Drug Injector Spring Layout for High-Force Compact Delivery
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Solution Overview
Problem
Existing drug delivery devices using compressed springs are limited in the maximum force and power they can deliver due to design constraints, particularly in maintaining a comfortable device length and avoiding excessive stress on the spring material.
Innovation Solution
A drug delivery device design featuring a drive mechanism with a spring that decompresses externally to the syringe barrel, utilizing a force transmitter with an inner diameter larger than the syringe barrel, and incorporating a damping mechanism to manage force transfer and minimize deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the compressed spring decompresses into the syringe during injection, then the device length is reduced, but the spring outer diameter is limited and the maximum force is restricted
Solution Approach 1:
The spring is positioned to decompress in a direction perpendicular to the syringe axis, utilizing radial space instead of axial space. This dimensional change allows the spring to achieve full expansion for maximum force generation without increasing the overall device length, resolving the contradiction between compact length and injection force capability.
2Force
If the spring outer diameter is increased to generate higher force, then the maximum force increases, but the device length increases beyond comfortable range
Solution Approach 1:
The spring decompression path is oriented radially outward from the syringe barrel rather than axially along it. This allows the spring to achieve its full outer diameter for force generation while the device maintains a compact axial length suitable for patient comfort.
3Force
If the spring stress is increased to generate higher force, then the maximum force increases, but the spring material may exceed yielding stress
Solution Approach 1:
The spring design parameters including wire diameter, coil density, and material selection are optimized to achieve the required force output while maintaining stress levels below the yielding stress threshold. The spring decompressing externally allows for a larger diameter spring with lower stress concentrations, improving reliability.
4Force
If the drive mechanism is designed to deliver high injection forces, then the injection force increases, but the device complexity increases
Solution Approach 1:
The spring is extracted from the traditional internal position within the syringe and repositioned to decompress externally alongside the syringe barrel. This simplifies the drive mechanism by eliminating the need for complex internal guide structures and force transmission components, reducing overall device complexity while maintaining high injection force capability.
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 design allows for higher injection forces, reduced device length, improved handling of high viscosity drugs, and minimizes component breakage while providing haptic and audible signals for user feedback.
Implementation Method 1
Compressed springs are often the preferred choice for providing the required injection drive force
Implementation Method 2
the compressed spring decompresses into the syringe during the injection
Implementation Method 3
incorporating a damping mechanism to manage force transfer and minimize deformation
Data Source
AI summary
A drug delivery device may include a housing having an opening, a drug storage container, a plunger rod, and a drive mechanism. The drug storage container may have an inner surface at least partially defining a drug storage chamber and an outer surface defining an outer diameter. The drug storage container may further include a plunger stopper and a delivery member having an insertion end configured to extend at least partially through the opening during a delivery state. The drive mechanism may be activatable to drive the plunger stopper in a distal direction to expel a drug from the drug storage container through the delivery member. The drive mechanism may have an inner surface with an inner diameter greater than the outer diameter of the outer surface of the drug storage container.