The valve protects {TAIL ~ the ink} in {HEAD ~ the ink supply} from contaminants that can migrate up the ink line during shut down periods 
The valve protects { TAIL ~ the ink } in { HEAD ~ the ink supply } from contaminants that can migrate up the ink line during shut down periods
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH