The pressure for moving {HEAD ~ piston} 40 and mandrel 38 upwardly to open the valve is supplied to cylinder 42 below the piston through lateral opening 60 in {TAIL ~ the sidewall} of lower housing section 12 
The pressure for moving { HEAD ~ piston } 40 and mandrel 38 upwardly to open the valve is supplied to cylinder 42 below the piston through lateral opening 60 in { TAIL ~ the sidewall } of lower housing section 12
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH