Variable rate feeder

A variable rate feeder (often shortened to belt feeder, or simply feeder) is a piece of industrial control equipment used to deliver solid material at a known rate into some process.
Belt feeders vs. belt conveyors.
In both form and function, belt feeders are essentially short belt conveyors. There are a few key areas in which the two differ, however:
Transport mechanisms.
A number of different techniques and transport mechanisms are used, but these broadly split into these categories, in descending order of accuracy:
Any of these may be combined with subsequent checks from beltweighers or (in the case of grains, powders and liquids) flowmeters to provide a more accurate flow of material.