Patented and am now manufacturing a new kind of butterfly valve. The design was geared towards a plastic valve that would be used on an outlet to a storage tank. where the pressure would always be in one direction only, and the valve had to be leak free for long periods of time. A further criteria was that the spindle seal shouldn't be under pressure - i.e. the spindle had to be on the outlet side of the valve.  The resulting geometry caused a standard butterfly valve to be self opening due to the pressure imbalance on the disk. My design has overcome this and in fact I have a valve that is now self closing. The design is such that the valve could be self closing or neutral.
I am curious as to what the patented features are. Traditional double-offset butterfly valves are self-closing due to dynamic torque, with the torque peak occurring at about 75 degrees open.  With the shaft upstream, they would be self-closing at the seat due to the moment generated by the pressure against the back of the disc and the stem offset.  The favored flow direction for a double offset butterfly is with the shaft downstream and the disc /seat upstream, but this is mostly to take the pressure off the packing while the valve is closed. 

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