Abstract:
A granular material grinder and method of use includes a hammer mill for reducing incoming granular material into particulate material, a microgrinder for reducing the particulate matter into microground powder by particulate matter to particulate matter collisions, and a product collector to collect the microground powder portion. The granular material grinder having the feature of being operated in a closed system to facilitate efficient recovery of grain into microground powder and operable in a cooled inert gas to prevent any compound degradation due to temperature or oxygen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a Divisional Application of U.S. application Ser. No. 10/953,652 filed Sept. 29, 2004, now Pat. No. 7,159,807, which application is are hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   The grinding of particulate matter has involved a number of different approaches all of which present varying problems. Grinders in the prior art typically use blades or impellers to mechanically break down granular material into smaller pieces. However, this mechanical breakage is limited to the interaction of the blades or impellers upon the granular material. Accordingly, it is an objective of the present invention to create an environment which is influenced by impellers but does not require direct contact by the impellers upon the particulate matter to greatly reduce size. 
   Also in the prior art, grinders have been developed which grind material in a water or liquid environment in order to achieve a reduced particle size. However, water or liquid processing creates problems such as the leaching of soluble solids from the granular material and also creates the high energy problem of removing the water or liquid once the granular material is ground into powder. Accordingly, a further objective of the present invention is the provision of a granular material grinder that reduces particle size without the use of a water or liquid as a carrier. 
   U.S. Pat. No. 2,752,097 to Lecher discloses a grinder for producing ultra fine particles which creates vortexes around rotating paddle wheels which causes particles to strike the outside wall. However, Lecher is a low volume system that creates high heat that must be cooled with a large air volume. In addition, the Lecher environment is subject to stresses that may damage the equipment. Accordingly, a further objective of the present invention is to produce a granular material grinder that does not emphasize particle collision with the inside of the chamber or impellers and has a lower operating temperature. 
   The market place is demanding materials that are microground and yet their chemical composition is not changed. For example, even slight changes in chemical compositions of pharmaceutical products or dietary supplements may inactivate the chemical composition or physical characteristic. Accordingly, a still further objective of the present invention is to control the operating parameter such that the temperature, carrier gas, and mechanical interaction do not damage these critical commercial products. 
   Another objective of the present invention is the provision of a method and process for grinding granular material that is economical and safe. 
   These and other objectives will become apparent from the following description. 
   BRIEF SUMMARY OF THE INVENTION 
   The foregoing objectives may be achieved by an apparatus for grinding granular material having a hammer mill that reduces incoming granular material into particulate material that is temperature controlled, a microgrinder receiving the particulate material from the hammer mill that has an impeller rotatably mounted that accelerates the particulate matter to strike against itself to create microground product, and a product collector which collects the microground powder so that it may be packaged. 
   The foregoing objectives may also be achieved by a process for grinding granular material that involves a first grinding step which reduces the size of grain into particulate pieces for mechanical breakage, a second grinding which reduces the size of particulate pieces through particulate piece to particulate piece collisions to form microground product, and a separating step to remove the microground product from the particulate pieces. 
   The foregoing objectives may also be achieved through a method of grinding particulate matter comprising suspending particulate matter in a flow of carrier gas and propelling particulate matter using the impeller to strike against a particulate matter going toward the impeller to fracture the particulate matter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan layout of the granular material grinder. 
       FIG. 2  is an enlarged view of the hammer mill as seen in  FIG. 1 . 
       FIG. 3  is an enlarged view of the microgrinder and product collector as seen in  FIG. 1 . 
       FIGS. 4A-C  are an enlarged view of particulate matter colliding to form microground product. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The granular material grinder of this invention is referred to in  FIG. 1  generally by the reference numeral  10 . The granular material grinder  10  is used to grind whole grain, such as corn, soybeans, wheat, etc., or other products such as gravel or coal. The granular material grinder  10  grinds these granular products into a microground powder. 
   As seen in  FIG. 1 , the granular material grinder  10  of the present invention is completely sealed to the atmosphere. In this completely sealed configuration, the granular material grinder  10  operates with a 100% recovery of the granular material  12  placed into the granular material grinder  10 . The grinder  10  could also be operated open to the atmosphere, however, in this configuration product is lost and a carrier gas such as nitrogen cannot be used. 
   As seen in  FIGS. 1 ,  2 , and  3  particulate matter  12  is placed in hopper  14  which is then sealed. Valve  16  is then opened allowing product to drop from the hopper  14  into a feed hopper  18 . The valve  16  illustrated is a manually operated gate valve; however, the valve may be operated electronically, pneumatically or hydraulically and may be a butterfly gate or of another configuration. 
   The feed hopper  18  empties into an auger  20  which is powered by motor  22 . The auger  20  pushes granular material  12  into the hammer mill  30 . The hammer mill  30  has a hammer mill housing  32  having a chamber  34  therein. The hammer mill housing  32  has a granular material inlet  36  and a carrier gas inlet  38 . The hammer mill housing  32  also has outlet  40 A and  40 B. 
   A screen  42  is placed within the carrier gas inlet  38  to increase the velocity of carrier gas passing through the hammer mill  30 . Inside the hammer mill housing  32  are rotating hammers  44  attached to shaft  46  and driven by motor  47 . The screen  42  also acts to keep the granular material  12  in contact with the hammers  44 . 
   The auger  20  pushes granular matter  12  into the hammer mill housing  32 . The drive motor  47  rotates hammers  44  to impact upon the granular matter  12  and reduces the size of the granular matter  12  through impact to produce particulate matter  48 . 
   A mechanical separator  50  is provided to accelerate carrier gas  64  that is without any particulate matter. The mechanical separator  50  may be a blower or a cyclone separator. The mechanical separator  50  is adapted to receive a mixture of carrier gas and particulate matter that is being recycled through the system. The mechanical separator  50  receives this mixture through inlet  52  and separates the carrier gas  64  from the particulate matter  48 . The mechanical separator  50  then moves the carrier gas through outlet  54  towards the carrier gas inlet  38  of the hammer mill  30 . In addition, the mechanical separator  50  feeds the separated particulate matter  48  through the particulate matter outlet  56 . An auger  58  is provided in fluid communication with particulate matter outlet  56  such that motor  60  turning the auger  58  places the particulate matter  48  from the particulate matter outlet  56  into the hammer mill  30  through recycled particulate matter inlet  62 . 
   The carrier gas  64  generally has no significant particulate matter within it; however, the presence of particulate matter within the carrier gas  64  is not troublesome unless it is larger than the holes present in the screen  42 . The carrier gas  64  enters the hammer mill  30  through the holes in the screen forcing product inward against the normal centrifugal force of the hammer mill  30  and out through outlet  40 A and through screen  42  and through outlet  40 B. 
   The velocity of the carrier gas  64  can be regulated by the number and size of the holes in screen  42  and the volume of carrier gas vacuumed through outlet  40 A. The vacuum at outlet  40 A is regulated by the revolutions per minute (RPM) of the fan motor  78 . The greater the flow of carrier gas  64  the greater the velocity of the carrier gas  64  through the screen  42  in hammer mill  30 . If the volume of carrier gas  64  remains constant, the larger the holes and/or the increase in number of holes in screen  42  will result in a lower velocity of carrier gas  64  through the hammer mill  30 . 
   The more volume of carrier gas  64  through the hammer mill  30  the more cooling effect and the lower the operating temperature of the grinding process. 
   Fan  70  has an inlet  72  joined in fluid communication to outlets  40 A and  40 B by pipe having an inlet  72  and outlet  74  with fan blades  76  therebetween. The fan  70  is powered by fan motor  78 . The fan  70  picks up particulate matter  48  that has gotten through the screen  42  and is dropping through the opening  40 B. The combination of the two products from outlets  40 A and  40 B are then transferred by the fan  70  to a connecting pipe to a microgrinder  80 . As shown in  FIG. 1 , only one microgrinder  80  is shown; however, in practice, several microgrinders  80  and particle collectors  120  may be used for each hammer mill  30  to increase the output of the system  10 . 
   The microgrinder  80  has a column  82  with a cavity  84  with a microgrinder inlet  86  with a positioning pipe  88  mounted within the microgrinder inlet  86 . The microgrinder inlet  86  is in fluid communication with the fan outlet  74 . 
   The microgrinder  80  has a top section  92 , a medial section  94 , and a bottom section  96 . The column  82  tapers downward from narrow to wide in the top section  92 , a taper downward from narrow to wide in the medial section that is greater than the top sections taper, and a taper downward from wide to narrow in the bottom section  96 . Alternatively, the top section  92  may be straight or tapered, larger at the top and small at the bottom. Alternatively, an optional straight section  95  between the medial section  94  and bottom section  96  may be used if more impellers are added to increase the displacement area of the impact zone. 
   Particulate matter  48  exits the positioning pipe  88  to strike at least one impeller  98  rotatably mounted in the column adjacent the microgrinder inlet  86 . The impeller  98  has opposite sides, one of the sides having a plurality of impeller blades  100  thereon for accelerating particulate matter  48  and producing vortex and/or other formation in carrier gas  64 . As shown in  FIG. 1 , three impellers  98  are located under the positioning pipe  88 . Two impellers  98  indicated by  102  are facing upward. One impeller  98  identified with numeral  104  has its impeller blade  100  facing downward. All three impellers  98  are attached to shaft  106  and driven by motor  108 . These impellers  98  produce vortexes; high and low pressure zones, and/or turbulence in which particulate matter  48  is exposed. The impellers  98  may be varied from upward or downward facing blades depending on the product being ground and the shape/size of vortex desired. In some instances, the impellers may have both upward and downward impeller blades. 
   As shown in  FIGS. 4A-C , the particulate matter  48  is impacted against one another due to the different effects of vortexes, high and low pressure zones, and/or turbulence on various sized particulate matter  48 . 
   The hammer mill  30  is the first grinding step. The hammer mill  30  produces a variety of sizes of particulate matter  48 . The efficiency of the grinding process in the microgrinder  80  is improved by having varied size particles to impact with each other. 
   The desired result within the microgrinder  80  is to produce vortexes, high and low pressure zones, and/or turbulence at an intensity so that the larger particles pass through with little effect while the smaller particles will have their direction altered. The smaller particles are spun in a circular motion within the relatively small vortexes created within housing  82  causing them to cross paths with the larger particles and impact them. 
   These random collisions between particulate matter  48  cause the particulate matter  48  to fracture and reduce in size to microground product or powder  114 . The random collisions are regulated by the speed and shape of the impellers  98  which are controlled by the RPM of motor  108 . Adjustments may also be made by adjusting valves  112  which regulate recycled or regrind product particulate matter  48  and carrier gas  64 . Adjustments to the valve  148  regulate the upward flow of carrier gas  64  and microground powder  114  into collection chamber  120 . 
   Microground product or finely ground powder  114  moves upward partially because of static electricity, partially by upward movement of carrier gas  64  regulating by valve  148  and partially by the decreasing radius shape of housing  82 . 
   Heavier particles work there way downward due to the shape of housing or column  82 , because of gravity, because of the low velocity of the fluidized bed not being able to hold larger particles in suspension, and partially due to centrifugal force. The centrifugal force assists in the separation because larger particles are forced to the conical inner outer surface of the microgrinder  80  whereas the microground product  114  moves upward through the center core of the microgrinder  80 . 
   Therefore, the three factors which affect the final grind are the impellers  98  shape, design, upward or downward position, and speed; the housing shape, design, and position relative gravity; and the flow of carrier gas  64  in the housing  82 . The impeller design  98  is primarily responsible for the creation of the vortexes in the housing  82 . Smaller vortexes hold smaller, lighter particles for a longer amount of time in an impact zone with larger particles providing the opportunity for finer, smaller particles sizes to be created. 
   The housing  82  can be matched to the impellers  98  to give some variance in the vortex size because the vortexes are formed in the space between impellers outer edges and the inner wall of the housing  82 . By altering cones and rings upon the housing  82  the impact zone can be altered to obtain the desired effect in grinding efficiency. In addition, by increasing the flow of carrier gas  64  in the housing  82  the volume of microground powder  114  processed will increase. Particulate matter  48  may then be increased requiring more particulate matter  48  to be transported back to the hammer mill  30  through the recycled particulate matter  48  pipe. The carrier gas  64  flow in the housing  82  can be increased or decreased conversely by increasing or decreasing the cross sectional area or tapers changing the column  82  at any given point. 
   The granular material grinder  10  has a product collector  120  positioned above the microgrinder  80 . The product collector has a shell  122  with a collection chamber  124  formed therein. The shell  122  having a collector inlet  126  and a collector outlet  127 . The collector inlet  126  is in fluid communication with the microgrinder outlet  90 . The product collector  120  has an inner surface  128 . Wipers  130  attached to shaft  132  and driven by motor  134  clean microground product from the inner surface  128  of the product collector  120 . The wipers  130  drop the microground powder  114  from the inner surface  128  to the product collector outlet  127  to the product hopper  140 . 
   The product hopper  140  is in fluid communication with the collector outlet  127 . The product hopper  140  has an inlet  142 , a recycled outlet  144 , and a valve  148  attached controlling the amount of carrier gas  64  leaving the outlet  144 . Attached to the bottom of the product hopper  140  is an auger  150 . 
   The product hopper  140  is filled thorough the normal operation of the wiper system. Opening valve  154  and rotating auger  150  by auger motor  152  fills a product bag (not shown). Valve  154  is then shut to replace a product bag. The valve  154  is closed between filling product bags to maintain the seal throughout the entire granular material grinding system. 
   Carrier gas  64  is recycled from the product hopper  140  back through the process where it joins with a mixture of particulate matter  48  and carrier gas exiting the recycled outlets  110  of the microgrinder  80 . These combined recycled streams are in fluid communication with the recycled mixture inlet  52  of the mechanical separator  50 . As mentioned previously, the mechanical separator  50  creates a stream of carrier gas  64  and a particulate matter stream that exits out the particulate matter outlet  56 . 
   When operated in a closed loop, 90-100% of the entering granular material is recovered as microground product and preferably 98-100% of the entering granular material is recovered as microground product. When operated continuously 100% of entering granular material is converted to microground product. 
   The carrier gas  64  is recycled continually throughout the entire process. The carrier gas may be atmospheric air or an inert gas such as nitrogen. When using an inert gas the gas is entered into the process using a cylinder  160  of nitrogen gas connected to the piping of the granular material grinder  10 . As shown, this nitrogen is attached at a point of the carrier gas outlet of the mechanical separator  50 . However, the inert carrier gas may be placed into the system at other numerous places of the system. Alternatively, the carrier gas may be a reactionary gas chosen to change the chemical and/or physical properties of the microground product  114 . 
   In addition, a refrigeration system  162  may be used to control the temperature of the carrier gas. Alternatively, a refrigerated cooling jacket may be around any portion of the system  10  or all of the system  10  to control temperature. The process is operated in a closed loop to maintain the system, particulate matter, microground powder and carrier gas between 50-100° F. and preferably between 50-70° F. These temperatures are preferred because of the reduced risk of degrading viable components of whole grain entering into the process. If the microground powder is a pharmaceutical, vitamin, or other neutraceutical there may be different preferred temperatures to protect the integrity of the microground powder. The refrigeration system is located at the carrier gas outlet of the mechanical separator  50  to minimize damage to the refrigeration system that may be encountered because of particulate matter entering the refrigeration system. 
   As shown, the granular material grinder  10  is manually controlled by adjusting the valves and RPM of the motors. Alternatively, a programmable control system may be employed to control the granular material grinder  10 . 
   The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. In the foregoing, it can be seen that the present accomplishes at least all of its stated objectives.