It's going to be hard to explain. The spring or springs push on the three levers which in turn pull on the bolts which pulls the steel plate against the fiber disk and towards the pulley casting. Press on the button and the levers move to loosen the three bolts .
That was a short but precise explanation. Thank you very much. After again studying my PTO, I now can pretty much conceptualize how this works. Very ingenious.
I still cannot see how the bearing drives the pto. I understand how the PTO is attached to the bearing (set screws and snap ring hold it in place). And I undestand how the bearing is attached to the crankshaft (bearing is attached to the collar which is attached to the crankshaft). But with the pto off, I can spin the bearing without the crankshaft spinning. What makes that bearing lock up so that its outer diameter spins and drives the PTO?
Now that I understand this thing, I think most of my problem is associated with the bearing not being flush with the end of the crankshaft. It is too far in. I'll fix that and also keep working on getting those last two set screws out of the pto but the inner cone shaped one is sheared off and the outer one has the hex socket completely destroyed by a previous owner.