US Patent 9884723 Spiral conveyor system

A spiral conveyor system with a positive drive system includes a rotating drum with at least one rib that is attached to drum. The rib includes a drive face for engaging a conveyor belt. The height of the rib above of the surface of the drum varies along a length of the drive element. The rib may be directly attached to the drum or may be a part of a drive element attached to the drum. The conveyor belt includes at least one belt surface configured to engage the at least one drive face, such as a protruding tab with a flat surface.