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