There are several demands made on the cutting header of a harvesting machine. The first demand is that the crop be cut at the desired height and be delivered as desired for further treatment in the harvester. Therefore, the cutting header must be adjustable in accordance with often very varied harvesting conditions or other specific demands. As an example may be mentioned the demands made on the header of a whole crop harvester, which include a very low stubble height. Prior art often includes adjustable skids in combination with a spring balancing system to make the header follow the ground contour closely. In this case it is very important that the header is well balanced. In other words the weight of the header must not exceed the carrying ability of the skids in case the skids run into an elevation. Otherwise the header easily digs into the ground, which implies a great risk for extensive damage. In other words, the header must be floating. It has been difficult to unite these demands according to prior art. This is especially true for very large and heavy cutter headers, with a great mass to be accelerated and hence a low mobility.
Prior art also includes the use of mobile headers in combination with sensing runners or other sensing elements underneath the cutter-bar, which detect unevenness of the ground and feed impulses to the hydraulic cylinders of the integrated cutting header. These known systems also include hydraulic balancing. The purpose is to control the set stubble height automatically. The existing systems have not, however, solved the above problem, and have in practice exhibited certain other drawbacks, such as a risk of having the reel run into the cutter-bar when working at a low height if the header is raised quickly as a result of the detectors sensing some elevation of the ground underneath the cutter-bar.