Stair climbing hand truck

1. A hand truck for climbing stairs, the hand truck comprising:

a frame having handles proximate a first end and at least two freely rotatable wheels proximate a second end, the frame further having a lifting surface extending outwardly from the frame proximate the second end; and

a stair climbing mechanism engaged with the frame proximate the second end and having:

a motor

an output shaft drivingly connected to the motor, the output shaft having two ends;

at least two rotatable endless loop drive elements generally parallel with respect to each other, the drive elements being drivingly connected to each of the ends of the output shaft;

each drive element including at least one abutment member engaged with and extending outwardly therefrom, whereby the motor drives the drive elements to cause rotation of the abutment members, the abutment members interacting with the stairs to lift the hand truck up the stairs, the drive elements of the stair climbing mechanism each being rotatable about an upper shaft and a lower shaft, each of the upper and lower shafts extending between and generally transverse to the drive elements; and

at least two intermediate endless loop drive elements coupling each end of the output shaft with the lower shaft so that rotation of the output shaft causes rotation of the lower shaft to drive the drive elements around the upper and lower shafts even if one of the intermediate drive elements were to fail.

2. The hand truck of claim 1 wherein the intermediate drive elements are chains.