DE202014008855U1 - Screening machine with drive - Google Patents

Abstract

Screening machine with a screen box (10) which can be set in vibration by means of a drive and which can be supported elastically, preferably via springs (13), on a solid surface (12) in an operating position of the screening machine, furthermore with one on the screen box (10) elastically coupled swing frame and with a sieve surface (6) formed by sieve mats (3), the sieve mats (3) by alternately fastening to the sieve box (10), preferably to the sieve cheeks (7) connecting sieve box cross members (1), and on The oscillating frame is alternately compressed and stretched at least in sections, characterized in that the drive comprises the following components: - at least one motor (17a, 17b) - at least two drive shafts (4a) coupled to the screen box (10) and driven in opposite directions by the at least one motor , 4b), wherein - each of the drive shafts (4a, 4b) has an unbalanced mass (15a, 15b) and wherein - the unbalance mass Differentiate the amounts (15a, 15b) of the drive shafts (4a, 4b) from one another in order to set the sieve box (10) in an elliptical oscillating movement.

Description

FIELD OF THE INVENTION

The present invention relates to a screening machine with a movable by means of a drive vibrating, Siebwangen having screen box, which is supported in an operating position of the screening machine elastic, preferably by springs on solid ground, further with an elastically coupled to the sieve box swing frame and with a through Screen mats formed screen surface, wherein the screen mats are alternately compressed and stretched by alternately attachment to the screen box, preferably connecting to the screen cheeks screen box cross members, and the swing frame at least in sections.

STATE OF THE ART

From the AT 393,636 B is a screening machine with a Siebwangen having a sieve box and constructed of sieve mats screen surface known. The screen mats are alternately connected to the screen box and a swing frame and are at least partially alternately compressed and stretched during operation of the screening machine and are therefore deformable. This results in a sort of whip effect for the screenings, which has a positive effect on the screening performance and counteracts blockages (susceptibility to stickiness) of the screen mats.

The vibration excitation takes place in such screening machines by a drive which excites the screen box to a linear or a circular fundamental vibration.

The drive consists of at least one motor and at least one drive shaft with an imbalance mass, but in any case depends on the desired throughput of the screenings. The throughput is to be regarded as the criterion which determines the size and thus also the weight of the screening machine. Screeners with high throughput therefore have a correspondingly high mass. From a vibration mass of 3,500 kg to 4,000 kg (oscillating mass without springs and supports) a drive with a single drive shaft with unbalanced mass is no longer sufficient to put the screen box in vibration, which serve the screening and conveying process. The size of drive shafts with imbalance masses can only be increased to a limit size.

In such cases, two or more drive shafts with imbalance masses are used, which are then driven either by one or more motors. In most cases, however, two motors are used in generic vibrating machines with high throughput, each motor drives a drive shaft with imbalance mass.

A linear fundamental is usually generated by two counter-rotating drive shafts, which are coupled to the screen box and are equipped with identical imbalance masses. The two counter-rotating drive shafts are fed to a forced synchronization, which aligns the position of the imbalance masses of the two drive shafts to each other so that the sieve box is excited to a linear oscillation. This happens for example by means of a transmission which is coupled to a motor. In other words, in this case an engine drives both drive shafts in opposite directions via a transmission. Such screening machines require in an operating position a minimum inclination of the screen surface of 4 ° to 6 ° relative to the horizontal in order to ensure a sufficient flow rate.

A circular fundamental vibration of the sieve box, however, is generated in screens with lower throughput usually by a single imbalance drive. In high-throughput screening machines, two synchronized drive shafts forcibly synchronized by means of toothed belts are used, which are likewise equipped with identical imbalance masses. However, in this case, the forced synchronization ensures that the imbalance masses of the two drive shafts are mutually positioned so that the sieve box is excited to a circular oscillation. Such screening machines require in an operating position a minimum inclination of the screen surface of 8 ° to 10 ° relative to the horizontal in order to ensure a sufficient flow rate.

In summary, it can be stated that generic screening machines with an elastic / resilient supportable against a background screen box and an elastically coupled thereto swing frame are indeed characterized by a good screening performance, but require a relatively strong inclination of the screen surface, which build such screening relatively high.

Moreover, high throughput rates require high-weight screening machines and consequently the use of drives with two drive shafts, which, however, have to be fed into forced synchronization, which increases the production costs.

In addition, the setting of the fundamental vibration of the screen box is often complex because connected to an intervention in the drive, for example, with an exchange of imbalance masses.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide a generic same screening machine with improved screen performance available, which also builds smaller.

It is a further object of the present invention to provide a generic screening machine which allows a simple variation of the basic vibration of the screen box without having to replace drive shafts or imbalance masses.

PRESENTATION OF THE INVENTION

• – mindestens einen Motor (17a, 17b)
• – mindestens zwei an den Siebkasten (10) gekoppelte, von dem mindestens einen Motor gegenläufig angetriebene, Antriebswellen (4a, 4b), wobei
• – jede der Antriebswellen (4a, 4b) eine Unwuchtmasse (15a, 15b) aufweist und wobei
• – sich die Unwuchtmassen (15a, 15b) der Antriebswellen (4a, 4b) voneinander betragsmäßig unterscheiden, um den Siebkasten (10) in eine elliptische Grundschwingung zu versetzen.

This object is in a screening machine with a displaceable by means of a drive vibrating, Siebwangen having screen box, which is supported in an operating position of the screening machine elastic, preferably via springs, on solid ground, and further with an elastically coupled to the screen box swing frame and with a Siebmatten formed by sieve mats is formed by sieve mats, wherein the screen mats are alternately compressed and stretched by alternating attachment to the screen box, preferably on the Siebwangen connecting Siebkastenquerträgern, and the swing frame at least in sections, achieved in that it is provided according to the invention that the drive comprises the following components:

• - at least one engine ( 17a . 17b )
• - at least two to the sieve box ( 10 ), driven by the at least one motor in opposite directions, drive shafts ( 4a . 4b ), in which
• - each of the drive shafts ( 4a . 4b ) an imbalance mass ( 15a . 15b ) and wherein
• - the unbalance masses ( 15a . 15b ) of the drive shafts ( 4a . 4b ) differ from each other in terms of amount to the screen box ( 10 ) into an elliptical fundamental vibration.

It has surprisingly been found that an elliptical fundamental oscillation does not interfere with the vibration system consisting of sieve box and swing frame, but on the contrary, compared with the previously used linear and circular fundamental oscillations reinforced so that on the one hand and the whip effect described above is reinforced, which has a positive effect on the elimination of clogging of the screening mats. Moreover, however, it has also been found that an elliptical fundamental vibration of the sieve box means that the inclination of the sieve surface in an operating position relative to the horizontal can be substantially lower than in genus-like sieving machines, without losing this sieving performance.

According to a preferred embodiment of the invention, it is provided that only one drive motor is used, which drives both drive shafts forcibly synchronized. In particular, in screening machines of small size can be particularly energy-efficient to dispense with an additional engine.

According to a further preferred embodiment of the invention, however, it is also provided that for each of the at least two drive shafts, a separate drive motor is used to independently drive the at least two drive shafts. Surprisingly, it has been found that - unlike the prior art - synonymous with generic screening machines with high throughput and high vibration mass in the case of elliptical fundamental vibration of the screen box no forced synchronization of the drive shafts is required, but synchronize the two drive shafts independently and that way in that an elliptical fundamental vibration of the sieve box sets in, which results in a simpler and more cost-effective production because the costs for forced synchronization are eliminated.

According to a further embodiment variant of the invention, the at least two drive shafts are arranged substantially parallel to one another, preferably parallel to the sieve box cross members. This arrangement represents a particularly simple and therefore also favorable execution.

According to a further embodiment, it is provided that the at least one motor and the at least two drive shafts are arranged on an upper side of the screen box facing away from the solid surface, resulting in a particularly space-saving design of the screening machine, because a narrower construction can be provided.

According to a further preferred embodiment of the invention, it is provided that the at least one motor and / or the at least two drive shafts along a longitudinal direction of the screen box, that are arranged displaceable and fixable in or against the conveying direction on the screen box, whereby the inclination of the main axis of the elliptical Fundamental vibration can be changed, which in a relatively simple manner, the screening performance and the susceptibility to pinholes can be influenced without having to make changes to the imbalance masses of the drive shafts, be it in terms of mass itself or the arrangement of the drive shafts relative to each other.

According to a further preferred embodiment of the invention, it is provided that the at least one motor and the at least two drive shafts form a drive block which, in an operating position of the screening machine and in a direction orthogonal to the longitudinal direction of the sieve box and parallel to the solid ground, does not project beyond the components of the screening machine which do not form the drive block, whereby the screening machine as a whole builds narrower and the width of which is determined essentially by the distance of the wire cheeks.

According to a further particularly preferred embodiment of the invention, it is provided that in the operating position, the screen surface is inclined at an angle to the horizontal in a conveying direction, wherein the angle is at most 6 degrees, but more preferably less than 3 degrees. This reduction of the angle makes it possible for the screening machine - with at least constant screening capacity - to build lower than comparable screens of the prior art, which increases the possibilities of use, in particular with regard to mobile applications, since this also simplifies road transport, for example.

In order to create the possibility of selective fractionation with multiple screen surfaces, at least one additional screen surface is provided according to a further embodiment variant.

According to a further preferred embodiment variant of the invention, it is provided that the at least one additional screen surface is arranged between the screen surface formed by the screen mats and the top side of the screen box and is fastened to the screen cheeks. It can be provided that the at least one additional screen surface is formed by a rigid grid, preferably metal grid, which is particularly simple and inexpensive to manufacture. Thus, it is conceivable that the rigid screen surface is formed as a simple, wire-grid-shaped surface, or by additional screen mats.

According to a further embodiment, it is provided that the additional screen surface and the screen surface are substantially parallel to each other, whereby the overall height can be kept low.

In order to prevent sprayed particles and / or dust from escaping in the region or along the push rods and possibly impairing the environment, it is provided according to the invention that the swing frame comprises push rods elastically coupled to the wire cheeks and the swing frame cross members connecting them and at least one push rod a push rod cover is provided. Furthermore, it is provided according to the invention that the push rod cover has a U-shaped cross-section normal to the longitudinal extent of the respective push rod and that the push rod cover is tightly connected to the wire cheeks and the respective push rod with respect to the operating position to the outside tightly surrounds. Ie. the push rod cover surrounds the respective push rod in the operating position closely up and down and seen in the direction of the longitudinal extension of the push rod forward and backward.

The tight connection can be realized by the push rod cover has a, preferably continuous, sealing lip made of plastic, vorzusgweise rubber, with which the push rod cover connects to the wire cheeks. To ensure that the push rod cover with respect to the operating position, the respective push rod also front and hung, d. H. Seen in the longitudinal direction of the push rod before and after the push rod, tightly surrounds, and the cross section of the push rod cover in a plane parallel to the longitudinal extent of the push rod and parallel to the swing frame cross members can be U-shaped. Accordingly, the push rods are also protected against coming in the operating position from the outside spray and / or dust and / or dirt.

In a preferred embodiment of the invention, the elastic connection of the push rods to the wire cheeks by means of rubber buffer. This is easy and inexpensive to manufacture. Accordingly, it is provided in a preferred embodiment of the screening machine according to the invention that the push rod cover and the respective push rod associated rubber buffer surrounds tightly to avoid contamination of the rubber buffers or the coupling or storage of the push rods. Accordingly, the push rods and their elastic coupling or storage on the wire cheeks are protected against coming in the operating position from the outside spray grain and / or dust and / or dirt.

According to a further embodiment, it is provided that the attachment of the screen mats is realized on the swing frame by attachment to the swing frame cross members, which is a particularly stable and at the same time simple design.

In a further embodiment of the screening machine according to the invention, it is provided that the screen surfaces have different inclinations. Thus, different screen effects can be achieved with a single screening machine.

According to an additional preferred embodiment of the invention, it is provided that in the operating position of the screening machine, the main axis 29 the elliptical fundamental vibration of the sieve box underlying ellipse by an angle α between 25 ° and 65 °, preferably between 30 ° and 60 ° in the conveying direction increasingly inclined to the horizontal runs. Under increasingly inclined is to be understood that the main axis 29 with progressive conveying direction 22 from the underground 12 moved away. The adjustment of the inclination of the main axis 29 the elliptical fundamental oscillation underlying ellipse is done by appropriate choice of the drive in particular the imbalance masses and their positioning to each other or by appropriate positioning of the at least one motor or at least two drive shafts on the screen box. A fundamental vibration formed in this way in the case of generic screening devices provides a particularly high screening performance with a low susceptibility to pinholes.

According to a further preferred embodiment of the invention, it is provided that exactly two drive shafts are provided, wherein for each of the drive shafts, at least one own drive motor is used to drive the two drive shafts independently of each other, wherein in an operating state and in a projecting view of the Drive shafts arranged on the first drive shaft unbalanced mass between 170 ° and 190 °, preferably offset by 180 ° to the arranged on the second drive shaft unbalanced mass, d. H. when the imbalance mass of the first drive shaft is at 0 °, the imbalance mass of the second drive shaft is between 170 ° and 190 °, preferably at 180 °.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail with reference to exemplary embodiments. The drawings are exemplary and are intended to illustrate the inventive idea, but in no way restrict it or even reproduce it.

Showing:

1 a side view of a screening machine according to the invention

2 a sectional view along the section line AA in 1

3 a longitudinal section of a screening machine according to the invention according to 1

4 an oblique view of another embodiment of the screening machine with two movable screen surfaces

5 a side view in section of another embodiment of the screening machine according to the invention with two movable screen surfaces

WAYS FOR CARRYING OUT THE INVENTION

1 shows a side view of a screening machine according to the invention in an operating position. The screening machine consists of a sieve box 10 that by two wire cheeks 7a . 7b is formed, which between the sieve surface 6 (please refer 2 ), which through Siebmatten 3 is formed. The screen cheeks 7a . 7b are at least on Siebkastenquerträger 1 connected with each other.

The screening machine has a task area 23 and a delivery area 24 on. In the event that the screen cheeks 7a . 7b provided on its upper side with a (not shown) cover is the task area 23 designed as a task opening and the delivery area 24 as a discharge opening.

The sieve box 10 is by means of springs 13 opposite, preferably on a solid, preferably horizontal surface 12 supported.

Furthermore, the screens shown by way of example in the figures comprise exactly two by means of motors 17a . 17b independent of each other (not necessarily synchronized) and counter-rotating drive shafts 4a . 4b with unbalanced masses attached to it 15a . 15b (see. 3 and 4 ). With a drive designed in this way, most applications can be covered in practice by means of a screening machine according to the invention.

In principle, however, special variants are conceivable in which only one engine via a transmission both drive shafts 4a . 4b drives in opposite directions. However, such a variant is much more complex.

In principle, the use of multiple drive shafts, which are each driven independently of one another by a separate motor, is also conceivable as a special embodiment variant.

In the illustrated, inventive screening machines, the imbalance masses differ 15a . 15b the two drive shafts 4a . 4b from each other both in terms of amount and their positioning on the drive shafts. In the in 3 illustrated projecting view of the drive shafts 4a . 4b is the one on the first drive shaft 4a arranged imbalance mass 15a between 170 ° and 190 °, preferably offset by 180 ° to the second drive shaft 14b arranged imbalance mass 15b arranged. The same applies to 5 , The two figures show the screening machines shown in each case in an operating situation, ie with rotating drive shafts 4a . 4b for example at 800 rpm.

Due to the opposition of the drive shafts 4a . 4b as well as the different imbalance masses 15a . 15b is ensured that the so on the screen box 10 coupled drive shafts 4a . 4b the springy or elastic on the ground 12 stored sieve box 10 to excite to an elliptic fundamental.

It should be noted that, for the purposes of this description, there is always one imbalance mass per drive shaft 4a . 4b is spoken. However, it is clear to a person skilled in the art that several imbalance masses per drive shaft can be provided and an unbalanced mass in this case is to be regarded as a resultant imbalance mass resulting from the sum of the unbalanced masses, which causes the same with respect to vibration excitation as the plurality of imbalance masses.

The two motors 17a . 17b as well as the two drive shafts 4a . 4b form a drive block 9 made of a housing-like structure and the rotating components, such as the drive shafts 4a . 4b protectively surrounds. For thermal reasons, the motors are 17a . 17b outside the housing, but at least on the drive block 9 arranged. This is at the top of the wire cheeks 7a , b attached to this and extends from a wire cheek 7a to the other screen cheek 7b ,

Preferably, the entire drive block is on the sieve box 10 , especially on the wire cheeks 7a . 7b slidably arranged to the elliptical fundamental of the sieve box 10 to be able to influence, specifically to the inclination of the main axis 29 to vary the elliptical fundamental. However, it is also possible variants, in which the motors 17a . 17b as well as the drive shafts 4a . 4b not to a drive block 9 are summarized. In this case, these components are then individually displaceable on the sieve box 10 arranged to the main axis 29 the basic elliptical vibration of the sieve box 10 to be able to vary.

To the sieve box 10 Furthermore, a swing frame is elastically coupled, which forms an additional vibration system. The swing frame consists of push rods 5a . 5b , each with a push rod 5a . 5b on an outside of a wire cheek 7a , b between elastic, on the wire cheeks 7a . 7b arranged rubber buffers 14 is held, as well as the push rods 5a . 5b connecting swing frame cross member 2 ,

The connection of the push rods 5a . 5b to the swing frame cross member 2 via fastening components 8th (please refer 2 ), which the Siebwangen 7a . 7b penetrate into openings provided for this purpose.

The sieve surface 6 is through sieve mats 3 educated. Every screen mat 3 is alternately on a swing frame cross member 2 and a Siebkastenquerträger 1 attached. Due to the elastic connection of the swing frame cross member 2 over the swing frame to the swinging screen box 10 forms a relative movement between the two systems, which leads to the Siebkastenquerträger 1 and the swing frame cross member 2 move cyclically either towards or away from each other causing the screen mats 3 alternately either compressed or stretched. This whip effect has a positive effect on the screening performance and blockages (susceptibility to stickiness) of the screen mats.

According to a particularly preferred embodiment, the screening machines shown in addition to the screen surface 6 yet another screen surface 25 on, preferably over the screen surface 6 is arranged. The two screen surfaces 6 . 25 are arranged substantially parallel to each other, thus have the same inclination relative to the horizontal. The alternatively provided screen surface 25 can be either identical to the screen surface 6 be executed, thus also an elastic to the sieve box 10 Formed coupled additional vibration system, as for example in 4 and 5 is shown or form a conventional screen surface, for example as a rigid grid or as not elastic to the screen box 10 coupled screening mats 26 be trained as in the 1 to 3 is shown.

In the case of more than one screen surface, different fractions can be screened with a single sifting machine.

In the event that the additional screen surface is an additional oscillating system, the fastening components 8th as in 5 be seen, also be formed longer and along the outer surfaces of the wire cheeks 7a . 7b extend substantially vertically. This allows both the swing frame cross member 2 the lower screen surface 6 as well as those of the upper screen surface 25 on each of the same fastening components 8th be attached.

Regardless of the number of screen surfaces, it is for the further promotion of the screenings required that the screen surface 6 . 25 in the conveying direction 22 is inclined. The sieve surface 6 runs in the operating position in the conveying direction 22 decreasing at an angle inclined to the horizontal, wherein the angle is at most 6 degrees, but preferably less than 3 degrees. Thus, in the operating position is a beginning 18 the sieve surface 6 towards one end 19 the sieve surface 6 increased, wherein in the conveying direction 22 seen the beginning 18 before the end 19 is arranged.

As in the sectional view of 2 is recognizable, are the screen mats 3 bent upwards in the edge area to prevent unwanted leaving of the coarse screened material ("coarse grain").

To prevent dust, sprayed-on screenings ("spray grain") or impurities in the area by means of rubber buffers 14 mounted push rods 5 from the inside of the screening machine or from the sieve box 10 enters the outside to the outside, can for each push rod 5 a push rod cover 11 be provided, cf. 2 , This covers the push rod 5 over its entire longitudinal extent tight. In order to improve the tightness, a sealing lip made of plastic, preferably rubber (not shown) may be provided, with which the push rod cover 11 to the wire cheek 7 followed.

As 2 it can be seen, is the U-shaped cross-section of the push rod cover 11 so dimensioned that not only the entire push rod 5 but also the rubber bumpers 14 , by means of which the push rod 5 at the sieve box 10 is stored tightly surrounded. In this way, a tight enclosure of the push rods 5 and the associated rubber buffer 14 realized from five sides. The push rod cover 11 can, as shown, be composed of several parts. Basically conceivable, however, is also a one-piece version (not shown).

To the operation of the vibrating system, in particular the deflection of the push rods 5 to be able to control are viewing windows 20 intended. These are typically made of Plexiglas.

LIST OF REFERENCE NUMBERS

1

Siebkastenquerträger

2

Swing frame crossbeams

3

screen mat

4a, b

drive shafts

5a, b

pushrod

6

Screen area

7a, b

screening cheeks

8th

attachment member

9

drive block

10

screenbox

11

Pushrod cover

12

underground

13

feather

14

Plastic buffer

15a, b

unbalanced masses

16

Swing frame level

17a, b

motors

18

Beginning of the sieve area

19

End of the sieve surface

20

window

21

normal direction

22

conveying direction

23

remit

24

delivery area

25

Additional screening surface

26

Additional screen mat

27

Top of the screening machine

28

Longitudinal direction of the sieve box

29

Main axis of the fundamental oscillation underlying ellipse

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• AT 393636 B [0002]

Claims (20)

Sieving machine with a by means of a drive vibratable, Siebwangen ( 7 ) ( 10 ), which in an operating position of the screening machine elastic, preferably via springs ( 13 ), on firm ground ( 12 ) is supportable, further with a to the screen box ( 10 ) elastically coupled oscillating frame and with a through sieve mats ( 3 ) formed Siebfläche ( 6 ), whereby the screen mats ( 3 ) by alternating attachment to the sieve box ( 10 ), preferably on the Siebwangen ( 7 ) connecting screen box crossbeams ( 1 ), and at least partially alternately compressed and stretched on the oscillating frame, characterized in that the drive comprises the following components: - at least one motor ( 17a . 17b ) - at least two to the sieve box ( 10 ), driven by the at least one motor in opposite directions, drive shafts ( 4a . 4b ), wherein - each of the drive shafts ( 4a . 4b ) an imbalance mass ( 15a . 15b ) and wherein - the imbalance masses ( 15a . 15b ) of the drive shafts ( 4a . 4b ) differ from each other in terms of amount to the screen box ( 10 ) in an elliptical oscillatory motion. Screening machine according to claim 1, characterized in that only one drive motor ( 17a ) is provided which forcibly drives both drive shafts. Screening machine according to claim 1, characterized in that for each of the at least two drive shafts ( 4a . 4b ) a separate drive motor ( 17a . 17b ) is provided to independently drive the at least two drive shafts. Screening machine according to one of claims 1 to 3, characterized in that the at least two drive shafts ( 4a . 4b ) are arranged substantially parallel to one another, preferably parallel to the Siebkastenquerträgern ( 1 ). Screening machine according to one of claims 1 to 4, characterized in that the at least one motor ( 17a . 17b ) and the at least two drive shafts ( 4a . 4b ) on a solid ground ( 12 ) facing away from the top ( 27 ) of the sieve box ( 10 ) are arranged. Screening machine according to one of claims 1 to 5, characterized in that the at least one motor ( 17a . 17b ) and / or the at least two drive shafts ( 4a . 4b ) along a longitudinal direction ( 28 ) of the sieve box ( 10 ) are arranged displaceable and fixable on the sieve box. Screening machine according to one of claims 1 to 6, characterized in that the at least one motor ( 17a . 17b ) and the at least two drive shafts ( 4a . 4b ) a drive block ( 9 ) in an operating position of the screening machine and in a direction orthogonal to the longitudinal direction ( 28 ) of the sieve box ( 10 ) and parallel to the solid ground ( 12 ) which are not part of the drive block ( 9 ) forming components of the screening machine ( 10 ) is not exceeded. Screening machine according to one of claims 1 to 7, characterized in that in the operating position, the screen surface ( 6 ) in a conveying direction ( 22 ) at an angle inclined to the horizontal, wherein the angle is at most 6 degrees, more preferably less than 3 degrees. Screening machine according to one of claims 1 to 8, characterized in that at least one additional screen surface ( 25 ) is provided. Screening machine according to claim 9, characterized in that the at least one additional screen surface ( 25 ) between the through the screen mats ( 3 ) formed Siebfläche ( 6 ) and the top ( 27 ) of the sieve box ( 10 ) is arranged and on the Siebwangen ( 7 ) is attached. Screening machine according to claim 10, characterized in that the at least one additional screen surface ( 25 ) is formed by a rigid grid, preferably metal grid. Screening machine according to claim 10, characterized in that the at least one additional screen surface ( 25 ) by additional sieve mats ( 26 ) is formed. Screening machine according to one of claims 10 to 12, characterized in that the additional screen surface ( 25 ) and the screen surface ( 6 ) are substantially parallel to each other. Screening machine according to one of claims 1 to 13, characterized in that the oscillating frame to the Siebwangen ( 7 ) elastically coupled push rods ( 5 ) as well as these connecting swing frame cross beams ( 2 ). Screening machine according to claim 14, characterized in that for at least one push rod ( 5 ) a push rod cover ( 11 ) is provided that the push rod cover ( 11 ) normal to the longitudinal extent of the respective push rod ( 5 ) has a U-shaped cross section and that the push rod cover ( 11 ) close to the wire cheeks ( 7 ) and the respective push rod ( 5 ) with respect to the operating position to the outside tightly surrounds. Screening machine according to claim 15 or 16, characterized in that the push rods ( 5 ) by means of rubber buffer ( 14 ) elastic to the wire cheeks ( 7 ) and that the push rod cover ( 11 ) and the respective push rod ( 5 ) associated rubber buffer ( 14 ) surrounds tightly. Screening machine according to one of claims 14 to 16, characterized in that the attachment of the screening mats ( 3 ) on the swing frame by attachment to the swing frame cross beams ( 2 ) is realized. Screening machine according to one of the preceding claims, characterized in that in the operating position of the screening machine, the main axis 29 the elliptical fundamental vibration of the sieve box ( 10 ) underlying ellipse between 25 ° and 65 °, preferably between 30 ° and 60 ° in the conveying direction increasingly inclined to the horizontal runs. Screening machine according to one of the preceding claims, characterized in that exactly two drive shafts ( 4a . 4b ) are provided, wherein for each of the drive shafts, at least one own drive motor ( 17a . 17b ) is provided to independently drive the two drive shafts and in an operating situation and projecting view of the drive shafts ( 4a . 4b ) on the first drive shaft ( 4a ) arranged imbalance mass ( 15a ) between 170 ° and 190 °, preferably offset by 180 ° to the second drive shaft ( 14b ) arranged unbalanced mass ( 15b ) is arranged. Sieving machine according to one of the preceding claims, characterized in that it has a mass of at least 3,500 kg, preferably of at least 4,000 kg.

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