US Patent 7690412 Drive axle with air passage for tire inflation system

A drive axle assembly includes a non-rotating spindle having a cylindrical body defining an internal cavity and an axle shaft assembly mounted within the internal cavity for rotation about an axis. A seal assembly is positioned within the internal cavity to provide a sealed chamber between the axle shaft assembly and the non-rotating spindle. A first air passage is formed within the cylindrical body and includes an air inlet to be in fluid communication with an air supply and an air outlet in fluid communication with the sealed chamber. A second air passage is formed within the axle shaft assembly and receives air input from the sealed chamber and includes an air output to be associated with at least one tire.