Interesting and rare gear design. I could't find any information about this or what it is even called, but luckily nice people from Reddit helped me to figure it out. One interesting example of usage is in motion picture camera patent from year 1960: https://patents.google.com/patent/US3120781A/
It would be nice to hear if you have seen this been used somewhere.
Parts are easy to print and assembly can be done with superglue. Also drop of oil won't hurt in bearing surfaces.
- 13.2.2018 Updated "Worm" gear. Runs smoother and has less play.