According to another embodiment of the invention, the pockets are defined by {HEAD ~ inturned edges} on the covers which embrace a boundary of a recess formed in {TAIL ~ the surface} of the movable element exposed to hot gases of combustion 
According to another embodiment of the invention , the pockets are defined by { HEAD ~ inturned edges } on the covers which embrace a boundary of a recess formed in { TAIL ~ the surface } of the movable element exposed to hot gases of combustion
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH