shutter means for selectively closing said first and second pipes, said shutter means being pivotally mounted to {TAIL ~ a fourth and a fifth walls} of {HEAD ~ said housing}, said fourth and fifth walls being opposed against each other 
shutter means for selectively closing said first and second pipes , said shutter means being pivotally mounted to { TAIL ~ a fourth and a fifth walls } of { HEAD ~ said housing } , said fourth and fifth walls being opposed against each other
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH