US Patent 11306835 Flapper valves with hydrofoil and valve systems

Pivot valves have a valve seat and a valve closure mounted for pivoting movement through a closure chamber in a passage. The pivot valves may be selectively set in a check mode and an open mode. Flapper valves have a hydrofoil extending from a flapper. Valve assemblies comprise the pivot valves and flapper valves and have an open condition, a check condition, and a shut-off condition.