Device for the preparation of coated products for construction and maintenance of highways

A device for the preparation of coated products from aggregate, powdery matter and binder, comprising a platform, a cylindrical dryer and mixer drum having an inlet end and an outlet end, means mounting said drum for rotation about its longitudinal axis on said platform, means for driving said drum in rotation, means for continuously feeding aggregate and powdery matter to said inlet end of said drum, a burner projecting into said inlet end of said drum, a fixed chamber for discharge of coated product and for exhaust of the gases in circulation in the drum, said fixed chamber being in communication with said outlet end of said drum, means for supplying binder to said drum, said drum being arranged so that said inlet end is at a level higher than the level of said outlet end to promote the circulation of the products in said drum, said drum comprising in succession in the direction of flow of the products therethrough from said inlet end;

• a first zone for introduction of aggregate and powdery matter supplied by said feeding means, and including blades projecting inwardly of the drum arranged in a spiral on the inner surface of the wall of said drum,
• a second zone for preheating and predrying of the aggregate and homogenization of the mixture of aggregate and powdery matter, and including means for lifting the aggregate and powdery matter provided on the inner surface of said drum, the transverse section of said lifting means taken in a plane perpendicular to the axis of said drum being variable along said second zone such that the capability of retention of said lifting means increases in the direction of advance of the products, said capability of retention being low at the inlet to said second zone, such that relatively little material will be lifted and dropped at said inlet to said second zone and thus will not interfere with the flame from the burner,
• third zone for drying, mixing and heating the products, said binder supplying means discharging at the inlet of said third zone, the inner surface of the wall of said drum being provided in said third zone with further lifting means, the transverse section of which is identical with the transverse section of said lifting means at the outlet of said second zone, said further lifting means having a high capability of retention such that the products form a substantially continuous curtain across the whole transverse section of said drum at the inlet of the third zone to isolate the third zone and the binder supplying means from the second zone.