EP1577023B1 - Screening machine for drums having different diameters - Google Patents

Abstract

The sieving device has a frame unit which has at least one support means (3) for the mounting of a drum. The support means in a first position (5) are designed for the mounting of a drum of a first diameter (7) and in a second position for the mounting of a drum of a second diameter. The support means may be constructed for the mounting of at least three, four, or more drums with different diameters. The support means have at least two support elements (9) which are constructed preferably as rolling bodies (10).

Description

The invention relates to a screening machine with a frame device for rotatably holding a screen drum. The sieve drum can be designed as a drum screen. It is also possible that a separate screen is stretched on the drum.

More particularly, the present invention relates to a mobile drum screening machine which is moveable, e.g. as a trailer.

Drum screening machines have become known in the art. Exemplary is in the in the DE 298 09 345 U1 disclosed screening machine referenced.

Such drum screening machines are e.g. used by contractors carrying out contract work. They are used, for example, for sifting compost material or rubble. Different sieving fineness can be used for different requirements and for different materials to be sorted. Many owners of drum lathes have a plurality of drums of different characteristics for different purposes and materials. Some owners also have a number of identical drums for a number of identical machines or one or more drums in reserve.

So far, the use of a drum of a certain diameter was only possible on one machine. It was not possible to use a drum sieve with a certain screen diameter for one specific type of machine to be used on a different type of machine, which was designed for a different drum size.

If the owner now buys a new modern drum screen machine with a larger drum diameter, he can not re-use the old drums because they have a smaller screen diameter and a smaller diameter for the drive.

A screening machine with replaceable drum is from the WO-A-2005/014186 known.

Although in the prior art a trommel screen has become known in which different sized screen diameter can be used, but in this machine this is achieved in that the tread still has the same large diameter in drum screens of different screen sizes. This means that the owner can not continue to use the smaller drums when buying a larger machine because they have too small a diameter of the tread. With such a machine, the owner can therefore buy only additional smaller drum screens with a correspondingly large tread, but not continue to use the older smaller drum screens when buying a larger drum screen.

It is therefore the object of the present invention to provide a further device with which drum sieves of different screen diameters can be used.

This object is achieved by the subject matter of claim 1.

Preferred developments of the invention are subject of the dependent claims.

The present invention according to claim 1 provides a screening machine having a rack means. The rack means is provided with at least one support means for holding a drum. At least one support means is in a first position for holding a drum first diameter and formed in a second position for holding a drum of a second diameter.

The screening machine according to the invention has many advantages.

By making the drum screen machine capable of accommodating two drum diameters, further use of (e.g., older) drums of smaller diameter can be made possible, although the drum screen machine is also adapted for the operation of drums of larger diameter. With the present invention, the (flexible) reuse of smaller drums is made possible. This was not possible in the prior art. This makes the cost-effective transition to a more modern and efficient system possible, whereby the existing drums can continue to be used. As a result, significantly less investment is required if the system changes.

In a preferred embodiment of the invention, the or at least one support means for holding at least three or four drums with different diameters is formed. Preferably, the support means may also be suitable for holding or supporting even more different drum diameters.

Preferably, at least two, preferably at least four, supporting means are provided. For a particularly reliable support of the drum is achieved.

In a preferred embodiment, at least one support means comprises at least two support elements, which are preferably formed as a rolling body. Rotatable support elements are very advantageous because it allows a simple and reliable rotatable support or a rotatable holding the drum.

In a preferred embodiment of one or more of the previously described embodiments of the invention is at least a support means received pivotally. If the support means comprises support elements, then the support elements are preferably pivoted with.

Preferably, at least one support means is designed such that the support means can be transferred by pivoting from the first position to at least the second position. Also several positions are possible. It is particularly preferred that a simple return from the second to the first position is possible, preferably by pivoting back. If two drum sieve sizes are receivable, then it is preferred that a 180 ° swivel takes place.

It is also possible that at least one support means is slidably or spatially received by a recording. For example, may be provided instead of the pivotability Verschiebbarkeit. It is also possible that in addition to the pivoting a displacement of the support means or the support means is possible. Preferably, a displacement in the radial direction with respect to a drum, so that there is a point of intersection on the virtual central axis of the drum with linear displacement of several support means.

By arranging the support means in a second receptacle, the device can be retrofitted to accommodate a different drum diameter. There, the support means are suitably fixed, e.g. screwed or plugged and e.g. provided with a safety pin.

Preferably, the virtual central longitudinal axis of a male drum is held substantially in the same place, regardless of the drum diameter. This means that two drums of different diameters are kept substantially concentric with each other. If the drums supported at its outer diameter, the support point must be higher for drums with a smaller diameter. This means that by transferring from the first to the second position or vice versa, the height of the support point or breakpoint is changed.

Preferably, a breakpoint is higher in the second position than in the first position.

In preferred embodiments, the rack means is adapted to receive at least one drum having a diameter of a group of diameters which comprises at least the diameters 1.5m and 1.8m and 2m and 2.2m. Particularly preferred is the inclusion of drums of diameter 2 m and 2.2 m possible. Also preferred is the inclusion of drums of diameter 1.8 m and the diameter 2 m, or the inclusion of drums of diameter 1.5 m and the diameter of 1.8 m, or the inclusion of drums of diameter 1.8 m and of diameter 2.2 m. The inclusion of drums of other diameters, in particular as are customary in the prior art, is preferred.

It should be noted at this point that under different drum diameters in the context of this invention significant differences in diameter are understood. The difference of e.g. 1 cm in diameter is not considered essential. This is different for larger differences of 10 or 20 cm or more. Even 5 cm can mean a significant difference.

Preferably, a housing is provided, which surrounds a drum at least on the longitudinal sides, at least partially. Preferably, a side wall is provided on each longitudinal side in the direction of travel, which substantially covers at least the lateral region of the drum.

In a preferred embodiment, the (horizontal or radial) distance of the housing wall on a first longitudinal side is greater than on the second longitudinal side. In the prior art, an equal distance is provided on both longitudinal sides, ie between the respective drum outer wall and adjacent housing inner wall.

A different distance on both sides is very advantageous, because during the rotary movement of the drum, the material conveyor arranged in the drum, such as e.g. a screw conveyor, the material to be screened on the first longitudinal side with taken up. This is due to the rotational movement. Sifted fine material passes through the drum screen to the outside. The fine material then falls down the side wall and reaches the drum conveyor belt for the fines.

Individual parts can, however, get stuck in the screen wall, so that a portion of the respective parts protrudes outwards. Therefore, on the first side, on which the material in the drum is transported upwards (by taking the material with it), a sufficient distance from the housing wall should be provided in order to avoid blocking. This page is labeled here with first page. On the other hand, on the other hand, a significantly smaller distance from the housing wall is sufficient, since material present in the screen wall drops out again in the upper rotational range of the drum. Or the drum screen is replaced by any cleaning device, in the form of e.g. a cleaning broom, freed from stuck material again. This can be done by the cleaning brush with its bristles free the screen openings of the drum screen of fixed components. Overall, a smaller overall width is achieved by the different lateral distances, or it is possible with the same overall width a larger drum diameter.

In a further development of the invention, a task bunker is provided which preferably has a bunker conveyor belt designed as a conveyor cassette.

Preferably, the bunker conveyor on the bottom drive means, which cooperate with the drive roller. This is advantageous because in the prior art so far the drive roller on the belt tension transmitted the force. In the area of the bunker conveyor, the introduction of force is usually difficult, since the material to be transported is generally not pulled, but pushed.

This is because the bunker conveyor extends into the screen drum to ensure reliable transport of material into the drum, and the fact that the driven roller is usually not introduced into the drum for reasons of space. Therefore, the other roller is driven, which now causes a sliding of the conveying material. The force relationships are not ideal. Therefore, drive means on the underside of the bunker conveyor belt are very advantageous, especially when they interact with drive means on the drive roller.

Preferably, the drive means of the bunker conveyor belt is designed as a toothing or as cleats.

Advantageously, a toothing is provided on at least one drive roller. Particularly preferred on the drive roller of the bunker conveyor belt, in particular if the bunker conveyor belt has corresponding drive means.

Preferably, at least one control device is provided for controlling the screening machine or at least parts thereof.

Advantageously, at least the control and / or adjustment of the conveying speed of at least one component is possible by means of or by means of at least one control device. Particularly preferred is the control and / or adjustment the conveying speed of the bunker conveyor belt possible.

For screening machines, larger drum diameters are desirable because larger diameters increase performance. Increasing drum diameters, however, represent a major engineering challenge as the overall width is limited to about 2.5 meters. The possible width for mobile systems is determined by the respective road width. For other road widths other maximum drum diameters are possible.

In recent years, a drum screen machine with 2 m drum diameter has been used. The development step of 1.8 m diameter to 2 m drum diameter is very considerable due to the maximum permissible overall width, since the transport width of the machine must not exceed significantly more than 2.5 m. It should be noted that the drum is still surrounded by a housing. Furthermore, a lateral discharge belt is usually provided on the housing, which increases the width considerably.

In an advantageous development, a larger drum diameter is made possible while maintaining the overall width.

For this purpose, the screening machine comprises e.g. a housing having a first sidewall and a second sidewall between which a drum is rotatably received. In this case, a first distance of a first side wall to the drum is greater than a second distance of a second side wall to the drum.

Distance is understood here as the shortest typical lateral or even radial distance. In particular, this is the typical lateral distance equal to the largest width of the Screening machine, or understood the typical lateral distance equal to the largest drum width.

This embodiment has many advantages.

Through these adjustments, it has now been possible to increase the drum diameter again considerably to 2.2 m. Thus, the performance of the system, which is due to the screen surface, increased significantly. The throughput of material to be screened is much higher.

On the drum side, which takes material up when turning, the side clearance should be sufficient, while the side clearance on the other side can be quite small.

In another embodiment, the mobile screening machine comprises a housing for receiving a drum. Furthermore, at least one conveying device for discharging material is arranged laterally on the housing. The lateral conveyor has an upper and a lower transport roller. The upper transport roller has a larger diameter than the lower transport roller.

Even with this configuration, a smaller overall width is possible with the same drum diameter or a larger drum diameter with the same overall width.

Preferably, the upper transport roller is driven.

In a preferred embodiment, at least one upper part of the lateral conveyor, for example in the form of a conveyor belt, can be folded. Preferably, the upper part is foldable for transport. Particularly preferably, the folded-in part is then arranged at least partially above the drum during transport.

The frame device is preferably structured in such a way that a (virtual) central longitudinal axis of a drum is arranged laterally offset relative to a center line of the frame device in the longitudinal direction. This is advantageous because a lateral conveyor is provided on one side next to the drum. Then a laterally offset structure instead of a symmetrical structure is advantageous because the maximum lateral projection is limited.

Further advantages and possible applications of the present invention will become apparent from the following embodiment, which is explained with reference to the figures.

Fig. 1

eine erfindungsgemäße Siebmaschine in Transportstellung in einer perspektivischen Ansicht;

Fig. 2

die Siebmaschine nach Fig. 1 in Arbeitsstellung in einer perspektivischen Ansicht;

Fig. 3

eine große Siebtrommel in der Siebmaschine nach Fig. 1 in einer schematischen Vorderansicht;

Fig. 4

eine vergrößerte Darstellung einer Lagerschwinge zur Lagerung der großen Siebtrommel nach Fig. 3;

Fig. 5

einen Ausschnitt einer schematischen Vorderansicht einer kleineren Siebtrommel in der Siebmaschine nach Fig. 1;

Fig. 6

eine stark schematische Ansicht der Siebtrommel im Gehäuse der Siebmaschine nach Fig. 1;

Fig. 7

eine stark schematische Ansicht des Austragsförderbandes für Feinkorn der Siebmaschine nach Fig. 1;

Fig. 8

eine schematische Ansicht der Siebtrommel nach Fig. 1 mit dem Trommelantrieb in der Ruhestellung;

Fig. 9

eine schematische Ansicht der Siebtrommel nach Fig. 1 mit dem Trommelantrieb in der Eingriffsstellung; und

Fig. 10

eine vergrößerte schematische Ansicht des in Fig. 8 dargestellten Trommelantriebs in der Ruhestellung.

In the figures show:

Fig. 1

a screening machine according to the invention in transport position in a perspective view;

Fig. 2

the screening machine behind Fig. 1 in working position in a perspective view;

Fig. 3

a large sieve drum in the screening machine after Fig. 1 in a schematic front view;

Fig. 4

an enlarged view of a bearing rocker for storage of the large screen drum after Fig. 3 ;

Fig. 5

a section of a schematic front view of a smaller screen drum in the screening machine according to Fig. 1 ;

Fig. 6

a highly schematic view of the screen drum in the housing of the screening machine after Fig. 1 ;

Fig. 7

a highly schematic view of the discharge conveyor belt for fine grain of the screening machine according to Fig. 1 ;

Fig. 8

a schematic view of the screen drum after Fig. 1 with the drum drive in the rest position;

Fig. 9

a schematic view of the screen drum after Fig. 1 with the drum drive in the engaged position; and

Fig. 10

an enlarged schematic view of the in Fig. 8 shown drum drive in the rest position.

The embodiment will now be described with reference to the figures. In FIG. 1 is a mobile screening machine 1 in the transport position 35 and in FIG. 2 shown in the unfolded working position 36.

The trommel screen 1 has a frame 2 with wheels 42, on which the drum 4 is rotatably supported. By replacing the drum 4 different drums 7, 8, as in Figures 3 and 5 is shown to be used with different diameters. In this case, the running in the embodiment as a support rocker 3 support means in FIG. 3 in the first position 5 for big drums and in FIG. 5 shown in the second position 6 for smaller drums.

At a first end 43 of the trommel screen 1, the total mobile, mobile drum trommel 1 can be attached in the transport position 35 to a vehicle.

At the first end 43 is the feed bunker 17, which includes the bunker hopper 18 and the bunker conveyor belt 22. The loading is carried out, for example, by means of a wheel loader or an excavator (not shown in each case) in the hopper 17. Below the task bunker is the drive unit 19 of the screening machine. 1

The bunker conveyor belt 22 is designed as a conveyor belt cassette, in which all drive elements such as drive roller, guide roller, conveyor belt, gear and hydraulic motor, etc. are integrated. The conveyor cassette is inserted into the bunker hopper 18 and fixed. The bunker conveyor belt has at the bottom studs 45 which engage in the drive roller, which is also toothed (not shown).

The bunker conveyor belt 22 projects into the drum 4 and reliably conveys the material to be screened into the drum 4. At the material outlet side of the hopper 17, a sealing ring is attached to the bunker hopper 18, which seals the bunker 17 to the screen drum 4 out. The tolerance is about 10 mm in the embodiment. Depending on the application, larger or smaller tolerances may be present.

The feed rate of the bunker conveyor belt 22 can be adjusted by means of a control device 49 depending on the size of the screen and the screen material. The controller may include one or more potentiometers.

Seen from the first end 43 of the screening machine in the direction of the second end 44, the screening bunker 17 is adjoined by the screening drum 4.

The sieve material coming from the feed hopper 17 falls into the sieve drum 4. This rotates in operation at a speed of about 10 to 23 revolutions / min. An introduced on the inside of the drum shell conveyor screw 50 takes over the material transport within the sieve drum. The screw conveyor is welded in the embodiment.

Overall, the screen drum 4 consists of the perforated drum shell, the screw conveyor 50, the two races for rotatable holding, a drive section which is equipped with a Gummireibbelag, an inlet ring 51 at the beginning of the drum and optionally one or more axial rings (not shown) for stabilizing and securing the drum in the axial direction.

By the rotation 30 of the drum 4, the screen material is taken up and falls down again from a certain point. The material in the drum 4 behaves in a manner similar to an overturning wave in the sea. Seen from behind, the material is in a range from 2 o'clock to 6 o'clock. The drum moves counterclockwise in this view. Seen from the front in the conveying direction, ie viewed from the first end 43 in the direction of the second end 44, the material is approximately in an angular range between 6 and 10 o'clock.

As in the schematic representation after FIG. 6 can be seen, is on the side of the side wall 12, a horizontal distance 15 between the drum 4 and the side wall 12 before. On the opposite side of the side wall 13, the minimum horizontal distance 16 is present. Here in the exemplary embodiment, the distance 16 is significantly smaller than the distance 15. The distance may be, for example, 80% or 50% or only 33% of the distance 15. As a result, valuable space is gained in width. Here it is so that the greater distance 15 is present on the side on which the conveying material is transported up in the drum.

The finer content in the sieve material, the fine grain, passes through the sieve perforations, while the coarse fraction, the oversize grain, remains in the drum. The oversize is conveyed by the augers 50 to the end of the drum and then out there.

In the embodiment, the screen drum has a diameter of 2200 mm and a length of 5500 mm. The unperforated area has a length of approx. 320 mm at the front and at the back. In this non-perforated area are the rollers for rotatable support of the screen drum and the drive area with the rubber lining.

The drum is mounted on four support means in the form of bearing rockers 3. Each bearing rocker 3 has a wheel pair with wheels 10 for rotatably supporting the screening drum 4. These pairs of wheels are rotatably received on the bearing rockers 3. Each bearing rocker 3 is pivotally mounted on the frame 2 or the housing 11.

It is also possible to use only four carrying wheels 10. These are then fastened with a flange on the frame 2.

The drive of the drum 4 is done by means of a roller chain 31 at the on each fourth member two angled tabs (not shown) are located. These tabs are on the Gummireibbelag 52 of the drum 4.

A drive sprocket (not shown) is connected to a motor. In the exemplary embodiment, the motor is designed as a hydraulic motor 29. This motor is attached to a rotatably mounted engine console or to a flange 41. The rotatably mounted motor flange or flange 41 is moved by means of an adjusting device, which is designed in the embodiment as a hydraulic cylinder 33. The hydraulic cylinder 33 is fixed on the one hand to the pivot point 40 on the flange 41 and on the other hand rotatably mounted on the frame via a pivot point 55. By the rotational movement of the motor console or the flange 41, the chain 31 is biased.

A cleaning brush 25 is provided in an upper area. This has the task to rid the screen drum 4 of adhesions by screen material at the holes and webs of the screen drum. The cleaning brush 25 consists of a mounted shaft, are mounted on the round broom discs with a plastic trim. The cleaning brush 25 in total and its cleaning discs (the brooms) have no separate drive, but are taken by the drum and rotated.

The plastic bristles of the round broom discs pierce the sicuret holes, freeing them from dirt and buildup. The bristles and brush discs wear out over time. To compensate for the wear and to achieve a sufficient cleaning result even with partially worn bristles, the broom can be readjusted. In the embodiment, this is done by means of hydraulic cylinders.

The discharged from the drum fine material passes either directly or via chutes on the drum conveyor belt 20. This sits longitudinally under the drum and transports the fine material to the rear. There, the material is transferred to a short cross conveyor belt 21 and then passes to the discharge conveyor 23 for fine grain, which is employed with an inclination of about 30 ° to the horizontal. Subsequently, the fine material is poured free on heap. The discharge conveyor 23 for fine grain is folded for transport to the screening machine. In addition, the upper part 34 of the conveyor belt is still folded in hydraulically and settles over the sieve drum.

In the illustrated embodiment, the fine grain discharge conveyor belt 23 comprises a lower transport roller 27 and an upper transport roller 26 serving as a drive roller. According to this embodiment, the roller 27 has a significantly smaller diameter 54 than the drive roller 26, which has a diameter 53.

The oversize material falls from the screen drum 4 onto a longitudinal discharge conveyor belt 24 for oversize grain. The conveyor belt has a slope of about 25 ° to the horizontal. The material falls free on heap at the end of the belt. This band is also folded for transport and the upper part 46 kinked.

The primary drive of the screening machine is via an industrial diesel engine. The secondary drive of the individual components takes place via hydraulic pumps attached to the diesel engine. Depending on the version, the diesel engine may have a different output, which here is 90 kW.

It is possible to use screening drums of different drum shell diameters and different raceway diameters.

Given dimensions of the bunker conveyor belt 22 or the bunker conveyor cassette, this represents certain requirements for the positioning of the screen drum, because the bunker conveyor belt 22 must indeed be inserted into the screen drum. The free cross section of the screening drum in height of the bunker conveyor belt 22 must be sufficiently large for receiving the same.

This is usually ensured when the axial center axis of the drums within the machine remains the same, regardless of the diameter of the drum 7, eighth

Otherwise, the lateral extent of the bunker conveyor belt 22 can be reduced, but this can be associated with capacity losses.

In the exemplary embodiment, pivoting of the bearing rockers 3 ensures that the (virtual) axial center axis 37 of drums with different diameters remains the same. Since the pivot points of the wheels 10 are offset by the distance 47 relative to the Verschwenkungspunkt 14, a drum with a different radius by twice the distance 47 is recorded in register by pivoting the bearing rocker 3 by 180 °.

Each bearing rocker 3 has an impeller pair. The wheels 10 are mounted on the rotatable bearing rocker 3 and stored there. The pivot point 14 of the bearing rocker 3 and the axes of the wheels 10 are not on a line but are offset by the distance 47, which is 50 mm in the embodiment.

In the first position (see FIG. 3 ), namely the position of the larger drum are the axes of the wheels below the pivot point of the bearing rocker 3. If now a smaller drum are used, the bearing rocker 3 is pivoted by 180 °. Now the axes of the races are above the pivot point 14 (see FIG. 5 ). Due to the offset of two times 50 mm results in a radius change of 100 mm and a diameter change of 200 mm. If the first position is designed for a diameter of 2.2 m, then the second position is suitable for receiving a drum of 2 m diameter. The same applies to drums with 1.8 m and 2 m diameter.

By adapting the distance 47 to desired conditions (e.g., 1.5 m and 1.8 m diameter) different bearing rockers 3 can be made available for different applications.

Also possible is a bearing rocker, which has three wheels, which are arranged in a triangle to each other. The central pivot point 14 of such a bearing rocker 3 should then have a different distance from all three axes of the wheels 10. Now, by turning by 120 ° each, the screening machine can be prepared for receiving a sieve drum with one of three diameters.

The already described pivotally mounted drum drive 28 is biased by a hydraulic cylinder 33. If the screening machine is started, an automatic, time-delayed starting of the individual components takes place at the push of a button.

This is very advantageous since in particular inexperienced operators, the individual components under certain circumstances in an inappropriate order on or off, If, for example, the bunker conveyor belt turned off when the machine last issued, it may happen that the operator in the meantime of the bunker conveyor belt 22 in move the drum 4 registered material back by scoop must, which can be associated with a considerable amount of work and time.

To start the two discharge belts for the fine grain and the oversize 23, 24 are started, then the cross conveyor 21 and then the drum conveyor 20, then the automatic chain tensioner (the hydraulic cylinder 33) of the drum drive 28, then the screen drum and finally the bunker conveyor belt 22 of the Task bunker 17.

The shutdown takes place in reverse order, inter alia to avoid the disadvantage described above.

The bias in the exemplary embodiment is such that the clamping cylinder designed as a hydraulic cylinder 33 is subjected to a specific, predetermined pressure. As a result, the drum drive 28 with the drive motor 29 is brought from the rest position into the engaged position and the roller chain 31 is tensioned. The flange 41 with the drive motor 29 is thereby pivoted about the pivot point 32.

In the new state of the chain drive is a mean or even a slight deflection of the hydraulic cylinder 33. Due to the force of the hydraulic cylinder 33 conditionally, the roller chain 31 is tensioned. The biasing force is due to the working pressure of the hydraulic cylinder 33.

If the roller chain 31 has lengthened after several operating days, for example, the desired preload is set again at any time during starting. Upon elongation of the roller chain 31, the hydraulic cylinder 33 extends only slightly further until the counterforce of the hydraulic force of the hydraulic cylinder 33 holds the balance. Thus, here is a self-adjusting system. This reduces the need for maintenance enormously. Also, the wear is reduced and increases the service life. Too low a bias in the roller chain 31 can lead to slippage of the chain and increased wear.

In one embodiment, after tension of the hydraulic cylinder 33 and after the drum drive 28 has been brought into the engaged position, then the pressure is shut off by means of a directional control valve. The hydraulic cylinder 33 and thus the drum drive 28 now remain in the engaged position 38 until the operation is terminated. During an operating day or a continuous operating period, elongation of the roller chain 31 generally does not occur or occurs only to a negligible extent, so that the pretension in the roller chain 31 is substantially preserved. If the bias still decreases, the hydraulic cylinder 33 can be repositioned by stopping and restarting the screening machine, so that then the desired bias is applied again.

Alternatively, the pressure in the hydraulic circuit may be measured continuously or at predetermined periodic intervals with a sensor (not shown). If then the measured pressure falls below a certain level, in one embodiment, the pressure in the hydraulic circuit is brought back to nominal level. The time intervals of the measuring points may also depend on the measured pressure. It is also possible that the time intervals depend on the load of the drum drive and e.g. is measured more often when a high load is present.

In another preferred embodiment, the biasing force of the chain is controlled by maintaining the pressure in the hydraulic circuit at a desired level. The absolute pressure or the prestressing force can in particular also depend on the load of the drum drive and correlate therewith.

In another embodiment, the hydraulic cylinder 33 remains under pressure during operation. Then a continuous self-tension is realized.

In all embodiments, a spring 48 may be arranged in the circuit of the hydraulic cylinder 33, which in the embodiment is designed as a hydraulic spring in the form of a nitrogen blanket. This hydraulic spring 48 can compensate for the non-circularity of the drum 4 and the chain drive 28.

An advantage of such a hydraulic spring 48 is that the roller chain 31 always has the same bias. This contributes to an increase in the life of the entire chain drive.

If the screening machine 1 is switched off, the directional control valve is actuated and switches over. Now the hydraulic circuit of the hydraulic cylinder 33 is unlocked, the cylinder moves to the rest position 39 and the chain 31 is relieved. In the unloaded state, the chain 31 can be taken from the sprocket (not shown). This is e.g. necessary to change the drum 4.

A second possibility is to connect the hydraulic circuit of the hydraulic cylinder 33 with the hydraulic circuit of the drive mo reed 29 of the screen drum drive 28. Thus, should the pressure in the drive motor 29 increase (for example, by heavier screen material), the pressure of the hydraulic cylinder 33 is also increased and thereby the bias of the drive chain 31st

This load-dependent control circuit prevents slippage of the drive chain 31 aut the drum 4, even under the toughest conditions.

Another advantage of the hydraulic tensioning of the chain is that the drum can be shortened, e.g. can run backwards for maintenance or longer.

Claims (12)

1. A screening machine (1), comprising:

   a frame device (2) provided with at least one support means (3) for supporting a drum (4); characterized in that the support means is configured in a first position (5) for supporting a drum having a first diameter (7), and in a second position (6) for supporting a drum having a second diameter (8).
2. The screening machine according to claim 1, characterized in that the support means (3) is configured for supporting at least three, four or more drums (4) having different diameters.
3. The screening machine according to claim 1 or according to claim 2, characterized in that at least two, preferably at least four support means (3) are provided.
4. The screening machine according to at least one of the preceding claims, characterized in that at least one support means (3) comprises at least two support elements (9) which are preferably configured as rolling bodies (10).
5. The screening machine according to at least one of the preceding claims, characterized in that at least one support means (3) is received pivotally and/or at least displaceably.
6. The screening machine according to at least one of the preceding claims, characterized in that at least one support means (3) is configured such that the support means (3) can be transferred by pivoting from the first position (5) at least into the second position (6).
7. The screening machine according to at least one of the preceding claims, characterized in that the frame device (2) is configured for receiving at least one drum (4) having a diameter out of a group of diameters comprising at least the diameters 1.5 m and 1.8 m and 2 m as well as 2.2 m.
8. The screening machine according to at least one of the preceding claims, characterized in that a housing (11) is provided which surrounds a drum (4) at least on the side walls (12, 13) at least in part wherein preferably the distance (15) of the housing wall is larger on a first side wall (12) than on the second side wall (13).
9. The screening machine according to the preceding claim, characterized in that a bin conveyor belt (22) is provided which on its bottom surface comprises drive means cooperating with the drive roller, wherein the drive means are preferably configured as toothing and/or as lugs and preferably at least one drive roller (26) comprises a toothing.
10. The screening machine according to at least one of the preceding claims, characterized in that a control device (49) is provided.
11. The screening machine according to at least one of the preceding claims, characterized by at least one conveying device (23) arranged on the side of the housing (11) for discharging materials, preferably comprising one upper and preferably one lower transport roller (26, 27), wherein the upper transport roller (26) may be larger in diameter (53) than the lower transport roller (27).
12. The screening machine according to at least one of the preceding claims, characterized in that the frame device (2) is structured such that a central longitudinal axis (37) of a drum is arranged laterally offset relative to a center line of the frame device (2).

Images