Automatic flooding protection for underground ventilation ducts

Apparatus for preventing downward flow of substantial amounts of surface water into an underground ventilation duct communicating upwardly to a surface opening, comprising:

• a support having a top opening for fluid communication with said surface opening, a support floor, and a lower opening in a portion of the support lower than the top opening and higher than the support floor for fluid communication with a proximate portion of said ventilation duct,
• said support supporting one or more sets each comprising a vertically mounted seat and paired water buoyant gate;
• said seat upwardly demarcating in said set, on a side of the seat proximate said ventilation duct, at least one proximate passageway portion for fluid communication with said ventilation duct through said lower opening, and demarcating, on an opposite side of the seat, at least one distal passageway portion distal from said lower opening in fluid communication with said top opening of said support,
• said buoyant gate including a pivotation mount and being:
• positioned lower than said seat in said set,
• normally disposed horizontally,
• of sufficient size to block said proximal passageway portion, and
• responsive to water rising in said support by floatingly pivoting upwardly until engaging said seat on at least an end portion of the gate distal to said pivotation mount, blocking said proximate passageway portion.

Apparatus for preventing downward flow of substantial amounts of surface water into an underground ventilation duct communicating upwardly to a ground surface opening, comprising:

• an enclosure comprising a floor, a top opening, opposed side walls, and opposed first and second end walls between the side walls, the second end wall terminating higher than the floor to form an opening in a lower portion of the enclosure, said walls and floor being joined,
• said enclosure being adapted to nest within said surface opening,
• said opening in said lower portion being situated for ventilation communication with a proximate portion of said ventilation duct,
• said enclosure supporting:
• a plurality of paired seat and water buoyant gate sets,
• each seat being mounted vertically relative to a portion of a passageway under said seat for fluidly communicating beyond such portion to said top opening and to said lower opening,
• each said buoyant gate including a pivotation mount and being positioned lower than said seat in the set of which it is part, being normally disposed horizontally, being of sufficient size to block said passageway portion, and being responsive to water rising in said enclosure by floatingly pivoting upwardly until engaging said seat on at least an end portion of the gate distal to said pivotation mount, blocking said passageway portion,
• a trough under a portion of said top opening over said lower portion opening, and
• a sloped surface into which said trough flows water received through said top opening, said sloped surface declining in a direction to flow water away from said lower portion opening.

A method of preventing downward flow of substantial amounts of surface storm water into an underground ventilation duct communicating upwardly to a surface opening, comprising

• interposing between said surface opening and said ventilation duct an enclosure upwardly open in fluid communication with said surface opening and opening in a lower portion of said enclosure for venting communication through said enclosure with a proximate portion of said ventilation duct,
• providing at least one seat and water buoyant gate set in said enclosure, each seat being mounted vertically relative to a portion of a passageway under said seat for fluidly communicating beyond such portion to said top opening and to said proximate portion of said ventilation duct, each said buoyant gate including a pivotation mount and being positioned lower than said seat and said passageway, being normally disposed horizontally, being of sufficient size to block said passageway, and being responsive to water rising in said enclosure by floatingly pivoting upwardly until engaging said seat on at least an end portion of the gate distal to said pivotation mount, blocking said passageway,
• said enclosure holding water when a gate of a set engages a seat of the set, said enclosure allowing ventilation between said top opening and said ventilation duct so long as rising water in said enclosure has not closed the gate on the seat in every set.

A method for providing less restrictive airflow through a support structure interposed in a underground ventilation duct system between a ventilation duct and a surface opening of the ventilation duct to prevent downward flow of substantial amounts of surface water into the ventilation duct, said support structure having a top opening for fluid communication with said surface opening, a support floor, and an opening in a lower portion of the support higher than the support floor for fluid communication with a proximate portion of said ventilation duct, said surface opening having a fixed length between selected opposing sides of the opening comprising:

• providing in said structure one or more sets each comprising a seat and a paired water buoyant gate normally disposed perpendicular to said seat,
• arranging each said set in said support to provide airflow from said lower portion opening to said surface opening that is a nominal fraction of the airflow from said ventilation duct to said surface opening absent presence of said apparatus, said fraction having the numerator 1 and a denominator which is the sum of 1 plus the number of said sets,
• the seat of at least one set being mounted under said top opening spaced from one of said opposing sides a distance nominally equal to said fraction applied to said fixed length,
• said buoyant gate of a set having a seat engagement height nominally equal to said fraction applied to said fixed length, being positioned lower than said seat, and responsive to water rising in said support by floatingly upwardly until engaging said seat and blocking passage for air flow under said seat.

An apparatus to block flow of substantial amounts of surface water into an ventilation duct communicating from underground to a structure below grade level comprising a floor and an opening at grade level, said apparatus comprising:

• a seat support adapted to be secured within said structure below said grade level opening,
• a seat supported vertically by said seat support, said seat being secured to transect a lower portion of said structure under said grade level opening at a location substantially less restricting airflow between said grade level opening and said ventilation duct, said seat defining within said structure on one side of the seat a portion proximate said ventilation duct and on the other side of the seat a portion distal to said ventilation duct, said seat having an upper inner margin defining a top of an entrance communicating said side proximate said ventilation duct and said side distal to said ventilation duct,
• a water buoyant gate having a seating surface sized to engage said seat, said buoyant gate being normally horizontally disposed within said structure in said distal portion lower than said entrance and being pivotally movably mounted with respect to said seat, said buoyant gate being responsive to water rising in said structure by floating relatively upwardly for moving said buoyant gate until said buoyant gate engages said seat, whereby said buoyant gate obstructs water entering said structure through said opening from passing through said horizontally oriented entrance.

An apparatus to prevent flow of surface water into an ventilation duct communicating from an underground tunnel to and exiting in a structure below grade level comprising a floor and an opening at grade level, said apparatus comprising:

• a support assembly mounted in said structure and having upper and lower extremities,
• a shelf fastened to said support assembly between said upper and lower extremities and extending horizontally in the direction of the longest distance in opposing sides of said opening, said shelf defining below it a horizontally oriented flow passageway in the structure extending from said exit of said ventilation duct an extent along said direction effective to substantially less restrict airflow between said opening and said ventilation duct, said horizontally oriented flow passageway extending a distance equal to about half the longest distance in opposing sides of said opening,
• a seat vertically mounted to said support assembly below said shelf around said horizontally oriented flow passageway defining an entrance of the horizontally oriented flow passageway into said portion of the structure beyond the shelf, and
• a buoyant gate which floats in water, said buoyant gate being pivotally mounted pivoting about an axis perpendicular to the direction of said longest distance and responsive to water rising in said structure by floating relatively upwardly until said buoyant gate engages said seat, said buoyant gate being of sufficient size to block said horizontally oriented passageway and thereby materially prevent water flowing into said structure from passing through said horizontal passageway into said ventilation duct thence into said underground tunnel.