EP0335096B1 - Apparatus for mixing and homogenizing fluid products - Google Patents

Abstract

An apparatus for mixing and homogenising fluid products comprises a vacuum vessel (1) which can be closed by a cover (3), a homogenising device (16, 17) arranged underneath the former and a mixing or stirring device (18-23) fitted to the cover. The homogenising device (16) is arranged at a vertical suction distance above the vessel bottom (13) and, in the lower part of the vacuum vessel (1), a rotatable hollow guide cone (34) is provided which widens upwards to an annular flow gap towards the vessel wall (36). The material extracted laterally from the vessel bottom (13) is conveyed into the upward-widened guide cone (34) and along the conical inner surface upwards/outwards to the upper edge (38) and along the annular flow gap thereof to the vessel wall (36). The material thus largely spreads uniformly with steady thinning of the layer and flows in a thin annular stream (from) the upper edge (38) of the cone to the vessel bottom (13) and is again conveyed upwards by the homogenising device (16). The large shear forces in the region of the upper edge (38) of the guide cone (34) here contribute to more extensive comminution and homogenisation of the material. <IMAGE>

Description

The invention relates to a device for mixing and homogenizing flowable products, in particular for the pharmaceutical, cosmetic and food industry, with a vacuum container which can be closed by a lid, a homogenizing device arranged at the bottom thereof and a mixing or stirring device arranged on the lid.

A device of this type is known from DE-A-15 07 528. There, an agitator with agitating arms which protrude close to the container wall is driven by a drive motor hanging under the container bottom and a mixing mechanism led down from the lid is driven by a motor which has just been arranged. The toothed colloid mill used as a homogenizer is arranged eccentrically hanging on the bottom of the container and conveys the material through a circulation line for degassing to a centrifugal plate arranged under the lid, which Spreads well by centrifugal force and then hurls it through a ring sieve. In this way, in addition to the treatment processes already mentioned, emulsification, dispersion and wetting can also be carried out in the same device.

However, this older design also has some disadvantages. On the one hand, the design as such is too complex, the circulation line can clog or also hinder the uniformity of the flow, and the goods are stressed in many ways by this circulation, in particular warmed and sometimes at least momentarily undergoes a change in quality.

Furthermore, a device for mixing and / or degassing highly viscous media under vacuum is known from DE-PS 24 45 287, with an equally shaped tube revolving in a conical or cylindrical vacuum container, on the outside of which a conveyor spiral is formed. The processed mass between the inner wall of the container and the outer surface of the circumferential tube is conveyed upwards by means of a drag flow to an overflow, from where it flows back into the material level. The main aim here is to degas the highly viscous material as completely as possible and that the rotor should be able to be driven at a variable speed. A low speed is sufficient for this, which is also preferred there. In any case, the rotor can hardly be operated at high speeds, since the entire upward conveyance is brought about by the screw spiral, which can easily lead to overheating and therefore to an undesirable change in the quality of the material.

Finally, a device for accelerating the uniform mixture of powder and liquid is known from Japanese Patent Application Laid-Open No. 57-127431 (A), the defoaming being achieved first of all by combining a vacuum mixer for liquid and powder uses fluid with a device for comminuting the powder in the rotating mixture. A constant amount of liquid is placed in a vacuum container, then a high-speed drive and a slow-speed drive are started in order to supply a constant amount of powder and then to seal the container.

A standing screw pump with stirring blades rotates and mixes the liquid as it runs over the top surface of an umbrella-shaped plate, with two or more cone-shaped rollers running on their axes along the surface of the plate and with a device being provided that the aggregates of undispersed and dispersed powder repeatedly crushed in the mixed liquid and subjected to vacuum for a predetermined time. This device accelerates the uniform mixing of the liquid, whereby foaming occurs.

The screw conveyor used there, however, does not allow fine particles to be dispersed in a liquid phase due to the very low impact of shear forces, which is why the object of the invention is a homogenizer which, in contrast to the screw conveyor design, generates significantly higher shear forces and thus also disperses fine particles in a liquid phase enables.

On the other hand, an optimal degree of deaeration is only achieved when the product is exposed to the vacuum as a film for a certain time. This film formation is achieved in the subject matter of the invention by the guide cone, since the dispersed suspension is spread out into a thin film on the inside of the cone by the centrifugal force that occurs, which layer is increasingly thin in layers runs steeper, so that even the finest air bubble is exposed and burst.

Furthermore, the device according to the Japanese laid-open patent lacks the preferred function of two-stage processing of the product, as is achieved in the subject of the application by alternating right and left rotation of the central shaft.

Both versions have in common that they enable rapid mixing of powder in a similar manner by mixing propellers with high throughput. When changing the direction of rotation, however, the mixing propeller transports the product transversely downward, so that inevitable dispersion must take place via the high-shear tooth colloid mill. In addition, the possibility of reversible treatment of dispersions on units of less than 10 mµ particle size and the removal of microbubbles from a suspension in a very short time is eliminated by the possibility of optimal film distribution on the inside of the guide cone.

The subject matter of the invention is therefore clearly superior to the proposal from the Japanese published patent application, which is shown in increased production output and in significant improvements in product quality, and can thus be used as an indication of higher quality of invention.

The invention is based on the device defined at the outset for mixing and homogenizing flowable products and pursues the task of changing the known mixing and homogenizing device in the simplest possible manner in such a way that the material is uniform, if possible without stopping Experienced stress.

On the basis of the type defined at the outset, the device according to the invention is characterized in that the homogenizing device is arranged with such a vertical suction distance above the bottom of the container, that the flowable product can be sucked off for carrying out a treatment, and that in the lower part of the vacuum container a Homogonisiereinlaufende rotating hollow guide cone is provided, which widens upwards and forms a flow ring gap with the container wall.

In this way, the homogenizing device can suck the material directly to the side of the container bottom and convey it into the guide cone, which widens upwards. The material is conveyed upwards / outwards along the conically widened inner surface of the guide cone up to its upper edge into the flow ring gap which it forms with the container wall. The material spreads evenly with constant thinning of the layer and flows in a thin ring stream from the top of the cone to the bottom of the container.

There is also a fairly extensive degassing of the goods; it is essential, however, that the wall of the guide cone does not have to be equipped with pronounced conveyor blades, so that the guide cone only needs to support the conveying effect exerted by the homogenizing device on its wall and can thereby develop its guiding function for the spreading of the material over the container cross section. As a result, much higher rotational speeds are permissible than with a conveyor spiral arranged on the entire outer surface. The material is also only slightly rotated by the guide cone, so that there are large speed differences on the wall of the guide cone, which result in high shear forces and thus cause further comminution and homogenization of the material.

Because the vacuum container is constantly on during processing remains connected to a vacuum pump, the gas content of the goods is reduced from circulation to circulation. This proportion, like the degree of homogenization or the other desired properties of the good, can be measured automatically and, if necessary, the process can be terminated if minimum qualifications are met with regard to a series of predetermined measured values.

Narrow flow cross sections result at most in the homogenizing device acting as a circulation pump. There is therefore no risk of any constipation, overuse or change in the quality of the goods, which can relax very largely and evenly. The guide cone itself contributes to the homogenization through the thin-layer flow on its surface and also to the dispersion caused by the force of gravity of the goods. It also takes on a limited function for the mixture of the good components.

According to a preferred embodiment of the invention, the homogenizing and mixing or stirring device are driven by two drive shafts arranged centrally in the container axis, the inner drive shaft being at least connected to the homogenizing device, while the outer drive shaft is connected to a cage-like stirring basket. The drives are expediently arranged on the container lid. The latter enables better overview and sealing as well as easier maintenance. The assignment of the various aggregates is also simplified. In addition, the guide cone can thus be connected to the rotor of the homogenizing device, for example by being attached to the inner drive shaft by a spoke star.

The surface of the guide cone can have a precisely geometrically smooth surface, but can also be structured, preferably in the circumferential direction, in particular at the same spacing be radially changed, such as wavy, tapered or arched out of the surface line.

The stator of the homogenizing device can be attached to the arms of the mixing basket that are clinging to the container wall. The direction of rotation and the speed of rotation of the homogenizing device are therefore predetermined by the difference or sum of the speeds of the two drive shafts. This favors the use of a toothed colloid mill which is set up for reversing operation and which, owing to its low weight and small dimensions, can be reliably held and guided even at higher speeds without impairing its fine grinding and emulsifying function.

The circulation capacity of the homogenizing device or the toothed colloid mill can be significantly increased if, according to a further development of the invention, the mill rotor has or forms an axial screw wheel, in particular for its attachment to the inner shaft, with conveyor blades separated from one another by spacing sectors in an annular conveyor channel. In this way, two currents rotating in the same direction can be used, firstly the external flow leading from the already existing outlet of the toothed colloid mill close to the inner wall of the guide cone and secondly an internal flow surrounding the inner shaft in the guide cone.

In certain operating states, it may be expedient to throttle or shut off the internal flow, which can be accomplished by a cover element arranged on the axial paddle wheel, which can be pivoted between stops around the circumferential angle of a spacing sector. This can be done arbitrarily, but is preferably carried out automatically by the pumping medium remaining with respect to the rotor, in particular when the rotor reverses in speed.

In this way it can be ensured that the internal flow only runs in the same direction as the normal outlet of the toothed colloid mill, that is, the material is not circulated only around the edge of the pump rotor.

In order to break the vortex formation that easily occurs during mill operation with parts that can only be rotated about a common axis and to calm the flow, a vortex breaker can project cantilevered from above approximately axially at a radial distance from the container axis into the guide cone. This arm attached to the slow-moving agitator basket counteracts above all the turbulence resulting from the fast-running homogenizing device.

The homogenizer and agitator are preferably connected to different drive motors, of which at least one is reversible and at least one, in particular both, is or is speed-controllable. In this way, practically all deviations from the preprogrammed processing result can be corrected.

In order to facilitate this, at least one, in particular both, drive motors is or are expediently connected to a control for automatically controlling the drives according to predetermined or automatically detectable operating data of the device and / or the processed goods.

A control computer of the device is preferably assigned a comparison computer which determines control values from all the specifications and functional values supplied to it and prepares them for transmission to the drive motor or motors.

Further refinements and advantages of the invention are defined in the subclaims and are now intended to be based on the schematic representation of a device according to the invention for mixing and homogenizing flowable products to be discribed.

Fig. 1

eine schematische Übersichtsdarstellung dieser Vorrichtung mit Schaltbild,

Fig. 2

einen vergrößerten Teilschnitt einer Zahnkolloidmühle der Homogenisiervorrichtung,

Fig. 3

eine Ansicht auf ein in der Zahnkolloidmühle fest angebrachtes Schaufelrad in der Öffnungsstellung einer Abdeckvorrichtung,

Fig. 4

die Darstellung aus Fig. 3 mit geschlossener Abdeckvorrichtung und

Fig. 5

einen Umfangsschnitt durch das Schaufelrad nach der Linie V-V in Fig. 4.

Show it

Fig. 1

1 shows a schematic overview of this device with a circuit diagram,

Fig. 2

2 shows an enlarged partial section of a tooth colloid mill of the homogenizing device,

Fig. 3

1 shows a view of a paddle wheel fixedly attached in the toothed colloid mill in the open position of a covering device,

Fig. 4

the representation of FIG. 3 with the cover device closed and

Fig. 5

a circumferential section through the paddle wheel along the line VV in Fig. 4th

In the drawing, (1) denotes a vacuum container, the upper opening of which can be closed by means of flanges (2) by a cover (3). This lid can be raised in a known manner, for example by one or more hydraulic cylinders or other drive motors, in order to make the interior (4) of the container accessible for cleaning purposes, for example.

The material to be processed can optionally be filled into a funnel (5) arranged on the lid (3). Its connection to the interior (4) is hermetically sealed by a slide (6) which can be adjusted by means of a crank or similar operating element (7).

However, the material can also be sucked in via the funnel (10) and line (11) with shut-off valve (12) through the container bottom (13) under vacuum. The finished material is optionally discharged by opening an outlet valve (14) which is located centrally in the container axis (19) in the container base (13).

The vacuum container (1) is connected in a manner not shown to a vacuum pump. It can be provided in the lower cup-shaped container part or in the lid (3). The lower part of the container has a double jacket (15) through which the heating and / or cooling medium flows. For example, the container can be fixed, movable on a carriage, tiltable about a horizontal axis or arranged on a turret body rotatable about a preferably vertical axis and the like.

A homogenizing device (16), which preferably has a toothed colloid mill (17), and a stirring basket (18) are rotatably mounted in the vertical container axis (19). The homogenizer can be driven by the inner shaft (20) and the stirring basket (18) by means of a tubular outer shaft (21). While the inner shaft (20) starts from the upper mixer motor (22), the outer shaft (21) is connected to the lower agitator motor (23) and is mounted in a bearing tube (8) that is flanged onto the cover (3). Both shafts are hermetically sealed through the cover (3) through ring seals (24, 25). Compared to an arrangement of the motors (22, 23) below the tank bottom (13), this facilitates the rotating leadthrough and sealing.

Both motors (22, 23) and their shafts (20) and (21) can be driven according to the arrows (28) and (29) in both directions of rotation with variable speed, preferably using frequency converters.

The stator (30) of the toothed colloid mill (17) is held firmly on the stirring basket (18), while the rotor (31) is connected to the inner shaft (20). The effective rotational speed of the tooth colloid mill thus corresponds to the vectorial difference in the rotational speeds of the shafts (20) and (21). You expediently run in opposite directions.

A guide cone (34) sits on the inner shaft (20) by means of a sleeve (32) and spoke arms (33) just above the toothed colloid mill, which cone extends the shape of e.g. from the top of the toothed colloid mill to the middle of the container. has a smooth truncated cone with a tip angle of about 60 ° and comes close to the inner surfaces of the mixing bowl (18). While the outer shaft (21) with the mixing bowl has a speed in the range of 20-100 U / min, the inner shaft (20) runs at a rotation speed of approx. 500-3000 U / min. Since all parts rotate around the shaft of the axis (19), a pronounced central vortex is usually established. In order to counteract this, a vortex breaker (35) is led down from the stirring basket (18) at a radial distance and parallel to the container axis (19) into the guide cone (34). In this way, the local axis of rotation is shifted out of the container axis (19) with constant change, which brings a further mixing effect.

The spoke arms (33), like the vortex breaker (35) and the other rods (26) of the stirring basket (18), are designed as cylindrical tubes, but can also have other suitable shapes. The stirring basket (18) also has a plurality of scraper blades (37) on the inner wall (36) of the vacuum container (1) and scrapers (47) or the like on the outer wall surface of the guide cone.

From the drawing it can easily be seen that there is constant thin-layer circulation of the treated material in the vacuum container. The material is taken up by the toothed colloid mill (17) during normal operation from the container base (13), crushed, homogenized and conveyed up into the interior of the guide cone (34), where it runs up under centrifugal action on its inner wall and diagonally upwards / outwards is thrown. Particularly high shear forces occur on the contact surface of the goods on the guide cone (34). An approximately hyperbolic liquid level is formed in the lower part, the thickness of the material layer becoming smaller and smaller towards the upper edge (38) of the guide cone, until the material is thrown outwards towards the inner wall (36) or from the upper edge (38) onto the Container bottom (13) runs down. When the desired final state is reached after a series of processing cycles, the finished goods are discharged.

As can best be seen from FIG. 2, an axial paddle wheel (46) with an inner ring (54) and an outer ring (55) is used to fasten the rotor (31) of the toothed colloid mill (17), which is arranged in an annular manner by means of star-shaped conveying blades (49) Delivery channel (50) are connected. In this way, a strong rotational flow is built up centrally to the container axis (19) in the guide cone (34), which serves primarily for mixing, while the smaller quantity of material passed through the pump teeth (56) between the stator and rotor is primarily exposed to the homogenization. When returning to the bottom of the container, the material flows mix again and again, so that approximately the same quality of the material can always be achieved in the entire vacuum container.

However, while the external flow is independent of the direction of rotation of the rotor (31), the direction of flow in the delivery channel (50) is reversed when the direction of rotation changes. In order to largely avoid or at least reduce opposing flows, a cover member (51) in the form of a cover disk is therefore mounted above the delivery channel (50) in the paddle wheel (46). This covering element has three sector wings (57) which form spacing sectors (58) of equal size between them, each with a tip angle of 60 °. The conveyor blades (49) have the same sector area, so that the paddle wheel (46) as well as the cover member (51) have the approximate shape of a Maltese cross Has. In the open position in FIG. 3, the conveying blades (49) are therefore covered by the sector blades (57) in their position (57) from FIG. 5, so that conveying can be carried out through the spacing sectors (58). In contrast, in the closed position according to FIG. 4, the sectors of the same size join together. This can be designed as required so that the flow is completely or partially blocked.

In order to achieve a complete blockage, a triangular cross section is provided for the conveyor blades (49) according to FIG. 5, but this is unfavorable for flow, especially if the end face is at the front in the circumferential direction. To improve the shape of the flow, a triangular extension (49 ') can be connected to this end face in the opposite position.

The conclusion can be improved once with aerodynamically thin conveyor blades (49) if two covering members (51) are arranged one above the other, one of which is firmly connected to the pump wheel or the pump rotor, while the other remains in a first direction of rotation under the fixed covering member , but is completely swung out from under this by reversing the speed. In this way, a plurality of sector-shaped lamellae can also be arranged one above the other and swung out in succession about the container axis (19). Here too, however, the flow cross section of the delivery channel (50) is restricted.

However, this cross section can be obtained entirely if a central shutter, as is known in photographic cameras, or a shutter in the manner of a photographic aperture is used. For example, you can swivel two panel elements from opposite sides towards the center, so that for four cover elements a total of only two layers the thickness of a lamella needed. In this way, the conveying channel (50) can be fully opened, for example when the diaphragm is open. However, in order to reduce possible vibrations, it is recommended to be able to work in normal conveying operation with the shafts (20, 21) rotating in the opposite direction and thus with the greatest vectorial speed difference or effective speed of the rotor (31) relative to the stator (30). The slats are held firmly on the outer stops by centrifugal force.

In the closed position of the cover or the lock, the slats must be pressed inwards against the effects of centrifugal force. They are then subjected to greater vibration, so that here the shafts (21, 22) should run in the same direction in order to achieve the lower effective speed of the mill rotor.

Part of the goods can also be taken continuously or intermittently as a sample and checked for its nature, such as viscosity, grain size, temperature and the like. Detectors can also be embedded in the rotatably held container (1).

In this way it is possible to preselect certain operating values, in particular the motor current consumption, with a speed of approximately 800 rpm, for example, at a setting of 20 amps. at a viscosity of 5000 cp. If the viscosity drops to approx. 1000 cp due to processing and wetting of the dry products, the speed increases to approx. 1300 rpm until the preset 20 amps are reached again. This current consumption can be specified either for one of the two individual motors or for both motors. It is also possible to specify a ratio of the current consumption, as well as the ratios of different operating values, and to keep it constant as it continues. Above all, it can be specified exactly what energy should be used in the unit of time. These default values can also be automatically adjusted in addition to other operating values.

Claims (19)

1. Apparatus for mixing and homogenising free-flowing products, in particular for the pharmaceutical, cosmetics and foodstuffs industries, having a vacuum container (1), which can be closed by a cover (3), a homogenising device (16) which is disposed at the bottom inside the vacuum container, and a mixing and agitating device (18, 22, 23) disposed on the cover (3), characterised in that the homogenising device (16) is disposed at such a perpendicular distance above the container base (13), that the free-flowing product can be drawn off in order for treatment to be performed; and in that the lower part of the vacuum container (1) is provided, directly above the homogenising device, with a rotatable, hollow guide cone (34) which opens into the homogenising device, which widens upwardly, and which defines an annular flow gap with the container wall (36).
2. Apparatus according to Claim 1, characterised in that the homogenising device (16) and the agitating device (18) can be driven by two drive shafts (20, 22) which are disposed centrally in the container axis (19), in particular by the container cover (3), the inner drive shaft (20) being connected at least to the homogenising device (16), whilst the outer drive shaft (22) is connected to a cage-like agitator basket (18).
3. Apparatus according to Claim 2, characterised in that the guide cone (34) is secured to the inner drive shaft (20) by a star of spokes (32, 33).
4. Apparatus according to Claim 3, characterised in that the spokes of the star of spokes have externally a cross-section which is favourable to flow, in particular a cross-section with a conveying effect.
5. Apparatus according to any one of Claims 1 to 4, characterised in that the surface of the guide cone (34) is precisely and geometrically smooth.
6. Apparatus according to any one of Claims 1 to 4, characterised in that the guide cone (34) has a structured, radially varied surface, preferably in the peripheral direction, in particular with identical division spaces.
7. Apparatus according to Claim 6, characterised by the undulating structure of the surface of the guide cone (34) in the manner of a wash board.
8. Apparatus according to Claim 7, characterised in that the undulation extends inclined relative to the axial plane of the guide cone (34) in the peripheral direction, in particular helically.
9. Apparatus according to any one of Claims 6, 7 or 8, characterised in that the wall of the guide cone (34) is curved out of a generated line.
10. Apparatus according to any one of Claims 1 to 9, characterised in that the guide cone (34) has a toothed upper edge (38) and/or is provided with wall apertures.
11. Apparatus according to any one of Claims 1 to 10, characterised by strippers (47) which are retained inwardly on the agitator basket (18) and abut the outer surface of the guide cone (34).
12. Apparatus according to any one of Claims 1 to 11, characterised in that the stator (30) of the homogenising device (16, 17) is mounted on the arms of the agitator basket (18) which are adapted internally to the container wall.
13. Apparatus according to Claim 12, characterised in that the homogenising device (16) comprises a toothed colloid mill (17) which is arranged in particular for reversing operations.
14. Apparatus according to Claim 13, characterised in that the mill rotor (30) comprises or forms an axial impeller which is used in particular to secure the latter to the inner shaft (20) and which has conveyor blades (49) which are separated from one another by spacer segments (48), in an annular conveying duct (50).
15. Apparatus according to Claim 14, characterised by a locking member (51) which is disposed on the axial impeller (46) and which can be pivoted between stops about the peripheral angle of a spacer segment (48), in particular by the conveying medium retained opposite the rotor (31), automatically between opening and closing positions with respect to the conveyor blades (49).
16. Apparatus according to any one of Claims 1 to 15, characterised by a vortex breaker (35) which projects from the top approximately axially at a radial distance from the container axis (19) in a cantilevered manner into the guide cone 34).
17. Apparatus according to any one of the preceding claims, characterised in that the homogenising device (16) and the agitator (18) are connected to different drive motors (22, 23) of which at least one is reversible and at least one, in particular both, is/are formed such that the speed can be regulated.
18. Apparatus according to Claim 17, characterised in that at least one, and preferably both, drive motors (22, 23) is/are connected to a control device for automatically controlling the rotational speeds in order to keep the drive output constant according to predetermined or automatically detectable operating data of the apparatus and/or of the processed material.
19. Apparatus according to Claim 18, characterised in that a comparator computer (45) which determines control values from all the requirements and functional values supplied to it and prepares them for further transmission to the drive motor or motors (22, 23), is associated with a control apparatus (42).

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