Mining machine having synchronized oscillating cutter heads

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 SPACES AXES RESPECTIVELY; CUTTING MEANS CARRIED AT THE OTHER END OF EACH OF SAID SUPPORT ARMS THE IMPROVEMENT COMPRISING FLUID OPERATED DRIVE MEANS FOR SAID SUPPORT ARMS FOR OSCILLATING SAID SUPPORT ARMS THROUGH A GIVEN CYCLE ABOUT SAID AXES IN OPPOSITE DIRECTIONS, RESPECTIVELY; SAID DRIVE MEANS HAVING A PAIR OF VALVES THEREIN EACH HAVING A MEMBER POSITIONABLE TO DIRECT FLUID FLOW THROUGH SAID DRIVE MEANS TO SYNCHRONIZE THE OSCILLATIONS OF SAID SUPPORT ARMS; AND CONTROL MEANS COOPERABLE WITH SAID VALVES OPERATIVE TO POSITION SAID MEMBERS RELATIVE TO SAID VALVES IN RESPONSE TO A VARIATION IN THE OSCILLATION RATE OF ONE OF SAID SUPPORT ARMS TO DIRECT THE FLUID FLOW TO CAUSE A LIKE CHANGE IN THE OSCILLATION RATE OF THE OTHER OF SAID ARMS.