The present invention is in the nature of an improvement over mixers of granular material of the general type disclosed in U.S. Pat.  No.  3,638,920 and others.  These prior art devices utilize screw or auger conveyors to effect mixing of material in a hopper-like container, some including rotary agitator vanes or paddles in combination with auger conveyors. 
An important object of this invention is the provision of a feed mixer that is highly simplified in structure, that is efficient in its operation, and which utilizes a discharge control arrangement which is effective in preventing leakage of finely ground material from the container.