Needle Guard Trigger Locking for Reliable Self-Injection
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Solution Overview
Problem
Medical injection systems for self-administration often fail due to the injection step being triggered before the needle pricking is complete, leading to improper needle insertion and wastage of drug composition.
Innovation Solution
A medical injection system with a syringe, plunger rod, injection lock, and needle guard that ensures the injection step cannot start until the needle pricking is complete, using a trigger mechanism to disengage the lock at the end of the needle pricking step, and a needle guard that adjusts the needle exposure and provides a safe disposal position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection step is triggered before the end of the needle pricking step, then the operation is simplified and faster, but the injection may fail due to improper needle insertion depth
Solution Approach 1:
The injection lock is engaged with the plunger rod before needle insertion begins, pre-preventing the injection step. The lock remains engaged throughout the needle pricking step, ensuring the needle reaches proper depth before the injection can be triggered. This preliminary locking action guarantees that needle insertion is complete before drug delivery starts.
Solution Approach 2:
The injection lock acts as an intermediary mechanism between the needle guard and the plunger rod. It translates the completion of needle insertion into the enabling of the injection step by disengaging from the plunger rod only when the needle guard reaches its retracted position, indicating proper needle insertion depth.
2Reliability
If a locking mechanism is added to prevent premature injection, then the injection success rate improves, but the device complexity increases
Solution Approach 1:
The injection lock combines multiple functions into a single component: it engages with the plunger rod to prevent premature injection, interacts with the needle guard to detect insertion completion, and automatically disengages to enable the injection step. This merging of functions into one element avoids the need for separate sensors, actuators, and control systems.
Solution Approach 2:
The injection lock is designed to automatically engage and disengage based on the mechanical position of the needle guard and plunger rod. No external control system or user intervention is needed to manage the locking state - the mechanism self-regulates the injection timing based on the physical state of the other components.
3Ease of manufacture
If the injection lock directly contacts the proximal edge of the barrel, then the manufacturing cost is reduced and assembly is simplified, but the precision of needle insertion control may be affected
Solution Approach 1:
The proximal edge of the barrel serves as a self-positioning reference for the injection lock. During assembly, the lock naturally positions itself relative to this fixed reference point, eliminating the need for precision-machined adjustment features or complex alignment procedures. The mechanical interaction between the lock and barrel edge automatically establishes the correct geometric relationship.
Data Source
AI summary
A medical injection system comprising: a syringe provided with a barrel, a stopper and an injection needle; a plunger rod which engages with the stopper; an injection lock preventing relative movement of the plunger rod with respect to the barrel; and a needle guard comprising a trigger portion and configured to slidably engage the barrel so as to define a first position covering the injection needle and a second position not covering a predetermined portion of the injection needle. The trigger portion is adapted to disengage the injection lock from the plunger rod when the needle guard moves from the first position to the second position.