Method and device for setting the pre-tension of blades of a granulating device

A method of setting pre-stressing, by which blades ( 11 ) of a granulating head carried by a shaft ( 12 ) which is driven by a motor ( 21 ) and which is displaceable in the axial direction of a granulating device abut against the perforated plate ( 8 ), makes use of the torque of the motor ( 21 ) for the said setting. To this end, the shaft ( 12 ) is adjusted at a constant speed in both axial directions in succession, the pattern of the torque M of the motor ( 21 ) being recorded over the displacement path x of the shaft ( 12 ) for both directions. The differential dM/dx is formed from this and the position x0 of the shaft is then determined for dM/dx =0. Starting from the said position x0 a position x=x0+xz of the shaft ( 12 ) is set, in which xz represents the desired advance of the shaft ( 12 ) in the direction towards the perforated plate ( 8 ). The device for carrying out this method provides for a sensing device ( 66 ) for the time pattern of the torque M of the motor ( 21 ). The output signal of the said sensing device ( 66 ) influences an actuating drive ( 75 ) for the displacement of the shaft ( 12 ). In addition, a device ( 69 ) for forming the differential dM/dx is provided, as well as a device ( 70 ) for determining the position x0 of the shaft ( 12 ) for dM/dx =0. The said two devices are connected to the actuating drive ( 75 ).