Fiberoptic Lightguide Cushioning for Autoclave Thermal Stress
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Solution Overview
Problem
Fiberoptic lightguides with fused ends face thermal expansion and contraction issues due to differing coefficients of expansion between fused glass and metal end fittings, leading to potential cracking and failure during autoclaving cycles, and pose challenges in sterilization due to potential gaps for bioburden entry.
Innovation Solution
A layer of cushioning material, such as polytetrafluoroethylene (PTFE) tape, is applied between the fused fiber mass and the metal end fitting to accommodate thermal expansion differences and prevent cracking, while ensuring no gaps for bioburden entry, using a thickness that fills the space and compresses to absorb compressive forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fused glass end is directly connected to the metal end fitting, then the light transmission is maximized, but thermal expansion differences cause cracking and failure during autoclaving cycles
Solution Approach 1:
A layer of cushioning material is introduced between the fused glass end and the metal end fitting to act as an intermediary that absorbs thermal expansion differences. This cushioning layer prevents direct contact between the two materials with incompatible thermal expansion coefficients, thereby preventing cracking while maintaining structural integrity during autoclaving cycles.
Solution Approach 2:
The cushioning material is designed with specific physical parameters including a thickness of about 0.002 to 0.006 inch and compressive strength properties that allow it to deform under thermal stress. By carefully selecting and controlling these parameters, the cushioning layer can absorb expansion forces while maintaining adequate light transmission and preventing damage to the fused glass end.
2Reliability
If a cushioning material layer is added between the fused fiber mass and metal end fitting, then thermal expansion damage is prevented, but the device complexity and manufacturing steps increase
Solution Approach 1:
The cushioning material is applied as a thin film or layer with a thickness of only 0.002 to 0.006 inch. This thin-film approach provides the necessary thermal expansion accommodation while adding minimal structural complexity. The thin film can be wrapped or applied directly to the fused glass end before insertion into the end fitting, simplifying the assembly process compared to more complex mechanical expansion compensation mechanisms.
3Reliability
If the cushioning material thickness is increased to better accommodate thermal expansion, then crack prevention is improved, but light transmission may be reduced due to increased interstitial spaces
Solution Approach 1:
The thickness of the cushioning material is precisely controlled within the range of 0.002 to 0.006 inch. This parameter optimization ensures that the layer is thick enough to accommodate thermal expansion differences and prevent cracking, yet thin enough to minimize light transmission losses. The compressive strength and elasticity parameters of the material are also selected to maintain adequate optical coupling while providing thermal stress relief.
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 cushioning layer effectively prevents cracking of the fused fiber mass during thermal cycling and maintains sterility by filling the space between the fiber mass and end fitting, enhancing the durability and reliability of the fiberoptic lightguide.
Implementation Method 1
differing coefficients of expansion between fused glass and metal end fittings, leading to potential cracking and failure during autoclaving cycles
Implementation Method 2
using a thickness that fills the space and compresses to absorb compressive forces
Data Source
AI summary
A flexible lightguide having at least one fused fiberoptic end secured within an end fitting with a layer of cushioning material sandwiched between the fused fiberoptic end and end fitting. The layer of cushioning material accommodates the differences in thermal expansion and contraction of the fused fiberoptic end and end fitting to prevent damage to the fused fiberoptic end such as during multiple cycling in an autoclave. As one example, the layer of cushioning material may be provided by wrapping the fused fiberoptic end with PTFE tape, thread seal tape, or the like.