Elastic Syringe Needle Protection Cap With 5.5 N Withdrawal Force
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Solution Overview
Problem
Existing needle protection devices for syringes require a withdrawal force less than 5N, posing reliability risks and are not adequately robust for secure handling.
Innovation Solution
A needle protection device with an elastic cap having specific internal cavity dimensions and a radial annular projection forming a step, ensuring a withdrawal force of at least 5.5N, featuring a ratio of the internal diameters d/Dcav greater than or equal to 12%, and optionally a rigid shell for additional protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional needle protection devices are used, then the device is simple to manufacture, but the withdrawal force is too low (less than 5N) causing reliability risks
Solution Approach 1:
The patent applies parameter changes by precisely controlling the internal diameter dimensions of the elastic cap (Dcav between 3.5-4.1mm) and the annular projection (Dproj between 3.0-3.6mm), ensuring the ratio d/Dcav is at least 12%. This dimensional parameter optimization generates a withdrawal force of at least 5.5N while maintaining the simplicity of the elastic cap structure without adding complex components.
2Force
If the elastic cap material is made more robust, then the withdrawal force increases, but the manufacturing cost and complexity increase
Solution Approach 1:
Rather than changing the material properties of the elastic cap, the patent achieves higher withdrawal force (at least 5.5N) by optimizing geometric parameters: the internal diameter Dcav of the elastic cap is controlled between 3.5-4.1mm, the internal diameter Dproj of the annular projection is controlled between 3.0-3.6mm, and the ratio d/Dcav is maintained at至少12%. This allows using standard elastic cap materials while achieving the required force through precise dimensional design.
Solution Approach 2:
The patent creates a localized excessive action at the annular projection where the radial dimension d creates a significant mechanical interference fit with the syringe body. This localized geometric feature generates disproportionate withdrawal force relative to the overall device complexity, achieving at least 5.5N without requiring the entire elastic cap structure to be overly robust or complex.
3Reliability
If a rigid shell is added for additional protection, then the reliability increases, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent employs a flexible elastic cap as the primary protective element that combines both protection and secure attachment functions. The elastic cap with optimized internal dimensions (Dcav 3.5-4.1mm, Dproj 3.0-3.6mm, d/Dcav ≥12%) provides sufficient reliability through its flexible yet structurally optimized design, eliminating or reducing the need for an additional rigid shell while maintaining needle protection effectiveness.
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 device provides a secure and reliable needle protection with a withdrawal force of at least 5.5N, ensuring robust handling and ease of assembly, while maintaining cost-effectiveness.
Implementation Method 1
depending on the material used for the flexible part of the protective device, the withdrawal force required to remove the protective device may be too low
Data Source
Figure 1~2
AI summary
Cap (11) defining a cavity (12) delimited by lateral walls (13) and end walls (14), said end wall (14) receiving in a sealed manner a tip (24) of a needle (23), said cavity comprising a first section (12a), a second section (12b) connected to said first section, said second section being cylindrical and having an internal diameter (Dcav), and a third section (12c) connected to said second section, a projection (16) being disposed between said first and second sections, said projection having an internal diameter (Dproj) and cooperating in a sealed manner with a front part (22) of the body (21) of a syringe (20), such that said projection forms a step having a radial dimension (d) corresponding to the difference between Dcav and Dproj, in which said internal diameter (Dcav) of said second section (12b) is between 3.5 mm and 4.1 mm, said internal diameter (Dproj) of said radial annular projection (16) is between 3.0 mm and 3.6 mm, said radial dimension (d) is greater than or equal to 0.50 mm, and said ratio (d/Dcav) is greater than or equal to 12%, to generate a withdrawal force of said protective device (10) of at least 5.5 N.