Patent Publication Number: US-11020716-B2

Title: Static mixer, method of assembling a static mixer and dispensing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a U.S. National Stage application of International Application No. PCT/EP2016/069187, filed Aug. 11, 2016, which claims priority to European Application No. 15182961.1, filed Aug. 28, 2015, the contents of each of which are hereby incorporated herein by reference. 
     BACKGROUND 
     Field of the Invention 
     The present invention relates to a static mixer for mixing together at least two components comprising: a mixer housing; a mixing element arranged at least partly within the mixer housing; and a mixer inlet section having at least two inlets disposed at an input side and at least two outlets disposed at an output surface. The invention further relates to a dispensing apparatus and to a method of assembling a static mixer. 
     Background of the Invention 
     A wide variety of ways of dispensing two-component masses from cartridges is known in the prior art. The materials to be dispensed are typically a matrix material and a hardener. Two-component materials are typically used as impression materials, e.g. on the formation of dental impressions, as a cement material for prosthetic restorations, as a temporary cement for trial cementing restorations or for cementing temporary crowns. Further applications of two-component materials are in the building industry where they are e.g. used as a replacement for mechanical joints that corrode over time. Adhesive bonding can be used to bond products such as windows and concrete elements. The use of multi-component protective coatings, for example moisture barriers, corrosion protection and anti-slip coatings, is also becoming increasingly common. Examples of flowable materials which can be used are, for example, distributed by the company Coltene using the tradename AFFINIS® or by the company DMG using the tradename PermaCem. 
     The following kinds of two-component materials are used in the building industry:
         epoxy highly filled with fillers, such as carbon black or silica, used e.g. as a filling paste or putty;   silane-modified polyurethane (PU) used e.g. as a sealant;   PU acrylate resin used e.g. as an adhesive for windscreens; and   poly sulfides used e.g. as an oil resistant sealant that is provided between concrete panels at gas or petrol stations.       

     These materials are typically highly viscous and are almost solid and hence require large static mixers, having a diameter typically larger than 10 mm, in order to be discharged from a cartridge and subsequently mixed. 
     SUMMARY 
     Filled cartridges can come in different ratios referred to as 1:1, 2:1, 4:1 and 10:1 etc., the numbers specifying the ratios of the amounts of each of the two materials that are to be dispensed. The reason for these different ratios is to allow a wide variety of different compositions to be mixed and dispensed. For example, some compositions require more hardener, and some require less hardener. Also, some compositions require more mixing. 
     Static mixers, also referred to as mixing tips, are known from the prior art. The static mixers are adapted to mix the compositions as they exit the cartridge. In this respect different length and different diameter mixing tips are provided to ensure a thorough through mixing of the various two-component mixtures. The mixing tips typically have an insert resembling e.g. an open spiral which forces the two-components into contact with one another and exerts forces on them causing them to mix. 
     The individual components of the multi-components to be mixed are frequently fairly expensive so there is a need to reduce the volume of material lost after a mixing process has taken place. This is in particular true for large static mixers, i.e. static mixers typically having diameters larger than 10 mm, that are used e.g. in the building industry. In order to reduce the volume remaining in a static mixer, specific designs have been implemented resulting in a reduced length static mixer. However, the reduction in length has led to very complicated designs of static mixers. Since the static mixers are frequently manufactured in an injection molding process, the production of static mixers has become very demanding in effort and cost, as highly complex molds are necessary. At times the manufacture may be impossible, as the provision of undercuts and recesses in the static mixer means that the previously used molds can no longer be used. 
     For this reason it is an object of the present invention to provide a static mixer in which the volume of the multi-component material left after use of the static mixer is reduced in comparison to the prior art. It is a further object of the invention to provide a static mixer in which the flow of multi-components through the static mixer is improved. It is yet a further object of the invention to provide a static mixer in which the through mixing of the multi-components is improved. 
     This object is satisfied by a static mixer having the features discussed herein. 
     In particular, such a static mixer is suitable for mixing together at least two components and comprises: a mixer housing; a mixing element arranged at least partly within the mixer housing; and a mixer inlet section having at least two inlets provided at an input side and at least two outlets provided at an output surface; wherein the at least two outlets are in fluid communication with the at least two inlets; and wherein the mixer housing, the mixing element and the mixer inlet section are formed as separate elements. The static mixer is characterized in that the mixing element comprises a plug element and the mixer inlet section comprises a counter plug element engaging the plug element. The static mixer is further characterized in that the mixing element and the mixer inlet section are plugged together in a rotationally fixed manner by a plugged connection. 
     Providing a three part static mixer enables the use of molds for injection molded processes to produce the static mixer. This leads to a reduction in the cost of manufacture and to reproducible production results. 
     Moreover, the handling and assembly of the static mixer is improved as the three parts can simply be plugged together after their respective production. 
     Furthermore, as the mixer inlet section and the mixing element are plugged together in a rotationally fixed manner, the mixing process is improved. This is because the orientation of the two parts relative to one another is improved, so that the components to be mixed are guided and fed into the mixing element such that the components arrive at the correct inlets of the mixing element improving the mixing result and more importantly also allowing a reduction in length of the static mixer. A reduction in length of the static mixer leads to a reduction in any residual volume that is left in the static mixer after its use. 
     In this connection it must be noted that the plug element and the counter plug element can be a plug and socket type connection. In one design the socket can be disposed at the mixing element, in a different design the socket can be provided at the mixer inlet section. The corresponding plug is then disposed at the other element. 
     Having regard to medium to high mixing ratios of 2:1, 4:1 or 10:1 etc, the flow of the low volume component can be controlled by maintaining a diameter of the flow path to the mixing element comparatively small and to introduce this component directly into the optimal spot of the mixing geometry and to thereby permit the other component to enter the mixing geometry at the position ideal for it and to thereby prevent undue forerunning of either of the components. 
     Similar guide mechanisms can also be employed for low to medium mixing ratios of 1:1 to 2:1 mixers using a static mixer in accordance with the invention, making the concept universally applicable to static mixers. 
     By providing a plug element and a counter plug element to connect the mixer inlet section and the mixing element, a distance between the mixing element and the mixer inlet section can be reduced. A reduction in the distance between the mixing element and the mixer inlet section leads to a reduction in the residual volume of components left behind in the static mixer. 
     In this connection it should be noted that the feature according to which the mixing element is at least partly provided within the housing means that at least mixer elements of the mixing element are arranged within the mixer housing and that, for example, components of the plug element may project out of the mixer housing in order to cooperate with the mixer inlet section. In this regard at least 70%, preferably 80 to 95% of the mixing element are typically arranged within the mixer housing. 
     Preferably the mixing element and the mixer inlet section are held together in an axial direction by the plugged connection that is formed by the plug element and the counter plug element and/or by at least one element of the mixer inlet section cooperating with at least one element of the mixer housing. 
     Forming the plugged connection between the mixer inlet section and the mixing element ensures that these components can remain connected outside of the housing. Alternatively or additionally forming the plugged connection between the housing and the mixer inlet section ensures that the three parts can be connected to one another in a preferably secure manner, such that any pressure arising within the static mixer does not result in the static mixer coming apart. 
     Advantageously the plugged connection, preferably between the plug element and the counter plug element, comprises a clamping connection and/or a frictional connection, such as at least one nose frictionally engages one of the mixer inlet section and the mixing element, and/or a latching connection of the plug element and the counter plug element. Such connections can easily be produced in a cost effective manner. 
     It is preferred if the mixing element and the mixer inlet section are aligned in a fixed predefined rotational angular relationship by the plug element and the counter plug element. 
     In this connection a predefined rotational angular relationship means that when the mixing element and the mixer inlet section are plugged together by the plugged connection that the outlets of the mixer inlet section are aligned relative to the mixing element. 
     Utilizing the plug and counter plug element to achieve the fixed predefined rotational angular relationship means that the two components mixing element and mixer inlet section can be tailored to one another to permit the desired flow of components from he mixer inlet section into the mixing element. 
     Optionally the plug element and the counter plug element comprise coding means or element, in particular a thickened end or a bulge cooperating with a corresponding recess or groove, allowing the mixing element and the mixer inlet section to be plugged together only in the predefined rotational angular relationship. 
     The provision of coding element advantageously permits the correct placement of the plug element relative to the counter plug element to ensure, on the one hand, the predefined rotational angular relationship, and, on the other hand, the correct alignment of the two components relative to one another. 
     In this connection it should be noted that the thickened end or bulge can be provided on either of the plug element and the counter plug element and that the corresponding recess or groove is then respectively provided on the other one of the plug element and the counter plug element. 
     The plug element preferably comprises a wall section provided at an input end of the mixing element and the counter plug element comprises a groove provided on the output surface. Providing the plug element at the mixing element and the corresponding socket at the mixer inlet section makes these parts particularly simple to manufacture. 
     In this connection it should be noted that the coding element can be provided at the wall section, so that the wall section advantageously carries out an alignment and coding function. 
     In a preferred design the wall section is arranged between the at least two outlets so as to separate the components leaving the at least two outlets before entering inlets of the mixing element. Providing the wall section such that the components are separate from one another before entering inlets of the mixing element ensures the optimum mixing results and hence permits a reduction in the length of the mixing element. 
     Preferably the wall section has a straight planar shape, and/or comprises a thickened end, and/or has at least partially a U-shaped cross section, and/or has at least partially a T-shaped cross section. 
     Such shapes have been found to be beneficial to ensure the connection between the mixing element and the mixer inlet section in a rotationally fixed manner and indeed even in a coded manner, so that the components can only be plugged together in one orientation. 
     Providing a wall section having a U-shaped cross-section, for example, enables the provision of a groove within the wall section of the plug element. This groove can then act as an extension of the flow path from the inlet of the mixer inlet section to the mixing element. 
     Advantageously the at least two inlets have respective inlet openings and the at least two outlets have outlet openings, with the outlet openings being formed in the output surface of the mixing inlet, wherein a surface area of at least one of the inlet openings is smaller than a surface area of the corresponding outlet opening. 
     Providing at least one outlet opening that is larger in area than an inlet opening means that one can manipulate the flow of at least one component in the direction towards the mixing element in a desired way. 
     It is preferred if the output surface of the mixer inlet section has an at least substantially slanted contour at an outlet side of the mixer inlet section with respect to a longitudinal axis of the static mixer, with the outlet side being disposed remote from the inlet side, with the at least substantially slanted contour of the output surface preferably being adapted to a shape of an inlet surface of the mixer housing. 
     Forming the output surface of the mixer inlet section in a convex manner and correspondingly adapting the inlet surface of the mixer housing means that a flow path extending through the mixer inlet section can be extended from the outlet of the mixer inlet section to the inlets of the mixing element in a desired way through cooperation with the housing. This means that there is no region between the outlets of the mixer inlet section and the inlets into the mixing element in which the flow path of the components experiences an unwanted deflection at the mixer housing. This leads to improved mixing results. 
     In this connection it must be noted that the slanted contour means that the correspondingly convexly shaped surface can be formed as part conical or cone shaped, part truncated cone like, as part chamfered surfaces or as part pyramid like surfaces etc. The specific shape chosen is ideally selected to ensure the optimum flow path to the inlets of the mixing element. 
     In this connection it should also be noted that the at least substantially convexly shaped surface, respectively the at least substantially slanted contour, refers to the general shape of that part of the surface of the mixer inlet section that is adjacent to the mixer housing and in which no openings, such as the outlet openings or the counter plug element are provided. 
     Preferably the static mixer has a longitudinal axis and at least two flow paths extend between the at least two inlet and outlet openings, wherein each inlet and outlet opening has a geometric center, with the geometric center of at least one, preferably of each, of the at least two outlet openings being spaced less far apart from the longitudinal axis than the geometric center of at least one, preferably of each, of the at least two inlet openings. 
     Guiding the flow paths of components to be mixed towards the longitudinal axis through the mixer inlet section means that the components can enter the mixing element at the optimum spot. 
     Advantageously, in a region of the at least two outlets, the at least two flow paths are configured to cooperate with the mixer housing, preferably with an inlet surface of the mixer housing, to provide a component flow guide region at inlets of the mixing element, wherein the at least two outlets of the mixer inlet section are preferably arranged to at least partly overlap with inlets of the mixing element, in particular with the inlets of the mixing element being formed by the mixing element and/or by spaces formed between the mixing element and an internal wall of the mixer housing. 
     Such a design leads to an improved flow path between the mixer inlet section and the mixing element in which the flow path of the components experiences less unwanted deflections at the mixer housing leading to improved mixing results. 
     It is preferred if at least one region of at least one of the at least two outlets adjacent to the corresponding outlet opening is configured such that its cross-section perpendicular to the respective one of the at least two flow paths is enlarged in comparison to the corresponding inlet, in particular such that the flow path extending between the inlet opening and the outlet opening is directed and enlarged in a direction towards at least one inlet of the mixer element. 
     Enlarging a volume of the outlet in the region of the outlet opening means that a flow path towards the inlets of the mixing element can be tailored to direct the components towards the mixing element. 
     Advantageously the mixing element comprises a plurality of mixer elements arranged one after another for a repeated separation and re-combination of streams of the components to be mixed. 
     It is preferred if at least one recess is provided at an outlet side of the mixer inlet section, wherein one of the at least two outlets opens into a base of the at least one recess. Such a recess advantageously forms a collecting region for a component to be directed into the inlets of the mixing element. 
     Advantageously a cross-sectional area of the at least one recess is preferably larger than the cross-sectional area of the one of the at least two outlets. Such a recess provides a comparatively large volume collecting region for guiding the component towards the inlets of the mixing element. 
     The depth of the recess in the axial direction can preferably amount to at least a third, in particular to at least half of the diameter of the outlet, alternatively the depth of the recess in the axial direction is preferably equal to or larger than the diameter of the outlet. Such a recess also provides a comparatively large volume collecting region for guiding the component towards the inlets of the mixing element. 
     Preferably the at least one recess has a cross-sectional shape that deviates from a circle. Advantageously such that the at least one recess has an elongate shape that is in particular extended towards the longitudinal axis. Thereby an as large as possible free space is generated in the mixer inlet section for the collection region. In this connection it should be noted that a recess can be disposed within each outlet, to provide an as large as possible free space for the collection region provided for each outlet. 
     In some designs it can be advantageous if the at least one recess is connected to the other one of the at least two outlets and/or to a further recess in a direction transverse to the longitudinal axis. Thereby at least one maximum volume collecting region can be generated in the mixer inlet section. 
     In this connection it should be noted that once the plug element engages the counter plug element the two outlets are separated, so that a maximum volume collecting region can be generated in the mixer inlet section for each outlet and hence for each flow path. 
     For an as good as possible mixing result the mixing element can comprise mixer elements for separating the material to be mixed into a plurality of streams, as well as means for the layered merging of the same, including a transverse edge and guide walls that extend at an angle to said transverse edge, as well as guide elements arranged at an angle to the longitudinal axis and provided with openings, wherein said mixing element comprises a transverse edge and a following transverse guide wall and at least two guide walls ending in 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 transverse edge and at least two openings on the other side of said transverse edge. 
     Alternatively the mixing element can comprise mixer elements for separating the material to be mixed into a plurality of streams, as well as a structure or means for the layered merging of the same, including separating edges and a transverse edge that extends at an angle to said separating edges, as well as deflecting elements arranged at an angle to the longitudinal axis and provided with openings, wherein said mixing element comprises at least two separating edges with following guide walls with lateral end sections and with at least one bottom section disposed between said guide walls, and a transverse edge arranged at one end of a transverse guide wall, thereby defining at least one opening on one side of the transverse edge and at least two openings on the other side of the transverse edge. 
     In a further aspect the present invention relates to a dispensing apparatus comprising a multi-component cartridge and a static mixer as described in the foregoing that is connected to the multi-component cartridge, with the multi-component cartridge preferably being filled with respective components. 
     Preferably the mixer elements of the mixing element are held together by struts, with the struts also acting as further guide and deflecting walls. 
     Such designs of mixing elements have been found particularly advantageous to improve the mixing results and at the same time to achieve the desired reduction in length of the static mixer. 
     In a further aspect the present invention relates to a method of assembling a static mixer, comprising a mixer housing, a mixing element and a mixer inlet section that are formed as separate elements, the method comprising the steps of:
         engaging a plug element of the mixing element and a counter plug element of the mixer inlet section;   guiding the engaging mixing element and mixer inlet section into the mixer housing to arrange at least a part of the mixing element within the mixer housing; wherein the mixing element and the mixer inlet section are plugged together in a rotationally fixed manner by a plugged connection.       

     Advantageously the static mixer used in such a method can be further developed in accordance with the static mixer described herein. 
     In a further aspect the present invention relates to a use of a static mixer of the kind described herein or of a dispensing apparatus of the kind described herein in order to dispense components from a multi-component cartridge via the static mixer. 
     In a further aspect the present invention relates to a mixer inlet section. The mixer inlet section comprises a counter plug element of the kind described herein. 
     In a further aspect the present invention relates to a mold for the mixer inlet section. The mold is then adapted such that it provides recesses and undercuts matching the negative shape of the mixer inlet section in a similar manner as the static mixer described in the foregoing. 
     In a further aspect the present invention relates to a mixing element. The mixing element comprises a plug element of the kind described herein. 
     In a further aspect the present invention relates to a mold for the mixing element. The mold is then adapted such that it provides recesses and undercuts matching the negative shape of the mixing element in a similar manner as the static mixer described in the foregoing. 
     Likewise, the method in accordance with the invention can be adapted in a similar manner as the static mixer and/or the dispensing apparatus described in the foregoing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail hereinafter with reference to the drawings. 
         FIGS. 1A and 1B  are a first type of static mixer in a first type of mixer housing; 
         FIGS. 2A to 2E  are a first type of mixer inlet section; 
         FIGS. 3A to 3C  are a first type of mixing element; 
         FIGS. 4A and 4B  are perspective part views of the first type of static mixer; 
         FIGS. 5A and 5B  a second type of static mixer in a second type of mixer housing; 
         FIGS. 6A to 6E  are a second type of mixer inlet section; 
         FIGS. 7A to 7C  a second type of mixing element; 
         FIGS. 8A and 8B  are perspective part views of the second type of static mixer; 
         FIG. 9  is a dispensing apparatus; and 
         FIG. 10  is sectional views of molding devices. 
     
    
    
     DETAILED DESCRIPTION 
     In the following the same reference numerals will be used for parts having the same or equivalent function. Any statements made having regard to the direction of a component are made relative to the position shown in the drawing and can naturally vary in the actual position of application. 
       FIG. 1A  shows a side view of a first type of static mixer  10  having a first type of mixer housing  12 . The mixing element  16  (see  FIG. 1A ) and part of the mixer inlet section  14  (see  FIG. 1B ) are arranged within the mixer housing  12 . One inlet  18   a  into the mixer inlet section  14  can be seen, as can alignment means or device  20   a ,  20   b  by which the mixer inlet section  14  is aligned relative to a cartridge  100  (see  FIG. 9 ). 
       FIG. 1B  shows a section through the static mixer  10  of  FIG. 1A  when the static mixer  10  is rotated by 90° about the longitudinal axis A. Both of the inlets  18   a ,  18   b  into the mixer inlet section  14  can be seen in this position. Furthermore, the mixing element  16  is arranged within the mixer housing  12 . 
       FIGS. 2A-2E  show various views of the mixer inlet section  14  of  FIGS. 1A and 1B .  FIG. 2A  shows a top view of the mixer inlet section  14 . The mixer inlet section  14  has a generally circular shape in the top view. The mixer inlet section  14  has two outlets  22   a ,  22   b  each having an outlet opening  24   a ,  24   b . A counter plug element  26  is arranged between the outlets  22   a ,  22   b . In the present example the counter plug element  26  is configured as a socket. 
     The counter plug element of  FIG. 2A  is formed by a first groove  26   a  and a second groove  26   b  extending transverse thereto. Noses  28  are disposed within the first and second grooves  26   a ,  26   b . The noses  28  are adapted to cooperate with a plug element  30  (see  FIGS. 3A to 3C ) such that they frictionally engage the plug element  30  to fix the plug element  30  relative to the counter plug element  26 . 
     The counter plug element  26  is configured such that the plug element  30  can only be inserted in one direction into the mixer inlet section  14 . Thereby the shape of the counter plug element  26  acts as coding element for the insertion of the generally T-shaped end of the plug element  30 . 
     The outlet openings  24   a ,  24   b  are respectively formed in an output surface  32  of the mixer inlet section  14 . Adjacent to the outlet opening  24   b  a recess  34  is formed within the outlet  22   b . The recess  34  expands a volume of the outlet  22   b  relative to the inlet  18   b.    
     The recess  34  has an elongate shape and thereby enlarges and directs a flow path of a component  102   b  (see  FIG. 10 ), flowing from the inlet  18   b  to the outlet  22   b . The recess  34  thereby acts as a guide reservoir for the component  102   b  that flows into the mixing element  16 . 
     The guide reservoir enables the component  102   b  to be directed into inlets  36  (see  FIGS. 3A to 3C ) of the mixing element  16 , so that an ideal point of entry for the component  102   b  into the inlets  36  can be selected. 
     In order to improve the introduction of the components  102   a ,  102   b  into the mixing element  16 , the outlets  22   a ,  22   b  of the mixer inlet section  14  are spaced less far apart than the corresponding inlets  18   a ,  18   b.    
     The outlet opening  24   a  is approximately a tenth of the size of the outlet opening  24   b . This is because the mixer inlet section  14  is used for multi-components having a medium to high mixing ratio such as 4:1 and 10:1, this means that one of the components is introduced into the mixing element at a ratio of 4:1 or 10:1 with respect to the other component. 
       FIG. 2B  shows a bottom view of the mixer inlet section  14 . The inlets  18   a ,  18   b  have a substantially circular shaped inlet opening  38   a ,  38   b . The shape of the inlet opening is selected so that the inlets  18   a ,  18   b  can be connected to outlets of a cartridge  100  (see  FIG. 10 ). 
     The inlets  18   a ,  18   b  are in fluid communication with the respective outlets  22   a ,  22   b , so as to guide components from the cartridge  100  to the mixing element  16 . 
     The alignment devices  20   a ,  20   b  are used in order to align the mixer inlet section  14  with the cartridge  100 . In order to connect the mixer inlet section  14  of the static mixer  10  to the cartridge  100  in a coded and aligned manner the alignment devices  20   a ,  20   b  have a different size so that these can only be positioned in one way. Moreover, the alignment devices  20   a ,  20   b  have a generally T-shaped cross-section for this purpose. An attachment means or device (not shown) such as a retainer nut can additionally be used to, at least intermittently fixedly, connect the static mixer  10  to the cartridge  100 . 
     Having regard to the high ratio mixer inlet section, the inlets  18   a ,  18   b  are also of different size so that these can only be placed on to the cartridge  100  in one way and thereby also act as a coded alignment devices. 
       FIG. 2C  shows a side view of the mixer inlet section  14  of  FIG. 2A . The outlets  22   a ,  22   b  of the mixer inlet section  14  are connected to one another via a volume forming at least a part of the counter plug element  26 . Once the plug element  30  cooperates with the counter plug element  26 , the outlets  22   a ,  22   b  are separated from one another by the plug element  30  (see  FIGS. 4A and 4B ). 
     Moreover, one can see a side view of the generally T-shaped alignment devices  20   a ,  20   b  in  FIG. 2C . 
     The mixer inlet section  14  has a projection  40  arranged adjacent to the output surface  32 . This projection is adapted to cooperate with a groove  42  (see  FIG. 1B ) arranged in the mixer housing  12  in order to latch the mixer housing  12  to the mixer inlet section  14 . 
       FIG. 2D  shows a section through the mixer inlet section  14  along the sectional line B-B of  FIG. 2C . The outlet  22   b  is arranged such that at least a part of the outlet opening  24   b  is arranged around the longitudinal axis A of the static mixer. Thereby the component is guided from the inlet  18   b  to the mixing element  16 . 
     One can see how the flow path  44   b  between the inlet  18   b  and the outlet  22   b  is directed towards the longitudinal axis A. Through the provision of the recess  34 , the diameter of the flow path  44   b  (the same is true in analogy for the flow path  44   a ) experiences no constrictions in the region of the outlet  22   b . This is because a distance between the mixer housing  12  and the recess  34  is selected such that the diameter of the flow path  44   b  is kept at least substantially equal throughout the mixer inlet section  14  and up to the mixing element  16 . For this reason the flow of the component  102   b  experiences significantly less flow resistance on its passage through the mixer inlet section  14  up to the mixing element  16  on being discharged from the cartridge  100  in comparison to prior art static mixers (not shown). Likewise the flow path  44   a  between the inlet  18   a  and the outlet  18   b  is shifted towards the longitudinal axis A. 
       FIG. 2E  shows an enlarged view of the generally T-shaped counter plug element  26 . The outlets  22   a  and  22   b  are connected to one another via the counter plug element  26 . The connection is closed once the plug element  30  is inserted into the counter plug element  26  (see  FIG. 4 ). Furthermore, four noses  28  are visible in the region of the first groove  26   a . The four noses  28  are configured to engage the corresponding plug element  30 . 
       FIGS. 3A to 3C  show various views of a first type of mixing element  16 . The mixing element  16  comprises mixer elements  46  for separating the material to be mixed into a plurality of streams, as well as layered merging of the same. The layered merging is accomplished by a structure that comprises transverse edges  48  and guide walls  50  that extend at an angle to the transverse edges  48 , as well as guide elements  52  arranged at an angle to the longitudinal axis A and including openings. 
     The individual mixer elements  46  are connected to one another by struts  54 , with the struts  54  also acting as further guide and deflecting walls. The number of mixer elements  46  and the corresponding length of the struts  54  is selected in dependence on the kind of material that is to be dispensed with a certain static mixer  10 . For some applications five mixer elements  46  may be sufficient whereas for others ten or more mixer elements  46  may need to be connected to one another by struts  54 . 
       FIG. 3A  shows a side view onto the mixing element  16 . At the right hand side of the mixing element  16 , there is a plug element  30 . This is composed of a wall section  56 . Some of the wall section  56  has a U-shaped cross-section that leads into a T-shaped cross-section. A groove  58  is formed in the wall section  56  that extends from the T-shaped cross-section through the U-shaped cross-section and towards an inlet  36  of the mixing element  16 . 
       FIG. 3B  indicates how this groove extends from a surface  60  of the plug element  30  towards the inlet  36  of the mixing element  16 . The groove thereby extends the flow path  44   a  from the mixer inlet section  14  into the mixing element  16  (see also  FIG. 4  in this regard). 
       FIG. 3C  like  FIG. 3B  shows how the T-shaped wall section  56  is formed by a first wall  62  and a second wall  64  extending transverse thereto. The groove  58  is formed extending from the surface  60  within the second wall  64  towards the inlet  36  of the mixing element  16 . 
       FIGS. 4A and 4B  show perspective part views of the first type of static mixer  10 . In particular one can see how the flow path  44   a  extends from the inlet  18   a  of the mixer inlet section  14  via the outlet  22   a  and the groove  58  towards one of the inlets  36  of the mixing element  16 . 
     Likewise the flow path  44   b  extends from the inlet  18   b  via the outlet  22   b  of the mixer inlet section towards inlets  36  of the mixing element  16 . The flow path  44   a  is smaller in diameter than the flow path  44   b , as the mixer inlet section  14  and the mixing element  16  currently employed are used for high mixing ratios of e.g. 4:1 and 10:1. 
     Moreover, the section shown in  FIG. 4A  indicates how the flow path  44   b  is enlarged in the region of the outlet  22   b  in comparison to the inlet  18   b . This enlargement of the flow path  44   b  is further highlighted in  FIG. 4B  where one can see how the flow path  44   b  extends around the second wall  64  up to the first wall  62  of the wall section  56  of the mixing element  16 . The flow path  44   b  is extended such that it comes into contact with substantially the whole width of the mixing element  16  in the region of the inlets  36  where it extends around the second wall  64 . The region of the outlet  22   b  is arranged such that the component  102   b  flowing through the flow path  44   b  arrives in a directed manner at the inlet  36  of the mixing element  16 . 
     Both  FIGS. 4A and 4B  show that the flow paths  44   a ,  44   b  are shifted with respect to the longitudinal axis A from the inlets  18   a ,  18   b  towards the longitudinal axis A in the regions of the outlets  22   a ,  22   b . Thereby the components  102   a ,  102   b  flow into the mixing element  16  in a more directed manner and can be introduced into the mixing element  16  in an optimum way, so that a mixing result is improved. This also leads to a reduction in the length of the mixing element  16  and hence to a reduction in the residual volume remaining in the static mixer  10 . 
     Moreover, the shift of the flow paths  44   a ,  44   b  takes place within the mixer inlet section  14 , so that a spacing between the mixer inlet section  14  and the mixing element  16  can be reduced leading to a further reduction in the residual volume remaining in the static mixer  10 . This is advantageously achieved in a mixer inlet section  14  having the same height as prior art mixer inlet sections (not shown). 
       FIGS. 5A and 5B  show a second type of static mixer  10  in a second type of mixer housing  12 . The mixer is typically used for low ratio mixing of components such as 1:1 or 2:1. 
       FIGS. 6A to 6E  show a second type of mixer inlet section  14  designed for 1:1 and 2:1 mixing ratios.  FIG. 6A  shows a bottom view of the mixer inlet section  14  in which the inlets  18   a ,  18   b  and the corresponding inlet openings  38   a ,  38   b  are of equal size. 
       FIG. 6B  shows a top view of the mixer inlet section  14  in which the outlets  22   a ,  22   b  and the corresponding outlet openings  24   a ,  24   b  are of equal size. A counter plug element  26  having only a first groove  26   a  extends between the outlets  22   a ,  22   b . A recess  66  is arranged at an end of the first groove  26   a . This recess  66  is adapted to cooperate with a bulge  68  (see  FIG. 7 ) configured at the plug element  30  of the mixing element  16 . 
     As the outlets  22   a ,  22   b  have the same size, the side view of  FIG. 6C  appears to have a continuous outlet opening  24   a ,  24   b . As can be seen from  FIG. 6D  this is because the mixer inlet section  14  has a free space extending into the recess  34  and adjacent to the first groove  26   a  into which free space the plug element  30  of the mixing element  16  is inserted to separate the outlets  22   a ,  22   b  from one another so that a mixing of components only takes place once the components enter the mixer elements  46  of the mixing elements  16 . 
     Like with the outlet  22   b  of  FIGS. 2A to 2E , both of the outlets  22   a ,  22   b  have a recess  34  adjacent to the output surface  32 . This recess  34  expands a volume of the respective outlet  22   a ,  22   b  in an elongate way to form a component flow guide region adjacent to the output surface  32 . The component flow guide region acts as a region in which the components  102   a ,  102   b  can flow into the inlets  36  of the mixing element  16  in a directed manner. In order to complement the directed flow of the components a shape of an inlet surface of the mixer housing  12  is adapted to the shape of the output surface  32  of the mixer inlet section  14 . In the present example the output surface  32  has a part spherical shape. 
     As can be seen in the section of  FIG. 6D , the inlets  18   a ,  18   b  start merging into the outlets  22   a ,  22   b  at approximately a third of the length between the inlet openings  38   a ,  38   b  and a top most part of the outlet openings  24   a ,  24   b . The outlets start at approximately two third of a length between the inlet openings  38   a ,  38   b  and a top most part of the outlet openings  24   a ,  24   b . The same is true for the example shown in  FIG. 2A to 2E . 
       FIG. 6E  shows an enlarged view of the region of the first groove  26   a . A nose  28  is visible within the recess  66 . This, like the other noses  28  configured in the first groove  26   a , is designed to frictionally engage the wall section  56  of the plug element  30  when the plug element  30  cooperates with the counter plug element  26 . 
       FIGS. 7A to 7C  show perspective views of a second type of mixing element  16 . The mixer elements  46  of the mixing element  14  are configured like the embodiment shown in  FIGS. 3A to 3C . The difference is to be seen in the wall section  56  of the plug element  30 . 
     The wall section  56  shown in the side view of  FIG. 7A  has a generally planar shape with a bulge  68  configured at an end thereof. The bulge  68  is configured so that it extends substantially in parallel with the longitudinal axis A. 
       FIG. 7B  shows a further side view when the mixing element  14  is rotated by 90° about the longitudinal axis A. One can see how the wall section  56  has a thinner diameter in comparison to the bulge  68 . 
       FIG. 7C  shows a further rotation of the mixing element  14  by 90° about the longitudinal axis A. Now the bulge  68  is positioned at the top of the wall section  56  of the plug element  30 . The bulge  68  is a coded alignment element, so that the plug element  30  can only be plugged into the counter plug element  26  of the mixer inlet section  14  of  FIG. 6A to 6E  in one way. 
       FIGS. 8A and 8B  show perspective part views of the second type of static mixer  10 . Both flow paths  44   a ,  44   b  are directed from the inlets of the mixer inlet section  14  to the inlets  36  of the mixing element  16 . Thereby a geometric center of the outlet openings  24   a ,  24   b  is spaced less far from the longitudinal axis A than a geometric center of the inlet openings  38   a ,  38   b  to direct the flow path  44   a ,  44   b  of the components  102   a ,  102   b  towards the inlets  38 . 
       FIG. 9  shows a dispensing apparatus  98  comprising a multi-component cartridge  100  and a static mixer  10 . The multi-component cartridge  100  is filled with respective components  102   a ,  102   b . The components  102   a ,  102   b  can be discharged from the cartridge  100  by a plunger (not shown) into the inlets  18   a ,  18   b  of the mixer inlet section  14  of the static mixer  10 . The static mixer  10  is connected to the cartridge  100 , on the one hand, by the alignment elements  20   a ,  20   b  for a coded alignment between the static mixer  10  and the cartridge  100 . On the other hand, the static mixer  10  is connected to the cartridge  100  by a retainer nut (not shown). The retainer nut is adapted to cooperate with the cartridge  100  and engages the mixer housing  12  of the static mixer  10  in order to fix the static mixer  10  to the cartridge  100 . 
       FIG. 10  shows a schematic sectional view of a molding device Ma for a mixing element  16  as described herein, and a sectional view of a molding device Mb for a mixer inlet section  14  as described herein. The molding devices have respective inputs for the components to be injected (not shown) and for any required vacuum apparatus (also not shown). In order to mold the specific components, inserts specific for any shapes of the components are also introduced into the molding devices Ma, Mb. 
     Using the molding devices Ma, Mb mixer inlet sections  14  and mixing elements  16  as described herein can be produced.