US PATENT SUBCLASS 454 / 177
.~.~.~ Horizontal and vertical perforated or slotted ducts

Current as of: June, 1999
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454 /   HD   VENTILATION

173  DF  STORAGE AREA FOR PERISHABLES {2}
174  DF  .~ Harvested crop ventilation {2}
175  DF  .~.~ Having perforated or slotted duct contacting crop {4}
177.~.~.~ Horizontal and vertical perforated or slotted ducts {1}
178  DF  .~.~.~.~> With air pump

DEFINITION

Classification: 454/177

Horizontal and vertical perforated or slotted ducts:

(under subclass 175) Subject matter comprising two or more such conduits having a series of holes or elongated openings therealong for admitting fresh air into the ventilated space, one of the conduits extending parallel to and another perpendicular to the force of gravity.

(1) Note. A floor duct is considered to be horizontal and a vertically extending wall duct is considered to be vertical.