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