ALEXANDRIA, Va., Sept. 23 -- United States Patent no. 12,421,729, issued on Sept. 23.
"Spiral staircase" was invented by Aaron Todd Francis (San Jose, Calif.) and John C McCune (San Martin, Calif.).
According to the abstract* released by the U.S. Patent & Trademark Office: "A staircase is provided that includes a column and steps. Each step: is coupled to the column and extends outside of, and away from, the column; includes a tread surface; and can move longitudinally along the column. The staircase can transition to a plurality of states by an actuation system, including closed and open states. The closed state includes the steps positioned at the upper end with the tread surfaces of the plurality of steps oriented around the upper end ...