US PATENT SUBCLASS 405 / 144
.~.~.~ Door or bulkhead

Current as of: June, 1999
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405 /   HD   HYDRAULIC AND EARTH ENGINEERING

132  DF  UNDERGROUND PASSAGEWAY, E.G., TUNNEL {6}
138  DF  .~ Boring {4}
141  DF  .~.~ Shield {6}
144.~.~.~ Door or bulkhead

DEFINITION

Classification: 405/144

Door or bulkhead:

(under subclass 141) Method or apparatus including either a movable closure for closing off a portion of the entrance into the shield or a partition adjacent the face of the tunnel which allows the face region to be pressurized.