Autoinjector Locker Mechanism Prevents Accidental Activation
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Solution Overview
Problem
Autoinjectors often inadvertently trigger the injection mechanism during drop tests or accidental falls, particularly in a 'cap upward' position, leading to unintended activation.
Innovation Solution
An autoinjector design featuring a locker mechanism that remains in a locking position during drops but can be unlocked by the user's intentional action, preventing accidental activation by using a needle cover that moves to abut against the locker, causing it to rotate and unlock, allowing the holder to move to the active position only when intentionally pressed against an injection site.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the holder is allowed to move freely to trigger the injection mechanism, then the ease of operation is improved, but the reliability deteriorates due to inadvertent triggering during drops
Solution Approach 1:
The locker is positioned to preemptively block the holder's movement toward the active position before a drop can cause inadvertent triggering. The geometry of the locker and holder are designed such that during normal handling or accidental drops, the holder cannot overcome the blocking position, thereby preventing premature activation while allowing intentional activation when the needle cover moves to the retracted position
Solution Approach 2:
The system transitions from a static blocking mechanism to a dynamic one where the locker's blocking position is contingent on the needle cover's position. When the needle cover is in the retracted position, the holder can move to trigger injection; when the needle cover is in the extended position, the locker blocks the holder. This dynamic relationship allows the system to adapt its responsiveness based on the operational state
2Reliability
If the locker blocks the holder in all positions, then the reliability is improved by preventing accidental activation, but the ease of operation deteriorates because intentional activation becomes difficult
Solution Approach 1:
The locker's blocking function is made conditional on the needle cover's position. When the needle cover moves to the retracted position (indicating intentional activation), the holder is no longer blocked and can move to trigger injection. This dynamic unblocking mechanism ensures that the reliability protection is maintained during storage and handling but does not impede intentional activation when properly initiated
Solution Approach 2:
The needle cover acts as an intermediary element that mediates between the locker's blocking function and the holder's activation function. The movement of the needle cover to the retracted position serves as the triggering event that causes the locker to move away from the blocking position, thereby enabling the holder to activate the injection mechanism. This intermediary mechanism ensures that both reliability and ease of operation are satisfied
Data Source
AI summary
This autoinjector has a proximal end and a longitudinal axis A, and a housing configured to receive a medical container having a barrel defining a reservoir for containing a medical product, said barrel having a distal end provided with a needle and an opened proximal end configured to receive a plunger rod for pushing a stopper arranged inside the barrel. A needle cover is coupled to and movable with respect to said housing between a first extended position, a retracted position, and a second extended position wherein the needle cover moves back in the distal direction to shield the needle. An injection mechanism moves the plunger rod distally inside the barrel in order to expel the medical product contained inside the barrel. A holder is movable with respect to the housing between a passive position wherein the holder does not trigger the injection mechanism and an active position wherein the holder triggers the injection mechanism. A locker is coupled to the holder, the locker being movable with regard to the housing between a locking position, wherein the locker prevents the holder from moving to the activated position, and an unlocking position, wherein the locker rotates around the longitudinal axis A, thereby allowing the holder to move to the activated position, rotation of the locker from the locking to the unlocking position being caused by the needle cover moving towards the retracted position.