An overload protection mechanism for a plough beam (3). The plough beam (3) carrying a plough body (6) is retained in ploughing position by means of a flexible, power-exerting device comprising a fluid pressure operated piston cylinder (11, 11', 12, 12'), the piston rod (12) thereof being coupled to the front end of a strut (10) anchored (9) at the rear end of the plough beam (3). However, plough beam (3) carrying plough body (6) may leave the ploughing position when the plough body (6) hits an obstacle (8) positioned in the soil and capable of being passed by the plough body (6) through a rotation of the plough beam (3) at the front end thereof, cooperating with the plough beam carrier (4) through a hinge device (16, 16'), the plough beam (3) thereafter being brought to retake the position corresponding to the ploughing position of the plough body (6). In order to achieve a protected positioning of the piston cylinder (11, 11', 12, 12') and, simultaneously, secure that the strut (10) at all times will be subjected to a tensile strain as plain as possible and minimum bending load, the piston cylinder (11, 11', 12, 12') is mounted in the plough beam carrier (4) by means of a universal joint (13, 14, 15).