Left and right valves are provided in a lower surface of the cover on opposite sides of {HEAD ~ the seal} between {TAIL ~ the partition} and the cover 
Left and right valves are provided in a lower surface of the cover on opposite sides of { HEAD ~ the seal } between { TAIL ~ the partition } and the cover
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH