the seat includes the structure of the backrest and the structure of the cushion , the former foldable backward to provide by a slight simultaneous elevation of the cushion its transformation into a bed as the folded backrest and the cushion are placed horizontally with their surfaces aligned . the structures and of the backrest and cushion are connected to each other by a swivelling shaft about which they can both revolve freely , so that folding backward the structure of the backrest implies pushing and raising the structure of the cushion , as it is connected on its anterior part by a hinged connecting rod between the structure of the cushion and the general fixed structure of the seat .