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 {HEAD ~ the device carriage}  
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 { HEAD ~ the device carriage }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH