Patent Publication Number: US-9415361-B2

Title: Mixer for multi-component pastes, kit, and method of mixing paste components

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application is a divisional of U.S. application Ser. No. 11/575,763, filed Mar. 11, 2008, now allowed, which is a national stage filing under 35 U.S.C. 371 of PCT/EP2005/010156, filed Sep. 21, 2005, which claims priority to European Patent Application No. 04022595.5, filed Sep. 22, 2004, abandoned, the disclosures of which are incorporated by reference in their entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a mixer for multi-component pastes, a kit comprising at least one mixer, and a method of mixing paste components. 
     BACKGROUND OF THE INVENTION 
     Pasty multi-component masses, such as dental impression masses, are prepared by mixing devices in which the individual components of the mass are simultaneously supplied from separate cartridge cylinders to a mixer which dispenses the mixed paste from a front end. The mixer may be a static mixer or a dynamic mixer (having a rotary mixer element). The paste exiting from the front end of the mixer may be supplied directly onto an impression spoon or tray. 
     Examples of dynamic mixers are found in, e.g., WO 00/21652, EP-A-1 149 627, U.S. Pat. No. 5,249,862 or DE-U-297 05 741. These known dynamic mixers have as their rear end (inlet side) a central hexagonal opening for coupling to a drive shaft for rotating the inner body of the mixer, and further two additional inlet connectors for feeding the components which are to be mixed. 
     Depending on the viscosity and mixing ratio, the fact that the pressure builds up differently in the individual cartridge cylinders at the start of the device may cause the components to reach the mixer at different times. In such a case, the initial volume of paste exiting from the mixer has a mixing ratio which differs from a desired value and may therefore cure less perfectly or more slowly, or have other undesired properties. 
     U.S. Pat. No. 6,244,740 suggests a mixer for producing multi-component pastes. This dynamic mixer contains a deviating channel provided between the inlet opening for the component of the larger volume proportion and the mixing chamber, in order to delay the feed of this component with respect to the other component. Typically, the flow of the base paste is thus delayed compared to the flow of the catalyst. 
     US-A-2004/085854 describes a dynamic mixer having a delay chamber provided between the inlet opening for the component of the larger volume proportion and the mixing chamber, in order to delay the feed of this component with respect to the other component. The delay chamber has, inter alia, a boundary wall located in the flow direction of a paste component, on which the paste component backs up. The delay chamber also has at least one opening, which opens into the mixing chamber and which is arranged to be set back with respect to the boundary wall. The term set back in the sense of this invention is to be understood to mean an arrangement in which the opening does not adjoin the boundary wall directly but is arranged offset from the latter (see paragraphs [0040] and [0041]). The component flows into the mixing chamber only after the delay chamber is filled. 
     Mixers having channels of different lengths between the inlet openings of the mixer and the mixing chamber are described, e.g., in DE-U-203 02 987, U.S. Pat. No. 6,523,992, and US-A-2003/123323. 
     Further improvements in the mixing and dispensation of a mixed paste having a desired ratio of first and second components would be desirable. 
     SUMMARY OF THE INVENTION 
     In general, the present invention provides a mixer for producing a paste by mixing components. The mixer comprises a housing having a longitudinal axis, a rear end, and a front end provided with a discharge opening, and a mixing chamber formed in said housing and having an entry side facing the rear end of said housing, wherein the initial content of the mixing chamber is diverted from the discharge opening, and the subsequent content of the mixing chamber is extrudable from the discharge opening. The initial content is preferably permanently diverted. 
     Preferably, the mixer comprises a reservoir for permanently storing the initial content of the mixing chamber. More preferably, the mixer is configured such that when the initial content of the mixing chamber fills the reservoir, the subsequent content of the mixing chamber is extrudable through the discharge opening. Preferably, the reservoir preferably permanently stores the initial content of the mixing chamber. 
     Preferably, a mixing element is provided in said mixing chamber. Alternatively, the mixing chamber comprises projections extending from the wall of the housing. 
     The reservoir of the mixer according to the present invention is arranged such that it stores the initial content of the mixing chamber. The initial content of the mixing chamber is the first amount of material entering the mixing chamber from the dispensing cartridge, for example a base paste and/or a catalyst. In storing the initial material entering the mixing chamber, it is avoided that a mixture has an undesirable mixing ratio, i.e. contains too much of one of the components to be mixed. If the initial amount entering the mixer is stored in said reservoir, it substantially does not contaminate the mixing chamber. The mixing only starts after the reservoir is filled. At that point, all components to be mixed have entered the mixer so that the preparation of a desirable, balanced mixture is guaranteed. 
     Alternatively, the initial content of the mixing chamber is the initial amount of mixture being prepared in the mixing chamber. If the components to be mixed initially enter the mixing chamber at an undesired ratio, the initial mixture would not comprise the desirable mixing ratio. Thus, the initial amount of mixture is stored in the reservoir and is not dispensed from the mixer. This amount of mixture is discarded with the mixer after use. Hence, the user is prevented from using the first amount of mixture potentially having an undesirable mixing ratio. 
     Thus, in accordance with the present invention, the initial amount of material entering the mixing chamber from the dispensing cartridge or the initial amount of mixture being prepared in the mixing chamber is diverted from the discharge opening. This is in clear contrast to, for example, US 2003/123323, and U.S. Pat. No. 6,244,740 discussed above. According to US 2003/123323, the two ducts being provided upstream of the mixing chamber are formed so that the first duct requires a greater time of entry of the compound into the mixing chamber than the time required for the second component flowing through the second duct. U.S. Pat. No. 6,244,740 describes having a channel upstream of the mixing chamber to delay feed of one component with respect to the other component. 
     Several advantages are related to the present invention. 
     Since the first amount of mixture that is dispensable already comprises the desirable mixing ratio, the characteristics of the mixture should be more reliably present from the start. Furthermore, there is no color change of the impression material during the whole mixing process. Furthermore, it is of no concern whether there is initially more catalyst or more base paste entering the mixing chamber. At present, the foil bag for the dispensing cartridge containing the catalyst is filled up to 105% of the volume required with respect to the total amount of base paste, to reduce the likelihood that an amount of mixture comprises too little catalyst. With the present invention, this additional amount can be reduced or even eliminated. Finally, there is significant lower pressure loss in the mixer since the components do not have to flow through any kind of delay channel prior to entering the mixing chamber. 
     The rear end of the housing of the mixer is formed by a terminating plate, comprising separate inlet pipes adapted for connection with a dispensing cartridge containing the components. Preferably, the reservoir is located downstream of the terminating plate. 
     According to a first aspect of the present invention, the mixer comprises a reservoir which is adapted for filling in the longitudinal direction of the mixer. In other words, the reservoir of this aspect of the present invention is fillable or filled in an axial direction. That is, in the context of the present invention “axial” always refers to the longitudinal axis, and “radial” refers to a direction perpendicular to the longitudinal axis. 
     According to a first embodiment of the first aspect of the present invention, the reservoir is located at the front end of the housing. 
     It is preferred that the housing comprising a tubular element along the longitudinal axis of the mixer, i.e. concentric with the longitudinal axis. The tubular element furthermore projects from the discharge opening inwards into said mixing chamber. With such structure, the tubular element forms at the front end of the housing an annular reservoir between the outer surface of the tubular element and the inner surface of the housing. 
     In order to facilitate the flow of the mixture into the reservoir before it is dispensed from the mixer, and to ensure that the initial mixture is not dispensed but stored in the reservoir, the mixture further preferably comprises a baffle downstream of the front end of the mixing element. That means, the baffle is provided between the mixing element and the dispensing opening, such as the tubular element. According to the first embodiment of the first aspect of the present invention, the baffle comprises a circular plate in a plane transverse to the longitudinal axis of the mixer and at least one connection connecting the baffle plate to the wall of the housing. Preferably, the connection is in the plane of the baffle plate. Preferably, three connections are provided spaced from each other at 120° to connect the baffle plate with the housing. 
     Alternatively, according to another embodiment of the first aspect of the present invention, the baffle comprises a circular plate in a plane transverse to the longitudinal axis of the mixer and at least one connection connecting the plate to the tubular element. For example, the at least one connection is arranged to bridge the gap between the baffle plate and the tubular element, for example perpendicular to the plane of the baffle plate to connect the same to the tubular element. Preferably, the connections form extensions of the tubular element that bridge the gap between the rear end of the tubular element and the baffle plate. The plate preferably comprises a recess for receiving the front end of said mixing element, thus serving as a front end socket for the mixing element. 
     According to a further embodiment of the first aspect, the baffle is connected to the front end of the mixing element or an integral part of the mixing element. In this case, the baffle is for example a circular plate or a cone or a truncated cone being located at the tip of the mixing element. In case of a cone/truncated cone, the cone or truncated cone is connected with its peak to the front end of said mixing element. Thus, the diameter of the cone increases towards the dispensing opening which automatically deflects the flow of the mixture towards the reservoir. 
     In any case, the baffle plate preferably has a surface area that is large enough to prevent the initial mixture from directly reaching the dispensing opening. More preferably, the cross-sectional area corresponds to the cross-sectional area of the tubular element and/or dispensing opening. 
     According to a further alternative embodiment of the first aspect of the present invention, the mixer comprises a baffle located between the mixing element and the front end of the housing, and the baffle comprises a circular plate in a plane transverse to the longitudinal axis of the mixer and at least one connection connecting the plate to the wall of the housing, wherein in this embodiment the baffle further comprises a tubular wall extending from the plate along the longitudinal axis and towards the rear end of said housing. Thus, a cavity is formed on the baffle plate by the tubular wall. This cavity is open towards the mixing element so that it forms the reservoir that receives and stores the initial amount of the mixture. 
     In this embodiment, it is preferred that the housing comprises a first section having a first diameter, and a second section having a second diameter, wherein the second diameter is greater than the first diameter, and the second section is located downstream of the first section. The first and second sections are connected by a flange. The baffle is arranged within the second section of the housing. Furthermore, the tubular wall has preferably the same or a larger diameter as the first section of the housing. This assists in the storing of the initial mixture in the reservoir. After the reservoir is filled, the “overflow” flows around the tubular wall and baffle plate, and reaches the dispensing opening. 
     The mixer of a further embodiment of the first aspect of the present invention comprises a wall opening in the circumferential wall of the housing. This wall opening is located in the front end area of the housing and is also offset from the front end wall of said housing towards the rear end of the housing. In other words, the wall opening is not located at the tip of the mixer but is set back some distance. Furthermore, a deviating channel extends from the wall opening and terminates in a discharge opening such that the discharge opening is offset from said longitudinal axis. In this embodiment, the dispensing opening is not located on the longitudinal axis of the mixer at the mixer tip but eccentrically located at the end of the deviating channel. In this case, since the tip of the mixer is closed, a reservoir is formed at the tip. This reservoir stores the initial mixture until the level of the mixture in the reservoir reaches the wall opening. The material flow is then through the deviating channel to the dispensing opening. 
     A second aspect of the present invention makes use of gravitational force to store material in a reservoir. 
     The basic structure of the mixer according to an embodiment of the second aspect of the present invention is identical to that of the first aspect. However, it further comprises a wall opening in the circumferential wall of the housing, and a closed channel extending from the wall opening to the outside away from the wall of the housing. This closed channel forms a cavity which receives and stores the initial mixture. Preferably, the wall opening is arranged in a front end area of the housing. It is further preferred that the closed channel comprises an axis, wherein the axis of the closed channel is inclined relative to the longitudinal axis of the mixer. In other words, the channel branches off from the mixing chamber. The angle of inclination is preferably such that when the mixer is in use, the closed channel is oriented vertically with its opening at the top so that the initial mixture can easily enter the reservoir simply due to gravitation. 
     According to the third aspect of the present invention, the mixer comprises a reservoir which is adapted for filling along the longitudinal axis of the mixer. In other words, the reservoir of this aspect of the present invention is fillable or filled in an axial direction. This is identical to the first aspect. However, according to the third aspect, the reservoir is located at the rear end of the mixer. 
     A mixer according to an embodiment of the third aspect of the present invention comprises a housing that comprises a main section having a first diameter along its length and a first rear end and a first front end, and a second section having second rear end and a second front end. The diameter of the second section at least at the second rear end is greater than the first diameter. The second rear end of the second section forms the rear end of the housing, the first rear end is inwardly offset along the longitudinal axis from the rear end of the housing, and the second front end of the second section is connected to the main section in a circumferential area being offset from the first rear end towards the first front end of the main section. Preferably, the second section comprises a stepped configuration. Alternatively, the second section comprises the configuration of a truncated cone. 
     It is further preferred in this embodiment that an annular passageway is formed between the first rear end of the main section and the second section, allowing material flow from the second section into the main section. The interior of the main section forms the mixing chamber. 
     In the third aspect of the present invention, a reservoir is formed at the rear end of the mixer. Thus, the reservoir receives and stores the initial amount of the components entering the mixing chamber. Once the reservoir is filled with the initial amount of the components, the flow of the components is directed to the mixing chamber. The annular reservoir formed by the different sections of the housing having different diameters and rear ends being offset from each other in a longitudinal direction is preferably located underneath the inlet pipes of the terminating plate so that the initial component amounts are forced to first fill the reservoir before being mixed with each other. 
     According to a fourth aspect of the present invention, the reservoir is adapted for radial filling, in particular at the rear end of the housing. 
     The mixer of a first embodiment of the fourth aspect of the present invention has a housing that comprises at least one passageway through its circumferential wall. More preferably, the housing comprises a plurality of passageways through its circumferential wall being separated from each other by webs. According to this embodiment, the mixer further comprises at least one wall structure forming a cavity covering the at least one passageway on the outer surface of said housing. Preferably, the wall structure annularly surrounds said housing. 
     According to one alternative embodiment the at least one passageway is arranged in a rear end area of said housing. Alternatively, which is according to a fifth aspect of the present invention, the at least one passageway is arranged in a middle area of said housing between said front end and said rear end. 
     The wall structure preferably comprises a tubular section having a diameter that is greater than the diameter of the housing, and at least one flange section connecting the tubular section to the wall of the housing. 
     According to a further embodiment of the fourth aspect, the housing of the mixer comprises a main section having a first diameter and an area of increasing diameter between the main section and the rear end of the housing. The mixing element comprises a funnel-shaped element which is arranged at the rear end of the mixing element and rearwards of the main housing section. The diameter of the funnel-shaped element decreases from its rearmost end to the other end where it is connected to the shaft of the mixing element. The funnel-shaped element preferably is in the form of a truncated cone. The funnel-shaped element comprises at least one passageway at its frontmost end extending along the longitudinal axis of the mixer. 
     The funnel-shaped element defines an opening at its rearmost end having a diameter such that the components enter the mixer within the opening of the funnel-shaped element. In other words, the diameter is large enough to span the inlet pipes of the terminating plate of the mixer. 
     Preferably, the connection between the funnel-shaped element and the shaft of the mixing element is located rearwards from the rear end of the main section of the housing thus forming a annular cavity between the funnel-shaped element and the area of the housing having an increasing diameter. This annular cavity forms the reservoir receiving and storing the initial amounts of components entering the mixer. 
     In order to compensate for the axial forces acting on the mixing element due to the fact that the material flow of the components is first guided by the funnel-shaped element once the components have entered the mixer, the mixer preferably comprises a bearing-like or socket-like structure for the front end of the mixing element. 
     In order to enhance the radial material flow into the reservoir, the mixing element further comprises at least one paddle for deflecting the (axial) material flow into the reservoir. The at least one paddle is arranged at the mixing element at a longitudinal position corresponding to the longitudinal position of the reservoir, i.e. at the same level. 
     According to first embodiment of the sixth aspect of the invention, the shaft of the mixing element comprises a cavity and at least one passageway connecting the cavity with the mixing chamber. Preferably, the shaft is hollow along a substantial length thereof. Further preferably, the passageway is arranged at a rear end of said mixing element. This ensures that the initial amount of components does not contaminate the mixing chamber but is stored in the hollow shaft of the mixing element. 
     The mixer of a seventh aspect of the present invention comprises at the shaft of the mixing element a rearwardly-directed, L-shaped circumferential flange. The flange is located adjacent to the rear end of the mixing element. Because the L-shaped flange is open towards the rear end, a reservoir is formed. Since this flange is located at the rear end of the shaft, the initial amount of the components are stored in the reservoir and do not substantially contaminate the mixing chamber. Alternatively, the L-shaped flange can be located further downstream to store the initial amount of the mixture. 
     It is preferred in all aspects of the present invention that the mixing element comprises mixing vanes or mixing blades. Furthermore, the mixing element is preferably rotatable about the longitudinal axis of the mixer and comprises a hexagonal opening at its rear end connectable to the drive shaft of a dispensing apparatus. Alternatively, structures extending from a wall could form mixing vanes or blades if desired, or a combination of fixed vanes and moving vanes could be provided. 
     The present invention thus encompasses a mixer in which either a portion of the mixed material can be diverted, or portions of each of the unmixed material can be diverted individually (either to separate reservoirs or to a single reservoir). 
     The present invention also encompasses combinations of the aspects of the present invention. For example, the present invention encompasses the combination of a reservoir at the front end of the housing that is radially filled and a hollow shaft of the mixing element providing an additional reservoir. 
     The present invention also encompasses a kit comprising a dispensing cartridge and at least one mixer according to any of the aspects of the present invention. 
     The present invention also encompasses a kit comprising at least one of a first container and at least one of a second container, said first and second container containing the paste components to be mixed, and at least one mixer according to any of the aspects of the present invention. 
     Furthermore, the present invention also encompasses a method of mixing at least two paste components, said method comprising the steps of: a) discharging said paste components from a dispensing apparatus by using delivery pistons; b) introducing said components into a mixer being connected to said dispensing apparatus, said mixer having a mixing chamber; c) mixing said components; and d) discharging the mixture of said components from said dispensing apparatus; wherein said initial contents of said mixing chamber are stored therein before subsequent contents of said mixing chamber are discharged. 
     The invention will now be described with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal view of a first embodiment of the mixer according to a first aspect of the present invention, having a reservoir at the front end of the mixer; 
         FIG. 2  is a top view of the baffle plate of the mixer of  FIG. 1 ; 
         FIG. 3  is a longitudinal view of a second embodiment of the mixer according to the first aspect of the present invention; 
         FIG. 4  is a longitudinal view of a third embodiment of the mixer according to the first aspect of the present invention; 
         FIG. 5  is a longitudinal view of a fourth embodiment of the mixer according to the first aspect of the present invention; 
         FIG. 6  is a longitudinal view of the fourth embodiment of the mixer shown in  FIG. 5 , without the mixing element; 
         FIG. 7  is a longitudinal view of a fifth embodiment of the mixer according to the first aspect of the present invention; 
         FIG. 8  is a longitudinal view of the fifth embodiment of the mixer shown in  FIG. 7 , without the mixing element; 
         FIG. 9  is a longitudinal view of a sixth embodiment of the mixer according to the first aspect of the present invention; 
         FIG. 10  is a longitudinal view of a seventh embodiment of the mixer according to the first aspect of the present invention; 
         FIG. 11  is a longitudinal view of an embodiment of the mixer according to a second aspect of the present invention, having a reservoir at the front end of the mixer and using gravitational forces; 
         FIG. 12  is a longitudinal view of an embodiment of the mixer according to a third aspect of the present invention, having a reservoir at the rear end of the mixer; 
         FIG. 13  is a longitudinal view of a first embodiment of the mixer according to a fourth aspect of the present invention, having a reservoir at the rear end of the mixer; 
         FIG. 14  is a longitudinal view of the first embodiment of the mixer according to the fourth aspect of the present invention shown in  FIG. 13 , without the mixing element; 
         FIG. 15  shows a cross-sectional view of the reservoir of the mixer of  FIG. 13 ; 
         FIG. 16  is a longitudinal view of a second embodiment of the mixer according to the fourth aspect of the present invention, having a reservoir at the rear end of the mixer; 
         FIG. 17  is a cross-sectional view through the paddles of the mixer of  FIG. 16 ; 
         FIG. 18  is a cross-sectional view through the bearing pin of the mixer of  FIG. 16 ; 
         FIG. 19  is a cross-sectional view through the inlet funnel of the mixer of  FIG. 16 ; 
         FIG. 20  is a longitudinal view of a first embodiment of the mixer according to a fifth aspect of the present invention, having a reservoir at the middle of the mixer; 
         FIG. 21  is a cross-sectional view of the reservoir of the mixer of  FIG. 20 ; 
         FIG. 22  is a longitudinal view of a first embodiment of the mixer according to a sixth aspect of the present invention, having a reservoir within the mandrel of the mixing element of the mixer; 
         FIG. 23  is a longitudinal view of the mixer of  FIG. 22  with the mixing element; 
         FIG. 24  is a cross-sectional view of the mixer of  FIG. 22 ; 
         FIG. 25  is a longitudinal view of a second embodiment of the sixth aspect of the present invention; and 
         FIG. 26  is a longitudinal view of a first embodiment of a seventh aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     The mixer  100  according to a first embodiment of the present aspect of the present invention is shown in  FIG. 1 . It includes a housing  110  which has a mixing chamber  120  which is cylindrical throughout its principal part. The housing  110  has a longitudinal axis, a rear end  111  and a front end  112 . The mixing chamber  120  has an entry side  121  facing said rear end  111  of said housing  110 . At the rear end  111 , the housing  110  is formed by a terminating plate  150  forming the rear wall of the housing  110 . Furthermore, the mixer  100  shown in  FIG. 1  comprises a mixer element  130  supported by the housing  110 , in particular by the terminating plate  150 . A hexagonal opening (not shown in  FIG. 1 ) is provided at the rear end of the mixer element  130  for coupling to a drive shaft (not shown). The mixer element  130  is supported within the housing  110  for rotation about the longitudinal axis of the mixer element  130 . 
     The terminating plate  150  has two rearwardly extending inlet pipes  151 ,  152 , by which the mixer  100  may be coupled to the front end of a cartridge placed in a dispensing apparatus (not shown). In the embodiment illustrated, the mixer  100  is assumed to be adapted for producing a dental impression mass which is mixed, for example, from a pasty base substance and a catalyst substance at a specific ratio. To this end, the inlet pipe  151  and the inlet pipe  152  for the base substance and for the catalyst, respectively, have a cross-section area that provides the desired mixing ratio. 
     The two rearwardly projecting inlet pipes  151 ,  152  are integrally formed with the terminating plate  150  at positions off-set from the center bore. Preferably, the inlet pipes are positioned opposite to each other with regard to the center axis. The inlet pipes are adapted for being directly inserted into outlet openings of cartridges which contain the components to be mixed. Preferably, the outer surfaces of the pipe sockets are conically formed (with a rearward taper) to provide a sufficient seal between the inlet pipes and the outlet openings of the cartridges. 
     In  FIG. 1 , the inlet pipes are shown with different internal cross-sections to illustrate a case in which two components are to be mixed at a ratio different from 1:1. 
     At the front end  112  of the mixer  100 , a discharge opening  113  is provided for dispensing the mixed paste. 
     In a preferred embodiment, the mixer identified by numeral  100  consists of three molded synthetic resin parts, namely the housing  110 , the terminating plate  150  and the mixing element  130 . 
     The mixing element  130  comprises a shaft extending along the longitudinal axis of the mixing element  130 . A plurality of mixing vanes or blades  131  are located along the shaft as known in the art. Preferably, the mixing vanes are integrally formed on the outer surface of the shaft of the mixing element  130 . As shown in  FIG. 1 , the mixing vanes  131  are provided within the cylindrical portion of the mixing chamber  120  and end short of the internal chamber wall. 
     This basic preferred structure is common to various aspects of the present invention. 
       FIG. 1  is a longitudinal view of a first embodiment of the mixer according to a first aspect of the present invention. In this embodiment, the mixer comprises a reservoir  140  at the front end  112  of the mixer  100 . The housing  110  of the mixer  100  of this embodiment comprises a tubular element  114 . This tubular element  114  projects from the discharge opening  113  inwards into the mixing chamber  120 . Due to this tubular projection, an annular reservoir  140  is formed around the tubular element  114 . With such an annular reservoir surrounding the discharge opening  113 , the initial mixture is stored within the mixing chamber  120  and is not discharged through the discharge opening  113 . However, in order to insure that the initial mixture is indeed stored in the annular reservoir  140 , a baffle plate  160  is preferably provided between the tubular element  114  and the tip of the mixing element  130 . This baffle plate  160  deflects the flow of the mixture. In more detail, the mixture has to flow around the baffle plate  160  and is thus guided along the inner wall of the housing  110  into the reservoir  140 . Only when the reservoir  140  is filled will the mixture pass through the discharge opening  130  out of the mixing chamber  120 . The initial amount of the mixture is stored in the reservoir  140  until the mixer  100  is discarded, although some small amount of the mixture in the reservoir could be mixed within the chamber  120 . 
     The attachment of the baffle plate  160  is shown in more detail in  FIG. 2 . The circular plate  160  comprises at least one connection  161 . In the embodiment shown in  FIG. 2 , three connections  161  are provided. The three connections are spaced from each other at an angle of 120°. With these three connections  161 , the baffle plate  160  is connected to the wall of the housing  110 . Other acceptable numbers or ways of connecting a baffle plate to the wall of the housing can be designed. 
       FIG. 3  shows a longitudinal view of a second embodiment of the mixer  100  of the first aspect of the present invention. This second embodiment of the first aspect is substantially identical to the first embodiment shown in  FIG. 1 . However, in this embodiment, the baffle plate is not located in the space between the tip of the mixing element  130  and the tubular element  114 . Rather, the baffle plate  160  is connected to the tip of the mixing element  130  or forms an integral part thereof. This embodiment is advantageous in comparison to the embodiment of  FIG. 1  because there are no projections in the space between the baffle plate  160  and the wall of the housing  110  which would resist the flow of the mixture. 
     Another alternative is shown in  FIG. 4 .  FIG. 4  is a longitudinal view of the third embodiment of the mixer  100  according to the first aspect of the present invention. Like in  FIG. 3 , in  FIG. 4  a baffle  162  is connected to the tip of the mixing element  130 . However, in this embodiment, the baffle is in the form of a cone or truncated cone  162 . As can bee seen in  FIG. 4 , the truncated cone  162  is connected with its “tip” to the mixing element such that the diameter of the baffle cone  162  is increasing in the downstream direction of the mixture flow. This slope, on the one hand, provides the necessary deflection of the flow of the mixture so that the initial amount of the mixture reaches the reservoir  140 . On the other hand, due to the slope the axial forces acting on the baffle  162  are reduced. 
       FIG. 5  shows a longitudinal view of a fourth embodiment of the mixer  100  according to the first aspect of the present invention. In this embodiment, again a baffle plate  160  is provided. However, in contrast to what is shown in  FIGS. 1 and 2 , the baffle plate  160  of  FIG. 5  is connected to and supported by the tubular element  114 .  FIG. 5  shows a plurality of connections or post(s)  163  that extend from the rear end of the tubular element  114  to support the baffle plate  160 . Between these posts  163 , passageways are formed that allow the mixture to flow to the discharge opening  113  once the annular reservoir  140  is filled. The front end of the mixing element  130  contacts the upper surface of the baffle plate  160  so that the flow of the mixture is guided into the reservoir  140 . Once the reservoir  140  is filled, the flow of the mixture is re-directed to the centre of the mixer and then out of the discharge opening  113 .  FIG. 6  also shows the embodiment of  FIG. 5 , however, without the mixing element. 
     In the longitudinal view of  FIG. 7 , which shows a fifth embodiment of the mixer  100  of the first aspect of the present invention, a modified baffle plate  160  can be seen. Again, baffle plate  160  is supported by the tubular element  114  by means of posts  163  forming passageways therebetween. However, in contrast to the embodiment of  FIG. 5 , the baffle plate  160  comprises a recess or socket  164 . This recess  164  is adapted to receive the front end of the mixing element  130 . Thus, the baffle plate  160  with its recess  164  forms a front end bearing-like or socket-like structure for the mixing element. This provides better stability for the mixer  100 .  FIG. 8  shows the same embodiment, however, without the mixing element. 
       FIG. 9  is a longitudinal view of a sixth embodiment of the mixer  100  according to the first aspect of the present invention. Like in  FIGS. 1 through 8 , the reservoir is formed at the front end of the mixer. Furthermore, the reservoir is formed such that it is fillable in an axial direction, i.e., along the longitudinal axis. In this embodiment, the baffle is formed by a baffle plate  160  which comprises one or more connections  161  to support the baffle plate at the wall of the housing  110 . Furthermore, baffle plate  160  comprises a tubular wall  165  that extends from the plate along the longitudinal axis of the mixer, and towards the rear end of the housing  110 . Thus, a cavity or trough forms the reservoir  140 . As can be easily seen in  FIG. 9 , the initial amount of mixture that comes from the mixing element is received in the reservoir  140 . When the reservoir  140  is full, the flow of the mixture is deflected so that the mixture flows around the baffle plate  160  towards the discharge opening  113 . 
     As an alternative to the connections  161  connecting the baffle plate to the wall of the housing, support webs are provided similar to those shown, e.g. in  FIG. 7 . 
     Preferably, in this embodiment, the housing does not have a constant cross-section along the entire length. Rather, the housing comprises a first section  115  having a first diameter, and a second section  116  having a second diameter. The second diameter is greater than the first diameter. The baffle member  160  is provided in the second section  116 . The two sections  115  and  116  are connected by means of flange  117 . In case the housing has such two sections  115  and  116 , it is preferable that the tubular element  165  of the baffle has a diameter that corresponds to the diameter of the first section  115  of the housing. This geometrical configuration ensures that the first amount of mixture is received in the reservoir  140  since the tubular element  150  is aligned with the first section  115  of the housing  110 . 
       FIG. 10  is a longitudinal view of a seventh embodiment of the mixer according to the first aspect of the present invention. Also in this embodiment, the reservoir is filled in the longitudinal direction of the flow of the mixture. In the embodiment shown in  FIG. 10 , the discharge opening  113  is not provided in line with the longitudinal axis of the mixer. Rather, the mixer is closed at this end. However, the housing  110  comprises a wall opening  119  in the circumferential wall of the housing. The wall opening  119  is located in the front end area  112  of the housing  110  and also offset from the front end wall of the housing  110 . In detail, the wall opening  119  is offset towards the front end  112  of the housing  110  such that a cavity or trough is formed between the wall opening  119  and the front end wall of the housing  110 . Furthermore, a deviating channel  118  extends from the wall opening  119  and terminates in the discharge opening  113 . Thus, the discharge opening  113  is offset from the longitudinal axis of the mixer  100 . The deviating channel  118  may have different forms. In the preferred embodiment shown in  FIG. 10 , the deviating channel  118  comprises a right angle so that the mixture is first directed through the wall opening  119  transverse to the longitudinal axis of the mixer, and then redirected in a direction parallel to the longitudinal axis of the mixer  100 . Alternatively, the channel axis is inclined to the axis of the mixer. As can be seen in  FIG. 10 , the mixture enters the deviating channel  118  after the reservoir  140  is filled. 
       FIG. 11  shows a first embodiment of the mixer  200  according to a second aspect of the present invention. According to the second aspect of the present invention, the mixer uses gravitational forces to fill the reservoir. In the preferred embodiment shown in  FIG. 11 , the reservoir  240  is formed at the front end  212  of the mixer  200 . 
     Mixer  200  comprises a housing  210  with a front end  212  and a rear end  211 . The housing furthermore forms a mixing chamber  220  having an entry side  221  adjacent to a terminating plate  250 . Like in the embodiments shown in  FIGS. 1-10 , terminating plate  250  comprises inlet pipes. In  FIG. 11 , inlet pipe  252  only is shown. In the mixing chamber  220 , mixing element  230  with mixing vanes  231  is provided. 
     At the front end  212  of the housing  210 , there is provided a discharge opening  213 . Furthermore, the front end  212  of the housing  210  comprises a closed channel  260 . The closed channel  260  forms a cavity or trough, forming the reservoir  240 . As shown in  FIG. 11 , the closed channel  260  comprises an axis, and the axis of the closed channel  260  is inclined relative to the longitudinal axis of the mixer  200 .  FIG. 11  shows the typical position of the mixer during use. Thus, the mixer is typically inclined during use. This typical inclination is taken into account for the inclination of the axis of the closed channel relative to the longitudinal axis of the mixer. Thus, the axis of the closed channel is inclined relative to the longitudinal axis of the mixer such that the axis of the closed channel is vertical when the mixer is in its typical dispensing position. The first amount of mixture thus flows into the reservoir  240  due to the gravitational forces. When the reservoir  240  is filled, the mixture flows out of the discharge opening  213 . 
       FIG. 12  is a longitudinal view of a first embodiment of the mixer according to a third aspect of the present invention. According to the third aspect of the present invention, the reservoir is provided at the rear end of the mixer, and is Tillable in an axial direction. 
     The mixer  300  shown in  FIG. 12  comprises a housing  310  with a rear end  311  and a front end  312 . A discharge opening  313  is provided at the front end  312 . The housing  310  furthermore provides a mixing chamber  320 . In the mixing chamber  320 , a mixing element  330  with mixing blades or vanes  331  is provided. The housing  310  is closed at its rear end with terminating plate  350 .  FIG. 12  shows inlet pipes  351  and  352 . 
     The housing  310  according to this embodiment comprises a main section  314 . The main section  314  has a first diameter along its length and a first front end  315  and a first rear end  318 . Furthermore, housing  310  of the mixer  300  of this embodiment comprises a second section  370  having a second rear end  371  and a second front end  372 . The diameter of the second section  370  is greater than the first diameter of the main section  314  at least at the second rear end  371 . The second rear end  371  of the second section  370  forms the rear end  311  of the housing  310 . Furthermore, the first rear end  318  is inwardly offset along the longitudinal axis of the mixer  300  from the rear end  311  of the housing  310 . Thus, a passage  317  is formed between the terminating plate  350  and the first rear end  318  of the main section  314 . The second front end  372  of the second section  370  is connected to the main section  314  in a circumferential area which is offset from the first rear end  318  towards the first front end  315  of the main section  314 . Due to this offset connection between the second section and the main section, a reservoir  340  is formed. In particular, in the embodiment shown in  FIG. 12 , the reservoir  340  is annular and surrounds the rear end  318  of the main section  314  along a certain longitudinal length. 
     In the preferred embodiment shown in  FIG. 12 , the second section comprises a stepped configuration, i.e. the second section comprises a certain length having a constant diameter, and is then connected to the main section by means of a flange  372 . However, alternative designs are also possible. For example, the second section  370  may have the form of a truncated cone with its diameter increasing from the main section towards the terminating plate. 
     A mixer having a reservoir at the rear end of the housing stores the initial amount of the components that enter the mixing chamber. For example, in the embodiment shown in  FIG. 12 , the diameters of the main section and the second section of the housing are such that the reservoir  340  is provided underneath inlet pipes  351 ,  352 . Thus, the initial amount of components entering the mixer through inlet pipes  351  and  352  axially flows into the reservoir  340 . This provides that only a balanced amount of the components finally enters the mixing chamber  320  so that a mixture having a desired mixing ratio is prepared. Thus, the present invention encompasses a mixer in which either a portion of the mixed material can be diverted, or portions of each of the unmixed material can be diverted individually (either to separate reservoirs or to a single reservoir). 
     In the embodiment shown in  FIG. 13 , the reservoir is also formed at the rear end of the housing. However,  FIG. 13  is a preferred embodiment of a fourth aspect of the present invention. According to the fourth aspect of the present invention, the reservoir is not filled in an axial direction but rather in a radial direction. 
     The mixer  400  shown in  FIG. 13  comprises a housing  410  having a rear end  411  and a front end  412 . Discharge opening  413  is provided at the front end  412 . In the mixing chamber  420 , a mixing element  430  with mixing vanes  431  is provided. The housing  410  is closed by the terminating plate  450  having inlet pipes  451  and  452 . 
     In the embodiment shown in  FIG. 13 , the housing again comprises a main section having a first diameter and a second section  470  having a second, greater diameter. The second section  470  has a rear end  471  and a front end  472 . In the embodiment shown in  FIG. 13 , the housing comprises at least one passageway  417  through its circumferential wall. Preferably, a plurality of passageways  417  are provided. The second section  470  forms a wall structure that forms a cavity covering the at least one passageway on the outer surface of the housing. Thus, a reservoir  440  is formed. In the preferred embodiment of  FIG. 13 , the wall structure annularly surrounds the housing  410 . 
     Furthermore, the shaft of the mixing element  430  comprises at least one paddle  432  that pushes the initial amount of the components radially into the reservoir  440  as the mixing element rotates. 
       FIG. 14  shows the embodiment of  FIG. 13  without the mixing element  430  so that the plurality of passageways  417  formed between posts or webs  416  can be seen more clearly. 
       FIG. 15  shows a cross-sectional view of the reservoir of the mixer  400  of  FIG. 15 .  FIG. 15  particularly shows the mixing element  430  with mixing vanes  431  and the paddles  432 . The annular reservoir  440  is formed within wall structure  470 , and the first amounts of the components enter the reservoir  440  through the passageways  427  formed between posts  416 . 
     A second embodiment of the fourth aspect of the present invention is shown in  FIG. 16 . Here, the housing  410  comprises a main section having a first diameter and an area of increasing diameter between said main section and the rear end  411  of the housing  410 . Furthermore, the mixing element  430  comprises a funnel-shaped element  434 . This funnel-shaped element  434  is arranged at the rear end of the mixing element  430 , and also rearwards of the main housing section. Thus, the funnel-shaped element is provided within the area of the housing having the increasing diameter. The diameter of the funnel-shaped element  434  decreases from its rearmost end to the other end where it is connected to the shaft of the mixing element  430 . Thus, the funnel-shaped element  434  rotates with the mixing element  430 . In order to allow flow of the components towards the mixing chamber  420 , the funnel-shaped element  434  comprises at least one passageway at its front end. The at least one passageway allows flow of the components along the longitudinal axis of the mixer  400 . On the other hand, at its rear end, the funnel-shaped element  434  defines an opening having a diameter such that the components enter the mixer within the opening of the funnel-shaped element  434 . 
     As can be seen in  FIG. 16 , the connection between the funnel-shaped element  434  and the shaft of the mixing element  430  is located rearwards from the rear end of the main section of the housing  410 . Thus, a cavity is formed between the funnel-shaped element  434  and the area of the housing  410  having the increased diameter. This cavity forms the reservoir  440 . Since the rear end of the main section of the housing is offset from the funnel-shaped element  434 , at least one passageway  417  is formed through which the initial amount of the components to be mixed enters the reservoir  440 . 
       FIG. 16  also shows the hexagonal recess  433  and the rear end of the shaft  435  of the mixing element  430  for driving the mixing element. 
     Furthermore, at the front end of the mixing element  430 , a bearing-like structure or socket  480  is provided in order to cope with the axial forces acting on the mixing element  430  due to the provision of the funnel-shaped element  434  at the rear end of the mixing element. 
       FIG. 17  shows a cross-sectional view through the paddles  432  of the mixer  400  of  FIG. 16 .  FIG. 17  shows the mixing element  430  comprising six paddles  432  and four mixing vanes  431  (as can be seen in  FIG. 16 , a sequence of mixing vanes  431  is provided). Furthermore,  FIG. 17  shows a passageway  417  into reservoir  440 . 
       FIG. 18  shows a cross-sectional view through the socket  480  for the front end of the mixing element  430 . The socket  480  has an annular form so that a through-hole  481  is formed. This through-hole  481  receives the front end of the mixing element  430 . The annular socket  480  is connected to the wall of the front end  412  of the housing by means of at least one, preferably three, connections  482 . 
       FIG. 19  shows a cross-sectional view through the inlet funnel of the mixer  400 .  FIG. 19  shows the hexagonal recess  433  for the drive shaft. Furthermore, the paddles  432  and the mixing vanes  431  are shown.  FIG. 19  also shows the rear end  411  of the housing that provides the cavity, i.e. reservoir  440  as well as the funnel-shaped element  434 .  FIG. 19  also shows the passageway  417  into the reservoir. 
       FIG. 20  shows a first embodiment of the mixer  400  according to the fifth aspect of the present invention. According to the fifth aspect of the present invention, radial forces are used to fill the reservoir  440 . However, in this aspect of the present invention, the reservoir is formed in an area in the middle of the mixer  400 . In this embodiment, the housing  410  comprises a plurality of passageways  417  to the outside. However, these passageways  417  are covered by a wall structure  470  that forms a cavity, i.e. reservoir  440 . In the embodiment of  FIG. 20 , the wall structure  470  annularly surrounds the housing  410  of the mixer  400  so that an annular reservoir  440  is provided. According to  FIG. 20 , the wall structure comprises a U-shaped form having a tubular section  471  and flange sections  472  that form the legs of the U. At the same level of the passageways  417 , the shaft of the mixing element  430  comprises paddles  432  that press the initial amount of the mixture into the reservoir  440 . Thus, according to the fifth aspect of the present invention, it is again the first amount of the mixture that is stored in the reservoir. 
     A cross-sectional view at the level of the passageways of the embodiment of  FIG. 20  is shown in  FIG. 21 . 
     A sixth aspect of the present invention is shown in  FIGS. 22-25 . According to this aspect of the present invention, the reservoir is provided within the mixing element. 
     The mixer  500  according to the sixth aspect of the present invention comprises a housing  510  with a rear end  511  and a front end  512  with discharge openings  513 . Terminating plate  550  with inlet pipes  551  and  552  closes the housing  510  at the rear end thereof. A mixing element  530  is provided in the mixing chamber  520 . The mixing element comprises mixing vanes  533  as well as a reservoir  540 . Thus, the shaft of the mixing element  530  is hollow. One or more passageways  517  are provided at the rear end of the shaft  535  of the mixing element  530 . Thus, the initial amount of the components flow into the hollow cavity of the mixing element before the mixing chamber  520  is contaminated. 
       FIG. 23  shows a different view of the embodiment of  FIG. 22 . In  FIG. 23 , the passageways  517  and the wall elements  516  located in between are clearly shown. 
     A cross-sectional view of the mixer of  FIG. 22  is shown in  FIG. 24 .  FIG. 24  shows the mixing vanes  531  as well as the paddles  532  that cause a deflection of the flow of the components into the reservoir  540 . 
     A second embodiment of the sixth aspect of the present invention is shown in  FIG. 25 . In this embodiment, the shaft  535  of the mixing element  530  comprises circular or elliptical openings  517   b  at the rear end of the shaft  535  so that the initial amount of the components are directed into the reservoir  540   b  within the shaft  535 . However, according to this aspect of the present invention, a second reservoir  540   a  is formed which is identical to the reservoir  440  shown in  FIG. 13 . Passageways  517   a  are provided so that the reservoir  540   a  is filled with the initial amount of the components to be mixed. 
       FIG. 26  shows a seventh aspect of the present invention, a mixing element  630  is provided within the housing  610 . The mixing element  630  comprises mixing vanes  631 . Furthermore, the mixing element comprises a rearwardly directed L-shaped circumferential flange  636 . This L-shaped flange  636  forms an annular reservoir  640 . In order to store the initial amount of the components to be mixed, the L-shaped flange  636  is located at the rear end of the mixing element.