EP1007229B1 - Method and device for vibration screening - Google Patents

Abstract

Method and apparatus for the vibration screening of coating powders in particular, wherein a screening cloth is used, which is supported loosely on a screen frame and fixed to a clamping frame, wherein the screening cloth may additionally be supported on co-vibrating braces.

Description

The invention relates to a method for sieving bulk goods and liquids, in particular also of powder coating particles, and a device for carrying them out of the procedure.

In general, the screening of bulk material is used to separate contaminants (Protective screening) and the separation of bulk material into fractions of a certain Particle size or a certain particle size range (classification). Bulk goods can be, for example, granules, powders and lacquers.

In the production of powdered lacquers using extrusion processes the resulting coarse-grained material is ground and then one Screening process e.g. to separate unwanted oversize and Impurities fed.

Various sieving techniques are known, the sieve also with Ultrasound frequency can be excited. For example, eddy current sieves, Swash sieves, vibration swash sieves and turbo sieves are known.

With eddy current sieves, the material to be sieved is in one Sieve hose and is pressed against the sieve fabric by a swirling movement. Here can smear especially with fine-grained material and thereby a Obstruction of the screening process occur.

In the case of tumbling and vibration screening, the screens used are, for example set in motion with electro-magnetic drives. The tumbler screens work with firmly clamped sieves, which over the Sieve frames need to be tensioned.

By applying ultrasound, an additional vibration-like movement of the screen mesh are generated. The screen mesh heats up, causing the sieve fabric, in particular in the case of fine-grained material which tends to smear can completely clog.

In general, high costs arise with the conventional screens mentioned New covering and cleaning work through the necessary work and Time. The sieving performance does not reach the desired values.

DE-A-195 34 629 describes a vibrating screen in which a screen fabric rests on a sieve frame and only partially on it, namely on three sides, is fixed.

According to DD-A 227 891 and DD-A 270 476, spray booths are used for Powder coatings of workpieces described in which the cabin floor as Vibration sieve bottom is designed. The sieve insert of this floor can for example have a diameter of 200 mm and a sieve width of 200 μm. An external vibration motor serves as the drive. The maximum amplitude of the sieving process has a value of 0.2 mm, the vibration being infinitely variable. On A similar principle is also described, for example, in EP-A-0 611 605. The Sieve devices described are as a compact unit directly in the spray booth installed and are used for the preparation and recycling of powder overspray.

The sieve trays require a complex construction in order to achieve the required Allow angle of inclination. They are not suitable for mobile use.

The object of the present invention is therefore a method and a device for screening, especially powder coatings, to find one that is special Design independent, easy to use and therefore cost-saving Screening process with a high screening performance as well as a low and simple one Enable cleaning and energy expenditure to be carried out.

It has been shown that this problem can be solved technically simplified process for protective screening and classification, which involves sieving screen mesh used is held in a loose screen covering and during the Sieving process can rest on a co-vibrating strut.

The invention therefore relates to a method for sieving by means of vibration sieving using a sieve fabric placed on a sieve frame, the is characterized in that the screen fabric with loose screen covering on the Sieve frame is placed and fixed with a tenter frame, the sieve fabric can also rest on a bracing that vibrates with the screen mesh, except that part of the screen fabric is not through the stenter is fixed.

With a common drive, e.g. a pneumatic, electrical and / or hydraulic drive, the screen mesh can be set in a vibration-like movement become. At the same time as the screen mesh, the bracing also vibrates. One on that Bulk material applied, for example powder coating particles, or a liquid material, e.g. an aqueous dispersion or suspension can be produced by the Vibrating movement of sieve fabric and bracing in the desired way Impurities or oversize particles are separated.

According to the invention, the protective screening or classification is carried out by a loose one Sieve covering. A loose screen covering means that the screen fabric is loose rests on a sieve frame and loose on the sieve frame by a tenter frame is fixed. The tenter frame is simply over that on the screen frame the screen fabric is placed on top and fixed between the screen and stenter frame Such loose covering is only intended to prevent the sieve fabric from slipping. An additional firm bracing of the screen fabric by, for example, lateral additional force on the screen mesh is not necessary.

The vibrating bracing according to the invention, on which the screen fabric during Screen process can rest, is preferably integrated in the screen frame. The Bracing can e.g. in the form of bars or grids in any way, e.g. parallel or diagonally, attached to the sieve frame and made of any material.

It can also act as an independent component between the screen mesh and screen frame are located, the screen fabric is preferably above the strut.

The vibrating strut is constructed and arranged so that no obstruction of the sieving process and therefore no impairment of the sieving performance, but an intensification of the sieving process and an increase in the sieving performance.

The strut is preferably located under the screen fabric Sieve frame as a rod arranged parallel to the sieve frame or in the form of several rods built-in.

The screen fabric preferably lies on the strut during the screening process.

The drive that can be used is via suitable devices with the screening device connected. An electrically controllable drive is preferably used, for example an unbalance motor.

In the case of an electric drive, the frequency of the movement can be over one Potentiometer can be regulated and can e.g. in a range from greater than 0 to 480 Hz lie.

The electric drive is preferably controlled continuously.

Another object of the invention is a device for vibration screening to carry out the method according to the invention with a on a screen frame applied screen fabric, which is characterized in that the screen fabric with loose Screen tension placed on the screen frame and with a frame (hereinafter referred to as Called stenter) is fixed and can rest on a strut, so is designed so that it can vibrate with the screen fabric, with the exception that that part of the screen fabric is not fixed by the stenter. The stenter only serves to To keep sieve fabric on the sieve frame without tensioning the Mesh is necessary. The sieve fabric is therefore with a low (loose) Screen tension before.

The device according to the invention can in particular consist of a holder, a Cover with devices for the product supply, for the discharge and for the Drive, as well as a sieve frame with a sieve fabric and a stenter frame consist.

The attached figures show exemplary embodiments of the inventive method and the inventive device.

According to Figure I, a cover (2) is attached to a holder (1) Has devices for the product supply (3) and the discharge (4). On the Cover (2) is an unbalance motor (5), which on a on the cover (2) sliding plate is attached. The one connected to the bracket (1) Cover (2) is connected to the support frame (11) by means of vibrating metals (10).

Figure II shows the holder (1) with corresponding locking devices, e.g. Locking tensioner with hinges (12) for the lid (2). In the holder (1) the sieve unit, consisting of the sieve frame (6), with the vibrating one Bracing (13), the screen cloth (7) and the tensioning frame (8). To after inserting the sieve unit, a seal (9) is placed on the holder (1), before the holder (1) with the sieve unit inside it through the cover (2) is closed.

In the following the invention will be better understood with reference to the Numbers explained in Figures 1 and 2; it goes without saying that the Construction of the embodiments given by way of example in the figures varies can be.

The holder (1) can be used with a funnel and this in turn with a Collection container of any type and size can be connected or above this be arranged. The funnel can have a smooth surface or grooves on the inside, Grooves or similar structures in the direction of the tapered Have funnel opening for guiding the screened material. The bracket (1) can also be connected to any other usual filling or collecting device or be arranged above this.

The cover (2) on the holder (1) closes with it connected. This can be done by appropriate conventional mechanical Closures, for example closure clamps, hooks, screw connections and like. In addition, closing the bracket (1) with the lid (2) done, for example, by applying a vacuum. When closing comes it is important that the holder (1) and cover (2) are connected to one another in a sealing manner are. There is preferably one between the holder (1) and the cover (2) Seal (9) made of conventional material, which for example has a thickness of 2 to 3 mm can have and can be self-adhesive.

The lid (2) is equipped with devices for the product feed (3), the discharge (4) and equipped the drive (5).

The product feed (3) can be made in any way from an inlet in the lid (2) Size and shape exist and are located anywhere on the cover (2). The discharge (4) is used to remove unwanted screenings. This can for example powder material with undesirable grain size, the so-called "Coarse grain" or impurities. Furthermore, in the case of screening liquid materials, e.g. of aqueous dispersions and suspensions. Impurities appear as unwanted screenings. The discharge (4) is located preferably on the opposite side of the product feed device (3) on the cover (2).

There are also devices for the vibration drive on the cover (2) (5). This can e.g. Feeders for the usual, familiar to the expert, pneumatic, electrical and / or hydraulic drive. The drive (5) but can also directly on the lid (2) or at another point of the be fixed device according to the invention. Preferably an electric one Drive used, especially an unbalance motor. This can preferably be direct slidable on the lid (2), e.g. on a sliding plate, which in turn attached to the lid (2), may be arranged.

The holder (1) contains the sieve frame (6), the sieve fabric (7) and the Tenter frame (8). The sieve frame (6) serves to hold the sieve fabric (7), which is loosely placed over it. With the stenter (8) the sieve fabric (7) manually pressed onto the sieve frame (6) and thereby between the sieve frame and Tension frame loosely fixed.

The sieve frame (6) can have a vibrating strut (13) which the screen fabric (7) can rest on during the screening process. The Bracing (13) can, as explained above, also as an additional element between Screen frame (6) and screen fabric (7) must be installed. You can, for example, from a or several rods diagonally or parallel to the sieve frame (6) or out lattice-shaped grids exist.

The strut is preferably located on the screen frame (6) in the form of 1 to 2 bars arranged parallel to the frame.

The sieve frame (6), the strut (13) and the tensioning frame (8) can be made of any material. They are preferably made of metal.

The screen fabric can have any mesh size, depending on the requirement for screening. For example, the size of the mesh screen can be up to 100 µm or Amount to 200 µm.

The material of the screen fabric can e.g. Metal, plastic or textile material mixed fabrics are also possible.

Stainless steel or plastic screen fabrics are preferably used.

The sieve insert consisting of sieve frame (6), sieve mesh (7) and stenter frame (8) can vary in diameter according to requirements and any Have shape, for example, be rectangular, square or round. The lid (2) and the holder (1) according to the invention can correspond to the shape of the Sieve insert can be adjusted.

For example, areas of 0.1 to 1.5 m ² can be selected as active screen areas. Depending on the requirements, smaller or larger formats can also be selected.

The cover (2) which can be firmly connected to the holder (1) can be moved Connecting pieces (10) with a support frame (11). The moveable Connecting pieces (10) represent vibrating bodies, which the wave-like movement not hinder the sieving process. These vibrating bodies can, for example Vibrating metals, recirculating ball units or rubber sleeves. They are too Suspensions, for example by using tension or compression springs on Carrying frame (11) can be used. Vibrating metals are preferably used.

The support frame (11) is used for the fixed installation of the invention Device for example on the wall or ceiling of the production room.

The support frame (11) with the connected sieve unit can also move freely, e.g. on rollers, be designed so that the screening device according to the invention spatially can be used independently, depending on local requirements.

For the sieving process, the sieve unit consists of sieve frame (6), sieve fabric (7), and Clamping frame (8) and, if necessary, the seal (9), in the holder (1) inserted and closed by the cover (2). Through the product feed (3) the material to be screened is entered. The sieve unit with the one in the Sieve unit (7) and the vibrating strut (13) is set in a vibration-like movement by the drive (5) and thereby the material on the screen moves and corresponding to the selected sieve mesh fraction. The screenings collect, for example in a collection container.

The generated vibration-like movement of the sieve unit also causes Movement of the screened material, in particular the bulk material, on the screen fabric (7) in a certain direction. The direction of movement of the screened material can be controlled are determined by the mode of operation of the drive (5). Preferably the Direction of movement controlled so that the screened material, in particular the bulk material, is moved in the direction of the discharge (4) during the screening process. That on the Sieve cloth (7) can leave unwanted material in this way the discharge (4) can be removed.

Simultaneously with the sieving process according to the invention can be generated by the Movement of the screen fabric completely removing the remaining screen material from the Surface of the screen fabric can be achieved. This "self-cleaning effect" can increase proportionally by appropriately controlling the movement via the drive (5). For example, the drive (5) on the cover (2) can be used for this purpose Sliding plate can be moved.

With the inventive method and the device are in particular Bulk goods of any type and shape can be sieved. They are particularly suitable for that Sieving powder paint particles. A screening process is made possible, which is both a Classification of the powder material to be sieved enables separation as well of impurities (protective screening).

It is also possible to use liquid materials, e.g. aqueous dispersions or suspensions, with the inventive method and the device of Separate impurities or coarser components.

A simple and thus cost-saving sieving process can be achieved by the method and the device according to the invention, whereby in particular bulk materials, for example powder particles and in particular powder coating particles, can result in the desired particle size with a high sieving rate. For example, specific sieving capacities can be achieved under production conditions of more than 1800 kg / h m ² , with problematic powder coating products, such as matt textured powder lacquers, a specific sieving capacity of more than 1000 kg / hm ^{2 is} high compared to prior art sieving machines.

Furthermore, a consistently good product quality is guaranteed because for example caused by rotating or rubbing parts Development of heat, sticking or smearing can be avoided can. Furthermore, the screening process according to the invention enables a periodic effective cleaning of the screen covering. For example, the Cleaning time when changing products is only about 20 to 25% conventional sieving processes. The screening device according to the invention can without Technical aids disassembled, cleaned and assembled within a very short time become. By manually inserting the screen cloth (7) between the screen frame (6) and tensioning frame (8), as already explained, is an easy to handle Fixing the screen fabric (7) achieved without additional firm tension of the Screen fabric in a horizontal plane. Due to a comparatively low height of the Siebes, for example, do not require metering screws, as is the case with the conventional screening machines are used.

The invention is explained using an example:

example

A powder coating, produced according to the usual powder extrusion process, is after usual grinding to grain sizes in the range of 5 microns to 120 microns Sieving fed. For comparison, the screening takes place according to the methods of known prior art and according to the method of the invention. It sieves with a mesh size of 160 µm were used.

The following table shows a comparison of the results achieved: Standard screening machines screening device according to the invention power consumption 2500 watts 2100 watts 3000 watts 4500 watts 260 watts active screen area 2.0 sqm 0.8 sqm 0.32 sqm 0.64 sqm 0.46 sqm Max. screening capacity up to 400 kg / h up to 2500 kg / h up to 400 kg / h up to 1000 kg / h > 1000 kg / h specific sieving capacity 200 kg / hm ² 313 kg / hm ² 1250 kg / hm ² 1563 kg / hm ² 2174 kg / hm ² Type of cleaning Ultrasonic Ultrasonic mechanically mechanically mechanically cleaning time approx. 120 min. approx. 60 min. approx. 20 min. approx. 30 min. 5 min. new covering of the sieve frame / duration by specialist company by specialist company even / approx. 15 minutes. even / approx. 30 min. itself / 5 min. Screen covering costs per piece 1800, - DM 700, - DM 45.00 DM 90, - DM 20, - DM Screen frame costs per piece 10,800 DM 4500, - DM 1200, - DM 2400, - DM 100, - DM About grain losses Yes Yes Yes Yes No Compressed air consumption deleted deleted approx. 1 m ³ / h approx. 2 m ³ / h deleted

The standard screening machines are company products as they are currently Technology for the screening of powder coatings in particular are offered.

The active screen area is the one actually available for the screening process Screen surface.

The specific sieving capacity results from the ratio of active sieving area and Sieving capacity for a given mesh size.

It should be noted that the specific sieving performance when using the invention Despite the reduced active screen area, the values are significantly higher than those of conventional screening machines.

Furthermore, the high cost of cleaning the screen for Screen covering and the renewal of the screen frame compared to the invention documented.

Overall, it should be noted that in comparison to the known prior art sieving using the invention has a higher specific sieving performance while reducing energy consumption and costs for the Cleaning and renewal of screening machine parts can be achieved.

Claims (14)

1. Method for screening by vibration screening using a filter screen (7) placed on a screen frame (6), characterised in that the filter screen (7) is placed with loose screen tensioning onto the screen frame (6) and fixed to a tension frame (8), wherein the filter screen (7) can additionally be placed on cross-struts (13) vibrating in conjunction with the filter screen (7), with the exception that a portion of the filter screen (7) is not fixed by the tension frame (8).
2. Method according to claim 1, characterised in that the vibration screening is produced by a pneumatic, hydraulic or electric drive.
3. Method according to claims 1 and 2, characterised in that both the filter screen and the cross-struts are set vibrating owing to the vibration screening.
4. Method according to claim 1 to 3, characterised in that the direction of movement of the article to be screened on the filter screen is controlled via a drive.
5. Method according to claim 4, characterised in that the movement of the article to be screened is controlled via the direction of rotation of an electric drive.
6. Method according to claims 1 to 5, characterised in that bulk materials in the form of powder particles, in particular coating powder particles and liquid materials, for example aqueous dispersions or suspensions, are used as articles to be screened.
7. Method according to claims 1 to 6, characterised in that there is a protective screening of bulk materials and liquid materials and a classification of bulk materials.
8. Device for vibration screening for carrying out the method according to any of claims 1 to 7 with a filter screen (7) placed on a screen frame (6), characterised in that the filter screen (7) is placed with loose screen tensioning onto the screen frame (6) and is fixed with a tension frame (8) and can be placed on cross-struts (13) designed in such a way that they can vibrate in conjunction with the filter screen (7), with the exception that a portion of the filter screen (7) is not fixed by the tension frame (8).
9. Device according to claim 8, characterised in that it consists of a holding device (1), a cover (2) located thereon with devices for the product supply (3), for the outlet (4) and for the drive (5), the screen frame (6) being placed on the holding device (1).
10. Device according to claim 8 and 9, characterised in that the cross-struts (13) consist of one or two rods arranged parallel to the frame (6).
11. Device according to claims 9 and 10, characterised in that the cover (2) can be securely connected to the holding device (1).
12. Device according to claims 9 and 11, characterised in that the cover (2) which can be securely connected to the holding device (1) is connected by one or more moving connecting pieces (10) to a supporting frame (11).
13. Device according to claims 9 to 12, characterised in that the outlet (4) is arranged opposed to the product supply (3) at the other end of the cover (2).
14. Device according to claims 9 to 13, characterised in that the screen tensioning of the filter screen (7) is loose between screen frame (6) and tension frame (8).

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