Autoinjector Median Window Arrow Shape Anti-Rolling Design
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Solution Overview
Problem
Existing autoinjectors with elongated cylindrical shapes are prone to rolling on inclined surfaces, risking loss or damage, and may be used incorrectly by uninformed users, leading to needle stick injuries and dose loss.
Innovation Solution
The autoinjector design incorporates non-cylindrical anti-rolling features, such as radially projecting edges on the middle and distal parts, and an arrow-shaped middle window to indicate the correct usage direction, preventing rolling and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the autoinjector has an elongated cylindrical shape, then it is simple to manufacture, but it rolls on inclined surfaces causing loss or damage
Solution Approach 1:
The patent introduces asymmetric elements (protrusions and recesses) on the cylindrical body of the autoinjector. These asymmetric features create non-circular contact points that prevent rolling motion while maintaining the overall cylindrical shape for manufacturing simplicity. The protrusions and recesses form complementary pairs that interlock with corresponding features on the cap and base, creating stable positioning without requiring complete redesign of the cylindrical form factor.
2Ease of manufacture
If the autoinjector has an elongated cylindrical shape, then it is simple to manufacture, but it may be used incorrectly leading to needle stick injuries
Solution Approach 1:
The asymmetric protrusions and recesses serve as mechanical guides that only allow proper alignment of the autoinjector with the injection site. The directional orientation required for the protrusions to engage with corresponding recesses ensures that the needle points in the correct direction, preventing misuse and potential needle stick injuries while maintaining the simple cylindrical manufacturing approach.
Solution Approach 2:
The mechanical interlocking features automatically guide the user into the correct orientation during the injection process. The design itself provides the guidance function through its geometric constraints, eliminating the need for additional labels, instructions, or user knowledge about proper orientation. The structure enforces correct usage through its physical geometry.
3Reliability
If radially projecting edges are added to prevent rolling, then stability on inclined surfaces is improved, but device complexity increases
Solution Approach 1:
The protrusions and recesses serve multiple functions simultaneously: they prevent rolling on inclined surfaces, provide mechanical guidance for proper orientation, enable cap retention through interlocking, and facilitate user grip. By combining these functions into a single structural feature set, the patent avoids adding separate components for each function, thereby limiting the increase in device complexity while achieving multiple stability and usability goals.
Data Source
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Figure 5~6d
AI summary
The invention relates to an auto-injector which includes a body (1) suitable for receiving a vessel containing a fluid product and including a plunger (P) and a needle, such as a pre-filled syringe, said body (1) including a distal portion, a median portion and a proximal portion, said median portion of said body (1) including at least one median window (12) making it possible, prior to use, to see 100% of the fluid product contained inside said vessel and making it possible, after injection, to see said plunger (P), said at least one median window (12) being arrow-shaped on the outside, pointing towards the proximal portion of said body (1), the proximal portion (121) of said at least one median window (12) including a triangular end portion, forming the tip of the arrow, the base of said triangular end portion, opposite said tip, forming the widest portion of said median window (12).