Shielded vent port

A pressure-equalization vent port for equalizing the pressure on opposed sides of an enclosure wall, comprising:

• a frame shaped for fitting an opening in said wall, said frame having a conduit therethrough, said conduit having a top wall, a bottom wall, side walls and open ends;
• a plate disposed within said conduit, the periphery of said plate being sealingly joined to said walls of said conduit to prevent the passage of air between said plate and said walls, said plate being sloped with respect to said top and bottom walls whereby said plate has upper and lower surfaces, said plate having a large aperture therethrough;
• riser means in sheet-like form disposed against said upper surface of said plate at the periphery of said aperture for preventing flow of air through said aperture in a downward direction;
• and
• spindle means disposed for permitting movement of said riser means in a direction essentially perpendicular to the plane of said plate at said aperture and upwardly therefrom for flow of air through said aperture only in said upward direction when the pressure on that end of said conduit proximate said lower surface of said plate is greater than at the other end of said conduit by an amount sufficient to overcome the weight of said riser means, said spindle means being mounted to said port in a direction essentially perpendicular to said plate, said riser means having a closely fitting aperture for passage of said spindle means therethrough and said spindle means having an expanded upper end for limiting the upward excursion of said riser means.