Used Feeders Feeders are designed to regulate or make uniform the flow of ingredients into a process from a bin or bulk hopper. Screw feeders such as Acrison, have a hopper that is agitated to prevent clumping, and a screw feeder to provide the uniform feed flow. Belt or apron feeders are conveyor belts that regulate the feed flow. Weigh belt feeds used weigh scales under the belt to regulate the ingredient addition to the process by weight. Pan feeders or vibratory feeders also provide a uniform flow into the process, however in this type of feeder the product is moved along by the vibration of the pan. Rotary feeders or star feeders are actually star valves, or rotary valves. The rpm of rotor inside the valve housing regulates the feed into the process.