Corn cobs have, for many years, added a certain measure of value to the harvest. Prior to the early 60's, the common corn harvesting practice was to pick the ears in the field, transport the crop to corn cribs, and later shell the corn off the cob at stationary shellers. The need to dispose of the cobs, after shelling, spurred most of the early research for useful corn cob end products. However, using stationary shellers limited the volume of cobs which had to be dealt with.
The advent of in-field shelling, by self-propelled combine harvesters, created extreme efficiencies. The combine harvesters were designed to recover only shelled corn, or shelled corn incorporating only small amounts of cob, while crushing and discharging most of the cob back onto the ground. Early attempts to recover the cobs included adjusting the fingered vanes, on the harvester's chaffer, in order to open them wider and thus allow larger amounts of broken cob to fall through. However, this caused pieces of cob to lodge in the fingers and plug the chaffer. Accordingly, the vanes were lowered back to prevent plugging. Thus, only reduced volumes of cob residuals could be obtained for corn-and-cob-mix products.
In fact, in 1986, Chester McBroom was granted a patent on the Corn Cob Saver Sieve (U.S. Pat. No. 4,600,019). One drawback was the cobs could not be directly retrieved from the combine harvester. However, McBroom discovered, inter alia, that a cob-saving sieve structure need only have its inclined parallel vanes at an angle of 45°, and have the spacing between vanes 2″ apart, to allow shelled corn and harvested cob segments to pass therethrough. His goal was to provide a corn and cob segment mix.
Retrieval of cobs directly, separately, and automatically from the combine was nevertheless undertaken by Larry Shrawder and disclosed in 1989 (U.S. Pat. No. 4,892,505) and then in 1993 (U.S. Pat. No. 5,256,106). Therein, combine harvest separator arcs were modified to a circular shape, from elliptical; and, the cross bar spacing on sieve slots was altered; and a cob conveyor was added. Again, the sieve slots were altered to a width of only 2-3 inches. His process and the special features of his combine design still limited harvesting to only cobs having lengths which did not exceed 2-3 inches.
In 1999, Vernon L. Flame, in U.S. Pat. No. 5,941,768 entitled Corn Cob Collecting Apparatus For Use With Combines, dealt with the problem of harvesting dry corn cobs. He found that the cobs could not be effectively separated from the stalks, husks, etc. through the use of air. Accordingly, he did not attempt to have cobs fall through the openings of a chaffer sieve. His solution was to use a wheeled apparatus connected to the rearward end of the combine in order to achieve separation of the cobs from a stream of crop material being discharged at the rearward end of the combine, where said end normally was designed to discharge the corn cobs, stalks, husks, etc. onto the ground.
In 2002, U.S. Pat. No. 6,358,141, by Stukenholtz, disclosed an on-board system for separating whole corn cobs by modification to the sieve and straw walker system. However, the system although allowing for the 2 inches between fingered vanes of the chaffer to allow the width of the cobs, offers no other sieve design modifications.
In recent years, as the demand and utilization of fossil fuels has skyrocketed, likewise has the demand for corn cobs as alternative renewable energy sources and as feedstock for environmentally friendly biodegradable packaging. Enormous volumes of corn cobs are needed as a principal feed stock for ethanol fuels. One company plans on harvesting cobs from plots having a minimum of 4000 acres as a component of their system that will eventually handle harvesting as much as 275,000 acres of cobs by as early as 2011. The cobs will be used, inter alia, by public utility companies as biomass to co-fire with coal, because the cob's burn value is competitive with that of wood.
For projects of this size and volume, cobs will be stored outside. Since broken cobs would more readily mold, and decay than whole cobs, the goal currently is to harvest the cobs as whole, or in lengths as long as possible. The industry therefore needs no cobs less than 3 inches in length, and as many whole cobs as possible. If the cobs were broken up, they would require storage in a dry environment, and much greater cost. One principal stumbling block to advancements in higher cob volume and higher pass throughs in sieve design was pointed out by Gordon in U.S. Pat. No. 7,011,579, issued in March 2006. Gordon pointed out that the proper opening between louvers is necessary, but if the opening is too large, straw and other material fall through contaminating the grain.
An improved chaffer and cleaning system for combine harvesters that would significantly enhance the recovery and harvesting of whole corn cobs, greater than 3″ in length, would fulfill a longfelt commercial need and provide a novel and unexpected technical advancement in the art.