A bi-fold door is equipped with door lifting devices operated with a reversible electric motor drive to selectively open and close the door. The door lifting devices have winches operable to wind and unwind elongated webs connected at one end to rotatable members of the winches and anchored at the opposite end of the door. Anchors mounted on the door have adjustable sleeves operable to take up slack of the webs. The door moves at an increasing rate of speed from its closed to open positions and a decreasing rate of speed from its open to closed positions.