Plastic Spring Needle Retraction Mechanism
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Solution Overview
Problem
Hypodermic syringes pose a risk of puncture wounds and infection due to incomplete needle coverage by existing safety devices, which can decompress over time, leading to incomplete protection after use.
Innovation Solution
A device with a sinusoidal or spiral spring element made of plastic, which is tensioned during syringe use to automatically retract the needle into the housing, ensuring complete coverage and preventing reuse, combined with snap-in hooks for secure storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a prestressed helical spring is used to retract the needle after injection, then the needle can be covered by the housing, but the spring may decompress over time due to material fatigue, leading to incomplete needle coverage and potential puncture wounds
Solution Approach 1:
The patent changes the spring element from a metal helical spring to a plastic sinusoidal or spiral spring element. This material parameter change eliminates the decomposition issue while maintaining the retraction function. The plastic material provides consistent elastic properties over the device's service life without the fatigue problems of metal springs.
Solution Approach 2:
The patent applies different material properties to different parts of the spring system. The spring element is made of plastic with specific elastic properties tailored for the retraction function, while the housing and other structural components use different materials optimized for their specific functions. This local optimization ensures each component performs its function reliably.
2Force
If the spring element is made of metal, then it provides strong restoring force, but it may decompress and fatigue over time, compromising safety
Solution Approach 1:
The patent fundamentally changes the material parameter from metal to plastic for the spring element. This material substitution maintains sufficient restoring force for needle retraction while eliminating the time-dependent decomposition and fatigue issues inherent in metal springs. The plastic material provides stable, predictable elastic properties throughout the device's service life.
3Ease of manufacture
If the device structure is simplified to reduce costs, then manufacturing becomes easier, but the safety mechanism may become less reliable
Solution Approach 1:
The patent simplifies the spring element design by using injection-molded plastic sinusoidal or spiral springs instead of complex metal helical springs. This parameter change in material and geometry reduces manufacturing complexity and cost while maintaining or improving reliability. The plastic springs can be directly molded into the housing, reducing assembly steps and potential failure points.
Solution Approach 2:
The patent combines the spring element with the housing structure, integrating the retraction mechanism into the existing device architecture. This merging eliminates separate components and assembly steps, simplifying manufacturing while ensuring the safety mechanism remains reliable through integrated design.
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 solution effectively prevents puncture wounds and infections by ensuring the needle is fully retracted and securely stored after use, avoiding material fatigue and unintentional activation, while maintaining low production costs and simplicity.
Implementation Method 1
tensions at least one spring element with the build-up of a restoring force... the at least one spring element is disposed such that the outer housing and the injection container are displaced towards one another, relative to one another, by the restoring force
Data Source
AI summary
A device for receiving a hypodermic syringe comprises an outer housing which has at one end a supporting element with an opening for an injection cannula and which has on its inner surface fixing means for engaging in counter-fixing means which are arranged on the outer surface of an injection container, and a displacement element which has at its end opposite the supporting element an actuating element on which at least one means is arranged which, during displacement, tensions a spring element with the build-up of a restoring force and, if a hypodermic syringe is received in the device, disengages the fixing means from the counter-fixing means. The spring element is disposed such that the outer housing and the injection container are moved relative to one another by the restoring force to such an extent until the injection cannula is fully received in the outer housing.