A drive wheel 10 is shown to include a support member 12 and, a wheel member 11 having a surface contacting portion 18 extending about a periphery of the wheel member 11. A drive shaft 24 includes a drive device 25 arranged to engage a drive surface 26 on the wheel member 11 such that the wheel member...http://www.google.de/patents/US6474434?utm_source=gb-gplus-sharePatent US6474434 - Drive wheel
