When top plate 10 is lowered by {HEAD ~ displacement} of {TAIL ~ cylinder} 62, fluid extension ducts 182 compress springs 186 and thereby maintain the seal 
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When top plate 10 is lowered by { HEAD ~ displacement } of { TAIL ~ cylinder } 62 , fluid extension ducts 182 compress springs 186 and thereby maintain the seal
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH