{HEAD ~ The chair} , device carriage , and footrest assembly are coupled to {TAIL ~ the shaft} to selectively pivot together about the shaft , and in such a manner that a constant spatial relationship is maintained between the chair and the device carriage  
are coupled to
{ HEAD ~ The chair } , device carriage , and footrest assembly are coupled to { TAIL ~ the shaft } to selectively pivot together about the shaft , and in such a manner that a constant spatial relationship is maintained between the chair and the device carriage
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH