Abstract: A device for the production of solid mixtures comprises a mixing drum 12 having a rectangular opening 20. The rectangular opening 20 is bordered by a first edge 18 lying in a plane. A seal 21 is disposed in the vicinity of the first edge 18 which likewise lies in a plane and which borders and completely surrounds the rectangular opening 20 both in the vicinity of the mixing drum 12 as well as in the vicinity of the end walls 11. The rectangular opening 20 extends over the entire mixing region 15 and is sealed by one single door 16 in a dust-tight manner. The door 16 is bordered by the second edge 19 which likewise lies in a plane and which seats on the first edge 18 when the door 16 is closed.