Collet Friction Stabilizes Endoscopic Needle Knife Wire
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Solution Overview
Problem
Endoscopic needle knives face issues with longitudinal movement of the cutting wire due to external forces such as hysteresis and tissue contact, leading to uncontrollable exposure of the cutting wire during electrosurgical procedures.
Innovation Solution
A collet is coupled to the distal end of the tubular member, featuring a central lumen that exerts a frictional force on the cutting wire, preventing unwanted longitudinal movement caused by external forces while allowing controlled movement by the operator through a mechanism, ensuring the cutting wire remains at the desired position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cutting wire is allowed to move freely within the tubular member, then the operator can easily control the wire's position, but external forces cause unwanted longitudinal movement and uncontrollable exposure of the cutting wire
Solution Approach 1:
The collet acts as an intermediary component between the cutting wire and the tubular member. It provides a controlled interface that allows the operator to move the wire while blocking external forces from causing unwanted movement. The collet's internal geometry and friction characteristics mediate between free movement and complete constraint.
Solution Approach 2:
The frictional force parameter of the collet is specifically designed to be greater than external forces (hysteresis, tissue contact) but less than the operator's control force. This parameter differentiation allows selective responsiveness to different force magnitudes, enabling controlled movement while preventing unwanted displacement.
2Reliability
If a collet is introduced to prevent cutting wire movement, then the stability and position control of the cutting wire is improved, but the device complexity increases
Solution Approach 1:
The collet introduces localized structural features only at the distal end where wire stability is needed, rather than redesigning the entire device. The collet body with its specific internal geometry and friction characteristics provides the necessary constraint only at the critical interface between the wire and tubular member.
Solution Approach 2:
The device is segmented into distinct functional components: the tubular member, the collet, and the cutting wire. The collet is a separate, modular component that can be designed and manufactured independently, allowing for optimized wire stabilization without complicating the overall device architecture.
3Reliability
If the collet exerts high frictional force on the cutting wire, then unwanted movement is prevented, but the operator's ability to reposition the wire is reduced
Solution Approach 1:
The frictional force parameter is specifically engineered to fall within a target range that differentiates between external forces and operator control forces. By adjusting the collet's internal geometry, surface properties, and material characteristics, the friction parameter is optimized to block small external forces while allowing larger operator-applied forces to move the wire freely.
Solution Approach 2:
The system exhibits dynamic friction characteristics where the resistance to movement depends on the magnitude of the applied force. The collet provides high friction resistance to small external forces (hysteresis, tissue contact) but allows easy movement when larger forces are applied by the operator, creating a force-threshold-based control system.
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 collet effectively stabilizes the cutting wire, maintaining its position during procedures by creating a frictional force greater than external forces but less than the control mechanism's force, ensuring precise exposure and operation of the cutting wire.
Implementation Method 1
The inner surface may create a frictional force with the cutting wire when the proximal portion is coupled to the distal end of the tubular member. The frictional force may prevent longitudinal movement of the cutting wire caused by one or more external forces during operation of the endoscopic needle knife.
Data Source
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AI summary
An endoscopic needle knife may include a collet coupled to a distal end of a tubular member of the needle knife. A cutting wire may be disposed within a cutting wire lumen of the tubular member and a central lumen of the collet. An inner surface of the collet body may create a frictional force between the cutting wire and the inner surface so that the cutting wire is resistant to longitudinal movement relative to the tubular member caused by external forces. The frictional force may also be less than a longitudinal force exerted on the cutting wire by a handle assembly or other control mechanism that is used to longitudinally move the cutting wire within the tubular member and the collet.