Patent ID: 8739364

Claim:
An apparatus comprising: a wheel having an axle; a round disk connected to said axle, said round disk having a disk middle connected to said axle and a disk circumferential surface surrounding said wheel and said disk middle; a round ring having an inner ring surface connected to said disk circumferential surface of said round disk, said round disk being positioned within said round ring, said round ring contacting said round disk along a first plane, said axle being coplanar with said first plane, and said round ring comprising a ring circumferential outer surface having threads; a threaded cylinder having an inner threaded cylinder surface connected to said threads in said ring circumferential outer surface, said round ring being positioned within said threaded cylinder; and a worm gear connected to said threaded cylinder and contacting said round ring, rotation of said worm gear rotating said threaded cylinder relative to said round ring and thereby moving said wheel one of toward and away from said threaded cylinder.