Air cylinder with hydraulic control

Claim 1

A HYDRAULICALLY CONTROLLED AIR CYLINDER COMPRISING A MAIN CYLINDER, A HOLLOW PUSH ROD EXTENDING AXIALLY INTO SAID CYLINDER, AN AIR PISTON FIXED TO SAID PUSH ROD IN SAID CYLINDER AND PROVIDING A REAR AIR CHAMBER ON ONE SIDE OF SAID AIR PISTON AND A FORWARD AIR CHAMBER ON THE OTHER SIDE OF SAID AIR PISTON, A HYDRAULIC CONTROL CARTRIDGE IN SAID PUSH ROD COMPRISING A TUBE HAVING AN EXTERNAL DIAMETER LESS THAN THE INTERNAL DIAMETER OF SAID PUSH ROD TO PROVIDE AN ANNULAR AIR PASSAGE BETWEEN SAID TUBE AND PUSH ROD, A HYDRAULIC PISTON ROD FIXED TO AND AXIALLY ARRANGED IN SAID CYLINDER, SAID HYDRAULIC PISTON ROD EXTENDING THROUGH SAID AIR PISTON, A HYDRAULIC PISTON ASSEMBLY MOUNTED ON SAID HYDRAULIC PISTON ROD IN SAID TUBE ABD PROVIDING A REAR OIL CHAMBER ON ONE SIDE OF SAID PISTON ASSEMBLY AND A FORWARD OIL CHAMBER ON THE OTHER SIDE OF SAID PISTON ASSEMBLY, MEANS PROVIDING AN OIL FLOW PASSAGE THROUGH SAID PISTON ASSEMBLY FROM ONE OF SAID OIL CHAMBERS TO THE OTHER, MEANS CONTROLLING OIL FLOW THROUGH SAID OIL FLOW PASSAGE, AND A COVER SLIDABLY MOUNTED IN SAID TUBE ADJACENT EACH END THEREOF AND CLOSING A RESPECTIVE ONE OF SAID OIL CHAMBERS, A FIRST ONE OF SAID COVERS BEING EXPOSED TO AIR IN SAID FORWARD AIR CHAMBER AND A SECOND ONE OF SAID COVERS BEING EXPOSED TO AIR IN SAID REAR AIR CHAMBER, SAID COVERS HAVING FLOATING MOVEMENT IN SAID TUBE IN RESPONSE TO DIFFERENTIAL FLUID PRESSURES THEREON, SAID AIR PISTON ROD HAVING A PORT COMMUNICATING WITH SAID FORWARD AIR CHAMBER AND SAID ANNULAR AIR PASSAGE, MEANS PROVIDING AN AIR INLET AND OUTLET PORT COMMUNICATING WITH SAID FORWARD AIR CHAMBER, AND MEANS PROVIDING AN AIR INLET AND OUTLET PORT COMMUNICATING WITH SAID REAR AIR CHAMBER.