Importance

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Abstract

A roll-up door for enclosing a 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 pair of first pulleys are secured to opposite ends of the drum and one end of a flat belt is secured to each first pulley, while the opposite end of each belt is dead-ended on a fixed object. A counterbalancing weight is attached to the belt intermediate its ends and exerts a counterbalancing force to wind door panel on the drum. A pair of second pulleys are secured to opposite ends of the drum and located adjacent the first pulleys. One end of a second flat belt is secured to each second pulley, while the opposite end of each second belt is connected to the lower end of the door panel. A drive member, such as a hydraulic motor, is operably connected to the drum and operation of the motor in one direction will unwind the door panel from the drum and move the door to a closed position, while operation of the motor in the opposite direction will wind the door panel on the drum to move the door panel to an open position. A resilient member of spring is connected to the second belt intermediate its ends and exerts a biasing force to stretch the door panel.

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First Claim