EP0271828A2 - Roller mill and method for feeding granular material - Google Patents

Abstract

Rolling mill, in particular flaking mill, for granular material with at least two rolls (1, 2), in particular with a fixed roll and loose roll, which are held or pressed against one another by a pressure device, a product feed which extends on both sides via the axial ends of the rolls, in particular the roll gap (3), and on both sides of the axial ends of the rolls, which are in the middle or directly against the end faces and which at least partially cover the area between the rolls, serve as return lines (9), which preferably run along their entire length to the rolls (1 , 2) are open towards the ends of the nip (3) and are each carried out with a guide surface (13) above the nip in the area between the rollers.

Description

The invention relates to a rolling mill, in particular to a flaking rolling mill, according to the preamble of claim 1, and to a method according to claim 10.

The quality of the material processed with rolling mills, for example of seeds such as grain or soy, depends on the uniform working conditions along the entire working surface or working line of the rollers pressed against one another. If rollers are pressed against each other without processing any intermediate material, higher surface pressures or different speeds (as is the case with flaking mills) can damage the surface. Such surface damage or different surface wear can also take place when the material to be processed is supplied unevenly. The poorer the material supply in the end regions of the rollers, the more these regions will be subject to different wear compared to the central regions of the rollers. This different degree of wear causes premature reworking of the roller surfaces, which causes long downtimes, since the surface treatment must be carried out with a particularly high level of precision and therefore corresponding effort.

It has already been proposed (US Pat. No. 3,282,199) to provide collecting devices in the two end regions of a rolling mill below the nip, which end with a wedge surface on the rolls. These collecting devices are via pipelines in which the granular material is conveyed pneumatically. connected to the product feed, through which the product is fed to the entire roll gap. With such a device, it is possible to return the granular, possibly poorly processed, material emerging from the nip, but on the one hand there is a relatively high expenditure of energy due to the pneumatic conveying and the return via the feed, on the other hand the uniformity of the wear of the rollers or , This does not secure the supply.

From DE-PS 29 00 922 a rolling mill is known, the rollers of which have a reduced diameter at their end regions, with catch devices for the product being provided on both sides below the rollers at their two ends, which are fed back to the product feed of the rolling mill via screw conveyors. Even if the design of the tapered diameter at the roller ends leads to an improvement because they prevent metal contact of the rollers in the end region, the same disadvantages as those explained in the device according to the above-mentioned patent also occur here.

A roller mill is described in US Pat. No. 4,193,555, in which the product is fed in over a width which extends briefly over the longitudinal extent of the roller gap. Covers are provided on both sides of the roll gap, which are pressed against the end faces of the rolls. One or more recesses are provided in these covers for better guidance of the product into the roll gap. These recesses extend into the roll gap and therefore cause the product to back up in front of the roll gap, since the (smaller) roll gap is unable to absorb the grains of the product. Accordingly, the recesses were more than grooves of a relatively thin plate. In practice, one roller could be lifted from the other at one end, while the other roller was lifted at the other end.

The present invention has for its object to provide a rolling mill or a method in which the product feed and the product return are coordinated with one another in such a way that uniform processing of the granular material is ensured with uniform wear of the rollers.

According to the invention this object is achieved by the features of the characterizing part of claim 1.

A product feed that extends beyond the axial ends of the rollers on both sides ensures that even in the end region of the rollers or of the roller gap, a uniform feed of the granular material is possible in relation to other regions of the roller gap. Because the product feeder opens out with a guide surface above the roll gap, a real return of the granular product of the product fed via the roller end can be achieved, with a braking of the feed of the granular product to the roll gap, as is the case with a design according to the aforementioned US -PS in practice, and too little product at the roller ends is avoided.

By designing the product guide as a product return line for the granular material fed relatively far beyond the axial end of the rolls, i.e. with a corresponding depth, a particularly large product feed in the end region of the roll gap is also required, which - as has been shown - in practice a larger one Uniformity of wear of the rollers leads and the rolling or grinding of the rollers (which are driven at flaking mills at slightly different speeds) is prevented with certainty.

If the guide surfaces form an angle with the horizontal, preferably from 20 ° to 60 °, in particular from approximately 30 °, particularly good product return can be achieved since the granular product is deflected particularly favorably on these surfaces or is reflected, whereby a particularly high supply of the granular material is achieved in the end region of the rollers, the shape of the surface being relatively favorable for the production if the angle is 30 °.

As can be seen from the later description, the guide surfaces can be movable. However, if the guide surfaces are rigid, vibrations that would cause irregular influences on the product inlet into the roll gap can be avoided particularly easily, the construction being simplified.

If the guide surfaces are made separately from the return lines, there is a particularly high level of design freedom, while at the same time the maintenance of the rolling mill can be carried out in a particularly simple and user-friendly manner by facilitating dismantling of the return line, and the transmission of vibrations is also more easily avoided.

If the guide surface, in particular on a collecting cup, is held by a reinforcing plate serving as a supporting surface, the guide surface, e.g. of the collecting cup, are more easily kept free from vibrations emanating from the rollers.

If the return lines lead to the product feed or to the feed device, then particularly easy product feed as well as product return to the roll nip is realized.

As already mentioned, the invention has for its object to provide an improvement in the sense of a more even wear. A first step in the further development is based on the knowledge that part of the resulting unevenness in the wear and tear is due to the fact that the granular ground material is already homogenized when it is filled into the funnel, by the finer particles parts practically take a different route through the grinding mill than the coarser components. However, since the finer parts influence wear differently than the coarser parts, this is at least one cause of the problem.

Therefore, the features of claim 8 are proposed as the next step in the solution to the problem. The fact that the mixing device or the like directly in the hopper, trough. is arranged, segregation can no longer take place subsequently. However, it has been shown that such an arrangement is generally advantageous in rolling mills in which the rollers run at different speeds and are pressed against one another in the process. The term "free-ending arms" is to be understood in a somewhat broader sense in such a way that at least some of the arms at their ends projecting into the mixing chamber are not connected to one another, so that free areas remain between them.

If also a partition a direct passage of the goods from the entrance of the hopper, trough or the like. prevented directly to the feed opening, it is ensured that the mixing device can also develop an improved, intensive effect. In the operation of such a mill mill, the hopper is normally completely filled with granular material, so that the mixing device itself can have an effect even without the partition. However, the partition wall at least partially surrounding the mixing chamber ensures a sufficiently long dwell time in the area of the mixing device so that it can develop a better mixing effect.

It is also expedient for the mixing device to be arranged directly on the partition, since this keeps the path to the feed opening, via which separation may possibly occur again, small. The mixing device is preferably also located directly in front of the connection opening and covers it at least partially and prevents the goods from being able to bypass the mixing device unmixed. Cover walls could also be provided, but such walls influence the flow properties and the pressure conditions in the mixing chamber, which is why the solution mentioned is more advantageous.

Although it is known for liquid material to use stirring arms as a mixer, it is preferred for the present purposes if the mixing device has at least one mixing rotor with mixing arms or blades within the grinding chamber, which is mounted at least approximately parallel to the rollers. Mixing rotors have become known in numerous different designs, for example with arms which have ploughshare-like tools which throw the material to be mixed on both sides. For the present purposes, however, it is more advantageous if the mixing rotor is designed as a mixing screw, expediently with interrupted screw flights, as has also become known in the most varied of designs. If the hopper, trough or the like. has an inlet opening which extends only over a partial length, as will generally result in the case of automatic feeding, then it is advantageous if the mixer screw has screw flights conveying to opposite sides from this inlet opening, so that the mixer screw has a dual function, namely the Mixing and promoting fulfilled. The conveying function serves to feed the supplied material as evenly as possible over the length of the rollers, which is why such an embodiment is advantageous regardless of the design of the inlet opening.

It also serves to make the feed more uniform if the mixing rotor has mixing arms which are assigned counter arms, for example on an adjacent rotor, for dissolving agglomerates. This adjacent rotor can then preferably also be designed as a mixer rotor, it being possible for larger agglomerations to be resolved either by the radial proximity of the two rotors, or else by the arms and counter-arms at least partially interlock. However, it is structurally simpler if the counter arms are stationary stator arms which engage between the mixer arms.

The method according to the invention for feeding granular material to a rolling mill, in particular to a flaking rolling mill, to which the material is fed beyond the axial length of the rollers, consists essentially in the fact that the granular material extends at least 1 cm beyond the axial length of the rollers fed, recorded there and returned to the nip above the nip zone in which the material is gripped and compressed by the rollers.

With a method of this type, it is possible in a particularly simple manner, without using additional energy, to feed the product which is forced out of the roll nip back into the roll nip and thus for processing.

• Fig. 1 ein Walzwerk im Schrägriss mit Produktzufuhr bzw. Einfüllkasten;
• Fig. 2 eine Produktrückführung mit Auffangbecher in Sei­tenansicht, teilweise im Schnitt;
• Fig. 3 die Produktrückführung gemäss Fig. 2 in Stirn­ansicht der Walzen;
• Fig. 4 die Produktrückführung gemäss Fig. 2 in Sicht von oben
• Fig. 5 eine Rückführleitung mit Keilblech in Seitenan­sicht und
• Fig. 6 die Rückführung gemäss Fig. 5 im Schnitt nach der Linie VI-VI der Fig. 5; die
• Fig. 7-9 eine weitere Ausführungsform in den in Fig. 2 bis 4 entsprechenden Ansichten;
• Fig. 10 ein Walzwerk mit einen Einfüllkasten, -trog od. dgl., wobei die Walzen in Seitenansicht, der Einfüllkasten in einem Schnitt etwa nach der Li­nie X-X der Fig. 11 dargestellt ist; die
• Fig. 11 eine Schnittansicht nach der Linie XI-XI der Fig. 10;
• Fig. 12 einen Schnitt nach der Linie XII-XII der Fig. 10; und
• Fig. 13 eine Variante zu einem Detail aus der Darstellung der Fig. 10 in grösserem Massstab.

The invention is explained in more detail below with the aid of schematic drawings. Show it

• 1 shows a rolling mill in an oblique view with a product feed or filler box;
• Figure 2 is a product return with collecting cup in side view, partially in section.
• 3 shows the product return according to FIG. 2 in an end view of the rollers;
• 4 shows the product return according to FIG. 2 in a view from above
• Fig. 5 is a return line with wedge plate in side view
• FIG. 6 shows the return according to FIG. 5 in section along the line VI-VI of FIG. 5; the
• FIGS. 7-9 a further embodiment in the views corresponding to FIGS. 2 to 4;
• 10 shows a rolling mill with a filling box, trough or the like, the rollers being shown in a side view, the filling box in a section approximately along the line XX in FIG. 11; the
• Fig. 11 is a sectional view taken along the line XI-XI of Fig. 10;
• Fig. 12 is a section along the line XII-XII of Fig. 10; and
• FIG. 13 shows a variant of a detail from the illustration of FIG. 10 on a larger scale.

A rolling mill according to FIG. 1 has two rolls 1 and 2, one roll preferably being designed as a fixed roll and the further roll being pressed against it in parallel. A nip 3 is formed between the two rolls 1, 2, i.e. an area where the grains of the product are caught and crushed. Above the roller gap, a product feed 4 is provided, to which a filling funnel or box 5 connects, to which the granular material is fed in a trough 7 via a chain conveyor 6.

A mixing chamber with a mixing device with freely ending mixing arms is provided in the hopper, as will be explained later with reference to FIGS. 10 to 13. The discharge from the product feed takes place via the feed roller 8. As can be seen particularly clearly in the drawing, both the product feed and the feed roller extend axially over the rollers or beyond the nip. At both ends of the feed roller 8, product guides 9 are provided, which are channel-shaped and open above the roller gap with a guide surface in the area between the rollers. Such a rolling mill is particularly suitable as a flaking rolling mill, for example for oil seeds.

In the embodiment according to FIGS. 2 to 4, the rollers have bevels 10, the product guide or return line 9 opening into a collecting cup 11 which rests on a reinforcing plate 12. The collecting cup has a guide surface 13 which includes an angle ϑ with the horizontal, expediently from 20 ° to 60 °, and in the preferred exemplary embodiment shown in the range of 30 °. The reinforcing plate 12 is releasably attached to a support 14 which is mounted on the frame 20 of the rolling mill. The reinforcing plate 12 has a tip 13 der which forms a continuation of the guide surface 13, projects between the bevels 10 and is designed accordingly, so that the guide surface 13, as can be seen particularly clearly in FIG. 3, above the nip 3 in the area between the two rollers 1, 2 opens. The mode of operation is now such that the granular material to be processed is fed uniformly to the nip 3 via the feed roller 8. However, the feed at the roller ends is increased since the feed roller 8 conveys the product beyond the roller ends, and the product via the product guide (which is of a relatively great depth of at least 1 cm, preferably from 2 to 8 cm and in particular from 5 to 6 cm ,) builds up a certain reservoir of material to be returned, which is fed to the roller ends. This reservoir is thus formed precisely from the end area which is conventionally the most uneven and the worst supplied, so that the supply of product over the roll length is evened out or even a somewhat stronger delivery to the end areas is desired in order to prevent the end wear being too slight to avoid with certainty.

In the embodiment shown in FIGS. 5 and 6, a wedge plate 15 is provided, which is adapted to the lateral surfaces of the rolls 1, 2, possibly cooperating with the bevels 10 of the rolls 1 and 2. This wedge plate 15 has a guide surface 113 at a distance from the nip 3, which is provided at the end of the return line 109. Here, too, it would be possible to design the wedge plate 15 as a part separate from the guide surface 113 in order to avoid vibrations or to facilitate dismantling.

As can be seen particularly clearly in FIG. 6, the return line 109 has an essentially triangular cross section, one side being oriented essentially parallel to the end faces 18 and 19 of the rollers 1 and 2. A product guide, which extends to the product feed or to the feed device 8, can also open into this return line 109.

In the embodiment according to FIGS. 7 to 9, instead of a rigid guide surface 13 or 113, a movable 213 in the form of a lateral surface of a roller 16 tapered according to the bevel 10 of the rollers 1, 2 is realized in a top view (FIG. 9). In addition, a rigid (partial) guide surface 113 can be provided.

The roller 16 is attached to a fork-like, e.g. two arms 22, support 21 rotatably mounted about an axis 23 and pressed by a loading device (e.g. also pneumatically or hydraulically), in the simplest case by a compression spring 24 only indicated. Alternatively, the carrier 21 itself can be designed as a leaf spring firmly clamped in the region of the pivot bearing 17, a separate pivot bearing being not necessary.

As can be seen, the lateral product guide 209 is then in the region of the roller 16 (which rotates frictionally with the rollers 1, 2 in the sense of the arrow drawn in FIG. 7) Conveniently designed as a wedge plate 115, which does not need to adapt to the lateral surface of the rollers 1, 2.

By using a movable guide surface 213 or a roller 16, the material is forced into the nip 3, which can be advantageous for some products. In general, however, a rigid guide surface 13 or 113 will be structurally simpler, easier to maintain and therefore preferred.

In a modification of the invention, a height adjustment can be provided for the guide surface 13 or 113 or 213 in order to enable adaptation to widely differing grain sizes. A particularly uniform distribution of the product results in any case if the product guide has a maximum depth in the axial direction of the rollers of at least 1 cm, preferably of 2 to 8 cm, in particular of 5 to 6 cm, which already shows the possibilities of the method according to the invention. since such a far-reaching supply was avoided.

According to FIG. 10, the two rollers 1, 2 of the squeeze roller mill are mounted within a housing A, to which the material to be processed can be fed via a feed plate A3. The two rollers 1, 2 are pressed against each other in the usual manner, not shown, and are driven at different peripheral speeds, as indicated by arrows A4, A5.

The feed plate A3 is mounted in the filler box 5 (see FIG. 1) so that it can pivot about an axis A7. The filler box 5 is placed on the housing A. A swivel arm A8 is connected to the feed plate A3 and engages with a pin A9, which in turn is attached to a slide A10 which can be fixed in different positions.

Provided above the feed plate A3 is the feed roller 8 (see FIG. 1), which is opposite the lower edge A12 of a metering sector A14 which can be pivoted about an axis A13. A piston-cylinder unit A15 is attached to the metering sector A14 in an articulated manner, the piston rod A16 of which is fixed at a point A17 of the filler box. Depending on the relative position of the piston rod A16, there will therefore be a different position of the edge A12 relative to the feed roller 8 and thus a corresponding metering of the feed material. For this purpose, the unit A15, which may be a pneumatic or hydraulic one, may be controlled by appropriate adjustment of the fluid supplied to it, or may also be regulated automatically by keeping the current of the drive for the rollers 1, 2 constant.

Although this type of feeding is preferred, it would also be conceivable, instead of the sector A14 delimiting the feed gap 18 anstelle between the roller 8 and the edge A12, to provide a further roller which interacts with the feed roller 8 and is correspondingly adjustable by the desired gap 18ʹ to set. However, it is understood that the construction shown is less expensive. In any case, however, a magnet A19 is expediently provided after the feed device 8, A12-A17, 18ʹ in order to attract any iron parts from the goods passing by. The feed roller 8 is fed the material, which usually fills the entire area above the feed roller 8 and the sector A14, via an inclined funnel plate A20.

According to the solution proposed here, a mixing chamber A21 is provided above the funnel plate A20. This mixing chamber A21 is delimited by a further funnel plate A22 with a greater inclination than the plate A20 and on the other hand by a vertical wall A23 from both long sides. At the bottom, the chamber A21 is closed off by a trough-shaped partition A24, which prevents the granular material flowing in via a filling opening 25 and a feed pipe 26 of rectangular cross-section (cf. FIGS. 1, 2) from flowing in directly from the gap 18 durch formed feed opening to the rollers 1, 2 to flow. Essentially the only connection between the mixing chamber A21 to the feed opening 18ʹ is provided via a relatively wide, slot-shaped connection opening 27. If desired, this slot opening can be expanded further by pushing up a sliding wall 28 connected to the vertical wall A23 and fixing it in the respective position. The sliding wall 28 can then be fixed in any position with the aid of clamping screws 29.

Within the mixing chamber A21, a mixing device 30 is provided, expediently in the region of the trough formed by the partition, which also largely covers the connection opening 27 and thus prevents material coming from the filling opening 25 from being unmixed directly into the connection opening and from there into the feed gap 18ʹ arrives. This mixing device 30 preferably has a rotor 31 with freely ending mixing arms 32, at the ends of which mixing blades 33 are attached. These mixing blades 33 preferably form the turns of a mixer screw, as can be seen from FIGS. 11 and 12. This mixer screw expediently has interrupted screw flights in the manner shown, in order thereby to improve the mixing effect. Such interruptions of the worm threads are provided both in the radial direction between the rotor 31 and the vanes 33, and in the axial direction between individual vanes 33 each fastened to an arm 32.

In this way, there is the effect that the material flowing slowly through the mixer chamber A21 is locally pushed away from the vanes 33 when the rotor 31 rotates in the direction of the arrow 34 (FIGS. 10, 11), whereupon material from other locations into the space cleared by the pushed away goods. Due to the radial interruptions of the screw flights, however, part of the goods will remain undisplaced and mix with the newly added goods, or the pushed material can dodge in the axial interruptions and mix with the advancing good. It should be pointed out here that in this case the conditions for mixing are completely different from those in most mixers for granular material, in which the same is swirled within a free space. In contrast, as already mentioned, practically the entire filler box 5, 6 is filled with granular material from the inlet opening 25 to the feed opening 18öffnung, so that such a swirling effect is out of the question.

The fact that the mixing blades 33 are each attached to an arm 32, as in a preferred embodiment, makes it possible to influence their mixing action by rotating the arms 32 about their longitudinal axis. The arms 32 are then fixed in their respective position by means of clamping screws or other devices known per se. On the one hand, this changes the inclined position of the mixing blades 33, on the other hand creates more or less large spaces between them.

Under the mentioned difficult conditions for the mixing process, it is important that the mixing device 30 is not exposed to the full pressure of the material coming in from above through the inlet opening 25, because otherwise the grains agglomerate so much under the pressure that the interruptions of those of the Wings 33 formed worm are no longer sufficient to achieve the mixing effect because the agglomerated material is also pushed in the radial interruptions by the wings, since it adheres to the other grains in a frictionally locking manner. However, since the friction depends, among other things, on the pressure, the mixing effect can be improved in that the mixing chamber A21 has a cross section which is widened compared to the cross section of the inlet opening 25. Such an expansion occurs in the axial direction of the rotor 31 (or parallel to the axes of the rollers 1, 2) in that the feed tube 26, which is rectangular in cross section, has a length l (FIG. 11), the mixing chamber A21 in the region of the rotor 31 on the other hand, a large length L. This relieves pressure, especially on the sides. To this relief In order not to lose any material that has accumulated again within the mixing chamber A21 above the mixing device 30, it is advantageous if side walls 35 (FIG. 12) are provided in alignment with the feed pipe 26 up to a certain height of the mixing chamber A21. Below these side walls 35 there is then a sudden pressure relief on the sides, which favors the mixing effect of the mixing device 30 there.

However, in order to obtain pressure relief over the entire length of the mixing device 30, the width b of the feed pipe 26 is also smaller than the width B of the mixing chamber A21 following the inlet opening 25. For this reason, the angle of the funnel plate A22 is also relatively steep. preferably greater than 60 °, so that the material is not compressed again too strongly against the mixing device 30. Here, too, a certain adjustability can be created by moving the sliding wall 28 with its side walls 135, it possibly being expedient to be able to adjust the side walls 135 separately from the front wall 28.

However, the extension of the mixing chamber A21 in the longitudinal direction due to the differences in the dimensions l and L means that less material would be fed to the rollers 1, 2 on the sides, towards the end faces, than in the middle. However, since the sides of the rollers 1, 2 usually suffer less wear than the central region, it is even more desirable to feed more material there. For each of these two reasons in itself, it is therefore expedient if the mixer screw 30 is provided with screw flights of opposite conveying direction, ie screw flights to be conveyed outwards against the sides, as clearly shown in FIGS. 11 and 12. In addition or alternatively, a further measure may be taken, which consists in that the partition A24 has recesses on the sides which are most clearly evident from FIG. 12. The size of these recesses may be adjustable with the help of sliding plates 37 (FIG. 11), and with the help of fixing screws 38 can be locked in any position. Instead of the arcuate recesses 36, it would of course also be conceivable to provide the partition A24 in the lateral area with openings or openings. In any case, the recesses 36 form, as it were, extensions of the lateral connection opening 27 from the mixing chamber A21 to the feed opening 18ʹ.

The granular material can be supplied via the pipe 26 from a silo and / or via a transport device, in particular via the chain conveyor 6 (FIG. 1). This may lead to the formation of agglomerates under various influences (pressure, moisture, etc.), which is disadvantageous on the one hand for mixing by the mixing device 30, but on the other hand also for the feed via the feed device 8, A2-A17, 18ʹ. This applies regardless of whether, as shown, a feed device with a roller is used or whether the feed is carried out only via a vibrating plate which is opposite sector A14. Such agglomerates would be even more unfavorable if there was no separate feeding device at all below the mixing chamber A21, as has already been proposed on various occasions. Although the activity of the mixing device 30 already partly acts in the sense of dissolving such agglomerations, it is advantageous if an additional dissolving device is provided.

10 and 11 is provided by knives 39 which act as stator tools and which on clamping projections 40 (FIG. 11) of an inclined wall 41 by means of elongated holes 42 (FIG. 10) of these knives 39 penetrating clamping screws 43 (FIG. 11) are adjustably attached. However, if you want to make the inclined position of the mixing blades 33 adjustable by rotating the arms 32, it is expedient if the stator tools 39 can be fixed in any position on a (or more shorter) clamping bar running across the inclined wall 41 and perpendicular to the knives 39 . If necessary, you can two such knives 39 can also be arranged between two mixing blades 33.

As can be seen, the knives 39 extend almost to the surface of the rotor 31 and are each inserted between two screw wings 33 (cf. FIG. 11), from the end edges of which they are expediently so small that they are used for a resolution of Work together with these edges. An alternative solution will be described later with reference to FIG. 3.

The mixing device 30 can either be driven by a common drive source, which also drives the rollers 1, 2 and / or the feed roller 8. A drive wheel 43 (FIGS. 11, 12) is provided for this. If desired, however, a separate motor can also be provided for the mixing device 30.

While the stator arms or knives 39 act more in the axial direction by interacting with the end edges of the vanes 33 in the sense of dissolving, this can also be done by the interaction of the mixing device 30 and its arms 32 or vanes 33 with counter-arms arranged offset in the radial direction, as will now be described with reference to FIG. 13. However, it should be mentioned that it is of course also possible to provide stator arms 39 in a configuration according to FIG. 13, if desired for each of the two mixing devices 130, 230 shown in FIG. 13.

13 shows the mixing chamber A21 in a modified embodiment. Parts of the same function have the same reference numerals as in the previous figures, parts of a similar function have the same reference numerals, but with an added hundreds digit.

In contrast to the illustration in FIG. 10, two identically designed rotors 131 are provided here, which are attached to arms 132 Wear snail wing 133. As the arrows showing the direction of rotation show, the direction of rotation of the two rotors 131 is opposite to one another, it being possible, if desired, to also provide a different speed. For example, the rotor 131 of the mixing device 130 can rotate at a higher speed than that of the mixing device 230. This is because the mixing device 230 is arranged between the mixing device 130 and the connection opening 27 and acts as a shield to a certain extent. For other mixer designs it may be appropriate to provide the same direction of rotation for both rotors, but the dissolving effect is greater with the opposite direction of rotation. It goes without saying that the arms 132 can also be designed to be rotatable about their longitudinal axis here.

Instead of the stator arms 39 of the previously described exemplary embodiment, the arms 132 of the mixing device 230, which have the wings 133, interact with those of the device 130, whereby it may be expedient to provide the mutually directed front edges 44 of the wings 133 with lugs, which may also be used as short rails extending parallel to the longitudinal axis of the rotors 131 can be formed. In this way, any agglomerates between the two rotors 131 are dissolved. In addition, of course, there is better mixing, although it has also been shown that a single rotor 30 (FIG. 10) is sufficient for most applications, which is also structurally simpler. It should be mentioned that the two mixing devices 130, 230 expediently have essentially the same conveying direction in the case of being designed as a mixer screw (in particular according to the illustration in FIG. 11, opposite conveying directions starting from the longitudinal axis of the feed pipe), but it is possible to improve the Mixing effect of one or the other rotor, in particular the rotor of the device 230, to assign an opposite conveying direction to that of the device 130 over short sections.

It has already been described above that the size of the connection opening 27 can be adjustable by adjusting the sliding wall 28. In the embodiment according to FIG. 13, an additional adjustment possibility is provided, which above all influences the dwell time in the area of the mixing device 230 and thus the degree of mixing. It is a sliding extension wall 124 of the partition A24, which can be fixed in different positions with the aid of clamping screws 45.

Numerous further variants are conceivable within the scope of the invention; for example, it was mentioned above that the mixing action of the preferred mixer screws, due to the fact that the mixing chamber is completely filled in each case, is not based on a swirling effect, as in most mixers for granular material. The effect of the mixer screws shown is much more comparable to that used for mixing plastics. Nevertheless, the invention is by no means restricted to this type of mixing device. For example, it would be conceivable to arrange an additional feed device at the inlet 25 of the mixing chamber, which practically relieves the mixing chamber of the feed and thus of the pressure of the material to be processed, so that the use of vortex mixers of a conventional design, for example, but also with pneumatic vortexing, is also conceivable . Furthermore, reciprocating mixing arms could also be provided instead of a rotating mixer device. However, it goes without saying that, on the one hand, the last-mentioned mixing arms have a lower efficiency, and that the additional feed device mentioned in the region of the inlet opening 25 would also mean additional equipment outlay.

In the case of very long roller lengths, it may also be expedient to subdivide the connection opening 27 so that the partition A24, which is free-floating per se, is not exposed to vibrations, so that practically several connection openings result. Furthermore, it is of course not necessary to regulate the supply to provide a variable feed opening 18 'because the metering control can also be obtained by different speeds of the feed roller 8.

Claims (10)

1. Rolling mill, in particular flaking mill, for granular material with at least two rollers, which are held or pressed against one another by a pressure device, with a product feed, via which the material can be fed on both sides beyond the axial ends of the rollers, and with one on each side of the axial ends of the rollers, the product guide lying opposite the end faces and at least partially covering the area between the rollers, characterized in that the product guide is fed as return lines (9; 109; 209) for the axially via the ends of the rollers (1, 2) Is well formed in the nip (3) and, with a respective guide surface (13, 113; 213), discharges the material above the nip (3) that grabs and compresses the granular material into the area between the rollers (1, 2). 2. Rolling mill according to claim 1, characterized in that it has at least one of the following features: a) the guide surfaces (13; 113) form an angle (ϑ) with the horizontal, preferably from 20 ° to 60 °, in particular from 30 °; b) the guide surfaces (13; 113) are rigid; c) the rollers (1, 2) are beveled conically at their ends and the guide surface (13, 13ʹ) or a part (12) connected to it protrudes in a wedge shape between the conical surfaces of the rollers (1, 2), and nestles in a particularly sealing manner with a small gap to the conical surfaces of the rollers (1, 2). 3. Rolling mill according to claim 1 or 2, characterized in that the return lines (9) are formed separately from the guide surfaces (13) (Fig. 2-4). 4. Rolling mill according to claim 1, 2 or 3, characterized in that the guide surfaces (13) are provided in a collecting cup (11) which is arranged above the roll gap (3) (Fig. 2-4). 5. Rolling mill according to one of claims 1 to 4, characterized in that the guide surfaces (13), in particular the collecting cup (11), are held by a reinforcing plate (12) serving as a supporting surface (Fig. 2-4). 6. Rolling mill according to one of claims 1 to 5, characterized in that trough-shaped return lines or product guides (9) are provided, which preferably open into a collecting cup (11). 7. Rolling mill according to one of claims 1 to 6, characterized in that the return line (9; 109; 209) has a maximum depth in the axial direction of the rolls (1, 2) of at least 1 cm, preferably of 2 to 8 cm, in particular of 5 to 6 cm, the axial depth preferably being selected to be at least 1%, suitably about 2% to 5%, of the roll length. 8. Rolling mill according to one of claims 1 to 7, characterized in that a hopper, trough or the like. (6) with a mixing chamber (21) is provided, in which a mixing device (30; 130, 230) with freely ending mixing arms or the like. (32, 33; 132, 133) is provided,

and that preferably at least one of the following features is realized: a) in the mixing chamber (21) projecting ends or at least the majority of the mixing arms or the like. (32, 33; 132, 133), in particular all mixing arms or the like, are not connected to one another, they expediently have widenings (33) at their free ends and are held rotatably about their longitudinal axis and can be fixed in the respective position; b) the mixing device (30; 130, 230) has at least one mixing rotor (31; 131) within the mixing chamber (21), which is mounted at least approximately parallel to the rollers (2), the mixing rotor (31; 131) in particular is designed as a mixer screw, expediently with interrupted screw flights (FIGS. 2, 3); c) after its inlet opening (25), the mixing chamber (21) has a cross section (B, L) enlarged, in particular at least transversely to its longitudinal extent measured parallel to the roller axes, compared to the cross section (b, 1) of the inlet opening (25),

wherein in the case of a cross-section (L) widening in the longitudinal direction relative to the inlet opening (25), the mixer screw (30) preferably has screw flights conveying to opposite sides from this inlet opening (25) and / or
walls (35) running in alignment with the inlet opening (25), in particular on the sides facing the ends of the rollers (2), are provided, through which the material can be fed to the mixing device (30; 130, 230). d) the mixing arms (32, 33; 132, 133) of the mixing rotor (31; 131) are assigned counter-arms (39; 132, 133), for example on an adjacent rotor (230), to dissolve agglomerates, but are preferably stationary, between the mixer arms (32, 33) engaging stator arms (39), the can optionally be fixed in different positions by means of a fixing device; e) the mixing chamber (21) is within the hopper, trough or the like. (6) in front of a feeder (11-18) for the metered feeding of the granular material to the rollers (2). 9. Rolling mill according to claim 8, characterized in that the mixing chamber (21) through a partition (24; 124) against direct passage of the goods from the entrance (25) of the hopper, trough or the like. (6) is shielded directly from the feed opening (18), but is connected to the feed opening (18) via at least one connecting opening (27),

and that preferably at least one of the following features is realized: a) the mixing device (30; 130, 230) is arranged directly on the partition (24), preferably also directly in front of the connection opening (27); b) the connecting opening (27) extends at least over the largest part of the roller length, in particular over essentially the same length, the one-piece partition wall (24) attached to a trough wall (22) preferably being provided in the region of the underside of the mixing chamber (21) and is expediently curved around the mixing rotor (31) and the connecting opening (27) extends on the side opposite this trough wall (22); c) on the sides facing the ends of the rollers (2), the connection opening cross section is larger than in the middle, the partition (24) preferably having recesses (36) in the region of the ends of the rollers (2); d) at least one adjusting device (28, 37; 124) is provided for adjusting the size of the connecting opening (27). 10. Method for feeding granular material to a rolling mill, in particular to a flaking rolling mill, to which the material is fed over the axial length of the rollers, characterized in that the granular material is fed over at least 1 cm beyond the axial length of the rollers, recorded there and returned to the nip above the nip zone in which the material is picked up and compressed by the rollers.

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