Abstract:
An apparatus for mixing comprising a vessel  302  for holding a product comprising a liquid base and an ingredient, a rotor  304  for providing a first flow  306  of said product inside said vessel and a double agitator for providing a second flow  312  of said product inside said vessel. The double agitator comprises a first agitator  308  arranged to rotate in an outer section of said vessel, and a second agitator  310  arranged to rotate in an inner section of said vessel.

Description:
TECHNICAL FIELD 
       [0001]    Generally it is presented apparatuses and methods related to the field of mixing. More particularly, the apparatuses and methods are related to so-called high shear mixing. 
       BACKGROUND 
       [0002]    Today when producing high viscous products, such as ketchup or mayonnaise, high shear mixing is often used. High shear mixing differs from other mixing in that high shear mixing can form mixtures of ingredients that do not naturally mix, such as mixing oil and water into an emulsion. In order to form this high shear a rotor, also known as impeller, can be used in combination with a stator. In one example of a high shear mixer, Tetra Pak High Shear Mixer™, the rotor is placed in a bottom part of a vessel and the stator provided with openings is placed such that this surrounds the rotor. 
         [0003]    For high viscous products, such as mayonnaise, it is today common to use an external pump to make sure that sufficient transportation flow is achieved inside the vessel. Since an extra pump increases the cost for the equipment as well as the operational cost, due to that the pump and the additional piping increases product losses, it is in the interest of food producers to find a new way of mixing high viscous products more cost efficiently. 
       SUMMARY 
       [0004]    Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problems. 
         [0005]    According to a first aspect it is provided an apparatus for mixing, said apparatus comprising a vessel for holding a product comprising a liquid base and an ingredient, a rotor for providing a first flow of said product inside said vessel, a double agitator for providing a second flow of said product inside said vessel, wherein said double agitator comprises a first agitator arranged to rotate in an outer section of said vessel, and a second agitator arranged to rotate in an inner section of said vessel. 
         [0006]    The ingredient may be a liquid ingredient or a solid ingredient. 
         [0007]    The first flow and said second flow may coincide at least partly. 
         [0008]    The first flow and said second flow may form a transportation flow providing for that said product in said outer section of said vessel is transported towards a top of said vessel, and for that said product in said inner section is transported towards a bottom of said vessel. 
         [0009]    The first agitator and said second agitator may be individually controlled. 
         [0010]    The first agitator and said second agitator may counter-rotate. 
         [0011]    The second agitator may be arranged to scrape an inner wall of said tank during rotation. 
         [0012]    The apparatus may further comprise a stator at least partly surrounding said rotor. 
         [0013]    The apparatus may further comprise a control device provided with a number of programs for different products, each program comprising instructions on rotational speed for said first agitator, said second agitator and/or said rotor, respectively. 
         [0014]    The first agitator and/or said second agitator may be driven by a motor provided with a planetary gear. 
         [0015]    According to a second aspect it is provided a method for forming a product, said method comprising placing a liquid base and an ingredient in said vessel, mixing said liquid base and said ingredient into a mixture by providing a first flow of said product in said vessel by using a rotor, providing a second flow of said product inside said vessel by using a double agitator comprising a first agitator rotating in an outer section of said vessel and a second agitator rotating in an inner section of said vessel. 
         [0016]    The first flow and said second flow may coincide at least partly. 
         [0017]    The first agitator, said second agitator and said rotor may be individually controlled. 
         [0018]    The first agitator and said second agitator may counter-rotate. 
         [0019]    The method may further comprise scraping an inner wall of said tank during rotation by using said second agitator. 
         [0020]    The step of mixing said liquid base and said ingredient into a mixture may further comprise forming a shear between said liquid base and said ingredient by using said rotor and a stator, said stator at least partly surrounding said rotor. 
         [0021]    The method may further comprise adding particles to said mixture, and stirring said particles and said mixture by using at least one of said first agitator and said second agitator. 
         [0022]    The first and/or said second agitator may move during operation in a non-concentric path. 
         [0023]    According to a third aspect it is provided a processing line comprising an apparatus according the first aspect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, wherein: 
           [0025]      FIG. 1  illustrates an example of an arrangement, comprising a tank with a stirring device, used for mayonnaise production. 
           [0026]      FIG. 2  illustrates an example of a two-step approach for producing products comprising an emulsion and vegetables, such as cole slaw. 
           [0027]      FIG. 3  illustrates schematically a mixer provided with a double agitator. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]      FIG. 1  illustrates an arrangement  100  used for producing mayonnaise. Ingredients are added and transferred to a tank  102  via an inlet  104  connected to a pipe  106 . In the tank  102 , stirring panels  108  mounted on an shaft  110  provide for that the ingredients are stirred together. In order to rotate the shaft  110  a motor  112  is used. Most often the inlet  104  is placed in an upper portion of the tank  102  and an outlet  114  is placed in a bottom portion of the tank. In order to provide for that the ingredients are able to circulate through the tank a number of times until desired product properties are achieved, a pump  116  placed after the outlet  114  is used. 
         [0029]    Oil is added in a node  118 . In order to provide for that a correct amount of oil is added this may be adjusted relative to the flow. After the oil has been added a mixer  120 , such as a mixing valve, is used for partly mixing the oil with the other ingredients. 
         [0030]    In order to control if the ingredients should be transported back to the tank for further stirring or to a next step of a processing line, a first valve  122  and a second valve  124  may be used. The first valve  122  is placed on the pipe  106  and the second valve  124  is placed on a pipe leading to e.g. a filling machine for filling the mayonnaise in packages. By having the first valve  122  opened and the second valve  124  closed the ingredients are fed back to the tank, and by having the first valve  122  closed and the second valve  124  opened the product is fed to e.g. the filling machine. 
         [0031]    A drawback with the arrangement  100  illustrated in  FIG. 1  is that a pump is required for re-circulating a mixture of the ingredients and the oil until desired product properties are achieved. In addition to that the pump is required, a further drawback is that product losses will increased due to the pipe  106  used when re-circulating the mixture. 
         [0032]      FIG. 2  illustrates two parts of a production line  200  for cole slaw or other products comprising an emulsion and vegetables. 
         [0033]    In a first part  202  the emulsion is formed, e.g. by using the arrangement illustrated in  FIG. 1 . After having formed the emulsion this is transferred to a second part comprising a stirrer  204 . The stirrer can be provided with an inlet  206  for vegetables, a shaft  208  provided with a number of stirring panels  210 . The shaft  208  may be rotated by using a motor  212 . 
         [0034]      FIG. 3  illustrates a mixer  300  provided with a double shaft agitator. The mixer  300  can comprise a vessel  302  provided with a mixing unit  304  in its lower part. The mixing unit  304  may be a high shear mixing unit. This high shear mixing unit may comprise a rotor, such as an impeller, and a stator. The stator may be formed such that this surrounds the rotor, and may comprise a number of openings in order to provide for improved high shear mixing. 
         [0035]    The mixing unit  304  may be designed such that this in operation forms a first flow  306  inside said vessel  302 . If the vessel is filled with a high viscous product, such as mayonnaise, the first flow  306  will, as illustrated in  FIG. 3 , appear in the lower part of the vessel. 
         [0036]    In order to provide for that a transport flow is formed such that also the product in the upper part of the vessel is transported down to the mixing unit  304  a double agitator can be provided. The double agitator can comprise a first agitator  308  and a second agitator  310 . The first agitator  308  may comprise one or several elements extending to an outer section of the vessel. In order to form a flow of the product, for instance upwards, the element may be provided with panels. 
         [0037]    The first agitator  308  may be arranged to scrape the inside of the vessel when being rotated. An advantage of this is that if the vessel is provided with a heating/cooling jacket the first agitator will provide for an improved thermal transfer since the circulation of product being close to the inside of the vessel is improved. Another advantage is that the risk of overheating product close to the inside of the vessel is reduced. This in turn may imply that the cleaning time for the vessel can be reduced. 
         [0038]    The second agitator  310  may be placed centrally in the vessel as illustrated in  FIG. 3 . The second agitator may be provided with panels in order to provide for that a desired flow inside the vessel can be formed. As illustrated in  FIG. 3 , the second agitator  310  may have impeller-like panels. 
         [0039]    The panels of the first and second agitator may be formed such that a second flow  312  inside the vessel is formed. In order to achieve this flow the first and second agitator may counter-rotate. 
         [0040]    The first flow  306  and the second flow  312  may be such that these coincide at least partly. A positive effect of this is that it is made sure for high viscous products, such as mayonnaise, that also the product in the upper part of the vessel is transported to the mixing unit  304  and there being subjected to mixing. This in turn has the effect that the product does not have to be re-circulated outside the vessel and hence that no external pump or piping is needed. 
         [0041]    In order to provide for that the first agitator  308  and the second agitator  310  can counter-rotate, the first agitator  308  may comprise a first shaft  314  and the second agitator  310  may comprise second shaft  316 , wherein the first shaft  314  is hollow and the second shaft  316  is placed in its upper section inside said first shaft. By having this arrangement, the first shaft  314  may be rotated by a first motor  318 , for instance a gear motor, and the second shaft  316  may be rotated by a second motor  320 , such as a gear motor, and by having individual motors these can be controlled individually, for instance, such that they counter-rotate. In order to achieve a non-concentric path for one or both of the agitators planetary gears can be used. 
         [0042]    Even though not illustrated in  FIG. 3 , an inlet for oil or other ingredients may be present in the vessel. 
         [0043]    By having the mixer provided with the double agitator as illustrated in  FIG. 3  the two-step approach illustrated in  FIG. 2  can be avoided. After having formed the emulsion in the mixer  300  the vegetables can be added via an inlet, not illustrated in  FIG. 3 , and stirred into the emulsion by using the first and/or the second agitator. An advantage of this flexibility is that less equipment is necessary for producing this kind of product. 
         [0044]    The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.