A slidable sleeve slides along the hollow body to close {HEAD ~ the orifices}, causing {TAIL ~ the plunger} to rise and carry accumulated fluid to the well surface 
A slidable sleeve slides along the hollow body to close { HEAD ~ the orifices } , causing { TAIL ~ the plunger } to rise and carry accumulated fluid to the well surface
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH