1. Field of the Invention
The present invention is directed to a ground contact height sensor for a harvesting header having two pivotally coupled rigid arms.
2. Description of the Prior Art
Agricultural combines may be provided with header height control systems to control the position of the harvesting header relative to the ground. Ground contact sensors may be used to determine the distance of the bottom of the header to the ground. These ground contact sensors generally comprise a downwardly extending arm that contacts the ground below the header. As the arm is deflected upwardly by an obstruction the arm moves a mechanical linkage or a potentiometer which signals the automatic header height control system raising the harvesting header.
In one sensor configuration a J-shaped rigid arm is coupled to a transverse rotatable shaft. As the arm is deflected the shaft is rotated shifting a potentiometer or a mechanical linkage. Because of the J-shape and the rigid nature of the arm it can be difficult to store these arms inside the floor of the header. In addition, these J-shaped arms have a relatively narrow radius, so it can be difficult to put the combine in reverse without damaging the sensor.
In another sensor configuration bowed spring steel hoops form the arms. The hoops can be flattened out to fit within a recess under the floor of the platform. In addition, the hoops form a large radius facilitating reverse movement of the combine. However hoop sensors can be easily damaged during sharp turns if they are following a furrow.
It is an object of the present invention to provide a ground contact height sensor that can be easily stored within a recess under the floor of the header, that will not be easily damaged during sharp turns, and that will not be easily damaged during reverse movements.
The sensor comprises a transverse rotatable shaft, a first rigid arm, a second rigid arm and a connecting member. The rotatable shaft is rotatively mounted to the frame of the header. The first rigid arm has a first end that is rigidly mounted to the rotatable shaft. The first arm extends downwardly and rearwardly from the rotatable shaft in a curved manner. The second rigid arm is pivotally coupled to the second end of the first rigid arm. The second rigid arm extends upwardly and rearwardly from the second end of the first rigid arm. The first and second rigid arms defining a relatively large radius. A connecting member secures the rearmost end of the second rigid arm to the frame of the header. In the illustrated embodiment the connecting member comprises a chain. To maintain the radius of the two pivotally connected rigid arms the hinge joint joining the two rigid arms is provided with a torsion spring. The limits of the pivoting movement is controlled by stops.