Plunger Release Mechanism for Complete Auto-Injector Dosing
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Solution Overview
Problem
Existing drug delivery devices, particularly manual devices and auto-injectors, face issues such as incomplete doses due to user error, high injection forces, and difficulties for elderly or dexterity-impaired individuals, and require improvements in plunger release mechanisms to ensure proper dose delivery.
Innovation Solution
A drug delivery device with a plunger release mechanism featuring a profiled slot and sleeve ramp system that allows the plunger to be rotated and released in a controlled manner, preventing unintended advancement and providing audible feedback, ensuring complete dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a manual plunger device is used, then the user can control the injection process, but the user must continuously press the plunger which increases injection forces and may lead to underdosing
Solution Approach 1:
The device pre-loads a spring mechanism that automatically provides the injection force when activated. The user simply needs to trigger the release mechanism rather than manually pressing the plunger throughout the injection, thereby reducing required user force while ensuring complete dose delivery
Solution Approach 2:
The spring-loaded mechanism performs the injection action automatically once triggered. The system self-regulates the plunger movement and medication delivery without requiring continuous user intervention, eliminating the need for the user to sustain injection force
2Reliability
If a manual plunger device is used, then the user can control the injection, but stopping pressure may lead to underdosing
Solution Approach 1:
The device incorporates a profiled slot and plunger boss mechanism that provides mechanical feedback and control. The angled surfaces guide the plunger movement and provide audible/ tactile feedback upon release, ensuring the user knows when the injection is complete and cannot stop prematurely
Solution Approach 2:
The plunger is pre-positioned and the spring is pre-loaded during device preparation. Once activated, the mechanism ensures complete plunger travel to the end position, preventing underdosing even if the user releases the trigger early
3Reliability
If the plunger is secured to prevent accidental advancement, then storage safety is improved, but the release mechanism becomes more complex
Solution Approach 1:
The release mechanism is divided into separate functional elements: a profiled slot in the housing, a plunger boss on the plunger, and a sleeve with angled surfaces. These segmented components work together through simple geometric interactions rather than a complex multi-component locking system
Solution Approach 2:
Instead of using a complex locking mechanism to prevent plunger movement, the design uses a simple blocked slot that prevents movement in the forward direction. Rotation of the plunger or activation of the sleeve releases the blockage, allowing controlled advancement. This inverted approach simplifies the overall mechanism
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
The mechanism ensures consistent and complete dose delivery with reduced user effort, providing audible feedback and preventing accidental plunger advancement, suitable for various medicament types and delivery methods.
Implementation Method 1
a sleeve ramp adapted to engage a projection such as a rib or boss on the plunger to rotate the plunger to release the first plunger boss from the profiled slot when the sleeve is moved in a proximal direction
Implementation Method 2
the profiled slot is adapted to induce a torque to the plunger when an axial force is applied to the plunger, wherein the profiled slot comprises at least one angled surface adapted to engage the first plunger boss to induce a torque in a first rotational direction to the plunger
Data Source
AI summary
A drug delivery device comprises a housing adapted to receive a medicament container, a plunger and a plunger release mechanism that comprises a first plunger boss arranged on the plunger, a profiled slot arranged on the housing and adapted to be engaged by the first plunger boss so as to inhibit movement of the plunger in a distal direction. The plunger is rotatable about a longitudinal axis to release the first plunger boss from the profiled slot so as to allow movement of the plunger in the distal direction. A sleeve is coupled to the housing to permit movement of the sleeve relative to the housing. A sleeve ramp is arranged on the sleeve and adapted to engage a rib or boss on the plunger to rotate the plunger to release the first plunger boss from the profiled slot when the sleeve is moved in a proximal direction.