Injection Device Needle Shroud Auto-Lock Mechanism
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Solution Overview
Problem
Existing injection devices fail to automatically lock the needle shroud in its fully projecting position after injection, potentially leaving the needle exposed unless manual intervention is used.
Innovation Solution
An injection device with a needle shroud that is spring-urged forward to enclose the needle, featuring a drive member that captures the shroud in its extended position using abutments and arms to prevent retraction, ensuring the shroud remains locked after the injection is completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the needle shroud is spring-urged forward to enclose the needle, then the needle is protected after injection, but the shroud may retract and expose the needle before injection is complete
Solution Approach 1:
The drive member automatically performs the locking function without requiring manual intervention. After the injection is complete, the drive member's arms engage with the needle shroud's abutments to automatically lock it in the extended position, making the system self-servicing rather than requiring user action to secure the needle protection.
Solution Approach 2:
The drive member is pre-configured with arms that can engage the needle shroud. Before the injection completes, these arms are positioned to potentially engage the shroud, and upon completion of injection, they automatically engage to lock the shroud in place, preparing the locking mechanism in advance rather than requiring post-injection user action.
2Power
If the drive member is made spring-actuated to propel the syringe, then the injection force is sufficient, but the drive member may retract after injection compromising needle protection
Solution Approach 1:
The drive member transitions from a dynamic spring-actuated state during injection to a static locked state after injection. The arms on the drive member are designed to be flexible during the power stroke but then engage with abutments on the needle shroud to create a rigid, locked configuration that maintains the shroud in the extended position.
Solution Approach 2:
The drive member is segmented into functional zones: the spring-actuated portion provides injection power, while the extended arms provide the locking function. This segmentation allows the same component to perform both the high-power injection stroke and the subsequent locking function without requiring separate mechanisms.
3Ease of operation
If the needle shroud is forced to retract during injection, then the needle can be inserted, but the shroud must be reliably returned to protective position afterward
Solution Approach 1:
The system uses mechanical feedback through the drive member's arms sensing the completion of injection. When the syringe reaches its forward position, this triggers the arms to engage with the needle shroud's abutments, automatically signaling and executing the return to protective position without requiring user judgment or action.
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
Ensures the needle shroud automatically returns to a protective position post-injection, preventing accidental needle exposure and enhancing user safety by maintaining the shroud in its extended position without manual intervention.
Implementation Method 1
the shroud is normally spring-urged forwardly to a needle protecting position
Implementation Method 2
The drive member will generally be spring-actuated
Data Source
AI summary
An injection device for a syringe incorporates a housing (1) for a syringe (29). A needle shroud (15) is captive to the leading end of the housing and is movable before use between extended and retracted positions. A drive member (17) is releasable from a rearward position within the housing to urge the syringe forwards to project its needle (30) beyond the retracted needle shroud (15) and then to express a dose through the needle. Locating members (12) on the housing capture the drive member (17) at its forward position (attained after expressing the dose). The captured drive member (17) is also arranged to block retraction of the needle shroud (15) from its extended position.