DK2364770T3

DK2364770T3 - Mixer tool

Info

Publication number: DK2364770T3
Application number: DK11001604.5T
Authority: DK
Inventors: Guido Egler
Original assignee: Teka Maschb Gmbh
Priority date: 2010-03-11
Filing date: 2011-02-28
Publication date: 2017-01-23
Also published as: PT2364770T; EP2364770A1; EP2364770B1; PL2364770T3; ES2608674T3; DE102010011113A1

Description

The present invention relates to a tool for a mixing device, in particular for a mixing device for mixing solids.

Mixers for mixing solids, in particular for the manufacture of hydraulically bonded substances such as concrete or mortar, are familiar in a range of different types. An essential requirement in respect of such mixers is, on the one hand, an adequate mixing effect in order to ensure good homogeneity of the mixing and the best possible prevention of the build-up of the material to be mixed on the mixing tools that are used. The homogeneity is an essential prerequisite for the manufacture of products with constant product quality in accordance with the specifications.

In particular in the case of so-called ring trough mixers, in which mixing tools are guided on mixer arms through a ring-shaped mixing chamber (suchlike mixers are used extensively in the manufacture of concrete and mortar), the achievement of an adequate mixing effect often calls for special measures, which, on the one hand, can reside in the geometrical configuration of the mixing tools themselves, in the choice of the speed of rotation and the direction of rotation of the mixer arms or also in the geometrical arrangement of the mixer arm in the mixing chamber.

In addition to the actual mixing tools, scraper devices also after find an application as a rule in suchlike mixers, with the intention of preventing any build-up or adhesion of the material to be mixed on the bottom surface or the side walls of the mixer.

In addition, so-called agitators find an application in a number of mixers of this kind, with the intention of increasing the mixing effect. These are generally arranged in such a way that they produce their effect where the flow of solids being mixed has settled down once more from the effect of the actual mixing tool to such an extent that the flow of solids being mixed runs essentially parallel, with inadequately thorough mixing at these points as a consequence thereof.

The mixing or agitating tools that are used usually have rectangular or square cross sections. Suchlike tools have the disadvantage that they produce an area of shadow in the flow. The result of this is that material from the solids being mixed can build up or adhere on the surfaces and edges of the tools, in particular also on the fastening elements by means of which the actual mixing or agitating tools are connected to appropriate drive shafts. If suchlike material becomes detached again at a later stage and falls back into the material to be mixed, this can lead to inhomogeneities in the composition of the end product and thus to products that are not in accordance with the specifications. This problem becomes particularly serious if a change of product has taken place in the intervening period, that is to say if a different product, for example with a different colour, is to be produced in the mixer. Materials which become detached from a previous product batch lead to colour changes in the product, which are not accepted by the customer. The human eye is very sensitive to even minor changes in colour.

In order to avoid these problems, it is absolutely essential in any batch change, in particular in the case of different colour settings, that all product and feedstock material residues from the previous product batch are removed completely by appropriate cleaning. This requires a considerable commitment of time and financial resources, and produces a considerable quantity of waste water, which must be disposed of in a correspondingly expensive manner.

For the reasons outlined above, it is important to make mixing or agitating tools available, in which the build-up of material is minimized and, at the same time, the mixing effect is not compromised. In addition, light cleaning should be possible in conjunction with a batch change.

Familiar from DE 198 05 639 are agitating tools, which have a body in the form of a pyramid or a frustum of a pyramid with a polygonal base surface. These tools preferably have the form of a bell that is open towards the bottom, so that the fastening elements, with which the agitating tools are fastened to the supporting arm, can be arranged inside the body of the agitating tool. Their form that is open towards the bottom means that these fastening elements are accessible for replacement.

Direct exposure of the fastening elements to the flow of solids being mixed is avoided through this configuration according to DE 198 05 639, the effect of which is to reduce wear, and the replacement of the agitating tools should be possible without difficulty. It is possible, however, for solids being mixed to be deposited with time in the hollow cavity of the bell that is open towards the bottom, which to all intents and purposes can only be removed mechanically, since, due to the absence of a flow, re-separation during operation is no longer possible; this leads to the need for more meticulous cleaning, since hollow cavities of this kind are difficult to clean completely. A further consideration is the fact that a nut of the fastening element, which is arranged in the open hollow cavity of the tool, becomes extremely stiff in operation over longer periods due to the build-up of the material, which impedes a tool change. Finally, the geometrical configuration of these agitating tools imposes the need for a relatively complicated fastening to the appropriate supporting arm.

On the whole, therefore, the agitating tools according to DE 198 05 639 cannot be fully satisfactory as far as concerns the flexibility during the product change and the exchange of the agitating tools. Since suchlike tools are typical wearing parts of suchlike mixers, which require to be replaced at regular intervals, their easy change is likewise an important criterion in order to avoid lengthy and costly downtimes of the mixer.

Familiar from DE 196 40 770 is a blade for rotating stirrers intended for mixing abrasive substances, in which the pressurized side of the blade is provided with a wear-resistant layer of a granular material. This layer must be applied to the surface of the basic body of the blade. This should be possible for stability reasons (the blades are subjected to considerable mechanical loading during the mixing process), but without adversely affecting the structure of the metallic basic body. This requires expensive subsequent machining of the basic body.

Although the blades described in DE 196 40 770 have an extended service life (if only through the greater material thickness due to the applied protective layer), namely compared with corresponding blades from the prior art, the increased roughness of the surface leads to an increase in the danger of build-up. JP 04235728A discloses a device for the efficient mixing of highly viscous liquids, in which one component part in each case serves to provide a connection of the stirrer blades to the shaft. The stirrer blades themselves are of L-shaped turned execution in this case and exhibit no recess in the region of or adjacent to the shaft, on which the stirrer blades exhibit a greater distance to the mixer bottom than in the region of the more remote perpendicular stirring sections of the stirrer blades. DE 29 51 973 A1 describes an impeller stirrer, which cannot be introduced as an entire unit into the mixing unit, but is assembled initially in the mixing unit. In order to introduce the stirring wings into the mixing unit, these are pushed together from their stirring position and are then guided vertically through the opening of the mixing unit. A connection of the stirring wings to the shaft only takes place in the mixing unit. US 4601583 A describes a mixer with separable wings. This is intended to solve the problem that it is technically very challenging to connect the wings securely to the shaft if these have been introduced into the mixing device separately from one another. The disclosed solution is intended in this case to be found in a special coating of the component parts, which are capable of being firmly connected to one another in the event of heating to a specific temperature. US 2008 013 04 06 A discloses a mixing device for mixing viscous liquids and building materials, wherein the blade leaves can be welded to the shaft. At the same time, the blade leaves adjoining the disclosed stay run in a straight line and without forming a slope.

The object of the present invention is accordingly to make available a tool for a mixing device, which tool exhibits the above-mentioned disadvantages either not at all or only to a limited extent.

This object is accomplished by a tool according to claim 1.

Preferred embodiments of the invention can be appreciated from the dependent claims and from the following description.

The inventive tool has a central shaft with a stay arranged at the lower end of the shaft at an angle of more than 80 and less than 100° relative to the axial direction of the shaft, which has at least one mixing blade or which forms at least one mixing blade.

The so-called planetary mixers that are frequently used in the manufacture of concrete or mortar or similar materials typically have a drive with a motor and a transmission unit above the mixing trough. The transmission usually possesses a slowly rotating part, often designated as a rotor, as well as a more rapidly rotating part integrated in the rotor, often also designated as a star. During the mixing process, this so-called star is caused to move by the rotor of the transmission about the centre of the mixer. A holder is mounted as a rule on the star of the transmission, for the purpose of fastening mixing arms, present on the end of which are mixing blades which run directly over the mixer bottom. The geometrical configuration of the mixing arms in this case is executed in diverse, and at times complex, variations in order to achieve a good mixing effect.

In contrast to this usual configuration, the inventive tools have a simple central shaft, which, as a general rule, is oriented perpendicularly downwards with the drive arranged above, that is to say it is immersed vertically into the solids being mixed. This simple shaft replaces the usual mixing arms, which as a rule are installed on a hub, which is constructively much simpler and also makes a simpler configuration of the transmission itself possible for driving the shaft. Through the provision of a height-adjustable flange holder on the star of the transmission, a simple height adaptation of the inventive tool is possible for the optimal positioning of the tool in relation to the bottom of the mixing device, but without costly modifications being necessary in the actual mixing chamber itself or mixing arms having to be exchanged.

In the usual configuration that is familiar from the prior art, the appropriate adaptation on the bottom of the mixing device is achieved to some extent by the exchange of the mixing blades or by configurations that require expensive sealing, in which the height adjustment takes place by means of moving parts which lie in the region of the solids being mixed. By comparison, the inventive tool is of much simpler constructive design and is also easier to maintain, since neither does it have moving parts in the region of the solids being mixed, nor is there a requirement for fastening or configuration devices which could come into contact with the solids being mixed and can exhibit a tendency to contamination. Contamination leads to malfunctions, which in turn result in downtimes, which is in any case undesirable for financial reasons.

The drive device is connected appropriately in a force-transmitting manner to the central shaft, with the result that the inventive tool is caused to move by the solids being mixed. The constructive configuration of the connection of the shaft and drive device can be effected in a manner that is known per se, and pertinent options in this respect are familiar to a person skilled in the art. A detailed description in this context can thus be dispensed with at this point.

Arranged on the central shaft substantially at a right angle thereto is a stay, which, in the event of the vertical installation of the shaft in the mixing device, lies correspondingly horizontally and quasi-parallel on the bottom of the mixing device. The expression substantially at a right angle should be understood in this context to denote that deviations in the angle of the principal axes of the shaft and the stay of 90° (as it arises in the case of an exactly right-angled arrangement) are possible to a small extent (as a rule less than 10°, and preferably less than 5°), provided that the geometrical configuration of the mixer bottom permits this. Advantageously, however, the longitudinal axis of the stay lies exactly at a right angle to the longitudinal axis of the central shaft. In the case of a flat mixer bottom, of which the plane lies perpendicular to the longitudinal axis of the shaft of the inventive tool, the envisaged good thorough mixing as a rule requires an arrangement of the mixing blades directly above the bottom of the mixer, which presupposes parallelism of the stay in relation to the mixer bottom, if the stay has a mixing blade or forms a mixing blade at both ends. This in turn requires perpendicularity of the longitudinal axis of the stay to the longitudinal axis of the central shaft, if the latter is to be installed in the simple manner indicated above.

The central shaft and the stay arranged thereon are especially advantageously embodied in a single piece, that is to say they are produced from a one-piece blank by appropriate configuration (e.g. by cutting machining or the like). Due to this form of construction, it is impossible to dispense with fastening devices for fastening the stay to the central shaft, which during operation could enter the region of flow of the solids being mixed and accordingly can exhibit a tendency to contamination. The undesired build-ups and deposits mentioned by way of introduction are formed particularly easily at such locations. It is also possible in principle, however, to fasten the stay to the shaft with appropriate, concealed fastening devices that are not subjected to the influence of the solids being mixed.

At least one mixing blade is arranged on at least one end of the stay that is remote from the shaft, or else the stay itself forms a suchlike mixing blade. A mixing blade is preferably present at each end of the stay or is executed there. The expression arranged denotes in the sense of the present invention that the mixing blade is configured without fastening devices that are present in the region of the solids being mixed. This can be achieved in principle by the attachment of a mixing blade having an appropriate geometrical configuration (see below) to the stay by means of adhesive bonding or welding. In contrast to screwed connections or the like, in the case of adhesive bonding or welding, no weak points lying in the region of the solids being mixed, which exhibit a tendency to build-ups or adhesions of the solids being mixed, are provided by fastening devices.

According to a preferred embodiment, the mixing blades are embodied in a single piece with the stay, that is to say the stay and the mixing blade are manufactured from a single workpiece. By comparison with adhesive bonding, as described above, the risk of the separation of the mixing blade during the mixing process, where considerable mechanical loads are imposed on the mixing blade, is avoided in this way. By comparison with welding, there is no longer a risk of the microstructure of the material being negatively influenced by the welding process, which can have a negative effect on the strength and the abrasion resistance.

The configuration of the central shaft, the stay and the mixing blade in a single piece is particularly advantageous, since any kind of fastening device is thereby avoided, or the aforementioned risks of adhesive bonding or welding at the mechanically heavily loaded ends of the stay that are remote from the central shaft can be avoided. As mentioned by way of introduction, the achievement of a thorough mixing effect is of vital importance. In order to accomplish this, at least one mixing blade of the inventive tool has a curvature on the outer section relative to the central shaft. This curvature is round in form, preferably of approximately circular embodiment. What is accomplished by this arrangement of the mixing blade is that the solids being mixed are collected from the centre of the mixer and can be distributed with vigour over the entire mixer surface in the region of the outermost radius of the mixing device that can be reached with the inventive tool.

What is accomplished in addition by a round, preferably circular configuration of the curvature is that a certain material flow also comes about on the rear side of the mixing blade. This reduces the risk of build-ups on the rear side of the inventive tool, which, because of the material flow that is practically absent on this rear side in conventional mixing tools, can only be removed mechanically to all intents and purposes with appropriate downtimes of the mixing devices.

In the preferred embodiment of the inventive tool having one mixing blade at each end of the stay, the curvature is advantageously so configured that the direction of curvature of the two mixing blades relative to the vertical principal plane of the stay runs in the opposite direction.

The mixing blade is configured rising towards the outside in a convex or concave manner, most preferably approximately round or circular, that is to say the vertical height of the mixing blade at the outer end that is remote from the shaft end is larger than at the part of the stay immediately adjacent to the shaft, at which the arrangement of the mixing blade begins. The slope in this case can be configured as desired in principle, although it is preferable if this is done without the formation of edges or comparable transitions, since these in turn could have a negative influence on the mixing effect.

The ejection and self-cleaning properties of the inventive tool are further improved by the sloping embodiment, as described above.

According to another preferred embodiment of the inventive tool, at least one inner region of the stay has at least one jacket surface running diagonally to the vertical plane of the stay. According to one particularly preferred embodiment, all regions of the stay, which are situated between the inner end of the mixing blade and the central shaft, have a suchlike jacket surface running diagonally to the vertical plane of the stay.

An especially preferred arrangement of the inventive tool is characterized in that at least one, and preferably all the inner regions of the stay, which, as indicated above, have two jacket surfaces running with a different slope diagonally to the vertical plane of the stay. The slope of one jacket surface can thus run oriented downwards in relation to the vertical plane of the stay, whereas the slope of the second jacket surface can run oriented upwards in relation to the vertical plane of the stay.

According to an especially preferred embodiment, the jacket surfaces that are oriented diagonally to the vertical plane form a pyramidal structure. A suchlike especially preferred embodiment of the inventive tool is represented in Fig. 3 in a spatial perspective.

The stay is configured so that a passageway is formed in an inner region between the mixing blade and the central shaft on the lower side of the stay, which is allocated to the bottom of the mixing device, through which the solids being mixed can remain in the centre of the tools during the mixing process or can flow through slowly underneath the stay. The self-cleaning properties of the inventive tool can also be improved as a result. This is accomplished in that at least one inner region of the stay exhibits, on its underside that faces towards the mixer bottom, a greater distance to the mixer bottom than the mixing blade(s), in comparison with the region which is formed by the mixing blade(s). This can be achieved constructively simply by an appropriate arrangement of the stay with a vertical recess, wherein said recess is preferably curved in turn without forming edges, and is preferably of circular configuration. In Fig. 1, this recess can be seen on the underside of the stay of the inventive tool.

One illustrative embodiment of the inventive tool is explained in more detail below on the basis of the drawings. I n the drawings,

Fig. 1 depicts an inventive tool wherein the vertical plane of the stay lies parallel to the surface of the blade,

Fig. 2 depicts a top view of the inventive tool according to Fig. 1 from above, and

Fig. 3 depicts a perspective spatial representation of the inventive tool in Fig. 1.

The central shaft 1, on which the stay with inner regions 3 or 3' of the stay as well as mixing blades 4 and 4' of the stay are arranged, can be seen in Figure 1. According to the illustrated embodiment of the invention, the mixing blades are designed sloping towards the outside, wherein the slope is configured with a round form or a circular form. The centre of the imaginary circle, which is determined by the curvature, in this case lies on the perpendicular prolongation of the line through the point of the inner region at which the curvature of the mixing blade begins. The preferred arrangement of the underside of the stay with a recess that faces towards the mixer bottom can also be appreciated from Figure 1, furthermore. The mixing blades sweep along the mixer bottom in the region 2 or 2', whereas a passageway of the described kind is formed in the inner region 3 or 3' of the stay. The configuration of the recess without edges, being circular in the example, is clearly visible. The reference designations 5 or 5' designate inclined jacket surfaces of the inner regions 3 or 3'.

Figure 2 depicts the inventive tool according to Figure 1 in a top view from above, from which it can be clearly appreciated that the two ends of the stay exhibit a curvature in the opposite direction to the vertical principal plane of the stay. The inclined jacket surfaces in the inner regions of the stay are also shown schematically.

Figure 3 finally depicts a spatial perspective representation of the inventive tool according to Figure 1 or 2. The central shaft 1 has a cylindrical cross section and is formed in one piece with the stay. The section 2 of the stay that sweeps along on the mixer bottom can also be appreciated, as can the slope and the curvature of the mixing blade 4 or 4'. Finally, the inclined jacket surfaces 5 or %' can also be clearly seen in this representation.

The inventive tool is suitable for installation in practically all mixing devices, of the kind that are customarily used for the manufacture of concrete or mortar or similar materials and are described in the literature in many different embodiments and are commercially available. The group of so-called pan mixers will be mentioned here only by way of example, and among these in particular the so-called planetary mixers having a motor and a transmission unit arranged above the mixing trough, as already mentioned in the preceding description. The constructive configuration of such mixers is familiar to a person skilled in the art and, as a result, does not require to be described in more detail at this point. The installation of the tool and the force-transmitting connection to the engine and transmission unit also does not require a more detailed description here.

The effective introduction of the mixing energy into the solids being mixed can be accomplished by means of the inventive tool, and a good mixing quality can be accomplished even with very different filling volumes of the mixer. The small deposit surfaces and the high self-cleaning properties of the inventive tool, which result in the fact that not only does a mixing effect arrive in the horizontal direction, but also a material flow is achieved in the vertical direction, during the mixing process, represent significant advantages in the practical application of the inventive tool. The material flow in the vertical direction, which is accomplished in particular by inclined jacket surfaces, as described above, causes the solids being mixed to flow over the tool during the mixing process, which leads to appropriate material movement also on the rear side of the tool and thereby prevents build-up and adhesions on the rear side.

Claims

1. A solid mixer mixing tool, having a central shaft (1) and a lower end of the shaft (1), which has an angle of greater than 80 ° and less than 100 ° to the axis of the shaft (1) and comprises at least one mixing vane (4, 4 '), or forming at least one mixing vane (4, 4'), wherein a) at least one mixing vane (4, 4 ') comprises a curvature on the outermost section of the central shaft (1), and which curvature in the outward direction is convex or concavely ascending; and c) at least one inner region of the taper on the underside facing the mixer floor, as compared to the area formed by the mixing vane (4, 4 '), has a greater distance to the mixer floor than the mixing vane.

Tool according to claim 1, characterized in that the scraper and the mixing blade (4, 4 ') are designed as a single piece.

Tool according to at least one of claims 1 or 2, characterized in that the horizontal end at both ends comprises mixing vanes (4, 4 ').

Tool according to at least one of claims 1 to 3, characterized in that at least one inner region (3, 3 ') of the horizontal stripe comprises at least one cutting surface (5, 5') extending oblique to vertical plane.