Autoinjector Cap Locking Tab Retainer Mechanism
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Solution Overview
Problem
Autoinjectors risk inadvertent activation during drop tests due to kinetic energy causing the needle cover to move towards the retracted position against the safety spring, potentially triggering the injection mechanism.
Innovation Solution
An autoinjector design featuring a housing with a cap and retainer system, where a locking tab on the cap maintains the retainer in a blocking position, preventing the needle cover from moving to the retracted position as long as the cap is attached, thus preventing accidental activation. The retainer includes a distal abutment surface that radially moves between blocking and release positions, and a flexible leg acts as a ratchet to enhance resistance during drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the needle cover is held back by a safety spring in the extended position, then the needle cover can be automatically triggered during injection, but the autoinjector may be inadvertently activated during drop tests
Solution Approach 1:
The retainer is pre-positioned in the blocking position before use, preventing any proximal movement of the needle cover. This preliminary blocking action ensures that even if kinetic energy from a drop test causes the needle cover to move, it cannot engage the injection mechanism. The cap with locking tab maintains this preliminary blocked state during transport and storage.
Solution Approach 2:
The retainer acts as an intermediary component between the needle cover and the injection mechanism. It introduces an additional element that must be overcome before the needle cover can trigger injection. The retainer's distal abutment surface physically blocks the needle cover's proximal movement, serving as a mediator that prevents direct interaction between the needle cover and the injection trigger.
2Reliability
If the retainer blocks proximal movement of the needle cover, then inadvertent activation is prevented, but the structure becomes more complex
Solution Approach 1:
The locking tab is integrated into the cap structure, and the retainer is integrated into the housing structure. These components work together as a unified blocking system rather than separate independent elements. The cap and housing are removed as a single unit after use, simplifying the user interaction despite the added internal complexity of the retainer and locking tab.
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 autoinjector successfully prevents inadvertent activation during drop tests, ensuring the injection mechanism is not triggered unintentionally, allowing it to pass robustness testing without risk of pre-activation.
Implementation Method 1
a safety spring arranged within the housing and configured to urge the needle cover in a distal direction
Implementation Method 2
a retainer coupled to the housing for blocking a proximal movement of the needle cover from the first extended position to the retracted position as long as the cap is attached to the housing
Implementation Method 3
the cap includes a locking tab radially abutting against the retainer for maintaining the distal abutment surface of the retainer in the blocking position
Implementation Method 4
a flexible leg acts as a ratchet to enhance resistance during drops
Data Source
Figure 1~2B
Figure 3~4B
Figure 5A~5B
AI summary
This autoinjector (1) includes a housing (2) extending along longitudinal axis A and having an opened distal end (22), said housing (2) being configured to receive a medical container (100) having a barrel (101) defining a reservoir for containing a medical product, said barrel (101) having a distal end (102) provided with an injection needle (103). A needle cover (4) is coupled to and axially movable with respect to said housing (2) between a first extended position, a retracted position, and a second extended position. A a cap (5) is removably attached to the opened distal end (22) of the housing (2). A retainer (3) is coupled to the housing (2) for blocking a proximal movement of the needle cover (4) from the first extended position to the retracted position as long as the cap (5) is attached to the housing (2). The retainer (3) includes a distal abutment surface (30) which is radially movable between a blocking position in which said distal abutment surface (30) abuts against a proximal abutment surface (43) of the needle cover (4), and a release position in which said distal abutment surface (30) is radially shifted away from the proximal abutment surface (43) of the needle cover (4). The cap (5) includes a locking tab (6) radially abutting against the retainer (3) for maintaining the distal abutment surface (30) of the retainer (3) in the blocking position.