Ratchet
thingiverse
I saw this design in a the web page (http://www.robives.com/taxonomy/term/9?page=4) about mechanism in paper, I decided do it in solidworks, the gear wheel have 60 mm of diameter. http://www.youtube.com/watch?v=697Wxbaw1UI
Download Model from thingiverse
With this file you will be able to print Ratchet with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Ratchet.