Device 3, wherein the valve is contained with play between two grids mounted in series with the port, and wherein {HEAD ~ the overall mean diameter} of {TAIL ~ the apertures} of each grid is less than the mean diameter of the port 
Device 3 , wherein the valve is contained with play between two grids mounted in series with the port , and wherein { HEAD ~ the overall mean diameter } of { TAIL ~ the apertures } of each grid is less than the mean diameter of the port
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH