Three-stage self-propelled crane

Claim 1

A self propelled crane with three hydraulic lifting stages which may be mounted on motor vehicles, characterized in that the first lifting stage comprises a hydraulic cylinder (7) having a piston (8) for actuating in a lifting movemenT, a pantograph system of levers comprising an arm (18) pivotally connected proximate the mid-point thereof to said piston (8) of tie rods (15) pivotally coupled to the end of said arm (18), a first order a fork-shaped support (5) pivotally coupled to the opposite end of said tie rods (15), the base of said support (5) being pivotally connected to the bottom of the hydraulic cylinder (7); a second order of tie rods (16) pivotally coupled, respectively, to the ends of said fork-shaped support (5), to said central arm (18) and to a pair of tie rods (22) for providing the lifting thrust to a group of two levers (20, 25) and to a pair of tie rods (32); a cradle member (31) pivotally coupled to said tie rods (32); two pairs of levers (37, 38) pivotally coupled to said cradle member (31) and which, together with said cradle member (31) and an analogous second member (41) mounted in opposition to said cradle member (31), form a first parallelogram, a second parallelogram being defined by doubled levers (44, 45) terminally articulated to a bracket (48) having a triangular outline and a nacelle (49) carried by said bracket (48); said second parallelogram (44, 45) being controllable as to its position with respect to the member (41) which supports it, by the action of a hydraulic cylinder and piston (54, 55).