Plunger Restricted Safety Syringe Locking Mechanism
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Solution Overview
Problem
Conventional syringes lack effective safety features to prevent accidental needle stick injuries, which pose serious health risks due to the potential for needle exposure before or after the cap is replaced.
Innovation Solution
A syringe design featuring a barrel with a lockable plunger mechanism that secures the needle inside the barrel after use, utilizing a first catch that snaps into a lock section, preventing the needle from being pushed forward or pulled out, thus ensuring the needle tip remains out of alignment with the barrel opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap is used to cover the needle, then needle stick injury risk is reduced, but the cap may fall off inadvertently or be removed before use
Solution Approach 1:
The plunger is segmented into multiple functional zones: a forward segment with a bevel for initial engagement, a medial segment for fluid injection, and a rear segment with a lock section containing notches. This segmentation allows the plunger itself to provide progressive safety functions without relying solely on an external cap.
Solution Approach 2:
The lock section with notches is pre-configured in the barrel to receive the first catch before use. When the plunger is fully inserted, the first catch automatically engages with these notches, preliminarily securing the needle in place before the actual injection procedure begins.
2Ease of operation
If the plunger is made freely movable for injection, then ease of use is improved, but accidental needle exposure may occur
Solution Approach 1:
The plunger transitions from a static safety state (locked during transport and storage) to a dynamic operational state (movable during injection). The lock mechanism allows controlled movement during use while maintaining security during non-use periods, adapting the safety characteristics to the operational phase.
Solution Approach 2:
The lock section with notches and the first catch on the plunger create a preliminary anti-action mechanism that prevents the plunger from moving forward beyond the safe position. This counteracting force is engaged automatically when the plunger is inserted, preventing accidental needle exposure before the user intends to inject.
3Reliability
If a locking mechanism is added to prevent needle exposure, then safety is improved, but device complexity increases
Solution Approach 1:
The locking function is merged into the plunger and barrel structures themselves. The lock section with notches is integrated into the barrel, while the first catch is integrated into the plunger body. This merging eliminates the need for separate locking components, maintaining reliability while minimizing added complexity.
Solution Approach 2:
The locking mechanism is self-activating through the natural insertion motion of the plunger. As the plunger is pushed into the barrel, the first catch automatically engages with the notches in the lock section without requiring additional user actions or complex actuation mechanisms. The structure serves its own safety function through its basic operational movement.
Data Source
AI summary
To prevent accidental needle stick injuries, a syringe has a plunger configured to pull the syringe needle into the syringe barrel after clinical use. The syringe has an additional safety feature that restricts subsequent movement of the plunger. After the needle is pulled entirely into the barrel, movement of the plunger is restricted by a notch on the barrel to prevent the needle tip from being pushed accidentally through the barrel wall.