What is the function of the chain in a chainbar?

Thank you in advanced!

It acts as a four bar to keep the two nonrotating bars parallel. Think of the two length of chain as two arms of a four bar linkage.

The major benefit of a chainbar over a 4 bar is that you can only get 160-170 degrees of travel out of the 4 bar, and you can get well over 180 degrees out of a chain bar. The trade off is you lose some strength and add a little complexity.

If your limited on metal, a chain bar might be a better option too.

You can build a four bar to travel more than 180 degrees.

The chain is responsible for making the raising end parallel to the ground.

Yep, but not as compactly.