Abstract: A closure device for sealing an aperture of a storage container includes a trap frame, and a trap door connected to the trap frame for movement with respect to the trap frame. The trap door is movable between an open condition and a closed condition, and the trap door in the closed condition seals the aperture. The trap door includes a traversing frame having two side supports and multiple inner rollers extending between the side supports. A belt surrounds the traversing frame, and revolves around the traversing frame as the trap door moves between the open and closed condition. The belt is connected to the trap frame such that at least a portion of the belt remains stationary in relation to the trap frame while the traversing frame moves, and at least a portion of the belt moves in relation to the trap frame while the traversing frame moves.

Abstract: A closure device for sealing an aperture of a storage container includes a trap frame, and a trap door connected to the trap frame for movement with respect to the trap frame. The trap door is movable between an open condition and a closed condition, and the trap door in the closed condition seals the aperture. The trap door includes a traversing frame having two side supports and multiple inner rollers extending between the side supports. A belt surrounds the traversing frame, and revolves around the traversing frame as the trap door moves between the open and closed condition. The belt is connected to the trap frame such that at least a portion of the belt remains stationary in relation to the trap frame while the traversing frame moves, and at least a portion of the belt moves in relation to the trap frame while the traversing frame moves.