Bi-fold door construction

An industrial door comprising a pair of side panels (5) and a pair of central panels (6) with each central panel having approximately twice the horizontal width of a side panel. The upper end of one side edge of each side panel is pivoted to the jamb of a doorway (2), while the upper end of the opposite side edge of each side panel is pivoted to the adjacent side edge of a center panel. A track (30) is located above the doorway (2) and a pair of trolleys (24) are mounted for movement on the track (30). Each trolley (24) includes a vertical pivot shaft (23) which is connected to a center panel (6) at a location midway of the width ofthe panel. A drive mechanism is mounted in the header (4) and includes an endless cable (31) which is connected through a torque arm (33) to the shaft of each trolley. Operation of a reversible drive mechanism in one direction will operate through the cable (31) to move the panels to a closed position where they enclose the doorway (2), while operation of the drive mechanism in the opposite direction will move the panels to the open or folded position. Flexible weather strips (70) can be connected between the side edge of each side panel and the door jamb, and similarly flexible weather strips (83) can interconnect the adjacent side edges of the side panels and center panels. To ensure that the panels fold in the proper manner, resilient shock cords (85) interconnect the adjacent side edges of the side and center panels.