Autoinjector Plunger Damping for High-Viscosity Drug Delivery
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Solution Overview
Problem
Autoinjectors using spring mechanisms often deliver excessive force during drug delivery, leading to discomfort, potential container breakage, and drug product damage due to high kinetic energy, particularly with higher viscosity drugs.
Innovation Solution
Incorporating a damping mechanism, such as a dashpot or energy-absorbing material, to reduce the velocity of the plunger before it impacts the drug container stopper, thereby reducing the kinetic energy applied and minimizing discomfort and potential damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If spring force is increased to deliver higher viscosity drugs, then drug delivery capability is improved, but kinetic energy and impact force increase causing discomfort and potential damage
Solution Approach 1:
A damping mechanism is introduced between the plunger and the stopper to absorb excess kinetic energy before impact. The damping mechanism includes a damper rod connected to the plunger and a damper housing with damping elements that reduce the velocity of the plunger before it impacts the stopper, thereby preventing discomfort and potential damage while maintaining the ability to deliver higher viscosity drugs
2Use of energy by moving object
If spring constant is increased to provide sufficient energy for drug delivery, then energy availability is improved, but velocity squared effect causes excessive kinetic energy
Solution Approach 1:
The damping mechanism acts as an intermediary between the spring-driven plunger and the stopper. It selectively absorbs the excess kinetic energy portion while allowing the necessary driving force to pass through, thereby decoupling the relationship between spring constant and impact energy
3Object-affected harmful factors
If plunger velocity is reduced to minimize impact, then comfort and safety are improved, but drug delivery energy may be insufficient
Solution Approach 1:
The damping mechanism is positioned to engage before the plunger impacts the stopper, reducing velocity only during the final approach. During the main drug delivery stroke, the damping mechanism allows sufficient energy transmission to maintain effective drug delivery capability
4Object-affected harmful factors
If damping mechanism is added to reduce velocity, then impact force is reduced, but device complexity increases
Solution Approach 1:
The damping mechanism is nested within the existing plunger assembly structure. The damper rod is integrated with the plunger, and the damping elements are housed within the existing damper housing, minimizing additional space requirements and structural complexity
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 damping mechanism ensures a more comfortable and safer drug delivery process by reducing the impact force, preventing container breakage, and allowing for the use of higher viscosity drugs without damage, while maintaining the intended spring force load.
Implementation Method 1
a working fluid displaceable by the piston assembly for resisting movement of the plunger
Implementation Method 2
a damping mechanism for reducing the velocity of the plunger prior to acting on the stopper
Data Source
AI summary
An injection device, method, and system for drug delivery includes a primary container for storing a drug, the container having a stopper movably disposed in the container for expelling the drug, an injection drive mechanism comprising a plunger for acting on the stopper and an energy source for exerting a force on the plunger to cause the plunger to act on the stopper to expel the drug, the force causing the plunger to accelerate to a velocity prior to acting on the stopper, and a damping mechanism for reducing the velocity of the plunger prior to acting on the stopper. The damping mechanism can include a dashpot or an energy absorbing material associated with the plunger. Alternatively or additionally, the damping mechanisms can include absorbing material disposed between support members of an outer casing of the injection device and the primary container.