Hydraulic drill feed control

Claim 1

IN APPARATUS OF THE CHARACTER DESCRIBED FOR FLUID PRESSURE CONTROL OF THE FEED OF A ROCK DRILL TOWARD A SURFACE TO BE DRILLED AND HAVING A ROCK DRILL WITH A FLUID PRESSURE DRIVEN ROTARY DRILL MOTOR AND A FIRST HIGH-PRESSURE FLUID VARIABLE DISPLACEMENT PUMP IN FLOW COMMUNICATION WITH SAID DRILL MOTOR AND FORMING THEREWITH A FIRST PRESSURE FLUID CIRCUIT, A FLUID PRESSURE DRIVEN ROTARY FEED MOTOR AND SECOND HIGH-PRESSURE FLUID VARIABLE DISPLACEMENT PUMP IN FLOW COMMUNICATION WITH SAID FEED MOTOR AND FORMING THEREWITH A SECOND PRESSURE FLUID CIRCUIT, AND MEANS FOR DRIVING SAID PUMPS, THE COMBINATION WHICH COMPRISES FIRST ADJUSTING MEANS CONNECTED TO SAID FIRST PUMP FOR CONTROLLING THE DISPLACEMENT OF SAID PUMP AND THE TORQUE OF SAID DRILL MOTOR IN RESPONSE TO FLUID PRESSURE AND INCLUDING MEANS FOR SENSING FLUID PRESSURE IN SAID FIRST CIRCUIT FOR ACTUATION OF SAID FIRST ADJUSTING MEANS, SECOND ADJUSTING MEANS CONNECTED TO SAID SECOND PUMP FOR CONTROLLING THE DISPLACEMENT OF SAID SECOND PUMP AND THE TORQUE OF SAID FEED MOTOR IN RESPONSE TO PRESSURE AND INCLUDING MEANS FOR SENSING FLUID PRESSURE IN SAID SECOND CIRCUIT FOR ACTUATION OF SAID SECOND ADJUSTING MEANS, AND CONTROL MEANS CONNECTED TO SAID SECOND ADJUSTING MEANS AND IN FLOW COMMUNICATION WITH SAID FIRST AND SECOND CIRCUITS AND RESPONSIVE TO A PREDETERMINED MAXIMUM PRESSURE IN EITHER OF SAID CIRCUITS FOR ACTUATING SAID SECOND ADJUSTING MEANS TO REDUCE THE DISPLACEMENT OF SAID SECOND PUMP WHEN SAID PREDETERMINED MAXIMUM PRESSURE IS REACHED.