Mecanum wheel
If the original patent was November 1972, then surely it had long-since expired by 1997, which then begs the question of why it was necessary that: "In 1997, Airtrax Incorporated and several other companies each paid the US Navy $2,500 for rights to the technology"<p>Is there something about US patents not mentioned in <a href="https://en.wikipedia.org/wiki/Term_of_patent_in_the_United_States" rel="nofollow">https://en.wikipedia.org/wiki/Term_of_patent_in_the_United_S...</a> ?