Rather, the piston head 82 itself would close a vent hole and prevent escape of {HEAD ~ fluid} into {TAIL ~ the helically swept channel} 68 
Rather , the piston head 82 itself would close a vent hole and prevent escape of { HEAD ~ fluid } into { TAIL ~ the helically swept channel } 68
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH