Image Number 4 for United States Patent #4391528.
A silo for mixing dried and powdery materials such as cement. A number of discharge apertures positioned at different places at the bottom of a mixing silo are connected by conduits to a common receptacle such as an homogenizing silo. A flow control gate is coupled to each discharge aperture to allow material flow to the receptacle to be controlled. Three modes of operation are disclosed: a single flow-mode wherein the flow control gates are opened sequentially one at a time, a dual-flow-same-rate mode wherein pairs of flow control gates are sequentially opened to the same extent, and a dual-flow-different-rate mode wherein pairs of flow control gates are sequentially opened to different extents. A level sensor in the homogenizing silo is connected to a level indicator circuit which emits level indicator signals indicating whether the material in the receptacle is rising or falling, thereby allowing automatic adjustment of the material flow rate into the receptacle up to a predetermined cut-off level. A flow control gate selector circuit connected to a variable timer and to a mode control circuit selects which flow control gates will be opened, and an alternator for every pair of flow control gates is connected to the mode control circuit and to the flow control gate selector circuits to vary the flow rate during different alternator periods when the dual-flow-different-rate mode is selected.