Air inflation system for trailer axles

An air inflation system for a trailer having at least one axle with at least one wheel having a pneumatic tire at each end of the axle and said trailer having an air supply and a lubrication compartment at each end of the axle for lubricating the wheel bearings comprising,

• an air conduit between the air supply and the axle supplying air and pressurizing the inside of the axle with air,
• a stationary air sealing barrier sealingly connected adjacent each end of the axle and positioned between the lubrication compartments and the air in the axle for sealing the air inside the axle between said barriers,
• a pneumatic rotary union supported and positioned in the center of each barrier and having an air passageway extending therethrough and in communication with the air inside of the axle, said union having a first stationary part and a second rotatable part sealingly rotatable relative to each other, said first stationary part sealingly secured to the barrier, and the second rotatable part positioned exposed to the lubrication compartment,
• a rotatable air connection connected between the second rotatable part and the tires and extending through the lubrication compartment, and
• a removable oil sight plug having a relief valve, said relief valve axially connected to each lubrication compartment, and said relief valve being biased to a normally closed position for retaining lubrication in the compartment, but said valve being opened if subjected to a predetermined air pressure in the lubrication compartment.