Abstract:
Methods and apparatuses are provided for applying accurately metered, minute quantities of concentrated additives from bulk sources of supply to successive masses of material presented for treatment. The methods of the invention comprise mixing an additive with a small amount of a liquid carrier to form a suspension, causing the suspension to foam, and applying the resulting foamed suspension to a material such as animal feed. The apparatuses of the invention provide for a pass-through chamber within which separate streams of a liquid carrier, an additive substance, and preferably a foaming agent are merged together. Each of the streams are directed into the chamber in a metered flow to incrementally combine the streams. A suction pump at the downstream end of the chamber draws the prepared product out of the chamber and advances it toward an ultimate delivery site. By utilizing foam, the methods and apparatuses of the invention require very little carrier liquid and result in a product which can be evenly and thoroughly distributed over the animal feed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with methods and apparatuses for applying a foamed product, comprising very small amounts of additive substances and requiring very small amounts of liquid carrier, to a large mass of materials such as animal feed. The product can be foamed by use of a foaming agent (either with or without subsequent agitation) or by agitating a suspension comprising the additive and liquid carrier without the addition of a foaming agent. Agitation can be carried out by any conventional mixing or vibrating mechanism or by injecting air under pressure into the suspension. Foaming of the suspension results in a product having increased surface area thus permitting an even, thorough distribution of the foamed additive onto the animal feed. 
     2. Description of the Prior Art 
     Animal feed additives, such as vitamins, innoculants, and nutritional supplements, are generally mixed with animal feed after the pellet is formed. Typically, a quantity of the additive material is measured by hand and added to a tank containing a specific, measured quantity of a liquid carrier such as oil or water. A stirrer is provided within the tank in an attempt to maintain the additive(s) in suspension, and the tank is then pressurized to direct the mixture through a spray nozzle and onto the feed pellets. This method has many drawbacks. An excess amount of the additive/liquid carrier suspension must be prepared in order to ensure the amount is sufficient to treat all of the feed. While this leads to wastage, the alternative is to make too little additive/liquid carrier suspension, thus requiring additional time and labor to prepare a new batch. Another drawback with this method is that the tank and mixing apparatus must be thoroughly cleaned after each use in order to prevent the growth of algae and other undesirable organisms. 
     Many of these problems were eliminated by the dosifying apparatus patented in U.S. Pat. No. 5,718,507 which provides a system for applying accurately metered, minute quantities of concentrated additives from bulk sources of supply to successive masses of material. While the system of the &#39;507 is a vast improvement, it still requires the use of a large quantity of a liquid carrier (such as water) for the additives in order to ensure that all of the feed is covered with the additive. This results in wet feed which leads to mold growth on and spoilage of the feed. Furthermore, it is expensive and undesirable to use large quantities of the liquid carrier. This is especially true when water is the carrier, and the system is being used in an area where water is not plentiful. Finally, the spraying of the liquid carrier/additive suspension disclosed in the &#39;507 patent results in splattering of the suspension, creating a wet, messy dispensing area and wasting valuable additives. 
     SUMMARY OF THE INVENTION 
     The instant invention overcomes the problems described above by providing a method and apparatus for foaming a suspension comprising an additive and a small quantity of a liquid carrier and dispersing the foamed suspension onto bulk quantities of animal feed. This additive-containing foam is distributed evenly and thoroughly over the surface of the animal feed without wasting the additives or resulting in wet feed which will easily spoil. 
     In more detail, the additives, either in dry or liquid form, are carefully dispensed in a metered flow into an ongoing stream of carrier liquid in a pass-through tubular mixing chamber. Preferably, the additive is dispensed by gravity into the stream of carrier liquid as it passes through the chamber such that each increment of the moving liquid is matched up with a corresponding increment of the additive material to form a suspension having a first volume. The resulting suspension is then foamed so that the resulting foamed suspension has a second volume which is at least about 1½ times greater than the first volume, preferably from about 15-30 times greater, and more preferably about 20 times greater. Foaming of the suspension can be carried out in several ways. For example, the suspension can be agitated, such as by introducing air (preferably at an air pressure of from about 5-50 psi) directly into the suspension, thus causing it to foam. If this does not create sufficient foaming, foaming of the suspension can also be achieved by the addition of a foaming agent to the suspension. If necessary, the suspension containing the foaming agent can then be agitated in some manner in order to increase the foaming of the product. This agitation can be carried out by some shaking means, or air can be introduced into the suspension containing the foaming agent (preferably at an air pressure of from about 5-50 psi) in order to increase the foaming. Suitable foaming agents in accordance with the invention include any edible foaming agent such as starch-based foaming agents, milk-based foaming agents, or fatty acid-based surfactants. Preferably, the chosen foaming agent(s) will not negatively interact with the additives to be dispersed on the feed. The apparatuses and methods of the invention can be used to apply virtually any substance, dry or liquid, that the user wishes to apply to a bulk material such as animal feed. For example, vitamins, innoculants, nutritional supplements, and pharmaceutical agents are all substances which can be applied in accordance with the invention. Finally, any liquid carrier known in the art is suitable for use in the instant invention, with water being a particularly preferred liquid carrier. 
     The resulting foamed product is then dispersed or otherwise applied to the mass of waiting animal feed. A suction at the chamber outlet draws the foamed product away from the chamber in a smooth flow. In its preferred form, the chamber is arranged in an upright condition with its outlet disposed at the bottom of the chamber, and the additive and foaming agent inlets located in a position to drop the additive and foaming agent directly into the outflowing stream of liquid. If necessary, the foamed product (which includes the carrier, additive, and foaming agent) may be passed through a region downstream from the mixing chamber wherein the ingredients are agitated. This may be necessary if it is not feasible to foam the product while it is still in the mixing chamber or if increased foaming of the product is desired. Furthermore, air may be injected into the system at that location in order to assist in propelling the product along the line downstream from the mixing chamber as well as to further increase the foaming of the product. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic drawing of a dosifying or materials application system in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The system of the present invention includes a hopper or other container  10  serving as a source of supply for concentrated additive and a hopper or other container  12  serving as a source of supply for a foaming agent. In the illustrated embodiment, the hopper  10  is designed to store a supply of dry additive, but the hopper could be designed for holding liquid additive as well. Suitable metering mechanism in the nature of an auger or other means feeds the dry additive  14  from the hopper  10  toward a tubular, pass-through mixing or combining chamber  16  where the additive  14  is combined with a suitable liquid carrier, such as oil or water. In the illustrated embodiment, a vibrator  18  coupled with a downwardly sloping delivery conduit  20  serves to accurately meter the dry additive  14  into the chamber  16 . 
     Hopper  12  is designed to store a supply of a foaming agent. A suitable metering mechanism feeds the foaming agent  22  from hopper  12  toward chamber  16  where the foaming agent  22  is combined with the additive  14  and the liquid carrier. A vibrator  24  coupled with a downwardly sloping delivery conduit  26  serves to accurately meter the foaming agent  22  into chamber  16 . 
     The chamber  16  is preferably arranged in an upright disposition so that an inlet  28  is presented at its upper end and an outlet  30  is presented at its lower end. The delivery conduits  20 ,  26  from the additive supply hopper  10  and foaming agent supply hopper  12 , respectively, project down into the outwardly flaring inlet  28  so that the additive  14  and the foaming agent  22  are dropped in a metered flow directly into the inlet  28 , preferably in the center thereof. 
     At least one type of liquid carrier is supplied to the mixing chamber  16  for combining with additive  14  and foaming agent  22 . In the illustrated embodiment, one delivery conduit  32  leads from a source of bulk supply of liquid carrier  34 , such as water, and empties directly into the inlet  28 . A pump  36  moves the carrier through the conduit  32 , and a variable outlet orifice  38  in conduit  32  permits the rate and volume of flow to be controlled. If desired, a second delivery conduit  40  for a liquid carrier may be provided, depending upon the ultimate mixture to be obtained, such conduit  40  containing a second liquid carrier  42 , having a second pump  44 , and being provided with a second variable outlet orifice  46 . 
     A discharge pump  48  is coupled with the chamber outlet  30  so as to draw a suction on the chamber  16 . Thus, additive, foaming agent, and liquid carrier introduced onto the inlet  28  by their respective sources of supply are combined within the chamber  16  into a mixed product which is then pumped to downstream portions of the system by the discharge pump  48 . The capacities and flow volume rates of the pumps  36 ,  44 , and  48 , as well as the relative cross-sectional sizes of the outlets  30 ,  38 , and  46  should be so regulated that the product formed within the chamber  16  does not collect in a pool within the chamber but instead is constantly flowing through the chamber at a steady rate. The liquid carrier is presented to the inlet  28  in the form of a steady stream for mixing with the metered flow of the additive and the foaming agent. In this way, the additive and foaming agent combines with the liquid carrier increment by increment, instead of all at one time as in a vat type mixing system. Furthermore, the incoming liquid continuously washes the walls of the chamber to keep the additive from sticking to those surfaces. 
     It is highly desirable to obtain smooth, laminar flow of the product through the chamber  16 . Therefore, it may be desirable in some instances to not only draw a suction on the outlet  30  of the chamber  16  with the pump  48 , but also to form a suction vortex illustrated by the number  50  within the mixed product above the outlet  30 . When the vortex  50  is present, the product swirls around the interior of the chamber  16  in a laminar flow manner, and thus moves quickly through the system without causing dead spots in the flow where the additive can settle out. The swirling vortex also assists in foaming the product and keeps the additive from sticking to the walls of the chamber. The vertical orientation of the chamber  16  is beneficial in creating the suction vortex inasmuch as the force of gravity helps draw the liquid out of the chamber  16  through the outlet  30 . Preferably, the cross-sectional area of the outlet  30  exceeds the effective combined cross-sectional areas of the outlet orifices  38  and  46  at all times so that the product within chamber  16  cannot collect to such a level that it will engage the bottom ends of the additive delivery conduit  20  and foaming agent delivery conduit  26 . Additionally, it is preferred that the upper end of the chamber  16  at the inlet  28  be generally funnel shaped with sloping interior surfaces. The streams thus entering the chamber  16  engage and flow along the sloping surfaces of the inlet  28  toward the outlet  30  with a tendency to swirl as they flow. A vibrator  52  below the inlet  28  is mechanically coupled with the chamber  16  and may be utilized to oscillate the chamber  16  in a circular motion so as to augment the swirling action obtained within the chamber  16  and the conical inlet  28  as well as to assist in foaming the product. 
     Intersecting the additive supply conduit  20  and foaming agent supply conduit  26  at a point above the chamber  16  is a gas delivery passage  54  having a variable outlet orifice  56 . The passage  54  may be used to supply the chamber  16  and downstream portions of the system with an additive gas under pressure. On the other hand, the passage  54  could also be used to simply draw in ambient air in regulated amounts so as to adjust the suction available from the pump  48 . Or, passage  54  could be used to provide air in order to increase the foaming of the additive  14  in the liquid carrier  34 . In any case, the upper end of the chamber  16  is preferably provided with a closure  58  that seals the chamber  16  from the atmosphere, except that air which may be supplied via the passage  54  when the same is used to admit ambient air. In some situations, such as when no gas is desired to be introduced to the chamber  16 , the closure  58  may be eliminated such that the funnel area is completely open to the atmosphere, except that air which may be supplied via the passage  54  when the same is used to admit ambient air. 
     The pump  48  discharges the product with positive pressure into a discharge conduit  60  leading to a dispensing head  62 . In one use of the invention, the dispensing head  62  may be positioned in such a manner so as to release the product in the form of a foam  64  that is directed onto the contents of an open top container  66  forming part of a truck  68 . The container  66  with its mass of animal feed and dose of foamed micro-ingredients from the additive supply hopper  10  can be thereafter delivered to the feeding site or other locations for ultimate distribution. 
     In some situations, it may be desirable to provide an augmentation chamber  70  within the discharge conduit  60  which subjects the product to agitation and additional mixing after the ingredients have been combined within the chamber  16  and moved through the discharge pump  48 . The augmentation chamber  70  may take a variety of different forms including, for example, a set of staggered deflecting baffles or the like within the path of flow of the product to force the product to move in a serpentine path and create turbulence. Thus, augmentation chamber  70  further serves to increase the foaming of the additive/liquid carrier/foaming agent mixture, providing better coverage of the mixture over the animal feed. 
     It may also be necessary to add positive pressure air to the discharge conduit  60  downstream from the pump  48  to assist in transferring the product through the augmentation chamber  70  and the rest of the downstream portions of the discharge conduit  60 . Such positive pressure air may be supplied by an air pump  72  connected to the discharge conduit  60  via a supply line  74 . A control valve  76  in the line  74  regulates the volume of air added to the discharge conduit  60 , and a check valve  78  downstream from the control valve  76  but upstream from the discharge conduit  60  prevents product from entering the air supply line  74  to any significant extent. Another check valve  80  in the discharge line  60  downstream from the pump  48  prevents air from the supply pump  72  from entering the discharge pump  48 . The air from pump  72  can also be utilized to dry out the discharge line  60  and the augmentation chamber  70  after each batch of product has been prepared and distributed. Preferably, the entire system is flushed prior to such drying action by simply allowing the appropriate liquid carrier  34  or  42  to pass through the chamber  16 , pump  48  and discharge conduit  60  without the introduction of any additive or foaming agent from the supply hoppers  10 ,  12 , respectively. 
     When the truck  68  arrives at the dispensing station as illustrated in the drawing, the contents of the container  66  may be weighed using a scale  82  that inputs the resulting information to a computer  84  such that, when the weight of the contents is known, the computer  84  can then appropriately signal the rest of the system to release only the appropriate amount of additive from hopper  10  and foaming agent from hopper  12  for the particular job. Thus, for each truck that arrives, the system has the ability to adjust itself to supply a batch of additive in accordance with a pre-established concentration schedule and accordingly adjust itself to supply the amount of foaming agent necessary to achieve appropriate foaming levels. In other words, if a certain amount of additive is desired per each unit of mass to be treated, that concentration can be maintained despite significant variations in the weights of successive masses of materials delivered to the dispensing station. It is only necessary to so program the computer  84  that it will allow only the proper amount of additive to be released from hopper  10  that is appropriate for the particular mass of material at the dispensing station, as well as the proper amount of foaming agent which appropriate for the type and amount of additive to be dispensed. 
     It is also to be understood that the present invention contemplates the use of several different additive hoppers  10 , each containing their own particular additive. Furthermore, several different foaming agent hoppers  12  could be utilized so that the foaming agent, or combination of foaming agents, could be selected based upon the particular additive(s) which would be used. Thus, the weight of the mass of material within the truck container  66  can be utilized to determine how much additive from several different hoppers is to be dispensed to the material within the truck container. Each additive hopper would preferably be associated with its own mixing chamber, foaming agent supply hopper, and liquid carrier supply stream, as well as its own discharge line to the point of dispensing the product onto the material within the truck container. At that location, the various lines could be merged together into a common dispensing head, or the truck could be advanced seriatim along a line of several different dispensing heads according to the number of hoppers utilized. 
     It is also important to appreciate that the present invention has particular utility in connection with the preparation and dispensing of relatively small amounts of additive compared to the relatively large masses of materials contained within the successive truck containers  66 . Furthermore, the use of a foaming agent allows for substantially less liquid carrier (which is generally water) to be used than has been necessary in the past. Those skilled in the art will appreciate that using such a small amount of liquid carrier decreases the problems associated with wet feed (such as mold growth and feed spoilage) while still achieving even, thorough distribution of the additives over the feed. Furthermore, using smaller quantities of a liquid carrier such as water is better for the environment. Finally, dispersing a foam on the feed rather than spraying a liquid on the feed avoids the mess created by the splattering liquid 
     Prior to the instant invention, thoroughly and uniformly dispersing 320 mg of Micro-cell® (a microbial feed additive for beef cattle available from Biotal, Inc., Eden Prairie, Minn.) over 16,000 lbs of feed required mixing the Micro-cell® with 20 gallons of water. By foaming the product in accordance with the invention, the same quantity of Micro-cell® can be uniformly dispersed over 16,000 lbs of feed with only 1.25 gallons of water, a 93% decrease in the volume of water required. 
     The methods of the invention can be utilized with any known feed additives. Those additives include vitamins such as vitamins A, D, and E, and nutritional additives such as RUMENSIN® 80 (Elanco Animal Health, Indianapolis, Ind.), any TERRAMYCIN® product (Pfizer Animal Health Division, Lee&#39;s Summit, Mo.), TYLAN 40 (Elanco Products Co., Indianapolis, Ind.), MGA 500® (The Upjohn co., Kalamazoo, Mich.), and Biotal Micro-cell®. Furthermore, the methods of the invention are not limited to applications on feed for beef cattle, but can also be used on feed for sheep, swine, fowl, or virtually any other animal for which additives must be dispersed efficiently on bulk quantities of feed. The feed can be in the form of pellets, finely ground meal, grains, corn, or any other form which may be desired. 
     Suitable foaming agents for use with the instant invention include any edible foaming agent such as starch-based foaming agents, milk-based foaming agents, or fatty acid-based surfactants. Preferably, the chosen foaming agent(s) will not interact with the additives to be dispersed on the feed. Or, as an alternative to adding a foaming agent, the additive/liquid carrier mixture can be foamed with air at a pressure of from about 5-50 psi. In the embodiment illustrated, the air could be delivered via passage  54  causing the additive/liquid carrier mixture to foam within mixing chamber  16 , or the air could be delivered by pump  72  through line  74  for foaming within conduit  60  and augmentation chamber  70 . Finally, the liquid carrier could be carbonated in order to create a foam.