Why A Retractable Pen?
Click! Click! Retractable pens feature a very clever mechanism called a "push-push" mechanism. This type of mechanism exists in many forms: old push light switches, cabinet latches, sim card readers, and more. But this is probably the most recognizable implementation.
The main question: why does the pen tip press out when you push the pen down, but the pen tip retracts when you push down again? Let's get into it.
What is A Push-Push Mechanism?
A Push-Push Mechanism allows the user to toggle between two states (on/off, open/closed) with the push of one input. In this case, the press of the pen moves the pen tip out then back in.
The bottom barrel of the pen is home to some important parts that give the ballpoint pen its name, but most of those parts don't actively contribute to the push-push mechanism. For that, we need to look at the top of the pen.
Let's explore how these parts move
To better understand the mechanism, let's look more closely at three critical parts.
Okay, Time to Walk Through the Mechanism
Now that we're familiar with the main parts and the flattened view, let's walk through the mechanism, step by step.
Let's Put It All Together
Let's zoom out and use the pen, at full speed. Keep an eye at the top to see the mechanism in action.
CLICK!
