Harvesters – Motorized harvester – With condition-responsive operation
Reexamination Certificate
2000-11-17
2002-09-03
Pezzuto, Robert E. (Department: 3671)
Harvesters
Motorized harvester
With condition-responsive operation
Reexamination Certificate
active
06442916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to agricultural combines. It relates particularly to the threshing assembly in a rotary combine.
BACKGROUND OF THE INVENTION
An agricultural combine is a common and well-known machine for harvesting crop materials. Agricultural combines are available in various designs and models to perform the basic functions of reaping crop materials from a crop field, separating the grain from the non-grain crop materials, and discarding the non-grain crop materials back onto the crop field.
A typical combine includes a crop harvesting apparatus, or header, which reaps ripened crop plants from the crop field. The header then feeds the crop materials rearwardly to a threshing apparatus. One type of threshing apparatus that is well-known to those skilled in the art is a rotary thresher. In such a system, the crop materials are introduced to the front end of a rotor assembly, which is oriented longitudinally within the combine body with the rear end positioned angularly upwards from the front end. The crop materials are then threshed in the annular space between a rotating rotor and the inside of a rotor housing.
Along the exterior of the rotor is a series of rasp bars which repeatedly, but gently, strike the crop plants as they spiral through the annular space between the rotor and rotor housing. The rasp bars also cooperate with spiral vanes along the interior of the rotor housing so that the crop plants feed rearward through the rotor assembly.
As the crop materials feed through the rotor assembly, the fine materials are separated from the course materials. Typically, the fine materials include grain, partial grain heads, and broken pieces of crop stalks; while the course materials include crop stalks, leaves, and empty grain heads. The unwanted course materials continue their rearward travel through the rotor assembly and are discharged out from the rotor assembly's rear end. On the other hand, the fine materials pass through openings in the concave and grate which are positioned along the bottom side of the rotor housing. These materials are then further separated in an area below the rotor assembly by a series of moving sieves in conjunction with a forced air flow. After final separation, the grain is directed to an onboard grain bin through an augering system, with the unwanted fine materials, sometimes referred to as chaff, being discharged out the rear end of the sieves.
The effectiveness of the threshing system can have a significant impact on the success of a farm's harvesting operations. For example, the efficiency of the threshing system directly affects the time required to complete the harvest. Typically, farmers prefer the harvesting operations to proceed as quickly as possible. One reason that a quick harvest is desirable is the unpredictability of the weather and the risk of losing a portion of the crop due to rain, snow, wind, or hail. Another reason for this urgency is the high cost of the harvesting operation, which includes the cost of combines, trucks, and labor. By operating quickly and efficiently, a farmer can lower the cost of the harvesting operation by harvesting a larger area of land with the same equipment and manpower. Therefore, threshing systems which separate grain and non-grain materials more quickly are desirable.
In addition, grain losses have an adverse impact on the financial profits of the harvesting operations. Grain losses occur when the threshing system fails to separate some of the grain from the non-grain materials. This unseparated grain is then discharged from the threshing system along with the non-grain materials and is spread back onto the crop field where it is left unrecovered. Farmers are particularly concerned with grain losses because the grain yield from the harvest disproportionately affects the farmer's profits. Typically, the harvest represents the farmer's sole source of revenue, which necessarily must be sufficient to cover all the costs that the farmer has expended to raise the crop. Crop losses, thus, directly reduce the farmer's profits by reducing the amount of recovered grain that can be sold. Therefore, threshing systems which minimize the amount of lost grain are desirable.
Grain damage also directly reduces the farmer's financial revenues from the harvesting operations. Grain damage occurs when the mechanical threshing system repeatedly strikes the grain with a sufficient impact to crack the grain into fragments. Typically, the amount of damaged grain increases as the grain is threshed longer in the rotor assembly. Thus, greater amounts of grain damage are usually experienced near the rear end of the rotor than at the front end. Damaged grain is less valuable to grain consumers, however. As a result, the farmer receives a lower price if the grain includes an unacceptably high level of fragmented grain. Therefore, a threshing system which minimizes grain damage by quickly separating the grain near the front end of the rotor is desirable.
Manufacturers of combines commonly provide a number of different adjustments that can be made to the threshing system in order to achieve an optimal balance of efficiency, grain loss, and grain damage. For example in one adjustment, the position of the concave can be changed to modify the shape of the annular threshing space between the rotor and the concave. This adjustment is used to balance the flow of fine materials through the concave and grate, which then fall onto the sieves. Experience has shown that the sieves operate most efficiently when a shallow mat of crop material is spread across the top of the sieves. Optimally, this mat will be thick enough to prevent the cleaning fan air from escaping through the sieves but will be thin enough to allow the grain to sink down through the mat. Additionally, the optimal mat will spread evenly across the width of the sieves but will be somewhat thicker towards the front of the sieves and thinner towards the rear of the sieves. Typically, the concave can be repositioned both in a vertical direction and a side-to-side direction in order to achieve a desired material flow from the rotor assembly to the sieves. Thus, by adjusting the concave inward towards the rotor's axis, a greater amount of fine materials will drop to the sieves along the front end. On the other hand, by adjusting the concave outward and away from the rotor, the material flow to the sieves will move rearward along the axis of the rotor. In a like fashion the concave can be adjusted side-to-side to balance the material flow laterally along the width of the sieves.
The sieves are also adjustable by either pivoting them towards a closed position or pivoting them towards an open position. Generally, the sieves are adjusted based on the amount of crop material that falls from the concaves. Thus, when a large amount of material falls to the sieves, the sieves will be opened in a wide position to accommodate the extra material. On the other hand, the sieves will be closed in a narrower position when smaller amounts of materials fall to the sieves.
Similarly, the speed of the cleaning fan can be adjusted to accommodate the volume of material flow from the rotor assembly. In this case, more airflow is needed when large amounts of material are present on the sieves. When smaller amounts of material are present, the fan speed is decreased for less air flow.
In another adjustment, the angle of the spiral vanes on the inside or the rotor housing can be changed. The angle of the spiral vanes determines the rate at which the crop materials travel rearward through the annular threshing space. Similar to the theory of a screw thread, a high spiral angle causes the crop materials to feed more quickly through the rotor assembly; whereas a low spiral angle slows the feed rate through the rotor assembly. This adjustment, therefore, causes the material flow to the sieves to be moved forward or rearward along the axis of the rotor.
In a final set of adjustments, the rotational speed of the rotor and the
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