Thumb-Actuated Screw Actuator for Stent Release
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Solution Overview
Problem
Existing hand-held actuator devices for stent delivery systems lack effective tactile feedback, are limited in stent length handling, and have complex mechanisms, making them uncomfortable and inefficient for releasing self-expanding stents, especially those longer than 30 cm.
Innovation Solution
A hand-held device with a molded plastic frame, a one-way reel mechanism, and a thumb pad slider that provides tactile feedback through a detent system, allowing for stepless wire pulling and audible feedback, designed to accommodate stents of any length without additional mechanical components, enhancing ergonomic comfort and ease of use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an index-finger-triggering-system is used to pull back the sleeve, then the device can be operated one-handed, but the operator receives poor tactile feedback and the mechanism is limited in handling long stents
Solution Approach 1:
The patent implements a thumb-actuating-screwing-system where the operator directly rotates a screw mechanism with their thumb. This direct mechanical connection provides continuous tactile feedback through the screw threads and detent mechanism, allowing the operator to feel the progression of stent release. The detent system provides discrete tactile clicks that confirm each increment of sleeve retraction, eliminating the information loss present in trigger-based systems.
Solution Approach 2:
The screw mechanism acts as an intermediary between the operator's thumb motion and the sleeve retraction. Instead of directly pulling the sleeve or using a trigger cable, the thumb rotates the screw, which converts rotational motion into linear motion to retract the sleeve. This intermediary mechanism amplifies the operator's input and provides mechanical advantage while maintaining tactile feedback.
2Volume of moving object
If the track length in the hand unit is limited, then the device remains compact, but it cannot release self-expanding stents longer than the track length
Solution Approach 1:
The patent employs a screw mechanism that converts limited rotational motion of the thumb into extended linear displacement of the sleeve. The screw threads multiply the displacement, allowing a compact hand unit to retract sleeves and release stents much longer than the physical dimensions of the device. This dynamic mechanical advantage resolves the contradiction between compact size and long stent handling capability.
3Loss of information
If a thumb-actuating-screwing-system is used, then tactile feedback is improved, but the thumb must be lifted between every turn making control less comfortable
Solution Approach 1:
The screw mechanism allows continuous rotational motion of the thumb without requiring lifting or resetting between turns. The operator can continuously rotate the screw in one direction, providing both continuous tactile feedback and continuous sleeve retraction. This eliminates the discontinuous lifting action required by other mechanisms, maintaining both tactile feedback and operational comfort.
4Reliability
If a detent system is used to restrain the reel, then the reel holds position during return stroke, but the mechanism becomes more complex
Solution Approach 1:
The detent system uses simple, inexpensive mechanical elements such as spring-loaded detent balls or cam-based detents that engage with notches or ramps on the screw mechanism. These are basic mechanical components that add minimal complexity while providing reliable position holding. The detent mechanism is a standard, well-understood mechanical solution that achieves reliability without significant complexity increase.
Data Source
AI summary
A hand-held actuator device for releasing into the body from a delivery system a medical prosthesis, like a stent, comprising a frame that acts as a housing, a reel for receiving a wire, a manually operable slider mounted to the frame and a one-way connection between the slider and the reel. Actuating the slider causes the reel to wind up the wire and release the medical prosthesis.