Nested Spring Autoinjector Drive Mechanism
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Solution Overview
Problem
Existing autoinjectors with a single spring for both needle insertion and drug delivery often require excessive force for one function over the other, leading to increased size, complexity, and risk of drug container breakage, while dual-spring systems with interlock mechanisms add size and complexity.
Innovation Solution
A release mechanism is positioned at least partially within the drive members to control the sequence of two drive members, allowing for reduced maximum spring force and compact design, with one spring nested inside the other, and a noise-generating mechanism to indicate completion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spring is used to provide motive power for both needle insertion and drug delivery, then the device complexity is reduced, but the maximum spring force required increases excessively
Solution Approach 1:
The single spring system is segmented into two separate springs: a first spring dedicated to needle insertion and a second spring dedicated to drug delivery. This segmentation allows each spring to be optimized for its specific function, with the first spring providing high force for needle insertion and the second spring providing controlled force for drug delivery, thereby reducing the maximum force requirement compared to a single spring system.
Solution Approach 2:
The first spring is positioned within the second spring, creating a nested configuration. This nesting arrangement allows both springs to coexist in a compact space while maintaining their independent functions. The nested structure enables the first spring to drive needle insertion while the second spring remains compressed and ready to drive drug delivery, eliminating the need for a single high-force spring.
2Volume of moving object
If a single spring is used for both functions, then the device size is reduced, but the risk of drug container breakage increases
Solution Approach 1:
By segmenting the drive function into two separate springs, the force applied to the drug container during delivery is reduced and better controlled. The first spring handles needle insertion without directly acting on the drug container, while the second spring provides the gentler, more controlled force needed for drug delivery, significantly reducing the risk of breaking fragile glass syringes or cartridges.
Solution Approach 2:
The nested spring configuration provides inherent cushioning and force distribution. The first spring's action is decoupled from the drug container, and the second spring is pre-compressed to provide a controlled, cushioned delivery force. This beforehand preparation of the spring system prevents excessive force from being applied to the drug container, protecting it from breakage.
3Force
If two separate springs are used with an interlock mechanism, then the force for each function can be tailored, but the device complexity and size increase
Solution Approach 1:
The first spring is nested within the second spring, creating a compact dual-spring system that eliminates the need for complex interlock mechanisms. The nested configuration naturally sequences the operations: the first spring drives needle insertion while contained within the second spring, and upon completion, the second spring is free to drive drug delivery. This spatial arrangement provides inherent sequencing without additional mechanical complexity.
Solution Approach 2:
The two spring systems are merged into a single nested assembly rather than being separate components requiring coordination mechanisms. The first spring operates within the confines of the second spring, and their combined structure provides both force tailoring and sequential operation through their physical arrangement, eliminating the need for separate interlock 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
This approach reduces pain and distress, minimizes the risk of drug container breakage, decreases device size and cost, and enhances portability by allowing accurate control of needle insertion and drug delivery sequences while maintaining a simplified user interface.
Implementation Method 1
a first drive member comprising a first helical spring configured to drive a first component
Implementation Method 2
a second drive member comprising a second helical spring configured to drive a second component, wherein the second component is a pusher configured to push the plunger within the drug container to deliver the drug
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The invention provides a delivery mechanism for an autoinjector comprising: a first drive member configured to drive a first component in an axial direction; a second drive member configured to drive a second component in an axial direction; and a release mechanism configured to control a sequence of release of the first drive member and the second drive member, wherein the release mechanism is positioned at least partially within the first or second drive member.