Slider-Crank Needle Retraction in Disposable Drug Delivery
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Solution Overview
Problem
Existing drug delivery devices with rigid needles face issues of needle retraction failure due to power loss, complexity in retraction mechanisms, and safety concerns, particularly in disposable devices with complex arrangements.
Innovation Solution
A drug delivery device with a disposable unit featuring a slider-crank linkage mechanism, a spring-biased needle actuation system, and a rotatable actuation disc to ensure safe, reliable, and compact operation, including a stopper to secure the needle in the retracted position after use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power-dependent retraction mechanism is used in rigid needle devices, then the needle can be retracted after drug delivery, but the device complexity increases and reliability decreases due to power loss risks
Solution Approach 1:
The spring-loaded mechanism automatically retracts the needle after drug delivery without requiring external power or control systems. The spring stores mechanical energy during the injection phase and automatically releases it to retract the needle, making the system self-sufficient and eliminating power dependency.
Solution Approach 2:
Instead of using an active motor-driven mechanism to retract the needle, the invention uses a passive spring-loaded mechanism that naturally wants to retract the needle. The system inverts the conventional approach by having the retraction force come from a pre-loaded spring rather than an active motor.
2Reliability
If a spring-loaded automatic retraction mechanism is used, then reliability is improved by eliminating power dependency, but the device complexity increases due to the mechanism arrangement
Solution Approach 1:
The spring-loaded retraction mechanism is integrated into the existing needle assembly structure. The spring is positioned within the housing and directly coupled to the needle, merging the retraction function with the existing mechanical structure rather than adding a separate complex system.
Solution Approach 2:
The entire needle assembly with the spring-loaded retraction mechanism is designed as a disposable component. This allows the use of a simple mechanical spring rather than a complex reusable mechanism, as the spring only needs to function reliably for a single use before the entire assembly is discarded.
3Productivity
If the needle remains in extended position for subcutaneous delivery, then drug delivery function is maintained, but safety risk increases if the device fails or loses power
Solution Approach 1:
The spring is pre-loaded during manufacturing to store mechanical energy in the opposite direction of needle extension. This preliminary anti-action ensures that when the motor fails or power is lost, the spring automatically pushes the needle back into the housing, counteracting the harmful extended position.
Solution Approach 2:
The spring-loaded mechanism provides a safety cushion against power failure or motor malfunction. By having the spring pre-positioned and pre-loaded, the system has a built-in fail-safe that will automatically retract the needle if the active delivery system fails, preventing needle injury.
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
Ensures safe, reliable, and economical drug delivery with a compact design, ensuring the needle is securely retracted after use, reducing the risk of injury and maintaining sterility.
Implementation Method 1
a spring biasing the slider-crank linkage mechanism from a first retracted position prior to use where the needle is fully inserted within the housing towards an extended position for drug administration and further to a second retracted position after use
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
A drug delivery device (1), including a delivery unit (3) comprising a subcutaneous delivery system including a needle support (10), an injection needle (9) mounted on the needle support, and an injection needle actuation mechanism configured to engage and slidably move the needle support from a retracted position where the injection needle is within a housing (2) of the drug delivery device to an extended delivery position where the injection needle projects through a skin contact wall of the housing. The needle actuation mechanism comprises a slider-crank linkage mechanism (11) comprising a crank rod (13) pivotally connected to the housing, a connecting rod (14) pivotally connected to the crank rod and pivotally connected to the slidable needle support (10), and a spring (12) biasing the slider-crank linkage mechanism from a first retracted position prior to use where the needle is fully inserted within the housing towards an extended position for drug administration and further to a second retracted position after use.