contact pressure as will be clear in particular from fig6 the chains 58 59 form in combination with the supporting part 30 and the supporting fork 48 and also the first supporting assembly 66 and the second supporting assembly 70 a parallelogram guide for the two disc brushes 88 89 that is to say in the region of the chassis 14 the two chains 58 and 59 each define a first articulation point 112 and the bearing blocks 40 of the supporting bracket 36 form in the region of the chassis 14 a second articulation point 114 in the region of the sweeping brush device 65 the chains 58 59 are coupled at a third articulation point 116 to the first supporting assembly 66 the second supporting assembly 70 rigidly coupled to the prongs 49 50 of the supporting fork 48 is coupled at a fourth articulation point 118 in the form of the ball pins 99 to the first supporting assembly 66 during operation of the sweeper 10 the disc brushes 88 89 assume a sweeping position in which they act upon the ground surface that is to be cleaned with a contact pressure prescribable by the position of the spring bolt 106 when starting from the sweeping position the supporting fork 48 is pivoted by the piston cylinder unit 45 about the first horizontal pivot axis 32 the disc brushes 88 89 are raised parallel to the ground surface i e the orientation of the axes of rotation 93 94.