Mechanised tarp system for tipping lorry, tipper with tarp system

The system has a cover gripping hoop (37) comprising an indexing finger complementary to a finger (22) of a carriage (19). The fingers are gripped with one another when a swinging arm (31) is in lowered position. The carriage is returned toward receiving end of an open carrier so as to make integration of the carriage and the hoop and allow displacement of the hoop and secondary hoops during driving of the carriage. The carriage and the hoop are disintegrated when the carriage is returned toward the end and the arm is raised or one of lateral sides of the open carrier is opened.