Patent Abstract:
The static mixer comprising mixing elements for separating the material to be mixed into a plurality of streams and a mechanism for the layered junction of the same, a transversal edge and guide walls that extend at an angle to said transversal edge, as well as deflecting elements arranged at an angle to the longitudinal axis and provided with openings, includes mixing elements comprising a transversal edge and a following transversal guide wall and at least two guide walls with lateral end sections and at least one bottom section disposed between said guide walls, thereby defining at least one opening on one side of said transversal edge and at least two openings on the other side of said transversal edge. In addition to a high mixing efficiency and a low pressure drop, a mixer of this kind provides reduced dead volumes and is thus more effective than mixers of the prior art.

Full Description:
This application is a continuation application of U.S. patent application Ser. No. 10/727,049, filed Dec. 4, 2003, which is abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a static mixer comprising mixing elements for separating the components to be mixed into a plurality of streams, as well as means for the layered junction of the same, including a transversal edge and guide walls that extend at an angle to said transversal edge, as well as deflecting elements arranged at an angle to the longitudinal axis and provided with openings. 
     PRIOR ART 
     A static mixer of this kind is e.g. known from U.S. Pat. No. 5,851,067. This patent in turn is a further development of U.S. Pat. No. 5,944,419. These references disclose a mixer that is divided into chambered strings; according to the first cited U.S. patent, four chambered strings are created by four alternately disposed passages and the mixer further comprises re-layering chambers. In the second cited mixer, two flanges or alternatively two pairs of flanges crossing one another are disclosed with passages disposed in such a manner that respective bottom section plates are situated above respective openings. 
     Although mixers of this kind achieve a better mixing of the components with reference to its length and exhibit a smaller pressure drop than conventional mixers using mixing helixes, they include relatively large dead volumes in which the composition will harden, thereby leading to an eventual plugging of the mixer. 
     SUMMARY OF THE INVENTION 
     On the background of this prior art, it is the object of the present invention to provide a static mixer achieving a high mixing efficiency with reduced dead volumes and reduced pressure drop. This object is attained by a static mixer wherein said mixing element comprises a transversal edge and a following transversal guide wall and at least two guide walls ending into a separating edge each with lateral end sections and with at least one bottom section disposed between said guide walls, thereby defining at least one opening on one side of said transversal edge and at least two openings on the other side of said transversal edge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail hereinafter with reference to drawings of exemplary embodiments. 
         FIG. 1  schematically shows a first exemplary embodiment of a mixer of the invention in a perspective view, 
         FIG. 2  schematically shows the starting position prior to mixing, 
         FIG. 3  shows a corresponding mixing diagram, 
         FIG. 4  shows a flow diagram of the mixing operation, 
         FIG. 5  shows the mixer of  FIG. 1  in the inverse flow direction, 
         FIG. 6  schematically shows the starting position of the mixer of  FIG. 5  prior to mixing, 
         FIG. 7  shows a mixing diagram relating to  FIG. 6 , 
         FIG. 8  shows a flow diagram of the mixer of  FIG. 5  in the mixing operation, 
         FIG. 9  schematically shows a second exemplary embodiment of a mixer of the invention in a perspective view, 
         FIG. 10  shows the starting position prior to mixing, 
         FIG. 11  shows a diagram of the mixing operation in the mixer of  FIG. 9 , 
         FIG. 12  shows a flow diagram of the mixing operation in the mixer of  FIG. 9 , 
         FIG. 13  shows a combination of mixing elements according to the invention and of a mixing helix known per se in the prior art, 
         FIG. 14  shows a detail of an alternative embodiment of  FIG. 9 , 
         FIG. 15  schematically shows another exemplary embodiment of a mixer of the invention, 
         FIG. 16  shows a flow diagram of the mixing operation in the mixer of  FIG. 15 , and 
         FIG. 17  shows an enlarged detail of the mixer of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a detail of a first exemplary embodiment of a mixer  1  of the invention that comprises a number of identical mixing elements  2 ,  2 ′, and  2 ″, which are superimposed on one another while each successive element is rotated by 180° with respect to the longitudinal axis. Mixing enclosure  3  is schematically shown at one end. 
     Seen in the flow direction, i.e. from the bottom of the drawing, one end of each individual mixing element  2  comprises a transversal edge  8  of a transversal guide wall  8 ′ that is followed by two end sections  6  and  7  extending perpendicularly thereto and including complementary lateral openings  11  and  12 , and by a bottom section  9  and a complementary bottom section opening  10 , the latter extending between two guide walls  4 ′,  5 ′ each of which ends in a respective separating edge  4 ,  5 , where the guide walls are aligned in parallel with the longitudinal center axis. In the present example, the end sections extend over half the length of the separating edges. The openings, resp. their cross-sectional areas, and the length of the webs essentially determine the pressure drop between the inlet and the outlet of the mixer. 
     The mixing element  2 ′ following mixing element  2  comprises the same components and structures, but it is superimposed on first mixing element  2  in a position rotated by 180° with respect to the longitudinal axis. The following mixing elements are also identical to mixing element  2  and arranged one after another while rotated by 180° each as seen in the longitudinal direction. The flow direction is indicated by arrow  13 . 
       FIG. 2  indicates the distribution of the two components G and H at the mixer entrance, each component being supplied from a container of a double cartridge or a dispensing appliance having separate outlets, see  FIG. 13 . In the present example, according to the flow direction, the mixer entrance is shown at the bottom. After their entrance on either side of transversal edge  8 , the components G and H spread along transversal guide wall  8 ′ and are divided into three streams by guide walls  4 ′,  5 ′, so that six streams AG, BG, CG and AH, BH, and CH are finally produced, to which respective chambers DG, EG, FG; DH, EH, FH may be associated in the mixer. 
     During further dispensing, the six streams reach the following mixing element  2 ′. In the process, on one side of the transversal edge, the mixed and spread streams AG, BG, and CG are displaced through lateral openings  11  and  12 , and on the other side of the lateral edge, the spread streams AG, BH, GH are displaced through bottom opening  10 , as indicated in  FIG. 3  schematically. Thus, at the end of element  2 , the mixed streams A 1 .G and C 1 .G with B 1 .G as well as A 1 .H and C 1 .H with B 1 .H=A 1 . 1  and C 1 . 1  with B 1 . 1  and A 1 . 2  and C 1 . 2  with B 1 . 2  are obtained according to the diagram of  FIG. 3 . After having reached the second mixing element  2 ′, the mixed streams spread on either side of the lateral edge. 
     Then, the mixed and spread streams A 2 . 1 , B 2 . 1 , and C 2 . 1  are displaced outwards through lateral openings  11  and  12 , and the mixed streams A 2 . 2 , B 2 . 2 , and C 2 . 2  are displaced inwards through bottom opening  10 , as follows from  FIG. 3 , whereupon these streams are spreading again. 
     In the next step, the displacement occurs in the other direction, i.e. streams A 3 . 1 , B 3 . 1  and C 3 . 1  are displaced inwards and A 3 . 2 , B 3 . 2  and C 3 . 2  outwards, as shown in  FIG. 3  as well. Again, when entering the following element, the components spread on both sides of the lateral edge and are subsequently displaced again to reach the following mixing element. 
     The arrangement and the construction of the mixing elements result in a three phase sequence of the mixing process, in which the composition is first divided, then spread and subsequently displaced, only to be divided, spread, and displaced again in the following step. 
     This is shown in the diagram of  FIG. 4 , in which the three steps of dividing, displacement and spreading are illustrated in three stages. In the diagram of  FIG. 4 , separating is symbolized by I, displacement by II, and spreading by III, while the three mixing elements resp. mixing stages are designated by  2 ,  2 ′,  2 ″. This diagram clearly shows that in mixing element  2 , the two components G and H are first divided into two and subsequently into three respective streams, i.e. into six streams AG, BG, CG and AH, BH, GH, then on the one side three mixed streams are displaced through the two lateral openings as two streams and on the otzher side the three other mixed streams are displaced through bottom opening  10  to form a single stream, and then again to be spread as three mixed streams. 
     In an alternative embodiment for a larger mixer, more than two separating edges and guide walls may be provided, e.g. three separating edges and guide walls, which in the case of two components divide the material into more then six streams, while the bottom walls resp. openings are arranged in alternate directions resp. mutually offset. Also, as in the preceding example, a transversal edge is provided, so that the streams are divided into two portions. The result is an analogous configuration of a mixing element comprising more than one transversal edge and more than two separating walls. 
     Alternatively, it is also possible to operate the mixer in the reversed direction with respect to the flow direction, so that the material first reaches the separating edges rather than the transversal edge. Thus, the composition is first divided into three parts and then, during its passage through the two openings, into two parts. In this inverse flow direction, the two outer streams unite and spread on one half of the transversal edge while the two middle streams unite and spread on the other half of the transversal edge. 
     In  FIGS. 5 to 8 , mixer  1  is reversed by 180° with respect to  FIG. 1  while the flow direction remains the same. For a better understanding, the individual components of the mixing element are listed again. At one end, seen from below in the direction of flow, the individual mixing element  2  comprises two separating edges  4  and  5  pertaining to respective guide walls  4 ′,  5 ′, which are aligned in parallel to the longitudinal center axis and comprise, perpendicularly thereto and on either side of the guide walls, two end sections  6  and  7  and a bottom section  9  situated between the guide walls and extending over half of the guide walls. Perpendicularly to the end sections, at the center of the guide walls, a transversal guide wall  8 ′ is arranged which comprises a transversal edge  8  at the other end of the mixing element. 
     The two end sections and the bottom section are complementarily associated with bottom section opening  10  between the guide walls and with the two lateral openings  11  and  12  on either side of the guide walls. The openings, resp. their cross-sectional areas, essentially determine the pressure drop between the inlet and the outlet of the mixer. 
     The mixing element  2 ′ following mixing element  2  comprises the same components and structures and is disposed on first mixing element  2  in a position rotated by 180° with respect to the longitudinal axis. Likewise, the following mixing elements are also arranged one after another in positions rotated by 180° each with respect to the longitudinal axis. The flow direction is indicated by arrow  13 . 
     In  FIG. 5 , the distribution of the two components G and H at the mixer inlet is indicated, each component being supplied from a container of a double cartridge or a dispensing appliance having separate outlets, see  FIG. 13 . In the present example, according to the flow direction, the mixer inlet is shown at the bottom. When entering the first mixing element  2 , the two components are divided by separating edges  4  and  5  into six streams AG, BG, CG and AH, BH, and CH. 
     During further dispensing, the six streams reach the following mixing element  2 ′. In the process, the respective pairs of streams A 1 .G and A 1 .H, B 1 .G and B 1 .H, and C 1 .G and C 1 .H=A 1 . 1  and A 1 . 2 , B 1 . 1  and B 1 . 2 , and C 1 . 1  and C 1 . 2  are mixed with one another according to  FIG. 7  while due to the geometrical structure of mixing element  2 , stream A 1 . 1  displaces stream A 1 . 2  to reach the following mixing element through lateral opening  11 , stream B 1 . 2  displaces stream B 1 . 1  to reach the following mixing element through bottom section opening  10 , and stream C 1 . 1  displaces stream C 1 . 2  to reach the following mixing element through lateral opening  12 . When they arrive at the second mixing element  2 ′, the mixed streams B 2 . 1  and B 2 . 2  spread on one side of transversal edge  8  on the entire half A 2 . 1 -B 2 . 1 -C 2 . 1 , and likewise, the two mixed streams A 2 . 1 , A 2 . 2  and C 2 . 1 , C 2 . 2  spread on the other side of transversal edge  8  on the half A 2 . 2 , B 2 . 2 , and C 2 . 2  shown at the front of the Figure. 
     In the next step, a displacement in the other direction results, i.e. stream B 2 . 1  displaces stream B 2 . 2 , stream A 2 . 2  displaces stream A 2 . 1 , and stream C 2 . 2  displaces C 2 . 1 , as appears in  FIG. 3  as well. Again, when entering the following mixing element, the components spread on a respective half and are subsequently displaced again to reach the following mixing element. 
     Here also, the arrangement and construction of the mixing elements result in a three phased sequence of the mixing process in which the composition is first divided, then displaced and finally spread, only to be divided, displaced, and spread again in the following step. 
     This follows from the diagram of  FIG. 8 , in which the three steps of dividing, displacing, and spreading are illustrated in three stages. In the diagram of  FIG. 8 , separating is symbolized by I, displacing by II, and spreading by III, while the three mixing elements as well as the corresponding mixing stages are designated by  2 ,  2 ′,  2 ″. This diagram clearly shows that in mixing element  2 , the two components are divided into six streams, then a respective stream displaces the other one to spread towards the second mixing element  2 ′ in such a manner that the central streams form one half on one side of transversal edge  8  and transversal guide wall  8 ′ while the two outer pairs of streams jointly form the other half on the other side of the transversal edge and the transversal guide wall. 
     The mixers described above not only provide an intimate mixing of the materials but first of all a lower pressure drop as well as reduced dead volumes as compared to other mixers mentioned in the introduction. 
     Based on this simplified discussion of the schematic mixing operations, the following variations are possible: In these exemplary embodiments, mixers having rectangular resp. square cross-sections have been described, and the two impinging components have the same cross-sectional area. However, this need not always be the case, but any cross-sectional, resp.volume stream ratio of the two components G and H may be chosen at the inlet section, e.g. between 1:1 and 1:10, whereby the dimensions of the mixing elements remain the same. It is however possible to envisage specially adapted mixing elements. This means that the transversal edge need not be arranged on the center line of the mixing element. The same applies to the distance between the separating edges and the guide walls. 
     Furthermore, the separating edges and guide walls may be arranged at a mutual angle, and likewise, the end sections and the bottom section as well as the transversal edge may be arranged at a mutual angle, so that the openings are not necessarily rectangular or square. Also, the edges, e.g. the transversal edge, may incorporate a bend. The mixing elements need not be arranged one after another in positions rotated by 180°, but any angle from 0° to 360° is possible. 
     It is also possible to arrange the previously described mixing elements in an enclosure having a cross-section other than rectangular, e.g. in a round, an orbicular, resp. cylindrical, a conical, or an elliptic enclosure. 
     Whereas the previously described mixing elements provide good mixing properties, the walls arranged at an angle still include dead volumes giving rise to cured material in spite of the improved design. A further reduction of the dead volume is provided by a mixer having mixing elements with curved walls. A mixer of this kind is represented in  FIGS. 9 to 12 . 
       FIG. 9  shows a mixer  14  with a regular cylindric housing as a particular case of a round mixer having mixing elements with curved walls, including mixing elements  15 ,  15 ′, and  15 ″ and enclosure  16 . In analogy to the first mixer  1 , at one of its ends, i.e. at the bottom as seen in the flow direction, mixing element  15  comprises a transversal edge  21  where two guide walls  17 ′,  18 ′ originate which end in respective separating edges  17 ,  18 . The guide walls each comprise a respective end section  19  and  20  with lateral openings  24 ,  25 , a bottom section  22 , and a complementary bottom section opening  23 . 
     The individual sections are not as clearly demarcated here as in the first exemplary embodiment. In contrast to the rectangular mixing element  2 , the two guide walls  17 ′,  18 ′ form a curved and continuous transition between separating edges  17  and  18  situated at one end thereof and transversal edge  21  at the other end. This curved configuration of the guide walls, resp. their transition to the transversal edge appears in  FIG. 9 , the schematized transition being shown in  FIG. 12 . 
     The operation of this second exemplary embodiment is the same as in the first example. In analogy to the latter, the material stream consisting of the two components G and H is divided into a total of six streams AG, BG, CG, AH, BH, and CH as it leaves the first mixing element  15 . 
     In this example, the mixing operation is effected in analogy to the first exemplary embodiment, whereas the guide walls are no longer arranged in a sharp, rectangular disposition but run towards each other in a V-shaped configuration and have a curved shape. The mixing principle according to  FIG. 11  is the same as in the first example, i.e. the central stream BG=B 1 . 1  in  FIG. 11  mixes with the two other streams AG=A 1 . 1  in  FIG. 11  and CG=C 1 . 1  in  FIG. 11  and is displaced through lateral openings  24 ,  25 , and spreads while on the other side of the transversal edge, the two outer streams AH=A 1 . 2  and CH=C 1 . 2  mix with central stream BH=B 1 . 2  are displaced through bottom section opening  23 , and spread. Due to the curved construction and the V-shaped arrangement of the guide walls, dead volumes are substantially reduced, thereby resulting in reduced losses. On the other hand, this arrangement results in a further reduced pressure drop. 
     It is conceivable in this exemplary embodiment that the two guide walls  17 ′,  18 ′ are provided at the transition to transversal wall  21  with an additional web  152  disposed in the longitudinal axis and transversally to the transversal wall, which would theoretically divide the material into three rather than two parts at the exit near the transversal wall, see  FIG. 14  illustrating a mixing element  151 . However, such an additional web offers no advantages but rather the inconvenience that the material may not spread on that side. It is also possible to provide such a web in the first, rectangular mixer, i.e. below floor  9  and along transversal edge  8 . However, the following considerations and the claims do not take account of this additional partition. 
     Also, the diagram of  FIG. 12  will be interpreted in analogy to the diagram of  FIG. 4  with the difference that the perpendicular guide walls  4 ′,  5 ′ provided according to  FIG. 4  are V-shaped here and end in the transversal edge. 
     In analogy to the first example, the cross-sectional, resp. volume stream ratios of the components G and H may be different from 1:1, and most importantly, the guide walls leading from the separating edges to the transversal edge may assume a multitude of geometrical shapes while the mixing elements may be reversed to the shown arrangement with regard to the flow direction. Also, the mixing principle is the same in each case, i.e. the central streams mix with each other and spread on one side of the transversal edge, and then the two outer pairs of streams spread on the respective other side of the transversal edge. Furthermore, the successive mixing elements need not necessarily be rotated by 180° each with respect to the longitudinal axis as shown in  FIG. 9  but may be disposed in any orientation. 
     In the exemplary embodiment of  FIG. 13 , a novel mixer arrangement is shown which achieves particularly good results with the described mixing elements.  FIG. 13  shows a mixer  36 , mixer enclosure  16  and the mixer entrance with inlets  32  and  33  and outlet openings  34  and  35 . As in the mixers of the prior art using mixing helixes, entrance edge  31  of the first helix mixing element  28  extends transversally across the two outlet openings  34 ,  35 . The two separating edges of first mixing element  15  of first mixing group  27  are disposed transversally to outlet edge  30  of the first helix mixing element. The first mixing group  27  consists of the mixing elements  15 , of which four are illustrated here by way of example. This group is followed by the second helix mixing element  28 ′, which in turn is followed by a second mixing group  27 ′. This second mixing group also consists of four mixing elements  15 ′, which however are reversed by 180° in the direction of flow against the first mixing group, i.e. with the transversal wall directed towards the inlet, whereby this group has a similar effect as that of  FIG. 9 . 
     Furthermore, it follows from  FIG. 13  that transversal edge  21  of the last mixing element of each mixing group is perpendicular to entrance edge  31 ′ of mixing helix element  28 ′. The periodical insertion of a mixing helix element serves the purpose of efficiently peeling the material from the walls and of re-layering it, thereby providing a further improvement of the mixing efficiency. 
     In  FIG. 13 , three mixing groups and three mixing helix elements are shown, but it is understood that the number of mixing groups and mixing elements may vary according to the intended purpose. Thus, both the number of mixing elements per mixing group and the number of mixing helix elements between the mixing groups may vary. All considerations concerning the mixing operation and the application of conventional mixing helixes also apply for the homogenization of materials and for mixing arrangements using mixing elements according to  FIG. 15 . 
     The exemplary embodiment of  FIGS. 15-17  is based upon the exemplary embodiment of  FIG. 1  with straight element walls, the mixing elements however being arranged in a regular cylindrical housing. In this exemplary embodiment, several features are indicated which provide both an improvement of the mixing action and a reduction of the dead volumes resp. of the losses associated therewith, and thus allow a substantially increased overall efficiency. It is understood that not all of these features need be provided in all mixing elements or mixing groups at the same time. 
       FIG. 15  shows a mixing element arrangement  40 , whereby the housing is not shown, including inlet portion  41  with inlets  42 ,  43  and outlets  42 ′,  43 ′ as well as mixing section  44  with the mixing elements. Up to the first transversal edge  45 , the components are separated by a separating wall  46 . In this exemplary embodiment, five mixing elements  47   a - 47   e  are integrated in a first mixing group  47 , while the second mixing group  48  comprises two mixing elements  48   a  and  48   b  and the following mixing group  49  again includes five mixing elements  49   a - 49   e.    
     Using the mixer according to  FIG. 1 ,  15  or  17  it may be advantageous to provide that the height ZL of guide walls  50 ,  51 , which are reached by the material after the transversal guide wall, is greater than the height ZQ of the transversal guide walls, e.g. by a preferred factor comprised between 1.1 and 2.0, more particularly 1.5. This lengthening of the double guide walls provides an improved alignment of the material, which is thereby allowed more time to spread before being divided again. Furthermore, the lengthening of the double guide walls results in a reduction of the number of mixing elements required to achieve an equal or better mixing quality. 
     In analogy, when using the mixer according to  FIG. 5  in the reversed flow direction it may be advantageous to provide for a greater height ZQ of the transversal guide wall, reached after the guide walls by the material, than the height ZL of the guide walls, also with a preferred ratio of 1.1 to 2.0, in particular 1.5. 
     A second feature common to all mixing elements are measures for reducing the dead zones, which are particularly important in the case of straight walls and cause volume losses and local curing of the material. To this end, such dead zones are filled in. Different dead zone obturations TZV are indicated especially in  FIG. 17 . Thus, bottom section  9  comprises dead zone obturations TZV 1  of a first type that are directed towards the preceding mixing element. The mixing elements having no inclined webs, i.e. mixing elements  47   a - 47   e  and  49   a - 49   e , also comprise dead zone obturations TZV 2  on the inwardly facing sides of the bottom sections. On the outside of guide walls  50  and  51  a third and fourth type of dead zone obturations TZV 3  and TZV 4  are provided in those locations where no inclined webs are present. 
     At straight walls, wall layers are formed that cause layer defects during layer formation. For the detachment of such layers, for the promotion of the longitudinal mixing action in the direction of the double guide walls, and for equalizing the concentrations, inclined webs are provided on the inside and on the outside of the guide walls. 
     In the mixer of  FIGS. 15 and 17 , these inclined webs are attached to the central mixing group  48  where internal inclined webs  52  and external inclined webs  53  are visible, both of which are attached to guide walls  50  and  51  of mixing elements  48   a  and  48   b.    
     Wall layers appear not only on the guide walls but also on the inner wall of the mixer enclosure. To optimize the layer formation, longitudinal webs are provided which connect the double guide walls on the outside. The longitudinal webs need not be provided in all mixing groups. In the exemplary embodiment of  FIGS. 15 and 17 , the longitudinal webs  54  are attached to the first and second mixing groups  47 ,  48 , but they might as well be attached to the third or to any other mixing group, or alternatively in the same way as in mixing group  48 . 
     The suggested measures resp. features are preferably used jointly, but embodiments where only some of the measures are applied are conceivable too. 
     The flow diagram of the mixing operation is shown in  FIG. 16 . 
     At A, the two components spread on the respective side of transversal guide wall  55 . At B, the portion on the right side moves towards the center and spreads over the entire length of guide walls  50 ,  51  while the portion on the left side divides into two halves and forms the outer two thirds. At C, these three streams are divided transversally. At D, the left half is guided towards the center and spreads over the entire length of the guide walls while the portion on the right side is divided and the halves reach respective sides of the guide walls, whereupon a transversal edge follows again, etc. 
     The following claims are applicable in the simplified case where the transversal edges and guide walls do not comprise any webs as web  152 , which do not change the general mixing principle of the mixing elements. Moreover, the definition of a transversal wall includes a possible duplication of the transversal edge into two parallel transversal walls as this does not change the mixing principle either.

Technology Classification (CPC): 1