Automatic control for continuous mining machine

Claim 1

IN A CONTINUOUS MINING MACHINE, A MAIN FRAME, A PAIR OF BOOM ARMS PIVOTALLY MOUNTED ON SAID MAIN FRAME FOR MOVEMENT ABOUT VERTICAL AXES AT THE FRONT OF SAID MAIN FRAME AT OPPOSITE SIDES THEREOF, A SIDE CUTTING MINING HEAD ROTATABLY MOUNTED ON EACH BOOM ARM AND EXTENDING LONGITUDINALLY THEREALONG AND IN ADVANCE THEREOF, INDIVIDUAL HYDRAULIC CYLINDERS AND PISTONS CONNECTED BETWEEN SAID MAIN FRAME AND SAID BOOM ARMS FOR FEEDING SAID MINING HEADS TOWARD EACH OTHER AND RETRACTABLY MOVING SAID MINING HEADS WITH RESPECT TO EACH OTHER, STOP MEANS FOR LIMITING INWARD MOVEMENT OF SAID MINING HEADS TOWARD EACH OTHER AND PERMITTING RETRACTABLE MOVEMENT OF ONE MINING HEAD COMPRISING A CONTROL LINE CONNECTED BETWEEN SAID CYLINDERS ADJACENT ONE THEREOF, A SHUTTLE VALVE IN SAID CONTROL LINE, RETURN LINES LEADING FROM THE SAME ENDS OF SAID CYLINDERS AS SAID CONTROL LINE AND SPACED INWARDLY ALONG SAID CYLINDERS WITH RESPECT TO THE CONNECTIONS OF SAID CONTROL LINE TO SAID CYLINDERS, PRESSURE LINES CONNECTED TO OPPOSITE ENDS OF SAID SHUTTLE VALVE AND LEADING FROM THE OPPOSITE ENDS OF SAID CYLINDERS FROM SAID CONTROL LINE, AND HOLDING SAID SHUTTLE VALVE IN POSITION TO BLOCK THE PASSAGE OF HYDRAULIC FLUID FROM ONE CYLINDER TO THE OTHER AND THEREBY STOP FEEDING MOVEMENT OF SAID MINING HEADS TOWARD EACH OTHER WHEN THE PRESSURE ON OPPOSITE SIDES OF SAID SHUTTLE VALVE IS BALANCED AND SAID PISTONS HAVE MOVED TO BLOCK THE RETURN OF FLUID FROM SAID CYLINDERS THROUGH SAID RETURN LINES, AND RELEASING PRESSURE FROM ONE END OF SAID SHUTTLE VALVE UPON THE RELEASE OF PRESSURE TO ONE OF SAID CYLINDERS, TO ACCOMMODATE THE PASSAGE OF FLUID UNDER PRESSURE FROM ONE CYLINDER TO THE OTHER TO RETRACTABLY MOVE ONE PISTON AND MINING HEAD UPON EXTENSIBLE MOVEMENT OF THE OTHER PISTON AND CONTINUED FEEDING MOVEMENT OF THE ASSOCIATED MINING HEAD.