a sorter has a tray moving cam construction which is an assembly of molded plastic parts including an elongated noncircular shaft and a pair of similar cam parts turned 180 °, end - to - end and having a hub slidably applicable to the shaft from opposite ends , or over opposite ends of a supporting core shaft , the hubs or the core shaft having an axial opening conforming with the non - circular shaft keying them together for rotation , and complemental cam segments on the hubs combine to provide a complete cam profile when the cam parts are applied to the shaft or core shaft in opposite axial directions from opposite ends of the shaft . the shaft and cam parts may have complemental interengaging portions locking the cam parts in operative assembled relation on the shaft against relative axial movement , or the cam parts and the core may have complemental inter - engaging portions locking the cam parts in assembled relation on the shaft or the core shaft but permitting longitudinal movement of the assembled cam or cam and core on the shaft .