Abstract: In an axial fan, the angle of curvature of the median line of each blade in axial projection is nil at the hub and for about one third of the radial extension of the blade from the hub. The blade angle of each blade is substantially constant along the blade and the chord between the leading edge and the trailing edge of each blade is substantially constant along the blade between the hub and the outer ring.

Abstract: The device is mounted in an agricultural machine comprising two links for drawing an implement, a lifter member and a central control unit for controlling the member. The device comprises: two horizontal bars carried in the form of brackets from the chassis of the machine; and four resistive elements deposited on flat faces of the bars symmetrically with respect to a neutral axis defined in this latter, made of a material having an electrical resistance proportional to the deformations to which they are subject and connected in a Wheatstone bridge circuit in such a way such that this arrangement generates an electrical signal proportional to the imbalance of the bridge caused by the deformations to which the elements are subjected, and which are transmitted from the traction force on the implement.