EP0694341A1 - Device for cleaning screens - Google Patents

Abstract

The sieve box (1) and sieve frame (3) have matching strip dividers (12') pref. for a two-side fines discharge. The sieve frame can have additional transverse dividers (13) forming several fields, and a corresp. number of cleaning elements (6) are provided. The sieve frame pref. has the lowest possible height and is designed as a freely interchangeable insert frame, typically of metal. The sieve box can be made of wood forming an outer frame with 1 to 3 ducts. The surfaces, contacting the prod. are coated with plastics, and the base plate of the box can be made of metal or plastics. <IMAGE>

Description

The invention relates to a device for cleaning screens, in particular the screens of plan sifters in mills, which act as freely movable cleaning elements in a screen box with a base plate and fine material discharge and an insert screen frame.

A plan sifter, especially the large plan sifter or square plan sifter, is a large cube shape with large flat elements and is a special separating device, which is characteristic for the sifting of grist-like, semolina and flour-like products in the milling process technology, and for sorting different types of grains such as wheat, Rye, corn, barley, etc. is used.

In many separation techniques, for example in chemical process engineering, it is known to reduce the product moisture, if necessary, so that the separation devices do not become clogged. In contrast to this, optimum grinding moisture must be sought for the processing of ground grain products, to make flour, semolina, haze, etc. However, because grinding and sifting have to be carried out repeatedly in a grain mill, the moisture depends on the grinding and not on the best possible visual effect.

It is known that many grinding fractions have poor flow behavior or visual behavior due to the high humidity, as can also be experienced in connection with flour sieving in the domestic kitchen.

All possible sizes of mesh sizes are used in a plan sifter, from the finest, for example 80 microns, to the coarsest. The same applies to everyone, to achieve maximum visual performance without any sieve mesh clogging. The highest possible throughput and the highest possible quality of the ground products must be achievable. In contrast to the classic sieving technique, a closed product layer of up to several centimeters is maintained with the miller sifting over the sieve covering. This ensures that a greater downward pressure (gravity) acts on the finer, heavier parts against the screen covering, which leads to a higher throughput or more screening capacity. On the other hand, more flat shell parts than coarse material should float off with the layer as a top screen. This type of "thick-film sifting" brings greater difficulties to the wet products and has a strong tendency to clog the screen fabrics.

Over the past 100 years, systematically more efficient plansifters have been developed and screen cleaning has been continuously improved. Countless variations of shapes and materials have been tested and partly used in practice. Few shapes have survived in large-scale plansifters, although interestingly 5 to 10 centimeters long textile belt pieces with a metal button in the middle have been widely used for screen fabric cleaning. The screen fabric cleaners are individually inserted or locked between the screen fabric covering and a supporting grate. The underside of the sieve frame is therefore covered with a metal grid, which is the task for the sieve fabric cleaners. The metal grille usually has a slight ripple, so that the metal button receives strong impacts from the metal grille. The belt piece receives a rattling and noise-generating, intensive traveling movement due to the oscillating or circular movement of the entire plan sifter. In this way, the mesh openings with the fringed ends of the belt pieces are kept free or clean. The metal grille and the metal button have an important function for the movement of the screen cleaner. The movement also creates a disadvantage as a disadvantage audible noise. Sieve cleaning pieces made of plastic in various forms are also known and work in the same way.

Another problem in plansifters is that the base plate is kept completely free. The fine material (diarrhea) that has fallen through the sieve mesh should be cleared from the base plate with the shortest possible dwell time and discharged through side slots. A separate category of cleaning elements, the so-called floor cleaners, was also developed for this. Common shapes are triangular and quadrangular, rhombus or polygon shapes.

Many factors influence the way the plansifters work. For example, a freshly covered sieve frame regularly works better, since not only the wear of the covering but also the degree of tension in the sieve fabric is important. Experience shows, however, that a plan sifter has natural performance limits even in the best condition. The intensity of the oscillating movement, ie the maximum acceleration, is also limited, on the one hand by the maximum permissible forces in the plan sifter housing, and on the other hand also by the movement behavior of the goods. Accelerating forces that are too strong impede the free flow of the material. Accelerating forces that are too strong impede the free flow of the material. Depending on the specific quality of the individual visual fractions, the performance data are given.

In a mill, the plan sifter is the machine that requires the greatest effort in terms of cleaning. In recent times, great importance has been attached to the fact that the processing machines are as self-cleaning as possible, but can be cleaned easily and with little effort if necessary.

The screen frames of plan sifter screens today have a smooth floor on which the freely movable floor clearers rest. There are usually corrugated grids or support grids for support between the bottom and the covering of the screen arranged by cleaning elements. From EP-A-330 846, however, designs without corrugated mesh are already known.

The cleaning elements can e.g. braided belt material, which is provided with a metal button on the underside and which start to vibrate when moving over the corrugated grille, so that they hit the screen covering lightly and clean it. This also causes a significant level of noise.

However, other forms of cleaning elements are also known, such as Screen cleaner in the form of equilateral triangles (US-PS 2086199) u. Like. According to EP-A-330 846, such screen cleaners can also have the basic shape of a three-armed star, without the use of corrugated grids, and consist of elastic material. Furthermore, these sieve cleaners are supported on the smooth sieve bottom with a stem-like foot. The cantilevered arms of the star achieve a high moment of inertia during the tilting movement with a relatively low overall weight, so that sufficiently violent blows are exerted on the fabric. The arms of these screen cleaners are provided with recesses that quickly clog and require additional cleaning.

The invention was based on the object of designing a device for cleaning sieves, in particular the sieve frame - so-called sieve cleaners - in such a way that the disadvantages of the prior art described are avoided, the handling and in particular the cleaning performance and the self-cleaning of the sieve cleaners should be improved.

The solution according to the invention is characterized in that the arms of the screen cleaner have a largely square cross-sectional shape with a roof-shaped elevation. This roof-like elevation in turn preferably has a triangular, trapezoidal or round cross section.

Knowing the solution according to the invention, its advantages are also obvious. The roof-shaped elevation of the arms prevents the regrind from sticking to the sieve cleaner (sanitation) and also improves the cleaning performance. Furthermore, the bending behavior of the arms can be adapted to the requirements and kept constant. The fact that such a solution is not obvious is shown solely by the development of screen cleaners to date, which does not reveal any comparable simple and reliable solutions.

The sieve cleaner can be placed on the base plate in the clearing fields. The screen cleaner is provided with a wobble foot, which is preferably made of non-metal material, which is arranged in the area of the vertical axis of gravity of the screen cleaner, for the purpose that a constant change of screen fabric cleaning and floor clearing takes place due to the corresponding wobbling movements.

According to a first embodiment, the screen cleaner is designed as a boomerang with two projecting arms which have cleaning means for the screen fabric projecting upwards, a bottom and slot clearing nose preferably being arranged on the screen cleaner opposite to the projecting arms.

According to a second embodiment, it has a three-arm design, with cleaning agents for the screen fabric being arranged on at least two arms and one arm having a bottom and slot clearing nose which is extended outwards.

According to a further embodiment, it is designed with 4 arms, with at least one arm having an elongated bottom and slot clearing nose.

In all configurations, however, it is very important that it is made of resilient material, preferably of plastic without metal. This ensures that with each impact of an arm on the side parts of the screen box or on the web strips, the screen cleaner is thrown in any direction via the corresponding spring force. By means of corresponding uninterrupted movements, including the wobble movement, it is statistically seen that every batch, be it the base plate or the screen fabric, is cleaned with great frequency. Even the smallest quantities of fine goods are transported away. The sieve cleaner should be selected so large that it has a certain mass and, with its largest horizontal dimension, is more than 50% of the correspondingly smallest dimension of the individual clearing fields. An optimal cleaning effect has also been found in all tested shapes if the clearing fields formed have a square shape in the floor plan if possible, since then the screen cleaners will optimally clean in all spatial directions or quickly clear the product.

The previous optimal function was obtained when the arms have a cross-section with a roof-shaped elevation, with the tip up and the wide part down. This not only supports the product movement over the base plate, but also helps that the screen cleaner stays clean even without product buildup. The arms preferably have different cleaning agents, for example bristles or knobs and / or cleaning ribs. Floor cleaning is optimal if a sliding foot is only arranged on one arm.

The screen cleaner should be built slightly lower than the free height between the floor and the screen covering. So that both the bottom and the screen fabric are processed equally, the screen cleaner is provided with a wobble foot in the central area, so that the extreme ends of the arms next to the horizontal movement of the screen cleaner above the bottom in a constant interplay of up and down movements, up and down, work on both levels.

Another particularly advantageous embodiment is that the arms are provided with a plastic impact head at their extreme ends. On the one hand, this serves as protection for the fabric cleaning agent in the form of knobs or brushes, on the other hand, it enables the sieve frame to be as low as possible, and it supports the jumping movement of the sieve cleaner so that the element is not damaged.

The invention is particularly advantageously used in a plan sifter, the housing of which has a plurality of sieve stacks, each consisting of a larger number of sieve boxes with a base plate, sieve frame and sieve channels and having a rectangular or square shape, the sieve frames covered with sieve fabric in relation to the sieve box are interchangeable and the sieve boxes above the base plate together with the sieve frames form free diarrhea and product discharge spaces into which sieve cleaners can be placed, resting on the flat base plate, the sieve frames being designed to be rust-free to reduce the sound pressure from the source noise.

Since it was previously not possible to significantly reduce the noise of a large plan sifter, surprisingly, a noise level of only a little more than 72 dB (A) resulted in a plan sifter according to the invention, compared to 84 dB (A) in comparable plan sifters of the prior art . An important measure is seen in the choice of special screen cleaners, preferably made of non-metal material, and the screen frame without the previous metal support gratings for the screen fabric cleaners. There are no longer any relative movements from metal to metal.

The invention is explained in more detail below with the aid of exemplary embodiments.

Fig. 1

einen Siebrahmen in einer Auflegebewegung auf einen Siebkasten ;

Fig. 2

ein Grundriss eines Siebkastens mit eingelegtem Siebrahmen, teilweise ohne Siebgewebe ;

Fig. 3

einen Schnitt a - a der Figur 2 ;

Fig. 4

einen Schnitt b - b der Figur 2 ;

Fig. 5

einen einzelnen Einlege-Siebrahmen ;

Fig. 6

einen Schnitt c - c der Figur 5, wobei mehrere Einlege-Siebrahmen gestapelt sind ;

Fig. 7

einen Stapel von Siebkasten mit Auflegebewegung des obersten Einlege-Siebrahmens ;

Fig. 8

einen Grossplansichter mit eingebautem Siebstapel ;

Fig. 9

zeigt einen Siebreiniger mit Bumerang-Form im Grundriss :

Fig. 9a

eine Ansicht gemäss Pfeil a ;

Fig. 9b

eine Seitenansicht gemäss Pfeil b und

Fig. 9c

den selben Siebreiniger im Einsatz bei der Schlitzreinigung ;

Fig. 10

zeigt einen 3-armigen Siebreiniger im Grundriss

Fig. 10a

den 3-armigen Siebreiniger bei der Schlitzreinigung

Fig. 10b

einen Schnitt J-J der Figur 10 ;

Fig. 10c

einen Schnitt H-H der Figur 10 ;

Fig. 11

zeigt einen 4-armigen Siebreiniger im Grundriss in einer Eckreinigungsposition ;

Fig. 11a

in einer Reinigungsposition im Schlitz- sowie am Siebgewebe ; und

Fig. 11b

in Siebreinigungsposition.

Show it :

Fig. 1

a sieve frame in a laying motion on a sieve box;

Fig. 2

a floor plan of a sieve box with an inserted sieve frame, partly without sieve fabric;

Fig. 3

a section a - a of Figure 2;

Fig. 4

a section b - b of Figure 2;

Fig. 5

a single insert screen frame;

Fig. 6

a section c - c of Figure 5, wherein a plurality of insert screen frames are stacked;

Fig. 7

a stack of sieve box with laying movement of the top insertion sieve frame;

Fig. 8

a large plan sifter with built-in sieve stack;

Fig. 9

shows a sieve cleaner with boomerang shape in the floor plan:

Fig. 9a

a view according to arrow a;

Fig. 9b

a side view according to arrow b and

Fig. 9c

the same screen cleaner used for slot cleaning;

Fig. 10

shows a 3-arm screen cleaner in the floor plan

Fig. 10a

the 3-arm screen cleaner for slot cleaning

Fig. 10b

a section JJ of Figure 10;

Fig. 10c

a section HH of Figure 10;

Fig. 11

shows a 4-arm screen cleaner in the floor plan in a corner cleaning position;

Fig. 11a

in a cleaning position in the slit and on the screen mesh; and

Fig. 11b

in screen cleaning position.

In the following, reference is now made to FIGS. 1-4. A screen box 1 has a plurality of discharge channels, two discharge channels for the screen repulsion or for the coarse material, 2A and 2A 'and a discharge channel 2F for the screen diarrhea or the fine material.

A sieve frame 3 is drawn in Figure 2 in a slightly inclined position and represents a laying movement of the sieve frame 3 on the sieve box 1. The inner surface of the sieve box 1, below the sieve frame, is closed with a flat base plate 4, so that the fine material or the sieve diarrhea can only be cleared from the base plate 4 through lateral slot openings 5 (FIG. 3). Sieve cleaners 6 and 6 'are placed on the base plate 4 before the sieve frame 3 is inserted. The screen cleaners 6 and 6 'have a double function, with a scraper foot 7 the screen diarrhea on the flat base plate 4 is to be cleared out. According to the example in FIGS. 1-4, the fine material is only discharged via the discharge channel 2F, so that the fine material must be moved in a corresponding longitudinal direction arrow 9 over the entire length of the floor against the slot openings 5. The sieve box 1 has web strips 12 'directly above the floor, which divide the surface of the base plate 4 into three longitudinal fields. These web strips 12 'serve primarily to increase the stability of the base plate 4. The sieve frame 3 also has web strips 12 which are arranged exactly above the web strips 12 of the base plate.

The sieve frames additionally have transverse web strips 13. This results in the example of FIGS. 1-4 not only clearing fields B, D and F, as they result from the web strips 12 'of the base plate 4, but also by the additional subdivision of the Sieve frame 3 with the cross bars 13 additional clearing fields A, C and E. The number of clearing fields (A ... F) is thus determined by the corresponding subdivisions of the insert sieve frame. It is crucial that a screen cleaner 6 is inserted in each of the common clearing fields formed in this way, which combines, both keeps the screen fabric free at the top and clears the bottom at the bottom. Figures 3 and 4 each show a section of Figure 2, two screen boxes 1 are placed on top of each other. A sieve frame 3 is inserted in each of the sieve boxes 1, so that a free product fall-through and discharge space 11 is formed between the sieve cloth 10 and the base plate 4, in which the sieve cleaners 6, 6 'etc. can move freely. The scraper foot 7 of the screen cleaners 6, 6 'also has the function here of removing the fine material from the cleaning field B to A or. D to C resp. F to promote E, which is easily possible because the cross bars 13 are arranged only on the sieve frame 3 and not on the base plate, so that a slot 5 'is formed at the corresponding location above the base plate. With knobs or brushes protruding upwards, the screen fabric 10 is continuously cleaned cleanly over the entire screen area. The screen cleaner has a wobble foot 14 in its central area, so that the screen cleaner alternately fulfills the corresponding function once by slightly tilting movements upwards and downwards and, apart from friction and inertia forces, can move freely over the flat base plate 4.

A multi-armed design of the screen cleaners 6, 6 'has the great advantage that every surface part of the screen fabric is just as in the bottom plate, up to the outermost corners is kept clean. The screen cleaners ensure an optimal cleaning effect in all room directions. The relatively large mass of the screen cleaner 6, 6 ', as well as the low-friction base plate support a very intensive movement of the screen cleaner 6, 6'. Even during long periods of operation, the screen cleaner is able to keep the screen mesh and base plate clean.

FIG. 5 shows an almost ideal clearing or cleaning field division with 9 fields, the sieve fabric 10 being shown only over half the sieve frame 3. The length of a cleaning field is denoted by Län and the width by Bre. Considerable forces are used to cover the screen. Another key point of the new invention is that the sieve frames are made from thin and light metal strips, which relates in particular to the frame profiles 13, 13 'and 14. As can also be seen from FIG. 6, the sieve frames 3 have a covering on one side only, namely the sieve fabric tension. On the opposite side, the sieve frame is open, so that the sieve fabric 10 is now equally freely accessible and easy to clean on both sides for the first time when inserting or replacing sieve frames.

The entire light metal frame can be produced in one piece using a metal die-casting process or, preferably, as a welded construction. It is very important that the frame allows a minimal deflection in the elastic area due to the tensile forces from the screen covering, which supports the maintenance of the tension in the screen fabric during operation. The deflection is symbolically indicated by line 15 (Figure 5). For a screen change, a larger number of reserve screen frames 3 with different coverings must be kept ready. The fact that the sieve frames have sufficient inherent rigidity with very thin frame profiles and only about half the thickness D compared to the known sieve frames means that they require little space for replacement storage, as can be seen from FIG. 6 is. However, the web strips 12, 12 'are expediently also produced from a corresponding metal profile, which can be a solid or hollow profile. The use of an all-metal frame has proven to be particularly advantageous. Such a frame has high flexural rigidity if a corresponding elasticity value is preferred. The screen frame can also be designed as a metal, wood or metal-plastic composite.

FIG. 7 shows a stack of 8 sieve boxes 1 stacked one on top of the other, 3-arm sieve cleaners being inserted.

FIG. 8 shows an entire square plan sifter, the door 18 for a sieve compartment being removed and an entire sieve stack 16 being visible. The sieve stack 16 has a sieve box 1 in a known square plan sifter 24. With the sieve box, the number of sieve boxes and sieve frames can be increased by at least 10% while maintaining the space for product conveyance above the sieve and at the same height of the plan sifter housing. The entire plan sifter 17 has a swing drive, not shown, which forces all screens to have a circular movement, for which purpose the plan sifter 17 is suspended on bars 19 as a cantilever. The goods are fed to the sieve stacks via inlet connectors 20, 20 'etc. and the sorted goods are discharged via discharge connectors 21, 21' etc.

9, 9a and 9c, a screen cleaner is designed as a boomerang 30, with two typical, angled cleaning arms 31, respectively. 31 '. The two arms are provided with knobs 32, which have the function of screen fabric cleaning. The boomerang 30 is provided in the vertical axis of gravity S with a wobble foot 14 which is a dimension "X" of a few millimeters compared to the two support feet 33 and. 33 'protrudes. Furthermore, the boomerang 30 opposite to the two arms 31, respectively. 31 'has a bottom and slot broaching nose 34 which projects so far that the corresponding part of the fine material passes through the slot 5 can push through, as expressed in Figure 9c. So that the necessary impacts from the side parts 35, for example of the sieve frame 3, also occur when cleaning the slot, the boomerang 30 has an arch 36 in the direction of the bottom and slot clearing nose 34. For the proper functioning of the cleaning element, it is very advantageous if only the wobble foot 14 protrudes, but the support feet 33, 33 'and the lower floor clearing edge 37 of the slot and floor clearing nose 34 are of identical height. This creates a free interplay between the operational elements, and it results statistically, with very high accuracy, corresponding to approximately the same number of work assignments. In FIG. 9c, the knobs 32 are simultaneously in use for cleaning the screen fabric 1 and the bottom and slot clearing nose 34 for cleaning the slot 5.

FIG. 10 shows a 3-star 40 in which three arms 41, 41 'and 41' 'are offset by 120 ° to one another. To protect the screen fabric cleaning agent, for example for the knobs 32, each of the arms is designed on the outside as a baffle head 42, which is the actual abutment part for the screen cleaner. As can be seen from the two sectional drawings H-H and J-J, the arms 41, 41 'and 41' 'each have a roof-like shape in cross section. The two arms 41, 41 'are of identical design, but the arm 41' 'additionally has a bottom and slot clearing nose 34.

FIGS. 11-11b show a 4-star 50. Arms 51 and 51 'are of identical design, arm 51''is similar, but has a cleaning rib 52 instead of the cleaning knobs. In analogy to the 3-star 40, the arm 51 '''additionally has a bottom and slot clearing nose 34. In FIG. 11a, the knobs 32 are used for cleaning the screen fabric, whereas in FIG. 11b bristles which are on the arm 51 '''are inserted, clean the screen fabric 10. FIG. 11 shows the 4-star cleaner 50 in the phase of cleaning a corner of the bottom 4 of the sieve box 5 pushed, by the relative movement BS between the 4-star cleaner 50 and the plan sifter or the bottom 4 according to arrow BP. It is possible to build screen cleaners with even more arms, but these no longer have any advantages in terms of cleaning intensity.

Claims (7)

Device for cleaning sieves such as sieves from plan sifters, in such a way that the cleaning element is combined, is designed upwards as a screen fabric cleaner and downwards as a floor scraper and preferably has a wobble foot in the region of its vertical axis of gravity, and that the cleaning element is of poor design and cleaning agent for has the sieve fabric, which are attached to the outer ends of the arms, the arms having a spring-elastic behavior due to their shape and the construction material,
characterized by
that the arms (31, 41) of the screen cleaner (6, 6 ') have a square cross-sectional shape with a roof-shaped elevation. Device according to claim 1,
characterized by
that the roof-shaped elevation has a triangular, trapezoidal or rounded cross section. Device according to claim 1,
characterized by
that the screen cleaner is designed as a boomerang (30) with two projecting arms (31), which have cleaning agents for the screen fabric (10) protruding upwards, preferably on the screen cleaner (6, 6 ') opposite to the projecting arms (31) a bottom and slot clearing nose (7, 34) is arranged. Device according to claim 1,
characterized by
that the screen cleaner is designed as a 3-star (40), with detergent for the screen fabric (10) on at least two arms (41) upwards and one on the outside on one arm (41) elongated bottom and slot clearing nose (7, 34) is arranged. Device according to claim 1,
characterized by
that the screen cleaner is 4-armed (50) and at least one arm (31, 41) has an extended bottom and slot clearing nose (7, 34). Device according to one of the claims 1 - 5,
characterized by
that the screen cleaner (6, 6 ') has 2 or more arms (31, 41) and has floor clearing means and preferably with its largest horizontal dimension is more than 50% of the correspondingly smallest dimension of the individual clearing fields. Device according to one of the claims 1 - 6,
characterized by
that the arms each have different cleaning agents, such as bristles or knobs (32) and / or cleaning ribs.

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