Retractable Needle Syringe Hub Mechanism for Safety
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Solution Overview
Problem
Conventional syringes with retractable needles face challenges in high-volume manufacturing, reliability, and user safety, particularly for bodily fluid collection and transfer, with existing designs often requiring tight tolerances and prone to premature activation or reuse.
Innovation Solution
A retractable needle assembly with a hub and plunger mechanism that allows the needle to automatically retract into the housing upon fluid withdrawal, featuring a frictional fit and seal to ensure safe handling and prevent reuse, while maintaining operational reliability and ease of assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional retractable needle syringes are designed with tight tolerance requirements for multiple components, then the retraction function can be activated reliably, but the manufacturing complexity and difficulty increase significantly
Solution Approach 1:
The syringe is divided into functionally independent modules: a hub assembly containing the needle and retention features, a plunger assembly for fluid control, and a barrel housing. This segmentation allows each module to be manufactured and assembled independently, reducing overall manufacturing complexity while maintaining reliability of the retraction function through standardized interfaces between modules.
Solution Approach 2:
The needle retention features are extracted as separate functional elements within the hub assembly, including a retention flange and retention features that can be independently manufactured and assembled. This extraction allows the retraction mechanism to be simplified while maintaining reliable needle containment through dedicated retention structures rather than relying on tight tolerances across multiple components.
2Productivity
If retractable needle syringes are manufactured at high volumes, then productivity increases, but maintaining reliability becomes more difficult due to assembly challenges
Solution Approach 1:
The syringe components are segmented into modular assemblies that can be pre-manufactured and quality-tested separately, then rapidly assembled through standardized interfaces. This modular approach enables high-volume production while maintaining reliability, as each module can be optimized for its specific function and assembled through repeatable processes.
Solution Approach 2:
The hub assembly includes self-aligning and self-retaining features such as a retention flange with engagement features that automatically secure the needle in place during assembly. These self-service mechanisms reduce the skill level and precision required during high-volume assembly operations, maintaining reliability even as production volume increases.
3Object-affected harmful factors
If the needle is designed to retract automatically upon plunger movement, then user safety is improved by preventing needle exposure, but the device complexity increases
Solution Approach 1:
The retraction function is merged with the existing plunger operation by designing the hub assembly so that needle retraction is coupled to plunger movement through shared structural elements. The retention flange and hub interact such that plunger advancement automatically drives needle retraction into the barrel, combining fluid delivery and needle containment functions into a single integrated mechanism.
Solution Approach 2:
The needle retraction mechanism is designed to be self-actuating through the mechanical interaction between the plunger, hub, and retention flange. When the plunger is advanced, it automatically engages the retention flange and pulls the needle into the barrel without requiring separate actuators, sensors, or control systems, thereby minimizing device complexity while ensuring user safety.
4Object-affected harmful factors
If frictional fit and seal mechanisms are used to prevent reuse, then safety is improved, but manufacturing precision requirements increase
Solution Approach 1:
The anti-reuse mechanism is segmented into dedicated retention features within the hub assembly, including a retention flange with specific frictional engagement surfaces. These segmented retention features can be manufactured with controlled friction characteristics through standardized processes, reducing the need for tight tolerances across the entire assembly while maintaining effective reuse prevention.
Solution Approach 2:
The frictional fit characteristics are controlled through material selection and surface treatment parameters rather than tight dimensional tolerances. By optimizing the coefficient of friction and contact pressure through material properties and geometric parameters, the design achieves reliable reuse prevention without requiring high-precision manufacturing, thereby reducing manufacturing precision requirements.
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
Enables safe and reliable high-volume production of syringes with retractable needles, ensuring user safety by preventing needle exposure and reuse, while maintaining functionality for fluid collection and transfer without interfering with conventional practices.
Implementation Method 1
The hub is frictionally engaged within the hollow bore such that sufficient force must be applied to the elongate plunger to overcome the frictional engagement and advance the hub within the hollow bore.
Data Source
Figure 1~3
Figure 4~5
AI summary
A syringe assembly (100) for fluid collection includes a housing (102) having a sidewall defining a hollow bore therein, and an elongate plunger (122) with the distal end of the plunger forming a chamber within the hollow bore for containing a fluid therein. The plunger is adapted for slideable movement within the hollow bore between an initial position and a retracted position. The assembly includes a needle hub (112) disposed within the hollow bore proximal of the stopper (130) and supporting a cannula (114). The hub is adapted to automatically transition from an initial position in which at least a portion of the cannula is disposed external to the housing, to a retracted position in which the cannula is fully shielded by the housing, upon transition of the elongate plunger from the initial position to the retracted position.