The invention relates to a working machine, in particular in the form of a surface cutter, comprising a working assembly (2) which can be driven by a motor (5). The motor can be connected to the working assembly via a power-branching transmission (6) comprising a first mechanical power branch (7) and a second electric or hydraulic power branch (8), the first and second power branches being combined by a summation transmission (9) which can be coupled to the working assembly on the output side and provides a variable transmission ratio between the first mechanical power branch and the working assembly, wherein the variable transmission ratio is adjusted by the rotational speed of the second electric or hydraulic power branch. According to the invention, a blocking device (24) is provided for blocking the variability of the transmission ratio, which can be adjusted between the first mechanical power branch and the output side of the summation transmission by the rotational speed of the second electric or hydrau
