Solid material comminution or disintegration – Processes – Miscellaneous
Reexamination Certificate
2000-11-27
2003-04-22
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
Miscellaneous
C241S301000
Reexamination Certificate
active
06550700
ABSTRACT:
BACKGROUND OF THE INVENTION
The corn kernel, illustrated in
FIG. 1
, has a number of components, each being best suited for various uses. The process of modern dry corn milling seeks to segregate and separately process the below-identified parts of a kernel of corn as each part has a separate commercial use. The hard outer shell is called the pericarp or the bran coat. The end of the corn kernel which adheres it to the corn cob is called the tip cap. The interior of the corn kernel consists of the endosperm and the germ. The endosperm is generally broken into two parts: soft endosperm and hard endosperm. For purposes of human consumption, the hard endosperm generally produces grits and corn meal, and the soft endosperm generally produces corn flour. The germ contains a much higher percentage of fat compared to the other parts of the kernel and is the source of corn oil.
Of course, dry corn milling is an ancient practice to the human race, dating back many, many years. Historically, mill stones were utilized to grind the corn into meal. Wind- and water-powered mills developed several hundred years ago allowed for increased efficiency in the processing of corn. For the last hundred years, milling operations have utilized roll milling equipment in an effort to separate the components of the corn kernel for more particularized uses.
Modern roll milling equipment utilizes contiguous rollers with varying sized corrugations and varying sized roller gap spacings to grind corn or other grains to achieve the desired particle size fractionation. Typically, mills employ rollers in series with increasingly narrow gaps in a gradual milling process. Through this process, the broken kernels are segregated by size which ideally results in various parts of the corn kernel being segregated and removed to differing processing pathways, often referred to as streams.
Initially, in a typical milling process, after cleaning the hard outer shell, the corn kernel is fractured via a mechanical process thereby freeing and removing the germ from the remaining parts of the kernel—a step called degermination. The remaining parts of the kernel are broken up by the series of rollers. As this material is processed, the hard outer shell (bran) flakes are removed and the remaining inner meat of the kernel—the soft and hard endosperm—are ground further as differing product streams pass through the series of rollers and sifters which separate product by particle size. The end products of the dry corn milling operation are bran, grits, meal, flour, and high fat germ.
A flow scheme typical of prior art mills is illustrated in U.S. Pat. No. 5,250,313. In FIG. 5, of the '313 patent (reproduced herein as FIG.
2
), the incoming corn is cleaned, washed, tempered to the appropriate moisture content, fractured or degerminated, and dried. Various designs exist to carry out the step of degermination. For example, the Ocrim™ degerminator uses a spinning rotor having combination blades to operate against a horizontal, perforated cylinder that only allows partial kernels to pass. The rotor and breaker bars are set to break the corn against a spiral rotor bar and a cutting bar. Another known degerminator is the Beall™ degerminator. In the Beall™ degerminator, grinding occurs through an abrasive action of kernel against kernel, and kernel against a nested conical surface and screen. Impact-type degerminators are also used. An example is the Entoletor™ degerminator. The Entoletor™ includes a vertical drive shaft that operates a rotor. Kernels are fed downwardly towards the rotor where they are accelerated outwardly to impact a surrounding liner surface.
Generally, the product from the degerminator is separated into a first stream that is relatively rich in endosperm and a second stream that is relatively rich in germ and bran. Specifically, with reference again to
FIG. 2
, the degerminated corn is aspirated to effect initial density separation of the fractured kernel. The tailings and liftings from the aspirators are further separated through additional aspiration or the use of gravity tables. In general, bran, whole germ and germ contaminated particles obtained via density separation are lighter than other constituent parts and may be partially removed via gravity separation to be directed through a series of germ rollers and sifters (which may further separate germ from other components for separate processing in an oil recovery process). Separated, primarily endosperm-containing streams from the gravity tables and aspirators may be directed to different break rollers depending on the particle size of the stream. For example, those primarily endosperm-containing streams having smaller particle sizes may be directed past the first and second break rollers, or as illustrated in
FIG. 2
, beyond to later break rollers.
The “break rollers” used in a gradual break process typically comprise corrugated rollers having roller gaps that cascade from wider roller gaps for the 1st break roller to more narrow roller gaps for subsequent break rollers. Roller gaps are the spacings between the exterior or “tip” portions of the corrugations on opposing rollers. The use of 5 break rollers is typical, and roller gaps may vary depending on the desired finished product. Typical roller gap distances on prior art systems range from about 0.01 to about 0.07 inches, wherein smaller gaps result in finer particles. In general, the break rollers are operated such that opposing corrugated roller faces rotate at differing rates. Most roller corrugation configurations present a sharp edge and a dull edge as determined by the slope of the corrugation surface. Therefore, breaking may occur under a sharp to sharp, sharp to dull, dull to sharp, or dull to dull arrangement of opposing corrugations.
After break rolling, the further-broken particles are separated, typically by a sifting process. From there, larger particles are further rolled in a subsequent break roller (and the further-broken particles are again sifted), or they are passed on to drying or cooling steps or additional sifting steps to isolate finished products (flour, meal, grits, etc.). Typical finished-product requirements may be found generally in 21 CFR §§137.215-285 (1993). Of course other products may be desired by particular purchasers. The remaining particles that fail to pass the post germ sifting steps are typically sent to a germ handling process (labeled oil recovery in FIG.
2
). The finer particles obtained from the germ roller siftings are processed in a manner generally similar to the finer particles from the break rollers.
In years past, all corn was received and milled with the dry miller accepting whatever percentage of the final product that could be derived from the corn. However, in an effort to maximize production of specific food products, today it is desirable to be able to select corn hybrids which have a higher proportion of the desired component. In traditional wet corn processing, the desired components are the soft endosperm and the germ. In traditional dry corn milling operations, the desired component is the hard endosperm.
With the advent of hybrid corns being developed in the 1930s, dry millers began to seek information in advance as to what percentage or yield of grits could be expected from a particular hybrid in the miller's production facilities. The sources of this information were “candling”, speculation regarding grain millability characteristics based on agronomic data, and the collection of sample data from actual dry corn milling production runs.
Candling refers to the process of shining a light through a sample of kernels to obtain a very rough estimate of the relative percentage of germ, hard endosperm and soft endosperm in the kernels. Candling therefore is an imprecise method that may, literally, rely on the observation of shadows and which cannot provide detailed information to teach a miller how a given sample will perform in a given mill.
Analysis of grain based on agronomic data requires the observance of physical traits and a great
Griebat John
Strief David
Johnson Glenn
Rosenbaum Mark
Stilwell Douglas J.
The Quaker Oats Company
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