Autoinjector Plunger Loading Mechanism for Low Energy Delivery
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Solution Overview
Problem
Autoinjectors using spring structures often transmit excessive force to the drug product during delivery, leading to mechanical bumps, potential container breakage, and discomfort to users, especially when administering high viscosity drugs.
Innovation Solution
An injection device with a plunger loading mechanism that reduces or eliminates the distance between the plunger and stopper before activation, using a second energy source with a lower potential energy to mitigate the impact and ensure smooth drug delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a spring structure with high spring constant is used to provide sufficient energy for drug delivery, then the energy for drug delivery is sufficient, but excessive force is transmitted to the drug product and primary container causing mechanical bumps, potential breakage, and discomfort
Solution Approach 1:
The system divides the spring structure into two separate springs: a first spring (drive spring) that stores and releases energy to drive the plunger, and a second spring (loading spring) that gradually loads the plunger before delivery. This segmentation allows the first spring to provide sufficient energy while the second spring mitigates excessive force transmission to the drug product.
Solution Approach 2:
The second spring performs preliminary action by gradually loading the plunger onto the stopper before the main drug delivery event. This preliminary loading reduces the distance between plunger and stopper, ensuring that when the first spring releases energy, the plunger does not accelerate excessively and transmit harmful forces to the drug product.
2Adaptability or versatility
If higher viscosity drugs are delivered via autoinjectors, then the range of deliverable drugs is expanded, but the requisite spring forces increase leading to higher kinetic energy and potential dose completion issues
Solution Approach 1:
The segmented spring system allows the second spring to provide gradual loading force appropriate for high viscosity drugs, while the first spring provides the additional energy needed for complete dose delivery. This segmentation enables the system to handle higher viscosity drugs without excessive force transmission.
Solution Approach 2:
The system changes the force application parameters by using two springs with different characteristics: the second spring provides gradual, controlled loading force, while the first spring provides the higher force needed for viscous drug delivery. This parameter differentiation allows delivery of high viscosity drugs while maintaining control over kinetic energy.
3Power
If the plunger is allowed to accelerate to high velocity before acting on the stopper, then the energy for complete dose delivery is ensured, but the slap and bump generated causes user discomfort and potential structural damage
Solution Approach 1:
The second spring performs preliminary action by gradually loading the plunger onto the stopper before the main delivery event. This reduces the initial distance between plunger and stopper, preventing excessive acceleration and the resulting slap and bump that would cause user discomfort and potential damage.
Solution Approach 2:
The second spring acts as a cushioning mechanism before the main energy release. It gradually compresses and stores energy, then releases it in a controlled manner that cushions the plunger's movement, preventing harmful acceleration and the associated slap and bump effects.
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 solution reduces kinetic energy applied to the drug product, minimizing physical disturbances and potential damage to the container, enhancing user comfort and safety for a broader range of drug deliveries.
Implementation Method 1
a second energy source such as a container biasing member that may be a spring having a second selected potential energy applying a second force on the container
Implementation Method 2
a first energy source having a first selected potential energy for exerting a first force on the plunger to cause the plunger to act on the stopper
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An injection device, method, and system for drug delivery includes a container for storing a drug, the container having a stopper movably disposed in the container for expelling the drug; an injection drive mechanism having a plunger for acting on the stopper and an energy source having a first selected potential energy for exerting a force on the plunger to cause the plunger to act on the stopper to expel the drug; and a plunger loading mechanism for substantially preventing the plunger from accelerating to a predetermined velocity before it acts on the stopper. The plunger loading mechanism may be a spring having a second selected potential energy for reducing or eliminating a distance between the plunger and the stopper, prior to the plunger accelerating to the velocity. The second selected potential energy of the spring may be less than the first selected potential energy of the energy source.