A spring is supported on the counterholder and is intended for prestressing {HEAD ~ a closing part} against {TAIL ~ a valve seat} 
against
A spring is supported on the counterholder and is intended for prestressing { HEAD ~ a closing part } against { TAIL ~ a valve seat }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL