| 摘要 |
<p>A roll-up door for enclosing the doorway in a building. The door comprises a horizontal rotatable drum mounted above the doorway and a flexible door panel is wound on the drum. A pulley is secured to each end of the drum and the first ends of a pair of belts are secured to each pulley and the belts are wound in overlapping relation on pulley so that adjacent convolutions of each belt are separated by convolutions of the other belt. The free end of one belt is dead-ended on the frame, and a counterbalancing weight is attached to the belt intermediate its ends and exerts a counterbalancing force to wind the door panel on the drum. The free end of the second belt is connected to the lower end of the door panel and a pair of springs are connected to the second belt intermediate its ends and the springs exert a tensioning force to stretch the door panel when the door panel is in the closed position.</p> |
