The lifting device comprises abiased slide shoe adapted to be slidable with respect to a member of an openable structure, a lifting arm having two ends, one end adapted to be pivotally connected with a member of the structure and the other end associated with said slide shoe, and a braking device comprising at least one brake shoe slidable on a respective brake face of said lifting device, said braking device modulating the force resulting from the bias on said biased slide shoe. An adjusting device is adapted to adjust said progressive modulation of said force resulting from the bias on said biased slide shoe, and comprises a manipula- tion member, which when manipulated by a user activates said adjusting device to adjust a brake force of said brake shoe exerted on said brake face in a given position of said brake shoe.