EP0155556B1 - Air suction device for a sifting or sorting apparatus - Google Patents

Abstract

In the case of an apparatus for cleaning grits, which has a plurality of superimposed screen layers, which can be vibrated by means of at least one unbalance exciter and with an inlet or outlet for the product inlet or screen discharge arranged at one end, collecting means with adjustable setting flaps for the screenings, as well as an air circulation through the screen layers over an air distribution chamber in a suction collecting channel adjustable by means of adjusting flaps, it is provided that the apparatus is constructed as a stand with a stand head, a stand base and a vertical intermediate support connecting said two parts, the screen layers being constructed as a dust box and being vibratably supported in the vicinity of the stand base, the stand top being formed by the upper air distribution chamber.

Description

The invention relates to a device for extracting air for sighting or classifying devices according to the preamble of claim 1.

Sighting and classifying devices are special machines that are used in large numbers in grain milling. It is used to separate grain as well as regrind into the desired fraction.

In both types, a work table forms the heart of the device, through which the material to be separated is conveyed by a vibration movement. Supported by an air velocity that is adapted to the fineness of the product, the goods are separated according to their weight as well as their size or a corresponding form factor. A prerequisite for high separation quality is, in particular, a quantity of air that can be controlled over the entire length of the machine, for which purpose an upwardly tapering air distribution space with a number of approximately 10 to 20 air duct chambers is used. A throttle element is assigned to each air guide chamber or bulkhead, with which the amount of air can be adjusted in accordance with the desired separation work. Up to now, the air has been centrally aspirated at one point in known machines from the air distribution room.

From AU-B-483 698 a device for cleaning and separating granular material is known, in which material conveyed on a sieve is first partially sucked into a cyclone-type centrifugal separator for separation purposes.

This centrifugal separator has in its center a suction channel running transversely to the flow direction within the separator. Air and lighter particles carried on the inner wall of the centrifugal separator can be drawn off via individual openings in the outer wall of the transverse suction channel. Heavier particles, which move closer to the inner wall compared to the lighter particles in the centrifugal separator, are excreted at their opening in the outer wall after separation in the centrifugal separator so that they are not yet completely circulated.

However, this device has the disadvantage that the homogeneous air flow is disturbed due to the edges of the openings in the suction channel, but also due to the edges of the opening in the outer wall of the centrifugal separator. At these points, air vortices arise, but also dead spaces in which material is undesirably deposited, which worsens the flow properties within and thus the suction and separation effect of the device as a whole.

A similar device is known from DE-A-2 342 091, in which a deflection sifter which is curved approximately 180 ° in a circular manner also has in its center a separating channel which runs transversely to the flow direction in the deflection sifter. With this device, coal grains are to be freed of dust-like particles adhering to the surface and the coal fraction lying above 0.5 mm is thrown out of the gas flow during the 180 ° deflection in the classifier and discharged via a line into a setting machine. The dust-like fraction below 0.5 mm is removed with the gas flow through the gas exhaust pipe arranged on the deflector into a dust separator. Vortexes also occur in this gas stream, whereby in addition to the disadvantages already described in AU-B-483 698 with regard to vortex formation such as this, a flap which changes the free flow cross section in the flow beginning region of the deflector sifter very quickly has particle deposits which immediately cause a disturbance the function of this valve.

Finally, from FR-A-926 612 a suction channel is known which is partially installed or embedded in a hood similar to an air distribution space. The sucked-in air sweeps in opposite directions on both inner sides of the suction channel, and the air flow vortices thus formed mutually eliminate each other when they meet. At these points of elimination of the air, undesired dead spaces ultimately arise, which lead to undesired product deposits and require frequent and time-consuming cleaning.

Proceeding from this, the object of the invention is to eliminate these disadvantages as far as possible with a simple structure.

According to the invention, this is achieved in the device of the type mentioned at the outset by the features of the characterizing part of claim 1.

The tan gential transition creates a cyclone flow in the suction channel, which has the advantage that neither dust nor other particles can be deposited. The invention thus not only ensures that the machine is kept clean, but also improves its operational safety.

If a throttle is assigned to each air guide chamber, a strong vortex flow is advantageously formed in the suction channel regardless of the open position of the throttle. In addition, it was found that even the complete closing of individual throttles did not affect the vortex formation or the automatic cleaning of the suction channel.

Once optimal positions for the chokes have been found, they can easily be used again at any time if the same process is repeated.

In an advantageous embodiment of the device according to the invention, the throttles can be arranged in the transition area between the air distribution space and the suction duct, which results not only in a compact design but also in a favorable guidance of the air flow, because the transition area and the throttles form only one common disturbance in the air flow.

The throttles are very particularly preferably designed as adjusting slides. It has been shown that, in connection with the tangential transition from the air distribution space into the suction channel, adjustment slides allow a very precise and almost linear adjustment of the local air flow rate over a wide range, since the deflection angles for the air flow are changed only slightly. In devices with less stringent requirements for the setting accuracy of the air quantity, the throttle elements can preferably be designed as adjusting flaps and, seen in the direction of flow of the air, can be arranged behind the air distribution space.

A further, very advantageous embodiment of the device according to the invention also consists in the suction channel being designed as a separate component and the air distribution space being placed as a lying cyclone (“backpack-like”). On the one hand, this makes it possible to save on the overall height of the overall device, but at the same time it is also inexpensive to manufacture, particularly if the suction channel has a constant cross section. With regard to this constant cross-section, tests have shown that, especially with difficult flour-like goods, ie for the corresponding semolina passages, there is virtually no longer any undesirable product deposits. It is also very advantageous if the suction channel is at least partially rounded in cross section, preferably circular. It has also proven to be particularly favorable if the diameter of the cross section of the suction channel is approximately one third to one fourth the width of the sieve layers.

• Fig. 1 eine Längsansicht einer Grießputzmaschine mit einer erfindungsgemäßen Absaugvorrichtung;
• Fig. 2 den Schnitt 11-11 aus Fig. 1;
• Fig. 3 eine schematische Darstellung des oberen Luftverteilraumes mit Absaugkanal und Klappenverstellung bei einer erfindungsgemäßen Vorrichtung;
• Fig. 4 eine Schnittdarstellung längs IV-IV in Fig. 3;
• Fig. 5 eine zur Darstellung nach Fig. 3 geänderte weitere Ausführungsform einer erfindungsgemäßen Vorrichtung mit Schieberverstellung, sowie
• Fig. 6 eine Detail-Draufsicht auf die in Fig. 5 dargestellte Vorrichtung.

The invention is explained in more detail below in principle by way of example with reference to the drawing. Show it:

• Figure 1 is a longitudinal view of a semolina cleaning machine with a suction device according to the invention.
• FIG. 2 shows the section 11-11 from FIG. 1;
• Figure 3 is a schematic representation of the upper air distribution space with suction channel and flap adjustment in a device according to the invention.
• Fig. 4 is a sectional view along IV-IV in Fig. 3;
• 5 shows a further embodiment of a device according to the invention with slide adjustment modified as shown in FIG. 3, and
• Fig. 6 is a detailed top view of the device shown in Fig. 5.

First of all, reference should be made to FIGS. 1 and 2, in which a so-called “double machine” is shown, which consists of two semolina cleaning machines that are completely separate in terms of working technology, as shown in FIG. 2. These two semolina cleaning machines are arranged on the left and right with respect to a central stand construction.

1 shows an inlet 1 at the top left for the product to be supplied to the device and outlet 2 at the bottom right for the screen rejection. Furthermore, three screen layers 3 arranged one above the other are provided, an inner collecting device 4 and an outer collecting device 5 being arranged beneath them (FIG. 2), in which the sieve diarrhea is collected. As a rule, each individual collecting device 4 or 5 has two processes 6 or 7. The sieve layers 3 are each combined to form a cleaning box 8 (FIG. 2), so that each cleaning box 8 is assigned two outlets 2 for the screen rejection and four outlets 6 and 7 for the screen diarrhea in accordance with the illustrated embodiment. Each cleaning box 8 is supported by an end support 12 (FIG. 1) via oscillating elements or hollow rubber springs 13 on a stand base 10 of a stand 9 so that it can vibrate. An unbalance exciter 14 is fixedly connected to the end support 12, the direction of impact (cf. arrow 15 in FIG. 1) can be adjusted by rotating the unbalance exciter 14 on a tubular cross connection 16. Likewise, what is known can regulate the strength of the unbalance forces by appropriate adjustment of the unbalance weights 17. At the cross connection 16, two unbalance exciters 14 are attached and electrically connected so that they rotate in opposite directions. This eliminates their lateral unbalance components and there is a purely linear longitudinal vibration in the direction of arrow 15. A cover 18 is attached above the unbalance exciters 14, which is designed as part of the vibrating system for structural simplification.

The collecting device 4 is designed as a vibrating conveyor trough, which rests on both end sides on a support 19 mounted in rubber (FIG. 1). The oscillation drive of the collecting device 4 takes place via a lever 20 which connects the oscillating end support 12 to the support 19. Depending on the height of the point of application of the lever 20 on the support 19 (this height can be adjusted), the swing stroke of the collecting device 4 can thus be selected or adjusted independently of the swing stroke of the cleaning box 8. The stand 9 carries all non-vibrating components directly, the vibrating elements being mounted above the lower part of the stand. The stand 9 also has a vertical support 21 on each end side (FIG. 2), which merges into a foot construction at the bottom via an extension. According to the illustration in FIG. 2, the vertical support 21 extends a little beyond the uppermost sieve position and supports the stand head 11, which essentially forms the upper air distribution space 22. This upper air distribution chamber 22 has a tapered shape and is upwardly ^g over its length by bulkheads 23 into sixteen separate Luftführun skammern 24 divided. The bulkheads 23, as can be seen in FIG. 1, are brought close to the uppermost sieve layer, the distance being chosen so that it is somewhat larger than the greatest layer thickness "S" of the material which ever occurs (see FIG. 3 and Fig. 5).

The upper inclined surfaces of the air distribution space 22 have transparent windows 25 over their entire length (FIG. 2), so that the flow behavior of the material over the top sieve layer 3 can be controlled with an electric light source from the outside of the device. 3 and 4 can be seen between the upper end of the air distribution space 22 and one sitting on the air distribution space 22. Suction manifold 27 throttles in the form of adjusting flaps 28, which can be individually adjusted according to the respective air requirement via a head 29. 3 to 6 show, the inner walls of the air distribution space and the suction duct adjoin one another in a transition area such that the air passes tangentially into the suction duct, so that a cyclone flow forms in the suction duct.

When the semolina cleaning machine shown is started up, the vibrator 14 is switched on so that the cleaning box 8, the bottom 32 and the collecting devices 4 and 5 carry out the preselected oscillating movement in the longitudinal direction of the device. Likewise, the entire device is placed in a slight negative pressure via the suction collecting duct 27 or an aspiration associated therewith. Depending on the separation task, all slides and flaps 28 are provisionally adjusted, after which the product can be fed into the inlet 1. The product immediately falls on the top sieve layer 3. Due to the shaking movement which is imprinted on the material, as well as the sieve layers deliberately inclined downwards from the inlet 1 to the outlet 2 and the air flow through the sieve layers 3, the product behaves like a liquid (fluidized ). The central task of the semolina cleaning machine lies in the actual sieving process. So the air flow must not be adjusted so much that the entire product layer could be lifted off the sieve layers. Rather, the air primarily serves the function of locating the product and distributing it evenly over the entire surface.

Depending on the task, it is required that the product should be fractionated into coarse, medium and fine size or into cooking size and medium size etc. In the second case, e.g. B. the first six chutes 34 can be directed into the collecting device 4, the subsequent eleven chutes 34 into the collecting device 5. In this case, the two sieve passes are finished products that can be delivered to the corresponding storage cells or to the consumers. The screen rejects at the outlets 2 are partially re-ground or comminuted and then reach a second, appropriately set, semolina cleaning machine.

The specific sieve mesh sizes suitable for the respective task must be selected in each semolina cleaning machine.

Once the semolina cleaning machine is in full operation, the miller's actual task begins, namely the assessment of the functioning of the device and the quantitative and qualitative assessment of the fractions obtained.

For this purpose, the light source 26 (FIG. 2) is switched on, so that the entire space within the air distribution space 22 is illuminated. The flow behavior of the product within the individual air guide chambers 24 can be observed through the windows 25 over the entire length. If an image similar to the boiling water appears in one or more air guiding chambers 24, the amount of air in the relevant air guiding chambers 24 is throttled via the adjustment flaps 28. Conversely, a jam can also occur at individual points: here the local air volume must be increased accordingly. If the flow behavior of the product is flawless and if there are no parts in the mixed product (outlets) that belong to sieve diarrhea, the quality of the sieve diarrhea is checked again and the chutes 34 are adjusted to the correct collecting devices 4 and 5, respectively.

As can be seen from FIG. 1, two different processes 6 and 7 can be selected from each collecting device 4 or 5, so that four different fractions can be separated from each cleaning box 8. The cross section of the suction channel 27 increases in the direction of the air flow.

5 and 6 show, as an alternative to FIGS. 3 and 4, a further advantageous embodiment. Instead of the adjustment flaps 28 used there, sliders 40 are used in the solution of FIGS. 5 and 6. These sliders 40 allow more precise adjustment of the air requirement in all slider positions. A proportional change in cross-section of the slide opening is caused in accordance with the revolutions of the head 29. If a flap 28 were used instead of a slider 40, no similar, proportional cross-sectional change would occur in this case, however, since in such a case the effective opening cross-section would no longer change in proportion to the rotation of the head 29. The slide solution also has the further advantage that the free cross section of the suction collecting duct 27 is not influenced by the different open positions of the slide 40.

5 and 6, in particular, it has been shown that the suction collecting duct 27 can be designed with a constant cross section in the air flow direction. Corresponding practical tests have shown that the suction device according to the invention can also be used in particular in separation devices which primarily work according to their weight, as well as in different versions of light-grain readers and also in combined machines. Work processes are always carried out by the machines mentioned, in which larger work surfaces in a plurality smaller, controllable areas of the air volume must be divided, but it must be possible to control the air volume only above the bed layer (usually on the suction side). This gives good controllability of the air volume for suction operation without the disadvantages that often occur in the prior art due to the strong dusting of the corresponding throttle ducts.

Claims (8)

1. Device for the extraction of air for separating or grading machines, having an air distribution chamber (22) above the screen layers (3), which has a multiplicity of air circulation chambers (24) formed by partitions, and to whose upper region a suction channel (27) extending over its entire length is connected, characterized in that the inside walls of air distribution chamber (22) and suction channel (27) connect to each other in a transition region in such a way that the air passes tangentially into the suction channel (27), so that a cyclone flow forms in the suction channel (27).

2. Device according to Claim 1, characterized in that a throttle (28) is allocated to each air circulation chamber (24).

3. Device according to Claim 2, characterized in that the throttles (28) are disposed in the transition region between the air distribution chamber (22) and the suction channel (27).

4. Device according to Claim 2 or 3, characterized in that the throttles are designed in the form of adjusting slides (40).

5. Device according to Claim 2 or 3, characterized in that the throttles are designed as adjusting flaps (28) and, viewed in the direction of flow of the air, are disposed downstream of the air distribution chamber (22).

6. Device according to one of Claims 1 to 5, characterized in that the suction channel (27) is designed as a separate component and is placed on the air distribution chamber (22) as a horizontal cyclone.

7. Device according to one of Claims 1 to 6, characterized in that the suction channel (27) has a constant cross-section.

8. Device according to one of Claims 1 to 7, characterized in that the suction channel (27) has a round, preferably circular cross-section.

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