when said {HEAD ~ support frame} is upwardly opened by {TAIL ~ a predetermined angle} from the closed position via said hinge means, said coupling shaft is pressed to the lower ends of said oblong holes while being urged by said urging means, so that said rear side frame is supported by said support frame 
is upwardly opened by
when said { HEAD ~ support frame } is upwardly opened by { TAIL ~ a predetermined angle } from the closed position via said hinge means , said coupling shaft is pressed to the lower ends of said oblong holes while being urged by said urging means , so that said rear side frame is supported by said support frame
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH