Self-leveling seat for tractors

Claim 1

A SELF-LEVELING SEAT FOR TRACTORS AND THE LIKE COMPRISING A CLOSED FLUID-FILLED LOOP, A FLUID DISPLACEMENT DEVICE CONNECTED IN SAID CLOSED LOOP AND OPERABLE TO DISPLACE THE FLUID THEREIN SELECTIVELY IN EITHER DIRECTION, A CHECK VALVE MEANS CONNECTED IN SAID CLOSED LOOP IN SERIES WITH THE FLUID DISPLACEMENT DEVICE AND SERVING NORMALLY TO PREVENT DISPLACEMENT OF THE FLUID IN SAID LOOP WHEN THE SEAT IS SUBSTANTIALLY LEVEL, A TWO-WAY TILTABLE SEAT STRUCTURE HAVING A CONNECTION WITH THE FLUID DISPLACEMENT DEVICE, WHEREBY THE WEIGHT UPON THE SEAT STRUCTURE IS THE SOLE OPERATING FORCE FOR THE FLUID DISPLACEMENT DEVICE AND THE SOLE MEANS OF PRESSURIZING THE FLUID WITHIN SAID LOOP RESPONSIVE TO TILTING OF THE SEAT IN EITHER DIRECTION, AND A TILTRESPONSIVE ACTUATOR FOR THE CHECK VALVE MEANS OPERABLE UPON TILTING OF THE SEAT STRUCTURE IN EITHER DIRECTION TO OPEN THE CHECK VALVE MEANS AND ALLOW THE FLUID IN SAID CLOSED LOOP TO BE DISPLACED BY SAID DISPLACEMENT DEVICE IN A DIRECTION TO LEVEL THE SEAT, THEREBY RETURNING THE SEAT STRUCTURE TO A SUBSTANTIALLY LEVEL POSITION, THE CHECK VALVE MEANS SIMULTANEOUSLY PREVENTING DISPLACEMENT OF THE FLUID IN THE OPPOSITE DIRECTION IN SAID CLOSED LOOP.