Stair climbing cart

A hand truck for supporting heavy loads comprising:

• an upright frame having a pair of laterally spaced side rails, each rail including a handle portion at one end and a foot portion at the other end, said foot portions being secured together by a cross-member to form a rest for supporting a load;
• a generally U-shaped shroud fixed to and covering a portion of said spaced rails, said shroud having downwardly extending leg portions, a transverse horizontal axle rotatably secured between said downwardly extending leg portions;
• and
• a ground engaging wheel assembly rotatably mounted to each end of said axle, each ground engaging assembly including three rubber-tired wheels mounted in an equilateral triangle configuration, said wheels being rotatably supported on axles mounted between a pair of support members, said assembly being rotatably secured at the center of said pair of support members to said axle, and lines connecting the rotational axes of said wheels forming an equilateral triangle;
• said support members are Y-shaped and having legs of equal length, said wheels being rotatably connected to the free ends of said legs;
• a locking mechanism being provided for holding said hand truck in a set position, said locking mechanism including a sprocket fixed on said axle inwardly of each wheel assembly and between said wheel assembly and each said downwardly extending leg, each sprocket having a plurality of locking positions for holding said hand truck in a set inclined position, a transverse horizontal lock bar mounted in slots extending through said downwardly extending legs above said sprockets, and each end of said lock bar being spring biased for engagement with said sprocket by spring biasing assemblies;
• and
• each said spring biasing assembly including a U-shaped bracket support mounted to the inside wall of said downwardly extending leg, each said end of said lock bar passing through a slot in said bracket and through said slot in said downwardly extending leg, said slots being elongated to permit said lock bar sufficient vertical movement so as to move into and out of engagement with said sprockets, each end of said lock bar being spring biased downwardly by a spring mounted on a rod mounted in said bracket, and one end of said rod being secured to said bar and its other end linearly movable in an opening in said bracket.