ALEXANDRIA, Va., March 17 -- United States Patent no. 12,577,832, issued on March 17, was assigned to Assa Abloy Entrance Systems AB (Landskrona, Sweden).
"Door operation system" was invented by Friedhelm Frede (Erwitt, Germany).
According to the abstract* released by the U.S. Patent & Trademark Office: "A door operation system (1) for a door (2) moves a protective barrier (3) between a rolled-in, open state and a rolled-out, closed state. First tracks (9a, 9b) are arranged on side frames (19a, 19b) at each side of the barrier. Curved or spiral tracks (13a, 13b) are arranged at each side of the barrier (3) to hold the barrier (3) in the rolled-in state. A drive unit (6) connected to the protective barrier (3) moves the barrier (3) between...