A conveyor mechanism comprised of a guide rail defining a path along which articles are to be conveyed, a drive mechanism supported on said guide rail and having a frictional drive wheel engaged with said guide rail, said drive wheel and said guide rail having a constant cross-sectional area of engagement along said path, said guide rail being formed with at least an ascending section extending upwardly from a horizontal section, and means for providing an increased reactive force of said drive wheel along said path only when traveling along said ascending section.