Two-Part Piston Rod Assembly for Priming-Free Injection Devices

The patent replaces the mechanical welding process with a threaded connection system. The piston rod base features an internal thread that engages with an external thread on the piston rod means, allowing assembly through simple screwing operations instead of complex laser welding. This mechanical threading system achieves precise alignment and connection without requiring advanced welding equipment or procedures.

The piston rod is divided into separate components (piston rod base and piston rod means) that can be independently manufactured and then assembled through threading. This segmentation allows each component to be produced using standard manufacturing processes without requiring complex welding operations, significantly improving ease of manufacture while maintaining connection strength through the threaded engagement.

The threaded connection system is designed with built-in gap compensation capability. As the piston rod means is screwed into the piston rod base, the threading automatically adjusts and compensates for any manufacturing tolerances or gaps between components. This preliminary design feature ensures reliable dose accuracy without requiring complex adjustment mechanisms or additional assembly steps.