Crop harvesting machine with calibration of the header float springs

A crop harvesting machine comprising:

• a crop header for cutting a standing crop from the ground comprising:
• a header frame;
• a cutter extending across a front cutter bar of the header frame for cutting the crop;
• a transport system operable to transport the crop to a central discharge opening of the header;
• a vehicle for carrying the header comprising:
• a vehicle frame having a first end and a second end;
• ground wheels for supporting the vehicle in movement across the ground including a pair of transversely spaced first wheels at the first end;
• a mounting system carried on the vehicle at the first end of the vehicle frame for supporting the header at a position in front of the first end;
• a spring float assembly attached to the mounting system at a position on the mounting system so as to connect the header frame to the mounting system and so as to allow floating movement of the header frame relative to the mounting system over a range of floating movement;
• a lift arrangement for providing raising and lowering movement of said position on the mounting system relative to the vehicle so as to change a distance of said position on the mounting system from the ground, said lift arrangement being arranged to hold the mounting system in fixed position determined by the lift arrangement to prevent float of the mounting system under loads from the header;
• the spring float assembly including a first and a second support arms spaced transversely of the header each extending forwardly from a respective one of first and second pivot connections on the spring float assembly to the header for supporting a respective one of first and second sides of the header;
• the spring float assembly including a first and a second resilient spring assemblies each of which flexes in response to the floating movement with each spring assembly being arranged on a respective side of the mounting system and engaging a respective one of the first and second support arms;
• the spring float assembly including said first and second resilient spring assemblies and said first and second pivot connections being mounted so as to be raised and lowered by said raising and lowering movement of said position on the mounting system;
• each of said first and second said resilient spring assemblies spring including a respective one of first and second actuators operable to adjust a length of the respective resilient spring assemblies and hence a spring force of the respective resilient spring assemblies;
• and a spring calibration system comprising:
• an initiator for initiating a calibration operation;
• first and second transversely spaced detectors for providing an output signal indicative of a position of a respective one of said first and second sides of the header within the range of floating movement;
• and a control system arranged, when the calibration operation is initiated, to:
• a) firstly operate the first actuator to increase the spring force of the first spring assembly by increasing the length of the first resilient spring assembly, to detect a predetermined position of the first side of the header within the range of floating movement and, when that position is reached as the spring force is increased, to set the first actuator at a condition of the first actuator determined by the spring force when the predetermined position is reached,
• b) secondly operate the second actuator to increase the spring force of the second spring assembly by increasing the length of the second resilient spring assembly, to detect a predetermined position of the second side of the header within the range of floating movement and, when that position is reached as the spring force is increased, to set the second actuator at a condition of the second actuator determined by the spring force when the predetermined position is reached.