Give it a few more days, the rats will begin to starve. They might have a bit of food stored but it will only last a few days. Just keep those door springs as tight as you can and still let the little chicken work the treadle.
If you ever see that the door isn't opening, that means the feeder got swarmed and you have some dead rats inside, smothered. Rarely happens, usually the rats leave before they figure out ten of them will open the feeder but the first time a rat dies inside the feeder will be the last time they touch that feeder. Like everyone says, they are smart.
If you ever do find dead rats blocking the door, pull the feeder up off the bracket, dump the feed on a tarp or into a big bucket, then once the feed in the lower feed tray is shaken out there will be enough room to shake the dead rats out. Dump them in a trash can with six inches of water just in case they are just stunned and you caught them before they died. Rats can jump out of an empty barrel but with a bit of water they can't. Clean out the feeder with bleach water and you are good to go.
This has only ever happened on commercial farms with thousands of rats, each feeder got swarmed in turn. First day, one angry customer called me. Second day, he called back, they had swarmed another feeder. Third day, he called back ecstatic, the rats were leaving the cleaned feeders alone and choosing a new feeder to swarm. They went through all 24 feeders. At the end of the week either all the rats had smothered themselves or left.