Auto Injector Automatic Needle Retraction Mechanism
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Solution Overview
Problem
Existing auto injectors require a two-step operation to prevent inadvertent triggering and lack automatic needle retraction, which can lead to exposure risks and user errors, especially during handling and dropping.
Innovation Solution
A disposable auto injector with a rotatable release shaft and a mechanical driver that allows for automatic needle retraction into the housing after injection, featuring a first and second injection lock mechanism and a retraction lock to ensure safe operation and prevent accidental needle exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the needle is exposed outside the housing for injection, then injection function is enabled, but needle exposure risk increases
Solution Approach 1:
The syringe is made dynamically movable between retracted and extended positions along the longitudinal axis. The driver mechanism enables automatic extension during injection and automatic retraction after injection, allowing the needle to transition between exposed and protected states based on operational phase
Solution Approach 2:
The needle is preliminarily positioned in a retracted state within the housing before injection begins. This preliminary retraction protects the needle during handling and transport, with automatic extension occurring only when injection is initiated
2Reliability
If automatic needle retraction is implemented, then safety is improved, but device complexity increases
Solution Approach 1:
The driver mechanism combines multiple functions into a single integrated system: it extends the syringe for injection, delivers the medication dose, and automatically retracts the needle. This merging of extension, injection, and retraction functions into one automated sequence reduces the need for separate manual operations
Solution Approach 2:
The device performs self-service through automatic needle retraction driven by the driver mechanism. After injection completion, the system automatically reverses syringe movement and retracts the needle without requiring manual intervention, enabling the device to protect itself
3Reliability
If a rotatable release shaft is used for locking, then resistance to dropping is improved, but manufacturing complexity increases
Solution Approach 1:
The release shaft utilizes rotational movement to engage and disengage locking positions. This rotational mechanism provides inherent resistance to linear dropping forces, as the shaft must rotate to change states rather than move linearly, preventing inadvertent triggering during accidental drops
Solution Approach 2:
The rotatable release shaft creates asymmetric locking geometry where the shaft's rotational position determines locked or unlocked states. This asymmetric design provides stable locking in the retracted position while requiring specific rotational input to unlock, preventing accidental activation from dropping
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 solution provides a safe and user-friendly operation by ensuring the needle is automatically retracted after use, reducing the risk of exposure and enhancing resistance to accidental triggering from device drops, while allowing for various driver configurations for different injection needs.
Implementation Method 1
a driver configured for applying a first force to the syringe thereby moving the syringe from the first position to the second position, and further configured for applying a second force to the syringe thereby moving the syringe from the second position to a retracted position
Data Source
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AI summary
The present application relates to a disposable auto injector (10) that can be safely operated for automatic injection of a dose of medication and having a housing (12) for accommodation of a syringe (18) with a needle (20), the syringe being movably positioned in the housing between a first position in which position the needle is accommodated inside the housing and a second position in which position the needle protrudes outside the housing (22), a driver configured for applying a force to the syringe thereby moving the syringe from the first position to the second position, and wherein the driver is also configured for applying a force to the syringe thereby moving the syringe from the second position to a retracted position in which position the needle is accommodated inside the housing upon user operation of a release member (42).