Endoscope Distal Tip Rib Structure for Thermal Stress Management
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Solution Overview
Problem
The difference in thermal expansion between the inner and outer tubular portions of a rigid endoscope during autoclaving cycles causes shearing stresses and failure of the epoxy adhesive joint, leading to separation.
Innovation Solution
A tubular assembly with a connecting rib rigidly coupling the outer and inner tubes, and a method of aggregating optical fibers into a single bundle using a tapered or curved member to manage thermal expansion and stress, ensuring the adhesive joint remains intact during autoclaving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy adhesive is used to join inner and outer tubes, then the joint provides initial strength, but the adhesive joint fails under thermal expansion stress during autoclaving
Solution Approach 1:
The patent divides the optical fiber bundle into multiple separate bundles (typically three) that are distributed around the inner tube, rather than using a single unified bundle. This segmentation allows each fiber bundle to independently manage thermal stress, preventing catastrophic failure of the entire optical system during autoclaving cycles.
Solution Approach 2:
The patent introduces a rib structure as an intermediary element between the inner and outer tubes. This rib acts as a stress distribution mechanism that prevents direct thermal stress concentration at the epoxy adhesive joint, thereby protecting the adhesive bond from failure during thermal expansion.
2Illumination intensity
If optical fibers are positioned between inner and outer tubes, then illumination function is achieved, but thermal expansion causes shearing stresses and separation
Solution Approach 1:
The optical fiber bundle is segmented into multiple separate fiber bundles positioned at different locations between the inner and outer tubes. This segmentation distributes the thermal stress across multiple independent elements rather than concentrating it in a single location, reducing the overall shearing stress on the adhesive joint.
Solution Approach 2:
The patent positions fiber bundles at specific locations around the inner tube, creating non-uniform local arrangements. This allows certain areas to have higher fiber density for illumination while other areas provide stress relief zones, optimizing both illumination function and thermal stress management.
3Temperature
If outer tube is allowed to expand during autoclaving, then thermal expansion is accommodated, but shearing stresses cause adhesive joint failure
Solution Approach 1:
The rib structure serves as an intermediary mechanical element that mediates between the expanding outer tube and the relatively stable inner tube. It distributes the thermal expansion forces across a larger area and prevents direct transmission of shearing stresses to the epoxy adhesive joint, allowing thermal accommodation without joint failure.
Solution Approach 2:
The rib structure is pre-installed between the inner and outer tubes to provide beforehand cushioning against thermal expansion stresses. This structural feature is designed in advance to absorb and distribute the forces generated during autoclaving, preventing sudden adhesive joint failure when thermal expansion occurs.
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 solution effectively withstands harsh autoclaving conditions by managing thermal expansion and maintaining the integrity of the adhesive joint, preventing separation and failure.
Implementation Method 1
During autoclave cycles the outer tube heats up and expands while the inner tube remains cool and does not expand. The difference in expansion results in shearing stresses that cause separation and failure of the epoxy adhesive joint.
Data Source
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AI summary
An endoscope distal tip and method of assembling same, the method including providing an endoscope tip tubular assembly including an outer tube rigidly coupled to an inner tube by at least one rib extending there between and providing a plurality of optical fibers within a space formed between the outer tube and the inner tube. The plurality of optical fibers are extended longitudinally within the outer tube and thereby divided by the at least one rib into at least two optical fiber bundles. The distal end sections of the at least two optical fiber bundles are aggregated into a single optical fiber bundle by inserting an aggregating member into a recess formed between a distal end of the at least one rib and a distal end of the endoscope tip tubular assembly. The aggregating member can be provided to encircle or partially encircle the inner tube or encircle or partially encircle the single optical fiber bundle.