Process and device for fabricating bituminous coated products from aggregates enclosing a large quantity of fines

Claim 1

In a process for fabricating bituminous coated products in a drying-mixing drum having an inlet and an outlet from aggregates enclosing an excess quantity of fines relative to the quantity required in the coated products, comprising continuously introducing the aggregates into the drum at one end of the drum by which end the flame of a burner penetrates, then conveying inside the drum, whose axis is slightly inclined to the horizontal, so as to put the aggregates in contact with hot gases of the burner which travel through the drum in the same direction as the aggregates and finally mixing the aggregates with a liquid bituminous substance and stirring so as to coat the aggregates with said substance, causing the aggregates to rise and to fall back within the drum so as to occupy a large part of the cross-section of the drum, during a part of the travel of the aggregates inside the drum corresponding to a zone of the drum for drying the aggregates, the improvement comprising: incorporating said liquid bituminous substance into the aggregates at the end of said drying zone by raising the aggregates in such manner that the excess fines which are separated from the aggregates during their contact with said hot gases remain in suspension in said hot gases circulating in the drum; hot mixing the aggregates and said bituminous substance in a mixing zone of the drum operative without raising the aggregates in the drum, in contact with an inner wall of the drum; collecting the hot gases at the outlet of the drum so as to entrain the excess fines out of the drum.

Claim 8

A device for fabricating bituminous coated products comprising a dry-mixing drum having a longitudinal axis, a case, an inlet at one end of the drum and an outlet at an opposite end of the drum, a burner combined with the drum so as to produce a flame which enters the drum through said inlet, said inlet being adapted to also receive aggregates, the drum having a group of successive zones between the inlet and the outlet, means for recovering coated products and hot gases which have travelled through the drum in communication with said outlet, the different successive zones comprising on an inner surface of the case of the drum fins which are different from one zone to the other, at least one of the zones having fins which ensure complete raising of the treated material and falling back of the material throughout the section of the drum, the device further comprising means for introducing a bituminous substance adjacent an outlet end of said zone ensuring the complete raising of the aggregates, and a mixing zone which follows said zone for drying with raising of the aggregates relative to the direction of travel of the aggregates through the drum and comprises mixing means on an inner surface of said case of the drum which ensure a mixing and stirring without raising the aggregates and the bituminous substance.

Claim 9

A device for fabricating bituminous coated products comprising a dry-mixing drum having a longitudinal axis, a case, an inlet at one end of the drum and an outlet at an opposite end of the drum, a burner combined with the drum so as to produce a flame which enters the drum through said inlet, said inlet being adapted to also receive aggregates, the drum having a group of successive zones between the inlet and the outlet, means for recovering coated products and hot gases which have travelled through the drum in communication with said outlet, the different successive zones comprising on an inner surface of the case of the drum fins which are different from one zone to the other, at least one of the zones having fins which ensure complete raising of the treated material and falling back of the material throughout the section of the drum, the device further comprising means for introducing a bituminous substance adjacent an outlet end of said zone ensuring the complete raising of the aggregates, and a mixing zone which follows said zone for drying with raising of the aggregates relative to the direction of travel of the aggregates through the drum and comprises mixing means on an inner surface of said case of the drum which ensure a mixing and stirring without raising the aggregates and the bituminous substance.