A butterfly valve that has a metal valve seat and a metal vane, providing fluid-tight metal-to-metal sealing. The valve seat is annular and has an inner circular line surface for engagement with the metal vane. The vane is a conical angle-transported disc, the upper face of the disc being angle-transported...http://www.google.fr/patents/US4037819?utm_source=gb-gplus-shareBrevet US4037819 - Butterfly valve having metal-to-metal sealing with conical angle-transported vane
Butterfly valve having metal-to-metal sealing with conical angle-transported ...
