I know of a few types of vibrating feeder, all of which work on the same principle: Release of static friction.
Static friction is why it's hard to start something moving, but once you've started, it goes much easier. Like sliding a heavy box across the floor.. You push and push and finally it just starts going and it's suddenly a lot easier. Here's a link:
hyperphysics.phy-astr.gsu.edu you exert a force strong enough to break static friction, the item won't move.
If you have a pile of stuff, be it pills, rocks, or dirt, the pull of gravity tries to get the pile to flatten out, but all the irregularities (even super-tiny ones) hold the items in a pile because of the combined static friction of all those things touching each other.
You can take stuff off of the bottom and edges and, after a while, the pull of gravity will be strong enough to overcome static friction somewhere and suddenly the pile (or a lot of it) collapses. But who wants that job?
One way to ease the problem is by using vibration. Even a tiny bit of vibration can cause the pile to jiggle enough so that the pieces turn and jostle. This eases the friction two ways: One is that sometimes the pieces touch each other on more smooth parts so they have less static friction and can spread out. The other is that pieces in the air (even momentarily, due to vibration) are easier to move... Which is less static friction. By moving them with vibration, you kinda 'break' the static friction.
In the end, the items on the bottom of the pile spread out more easily, making more room for items on the next layer up, and the pile begins to spread out.
If the feeder is a side-feed, then 3 sides of the bin hold the pile, the fourth isn't there and the stuff moves that direction. Some feeders, generally for rocks, gravel, and fill, have slots in them so that smaller items slide out the bottom and into a small-item bin, but larger ones continue moving down the chute to a bin for large items.
I once saw a device for moving heavy objects across a flat surface. It was just a plate that vibrated a very very tiny amount at a very high frequency, but that was enough to break the friction and you could push hundreds of pounds with your hands.
Static friction is why it's hard to start something moving, but once you've started, it goes much easier. Like sliding a heavy box across the floor.. You push and push and finally it just starts going and it's suddenly a lot easier. Here's a link:
hyperphysics.phy-astr.gsu.edu you exert a force strong enough to break static friction, the item won't move.
If you have a pile of stuff, be it pills, rocks, or dirt, the pull of gravity tries to get the pile to flatten out, but all the irregularities (even super-tiny ones) hold the items in a pile because of the combined static friction of all those things touching each other.
You can take stuff off of the bottom and edges and, after a while, the pull of gravity will be strong enough to overcome static friction somewhere and suddenly the pile (or a lot of it) collapses. But who wants that job?
One way to ease the problem is by using vibration. Even a tiny bit of vibration can cause the pile to jiggle enough so that the pieces turn and jostle. This eases the friction two ways: One is that sometimes the pieces touch each other on more smooth parts so they have less static friction and can spread out. The other is that pieces in the air (even momentarily, due to vibration) are easier to move... Which is less static friction. By moving them with vibration, you kinda 'break' the static friction.
In the end, the items on the bottom of the pile spread out more easily, making more room for items on the next layer up, and the pile begins to spread out.
If the feeder is a side-feed, then 3 sides of the bin hold the pile, the fourth isn't there and the stuff moves that direction. Some feeders, generally for rocks, gravel, and fill, have slots in them so that smaller items slide out the bottom and into a small-item bin, but larger ones continue moving down the chute to a bin for large items.
I once saw a device for moving heavy objects across a flat surface. It was just a plate that vibrated a very very tiny amount at a very high frequency, but that was enough to break the friction and you could push hundreds of pounds with your hands.