FR2777804A1 - Submerged mixer for producing emulsions - Google Patents

Abstract

The blades (1A to D) of the submerged mixer rotor are symmetrical about a horizontal plane and consist of two flat plates (P and P') at 90 deg to each other. The rotor fits inside a cylindrical stator with vertical slots in its walls, through which fluid is pushed. The rotor and stator are held between rings above and below, and the corners of the rotor (D and D') are cut away to accommodate these. The rings force fluid flow in the correct direction.

Description

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  The present invention relates to a rotor and stator device intended to be immersed in a tank which is filled with a first product, and to aspirate a second product introduced into the tank, so as to cause an emulsion between the first product and the second product, the rotor comprising several blades which are integral with a shaft and which are capable of rotating inside the stator, which has a body

  pierced with multiple ejection openings for the mixed product.

  Currently there are devices of this type which are immersed in tanks subjected to normal conditions of vacuum and pressure, which are filled with a first liquid product, generally aqueous or of very low viscosity, which have a generally cylindrical shape in a vertical position and have a slightly curved bottom, the lowest part of these tanks being in the cylindrical axis of the latter. The rotor and stator mixing devices are most often positioned close to the bottom of the tank, being off-center with respect to the cylindrical axis of the latter, in order to be able to provide, in this axis, a

valve for emptying the tank.

  More specifically, the rotor comprises a shaft provided, depending on the case, with two to eight blades, which is driven by a motor placed above or below the tank. The most commonly used blades are generally formed by dishes made of non-oxidizable material. The stator, meanwhile, comprises a generally cylindrical hollow body in vertical position of the crown type, open upwards and downwards, and pierced, over the entire periphery thereof, with multiple openings spaced regularly. These openings can have a circular, oblong or other shape. The rotor is positioned in the stator so that its shaft coincides with the central axis of the stator body, the peripheral part

  blades being very close to the internal surface of the stator body.

  The product which it is desired to mix, which may be a powdery, pasty, viscous or other product, is introduced to the bottom of the tank by

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  a valve which is placed outside the tank and which is connected to the bottom thereof on the side where the mixing device is placed. The product to be mixed is then drawn into the device from below, under the action of the rotation of the rotor shaft, the blades of which, by turning, cause it to mix with the product initially introduced. The mixed product is then expelled from the device through the multiple openings made in the stator. The problem with this type of mixing device is that the mixture obtained is not always very satisfactory, in particular when it is desired to mix a pulverulent product. Indeed, because of the low fluidity which characterizes them and the very small distance which separates the device from the bottom of the tank, the product which leaves the valve and which enters the tank does not arrive in its entirety at the 'interior of the device because, often, a part of it settles at the bottom of the tank. Therefore, the amount of product that has actually been mixed is less than expected.

  initially, which causes a significant waste of product.

  Another problem, which is encountered with these devices, results from the often impractical arrangement of the assembly -shaft of the rotor, drive motor-. It is indeed noted that the positioning of the device very close to the bottom of the tank generally requires having a relatively long shaft for the rotor, and therefore providing a system for guiding and connecting the shaft to the relatively engine complicated, based on rings, bearings, etc ..., which has the disadvantage of being directly in the tank. This type of arrangement entails a risk of product retention at the level of the various intermediate parts of the system for guiding and connecting the shaft, with the consequence

  annoying, the appearance of bacteriological problems.

  We also note that the choice of the combination - shape of the stator openings, blade profile - adopted in these devices is not sufficiently linked to obtaining an optimal shear rate and ejection efficiency . This choice is notably responsible, in practice, for the appearance of leaks at the peripheral corners of

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  each blade, resulting in the loss of a certain amount of product, or

  still obtaining an emulsion fineness which is not satisfactory.

  Finally, it should be noted that these mixing devices, from the point of view only of their arrangement and of their operating capacity, have a certain number of drawbacks, such as for example the fact of being fixedly positioned in the tank and d '' have a capacity

limited to 5m3.

  The present invention therefore essentially aims to remedy at least one of the drawbacks mentioned above of the devices

mixers of known type.

  To this end, the mixing device according to the invention is - to obtain

  high ejection speed of the mixed product and high flow rates -

  characterized in that each blade of the rotor has two sections disposed on either side of a line of radial direction, these sections having, with respect to the axis of the rotor, inclinations in opposite directions so that each pale has a concavity in a direction determined by the direction of

rotor rotation.

  In one embodiment, to minimize the quantity of products remaining in the tank, the mixing device is at a distance from the bottom of the

tank of this device.

  Preferably, to maximize the efficiency of the mixer, means are provided to prevent product flow outside the scope of the

blades in axial direction.

  Other features and advantages of the present invention

  will emerge during the following description of embodiments

  of the present invention, given with reference to the accompanying drawings in which: * Figure 1 is a perspective view of the rotor according to the invention; * Figure 2 is a top view of the rotor according to the invention; 0 * Figure 3 is a perspective view of the stator according to the invention in which must be adapted the rotor shown in Figures 1 and 2;

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  * Figure 4 is a vertical sectional view of the rotor and the stator as illustrated respectively in Figures 1, 2 and 3, representing the latter in the mounted state inside the mixing tank; * Figure 5 is an enlarged detail view of Figure 4, showing the direction of product flow; * Figure 6 is an enlarged partial perspective view showing the position of the trailing edge of one of the blades of the rotor of Figure 1 by

  compared to the openings made in the stator of figure 3.

  As can be seen in Figures 1,2 and 3, the mixer device Io according to the present invention is usually broken down into two separate parts, namely a movable part 1 called the rotor and a fixed part 2 called the stator. When the mixing device is in service, as shown in FIG. 4, the rotor 1 is adapted in close contact in the stator 2, and the assembly is immersed in a mixing tank 3 filled with a first product a, of the same type as the first product used in the mixing devices described above. To prevent the mixing device according to the invention from deteriorating in contact with the product u, it is made of a resistant material, which is preferably stainless steel. More particularly with reference to FIG. 3, it should be noted that the stator 2 according to the invention has a completely conventional shape and structure. Indeed, it comprises, in the same way as what was mentioned above, a hollow cylindrical body 2A in vertical position, open upwards and downwards to allow the introduction of the first product a and d 'A second product 5 (represented by arrows in Figure 4), the latter may be a viscous, pasty, powdery or other product. The body 2A is further pierced, over the entire periphery thereof, multiple identical openings O, regularly spaced, used for the ejection of the product constituted by the mixture of the products a (and y. In this embodiment o of the stator, said openings are vertical and have an oblong shape. But it will easily be understood that, depending on the type of products to be mixed, the openings O may have surface differences.

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  and shape, including being oblique, having a chevron shape, being

  formed by circular holes, etc.

  The rotor 1, meanwhile, also has, as can be seen in Figures 1,2 and 4, similarities to conventional rotors, in that it comprises several blades, for example four in number, designated respectively by the references 1A, 1B, 1C and 1D. As for the rotors of the state of the art which have been mentioned above, these are all identical, regularly distributed on a shaft 1E and intended to rotate inside the body 2A of the stator to allow the aspiration of the second product 5, then mixing of the latter with the product a. Since the place and the means of introduction into the tank 3 of the product P are exactly the same as those mentioned above, they do not

will not be described again.

  In the embodiment of the rotor as shown here, the 1 5 blades 1A, 1B, 1C and 1D are preferably integrally formed with the shaft IlE, and this is made integral in rotation with a shaft 4 by means of keys 5 (only one is shown). The shaft 4 is rotated by a motor (not shown) which is located below the mixing tank 3. The system -shaft 4, motor- is here much less complicated than that encountered in the prior art since it eliminates the problems of guidance and connection of the shaft 4 and therefore, it eliminates all the parts related to them. Consequently, we limit the risk of seeing the product a or p being deposited on certain parts of the tree 4. One of the main interests of the invention resides in the particular profile given to the blades 1A, 1B, 1C and 1D. With reference to FIGS. 1, 2 and 4, these respectively comprise two sides P and P 'on either side of a line L of radial direction, the two sides P and P' of each blade 1A, 1 B , 1 C and 1 D being symmetrical with respect to a plane containing the line L of radial direction and perpendicular to the axis of the rotor, said plane being the median plane of the body 2A of the stator. In the embodiment shown here, the lines L are perpendicular to the generatrices of the inner cylindrical part of the shaft 1 E. The sides P and P 'are substantially rectangular and planar and form an angle of between them, by

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  example, 90. Their corresponding free ends respectively constitute the two upper and lower horizontal leading edges B and B 'of the blade. The latter are, moreover, in known manner, bevelled in the direction of introduction of the products CL and P so that they penetrate more easily inside the mixing device. In this way, any loss of AC product liable to appear at the time of aspiration is avoided. Each blade 1A, 1B, 1C and 1D, due to the fold L, has a very specific trailing edge F, the section of which is in the form of V. The arrangement which has just been described makes it possible, inter alia , o to obtain a reversible mixing device, which is particularly advantageous at the time of the adaptation of the rotor 1 in the stator 2, the operator then no longer having to worry about the direction of assembly. It is also made so that the sides P and P 'of each blade 1A, 1B, 1C and 1 D are arranged on the shaft 1 E having, with respect to the axis of the rotor 1, inclinations in opposite directions so that each blade 1A, 1B, 1C, 1D has a concavity in a determined direction, corresponding to the direction

  of rotation of the rotor 1, which is represented by an arrow in FIG. 1.

  In order to avoid the problematic accumulation of product at the bottom of the tank 3, in particular in the case where the product f5 is found to be a pulverulent product, the invention provides for raising the mixing device with respect to the bottom of the latter. To do this, a flange 6 and a flange 7 of a conventional type, as shown in FIG. 4, are mounted respectively on the upper and lower peripheral edge of the body 2A of the stator and connected to each other using columns 8 of cylindrical shape, for example four in number (two balusters are shown), spaced at an angle of 90. The flange 7 is, moreover, connected to the bottom of the tank 3 using uprights 9 of cylindrical shape, for example four in number (two uprights are shown), spaced at an angle of 90, these being longer and of larger diameter than the posts 8. Each post 8 has its upper end connected to the flange 6 by a bolt 10 and its lower end connected to the flange 7 by a threaded rod 11. In a similar manner, each upright 9 at its upper end connected by

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  a bolt 12 to the flange 7, which, for this purpose, has a peripheral part more extended than that of the flange 6, and at its end

  lower connected to the bottom of the tank 3 by a threaded rod 13.

  Still with reference to FIG. 4, the collars 6 and 7 have the advantage of having a corresponding internal rim 6A and 7A which terminate respectively just above and just below the openings O of the body 2A of the stator. The upper and lower spaces, occupied respectively by the internal edges 6A and 7A, are each defined by the set of cutouts D and D '(shown in FIGS. 1 and 2) which have been made respectively in the area formed by the corner upper peripheral and lower peripheral corner of each blade 1A, IB, 1C and 1ID. The shape of the cuts D and D 'is substantially

  rectangular and follows the shape of the outline of the internal edges 6A and 7A.

  It is easy to see that the use of the collars 6 and 7 has a real advantage in practice because, in the event of a breakdown or an incident inside the mixing device, or else in the case of a simple revision of the latter, they allow a simple and rapid assembly and disassembly of the mixing device according to the invention. For example, it quite often happens that an operator accidentally drops a tool inside the mixing device, when the latter is in service, thereby causing major damage, in particular at the rotor blades. Instead of being obliged to change the whole mixing device assembly as he used to do previously, the operator will now have, thanks to the mixing device according to the present invention, the possibility of extracting it from the tank to fix it or just change part of it. The result

  therefore a certain economy for the industrialist.

  The flanges 6 and 7 also have another advantage, in that the user, depending on the type of products to be mixed, can easily

  o replace the existing mixing device with another more suitable.

  As can now be seen with reference to FIG. 6, the cutouts D and D ′ of each blade 1A, lB, 1C and 1D (only the blade 1A is shown) are such that once the rotor 1 is mounted on the inside the stator 2,

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  the distance between the horizontal lower edge b of the cutout D and the horizontal upper edge b 'of the cutout D' corresponds substantially to the length of the openings O of the stator 2. As will be explained below, the positional relationship existing between the trailing edge F with a V section and the openings O, which is specific to the mixing device according to the invention, promotes the increase in the shear rate and the ejection efficiency. We will now describe the operation of the mixing device

  according to the invention, mainly with reference to Figures 4 and 5.

  After having installed, via the uprights 9, the assembly constituted by the rotor 1, placed vertically inside the stator 2, the flanges 6 and 7 and the balusters 8, in the raised position in the mixing tank 3 filled with the first product a, the operator opens the valve connected to the bottom of the tank 3 to allow the introduction, in the direction of the arrows 1 5 A shown in Figure 4, of the second product P3 inside the latter , and starts the engine placed under the tank 3. The shaft 4 is then subjected to a rotational movement which is transmitted to the shaft 1E by means of the keys 5, thereby causing the blades 1A, 1B to rotate , 1C and 1D inside the body 2A of the stator, the concavity of these being turned in the direction of rotation of the shaft 1E of the rotor 1. The effect of this rotation leads, on the one hand, to I suction of the product ax in the mixing device through the upper opening of the body 2A of the stator, said product flowing in the direction of the arrows I shown in FIG. 5 and, on the other hand, the suction of all of the product p in the mixing device through the lower opening of the body 2A of the stator, said product flowing in the direction of the arrows 1 ′ shown in FIG. 5, this latter suction being very effective due to the large clearance defined between the mixing device and the bottom of the tank 3. The double suction thus created is all the more advantageous as it allows to provide a Pro mixer device capable of processing much larger flow rates than those usually treated, its capacity possibly reaching 30m3. This can be particularly interesting, for example in the large chemical, cosmetological or other industry. We also note that the

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  power absorbed by the motor is, at the time of this double aspiration, reduced in an effective manner, by the fact that the leading edges B and B 'of each blade 1A, lB, 1C and 1D are bevelled and are

  outside the body 2A of the stator.

  Following this double aspiration, the product flows coming from above and from below the mixing device meet inside of it. The advantage here is that the direction of penetration of the two flows is

  substantially vertical thanks to the presence of the two flanges 6 and 7.

  Thus, the flows of product ax and of product f, which are somehow channeled, can neither approach the upper periphery of the mixing device, nor approach its lower periphery, these being blocked respectively by the rim 6A of the flange 6 and the rim 7A of the flange 7. The fact of having provided these flanges 6 and 7 therefore solves one of the extremely troublesome problems relating to conventional mixing devices, which is that of product leakage at their periphery upper and lower, and which results in significant waste

  the amount of product used.

  In addition to this, the assembly formed by the mixing device and the two flanges 6 and 7 has the advantageous characteristic of constituting a sort of enormous compression chamber whose role is to channel in a substantially vertical direction, with a very high acceleration. , the product flows oa and 1 inside the mixing device. Given the creation of this acceleration and of the pressurization proper to the mixing device according to the present invention, the energy used to rotate the shaft 4 can be used more rationally and can be less than that usually used. . Instead of having for example a maximum speed equal to 3000 rpm, the shaft 4 will only rotate at a maximum speed of 1500 rpm, this resulting in substantial energy savings. o0 Under the effect of the rotation of the blades 1A, 1B, 1C and 1D, the product a then mixes with product 1, the quality of the mixture and the shear rate being significantly improved, in particular due to the very high pressure. important implementation inside the mixing device and the particular shape given to the blades. The product cc and the product p3 in fact mix particularly well because they are confined together in the respective folds of the blades 1A, 1B, 1C and 1D. The product from the mixture of products a and B then goes to the openings O of the body 2A of the stator in a substantially horizontal direction represented by the arrows E in FIG. 5. As can be seen in FIGS. 4 and 5, I space between the lower part of the internal rim 6A of the collar 6 and the upper part of the internal rim 7A of the collar 7 constitutes a very significant compression zone of the product Io resulting from the mixture of products a and 3, which having the advantage to obtain a finer emulsion before the ejection of the latter through the openings O of the body 2A of the stator. The fineness of the emulsion obtained is also greater due to the characteristic of the necking (or rolling) zone of the mixing device according to the invention, that is to say the zone of passage between the trailing edge F of the blades 1A, lB, 1C and 1D

  and the ejection openings O of the body 2A of the stator.

  As can be seen in FIG. 6, the privileged positional relationship between the trailing edge F of the blades (here the blade 1A) and the openings O formed in the body 2A of the stator is particularly advantageous from the point of view of the shear rate. got. Because the trailing edge F has a V-shaped section, that the distance between the lower edge b of the cutout D and the upper edge b 'of the cutout D' corresponds to the length of the openings O and that the line L in the radial direction of the blade 1A (respectively the blades 1B, 1C and 1D) is substantially in the median horizontal plane of the body 2A of the stator, the openings O, on the one hand, will never be completely blocked by the edge of leakage F as is the case in the prior art, and, on the other hand, will allow a more regular ejection of the mixed product, which will have the effect of causing a less disturbance in the flows and an increase in the shear rate, this favorably influencing the quality of the emulsion obtained. The exit speed of the mixed product, which is known to be linked to the shear rate, will therefore also be greater, thus making the mixing device according to the invention

also effective on this point.

  It goes without saying that the embodiment of the mixing device which has been described above has been given for information only and is in no way limiting, and that many modifications can be easily made by those skilled in the art without necessarily depart from the scope of the invention. Thus, the rotor, instead of having four blades, could have three, six or eight, or even more if the body 2A of the stator has a large diameter. It is also thus that the sides P and P 'of each blade, instead of usually making an angle of 90, could form an obtuse or acute angle between them. As regards the arrangement of the blades 1A, lB, 1 C and 1 D on the shaft 1 E of the rotor, nothing obliges their corresponding lines of piure L, which respectively separate their sides P and P ', are perpendicular to the generatrices of the inner cylindrical part of the shaft 1 E. The blades could be arranged as well, so that their corresponding fold lines L are perpendicular to the central vertical axis of the shaft 1 E or else still be horizontally offset from this axis. It could even also be envisaged to produce blades 1A, 1B, 1C and 1D which have a shape different from that described in the present invention. For example, the sides P and P 'could be respectively curved either inwards or outwards, the latter form having the advantage of making it possible to make a gain on the power absorbed by the rotor 1, to obtain a higher output flow and increase the compression ratio of the product from the mixture of products c and ï inside the body 2A of the stator. Another possibility for the shape of the blades would be to attenuate the folds L and to give the blades 1A, lB, 1C and 1D the shape of an arc of a circle or an arc of ellipse, the center of the circle and the focal points of the ellipse being situated respectively in the median horizontal plane and in the median vertical plane of the stator body 2A. The two free ends of these blades would of course continue, in the same way as what was mentioned in the

  description, to form their horizontal leading edges respectively

  upper and lower, and it would also make sure that each blade

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  1A, 1B, 1C and 1D is arranged on the shaft 1E with its concavity turned in the direction of rotation of the rotor 1. Finally, as regards more particularly the mounting of the mixing device inside the mixing tank 3, it could be wise to remove the bolts 11 and 12 so that no screwing element appears in the mixing tank 3, so as to make the mixing device usable without restriction in the pharmaceutical field. To do this, the upper end of each baluster 8 (by analogy, of each upright 9) would be provided with a threaded rod intended to engage in a corresponding blind hole,

  o formed in the collar 6 (by analogy, in the collar 7).

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Claims (10)

  1. rotor mixer device (1) with blades (1A, lB, 1C, 1D), this rotor being intended to be immersed in a tank (3), characterized in that each blade of the rotor comprises two sections (P, P ') on either side of a line (L) of radial direction, these sections having, with respect to the axis of the rotor (1), inclinations in opposite directions so that each blade has a concavity in a defined meaning, corresponding to the meaning of rotor rotation (1).   2. Device according to claim 1, characterized in that the two sides (P, P ') of each blade are symmetrical with respect to a plane io containing the line of radial direction (L) and perpendicular to the axis of the rotor (1).   3. Device according to claim 1 or 2, characterized in that the sides (P, P ') of each blade (1A, lB, 1C, 1D) of the rotor are substantially of   flat shape and form an angle of 90 between them.   4. Device according to any one of claims 1 to 3, characterized   in that the leading edges (B, B ') of each blade (1A, lB, 1C, 1D) of the rotor are bevelled.   5. Device according to any one of the preceding claims,   characterized in that the blades (1A, 1B, 1C, 1D) each have cutouts (D, D ') which are formed in the area formed by their upper peripheral corner and their corresponding lower peripheral corner.   6. Device according to any one of the preceding claims,   characterized in that it comprises means (6, 7, 9) so that the blades (1A, lB, 1C, 1D) of the rotor (1) are arranged at a distance from the bottom of the tank (3).   7. Device according to any one of the preceding claims,   characterized in that it comprises means (6, 7) for preventing the ejection of products by the rotor (1) outside the axial extent of the 3o blades (1A, 1B, 1C, 1D). 14 2777804   8. Device according to any one of the preceding claims,   characterized in that it comprises a stator (2) surrounding the blades (1A, lB, 1C, 1D) of the rotor (1), this stator (2) having a body (2A) pierced with a multiplicity of openings d ejection (O) of products (a, ô) to be mixed, and in that the radial direction lines (L) of the blades (1A, 1B, 1C, 1D) lie substantially in a median plane of this stator. 9. Device according to claim 8, characterized in that the ejection openings (O) of the stator (2) extend parallel to the axis of the rotor (1) o and have an extent, in axial direction, corresponding substantially to the axial extent of the free ends, away from the axis, of the blades of the rotor (1).   10. Device according to claim 5, characterized in that upper and lower flanges (6, 7), mounted on the stator (2), each comprise an internal flange (6A, 7A) which are positioned respectively in the upper space and the lower space defined   each by the set of cuts (D, D ').