Automatic Injection Device Cam Unlock Mechanism
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Solution Overview
Problem
Existing automatic injection devices require a three-step process for activation, which can be too complex and time-consuming for emergency situations, such as administering adrenaline during anaphylaxis.
Innovation Solution
A medical device for automatic injection that simplifies the activation process to only two steps: removing the cap and pressing the safety shield onto the patient's skin, utilizing a cam and plunger retainer mechanism to unlock the plunger rod for injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-step activation process is used (removing cap, pushing device onto skin to unlock button, pressing button), then safety is improved by preventing accidental activation, but the complexity of operation increases and time required for injection increases
Solution Approach 1:
The patent combines the button unlocking function and plunger rod unlocking function into a single automated sequence. When the device is pushed onto the patient's skin, the safety shield movement automatically triggers both the button unlock and plunger rod unlock through the cam mechanism, eliminating the need for separate manual unlocking steps while maintaining safety through the retained manual button press requirement
Solution Approach 2:
The device performs automatic functions upon detection of proper application. The cam mechanism automatically detects when the safety shield has moved sufficiently (indicating proper skin contact) and autonomously executes the button unlock and plunger rod unlock sequences, reducing manual intervention steps while maintaining safety through the initial manual activation requirement
2Reliability
If a three-step activation process is used, then safety is improved by preventing accidental activation, but the time required to administer injection increases
Solution Approach 1:
The patent merges the button unlocking and plunger rod unlocking operations into a single automated sequence triggered by safety shield movement. This consolidation eliminates intermediate manual steps, reducing the time from device application to injection initiation while preserving safety through the required manual button press that follows the automated unlock sequence
Solution Approach 2:
The device performs preliminary automatic unlocking actions (button unlock and plunger rod unlock) as soon as proper skin contact is detected through safety shield movement. This preliminary automation prepares the injection mechanism in advance, so that only a simple manual button press is needed to initiate the actual injection, significantly reducing total administration time while maintaining safety
3Reliability
If the plunger rod is locked in initial position, then safety is improved by preventing accidental injection, but the device complexity increases with locking mechanisms
Solution Approach 1:
The patent extracts the plunger rod locking function from a separate independent mechanism and integrates it into the existing cam mechanism that controls the safety shield. The cam's rotational positions naturally provide locked and unlocked states for the plunger rod, eliminating the need for additional dedicated locking components and reducing overall mechanism complexity while maintaining safety through the automated lock/unlock sequence
Solution Approach 2:
The cam mechanism serves multiple functions: it controls the safety shield movement, triggers the button unlock, and controls the plunger rod unlock. By making the cam a multi-functional component, the patent reduces the total number of separate locking and control mechanisms needed, simplifying the overall device structure while maintaining the safety function of preventing accidental injection through automated controlled unlocking
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 device improves ergonomics, simplifies operation, and reduces the time required to administer a full dose, while maintaining safety features to prevent accidental needlestick injuries.
Implementation Method 1
a cam (70) cooperating with the safety shield (60) so that a translation of the safety shield from the distal initial position to the proximal second position causes the cam to rotate within the body to an unlocking position
Implementation Method 2
a plunger retainer (80) comprising at least one elastic lever (81) including at least one retention member (82), the plunger retainer being configured to cooperate with the cam so that, in the initial position, each retention member lockingly engages the plunger rod (40) and, when the cam is in the unlocking position, the lever is deflected to disengage each retention member from the plunger rod
Data Source
AI summary
An automatic injection device including a body; a medical container including a barrel containing a product for injection, a distal tip provided with an injection needle and a stopper in sliding engagement within the barrel, the medical container being slidably arranged in the body between a proximal position and a distal position; a safety shield slidably mounted within the body between a distal initial position and a proximal second position; a plunger rod slidably arranged in the body from a releasably locked proximal initial position in which a distal tip of the plunger rod is proximally spaced from the stopper, the distal tip of the plunger rod being adapted push the stopper in the distal direction when the plunger rod is unlocked; a cam cooperating with the safety shield so that a translation of the safety shield from the distal initial position to the proximal second position causes the cam to rotate within the body to an unlocking position; a plunger retainer including at least one elastic lever including at least one retention member, the plunger retainer cooperating with the cam so that, in the initial position, each retention member lockingly engages the plunger rod and, when the cam is in the unlocking position, the lever is deflected to disengage each retention member from the plunger rod, thereby allowing the plunger rod to move in the distal direction to push the medical container.