Reducing drag on the web of a positive displacement sorter

A positive displacement sorter, comprising:

• a web comprising a plurality of parallel slats interconnected at their opposite ends with chain assemblies in an endless loop and a plurality of pusher shoes, each traveling along at least one of said slats;
• a driven sprocket assembly and a non-driven sprocket assembly, each of said sprocket assemblies comprising at least two sprockets on a shaft each for engaging one of said chain assemblies, said sprocket assemblies supporting said chain assemblies at opposite ends of said web wherein the sprockets of said non-driven sprocket assembly lock to said shaft such that teeth of said sprockets are generally in line with each other and said sprockets of said non-driven sprocket assembly rotate together;
• and
• side thrust wheels on opposite sides of said web.

A pair of chain assemblies for use with a web comprising a plurality of parallel slats interconnected at their opposite lateral end portions with said chain assemblies in an endless loop and a plurality of pusher shoes, each traveling along at least one of said slats, said pair of chain assemblies comprising:

• first and second endless chains;
• a plurality of vertical support wheels attached to each of said chains for supporting one lateral end portion of the web, wherein one of said support wheels is positioned at each of said slats;
• and
• a plurality of side thrust wheels attached to each of said chains and rotating on axis that are perpendicular to the axis of rotation of said support wheels, said side thrust wheels for resisting lateral movement of said web;
• wherein no more than one of said side thrust wheels is provided at each of said slats.