Plenum chamber flow restrictor and check valve

摘要

The flow restrictor (10) comprises a resilient and flexible porous membrance (12) over an air inlet port (18). In one embodiment an impervious member (130) is attached to the lower surface of the membrane over the air inlet port. The membrane balloons due to air flow through the inlet which greatly increases its effective cross sectional area as air flows into the plenum chamber. When air flow stops gravity and/or air pressure from the container forces the membrane against the seat (118) and the effective cross section of the membrane is reduced to approximately that of the inlet port.