Device comprising a movably arranged functional body and a safety mechanism for stopping movement of the functional body

A device for performing an action on a surface comprises at least one movably arranged functional body (21, 22), driving means for driving the functional body (21, 22), main safety means for decoupling the driving means from the functional body (21, 22) when a load exerted by the functional body (21, 22) in the direction of the driving means under the influence of resistance forces experienced by the functional body (21, 22) exceeds a predetermined maximum value, and additional safety means (40) which are movably arranged in the vicinity of the functional body (21, 22), and which are capable of exerting loads on the main safety means to different extents in different positions, at a side of the main safety means associated with the functional body (21, 22). The additional safety means may comprise a bar (40) having a non-circular cross-sectional area, which is rotatable about its longitudinal axis (41).