METHOD AND DEVICE FOR SCREENING EARTH, GRAVEL AND THE LIKE

Description

[0001] The present invention relates to the screening of such materials as earth, gravel and the like containing comparatively large-size objects, such as stones, root vegetables and the like, which are to be separated from the finer material. More precisely, the invention concerns a method and a device of the type recited in the preambles of appended claims 1 and 4, respectively, use being made of a rotatable screening drum which preferably is connected to a working machine, e.g. a tractor with a front loader.

[0002] This invention is based on the screening technique disclosed in EP-B1-0,178,656 (corresponding to SE-B-454,096). This prior-art technique employs a substantially grate-type screening basket which is connected to the front loader of a tractor and which, during screening, is rotated by means of a rotary shaft extending in the main direction of travel of the tractor. This prior-art screening device does, however, suffer from a number of drawbacks which chiefly are related to the alignment of the rotary shaft and its sole mounting point.

[0003] As appears from Fig. 4 of the above SE specification, the bearings of the screening basket will be subjected to a breaking action (observed in actual practice) when the basket is being loaded, which causes problems, especially when a considerable pushing force is required or when the front edge of the screening basket inadvertently encounters stones that are stuck in the ground. Another disadvantage is that it is difficult for the operator when sitting in the driver's seat of the tractor to supervise the screening work, since the rear part of the screening basket is a solid piece and therefore hides the screening compartment (see Fig. 5 of the SE specification). Also, the forwardly-directed rotary shaft usually necessitates that the width of the screening basket be smaller than the track gauge of the tractor, since the forces generated by the rotational motion of the basket might otherwise jeopardise the stability of the tractor sideways. It has been found in practical use that the width of the screening basket should not exceed 1.7 m.

[0004] Thus, there is a demand for a screening device which, by relying on a different principle of rotation, obviates these disadvantages. Efforts have previously been made to meet this demand, and e.g. GB-A-1,512,206 and EP-A-0,047,041 disclose screening devices which are equipped with grate-type, rotatable screening drums which are disposed transverse to the main direction of travel of the working machine. However, these drums have to be opened when to be fed with material, and closed to prevent the material from falling out of the drum during its rotation. Thus, the drums have to be provided with movable grating sections which are operated by means of hydraulic units. As a result, such grate-type screening devices become unnecessarily heavy and complicated, as well as liable to stoppages. In addition, the required operating equipment makes the construction more expensive.

[0005] Other background art is US-A-4,005,755 which relates to a machine which can be connected to a front loader and is adapted to take up and screen earth. This machine comprises a housing which essentially consists of two integral end walls and a front grating. Inside the housing, there is an endless chain drive whose transverse elements have substantially the same width as the housing. Also this machine suffers from drawbacks similar to those discussed above. Thus, there is a considerable risk that stones become wedged in the complicated chain drive. Further, the machine has a large number of movable parts, which is far from being an advantage.

[0006] SU-A-1.517,782 discloses a machine for cleaning and loading stones. It comprises a drum with four overlapping lattice walls 2. The walls 2 define collecting openings 5 which widen towards the interior of the drum (B₁ < B₂). To load the drum with stones from a heap, the drum is rotated clockwise and moved into the heap. Upon further rotation of the drum, impurities will leave the drum through the lattice walls. To unload the cleaned stones, the drum is rotated counter-clockwise. This prior art machine does only allow screening of the material at the loading site.

[0007] One object of the present invention is, therefore, to eliminate the above inconveniences by providing a simple, quick and efficient method for screening earth, gravel and the like, without necessitating any complicated equipment.

[0008] Another object of the invention is to provide a device for screening earth, gravel and the like, which obviates the above inconveniences and which is of simple construction and has but a few movable parts.

[0009] Yet another object of the invention is to provide a screening device having simple and reliable driving means and capable of efficiently taking up the forces to which it is subjected during the screening operation.

[0010] A further object of the invention is to provide a screening device easily connectible to a working machine, preferably to the front loader of a tractor vehicle, so that the device, by simple operation, can be moved into the earth or gravel to be screened and receive a suitable amount of material.

[0011] These objects, as well as other objects that will appear from the following description, have now been achieved by a method according to the invention, which is of the type stated by way of introduction and which further comprises the features recited in the characterising clause of claim 1.

[0012] These objects are also achieved by a device which is of the type stated by way of introduction and which further has the features recited in the characterising clause of claim 4.

[0013] Preferred variants and embodiments of the invention are recited in the appended subclaims.

[0014] The invention and its many advantages will be described in more detail below with reference to the accompanying drawings showing some embodiments. In the drawings,

Fig. 1 is a schematic perspective view showing a screening device according to the invention obliquely from in front,

Figs 2-5 are schematic cross-sections of a screening drum forming part of the device and shown in different operational positions,

Fig. 6 is a perspective view obliquely from in front and Fig. 7 is a perspective view obliquely from below of a slightly modified screening drum which has been disconnected from the other equipment.

[0015] Fig. 1 illustrates a device designed in accordance with the invention for screening such materials as earth, gravel and the like. In this case, the material to be screened is a mixture of relatively large objects 1 in the form of stones, and fine-grained material 2 in the form of earth. The main component of the screening device is a screening drum generally designated 3 which, by means of a substantially horizontal rotary shaft 4, is mounted on a frame 5. The frame 5, which is of known type (see, for instance, GB-A-1,512,206), is in conventional manner provided with means for connection to a working machine, in this case the front loader 7 of a tractor 6. Thus, the frame 5 and the drum 3 mounted thereon can be lifted, lowered and tilted by means of the front loader 7.

[0016] The screening drum 3 may be regarded as a body of revolution with respect to the axis of rotation or rotary shaft 4, and the circumferential surface of the drum 3 mainly consists of a curved screening element 8, one transverse edge of which is connected to a reinforcing metal sheet 9 in one piece (see Figs 6 and 7) and the other free, transverse edge of which extends into the drum 3. Further, the drum 3 has two integral vertical end walls 10, 11 of sheet metal, between which extend the curved screening element 8 and the flat reinforcing sheet 9. Both the screening element 8 and the reinforcing sheet 9 are connected, preferably by welding, to each other and to the periphery of the respective end wall 10, 11.

[0017] A driving unit 12, which is mounted on the frame 5 and arranged on the outside of the end wall 11, rotates the rotary shaft 4 and, consequently, the entire drum 3 mounted thereon. The driving unit 12 preferably is a known hydraulic motor connected to one end of the rotary shaft 4. If need be, there may, of course, be arranged a hydraulic motor at each end of the rotary shaft 4. In the embodiment shown, the rotary shaft 4 is, however, freely mounted on the forwardly-directed part of the frame 5 at the end wall 10 (not shown). For greater clarity, hydraulic lines and other equipment forming part of the hydraulic system are not shown in Fig. 1.

[0018] In the forward direction in Fig. 1 with respect to the main direction of travel of the tractor 6 (indicated by an arrow), the circumferential surface of the drum 3 is formed with an inlet opening 13 for the material to be screened. The opening 13 is defined by the front edge of the reinforcing sheet 9, the forwardly-directed edge of the end walls 10, 11, and the extension of the screening element 8 directed into the drum 3, as will be discussed in more detail below. For screening, the drum 3 is moved, by means of the tractor 6, in the direction indicated by the arrow into the earth 1, 2 until a suitable amount of material has been fed into the drum 3 through the opening 13. When the drum 3 is moved into the earth 1, 2, the rotary shaft 4 is either locked by a pressure-reducing valve or a non-return valve (not shown) in the hydraulic system, e.g. in the hydraulic motor 12, or locked mechanically by a locking means (not shown) which is mounted on the frame 5 and can be operatively applied against the outside of the drum 3. When a suitable amount of material has been fed into the drum 3, this is lifted and slightly tilted rearwards towards the tractor 6, which then takes the drum 3 to the screening site where the drum is rotated in a manner to be described further below.

[0019] Fig. 2 shows the drum 3 in the lifted screening position in which the frame 5 is tilted forwards-downwards. The screening drum 3 is rotated towards the tractor 6 in the direction indicated by the arrow, so that the fine material, i.e. the earth 2, is forced out of the drum 3 through the screening element 8, which preferably is a netting or grating. The large-size objects, i.e. the stones 1, that cannot pass through the screening element 8, are retained in the drum 3 by a wall 14 which is an extension of the screening element 8 and is directed into the drum. The wall 14 located in front of the opening 13 forms in the drum 3 a pocket 15 which, when the drum is rotated in the first direction, serves to retain the stones 1 inside the drum 3.

[0020] As appears from Fig. 3, the stones 1 are caused, when the drum is rotated further in the first direction, to roll away from the pocket 15 and via the wall 14 associated therewith to pass towards the inside of the reinforcing sheet 9. Thus, the pocket 15 and the wall 14 efficiently prevent the stones 1 from dropping out through the opening 13. It is, in addition, highly advantageous that the stones 1 impinge upon the reinforcing sheet 9, since this protects the screening element 8, which here is a netting. The reinforcing sheet 9 preferably has an angled portion 16 (see Fig. 2) which extends a distance onto the curved screening element 8 which thus is further protected from the impact by the stones 1.

[0021] To direct the stones 1 as desired when the drum rotates, the wall 14 is preferably arranged essentially midway between the rotary shaft 4 and the opening 13. To ensure that no stones 1 bounce out of the drum 3, the inner free transverse edge of the wall 14 advantageously extends beyond the plane passing through the centre of the rotary shaft 4 and the point of intersection between the front edge of the reinforcing sheet 9 and the front, bottom corners of the end walls 10, 11. However, the free transverse edge of the wall 14 has to be located at a distance from the inside of the drum 3, i.e. at a distance from the inside of the reinforcing sheet 9. It should be pointed out that the free transverse edge of the wall 14 preferably is perfectly parallel to the rotary shaft 4, as are of course the two transverse edges of the reinforcing sheet 9.

[0022] After the screening operation has been completed, only stones 1 remain in the drum 3, as shown in Fig. 4, and they are efficiently retained therein by the wall 14 and the inner pocket 15. The drum 3 is preferably stopped in this position, whereupon it is taken, by the tractor 6, to an emptying station where it is rotated in the opposite direction, as illustrated by the arrow in Fig. 4. During the rotational motion of the drum, the stones 1 are allowed to leave the pocket 15, and the drum 3 is, after being turned a limited distance, situated in the emptying position shown in Fig. 5, where the stones 1 slide on the sheet 9 and out of the drum 3 through the opening 13. The drum 3 is preferably stopped in this emptying position, or is slightly turned further clockwise (with respect to Fig. 5) to be completely emptied. Naturally, the frame 5 can be further tilted and/or shaken should any material have got stuck in the drum 3.

[0023] Thus, the method according to the invention for screening material is clearly illustrated in Figs 1-5. The material 1, 2 is fed into the drum 3, which is first brought to a screening position, in which it is rotated in a first direction, the stones 1 being retained in the drum 3. Then, the drum 3 is brought to an emptying position, in which it is rotated in the opposite direction, so that the stones 1 are removed from the pocket 15 and discharged from the drum 3 through the opening 13.

[0024] In practical tests, the screening device of this embodiment has proved to be particularly efficient. In the tests, the drum was rotated at a speed of about 7-15 rpm, and especially good results were obtained at a speed of about 10-12 rpm. During each screening cycle, the drum was rotated about 4-5 revolutions in the first direction, and about 0.5-1 revolution in the opposite direction. All in all, this represents a shorter screening cycle than could be achieved in prior-art screening devices of similar type.

[0025] Generally, a screening drum of this type should, to the largest possible extent, consist of a screening element. The practical tests mentioned above have shown that the drum is especially effective if about 70% of its circumferential surface is made up of the screening element, about 15% thereof is made up of the reinforcing sheet, and about 15% thereof is made up the opening. It will, however, be appreciated that these percentage figures are nothing but exemplifying target values.

[0026] Figs 6 and 7 illustrate a slightly modified screening drum generally designated 3' which has been disconnected from the other equipment and whose drive shaft has been removed. For reasons of manufacture, the netting-type screening element 8 extends slightly beyond the two end walls 10, 11. Further, the front edge of the reinforcing sheet 9 is bevelled, which makes it easier to move the drum 3' into the material to be screened. The bevelled portion is designated 17.

[0027] Figs 6 and 7 also illustrate a vertical partition 18 which is arranged in the drum 3' and essentially has a stiffening function. The partition 18 may be replaced with a similar structure, e.g. spoke-like struts, arranged between the drive shaft and the netting. In narrow drums, the partition as well as the rotary shaft may be dispensed with. If desired, the screening element 8 may also be replaceable in accordance with the contemplated degree of screening (different mesh widths). Also, the entire drum 3' may be replaceable.

[0028] Compared with the prior art, the screening device according to the invention confers several major advantages, some of which have been discussed earlier in the text. Owing to the fact that the drum 3 is disposed transversely and mounted at two points on the frame 5, the pushing forces generated when the drum is being loaded are taken up very effectively. Also, the robust construction results in excellent force absorption when the drum 3 is rotated. In the tractor 6, the operator has a clear view into the drum 3 all the time, and may thus supervise the entire screening operation.

[0029] It should also be added that the screening drum 3, 3' can be much wider than e.g. the screening device described in EP-B1-0,178,656 discussed by way of introduction. The inlet opening of the screening drum 3, 3' may advantageously have a width of up to about 3.0 m. Another considerable advantage to be emphasised is that the screening drum 3, 3' proper does not contain any movable parts at all. Further, the driving means are simple and of standard design.

[0030] Finally, it should be pointed out that the invention is by no means restricted to the embodiments discussed above, and that several modifications of the invention are conceivable within the scope of the appended claims. Thus, the screening device may, for instance, be connected to other working machines, and other frames, stands and driving means may be used. Further, the screening concept of the invention can be applied to other materials than those referred to herein.

Claims

1. Method for screening such materials as earth, gravel and the like containing comparatively large-size objects (1), such as stones, root vegetables and the like, which are to be separated from the finer material (2), in which method is used a screening drum (3) which is rotatable about a substantially horizontal axis of rotation (4) and which has a circumferential surface mainly consisting of a curved screening element (8) and further having inlet opening means (13) for the material to be screened, said drum (3) being first moved into said material so that a suitable amount thereof is fed into the drum (3) through the opening means (13), whereupon the drum (3) is rotated about its axis of rotation (4) in a first direction, such that the material contained in the drum is set in motion, the large-size objects (1) being retained in the drum (3) by means of pocket means (15) provided therein and defined by obliquely inwardly directed wall means (14) of the screening element (8) of the drum (3), and the finer material (2) being forced out of the drum through the screening element (8), the drum (3) being, after the finer material (2) has been forced out of it through the screening element (8), brought to an emptying position, in which it is rotated in the opposite direction, during which rotation the large-size objects (1), via the wall means (14), are removed from said pocket (15) and discharged from the drum (3) through the opening means (13), characterised in that the opening means of the screening drum used in the method comprises a single inlet opening (13), that the pocket means comprises a single pocket and that the wall means comprises a single obliquely inwardly directed wall the drum (3), when moved into the material to be screened, is blocked against rotation, and that the material taken into the blocked drum (3) during said movement through the single inlet opening is loaded on a flat reinforcing metal sheet (9) which forms part of the circumferential surface of the drum (3), and in that the drum (3) is brought to a screening position after the loading and before it is rotated in the first direction.

2. The method of claim 1, wherein the drum (3) is rotated at a speed of about 7-15 rpm, preferably about 10-12 rpm.

3. The method of claim 1 or 2, wherein the drum (3) is rotated about 4-5 revolutions in the first direction and about 0.5-1 revolution in the opposite direction during every screening cycle.

4. Device for screening such materials as earth, gravel and the like containing comparatively large-size objects (1), such as stones, root vegetables and the like, which are to be separated from the finer material (2), said device including a frame (5) with means for connection to a working machine (6), preferably to the front loader of a tractor, and a screening drum (3) which is mounted on said frame (5) and rotatable by a driving unit (12) and which has a circumferential surface mainly consisting of a curved screening element (8) and further having inlet opening means (13) for the material to be screened, the axis of rotation (4) of the drum (3) being substantially horizontal and transverse to the main direction of travel of the working machine (6), the drum (3) having interior pocket means (15) which is arranged inwardly of the opening means (13) and which is defined by obliquely inwardly directed wall means (14) of the screening element (8) of the drum (3) and which, when the drum (3) is rotated in a first direction, serves to retain the large-size objects (1) in the drum (3) while the finer material (2) leaves the drum (3) through the screening element (8) and which, when the drum (3) is rotated in the opposite direction and after the screening has been completed, allows the large-size objects (1) to leave the drum (3) through the opening (13) means via the wall means (14), characterised in that the inlet opening means comprise a single inlet opening, that the pocket means comprise a single pocket, that the wall means comprise a single obliquely inwardly directed wall the device comprises means designed to block the rotation of the drum (3) when it is moved into the material to be screened, and that the drum (3) has a flat reinforcing metal sheet (9) which forms part of the circumferential surface of the drum (3) and on which the material is loaded when the blocked drum (3) is moved into the material to be screened.

5. The device of claim 4, wherein the obliquely inwardly directed wall (14) is substantially parallel to the axis of rotation or rotary shaft (4) and arranged between said axis or shaft and the opening (13), and has a free, transverse edge located within the drum (3) at a distance from the inside thereof.

6. The device of claim 4 or 5, wherein the wall (14) forms an extension of the screening element (8) of the drum (3) that projects into said drum (3), said screening element consisting of a netting or grating.

7. The device of claim 4, 5 or 6, wherein the drum (3) comprises two opposing vertical end walls (10, 11) which are interconnected by means of the rotary shaft (4) extending therebetween, and by means of the screening element (8) extending between the peripheries of the end walls (10, 11), the reinforcing metal sheet (9) extending between the end walls (10, 11) and having a first transverse edge which is located on the circumferential surface of the drum and is parallel to the rotary shaft (4) and which is connected to the screening element (8), and a free second transverse edge which also is parallel to the rotary shaft (4) and defines the opening (13) which in addition is defined by the end walls (10, 11) and the wall (14).

8. The device of any one of claims 4-7, wherein the wall (14) is so directed into the drum (3) that the major portion of the material contained therein, in particular the large-size objects (1), impinge upon the reinforcing sheet (9) when the drum (3) is rotated.

9. The device of any one of claims 4-8, wherein about 70% of the circumferential surface of the screening drum (3) is made up of the screening element (8), about 15% thereof is made up of the reinforcing sheet (9), and about 15% thereof is made up of the opening (13).

10. The device of any one of claims 4-9, wherein the driving unit (12) is a hydraulic motor mounted on the frame (5) and connected to the rotary shaft (4).

Ansprüche

1. Verfahren zum Sieben von Material wie Erde, Kies u. dgl. enthaltend verhältnismässig grosse Gegenstände (1), z.B. Steine, Wurzelgemüse u.dgl., die von dem feineren Material (2) abzutrennen sind, bei welchem Verfahren eine Siebtrommel (3) verwendet wird, die um eine hauptsächlich horizontale Drehachse (4) gedreht wird und eine Umfangsfläche hat, die hauptsächlich aus einem gebogenen Siebelement (8) besteht und ferner Einlassmittel (13) für das zu siebende Material aufweist, wobei die Trommel (3) erst in das genannte Material hineinbewegt wird, so dass eine geeignete Menge davon durch die Einlassmittel (13) in die Trommel (3) gespeist wird, wonach die Trommel (3) um ihre Drehachse (4) in einer ersten Richtung gedreht wird, so dass das in der Trommel enthaltene Material in Bewegung versetzt wird, wobei die grossen Gegenstände (1) durch in der Trommel vorgesehene Taschenmittel (15) in der Trommel (3) zurückgehalten werden, welche durch schräg nach innen gerichtete Wandmittel (14) des Siebelements (8) der Trommel (3) abgegrenzt sind, und wobei das feinere Material (2) durch das Siebelement (8) aus der Trommel herausgepresst wird, wobei die Trommel (3) nach dem Herauspressen des feineren Materials (2) durch das Siebelement (8) in eine Entleerungsposition gebracht wird, in welcher sie in entgegengesetzter Richtung gedreht wird, bei welcher Drehung die grossen Gegenstände (1) über die Wandmittel (14) aus den Taschenmitteln (15) entfernt werden und durch die Einlassmittel (13) aus der Trommel (3) ausgetragen werden, dadurch gekennzeichnet, dass die Einlassmittel der im Verfahren verwendeten Siebtrommel einen einzigen Einlass (13) umfassen, dass die Taschenmittel eine einzige Tasche umfassen, und dass die Wandmittel eine einzige, schräg nach innen gerichtete Wand umfassen, dass die Trommel (3), wenn sie in das zu siebende Material hineinbewegt wird, gegen Drehung gesperrt wird, und dass das Material, das während dieser Bewegung durch den einzigen Einlass in die gesperrte Trommel (3) hineingebracht wird, auf ein flaches Verstärkungsblech (9) geladen wird, das einen Teil der Umfangsfläche der Trommel (3) bildet, und dass die Trommel (3), nach dem Laden und bevor sie in der ersten Richtung gedreht wird, in eine Siebposition gebracht wird.

2. Verfahren nach Anspruch 1, wobei die Trommel (3) bei einer Geschwindigkeit von etwa 7-15 UpM, vorzugsweise etwa 10-12 UpM gedreht wird.

3. Verfahren nach Anspruch 1 oder 2, wobei die Trommel (3) etwa 4-5 Umdrehungen in der ersten Richtung und etwa 0,5-1 Umdrehung in der entgegengesetzten Richtung in jedem Siebzyklus gedreht wird.

4. Vorrichtung zum Sieben von Material wie Erde, Kies u.dgl. enthaltend verhältnismässig grosse Gegenstände (1), z.B. Steine, Wurzelgemüse u.dgl., die von dem feineren Material (4) abzutrennen sind, wobei die Vorrichtung ein Gestell (5) mit Mitteln zum Verbinden mit einer Arbeitsmaschine (6), vorzugsweise mit dem Frontlader eines Traktors, und eine Siebtrommel (3) umfasst, die am Gestell (5) angebracht und mittels einer Antriebseinheit (12) drehbar ist und die eine Umfangsfläche hat, die hauptsächlich aus einem gebogenen Siebelement (8) besteht und ferner Einlassmittel (13) für das zu siebende Material aufweist, wobei die Drehachse (4) der Trommel (3) hauptsächlich horizontal ist und sich quer zur Hauptbewegungsrichtung der Arbeitsmaschine (6) erstreckt, wobei die Trommel (3) inwendige Taschenmittel (15) aufweist, die innerhalb der Einlassmittel (13) angeordnet und durch schräg nach innen gerichtete Wandmittel (14) des Siebelements (8) der Trommel (3) abgegrenzt sind und die beim Drehen der Trommel (3) in einer ersten Richtung dazu dienen, die grossen Gegenstände (1) in der Trommel (3) zurückzuhalten, während das feinere Material (2) die Trommel (3) durch das Siebelement (8) verlässt, und die beim Drehen der Trommel (3) in der entgegengesetzten Richtung und nachdem das Sieben durchgeführt worden ist, den grossen Gegenständen (8) gestatten, die Trommel (3) durch die Einlassmittel (13) über die Wandmittel (14) zu verlassen, dadurch gekennzeichnet, dass die Einlassmittel einen einzigen Einlass umfassen, dass die Taschenmittel eine einzige Tasche umfassen, dass die Wandmittel eine einzige, schräg nach innen gerichtete Wand umfassen, dass die Vorrichtung Mittel umfasst, die ausgebildet sind, um das Drehen der Trommel (3) zu sperren, wenn sie in das zu siebende Material hineinbewegt wird, und dass die Trommel (3) ein flaches Verstärkungsblech (9) aufweist, das einen Teil der Umfangsfläche der Trommel (3) bildet und auf das das Material geladen wird, wenn die gesperrte Trommel (3) in das zu siebende Material hineinbewegt wird.

5. Vorrichtung nach Anspruch 4, wobei die schräg nach innen gerichtete Wand (14) hauptsächlich parallel zur Drehachse (4) ist und zwischen dieser Achse und dem Einlass (13) angeordnet ist und eine freie Querkante aufweist, die in der Trommel (3) im Abstand von deren Innenseite liegt.

6. Vorrichtung nach Anspruch 4 oder 5, wobei die Wand (14) eine Verlängerung des Siebelements (8) der Trommel (3) bildet, das in die genannte Trommel (3) hineinragt, wobei das Siebelement aus einem Netzgewebe oder einem Gitterrost besteht.

7. Vorrichtung nach Anspruch 4, 5 oder 6, wobei die Trommel (3) zwei entgegengesetzte vertikale Stirnwände (10, 11) aufweist, die mittels der sich dazwischen erstreckenden Drehachse (4) und mittels des sich zwischen den Peripherien der Stirnwände (10, 11) erstreckenden Siebelements (8) miteinander verbunden sind, wobei das Verstärkungsblech (9) sich zwischen den Stirnwänden (10, 11) erstreckt und eine erste Querkante, die auf der Umfangsfläche der Trommel liegt und parallel zur Drehachse (4) ist und die mit dem Siebelement (8) verbunden ist, und eine freie zweite Querkante hat, die auch parallel zur Drehachse (4) ist und den Einlass (13) abgrenzt, der ausserdem von den Stirnwänden (10, 11) und der Wand (14) abgegrenzt ist.

8. Vorrichtung nach einem der Ansprüche 4-7, wobei die Wand (14) in die Trommel (3) hinein derart gerichtet ist, dass der Hauptteil des darin enthaltenen Materials, insbesondere die grossen Gegenstände (1), beim Drehen der Trommel (3) auf das Verstärkungsblech (9) aufprallen.

9. Vorrichtung nach einem der Ansprüche 4-8, wobei etwa 70% der Umfangsfläche der Siebtrommel (3) aus dem Siebelement (8) besteht, etwa 15% davon aus dem Verstärkungsblech (9) und etwa 15% davon aus dem Einlass (13) besteht.

10. Vorrichtung nach einem der Ansprüche 4-9, wobei die Antriebseinheit (12) ein Hydromotor ist, der am Gestell (5) angebracht und mit der Drehachse (4) verbunden ist.

Revendications

1. Procédé de tamisage de la terre, du gravier et des matières similaires contenant des objets (1) relativement grands, tels que les pierres et les racines comestibles, qui doivent être séparés de la matière plus fine (2), procédé dans lequel est utilisé un tambour tamiseur (3) qui peut tourner autour d'un axe de rotation (4) sensiblement horizontal et qui a une surface circonférentielle principalement composée d'un élément tamiseur courbe (8) et ayant en outre un moyen d'ouverture d'entrée (13) pour la matière à être tamisée, ledit tambour (3) étant premièrement déplacé dans ladite matière de sorte qu'une quantité convenable de celle-ci est admise dans le tambour (3) par le moyen d'ouverture (13), après quoi on fait tourner le tambour (3) autour de son axe de rotation (4) dans un premier sens de façon que la matière se trouvant dans le tambour est mise en mouvement, les grands objets (1) étant retenus dans le tambour (3) à l'aide d'un moyen de poche (15) prévu là-dedans et défini par un moyen de paroi dirigé obliquement vers l'intérieur (14) de l'élément tamiseur (8) du tambour (3), et la matière plus fine (2) étant expulsée du tambour à travers l'élément tamiseur (8), le tambour (3) étant, après que la matière plus fine (2) a été expulsée de ce dernier à travers l'élément tamiseur (8), amené à une position de vidage dans laquelle on le fait tourner dans le sens opposé, les grands objets (1) étant, pendant cette rotation, enlevés du moyen de poche (15) par l'intermédiaire du moyen de paroi (14) et évacués du tambour (3) par le moyen d'ouverture (13), caractérisé en ce que le moyen d'ouverture du tambour tamiseur employé dans ce procédé comprend une seule ouverture d'entrée (13), en ce que le moyen de poche comprend une seule poche, en ce que le moyen de paroi comprend une seule paroi dirigée obliquement vers l'intérieur, en ce que ledit tambour (3) est bloqué contre toute rotation lorsque déplacé dans la matière à être tamisée, en ce que la matière admise, par la seule ouverture d'entrée, dans le tambour (3) bloqué pendant ledit mouvement est placée sur une plaque de métal plate (9) de renforcement qui fait partie de la surface circonférentielle dudit tambour (3), et en ce que le tambour (3) est amené à une position de tamisage après que ladite matière a été ainsi placée sur la plaque de métal et avant qu'on ne le fait tourner dans le premier sens.

2. Procédé selon la revendication 1, dans lequel on fait tourner le tambour (3) à une vitesse d'environ 7 à 15 tours/min, de préférence d'environ 10 à 12 tours/min.

3. Procédé selon la revendication 1 ou 2, dans lequel on fait tourner le tambour (3) de 4 à 5 révolutions environ dans le premier sens et de 0,5 à 1 révolution environ dans le sens opposé pendant chaque cycle de tamisage.

4. Dispositif servant à tamiser de la terre, du gravier et des matières similaires contenant des objets (1) relativement grands, tels que les pierres et les racines comestibles, qui doivent être séparés de la matière plus fine (2), ledit dispositif comportant un châssis (5) ayant des moyens le reliant à une machine de travail (6), de préférence au chargeur frontal d'un tracteur, et un tambour tamiseur (3) qui est monté sur ledit châssis (5) et peut tourner à l'aide d'une unité d'entraînement (12) et qui a une surface circonférentielle principalement composée d'un élément tamiseur courbe (8) et ayant en outre un moyen d'ouverture d'entrée (13) pour la matière à être tamisée, l'axe de rotation (4) dudit tambour (3) étant sensiblement horizontal et transversal à la direction de roulement principale de la machine de travail (6), ledit tambour (3) ayant un moyen de poche intérieur (15) qui est prévu à l'intérieur du moyen d'ouverture (13) et qui est défini par un moyen de paroi dirigé obliquement vers l'intérieur (14) de l'élément tamiseur (8) dudit tambour (3) et qui, lorsqu'on fait tourner le tambour (3) dans un premier sens, sert à retenir les grands objets (1) dans ledit tambour (3) tandis que la matière plus fine (2) est évacuée du tambour (3) à travers l'élément tamiseur (8) et qui, lorsqu'on fait tourner le tambour (3) dans le sens opposé après que le tamisage a été terminé, permet aux grands objets (1) de quitter le tambour (3) par le moyen d'ouverture (13) par l'intermédiaire du moyen de paroi (14), caractérisé en ce que le moyen d'ouverture d'entrée comprend une seule ouverture d'entrée, en ce que le moyen de poche comprend une seule poche, en ce que le moyen de paroi comprend une seule paroi dirigée obliquement vers l'intérieur, en ce que ledit dispositif comporte des moyens conçus pour bloquer la rotation dudit tambour (3) lorsque celui-ci est déplacé dans la matière à être tamisée, et en ce que le tambour (3) est muni d'une plaque de métal plate (9) de renforcement qui fait partie de la surface circonférentielle du tambour (3) et sur laquelle est placée ladite matière lorsque le tambour (3) bloqué est déplacé dans la matière à être tamisée.

5. Dispositif selon la revendication 4, dans lequel la paroi (14) dirigée obliquement vers l'intérieur est sensiblement parallèle à l'axe de rotation ou l'arbre rotatif (4) et prévue entre ledit axe ou arbre et ladite ouverture (13) et est munie d'un bord transversal libre qui est situé à l'intérieur du tambour (3) à une distance de la surface intérieure de ce dernier.

6. Dispositif selon la revendication 4 ou 5, dans lequel la paroi (14) constitue un prolongement de l'élément tamiseur (8) du tambour (3) qui fait saillie dans ledit tambour (3), ledit élément tamiseur étant composé d'un treillis ou d'un grillage.

7. Dispositif selon la revendication 4, 5 ou 6, dans lequel le tambour (3) comporte deux parois d'extrémité (10, 11) verticales et opposées qui sont reliées l'une à l'autre à l'aide de l'arbre rotatif (4) s'étendant entre elles et à l'aide de l'élément tamiseur (8) s'étendant entre les périphéries des parois d'extrémité (10, 11), la plaque de métal (9) de renforcement s'étendant entre lesdites parois d'extrémité (10, 11) et ayant un premier bord transversal qui est situé sur la surface circonférentielle dudit tambour et est parallèle à l'arbre rotatif (4) et qui est relié à l'élément tamiseur (8), ainsi qu'un second bord transversal libre qui également est parallèle à l'arbre rotatif (4) et qui définit l'ouverture (13) qui en outre est définie par les parois d'extrémité (10, 11) et la paroi (14).

8. Dispositif selon l'une quelconque des revendications 4 à 7, dans lequel la paroi (14) est dirigée dans ledit tambour (3) de sorte que la partie principale de la matière se trouvant là-dedans, en particulier les grands objets (1), se heurte contre la plaque de métal (9) de renforcement lorsqu'on fait tourner le tambour (3).

9. Dispositif selon l'une quelconque des revendications 4 à 8, dans lequel 70% environ de la surface circonférentielle du tambour tamiseur (3) est composé dudit élément tamiseur (8), 15% environ de ladite surface est composé de la plaque de métal (9) de renforcement, et 15% environ de ladite surface est composé de l'ouverture (13).

10. Dispositif selon l'une quelconque des revendications 4 à 9, dans lequel l'unité d'entraînement (12) est un moteur hydraulique qui est monté sur ledit châssis (5) et est relié à l'arbre rotatif (4).

Drawing