Rotary valves by definition involve a circular movement. Actually two main circular movements on perpendicular axises. The transmission takes flexible joints, which for many years came in form of double-T-joints. I think the German term is Rollglieder, where Roll is obvious and -glieder means joints. We have seen ball&socket joints from especially GDR and Czech makers. And now mini-balls appear being what the best rotary instruments come with.
Today I saw a variant, which was new to me. The maker still exists as a repair shop and dealership, but apparently doesn’t make instruments any longer:
Source:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0677025371
Klaus