Redundant Switch Contacts for Safe Negative Pressure Wound Control

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Solution Overview

Problem

Existing negative pressure wound therapy systems with single user input elements can fail, leading to inability to stop negative pressure delivery, posing risks to wound healing and patient safety.

Innovation Solution

Incorporation of redundant activation and deactivation controls in the form of a switch with multiple contact pairs, ensuring delivery of negative pressure is halted if any contact pair fails to toggle properly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single user input element (switch) is used to control negative pressure delivery, then the device complexity is reduced, but the reliability of the system deteriorates because failure of the single switch can prevent stopping negative pressure delivery

Engineering Contradiction:
Improvecontrol structureVSAvoidswitch reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The single switch is segmented into multiple independent contact pairs (first pair and second pair of electrical contacts), each capable of independently controlling the negative pressure delivery. This segmentation allows the system to maintain functionality even if one contact pair fails, thereby improving reliability without significantly increasing overall device complexity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system incorporates redundant contact pairs as a preventive measure against switch failure. By having backup contact pairs ready before failure occurs, the system ensures that negative pressure delivery can be stopped even if one contact pair fails, cushioning against the potential harm of uncontrollable negative pressure delivery.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If redundant contact pairs are added to the switch, then the reliability of stopping negative pressure delivery is improved, but the device complexity increases

Engineering Contradiction:
Improvecontrol reliabilityVSAvoidswitch structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

Multiple contact pairs are merged into a single integrated switch assembly with a common actuator. This merging approach allows the redundant contacts to function together as one unified control element, improving reliability while minimizing the increase in device complexity by sharing mechanical components.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The switch assembly is designed with multi-functionality, where a single actuator controls multiple contact pairs that all serve the same function of controlling negative pressure delivery. This universal design allows one mechanical element to perform multiple electrical switching functions, improving reliability without proportionally increasing complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP3621667B1Redundant controls for negative pressure wound therapy systems
Publication Date: 2025.08.20 SMITH & NEPHEW PLC
  • EP3621667B1 patent drawingFigure 1
  • EP3621667B1 patent drawingFigure 2A
  • EP3621667B1 patent drawingFigure 2B

AI summary

Embodiments of negative pressure wound therapy systems and methods are disclosed. In one embodiment, a system includes a wound dressing, negative pressure source, switch, and control circuitry. The switch can include an actuator that toggles states of first and second pairs of contacts in response to a user input. The control circuitry can supply negative pressure with the negative pressure source when the state of the first pair of contacts is a first state and the state of the second pair of contacts is a second state, and the control circuitry can disable supply of negative pressure with the negative pressure source when the state of the first pair of contacts is not the first state or the state of the second pair of contacts is not the second state.