Autoinjector Axial Needle Shroud Rotation Mechanism
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Solution Overview
Problem
Conventional autoinjectors face challenges in delivering a consistent dose due to user dexterity requirements and potential misalignment during injections, particularly for elderly or arthritic patients, as they rely on manual force and alignment precision.
Innovation Solution
An improved autoinjector design featuring a needle shroud, chassis, and drive spring mechanism that allows axial movement to rotate the chassis, disengaging the biasing force and ensuring consistent injection depth, with a trigger button and resilient arms to facilitate needle extension and retraction, ensuring reliable medicament delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If manual force is used to drive the injection, then the device structure can be simple, but the user requires high dexterity and continuous force application
Solution Approach 1:
The autoinjector uses a spring mechanism that automatically provides the force needed for injection without requiring the user to continuously press a button or plunger. The device serves itself by storing mechanical energy in the spring and releasing it automatically to drive the plunger through the medication vial and deliver the injection.
Solution Approach 2:
The spring is pre-compressed and stored in a ready state before use, with the force already prepared and waiting to be released. This preliminary action eliminates the need for the user to apply force during the injection process, as the pre-stored energy in the spring automatically drives the injection when activated.
2Ease of operation
If a spring mechanism is used to provide injection force, then ease of operation is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple functions into a single integrated mechanism: the spring provides both the driving force for injection and the retraction force for the needle. The trigger mechanism simultaneously releases the spring and initiates the injection sequence, merging activation, injection delivery, and needle retraction into one coordinated action rather than separate mechanisms.
3Ease of operation
If the needle shroud is extended for injection, then injection access is improved, but alignment precision becomes more difficult to maintain
Solution Approach 1:
The needle shroud is designed to be dynamically extendable and retractable rather than fixed. It can be extended when needed for injection access and automatically retracted after use. This dynamic design allows the system to adapt between needing access (extended state) and needing precision/stability (retracted state), with the transition controlled by the spring mechanism.
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 autoinjector provides a user-friendly, consistent, and reliable method for administering medicaments, reducing the risk of incomplete doses and aligning issues, making it suitable for patients with limited dexterity.
Implementation Method 1
a drive spring applying a biasing force to the outer plunger. The biasing force is applied to the inner plunger when the inner plunger is engaged to the outer plunger
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
Described is an autoinjector (1) comprising a case (2), a needle shroud (3) slidably arranged in the case (2), a chassis (8) slidably arranged in the case (2) and rotatably coupled to the needle shroud (3), an outer plunger (7) selectively engaged to the chassis (8), an inner plunger (12) selectively engaged to the outer plunger (7), and a drive spring (6) applying a biasing force to the outer plunger (7). The biasing force is applied to the inner plunger (12) when the inner plunger (12) is engaged to the outer plunger (7). Axial movement of the needle shroud (3) relative to the case (2) causes rotation of the chassis (8) relative to the needle shroud (3). The rotation of the chassis (8) causes the inner plunger (12) to rotate relative to the outer plunger (7) and disengage the outer plunger (7) to remove the biasing force from the drive spring (6) on the inner plunger (12).