a vent follower which moves in relation to said vent position, said follower rigidly attached to {HEAD ~ said shaft} so as to rotate said shaft when said vent follower moves, said {TAIL ~ vent follower extending} between said shaft and said inside surface and said top and bottom plate, said vent follower forming a movable seal at said inside surface and said top and bottom plate 
a vent follower which moves in relation to said vent position , said follower rigidly attached to { HEAD ~ said shaft } so as to rotate said shaft when said vent follower moves , said { TAIL ~ vent follower extending } between said shaft and said inside surface and said top and bottom plate , said vent follower forming a movable seal at said inside surface and said top and bottom plate
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH 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