Self-Retained Wave Spring Biasing for Drug Delivery Cartridge Stability
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Solution Overview
Problem
Pen type drug delivery devices face issues with cartridge movement due to manufacturing tolerances and frequent needle assembly attachment/removal, leading to potential inaccuracies in medication dispensing.
Innovation Solution
A non-plastic, self-retained biasing element, such as a flexible wave spring mechanism, is used to securely hold the cartridge against the inner surface of the cartridge holder, preventing axial movement during use and handling, ensuring accurate dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cartridge is held loosely in the cartridge holder to accommodate manufacturing tolerances, then ease of assembly is improved, but cartridge stability deteriorates causing unwanted axial movement
Solution Approach 1:
The biasing element changes the positional parameter of the cartridge by applying a biasing force that maintains optimal contact between the cartridge and the distal end of the cartridge holder, compensating for manufacturing tolerances while preventing excessive movement
Solution Approach 2:
The biasing element acts as an intermediary component between the cartridge and the cartridge holder, providing a controlled force that ensures stable cartridge positioning without requiring tight manufacturing tolerances
2Stability of the object's composition
If the cartridge is held rigidly in the cartridge holder to prevent movement, then cartridge stability is improved, but device complexity increases
Solution Approach 1:
The biasing element is self-retained by the internal surface of the cartridge holder and automatically adjusts to maintain optimal cartridge positioning without requiring external adjustment mechanisms or complex assembly procedures
Solution Approach 2:
The biasing element provides a simple mechanical solution that changes the positional parameter of the cartridge through elastic deformation, achieving stable positioning without complex mechanisms
3Productivity
If the spindle presses on the bung during normal operation, then dose dispensing function is improved, but drug loss increases causing dose inaccuracy
Solution Approach 1:
The biasing element applies a preliminary force in the opposite direction to prevent the cartridge from moving away from the distal end of the cartridge holder, thereby preventing unwanted spindle contact with the bung that would cause drug loss
Solution Approach 2:
The biasing element provides continuous mechanical feedback by maintaining optimal contact between the cartridge and the cartridge holder, ensuring that the spindle only contacts the bung during intended dose dispensing operations
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 biasing element maintains cartridge position, preventing spindle contact with the bung during dose administration, ensuring accurate medication dispensing and reducing the risk of dose inaccuracies caused by movement.
Implementation Method 1
A non-plastic element for biasing a cartridge in a cartridge housing of a drug delivery device is provided
Implementation Method 2
A non-plastic, self-retained biasing element, such as a flexible wave spring mechanism
Data Source
AI summary
A method and system for biasing a cartridge in a drug delivery device. An element for biasing a cartridge in a cartridge housing of a drug delivery device is provided. This non-plastic element does not comprise a coil spring. A self retained element for providing a spring bias to a cartridge in a cartridge holder of a drug delivery device comprises a first member having a shape that allows passage of a spindle of the drug delivery device. A portion of the first member is self retained by an internal surface of the drug delivery device. The self retained element biases the cartridge against an inner surface of the cartridge holder. This cartridge could be a removable cartridge.