Patent Document

BACKGROUND OF THE INVENTION 
   This invention relates to devices for mixing substances, especially for dispersing, suspending, and emulsifying gases and/or liquids and/or free-flowing solid substances, with a rotor that has a partition plate, inner blades, and outer blades, and with a cup-shaped stator whose wall is penetrated by holes. The stator is positioned between the inner blades and the outer blades of the rotor, with the rotor and the stator being located in a mixing chamber. A first product inlet opens into the mixing chamber at one side of a partition plate, and with a second product inlet and a product outlet associated with the partition plate opening at the other side of the partition plate in question. 
   A prior art device is disclosed in U.S. Pat. No. 5,540,499. This prior art device has a stator that is located in a mixing chamber into which the substances to be mixed can be introduced through product inlet connectors. Rounded holes of identical dimensions are introduced into the wall of the stator up to an edge rail that closes off the stator. There is also a rotating rotor made with a partition plate and inner blades and outer blades, with the partition plate being located inside the rotor. Substances fed into the mixing chamber are mixed intensively with one another by the interaction of stator and rotor. Although such a device is also commonly called an in-line disperser, and will provide relatively good mixing results, it is desired to mix with higher throughput and the most flexible possible matching to the particular necessary mixture ratios. 
   DE-B-10 40 513 discloses a device for mixing substances that is designed as an immersion apparatus or a so-called batch disperser and that has a cylindrical stator with two rows of slotted stator holes in the wall of the stator in the circumferential direction oriented at an angle in the radial direction. An intermediate rail is provided between the rows of stator holes. The dimensions of the stator holes of one row are different from the dimensions of the stator holes of the other row. 
   The last-mentioned prior art device also has a cylindrical rotor that is mounted to rotate inside the stator, with the inner wall of the stator and the outer wall of the rotor being spaced at a very small distance from one another. The wall of the rotor is likewise provided with two rows of slotted rotor holes oriented radially, but with the dimensions of the rotor holes being the same in each row. There is a partition plate between the rows of rotor holes that is made to connect two mixing regions on the two sides of the partition plate with a number of axially oriented connecting holes. This prior art device, however, has the drawback that, because of the double task produced by the configuration of the immersion apparatus, namely having to circulate the contents of the tank in which it is immersed in addition to mixing the substances themselves, the mixing is unsatisfactory despite the connecting holes provided for better circulation, especially with relatively large tanks, so that the type of apparatus has not become popular for mixing large quantities of substances. 
   U.S. Pat. No. 6,000,840 also discloses a device designed as an immersion apparatus for mixing substances with a cylindrical stator that has two rows of elongated holes made in the wall. The holes in the rows are spaced radially from one another and are oriented to run in succession at an angle to a central plane of the stator. The rotor, mounted to rotate inside the stator, has V-shaped inner blades extending over the entire inside diameter and height of the stator, with the arms of the inner blades each being oriented perpendicular to the longitudinal direction of the holes. This does produce relatively good dispersing action, but the aforementioned drawbacks typical of immersion apparatus also exist. 
   SUMMARY OF THE INVENTION 
   The objective of the invention is to provide a mixing device in which very diverse throughputs and mixture ratios can be set, with relatively high throughput and with relatively little changeover work. 
   This objective is achieved with a mixing device according to a first embodiment of the invention, by providing that the edge rail is in the plane of a partition plate and that the (or each) partition plate divides the mixing chamber into separate mixing regions, with substance exchange between the mixing regions in the mixing chamber being prevented. 
   This objective is also achieved with a mixing device according to a second embodiment of the invention, by providing at least two rows of holes into the wall of the stator in the circumferential direction, with the dimensions of the holes of one row being different from the dimensions of the holes of the other row. A circumferentially continuous intermediate rail is provided between each two adjacent rows of holes. The intermediate rail is positioned in the plane of an associated partition plate of the rotor. The (or each) partition plate divides the mixing chamber into separate mixing regions, with substance exchange between the mixing regions in the mixing chamber being prevented. 
   The single general inventive concept underlying both embodiments of the invention is to configure the wall of the stator into different mixing regions of the mixing chamber by means of partition plates. This provides the ability to set throughput and mixture ratios in a first infeed of a substance into one mixing region that are different from the corresponding conditions of a mixing region positioned at the other side of the particular partition plate. In this case, the device according to the first embodiment of the invention can be considered as the limiting case of the device according to the second embodiment which has a single hole extending over the entire perimeter of the wall. 
   By providing at least one intermediate rail in the second embodiment of the invention, relatively large stators in the longitudinal direction can also be used without the risk of breaking strips of material between holes because of the mechanically stabilizing action of the intermediate rails. 
   By providing multiple partition plates and a corresponding number of substance inlets and substance outlets, multistage mixing processes can also be projected with devices according to the invention. 
   In a device according to the first embodiment of the invention, it is advantageous for separating the mixing regions to provide that the edge rail is thinner than the partition plate. 
   If no mixing action is to occur in the second mixing region, or very little mixing action, in a refinement of the device according to the first embodiment of the invention, it is suitable to provide a single row of holes, with the holes of this one row being oriented diagonally to the longitudinal direction of the stator. 
   In another refinement of the device according to the first embodiment of the invention, at least two rows of holes are provided. This refinement is intended for multistage mixing processes. 
   In a device according to the second embodiment of the invention, and in a device according to the first embodiment of the invention designed for multistage mixing processes, it is desirable for the widths of the holes in different rows to be different. In a further refinement in this regard, it is desirable for the number of holes in at least two rows to be different to set particularly different mixing proportions in different mixing regions. 
   In a device according to the second embodiment of the invention, and in a device according to the first embodiment of the invention designed for multistage mixing processes, it is desirable, for increased or reduced substance input, to provide that the holes of at least one row are oriented at an angle (diagonally) to the longitudinal direction of the stator. In a further refinement in this regard, it is desirable for the holes of at least two rows to be oriented at an angle to one another. In this way, different inputs of substances can be produced into the particular mixing regions. 
   In a device according to the second embodiment of the invention, and in a device according to the first embodiment of the invention designed for multistage mixing processes, for essentially complete separation of the mixing regions on both sides of a partition plate, it is desirable for each of the intermediate rails to be thinner than their associated partition plates. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a side elevational view of a mixing device according to the invention with two substance inlets and one substance outlet; 
       FIG. 2  is an elevational view, partially in cross section, of a first embodiment of a mixing device according to the invention with a stator which has two rows of holes; 
       FIG. 3  is a partially cutaway side view of a stator for the mixing device of  FIG. 2 ; 
       FIG. 4  is a partially cutaway side view of a stator for the mixing device of  FIG. 2 ; 
       FIG. 5  is an elevational view partially in cross section, of a second embodiment of a mixing device according to the invention with a stator which has only one row of holes that extends over only a portion of the height of the mixing chamber; and 
       FIG. 6  is a partially cutaway side view of a stator for the mixing unit of FIG.  5 . 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows, in side view, a tank  1 , in which a liquid is stored at the beginning of a mixing process as the first substance of a mixture of substances to be produced. A mixing mechanism  3  driven by a stirrer drive  2  reaches into the tank. The mixing mechanism  3  preferably extends to the lower region of the tank  1  in order to produce effective thorough mixing. 
   A product infeed valve  4 , which is connected also to a first product infeed line  5 , is attached at the bottom of the tank  1 , which is tapered downwardly. The first product infeed line  5  opens through a first product inlet connector  6  into a mixing unit  7 . 
   Also attached to the mixing unit  7  is a second product inlet connector  8 , to which a product inlet valve  9  is connected. The product inlet valve  9  is also connected to a second product infeed line  10 , which extends, in the illustration of  FIG. 1 , into a bag  11  filled with powder as the second substance. 
   To carry out the mixing process, the mixing unit  7  is connected to a mixer drive  12 . 
   Finally, the mixing unit  7  has a product outlet connector  13  to which a product outlet valve  14  is connected. The product outlet valve  14  is also connected to a product delivery line  15  that extends into the top of tank  1 . 
   When carrying out the mixing process for mixing the liquid stored in tank  1  as the first substance with the powder stored in the bag  11  as the second substance, the liquid and the powder arrive at the mixing unit  7 , and are mixed there with one another as explained in farther detail below, and the resultant product is transferred back into the tank  1 . There, the product that has just left the mixing unit  7  is mixed with the liquid in tank  1  and with the already mixed product already present in tank  1 , and is thereafter again fed to the mixing unit  7 , until the mixing process is complete with an end product that is located in tank  1 . 
     FIG. 2  is a partially cutaway view of a first embodiment of the mixing unit  7 . The mixing unit  7  has a drive shaft  16  which is connected to the mixing drive  12  of FIG.  1 . The drive shaft  16  is securely connected to a rotor  17  which is located in a mixing chamber  18 . Rotor  17  has a partition plate  20  extending outwardly radially from a plug bushing  19  connected to the drive shaft  16 . Axially oriented inner blades  21  are distributed circumferentially on the outer edge of the partition plate, or disc  20 . The inner blades  21  extend only on one side of the partition plate  20  in the embodiment according to FIG.  2 . The rotor  17  also has outer blades  22  spaced radially from inner blades  21 , and which extend essentially over the entire height of the mixing chamber  18  and are enclosed by an outer wall  23  of mixing chamber  18 . 
   The mixing unit  7  is also equipped with a stator designed as a double-row stator  24  which is attached to a cover flange  25  which closes off mixing chamber  18  in the area of the second product inlet connector  8 . The double-row stator  24  is cup-shaped with a circumferential wall  26  which is located between inner blades  21  and outer blades  22  of the rotor  17 . 
   Outer wall  23  of the mixing chamber  18  is apertured in an outlet area  27  in which the product outlet connector  13  is located. 
     FIG. 3  is a partially cutaway side view of double-row stator  24  of the mixing unit  7  according to FIG.  2 . Double-row stator  24  includes a number of first holes  29  provided in wall  26  and which are arranged circumferentially as trapezoids in a fist row  28 , uniformly spaced and with rounded corners. Double-row stator  24  also includes a second row  30  of second holes  31  which are likewise provided in wall  26 , uniformly spaced and with rounded corners. Second holes  31  of second row  30  are not as wide, circumferentially, as first holes  29  of first row  28 . The number of holes  31  in second row  30  is also greater than the number of holes  29  in the first row  28 . 
   In the embodiment of the double-row stator  24  according to  FIG. 3 , the holes  29 ,  31  are aligned at an angle to the longitudinal axis of the double-row stator  24 . Holes  29 ,  31  are also arranged at an angle to one another. 
   A continuous circumferential intermediate rail  32  is provided between holes  29 ,  31  of two rows  28 ,  30 . The width of intermediate rail  32  in the axial direction of double-row stator  24  is smaller than the width of partition plate  20  in the axial direction of rotor  17 . An edge rail  37  borders holes  31  at the ends of holes  31  opposite rail  32 . 
   In operation, the mixing process with a mixing unit  7  according to FIG.  2  and  FIG. 3  takes place as follows. Liquid or already partially mixed product flows in the first product inlet connector  6  from the tank  1  into the mixing chamber  18 . Powder as the second substance, for example, flows through the second product inlet connector  8  into the mixing chamber  18 . The mixing chamber  18  is divided into a first mixing region and a second mixing region by partition plate  20 , with one row  28 ,  30  of holes  29 ,  31  of different dimensions in each case acting in each mixing region. Since partition plate  20  is wider than intermediate rail  32  and since wall  26  of the stator is immersed between inner blades  21  and outer blades  22  of rotor  17 , it is guaranteed that substance exchange between the mixing regions is prevented. 
   In a mixing unit  7  according to  FIG. 2  with a double-row stator  24  according to  FIG. 3 , thorough mixing that is already relatively good occurs in the first mixing region because of the relatively large dimensions of the first holes  29 , combined with a relatively high throughput of the entering second substance. Because of the narrower dimensions of second holes  31  of the second row  30  compared to the dimensions of the first holes  29  of the first row  28 , substantially more intensive mixing of the product, which is already partially mixed, occurs in the second mixing region even just after beginning the mixing process, compared to the first mixing region, yet still with a sufficiently high throughput. The arrow-like orientation of holes  29 ,  31  also increases the transport action in both mixing regions compared to an orientation parallel to the longitudinal direction of the double-row stator  24 . 
     FIG. 4  shows a modification of the double-row stator  24  according to  FIG. 3  in which the second holes  31  of the second row  30  are oriented parallel to the first holes  29  of the first row  28 , and the holes  29 ,  31  in each case are at an angle to the longitudinal axis of the double-row stator  24 . In this modification, relatively intensive transport, especially of powder as the second substance, into the first mixing region is retained, while because of the orientation of the second holes  31  of the second row  30  modified from the direction of rotation of the rotor  17 , compared to the design according to  FIG. 3 , more intensive mixing is produced in the second mixing region with somewhat reduced throughput. 
   It is to be understood that other variants with regard to the orientation and dimensions of the holes  29 ,  31  of the rows  28 ,  30  can be provided for, depending on the particular throughputs and mixing intensities to be produced in the mixing regions in each case. For example, if the second substance infed through the second product inlet connector  8  has to be relatively intensively mixed even in the first infeed, but then must be subjected only to relatively low mixing forces, the holes in the first mixing region are of relatively small dimensions and in relatively large number, and the holes in the second mixing region are less numerous and of relatively large dimensions. 
     FIG. 5  shows a mixing unit  7  that is similar to the mixing unit  7  described with reference to  FIG. 2 , except for the stator. In this case, identical elements are given the same reference symbols and are not described below in further detail. The mixing unit  7  of  FIG. 5  is made with a single-row stator  33  as the stator, whose wall  34  extends only to the area of the partition plate  20  of the rotor  17  and thus only over the first mixing region of the mixing chamber  18 , so that the gap between the inner blades  21  and the outer blades  22  of the rotor  17  is open in the second mixing region. 
     FIG. 6  shows a side view of the single-row stator  33  according to FIG.  5 . Holes  35  are introduced into the wall  34  of the single-row stator  33  that are arranged in only one row  36  and are arranged at an angle to the longitudinal direction corresponding to the holes  29 ,  31  of the double-row stators  24  of FIG.  3  and FIG.  4 . The holes  35  end in a border or edge rail  37  at their end pointing toward the center of the mixing chamber  18  that is thinner than the partition plate  20 , corresponding to the intermediate rail  32  of the double-row stators  24 . 
   The mixing process using a single-row stator  33  corresponds basically to the mixing process with a double-row stator  24  described with reference to FIG.  2  and  FIG. 3 , so that the single-row stator  33  can be considered as the theoretical limiting case of a double-row stator  24  with a single hole in the second row extending over the entire circumference. When using a single-row stator  33 , the mixing process in the second mixing region is determined solely by the interaction of the inner blades  21  and the outer blades  22  of the rotor  17 , with no mixing, or only extremely little mixing, occurring because of this, for example in the case of products which are very sensitive to shear, such as microballoons, hollow beads, or thickening polymers. 
   While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Technology Category: 7