I call this mechanism "The Pactuator." I made it for my next project: a playable, mechanical version of Pac-Man called "Pac Machina." It was just meant to be a prototype, but I liked it so much that I made a little frame for it.
Read about the design of the Pactuator at http://upnotnorth.net/projects/pac-machina/pactuator/
Follow my progress on Pac Machina at