torpedo freewheel hub, which preceded eight years of construction work and was already so mature that it has barely changed over many decades, the company grew rapidly. By 1905, they were employing 1,800 employees and had a production of 382,000 torpedo hubs. Rapid growth Sachs's father-in-law, Wilhelm Höpflinger, received a patent for the first usable ball cage still used today in the ball bearing industry. Fichtel & Sachs was one of the world's leading companies for rolling bearings, where Sachs registered more than 100 patents, and bicycle hubs before the First World War. A further development boost brought the conversion of multiple of the factories to armaments during the war, when the number of employees rose from 5000 to 8000. In 1911, Karl Fichtel died and in 1912, in order to counter the high customs duties, Sachs acquired a factory in Černýš (Tschirnitz) on the river Ohře (Eger) in Bohemia. Somewhat later, a subsidiary factory was built in the United States. During the four years of the war, the number of Fichtel & Sachs employees increased from 3,000 to around 8,000. In addition to hubs and ball bearings of all kinds, armour products were manufactured in Schweinfurt. Today's main plant (North Plant), between Hauptbahnhof and Ernst-Sachs-Straße, is based on a weapons and projectile factory, which Fichtel & Sachs built here first, in what is now the eastern plant area. In 1919, the first works council was elected at Fichtel and Sachs, one year before the Works Councils Act () was implemented nationwide. In the inflation year 1923, the transformation into a public company took place. A holding company of the company, the Sachs GmbH, was founded in the same year in Munich. At the turn of the year 1927/1928, the number of employees rose to a provisional high of 9,026. The hub production accounted for 67% of the total production, the remainder fell on rolling bearings. Sachs founded a company pension, the Ernst-Sachs-Hilfe. Interwar period In 1929, on the eve of the great recession of 1929/30, Ernst Sachs sold the rolling bearing division with 3000 coworkers, which made about half of the enterprise, to the Swedish conglomerate SKF. This merged with the Schweinfurt Fries & Höpflinger AG, the Maschinenfabrik Rheinland from Krefeld, the Riebe-Werke and the rolling bearing production of the German weapons and munitions factories DWM, both in Berlin, to the United Ball Bearings AG (VKF, from 1953 SKF