Needle Shield Locking and Feedback in Auto Injection Devices
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Solution Overview
Problem
Prior art automatic injection devices can produce an audible sound during priming that is misinterpreted as medicament delivery, leading to users removing the device without completing the dose, potentially without any medicament being delivered.
Innovation Solution
An injection device with a moveable needle shield and a locking mechanism that prevents premature movement, combined with a sound-generating component to provide accurate audible and tactile indications of medicament delivery, ensuring the needle remains covered until the dose is complete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking mechanism is added to prevent premature needle shield movement, then reliability of medicament delivery is improved, but device complexity increases
Solution Approach 1:
The locking member is nested within the plunger rod assembly, with the shunt arms integrated into the plunger rod structure. The locking sleeve is positioned within the outer housing and interacts with the locking member. This nested arrangement allows multiple locking functions to be achieved without adding significant external components, thereby improving reliability while minimizing the increase in device complexity.
Solution Approach 2:
The locking mechanism operates automatically through the interaction between the plunger rod and locking member during the priming process. The shunt arms on the plunger rod automatically engage with the locking sleeve to lock the needle shield in the covering position, and later release it without requiring separate control mechanisms. This self-service operation improves reliability by ensuring consistent locking behavior while avoiding the complexity of additional control systems.
2Loss of information
If a sound-generating component is added to provide accurate feedback, then information accuracy is improved, but device complexity increases
Solution Approach 1:
The sound-generating component is merged with the existing locking member structure. The locking member serves dual functions: mechanically locking the needle shield and generating acoustic feedback through its interaction with the plunger rod. This integration provides accurate delivery status information without requiring a completely separate sound-generating system, thereby improving information accuracy while minimizing the increase in device complexity.
Solution Approach 2:
The locking member is designed with multi-functionality, serving both as a mechanical locking mechanism and as a sound-generating component. The same structural elements that provide locking functionality also produce audible feedback during operation. This universal design approach improves information accuracy by providing clear delivery status indicators while avoiding the complexity of adding dedicated sound-generating hardware.
3Object-affected harmful factors
If the needle shield is locked in the covering position during priming, then safety is improved, but ease of operation deteriorates
Solution Approach 1:
The locking mechanism is designed to be dynamic rather than static. The locking member automatically transitions between locked and unlocked states based on the position and movement of the plunger rod. During priming, the mechanism dynamically locks the needle shield in the covering position for safety, and automatically unlocks it when the priming is complete and the needle needs to be exposed for injection. This dynamic behavior improves safety during critical phases while maintaining ease of operation through automatic state transitions.
Solution Approach 2:
The locking mechanism performs preliminary locking action during the priming phase to ensure safety before the actual injection. The needle shield is automatically locked in the covering position during priming operations, and the system prepares for subsequent unlocking and needle exposure. This preliminary action ensures safety during the potentially hazardous priming phase while maintaining ease of operation by automatically managing the locking state throughout the injection process.
Data Source
AI summary
An injection device has an outer housing that receives a syringe containing medicament, a movable stopper, and a needle. A plunger rod moves the stopper and a needle shield moves relative to the outer housing between a needle covering position and a needle exposing position, where the needle exposing position is axially rearward of the needle covering position. The needle shield is biased axially forwardly toward the needle covering position. A locking member is axially moveable in the outer housing from a first axial position to a second axial position in response to forward axial movement of the plunger rod. A locking sleeve is axially movable relative to the outer housing between a non-locking position and a locking position, the locking position being axially rearward of the non-locking position, in which axial movement of the locking sleeve is selectively limited by the locking member when in the second axial position.