HK1055219A - Grain mill - Google Patents

Description

Flour mill

Technical Field

The invention relates to a grinding method and a grinding device, which have the application date of 3-17.1989 and the patent application number of 89101557.4.

The invention relates to a method for producing, for example, flour, semolina, middlings and the like, by means of a high-grade grinding system, the material is subjected to multiple grinding-roller grinding and screening.

Background

In industrial and commercial grain processing there currently appears to be a strong tendency to look at least partially backwards. Nutritionally complete staple foods are required, which in the case of cereals means almost symbolically flour milled with stone and wholemeal breads for making. More or less blame is that the development of the milling industry, which is the point of intersection between farmers on the one hand and bakers and consumers on the other, is wrong, since (through it) the important ingredients contained in the finished product either do not exist or are lost and remain. Such an observation is the result of an overly-advanced labor division, which is also compatible with the resulting "division of thought" situation of modern science, but ignores several fundamental facts:

providing good food according to the eating habits of most people, and the consumer should decide which food he would like to select as the staple food.

Processing losses should be minimized during food processing.

From an energy point of view, the food processing should be as economically as possible.

Good processing from the point of view of the nutritional physiology, so that the food can be absorbed as completely as possible, i.e. with less wastage, by humans and animals.

Good cleaning and processing of the food products to a fully hygienic standard, for example, the removal of unhealthy microorganisms, fungi, etc.

It is possible to produce a wide variety of different types of food products from the same raw material.

According to the old stone mill principle, whole wheat flour and whole/black flour are produced by grinding whole grains one or more times, if necessary, removing part of the outer shell and the outer surface layer of the grains. This principle has been used undoubtedly until decades ago. As a conventional flat milling flour system, there is an advantage in that almost all of the components in the grain remain entirely in the flour or grit and provide a very high nutrition to people through bread and its food products. However, this old method also has its disadvantages. The products obtained by such bulk milling have a limited durability for two reasons, in particular when stored poorly in warehouses. The corresponding "modified foods" are mostly used for immediate consumption and consumption. On the other hand, dust, bacteria, various fungal spores, and the like are generally adhered to the outer side of grains. It is these that affect the quality and storage properties of the product and cause the abrasive article to deteriorate after a short period of storage under harsh conditions.

It is also often overlooked that grains are composed of several widely different components. If the different components of the grain are obtained separately, they determine different characteristics of the different ground products, such as flour, meal, middlings, fodder, bran, etc., for example specific baking properties. The products (such as flour meal, white flour, etc.) which are necessary for certain purposes of use are only partially separated in the conventional flat grinding process and the whole grinding process. Only so-called high-grade mills make it possible to produce a wide variety of milled products, which are currently required by even ordinary eating habits, while maintaining the conditions and the basic facts listed above.

The selection of different components within the cereal grains for the flour to be made or mixed provides the finished product with a completely unique aroma (whole wheat bread, half-white bread, plaited bread, confectionery products, etc.). In particular, the high-grade milling machine can be used to remix the individual ground products into a whole-wheat flour or flour with a high protein content or with several germ fractions. Such advanced milling systems thus allow for more targeted processing of the grain. Similarly, the whole animal cannot be "integrally" chopped into meat pieces while meat processing is being performed.

This advanced milling process has many advantages that have been rarely utilized to date in the industrial community. A medium mill with less staff produces, for example, 100 to 200 tons of finished product per day. Older one-person operated stone mills produced one hundred to two hundred kilograms per day.

The characteristic of the high-grade grinding systems known at present is that the material is sieved after each passage through the grinding channel. This applies both to soft and hard wheat mills and to corn mills. This process is often repeated fifteen to twenty times twenty years ago. With recent developments, it has been demonstrated that on average twelve to fifteen mills can be used with equal success in good working conditions. Since the seventies, time-saving advanced milling processes used in advanced milling industry compared to previous long-term milling processes have become the prior art almost worldwide.

A good mill should be able to achieve the quality standards required by the subsequent processing industry (bakery, pasta, etc.) for completely different raw materials by mixing and targeted milling of grains of different qualities, in particular by very careful grading of different parts of the various grains.

To stand in competition, mills are known to win higher quality and profits when producing a certain number of high quality finished products from a certain number of raw materials. That is, a grain mill is constantly striving to achieve high yields of flour, meal, etc. Whereas a mill can only operate well if the quality standards are maintained. One aspect which is not insignificant to the overall economic efficiency is the use in the mill, for example the scale of the necessary production facilities which is directly dependent on the number of milling and screening channels. Recent efforts have demonstrated that in advanced milling industry, without direct reduction of the yield or quality of the milled product, the milling process cannot be shortened further, and thus the current development in the milling process has in fact been delayed.

Disclosure of Invention

The aim of the invention is to develop a new high-grade milling process, which can not only keep the flexibility of the mill and the adaptability to various special milling requirements and finished product quality specifications, but also keep the controllability of the milling operation, and improve the economic benefits of the milling plant.

The solution according to the invention is characterized in that the material is passed at least twice through the two-roll mill stage without a sifting process between the two-roll mills (device), and is sifted only after the two mills.

The first series of tests according to the novel process of the invention, which were carried out by all the persons skilled in the art, surprisingly and proved that the object set forth was completely achieved. Interestingly, however, as with the third mills without intermediate screens attempted in the beginning of modern mills, the results were clearly poor. This is due in part to the fact that the material is overheated at the milling efficiencies required today, and more importantly, because a significant fraction of the milled material is improperly ground in the three mills without intermediate screens, and more precisely, excessive fines are produced at a too early stage. This reveals approximately one important mystery in milling, i.e., each work step is performed under control and monitoring. The wholesaler should know by his experience how he should do everywhere. In practice, therefore, special conditions are created at each grinding stage, for example by adjusting the grinding gap, providing special grooves, the speed difference of the grinding rollers, the throughput through a grinding channel and the flow of the grinding mill.

It has been shown that it is important that each milling channel, and also the two milling stages of the double milling channel, be controllable and adjustable. In this way, the (human) interventions essential in production practice remain in the new solution, at least in relation to milling. For a good mill, milling is still a craft as before, but he can also use his own senses to guide the milling process in a responsible way.

It is particularly advantageous if the material is subjected to a combination of double grinding and single grinding, wherein the grinding stock is screened after passing through each double grinding channel and each single grinding channel.

It is particularly preferred that at least the first and second skin mills (B1 and B2) and the first and second core mills (C1 and C2) are each guided through a double mill without intermediate screening channels.

The material can be passed through the double grinding stage four to six times without sieving between the two grinding stages, and then sieved after the double grinding.

This allows the use of a combination of a plurality of double milling channels and two to six single milling channels, in particular in a core mill, with a screening after each channel.

However, it can be shown that the use of the new advanced milling process makes it possible to utilize the advantages of the invention more or less for each particular case, which makes it possible to reduce the plant costs by ten to thirty percent compared with the prior art.

The invention also relates to a grain milling plant for producing milled grain products such as flour, meal, middlings and the like, comprising a plurality of milling channels with pairs of milling rolls and a subsequent sifting channel with a flat sifter and a sifter chamber.

The new grain milling system is characterized in that it has at least two double milling channels with two milling roller pairs arranged one behind the other, and no screening device is arranged between the two milling roller pairs.

Since the new milling system allows a great concentration of operations, it is far superior in structure to the previous similar milling systems.

The new grain milling system is particularly advantageous in that it has two double milling channels each forming a roller mill unit, so that it is designed as an eight-roller mill with two roller pairs arranged one above the other.

This configuration of the eight-roller mill also offers new monitoring possibilities for the mills, who can monitor both milling stages simultaneously at the same time and at the same location. This means that the influence of a change, for example, of the first and second grinding roller pair or of the first grinding roller pair on the grinding result of the second grinding roller pair, which may not have changed, can be determined immediately. To the applicant's knowledge, this has hitherto not been possible in the field of high-grade mills. Since in the prior art screening is performed between each grinding, it is not necessary to wait for the material to pass through the screening device and the second grinding stage for the corresponding time, and since the various components are directed to other channels, the components of the ground material are changed by each intermediate interposed screening. It has been found that the minor disadvantage of having a very small portion of the material being crushed in the second grinding pass, which is unnecessary, is completely compensated for by the advantage of the direct control and intervention of the two grinding roller pairs.

The best solution at present is to use a combination of double and single milling channels with a screening channel after each.

It is particularly advantageous to use a combination of an eight-roll mill and a four-roll mill in this combination.

Furthermore, it is proposed that at least two eight-roller mills are provided, with an individual mill gap adjusting device being provided for each mill roller pair.

An adjustable feeding adjusting device and a funnel-shaped product guiding device for directly conveying the powder from the upper grinding roller pair to the lower grinding roller pair are respectively arranged on each grinding roller pair on the upper part of the eight-roller grinding machine, and each grinding roller pair is correspondingly provided with a grinding gap adjusting device. For taking samples after each grinding channel, the grinding roller pairs are also each provided with an inspection flap.

In addition, the feed chambers of the upper and lower pairs of grinding rollers are preferably connected to the suction device via passages.

Depending on the grinding requirements, it is furthermore proposed that each grinding roller pair is provided with an individual adjusting device and a respective dirt guard, the grinding rollers of each grinding roller pair are usually provided with different rotational speeds (speed differences), and the superposed grinding roller pairs preferably have a common control of the separating device.

If the rollers of each pair of grinding roller pairs are arranged in a horizontal plane, the control and maintenance work is more convenient.

The idea of the invention is further developed in such a way that a further great advantage is obtained in the whole apparatus if the grain mill is designed as a compact mill with a compact cleaning device, at least two eight-roller mill and a large flat screen.

Process integration is often somewhat disadvantageous. However, new grain mills have shown that a reasonable concentration is more favorable for a comprehensive understanding of the situation and allows a more rapid response. Thus, the operation of the flour mill is facilitated, and the same quality standard as that in the prior art can be achieved while the flour mill is suitable for a plurality of service conditions. The complexity of the milling process is significantly reduced. The inventive concept also provides a better starting point for a reasonable further increase in the degree of automation by providing a remote control device on each grinding gap adjustment device and a computer device for storing and recalling the particular grinding gap adjustment values set for each grinding task and all other machining and conveying device adjustment values. If the raw material and other parameters such as ambient temperature, air humidity, the conditions of all the parts (grooves of the grinding rollers, screen surface tension of the flat screen, etc.) are known, the mill can be fully automated over a long period of time without the need for a professional to be in the field directly, with a good adjustment. Thus, the present invention makes a great contribution to the perfection of high-grade mills, which does not require further complications in terms of equipment and operation, but rather simplifies it, with almost no impact on the work efficiency of the mill.

Drawings

Additional details of the invention are described further below. Wherein:

FIG. 1 is an eight-roll mill;

FIG. 2 is a front view of a drive and adjustment device of the mill of FIG. 1;

FIG. 3 is a new set of grain mills;

FIG. 4 is a flow chart of milling and sieving according to the prior art;

FIG. 5 is an example of a new milling and sieving flow diagram;

figure 6 is a schematic diagram of another embodiment of a milling and sieving process.

Detailed Description

Fig. 1 will now be described. The eight-roller mill 1 comprises two halves, wherein the left half is a leather milling channel 2, and the right half is a core milling channel 3. The dermatome passages 2 mostly have grooved grinding rollers 4 and 5, it being possible to see in the figure that the grinding roller 5 with the higher speed is indicated by a double arrow. A scraper brush 6 is arranged below the grinding rollers 4 and 5. In the core mill channels, smooth grinding rollers 7 and 8 and a doctor blade 9 for keeping the surface of the grinding rollers clean are used in most cases. In each case, the lower grinding roller pairs 4 ', 5' and 7 ', 8' are identical to the corresponding upper grinding roller pairs, and are either coarse-grained or fine-grained or smooth.

The grain is introduced into the roller mill 1 from the left or right by the feeder 10. Only in the case of processing large quantities of material, the left and right halves of the roller mill can be fed simultaneously, each half having to process half of the feed. In the feeder 10 there is a sensor 11, which in the figure is made in the shape of a so-called "christmas tree", which controls a feed mechanism 12 so that the material flowing on and to the feeder 10 is delivered in the same amount by the product feed mechanism 12. The material is guided directly into the grinding gap via a feed channel 13. A strong air flow is formed in the feed channel 13. This air flow can advantageously be ensured by two air ducts 14 which surround the grinding rollers 4, 5 and 7, 8. The powder material which has been subjected to the skin-milling by the upper roller pair 4, 5 is fed directly via a product outlet funnel 20 into the milling gap between the lower roller pair 4 ', 5'. The air in the lower pair of grinding rollers 4 ', 5' is also sucked in by the air passage 14. The powder is conveyed to the intermediate lifting device via a product outlet hopper 21 and a transfer element 22. All four pairs of grinding rolls 4, 5, 4 ', 5', 7, 8, 7 ', 8' can each have their grinding gap adjusted by an adjusting device 15. The remaining devices, such as the trash guard, the engaging and disengaging device, etc., are used as in a conventional four (mill) roller mill. See DE-PS 2730166 for its entirety. It has been found that the structural unit of a grinding roller pair shown in the applicant's publication can also be used very advantageously in an eight-roller mill. Thus, when an eight-roller mill is combined with a four-roller mill, all of the grinding rollers have the same basic structure in any case. This is a further advantage both to the manufacturer and to the user.

In the individual case, a feed grinding roller or a product distribution grinding roller can be arranged above the lower grinding roller pair. However, it is preferred to engage and disengage the two grinding roller pairs by means of a common sensor 11.

On the right side of the figure, an air outlet channel 18 is added to the product output funnel. The device is particularly advantageous for medium-flour and flour-like grinding stock, since the air passage is separate from the product passage, so that the falling flour flow can be guided compactly.

Each grinding roller pair (4, 5-7, 8) is provided with a separate grinding gap adjusting device which consists of a hand wheel 15 and a corresponding adjusting component. Furthermore, an electrical control device 16 can be provided, which can monitor the instantaneous distance values of the two grinding rollers via a display device 17. Furthermore, the electrical regulation can be carried out by means of a computer (R) and a memory SP.

Each grinding roller pair is provided with an inspection flap 19 which is in the closed position in the upper right-hand part of the figure and in the open position in the lower part. The check valve can be opened regardless of whether the roller mill is operating. The air pressure and thus the grinding conditions can be kept constant by the additional air ducts 14, 18 described above.

Fig. 2 is explained below, in which the adjusting mechanism is in the form of a modular unit 100 and a controllable actuating drive 100'. Two grinding rollers 104 and 105 are supported on the same carrier 101, and grinding roller 105 is pivotably mounted on a stationary eccentric pin 102, the engagement and disengagement of the grinding rollers being controlled by a respective lever 103 and a disengagement cylinder 106. By means of the pivoting movement of the lever 103, the eccentric pin 102 is correspondingly pivoted, so that the lower part of the pivotable bearing housing 107 is displaced horizontally, so that the distance between the two grinding rollers can be preset. This device is not suitable for carrying out accurate adjustment to the grinding roller. It is only suitable for bringing the grinding roller into the engaged or disengaged position, or into two fixed positions. The precise adjustment of the grinding rollers 104 and 105 is carried out by means of an adjusting screw 108. The screw, by its rotation, directly pivots the actuating arm 109 about a fixed pivot bearing 110. The shorter end of the upper side of the actuating arm 109 is connected via a tension rod 111 to the pivotable bearing housing 107 in a force-transmitting manner. The transmission of force is accomplished by a cutting edge that is part of the overload spring fuse 112 on one side. On the opposite side of the pull rod 111, there is an adjustable counter stop 113 and a pressure measuring device 114 with a pressure indicating device 115. In order to be able to adjust the grinding roller pair simultaneously during maintenance, the adjustment can be carried out on the respective side by means of the adjustment screws 143, 144. The adjusting screw 108 is held in position by a bearing 110' and can be operated by a hand wheel 116 with a display clock incorporated directly therein, or by a power tool, a drive chain 118 and a drive motor 119. The drive motor 119 is attached to the roller mill 126 and is connected directly to the adjustment spindle 108 via a slip clutch with a sprocket 123.

In addition, a position indicator 120 is directly connected to the adjustment spindle 108 so that each actuation of the sprocket 123 and handwheel 116 is registered by the position indicator 120 and transmitted to the desired position. Furthermore, fig. 2 only shows schematically a drive belt 128, which is used to drive the grinding rollers 104 and 105 and 104 'and 105'. An electrical power demand measurement and indication device 129 may also be provided in the drive system. This makes it possible, for example, to limit the electrical power consumption to a low value and a high value range, and to relatively separate the grinding rollers if a preselected range is exceeded.

All the signals of the roller mill are preferably coordinated and controlled by a computer R provided in the mill, which computer can recall the desired nominal values from a central computer with a memory SP. The position indicator is preferably provided with a position limit switch which is adjusted to a preselected limit value, so that incorrect adjustments are automatically prevented. The position-limit switch has the advantage that incorrect manual adjustment can also be prevented, since both a handwheel adjustment and an automatic adjustment would cause a corresponding displacement of the chain 118. The position indicator 120 may also be connected, just like the adjustment motor 119, to an input/output device which receives corresponding signals from a computer in the mill and provides these signals in response to a numerical display and manual input keys. Likewise, the pressure measurement and indicator devices 114, 115 may be connected to a computer within the mill. Depending on the extension of the mill, one or more safeties may be provided in a mill. If, for example, grooved grinding rollers are inserted, it is less important to monitor the grinding pressure, but it is advantageous to monitor the distance between the grinding rollers between the grinders, whether by means of a position indicator or by means of a distance meter. But the opposite is true for smooth grinding rolls. For smooth grinding rollers, pressure monitoring is more advantageous. The computer and the signal lines shown indicate that the computer and the memory can control many, sometimes even all, mills of a mill (system), and can coordinate their adjustment functions as needed.

It is furthermore particularly advantageous if the numerical display gives a value (clock 05:50) corresponding to the indication of the time measuring device, preferably the same value corresponding to the clock indication of the position indicating device of the hand wheel.

It is a particular advantage that empirical values of non-automatic and non-remote-controlled roller mills can be compared and used to construct or improve corresponding control programs.

Figure 3 shows a complete grain mill for greater simplicity. Roughly, the mill comprises a silo 30 for storing grain, a mixing and temporary storage silo 31, a processing system 32 and a product silo 33. After the product store 33, the product is delivered directly via a weighing device 34.

The detailed workflow is as follows:

slave trough 35, 35₁、35₂、35₃The desired cereal material mixture supplied is fed via a scale 36, a horizontal conveyor 37, a hoist 38 and a further horizontal conveyor 39 into a mixing bowl 40. The grains which have not been cleaned are discharged from the mixing bowl 40, and fed to a grain cleaning device 44 via a scale 41, a horizontal conveyor 42 and a hoist 43. Large impurities (sludge) are screened out in the compact cleaning device 45, stones are picked up, and the husk part is sucked off. (the entire content is included in the applicant's patent application CH-PA Nr.04626/87-6 in Switzerland). The material is then fed to a roller sifter 46 where the long and round seeds of the foreign plant are removed, the dirt adhering to the surface of the grain is removed by a brusher 47, a desired amount of water is added to a forced wetting device 48, and the wetted material is allowed to stand in a temporary holding tank 49 for a necessary period of time. The moistened grain, stored for about twelve to forty-eight hours, is taken from the temporary holding tank 49 or 50, lifted by the elevator 43', fed, after the addition of 0.1 to 0.3% of water (in the moistening device 51 before B1), and directly after the homogenization tank 52, towards the first grinding tunnel B1, i.e. the first double grinding tunnel 53.

The material is conducted for milling through double milling channels 53, 53 ', 54', etc., after each double milling the material is fed by a pneumatic conveyor 55 into the screening chamber of a large flat screen 56. The so-called rear grinding mill is designed as a single grinding mill 57 as in the past. From these individual grinding devices 57, the material is fed, after passing through a pair of grinding rollers of a corresponding four-roller mill, into a flat screen 58 of conventional dimensions according to the prior art. The finished product from the mill, through the large flat screen 56, the flat screen 58 or other screening units employed in the mill, such as a flour mill, etc., is stored in bins 59, 60, 61, 62, 63 and supplied as needed by the scale 34. The finished product may then be ready for shipment through bagging station 64 or tanker discharge 65. The entire plant is controlled by the mill technician through a central control unit with all the necessary computer means.

Another interesting advantage is that after the double milling channel, large classifiers with special large screening surfaces, for example thirty to sixty percent larger than the screening surface of a four-roll mill, can be used, which again increases the working efficiency.

It is estimated that the present invention saves ten to forty percent of the total space and machinery available in flat screen and roller mills, and does not cause the disadvantages of the new, unknown grinding principle while maintaining the yield of the milled powder and the quality of the finished product. The energy consumption can be obviously reduced.

A flow diagram of a standard grain mill according to the prior art is shown in figure 4. Simple dermatome passages (B1, B2, B3, B4) are shown as shaded pairs of symbolized abrasive rollers. This means that the pairs of grinding rollers are grooved.

The coarse material obtained after each passage through a single grinding channel (B1, B2, etc.) is sent to a screening channel in order to distinguish different particle sizes. Passing a portion of the material milled through B3 and B4 and through a bran brusher DBr₁And DBr₂To remove bran. Bran brusher Br₁And Br₂Is prepared from DBr₁And DBr₂Received and further separated into flour and bran. DBr₃In the special flat screen compartment DBr₁And (5) cleaning. Correspondingly, all filtered flour coming from the pneumatic conveying device is sieved in the flat sieve compartment DF. The materials discharged from B1 and B2 are directly discharged from a (coarse powder) wheat flour mill P₁And P₂And (5) cleaning.

Cardiotomy channel C1-C11 receives Div₁、P₁And P₂Sieving the powder. As in the case of the skin mill channel, the material to be ground is also introduced into the associated downstream screening chamber after each grinding in the core mill channel. The material flow is directed from the first milling channel to the first screening channel, from the second milling channel to the second screening channel, etc. in increasing order of numbers 1, 2, 3, etc. The screened material in each screening channel can be discharged as finished flour.

In the mill passage, a circle-indicated powder loosening device (for loosening agglomerates) or a special loosening device (with a conical circle) for tension loosening is respectively used between the grinding roller grinding device and the sorting machine.

Figure 5 shows a flow diagram of a mill with the same scale of tasks and production capacity as the mill of figure 4, figure 5 being a new solution and figure 4 being a prior art solution against which it is compared.

The pairs of grinding rollers arranged one above the other are double grinding devices in fig. 5. The first two dermabrasion channels B1 and B2 combine into a first double milling channel 53. B3 and B4 are second double milling channels, the first and second double milling channels being combined into a first eight roll mill 67 as shown in figure 3. Accordingly, the coring channels C1, C2, C4, and C5 comprise eight roll mill 68, and the coring channels C7, C8, C9, and C10 comprise eight roll mill 69. Only the core grinding channels C3 and C6 form single grinding channels, which, as in the prior art of fig. 4, here together form the four-roller mill 57 according to fig. 3.

The flow chart of fig. 5 is naturally only a preferred embodiment, which, as mentioned above, allows a great variety of possibilities within the scope of the invention. The structure is clearly simplified as seen in fig. 4 and 5, and the simplification is achieved by the new concept.

Fig. 6 is explained below. Figure 6 shows the case where a double milling channel is combined with a single milling channel. The double milling channels B1/B2 and C1/C2 are combined in a single one-roll eight-roll mill 70. The conveying pipe 141 conveys the milled material of the first double milling device B1/B2 to the first large screening chamber 73. The B3 and B4 coarse material of the third and fourth channels, respectively, were milled on a single milling channel of a four-roll mill 142. Lifts 143 and 144 feed the coarse material from the third and fourth channels into respective screening chambers 145 and 146. The first two centreing channels C1 and C2 are again formed as double mills, and the material produced by C2 is conducted via a pneumatic conveying line 140 into the second screen chamber 74. The centrefulls C3 and C4 are again designed as single grinding channels (four-roller mill 151) and the respective products are transported by lifts 147 and 148 into the respective third and fourth screen chambers 149 and 150. The subsequent centrefull mill channels, like the rear dermatome channels not shown, can be made as double or single mill channels as required by the particular mill. Large flat screens 73, 74, etc. can be combined in one particularly large flat screen 152, and correspondingly, the screening chambers 145, 146, 149, 150 can likewise be combined in a flat screen 153, as in the prior art.

Claims (9)

1. A mill for use in a method of milling grain into flour by the advanced milling principle, characterized in that the mill comprises:

the grinding roller grinding machine comprises a left half part and a right half part, wherein the two half parts form an integral 8-roller grinding machine, and each half part comprises two pairs of grinding rollers;

in each half part, two pairs of grinding rollers are continuously arranged up and down, wherein each pair of grinding rollers is positioned on a horizontal plane, and materials ground by the upper grinding roller pair directly enter the grinding gap of the lower grinding roller pair without any intermediate screening after passing through the grinding gap of the upper grinding roller pair;

each grinding roller pair is provided with a grinding gap adjusting device for adjusting the grinding gap.

2. A mill according to claim 1, characterized in that one of said halves comprises grooved grinding rollers and the other half comprises smooth grinding rollers.

3. Flour mill according to claim 1 or 2, characterized in that the rotational speed of the two grinding rollers in each pair of grinding rollers is different.

4. Flour mill according to claim 1, characterized in that an adjustable feed adjusting device is arranged on each upper grinding roller pair of the eight-roller mill.

5. Flour mill according to claim 1, characterized in that between two grinding roller pairs of one and the same half, an outlet funnel (20) is arranged for directing material from an upper grinding roller pair directly to the grinding gap of a lower grinding roller pair without intermediate screening.

6. Flour mill according to claim 1, characterized in that the feed passages of both the upper pair of grinding rollers and the lower pair of grinding rollers are fitted with suction means.

7. A mill according to claim 6, characterized in that the product outlet funnel (21) of the lower pair of grinding rollers is provided with gas outlet channels (18).

8. Flour mill according to claim 1, characterized in that for the milling gap adjustment means there are provided remote control means and computer means for storing and recalling the milling gap values set for each milling task.

9. Flour mill according to claim 8, characterized in that in each of said roller gap adjusting devices a holder (101) is provided for supporting the rollers (104, 105), one of the rollers (105) being pivotally fixed to a stationary eccentric pin (102), the engagement and disengagement of the rollers (104, 105) being controlled by a respective lever (103) and a disengagement cylinder (106), the eccentric pin (102) being correspondingly rotated by the pivotal movement of the lever (103) so as to cause the lower part of the pivotable bearing housing (107) to move horizontally; the grinding rollers (104, 105) are precisely adjusted by means of an adjusting screw (108), which screw (108) by means of its rotation directly pivots an adjusting arm (109) about a fixed pivot bearing (110), the shorter end of the upper side of the adjusting arm (109) being connected to a pivotable bearing housing (107) via a tension rod (111), the transmission of force being effected via a cutting edge which is part of an overload spring safety device (112) on one side, on the opposite side of the pull rod (111) there is an adjustable counter stop (113) and a pressure measuring device (114) with a pressure indicating device (115), the adjusting screw (108) is held in a fixed position by a bearing (110), and can be operated by means of a hand wheel (116) or by means of a power tool, a drive chain (118) and a drive motor (119), the drive motor (119) being connected directly to the adjusting spindle (108) via a slip clutch and a chain wheel (123).