Patent ID: 8002069

Claim:
A self-propelled agricultural work machine, comprising: a set of primary movers supporting a portion of the machine and operable for propelling the machine over the ground at a ground speed; a set of secondary movers supporting another portion of the machine and operable by at least one secondary fluid motor connected in driving relation thereto for driving the secondary movers for assisting the primary movers for propelling the machine; a mechanical transmission connected in driving relation directly to the set of primary movers, the transmission being selectably engageable in a plurality of speed ranges, including at least one road speed range for propelling the work machine between a zero ground speed and a predetermined high ground speed suitable for travel over public roads, and at least one low speed range within the road speed range for propelling the work machine between the zero ground speed and a predetermined low ground speed suitable for performing work functions in agricultural fields and slower than the predetermined high ground speed, the transmission being configured and operable for transitioning between the plurality of speed ranges only at the zero ground speed; a hydrostatic drive including a pump connected in a fluid loop with a primary fluid motor and operable for directing a flow of pressurized fluid through the loop at a fluid pressure to the primary fluid motor for controllably driving the primary fluid motor, the primary fluid motor being connected in driving relation to the mechanical transmission; a valve connected to the fluid loop and to the at least one secondary fluid motor and selectably operable in a power assist mode for diverting a portion of the flow of fluid in the loop from the primary fluid motor to the at least one secondary motor for controllably driving the at least one secondary fluid motor; a controller configured and operable for monitoring the speed range of the transmission, the fluid pressure in the loop, and the ground speed of the machine, the controller connected in operative control of the valve and programmed for automatically operating the valve in the power assist mode when the transmission is engaged in the at least one road speed range and the ground speed is below a predetermined transition speed less than the predetermined high ground speed.