Metal detector arrangement
View Patent ↗A forage harvester comprises a feeder for feeding harvested crop material to the processing mechanism along a crop feed path It is equipped with a foreign object detector for signaling the presence of foreign objects in said harvested crop. The detector comprises a sensor having a detection field extending into at least a portion of said path. The sensor is substantially symmetric with respect to a direction transverse to the crop feed path and the detector further comprises a restriction system distinct from said sensor, making said detection field asymmetric with respect to said transverse direction. As a result, the detector becomes less sensitive to noise caused by the other components of the harvester.
1. An agricultural harvesting machine comprising:
means for processing harvested crop material;
feeder means for feeding harvested crop material to said processing means along a crop feed path; wherein said feeder means includes at least one feeder roll having a substantially cylindrical wall made out of non-ferromagnetic material;
foreign object detector means for signaling the presence of foreign objects in said harvested crop, said detector means comprising a sensor having a detection field transverse to said crop feed path and extending into at least a portion of said path, wherein said sensor includes at least one magnet, wherein said detection field is a magnetic field, wherein said sensor is substantially symmetric with respect to a direction transverse to said crop feed path;
said detector means further includes restriction means distinct from said sensor, making said detection field asymmetric with respect to said transverse direction, wherein said restriction means comprise a ferromagnetic plate extending rearwardly from said sensor, and further wherein said sensor and said ferromagnetic plate are installed within said wall.
2. An agricultural harvesting machine according to claim 1 , characterised in that said restriction means comprise means restricting the detection field in the crop feed path rearward of said sensor
3. An agricultural harvesting machine according to claim 1 , characterised in that:
said feeder means comprise at least one hollow feeder roll;
said sensor is installed inside said hollow feeder roll;
said detection field substantially extends above and forward of said feeder roll; and
said restriction means restrict the detection field rearward of said feeder roll.
4. An agricultural harvesting machine according to claim 1 , characterised in that in that said sensor comprises a set of magnets which all have the same polarity.
5. An agricultural harvesting machine according to claim 1 , characterised in that said ferromagnetic plate is mounted adjacent said sensor on a side opposite to said crop feed path.
6. An agricultural harvesting machine according to claim 1 , characterised in that said sensor and said ferromagnetic plate are mounted to a shaft portion of said at least one feeder roll.
7. An agricultural harvesting machine according to claim 1 , characterised in that said ferromagnetic plate ends short of an inner surface of said wall.
8. An agricultural harvesting machine according to claim 1 , characterised in that said ferromagnetic plate is angled.
9. An agricultural harvesting machine according to claim 1 , characterised in that said sensor is mounted to said feeder means by non-ferromagnetic mounting means.
10. An agricultural harvesting machine according to claim 9 , characterised in that said mounting means comprise at least one of non-ferromagnetic bolts and spacers.