Rear wheel drive assist for a wheel tractor scraper

A wheel tractor scraper, comprising:

• a tractor portion having a power source operatively connected to at least one front driven wheel by at least one of a mechanical transmission or an electric transmission;
• a scraper portion pivotally connected to the tractor portion, the scraper portion having a bowl, a work tool, and a first and second rear wheel disposed on opposite sides of the scraper portion;
• and
• a fluid operated rear wheel drive assist, including:
• a work tool pump fluidly connected to a fluid operated work tool motor, the work tool motor being operatively connected to the work tool;
• a first drive motor operatively connected to the first rear wheel;
• a second drive motor operatively connected to the second rear wheel;
• a diverter valve selectively movable between a first position at which fluid flow is delivered from the work tool pump to the work tool motor, and a second position at which fluid flow is delivered from the work tool pump to the first and second drive motors;
• and
• a controller configured to control operation of the diverter valve, including
• when the rear wheel drive assist is engaged, controlling the diverter valve to the second position to provide fluid flow to the first and second drive motors to drive the first and second rear wheels to assist the at least one front driven wheel in propelling the wheel tractor scraper, and
• when the rear wheel drive assist is not engaged, controlling the diverter valve to the first position to allow fluid flow to the work tool motor and prevent fluid flow to the first and second drive motors connected to the first and second rear wheels while the at least one front driven wheel propels the wheel tractor scraper.

A wheel tractor scraper, comprising:

• a tractor portion having a power source mounted thereon, the power source being operatively connected to at least one front driven wheel;
• a scraper portion pivotally connected to the tractor portion, the scraper portion having a bowl, an elevator, and first and second rear wheels disposed on opposite sides of the scraper portion;
• and
• a closed-loop hydraulic rear wheel drive assist including:
• a reversible, variable displacement pump fluidly connected through a work tool conduit to a fluid operated elevator motor, the elevator motor being operatively connected to the elevator;
• a first drive motor operatively connected to the first rear wheel;
• a second drive motor operatively connected to the second rear wheel;
• and
• a diverter valve disposed along the work tool conduit and configured to divert a flow of pressurized fluid from the elevator motor to the first and second drive motors to engage the rear wheel drive assist;
• and
• a controller configured to control operation of the diverter valve, including
• when the rear wheel drive assist is engaged, controlling the diverter valve to provide fluid flow to the first and second drive motors to drive the first and second rear wheels to assist the at least one front driven wheel in propelling the wheel tractor scraper, and
• when the rear wheel drive assist is not engaged, controlling the diverter valve to allow fluid flow to the elevator motor and prevent fluid flow to the first and second drive motors connected to the first and second rear wheels while the at least one front wheel propels the wheel tractor scraper.