Importance

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Abstract

In an automatic hitch control system wherein a hitch is raised or lowered in response to operation of a valve, and the valve is controlled by solenoids which are selectively energized by connecting them to ground through switch drivers, a safety disconnect relay is provided for preventing uncommanded motion of the hitch such as might occur if the lead between a solenoid and its driver should be grounded or if the driver should fail in an 'on' state. The relay has contacts connected between the solenoids and the positive voltage for operating them. A microprocessor senses hitch position, the position of a quadrant lever and the speed of the tractor carrying the hitch. From the conditions sensed, the microprocessor determines if the tractor is moving, if the hitch is captured, if the hitch is moving and whether the hitch control system is in an open-loop control mode in which manual switches may be used to control hitch movement. If the hitch is not captured, or the hitch control system is in the open-loop mode, and uncommanded downward hitch motion is detected, the microprocessor energizes the safety disconnect relay to disable the hitch valve thereby preventing uncommanded downward motion of the hitch. When the hitch is captured and the control system is in a closed-loop control mode, feedback signals from the hitch act through a closed-loop to maintain the hitch at the position specified by the quadrant lever.

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First Claim