Medication Delivery Device Dose Limiting Mechanism
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Solution Overview
Problem
Existing medication delivery devices with dose setting limiting mechanisms hinder the resetting process after the medication cartridge is replaced, requiring significant effort to move the piston rod and limiting mechanism back to their initial positions.
Innovation Solution
A medication delivery device with a dose limiting mechanism that interacts directly with the piston rod only when attempting to set a dose exceeding the remaining medication, allowing for easy resetting without direct user interaction with the dose setting limiting mechanism, and featuring a locking member that prevents further dose increasing movement by locking the dose setting member with the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dose setting limiting mechanism is implemented to prevent setting doses exceeding remaining medication, then user safety and dosing precision are improved, but the device complexity and difficulty of resetting increase
Solution Approach 1:
The dose setting limiting mechanism is segmented into separate functional components: a dose setting member for user operation, a limiting mechanism with stop elements that interacts with the piston rod, and a locking member. This segmentation allows the limiting function to be integrated without requiring complete redesign of the dosing mechanism, thereby improving safety while controlling complexity.
Solution Approach 2:
The limiting mechanism acts as an intermediary between the dose setting member and the piston rod. It includes a first stop element that limits movement of the dose setting member and a second stop element on the piston rod, creating a mediating structure that prevents direct user manipulation while ensuring safe dose setting. This intermediary structure resolves the contradiction by providing safety without requiring complex direct control.
2Manufacturing precision
If the dose limiting member interacts directly with the piston rod to limit dose setting movement, then dosing precision is improved, but the ease of operation during resetting deteriorates
Solution Approach 1:
The limiting mechanism is designed with dynamic characteristics: the first stop element limits dose setting movement during normal operation, but the locking member can be actuated to disengage the limiting mechanism during resetting. This dynamic behavior allows the system to switch between precision dosing mode and easy resetting mode, resolving the contradiction between dosing precision and ease of operation.
Solution Approach 2:
During resetting, the limiting mechanism is temporarily discarded or disengaged through the locking member actuation, allowing the piston rod to be moved freely back to its initial position. After resetting, the limiting mechanism is recovered and re-engaged to resume precision dosing control. This temporary discarding and recovery resolves the contradiction between precision limiting and ease of resetting.
3Manufacturing precision
If the locking member is designed to prevent further dose increasing movement by locking the dose setting member, then dosing precision is improved, but the ease of operation deteriorates due to additional locking steps
Solution Approach 1:
The locking member is designed to automatically engage and disengage based on the operational state. During dose setting, the locking member self-activates to prevent exceeding the limited dose. During resetting, it can be easily actuated to disengage. This self-service characteristic reduces the need for complex manual control steps, maintaining ease of operation while ensuring precision.
Solution Approach 2:
The locking member provides tactile and visual feedback to the user about the locked state. When the dose limit is reached, the locking member engages and provides clear feedback that prevents further dose increasing movement. This feedback mechanism ensures dosing precision while making the locking function intuitive and easy to understand, resolving the contradiction between precision and ease of use.
Data Source
AI summary
A method of preventing setting a dose which exceeds an amount of medication contained in a medication receptacle of a medication delivery device. The device comprising a piston rod comprising a second stop element, a drive device for moving the piston rod, and a dose setting member for setting a dose. The method comprising the steps of moving a dose limiting member which comprises a first stop element axially with respect to the piston rod during dose setting, and utilizing the first and second stop elements to stop an axial movement of the dose limiting member in the proximal direction when the first and second stop elements catch, limiting a movement of the dose setting member for increasing a set dose of medication. The dose limiting member and the piston rod only interact directly, when the first and second stop elements catch.