a smaller size (for secure fit) to a larger size (for easy application). This parameter change allows the same object to satisfy both contradictory requirements at different times.

Inventive Principle:
Principle #35Parameter changes

2Ease of operation

If the liner material is made highly elastic to facilitate stretching during application, then the application ease is improved, but the precision of fit and contact pressure control deteriorates

Engineering Contradiction:
Improveapplication easeVSAvoidfit precision
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

Rather than relying on material elasticity, the invention uses a dynamic inflatable structure. The liner maintains a precise base circumference when deflated, ensuring accurate fit. During application, inflation dynamically increases the circumference to reduce stretching requirements. This separates the precision function (deflated state) from the application function (inflated state).

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention introduces a pneumatic system through the inflatable chamber to control the liner's dimensions. By using controlled air pressure, the system can precisely adjust the liner's circumference during application and maintain accurate fit dimensions when deflated, avoiding the trade-off between material elasticity and fit precision.

Inventive Principle:
Principle #29Pneumatics and hydraulics

3Ease of operation

If the liner is designed to be easily removable and reapplicable, then the ease of operation is improved, but the adhesion strength and secure positioning deteriorate

Engineering Contradiction:
ImproveremovabilityVSAvoidadhesion strength
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The inflatable chamber provides dynamic control over the liner's fit characteristics. When inflated during application, it expands to facilitate easy placement. When deflated during wear, it contracts to create strong adhesion and secure positioning. This dynamic state change allows the liner to be easily removable (by inflating to loosen fit) while maintaining strong adhesion during use (when deflated).

Inventive Principle:
Principle #15Dynamics

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 application and secure fit by expanding to accommodate the limb, with adjustable contact pressure and secure positioning, enhancing user comfort and convenience.

Implementation Method 1

the inner circumference of the prosthetic liner increases when the pressure of the volume increases. If fluid is drained from the volume, the inner circumference of the enveloping body decreases due to an elastic restoring force

Methodology Applied
Scientific EffectPressure: Pressure Increase

Implementation Method 2

an elastic restoring force preferably applied by the material of the enveloping body

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3448322B1Enveloping body
Publication Date: 2025.08.27 OTTOBOCK SE & CO KGAA
  • EP3448322B1 patent drawingFigure 1
  • EP3448322B1 patent drawingFigure 2
  • EP3448322B1 patent drawingFigure 3

AI summary

The invention relates to an enveloping body for at least partly enveloping a limb, comprising an enclosed volume (2) and a connection (3) for supplying fluid to the volume (2) and discharging it from the volume (2). The enveloping body (1) defines an inner circumference (4) and an outer circumference (5), the inner circumference (4) of the enveloping body (1) increasing as the pressure of the volume increases.