Auto-injector Removable Cap Connector Design
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Solution Overview
Problem
Auto-injectors with electrically powered drive systems face issues with needle cover replacement, where the needle can catch or snag, leading to bending or snapping, and the rubber needle sheath compressing undesirably, potentially causing locking issues or false readings during cap re-capping.
Innovation Solution
The removable cap is designed with a connector featuring needle cover gripping elements and a cap insert allowing limited axial travel, which helps prevent snagging and compression, ensuring safe re-sheathing and proper locking interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the removable cap is designed with a connector featuring needle cover gripping elements, then the reliability of cap locking is improved, but the device complexity increases
Solution Approach 1:
The cap is segmented into multiple functional components: a removable cap body, a connector with gripping elements, and a cap insert. This segmentation allows each component to perform its specific function independently, improving locking reliability while keeping the overall structure manageable through modular design.
Solution Approach 2:
The connector acts as an intermediary element between the removable cap and the needle cover. The gripping elements on the connector provide a controlled interface for engaging the needle cover, mediating the interaction to prevent direct snagging while ensuring reliable connection during re-capping.
2Reliability
If the cap insert allows limited axial travel of the connector, then needle snagging is prevented, but the ease of operation is reduced
Solution Approach 1:
The cap insert is pre-configured with a limited axial travel path that guides the connector's movement before the re-capping action is completed. This preliminary constrained movement ensures the needle cover is properly positioned and prevents snagging before the final locking engagement occurs.
Solution Approach 2:
The limited axial travel of the connector through the cap insert acts as a cushioning mechanism that absorbs and controls the movement dynamics during re-capping. This pre-planned limited travel prevents sudden movements that could cause needle snagging, cushioning the interaction between components.
3Reliability
If the connector central hub is in spaced relationship with the cap interior forward end wall, then needle compression is prevented, but the device complexity increases
Solution Approach 1:
The spaced relationship between the connector's central hub and the cap interior forward end wall creates a localized quality difference in the cap structure. This specific spatial arrangement at a critical location prevents compression forces from being transmitted to the needle, while other parts of the cap maintain their standard design.
Solution Approach 2:
The connector's central hub is designed with a specific spatial offset that copies the needle's required clearance distance. This copied dimensional relationship ensures the needle maintains adequate spacing from compressive surfaces throughout the re-sheathing process, preventing deformation without requiring complex active control mechanisms.
Data Source
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AI summary
Provided is a cassette unit suitable for use with an auto-injector having a drive unit. The cassette unit comprises a cassette unit housing defining a cassette unit housing cavity arranged for receipt of a syringe; a needle projection aperture; a needle cover defining a needle sheath for sheathing of a needle tip of the syringe; a removable cap that in a capping position fits over and thereby, acts such as to close off, the needle projection aperture, the removable cap defining a cap interior; provided to the removable cap, a cap insert; and provided to the cap insert, a connector defining one or more needle cover gripping elements for gripping the needle cover and the connector defines a central hub and the one or more needle gripper elements attach to the central hub and in spaced arrangement relative to each other. The connector locates within the removable cap such that the central hub of the connector is in spaced relationship with a forward end wall or surface of the cap interior and the needle cover gripping elements project away from the forward end cap wall or surface of the cap interior and towards the open end of the cap, and wherein the cap insert is shaped to allow for limited axial travel of the connector there within.