Patent attributes
A spiral conveyor for positively driving a hinged, modular conveyor belt along a helical path. The spiral conveyor includes a rotating cylindrical tower with parallel drive members extending from the bottom to the top of the tower on its periphery. Each drive member includes an outwardly protruding ridge extending from the bottom to the top of the tower for engaging the inside edges of the belt. In one version, the ridges at the entrance end of the spiral are movable to provide a gradually decreasing spacing between consecutive ridges as the belt enters the spiral. In another version, alignment elements at the entrance end align belt-edge structure with the tip ends of associated ridges to help engagement. In another version, the ridges at a discharge end of the tower are retractable between an extended position driving the belt and a retracted position.