Means for presetting and testing a desired pressure limit for hydraulically regulated refiner

Claim 1

IN A HYDRAULIC SYSTEM FOR POSITIONING AN AXIALLYADJUSTABLE ELEMENT IN A FIBROUS MATERIAL REFINING MACHINE BY THE MAINTENANCE OF A DESIRED CONSTANT PRESSURE, A DOUBLE-ACTING HYDRAULIC CYLINDER, A HYDRAULIC PUMP AND PUMP MOTOR, A FLOW CONTROL VALVE IN THE HYDRAULIC LINES FOR SAID CYLINDER, A PRESURE RELIEF VALVE AND A PRESSURE GAUGE IN THE DELIVERY LINE BETWEEN SAID PUMP AND SAID FLOW CONTROL VALVE, A CONTROL ELEMENT FOR SETTING SAID PRESSURE RELIEF VALVE, ELECTRIC MEANS FOR SELECTIVELY MOVING SAID FLOW CONTROL VALVE FROM NEUTRAL CLOSING-OFF POSITION, SWITCH MEANS CONTROLLING THE OPERATION OF SAID ELECTRIC MEANS AND CONTROLLING A MAIN CIRCUIT TO SAID PUMP MOTOR SO ARRANGED AS TO CLOSE SAID CIRCUIT TO SAID PUMP MOTOR WHENEVER SAID CONTROL VALVE IS MOVED FROM NEUTRAL CLOSING-OFF POSITION BY SAID ELECTRIC MEANS, AND ASSOCIATED TESTING SWITCH MEANS FOR CLOSING A CIRCUIT TO SAID MOTOR WHILE SAID ELECTRIC MEANS IS INACTIVE AND SAID CONTROL VALVE IS IN NEUTRAL CLOSING-OFF POSITION, WHEREBY THE UTILIZATION OF SAID TESTING SWITCH MEANS WILL CAUSE SAID PUMP TEMPORARILY TO BE OPERATED WHILE SAID FLOW CONTROL VALVE IS MAINTAINED IN SAID NEUTRAL CLOSING-OFF POSITION, THEREBY ENABLING THE PRESSURE IN THE HYDRAULIC FLUID DELIVERY LINE BETWEEN SAID PUMP AND SAID FLOW CONTROL VALVE TO BUILD UP QUICKLY FOR THE SETTING OF SAID PRESSURE RELIEF VALVE AND THE ESTABLISHING OF MAXIMUM PRESSURE FOR THE ENTIRE SYSTEM IN ADVANCE OF ACTIVATING THE SYSTEM.