Vibrating conveyor belts and feeders

Initially found on makezine.com: http://blog.makezine.com/archive/2010/09/vibrating_conveyor_moves_objects_wi.html

I've seen these before when visiting a company that makes robotics assembly systems. They vibrate parts in a matter that moves them along. This concept is often used in round feeders that orient and sort small parts. The original poster on makezine.com guesses that it employs slip stick motion, which uses the difference between static and sliding friction.

Here's a straight conveyor:


Here's a tablet feeder. Notice how incorrectly oriented parts are spilled over the edge into the middle of the feeder to randomly. At the company I visited (I can't remember the name), they also had ones with custom air-based orienting mechanisms for this specific part. A stream of air would be pointed at the parts as they move along (they had already been sorted into a straight line). If a part was upside down, the air would catch on a piece of the part and it would be blown off the line to start over. Acceptable parts did not have air-catching features and continued on.


Here's another application. This is used to sort different sized objects at a recycling plant. Smaller objects fall through holes as they continue along the belt, while larger objects move on over. This of course, could not be done with a belt. (However, maybe a belt with long strips down it lengthwise, or multiple thin belts? Larger objects would not fit through the gaps between the belts, but smaller objects would. The issue might be long and slender objects, like thin wood strips. They would still be able to fit through.)