Patent ID: 8177737

Claim:
A drainage device comprising: an internal chamber; at least one inlet port and at least one outlet port communicating with the internal chamber; at least one shutter disposed at least in part in the internal chamber; at least one first valve seat associated with the inlet port, the shutter being configured to bear against the first seat in order to isolate the inlet port from the outlet port when the pressure difference between the inlet and outlet ports is less than a predetermined first opening pressure; and at least one flow constriction associated with the outlet port, the shutter being configured to shut said constriction, while allowing a minimum, safety flow to pass at a rate that is greater than or equal to 2.5 mL/h even in a maximally-shut position, referred to as a “closed” position, which position is reached for pressure differences between the inlet and outlet ports that are greater than or equal to a predetermined closure pressure.