Drug Delivery Device With Radial Spring Drive for High-Viscosity Drugs
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Solution Overview
Problem
Existing drug delivery devices using compressed springs are limited by the maximum force and power they can generate due to design constraints, which restrict the outer diameter of the spring, leading to insufficient injection force for high-viscosity drugs and increased device length.
Innovation Solution
A drug delivery device with a spring drive mechanism that has an inner diameter larger than the syringe barrel, allowing the spring to decompress externally, and utilizes a force transmitter to transfer force to the plunger stopper, enhancing injection force while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the spring decompresses into the syringe during injection, then the device length is reduced, but the spring outer diameter is limited and maximum force is restricted
Solution Approach 1:
The spring is configured to decompress in a direction perpendicular to the syringe axis, extending radially outward from the syringe barrel rather than longitudinally into it. This dimensional change allows the spring to achieve full decompression length while maintaining a compact device footprint, and enables a larger spring outer diameter that can generate higher injection forces without increasing device length.
2Force
If the spring outer diameter is increased to generate larger force, then injection force is improved, but the device length increases
Solution Approach 1:
By redirecting the spring decompression path to a radial dimension rather than longitudinal, the design allows larger diameter springs to be used without proportionally increasing device length. The spring extends outward perpendicular to the injection axis, utilizing unused spatial volume to accommodate higher-force components.
Solution Approach 2:
The spring is positioned to nest around the syringe barrel during compression, with the syringe fitting within the spring's inner diameter. This nested configuration allows the spring to surround rather than occupy the same linear space as the syringe, enabling larger spring dimensions without increasing overall device length.
3Force
If a force transmitter is added to transfer force from spring to plunger, then injection force is enhanced, but device complexity increases
Solution Approach 1:
A force transmitter component serves as an intermediary element between the spring and plunger stopper, mechanically coupling them to transfer and amplify the spring's decompression force. This intermediary structure enables efficient force transmission while maintaining a relatively simple overall design through direct mechanical coupling rather than complex transmission mechanisms.
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 improved drive mechanism enables larger injection forces, reduces syringe component breakage, provides visual and haptic feedback, and minimizes spring deformation, while maintaining a shorter overall length and supporting high-viscosity drugs.
Implementation Method 1
the compressed spring decompresses into the syringe during the injection
Implementation Method 2
the maximum force and power that a spring can deliver in an autoinjector is limited
Data Source
Figure 1a~1c
Figure 2
Figure 3a~3c
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.