Approximately three years before Peress introduced the oil-filled hinge in 1929, Bernhard Dräger patented a cardan-type joint that formed a seal with two diaphragms. It is doubtful whether the joint worked at greater depths, as here, the pressure difference between the inner and outer atmosphere would have to be absorbed by the seals. Patent 460312 does not go into much detail about the effectiveness of the invention.
Therebreathersite was founded by Jan Willem Bech in 1999. After a diving career of many years, he decided to start technical diving in 1999. He immediately noticed that at that time there was almost no website that contained the history of closed breathing systems. The start for the website led to a huge collection that offered about 1,300 pages of information until 2019. In 2019, a fresh start was made with the website now freely available online for everyone. Therebreathersite is a source of information for divers, researchers, technicians and students. I hope you enjoy browsing the content!