Retractable Centesis Needle Nonlinear Spring Biasing
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Solution Overview
Problem
Existing retractable centesis needle devices lack initial sensitivity to tissue contact and exhibit increased resistance at a faster rate, leading to potential unintentional puncture risks and component weakening due to opposing spring configurations.
Innovation Solution
A hollow outer cannula with a sharp tip and a blunt-tipped inner cannula, biased by a first spring for initial sensitivity and a second spring that only contributes when the inner cannula is fully retracted, providing a nonlinear force profile for increased sensitivity upon contact and resistance during exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single spring is used to bias the inner cannula, then the device structure is simple, but the initial sensitivity to tissue contact is insufficient
Solution Approach 1:
The spring system is segmented into two distinct springs: a first spring that provides initial biasing force for sensitivity, and a second spring that engages only after a threshold displacement to provide additional resistance. This segmentation allows each spring to perform its specific function optimally without the complexity of a continuously varying single-spring system.
Solution Approach 2:
The spring system transitions from a static single-spring configuration to a dynamic two-spring system where the second spring is initially disengaged and only becomes active after the inner cannula displaces beyond a certain point. This dynamic engagement provides high initial sensitivity while maintaining structural simplicity.
2Reliability
If opposing springs are used to decrease initial resisting force, then initial sensitivity is improved, but the required force increases at a faster rate and excess forces weaken device components
Solution Approach 1:
The first spring is pre-loaded to provide the necessary initial biasing force for tissue contact sensitivity. The second spring is positioned to engage only after a threshold displacement, preventing excessive forces from acting on the device components during the critical initial contact phase.
Solution Approach 2:
The spring system transitions from a static single-spring configuration to a dynamic two-spring system where the second spring is initially disengaged and only becomes active after the inner cannula displaces beyond a certain point. This dynamic engagement provides high initial sensitivity while maintaining structural simplicity.
3Stability of the object's composition
If the second spring is engaged during the fully extended state, then continuous biasing force is maintained, but component weakening occurs due to excess spring forces
Solution Approach 1:
The first spring is pre-loaded to provide the necessary initial biasing force for tissue contact sensitivity. The second spring is positioned to engage only after a threshold displacement, preventing excessive forces from acting on the device components during the critical initial contact phase.
Solution Approach 2:
The spring system transitions from a static single-spring configuration to a dynamic two-spring system where the second spring is initially disengaged and only becomes active after the inner cannula displaces beyond a certain point. This dynamic engagement provides high initial sensitivity while maintaining structural simplicity.
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 device quickly signals tissue contact with lower initial force and requires higher force for sharp tip exposure, reducing unintentional puncture risks and minimizing spring-induced component weakening.
Implementation Method 1
A blunt tipped inner cannula is disposed within the channel and capable of sliding away from the housing to an extended state and toward the housing to a retracted state. The inner cannula is biased toward the extended state by a first biasing member disposed in the housing.
Implementation Method 2
A second biasing member also disposed in the housing acts in the same direction as the first biasing member when the inner cannula is in a fully refracted state. However, the second biasing member does not bias the inner cannula in any direction when the inner cannula is in a fully extended state.
Data Source
AI summary
A retractable centesis needle comprises a hollow, sharp tipped outer cannula extending from a housing. The outer cannula is generally tube-like and open at both ends to form a channel into a cavity in the housing. A blunt tipped inner cannula is disposed within the channel and capable of sliding away from the housing to an extended state and toward the housing to a refracted state. The inner cannula is biased toward the extended state by a first spring disposed in the housing. A second spring also disposed in the housing acts in the same direction as the first spring when the inner cannula is in a fully retracted state. However, the second spring does not bias the inner cannula in any direction when the inner cannula is in a fully extended state.