Importance

Loading Importance Indicators...

Abstract

Apparatus allowing ventilation through a ventilation shaft to an underground ventilation duct fluidly communicating through the ventilation shaft to an atmospheric opening of the shaft and on threat of flooding operable to prevent downward flow of surface water into the ventilation duct includes support sidewalls fitting in the shaft providing a ventilation passage between support top and bottom openings and a suspension member supported on opposed lateral sidewalls proximate the top opening holding one or more hinge connected panels that manually release to rotationally close the passage and are manually rotationally liftable to a home position allowing ventilation. A panel drain automatically closes when the panel is raised to home position. A releasable latching system between panel and a suspension member holder catches rising panels to hold them in home position. The suspension member may include end keys received in keyed supports so a specific panel faces a specific sidewall.

Loading the Abstract Image...

First Claim