EP3639915A1 - Multi-level stirring element - Google Patents

Abstract

The invention relates to a stirring element for an agitator for mixing and / or homogenizing flowable media, with at least two stirring bodies (2) having an inlet opening and an outlet opening for the flowable medium, the inlet opening (5) being larger than the outlet opening (6) , characterized in that the stirring elements (2) belonging to the stirring element (1) are arranged on different planes which are normal (perpendicular) to the stirring shaft and each have a defined distance from one another in the axial direction.

Description

The invention relates to an agitator for mixing and / or homogenizing flowable media according to the preamble of claim 1, and an agitator equipped with this agitator.

Agitators are used in a wide variety of applications. Possible areas of application include the manufacture of paints and varnishes or the manufacture of beverages and food. The use of agitators is also regularly required in the manufacture of pharmaceutical products and cosmetics, including in the manufacture of paper and ceramics. Depending on the respective area of application, different agitator arrangements are used for mixing and / or homogenizing the respective substances. For example, drum and container agitators, which are arranged in or on the respective container, or self-supporting stand agitators are known. Small to large-volume containers for storage or for the transport of mixtures of substances can also be equipped with an agitator to prevent segregation during storage or transport. The agitator is matched to the material to be stirred as well as the shape and size of the respective container.

Agitators generally comprise an electric motor-driven shaft, by means of which one or more agitating elements connected to the shaft in a rotationally fixed manner are moved on a circular path. Inserted in a container with a flowable Due to their movement, the medium flows around the stirring elements. Depending on the shape of the stirring elements, their arrangement in the container and the speed at which the stirring elements are moved, certain flow conditions occur in the material to be stirred which cause the mixture to be mixed.

Agitators are known which are operated at high speeds in order to achieve the desired mixing effect by swirling the material to be stirred. This can lead to air intake and / or foam formation, which are undesirable in certain applications. This is the case, for example, in the manufacture of paints or in the manufacture of ceramics. High speeds, especially in combination with sharp-edged agitators, can also cause shear forces that can damage mixtures of substances that are sensitive to impact and shear. The sensitive mixtures of substances also include certain foods or biochemical products.

When certain color pigments are added, color mixtures can also have such a sensitivity. The high flow velocities generally associated with the high rotational speeds can also lead to heating of the material to be stirred. When mixing and / or homogenizing temperature-sensitive substance mixtures, however, it is important to avoid such heating. At least in the cases mentioned above, it is necessary to use a substance-gentle stirring method and a corresponding stirring device which enables the material to be mixed effectively even at low speeds.

From the DE 39 01 894 A1 an agitator is known which enables complete mixing of a flowable medium with a relatively low movement speed of the agitating elements. It is therefore also suitable for the treatment of sensitive mixtures of substances. The slow movement speed The stirring elements cause counter currents to form in the material to be stirred, which promote the mixing effect. The stirring times can even be shortened. Low drive power and short stirring times also reduce the amount of energy required. The known agitator comprises a shaft for rotating the agitators, which comprise arms running perpendicular to the longitudinal axis of the shaft, each of which carries a stirrer body with a conical tube section. The cross section of the conical pipe section narrows against the direction of rotation, ie in the direction of flow. The inlet opening for the material to be stirred is thus larger than the outlet opening. The longitudinal axis of the conical pipe section is also inclined downwards in the direction of rotation.

The specific design and arrangement of the agitators and their low speed of movement are intended to bring about flow conditions which enable extensive detection of the agitated material and thus effective and efficient mixing.

An improved agitator is out DE 10 2008 005 018 known. In this agitator, the agitators are designed as tubular sections which have four side walls, at least one of which has an arcuate or polygonal course.

In the known agitators, the arms which carry the agitator bodies are arranged on a common hub which is connected to the shaft for common rotation. This simplifies manufacture and, above all, assembly on the shaft of the agitator. However, the use of such a hub is not absolutely necessary for the invention. Instead, it is conceivable to arrange the arms on the shaft in a different way.

The entirety of the hub (if present), arms and stirring bodies is referred to as stirring device in the context of this application. In the context of this application, the stirring elements of the stirring element, regardless of their special shape, are also referred to as beakers. A beaker in the sense of the invention is therefore any stirring body through which the mixed material flows during operation.

In the known stirring elements, the cups are arranged in a common plane perpendicular to the direction of the drive shaft.

This arrangement, however, limits the speed at which the cups can move through the mix. Higher speeds cannot be achieved without drastically deteriorating the stirring effect. As a result, only a limited service input can be implemented, which, however, e.g. would be necessary for gassing, dispersing, emulsifying and powder intake.

It is an essential object of the invention to provide a stirrer and a stirrer equipped therewith which can be operated at a higher speed.

It is a further important object of the invention to provide a stirrer and a stirrer equipped with it, which enables a greater power input into the mix without reducing the stirring action.

Another important object of the invention is to provide an agitator and an agitator equipped therewith which can be used effectively at both high and low speeds.

The invention achieves these and other objects by means of the combination of features of the independent claims.

Advantageous refinements are defined in the dependent claims.

The essence of the solution according to the invention consists in the arrangement of the beakers belonging to a stirring element of a stirring stage on different planes which are normal (perpendicular) to the stirring shaft and each have a defined distance from one another in the axial direction. With regard to the longitudinal extent of the agitator shaft, the individual cups of the agitator are not at the same height, i. H. that the distance between the shaft end and arm (attachment of the cups) is different.

This prevents a negative mutual influence of the cups. At low speeds, the stirring medium usually has a sufficiently small inertia to react to the force exerted by the individual cups of the stirring element before the next cup of the stirring element reaches the position of the previous cup. However, if the speed is increased until the inertia of the medium is sufficiently effective, the effect begins with the previously known agitators that the subsequent cup disrupts the flow that arises.

By arranging the cups on different levels, however, the beginning flow is picked up and strengthened.

By the possibility. To be able to use higher speeds and the effect of the gradual flow build-up, smaller cups can be used in diameter with constant circumferential speed.

This increases the efficiency of the agitator considerably.

The stirrer preferably consists of a hub (or the stirrer shaft or part of the stirrer shaft) on which spoke-like rods are attached, which serve as arms for carrying the cups and in turn connect the individual cups with the shaft or the hub.

In a preferred embodiment, each beaker of the stirrer basically has a conical shape, similar to that of DE 39 01 894 known stirring body. The cup has an inlet opening and an outlet opening opposite the mixed material, the diameter of the inlet opening being larger than that of the outlet opening.

It is preferred, but is not essential, that all beakers of the agitator are of the same shape and size.

The stirring element preferably consists of a metallic material such as steel.

In preferred embodiments, the stirring element comprises at least two, more preferably at least three, beakers, which are advantageously arranged symmetrically around the hub or stirring shaft.

The cups can advantageously be arranged such that their longitudinal axis extends at an angle not equal to zero to the plane perpendicular to the main axis of the agitator shaft, in which the attachment point of the corresponding arm lies on the hub or shaft. The cups are thus inclined or angled with respect to the direction of rotation of the stirrer. The angle does not have to be the same for all the beakers of an agitator. The cups can advantageously be movably attached to the arms so that their angular position with respect to the agitator shaft can be adjusted.

The agitator according to the invention comprises a drivable agitator shaft and at least one agitator according to the invention, each agitator at least comprises two stirring bodies (beakers) fixed to the shaft via a support arm. The agitator shaft can preferably be driven by an electric motor, so that each agitator body attached to the outside of a support arm can be moved along a circular path concentrically to the longitudinal axis of the shaft. The agitator preferably has at least one agitating element which comprises three agitating bodies arranged in a star shape at the corners of an imaginary isosceles triangle.

The support arm preferably has a low overall height in the direction of the longitudinal axis in order to reduce the flow resistance. A hub or sleeve, to which the support arms are fastened, is preferably used to fasten the stirring elements to the stirring shaft. It can be provided that the support arms are connected by a screw connection to the hub or directly to the agitator shaft. In addition, the stirring elements or the support arms can also be fastened to the stirring shaft by means of a plug-in connection, provided that a connection which is non-rotatable at least in the direction of rotation of the shaft is ensured.

A screw or plug connection for attaching the agitator to the agitator shaft of the agitator should be detachable in order to enable the exchange of the agitator. It can be provided that the cups are detachably and thus interchangeably arranged on the support arms. Depending on the type of material to be stirred or the size of the container, the stirrer or the stirring elements and / or beakers can then be matched to the respective application in terms of their specific shape, size or number.

It may be necessary to insert the stirring elements into a container. If the container has only a small opening, it can be advantageous if each cup is connected to the agitator shaft by means of a hinged and / or pivotable support arm. The support arms are then pivoted in order to insert the stirring elements into the container in an orientation parallel to the shaft longitudinal axis and the stirring bodies are brought together. In this way, the discharge of the Agitator are reduced, so that the insertion of the stirring elements is also possible through small openings. The agitators can be reset automatically by the action of the centrifugal forces when the agitator is started up. In addition or instead, resetting mechanisms can be provided, for example springs, which - if necessary to assist - cause the resetting of the stirring elements.

The above-described design of an agitator according to the invention or an agitator equipped with such agitators make it possible to save energy and time when mixing and / or homogenizing a flowable medium and thus allow a particularly efficient agitation process to be carried out. In addition, differently designed stirrers, stirrers or stirrer arrangements can be kept available and replaced if necessary, so that the right stirrer can be provided for every application. The specific design and arrangement of the stirring elements, which is matched to the material to be stirred and the container, also counteracts the formation of dead zones, since the material to be stirred is completely captured and mixed excellently.

• Fig. 1 Ansichten einer bevorzugten Ausgestaltung eines erfindungsgemäßen Rührorgans, und
• Fig. 2 die Ergebnisse eines Vergleichs der bevorzugten Ausgestaltung gemäß Fig. 1 mit einem bekannten Becherrührer.

An embodiment of the invention is explained below with reference to the drawings. Show it:

• Fig. 1 Views of a preferred embodiment of a stirring element according to the invention, and
• Fig. 2 the results of a comparison of the preferred embodiment according to Fig. 1 with a well-known stirrer.

Fig. 1 shows a stirring element 1 with three stirring bodies (cups) 2, which are each fastened to a hub 4 by means of a support arm 3. The cups 2 are symmetrical the hub or agitator shaft arranged around. The hub 4 is concentrically attached to an agitator shaft (not shown). The stirring element consists of a metallic material such as steel. In the exemplary embodiment, each cup 2 is attached to the support arm 3 by means of a welded connection, but instead can be carried out, for example, via a detachable connection, for example a screw connection, or by means of a swivel joint.

The stirring bodies or beakers 2 are conical hollow bodies with an inlet opening 5 and an outlet opening 6 of smaller diameter for a medium flowing through. All cups 2 of the agitator 1 are of the same shape and size in the exemplary embodiment, but could be different.

The inlet opening 5 lies in the direction of rotation of the agitator 1 provided in operation on the front of the cup, and the outlet opening lies correspondingly on its rear side.

The cups 2 are arranged on different planes which are normal (perpendicular) to the agitator shaft and each have a defined distance from one another in the axial direction. With regard to the longitudinal extent of the agitator shaft, the individual cups 2 of the agitating element 1 are therefore not at the same height, ie. H. that the distance between the shaft end and support arm 3 (attachment of the cups) is different for all cups 2.

The cups 2 are arranged so that their longitudinal axis extends at an angle unequal to zero to the plane perpendicular to the main axis of the agitator shaft, in which the attachment point of the corresponding support arm 3 lies on the hub 4. The cups 2 are thus arranged inclined or angled with respect to the direction of rotation of the stirring element 1. The angle does not have to be the same for all beakers 2 of a stirring element 1. The cups can be movably attached to the support arms 3 in such a way that their angular position relative to the agitator shaft is adjustable.

Not shown, but still part of the agitator is a (preferably electromotive) drivable agitator shaft, which is concentrically connected to the agitator for common rotation. The shaft can, for example, be part of a stand agitator or another agitator that can be inserted into a container containing a flowable medium.

The connection of the stirring element to the stirring shaft is expediently detachable, so that the stirring element can be exchanged and adapted to the respective application. Such an optimized agitator enables complete mixing of the material to be mixed in a very short time and with reduced drive power, so that the process can be described as particularly efficient.

Fig. 2 shows the power consumption of an agitator, which is provided with an agitator described above (lower curve), compared to the power consumption of an otherwise identical agitator, in which, according to the prior art mentioned at the beginning, all beakers are arranged in the same plane (upper curve). The mix is always the same in terms of type and quantity. The only difference is the arrangement of the cups, in three different levels in the invention, but in the same level in the prior art.

As Fig. 2 shows, the power consumption in the agitator according to the invention at speeds above 500 rpm is significantly lower than in the conventional agitator.

This corresponds to an improved performance input into the mix. The agitator according to the invention can also be operated at higher speeds than the conventional agitator without the stirring effect suffering.

Claims (9)

Stirring element for an agitator for mixing and / or homogenizing flowable media, with at least two stirring bodies (2) having an inlet opening and an outlet opening for the flowable medium, the inlet opening (5) being larger than the outlet opening (6), characterized in that the stirring body (2) associated with the stirring element (1) is arranged on different planes which are normal (perpendicular) to the stirring shaft and which each have a defined distance from one another in the axial direction. Stirring element according to claim 1, characterized in that the stirring body (2) have a conical shape. Stirring element according to claim 1 or 2, characterized in that at least two, more preferably at least three stirrer bodies (2) are arranged symmetrically around a hub (4) or a stirrer shaft by means of support arms (3). Stirring element according to one of the preceding claims, characterized in that the longitudinal axes of the stirring body (2) run at an angle unequal to zero to the plane perpendicular to the main axis of the stirring shaft, in which the attachment point of the corresponding support arm (3) lies on the hub or shaft. Stirring element according to one of the preceding claims, characterized in that the stirring body (2) is movably attached to the support arms (3) in such a way that its angular position relative to the stirring shaft is adjustable. Stirring element according to one of the preceding claims, characterized in that at least one, preferably each stirrer body (2) has a hinged and / or pivotable support arm (3) is connected to the hub (4) or the agitator shaft. Agitator for mixing and / or homogenizing flowable media with a drivable agitator shaft and with at least one agitator () according to one of Claims 1 to 5, each agitator (1) being fixedly connected to the agitator shaft in the direction of rotation. Agitator according to claim 7, characterized in that, during operation, the agitator bodies (2) are arranged rotationally symmetrically and at the same distance from one another. Agitator according to claim 7 or 8, characterized in that in operation the longitudinal axis of the support arm (3) is oriented substantially perpendicular to the longitudinal axis of the agitator shaft.

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