US Patent 7308900 Flat surface washing apparatus

An engine and high pressure pump are mounted onto a wheeled chassis. High pressure water is distributed to a rotating wand and nozzle assembly on the wheeled chassis so that as the chassis is moved along a linear path, high pressure water is sprayed onto an underlying surface to clean the surface. Optional diffusion plates may be used to prevent high pressure water from being sprayed directly onto the underlying surface in part of the rotational path defined by the wand and nozzle assembly.