Fecha de publicación: 16/07/1996 Fuente: WIPO "honey" A levelling mechanism for use a in lift system of a windrowing machine of the type including a tractor unit and a swather header to permit the use of a grain header which is held suspended above the ground rather than a hay type swather header which normally engages the ground during cutting. The type of lift systems used in some known hay windrowers include a pair of lift assemblies each of which has a single action lift cylinder. The two cylinders are supplied from a common supply line, and because the moving lift components of the two assemblies are individually activated by their respective cylinders the suspended grain header does not remain levelled under certain conditions, such as if there is a build up of greater crop weight at one end relative to the other. The present levelling mechanism includes a torsion bar carried at the front of the tractor unit, the torsion bar having radial arms at opposite ends which are connected to the moving component of the adjacent lift assembly so as to resist movement of the moving components out of unison, thus keeping the head level under normal cutting conditions.