Abstract:
An internal milling device for milling of corn or other grains and in particular for debranning corn kernels, or kernels or the like, and exposing or freeing germ in dry milling. The improvements include a modified internal milling rotor, modified screen sieve, additional and modified breaker bars, and an improved particle removal system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/894,974 entitled “Corn Mill” filed on Mar. 15, 2007 in the United States Patent and Trademark Office and of U.S. Provisional Patent Application No. 60/973,641 entitled “Corn mill having increased through production” filed on Sep. 19, 2007 in the United States Patent and Trademark Office. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to an improvement to machines for milling of maize, commonly referred to as corn, and in particular for debranning corn kernels and exposing or freeing germ. Other grains may be milled as well. The embodiment may be used in dry milling and in wet milling. Particularly, the improvement is directed to vertical mills, although it may also be used in horizontal mills. Most particularly, this improvement pertains to milling machines identified as degermers. The improvements include a modified internal milling rotor, modified screen sieve, additional and modified breaker bars, and an improved particle removal system. An improved degerming machine may include less than all improvements. 
         [0005]    2. Description of the Related Art 
         [0006]    Corn milling machines are well known wherein corn kernels are debranned and the germ freed or exposed by application of impact force. In dry milling, the steeping step is omitted, although the corn is tempered in water to permit the moisture content of the corn to increase, before being introduced to the mill. In wet milling, the corn kernel is steeped in an aqueous solution so the various parts—bran, endosperm and germ—may absorb sufficient water to be milled. The corn kernels are then removed from the water and supplied from a feeding inlet to a milling chamber having a milling rotor, which serves as an impeller. The kernels are then circulated by the milling rotor and milled until exiting. The milling rotor may include one or more resistance bars mounted on the rotor within the milling chamber. During circulation, kernels may be intermittently compressed, thereby fracturing the kernel and, when compressed and abrasively contacting one another, causing bran to separate from the bran and/or germ. A perforated screen may surround the milling chamber to permit kernel fragments, generally referred to as brokens, which may be germ, endosperm, bran or a combination thereof, of less than a maximum size to exit the milling chamber. The force applied to the kernels may also be affected by selection of the screen, which may retard kernels moving through the milling chamber, induce kernels to move more rapidly through the milling chamber, or have no effect on the speed at which the kernels pass through the milling chamber. Sufficient milling for exposing germ or for reduction of the kernel broken size may be controlled by requiring a minimum force be applied to a discharge gate by or through the adjacent kernels. Removal of sufficiently milled kernel brokens prior to reaching the top of the milling chamber may be permitted by sufficiently sized perforations in the screen. 
         [0007]    Various milling systems are known in the art for degerming of kernels. Some degermer are horizontally aligned, wherein kernels are input at one end of a horizontal-oriented mill, travel horizontally during milling and then exit. The Beall-type degermer is one such well-known horizontally-oriented mill. In a Beall-type degermer, corn is fed into and through the annulus at one end and between a rotating, conical rotor and a stationary concentric screen made of perforated metal. Both rotor and screen are textured with large nodes, which impede motion of the kernels as they are impelled by the rotor. A weighted discharge gate may be used to control the pressure and corn density in the process. This process dislodges germ from the endosperm by impact and bending stresses as the kernels move through the annulus and results in breakage of most of the kernels. As bran layers may remain with the pieces of endosperm after processing, further refinement may be necessary to reduce the fiber content of the endosperm product. 
         [0008]    Alternatively, vertical degermers may be used. Vertical degermers are known in the art wherein corn, or other grains, is continuously introduced to the mill at its base, which drives the previously-entered kernels upward. One such machine is the Satake Maize Degermer VBF. During rotation of the milling rotor in a vertical degermer, the corn is circulated horizontally by the milling rotor and is retained by the surrounding screen while being lifted by injection of additional corn from the base and induced upward by angled, elongated orifices through the screen. It is well known in the art that a polygonal screen rather than one that is circular may be used to vary the compression on the kernel during processing. Use of a polygonal screen results in compression of the kernel most particularly at the point where the screen and milling rotor are closest. Additionally, breaks or breaker bars may be installed about the screen that produce further localized areas of compression, which result in further fracturing of the kernels, or propagation of existing fractures within the kernels. 
         [0009]    Problematically, kernels that are sufficiently fractured early in the milling process continue to be milled with insufficiently fractured kernels, often resulting in excessive milling and thereby degradation of products. It is generally desirable to minimize the production of fine particles, as the fine particles are difficult to separate in order to recover them as a corn product. As a result breaker bars have been used in the prior art solely at the upper section of the screen in such vertical degermers to accelerate fracturing of the kernels immediately prior to discharge. The thickness of breaker bars substantially affects the output and milling time, as well as the power applied by the milling rotor to the kernels. Brokens generated by the milling are permitted to leave the milling chamber by holes or slots in the screens and collect at the base of the screen. Those brokens passing through the screen are known as throughs. The throughs are then ejected into piping by a paddle affixed to the lower section of the milling roller. The piping is connected to a negative or reduced pressure system, such as a vacuum pump, to draw the throughs along the piping, often laterally, and to a throughs collector. This is typically performed under general exhaust. 
         [0010]    Additionally, the screen surrounding the milling chamber wears, and often wears unevenly, particularly at the bottom. The constant abrasion of the corn kernels wears the periphery of the perforations of the screen. Due to the forces generated at the point of introduction of the corn kernels, particularly the bottom of the milling chamber in the vertical degermer, the screens wear first adjacent the point of introduction of the corn kernels. Such wear requires frequent screen replacement even though the upper portions of the screen remain usable. 
         [0011]    It is known in the art to temper the corn kernels to be milled by addition of a measured amount of water. Tempering permits control of the softening and expansion of bran layers while avoiding or limiting penetration of water into germ or endosperm. Absorption of water renders the layers of bran more pliable, and weakens the bond of bran to germ and endosperm. The water may be in liquid or steam form, or may be combined with other chemicals. The corn kernels are then retained in a holding tank for a specific period of time to obtain the desired level of moisture absorption. Various tempering methods are known to produce the desired moisture absorption. 
         [0012]    With the rise of bio-energy as an alternative to petroleum fuels, particularly in the nature of ethanol, the demand for endosperm, from which starch may be obtained, has increased. 
         [0013]    The prior art processes resulted in unacceptable percentages of fine particles of endosperm that are difficult to separate from the bran and germ particles in order to recover them as a corn product. 
         [0014]    There is therefore a need for a mill which more efficiently mills the corn kernels. 
         [0015]    It would therefore be an improvement to affect the corn kernels with breaker bars earlier in the milling process and to provide a system for removal of sufficiently fractured corn kernels throughout the milling process. 
         [0016]    It would therefore be a further improvement to induce more friction among the kernels in the milling chamber by surface conditions on the milling rotor. 
         [0017]    It would also be an improvement to separate endosperm from the kernel and to maintain the endosperm in the largest possible particle size, 
         [0018]    It would also be an improvement to provide a system capable of placing the milling chamber under a lowered air pressure to remove the larger quantity of throughs produced from the improved milling device. 
       SUMMARY OF THE INVENTION 
       [0019]    Accordingly, it is an object of the present invention to provide a process and apparatus for increasing the production of large particles of endosperm, and thus maximize yields of low-fat corn products and improve the value of the products. 
         [0020]    The present invention increases the effectiveness of a conventional vertical mill, typically of the type of vertical mill having a central rotor shaft with one or more resistance bars, i.e. protuberances, thereon, by introduction of several improvements. These improvements include one or more breaker bars affixed to the outer edge of the milling chamber below the standard row of breaker bars. The improvements further include multiple uniformly-spaced protuberances on the milling rotor coplanar with the standard and additional breaker bars. Additionally, uniformly spaced perforations in the screen are sized to permit throughs to escape the milling chamber and are not oriented to speed or retard processing through the milling chamber are provided. The improvements further include a segmented screen that includes a removable lower section to permit replacement after wear. The improvements further include a gravity separation of small and large throughs. The present invention increases the surfaces to fracture kernels, propagates earlier fractures through the kernels to permit degerming, sufficiently mills particles before reaching the discharge gate opening, and facilitates separation of tails and throughs. 
         [0021]    The present invention also provides a mill having increased effectiveness in debranning kernels and exposing or freeing the germ without excessive production of fines and flour. Unlike conventional mills, the present invention includes breaker bars at two vertical positions at the periphery of the milling chamber. The breaker bars intermittently increase the compressive force in the kernel about the breaker body not merely at the vertical position of the discharge gate opening, but also at planes below the discharge gate opening. The edge of each breaker bar provides the location for fracturing the bran and endosperm. The blade body terminates to provide an area for kernel decompression that may also encourage propagation of cracks within the kernels. A screen may be used to induce fracturing of kernels and to permit sufficiently milled kernel particles. Importantly in the present invention, the screen may be perforated with round orifices, which neither retard to induce vertical movement in the milling chamber, rather than slots, which are intended to increase or retard kernel flow through the milling chamber. Production of sufficiently milled particles, without excessive production of fines or flour, results. 
         [0022]    The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a cross-sectional top view of a whole corn kernel. 
           [0024]      FIG. 2  illustrates a front view of a debranned corn kernel. 
           [0025]      FIG. 3  illustrates a side view of a debranned corn kernel. 
           [0026]      FIG. 4  illustrates a cross-sectional side view of a typical milling machine known in the art. 
           [0027]      FIG. 5  illustrates a cross sectional side view of the feed inlet for the milling machine illustrated in  FIG. 4 . 
           [0028]      FIG. 6  illustrates an exploded view of a milling rotor known in the art. 
           [0029]      FIG. 7  illustrates an isometric view of the front and rear frames which retain the screen sections to define the outer edge the milling chamber. 
           [0030]      FIG. 8  illustrates a view of the front and rear sections of the screen with the row of breaker bars known in the prior art. 
           [0031]      FIG. 9  illustrates a top view of a breaker bar installed at the top of a screen. 
           [0032]      FIG. 10  illustrates a front view of the front and rear screens of the present invention. 
           [0033]      FIG. 11  illustrates an exploded view of a milling rotor of the present invention. 
           [0034]      FIG. 12  illustrates a side view of the present invention illustrating the throughs product discharge collector. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    Referring first to  FIG. 1 , a corn kernel  100  is illustrated for reference as to terms used herein. As illustrated in  FIG. 1 , a typical corn kernel  100  includes bran  102 , germ  104 , and endosperm  106 . As illustrated in  FIG. 1 , the germ  104  is embedded in one of the large, relatively flat sides  108  of kernel  100 . A debranned kernel  200 , comprising generally germ  104  and endosperm  106 , is illustrated in  FIGS. 2 and 3  from a front and side view, respectively, As used herein, “debranned” refers to a kernel having some, though not necessarily all, bran removed. 
         [0036]    A vertical mill  400  of a type known in the art is disclosed in  FIG. 4 . The purpose of mill  400  is to generally cause a portion of the bran  102  encasing the kernel  100  to be removed and to fracture the endosperm  106  sufficient to provide access to and/or to free the germ  104  attached thereto. The mill  400  also permits on-going removal of sufficiently milled brokens that may be separated into bran  102 , germ  104 , and endosperm  106  thereafter. As a result of the vertical orientation, vertical mill  400  has a top and a bottom. As illustrated in  FIGS. 4 and 5 , a detail of the bottom inlet portion of vertical mill  400 , in operation, kernel  100  is introduced to the mill  400  via a feeding inlet  402  located proximate the bottom of the milling chamber  404 , from which point the kernel  100  is conveyed by a feed screw  406  to a feed rotor  408 , which conveys the kernels  100  to milling chamber  404 . Alternative methods for introducing kernels  100  to milling chamber  404  at feeding inlet  402  are known in the art. 
         [0037]    A vertically-disposed milling rotor  412 , located in milling chamber  404 , is of a type known in the art. Referring to  FIG. 6 , the vertically-disposed milling roller  412  includes on its surface at least one resistor bar  602  and may include a spacer  604  between the resistor bar  602  and the milling rotor  412 . Any number of resister bars may be affixed to the milling rotor  412 . As illustrated in  FIG. 6 , the milling rotor includes include two resistor bars  602  each with one spacer  604 , although a mounting location for a third resistor bar  602  is found on the face of milling rotor  412 . 
         [0038]    Returning to  FIG. 4 , it is known that during rotation of milling rotor  412 , kernels  100  are induced to move in multiple planes by surface friction from adjacent kernels  100 , by the surface of milling rotor  412  and by the surface of resistor bars  602  illustrated in  FIG. 6 . It is also known to place a screen  410  surrounding milling rotor  412  and milling chamber  404  to provide the outer boundary of milling chamber  404 . Screen  410  is retained in place by frames  414 , illustrated in greater detail in  FIG. 7 . 
         [0039]    As kernels  100  are forced into milling chamber  404  by feed rotor  408 , the kernels  100  previously introduced are pushed toward the top of milling chamber  404  where milling chamber  404  communicates with a discharge gate at discharge outlet  420 . The amount of force exerted on materials to be milled, which may include kernels  100 , debranned kernels  200 , and brokens thereof, within milling chamber  404  may be controlled in part by the force necessary to open discharge gate at discharge outlet  420 , which may be varied by a weight  418  or any spring combination, and by the feed rate and force of feed rotor  408 . Absent the necessary force, the discharge gate does not open, retaining the materials to be milled within the mill  400  and resulting in additional milling within milling chamber  404 . 
         [0040]    As illustrated in  FIG. 8 , a typical screen  410  is constructed in two sections, a front screen  802  and a rear screen  804 . Screen  410  is constructed to fit within frame  414  (illustrated in  FIGS. 4 and 7 ), and may be constructed to present a constant surface or any number of panels, preferably as an equilateral polygon. As illustrated, screen  410 , when assembled, has twelve panels  806 . At least one panel  806  includes perforations  810  which permit brokens smaller than the perforation  810  to escape the milling chamber  404  and which may be arranged in rows  812 . Variations in the selection of the perforations  810  are well-known the art, including perforation size, shape and orientation. As illustrated in  FIG. 8 , round perforations  810  are included on ten of the twelve panels  806 . Perforations are not included on those panels  806  which are adjacent the portion of two-part frame  414  (illustrated in  FIGS. 4 and 7 ) where the two sections mount together and therefore do not permit communication through the screen  410 . These perforations provide surface edges against which materials to be milled may rub during rotation within the milling chamber  404  (illustrated in  FIG. 4 ). As can be appreciated, as the surfaces of materials to be milled contact other materials to be milled, and the perforations  810 , the bran  102  may be dislodged from the materials to be milled, transforming them to debranned kernels  200  and brokens thereof. 
         [0041]    Front screen  802  fits about discharge outlet  420  (illustrated in  FIG. 4 ) and therefore has reduced surface area on the panels  806  communicating with discharge outlet  420 . Screen  410  has an upper section  808 , typically the upper one-third of screen  410 . It is known in the prior art to increase the milling process by affixing breaker bars  814  to the screen  410 , which is affixed to frame  414 . It is also known to place the breaker bars  814  in a row  816  in the upper section  808  of the screen  410 , as lower placement may result in overmilling of kernels  100  before exiting milling chamber  404  through discharge gate  420 . As illustrated in  FIG. 8 , breaker bars  814  may be vertically-oriented and comprise breaker bars  818 ,  820 ,  822  and  828  which nearly span the upper section  808  and breaker bars  824  and  826  sized to fit the portion of length of upper section  808  reduced by discharge outlet  420 . Each breaker bar  814  is positioned proximate the intersection of two panels  806  to produce localized areas of compression, particularly when a resistor bar  602  (illustrated in  FIG. 6 ) rotates past. The breaker bars  814  may be affixed to screen  410  in any manner, but are most commonly affixed with a bolt and nut assembly  900  as illustrated in  FIG. 9 . 
         [0042]    It is most desirable that the kernels  100  be milled only once. As used herein, milling refers to each introduction of the kernel  100  into a milling chamber  404 . Likewise, it is most desirable the corn kernels  100  be sufficiently fragmented, particularly that the kernel be separated among bran, germ and endosperm, and thereafter removed from the milling chamber  404  before being milled into overly small “fines.” In the art, parts of kernels  100  which are not sufficiently milled to exit the milling chamber  404  through screen  410  prior to reaching the discharge spout  416  are referred to as “overtails” or as “tails,” while parts of kernels  100 , in the form of fragments of bran  102 , germ  104 , and endosperm  106 , or combinations thereof, which are sufficiently milled to exit the milling chamber  404  prior to passing through discharge spout  416  are referred to as the “through stream” or “through stock.” 
         [0043]    In the prior art, only twenty percent (20%) of the bran  102 , germ  104  and endosperm  106 , by mass, entering milling chamber  404  exited as throughs, while eighty percent (80%) of the bran  102 , germ  104  and endosperm  106 , by mass, exited as tails. As the tails contained large amounts of endosperm, the prior art required extensive further milling. 
         [0044]    As illustrated in  FIG. 10 , the improvements to the corn mill provide a higher percentage of throughs and a lower percentage of tails. In one embodiment screen  1000  is approximately 646 mm in height, approximately 281 mm in diameter at its outer diameter, and contains rows  1012  of round perforations  1010  each having a diameter of approximately 9 mm and arranged in rows from proximate the top of screen  1000  to proximate it bottom on each panel  1006  not adjacent the portion of two-part frame  414  where the two sections mount together. For 9 mm round perforations, the perforations are arranged in rows on 17 mm centers, where the rows are arranged in 8.5 mm centers and advanced laterally by 8.5 mm, although smaller centers may be used for more aggressive milling and through removal. Conversely, larger centers may be used for less aggressive milling and through removal. The milling rotor (not shown) has a diameter of approximately 250 mm. Alternatively, perforations  1010  may be of sizes other than 9 mm, such as a 7 mm diameter. Perforations  1010  ideally should be at least 6 mm in diameter and not more than 10 mm in diameter. Similarly, as can be appreciated, other dimensions may be used without departing from the spirit of the invention. More aggressive milling may be obtained by increasing the height of the screen  1010 , and therefore roller height, by reducing the diameter of the screen  1000 , by decreasing the relative size of the lower or third section  1050  of the screen  1000 , or by using a negative perforation, i.e. a slotted perforation which retards rather than encourages passage of corn through the mill  1200  illustrated in  FIG. 12 . 
         [0045]    Like the prior art, screen  1000  includes a row  1016  of breaker bars  1014  affixed in the upper section  1008  of the screen  1000 . The breaker bars  1014  may be vertically-oriented. The first row  1016  of breaker bars  1014  comprise breaker bars  1018 ,  1020 ,  1022  and  1028  which nearly span the upper section  808  and breaker bars  824  and  826  sized to fit the portion of length of upper section  808  reduced by discharge outlet  420 . As in the prior art, each breaker bar  1014  is positioned proximate the intersection of two panels  1006  to produce localized areas of compression, particularly when a resistor bar  602  rotates past. In connection with screen  1000  described above, breaker bars  1018 ,  1020 ,  1022 , and  1028  are approximately 4 mm thick, approximately 200 mm long and approximately 15 mm wide. In connection with the described milling rotor and chamber, breaker bars  1024  and  1026  are approximately 4 mm thick, approximately 100 mm long and approximately 15 mm wide. Likewise, the total number of breaker bars  1014  and their respective sizes may be altered to provide at least one breaker bar  1014  at the upper section of screen  1000  including adjacent discharge outlet  420 . 
         [0046]    In the preferred embodiment, screen  1000  includes a separable lower section  1050 . Lower section  1050  may be removed and replaced when worn, eliminating the need to replace the less worn remainder of screen  1000 . 
         [0047]    In the preferred embodiment, screen  1000  further includes a second row  1034  of breaker bars  1032  affixed to the center section  1030  of screen  1000 . The second row  1034  of breaker bars  1032  may be vertically-oriented and comprise breaker bars  1036 ,  1038 ,  1040 ,  1042 ,  1044 , and  1046  which nearly span the center section  1030  and which are of uniform size. In connection with the described milling rotor and chamber, each breaker bar  1032  is approximately 4 mm thick, approximately 15 mm wide, and approximately 200 mm long. 
         [0048]    The first row  1016  of breaker bars  1014  and, unlike the prior art, second row  1034  of breaker bars  1032  produce localized areas of compression, which result in further fracturing of the kernels, or propagation of existing fractures within the kernels. To avoid the overmilling present in the prior art, perforations  1010  are sufficiently sized to permit sufficiently milled brokens to exit the milling chamber  404  through screen  1000 . Thus, kernels that are sufficiently fractured early in the milling process do not continue to be milled after passing through screen  1000 . 
         [0049]    As described above, as a resistor bar  602  mounted on milling rotor  412  rotates past a breaker bar  1032 , a localized area of compression is created and released, causing fracture propagation through the materials to be milled. As illustrated in  FIG. 11 , this propagation is further encouraged by a modification to the milling rotor  1112 , which includes not only the resistor bars  1102  and the spacer  1104  between the resistor bar  1102  and the milling rotor  1112  but also a plurality of resistor prisms  1114  arrayed across the milling rotor  1112  co-planar with the first row  1016  of breaker bars  1014  and the second row  1034  of breaker bars  1032 . In the preferred embodiment, the milling rotor  1112  includes three (3) resistor bars  1102 . Intermediate the resistor bars  1102  are five (5) equally laterally-distributed columns  1116  of resistor prisms  1114 , for a total of fifteen (15) equally laterally-distributed columns  1116  of resistor prisms  1114 . Each resistor prism  1114  is a square protuberance. In the present embodiment each resistor prism measures 16 mm on each side and having a height of 6 mm, although the number of columns, rows and size of resistor prisms  1114  may be changed. Resistor prisms  1114  may be of any other shape, such as cylindrical, or any number of shapes. Each column  1116  is advanced over the prior column  1116  to present an alternating presence of resistor prisms  1114 . Thus, in operation, rotation of milling rotor  1112  not only induces localized areas within the milling chamber  404  where all materials to be milled in a vertical plane are equally induced to move laterally, but, by virtue of the alternating and discrete resistor prisms, vertical layers of materials to be milled are induced to move with varied force, thus inducing greater interaction among them. Moreover, the spacing between columns  116  of resistor prisms  1114  permits the force imparted to the materials to be milled in the milling chamber  404  to vary as they approach a breaker bar  1014  or  1032 . 
         [0050]    In operation, the application of friction and intermittent compressive force among materials to be milled within milling chamber  404 , between materials to be milled and the screen  1000 , and between the materials to be moved and the breaker bars  1014  and  1032  results in the separation of some or all of bran  102 , the fracturing of endosperm  106  into endosperm particles  107 , and the freeing of a substantial portion of germ  106  without overmilling. By maximizing the size of endosperm particles  107  and freed germ  106 , the highest value of the kernel may be realized. 
         [0051]    Germ  104  maintained in its whole state provides greater oil production. Endosperm  106  maintained in its whole state or in large brokens is suitable for high value end uses. 
         [0052]    This construction, together with the addition of a second row  1034  of breaker bars  1032  has been found to produce superior results. In particular, the 9 mm diameter perforation and their relative quantity per unit area has resulted in a high through stock with reduced tails. This construction has produces results the inverse of the prior art, with the majority of product exiting the mill as throughs. This increased through production, however, without further improvement to mill  400 , creates additional problems. 
         [0053]    Referring to  FIG. 4 , in the prior art, the throughs are removed from the mill  400  at the bottom of the screen  410  into a through removal passage  422  by a paddle  424  affixed to the lower section of the milling rotor  412 . The removal passage  422  was connected to a negative or reduced pressure system  426 , such as a such as a vacuum pump, to draw the throughs along the piping  428 , laterally and/or vertically, and to a throughs collector  430 . This is typically accomplished by a pump  426  communicating with the through removal passage  422 . The increase in throughs generated by the present invention, often at least double the throughs generated by the prior art, would require a substantial increase in pump capacity and therefore a significant increase in energy expenditure. 
         [0054]    Referring to  FIG. 10 , in a further embodiment, each of front screen  1002  and/or rear screen  1004  may be assembled from three (3) separate sections. Use of a first or top section  1008 , second or middle section  1030 , and bottom or third section  1050  as segments of front screen  1002  and/or rear screen  1004  permits interchange for replacement of screen sections with attached breaker bars. Similarly, segmented front screen  1002  and/or rear screen  1004  permits use of varying, including multiple, types of perforations  1010 . More than three (3) sections may be used, but three sections permits replacement of an entire section which may include breaker bars. 
         [0055]    As illustrated in  FIG. 12 , the present invention may further include a gravity removal system for through removal. Rather than attempting to remove throughs from the mill  1200  entirely by negative or reduced pressure, mill  1200  includes a through removal passage  1220  located adjacent the bottom of the milling chamber  1204  and paddle  1224  and connected to piping  1228  which depends downwardly, thus using gravity to move throughs from the mill  1200  and to fall to through collector  1222 . Collector  1222  may include a rotary air seal or lock, or other similar equipment, to separate piping  1228  from aspirator  1230 , thereby maximizing the reduced pressure drawn on piping  1228 . Ideally, collector  1222  does not permit pump  1226  to draw air from aspirator  1230 . Once induced toward the through collector  1222 , which may be a hopper, by pump  1226 , the throughs may be separated by density in an aspirator  1230 . A greater portion of throughs may therefore be handled by the mill  1200 . 
         [0056]    The process of this invention is further illustrated in the following example of wet milling, although the invention may also be used for dry milling. 
       EXAMPLE 
       [0057]    In the first step, water is added to a fixed quantity of whole corn kernels. Specifically, for #2 grade yellow corn, introduced to tempering at 7452 kg/hr with water is added at approximately 5% by weight at a rate of 373 liter/hr. The whole corn kernels are then retained in a holding tank for a period of six minutes. 
         [0058]    Next the corn kernels are introduced to a Satake Maize Degermer VBF modified with the screen and breaker bars described herein with a milling rotor rotating at 800 revolutions per minute (RPM). Two distinct stock separations—overtails and throughs—are generated. The overtails, referring to the product which does not pass through the 9 mm round perforated screen, consists generally of generally-debranned corn kernels (endosperm and germ) although some bran remains attached to the endosperm and germ, as well as some throughs which did not pass through the screen. The throughs, referring to product which has passed through the 9 mm round perforated screen, consists of bran, endosperm and germ reduced in size to less than 9 mm in diameter. 
         [0059]    A first sample bag of overtails, weighing 4.54 kg, is produced over a 20 second period. 
         [0060]    A second sample bag of overtails, weighing 4.48 kg, is produced over a farther 20 second period. 
         [0061]    In the example, the two 20 second time periods are proximate, but separated by some short time during bag change. 
         [0062]    Overtails are therefore produced at an average rate of 811.6 kg/hr. 
         [0063]    A first bag of throughs, weighing 18.25 kg, is produced in 10 seconds. 
         [0064]    A second bag of throughs, weighing 18.25 kg, is produced in 10 seconds. 
         [0065]    Throughs are therefore produced at an average rate of 6640.23 kg/hr. 
         [0066]    Overtails constitute 10.9% of the output. Throughs constitute 89.1% of the output. Sifting and aspiration, not included in this example, would separate the majority of the endosperm grit from the bran so the recovered endosperm may go to conventional purification and reduction, and ultimately become a useful end product. 
         [0067]    This configuration provides improved processing and removal of sufficiently milled germ. 
         [0068]    The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof.