Autoinjector Lock Ring Activation for Drop-Resistant Injection
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Solution Overview
Problem
Existing autoinjectors require additional manual operations for activation, are prone to inadvertent activation during drop tests, and suffer from material creep over long storage periods.
Innovation Solution
An autoinjector design featuring a rotatable lock ring that automatically unlocks upon needle cover retraction, replacing the need for a push button, and incorporates a lock ring arrangement that reduces sensitivity to impacts and material creep.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a push button is used for releasing the plunger rod, then the injection mechanism can be activated, but the device requires additional manual operations from the end user and is prone to inadvertent activation during drop tests
Solution Approach 1:
The patent removes the push button component entirely from the device. Instead of having a separate activation button, the system uses the needle cover retraction movement itself to trigger the plunger release through a cam mechanism. This extraction of the push button eliminates the need for additional manual operations while reducing device complexity.
Solution Approach 2:
The system performs self-activation where the retraction of the needle cover automatically triggers the plunger release mechanism. The cam converts the linear retraction movement into rotational movement that unlocks the plunger rod, eliminating the need for separate user activation actions. The device serves itself by using its own operational movements to trigger the injection sequence.
2Ease of operation
If a push button is positioned at the proximal end for activation, then the injection can be initiated, but the device is highly sensitive to impacts during drop tests causing inadvertent activation
Solution Approach 1:
By removing the push button entirely and relocating the activation function to the needle cover retraction mechanism, the patent eliminates the vulnerability point at the proximal end. The cam mechanism is positioned internally and triggered by the needle cover movement, making the device insensitive to external impacts during handling and transport.
Solution Approach 2:
The cam acts as an intermediary mechanism that converts the needle cover retraction movement into plunger release. This intermediary mechanism is positioned away from the proximal end, shielded within the device structure, and only activated by the intended needle cover retraction rather than external impacts.
3Reliability
If a retainer is used to maintain the plunger rod in initial position against spring stress, then the plunger can be held blocked, but the retainer may creep over time under compressed spring stress during storage
Solution Approach 1:
Instead of using a retainer that actively resists spring stress during storage, the patent inverts the approach by using a locking mechanism (cam and lock ring) that positively locks the plunger in position. The spring stress is contained and directed along the longitudinal axis, while the locking mechanism prevents any lateral movement or creeping of the plunger rod during storage periods.
Solution Approach 2:
The patent separates the functions of plunger retention during storage from plunger release during operation. The lock ring and cam mechanism provide stable retention during storage without being subjected to lateral stresses, while the injection mechanism provides reliable release when activated. This segmentation allows each component to optimize its specific function without compromising the other.
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
Facilitates easy activation without additional user input, enhances resistance to drop tests, and minimizes material creep, ensuring reliable operation over time.
Implementation Method 1
an initially compressed spring for moving the plunger in the distal direction
Implementation Method 2
the retainer being resiliently deformable between a rest position in which the retainer axially abuts against the plunger rod for blocking the plunger rod in said initial position, and a deformed position in which the retainer radially deflects to allow the plunger rod to move in the distal direction
Data Source
AI summary
The autoinjector includes a housing extending along longitudinal axis A and 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 an injection 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 axially movable with respect to said housing between a first extended position, a retracted position, and a second extended position. A cam is rotationally movable around the longitudinal axis A with respect to said housing between a blocking position and a release position, rotation of said cam from the blocking to the release position being caused by the needle cover moving from the first extended position to the retracted position. A plunger rod axially movable inside the housing between an initial position and an injection end position distally located relative to said initial position, under the action of biasing means configured for biasing the plunger rod in a distal direction towards the injection end position. A retainer is arranged for maintaining the plunger rod in the initial position against the action of the biasing means, the retainer being resiliently deformable between a rest position in which the retainer axially abuts against the plunger rod for blocking the plunger rod in said initial position, and a deformed position in which the retainer radially deflect to allow the plunger rod to move in the distal direction. A lock ring is arranged inside the housing for locking the retainer in the rest position. The lock ring is rotatable around the longitudinal axis A between a locking position, in which the lock ring prevents deformation of the retainer, and an unlocking position, in which the lock ring allows for deformation of the retainer, rotation of the lock ring from the locking to the unlocking position being caused by the cam moving from the blocking position to the release position.