Krone KR130 Tensioner Question

I recently bought an older KR130 in decent shape. The only significant problem was a bearing on the tensioner shaft had seized and crunched one side of the elevator chain into the axle beam. I removed the shaft, replaced both bearings, shims, washers, etc. and reinstalled it. It's clear that the chain tension can be adjusted by loosening the hex bolts and sliding the shaft up or down, but I can't figure what the function is of the large springs attached to the shaft brackets. Once the bolts are tighted, the shaft has no movement up or down -- how do the springs help to maintain chain tension?  In addition, the manual suggests not allowing the gap between the chain slats and the lower roller to be less than 20mm, but doesn't say what it  should be. Does anyone know what the gap is when it leaves the factory?

 

Thanks

 

 

 

 

 

Krone KR130 Tensioner Question