a metallic sleeve arranged over the magnets, wherein {HEAD ~ gaps} are formed between the magnets and {TAIL ~ the metallic sleeve}, and the shell is arranged over the metallic sleeve 
are formed between
a metallic sleeve arranged over the magnets , wherein { HEAD ~ gaps } are formed between the magnets and { TAIL ~ the metallic sleeve } , and the shell is arranged over the metallic sleeve
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH