If you’ve ever used a ballpoint pen with a clip on the top, you’ve probably noticed they bend pretty easily. The clip relies on you only bending it a small amount to clip it on to things; bend it too far, and it ends up permanently deformed. [Craighill] decided to develop a pen clip that didn’t suffer this ugly malady.
The problem with regular pen clips comes down to simple materials science. Bend the steel clip a little bit, and the stress in the material remains below the elastic limit—so it springs back to its original shape. Push it too far, though, and you’ll end up getting into the plastic deformation region, where you’ve applied so much stress that the material is permanently deformed.
[Craighill] noted this problem, and contemplated whether a better type of clip was possible. An exploration of carabiner clips served to highlight possible solutions. Some carabiners using elastically-deformed closures that faced the same problem, while others used more complicated spring closures or a nifty bent-wire design. This latter solution seemed perfect for building a non-deforming pen clip. The bent wire is effectively a small spring, which allows it to act as a clip to hold the pen on to something. However, it’s also able to freely rotate out from the pen body, limiting the amount of actual stress put on the material itself, which stops it entering the plastic deformation region that would ruin it.
It’s some neat materials science combined with a pleasant bit of inventing, which we love to see. Sometimes there is joy to be had in contemplating and improving even the simplest of things. Video after the break.
[Thanks to Keith Olson for the tip!]
Just make a normal pen clip out of nitinol. Dunk it in your coffee if you wreck it and the heat will straighten it out.
You can actually get nitinol with a transition temperature below room temperature and then its just superelastic.
This has been done already years ago. $100 gets you a pretty decent pen: https://riind.com/
I’m kind of confused, TBH, because the first two images in the article sure LOOK like photos of an actual Riind pen.
My Riind pen has a very similar clip, and it takes many types of ink refills. Had it for years and it’s been great.
Lamy Safari pens had that for decades, but the video is a nice explainer and they seems to have learn many things so it’s worthwhile.
It’s not the same mechanism, and they address it in the video.
Yes, but i have owned plastic giveaway-pens with that exact same mechanism. If you goolge enough, you can find a picute from a metal bending company with exactly this mechanism, stamped aut of sheet matal. The expalnation is good, I didn’t get that when I was 16.
It’s a very old mechanism, probably invented by someone in the 1850’s.
The problem and why it isn’t an improvement on the traditional version is that it has no backstop to prevent it from flying open on a bump, and the spring tension is rather feeble.
The problem of the clip snapping off or bending out of shape has been solved otherwise by a seesaw design, where the flexible pivot is tucked under so the back end of the beam presses to the side of the pen when you try to bend it too much. That changes the bending of the flexible pivot into a pulling action, which it can handle much better.
Then it’s just a matter of making the actual clip out of some other material that is not a flat piece of soft steel. Something that takes actual effort to break.