Crop threshing or separating – Cleaner – Sieve or grate
Reexamination Certificate
2002-01-25
2004-09-14
Will, Thomas B. (Department: 3671)
Crop threshing or separating
Cleaner
Sieve or grate
C460S099000
Reexamination Certificate
active
06790137
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to generally to agricultural combines and specifically to an improved chaffer/sieve for such combines.
BACKGROUND OF THE INVENTION
Agricultural combines are widely available machines which enormously speed the processes of harvesting, threshing and cleaning of all types of grains. By minimizing the labor required for harvesting, combines have contributed to the dramatic increase in availability and decrease in price of grains.
The combine machine traverses the field of grain in swathes which cover the area of the ripened crop. As it travels, the combine brings grain into its forward end and feeds it to a separating apparatus or thresher which threshes the grain, separating grain and grain heads from stalks, straw, dirt and other undesirable materials. An example of an axial flow rotor for threshing of the grain may be seen in U.S. Pat. No. 5,125,871, issued Jun. 30, 1992, to the same inventor as the present application. The present invention concerns the succeeding processing stage: the chaffing of the grain.
After passing through the threshing stage, the grain is theoretically perfectly threshed. In reality, however, while the separating apparatus is efficient, some chaff, unthreshed grain, other materials, stems, and/or straw remains intermixed with the grain and further steps of threshing, separating and cleaning are normally required.
The cleaning section of a conventional combine is located to receive grain and other material expelled from the separating apparatus. A typical cleaning section includes a chaffer and a sieve mounted so as to move back and forth reciprocally and a fan which produces a flow of air directed through the sieve and chaffer. The sieve is usually mounted below the chaffer, although it important to note that some combines have several layers of sieves and chaffers, or several in sequence. In theory, the chaffer blows the chaff and other “materials other than grain” (“MOG”) out of the stream of grain before the sieve sifts it. Reciprocation of the chaffer and sieve facilitates arrangement of the grain and other materials into a crop layer or mat on top of the chaffer. Separation of the crop material is largely facilitated by the air from the fan flowing upwardly through the passages between the louvered sieve and chaffer. Prior art chaffers/sieves include a series of adjacent louvers. A series of transverse elongated openings or passages are defined between the adjacent louvers to grade the material by density and size. Smaller, denser kernels of grain are allowed to fall through the openings despite the airflow upwards therefrom, after which they fall through the sieve mounted below the chaffer, whereas larger pieces of materials are blown or vibrated rearward in the airflow and off of the chaffer and sieve. The light material blown off the chaffer is discharged from the combine entirely, while heavier unthreshed heads of the crop still having grain is too heavy to blow and thus is moved off of the rear of the sieve, from where it is returned by the tailings system to the separating apparatus for rethreshing. Finally, there is larger MOG which is carried over the end of the chaffer and falls or blows away from there.
Thus four categories of material are created: first, the grain, which falls through the chaffer/sieve for storage, second unthreshed material which is sent back for rethreshing, and third chaff, which is blown entirely clear. Fourth, the larger material other than grain is carried off the end of the rethreshing louvers of the chaffer. To allow use of a single chaffer for grain crops of different sizes, the louvers may be adjusted in rotation, thus altering the spacing between the louvers and the characteristics of the air-flow/air-blast through them.
The proper opening between the louvers is necessary for efficient operation of the combine's chaffer. If the openings are too large, straw and other material ends up falling between them with the grain, contaminating the grain. On the other hand, if the louvers are adjusted to have openings which are too small, the individual grain requires a longer average time before finding a hole of sufficient size to pass through, thus causing a buildup of the grain, thus causing an unpredictable diminishment of the air flow, thus reducing both the speed and the efficiency of operation. Worse, some of the grain is carried off the back of the chaffer and if it falls through the louvers, is returned to the thresher unnecessarily, resulting in an excessive percentage of the grain being cracked, or if it is carried over the louvers ends up falling out the back of the combine and being lost. If the louvers are not evenly adjusted the grain may not receive uniform treatment, and in some areas, the MOG may fall through the chaffer while in others, even grain is blown away.
One particular issue is that the husk surrounding the grain may cling tightly to the grain, especially in a wheat crop, resulting in “white caps”: kernels slightly larger than the norm having husk still attached. Adjusting chaffers to use only size in a sifting or filtering apparatus to successfully reject the white caps while accepting the only slightly smaller grains which are fully threshed is a difficult process. The size difference between the chaffed and unchaffed grains can be minute: in wheat, the size difference may be as small as {fraction (5/1000)} of an inch.
An example of prior art that shows a commonly used louvered system is U.S. Pat. No. 4,511,466, issued Apr. 16, 1985 to Jones et al for “Chaffer Slat”. This clearly shows that the grain flow must make a turn in flow direction in order to advance to the clean grain collection system, this turn may be anywhere from 90 degrees to almost 180 degrees, depending upon circumstances. The grain density is greater than that of the chaff, and the grain has more inertia than does the chaff, and this inertia must be overcome in making the turn. Also, in order for the grain to fall through a louver chaffer it must rely on gravity to drop between the louvers and penetrate the blast of air passing in the exact opposite direction. As can be easily appreciated there is a conflict at this point: a powerful blast of air is needed to float the chaff above the chaffer and out the back end of the combine, but the blast must not be so strong as to prevent the grain (which is being driven backwards across the chaffer) from making its turn and falling against that air blast through the louvers to the clean grain collection system. It is also worth noting that while the grain flow path pictured in FIG. 1 of the '466 patent is depicted to closely follow the underside of each louver, in fact gravity and the reciprocating motion of the chaffer causes the grain to actually land upon the top side of the following louver. However, this contact with the topside of the following louver supports the grain and diminishes the effect of gravity in moving the grain downwards against the blast of air. In addition, the MOG tends to comprise a mixture which may include straight stalks of various lengths. With large numbers of such stalks continuously fluttering and twirling in the air blast, it is inevitable that some number of them randomly end up aligned parallel to the air blast. They can then fall with great ease straight into the air blast. The slats pictured by the '466 patent are unlikely to catch and filter out such stalks as the slats are themselves aligned parallel to the airflow, and thus a certain percentage of stalks can simply fall straight through the chaffer to contaminate the grain. One final problem with such devices is that the reciprocating motion of the chaffer/sieve combination tends to “stuff” the lighter, less inertia driven material, (chaff, and other materials other than grain) into the slanted louver openings, contributing to the problem of fouling of the chaffer/sieve.
In such a louver or air foil chaffer system reliance for filtration is on the size of the openings, but in any given crop, the grain varies in size by as much as 1
Barber Craig W
Petravick Meredith
The Law Office of Craig W. Barber
Will Thomas B.
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