POSITIVE DISPLACEMENT SORTER

A positive displacement sorter includes a plurality of interconnected parallel slats defining an endless web that travels in a longitudinal direction. The web has upper and lower runs and transition sections between the upper and lower runs. An upper surface of the upper run of the web defining an article-conveying surface. A plurality of pusher shoes travels along at least one of the slats in order to laterally divert articles on the conveying surface. Each of the shoes has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface is capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters selectively diverts at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails in a diverting state. A propulsion system propels the web. The propulsion system includes at least one drive assembly engaging a lower surface of the upper run or an upper surface of the lower run.