FIELD OF THE INVENTION

[0001 ] The invention relates to the field of mixing. More particularly, this invention relates to an apparatus for mixing components in a liquid mixture.

BACKGROUND TO THE INVENTION

[0002] Any reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in Australia or elsewhere.

[0003] Foam blocks or buns are produced for a range of applications including use as mattresses, cushions, pillows, seats and in a variety of sporting applications. One of the most common foam products is polyurethane foam which is formed by the reaction of an isocyanate with a polyol.

[0004] The characteristics, including the shape and density, of the foam article can be controlled during the manufacturing process in a number of ways. This is challenging not least because the foam forming reaction between the isocyanate and polyol is extremely fast, in the order of seconds, and so specialised systems must be put in place.

[0005] Proper mixing of the mixture of isocyanate and polyol components is crucial to ensure the production of a homogenous foam forming mixture which, in turn, will give a foam product with consistent density and other characteristics. One of the major challenges in the mixing process is to achieve this required level of homogeneity in the foam forming mixture within the extremely short time period available.

[0006] A typical mixer used in the manufacture of foam articles is an axial mixer or a static mixer. These mixers create axial flow, and the centrifugal forces resulting from this axial flow hold components against the walls of the mixer, which delays a complete mix. As such, one disadvantage of these mixers is that there is insufficient mixing. As mentioned hereinabove, this is extremely disadvantageous because the foam forming reaction between an isocyanate and polyol is extremely fast, and this inefficiency will cause inconsistencies in the resulting foam article. It will be appreciated that axial mixers result in 'dead zones' in the mixing chamber including vortexes under the impeller. A dead zone is a volume that receives insufficient mixing due the flow pattern of the apparatus. Attempts to overcome this problem have included mounting the impeller at an angle and mounting the impeller vertically offset. However, these solutions merely move the 'dead zones' to another location in the mixing chamber. It would be advantageous to provide a mixer that alleviates the problem of insufficient mixing. It should also be apparent that a mixer that alleviates this problem will result in a significantly improved foam article.

[0007] A second consideration is that the foam forming mixture must then be dispensed into a mould or other receptacle inside which the foam product will be formed. When the foam forming mixture is dispensed into the receptacle a wave effect is created due to the reverberation of the mixture from the receptacle walls. As the foam forming mixture is rapidly solidifying this can cause inconsistencies within the foam product.

[0008] There is a need for a mixing apparatus suitable for a range of mixing applications but particularly useful in addressing the unique challenges of mixing and dispensing of foam forming mixtures.

OBJECT OF THE INVENTION

[0009] It is an aim of this invention to provide a mixing apparatus and a method of using the same which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.

[0010] Other preferred objects of the present invention will become apparent from the following description. SUMMARY OF INVENTION

[001 1 ] According to a first aspect of the invention, there is provided a mixing apparatus comprising:

(a) a mixing chamber having at least one wall and a base projecting into the mixing chamber;

(b) an impeller having a shaft and a plurality of mixing blades located in a generally central position within the mixing chamber; wherein, the base is adapted to be separable from the at least one wall.

[0012] Preferably, the base is lowerable with respect to the at least one wall. In one embodiment, the base is a convex base.

[0013] Suitably, the base is provided with one or more elongate projections which extend from a floor thereof into the mixing chamber and connect the base to the at least one wall.

[0014] Preferably, the one or more elongate projections are connected to the at least one wall via hydraulic connectors which can be actuated to raise or lower the base with respect to the at least one wall.

[0015] Preferably, the base forms a fluid tight seal with a lower end of the end at least one wall.

[0016] The mixing chamber may be cylindrical with the at least one wall being a continuous wall.

[0017] The plurality of mixing blades are located at a lower extent of the impeller shaft.

[0018] In use, the mixing blades are located generally adjacent the base.

[0019] Preferably, the impeller further comprises a projecting bar extending from a central position on the lower end of the impeller shaft. [0020] Suitably, the projecting bar extends closer to the base than the mixing blades.

[0021 ] Preferably, the projecting bar is immediately adjacent to or in contact with the base.

[0022] Preferably, an upper extent of the impeller shaft is provided with a plurality of longitudinal blades.

[0023] Suitably, the longitudinal blades are curved and/or angled blades relative to the axis of the shaft.

[0024] Preferably, the mixing apparatus is a mixing apparatus for foam formation.

[0025] According to a second aspect of the invention there is provided a method of mixing and dispensing a liquid mixture including the steps of:

(a) providing a fluid tight mixing chamber having at least one wall and a separable base projecting into the mixing chamber and an impeller having a shaft and a plurality of mixing blades located in a generally central position within the mixing chamber;

(b) locating the impeller such that the mixing blades are generally adjacent the base;

(c) introducing one or more components to be mixed, at least one of which is a liquid, into the mixing chamber;

(d) actuating the impeller to cause rotation of the mixing blades until suitable mixing is achieved;

(e) lowering the base relative to the at least one wall to generate an opening around the extent of the at least one wall through which the liquid mixture is dispensed into a receptacle, to thereby mix and dispense the liquid mixture. [0026] The base may be lowered relative to the at least one wall by a hydraulic mechanism. In one embodiment, the base is a convex base.

[0027] In use, the mixing blades are preferably located between about 30 mm to about 100 mm, more preferably between about 35 mm to about 75 mm , even more preferably about 50 to 60 mm vertically above the floor of the base.

[0028] Preferably, the liquid mixture is a foam forming mixture.

[0029] Suitably, the foam is polyurethane foam.

[0030] Preferably, the mixing chamber is located centrally within the receptacle when the liquid mixture is dispensed.

[0031 ] The various features and embodiments of the present invention, referred to in individual sections above apply, as appropriate, to other sections, mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections as appropriate.

[0032] Further features and advantages of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order that the invention may be readily understood and put into practical effect, preferred embodiments will now be described by way of example with reference to the accompanying figures wherein:

[0034] FIG 1 is a perspective view of a mixing chamber component of a mixing apparatus;

[0035] FIG 2 is a perspective view of an impeller component of a mixing apparatus;

[0036] FIG 3 is a perspective view of a mixing apparatus, in a partial cut away view, being lowered into a receptacle;

[0037] FIG 4 is a perspective view of the mixing apparatus of FIG 3 when located partly within the receptacle; [0038] FIG 5 is a perspective view of the mixing apparatus of FIG 3 when located within the receptacle and with the base lowered to dispense the mixture;

[0039] FIG 6 shows the flow in an axial mixer with a flat base; and

[0040] FIG 7 shows the flow in a mixing apparatus of the present invention .

DETAILED DESCRIPTION OF THE DRAWINGS

[0041 ] In this patent specification, adjectives such as first and second, left and right, front and back, upper and lower, etc. are used solely to define one element or method step from another element or method step without necessarily requiring a specific relative position or sequence that is described by the adjectives.

[0042] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as would be commonly understood by those of ordinary skill in the art to which this invention belongs.

[0043] Although the discussion which follows addresses the use of the inventive mixing apparatus in the mixing and dispensing of a foam forming mixture it will be appreciated that the use of the apparatus is not so limited. The present mixing apparatus provides advantages in the mixing dynamics achieved within a mixing chamber and so may be equally useful in other industries where fast and effective mixing of components in a liquid is required. For example, application of the present mixing apparatus may be found in the paint formulation or minerals leaching fields.

[0044] In a first aspect of the invention, there is provided a mixing apparatus comprising:

(a) a mixing chamber having at least one wall and a base projecting into the mixing chamber; (b) an impeller having a shaft and a plurality of mixing blades located in a generally central position within the mixing chamber; wherein, the base is adapted to be separable from the at least one wall.

[0045] FIG 1 is a perspective view of a mixing chamber 200 component of a mixing apparatus 100. The mixing chamber 200 comprises a base 205 which has an upper surface forming a floor 210 of the mixing chamber 200. The floor 210 is an upwardly sloping surface such that, when in use, it projects into the mixing chamber 200 and ends in a rounded apex 215.

[0046] It is known that the distal region of an impeller moves faster than the proximal region of an impeller. This leads to inefficient mixing due to the volume below the proximal region (or center) of the impeller being insufficiently mixed. The present inventor has found that by using a base that projects into the mixing chamber this problem is alleviated. It is believed that this is due to the centre of the impeller being closer to the base, and the volume of the 'dead zone' being reduced. Furthermore, the distal region of the impeller will continue to facilitate movement in the mixture. In this regard, the mixture will be moved towards the base and continue along the contour of the base. Additional mixture will then force the mixture to be pushed up the sides of the at least one wall. As such, this upward movement alleviates the problem of the components being held to the at least one wall. It will be appreciated that the use of the base that projects into the mixing chamber results in efficient mixing. In one embodiment, the base may comprises one or more surfaces projecting into the mixing chamber. In an embodiment, the base comprises a single surface that projects into the mixing chamber. The base may suitably comprise a curved surface or a stepped surface that projects into the mixing chamber. In a preferred embodiment, the base comprises a convex surface projecting into the mixing chamber. In other words, the base may be a convex base projecting into the mixing chamber. In another embodiment, the base may be a cone shape that projects into the mixing chamber. For convenience of description, the base will be described herein as a convex base.

[0047] The convex base 205, in the embodiment shown, has a flattened rim 220 to allow a sealing contact to be formed therewith. In an alternative embodiment, the convex base may be an entirely convex surface without a flattened rim 220 and sealing contact may be made with the sloping surface by way of a rubber or plastic sealing material disposed on the surface to come into contact with the convex base 205. Two elongate projections 225 extend upwardly away from the floor 210 from roughly opposing points around the border of the convex base 205 to end in connectors 230 which are provided with connecting apertures 235.

[0048] In contact with the convex base 205 a chamber wall 240 defines the mixing chamber 200. It will be appreciated that since a cylindrical mixing chamber 200 is shown the chamber wall 240 is a single continuous wall. Other shapes having a number of walls, such as a rectangular or cube shape, may be contemplated in certain applications although the mixing dynamics will be affected by the presence of the right angles and vertices. The inner surface 245 of the chamber wall 240 will be in contact with the liquid mixture and the chamber wall 240 ends in a lower end face 250 which, in use, will abut with the flattened rim 220 of the convex base to provide a sealing contact to maintain the liquid mixture within the mixing chamber 200. As discussed, in embodiments where the entire surface of the convex base 205 slopes then the lower end face 250 may be provided with a rubber or like sealing material along its surface which then forms a watertight seal when in abutment with the floor 210 of the convex base 205.

[0049] It can be seen from FIG 1 that the convex base 205 is adapted to be separable from its sealing contact with the lower end face 250 of the chamber wall 240. To facilitate this there are provided, adjacent the open end 255 of the mixing chamber 200, two hydraulic connectors 260 which are further connected to a hydraulic system (not shown). The hydraulic connectors 260 have first open ends 265 in which to receive the connectors 230 of the elongate projections 225. An internal pin or the like may interact with the connecting apertures 235 of the connectors 230 to fasten them within the hydraulic connectors 260 and hence fasten the convex base 205 structure to the chamber wall 240 structure. There are two notches 270 formed in the upper extent of the chamber wall 240 which allow the interaction of a mechanical framework (not shown) which moves the mixing chamber 200 up and down and which also includes the hydraulic system.

[0050] It will be understood then that the hydraulic system can be engaged and disengaged to allow the convex base 205 to be raised or lowered to be in contact with or distanced from the chamber wall 240. Alternatively, the chamber wall 240 may itself move and the convex base 205 stay fixed in space with the same end effect thereby being achieved.

[0051 ] FIG 2 is a perspective view of an impeller 300 component of the mixing apparatus 100. The impeller 300 comprises a shaft 305 having a lower extent 310 and an upper extent 315. A collar 320 is formed around the lower extent 310 from which a plurality of mixing blades 325 radiate substantially horizontally. The mixing blades 325 may be curved propeller style blades which are known and used in the art of process mixing or formulation. A projecting bar 330 projects a short distance from a central position on the lower extent 310 of the impeller shaft 305. The projecting bar 330 may be directly connected to the end of the shaft 305, for example by welding, or may be fixed within a holder.

[0052] Towards the upper extent 315 of the shaft 305 a plurality of longitudinal blades 340 are affixed to the shaft 305 by one or more fasteners 345 which may be welded to the shaft 305. The longitudinal blades 340 are curved and/or angled with respect to the shaft 305 and, while they are not directly used in the mixing of the foam forming mixture, they provide distinct advantages in cleaning of the mixing chamber and hence improve the throughput of the process. [0053] All of the mixing apparatus 100 components discussed can be formed from materials which are standard in the industry including various steels such as mild steel and stainless steel.

[0054] FIG 3 is a perspective view of the complete mixing apparatus 100, in a partial cut away view, being lowered into a receptacle 500. FIG 4 shows the mixing apparatus 100 further lowered into the receptacle 500 while FIG 5 completes the series by showing the mixing apparatus 100 fully located within the receptacle and with the convex base 205 being lowered from the chamber wall 240 to dispense a foam forming mixture 400 which was contained therein.

[0055] In use, the mixing apparatus 100 is provided with the flattened rim 220 of the convex base 205 in sealing engagement with the lower end face 250 of the chamber wall 240 such that a watertight mixing chamber 200 is formed with an open end 255 through which foam forming components or reagents can be added. Alternatively, the floor 210 does not have a flattened region in which case the lower end face 250 is provided with a sealant material to seal with said sloping floor 210. In the case of a polyurethane foam a polyol, such as polypropylene glycol, may be added into the mixing chamber 200 along with any water, surfactants and catalysts that may be required. The final reagent to be added will be an isocyanate, such as toluene diisocyanate (TDI), which essentially kick starts the very fast foam forming reaction. In a typical run about 30 litres of TDI will be introduced into 70 litres of polyol. The time available for complete mixing is approximately 2 to 4 seconds from introduction of the TDI until the mixture must be dispensed. The impeller 300 will be activated prior to addition of the TDI such that the rapid rotation of the shaft 305 causes the spinning of the mixing blades 325 and the projecting bar 330.

[0056] The prior art uses propeller blade mixing of foam forming reagents but the mixing is not effective resulting in small concentration differences in different regions of the mixture. This will result in an inferior foam product. The present inventor has realised that effective mixing of the TDI into the rest of the liquid mixture cannot be achieved in the short time frame available with the mixing dynamics employed in the prior art. In these approaches the action of the propeller blades is to cause the foam forming mixture to be forced outwards in a swirling axial plane towards the vessel walls around which the mixture is then forced to move in a generally circular motion which delays complete mixing. The mixture is not drawn back in to the mixing zone immediately adjacent the blades frequently enough to achieve a homogeneous mixture with the available time. Further to this problem , the present inventor has recognised that a dead zone forms directly under the propeller head which results in limited mixing due to the low change over in mixture volume in this region.

[0057] The present mixing apparatus 100 addresses these shortcomings in the prior art by, firstly, the use of a floor 210 in the mixing chamber 200 which is convex thereby presenting a sloping surface to the foam forming mixture 400. In use, the mixing blades 325 are located between about 30 mm to about 100 mm, more preferably between about 35 mm to about 75 mm, even more preferably about 50 mm to 60 mm vertically above the apex 215 of the floor 210. This combination of a convex floor 210 with the mixing blades 325 located generally adjacent the convex base 205 (much closer than the prior art would locate the propeller blades to a flat bottomed floor) results in the spinning mixing blades 325 strongly forcing the foam forming mixture 400 against the floor 210. The foam forming mixture 400 is forced to follow the contour of the convex floor 210 and is then displaced vertically by further foam forming mixture 400 following behind it. The foam forming mixture 400 then follows the chamber wall 240 until it reaches the meniscus of the mixture, which due to this effect will sit higher than when employing a prior art approach, at which point it effectively tumbles or is forced by further foam forming mixture 400 back in towards the centre of the mixing chamber 200 which is the major mixing zone. It will be appreciated by the person skilled in the art that the distal regions of the impeller complete most of the work. In this regard, the centre of the impeller does little work and a vortex can form in the region below the centre of the impellor. This results in inefficient mixing. It is an advantage of the present invention that the distal region of the impeller is located further away from the convex base than the central portion (proximal end) of the impeller due to contour of the convex base so that the mixture flows towards the base.

[0058] It will be appreciated then that the present design of mixing apparatus 100 results in a much greater extent of vertical motion of the foam forming mixture 400 than the largely axial motion created by propeller blades located some distance from a flat bottomed floor of prior art mixing chambers. Preferably, the mixing blades 325 have a sharp leading edge and a sharp trailing edge to facilitate mixing. This sharp leading edge and sharp trailing edge allows an operator to alter the speed of the impeller to ensure that cavitation does not occur. In this regard, cavitation should be avoided as this hinders efficient mixing. Further, the provision of the projecting bar 330 has been found to prevent the formation of a dead zone in the region directly underneath the central axis of the mixing blades 325. The projecting bar 330 will project from the bottom of the shaft 305 such that it will be substantially or immediately adjacent the apex 215 of the floor 210. In fact it is preferable that the projecting bar 330 is located such that it is just in contact with the apex 215 of the floor 210. This results in any foam forming mixture 400 which would pass into this dead zone instead being diverted and maintained in the active mixing zones. Essentially, the dead zone found in prior art approaches has been eliminated by virtue of the projecting bar 330. The elimination of this dead zone by the projecting bar 330 has been found to provide surprisingly advantageous results in terms of achieving fast and complete integration of TDI uniformly throughout the foam forming mixture 400. The projecting bar 330 extends from a central position on the lower end 310 of the impeller shaft 305 such that it is less than 5mm, preferably less than 2mm from the apex 215 of the floor 210 and, most preferably, just in contact with the apex 215 such that contact between the two is made but without affecting the rotation of the shaft 305. The close relationship between both the mixing blades 325 and the projecting bar 330 with the floor 210 is indicated in FIG 3. [0059] A receptacle 500, which in the figures is a component of a vacuum mould apparatus, may be put into place before or during the foam mixing operation and the mixing chamber 200 lowered into an open end 505 thereof during the mixing process. It will be appreciated that the receptacle 500 is shown as rectangular shape for simplicity. In this regard, the receptacle 500 may be any shape. Non-limiting examples of the shape of the receptacle are cylindrical, spherical, square and cubed. FIG 5 demonstrates the process of dispensing the foam forming mixture 400 into the receptacle 500 after mixing is complete. The hydraulic system is activated and the hydraulic connectors 260 release the elongate projections 225 to allow them to pass through to a predetermined degree. This results in a lowering of the convex base 205 relative to the lower end face 250 of the chamber wall 240 and so creates an opening therebetween around the extent of chamber wall 240 through which the foam forming mixture 400 is dispensed into the receptacle 500 to be contained by the receptacle walls 510. Advantageously, the foam forming mixture 400 is thereby released from the mixing chamber 200 on a 360 degrees basis i.e. it is dispensed around the entire circumference of the lower extent of the mixing chamber 200. This helps ensure rapid dispensing but also lessens the distance the foam forming mixture 400 must travel before it encounters the receptacle wall 510 and so encourages faster settling of the foam forming mixture 400 and reduces wave or reverberation effects that are observed in the prior art when the liquid mixture is simply poured into a mould from one point in a chamber and, typically, this occurs at one end of the mould rather than in a central location as is enabled by the present mixing chamber 200 design.

[0060] During dispensing of the foam forming mixture 400 a further advantage of the convex floor 210 is observed beyond those provided during the active mixing stage. The convex surface of the floor 210 provides a controlled or agitation free run off into the receptacle 500 and so further reduces the chances of inconsistencies forming in the foam as it solidifies and rises. Although in FIG 5 the mixing chamber 200 is shown as being almost completely enclosed within the receptacle 500 this may not be the case when the foam forming mixture 400 is dispensed to ensure that the mixing chamber 200 itself does not contact the mixture 400 after it has been dispensed. This may be achieved by having the mixing chamber 200 at a more elevated position relative to the bottom of the receptacle or by raising the mixing chamber 200 during dispensing to thereby reduce splashing while minimising contact between foam forming mixture 400 and mixing chamber 200.

[0061 ] Once all of the foam forming mixture 400 has been dispensed into the receptacle 500 then the mixing chamber 200 can be raised by the mechanical framework out of the way and the receptacle 500 quickly moved to a further apparatus where the rising of the foam can be controlled under reduced pressure to thereby provide the final product.

[0062] Due to the batch nature of the process described it is essential for productivity that the next batch of foam forming reagents can be added into the mixing chamber 200 as soon as possible to repeat the process. For this to occur through a large number of cycles and without any substantial downtime it is critical for the mixing chamber 200 and the impeller 300 to be cleaned regularly. This involves dissolution of the foam forming mixture 400 which remained stuck to the inside of the mixing chamber 200. One prior art approach to this has been the use of solvents, such as dichloromethane, to redissolve the foam forming mixture 400. This is unsatisfactory due to the environmental impact of the use of chlorinated solvents. A further approach has simply been to introduce an amount of the polyol being used to produce the foam which can redissolve the foam forming mixture 400 and allow it to be immediately used in the next batch run. The problems generally encountered with this solution in the prior art are that, firstly, the newly introduced polyol is not evenly distributed around the mixing chamber in such a way as to remove all of the old foam mixture and, secondly, due to the ongoing rotation of the impeller shaft and blades to encourage spread of the polyol the polyol is sprayed outside of the confines of the mixing chamber causing a workplace hazard. [0063] The present mixing apparatus provides a solution to these problems by the provision of the longitudinal blades 340 located towards an upper extent 315 of the impeller shaft 305. The shape of these curved blades is functionally akin to an auger design and, upon introduction of the new polyol, immediately directs it outwardly towards the inner surface 245 of the chamber wall 240 to redissolve the old foam mixture but, importantly, also directs the polyol in a generally downwards manner such that it will not be thrown or sprayed out of the open end 255 of the mixing chamber to cause contamination of the surrounding area. Although the longitudinal blades 340 are not actively involved in the mixing of the foam forming mixture 400 they provide a distinct advantage to the present mixing apparatus 100 since they allow the effective, fast and safer cleaning of the mixing chamber 200 and the impeller 300, generally, between batch runs to thereby allow a high throughput of foam production to be maintained.

[0064] Finally, the production of different grades of foam requires the mixing of different relative amounts of reagents. The present inventor has found that the use of different mixing speeds provides distinct advantages in achieving complete mixing within the limited 4 second time frame. Ideally, the variable speed motor which drives the impeller 300 will be turned up until cavitation of the foam forming mixture is apparent and then the speed reduced just below that level. This can be tuned by software or the required speeds assessed by simple trial runs.

[0065] The present inventive mixing apparatus 100 and the use thereof provide advantages which have not been seen in the prior art allowing the mixing of approximately 100 litre volumes of foam forming mixture in 4 seconds to achieve a homogeneous mixture. The combination of the convex floor 210 in the mixing chamber 200 along with the close relative positioning of the mixing blades 325 to that floor 210 and the provision of the projecting bar 330 results in a vertical dynamic mixing flow path being generated which is more effective at forming a homogeneous foam forming mixture 400 in the limited time available than standard generally axial flow path chambers and which eliminates potential dead zones of limited mixing. The ability to lower the convex base 205 relative to the chamber wall 240 results in fast and minimally perturbed dispensing of the foam forming mixture 400 and allows this to occur in a central position within the receptacle 500. Finally, the additional longitudinal blades 340 enable rapid and efficient dissolution of old foam mixture within newly added polyol and so allows uninterrupted cycles of batch processing to be achieved.

[0066] FIG 6 shows the axial flow in axial mixer 600. The centrifugal forces resulting from the axial flow hold the components against the walls of the mixer, and delay a complete mix. The axial mixer 600 with a flat base 610 will have 'dead zones' where there is significantly less mixing. One such dead zone is directly underneath the center of the impeller 620.

[0067] FIG 7 shows the flow in a mixing apparatus 700 of the present invention. The mixing apparatus 700 of the present invention has a convex base 710 that projects into the mixing chamber. As a result, the components in the mixing chamber have a generally downward and circular flow. As such, the reagents in the mixing chamber are pushed down towards the convex base 710 which then follows the contour of the convex base 710. The components are then pushed up the sides of the wall and pulled back into the centre. It will be appreciated that such flow alleviates the problem of centrifugal forces holding the components against the walls of the mixer. In the present mixer, any dead zones that were near the corners are no longer present or significantly diminished.

[0068] The provision of a projecting bar 730 which extends from a centre position on the lower end of the impeller shaft 720 further alleviates the problem of the dead zone located directly beneath the centre of the impeller 720. The projecting bar 730 provides mixing or turbulence to this dead zone and pushes it into the surrounding reagents and flow. It should be apparent that the present mixing apparatus solves the problem of inefficient mixing. Additionally, the projecting bar 730 is preferably located adjacent the convex base so that the dead zone is effectively absent. Furthermore, the present mixing apparatus is particularly advantageous when used for foam formation because the problem of inefficient mixing is alleviated. As such, the use of the present mixing apparatus results in a foam product that is more consistent, and this is clearly desirable.

[0069] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this patent specification is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

[0070] In the claims which follow and in the preceding description of the invention, except where the context clearly requires otherwise due to express language or necessary implication, the word "comprise", or variations thereof including "comprises" or "comprising", is used in an inclusive sense, that is, to specify the presence of the stated integers but without precluding the presence or addition of further integers in one or more embodiments of the invention.