Forage harvesters are machines which chop crop gathered from a field into small pieces to produce animal feed. In the case of crops such as grass or alfalfa, these will have been pre-cut and left to dry in the sun, so that the crop only needs to be gathered by the harvester. With other crops, such as maize, the forage harvester may also be required to cut the crop. Thus, the harvesters may be fitted with different headers to suit the crop being harvested.
The crop, whether cut maize or gathered grass, is fed into a rotating knife drum or cutter which comminutes the product. With grass crops, this alone is sufficient to produce the desired forage. However, when harvesting maize for silage purposes, the cutting alone does not suffice due to the presence of kernels in the crop. The kernels need to be cracked in order to release the nutrient, as uncracked kernels are hard for animals to digest. As cutting alone is insufficient to crack all the kernels, the crop is additionally passed through a crop processor which comprises two closely adjacent rollers, typically having serrated surfaces, which rotate such that there is slippage between the adjacent surfaces. The gap between the rollers is set to suit the size of grain passing through and the speed, rotational energy of the rollers, relative movement and serration of the surfaces together ensure cracking of any kernels that are still intact after chopping by the cutter.
The momentum of the maize from the crop processor or the grass from the cutter, as the case may be, carries the crop into an accelerator or blower which then propels it up a tower to a discharge spout through which it is discharged into a wagon or a trailer drawn by a separate vehicle driven alongside the harvester.
When chopping kernel-free crops, such as grass or alfalfa, the crop processor is not required and leaving it in place in the crop flow path results in its rollers being unnecessarily subjected to wear. To avoid such wear, it has previously been proposed to remove the crop processor from the vehicle. For this purpose, it is known to provide to the rear of the crop processor, a service compartment to allow an operator to gain access for servicing of the chopper and the crop accelerator (blower) as well as mounting and removal of the crop processor. However, despite the improvement in accessibility offered by presence of the service compartment, the size and weight of the crop processor makes its removal a difficult and cumbersome task.
EP 1530894 proposes removing the crop processor by lowering it on a strap onto a trolley through a trap door in the floor of the service compartment. A problem with this proposal is that one has still to slide the trolley from under the harvester and such an operation can only safely be carried out in a workshop with level ground.