Stent Deployment Handle Rack Pinion Mechanical Advantage
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Solution Overview
Problem
The deployment of relatively long length self-expanding stents requires high forces to remove the sheath or retainer, which can interfere with the accuracy of stent placement.
Innovation Solution
A stent deployment handle with a housing, wheel, rack, and pinion gear system that provides a mechanical advantage through a larger wheel diameter, allowing for precise control and reduced force requirements by disengaging the rack from the pinion gear for easier pulling, thereby reducing the peak force needed for stent deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional delivery handle is used for long self-expanding stents, then the stent can be deployed, but high forces are required to remove the sheath which interferes with placement accuracy
Solution Approach 1:
The delivery handle is divided into distinct functional segments: a rack member attached to the sheath, a pinion gear for force multiplication, and a wheel for user input. This segmentation allows each component to perform its specific function optimally - the rack translates linear motion, the pinion provides mechanical advantage, and the wheel enables controlled force application, collectively reducing the force needed to remove the sheath while maintaining placement accuracy
Solution Approach 2:
The rack and pinion mechanism acts as an intermediary between the user's manual input and the sheath removal action. Instead of directly pulling the sheath with high force, the user rotates the wheel which turns the pinion, which then moves the rack to retract the sheath gradually. This intermediary mechanism transforms a high-force abrupt action into a low-force controlled process, solving both the force and accuracy problems
2Ease of operation
If high forces are applied to remove the sheath for long stents, then the sheath can be retracted, but the accuracy of stent placement is compromised
Solution Approach 1:
The delivery system transitions from a static direct-pull mechanism to a dynamic rack-and-pinion system. The wheel can be rotated to engage the pinion, which then dynamically moves the rack to retract the sheath in a controlled manner. This dynamic mechanism allows the operator to apply force gradually and reversibly, making sheath removal easier while maintaining precise control over stent placement position
Solution Approach 2:
The mechanical advantage provided by the rack and pinion changes the force parameter required for sheath removal. Instead of requiring high force directly applied to the sheath, the system transforms this into a lower force applied to the wheel, which is then amplified through the gear mechanism. This parameter transformation makes the operation easier while preserving placement accuracy through controlled motion
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 handle enables accurate placement of self-expanding stents with reduced force requirements, improving the precision and ease of deployment by providing a mechanical advantage and minimizing the force needed to retract the sheath, thus enhancing the accuracy and efficiency of stent placement.
Implementation Method 1
A stent deployment handle with a housing, wheel, rack, and pinion gear system that provides a mechanical advantage through a larger wheel diameter
Data Source
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AI summary
A handle (10) for delivering a medical device comprises a housing having therein a wheel, a rack (20), and a catheter member. The wheel comprises a pinion gear (28) that selectively engages gear teeth on the rack. The rack is selectively engaged and disengaged from the pinion gear in order to reduce the force necessary to manually pull the rack.