Mining machine having cutter arms oscillated in opposite directions and in phase

Claim 1

IN A MINING APPARATUS HAVING A MOBILE FRAME; A PAIR OF FORWARDLY EXTENDING ELONGATED SUPPORT ARMS MOUNTED AT ONE END THEREOF ON SAID MOBILE FRAME FOR PIVOTAL MOVEMENT ABOUT SPACED AXES RESPECTIVELY; CUTTING MEANS CARRIED AT THE OTHER ENDS OF EACH OF SAID SUPPORT ARMS; DOUBLE ACTING HYDRAULIC CYLINDER MEANS HAVING A PRESSURIZABLE HEAD PORTION AND A PRESSURIZABLE ROD PORTION FOR EACH OF SAID SUPPORT ARMS RESPECTIVELY, SAID CYLINDER MEANS MECHANICALLY CONNECTING SAID ARMS AND SAID FRAME, RESPECTIVELY; A HYDRAULIC CIRCUIT HAVING A FLUID PUMPING PORTION AND A FLUID RETURNING PORTION FOR ALTERNATELY PRESSURIZING SAID HEAD PORTIONS AND SAID ROD PORTIONS TO OSCILLATE SAID SUPPORT ARMS THROUGH A GIVEN CYCLE ABOUT SAID AXES IN OPPOSITE DIRECTIONS, RESPECTIVELY; VALVE MEANS FOR DIRECTING FLUID FLOW TO AND FROM SAID CYLINDER PORTIONS, INDIVIDUALLY; AND CONTROL MEANS OPERATING SAID VALVE MEANS IN RESPONSE TO A DECREASE IN THE OSCILLATION RATE OF ONE OF SAID SUPPORT ARMS FOR ESTABLISHING COMMUNICATION OF SAID CYLINDER HEAD AND ROD PORTIONS, ASSOCIATED WITH THE OTHER OF SAID ARMS, WITH SAID PUMPING AND RETURNING PORTIONS OF SAID CIRCUIT.