However, {HEAD ~ this valve mechanism} involves {TAIL ~ a large number} of parts and results in a complicated configuration 
involves
However , { HEAD ~ this valve mechanism } involves { TAIL ~ a large number } of parts and results in a complicated configuration
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH