Medical Overtube with Pulley Tensioning and Variable Stiffness
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Solution Overview
Problem
Existing overtubes for medical device insertion into body cavities face challenges in maintaining stable wire tension and guiding tools through bent sections, as the path lengths of wires change with bending, making it difficult to evenly pull the wires and maintain the shape of the overtube.
Innovation Solution
A medical device with a multi-lumen structure and pulley system where three wires are wound on pulleys, allowing for equal movement and tension distribution, and a variable stiffness portion with bending pieces that change stiffness upon contact, ensuring even wire pulling and shape maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If four wires are inserted into nested elements with symmetric disposal, then the total path length of opposing wires remains constant, but it becomes difficult to maintain stable wire tension when the overtube bends, as individual wire path lengths change
Solution Approach 1:
The patent divides the wire system into three separate wires instead of four, with each wire independently routed through the nested elements. This segmentation allows each wire to be controlled individually while maintaining overall shape stability, resolving the contradiction between shape stability and wire tension control.
Solution Approach 2:
The patent employs asymmetric wire routing where three wires are disposed at different positions rather than symmetric four-wire configuration. This asymmetric arrangement, combined with the pulley system, enables balanced tension distribution despite the asymmetric paths, solving the wire tension control problem while maintaining shape stability.
2Ease of operation
If the overtube is made flexible to navigate bent body cavities, then insertion smoothness is improved, but the overtube cannot maintain its shape when treatment is performed
Solution Approach 1:
The patent implements a dynamic stiffness control mechanism using nested elements that can transition between expanded and contracted states. When insertion is needed, the elements contract to allow bending; when treatment is performed, the elements expand to maintain shape stability. This dynamic adaptation resolves the contradiction between flexibility for insertion and rigidity for treatment.
Solution Approach 2:
The patent changes the physical parameter of stiffness by controlling the expansion state of the nested elements. The overtube transitions from a flexible state during insertion to a rigid state during treatment, allowing it to navigate bent cavities smoothly while maintaining shape stability when needed.
3Stability of the object's composition
If multiple nested elements are used to achieve shape lock function, then shape stability is improved, but the complexity of the wire pulling mechanism increases
Solution Approach 1:
The patent combines the wire tensioning function and the shape locking function into a single integrated mechanism. The pulley system that pulls the three wires simultaneously controls the expansion of multiple nested elements, merging two functions into one mechanism and reducing overall system complexity while maintaining shape lock stability.
Solution Approach 2:
The pulley system serves multiple functions: it tensions the wires, controls the expansion of nested elements, and maintains shape stability. This multi-functional design reduces the need for separate mechanisms, simplifying the overall wire pulling system while achieving shape lock stability.
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
Enables smooth insertion and stable guidance of medical devices through body cavities, including bent sections, by evenly distributing wire tension and maintaining the overtube's shape, regardless of the bending direction or shape.
Implementation Method 1
a first pulley disposed to be movable advance and retraction, a second pulley disposed to be movable advance and retraction
Implementation Method 2
a variable stiffness portion, the stiffness of which is configured to change with a compressive force in a longitudinal axis direction
Implementation Method 3
the close contact force between the nested elements increases. As a result, the shape of the overtube is temporarily fixed due to the frictional force generated between the nested elements
Data Source
AI summary
A medical device includes an insertion unit; and a drive unit, the insertion unit has first, second and third lumens, the drive unit has first and second pulleys disposed to be movable advance and retraction, first and second wires are wound on the first and second pulleys, respectively, and a pulling mechanism to pull the first and second pulleys toward a proximal end side, the first wire has a first end inserted into the first lumen and fixed to a distal end side of the insertion unit and a second end inserted into the second lumen and fixed to the distal end side of the insertion unit, and the second wire has a first end inserted into the third lumen and fixed to the distal end side of the insertion unit and a second end fixed to the drive unit.