Patent Application
20090034357
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.
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-1149 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.
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 US-B1-6 244 740 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.
The mixer 100 according to a first embodiment of the present aspect of the present invention is shown in
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
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
This basic preferred structure is common to various aspects of the present invention.
The attachment of the baffle plate 160 is shown in more detail in
Another alternative is shown in
In the longitudinal view of
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
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.
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
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
The mixer 300 shown in
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
In the preferred embodiment shown in
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
In the embodiment shown in
The mixer 400 shown in
In the embodiment shown in
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.
A second embodiment of the fourth aspect of the present invention is shown in
As can be seen in
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.
A cross-sectional view at the level of the passageways of the embodiment of
A sixth aspect of the present invention is shown in
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.
A cross-sectional view of the mixer of
A second embodiment of the sixth aspect of the present invention is shown in
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/10156 | 9/21/2005 | WO | 00 | 3/11/2008 |
