Patent ID: 8240331

Claim:
A negative pressure valve assembly comprising: a valve port assembly comprising a port and a flange substantially surrounding the port; and a valve comprising: a plate adapted to substantially cover the port and extending at least partially over the flange, the plate movable between a closed position, in which fluid may not flow through the port, and a plurality of open positions, in which fluid may flow through the port, the plate comprising: a minor edge; a major edge having a major edge length; and a plate biasing assembly stop located at a first position along the major edge, the first position more than 50% of the major edge length, as measured from the minor edge, the plate biasing assembly stop extending away from the major edge and comprising a stop plate; a hinge coupled to the plate along the minor edge, and rotatably coupling the plate to the flange; and a first plate biasing assembly rotatably coupled to the valve port assembly and contacting the plate biasing assembly stop to thereby supply a force to the plate that biases the plate towards the closed position, the first plate biasing assembly configured to exert a continuously increasing force to the plate that biases the plate to the closed position when the plate moves from the closed position to any one of the open positions.