DE102021204377A1 - Process for operating a screening device to keep the product quality constant with a fluctuating mass flow - Google Patents

Abstract

The present invention relates to a method for controlling a screening device 10, the screening device 10 having at least four clusters of imbalance exciter units U, each cluster having at least two imbalance exciter units U, each cluster being configured via a coupling point for impinging the screening device 10 with vibrations, two front clusters being arranged closer to the material application 30, two rear clusters being arranged closer to the material discharge, characterized in that the phase offset between the imbalance exciter units U is controlled within a cluster, the mass flow applied to the screening device 10 being measured as the input measurement variable, where the phase shift is reduced as the mass current increases.

Description

The invention relates to a method for keeping the separation properties of a screen constant even when the material application changes.

From the DE 10 2017 218 371 B3 and from the DE 10 2018 205 997 A1 Screen systems with vibration exciters arranged in groups are known. This arrangement in groups enables the operation of the screening device to be highly adaptable, which is not possible with the classic linear, elliptical or circular vibrators. This group of screening devices thus enables completely new control schemes.

From the DE 10 2019 204 845 B3 a method for setting and controlling at least one vibration mode of a screening device is known.

From the DE 10 2019 214 864 B3 a method for controlling and regulating a screening device is known.

It would be desirable to be able to adapt a screening device based on specific measured variables that have a correlation to educt properties in such a way that the product properties can be set in a targeted manner.

The object of the invention is to provide a method for keeping the separation of a screen constant even if the amount of material applied varies.

This problem is solved by the method with the features specified in claim 1 . Advantageous developments result from the dependent claims, the following description and the drawings.

The method according to the invention serves to control a screening device. The screening device used for the method has at least and preferably exactly four clusters of imbalance exciter units, with each cluster having at least two imbalance exciter units. Each cluster is formed via a coupling point for subjecting the screening device to vibrations. Two front clusters are located closer to material application and two rear clusters are located closer to coarse material discharge. At the material application, the material to be screened is applied to the screen of the screening device. The coarse material that does not fall through the screen migrates over the screen and reaches the coarse material discharge. The fine material falls through the sieve and thus reaches the fine material discharge.

According to the invention, the phase offset between the imbalance exciter units within a cluster is controlled. This enables a very variable adjustment of the screen properties and is easily possible by arranging the imbalance exciter units in clusters.

The mass flow applied to the screening device is measured as the input variable. For example, the mass flow is recorded by a weighing element arranged in the feeding conveyor belt. The phase offset is reduced as the ground current increases. This seems absurd at first, since reducing the phase offset causes the material on the screen to be moved more vertically, which reduces the conveying capacity over the screen, causing the material loading to increase even further beyond the level that is already increasing due to the increasing material flow. As a result, the quality of the screening can be kept constant with increasing loading, which would decrease with unchanged screening parameters due to the increasing amount of material on the screen. Due to the slowing down of the material transport, the material load on the screen falls disproportionately, but the quality of the screening remains unchanged. A plant which is to carry out the method according to the invention is therefore preferably designed with a comparatively large screening plant in order to be able to bear this additional increase. However, the product quality can be kept constant.

In a further embodiment of the invention, the mass flow of the coarse material discharge and the mass flow of the fine material discharge are recorded. The phase shift is controlled in such a way that the ratio of the coarse material discharge to the mass flow of the fine material discharge remains constant. As a result, the quality can be kept constant by an interactive control circuit. This is particularly advantageous because no exact prediction between ground current and phase shift has to be determined in advance, but rather it is regulated in each case and then measured to determine whether the adaptation goes too far.

In a further embodiment of the invention, the phase offset for the maximum permissible mass flow is set to 90°. In a further embodiment, as an alternative or in addition, the phase offset for the mass flow is set from zero to 0°. For the embodiment of the combination of these two embodiments, the phase offset between the maximum permissible mass flow and the mass flow is preferably changed linearly from zero from 90° to 0°.

• 1 Vorrichtung
• 2 erster Betriebszustand
• 3 zweiter Betriebszustand
• 4 Verfahren

The device to be used for the method according to the invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawings.

• 1 contraption
• 2 first operating state
• 3 second operating state
• 4 procedure

In 1 a screening device 10 is shown. This has a screen 20, for example a perforated plate. Material is applied to the material order 30 and conveyed over the screen 20 . Theoretically, all components that are smaller than the size of the screen holes fall through the screen 20 and are thus brought to the fine material outlet 50 . Anything larger is conveyed over the screen 20 and to the coarse material outlet 40.

In order to move the screening device 10 and thus the screen 20, the screening device has eight imbalance exciter units U, which are arranged in four clusters of two imbalance exciter units U each, with two imbalance exciter units U in each cluster each having a common coupling point for acting on the screening device 10 with Vibrations are formed. As a result, an oscillation that is generated by superimposition of the oscillations generated by the two unbalance exciter units U is effectively impressed on the screening device 10 .

The example shown is the simplest version with two unbalance exciter units U per cluster and four clusters, a front left cluster 60, a front right cluster 70, a rear cluster 80 and a rear right cluster 90. Of course, the clusters can also have three or more unbalance exciter units U and, for example, two additional clusters of imbalance exciter units U can also be arranged in the middle.

In 2 and 3 two modes of operation of a cluster of unbalance exciter units U are shown. The arrow inside of the unbalance exciter units U indicates the respective force vector, the arrows outside indicate the direction of rotation of the unbalance exciter units U.

2 both force vectors point vertically upwards and those of unbalance exciter units U rotate in opposite directions to each other. A phase shift is not implemented (0°), the cluster excitation therefore takes place in the vertical direction, which leads to a very small movement of material over the screen. 2 describes an operating state which can be set/controlled, for example for a cleaning function, in particular in connection with a variation in the speed of the respective imbalance exciter unit.

In 3 another operating state is shown. In this case, one force vector (the one on the left in the illustration) points upwards, and the second force vector (the one on the right in the illustration) points to the left, in particular orthogonally to the first force vector. The imbalance exciter units rotate in opposite directions to each other. In the operating state shown here, the phase shift is 90°. The resulting cluster excitation acts at an angle of 45° to the horizontal and thus leads to a comparatively fast material transport over the wire.

In 4 the procedure is presented as an example in terms of time and is greatly simplified. The incoming mass flow M is shown above against the time t. At some point the mass flow M increases, stays at this level for a certain time and then returns to the original value. The phase shift φ is reduced for this period of time, which means that the material is no longer transported over the screen as quickly as shown in the middle. The effect is that the loading B of the sieve increases disproportionately. The product quality remains almost unchanged.

reference list

B

loading

M

mass flow

u

imbalance exciter unit

φ

phase shift

10

screening device

20

Sieve

30

material application

40

coarse material discharge

50

fine material discharge

60

anterior left cluster

70

anterior right cluster

80

posterior left cluster

90

behind right cluster

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102017218371 B3 [0002]
• DE 102018205997 A1 [0002]
• DE 102019204845 B3 [0003]
• DE 102019214864 B3 [0004]

Claims (5)

Method for controlling a screening device (10), the screening device (10) having at least four clusters of imbalance exciter units (U), each cluster having at least two imbalance exciter units (U), each cluster having a coupling point for acting on the screening device (10) is designed with vibrations, with two front clusters being arranged closer to the material application (30), with two rear clusters being arranged closer to the material discharge, characterized in that the phase offset φ between the imbalance exciter units (U) is controlled within a cluster, with the input measured variable the mass flow applied to the screening device (10) is measured, with the phase shift φ being reduced as the mass flow increases. procedure after claim 1 , characterized in that the mass flow of the coarse material discharge and the mass flow of the fine material discharge is detected, the phase shift φ being controlled such that the ratio of the coarse material discharge to the mass flow of the fine material discharge remains constant. Method according to one of the preceding claims, characterized in that the phase offset φ for the maximum permissible mass flow is set to 90°. Method according to one of the preceding claims, characterized in that the phase offset φ for the mass flow is set from zero to 0°. procedure after claim 3 and 4 , characterized in that the phase shift φ between the maximum permissible mass flow and the mass flow from zero is changed linearly from 90° to 0°.

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