The present invention relates to a mechanical means for defrosting plates used in cold storage. Frost reduces the transfer of heat to the plates and partially or totally obstructs the passage of air. Several methods are used to remove frost from plates: hot water, sprayed steam, hot gas, heating elements. In the present invention, scrapers sweep the surface of the plates to remove the frost. This method allows to remove the frost while the plates are being discharged, which improves the performance of the plates and does not affect the residual charge of the plates. The proposed defrosting system is made up of vertical scrapers located on either side of the plates. The upper and lower extremities of the scrapers are fastened to scraper supports. These supports move along tubular guide bars which are parallel to and located beneath and above the plates. To ensure that the movement of the upper and lower supports is uniform, an endless screw is installed parallel to and centered between the upper and lower guide bars. A pinion is mounted on one end of each endless screw. The pinions located at the end of each endless screw are linked to the pinion of the drive motor by a chain. Limit switches are provided to invert the movement of the scrapers.