Device for shredding solid material The invention relates to a device for shredding solid material, comprising a frame which comprises a fixed bottom and a peripheral wall, a filter body connected rotatably in the frame and having a wall, a cutting body connected rotatably in the frame, wherein the cutting body is arranged eccentrically within the filter body, a reception space formed between the filter body and the frame, first drive means for driving a rotation of the filter body, second drive means for driving a rotation of the cutting body, a feeding opening for feeding the material to be shredded and an output opening in communication with the reception space for outputting shredded material.

Such a device is known for instance from WO-92/11945.

This known device comprises a rotatable drum, a cylindrical wall of which is substantially vertical, and a bottom which is provided with filter openings, such that shredded material can fall into a collecting box arranged below the drum. Near the bottom of the rotatable drum, a rotatable cutting body in the form of a disc with knives is provided.

The disc is eccentric with respect to the drum and parallel to the bottom of the drum. The material to be shredded is fed to the drum through a feed box arranged above the drum.

Such devices are used inter alia for shredding branches, tree-stumps or building waste. Herein it can happen that hard parts, such as stones or pieces of metal, come into the device together with the material to be shredded.

A disadvantage of the known device is that shredded material falls through the filter openings into the collecting box only when a shredded particle is located precisely before a filter opening.

An objective of the present invention is to provide a device for shredding solid material in which shredded particles have a larger chance of falling through the filter opening than in the known device.

To that end, the cutting body and the wall of the filter body of the device according to the invention are substantially cone-shaped and filter openings are provided in the wall of the filter body.

With such a device, shredded material is thrown against the wall of the filter body and slides downward along the cone-shaped wall. The shredded material passes a plurality of filter openings when sliding down, such that the shredded material having the right dimensions has a plurality of chances for falling through the filter openings into the collecting box.

In a preferred embodiment of the device according to the invention, the device is provided with removing means for removing polutions. Preferably, the removing means comprise a sliding gutter.

In such device, hard parts such as stones or pieces of metal which come into the device together with the material to be shredded can be removed from the device.

Hereby it is prevented that pieces can be thrown out of the drum by the cutting body which rotates in use, whereby dangerous situations can arise for operating personnel.

Above that, with such a device it is avoided that hard parts which are too large to fall through the filter openings stay present in the drum during operation and contact the knives of the cutting body again and again, whereby these are damaged severely.

These and other advantages of the device according to the invention will be explained elaborately in the following description of a preferred embodiment of the device according to the invention with reference to the drawing in which : figure 1 is a vertical cross-section of a schematically shown device according to the invention, and figure 2 shows the connection of a cutting knife in the cutting body according to the invention.

In figure 1, a device according to the invention for shredding solid material, such as for instance prunings,

tree-stumps or building waste, is schematically shown. The device according to the invention comprises a frame 1 with a peripheral wall 30 and a bottom 31, and a cover 2 connected detachably to the frame. In the cover 2 is arranged a feeding opening 3 for the material to be shredded. If desired, a holder for the material to be shredded can be arranged on the frame 1, which in a dosed way feeds the material to be shredded to the device through the feeding opening 3.

A filter body 5 rests on a flange edge 4 of the frame 1. The filter body 5 can rotate with respect to the frame 1. To this end, the filter body 5 is provided at an upper peripheral edge with wheels 6 which are received in a circular guiding groove 7 arranged in the flange edge 4.

The upper peripheral edge of the filter body 5 is further provided with a toothed ring 8. On the frame 1, a motor 17 is connected which can make the filter body 5 rotate, added by a gear wheel 19 which engages the toothed ring 8.

The filter body 5 is suspended rotating freely in the frame 1 and defines a filter space 23. The filter body 5 has a funnel-shaped wall 32 with filter openings 33, the size of which is determining the size of the chips allowed to pass. The filter body 5 may for instance be manufactured from a frame over which mesh is stretched, from metal strips arranged cross-wise and welded together, or from perforated plates. With its lower edge, the filter body 5 surrounds a non-moving, elevated bottom part 9 of the frame 1. An output opening 34 for hard parts is provided in the elevated bottom part 9, wherein a spiral-shaped sliding gutter 12 is arranged in the output opening 34.

At the outer circumference of the filter body 5, near the bottom 31 of the frame 1, urgers 10 are arranged. The urgers 10 thus are located in a reception space 24 formed between the filter body 5 and the frame 1. Further, an output opening 11 for shredded material is arranged in the bottom 31 of the frame 1.

A cutting body 14 is arranged rotatably in the filter

body 5. The cutting body 14 is truncated cone-shaped, wherein the top angle of the cutting body 14 corresponds to the top angle of the filter body 5. The cutting body 14 is eccentric with respect to the filter body 5, such that the cutting body 14"touches"the filter body 5.

At its lower side, the cutting body 14 is bearing- mounted in the elevated bottom part 9 with a shaft 25 by means of a bearing 13. At the top side, the filter body 14 is supported and bearing-mounted on the shaft 25 by means of a bearing 16 which is connected to the cover 2. During operation, the cover 2 takes care of the stable position of the cutting body 14. A motor 18 drives the cutting body 14 rotatably. Cutting knives 15 are arranged on the cone- shaped surface of the cutting body 14. The cutting knives 15 are connected detachably to the cutting body 14.

As shown in figure 2 in more detail, the cutting body 14 preferably has a three-part wall construction, which is constituted from an outer cone wall 20, a middle cone wall 21 and an inner cone wall 22. The outer cone wall 20 and the middle cone wall 21 are provided with openings and cooperate for receiving the cutting knives 15. The inner cone wall 22 takes care of securing the cutting knives 15.

In this way, a robust cutting body is obtained, of which the cutting knives 15 can be removed in a simple manner after removing the inner cone wall 22. Removing the inner cone wall 22 can be effected by means of a lifting implement. The lifting implement (not shown) can for instance be formed by a hydraulic arm which is connected to the frame 1. Such a hydraulic arm could serve as additional stabilizer for the cutting body 14.

In figure 2, a cross section of a part of the filter body 14 according to the line I-I in figure 1 is shown, which is a schematical representation of the connection of a cutting knife 15. The cutting knife 15 is substantially L-shaped with a foot 23. The cutting knife 15 is provided with a cutting edge 24. In the outer cone wall 20 of the cutting body 14, openings 25 are arranged through which the

cutting knife 15 can be put. The foot 23 prevents the cutting knife 15 from passing the opening 25. In the middle cone wall 21 of the cutting body 14, openings 26 are arranged, the dimensions of which correspond to the dimensions of the foot 23. Finally, the inner cone wall 22 prevents that the cutting knife 15 can be pushed out of the openings. For applying the cutting knives 15, first of all the middle cone wall 21 is placed in a predetermined manner in the outer cone wall 20, for instance aided by positioning cams. Subsequently, the cutting knives 15 are placed into the openings 25 and 26. Finally, the inner cone wall 22 is placed before the cutting knives 15 in the middle cone wall 21 as safety.

In another embodiment, not shown, the middle cone wall 21 is left away and the inner cone wall 22 touches the cutting knives 15 directly.

The cutting knives 15 are divided over the outer surface of the cutting body 14 according to a regular pattern. If desired, the cutting knives 15 may also be arranged on an upper face 26 of the cutting body 14, which cutting knives are connected to the cutting body 14 preferably with the aid of a bolt connection.

The operation of the device is as follows : The motors 17,18 are started by means of control means not shown, such that the filter body 5 and the cutting body 14 are rotating in opposite direction. For instance, seen from above, the filter body 5 rotates clockwise and the cutting body 14 rotates anticlockwise.

Therein, the relation between the rotational speed of the cutting body 14 and the rotational speed of the filter body 5 is large. Preferably, the filter body 5 rotates with 20- 25 revolutions per minute. The rotational speed of the cutting body 14 is preferably between 500 and 600 revolutions per minute. As a consequence of the cone-shape of the filter body 5 as well as the cutting body 14, the circumferential speeds of the filter body 5 and the cutting body 14 depend on the distance from the elevated bottom

part 9. Near the bottom part 9, the circumferential speeds are lower than near the cover 2.

In a preferred embodiment of the cutting body 14, the cutting body 14 is made hollow. Because the mass of the cutting body 14 is located substantially at the outer periphery of the cutting body 14, the cutting body 14 functions as a flywheel, which has an advantageous effect on the shredding functioning of the cutting body 14 and on the demand for energy for maintaining rotation of the cutting body 14 during operation. In another embodiment not shown, the cutting body 14 is made with a solid part which secures the cutting knives 15.

Preferably, the cutting body 14 is manufactured from metal. In the embodiment with the solid part, the solid part can be manufactured from plastic.

During operation, pulse forces act on the cutting body 14, whereby the cutting body 14 can come out of balance. The bearings 13,16 in the elevated bottom part 9 and the cover 2, respectively, prevent unbalance of the cutting body 14. To that end, the cover 2 is fixed to the frame 1, such that the frame 1, the elevated bottom part 9 and the cover 2 form one whole. Such a stabilization of the cutting body 14 can also be effected in another way, for instance by a plurality of stabilizer arms connected movably to the frame 1, which cooperate for stabilizing the cutting body 14 at the top side.

The material to be shredded is brought into the filter body 5 through the feeding opening 3. The material to be shredded will be moved towards the cutting body 14 by the rotational movement of the filter body 5. The cutting knives 15 shorten the supplied material, and chips jumping away from the cutting body 14 are thrown away into the direction of the casing 32 by the high rotational speed of the cutting body 14. The cone-shaped cutting body 14, the top angle of which is directed towards the bottom of the frame 1, will exert a pulse power on the material to be shredded, wherein the pulse force depends on the distance

from the bottom part 9. The particles jumping away obtain a speed in substantially downward direction by the shape of the cutting body 14. In this way it is prevented that fragments are thrown out of the device.

The shredded material slides downwards along the cone-shaped wall 32 and passes a plurality of filter openings 33. Through the filter openings 33, shredded material which is small enough falls into the reception space 23 formed between the filter body 5 and the frame 1.

Shredded material which still is too large is fed again to the cutting body 14 by the rotating filter body 5. This cycle repeats itself until all the material to be shredded has the desired size. In the outputted shredded material, the size of the particles will substantially correspond to the predetermined size of the filter openings 33 because the shredded material which has the right size has many times per cycle a chance of passing a filter opening 33.

Consequently, there is little spreading in the size of the particles.

When the material which is to be shredded contains much liquid, the shredded material tends to stick to the wall 32. This is for instance the case when the material to be shredded consists of wet and sticky material such as prunings. Hereby, a layer which covers the filter openings results at the innerside of the filter body 5. In order to prevent the built-up of such layer, the cutting body 14 preferably is placed within the filter body 5 in such a way that, during operation, the cutting knives 15 pass the wall 32 at a distance as small as possible. In this way, the cutting knives 15 keep the wall 32 clean and a layer cannot be formed.

At the inside of the wall 32, within the filter space 23, projections may be arranged, which assure that the material to be shredded does not stick between the cutting body 14 and the filter body 5.

Material which has fallen through the filter openings 33 in the wall 32 and has ended on the bottom 31 of the

frame 1, is displaced over the bottom 31 by the urgers 10 until the shredded material comes before the opening 11 and falls downward there. Subsequently, the shredded material can be removed in a known manner, for instance by means of conveyor belts.

From the state of the art, devices are known wherein the material to be shredded is supported against a stop in order to be subsequently broken by a cutting knife. In the device according to the invention, the shredding of the material takes place in the free filter space 23. This has an advantageous influence on the life of the device and particularly the cutting knives 15.

Hard parts possibly taken along, such as stones, are thrown against the wall 32, too. Subsequently, these roll down along the wall 32 and, if they are small enough, they fall through the filter openings 33 into the filter space 23. The second output opening 34 is arranged in the bottom of the frame 1 for hard parts which are too large to be removed through the filter openings 33. This second output opening 34 is located in the elevated bottom part 9, which is surrounded by the filter body 5. The second output opening 34 is provided with a spiral-shaped sliding gutter 12, of which the rotational direction of the downward going spiral is opposite to the rotational direction of the filter mantel 5. Shredded material which lies on the spiral-shaped sliding gutter 12 and does not yet has the right dimensions, is fed back to the cutting body 14 by the non-shredded material.

When hard parts such as metal fragments, stone and other parts not consisting of wood, are brought into the filter body 5 together with the material to be shredded, these will fall and/or lower towards the bottom part of the device as a consequence of their specific weight which is higher than the specific weight of the material to be shredded. This is also a consequence of the fact that, upon entry, the material to be shredded is still very coarse and voluminous and is particularly more voluminous than the

hard parts.

The material to be shredded as well as the hard parts are fed towards the cutting body 14 by the filter body 5.

The moment the hard parts contact the cutting body 14, these obtain a speed which is higher than the speed of the shredded material, such that the energy content of a hard part is higher than the energy content of a shredded particle. The hard parts thrown away force themselves through the shredded and the non-shredded material.

Because of the conical shape of the cutting body 14, the direction of the thrown away hard parts is substantially directed downward. Thereby, the hard parts will end mostly on the sliding gutter 12.

The material to be shredded which is located in the filter body 5, always sweeps the material lying on the sliding gutter 12 into the direction of the cutting body 14. A partial area of the sliding gutter 12 near a periphery of the elevated bottom part 9 is, however, unreachable for the material to be shredded.

In a downward direction of the sliding gutter 12, this partial area becomes larger and larger. Therefore, hard parts which reach this partial area between the sliding gutter 12 and the periphery of the elevated bottom part 9 can roll and/or vibrate downwardly without being hindered.

Because of the output possibility of hard parts through the second output opening 34, such hard parts do not contact the cutting knives 15 again and again. The second output opening 34 is of particular importance for removing hard parts which are too large for being removed out of the filter body 5 through the filter openings 33.

The dimensions of the material to be fed are exclusively determined by the size of the feed opening 3 and the filter space 23 between the filter mantel and the cutting body 14. Therefore, the device according to the invention is suitable for large pieces of material to be shredded, such as tree-stumps and tree-trunks.

With the device according to the invention, a shredding device has been obtained with a minimum of moving parts and which is suitable for shredding coarse material.

The energy need and sound emission of the device according to the invention are lower than with conventional shredding devices for coarse material. The entire device is preferably mounted on a rideable support (not shown). With the aid of for instance a tractor, the device mounted on the support can be moved from one operational place to the other.

The embodiments described above are given as non- restrictive examples. It will be clear for persons skilled in the art that several amendments and modifications of the exemplary embodiments are possible without departing from the invention as defined in the annexed claims.

For instance, the filter body 5 as well as the cutting body 14 can be driven by a common motor, wherein for instance a transmission box is intercoupled for achieving the differences in rotational speed.

Further, it is not necessary that the filter body 5 and the cutting body 14 have the same top angle, and the centre lines of the filter body 5 and the cutting body 14 do not need to be parallel.

Instead of the closed bottom 31 with the output opening 11 for shredded material, the part of the bottom 31 which is located outside the elevated bottom parts 9 can also be formed by a filter surface of which the filter openings are larger than the filter openings 33 in the wall 32. Then, shredded material can for instance fall on a vibrating bottom and be subsequently moved towards a conveyor belt. Also, the shredded material can be blown towards an output by the aid of a compressor in a known manner.

Above the partial area of the sliding gutter 12 which is unreachable for non-shredded material, a covering can be arranged such that under all circumstances it is assured that hard parts which reach the partial area under the covering are not swept into the direction of the cutting body 14 by the non-shredded material.