Abstract: A torsion spring counter balancing mechanism for a stacking panel shutter door includes one or more torsion springs one end of the or each torsion spring is fixable to a drive transmission shaft of the stacking panel shutter door, the drive transmission shaft being adapted to raise and lower the or each shutter of the stacking panel shutter door; and the other end of the or each torsion spring is fixable to a separate rotatable member of the stacking panel shutter door; whereby the mechanism is provided with means adapted to enable both the drive transmission shaft and the rotatable member to rotate, during opening and closing of the stacking panel shutter door, in such a manner as to cause respective ends of the or each torsion spring to travel at different speeds during the opening and closing sequence, which permits to keep the same size motor when panel numbers are varied.

Abstract: A fire shutter adapted to close off an area comprises a shutter curtain movable from an up position to a closed position, wherein the shutter curtain closes off the area when in the closed position, and at least one retractable guide, movable from a retracted position to an extended position and having a camber. The shutter curtain engages the at least one retractable guide as the shutter curtain moves from the up position toward the closed position, biasing the at least one retractable guide to the retracted position, and in the closed position the shutter curtain engages the camber and allows the at least one retractable guide to move to the extended position. The shutter curtain can also comprise front slats and rear slats, and an insulation package can be deployable from a non-deployed position to a deployed position within a space between the front slats and the rear slats.