Electro-hydraulically controlled positioning device

Claim 1

AN ELECTRO-HYDRAULICALLY CONTROLLED POSITIONING DEVICE COMPRISING A CYLINDER HAVING TWO CHAMBERS EACH ADAPTED FOR BEING SUPPLIED WITH PRESSURE FLUID, A PISTON SLIDABLY SUPPORTED IN SAID CYLINDER, A DISTRIBUTOR BODY HAVING A PAIR OF SPACED OPENINGS ECH IN COMMUNICATION WITH A RESPECTIVE OF SAID CHAMBERS AND CONSTITUTING OUTLETS FOR SAID PRESSURE FLUID, SLIDE VALVE MEANS ADAPTED TO ASSUME A NEUTRAL POSITION IN WHICH SAID OUTLETS ARE PARTIALLY CLOSED, MEANS SUPPORTING THE SLIDE VALVE MEANS FOR DISPLACEMENT IN OPPOSITE DIRECTIONS SUCH THAT DISPLACEMENT IN ONE DIRECTION GRADUALLY OPENS ONE OUTLET AND CLOSES THE OTHER OUTLET WHEREAS DISPLACEMENT IN THE OPPOSITE DIRECTION GRADUALLY CLOSES SAID ONE OUTLET AND OPENS SAID OTHER OUTLET, SAID SLIDE VALVE MEANS INCLUDING MEANS FOR CLOSING THE OUTLETS AND FOR DEFINING PARTICULAR OUTFLOW PATHS FOR FLUID DISCHARGE THROUGH THE OPENINGS TO CAUSE FORCES TO BE EXERTED ON THE SLIDE VALVE MEANS BY THE DISCHARGE FLUID WHICH ACT IN THE DIRECTION IN WHICH THE SLIDE VALVE MEANS IS DISPLACED, SAID SLIDE VALVE MEANS BEING DISPOSED PERPENDICULAR TO THE PATH OF THE FLUID DISCHARGED FROM THE OPENINGS AND BEING DISPLACEABLE IN SAID OPPOSITE DIRECTIONS IN A PLANE PERPENDICULAR TO SAID PATH OF THE FLUID DISCHARGED FROM THE OPENINGS, AND MEANS FOR DISPLACING SAID SLIDE VALVE MEANS IN SAID OPPOSITE DIRECTIONS AND INCLUDING ELECTRICAL CONTROL MEANS FOR DEVELOPING A FORCE TO MOVE THE SLIDE VALVE MEANS IN CORRESPONDENCE WITH A DESIRED MOVEMENT OF THE PISTON IN THE