Injection Device Dose Setting with Sequential Plunger Projections
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Solution Overview
Problem
Existing medical injection devices, such as prefilled syringes, face challenges in delivering accurate small doses and require high activation force to expel air bubbles, leading to decreased dose accuracy and complex structures.
Innovation Solution
An injection device with a barrel and plunger rod featuring radial projections and a dose setting member that allows for sequential abutment against radial projections, enabling easy and reliable dose setting through axial movement and radial positioning of the dose setting member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing medical injection devices are used to deliver small doses, then the device structure is simple, but the dose accuracy is poor
Solution Approach 1:
The plunger rod is segmented into multiple sections with N radial projections at different axial locations. Each projection corresponds to a specific dose level, allowing the device to deliver multiple different doses from a single barrel through sequential engagement of different projections with the dose setting member.
Solution Approach 2:
The dose setting member is designed to be movable relative to the barrel, allowing it to be positioned at different axial locations to select different doses. The member can be moved distally to engage different radial projections, dynamically adjusting the dose delivery capability without changing the barrel or plunger rod.
2Ease of operation
If high activation force is applied to expel air bubbles, then air bubbles are expelled, but the dose accuracy decreases
Solution Approach 1:
The plunger rod is divided into multiple sections with distinct radial projections, allowing the user to first engage a projection for air bubble expulsion and then engage a different projection for precise dose delivery. This segmentation enables separate optimization of air bubble handling and dose accuracy.
Solution Approach 2:
The device allows preliminary action of air bubble expulsion by engaging a radial projection designed for this purpose before the actual dose delivery. The user can perform the air bubble expulsion step first, then reposition the dose setting member to engage a different projection for accurate dose administration, ensuring both air removal and dose precision are achieved.
3Manufacturing precision
If the dose setting member is moved between multiple positions, then accurate dose selection is achieved, but the operation complexity increases
Solution Approach 1:
The radial projections are positioned at predetermined axial locations that automatically correspond to specific dose levels. When the dose setting member is moved to engage a particular projection, the geometry of the engagement itself provides visual or tactile feedback that confirms the correct dose is selected, making the operation self-verifying and intuitive.
Solution Approach 2:
The dose setting member and radial projections are designed with visual indicators that change or become visible as the member is moved to different positions. This allows the user to easily verify the selected dose through visual feedback, simplifying the operation while maintaining high dose selection accuracy.
Data Source
AI summary
An injection device including a barrel, a plunger rod received within the barrel and including N radial projections successively disposed at different locations along the axis of the barrel, N being an integer equal or greater than 2, a dose setting member configured to be removably mounted onto the barrel, and having N portions configured to sequentially abut axially against the N radial projections, respectively, when pushing the plunger rod axially within the barrel, and the dose setting member being configured to be moved relative to the barrel between N positions, wherein the nth radial projection axially faces the nth portion in the nth position, n being an integer lying between 1 and N.