Design of an Intrinsically Stable Motion Device for Building Site Elevators

This paper analyzes the introduction of a new handling system for construction site elevators, suitable for moving people and materials. More specifically, the aim is to introduce an inherently stable mechanism capable of introducing a high degree of safety during the use of the machinery. Currently, the system that allows the movement of the cabin exploits the coupling of an electric motor with a pinion at the end that meshes on a rack, perfectly welded on the column’s main structure. The latter is identified as a trellis with a triangular or sometimes square geometric shape, subdivided into modules to allow transport and adaptation according to the height needs to be reached. The electric motor provides fixed torque, both during the movement of the elevator and when the stopping point is reached, in the form of a braking system. If the motor cannot deliver such torque, safety devices will take over. Such a mechanism is called parachute, nothing more than a second pinion placed below the main one, always engaged with the rack. In case of emergency, it is activated for stopping, according to the provisions of the regulations, the cab. In this paper, the authors analyze a solution that exploits a screw and nut mechanism for cabin movement. The choice falls on this specific coupling since it is an irreversible mechanism in which spontaneous retrograde motion can be stopped without externally applied forces. The model presented will take advantage of a rack-and-pinion system, as in present devices normally used in construction sites, but with a helical gear type that will mesh with a finite screw. After careful dimensioning, the system will undergo kinematic and dynamic analysis to make the model applicable under real-world conditions.