Dual speed lifter for material handling machines

Claim 1

A HYDRAULIC ACTUATOR COMPRISING A TWO-PART CYLINDER STRUCTURE INCLUDING A SMALLER CYLINDER PORTION AND A LARGER CYLINDER PORTION INTERCONNECTED BY A COMBINED SUPPORT AND BARRIER PORTION, THE SAID SUPPORT AND BARRIED PORTION HAVING AN OPENING THERETHROUGH INTERCONNECTING THE SAID TWO CYLINDER PORTIONS, A FIRST PISTON RECIPROCABLE IN A FIRST ONE OF THE SAID CYLINDER PORTIONS AND FORMING WITH THE SAID SUPPORT AND BARRIER PORTION AND FORMING WITH FIRST PISTON ROD CONNECTED TO THE SAID FIRST PISTON AND EXTENDING OUTWARDLY OF THE SAID FIRST CYLINDER PORTION, A SECOND PISTON RECIPROCABLE IN THE SAID SECOND CYLINDER PORTION AND FORMING WITH THE SAID SUPPORT AND BARRIER PORTION A SECOND CHAMBER, A SECOND PISTON ROD CONNECTED TO THE SAID SECOND PISTON AND EXTENDING OUTWARDLY OF THE SAID SECOND CYLINDER PORTION, CONNECTIONS TO A SOURCE OF PRESSURIZED FLUID INCLUDING A VALVE FOR CONTROLLING FLUID FLOW, A FIRST CONDUIT CONNECTING THE SAID VALVE WITH ONE OF THE SAID CHAMBERS TO SUPPLY PRESSURIZED FLUID SELECTIVELY THERETO, A RELIEF VALVE IN THE SAID OPENING IN THE SAID SUPPORT AND BARRIES PORTION ALLOWING THE PASSAGE OF FLUID FROM THE SAID ONE CHAMBER TO THE OTHER CHAMBER ONLY UPON THE OCCURRENCE OF A PREDETERMINED FLUID PRESSURE IN THE SAID ONE CHAHAMBER, A SECOND CONDUIT CONNECTING THE SAID OTHER CHAMBER WITH THE SAID FIRST CONDUIT, AND A CHECK VALVE IN THE SAID SECOND CONDUIT PERMITTING FLUID FLOW THERETHROUGH ONLY FROM THE OTHER CHAMBER TO THE FIRST CONDUIT.