Fixed-Dose Injection Mechanism With End-of-Content Lockout
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Solution Overview
Problem
Existing multi-use fixed dose injection devices require users to manually strain a torsion spring and rotate a dose selection button before each injection to select and expel a predetermined dose volume, increasing the number of steps and complexity.
Innovation Solution
A spring-driven injection device with a housing structure, piston rod, and drive element that allows for automatic expulsion of a predefined plurality of equally sized dose volumes by using a torsion spring, where the drive element moves axially and rotates back under spring force, with an End-of-Content mechanism preventing further dose selection after the predefined number is reached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-use fixed dose injection device is designed to expel multiple predetermined dose volumes, then the device can be reused for multiple injections, but the user must manually strain a spring and rotate a dose selection button before each injection, increasing operational complexity
Solution Approach 1:
The spring is pre-strained during the manufacturing process to store sufficient energy for all predetermined dose volumes. This preliminary action eliminates the need for users to manually strain the spring before each injection, reducing operational steps while maintaining multi-dose capability
Solution Approach 2:
A single injection device is designed to perform multiple injections with predetermined dose volumes. The device integrates a reusable mechanism where the pre-strained spring universally powers all dose expel operations throughout the device's lifecycle, eliminating the need for separate dosing devices for each injection
2Adaptability or versatility
If a dose selection button is provided to select predetermined dose volumes, then the user can choose different dose sizes, but the mechanism increases device complexity and requires additional user steps
Solution Approach 1:
The dose volume is predetermined and pre-configured during manufacturing. The spring is pre-strained to a specific extent that corresponds to the intended dose volume, eliminating the need for a complex dose selection mechanism during use. The device is designed for a specific dose volume rather than allowing variable selection
Solution Approach 2:
The dose selection functionality is extracted from the user operation phase and moved to the manufacturing phase. Instead of providing a mechanism for users to select different dose volumes, the device is configured with a fixed predetermined dose volume that is determined before the device reaches the user
3Power
If the spring is manually strained before each injection, then the stored energy can be controlled for each dose, but the number of user steps and time required increases
Solution Approach 1:
The spring is pre-strained during manufacturing to store the exact amount of energy needed for the predetermined dose volume. This preliminary energy storage action eliminates the need for users to spend time straining the spring before each injection, reducing preparation time while maintaining controlled power delivery
Solution Approach 2:
The device automatically utilizes the pre-strained spring energy for each injection without requiring user intervention for energy storage. The mechanism is designed to self-utilize the pre-stored energy, eliminating the manual straining step and reducing time loss per injection
4Reliability
If an End-of-Content mechanism is implemented to prevent further dose selection, then the device cannot be misused after doses are exhausted, but the mechanism adds structural complexity
Solution Approach 1:
The spring is pre-strained to a specific extent that corresponds exactly to the number of predetermined dose volumes. After the spring is fully depleted following the predetermined number of injections, it cannot be re-strained by the user. This preliminary energy configuration inherently prevents misuse without requiring additional complex mechanical stop mechanisms
Solution Approach 2:
The spring itself acts as an intermediary that mediates between the user and the dose delivery system. The spring's pre-determined energy capacity serves as a built-in limiter that automatically prevents further operation after exhaustion, simplifying the End-of-Content mechanism to the spring's inherent energy depletion characteristic
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
Reduces the user's steps and complexity by allowing automatic and precise expulsion of equally sized dose volumes without manual spring straining, ensuring the device cannot be used for additional doses once the predefined number is exhausted.
Implementation Method 1
the expelling of the predetermined and substantially equally sized dose volumes is done automatically by a strained spring and wherein the predefined plurality of predetermined and substantially equally sized dose volumes can be expelled without the user re-straining the spring
Data Source
AI summary
The invention relates to a spring driven multi-use fixed dose injection device with an End-of-Content (EoC) mechanism. A housing structure contains a volume of a liquid drug which is expelled in a predefined number of substantially equally sized dose volumes. Each dose volume is expelled automatically with the assistance of a spring which is loaded with a force sufficient to expel the full number of the predefined plurality of predetermined and equally sized dose volumes. Each dose volume is prepared and released by moving a drive element a predetermined axial distance in the proximal direction away from an initial position, followed by a rotation of the drive element by the force of the spring back to the initial position during which rotation the drive element rotates the piston rod to move helically. The End-of-Content mechanism determines how many times the drive element can be moved proximally and comprises a longitudinal track structure associated with the piston rod which has a free length defined by a proximal stop associated with the piston rod which stop prevents the drive element from moving an additional predetermined axial distance in the proximal direction required to prepare a subsequent predetermined dose volume after the predefined plurality of predetermined and equally sized dose volumes have been selected.