Autoinjector Delay Mechanism for Complete Medicament Delivery
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Solution Overview
Problem
Current auto-injectors face challenges in ensuring complete delivery of medicament doses due to manufacturing tolerances and premature retraction of the syringe, leading to incomplete dosing and increased risk of needle stick injuries.
Innovation Solution
A delay mechanism is introduced in the auto-injector, utilizing a viscous fluid-filled cavity and a retraction sleeve with a decoupling system to slow down the retraction motion, ensuring the syringe is fully emptied and the needle is safely retracted, while a single compression spring handles both injection and retraction, reducing part count and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the syringe is retracted immediately after injection, then the device complexity is reduced, but the medicament delivery reliability deteriorates due to premature retraction before complete dose delivery
Solution Approach 1:
The delay mechanism is pre-configured with a viscous fluid in a cavity that automatically activates upon retraction initiation. The fluid's viscosity creates a time delay that ensures the syringe remains in place long enough to complete medicament delivery before retraction occurs, thus ensuring reliable dose delivery without adding complex control systems.
Solution Approach 2:
A viscous fluid is introduced as an intermediary substance between the retraction mechanism and the syringe. This fluid mediates the retraction process by creating resistance that delays syringe movement, allowing complete medicament delivery to occur before the syringe is retracted, thereby maintaining delivery reliability.
2Productivity
If the syringe retraction speed is increased, then the productivity is improved, but the safety deteriorates due to increased risk of needle stick injuries
Solution Approach 1:
The delay mechanism is pre-configured to automatically activate upon retraction initiation, creating a time buffer before the syringe actually moves. This preliminary delay ensures complete medicament delivery and allows the needle to be safely covered by tissue or a shield before rapid retraction occurs, reducing needle stick injury risk while maintaining fast overall injection speed.
Solution Approach 2:
The viscous fluid in the delay mechanism provides a cushioning effect that slows down the initial retraction phase. This cushioning allows the needle to be safely repositioned or covered before the syringe begins its main retraction movement, reducing the risk of needle stick injuries during the transition phase.
3Device complexity
If a single compression spring is used for both injection and retraction, then the device complexity is reduced, but the force control precision deteriorates
Solution Approach 1:
The delay mechanism is pre-configured with a viscous fluid that automatically engages when the spring begins to retract the syringe. This preliminary engagement creates a controlled delay that allows the spring to complete its full compression stroke for injection, then provides a gradual transition during retraction, ensuring precise force control throughout the entire cycle despite using a single spring.
Solution Approach 2:
The viscous fluid acts as an intermediary that modulates the force transmission from the single compression spring. During injection, the fluid allows full force transmission; during retraction, it creates a controlled resistance that modulates the spring force, ensuring precise control over the retraction process while maintaining the simplicity of a single-spring design.
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 ensures reliable and complete delivery of the medicament dose, reducing the risk of needle stick injuries and improving dosage accuracy by allowing the syringe to fully empty before retraction, and simplifies the mechanism with fewer components.
Implementation Method 1
a delay mechanism (36) for slowing down motion of the retraction sleeve (10) in axial direction of the auto-injector (1)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to an auto-injector (1) with a delay mechanism (36) for slowing down motion of a retraction sleeve (10) in axial direction of the auto-injector (1), the delay mechanism (36) comprising a circumferential outer wall (37) with a back collar (38) attached to a housing (2) of the auto-injector (1) and a circumferential inner wall (39) with a front collar (40) attached to the retraction sleeve (10) wherein a cavity is defined between the outer wall (37) and inner wall (39), the cavity sealed by the back collar (38) against the inner wall (39) and by the front collar (40) against the outer wall (37), the cavity filled with a viscous fluid, wherein at least one orifice is arranged in the delay mechanism (36) for allowing the viscous fluid to be pushed out as the volume of the cavity decreases due to axial motion of the component with respect to the housing. The retraction sleeve (10) is axially movably arranged in the housing (2) and serves for retracting the syringe (3) with the needle (4) into the covered position after delivering the medicament (M).