Patent Publication Number: US-6217442-B1

Title: Grain processing apparatus and methods

Description:
FIELD OF THE INVENTION 
     The present invention relates the processing of grain. 
     BACKGROUND OF THE INVENTION 
     Conventional roller mills require large spaces and skilled manpower to maintain operation. To make white flour grain is rolled and sifted, rolled and sifted in many steps to yield the white flour. In the process, most of the 45 minerals, which are in the grain to start with are lost. When processing wheat multiple breaking and sifting procedures remove the bran and separate the remaining particles into different grades. 
     The present invention proposes a novel apparatus that may be used for either debranning or milling grain. The apparatus can be provided at a more modest cost than existing debranning machines, making the milling of white flour readily available for large and small millers. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention there is provided a grain processor comprising: 
     a substantially cylindrical drum oriented substantially horizontally; 
     a rotor extending along the interior of the drum, said rotor comprising a plurality of radial impellers spaced around and spaced along the rotor; 
     rotor drive means for rotating the rotor in the drum; 
     grain inlet means for delivering grain to the drum; 
     air inlet means for admitting air into the drum adjacent a bottom side of the drum; 
     discharge means, including an opening in the drum at a top side thereof; and 
     vacuum means for drawing a flow of air and solids suspended in the flow of air from the drum, through the discharge means. 
     In one embodiment, the apparatus is used as a debranner for removing bran from grain. The debranner includes a grain outlet at the outlet of the drum for withdrawing the hulled grain and the bran is drawn through a vacuum plenum. 
     In another embodiment, the apparatus is used as a flour mill. The inlet air is automatically cooled. For some grades of flour, for example the flour used for making the flatbread known as chapati or roti, the air supply can be restricted, increasing the dwell time in the mill. The flour is removed through the plenum at the vacuum outlet from the drum. The plenum may have one side offset to provide a widened section and a deflector opposite the offset to deflect grain entering the plenum back into of the drum. 
     According to another aspect of the present invention there is provided a method of processing grain, comprising: 
     providing a drum; 
     providing in the drum a rotor including a plurality of radiating impellers; 
     introducing grain into the drum adjacent the inlet end; 
     rotating the rotor to cause the impellers to stir the grain in the drum; and 
     drawing a flow of air and grain particles suspended therein from the drum. 
     For debranning, the bran is withdrawn in the air flow and the debranned grain is removed from an outlet end of the drum. For milling, the vacuum system draws out the milled flour. The air flow carries out both flour and bran where the grain has not been debranned. The result is whole wheat flour. 
     For white flour, the debranner is used first first and then the mill. 
     Round rotor impellers are suitable for use with most grains and flour products. For semolina in some cases other cutters, for example the applicant&#39;s “Micronizers™” or knife heads may be used on the impellers. 
     The speed of the rotor and the dwell time of the grain in the drum have been found to be of importance in achieving the desired results. Exact parameters will depend on the mill size and configuration, and the grain being processed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, which illustrate an exemplary embodiment of the present invention: 
     FIG. 1 is a side view of an apparatus according to the present invention; 
     FIG. 2 is a longitudinal cross-section of the apparatus of FIG. 1; 
     FIG. 3 is a cross-section along line  3 - 3  of FIG. 1; 
     FIG. 4 is a cross-section along line  4 — 4  of FIG. 2; and 
     FIG. 5 is a detail showing an inlet screen that is useful for a debranning application. 
    
    
     DETAILED DESCRIPTION 
     Referring to the accompanying drawings, there is illustrated a mill  10 . This includes a stand  12  supporting a horizontal cylindrical drum  14 . The drum has an inlet end  16  and an outlet end  18 . Five rows of air inlet openings  20  (FIG. 4) extend along the bottom of the drum for letting air into the drum interior. A grain hopper  22  is mounted at one side of the drum for holding grain to be processed. Along the top of the drum is a vacuum plenum  24  for withdrawing air and suspended solids from the drum. At the bottom of the outlet end is a grain outlet  26  for discharging processed grain in debranning applications. The outlet may be closed with a sliding gate  27 . 
     With particular reference to FIGS. 2 and 3, the mill includes a rotor  28  extending along the center of the drum. The rotor includes an axial shaft  30  supported in bearings  32  at the ends of the drum. A set of impeller sockets  34  is mounted on the shaft. These sockets radiate from the shaft and are arranged in four orthogonal rows extending along the shaft. Impeller rods  35  are fixed in the respective sockets to sweep the interior of the drum as the rotor rotates. 
     At the inlet end of the apparatus, the shaft projects beyond the end of the drum and carries a pulley  36 . This is connected through a belt  38  to a drive pulley  40  mounted on the drive shaft of an electric motor  42 . 
     Below the air inlet openings  20 , a hopper  44  extends the length of the drum to capture grain escaping through the air openings. An auger  45  along the bottom of the hopper delivers the collected grain to the outlet end of the drum, where it is elevated by an auger  46  to a third auger  47 . Auger  47  opens into the bottom of the drum towards the inlet end and is inclined somewhat in the direction of rotation of the rotor. This returns the grain to the drum. The hopper  44  has screen side walls  48  to allow the inflow of air, while retaining grain and excluding the entrance of foreign matter. 
     Grain is delivered to the interior of the drum by an auger  49  including auger tube  50  opening into the bottom of the drum towards the inlet end and inclined somewhat in the direction of rotation of the rotor. This auger is generally parallel to the recycling auger  47 . The auger tube  50  contains helical flighting  52  that retains a plug of grain in the auger tube to form an air lock preventing significant air inflow into the drum through the auger tube. The supply auger  49  is supplied with grain from the hopper  22  through a tube  54 . Supply auger  49  is driven by a motor  56 , while recycling auger  47  is driven by hydraulic motor  57 . 
     The vacuum plenum  24  along the top of the mill includes a set of four vacuum ducts  58  along the top of the plenum. On the upstream side of the plenum, that is the side which the rotating impellers approach, is a deflector  60  that deviates from the cylindrical configuration of the drum and curves inwardly to deflect grain towards the center of the drum, away from the open bottom of the vacuum plenum. This assists in preventing grain kernels from being drawn from the drum with the fines from the process. Above the deflector, the adjacent side  61  of the plenum has a wide V-shape, widening the plenum so that air flow into the plenum will partially stagnate, allowing large suspended particles to drop from the suspension and also cooling the flow. A downwardly sloping deflector plate  62  on the opposite side of the plenum extends across the throat of the plenum to intercept any grain kernels that pass through the throat. A vacuum duct leads from the ducts  58  to a filter schematically illustrated at  64  for removing suspended solids from the air flowing from the outlet. 
     Near the top of the plenum are three air inlet ducts  66 . These have valves  68  mounted on a common shaft  70  to control the air flow into the plenum  24 , and therefore the pressure in the plenum. A single control  72  rotates the shaft  70 . The ducts  68  are equipped with respective air filters  74 . 
     To use the apparatus as a flour mill, grain is loaded into the hopper  22  for delivery to the interior of the drum using the auger  49 . The auger delivers the grain into the apparatus towards the inlet end and at least partially in the direction of rotation. Vacuum is applied to the plenum  24  through the vacuum ducts  58  and the rotor is driven clockwise as seen from the inlet end. The dwell time is adjusted by controlling the vacuum applied to the fines outlet to allow the grain to remain in the drum for a time sufficient to be pulverized to a fine flour which is drawn out of the drum through the fines outlet. The bran that accompanies the flour as it is withdrawn is coarser than the flour particles and may be separated from the flour using a coarse screen in the filter  64 . 
     To use the mill for debranning grain, a grain outlet  26  is provided at the bottom of the outlet end of the apparatus. As shown in FIG. 5, each row of air inlet openings  20  for the drum is covered with a screen  76  mounted on the outside of the drum to prevent grain particles from falling from the drum. Covering the screen is a valve plate  78  with a set of ports  80  that normally align with the respective inlet openings  20  in the row. The ports  80  are tapered conically for accelerating the air flow into the drum so that when the air flow enters the drum, its sudden expansion produces a significant temperature drop. Two brackets  82  mount each valve plate on the drum for sliding movement along the drum, allowing the inlet openings  20  to be opened or closed by movement of the valve plates. 
     In debranning, the rotor is driven more slowly than in a milling operation. The impellers agitate the grain to break up and separate the hull or bran from the seeds. The loose bran is relatively light weight and is easily suspended in the air flow through the grain, from the air inlets  20  to the vacuum plenum  24 . The relatively coarse bran is separated from the air stream using a screen type filter. The air flow through the drum is of reduced temperature because of the venturi effect of the ports  46 , thus keeping the process at a moderate temperature so that the nutrients in the grain are not degraded. 
     While one embodiment of the present invention has been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention and are intended to be included herein. The invention is to be considered limited solely by the scope of the appended claims.