Dose Setting Assembly for Medical Injection Devices
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Solution Overview
Problem
Existing medical injection devices, such as syringes, face challenges in accurately dispensing medical fluids due to closely spaced graduation lines that are difficult to read, leading to potential over- or under-delivery of the intended dose, and the difference in static and dynamic friction forces that can result in unintentional plunger movement.
Innovation Solution
A dose setting assembly for medical injection devices that includes a backstop and removable dose setting members to control the plunger rod's movement, allowing for precise dosing without relying on barrel graduations and ensuring controlled priming and storage, featuring a backstop attachable to the barrel flange and dose setting members that maintain the plunger rod in predetermined positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If graduation lines are closely spaced to provide detailed volume measurement, then measurement precision is improved, but readability deteriorates making it difficult to read and dispense accurate doses
Solution Approach 1:
The patent introduces a dose setting member as an intermediary component that mediates between the user and the closely spaced graduation lines. This member features widely spaced indicia (markings) that are easy to read, allowing users to set doses accurately without directly reading the difficult-to-read graduation lines on the barrel. The dose setting member translates the fine graduation scale into coarser, more readable indicators.
2Reliability
If static friction force is high to prevent accidental plunger movement, then reliability is improved, but ease of operation deteriorates requiring excessive force to initiate plunger movement
Solution Approach 1:
The patent applies dynamics by making the friction characteristics variable rather than constant. The dose setting member includes a surface with varying friction properties: a first portion with high static friction to prevent accidental movement, and a second portion with low static friction that allows easy plunger movement when needed. This dynamic friction profile enables the system to switch between stable and movable states as required.
Solution Approach 2:
The patent applies local quality by creating different friction characteristics at different locations on the dose setting member. The surface in contact with the plunger rod has localized regions of high and low friction, allowing the plunger to be held firmly in position during storage and transport, but easily moved when the user needs to adjust the dose or prime the device.
3Manufacturing precision
If dose setting members are permanently fixed to control plunger position, then manufacturing precision is improved, but adaptability deteriorates preventing adjustment for different dosing requirements
Solution Approach 1:
The patent applies segmentation by dividing the dose control function into separate, removable dose setting members. Each member can be independently manufactured with precise positioning features, and multiple members can provide different dose settings. Users can select and attach the appropriate dose setting member based on the required dose, providing both manufacturing precision and adaptability.
Solution Approach 2:
The patent makes the dose setting system dynamic by allowing the dose setting members to be removably attached and detached from the injection device. This enables users to change dose settings by swapping members, providing adaptability for different dosing requirements while maintaining precise control when a specific member is attached.
Data Source
AI summary
The dose setting assembly for a medical injection device including a barrel defining a reservoir adapted to contain a medical injection fluid, an open proximal end and a distal end including a hub portion, a flange disposed at the proximal end of said barrel, and an elongated plunger rod having a plunger flange at a proximal end and a stopper a distal end. The plunger rod being able to slidably move within the barrel, includes a backstop attachable to the flange of the barrel and a dose setting member secured on the backstop, configured to maintain the plunger rod in a predetermined position, the dose setting member being transversally removable from the backstop to authorize the plunger rod to move towards the backstop and abuts onto said backstop.