Injection Dose Limiter Mechanism Preventing Overdose
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Solution Overview
Problem
Existing injection devices lack an effective mechanism to prevent the user from setting a dose that exceeds the amount of medication remaining in the reservoir, which can lead to incorrect or fatal medication administration.
Innovation Solution
A mechanism that includes a piston rod with a threaded outer surface, a housing with a threaded inner surface, and a limiter coupled to the driver, where relative rotation between the driver and piston rod moves the limiter to a stopping position, preventing the setting of a dose that exceeds the medication amount, utilizing a ratchet mechanism and locking means to ensure accurate dosing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a limiting mechanism is provided to prevent setting a dose exceeding the amount of medicament left, then dosing safety is improved, but device complexity increases
Solution Approach 1:
The limiter is integrated into the driver assembly, combining the dose setting function with the end-of-content limiting function in a single integrated component. The limiter forms part of the driver that rotates during dose setting, eliminating the need for separate limiting mechanism components and reducing overall device complexity while maintaining dosing safety
Solution Approach 2:
The driver serves multiple functions: it transmits rotational motion from the dose setting member, engages with the piston rod through threaded engagement, and incorporates the limiter to prevent excessive dosing. This multi-functionality reduces the number of separate components needed in the injection device
2Measurement precision
If the limiter is positioned to prevent excessive dosing, then dosing accuracy is improved, but the space available for other components is reduced
Solution Approach 1:
The limiter is positioned within the hollow interior of the driver, utilizing the empty space inside the driver structure. This nested arrangement allows the limiter to occupy the internal volume of the driver rather than requiring additional external space, maintaining compact device dimensions while ensuring accurate dose limiting
3Reliability
If a threaded engagement mechanism is used between piston rod and housing, then dosing reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The threaded engagement between the piston rod and housing is designed to be self-aligning and self-adjusting during assembly. The threads automatically find their correct engagement position through simple insertion and rotation, eliminating the need for precise pre-positioning or complex alignment procedures during manufacturing, thereby reducing manufacturing precision requirements while maintaining dosing reliability
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
Prevents the setting of excessive doses by ensuring the limiter moves to a stopping position, thereby preventing further rotation and ensuring accurate dosing, even under high torque applications, and provides a non-accumulative solution where the limiter returns to its initial position after dosing, enhancing safety and preventing overdose.
Implementation Method 1
a piston rod having a threaded outer surface; a housing defining a passage for the piston rod, the passage having a threaded inner surface for engagement with the threaded outer surface of the piston rod, the housing being arranged with respect to the piston rod such that rotation of the piston rod in relation to the housing causes the piston rod to be displaced relative to the housing in a longitudinal direction
Data Source
AI summary
A mechanism for preventing setting of a dose, which exceeds the amount of a medicament in a reservoir in an injection device. The device can contain a threaded piston rod, a limiter and a driver. The three elements can be arranged such that during dose setting, the limiter is moved towards an end-of-content position, wherein dose setting is limited. The invention contains an accumulative and a non-accumulative embodiment. The invention further relates to a mechanism for preventing ejection of a dose exceeding the set dose.