ALEXANDRIA, Va., June 16 -- United States Patent no. 12,303,644, issued on May 20, was assigned to ANDREAS FAHL MEDIZINTECHNIK-VERTRIEB GMBH (Cologne, Germany).
"Speaking valve" was invented by Andreas Fahl (Cologne, Germany).
According to the abstract* released by the U.S. Patent & Trademark Office: "The invention relates to a speaking valve, having at least a housing and an actuation means for actuating the speaking valve, the actuation means having a distal pressure surface that has a first partial surface and a second partial surface, the first partial surface having a first average roughness (Ra1), and the second partial surface having a second average roughness (Ra2), the first average roughness and the second average roughness diff...