Auto-Injector Syringe Retainer for Automatic Dispensing
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Solution Overview
Problem
Auto-injectors lack a mechanism to automatically dispense medication without user intervention, as existing designs require separate actuation of the firing assembly, which can be cumbersome and inefficient.
Innovation Solution
The apparatus includes a firing assembly with a retainer that prevents forward movement of the plunger rod until the end of the insertion stroke, allowing the plunger rod driver to dispense medication automatically once the retainer disengages, utilizing a combination of axial movement and rotational interaction to ensure precise timing and force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a retainer mechanism is added to prevent forward movement of the plunger rod until the end of insertion stroke, then automatic dispensing is achieved and user intervention is eliminated, but device complexity increases
Solution Approach 1:
The retainer mechanism is integrated into the existing firing assembly components, merging the retention function with the plunger rod driver and rearward portion structures rather than adding completely separate mechanisms. This combining approach achieves automatic dispensing while minimizing the increase in overall device complexity.
Solution Approach 2:
The retainer is pre-configured in the firing assembly to automatically engage and disengage at specific points during the insertion stroke. The mechanism is designed beforehand to prevent forward movement until the appropriate moment, enabling automatic dispensing without requiring user intervention or complex control systems.
2Reliability
If the retainer disengages at the end of the insertion stroke to enable automatic dispensing, then medication delivery is improved, but precision of timing control becomes more difficult
Solution Approach 1:
The patent replaces complex electronic or sensor-based timing control systems with a purely mechanical retainer mechanism. The disengagement timing is determined by the physical geometry of the retainer and its interaction with the plunger rod driver, eliminating the need for precise electronic timing control while ensuring reliable medication delivery.
Solution Approach 2:
The retainer mechanism is designed to automatically control the timing of plunger rod release based on the insertion stroke progression. The mechanism self-regulates the disengagement point through its mechanical design, eliminating the need for external control systems and reducing manufacturing precision requirements for timing control.
3Force
If the plunger rod driver is configured to drive the plunger rod forward relative to the rearward portion, then force application is improved, but friction and resistance increase
Solution Approach 1:
The firing assembly is divided into distinct segments: the rearward portion, the plunger rod driver, and the plunger rod itself. This segmentation allows the plunger rod driver to apply force efficiently to the plunger rod while the retainer manages the interaction with the rearward portion, reducing overall friction and energy loss in the system.
Data Source
AI summary
An apparatus (100) for use with an auto-injector configured to receive a syringe and comprising: a firing assembly (102) comprising a rearward portion (108), a plunger rod (110) moveable forward relative to the rearward portion (108) and a plunger rod driver (112) configured to drive the plunger rod (110) forward relative to the rearward portion (108); an insertion driver (106) configured to drive the syringe forwards on an insertion stroke for inserting a needle of the syringe into an injection site; and wherein the firing assembly (102) further comprises a retainer (114) engaged with the plunger rod (110) and/or the rearward portion (108) and configured to prevent forward movement of the plunger rod (110) relative to the rearward portion (108), and to disengage from the firing assembly (102) at a point on the insertion stroke.