WO2014091240A2

WO2014091240A2 - Improvements in or Relating to Cutting Material

Info

Publication number: WO2014091240A2
Application number: PCT/GB2013/053284
Authority: WO
Inventors: Richard Larrington
Original assignee: Richard Larrington Limited
Priority date: 2012-12-13
Filing date: 2013-12-13
Publication date: 2014-06-19
Also published as: GB2526710A; GB201222530D0; GB201512167D0; WO2014091240A3

Abstract

Apparatus and method of cutting a material comprising rotationally passing teeth of a rotary cutting device mounted within a housing alongside a non-rotary fin attached to an internal surface of the housing and pushing the material through holes in the fin from one side of the fin to an opposite side and cutting the material pushed through the holes on the opposite side of the fin. Also disclosed is a sorting apparatus and method.

Description

IMPROVEMNETS IN OR RELATING TO CUTTING MATERIAL

The present invention relates to an improved apparatus and method for the cutting of material of random lengths, and in particular material of a biological nature.

In particular, the present invention relates to the handling of an agricultural fibrous material such as straw derived from the harvesting of crops. It is well known that, in the harvesting of cereal crops such as oats, barley and wheat, the growing cereal attains various stem lengths and that a conventional combine harvester serves to cut the growing stems and subsequently separate the cereal crop from the associated straw. The straw is then discharged from the combine harvester.

At this stage, the straw is either discharged onto the ground for subsequent packaging into standard sized bales or alternatively fed to a baling apparatus which packs the straw into large bales. It will be appreciated that the straw material is very randomly arranged and distributed within a bale.

In practice this highly random distribution of the individual lengths of the straw has various applications such as for use as a bedding material for animals or as a protective covering for a field crop such as carrots over the winter months. When the baled straw is required to be used, the content of a bale is presently distributed by machines called straw spreaders which are arranged to be able, initially, to remove the binding strings from a bale and to then convey the content of the bale through a region of the machine within which the straw is separated out from its very tight compressed baled state into a loose conglomerate which is conveyed to a discharge zone of the spreader machine from which it is spread onto a field.

Known methods of cutting an agricultural bi-product such as straw use a rotating device which turns around a shaft at a range of speeds. Some apparatus might have a number of cutting-style blades so that as the straw material is brought into contact with the cutting edge of the blade, the straw material is cut and reduced in size. Such a cutting system could also use a solid edge to cut against. A problem is that since the straw for such cutting systems is stripped from a straw bale, the bale may contain stones or other hard non-straw particles packed inside the bale, which could damage any cutting machinery parts. In addition, if the straw material to be cut has solid particles like stones within the material, these solid particles can also cause the formation of sparks which, amidst a combustible material like straw could cause a fire.

According to a first aspect of the present invention, there is provided apparatus comprising a housing, a rotary cutting device mounted for rotation within the housing and a non-rotary fin attached to an internal surface of the housing and including a plurality of holes therethrough, the rotary cutting device including a plurality of teeth for rotationally co-operating with the fin to cut a material.

According to a second aspect of the present invention, there is provided a method of cutting a material comprising rotationally passing teeth of a rotary cutting device mounted within a housing alongside a non-rotary fin attached to an internal surface of the housing and pushing the material through holes in the fin from one side of the fin to an opposite side and cutting the material pushed through the holes on the opposite side of the fin.

Owing to these two aspects, a material can be separated, cut and reduced in size in a broken and split fashion.

Preferably, the non-rotary fin comprises a curved upper edge in order to allow passage of the rotary cutting device over that upper edge. Advantageously, the upper edge of the non-rotary fin is arranged to be eccentric relative to the rotational path of the teeth of the rotary cutting device, the arrangement being such that the height of the fin from where it is attached to the internal surface of the housing to the upper edge at one end of the fin is less than the opposite end. In this way, the teeth passing by the fin overlap a side of the fin progressively more on the rotational path of the teeth until the point where the maximum degree of overlap is substantially at the end of the fin where the height between its base and the upper edge is the greatest. Advantageously, the rotary cutting device includes a spirally arranged flange or plate about a rotatable shaft to which it is attached. The teeth of the rotary cutter are arranged to be at the radially outer edge of the spirally arranged flange. In a preferred embodiment, a pair of adjacent teeth at desired intervals around the spiral flange is off-set relative to the surface of the flange with the other intervening teeth remaining co-planar with the flange.

According to a third aspect of the present invention, there is provided apparatus comprising a rotary cutting device having a rotatable shaft and a plurality of cutting elements extending outwardly in a plane from the rotatable shaft, the radially outermost ends of a pair of adjacent cutting elements being off-set from said plane.

According to a fourth aspect of the present invention, there is provided a method comprising arranging about a rotatable shaft a plurality of cutting elements extending outwardly in a plane from the rotatable shaft and off-setting the radially outermost ends of a pair of adjacent cutting elements from said plane.

Owing to these two aspects, it is possible to produce a rotary cutter device for cutting material to a desired size range.

Preferably, cutting elements are made of a metallic material and the off-setting of the pair of adjacent cutting elements is by initially heating the region of the pair and then manipulating the radially outermost ends of the pair into the desired position.

Preferably, the cutting elements are cutting teeth at the outer edge of a flange or plate attached to the rotary shaft, the flange or plate extending outwardly from the shaft. The off-setting of the teeth is advantageously carried out to enable the rotary cutting device to co-operate with a non-rotary fin for cutting the material.

According to a fifth aspect of the present invention, there is provided sorting apparatus comprising at least one outer roller and an inner roller, there being a material specific gap between the at least one outer roller and the inner roller, wherein the inner roller includes a radially outwardly extending rib, the rib extending outwardly from the outer surface of the lower roller by an amount substantially corresponding to the gap.

According to a sixth aspect of the present invention, there is provided a method of sorting material comprising introducing a material to be sorted to a location between an outer roller and an inner roller, there being a gap between the outer and inner rollers, rotating the outer and inner rollers and thereby rotating a radially outwardly extending rib on the inner roller and extending outwardly from the outer surface of the lower roller by an amount substantially corresponding to the gap, expelling unwanted material and passing a desired material through the gap.

Owing to these two aspects, a material can be pre-sorted for subsequent processing so as to reduce the risk of damage caused by the unwanted material to the machinery for the subsequent processing. For example, a fibrous material such as straw is collected from fields with a mixture of stones and other non-straw matter which needs separating if the straw is to be processed in some way, such as cutting the straw, so that the foreign matter does not damage the subsequent processing machinery, such as cutting devices or create a fire hazard.

According to a seventh aspect of the invention, there is provided a method of producing from a supply of a mixed material a desired material within a predetermined size range, including moving the material along a predetermined path to a cutting zone, causing the material when in the vicinity of the cutting zone to fall onto a rotary cutting device having an axis of rotation and a cutting action involving the material being cut by the relative movement between the rotary cutting device and a non-rotary fin eccentrically located relative to the rotary cutting device such that during the cutting of the material, a radially outer end of a cutting element of the rotary cutting device initially reaches an outer limit of the fin and subsequently reaches progressively further inwardly of the fin.

According to a eighth aspect of the invention, there is provided apparatus for producing from a supply of a mixed material a material within a predetermined size range, comprising means for moving the material along a predetermined path to a cutting zone including a rotary cutting device having a plurality of cutting elements, and a non-rotary fin defining a cutting path of the cutting elements, wherein the fin is eccentrically located relative to the rotary cutting device, the arrangement being such that along the cutting path a radially outer end of a cutting element of the rotary cutting device initially reaches an outer limit of the fin and subsequently reaches progressively further inwardly of the fin.

According to a ninth aspect of the present invention, there is provided apparatus for producing from a supply of a mixed material a material within a predetermined size range, comprising means for moving the material along a predetermined path to a cutting zone including a rotary cutting device having a plurality of cutting elements, and a non-rotary fin for co-operation with the cutting elements to cut the material by relative movement therebetween, wherein first and second cutting elements are arranged to have a gap therebetween for the non-rotary fin to pass through. Owing to these aspects, the fibrous material is progressively cut or sliced in a nonvolatile environment.

In order that the present invention can be clearly and completely disclosed, reference will now be made, by way of example only, to the accompanying drawings, in which:-

Figure 1 is a perspective view from above of part of a material pre-sorting device, Figure 2 is similar view to that of Figure 1 , but of a second embodiment of the presorting device,

Figure 3 is a perspective view of part of a rotary cutting device

Figure 4 is a similar view to figure 3 of the rotary cutting device,

Figure 5 is a view similar to Figure 4 but of a magnified part of Figure 4,

Figure 6 is a perspective view of a section of a housing for the rotary cutting device, Figure 7 is a perspective view of non-rotary fins of the housing,

Figure 8 is a perspective view showing the co-operation between the non-rotary fin and the rotary cutting device,

Figure 9 is a plan view of an end plate for a housing of the rotary cutting device, and Figure 10 is a perspective view of a downstream end of a machine comprising a plurality of rotary cutting devices.

Referring to Figures 1 and 2, prior to a fibrous material, such as straw, being delivered to a rotary cutting device (shown in Figures 3 to 5), it can be pre-sorted if the material is a mixture of unwanted and wanted material. In the case of straw, for example, a bale of straw can contain non-straw matter from the field, such as stones. In order to pre-sort the wanted material from the unwanted material, material pulled or shredded from the original baled form, a series of rollers can be employed upon which the straw can fall by gravity down onto. The pre-sorter comprises at least one outer and as shown upper roller 20, of which two are shown, and at least one inner and as shown lower roller 22. The rollers 20 and 22 have axes of rotation arranged substantially parallelly to each other. There is a small gap between the outer surfaces of the outer and inner rollers 20 and 22. Furthermore, the inner roller has around its circumference a rib or band 24 which extends outwardly to substantially the same extent as the gap between the rollers 20 and 22. In Figure 1 , the rib or band 24 is spirally arranged about the outer surface of the inner roller 22 and in Figure 2, the rib or band 24 is in the form of a series of such ribs or bands arranged parallelly to each other along substantially the length of the inner roller 22. The gap between the rollers 20 and 22 where it is not interrupted by the presence of the rib or band 24, which is preferably continuous, allows the passage of the wanted material therethrough whilst the rib or band assists in the separation and carrying away of any unwanted material above a certain size. In practice, the gap between the rollers 20 and 22 allows soft material like straw to be squashed between them whilst hard material such as stones cannot pass through the gap and is removed by the rib or band 24 before the next shredding stage as described below. This gap can be adjustable according to the material required to pass through the pre-sorter system. The rollers 20 and 22 can be arranged to be positioned length ways under shredding rotors stripping straw from a bale or they can be positioned diagonally across the shredding rotors. The principle task of the rollers 20 and 22 and the gap therebetween is to squash the material to be processed and not allow any hard objects to get through the gap and into the subsequent cutting system. The rollers are also designed to be in a rise and fall position relative to each other, the high position to receive the material and the lower inner roller 22, which is driven, to drive the material between the rollers. The circumferential distance of the rib or band 24 may be varied as this controls the speed of any hard elements moving along the rollers away from the shredding area and into a hard material trap. The rollers 20 and/or 22 can be powered electrically, hydraulically or mechanically and some turn by the force of the material being forced into the gap thereby generating a turning movement. The speed of the rollers can be altered to the processing speed required. As mentioned above, the main task of the rollers 20 and 22 is to squash the material passing between them, that is to squeeze and flatten the material. With a material such as straw, this action breaks the structure of the straw stems resulting in a material which is easier to subsequently shred or chop downstream of the pre-sorter. As a particular example, Miscanthus straw has knuckles along the stem similar to that of bamboo canes that are relatively very hard. By squeezing and flattening this particular material, the structure of the stems is broken and the stems splinter. The broken splinters of the stems can then be chopped into much smaller pieces.

Once the material is through the rollers 20 and 22 it then enters a housing of a rotary cutting device. The housing is preferably in the form of a tubular structure enclosing the rotary cutting device. Referring to Figures 3 to 5, an apparatus 2 for producing, from bales of straw or like fibrous material, cut lengths of the straw having lengths within predetermined ranges comprises a rotary cutting device 4 shown in the form of a rotary shaft 6 having an axis of rotation A and a flange or plate 8 arranged about the shaft 6 in a spiralled manner. Around the radially outer edge of the flange 8 there are a plurality of cutting elements in the form of teeth 10. An elongate housing 12 (a section of which is shown in more detail in Figures 6 and 7) extending substantially the length of the shaft 6 includes a plurality of non-rotary plates or fins 14 attached to an inside surface of the housing 12 arranged substantially parallelly to each other and spaced equidistantly from each other. Alternatively, the fins 14 may be arranged so that the distance between them decreases in a downstream direction to ensure that the material is chopped to the desired size range. For instance at the upstream end of the tubular housing 12 the fins may start at a spacing of around 120mm gradually narrowing in the downstream direction to a spacing at the opposite end of the housing 12 of around 50mm.

Referring to Figures 6 and 7, each fin 14 is welded to the inside surface of the housing, is generally crescent-shaped and includes a curved edge 16. As the device 4 rotates by way of the shaft 6, one of the teeth 10 reaches an uppermost point of the fin 14 with the radially outer tip of the tooth 10 not quite overlapping the curved edge 16. As the device 4 continues to rotate and since the curved edge 16 is located eccentrically with respect to the rotational path of the device 4, the degree of overlap between the a tooth 10 and the fin 14 gets progressively more along a cutting path so that the radially outer tip of a tooth 10 progressively reaches a deeper position relative to the curved edge 16 until the end point of the cutting path at the end of the curved edge 16. Each fin 14 includes a plurality of through holes 18 which gradually increase in size along the length of the fin 14. The housing 12 preferably forms a tube-like structure about the device 4 and enclosing or substantially enclosing the device 4 therein.

The fins 14 may also be removably attachable to the inside surface of the housing 12 and a portion of the housing 12 including the fins 14 may be an obturating portion of the housing 12 which may be attached to the remainder of the housing by a hinge device. In this way the portion could be openable to enable maintenance, repair and replacement of the fins 14 if one or more of them become damaged from relatively hard matter such as stones which can be present in the material, especially if the sorting apparatus described above is not used, as could be the case, for example, for bulky crop materials such as sugar beet or parsnips. Moreover, the fins 14 could be introduced from externally of the tubular housing 12 through openings such as slots in the housing 12. The fins introduced into the housing 12 in this way could be attached to the external surface of the housing 12 and thus easily accessible for maintenance, repair and replacement.

Referring to Figure 8, the fins 14 are in such a position that the teeth 10 of the spiral flange 8 pass between them. As the rotary cutting device 4 passes along one side of the fin 8, the angle of the turning spiral flange 8 captures straw inside the housing 12 and forces the material up against the side of the fin 14. As the rotary device 4 continues to turn more material is captured and forced between the flange 8 and the side of the fin 14. The material is then forced into the througholes 18 in the fins 14 and this acts to shred and grind the material breaking it down. Following a leading tooth 10 in a pair of adjacent teeth, another tooth 10 in the spiral formation moving along the opposite side of the fin then cuts into the material which is being forced through the throughholes 18. In order that the pair of teeth can traverse the fin 14 in this way, the adjacent teeth 10 have to be manipulated upon manufacture or before use so that they are non-planar with or off-set from the flange 8 from which they emanate. It will be noted from Figure 8 that the spaces between teeth 10 which are co-planar with the flange 8 are V-shaped, whereas the space between the pair of offset teeth 10 appears a more U-shaped configuration. The preferred method of offsetting this pair of teeth 10 is using heat and then manipulating the teeth 10 into the desired off-set positions. At the end of the cutting path of the device 4 where the height of the fin 14 from the inside surface of the housing 12 is at its greatest and where the edge 16 of the fin 14 reaches its closest point to the inside of the flange 8 the material carried by that pass and forced through the througholes 18 is broken, split and shredded to a desired size or within a desired size range.

On the opposite side of the fin 14, the following tooth 10 as described has cut the material that is forced through the thoughholes 18. Such a repeated action at high speed causes a flow of material along a transfer path within the housing 12. This shredding or chopping action happens several times dependent upon the number of fins 14 in the housing 12 until the material reaches the downstream end of the inside of the housing 12.

The length and spacing of the fins 14, the dimensions of the housing 12, and the size and shape of the spirally arranged teeth 10 including their angles relative to each other can vary according to required size and specification of the desired end product.

The fins 14 can be positioned in many locations inside the housing 12 to suit the cutting and slicing requirements. The fins 14 may also substantially surround the internal surface of the housing 12 and may or may not include the througholes 18. In addition, they could have a rough surface to form a grinding surface as the device 4 turns. A washing and/or lubrication system (not shown) can be attached to the housing 12 and comprising at least one fluid inlet conduit and at least one fluid outlet conduit for allowing the introduction and removal of a washing and/or lubricating fluid substance. This system may also be used to introduce enzymes to the material. Enzymatic pre- treatment promotes the breaking down of the material to lower molecular weight substances, which are more readily utilised by the bacteria in an anaerobic digester. Enzyme application into the housing 12 not only promotes biogas production but also increases the yield of biogas from an anaerobic digester.

Once the pre-sorted material has passed through the housing 12 and cut into the desired size range as described above, at the downstream end of the housing 12 opposite to the in-feed of the material there can be a fixed plate holding a bearing housing which the rotary cutting device 4 uses to support itself whilst turning. About this bearing there may be a spoked wheel device. The rotational movement of the rotary cutting device 4 makes the shredded material pass through the spoked wheel device.

A further fixed plate 26, as shown in Figure 9 may be attached to the output end region of the housing 12. The plate 26 comprises a central opening 28 to accommodate any rotary parts extending to the output end region of the housing 12 and a plurality of smaller radially extending openings 30. The plate 26 also includes a plurality of fixing holes 32 about its outer edge region to fix the plate 26 to the housing 12. The size of the radially extending openings 30 can be varied according to the desired end product and thus the plate 26 can form a filter plate. The rotation and spiral movement of the rotary cutting device 4 makes the shredded material pass through the plate 26 and only material small enough to pass through the radially extending openings 30 will be output from the housing 12. Any larger material is retained in the housing 12 until it is broken or smashed to a size which enables it to pass through the fixed plate 26. The openings 30 advantageously have tapered walls being slightly wider at the output side which assists in the prevention of the openings 30 becoming clogged up with cut material which can be the case, depending on the material being cut, if the walls of the openings 30 are parallel.

At the downstream end of the housing 12 but still inside the housing there is preferably a gap between the end of the flange 8 of the rotary cutting device 4 and the fixed plate at the downstream end of the housing 12. This gap allows a mass of cut material to build-up at the downstream end of the housing 12 and for that mass to expand and contract as the rotary cutting device 4 rotates. In this way the apparatus does not stall as can be the case when the flange 8 terminates close to the fixed plate when too much cut material can collect and be compressed at the downstream end of the housing 12. In addition, at the region of this gap, an unwanted material trap could be positioned beneath the tubular housing 12 such that unwanted material, such as stones (which could be present, especially if the sorter described in relation to Figures 1 and 2, is not used, for example, where the material is a relatively bulky crop such as sugar beet and parsnips) could be collected therein. Such trap could be in the form of a box-like container having a removable portion to remove and discard the unwanted material to be collected.

Downstream of the plate 26 there may further be a rotary cutting head (not shown) preferably mounted relatively closely to the fixed bearing plate. As the material passes through the radially extending openings 30 of the fixed plate 26 the cutting head acts like scissors and further cuts the passing material. The cutting head and the fixed plate 26 can have various designs according to the desired end product, the size of material which is being processed and the rate at which the material is required to pass through the system. Alternatively, the rotary cutting head could be placed on the opposite side of the plate 26 acting against the spoked wheel device mentioned above.

Although the apparatus and methods described above have concentrated on fibrous material such as straw, there are many other applications within the processing industry, for example, the breaking up of food waste to a suitable state to form animal feed, to shred sugar beet or maize to feed an anaerobic digester, to incorporate into a machine like forage harvesters, or to incorporate onto a muck- spreader to shred waste in order to assist in transferring the material a distance away from the machine without wind disturbance before spreading the material. Animal manure may also be used in an anaerobic digester for the production of biogas. In relation to sugar beet and maize, the form that these materials and similar materials, for instance parsnips, usually enter anaerobic digesters is a coarsely chopped mass with a relatively large range of particle size. The apparatus described herein reduces these materials to a relatively very small particle size having a relatively narrow size range. In fact, the output of the apparatus described for chopped crops such as maize, sugar beet and parsnips is very fibrous and is an almost a pulp-like end product. The advantage of this is that this end product has a much greater surface area to volume ratio resulting in more ideal conditions for the micro-organisms in the anaerobic digester to break down the material. In this way, there would be a far more efficient production of biogas from the digester.

If used for cutting and shredding straw, the fine size or relatively small size range of straw particles achievable is particularly useful for burning at a biomass power plant. In addition, the act of chopping the material pre-warms the material, which is advantageous for a possible subsequent pelletising process, which pellets are then burned in the biomass power plant.

If desired, a plurality of rotary cutting devices 4 may be used in series in order to obtain the final desired end product. Figure 10 shows the downstream end of a machine having a plurality, four in this case, of cutting devices 4 arranged next to each other.

Therefore, in use, an arrangement can be that a number of bale-shredding rotors operate at high speed to shred a straw bale which is moved towards the shredding rotors. The shredded material then falls onto a conveyor belt which in turn moves the straw at high speed, for example a stream of straw 300mm deep by 1700mm wide material at a rate of 30 tons per hour, the amounts being changeable depending on the particular application. Downstream of the conveyor belt the rotary cutting device 4 receives the straw. This device 4 rotates in the same rotational direction as the conveyor belt, and receives the material from the conveyor and at high speed and lifts and throws the material upwardly. The lifting and throwing process helps to divide the straw from the stones. The material then under gravity returns back onto the top of the rotary cutting device which catches the material on its teeth 10 and takes the material around to fins 14. Since these fins 14 are fixed in such a position that as the toothed device 4 turns the thin end of the fin engages between the teeth 10 of the device 4. The engagement between the teeth 10 and the fin 14 increases until the largest part of the fin 14 is fully engaged between the teeth 10. Thus, the distance between the fin 14 and the inside edges of the teeth 10 gets less and less as the device 4 turns, so that the material then begins to be sliced and broken down. As the rotation increases and the gap between the fin 14 and the teeth 10 reduces to a minimum, the material is completely severed and is divided.

Any stones or other unwanted material still contained within the straw and which cannot be cut also descends down onto the rotor, but owing to the gradual increase in the degree of overlap between the teeth 10 and the fin 14 such unwanted material is pushed away so that any hard material cannot get trapped in the cutting path. Such unwanted material could be collected in the unwanted material trap described above. The gap allowed between the flanges 8 can be varied according to design and the type of unwanted material that might have got into material to be cut into pieces.

The cutting apparatus described herein is able to produce large volumetric outputs whilst being run with relatively small power, for example, 60kW. The power requirement of a single tubular housing and rotary cutting device could be as slow as 45kW whilst other systems would use up to 350kW to achieve the same size reduction of the material, which is a significantly larger amount of power.

Claims

1 . Apparatus comprising a housing, a rotary cutting device mounted for rotation within the housing and a non-rotary fin attached to an internal surface of the housing and including a plurality of holes therethrough, the rotary cutting device including a plurality of teeth for rotationally co-operating with the fin to cut a material.

2. Apparatus according to claim 1 , wherein the non-rotary fin comprises a curved upper edge.

3. Apparatus according to claim 2, wherein the upper edge of the non-rotary fin is arranged to be eccentric relative to the rotational path of the teeth of the rotary cutting device, the arrangement being such that the height of the fin from where it is attached to the internal surface of the housing to the upper edge at one end of the fin is less than the opposite end.

4. Apparatus according to any preceding claim, wherein the rotary cutting device includes a spirally arranged flange about a rotatable shaft.

5. Apparatus according to claim 4, wherein the teeth of the rotary cutter are arranged to be at the radially outer edge of the spirally arranged flange.

6. Apparatus according to claim 4 or 5, wherein a pair of adjacent teeth at desired intervals around the spiral flange is off-set relative to the surface of the flange with the other intervening teeth remaining co-planar with the flange.

7. Apparatus according to any preceding claim, wherein the housing includes a plurality of non-rotary fins arranged substantially parallelly to each other and spaced equidistantly from each other.

8. Apparatus according to any one of claims 1 to 6, wherein the housing includes a plurality of non-rotary fins arranged so that the distance between them decreases in a downstream direction.

9. Apparatus according to claim 8, wherein the fins start at a spacing of around 120mm gradually narrowing in the downstream direction to a spacing at the opposite end of the housing of around 50mm.

10. Apparatus according to any preceding claim, wherein the plurality of through holes gradually increase in size along the length of the fin.

1 1 . Apparatus according to any preceding claim, wherein the or each fin has a roughened surface.

12. Apparatus according to any preceding claim, and further comprising a washing and/or lubrication system (not shown) attached to the housing and including at least one fluid inlet conduit and at least one fluid outlet conduit.

13. Apparatus according to claim 12, wherein the fluid inlet conduit is utilised to introduce an enzymatic pre-treatment substance into the housing.

14. Apparatus according to any preceding claim, and further comprising a fixed plate attached to an output end region of the housing.

15. Apparatus according to claim 14, wherein the fixed plate comprises a plurality of openings.

16. Apparatus according to claim 15, the openings have tapered walls being slightly wider at the output side of the fixed plate.

17. Apparatus according to any one of claims 14 to 16, wherein there is a gap between a downstream end of the rotary cutting device and the fixed plate.

18. Apparatus according to any one of claims 14 to 17, and further comprising a rotary cutting head associated with the fixed plate.

19. Apparatus according to any preceding claim, and further comprising upstream of the cutting device, a sorting apparatus comprising at least one outer roller and an inner roller, there being a material specific gap between the at least one outer roller and the inner roller, wherein the inner roller includes a radially outwardly extending rib, the rib extending outwardly from the outer surface of the lower roller by an amount substantially corresponding to the gap.

20. A method of cutting a material comprising rotationally passing teeth of a rotary cutting device mounted within a housing alongside a non-rotary fin attached to an internal surface of the housing and pushing the material through holes in the fin from one side of the fin to an opposite side and cutting the material pushed through the holes on the opposite side of the fin.

21 . A method according to claim 20, the arrangement being such that the fin includes a curved upper edge and is located eccentrically with respect to the rotational path of the cutting device, wherein as the cutting device rotates, one of the teeth reaches an uppermost point of the fin with the radially outer tip of the tooth not quite overlapping the curved edge and as the device continues to rotate the degree of overlap between the tooth and the fin gets progressively more along a cutting path.

22. A method according to claim 20 or 21 , wherein the rotary cutting device includes a flange arranged about a shaft in a spiralled manner, and wherein as the cutting device passes along one side of the fin, the angle of the turning spiral flange captures the material inside the housing and forces the material up against the side of the fin.

23. A method according to claim 22, wherein as the cutting device continues to turn, the material is forced through the holes in the fin.

24. A method according to any one of claims 20 to 23, wherein the teeth of the cutting device extend outwardly in a plane from a rotatable shaft and off-setting the radially outermost ends of a pair of adjacent teeth from said plane.

25. A method according to any one of claims 20 to 24, and further comprising, prior to said cutting, sorting the material comprising introducing the material to be sorted to a location between an outer roller and an inner roller, there being a gap between the outer and inner rollers, rotating the outer and inner rollers and thereby rotating a radially outwardly extending rib on the inner roller and extending outwardly from the outer surface of the lower roller by an amount substantially corresponding to the gap, and expelling unwanted material by way of transporting the unwanted material by the rib and passing a desired material through the gap.

26. A method according to any one of claims 20 to 25, and further comprising introducing into the housing an enzymatic pre-treatment substance.

27. Apparatus comprising a rotary cutting device having a rotatable shaft and a plurality of cutting elements extending outwardly in a plane from the rotatable shaft, the radially outermost ends of a pair of adjacent cutting elements being off-set from said plane.

28. Apparatus according to claim 27, wherein the cutting elements are cutting teeth at the outer edge of a flange attached to the rotary shaft, the flange extending outwardly from the shaft.

29. Apparatus according to claim 27 or 28, the arrangement being such that the cutting elements co-operate with a non-rotary fin for cutting a material.

30. A method comprising arranging about a rotatable shaft a plurality of cutting elements extending outwardly in a plane from the rotatable shaft and off-setting the radially outermost ends of a pair of adjacent cutting elements from said plane.

31 . A method according to claim 30, wherein the off-setting of the teeth enables the cutting elements to co-operate with a non-rotary fin for cutting a material.

32. Sorting apparatus comprising at least one outer roller and an inner roller, there being a material specific gap between the at least one outer roller and the inner roller, wherein the inner roller includes a radially outwardly extending rib, the rib extending outwardly from the outer surface of the inner roller by an amount substantially corresponding to the gap.

33. Sorting apparatus according to claim 32, wherein the outer and inner rollers have axes of rotation arranged substantially parallelly to each other.

34. Sorting apparatus according to claim 32 or 33, wherein the rib is spirally arranged around the inner roller.

35. Sorting apparatus according to claim 32 or 33, wherein the rib is in the form of substantially parallel bands arranged about the inner roller.

36. A method of sorting material comprising introducing a material to be sorted to a location between an outer roller and an inner roller, there being a gap between the outer and inner rollers, rotating the outer and inner rollers and thereby rotating a radially outwardly extending rib on the inner roller and extending outwardly from the outer surface of the lower roller by an amount substantially corresponding to the gap, expelling unwanted material and passing a desired material through the gap.

37. A method of producing from a supply of a mixed material a desired material within a predetermined size range, including moving the material along a predetermined path to a cutting zone, causing the material when in the vicinity of the cutting zone to fall onto a rotary cutting device having an axis of rotation and a cutting action involving the material being cut by the relative movement between the rotary cutting device and a non-rotary fin eccentrically located relative to the rotary cutting device such that during the cutting of the material, a radially outer end of a cutting element of the rotary cutting device initially reaches an outer limit of the fin and subsequently reaches progressively further inwardly of the fin.

38. Apparatus for producing from a supply of a mixed material a material within a predetermined size range, comprising means for moving the material along a predetermined path to a cutting zone including a rotary cutting device having a plurality of cutting elements, and a non-rotary fin defining a cutting path of the cutting elements, wherein the fin is eccentrically located relative to the rotary cutting device, the arrangement being such that along the cutting path a radially outer end of a cutting element of the rotary cutting device initially reaches an outer limit of the fin and subsequently reaches progressively further inwardly of the fin.

39. Apparatus for producing from a supply of a mixed material a material within a predetermined size range, comprising means for moving the material along a predetermined path to a cutting zone including a rotary cutting device having a plurality of cutting elements, and a non-rotary fin for co-operation with the cutting elements to cut the material by relative movement therebetween, wherein first and second cutting elements are arranged to have a gap therebetween for the non-rotary fin to pass through.