The method involves coupling partial torques (M3, M7) of corresponding two drive inputs of a power-split transmission unit (14) with each other by a planetary drive based on a superposition principle such that speed of a transverse conveyor device (2) i.e. transversal screw conveyor, is controlled or regulated based on a control process. A drive of the device is a part of the transmission unit. One of the drive inputs is comprised of a part of a drive train with a mechanical coupling- and connecting device for a driven shaft of a combustion engine. An independent claim is also included for a device for operating an accessory device for a field chopper, baling press and self-loading trailer.
