Safety Needle Constant Force Spring Retraction
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Solution Overview
Problem
Commercially available retractable safety needles with compression spring mechanisms experience extreme force changes during retraction, leading to potential needlestick injuries and blood splattering, and require increased device cross-section due to bulkiness, necessitating a solution for a constant force mechanism that is simple, low-cost, and easily integratable.
Innovation Solution
A safety needle with a spring biased retraction mechanism utilizing a constant force spring operatively connected to the needle hub, providing a consistent force throughout the retraction process, which is positioned within a cavity in the hollow body and can be made from materials like type 301 stainless steel, ensuring smooth and controlled needle retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If compression springs are used to provide retraction forces, then the needle can be retracted automatically, but extreme force changes occur during retraction causing needlestick injuries and blood splattering
Solution Approach 1:
The patent transitions from using compression springs to constant force springs, fundamentally changing the force delivery parameter. Constant force springs maintain a substantially uniform force throughout their extension and retraction cycles, eliminating the extreme force variations characteristic of compression springs. This parameter change directly addresses the harmful force fluctuations during needle retraction while preserving automatic retraction functionality.
2Extent of automation
If compression springs are used to provide retraction forces, then the needle can be retracted automatically, but the device cross-section must be increased to accommodate the bulky spring
Solution Approach 1:
The patent replaces compression springs with constant force springs, which have a fundamentally different structural configuration. Constant force springs typically have a more compact form factor, especially when coiled, allowing them to fit within smaller device cross-sections while still providing the necessary retraction force. This enables automatic retraction functionality without increasing the overall device size.
3Ease of operation
If constant force spring is used, then smooth and controlled retraction is achieved, but the spring mechanism complexity increases
Solution Approach 1:
The constant force spring mechanism is designed to be self-regulating, providing inherently smooth and controlled retraction through its constant force characteristic. The spring's design allows it to deliver force uniformly throughout its range of motion without requiring additional control mechanisms, damping elements, or complex regulation systems. This self-service approach achieves smooth operation while actually simplifying the overall mechanism compared to what would be needed with compression springs.
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 constant force spring mechanism ensures safe and controlled retraction of the needle, minimizing the risk of needlestick injuries and blood splattering while maintaining a compact device design, providing a stable and reliable solution for medical procedures.
Implementation Method 1
The constant force spring is configured to bias the needle hub towards the retracted position wherein the spring provides a substantially constant force to the needle assembly while the needle assembly moves from the advanced position to the retracted position
Data Source
AI summary
A safety needle is provided. The safety needle includes a substantially hollow body and a needle assembly that includes a needle supported on a needle hub. The needle hub is movable in relation to the hollow body from an advanced position wherein a sharp tip of the needle extends from the hollow body to a retracted position wherein the sharp tip of the needle is positioned within the hollow body. The safety needle also includes a spring biased retraction mechanism that includes a constant force spring operatively connected to the needle hub. The constant force spring is a generally flat strip of prestressed material that is formed into constant coils around itself. The constant force spring is configured to bias the needle hub towards the retracted position wherein the spring provides a substantially constant force to the needle assembly while the needle assembly moves from the advanced position to the retracted position.