Abstract: A circular door operating method and apparatus comprising two pairs of arcked door leaves, two pairs of arcked fixed panels arranged so as to form an enclosure defining a cylindrical wind blocking compartment. Each door leaf is hinged at an end and releasably coupled at the other end to a hanger assembly traveling on a circular track by means of a pulley mechanism. When a door leaf is released from the hanger assembly to pivot about upper and lower hinge mechanisms for operation as a hinged door, not only the upper and lower hinge mechanisms firmly support the door leaf in place but also a control unit disables the sliding door operation, thus providing a quick and safe escape from the building in the event of an emergency.

Abstract: An automatic tension adjusting mechanism for a winding and transmitting device for an automatic door includes a base fixed in a casing; a mount for a transmission wheel around which a belt is wound; the mount being disposed on the base slidably in the right and left directions where the mount forces the belt to be strained and relaxed, and being resiliently energized at all times in one of the directions where the mount forces the belt to be strained; a saw-toothed stop part provided on the mount and adapted to extend in the right and left directions; and an engagement piece provided on the base and adapted to be moved between an engagement starting position with the stop part and a disconnection position from the stop part; a spring between the base and the engagement piece for energizing the engagement piece in a direction where the engagement piece is engaged with the stop part; a tapped hole made in one of the members of the base and the mount; and a bolt screwed into the tapped hole.