Endoscope Coil Tubular Body Spring Constant Ratio
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Solution Overview
Problem
Existing endoscope treatment instruments with coil-shaped tubular bodies face issues with stress concentration and plastic deformation due to differences in inner diameters at connecting portions, leading to operational challenges when curved and subjected to compressive forces during tissue clipping.
Innovation Solution
A treatment instrument with a coil-shaped tubular body featuring a first coil with a spring constant of 15 N/mm to 500 N/mm and a second coil with a differing spring constant, connected coaxially, where the ratio of spring constants is between 1.0 and 2.0, and a torsion spring constant of at least 25 N mm/rad, ensuring balanced stress distribution and reduced slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the tubular body is constituted by a distal end side coil and a proximal end side coil with different inner diameters connected via a connecting portion, then the tubular body can be formed to have different wall thicknesses and inner diameters at different sections, but a step arises due to inner diameter differences at the connecting portion causing stress concentration and plastic deformation when curved
Solution Approach 1:
The patent applies parameter changes by carefully controlling the ratio of spring constants between the distal end side coil and proximal end side coil to be within 1.05 to 1.30. This parameter optimization ensures smooth stress distribution at the connecting portion while maintaining the desired inner diameter variations, thereby eliminating stress concentration and plastic deformation when the tubular body is curved.
2Ease of operation
If the distal end side coil is made softer than the proximal end side coil to facilitate operation along curved paths, then ease of operation is improved, but the structural integrity and resistance to compressive forces are reduced
Solution Approach 1:
The patent optimizes the spring constant ratio parameter to fall within the specific range of 1.05 to 1.30, which balances the softness needed for curved path operation with the structural integrity required to resist compressive forces. This parameter control ensures that the distal end side coil remains softer than the proximal end side coil for ease of operation while preventing excessive softening that would compromise strength.
3Strength
If the connecting portion is made harder than both coils to provide structural support, then strength is improved, but stress concentration occurs at the interface with the softer coils when curved
Solution Approach 1:
The patent resolves this contradiction by optimizing the spring constant ratio between the coils to within 1.05 to 1.30. This parameter control ensures that the harder connecting portion does not create excessive stress concentration at the coil interfaces when curved, while still providing the necessary structural support. The optimized ratio allows gradual stress transition across the connecting portion.
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 design suppresses stress concentration and plastic deformation, enhancing operational efficiency and ease of use by allowing the tubular body to curve smoothly along the endoscope insertion channel while maintaining effective tissue clipping.
Implementation Method 1
a first coil (10) that has a spring constant per unit length of 15 N/mm to 500 N/mm and a second coil (11) that has a spring constant differing from the spring constant of the first coil
Implementation Method 2
a torsion spring constant per unit length of either the first coil or the second coil with a smaller spring constant per unit length is not less than 25 N mm/rad
Data Source
AI summary
A clip device 1 that has a coil-shaped tubular body 6 that is inserted through a curvable treatment instrument insertion channel of an endoscope, the tubular body 6 includes a proximal side coil (first coil) 10 that has a spring constant per unit length of 15 N/mm to 500 N/mm and is disposed on the proximal end side of the tubular body 6; and a distal end side coil 11 that is connected to the distal end of the proximal side coil 10, has a greater inner diameter than the inner diameter of the proximal side coil 10, has a spring constant per unit length of 15 N/mm to 500 N/mm, and has a spring constant that differs from the spring constant of the proximal side coil 10, with the ratio of the spring constants of the proximal side coil 10 and the distal end side coil 11 is greater than 1.0 and less than or equal to 2.0. In accordance with the present invention, it is possible to provide a treatment instrument for an endoscope, in which even in a case where a strong compressive force is applied to the coil-shaped tubular body in a curved channel of endoscope, it is possible to suppress a plastic deformation of the tubular body due to a slippage of the coil wire.