GB2234449A

GB2234449A - Rotary mixers

Info

Publication number: GB2234449A
Application number: GB9015179A
Authority: GB
Inventors: Huber Siegfried; Klinar Gottfried
Original assignee: F Kurt Retsch GmbH and Co KG
Current assignee: F Kurt Retsch GmbH and Co KG
Priority date: 1989-07-11
Filing date: 1990-07-10
Publication date: 1991-02-06
Also published as: GB9015179D0; ES2030329A6; IT1246979B; IT9020910A1; DE4022012A1; IT9020910A0

Abstract

A mixer has a container (1) which is rotatable about an axis (4). There are formed within the container (1), successively in the direction of rotation (5), chambers which have different filling volumes and which are formed such that they are open in the direction of the axis of rotation. In one form the chambers are delimited by walls (6) within the container (1) which run crosswise to the axis of rotation (4) and which are arranged in an offset manner in the axial direction. In other forms, Fig. 11, the dividing walls (12) are formed so that they are asymmetrical to the axis of rotation. <IMAGE>

Description

MIXERS The invention rellates to mixers in which a Container is mounted

for rotation about an axis.

Such mixers are used, as a rule, for intensive thorough mixing of pourable, particularly granular, solids, mixing being achieved by respective reversal of the layer arrangement as the container rotates. These mixers are, however, not readily suitable for effectively mixing sensitive bulk materials which are inclined to form pellets easily, as well as bulk materials which have considerable density differences, grain size variations or varying grain shape. Conditional upon the rotational symmetry of the rotatably mounted container, in known mixers substantially identical mixing processes are repeated, these processes resulting in insufficient homoaenization of mixing, more particularly when attempting to mix, intensively, solids which are difficult to mix together.

According to the present invention there is provided a mixer comprising a container which is rotatably about an axis, there being within the container, successively in the direction of rotation, chambers which have different filling volumes and which are formed such that they are open in the direction of the axis of rotation. This mixer is particularly suitable for mixing sensitive bulk materials and above all permits mixing of substances which are difficult to mix and which have considerable density differences, grain size variations or the like, with substantially less expenditure of time.

By providing individual chambers with different filling r volumes, with each rearrangement process, that is, for example, when discharging the contents Of one c',lxamber into the following chamber, the geometry of the resultant poured cone in the following chamber is changed to such an extent that, in addition to the mixing, which is achieved by discharging, a new kind of layer arrangement also develops.

In a particularly simple manner the chambers, which succeed one another in the direction of rotation, have different cross-sectional areas parallel to the axis of rotation. These cross-sectional areas each form the base of the following poured cone after discharge and, with different dimensioning of the cross -sec tional areas of successive chambers, the quantity of the bulk material, transported into the following chamber in a unit of time, is arranged in layers to a different height, whereby the thorough-mixing effect is substantially improved. When material is delivered from one chamber to the next, however, more particularly with different cross-sectional areas of these chambers, a different division of the material flow also results and resultant change of the partial volumes and geometry of the charge occur, with rotation of the container about its axis, according to various geometrical patterns so that a situation is prevented where partial processes of the mixing can be repeated.

The successive partial processes of the mixing process result in a respectively changing run-off pattern, whereby demixing or agglomerating processes and pellet- formation processes are certainly prevented. The mixing conditions, which change constantly in this way, can, advantageously, also be used analytically and it is possible to examine with such a mixer, in a short time, the mixing behaviour of different bulk materials.

To this end, each mixing result which can be achieved, can be compared with others achieved in each ----se after a predetermined number of revolutions of the container.

It is possible with such a mixer, more particularly, to mix substances which are difficult to mix, such as straw clippings and Styropor or the like, in a reliable manner in the shortest time to give a homogeneous mix.

In a constructive refinement of the present mixer the different chamber filling volumes are obtained by delimiting the chambers by guide plates which run in the longitudinal direction or axial direction and define jointly with the wall of the container, in each case, chambers of different geometry. With corresponding inclination of the axis of rotation at the same time, continuous conveyance of the bulk material can be achieved in accordance with the force of gravity in the longitudinal direction of the rotatably mounted container and with, at the same time, particularly intensive thorough mixing. A particularly favourable development consists, in this connection, in that the guide plates enclose an exterior angle of > 900 at their edge, furthest from the axis, with a tangent to an envelope circle, the centre of which lies in the axis of rotation of the containeri which contacts the edge.

In addition to such a development of chambers which is achieved by means of guide plates running in the longitudinal direction or axial direction, a division of the material flow when delivering from one chamber to the following chamber can also be achieved in a particularly simple manner in that arranged within the container are walls which run crosswise to the axis of rotation and extend over a cent--al angle of and in that walls, which are adjacent in the are arranged in an offset manner in the axial direction. By offsetting adjacent walls in the axial direction, one portion of the contents of a leading chamber always reaches the following chamber and rearrangement takes place in a further. sequence under the influence of the force of gravity as the bulk material, which is delivered into the following chamber, seeks to be distributed over the respective cross-sectional area which remains as far as a following transverse wall.

A particularly simple and stable construction, whilst developing correspondingly tight chambers, can be achieved in this connection in that the walls end at a distance from the axis of rotation and are rigidly connected with the casing of the container. The rigid connection of the walls can be achieved by means of welding with a tubular container casing, the development preferably being effected in that the container is formed in a tubular manner and in that the casing of the container, in each case, forms the base of the chamber. In this way, a particularly simple and effective mixer is provided.

The mixer can also be produced in a particularly simple manner, and particularly favourable mixing behaviour can be achieved, by providing that the guide plates each have a bent edge, which runs parallel to the axis of rotation, and are connected with their free ends to the casing of the container, whereby a corresponding stable construction is provided with a small number of components.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a longitudinal section through a first form of mixer; Figures 2, 3 and 4 are sectional views on line IIII of Figure 1 of different forms; Figure 5 is a side view in the direction of arrow v in Figure 6 of a modified form of mixer which is formed so that it is divided in the longitudinal direction; Figure 6 is a sectional view on line VIVI of Figure 5; Figure 7 is a perspective partial view of a further modified form? where the outer wall of the mixer has a shape varying from a circular-cylindrical shape; Figure 8 is an end view of a form, which is similar to Figure 7, with a differently formed peripheral surface; Figure 9 is a partial sectional view on line IX-IX of Figure 8, where again there are represented parting walls which are formed in the interior of the mixer; Figures 10, 11 and 12 show different forms of mixer dividing walls, particularly for use in batch mixers; and Figures 13, 14 and 15 are sectional views on the axis of rotation of the mixer container showing mixer walls running substantially in the longitudinal direction of the mixer.

Referring first to Figure 1, a tubular container 1 of 5 the mixer has a feed opening 2 for material which is to be mixed and a discharge opening 3. The mixer is rotatably mounted about an axis 4, the direction of rotation being indicated by an arrow 5. There are provided inside the mixer a plurality of walls or planes of division 6 which run crosswise to the axis of rotation 4and are arranged in an offset manner in the longitudinal direction of the container.

In Figures 2 to 4 there are shown different forms of the parting walls or planes of division 6.

Rotation of the substantially cylindrical container 1 results in a division of the material which is to be mixed, diagrammatically indicated at 7 in Figure 1, on account of the parting walls 6 which are arranged in an offset manner in the longitudinal direction of the container. During each rotation, on account of the division of the material at the opposing parting wall 6, which is arranged in an offset manner. a different development of the poured cone results, as the material seeks to be distributed over the available cross- sectional area between the individual parting walls.

The distances between individual parting walls are dimensioned differently in order to attain different cross-sectional areas thereby to provide within the container, successively in the direction of rotation, chambers which have different filling volumes and which are formed such that they are open in the direction of the axis of rotation. This results, in individual 1 ? chambers, in different heights of the bed of material.

Because the parting walls 6 are arranged in an offset ntanner, rotation results in conveyance of the material which is to be mixed in an axial direction, even without inclination of the cvlinder axis. The inner edges 8 of the parting walls facing the axis 4 end, this connection, at a distance from the axis 4 and the contour of the edges 8 is formed in accordance with the material which is to be mixed and its properties. The walls thereby extend over an angle of a maximum of 1800 in the peripheral direction of the container 1.

In all, mixing takes place by means of a division of the masses contained in a delimited filling volume, by a rearrangement of the masses as a result of rotation of the mixing container and by a recombination of t'j-1e masses. A division can then take place, as represented in Figures 1 to 4, by discharging into at least two respective further chambers, in which case with continuous mixing operation this takes place, for example, by means of the parting walls 6 of the preferably cylindrical mixing arrangement 1, which walls are arranged alternately and in an offset manner. Rearrangement of the individual masses then takes place in that the partial volumes are different in the terms of size and geometry and in that the runs of movement of the discharging processes occur according to various geometrical patterns. In this way, a situation is prevented where the partial processes and discharging processes of the mixing can be repeated with regard to the marginal conditions and/or starting conditions and the run-off pattern so that demixing or agglomeration or formation of pellets, as the case may be, is prevented in a reliable manner.

There is presented in Figures 5 and 6 a nxer 1 which, for improved possibility of cleaning, consists of two half parts 9 which are connected with each other in a suitable manner, for example, by way of screw connections 10. As can be seen from Figure 6, there are again provided parting walls 6 which are correspondingly formed to shape.

In the forms according to Figures 7 to 9, the container has a peripheral shape varying from a circular- cylindrical shape, the areas which vary from the circular-cylindrical shape being denoted by references 11. These areas which are provided with recesses, or deformations, substantially run in the longitudinal direction of the container and are formed, more particularly in the development according to Figure 8, so as to be asymmetrical so that there result together with parting walls, which in turn extend substantially normal to the axis of rotation 4 and are arranged in an offset-manner, very different partial volumes of the individual chambers which succeed one another or are side by side in the interior of the mixer. The parting walls are, in this connection, only represented in Figure 9 for the sake of clarity, merely the greatest outer contour being indicated in the representation according to Figure 9 for the sake of simplicity.

The installations or dividing walls which are represented in Figures 10 to 12. can be used more particularly for batch mixers, for example, for analytical or preparative purposes. The dividing walls 12, which are formed so that they are asymmetrical to the axis of rotation 4, thereby delimit different partial volumes with the container wall 1. which is diagrammatically indicated in Figure 10, and the individual portions 13 of the walls 12 enclose i different angles with the axis of rotation 4 so that rotation in the direction of the arrow 5 results in a rearrangement of the material being mixed in a partial volume delimited between the walls 12 and the container wall. In this case it is possible for the partial volumes to be divided with different shapes according to Figures 10 to 12, for example, in a ratio of 1: 1/2: 1/2. With such a development of the walls the longitudinal conveying action is dispensed with and such a mixer is used more particularly for investigation purposes, for example, for the quantification of the mixability of materials which are particularly difficult to mix.

In Figures 13 to 15 walls run, for the purpose of 15 delimiting chambers with different volumes, substantially in the longitudinal direction, -4.e. , in the direction of the axis of rotation 4. In this connection, in the case of the form shown in Figure 13 there are provided plane walls 14 which are formed so that they are asymmetrical to the axis of rotation 4 so that in different positions of rotation different filling volumes and different cross- sectional areas result. The guide plates or walls 14 thereby enclose, with a tangent at the envelope circle of the casing 1, an angle OC- which in each case is greater than or at least equal to 900.

In the case of the form shown in Figure 14, there are provided walls 15 which run in the longitudinal direction or axial direction, have differing heights h and which, for the purpose of forming different crosssectional areas with each other, can each enclose a different central angle.

The form shown in Figure 15 has, in turn, a peripheral ar- hape of the container 1 vary-ing from a circu- cylindrical shape and there are Provided, furthermore, guide plates or walls 15 which, similar to the form of Figure 14, run in an axial direction, are arraiirje,-' substantially radially, are distriOuted asymmetrically over the inner periphery of the container inner casing and have differing heights.

In order to achieve, in the case of the last-described forms, conveyance of the material, which is to be mixed, from an entrance opening lying on one face to an outlet opening lying in the region of the opposing face. the container can be arranged with a suitable axis of rotation.

_P L

Claims

1. A mi.xer comprising a container which is rotatably about an axis, there being within the container, successively in the direction of rotation, chambers which have different filling volumes and which are formed such that they are open in the direction of the axis of rotation.

2. A mixer as claimed in claim 1. wherein the chambers, which succeed one another in the direction of rotation, have different cross-sectional areas parallel to the axis of rotation.

3. A mixer as claimed in claim 1 or 2, wherein the chambers are delimited by guide plates which run in the axial direction.

4. A mixer as claimed in claim 3. wherein the guide plates enclose an exterior angle of 900 at their edge, furthest from the axis, with a tangent to an envelope circle, the centre of which lies in the axis of rotation of the container, which contacts the edge.

5. A mixer as claimed in claim 1, wherein arranged within the container are walls which run crosswise to the axis of rotation and extend over a central angle of 1800. these walls, which are adjacent in the container, being arranged in an offset manner in the axial direction.

6. A mixer as claimed in claim 5, wherein the walls end at a distance from the axis of rotation and are rigidly connected with the casing of'the container.

7. A mixer as claimed in any one of claims 1 to 6, wherein tfle container is formed in a tubul;-:,r manner and the casinq of the container forms the base of the chambers.

8. A mixer as claimed in claim 3 or 4, wherein the guide plates each have a bent edge which runs parallel to the axis of rotation, and are connected with their free ends to the casing of the container.

9. A mixer substantially as hereinbefore described with reference to any of the Figures of the 10 accompanying drawings.

published 1991 atThe Patent Office. State House, 66/71 High Holborn. London WCIR47?. Further copies may be obtained fron Sales Branch. Unit 6, Nine Mile Point, Cwnifelinfach, Cross Keys. Newpom NPI 7HZ. Printed by Multiplex techniquei ltd. St Marv Cray. Kent 1 1