Abstract: The safety braking device comprises a case for mounting on the unit and in which there is journalled a shaft carrying a drive wheel engaged with a surface along which surface the unit moves. Fixed brake discs prevented from rotating with respect to the case are interposed between movable discs mounted on the shaft to rotate with the shaft. Screws extend through the movable discs and each have a head at one end and a gear pinion screwthreadedly engaged on the opposite end of the screws for axially tightening the discs together. The gear pinions are meshed with a gear wheel fixed to a support member which is mounted on the shaft to be rotatable by the shaft through the effect of friction between the shaft and support member.