Spring Force Assembly for Syringe Stopper Buckling Prevention
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Solution Overview
Problem
Existing spring force assemblies in infusion pump devices are prone to kinking, buckling, and require complex and costly manufacturing, making them difficult to mount and recompress, which can lead to dosing errors and increased manufacturing costs.
Innovation Solution
A spring force assembly with a helical compression spring supported by brace elements and coupling elements that restrict expansion, providing a consistent force and preventing buckling, and featuring a damping mechanism to control expansion velocity, allowing for easy assembly and recompression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a compression spring is used to bias the stopper, then the stopper can overcome friction with the cartridge wall, but the spring is prone to kinking and buckling
Solution Approach 1:
The spring force assembly is divided into multiple functional segments: a compression spring for generating bias force, brace elements for structural support, and coupling elements for connecting to the stopper. This segmentation allows each component to perform its specific function optimally while reducing the risk of overall system failure.
Solution Approach 2:
The spring force assembly combines multiple materials and structural elements (spring element, brace elements, coupling elements) into a composite system. The brace elements provide rigid support while the spring element provides elastic force, creating a composite structure that overcomes the limitations of a simple spring.
2Force
If strong compression springs are used to overcome sticking force, then the stopper can be actuated, but the springs require complex and costly manufacturing
Solution Approach 1:
By segmenting the force generation function across a compression spring and structural support elements, the design allows for simpler, more standardized manufacturing of each component while achieving the required overall force output.
Solution Approach 2:
The brace elements act as intermediary structures that distribute and transmit the spring force, allowing the use of a less extreme spring design while still achieving the necessary stopping force through the combined mechanical advantage of the assembly.
3Force
If the spring is allowed to expand freely, then it can provide maximum force, but it becomes difficult to mount and recompress
Solution Approach 1:
The coupling elements segment the spring's expansion motion, providing defined attachment points and guidance. This segmentation allows the spring to expand and contract along a controlled path, making it easier to mount and recompress while maintaining force generation capability.
4Speed
If the spring expands rapidly, then it can quickly actuate the stopper, but it causes dosing errors and requires damping control
Solution Approach 1:
The coupling elements are designed to dynamically control the spring's expansion velocity. They allow rapid initial expansion for quick stopper actuation but incorporate constraints that prevent excessive speed, thereby maintaining dosing accuracy while achieving fast response.
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 ensures reliable operation with minimal force variation, prevents buckling and kinking, simplifies assembly and recompression, and reduces manufacturing costs while maintaining consistent dosing accuracy.
Implementation Method 1
a spring element arranged along a longitudinal axis, comprising: a first brace element arranged on one longitudinal end of the spring element; a second brace element arranged on the other longitudinal end of the spring element
Implementation Method 2
featuring a damping mechanism to control expansion velocity
Data Source
AI summary
A spring force assembly for biasing a displaceable stopper of a liquid medicament cartridge including a spring element arranged along a longitudinal axis, with brace elements and coupling elements, with the coupling elements restricting the distance between the brace elements which also restricts the possible expansion of the spring element.