venturi region 28 fig4 the air entrained material is then conveyed by conduit 22 from a venturi region outlet to replenish the material in the tank 14 the material particles settle in the tank and exhaust air flows through conduit 30 to the diffuser 26 fig3 and 4 illustrate some details of the rotary feeder and air lock 20 and venturi region 28 the rotary feeder and air lock portion has a cylinder 32 rotatable about an axis 49 fig8 in a counter clockwise direction as shown by the arrow in fig3 the cylinder 32 has a plurality of wedge shaped pockets such as 34 which take on product from the hopper 18 when opening upwardly and release product downwardly into the venturi region after about one half revolution the cylinder fits within cylindrical sidewalls sufficiently closely to prevent any significant air passage at around a five o 39 clock position the material falls from the wedge shaped segments and is funneled by seed ramps into the venturi region 28 below it is important to be able to purge the tank filling system for example prior to an extended period of non use or preparatory to utilizing the air cart with a different agricultural product a valve 36 is pivotable about a pivot 38 from the horizontal or 9 o 39 clock position of fig5 clockwise to the 12 o 39 clock position of fig6 fig5 shows the valve in the normal tank filling position where air flow from the venturi nozzle 40 joins with agricultural material from the hopper 18 and proceeds through.