When materials in drawn from a hopper or bin to a conveyor, an automatic feeder should be used (unless the material in dry and free running e.g. grain). The satisfactory operation of any conveyor depends on the material being fed to it in an even and continuous stream. The automatic feeder not only ensures a constant and controlled feed, irrespective of the size of material, but saves the expense of a man who would otherwise be required at the feeding point. A commonly used simple feeder would be a reciprocating plate feeder consisting of a plate mounted only wheels and forming the bottom of the hopper. The plate is moved by connecting rods from cranks or eccentrics. But a negative point of this feeder is that it is not self clearing.
Vibrating Feeders
These type of feeders consists of an inclined downward slight and vibrated
• By a high speed unbalanced pulley
• By electro magnetic vibration from one or more solenoids
• By the slower pulsating secured by mounting the plate on reward incline real springs.
Electric Vibrating Feeders
These operate magnetically with a large number of short strokes (7200 /min from on AC in small sizes and 3600/min from a pulsating DC in the larger sizes). It is built to feed a few pounds per min to 1250 tones per hour and will handle any material that doesn't adhere to the pan. It is self cleaning, instantaneously adjustable for capacity and controlled from any point near or remote. It is usually supported from above with spring shocks absorbers or from below with similar spring foot supports. A modified form can be set to free a weighed constantamount hourly for process control.
The Ratio Feeder
It is a fight-conveyor type of unit having 2 converging sets of flight moving lengthwise along its bed. At the inlet end, the flights provide a wide carrying surface, but as they approach the narrow outlet throat section they meet together to reduce the carrying width. This construction in possible in the use of welded link chain, which is flexible horizontally to permit the converging and flexible vertically to permit the driving over the pocket wheel that propels the chain. Such a feeder will accept a large, sudden surge of material will carry it away from the delivery means and will then "ration" it out onto a belt at a uniform rate.
