Given the commercial success of the product (however limited) the Board should revisit the question of the obviousness of the springy-washer-thing.
(Again, we don't know many things. We especially don't know Patent. Entertainment purposes only, as always.)
http://www.cafc.uscourts.gov/sites/default/files/opinions-orders/17-1362.Opinion.7-3-2018.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.