Abstract: A pilot controlled membrane valve for ventilating containers or the like comprises a valve housing having a first valve seat between the inlet and outlet of the housing. First valve means, movable between a closed position engaging said first valve seat and an open position, include a first membrane extending transversely through the housing and defining with the latter to one side of the first valve seat a valve chamber, which is connected by an overpressure passage means to the inlet. The valve includes further a pilot valve having a second seat, second valve means including a second membrane and being movable between a closed position engaging the second valve seat and an open position, a second outlet, means biasing the second valve means to the closed position and chamber means under atmospheric pressure surrounding the biasing means, in which the cross-section of the second valve seat and that of the second outlet is greater than the open cross-section of the overpressure passage means.

Abstract: A pilot controlled membrane valve for ventilating containers or the like comprises a valve housing having a first valve seat between the inlet and outlet of the housing. First valve means, movable between a closed position engaging said first valve seat and an open position, include a first membrane extending transversely through the housing and defining with the latter to one side of the first valve seat a valve chamber, which is connected by an overpressure passage means to the inlet. The valve includes further a pilot valve having a second seat, second valve means including a second membrane and being movable between a closed position engaging the second valve seat and an open position, a second outlet, means biasing the second valve means to the closed position and chamber means under atmospheric pressure surrounding the biasing means, in which the cross-section of the second valve seart and that of the second outlet is greater than the open cross section of the overpressure passage means.