{HEAD ~ The valve} is opened and closed by means of communicating bellows which are controlled by the pressure difference between {TAIL ~ two sections} in the valve having different areas 
{ HEAD ~ The valve } is opened and closed by means of communicating bellows which are controlled by the pressure difference between { TAIL ~ two sections } in the valve having different areas
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH