| 摘要 |
EXTENSION AXLE APPARATUS FOR OVER-THE-ROAD TRAILER ASSEMBLY An extension axle unit for an over-the-road tractor/trailer for carrying earth moving equipment, and other heavy loads includes a rigid connecting beam affixed to the end of the trailer bed. A wheeled support frame is connected to the connecting beam by a parallelogram structure including upper and lower arms, and connects the unit to follow directly behind the trailer. The parallelogram structure is pressurized through hydraulic cylinder units to maintain the extension frame in level relationship to the trailer frame as the tractor/trailer assembly moves over uneven terrain thereby maintaining proper load distribution on the several axles and avoiding and maintaining smooth ride with minimum stress within the trailer and extension assembly. A plurality of hydraulic cylinder units are mounted within the parallelogram structure and pressurized from a hydraulic source to maintain load distribution, with a selected maximum load on the wheels. Various hydraulic valving systems are shown, with an accumulator within the system, to maintain pressure conditions after presetting of the assembly. The assembly includes a free float condition for the hydraulic cylinders under which the extension axle merely follows behind the trailer assembly in the absence of a load on the tractor/trailer assembly. The wheels are self-steering to eliminate any loading of the trailer and tipping of the trailer.
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