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 underground ventilation duct includes one or more hinged panels closing a ventilation passage between the top and bottom of a support fitting in the shaft to prevent flooding. The panels have handles on their topside and pivotable arms on their underside and are liftable to an upright home position allowing ventilation, using tools to reach through grating covering openings on the shaft and lift the panel handles and after the panels are partially lifted, using reach tools to engage and lift the arms to press them again support sidewalls to exert lateral force on underside of the panels to complete upward rotation to the home position.

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 underground ventilation duct includes one or more hinged panels closing a ventilation passage between the top and bottom of a support fitting in the shaft to prevent flooding. The panels have handles on their topside and pivotable arms on their underside and are liftable to an upright home position allowing ventilation, using tools to reach through grating covering openings on the shaft and lift the panel handles and after the panels are partially lifted, using reach tools to engage and lift the arms to press them again support sidewalls to exert lateral force on underside of the panels to complete upward rotation to the home position.

Apparatus for allowing ventilation for underground tunnels through a ventilation shaft opening to atmosphere yet preventing underground flooding from surface waters pouring through the grate comprises an assembly that fits within the ventilation shaft and includes one or more panels mounted on a pivot axis and rotatable upwardly by human action raising the panel past a center point of the pivot axis to an upright inwardly leaning home position that allows ventilation as usual but by manual push or pull of the panels past the center point of the pivot axis lets the panels rotationally fall under gravitational impetus to a lower sealing position closing a passage between the ventilation shaft and atmosphere to prevent water from entering the underground tunnels.

Apparatus for allowing ventilation for underground tunnels through a ventilation shaft opening to atmosphere yet preventing underground flooding from surface waters pouring through the grate comprises an assembly that fits within the ventilation shaft and includes one or more panels mounted on a pivot axis and rotatable upwardly by human action raising the panel past a center point of the pivot axis to an upright inwardly leaning home position that allows ventilation as usual but by manual push or pull of the panels past the center point of the pivot axis lets the panels rotationally fall under gravitational impetus to a lower sealing position closing a passage between the ventilation shaft and atmosphere to prevent water from entering the underground tunnels.

Apparatus for allowing ventilation for underground tunnels through a ventilation shaft opening to atmosphere yet preventing underground flooding from surface waters pouring through the grate comprises an assembly that fits within the ventilation shaft and includes one or more panels mounted on a pivot axis and rotatable upwardly by human action raising the panel past a center point of the pivot axis to an upright inwardly leaning home position that allows ventilation as usual but by manual push or pull of the panels past the center point of the pivot axis lets the panels rotationally fall under gravitational impetus to a lower sealing position closing a passage between the ventilation shaft and atmosphere to prevent water from entering the underground tunnels.

Apparatus for allowing ventilation for underground tunnels through a ventilation shaft opening to atmosphere yet preventing underground flooding from surface waters pouring through the grate comprises an assembly that fits within the ventilation shaft and includes one or more panels mounted on a pivot axis and rotatable upwardly by human action raising the panel past a center point of the pivot axis to an upright inwardly leaning home position that allows ventilation as usual but by manual push or pull of the panels past the center point of the pivot axis lets the panels rotationally fall under gravitational impetus to a lower sealing position closing a passage between the ventilation shaft and atmosphere to prevent water from entering the underground tunnels.

The disclosure discloses an underwater cover device, comprising a cover body and a gas source connected to the cover body. The cover body has an open end face directed towards an underwater surface, forming a gap between the open end face and the underwater surface. A rotating water flow is formed inside the cover body, and the gas source supplies air into the cover body. The rotating water flow prevents the air from escaping through the gap between the cover body and the underwater surface, thereby forming a water-free space on the underwater surface. This device is applicable to underwater surfaces at any inclination angle and can effectively establish a water-free space even if there is a gap or no contact between the underwater cover device and the underwater surface, demonstrating excellent applicability.