Self-Retracting Syringe Spring Mechanism Needle Safety
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Solution Overview
Problem
There is a need for improved automatic self-injection technology that mitigates the risk of needle stick injuries and facilitates self-medication by providing a mechanism for automatic injection and retraction of hypodermic needles, ensuring safety and increased patient compliance with medical therapy.
Innovation Solution
The development of an automatic injection and retraction syringe with a housing, plunger rod, power means, latch, and dynamic seals, which includes a spring mechanism for needle retraction and a fluid containment system with a permanently attached hypodermic needle, allowing for safe and efficient injection and immediate retraction of medicinal fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual injection devices are used, then patients can receive injections, but the risk of needle stick injuries and pathogen transmission increases
Solution Approach 1:
The syringe is pre-loaded with the therapeutic substance and the needle is pre-positioned in a retracted state within the housing. All preparation steps are completed beforehand, so that upon activation, the device automatically performs insertion, injection, and retraction without requiring manual intervention during the critical phases, thereby eliminating needle stick injury risk.
Solution Approach 2:
The device is designed to automatically perform the complete injection sequence without manual operation. The spring mechanism self-activates upon cap removal, automatically inserting the needle, injecting the substance, and retracting the needle back into the housing. The system serves itself through the stored mechanical energy in the spring, eliminating the need for manual needle handling.
2Ease of operation
If automatic self-injection devices are used, then patient compliance improves, but device complexity increases
Solution Approach 1:
The device is divided into distinct functional modules: a housing containing the spring mechanism, a plunger rod for fluid delivery, a needle assembly with dynamic seals, and a cap for activation. This segmentation allows each component to perform its specific function independently while simplifying the overall design and manufacturing process.
Solution Approach 2:
The spring mechanism serves multiple functions: it propels the plunger rod forward for injection, drives the needle assembly for insertion and retraction, and provides the force for dynamic seal movement. This multi-functionality reduces the need for separate actuators and control systems, thereby simplifying the device while maintaining automatic operation.
3Object-affected harmful factors
If self-retracting needle mechanisms are used, then needle stick injury risk is reduced, but device complexity increases
Solution Approach 1:
The injection and retraction functions are merged into a single spring-driven mechanism. The same spring that propels the plunger forward also drives the retraction of the needle assembly through the dynamic seals. This merging eliminates the need for separate retraction actuators and control systems, simplifying the device while ensuring automatic needle retraction.
Solution Approach 2:
The dynamic seals serve as intermediaries between the spring mechanism and the needle assembly. These seals transmit the retraction force from the spring to the needle while maintaining fluid containment. The seals enable the complex retraction motion without requiring direct mechanical connection, thereby simplifying the overall retraction mechanism.
4Reliability
If dynamic seals are used for fluid containment, then fluid leakage is prevented, but friction increases
Solution Approach 1:
The dynamic seals are designed with optimized geometric parameters including cross-sectional shape, contact surface area, and material hardness. These parameters are carefully selected to achieve the minimum necessary sealing force while minimizing friction during the retraction motion. The seal geometry is tailored to balance fluid containment reliability with low-friction operation.
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 syringe effectively reduces the risk of needle stick injuries by automatically retracting the hypodermic needle after injection, enhancing patient safety and compliance with medical therapy through a reliable and user-friendly self-injection mechanism.
Implementation Method 1
power means, preferably comprising a spring, resides internal to the housing
Implementation Method 2
The plunger rod is configured to impinge upon the dynamic seal upon actuation of the syringe and transfer force thereto
Data Source
AI summary
A self-retracting syringe has an injection assembly and a retraction assembly. The injection assembly has a housing, a spring rest, and a spring that is restrained initially in compression between the housing and the spring rest. A plunger rod is disposed inside the coil of the spring. A coupler in contact with the spring rest and the plunger rod releasably couples the plunger rod to the spring rest. When a latch is released, the plunger rod moves distally to urge a seal forward, which seal movement causes a hypodermic needle to extend and a medicament to be expelled through the hypodermic needle. A retraction assembly returns the hypodermic needle into the syringe body after the medicament is expelled. Embodiments of retraction assembly provide an inlet through which fluid may be introduced into the syringe through said hypodermic needle. Methods for filling the syringe are also described.