PELTOLA, Aleksi (Kivenlahdenkatu 3 B 24, Espoo, FI-02320, FI)
RINNE, Antti (Itätuulenkuja 1 B 44, Espoo, FI-02100, FI)
PELTOLA, Aleksi (Kivenlahdenkatu 3 B 24, Espoo, FI-02320, FI)
| CLAIMS 1. A mixer that is arranged to be used in a metallurgical process for example as a mineral slurry reactor (R) , as a conditioner (C) , or as a flotation machine (FC), said mixer including - a container (1) comprising a vertical side wall (2) and a bottom (3), - a mixer unit (4) including a drive shaft (5) that extends vertically in the container, and to which drive shaft there is connected an agitator (6), and an electric motor (7) for rotating the drive shaft, characterized in that the electric motor (7) is a permanent magnet motor provided with a vertical rotor axis (8), its lower end being fixedly connected directly to the upper end of the drive shaft (5) . ~2r. A mixer according to claim ϊ~, characterized in that: the upper end of the drive shaft (5) comprises a first fastening flange (9) and the lower end of the rotor axis (8) comprises a second fastening flange (10) arranged to be attached to the first fastening flange (9) . 3. A mixer according to claim 1, characterized in that the rotor axis (8) and the drive shaft (5) constitute a single monolithic piece. 4. A mixer according to any of the claims 1 - 3, characterized in that the permanent magnet motor (7) is supported to a separate support structure (11) that is placed on top of the container (1) . 5. A mixer according to any of the claims 1 - 4, characterized in that the permanent magnet motor (7) includes a stator (12), which is attached to said support structure (11) provided above the container, and a rotor (13), provided with a number of permanent magnets on the perimeter thereof, said rotor being fixedly connected to said vertical rotor axis (8); and that the rotor axis (8) is geared to be rotary with respect to the stator (12) using an upper bearing (14) and a lower bearing (15), said bearings at the same time constituting the bearing of the drive shaft (5) for receiving the load caused by the mixing process. 6. A mixer according to claim 5, characterized in that the stator (12) includes preferably a monolithic metal segment provided with a central, vertical through hole (16), the inner wall (17) defining the hole being provided with an upwardly oriented upper seat (18), and with a dowjiwardly oriented l.ow_e.r_. seat . - --9-)-/— which is ^•r-tie^l^^^ a^^d^ air-t-^-Om-A-e—upper—s-eai - an upper flange (20), in which the upper bearing (14) is centrally arranged, said upper flange being attached to the upper seat (18) , and - a lower flange (21), in which the lower bearing (15) is centrally arranged, said lower flange being attached to the lower seat (19) . 7. A mixer according to any of the claims 1 - 6, characterized in that the container (1) is upwardly open . 8. A mixer according to any of the claims 1 - 7, characterized in that the container (1) is upwardly closed . 9. A mixer according to any of the claims 1 - 8, characterized in that the drive shaft (5) comprises a void space in the direction of the vertical a wherein the void space is open at the ends of vertical axis and is symmetrical thereto. |
FIELD OF INVENTION
The invention relates to a mixer defined in the preamble of claim 1.
BACKGROUND OF INVENTION
In the prior art there is known a mixer that is arranged to be used in a metallurgical process for example as mineral slurry conditioner, reactor or flotation machine. The mixer includes a container, the interior of said container being defined laterally by a vertical side wall and downwardly by a bottom. Further, the mixer includes a mixer unit provided with a drive shaft that extends vertically in the container. One or several agitators are connected to the drive shaft. An electric motor is provided for rotating the drive shaft. In the prior art, the operation of a drive shaft is arranged by a high-speed electric motor, such as a conventional cage induction motor that drives the drive shaft by intermediation of a gearbox or V-belt power transmission. In order to provide bearing for the drive shaft, there is arranged a separate thrust bearing unit that is supported against a support structure placed above the flotation cell.
The drawback with the prior art is that a gearbox weakens the efficiency of power transmission. Another drawback is the large volume of space required by the power transmission structure in the vertical direction. Yet another drawback is that the current combination of an electric motor and a gearbox as well as a bearing unit is complicated in structure and includes many elements that are susceptible to wearing
CORRECTED VERSION and malfunctions, which reduces reliability and ' results in a continuous need for maintenance. The dust emitted from the process causes wearing of the seals. Moreover, the drive and power transmission equipment is heavy-weight and requires a robust support structure, which results in increased expenses.
OBJECT OF INVENTION
The object of the invention is to eliminate the above mentioned drawbacks.
A particular object of the invention is to introduce a simple, reliable, small-size and light-weight drive apparatus for operating the drive shaft of a mixer, which drive apparatus includes few elements susceptible to malfunctions and requires little maintenance .
Yet another oTrj ect of th ~ e invention is to introduce a mixer where a separate bearing unit is not needed at all, but where the bearing of the electric motor simultaneously constitutes the bearing of the drive shaft . SUMMARY OF INVENTION
A mixer according to the invention is characterized by what is set forth in the appended claim 1.
According to the invention, the electric motor is a permanent magnet motor provided with a vertical rotor axis, its lower end being fixedly connected directly to the upper end of the drive shaft.
An advantage of the invention is that the direct drive of the drive shaft by the permanent magnet motox improves power transmission efficiency, because any gearing is not needed, which means that gear losses are eliminated. By using a permanent magnet motor, it is possible to achieve slow start with a high torque, and its rotation speed can be adjusted by a simple arrangement. A permanent magnet motor can be made flat, small-size and light-weight, in which case it does not take up a lot of space, and the support structures can be designed to be lighter than in the prior art. The dust emitted from the process does not damage the permanent magnet motor. Yet another advantage is that the bearings of the rotor axis of the permanent magnet motor and of the drive shaft can be integrated, i.e. the same bearings can be used for supporting both the rotor axis of the permanent magnet motor and the drive shaft and for receiving the load caused by the mixing process.
Sard— ixed—connection—betwee —the—rotor—axis—and—the drive shaft can first of all be carried out in such a way that the lower end of the rotor axis is attached directly to the upper end of the drive shaft. In an embodiment of the mixer, the upper end of the drive shaft comprises a first fastening flange and the lower end of the rotor axis of the electric motor comprises a second fastening flange arranged to be attached by a bolted joint to the first fastening flange.
Alternatively, the fixed connection may also be carried out in such a way that the rotor axis and the drive shaft constitute a single monolithic piece manufactured for example by casting from a metal.
In an embodiment of the mixer, the permanent magnet motor is supported to a separate support structure that is placed on top of the container. In an embodiment of the mixer, the permanent magnet motor includes a stator that is attached to said support structure located above the container, and a rotor provided with permanent magnets on the perimeter thereof, said rotor being fixedly connected to said vertical rotor axis. The rotor axis is geared to be rotary with respect to the stator, preferably by an upper bearing placed above the rotor, and preferably by a lower bearing placed below the rotor, which bearings at the same time constitute the bearing of the drive shaft and receive the load caused by the mixing process. The bearing of the drive shaft by the bearing of the permanent magnet motor eliminates the need for a separate bearing unit. The upper and the lower bearing can also be located on the same side of the motor, i.e. both may be located above the rotor or below the rotor, and also outside the actual stator, i.e. above or below the stator in the direction of the rotor axis.
In an embodiment of the mixer, the stator includes a preferably monolithic metal segment provided with a central, vertical through hole, and in the inner wall defining said hole there is formed an upwardly orientedupper seat, and a downwardly oriented lower seat, which is vertically spaced apart from the upper seat. Moreover, the stator includes an upper flange, in which the upper bearing is centrally arranged, said upper flange being attached to the upper seat. Further, the stator includes a lower flange, in which the lower bearing is centrally arranged, said lower flange being attached to the lower seat.
In an embodiment of the mixer, the container is upwardly open. In another embodiment of the mixer, the container is upwardly closed.
In one embodiment of the mixer, the drive shaft comprises a void space in the direction of the longitudinal axis, wherein the void space is open at the ends of the longitudinal axis and is symmetrical thereto.
LIST OF DRAWINGS
The invention is explained in more detail below by means of exemplary embodiments and with reference to the appended drawings, where
Figure 1 illustrates a schematical cross-section of a first embodiment of a mixer according to the invention, Figure 2 illustrates a schematical cross-section of a second embodiment of a mixer according to the invention, and
Figure 3 shows the permanent magnet motor of the mixer illustrated in Figures 1 and 2 in an axonometric view and in partial cross-section.
DETAILED DESCRIPTION OF INVENTION
Figure 1 illustrates a mixer that is arranged to be used in a metallurgical process as a mineral slurry reactor R, and Figure 2 illustrates a mixer to be used as a conditioner C.
In this example, the mixer includes an upwardly open (an upwardly closed alternative is also conceivable) container 1, the interior of said container being defined laterally by a vertical side wall 2 and downwardly by a bottom 3. An upwardly closed container would additionally comprise a cover which is not shown in the figure. The mixer includes a mixer unit 4. The mixer unit includes a drive shaft 5 that extends vertically in the container. An agitator 6 is connected to the drive shaft. There can be one or several agitators 6 arranged along the length of the shaft, and they can represent any known types of agitators, such as blade mixers (Figures 1 and 2),. spiral mixers (not illustrated) etc.
An electric motor 7 is provided for rotating the drive shaft 5. The electric motor 7 is a permanent magnet motor provided with a vertical rotor axis 8, its lower end being attached directly to the upper end of the drive shaft 5. For fastening, the upper end of the drive shaft 5 is preferably provided with a first " fastening flange 9 ~ , and! trie lower end of the rotor axis is preferably provided with a second fastening flange 10, which is fitted to .be attached to the first fastening flange 9. The permanent magnet motor 7 is supported to a ' separate support structure 11 that is placed on top of the container 1.
Alternatively, the drive shaft 5 and the rotor axis 8 can be integrated without the flange connection.
In the example of Figures 1 and 2, the mixer includes only one assembly comprising an electric motor, a drive shaft and a mixer unit. Naturally, it is conceivable to couple several such assemblies to a single mixer. In addition, with reference to Figure 3, the permanent magnet motor 7 includes a stator 12, which is attached to said support structure 11 provided above the container .
A number of permanent magnets is arranged along the perimeter of the rotor 13 of the permanent magnet motor 7. The rotor 13 is fixedly connected to a vertical rotor axis 8.
The rotor axis 8 is geared to be rotary with respect to the stator 12, in this example by an upper bearing 14 placed above the rotor 13, and in this example by a lower bearing 15 placed below the rotor, which bearings at the same time constitute the bearing of the drive shaft 5 and receive the load caused by the mixing process. As an alternative to the example illustrated in the figure, it is also conceivable that both bearings are located on either side of the rotor 13. In this example, the stator 12 includes a monolithic metal segment provided with a central, vertical through hole 16, and in the inner wall 17 defining said hole there is formed an upwardly oriented, in this example annular, upper seat 18, and a downwardly oriented, in this example annular, lower seat 19, which is vertically spaced apart from the upper seat. Moreover, the stator 12 includes an upper flange 20, in which the upper bearing 14 is centrally arranged, said upper flange being attached to the upper seat 18. Further, the stator 12 includes a lower flange 21, in which the lower bearing 15 is centrally arranged, said lower flange being attached to the lower seat 19.
The invention is not restricted to the above described embodiments only, but many modifications are possible within the scope of the inventive idea defined in the appended claims .
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