Oil well pumping unit control circuit

Claim 1

A CONTROL CIRCUIT FOR THE ELECTRIC MOTOR OF AN OIL WELL PUMPING UNIT COMPRISING: SENSING CIRCUIT MEANS FOR SENSING THE CURRENT LEVEL TO THE MOTOR AND PRODUCING A FIRST ELECTRICAL SIGNAL REPRESENTATIVE OF THE CURRENT LEVEL, FIRST FILTER CIRCUIT MEANS INCLUDING A FIRST CAPACITOR FOR INTEGRATING THE FIRST ELECTRICAL SIGNAL OVER A PERIOD OF TIME EXCEEDING THE LOAD CYCLE OF THE MOTOR AND STORING A VOLTAGE ON THE FIRST CAPACITOR REPRESENTATIVE OF THE AVERAGE OF THE FIRST ELECTRICAL SIGNAL DURING THE TIME PERIOD, FIRST CONTROL CIRCUIT MEANS INCLUDING A VOLTAGE CONTROLLED FIRST AMPLIFIER MEANS FOR DRIVING THE COIL OF A FIRST RELAY, THE FIRST AMPLIER MEANS BEING CONNECTED TO THE FIRST FILTER CIRCUIT MEANS SUCH THAT THE FIRST VOLTAGE IS APPLIED TO CONTROL THE FIRST AMPLIFIER MEANS WHEREBY THE FIRST RELAY IS PULLED IN WHEN THE VOLTAGE ON THE FIRST CAPACITOR REACHES A LOW VALUE AND DROPS OUT WHEN THE VOLTAGE REACHES A HIGH VALUE, SECOND FILTER CIRCUIT MEANS INCLUDING A SECOND CAPACITOR FOR INTEGRATING THE FIRST ELECTRICAL SIGNAL OVER A PERIOD OF TIME EXCEEDING THE LOAD CYCLE OF THE MOTOR AND STORING A SECOND VOLTAGE ON THE SECOND CAPACITOR REPRESENTATIVE OF THE AVERAGE OF THE FIRST ELECTRICAL SIGNAL DURING THE TIME PERIOD, SECOND CONTROL CIRCUIT MEANS INCLUDING A VOLTAGE CONTROLLED SECOND AMPLIFIER MEANS FOR DRIVING THE COIL OF A SECOND RELAY, THE SECOND AMPLIFIER MEANS BEING CONNECTED TO THE SECOND FILTER CIRCUIT MEANS SUCH THAT THE SECOND VOLTAGE IS APPLIED TO CONTROL THE SECOND AMPLIFIER MEANS WHEREBY THE SECOND RELAY IS PULLED IN WHEN THE VOLTAGE ON THE SECOND CAPACITOR REACHES A LOW VALUE AND DROPS OUT WHEN THE VOLTAGE ON THE SECOND CAPACITOR REACHES A HIGH LEVEL, THE FIRST RELAY HAVING A FIRST SET OF NORMALLY OPEN CONTACTS CONNECTED, WHEN CLOSED, TO SUPPLY POWER TO THE MOTOR, AND A SECOND SET OF NORMALLY CLOSED CONTACTS CONNECTED, WHEN CLOSED, TO CHARGE THE SECOND CAPACITOR TO THE HIGH LEVEL, AND THE SECOND RELAY HAVING A THIRD SET OF NORMALLY OPEN CONTACTS CONNECTED, WHEN CLOSED, TO CHARGE THE FIRST CAPACITOR TO THE HIGH LEVEL, WHEREBY WHEN THE CURRENT TO THE MOTOR EXCEEDS A PREDETERMINED MAXIMUM, THE FIRST RELAY WILL DROP OUT TO STOP THE MOTOR AND CHARGE THE SECOND CAPACITOR AND INSURE THAT THE SECOND RELAY REMAINS DROPPED OUT, AND WILL REMAIN DROPPED OUT UNTIL THE FIRST CAPACITOR IS DISCHARGED SUFFICIENTLY FOR THE FIRST RELAY TO BE PULLED IN, AND WHEN THE CURRENT TO THE MOTOR FALLS BELOW A PREDETERMINED MINIMUM AFTER THE MOTOR HAS STARTED, THE SECOND RELAY WILL PULL IN, AND THE FIRST CAPACITOR WILL BE CHARGED UNTIL THE FIRST RELAY DROPS OUT TO STOP THE MOTOR UNTIL THE FIRST CAPACITOR IS DISCHARGED TO THE LOW LEVEL.