Biopsy Cannula Seal Structure for Low-Drag Fluid-Tight Motion
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Solution Overview
Problem
Current biopsy needle sets face challenges in maintaining a fluid-tight seal, especially during movement of components, which leads to inefficiency and drag, compromising the performance of biopsy devices.
Innovation Solution
The implementation of an outer cannula seal and an inner cannula seal, each featuring an interference ring, a beaded ring, and a flexible portion, allowing for longitudinal movement while maintaining a fluid-tight seal, utilizing an ethylene propylene diene monomer (EPDM) polymer and manufactured through a mold-forming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If O-rings are used to provide fluid-tight seals between needle set components, then sealing is achieved, but drag on moving cannulas increases and seal reliability deteriorates during movement
Solution Approach 1:
The patent employs a flexible membrane seal that spans across the cannula passage, allowing the cannula to move longitudinally through the sealed barrier. The membrane deforms elastically to accommodate cannula movement while maintaining fluid-tight sealing, eliminating the frictional drag generated by conventional O-rings that rely on frictional fits.
Solution Approach 2:
The invention replaces the mechanical friction-based sealing system (O-rings relying on frictional fits) with a membrane-based sealing system that uses elastic deformation and pressure differential to maintain seals during cannula movement, thereby reducing drag and improving efficiency.
2Reliability
If O-rings are used to seal between cannulas and housing, then sealing is provided, but lateral movement of cannulas compromises the seal
Solution Approach 1:
The flexible membrane seal accommodates both longitudinal and lateral cannula movements through elastic deformation. The membrane's flexibility allows it to conform to cannula position changes while maintaining fluid-tight sealing, providing adaptability without compromising seal integrity.
Solution Approach 2:
The membrane seal transitions from a static sealing approach to a dynamic one, where the membrane continuously adapts its shape and position in response to cannula movement. This dynamic sealing mechanism maintains reliability while enabling full range of motion for the cannulas.
3Reliability
If frictional fit seals are used with moving cannulas, then sealing is achieved, but efficiency of biopsy device decreases due to drag
Solution Approach 1:
The patent replaces the friction-based mechanical sealing system with a membrane-based system that uses elastic deformation and pressure differential. This substitution eliminates the frictional drag that reduces biopsy device efficiency while maintaining fluid-tight sealing throughout the cannula's range of motion.
Solution Approach 2:
The flexible membrane seal allows frictionless passage of the cannula through the sealed barrier, as the membrane deforms elastically rather than relying on frictional contact. This dramatically reduces drag and improves the overall efficiency and speed of the biopsy device operation.
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
These seals effectively prevent fluid leakage and reduce frictional drag, enhancing the efficiency and performance of biopsy devices by allowing smooth longitudinal movement of cannulas without compromising the seal.
Implementation Method 1
a flexible portion extending between the interference ring portion and the beaded ring portion. The outer cannula seal is configured to allow longitudinal movement of the outer cannula relative to the manifold while maintaining a fluid-tight seal therebetween
Implementation Method 2
O-rings generate seals using frictional fits (e.g., against outer and/or inner cannulas). As such, when those outer and/or inner cannulas move relative to the O-rings, the O-rings exert a drag on the outer and/or inner cannulas
Data Source
AI summary
A biopsy device includes an elongated housing having a manifold, an outer cannula partially and slidably disposed in the manifold, and an inner cannula partially and slidably disposed in a lumen of the outer cannula. The biopsy device further includes an outer cannula seal disposed between the manifold and the outer cannula, the outer cannula seal including an interference ring portion disposed adjacent an inner surface of the manifold, a beaded ring portion that contacts an outer surface of the outer cannula, and a flexible portion extending between the interference ring portion and the beaded ring portion.