Endoscope Bowden Cable Composite Guide Tube Tension Control
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Solution Overview
Problem
Conventional endoscopes face issues with maintaining tensioned pull-wires due to changes in the relative lengths of the pull-wire and guide tube, leading to reduced deflection of the articulated tip, especially when the guide tube shrinks during storage or use, which is problematic for disposable endoscopes where manufacturing costs need to be kept low.
Innovation Solution
The use of a Bowden cable with an outer guide tube comprising two sections: a steel section for stability and flexibility, and a polymer plastic section for cost-effectiveness and resistance to meandering, along with a termination means within the handle housing to maintain the desired length and prevent shrinkage-induced motion changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the guide tube is made of polymer plastic to reduce manufacturing costs, then the manufacturing cost is reduced, but the guide tube shrinks over time leading to loss of tension in the pull-wire
Solution Approach 1:
The guide tube is constructed as a composite structure with a polymer plastic outer layer for cost-effectiveness and an inner steel reinforcement layer for dimensional stability. This composite design allows the guide tube to maintain its length and tension properties while keeping manufacturing costs low, resolving the contradiction between cost reduction and reliability.
2Reliability
If the guide tube is made of steel to maintain stability and prevent shrinkage, then the tension maintenance is improved, but the manufacturing cost increases
Solution Approach 1:
Instead of using entirely steel construction which would be expensive, the invention uses a composite structure where polymer plastic provides the outer protective layer at low cost, while an inner steel reinforcement layer provides the necessary dimensional stability and shrinkage resistance. This balanced approach maintains reliability while controlling manufacturing costs.
Solution Approach 2:
The steel reinforcement is strategically positioned only in the critical inner region where shrinkage resistance is most needed, rather than making the entire guide tube from expensive steel. This localized application of high-cost material only where necessary resolves the contradiction between maintaining tension and reducing overall manufacturing cost.
3Reliability
If the pull-wire length is increased to compensate for guide tube shrinkage, then the deflection control is maintained, but the device complexity increases
Solution Approach 1:
The steel reinforcement is pre-installed within the guide tube during manufacturing to prevent shrinkage before the endoscope is put into service. This preliminary structural reinforcement eliminates the need for later adjustments or compensations, maintaining deflection control without adding operational complexity.
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
This solution ensures that the endoscope remains functional with full deflection control, even after shrinkage, by minimizing the impact of guide tube shrinkage on the pull-wire length, thus maintaining the intended motion and reducing manufacturing complexity.
Implementation Method 1
a first guide tube section has plastic and elastic properties
Implementation Method 2
a second guide tube section has plastic and elastic properties
Data Source
AI summary
A control mechanism for an endoscope (1) comprising a Bowden cable. the Bowden cable has an outer guide tube (9) having a first length between a proximal end and a distal end of said outer guide tube (9) and an inner pull-wire (15) having a second length between a proximal end and a distal end of said inner pull-wire (15). The second length is longer than the first length. The outer guide tube (9) comprises a first guide tube section (9′) and a second guide tube section, where said first guide tube section (9′) has plastic and elastic properties, which are different from the plastic and elastic properties of said second guide tube section (9″).