Syringe Plunger Rod Head for Easy Stopper Separation
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Solution Overview
Problem
Existing syringe designs make it difficult to separate the plunger rod from the stopper and syringe barrel for re-use or recycling due to high torque requirements and lack of friction, leading to challenges in disconnection.
Innovation Solution
A plunger assembly design where the distal end head of the plunger rod abuts the stopper without mechanical coupling, allowing separation by applying a rearward axial force, with flexible elements maintaining contact with the syringe barrel to facilitate easy removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the plunger rod is mechanically coupled to the stopper with threaded engagement, then the connection strength is improved, but the ease of separation deteriorates due to high torque requirements
Solution Approach 1:
The invention divides the connection system into two independent engagement mechanisms: a threaded cavity in the stopper and a corresponding threaded feature on the plunger rod. This segmentation allows the plunger rod to engage the stopper through threading for strong connection, while the separate distal end head maintains barrel contact without being mechanically coupled to the stopper, enabling easy separation by pulling the plunger rod away from the stopper after injection.
2Reliability
If the stopper is made of elastomeric material for CCI, then the sealing performance is improved, but the friction between stopper and barrel deteriorates, causing the stopper to rotate with the plunger rod during unscrewing
Solution Approach 1:
The invention introduces a distal end head on the plunger rod that maintains contact with the syringe barrel as an intermediary element. This distal end head acts as a mediator that provides the necessary friction and mechanical advantage during the unscrewing operation, allowing the user to rotate the plunger rod relative to the stopper without the stopper rotating along with it, thereby solving the problem of insufficient friction from the elastomeric stopper material.
3Ease of manufacture
If the plunger rod and stopper are designed for single-use disposal, then the manufacturing simplicity is improved, but the sustainability and recyclability deteriorate
Solution Approach 1:
The invention segments the plunger assembly into separable components: the plunger rod and the stopper. The plunger rod is designed with a distal end head that maintains barrel contact but is not mechanically coupled to the stopper, allowing the plunger rod to be easily separated and removed from the syringe barrel for recycling or reuse, while the stopper remains in the barrel for proper disposal, thus enabling sustainability without complicating the manufacturing process.
Data Source
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AI summary
A syringe is provided comprising a syringe barrel having a chamber configured for containing a fluid therein, and a plunger assembly axially movable within the chamber of the syringe barrel from a retracted position to an advanced position. The plunger assembly includes a plunger rod having a plunger rod proximal end and a plunger rod distal end, the plunger rod comprising a distal end head positioned at the plunger rod distal end. The plunger assembly also includes a stopper secured to the plunger rod distal end, the stopper having a proximal end and a distal end. With the plunger rod and stopper of the plunger assembly assembled, the distal end head is configured to abut the stopper without being mechanically coupled thereto, so that the plunger rod may be separated from the stopper and removed from the syringe barrel by applying only a rearward axial force on the plunger rod.