Patent ID: 7214130

Claim:
An air passage opening and closing device comprising: a plurality of air passages; and two air passage opening and closing doors respectively capable of being rotated round a rotary shaft so as to open and close the plurality of air passages, the air passage opening and closing device further comprising a fork-shaped spring means arranged at a position between a rotary shaft of one of the air passage opening and closing doors and a rotary shaft of the other of the air passage opening and closing doors, wherein a spring load of one arm portion of the fork-shaped spring means acts on one of the two air passage opening and closing doors so that a load caused by the door self-weight or a load caused by wind pressure can be canceled, and a spring load of the other arm portion of the fork-shaped spring means acts on the other of the two air passage opening and closing doors so that a load caused by the door self-weight or a load caused by wind pressure can be canceled.