Automatic height control for harvesting machine

A crop harvesting machine comprising:

• a main body;
• a draught member located at the forward end of the main body with respect to the direction of usual forward motion of the harvesting machine;
• a ground-engageable support means to support the main body, the support means being located rearwardly of said draught member;
• crop treatment means mounted on the main body and located between the forward end of the draught member and the ground-engageable support means for engagement with crop on the ground in a field
• characterized by
• a transverse mounting member pivotally attached to the forward end of the draught member for pivotal movement about a vertical and a horizontal axis relative to the draught member, the mounting member being adapted for attachment to the two draught links of an agricultural tractor whereby the forward end of the crop harvesting machine is supported by the draught links;
• a height sensing member mounted adjacent the crop treatment means so as to rest on the ground during use, the mounting of the height sensing member permitting movement of said member up and down in accordance with ground contours,
• a mast pivotally attached to the transverse mounting member and being adapted for connection to a top link of a tractor, and
• a linkage connected at one end to said height sensing member and connected at its other end to the mast pivotally attached to transverse mounting member, the linkage being operative in use, to pivot the mast, and to set up compression or tension in said tractor top link in accordance with up and down movement of the height sensing member.