Abstract: An agricultural machine has a machine frame adapted to move along the ground in a normal travel direction, a crop cutter on the front of the frame, and a crop comminuter carried on the frame behind the cutter. An intake device including a generally fixed feed element on the frame and another feed element displaceable on the frame toward and away from the fixed feed element is operated by a stoppable drive connected to the fixed feed element to feed the cut crop as a stream back in the transport direction to the comminuter. The displaceable element compacts the stream of cut crop against the fixed feed element. An accelerometer is connected between the displaceable feed element and the frame for joint displacement with the displaceable feed element and generates an output corresponding to acceleration of the displaceable feed element toward and away from the fixed element. The machine may also have an alarm.

Abstract: An apparatus for detecting magnetically sensible objects in an object stream longitudinally passing a predetermined location, for instance at the intake end of the conveyor of a field chopper, has according to the invention a support at the location extending transversely adjacent the object stream and having a pair of transverse ends and a center therebetween and a magnet assembly on the support having a north pole directed from between one of the ends and the center of the support transversely of the support and of the stream into the crop stream and a south pole directed parallel to the north pole from between the other end and the center of the support. The assembly forms between its poles a magnetic field having lines of force extending mainly transversely through the stream. Respective north and south sensing coils at least partially surround the respective poles so that a magnetically sensible object perturbing the field will generate respective currents in the coils.

Abstract: A hard foreign body in a stream of cut crop being moved by a conveyor in an agricultural machine to a crop comminuter of the machine is detected by first compressing the stream of cut crop transversely of its displacement direction between a pair of feed elements one of which is movable toward and away from the other and generating an actual-value output corresponding to the acceleration of the movable element toward and away from the other element. This output is compared with a set point corresponding to an acceleration level not normally exceeded by the element when the crop stream contains no hard foreign objects. An error signal is generated when the actual-value output exceeds the set point. When the error signal is issued advance of the conveyor is stopped and/or a warning is issued. The actual-value output is only generated when the acceleration of the movable feed element exceeds a predetermined limit. The actual-value output is a voltage and the set point is also a voltage.