EP0173831A2 - Hammer mill - Google Patents

Abstract

1. A hammer mill comprising a casing (2; 2a) which forms at least one grinding chamber (3) wherein a rotor (22) provided with protruding hammers (8) is rotatably supported together with its shaft (4), said hammers (8) subdivided in the direction of the axis of the shaft (4) into individual groups (110, 210, 310; 410, 510), and said casing (2, 2a) having at least one opening (13-13e; 41) each for supplying and for discharging mill stock, characterized in that setting means (15, 15b, 15c; 41) for the number of hammers (8), striking each particle of the mill stock, are provided in order to determine the fineness of grind and that to this end selectively either, preferably flexible, supply and/or discharge means (52) are selectively connectable to the casing (2a) in different, e.g. axial, positions relatively to the latter, and/or the grinding chamber (3) is to be fed through a plurality of supply openings (13-13e), arranged on different points of the casing (2), to each of which separate supply and/or shut off means (16 or 15, 15b, 15c) are assigned, whereby also a plurality of discharge openings are provided, if desired.

Description

The invention relates to a beater mill with a housing forming at least one grinding chamber, in which a rotor provided with projecting beating tools is rotatably mounted with its shaft, which beating tools are divided into individual groups in the axial direction of the shaft, the housing at least one opening each for the Has supply or discharge of the ground material.

Such a hammer mill has become known, for example, from DE-PS 1 016 048, the different groups of hammer tools being assigned to different rotor diameters. Thus, while the housing of this known impact mill has a stepped design, US Pat. No. 2,838,246 shows a conical impact mill housing, a group of impact tools being assigned to a single diameter. However, the invention is by no means limited to striking tools with different rotor diameters; rather, the division into groups can also be carried out by appropriate spacing or by arrangement at uniform or different axial distances.

The conventional impact machines are relatively difficult to adapt to different circumstances, such as different types of ground material or different quantities to be processed. To change the fineness of grind, sieves of different hole sizes are generally provided, by means of which the dwell time within the grinding chamber is practically determined, because any grain which does not correspond to the sieve hole size is beaten until it can pass through the sieve holes. The replacement of the sieves in the event of a change the regrind or the required fineness is associated with a certain amount of work, even if this could be reduced by various measures, for example in accordance with CH-PS 622 188.

In the case of larger quantities to be enforced, the entire mill diagram generally has to be changed, with several mills being connected in series or in parallel. Remedial action has already been sought here, as described for example in CH-PS ... (38 35/83). The use of several mills means a corresponding amount of space and costs.

The invention has for its object to provide a simplification in the adaptation of a single mill to different circumstances, and this is achieved according to the invention in that for determining the fineness of adjustment devices is provided for the number of impact tools acting on each product part, and that either either The mouth of at least one of these openings, namely the openings for the supply or removal of the ground material, can be released in the area of one or another group of striking tools and / or a plurality of supply or discharge openings are provided at different points in the housing and / or one Program control device is provided for switching over an AC motor having at least two speeds, the operating time being adjustable at one or the other speed with the aid of an adjusting device. As a result of the fact that the millbase is fed to the mill at different points and / or removed at different points (in particular in the axial direction of the rotor), a different number of impact tool groups is used accordingly. The same applies to the switching of the speeds, but solutions with a (controllable) DC motor - Because of the mostly alone available AC network - or with a variator gearbox - because of the high costs - have no practical significance. AC motors, in the form of pole-changing motors or Dahlander motors, can usually only be operated at two different speeds, which would in itself be insufficient to adapt to different finenesses or starting products. However, the fact that the respective operating time can be set leads to a kind of clocked operation, whereby any setting can be obtained by pulse width or frequency modulation.

This allows both an adaptation to the desired fineness of grinding and to a certain extent to different feed quantities. It is therefore possible within the scope of the invention to regulate the number of groups of percussion tools that come into effect as a function of the quantity supplied, which can be determined either by means of weighing devices or with the aid of flow meters. For a desired broad grain size spectrum, several openings can also be in operation at the same time, which will result in a uniform load on the mill and, overall, a reduced energy requirement. In the normal case, however, it may be sufficient to select a predetermined setting for a specific product and for a specific throughput. At least one closing device - e.g. one, in particular several openings of common sliders or flaps - can be provided. Another possibility would be, for example, that the opening can be moved in the axial direction and is provided with a flexible pipe connection or a hose.

It can be seen from the above explanations that a sieve is no longer absolutely necessary in the embodiment according to the invention. However, a sieve can be used, but it is no longer necessary to replace it in every case, since the fineness of the sieve is no longer limited to the sieve is determined. It may therefore only serve to separate the fine fraction of the ground material and thus to increase the capacity of the mill or to relieve it of the continuation of this fine fraction. The fineness of grinding now also depends in particular on the number of striking tool groups determined by the choice of the location of the released inlet and outlet openings. Regardless of whether a screen is present or not, but especially for the latter case, it is advantageous if at least one viewing device is connected to the rotor and is preferably arranged between two groups of striking tools. Such a viewing device can consist, for example, of a rotary screen or a rotary screen driven by the rotor to oscillate, through which a finer fraction of the ground material can be removed and the mill can thus be relieved. However, the viewing device preferably consists of a classifying wheel, in the middle of which a suction device for the finer regrind fraction is arranged. The larger part, however, is thrown out by the classifier wheel.

The permanent switching of the motors during clocked operation will not be a problem for laboratory mills or if the switching elements are appropriately oversized. Normally, however, it will be cheaper to keep the switching frequency as low as possible. However, this contradicts the desire for the most homogeneous grain size distribution possible. A solution to this problem can now be given in that the operating time for each speed is at least 1 minute, e.g. at least 3 minutes, and that the hammer mill is connected to a mixer.

• Fig. 1 eine Schlagmühle mit vertikaler Welle, zu der in Abwandlung die
• Fig. 2 die Anordnung eines Sichterrades zwischen zwei Schlagwerkzeuggruppen veranschaulicht;
• Fig. 3 eine weitere Ausführung mit horizontaler Rotorwelle;
• Fig. 4 eine Mühle mit polumschaltbaren Motor in einem Mühlendiagramm; und
• Fig. 5 ein Diagramm zur Veranschaulichung der Betriebsweise der Mühle nach Fig. 4.

Further details result from the following description of exemplary embodiments schematically illustrated in the drawings. Show it:

• Fig. 1 is a hammer mill with a vertical shaft, to which the modification
• Fig. 2 illustrates the arrangement of a classifier wheel between two groups of striking tools;
• 3 shows a further embodiment with a horizontal rotor shaft;
• 4 shows a mill with a pole-changing motor in a mill diagram; and
• 5 shows a diagram to illustrate the operating mode of the mill according to FIG. 4.

A beater mill 1 has a grinding chamber 3 surrounded by a housing 2. A rotor shaft 4 is rotatably mounted on the housing 2 and can be driven by means of a drive wheel 5. In principle, the rotor shaft 4 could be mounted "on the fly" with the aid of a single bearing 6, but it is advisable to arrange at least one second bearing 7 at the foot end or between two groups of striking tools. Striking tools 8 of this type are mounted in a known manner on a pivoting shaft 9, one of which is held by arms 10 each projecting from the rotor shaft 4 in a star shape. Each star of arms 10 thus forms a group of striking tools 8, wherein a plurality of star arrangements of arms 10 held axially apart from one another by bushes 11 or 12 can be combined into a single group, as is the case with the top four arm stars 10 based on one group 110 in FIG. 1.

The material to be ground is fed to this group 110 of impact tools 8 via at least one feed opening 13. This feed opening 13 lies somewhat above the group 110 and should serve only as an example of the arrangement of such an opening 13. In practice, it will be expedient to distribute a number of such supply openings over the circumference of the housing 2 or to arrange supply channels which widen in a funnel shape in accordance with the opening 13a in order to reduce this number and to even out the supply. The feed opening then extends according to the opening 13a in the form of a slot in the circumferential direction.

The feed opening 13 is assigned a closing device in the form of a flap 15 which can be pivoted about a pivot point 14 from the position shown in solid lines into the dashed position. The design as a flap is particularly recommended where simple pipe cross-sections have to be closed, ie if the pipe cross-sections are circular or polygonal, so that the flap 15 is arranged at a location where the feed channel 16 has such a cross-section, whereas the channel 16 in the region of the mouth opening 13 can easily be designed in the form of a slot in the manner of the opening 13a. If, on the other hand, the arrangement of such flaps is not desired for any reason, a slide valve with a slide plate as the closure element can itself be provided in the region of the mouth openings. Since only a single one of the openings 13, 13a or 13b or 13c is to be uncovered when the desired narrow grain spectrum is desired, the slide can be common to all openings 13 to 13c and itself have only a single passage opening. It is of course then expedient if the slide plate is adapted to the radius of curvature of the housing 2 and has a corresponding curvature. In the case of the arrangement of a plurality of feed openings over the circumference of the housing 2, it is of course also possible to arrange a single slide for at least several or all of the openings provided on this scope in order to open or close them together. But it might just be desirable separate closing devices must be provided for all supply openings distributed over a circumference, for example when each of these openings is connected to a supply (silo or the like) of another ground material to be mixed within the beating mill in the course of the grinding.

Especially for the uppermost group 110 of striking tools 8, however, it may also be expedient to provide feed openings 13d or 13e on the top of the housing 2 and, if appropriate, to arrange them distributed over the circumference of the housing 2. These feed openings 13d, 13e are of course also to be assigned a closing device in such a way that the content of the stock of regrind connected to them is fed to the central line 17 shown on the right in FIG. 1 when these openings 13d, 13e are closed, so that each one after the flap position of the flap 15 or the flaps 15b, 15c assigned to the orifices 13b, 13c, to be fed to one of the orifice openings 13 or 13a-c. These flaps 15-15c are expediently actuated by solenoids, it being sufficient if one of the flaps lies in the inclined position shown by means of the flaps 15b, 15c in order to feed the regrind supplied via the central line 17 to one of the orifices 13, 13b or 13c, whereas the mouth opening 13a is loaded when the flaps 15, 15b, 15c are aligned vertically. Accordingly, the circuit for the aforementioned solenoids, not shown, may be such that when the assigned switch is actuated, only one of the flaps 15, 15b, 15c moves into the inclined position. If, however, it is desired for constructional reasons to also bring the flaps underneath into the inclined position, as is shown by the flaps 15b, 15c, the switch associated with the flap 15b must be connected to the solenoid for the flap 15c via a valve be, for example via a diode blocking in the opposite direction, in order to ensure that the flap 15c is moved together with the flap 15b, but not vice versa Actuation of the switch for the flap 15c also moves the flap 15b. This also applies analogously to flap 15.

On the one hand, it is expedient for the feed openings to be arranged above the associated group of striking tools, as is shown in the openings 13 and 13b. However, this means that an appropriate space must be provided for this, which increases the overall length of the impact mill. Thus, while the feed opening 13b is assigned to a group 210 of striking tools 8 formed by a single arm star of the arms 10, the opening 13c is in turn assigned to a larger group 310. The regrind is fed directly to the group 310 of striking tools 8 through the feed opening 13c, so that an intermediate distance between the groups 210 and 310 is avoided. However, the upper row of striking tools 8 in the group 310, which lie opposite the mouth opening 13c, can hurl regrind particles against the incoming regrind, which may hamper the supply. In addition, the mouth opening 13c practically extends in height over the first two rows of striking tools from group 310, so that part of the inflowing material is not processed at all by the top row of this group 310. This may cause an unevenness in the processing of the regrind. Therefore, it is preferred if the mouth opening corresponding to the mouth 13a is slot-shaped, because not only can this improve the feed, but also the feed between two rows of striking tools 8 is possible. Therefore, the height of the slot of the mouth opening 13a in the axial direction is preferably less than the distance between two adjacent rows of striking tools 8.

In the area of the group 110 of striking tools 8, the housing 2 is designed without a screen, ie without perforation. Such In contrast to the illustration in FIG. 1, training can be provided for the entire hammer mill 1, the fineness of the end product being essentially dependent on the number of rows of hammer tools passed through. As can be seen, this number can be predetermined by opening at least one feed opening 13, 13a, 13b or 13c for the regrind fed via the central channel 17.

However, it is also possible to arrange particularly in the lower portions of a screen 18, thereby removing a fine fraction via a suction channel 19, and so the _V erarbeitungs- capacity of the hammer mill 1 may be increased. Since in this way less material is passed through in the lower area of the impact mill than in the upper area, it would also be conceivable to arrange it in such a way that the grinding stock is fed through two feed openings located one below the other, for example opening 13 and 13b. This can either be done in such a way that the flap 15 assumes a central position between the position shown in full lines and the position shown in broken lines; the flap 15b, however, remains in the position shown in full lines in FIG. 1, or by branching off the central one Channel 17 of the feed opening 13b (or another opening 13a or 13c) can be fed to regrind. If the sieve 18 (as shown) only extends over part of the axial height of the impact machine 1, it is expedient to arrange the sieve against the end region (viewed in the transport direction of the ground material). Of course, it is also possible to keep more than two supply openings unlocked.

If the sieve 18 is designed in such a way that a regrind fraction of the desired fineness can be discharged via the discharge duct 19 (by suctioning off via the duct 19), the coarse material collects accordingly Well at the lower end of the housing 2 in a funnel 20, where it can be discharged, for example, with the aid of a screw 21 and can be fed again to the impact mill 1 via the respective .. feed opening. If, on the other hand, the sieve 18 is designed in such a way that only the very finest fraction is removed via the discharge duct 19, whereas regrind with the respectively permitted grinding fineness also arrives in the funnel 20, then a sifting, for example with the aid of, must follow the striking machine 1 of seven. For some end products, however, the grain size distribution may be of less importance, so that there is no need for a screening process. For such regrinds, however, it can be expedient to design the housing 2 without a sieve with imperforate walls in all areas.

It should be pointed out that in the course of the operation of such a striking machine 1 it is possible to check the fineness of the grinding material discharged from the mill 1, for example by determining the quantity of the individual fractions from a subsequent sieving process with the aid of flow meters or weighing devices, and that, based on the ratio of the individual fractions, the flaps 15, 15b and 15c are controlled via a control loop in order to selectively open the corresponding openings 13 to 13c. It will be discussed later with reference to FIG. 3 that, in addition or as an alternative, the comminuted ground material can be removed after it has passed through a predetermined number of racket groups. The simultaneous arrangement of a plurality of feed openings and a plurality of discharge openings or of at least one opening each arranged in different positions relative to the rotor 22 seated on the shaft 4 (the rotor could also be displaceable) can be of particular interest if the different striking tools are different Groups ver are different and therefore have different effects. The group 110 of striking tools 8 can thus be designed especially for the preliminary comminution, whereas the lower striking tools 8 are adapted accordingly to a finer grinding. A different design of tools will be described below with reference to stator tools, which can be seen in FIG. 1. Analogously, the striking tools 8 can have different designs.

The use of stator tools is known per se, but is of particular interest in connection with the proposed design because the grinding fineness achieved depends very much on the number of rows of striking tools passed through and a "short circuit" between the respective feed opening 13 to 13c and the funnel 20 is to be prevented by material flowing along the housing wall. For this purpose, relatively narrow rows of pin-shaped stator tools 23 can be provided, which, however, can optionally also be provided with tools 24 extending parallel to the axis of the rotor 22. In order to prevent the "short circuit" mentioned, triangular stator tools 25 are particularly expedient in cross section, which rest with one side 26 on the housing wall and have an inclined side 27 which extends in the transport direction. The formation of the third side of this triangle is less critical, but it may be expedient to form this side 28 at right angles to the wall of the housing 2, because this allows the inclined surface 27 to extend close to the next row of striking tools. Regardless of the cross-sectional shape, it is advantageous if the stator tool 25 extends in a ring around the circumference of the housing 2. At least this should be below or (seen in the transport direction of the regrind) behind the respective feed openings.

If necessary, a plurality of such stator tools 25, which extend over a predetermined angular range, are arranged one behind the other in the axial direction and possibly offset in the circumferential direction, the extent of the offset being less than that of their extension, so that - seen in the axial direction - overlapping areas of two adjacent ones Stator tools 25 result. Of course, it is also possible to make the stator tools 25 only approximately triangular in cross section, e.g. trapezoidal or the like.

The impact mill la according to FIG. 2 is constructed similarly to the impact mill 1, but has an intermediate bearing 7a and a hollow shaft 4a between two groups 410, 510 of impact tools 8, which is connected to a vacuum source, not shown, in particular a suction fan, through which Air is sucked from the grinding chamber 3a in the direction of arrow 29.

At this point, the design and arrangement of the bearing 7a will be described in more detail, which is constructed similarly to the bearing 7 (FIG. 1) with slight differences. The housing 2a, which consists here of solid, unperforated walls, is provided at the height of the bearing 7a with a reinforcing ring 30 which transmits any radial forces which arise from the shaft 4a to an outer ring 31 and supports 32. Spokes 33 extend from the reinforcement ring 30 and support the bearing housing of the bearing 7a, which is constructed in a conventional manner. However, the bearing 7a has a cone 34 on its upper side, which ensures that any regrind particles falling thereon are discharged downwards.

This cone 34 of the bearing 7a can preferably also be used to cover suction openings 35 of the hollow shaft 4a. To improve the effect of the arrangement, a cell wheel 36 with a number of radial cell wheel walls 37 arranged between each suction opening 35 can be provided in the area of the suction openings 35 (the middle one in FIG. 2 is indicated by dash-dotted lines). The diameter of this cellular wheel 36 is expediently dimensioned such that it can be accommodated within the cone 34 or within the diameter of the intermediate bearing 7a. This configuration is only preferred, but it may also be desirable to provide a cell wheel 36 projecting beyond the cone 34 or the bearing 7a. In order to prevent direct incidence of regrind particles in the area of the cellular wheel 36 and the suction openings 35, an all-round roofing 38 can be provided below the bearing 7a. According to FIG. 2, a classifying wheel 39 is arranged below the cell wheel 36, which is fastened together with the cell wheel 36 on the hollow shaft 4a.

In the operation of the impact mill la, the regrind particles coming from the group 410 of impact tools 8 are on the one hand under the influence of gravity, and on the other hand under the influence of the suction effect exerted via the suction openings 35. As a result of their greater mass, larger regrind particles M1 are therefore deflected less strongly from their essentially vertical path by the suction effect and at most possibly fall onto the classifying wheel 39, from where they are thrown radially outwards and are thus fed to the next group 510 of striking tools 8. Fine regrind particles M2, however, are sucked into the area of the cellular wheel 36. Should a larger regrind particle accidentally get into the area of the cellular wheel 36, it will be thrown radially outward by it. However, the smaller regrind particles M2 have such a low mass that the centrifugal force given to them is in any case less than the suction effect on them, which is why the fine fraction _M 2 is sucked through the suction holes 35 into the interior of the hollow shaft 4a, from where it, for example, via a (not shown) rotary inlet. abqefü is rt _h. In this way, the striking tools located below the group 410 of striking tools 8 are freed from or relieved of already finished particles.

It has already been mentioned above that instead of a classifying wheel 39, a vibrating or rotating circular screen can also be arranged, the overflow of which is fed to the group 510 of impact tools 8, whereas the fine material portion is discharged laterally, for example, from the housing 2a of the mill 1a. Since a screening is usually carried out anyway after processing by a hammer mill, it can also be advantageous to provide such or a similar viewing device on the underside of the hammer mill, that is to say approximately below the bearing 7 in FIG. 1. Since the separating action of the viewing device shown can essentially be derived from the force ratio of suction action and centrifugal action, it may be expedient if the size of the suction power can be adjusted. This can be done by means known per se. The magnitude of the centrifugal force depends on the speed of the wheels 36, 39, which cannot be easily changed in view of the grinding result to be achieved. It can therefore be advantageous if at least one of the wheels 36 and 39 can be driven independently of the shaft 4a, for example in that the classifying wheel 39 has a ring gear projecting through the wall of the housing 2a, via which it can be driven from the outside, whereby it is rotatably mounted on the shaft 4a. It would also be possible to interrupt the shaft 4a above the cellular wheel 36 and to provide a coaxial hollow shaft for driving the cellular wheel 36 see. In this case, however, the group 510 of clubs would either have to be driven separately, or be ussenumfange 39 is connected to the group 410 at its _A, bypassing the separator wheel.

Another embodiment of a beater mill 1b with a horizontal shaft 4b is shown with reference to FIG. 3. In such a case, of course, special precautions are required to secure the regrind in the axial direction of the shaft 4b, especially since gravity is eliminated here for this purpose. Namely, while the regrind is introduced from above via a feed opening 13f, it is conveyed pneumatically by connecting a vacuum source sucking in the direction of the arrow 40 to a discharge opening 41 over the axial distance between the feed and discharge openings 13f and 41, respectively. Although the air may be also introduced at about the supply port 13f in the grinding chamber 3b, it is advantageous to have when uftzufuhröffnungen in the housing 2b _L 42 are provided, through which the axis of the shaft 4b parallel and transverse to the feed direction of the ground material from the supply port 13f directed air flow can be generated. The size of these air supply openings 42 can expediently be adjusted with the aid of a rotary slide 43. The setting can be done by hand, but the rotary valve 43 may have a ring gear 44 on its outer circumference, into which a pinion 45 of a servomotor 46 engages. The servomotor 46 is controlled by a control circuit 47, which are connected on the one hand to setpoint transmitters 48 and on the other hand to flow meters 49, which are only indicated schematically, and by means of which the ratio of the quantities of fractions of different fineness can be determined. This flow sensor can be designed as weighing devices, or as a _D urchflussmengenmesser.

With the help of the control loop 47, the strength of the _M ahlgutpartikel set and lb influence length of stay for the ground material within the hammer mill transporting air flow. Namely, the desired _grinding fineness not reached or achieved the coarse fraction of the ground material a preponderance, so may the cross-section of _O can be reduced 43 in order to decrease the transport speed for the material to be ground inside the grinding chamber 3b effnungen 42 with the aid of the slide. Since the impact mill lb is designed without a sieve, a longer dwell time of the ground material within the grinding chamber 3b means a higher impact frequency per supplied ground material.

The essential possibility for adjusting the Mahlgutfeinheit is but also in the embodiment according to Fig. 3 in the selection of the number of the coming into effect groups of _S 8. chlagwerkzeugen Here forms each ring arranged in a plane of impact arms 10 beating tools is a group, wherein the only discharge opening 41 can be displaced parallel to axis 4b and can thus be assigned to different impact tool groups. For this purpose, the housing 2b has an elongated opening 50 on its underside, which is largely covered by a slide 51. The slide 51 has only one opening, which receives a hose 52, the mouth of the hose 52 simultaneously forming the discharge opening 41. The same applies to this discharge opening 41 as was said above with reference to FIG. 1 with regard to the arrangement and shape of the inlet openings 13 to 13c, ie the discharge opening 41 is also preferably slit-shaped.

In order to ensure that the discharge opening is only arranged between two groups of striking tools 8, the slot 50 can be offset by individual discharge openings, corresponding to the cross section of the opening 41, to which the hose 52 is to be aligned. Additionally or alternatively, notches for certain positions of the hose 52 or

of the slider 51 may be provided. Another possibility is that the slide 51 is provided with a drive which can only be brought digitally into predetermined discrete positions. For this purpose, a follow-up control can be provided, for example, to which certain selector switches are assigned for each individual position.

It goes without saying that various of the described features of the embodiments according to FIGS. 1 to 4 can be interchanged or combined with one another. Thus, several discharge openings 41 can be provided analogously to the different supply openings 13 to 13c in FIG. 1. On the other hand, the various feed openings of FIG. 1 can be replaced by a single, displaceable feed opening analogous to the displaceable discharge opening 41 of FIG. 3. Just when a broad grain spectrum is desired, several of the feed openings 13-13e (possibly also several discharge openings) can also be opened or in operation at the same time. It has also already been mentioned that several feed openings can be distributed over the circumference of the housing, which of course also applies analogously to the discharge opening. It is also possible to provide a vertical-axis beater mill with different discharge openings (or a single movable one) analogous to FIG. 3, but a separating floor is expediently used just below the respectively opened discharge opening in order to prevent further falling of regrind particles . However, this can also be solved in such a way that the respective housing of the striking machine encloses a plurality of grinding chambers which are separate from one another, a group of striking tools being accommodated in each grinding chamber. Furthermore, if desired, a plurality of openings 41 (or feed openings) can also be connected to the slide 51, which results in a wider grain size spectrum. In case of Arrangement of several openings distributed over the circumference of the housing 2, the slide 51 can be displaceable in the circumferential direction instead of in the axial direction of the housing 2, in particular if supply and discharge openings are provided in the circumferential direction.

It has also been mentioned that the flaps 15, 15b, 15c of _F ig. 1 can be replaced by a slide, which may then be designed analogously to slide 51, the only opening of which can be aligned in each case with one of the feed openings 13 to 13c, wherein these feed openings are expediently designed to be of equal size to one another. 3, a viewing device, for example by means of a rotary screen, drum screen or the like, can also be provided in an embodiment according to FIG. 3.

Likewise, the striking tools may have different designs and, if desired, may also have axially extending extensions analogous to the pins 24 (FIG. 1). It has also already been mentioned that a combination of inlets (13-13c in FIG. 1) that can be released at different points can be provided with such outlets (41 in FIG. 3). The closing device can also be provided with a hole, e.g. sieve-like, plates or the like. be formed, which may be advantageous for air transportation.

A further variant can consist in that the slide 51, for example on its underside, is connected to a toothed rack, by means of which it can be adjusted by means of the pinion 45 of the servomotor 46 together with the connected circuit 47, 48, 49. In order to ensure an optimal position of the orifice 41 between two rows of striking tools, control via position sensors can be seen, as is known, for example, from elevators in buildings is. However, the precise positioning for the discharge opening 41 is less important than for a corresponding feed opening, because the risk of clogging by regrind particles ejected by the striking tools 8 is lower.

With regard to FIG. 2, it goes without saying that groups 410 and 510 of striking tools 8 can also be assigned an inlet or outlet opening or can be released in their area. Furthermore, the impact mill 1b can also be equipped with stator tools.

The discharge opening 41, which exposes a housing opening at various points, is of course preferably to be arranged in each case behind that group of striking tools 8 (seen in the transport direction of the ground material) which are just supposed to act on the ground material. If the grinding material is also at least partially under the influence of gravity in a vertical arrangement of the shaft 4 according to FIG. 1, a slight aspiration or suction effect is usually applied to the opening 19 in the usual way, and possibly also to the lower part 20 of the Housing 2 are created, although for some applications, gravity alone may be sufficient. Furthermore, instead of the hose 52, any other flexible connection, e.g. a pipe joint to connect rigid pipes. It would also be conceivable to provide a rigid, full-width slot connection for a tube corresponding to the hose 52, whereas the slide 50 carries a limited orifice opening 41 which can be moved over the slot width, although in the embodiment shown the pneumatic conditions are more favorable.

In the embodiment according to FIG. 4, the mill 1c is provided with a rotor 22, which is only indicated by dashed lines, the rotor shaft 4 of which can be driven by means of an AC motor 53 which can be switched over to two different speeds. From a group of silos 54, the material to be ground can be fed individually or together - depending on the circumstances - to the flow meters 49. The individual components are weighed separately or mixed by at least one, possibly also several scales 49 and reach the feed apparatus of the mill 1c.

In order to obtain different grain sizes or to bring materials to be ground and subsequently mixed together later on the grain size spectrum, the AC motor 53, which is designed as a three-phase motor, has a first group 55 of connections, which, for example, result in higher speed, and a second group of connections 56, which cause a lower rotational speed of the motor 53. Accordingly, a switch package S1 and S2 are to be switched in opposite directions, i.e. if the switch package S1 is open, the switch package S2 is closed and vice versa. These switch packs S1, S2 can be actuated with the aid of magnets 57, 58. An interrupter switch 59 is provided for switching off.

For the automatic operation of the switch groups S1, S2, a program control device P is provided which, for example, has an astable multivibrator 60, on the two outputs of which signals opposite to one another are connected to the two magnets 57, 58. The time constants of this multivibrator 60 can be adjusted with the aid of an adjusting device 61 to adapt to different products or different grinding finenesses. In principle, it is a matter of adjusting the respective time constants the resistances, which can be changed, for example, with the aid of setting buttons 62.

Of course, it is by no means necessary to arrange resistors in the narrower sense of this word, rather they can be formed by any component that results in an adjustable resistance, for example field-effect transistors. This latter design will be particularly advantageous if automatic control is to be achieved, with a control signal being supplied via a line 63 and 64, respectively. As will be explained later, it may be expedient to regulate the changeover from one speed to the other automatically via the flow meters 49, which is why the corresponding output signals, e.g. can be fed via a data bus 65 to a signal processing stage 66. If necessary, the two lines 63, 64 can be interrupted with the aid of switches S3, S4 and can thus be switched from automatic control to manual control.

It goes without saying that the program control device P can be designed in various ways, for example with the aid of time relays, which can optionally directly actuate the switch packs S1, S2. Likewise, digital circuits with a counter as a timer, mechanical program control devices with cams or contact disks, etc. are conceivable.

In the operation of the mill 1c, the motor 53 is switched back and forth between its two speeds. It has already been mentioned that it is favorable for impact mills of the usual size to keep the number of switching operations as small as possible. It is particularly favorable if only a single switching operation needs to take place within a batch, so that switching frequencies differ from one switching operation per at least one minute, generally three minutes.

However, this means that at the exit of the mill lc during a time t1 (FIG. 5), during which time the motor 53 runs at the higher speed and the individual particles of the ground material are hit more often by the beaters, therefore a finer proportion of ground material is obtained. At the end of the period tl, the speed is switched over and the rest of the ground material is ground at a lower speed for a time t2, so that each individual part of the ground material is hit less frequently by the beaters. In order to nevertheless obtain a homogeneous product, it is advantageous to connect a mixer 67 to the outlet of the mill 1c. The construction of this mixer 67 may be arbitrary in itself, but is preferably chosen in accordance with DE-OS 3 117 023, which describes a mixer of the type shown.

It is now also understood why the quantity meters 49 are important, since this can ensure that a predetermined quantity of the mill lc is supplied in each case during the operating times t1 or t2. Therefore, these times t1 and t2 can also be determined by the quantity meter or weighing device 49, the switchover being able to take place when a predetermined, possibly adjustable weight is reached. A corresponding signal is then supplied to the program control device P via the lines 63, 64, as a result of which the changeover is effected.

To save switching operations, it may be expedient if the next batch is first processed at the lower speed for a period of time t2 ', whereupon the system then switches to the higher speed.

This shows a method in which a product of a first fineness of fineness is produced during a first period of time t1 or t2 and a product of a second fineness of fineness is obtained during a second grinding time t2 or tl, whereupon both grinding products are fed to a mixer . The corresponding fineness can be achieved in any of the ways shown in FIGS. 1 to 4, but possibly also by a combination of several of these measures.

Within the scope of the invention, it is of course also possible to use AC motors with more than two switching options, for example corresponding pole-changing motors. If desired, instead of a single opening 41, the slide 51 can have a plurality of such openings - distributed in the axial and / or in the circumferential direction. Likewise, the combinations of the described features are possible, such as the combination of several feed or discharge openings with at least one displaceable.

Claims (15)

1. Impact mill with a housing forming at least one grinding chamber, in which a rotor provided with projecting impact tools is rotatably mounted with its shaft, which impact tools are divided into individual groups in the axial direction of the shaft, the housing having at least one opening each for the feed or Has removal of the ground material, characterized in that for determining the fineness of adjustment devices (15, 15b, 15c; 41) are provided for the number of striking tools applied to each product part, and that for this purpose the mouth of at least one of the openings (13, 13e, 13f; 41) can be released in the area of one or the other group (110-310) of striking tools (8) and / or a plurality of feed or discharge openings (13-13e) are provided at different points in the housing (2) and / or a program control device is provided for switching an AC motor having at least two speeds, with the aid of a vers the operating time can be set at one or the other speed. 2. Impact mill according to claim 1, characterized in that for the optional release of an opening mouth (13-13c) at least one closing device (15, 15b, 15c) - For example, one, in particular several openings common, slide or flaps - is provided. 3. impact mill according to claim 1 or 2, characterized in that with the rotor (22) at least one Viewing device (35-39), in particular connected to a classifying wheel (38), and is preferably arranged between two groups (410, 510) of striking tools (8). 4. impact mill according to claim 1, 2 or 3, characterized in that a plurality of openings (13, 13a-13e) are distributed in the axial direction over the housing (2),
and that the rotor shaft (4) is preferably arranged vertically and a feed opening (13-13c) is assigned to each group (110, 210, 310) of striking tools (8), the regrind being transported by a group (110, 210, 310) of striking tools (8) secondly, at least partially under the influence of gravity. 5. Impact mill according to one of claims 1 to 4, characterized in that the feed opening (13-13c) - seen in the transport direction of the ground material - in front of the associated group (110, 210, 310) of impact tools (8) and / or the The discharge opening (41) is arranged thereafter. 6. Impact mill according to one of claims 1 to 5, characterized in that the rotor shaft (4b) is arranged horizontally and a suction device is connected to the discharge opening for the transport of regrind, 7. Impact mill according to one of claims 1 to 6, characterized in that a preferably flexible feed and / or discharge device (52) can be connected to the housing in various, for example axial, positions relative to the housing,
and that in particular the feed or discharge device (52) is connected to a slide (51) for covering the housing opening (s) to be closed. 8. Impact mill according to one of claims 1 to 7, characterized in that the housing (2) between the impact tools (8) of the rotor (22) carries stator tools (23-25), which are preferably approximately annular at least behind the respective feed opening ( 13) extend around the inner circumference of the housing (2) and in particular in cross section are at least approximately triangular with one side (26) abutting the housing wall and an inclined side '(27) pointing inwards in the transport direction of the material to be ground. 9. Impact mill according to one of claims 1 to 8, characterized in that the mouth of at least one opening (13a) is slot-shaped in the circumferential direction of the housing (2), the slot height preferably being smaller than the axial distance between two adjacent rows of impact tools (8 ) is. 10. Impact mill according to one of claims 1 to 9, characterized in that a plurality of openings (13, 13a-13e) are distributed over the circumference of the housing (2). 11. Impact mill according to one of claims 1 to 10, characterized in that the regrind from the grinding chamber (3) without the interposition of a sieve can be removed directly via at least one discharge opening (20, 41) or that the major part of the housing wall (2 ) is designed without a sieve and a sieve (18) can only be connected upstream in the area of at least one discharge opening (19). 12. Impact mill according to one of claims 1 to 11, characterized in that both a plurality of feed openings (13-13e) and a plurality of discharge openings (41) are provided. 13. Impact mill according to one of claims 1 to 12, characterized in that at least one discharge opening (20) is connected to at least one feed opening (13, 13a-e) for the repeated feeding of the ground material, in particular its coarse fraction, into the grinding chamber (3), a viewer (35-39) preferably being interposed. 14. Impact mill according to one of claims 1 to 13, characterized in that at the entrance of the mill (lb, lc) a quantity measuring device (49) is provided for the regrind fed, the output signal of at least one setting device (42 - 47), e.g. an adjusting device for the strength of the transporting air flow and / or an adjusting device for the speed (v) of the AC motor (53) can be fed. 15. Impact mill according to one of claims 1 to 14, characterized in that the operating time for each speed is at least 1 minute, e.g. at least 3 minutes, and that the output of the impact mill (lc) is connected to a mixer (67).

Images