Pre-filled Syringe Piston Locking Mechanism for Sterility
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Solution Overview
Problem
Current pre-filled syringes are inadequately designed for injections requiring a priming step to remove air bubbles, leading to potential under-dosing and sterility breaches due to piston movement during freezing or air transportation.
Innovation Solution
A syringe design featuring a push rod that locks the piston in place and includes a backstop to prevent excessive medication expulsion and piston movement, ensuring precise dosing and maintaining sterility across temperature and pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pre-filled syringe is designed without a control mechanism for air bubble removal, then the device is simpler and easier to manufacture, but it is easy for users to expel excessive medication during priming, leading to under-dosing
Solution Approach 1:
The patent introduces a priming mechanism that allows controlled removal of air bubbles before injection. The syringe includes a priming port and control valve that enable users to expel air bubbles in a controlled manner before sealing the priming port, ensuring accurate dosing while maintaining manufacturing feasibility
Solution Approach 2:
The patent introduces a control valve as an intermediary component between the user and the medication fluid. This valve provides precise control over fluid expulsion during priming, allowing users to remove air bubbles without risking excessive medication loss, thereby maintaining both simplicity and dosing accuracy
2Device complexity
If the syringe piston is allowed to move freely during freezing, then the device is simpler, but the piston movement increases risk of sterility breach
Solution Approach 1:
The patent incorporates a piston constraint mechanism that prevents piston movement in both directions (toward and away from the outlet) before use. This preliminary constraint counteracts the expansion and contraction forces that occur during freezing and air transportation, maintaining sterility without requiring complex active control systems
Solution Approach 2:
The patent designs the piston constraint mechanism to accommodate thermal expansion and contraction by providing predetermined clearance and constraint features. The constraint mechanism allows for expected piston movement during temperature changes while preventing excessive movement that would breach sterility, cushioning against potential problems before they occur
3Device complexity
If the syringe is designed to prevent piston movement in one direction only, then the design is simpler, but it cannot prevent piston movement toward the injection outlet, compromising sterility
Solution Approach 1:
The patent employs asymmetric constraint features in the piston constraint mechanism, including a flange with asymmetric positioning relative to the syringe barrel. This asymmetric design provides effective constraint in both directions (preventing movement toward and away from the outlet) while maintaining structural simplicity through strategic placement of constraint elements
Data Source
AI summary
A pre-filled syringe for sterile medication fluid injection includes a syringe barrel with rotationally symmetric cylindrical bore, having a distal end and a proximal end; a syringe piston with rotationally symmetric external shape; a backstop mounted at the proximal end of the syringe barrel with an opening that is rotationally asymmetric about the axis through the syringe barrel; a push rod to move the syringe piston inside the syringe barrel, wherein at least one portion of the push rod is rotationally asymmetric about the axis through the syringe barrel, and upon rotation, the rotationally asymmetric portion of the push rod is aligned with the rotationally asymmetric opening of the backstop; and a seal component to cover the distal end of the syringe barrel.