Abstract: An agricultural harvesting machine having feed rolls for feeding crop material along a feed path to a cutterhead which chops the crop material is provided with a metal detector for detecting ferrous metal objects passing along the feed path. The metal detector comprises a plurality of magnets and a plurality of generally planar Hall effect sensing elements. The magnets collectively produce a detection field which extends into the crop feed path. Each sensing element is disposed such that the magnetic field produced by two adjacent magnets is normal to the plane of the sensing element. In addition the sensing elements are disposed in a plurality of planes all normal to the crop feed path. However, the sensing elements are disposed in planes oriented at different angles relative to the direction of crop feed.

Abstract: In a forage harvester, a shear bar is adjusted relative to the knives of a rotating cutterhead by selectively energizing first and second motors to move one or the other end of the shear bar toward the cutterhead. A vibration sensor senses vibration of the shear bar and controls a circuit to deenergize an energized motor when vibration is induced in the shear bar. The vibration may be caused by impact of the cutterhead knives on the shear bar (a true hit) or by random noise (detected as a false hit). To discriminate between false hits and true hits, an energized motor is stopped when a first hit (true or false) is detected. A timer is set to time an interval at least as great as the time it takes the cutterhead to make one revolution, and during this interval the vibration sensor is repeatedly sampled to determine if a second hit has occurred. If a second hit is detected during the interval the first hit is assumed to be a true hit.

Abstract: In one embodiment, an operator control panel includes an enclosure in which a liquid crystal display and a pair of lamps are disposed. A first reflective surface is located inside the enclosure, and a second reflective surface is located outside the enclosure. The lamps are positioned so that light rays from their filaments are projected rearwardly onto the first reflective surface and then forwardly onto the back of the liquid crystal display while other light rays from the lamp filaments are projected forwardly onto the second reflective surface and then downwardly onto the front of the control panel. In another embodiment of the operator control panel, the lamps are disposed outside the enclosure and the second reflective surface is omitted.

Abstract: Under the control of a microprocessor first and second motors alternately drive first and second ends of a shear bar for adjusting the position of the shear bar relative to cutter head. The shear bar is adjusted so that it is substantially parallel to the cutter head even though the cutter head and shear bar may not be parallel at the time the adjustment is initiated. A knock sensor is provided for sensing impacts between the cutter head and shear bar, the knock sensor output signal being converted to a digital value for controlling the adjusting sequence. A knocker is provided for inducing vibrations in the shear bar to thereby test the operability of the knock sensor and its output circuitry. The sensitivity of the adjustment system to the output of the knock sensor is set automatically before an adjustment sequence begins to account for variations in the knock sensor, its output circuitry, and "noise" vibrations induced in the shear bar by normal machine operation.