Patent ID: 7131765

Claim:
A helical-ribbon mixer having a rotation-symmetrical inner mixing vessel wall ( 2 ), a motor-driven central agitator shaft ( 3 ) therein, on which, on lateral agitator arms ( 5 ), at least one helical ribbon ( 4 ) is held close to the vessel wall downwardly sloping with a circular slope (SZ) in a direction of rotation (D), characterized in that the helical ribbon ( 4 ), vectorially combined circularly and radially, has a helical ribbon angle of slope (SN) relative to the horizontal that is greater than a gliding angle (G) on the helical ribbon ( 4 ) of a material (M) to be mixed; wherein the mixing vessel wall has a first cylinder section ( 21 ) and a second conical section ( 20 ) engaged together with a flat bottom region ( 23 ) near an outlet of the mixer, the mixing vessel wall having a steeper slope than that of the gliding angle (G), wherein the helical ribbon ( 4 ) is sloped radially downward toward the mixing vessel wall ( 20 , 21 ) at least where the mixing vessel wall ( 20 , 21 ) extends divergently or vertically upward; wherein the helical ribbon ( 4 ) has a helical ribbon width (B) between 10% and 20% of a helical ribbon radius (R) at that location; wherein the helical ribbon ( 4 ) has a lateral clearance (S) to the mixing vessel wall ( 2 ) and is radially sloped toward the same such that, when driven, it conveys the material (M) to be mixed partly outward further up and inwardly circulating at the bottom, and partly upward, and wherein the helical ribbon ( 4 F) incorporates on its side closest to the wall a downwardly divergent clearance angle (F).