US patent 4,522,407 was granted for the game in 1985.
US patent 4,435,756 and others were granted on this scheme.
But the US patent, 3944 735, is still in force.
His research was associated at total of 10 US patents.
In 1852, he took out a US patent for the same invention.
US patent 9041 was awarded the next year, on 15 June 1852.
He was awarded about 50 US patents in his 30 year career.
He was granted a US patent for this discovery in 1925.
US patents 4785789, 4903676, 4947810, 5769049, 5992386, 6123057, 6827061.
The company has five US patents granted, and several pending.
