The extended piece 11d is arc shaped at the free end portion, which protrudes from {HEAD ~ the free end portion} of {TAIL ~ the second joint portion} 2c of the core 2 
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The extended piece 11d is arc shaped at the free end portion , which protrudes from { HEAD ~ the free end portion } of { TAIL ~ the second joint portion } 2c of the core 2
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH