Electro-hydraulic system for operating elevatable chairs

Claim 1

IN AN ELEVATABLE CHAIR CONSTRUCTION INCLUDING A CHAIR SEAT AND A BACKREST WHICH IS MOVABLE BETWEEN AN UPRIGHT IN A RECLINING POSITION RELATIVE TO SAID SEAT, HYDRAULIC MEANS FOR ACTUATING SAID BACKREST BETWEEN SAID POSITIONS, A BASE STRUCTURE, A CHAIR SEAT FRAME STRUCTURE, SAID BASE STRUCTURE HAVING FIXEDLY THEREON AN UPWARDLY PROJECTING MANIFOLD TUBE STRUCTURE, A CYLINDER HAVING AN UPPER CLOSED END AND TELESCOPICALLY ENGAGED WITH SAID MANIFOLD TUBE STRUCTURE AND DEFINING WITH THE MANIFOLD TUBE STRUCTURE A PRESSURE CHAMBER, SAID CYLINDER HAVING A PLURALITY OF CIRCUMFERENTIALLY SPACED VERTICAL CYLINDER BORES SPACED FROM SAID CHAMBER AND COMMUNICATING WITH SAID CHAMBER AT THEIR LOWER ENDS, PISTONS IN SAID BORES HAVING PISTON RODS PROJECTING ABOVE SAID CYLINDER AND SUPPORTINGLY ATTACHED TO SAID CHAIR FRAME, STRUCTURE, SAID MANIFOLD TUBE STRUCTURE HAVING HYDRAULIC FLUID PASSAGE THEREIN COMMUNICATING ADJACENT TO THE UPPER END OF THE MANIFOLD TUBE STRUCTURE WITH SAID CYLINDER CHAMBER, MEANS FOR DELIVERING HYDRAULIC FLUID INTO SAID MANIFOLD TUBE PASSAGE AND THEREBY INTO SAID CHAMBER AND SAID BORES FOR SIMULTANEOUSLY ELEVATING SAID CYLINDER AND SAID PISTONS AND THEREBY EFFECTING COMPOUND ELEVATION OF SAID CHAIR FRAME STRUCTURE RELATIVE TO SAID BASE STRUCTURE, AND MEANS INCLUDING PASSAGE THROUGH SAID MANIFOLD STRUCTURE AND SAID CYLINDER AND SAID SEAT FRAME STRUCTURE FOR OPERATING SAID BACKREST ACTUATING HYDRAULIC MEANS.