Multi-part Plunger Jacket for Syringe Dead Volume Reduction
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Solution Overview
Problem
Medical syringes with passive needle protection face challenges in completely delivering medication while minimizing residual drug in the syringe body, often resulting in undesirable dead volumes due to mechanical enclosures required for needle retraction.
Innovation Solution
The syringe plunger is designed with a multi-part structure, including a needle holder and plunger jacket with inflow channels to ensure complete delivery, and a retraction system with a spring mechanism that provides haptic feedback upon needle retraction, ensuring the needle is securely enclosed within the syringe body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical enclosure is used to enclose the hollow needle during retraction, then needle safety is improved, but dead volumes are increased
Solution Approach 1:
The plunger is divided into multiple functional parts: a plunger body, a needle holder with retaining clip, and a plunger jacket. This segmentation allows the needle holder to mechanically enclose the needle for safety while the plunger jacket maintains open flow channels, thus resolving the contradiction between needle enclosure and minimal dead volume.
Solution Approach 2:
The plunger jacket acts as an intermediary element that provides alternative flow paths for the active substance. When the needle holder encloses the needle, the plunger jacket's inflow channels ensure continuous medication flow, mediating between the mechanical enclosure requirement and the need to minimize dead volume.
2Object-affected harmful factors
If the plunger completely encloses the hollow needle during retraction, then contamination risk is reduced, but medication delivery completeness is compromised
Solution Approach 1:
Different parts of the plunger assembly have different functional qualities: the needle holder provides mechanical enclosure and safety, while the plunger jacket maintains open inflow channels for complete medication delivery. This local differentiation of qualities allows simultaneous achievement of contamination prevention and complete medication delivery.
3Reliability
If the retaining groove dimensions are increased to improve needle retraction reliability, then needle engagement is improved, but needle breakage risk increases
Solution Approach 1:
The dimensions of the retaining groove and latching lip are precisely optimized to achieve the right balance: large enough to ensure reliable needle engagement and retraction, but small enough to avoid excessive stress concentration that could cause needle breakage. This parameter optimization resolves the contradiction between retraction reliability and needle integrity.
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
This design minimizes dead volumes, ensures complete medication delivery, and provides reliable and safe needle retraction with visual and haptic confirmation, reducing the risk of contamination and injury.
Implementation Method 1
a retraction system with a spring mechanism that provides haptic feedback upon needle retraction
Data Source
AI summary
A syringe with passive needle protection for administering a medicament dose to a patient, comprising a hollow body forming the syringe housing and containing the medicament active substance, at the distal end of which a hollow needle provided for injection of the active substance is mounted in a bearing sleeve, and in which a displaceable plunger provided at the end with a receiving hole for the hollow needle is arranged, for the most complete possible delivery of medicament while avoiding undelivered medicament residues. For this purpose, the piston is designed in several parts; in addition to a needle holder having a retaining clip for the hollow needle, it comprises a piston jacket which is shaped such that, when the needle holder is inserted, it leaves free inflow channels into the enclosed end of the hollow needle for the active substance on both sides of the retaining clip.