EP3127614B2 - Roller mill with cutting cutting operating type and back back operating type - Google Patents

Description

The invention relates to a roller mill according to the preamble of claim 1. Such a roller mill was already in use for training purposes in the commercial school Im Hoppenlau in Stuttgart before the priority date of the present application.

Such roller mills are used in mills for grinding ground material of vegetable origin, for example for grinding grain (for example wheat, barley, rye, oats, spelled) or other products (for example maize, cassava, cocoa beans, coffee beans, nuts). A back-to-back and a cut-to-cut operating mode (RR and SS operating mode, respectively) are described with reference to FIG Figure 1a and Figure 1b briefly explained below. A first roller (front roller) 12 and a second roller (rear roller) 14 are each rotatably mounted about their axis of rotation, the two axes of rotation running parallel to each other and between the two rollers 12, 14 a gap 13 for receiving the ground material. The circumferential surface of the front roller 12 is provided with a plurality of elevations (corrugations), each corrugation having a cutting surface (corrugating blade) 32 and a back surface (corrugated back) 34. The corrugated ridges are each aligned approximately tangentially to the outer surface of the front roller 12. The corrugated cutting edges 32, however, are approximately perpendicular to the jacket surface of the front roller 12. The same applies accordingly to the corrugating cutting edges 36 and the corrugated back 38 of the rear roller 14. The two rollers are driven so that they rotate at opposite speeds. This has the effect that the corrugation of the front roller 12 and the corrugation of the rear roller 14 in the region of the gap 13 move in the transport direction of the ground material (for example from top to bottom). The in Figure 1a RR mode shown, the front roller 12 rotates faster (for example by a factor of 2.5 faster) than the rear roller 14. Thus, two facing corrugated ridges 34, 38 of the front and rear rollers 12, 14 always approach each other when they run in in the gap 13, while two mutually facing corrugated cutters 32, 36 in the area of the gap 13 from each other remove (see Figure 1a ). In an SS mode, on the other hand, two facing corrugated cutting edges 32, 36 of the front roller 12 and the rear roller 14 approach one another in the area of the gap 13, while two facing corrugated ridges 34, 38 move away from one another (see FIG Figure 1b ).

The front roller is that roller in which the rear surface of each corrugation, viewed in the direction of movement of the respective corrugation, is in front of the cutting surface of the respective corrugation. That is, in the case of the front roller, the rear surface and then the cutting surface of the corrugation always enter the gap 13 first. In other words, in the front roller, the back surface of a corrugation is forward in the direction of movement and the cutting surface of the corrugation is behind. In the case of the rear roller, on the other hand, the cutting surface of a corrugation is in the front in the direction of movement and the rear surface of the corrugation is behind. In other words: the corrugated cutting edges 32 of the front roller 12 are each facing backwards, while the corrugating cutting edges 36 of the rear roller 14 are each facing forward.

A change from an RR mode to an SS mode can in principle be achieved in two different ways. One possibility is to make the rear roller 14 rotate faster than the front roller 14 in the SS mode. This is in Figure 1b illustrates where the rear roller 14 rotates, for example, three times as fast as the front roller 12. Such a change in the speeds is generally not easy to achieve in the roller mills customary today, since the front and rear rollers are controlled by a common motor a common transmission can be driven. The transmission usually has little or no setting options. Typically the speed ratio between the rear and front rollers is fixed. In such a case, the change from RR to SS mode succeeds in that the two rollers 12, 14 are removed from their respective bearings with the motor at a standstill, then rotated 180 ° about their respective suitable transverse axis and in this rotated position back into their respective storage used to be stored. The front roller 12 thus becomes the new rear roller 12 and the rear roller 14 becomes the new front roller 14.

The US 8,113,447 B1 relates to a process for grinding grain, but it also shows a roller frame, with all four possible operating modes (cutting-cutting, cutting-back, back-cutting, back-back) being possible for the process. However, since this document, as mentioned, a method and not Regarding roller mill, it cannot be deduced from the naming of the four possible operating modes that one and the same roller mill should control the respective operating modes. Ultimately, it is about optimizing the speed difference to maximize the oil yield achieved by the method, whereby it is stated that a maximum oil yield is obtained when the speed difference is in the range of 1.1: 1 and 1.4: 1 and in particular 1 , 3: 1.

The US 8,480,019 B1 relates to a roller for use in processing grain. It also discloses a corresponding arrangement with two rollers (see there Figure 2 ). The cutting-cutting or spine-spine operating modes are not discussed in more detail there. It is only stated that one roller should rotate between 10 and 200% faster than the other roller. For those in there Figure 2 The arrangement shown, this means that it remains within the stated range in any case with back-to-back operation if the left roller is the faster roller. Accordingly, it remains with the cutting-cutting operation if the right roller is the faster.

The WO 2009/067828 A1 discloses a roller mill which can optionally be equipped with corrugated rollers. It is stated, among other things, that the speed of the first grinding roller and the speed of the second grinding roller can be set independently of one another.

In order to allow a comfortable and quick change between the SS mode and the RR mode, the above-mentioned roller mill in the commercial school Im Hoppenlau in Stuttgart already provides that the change during operation by changing the speed of the first corrugated roller and / or the speed of the second corrugated roller is changed. In other words, the drive mechanism of the roller frame is designed so that the speed of the first corrugating roller and / or the speed of the second corrugating roller is possible during operation, that is, while both rollers are rotating normally. There is thus no need to stop the rollers and turn them by 180 ° in order to switch from S-S mode to R-R mode or vice versa.

On this basis, the invention is based on the object of lowering the manufacturing and operating costs of the roller mill without restricting functionality. To achieve this object, the invention provides that the first electrical machine and the second electrical machine have different power ratings. For example, for many applications (for example grinding grain) it can be sufficient if the electrical machine for driving the rear roller has a lower rated power than the electrical machine for driving the front roller. Since motors with a lower nominal power are more cost-effective than comparable motors with a higher nominal power, the manufacturing costs can be reduced. Furthermore, the energy consumption of motors with a lower rated power is lower, so that there is also a reduction in operating costs.

The ratio of the rated powers of the two electrical machines can be in the range between 1: 1.2 and 1: 5, for example. It is preferably in the range from 1: 2 to 1: 4. This achieves a good compromise between manufacturing costs on the one hand and versatility in use on the other.

In particular, it can be provided that the electrical machine that drives the front corrugated roller has the higher nominal power. In R-R mode, the front roller is the faster of the two corrugated rollers. In S-S mode, the rear roller is the faster, but even in S-S mode, relatively low power is sufficient to drive the rear roller, since relatively low speeds are typically selected in S-S mode.

According to one embodiment, a first frequency converter is assigned to the first electrical machine and a second frequency converter is assigned to the second electrical machine. The first electrical machine can be connected to an electrical voltage source via the first frequency converter. The second electrical machine can be connected to a second voltage source via the second frequency converter. The first and second electrical machines are preferably each connected to the same voltage source, for example to a private or public power grid, via the respective frequency converter. The voltage source can be an AC voltage source or a DC voltage source. The frequency of the voltage supplied by the AC voltage source can be between 20 Hz and 100 Hz, for example. Power supply networks generally supply an alternating voltage with an effective voltage of 110 V (for example in the USA) or 220 V (for example in Europe); The first and second frequency converters are advantageously suitable for connection to such an alternating voltage network. During operation, by controlling the first or second frequency converter, the Control the output frequency of the frequency converter concerned and thus the speed of the first or second electrical machine. In the simplest case, the speed of the first or second electrical machine is identical to the frequency of the output voltage (output frequency) of the first or second frequency converter. A first or a second control unit can be provided to control the first or second frequency converter. The frequency of the output voltage of the first or second frequency converter can be set by means of the first or second control unit. The first and second control units preferably have an operating unit, for example in the form of a rotary knob, for setting the desired output frequency. The first and the second control unit can have a common housing.

During operation, it is possible that one of the two electrical machines is operated as a motor and the other as a generator. This case can occur if the faster of the two rollers drives the slower one by frictional engagement and / or frictional engagement via the grist between the two rollers so strongly that the slower roller supplies a net electrical power that can be fed into the power grid or directly back into the electric machine of the faster roller flows. However, the case can also arise that the slower roller is driven partly via the electrical machine assigned to it and partly via frictional engagement and / or frictional engagement with the faster roller.

According to one embodiment, the energy generated by the electrical machine operated as a generator is at least partially used to drive the electrical machine operated as a motor. This can be implemented, for example, in that the first electrical machine and the second electrical machine are coupled to one another via a power coupler.

According to one embodiment, the first corrugated roller and the second corrugated roller have the same roller diameter. This means that the roller mill is equally suitable for both the RR mode and the SS mode. The first and the second corrugated roller are preferably identical in construction. This simplifies the manufacture, maintenance and, if necessary, repair of the roller frame.

It can be provided that the ratio of the speed of the first roller and the speed of the second roller can be varied in the range of 7: 1 and 1: 4.5. This area is considered to be sufficiently large to meet the current requirements with regard to different grist and different required properties of the meal or flour produced.

According to one embodiment, by changing the speed of the first corrugating roller and / or changing the speed of the second corrugating roller, a stepless change in a differential speed and a corrugating action number can be brought about. This is achieved, for example, in that a continuously adjustable first or second operating unit is provided for setting the speed of the first corrugating roller and / or for setting the speed of the second corrugating roller.

• Figur 1a und Figur 1b veranschaulichen einen R-R-Modus und einen S-S-Modus.
• Figur 2 zeigt schematisch ein Ausführungsbeispiel eines Walzenstuhls.
• Figur 3a und Figur 3b zeigen jeweils schematisch ein Ausführungsbeispiel mit einem Getriebe.
• Figur 4 zeigt ein Flussdiagramm eines Ausführungsbeispiels eines Verfahrens zum Betreiben eines Walzenstuhls.
• Figur 5 zeigt eine Tabelle mit Beispielen typischer Übersetzungsverhältnisse und Riffelstellungen einer Getreidemühle.

The invention is explained in more detail below with reference to the accompanying drawings. The same reference symbols designate the same or similar components.

• Figure 1a and Figure 1b illustrate an RR mode and an SS mode.
• Figure 2 shows schematically an embodiment of a roller mill.
• Figure 3a and Figure 3b each show schematically an embodiment with a transmission.
• Figure 4 FIG. 3 shows a flow diagram of an exemplary embodiment of a method for operating a roller mill.
• Figure 5 shows a table with examples of typical transmission ratios and flute positions of a grain mill.

Figure 2 shows schematically an example of a roller frame 10 with a first corrugated roller (first roller) 12 and a second corrugated roller (second roller) 14. The first roller 12 has a multiplicity of first corrugated blades 32 and first corrugated ridges 34. The second roller 14 has a plurality of second corrugated cutting edges 36 and second corrugated ridges 38. The roller mill 10 is designed to be operated either in a cutting-edge operating mode or in a back-and-back operating mode. In In the SS mode, the first cutting edges 32 and the second cutting edges 36 are brought closer to one another. In the RR mode of operation, the first ridges 34 and the second ridges 38 are brought closer to one another. A change between the SS operating mode and the RR operating mode can take place during ongoing operation by changing the speed of the first roller 12 and / or by changing the speed of the second roller 14. As in Figure 1 is also used in the example of Figure 2 the first roller 12 operated as the front roller and the second roller 14 as the rear roller.

The roller mill 10 comprises a first electrical machine 16 and a second electrical machine 18. The first roller 12 is mechanically and / or electromagnetically coupled or can be coupled to the first electrical machine 16, so that the first electrical machine generates a torque (in the example parallel to Y-axis, which is perpendicular to the plane of the drawing) can exert on the first roller 12 in order to cause a rotation of the first roller 12 about its axis of rotation (in the example parallel to the Y-axis). The second electrical machine 18 is mechanically or electromagnetically coupled or can be coupled to the second roller 14 and is thus able to exert a torque (in the example parallel to the Y-axis) on the second roller 14 in order to rotate the second roller 14 about it To cause rotation axis (in the example parallel to the Y-axis). In the normal grinding operation, the first roller 12 and the second roller 14 are operated in opposite directions. That is, the rotation speed vector of the second roller 14 is opposite to the rotation speed vector of the first roller 12. In the example, the rotational speed vector of the first roller 12 points against the Y direction (out of the plane of the drawing), while the rotational speed vector of the second roller 14 points in the positive Y direction (into the plane of the drawing). The two electrical machines 16, 18 can each be an alternating current, a three-phase or a direct current motor, for example. The maximum power (or the nominal power) of the first electric machine 16 is higher than the maximum power or the nominal power of the second electric machine 18. Furthermore, the maximum speed or the nominal speed of the first electric machine 16 is higher than the maximum speed or the nominal speed of the second electrical machine 18. The maximum power and / or the maximum speed of the first machine 16 is usually required in the RR mode. The maximum power and / or the maximum speed of the second electrical machine 18 is usually required in SS mode and is less than the maximum power or speed required by the first machine 16. In the example, the first electrical machine 16 has a nominal power of 7.5 kW and a maximum speed of 1000 revolutions per minute, while the second electrical machine 18 has a nominal power of 2.2 kW and a maximum speed of 200 revolutions per minute.

The first electrical machine 16 is connected or can be connected to a voltage source 26, for example an alternating current source, via a first frequency converter 20. The second electrical machine 18 is connected or can be connected to the voltage source 26 via a second frequency converter 22. The voltage source 26 can, for example, be a connection point to an extensive power supply network. The voltage source 26 can provide an alternating voltage of 220 V and 50 Hz, for example. Each of the two frequency converters 20, 22 uses the input voltage applied to its voltage input (for example the supply voltage supplied by the voltage source 26) to provide an output voltage with a suitable voltage output (which is connected to the first or second electrical machine 16, 18) To generate effective value and suitable frequency. The first frequency converter 20 thus supplies the first electrical machine 16 with an alternating voltage with a first frequency F1. The second frequency converter 22 supplies the second electrical machine 18 with an alternating voltage with a second frequency F2.

The roller mill 10 further comprises a first control unit 40 for setting the output frequency F1 generated by the first frequency converter 20 and a second control unit 42 for setting the output frequency F2 generated by the second frequency converter 22. The first control unit 40 and the second control unit 42 can each be coupled mechanically, electrically, electromagnetically or electromechanically to the corresponding first or second frequency converter 20, 22. The two control units 40, 42 can each have a user and / or a computer interface 44 or 46 in order to enable a user or computer to set the output frequencies F1 and F2 of the frequency converters 20, 22. In a simplest embodiment, the first frequency converter 20 and the first electrical machine 16 connected to it have a transmission ratio of 1: 1. In this case, the output voltage of the first frequency converter 20 with frequency F1 generates a corresponding rotation of the first roller 12 with the same frequency, that is to say rotational speed, F1. The same applies accordingly to the second frequency converter 22 and the second electrical machine 18 connected to it. Output frequencies F1 = 1000 Hz and F2 = 200 Hz can thus generate speeds D1 = 1000 per minute and D2 = 200 per minute, respectively. By means of the control units 40, 42 set the speeds D1 and D2 of the first and second rollers 12, 14 individually, in particular during operation, that is, while the rollers 12, 14 are rotating and while they are being supplied with energy by the frequency converters 20, 22. In particular, it is possible in this way to change from an SS mode (in which D2> D1) to an RR mode (in which D1> D2) and vice versa during operation.

If one of the two rollers 12, 14 rotates faster than the other (i.e. if D1> D2 or D2> D1), the faster rotating roller transfers energy to the ground material (e.g. grain) through mechanical contact with the slower rotating roller slower roller and thus partially or even completely drives it. In this case the electric machine of the slower roller acts as an electric generator. The electrical machine acting as a generator (either the first electrical machine 16 or the second electrical machine 18) then supplies electrical energy to the frequency converter (20 or 22) connected to it. In a simple embodiment (not shown), this energy flows at least largely back into the voltage source 26, for example into a power supply network. In the example shown, however, a power coupler 24 is provided, which electrically couples the two frequency converters 20, 22 to one another and thus returns the generated electrical energy to the frequency converter (20 or 22) of the faster rotating roller (12 or 14). The voltage source 26 is thus relieved. A suitable power coupler is offered by the company Eaton (formerly Moeller), for example. When using the power coupler 24, the speeds of the two rollers 12, 14 can be changed almost arbitrarily and independently of one another, without any major loss of energy.

At the in Figure 3a and Figure 3b schematically illustrated embodiment of the roller frame 10 from Figure 2 the rollers 12, 14 are driven by the respective electrical machine 16 or 18 via a first gear 17 or a second gear 19. The two transmissions 17 and 19 can each be a transmission with a fixed (that is, non-adjustable) transmission ratio, since the speeds of the first and second electrical machines 16, 18 can be varied. Manual transmissions can be dispensed with without any significant disadvantages.

The flowchart in Figure 4 FIG. 10 illustrates a method 200 of operating a rolling mill, for example, rolling mill 10 of FIG Figure 2 . During a first phase 202, the roller mill is operated in an RR mode. That is, the front roller rotates faster than the rear roller (D1 <D2). In a subsequent phase 204, the speed D1 of the front roller is reduced and the speed D2 of the rear roller is increased. This can be done during operation by reducing the speed of the first electrical machine and increasing the speed of the second electrical machine. In a subsequent phase 206, the rear roller rotates faster than the front roller. That is, D1 <D2. The rolling mill is now operated in an SS mode. In a subsequent phase 208, the speed D1 of the first roller is increased again and the speed D2 of the second roller is reduced again. During operation, this is achieved similarly to phase 204 by increasing the speed of the first electrical machine and reducing the speed of the second electrical machine. The rolling mill is now in an RR mode again.

In the table in Figure 5 Possibilities of a finely stepped or stepless speed adjustment of both corrugated rollers are presented by individually setting the rotational frequencies of the two electrical machines. For example, an operating mode for the gentle grinding of wheat in RR mode during ongoing production can be transferred to an SS mode with intensive grinding work, for example for grinding rye. For example, the gear ratios can be adjusted continuously during operation using a potentiometer or by specifying fixed frequencies stored in a recipe. This means that permanently programmed gear ratios can be stored, which are automatically changed when a recipe is selected (for example when switching from wheat to rye), for example from a computer via the interfaces 42, 46 (see Figure 2 ).

List of reference symbols

10

Roller mill

12

first corrugated roller

13th

gap

14th

second corrugated roller

16

first electric machine

17th

first gear

18th

second electric machine

19th

second gear

20th

first frequency converter

22nd

second frequency converter

24

Power coupler

26th

Voltage source

32

first serrated edge

34

first corrugated back

36

second serrated edge

38

second corrugated back

40

first control unit

42

second control unit

44

first user and / or computer interface

46

second user and / or computer interface

200

Procedure

202

first phase

204

second phase

206

third phase

208

fourth phase

Claims (9)

1. Roll frame (10) having a first corrugating roll (12) which has a multiplicity of first corrugating edges (32) and first corrugating backs (34), having a second corrugating roll (14) which has a multiplicity of second corrugating edges (36) and second corrugating backs (38), having a first electric machine (16) for driving the first corrugating roll and a second electric machine (18) for driving the second corrugating roll, the roll frame being designed to be operated either in an edge/edge operating mode, in which the first edges and the second edges are brought closer to one another, or in a back/back operating mode, in which the first backs and the second backs are brought closer to one another, wherein a change between the edge/edge operating mode and the back/back operating mode takes place during running operation by way of a change in the rotational speed of the first corrugating roll and/or a change in the rotational speed of the second corrugating roll, characterized in that, the first electric machine (16) and the second electric machine (18) have different nominal outputs.
2. Roll frame according to Claim 1, characterized in that the ratio of the nominal outputs of the two electric machines lies in the range between 1:1.2 and 1:5 and preferably in the range from 1:2 to 1:4.
3. Roll frame according to Claim 1 or 2, characterized in that that electric machine which drives the more rapid of the two corrugating rolls in the back/back operating mode has the higher nominal output.
4. Roll frame according to one of the preceding claims, characterized in that the first electric machine is assigned a first frequency converter (20), and in that the second electric machine is assigned a second frequency converter (22).
5. Roll frame according to one of the preceding claims, characterized in that, of the two electric machines, one is operated as a motor and one is operated as a generator.
6. Roll frame according to Claim 5, characterized in that the energy which is generated by the electric machine which is operated as a generator is used at least partially to drive the electric machine which is operated as a motor.
7. Roll frame according to one of the preceding claims, characterized in that the first corrugating roll and the second corrugating roll have identical roll diameters.
8. Roll frame according to one of the preceding claims, characterized in that the ratio of the rotational speed of the first roll and the rotational speed of the second roll can be varied in the range from 7:1 to 1:4.5.
9. Roll frame according to one of the preceding claims, characterized in that an infinitely variable change in a differential speed and in a number of active corrugations is brought about by way of the change in the rotational speed of the first corrugating roll and/or the change in the rotational speed of the second corrugating roll.

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