Patent ID: 7607365

Claim:
A drive mechanism for an extendable member comprising: a first side plate; a second side plate opposite said first side plate; a rack having a first surface and a second surface and being located between said plates; an engagement shaft extending between said first side plate and second side plate and contacting said second surface of said rack; a gear shaft extending between and supported by said first side plate and said second side plate such that said gear shaft is restrained from relative movement with respect to said engagement shaft, said gear shaft carrying a gear, said gear engaging said first surface of said rack such that upon rotation of the gear said rack is moved longitudinally between said plates; a rail located between said plates paralleling said rack, said gear shaft carrying a support roller contacting and supporting said rail; and a frame slidably retaining said first and second side plates for vertical movement of the plates and said supported shafts and said rack relative to the frame with said gear and said first surface of the rack remaining in engagement, said frame restricting lateral movement of the rack.