Medicament Delivery Plunger Rod Locking Mechanism
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Solution Overview
Problem
Existing medicament injectors struggle to allow patients to control the injection sequence, particularly for large doses or painful medications, as frictional locking mechanisms are inadequate in withstanding the force of the injection spring and ensuring temporary stops during delivery.
Innovation Solution
A medicament delivery device featuring a plunger rod with flexible locking means and stop engagements on its surface, allowing for manual control of the injection sequence through an activation button that releases and locks the plunger rod at different positions, enabling temporary stops during medicament delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If frictional locking mechanisms are used to hold the plunger rod, then the device structure is simple, but the locking reliability is insufficient to withstand the injection spring force
Solution Approach 1:
The patent replaces the friction-based mechanical locking system with a positive engagement geometric locking system. The locking lever with engagement surface interacts with the plunger rod through geometric interlocking rather than friction, providing reliable locking that can withstand the injection spring force without depending on friction coefficients.
Solution Approach 2:
The locking lever serves as an intermediary component between the user's manual operation and the plunger rod. It translates the user's pushing motion into precise geometric engagement or disengagement with the plunger rod, providing controlled and reliable locking/unlocking action that friction mechanisms cannot achieve.
2Device complexity
If friction forces are used to stop the plunger rod during injection, then the locking mechanism is simple, but the stopping capability is insufficient at high speeds
Solution Approach 1:
The patent replaces friction-based speed control and stopping with a geometric positive engagement system. The engagement surface and protrusion create mechanical interlocking that can instantaneously stop the plunger rod at any position during injection, regardless of speed, eliminating the limitations of friction-based control.
Solution Approach 2:
The locking lever is designed to be movable and flexible, allowing it to dynamically engage or disengage from the plunger rod based on user input. This dynamic geometric engagement provides instantaneous stopping capability that adapts to the plunger rod's motion state, unlike static friction-based systems.
3Productivity
If continuous injection is performed without stopping mechanisms, then the injection speed is fast, but the patient comfort deteriorates for large doses
Solution Approach 1:
The patent enables periodic interruption of the continuous injection process through the manually operable locking mechanism. Users can pause the injection at any point by engaging the locking lever, allow the medicament to diffuse into the tissue, and then resume by disengaging the lock, creating a controllable periodic action that balances speed and comfort.
Solution Approach 2:
The device empowers the patient to control their own injection process through the simple manual operation of the locking lever. The patient can independently decide when to pause or resume injection based on their comfort level, making the system self-regulating and patient-centered without requiring external assistance.
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
Enables patients to manage large or painful injections by allowing temporary stops and stepwise delivery, reducing discomfort and ensuring complete dose administration.
Implementation Method 1
resilient force means operably connected to said plunger rod for driving said plunger rod and thereby said at least one stopper towards the proximal end of the device
Implementation Method 2
an actuation means comprising flexible locking means releasably connected to said plunger rod for holding said plunger rod and thereby said resilient force means in a pre-tensioned state
Data Source
AI summary
The present invention relates to medicament delivery device comprising a generally tubular distal housing part (19); a generally tubular medicament container holder (16); a medicament container (18); a plunger rod (32); resilient force; an actuation means (34) comprising flexible locking means and an activation button; a release means (40); and a resilient means (60) characterized in that said plunger rod comprises a number of stop engagements (38) arranged on its outer circumferential surface and arranged to co-act with corresponding stop engagements (37) on the flexible locking means, such that when said activation button is proximally depressed said stop engagement (37) on said flexible locking means come out of contact from one stop engagement (38) of the plunger rod; and such that when said activation button (48) is released, said resilient means (60) forces the activation button and thereby the flexible locking means to move distally such that said stop engagements (37) on said flexible locking means come into contact with another stop engagement (38) of the plunger rod.