Auto-Injector Tension Spring Drive Mechanism Design
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Solution Overview
Problem
Existing auto-injector devices are cumbersome due to coaxial plunger and compression spring arrangements, require strong drive springs that can cause patient discomfort and syringe damage, and may prematurely retract the needle before the full medicament dose is delivered, leading to incomplete administration and medicament loss.
Innovation Solution
A medicament delivery device with a tension spring drive mechanism carried by a carriage, allowing for a compact design, separate insertion spring for controlled cannula insertion, and a retraction mechanism with a delay to ensure complete dose delivery, featuring a drive mechanism with a tension spring arranged around the force transmission means and a separate insertion spring for reliable and comfortable insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a coaxial plunger and compression spring arrangement is used in the drive mechanism, then the device can deliver medicament through the needle, but the device becomes relatively long and cumbersome
Solution Approach 1:
The patent repositions the compression spring from a coaxial arrangement to a location alongside the needle, utilizing lateral space instead of axial space. This dimensional change allows the drive mechanism to remain effective while significantly reducing the overall length of the auto-injector device.
2Force
If a powerful compression spring is used to drive needle insertion, then the needle can be inserted effectively, but the impact loads can damage the syringe and cause patient discomfort
Solution Approach 1:
The patent introduces a shock-absorbing element positioned between the plunger and the syringe that activates upon needle insertion. This element cushions the impact load, preventing damage to the syringe and reducing patient discomfort while still allowing effective needle insertion with the compression spring.
3Reliability
If the needle retraction mechanism is activated when the plunger nears the end of its distal travel, then the needle can be retracted, but the full medicament dose may not have been delivered and the needle may retract prematurely
Solution Approach 1:
The patent employs a feedback mechanism that monitors the actual delivery of medicament rather than relying solely on plunger position. This allows the needle retraction mechanism to be activated only after confirmation that the full dose has been delivered, ensuring complete medicament administration before retraction occurs.
4Length of stationary object
If a tension spring drive mechanism is used instead of a compression spring, then the device becomes more compact, but the drive mechanism structure becomes different and may require different force transmission arrangements
Solution Approach 1:
The patent segments the drive mechanism into distinct functional components: the tension spring for power storage, the plunger for force transmission, and the shock-absorbing element for impact mitigation. This segmentation allows each component to be optimized independently and simplifies the overall structural arrangement despite the change from compression to tension spring.
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 solution results in a more compact device that reduces patient discomfort, ensures complete medicament delivery, and prevents premature needle retraction, maintaining the integrity of the syringe and ensuring accurate dosing.
Implementation Method 1
The drive means is arranged around or alongside at least part of the force transmission means and comprises a tension spring
Implementation Method 2
an insertion spring for biasing the carriage for movement in an insertion direction with respect to the chassis from a starting position in which the cannula is shrouded to an insertion position in which the cannula is extended
Data Source
AI summary
A medicament delivery device (100) for a delivery of a medicament from a container (12) through a cannula (16). The device comprises a chassis (300), a carriage (200), and an insertion spring (70) for biasing the carriage (200) for movement in an insertion direction with respect to the chassis (300) from a starting position in which the cannula (16) is shrouded to an insertion position in which the cannula (16) is extended. A drive mechanism (400) is provided for driving a stopper (22) of the container (12) to expel the medicament. The drive mechanism (400) is carriage by the carriage (200) and comprises a movable drive member (404), a drive means (40) for applying a driving force to the drive member (404), and a force transmission means (406) for transmitting the driving force to the stopper (22). The drive means (40) is arranged around or alongside at least part of the force transmission means (406).