Needle Insertion and Retraction Mechanism for Drug Delivery
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Solution Overview
Problem
Existing drug delivery devices require significant user effort to insert and retract needles, especially against restoring forces like springs, making it challenging for unskilled users and potentially difficult when used on soft tissues.
Innovation Solution
A needle insertion and retraction mechanism powered by a single source of tension, utilizing a rotating part such as a wheel or ratchet that automatically extends and retracts the needle with continuous motion, reducing the need for opposing forces and simplifying the operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spring or tension source is used to retract the needle after injection, then the needle can be automatically retracted, but the user must press against this restoring force to insert the needle, increasing operation difficulty
Solution Approach 1:
The patent inverts the traditional approach by having the single tension source continuously pull the needle in one direction while using a ratchet mechanism to allow motion in both directions. The needle is pulled forward by the tension source during insertion, then the ratchet allows reverse motion for retraction without requiring the user to push against the tension source, as the tension source continuously pulls in the forward direction while the ratchet permits backward movement.
Solution Approach 2:
The ratchet mechanism acts as an intermediary between the user's pressing action and the tension source. It allows the user to press the button to extend the needle while the tension source pulls forward, and then allows the needle to retract when the button is released, without the user directly pushing against the tension source's restoring force.
2Ease of operation
If a single source of tension is used to power both insertion and retraction, then the mechanism simplifies operation, but requires a more complex motion translation mechanism to divide continuous motion into two parts
Solution Approach 1:
The patent uses periodic action through the ratchet mechanism, which allows the continuous motion from the single tension source to be divided into discrete phases: the needle extends when the button is pressed and the ratchet permits forward motion, then retracts when the button is released and the ratchet allows reverse motion. This periodic engagement and disengagement of the ratchet converts continuous tension into periodic bidirectional needle motion.
Solution Approach 2:
The mechanism uses dynamic elements including the movable ratchet that can engage and disengage, and the button that transitions between pressed and released states. These dynamic components allow the system to automatically divide the continuous tension source motion into the two required parts (insertion and retraction) based on the operational state, reducing the need for complex static mechanical divisions.
3Force
If the needle is extended and retracted by continued operation of a single tension source, then user effort is reduced, but the mechanism requires an interrupter to stop motion at predetermined locations
Solution Approach 1:
The ratchet mechanism provides self-service by automatically stopping the needle at predetermined locations without requiring additional user action or complex control systems. When the button is pressed, the ratchet allows forward motion until it engages at a predetermined position; when released, it allows reverse motion until it engages at the retraction position. The mechanism serves itself by using the inherent mechanical properties of the ratchet to automatically position the needle.
Solution Approach 2:
The interrupter function is achieved through periodic engagement of the ratchet mechanism at predetermined locations during the continuous cyclic operation. The ratchet naturally engages and disengages at specific points in the motion cycle, providing automatic stopping at predetermined locations without requiring separate control mechanisms, thereby reducing overall device complexity while maintaining the single tension source advantage.
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 solution simplifies the process for unskilled users by eliminating the need to press against opposing tension, making needle insertion and retraction easier and safer, while ensuring controlled force and velocity for insertion and withdrawal.
Implementation Method 1
Document WO 2011/101379 A1 discloses pertinent a needle insertion and retraction mechanism comprising a torsion spring as motion source
Implementation Method 2
This action also causes the actuation of a citric acid/sodium bicarbonate gas generator which generates a gas to move a piston within the cartridge, compressing the drug compartment
Data Source
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AI summary
A needle insertion and retraction mechanism for a drug delivery device, comprises a motion source, a user-operated control for the motion source, an interrupter for stopping motion of the motion source at a predetermined location and thereby dividing the motion into two parts which are continuous relative to each other. A motion translation mechanism connects the source of continuous motion to a needle, to extend the needle during the first motion part and to retract the needle during the second motion part. The needle is thus extended and retracted by continued operation of a single tension source rather than two tension sources operating in opposition to each other. The motion source may be a spring, and a winding mechanism may be provided to wind the spring. The second motion part may be initiated by pulling the adhered delivery device from the skin.