What occurs immediately upon the first press of the button to extend the pen?
Answer
The cam allows the spring tension to push the ink cartridge until it locks into the extended position
On the initial press, the cam structure guides the internal parts so that the energy stored in the spring forces the ink cartridge forward until it is secured by a ratchet or detent system.

#Videos
How Does a Clicky Pen Work? - YouTube
How a Retractable Ballpoint Pen Works - YouTube
Related Questions
What activates the extension and retraction of the writing point in a click pen?Which component is described as the 'heart of the mechanism' that translates vertical push into locking movement?What feature gives the click mechanism an appeal compared to a silent twist-action pen?What is a significant trade-off in tip protection when comparing a click pen to a capped pen?What is the primary indicator that the internal tolerances of a click pen mechanism are wearing down over time?What occurs immediately upon the first press of the button to extend the pen?Why is standard ballpoint (oil-based) ink commonly used in click pens for fast note-taking?Why is the click action favored over a simple cap for promotional pens?What is the engineering goal for high-end writing tools compared to disposable clickers?What modular benefit often comes with owning a well-designed click pen?