One of {HEAD ~ the end supports} of {TAIL ~ each support roller} is pivotally mounted for pivoting the support rollers in a plane defined by the axes of the support rollers 
of
One of { HEAD ~ the end supports } of { TAIL ~ each support roller } is pivotally mounted for pivoting the support rollers in a plane defined by the axes of the support rollers
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH