Issued Patents All Time
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 8075365 | Yo-yo having a string-formed response system | Hans W. Van Dan Elzen | 2011-12-13 |
| 7621796 | Yo-yo having a string-formed response system | Hans W. Van Dan Elzen | 2009-11-24 |