Retractable Syringe Plunger Spring Mechanism
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Solution Overview
Problem
The sharing of syringes without adequate sterilization contributes to the transmission of HIV and Hepatitis, and health professionals face risks of needlestick injuries from used syringes, highlighting the need for a retractable syringe that prevents reuse and injury while being cost-effective for mass distribution, especially in low-health-budget regions.
Innovation Solution
A retractable syringe design featuring a plunger with a biasing member, a controlling member, and a releasable needle retaining system that ensures safe and controlled needle retraction, including a locking mechanism to prevent reuse, facilitated by a spring for energy storage and a unitary plunger seal for efficient fluid delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retractable needle mechanism is implemented to prevent reuse and needlestick injuries, then syringe safety is improved, but device complexity increases
Solution Approach 1:
The retractable needle is nested within the syringe barrel, with the needle assembly contained inside the barrel and able to retract into it. This nesting approach allows the safety function to be integrated within the existing syringe structure rather than adding external components, thereby improving safety while minimizing complexity increases.
Solution Approach 2:
The spring-loaded mechanism automatically retracts the needle after injection without requiring manual intervention. The system serves itself by using the plunger's forward motion to trigger automatic needle retraction through the releasing member and biasing member interaction, eliminating the need for complex manual retraction mechanisms.
2Reliability
If a spring-loaded retraction mechanism is used, then needle retraction reliability is improved, but manufacturing cost increases
Solution Approach 1:
The spring mechanism is segmented into discrete components: the biasing member (spring), the releasing member on the plunger, and the needle assembly. This segmentation allows each component to be manufactured separately using standard manufacturing processes and then assembled, reducing overall manufacturing complexity and cost while maintaining reliability.
Solution Approach 2:
The releasing member acts as an intermediary between the plunger and the needle assembly, translating the plunger's forward motion into needle retraction. This intermediary mechanism simplifies the overall design by providing a clear mechanical linkage that is easy to manufacture and assemble, rather than requiring a complex direct coupling system.
3Reliability
If the plunger is designed to engage and retract the needle, then needle retraction control is improved, but ease of operation decreases
Solution Approach 1:
The plunger automatically triggers needle retraction through its own forward motion during the injection process. The releasing member on the plunger engages with the needle assembly as the plunger moves forward, causing automatic needle retraction without requiring the user to perform any additional actions. This self-service mechanism maintains ease of operation while ensuring reliable needle retraction control.
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 design provides a user-friendly, safe, and cost-effective retractable syringe that minimizes fluid wastage, ensures efficient delivery, and prevents needle reuse and injury, with a prefilled option suitable for mass consumption, particularly in third-world countries, while maintaining manufacturing efficiency and sterility.
Implementation Method 1
a biasing member, wherein the plunger rod, plunger outer and the controlling member co-operate to releasably maintain said biasing member in an initially energized state
Implementation Method 2
retraction of said retractable needle is facilitated by said biasing member, such as a spring, elastic or other device for storing energy
Data Source
AI summary
A retractable syringe, plunger and releasable needle assembly including a retractable needle, a needle seal, a retaining member and an ejector member. The retaining member has a mating surface for mounting to a complementary mating surface of an interior wall of a syringe barrel. The plunger comprises a plunger outer, a plunger rod frangibly connected to a controlling member, a spring and a unitary plunger seal capable of engaging the retractable needle, wherein the plunger rod, plunger outer and the controlling member co-operate to releasably maintain the spring in an initially compressed state. After delivery of fluid contents of the syringe, the plunger forces the ejector member to release the retractable needle from the retaining member. Decompression of the spring at the end of depression of the plunger facilitates retraction of the retractable needle when engaged with the unitary plunger seal.