Hydraulic system for swinging a crane boom

Claim 1

IN A CRANE HAVING A BOOM, A ROTATABLE SUPPORTING STRUCTURE ON WHICH THE BOOM IS MOUNTED TO SWING THE BOOM, MEANS INCLUDING A HYDRAULIC MOTOR FOR ROTATING SAID SUPPORTING STRUCTURE AND SWINGING THE BOOM, MEANS FOR CONTROLLING THE SUPPLY OF HYDRAULIC FLUID UNDER PRESSURE TO SAID HYDRAULIC MOTOR IN WHICH SAID CONTROLLING MEANS IS OPENED TO SUPPLY HYDRAULIC LIQUID UNDER PRESSURE TO THE HYDRAULIC MOTOR TO ROTATE SAID BOOM SUPPORTING STRUCTURE AND SAID CONTROLLING MEANS IS CLOSED TO STOP THE SUPPLY OF HYDRAULIC FLUID UNDER PRESSURE TO THE HYDRAULIC MOTOR TO STOP ROTATION OF SAID BOOM SUPPORTING STRUCTURE, A COUNTERBALANCE VALVE CONNECTED TO SAID MOTOR FOR FLOW OF THE HYDRAULIC FLUID THROUGH THE COUNTERBALANCE VALVE TO AND FROM THE HYDRAULIC MOTOR, SAID COUNTERBALANCE VALVE INCLUDING HYDRAULIC FLUID PRESSURE RELIEF MEANS FOR DISSIPATING THE ENERGY OF SAID MOTOR WHEN THE SUPPLY OF HYDRAULIC FLUID IS STOPPED BY CLOSING SAID CONTROLLING MEANS, BRAKE MEANS FOR HOLDING SAID ROTATING MEANS IN STATIONARY POSITION, A HYDRAULIC CYLINDER OPERATIVE BY HYDRAULIC FLUID TO RELEASE THE BRAKE, MEANS CONNECTING SAID COUNTERBALANCE VALVE TO SAID HYDRAULIC CYLINDER TO SUPPLY HYDRAULIC FLUID UNDER PRESSURE TO THE HYDRAULIC CYLINDER WHEN SAID CONTROLLING MEANS IS OPENED THEREBY TO RELEASE SAID BRAKE BY OPERATION OF THE HYDRAULIC CYLINDER AND MEANS FOR APPLYING THE BRAKE WHEN THERE IS NO HYDRAULIC FLUID SUPPLIED TO THE HYDRAULIC MOTOR