Control apparatus for material-unit stacker

Claim 1

APPARATUS FOR THE CONTROL OF A MATERIAL HANDLING VEHICLE COMPRISING: (A) A VEHICLE ADAPTED TO TRAVEL OVER A PREDETERMINED PATH OF TRAVEL AND CARRY MATERIAL-UNITS, SAID PATH OF TRAVEL HAVING A PLURALITY OF STATIONS ALONG SAID PATH OF TRAVEL; (B) DRIVING MEANS OPERABLY CONNECTED TO SAID VEHICLE FOR CAUSING MOVEMENT THEREOF ALONG SAID PREDETERMINED PATH OF TRAVEL; (C) SIGNAL SUMMING MEANS OPERABLY CONNECTED TO SAID DRIVING MEANS; (D) VOLTAGE DIVIDER MEANS HAVING TAPS TO PROVIDE VOLTAGES OF DIFFERENT MAGNITUDE WITH RESPECT TO A COMMON REFERENCE, SAID TAPS BEING REPRESENTATIVE OF DIFFERENT STATIONS ALONG SAID PREDETERMINED PATH OF TRAVEL; (E) CONTROL MEANS CONTROLLABLE BY AN OPERATOR FOR SELECTIVELY DETERMINING ONE OF SAID TAPS; (F) LINEAR VOLTAGE SIGNAL GENERATOR MEANS PROVIDING A VOLTAGE HAVING A POLARITY OPPOSITE THAT OF SAID VOLTAGE DIVIDER MEANS AND BEING CONNECTED TO SAID DRIVING MEANS TO PRODUCE A LINEAR VOLTAGE OF MAGNITUDE EQUAL TO THAT OF SAID VOLTAGE DIVIDER MEANS AND ALSO REPRESENTATIVE OF THE POSITION OF SAID VEHICLE ALONG SAID PREDETERMINED PATH OF TRAVEL; (G) PROXIMITY SENSING MEANS SENSING THE PROXIMITY OF SAID VEHICLE WITH RESPECT TO THE STATION SELECTED BY ONE OF SAID TAPS AND GENERATING AN ERROR SIGNAL REPRESENTATIVE OF THE POSITIVE DIFFERENCE;