Auto-injector Single Spring Dynamic Grounding Mechanism
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Solution Overview
Problem
Current auto-injectors face challenges such as user discomfort due to high injection forces and dexterity requirements, potential for incomplete doses, and increased risk of needle exposure, particularly for elderly or dexterity-impaired individuals.
Innovation Solution
An auto-injector design featuring a single compression spring for both needle insertion and retraction, a wrap-over sleeve trigger button for easy activation, and a shuttering mechanism to ensure complete dose delivery and safe needle retraction, reducing overall length and weight while enhancing user safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single compression spring is used for both needle insertion and retraction, then device complexity is reduced, but the spring must be sufficiently long to provide both functions
Solution Approach 1:
The patent applies dynamics by making the spring's grounding point movable rather than fixed. The distal end of the compression spring is grounded to the retractable shield assembly, which moves between retracted and extended positions. This dynamic grounding allows the spring to function in two modes: pushing the needle forward when the shield is retracted, and pushing the shield forward for retraction when the needle is deployed, thereby eliminating the need for a second spring while maintaining sufficient force for both operations
Solution Approach 2:
The single compression spring serves multiple functions: it provides the force for needle insertion, maintains the shield in its retracted position during storage, and provides the force for shield retraction after injection. The spring's single structure is utilized throughout the entire device lifecycle to perform what would traditionally require separate springs for each function, reducing overall device complexity
2Length of moving object
If the syringe is made slimmer to reduce overall device dimensions, then device size is reduced, but the structural strength may be compromised
Solution Approach 1:
The patent employs composite materials by combining polymers with glass reinforcement in the syringe barrel construction. This composite structure provides enhanced strength-to-weight ratio, allowing the syringe to be made slimmer while maintaining sufficient structural integrity to withstand the injection forces and maintain proper plunger engagement throughout the injection process
3Ease of operation
If the trigger button is designed for easy activation, then ease of operation is improved, but the mechanism for preventing accidental activation must be more sophisticated
Solution Approach 1:
The patent applies preliminary anti-action through the safety lock mechanism that prevents the trigger button from being activated unless the device is properly positioned against the injection site. The safety lock must be deliberately disengaged by applying pressure to the distal end of the device, which creates a deliberate action that prevents accidental activation while still allowing easy activation when intended
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 simplifies the injection process, reduces user effort, ensures complete dose delivery, and enhances safety by minimizing needle exposure risks, making it suitable for individuals with dexterity issues.
Implementation Method 1
a compression spring arranged to be grounded at a distal end in the housing for advancing the needle and for injecting the dose of medicament via a plunger and wherein the compression spring is arranged to have its ground in the housing switched to its proximal end for retracting the syringe
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~6
AI summary
The invention refers to an auto-injector (1) for administering a medicament (M), comprising: -a chassis (2), a syringe (3) with a hollow needle (4) and a stopper (6) -a drive spring (8) capable of, upon activation: advancing the needle (3), injecting the medicament (M), and retracting the syringe (3) with the needle (4) after delivering the medicament (M), -activating means (20) arranged to lock and release the drive spring (8), wherein the drive spring (8) is a compression spring arranged to be grounded at a distal end (8.1) in the chassis (2) for advancing the needle (4) and for injecting the dose of medicament (M) via a plunger (9) and wherein the drive spring (8) is arranged to have its ground in the chassis (2) switched to its proximal end (8.2) for retracting the syringe (3). A retraction sleeve (10) is axially movable arranged around the syringe (3), wherein the retraction sleeve (10) is fixable in a maximum proximal position for providing ground at the distal end of the drive spring (8), wherein the retraction sleeve (10) is arranged to take the syringe (3) with it when released and translated in distal direction (D), wherein the compression spring (8) is wrapped over the retraction sleeve (10) with its distal end bearing against a thrust face (13) on the retraction sleeve (10) and with its proximal end bearing against a thrust collar (37) arranged to be coupled to the plunger (9) for joint axial translation for advancing the needle (4) and for injecting the dose of medicament (M) and to decouple from the plunger (9) for retraction.