TECHNICAL FIELD

An impact rotor and an associated material processing system are disclosed. The material processing system has particular, but not exclusive, application for the devitalisation of weed seeds and fragmentation of organic matter. In such applications the rotor and processing system may be mounted on a combine harvester to process a chaff stream.

BACKGROUND ART

Weeds and weed control are, and always have been, one of the biggest constraints and costs to grain production. Weeds are a perpetual problem that limits the food production capacity of agricultural area around the globe. Weeds compete with the cultivated crops for water, sunlight and nutrients. In the past 50 years there has been a shift from tillage being the most important method to control weeds to herbicides being the most important tool to control weeds. Herbicides in general provide much better control of weeds than tillage methods and do not have the major issues of soil erosion, moisture loss and breakdown of soil structure. The widespread use and reliance of herbicides has resulted in weeds evolving resistance to herbicides. The herbicide resistance is now widespread and presents one of the biggest threats to global food security. Strategies to provide non-chemical weed control to complement herbicides are now paramount to reduce the selection pressure for herbicide resistance. One particular method of significant renewed interest is destroying weed seeds at harvest time to interrupt the weed cycle.

Many in-crop weeds share a similar life cycle to harvested crops. Once a crop matures and is harvested, there is a broad range of weeds that have viable seeds remaining on the plant above the cutting height of the harvester. These weeds enter the harvester and their seeds either end up in a grain tank, out with straw residues, or out with chaff residues. There are a range of factors that determine where a weed seed will end up at harvest time including moisture content, maturity, and harvester setup. A major factor that determines where a seed ends up is the aerodynamic properties of the seeds or its terminal velocity. Often a weed seed is much lighter than the grain being harvested. Crop cleaning systems used during harvesting employ a winnowing action to remove light chaff material from the heavier grain using airflow and mechanical sieving. The light weed seeds are caught in the wind and can exit the back of the harvester sieve. The residues and contained weed seeds are then spread on the ground to be a problem for next year. The residues also contain a proportion of grain being harvested that could not be separated by the harvester. This grain loss has the potential to become a volunteer weed after harvest. There is an opportunity to intercept and destroy weed seeds in the residues before allowing them to become a problem for next year’s crop.

One method to destroy these weed seeds is to use a milling technology. Milling technology has been used for particle size reduction of a range of feedstock for over a century. Milling technology can be separated into crushing and impact technology.

One system for seed destroying mill technology is described in WO 2018/053600 (Berry). Berry describes a weed seed processing system in the form of a multistage hammer mill. This mill has a plurality of milling stages arranged concentrically about each other. The plurality of milling stages is arranged so that substantially all material in a first inner most of the milling stages passes through all subsequent adjacent milling stages. The milling stages include a first milling stage and a second milling stage. A central feed opening enables material flow into a primary impact zone of the first milling stage. The first milling stage has an impact mechanism and a first screen arrangement. The impact mechanism rotates about a rotation axis. The first screen arrangement is disposed circumferentially about and radially spaced from the impact mechanism and is provided with a plurality of apertures through which impacted material of a first size range can pass. The second milling stage has a second arrangement disposed circumferentially about and radially spaced from the first screen arrangement and a circular array of impact elements disposed between the first screen arrangement and the second screen arrangement.

This system has proved to be effective in the field and installed on combines in many countries. The disclosed impact system was developed with the view to enhancing the performance material processing systems including, though not limited to, the above described system in Berry.

The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the impact rotor as disclosed herein. SUMMARY OF THE DISCLOSURE

In one aspect there is disclosed an impact rotor for a material processing system and capable of rotating about a rotation axis comprising: a base plate; a first circular array of hollow impact bars disposed about the rotation axis, wherein one end of each impact member is coupled to the base plate; each impact bar is provided with an outer surface being coated with hard facing; and a first support ring coupled to an opposite end of each impact bar.

In one embodiment the one end of each impact bar is welded to the base plate.

In one embodiment the opposite end of each impact bar is welded to the support ring.

In one embodiment the impact rotor comprises a second circular array of impact bars disposed about the rotation axis and co-centric with the first circular array, each impact bar of the second circular array comprising a hollow bar provided with an outer surface and having one end coupled to the base plate; and a second support ring coupled to an opposite end of each impact bar of the second circular array.

In one embodiment at least some of the hollow bars have a square or circular cross-sectional shape.

In a second aspect there is disclosed an impact rotor for a material processing system capable of rotating about a rotation axis comprising: a base plate; a first circular array of impact bars disposed about the rotation axis, each impact bar being made of a plastics material; a first support ring; and for each impact bar, one or more mechanical fasteners arranged to couple the impact bar to the base plate and the first support ring.

In one embodiment the one or more mechanical fasteners comprise at least one fastener that extends wholly through the impact bar and connects the first support ring to the base plate. In one embodiment the base plate is made from a metal or metal alloy.

In one embodiment the first support ring is made from a metal or metal alloy.

In one embodiment the impact rotor comprises a second circular array of impact bars disposed about the rotation axis and co-centric with the first circular array, each impact bar of the second circular array being made of a plastics material; a second support ring coupled; and for each impact bar of the second array, one or more mechanical fasteners arranged to couple the impact bars to the base plate and the second support ring.

In one embodiment the one or more mechanical fasteners comprise at least one fastener that extends wholly through at least one of the impact bars of the second array and connects the second support ring to the base plate.

In one embodiment of the frist or second aspects the impact rotor comprises one or more scrapers supported on an upper side of the base plate and outside of a radially outermost circular array of impact bars.

In one embodiment base plate comprises for each scraper, a radially extending lug on which an associated scraper is mounted.

In a third aspect there is disclosed a material processing system comprising: an impact rotor according to the first or second aspects; an impact mechanism connected to the base plate, the impact mechanism centered on the axis and having one or more radially extending hammers or flails; and a first stator structure surrounding the axis and located between the axis and the first circular array, the first stator structure comprising one or more first surface portions and a plurality of holes or gaps in or between the surface portions; and wherein material entering the material processing system is impacted by the impact mechanism and accelerated in a radial outward direction onto the first stator structure wherein the material is impacted on the first surface portions or passes through the holes or gaps. In one embodiment the impact processing system comprises a second stator structure surrounding the first circular array, the second stator structure comprising one or more second surface portions and a plurality of holes or gaps in or between the second surface portions, wherein material passing through the first stator structure and impacted by the first array is accelerated in a radial outward direction onto the second stator wherein the material is impacted on the second surface portions or passes through the holes or gaps in between the second surface portions.

In one embodiment the impact processing system comprises a third stator structure surrounding the second circular array, the third stator structure comprising one or more third surface portions and a plurality of holes or gaps in or between the third surface portions, wherein material passing through the second stator and impacted by the second array is accelerated in a radial outward direction onto the third stator wherein the material is impacted on the third surface portions or passes through the holes or gaps in or between the third surface portions.

In one embodiment the first stator structure comprises a one-piece element formed as, or into, a ring like structure.

In one embodiment the second stator structure comprises a one-piece element formed as, or into, a ring like structure.

In one embodiment the third stator structure comprises a one-piece element formed as, or into, a ring like structure.

In one embodiment any one or more of the stator structures is formed with one or more parts of increased width in a circumferential direction.

In a fourth aspect there is disclosed a material processing system comprising: an impact rotor according to the first or send aspects; an impact mechanism connected to the base plate, the impact mechanism centered on the axis and having one or more radially extending hammers or flails; and a stator arrangement comprising a top plate, at least one stator structure comprising one or more stator segments having opposite ends, and a respective stator ring for each of the at least one stator structure, wherein one end of the one or more stator segments is attached to the top plate and an opposite end of the one or more stator segments is attached to the first stator ring; wherein the top plate is co-centric with the base plate and spaced from the base plate by the stator structure.

In one embodiment each stator structure comprises a single segment wherein the single segment is a one piece planar element in which holes or gaps are formed and the planar element is rolled into a ring like configuration.

In one embodiment the holes or gaps are arranged in a matrix of columns and rows with axially extending parts of the element separating adjacent columns of holes or gaps, and circumferentially extending parts of the element separating adjacent the rows of holes or gaps and wherein some of axially extending parts are wider in a circumferential direction than other axially extending parts.

In one embodiment each stator structure comprises a plurality of segments, each segment including a screen provided with a plurality of holes respective blades on opposite sides of the screen wherein the blades lie in substantially radial planes with reference to the axis.

In one embodiment for at least one element the screen is arranged to lie inboard of radially inner edges of the blades.

In one embodiment for at least one element the screen is arranged to inboard of radially outer edges of the blades.

In one embodiment each stator structure comprises a plurality of segments which are evenly spaced about the axis, each blade orientated to lie in substantially radial planes with reference to the axis.

In a fifth aspect there is disclosed a material processing system comprising: an impact rotor according to the frist or second aspect; an impact mechanism connected to the base plate, the impact mechanism centered on the axis and having one or more radially extending hammers or flails; and a plurality of interchangeable stator arrangements wherein each stator arrangement comprises: a top plate, at least one stator structure comprising one or more stator segments having opposite ends, and a respective stator ring for each of the at least one stator structure, wherein one end of the one or more stator segments is attached to the top plate and an opposite end of the one or more stator segments is attached to the first stator ring; and wherein each of the plurality of stator arrangements have respective stator arrangements of different configuration to enable changing of the stator arrangements to suit a characteristic of material being processed by the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the mill as set forth in the Summary, specific embodiments will now be described, by way of example only, with reference to the covering drawings in which:

Figure 1 is a perspective view of one embodiment of the disclosed impact rotor;

Figure 2 is a side view of the impact rotor shown in Figure 1 ;

Figure 3 is a plan view of the impact rotor shown in Figure 1 ;

Figure 4 is a perspective view of a second embodiment of the disclosed impact rotor;

Figure 5 is a representation of a portion of one form of a material processing system incorporating embodiments of the disclosed impact rotor, a central impact mechanism, and a first stator arrangement;

Figure 6 is a radial section view of the material processing system shown in Figure 5;

Figure 7 is a representation of the first stator arrangement incorporated in the material processing system;

Figure 8 is a perspective view from below of second form of stator arrangement that may be used in a material processing system incorporating embodiments of the disclosed impact rotor; Figure 9 is a perspective view from the side of the stator arrangement and material processing system shown in Fig 8;

Figures 10-12 depict different views of third form of stator arrangement that may be used in material processing system incorporating embodiments of the disclosed impact rotor; and

Figure 13 depicts a fourth form of stator arrangement that may be used in material processing system incorporating embodiments of the disclosed impact rotor.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to Figs 1-3 a first embodiment of the disclosed impact rotor 10a which is suitable for use in for a material processing system, such as, but not limited to a multistage hammer mill as exemplified in the above referenced international publication WO 2018/053600 (Berry), the contents of which are incorporated herein by way of reference. The impact rotor 10a is capable of rotating about a rotation axis 12. The impact rotor comprises a base plate 14 and a first circular array 16a of hollow impact bars 18 which are disposed about the rotation axis 12. One end 20 of each impact bar 18 is coupled to the base plate 14. Each impact member 18 has an outer surface 22 which is coated with hard facing. The impact rotor 10a also has a first support ring 24a that is coupled to an opposite end 26 of each impact bar 18.

In one embodiment the impact bars 18 can be made from a mild steel tube hard-faced, for example by using a laser process with a tungsten carbide cladding.

The base plate 14 and the first ring 24 are also made of metal. This allows the impact bars 18 to be welded to the base plate 14 and 24.

The impact bars 18 may have a variety of cross-sectional shapes including, for example, and not limited to, square or circular. A further benefit is derived where the cross-sectional shape is symmetrical about a plane P (shown in Fig 3) that passes through a geometric center of the impact bar 18 and the rotation axis 12. This benefit arises when a material processing system (such as a multistage hammer mill of a type described in WO 2018/053600) incorporates two counter rotating and adjacent impact rotors 10a. As will be understood by those skilled in the art, when a processing system has a rotating impact rotor, the leading edge of impact surfaces with reference to the direction of rotation is subjected to substantially greater wear than the trailing edge. When there are two mills with counter rotating impact rotors, the worn leading edges of the respective rotors are on opposite sides of the impact bars, as are their respective non, or less, worn trailing edges. By swapping over the impact rotors of the two mills so that they are rotated in the opposite direction to that previously endured, the less worn trailing edges now become the leading edges. This effectively extends the working life of the impact rotor.

Alternately the benefits of this extended life may be realised by the use of (a) a serpentine belt, and associated idlers and pulleys; or (b) a reversing gearbox, which can be used to reverse the direction of rotation of the impact rotors 10a.

This embodiment of the impact rotor 10a also includes a second circular array 16b of hollow impact bars 18 disposed about the rotation axis 12 and co-centric with the first circular array 16a. One end 20 of each impact bar 18 in the second array 16b is coupled to the base plate 14. Each impact member 18 has an outer surface 22 which is coated with hard facing the same as for the first circular array 16a. A second support ring 24b is coupled to an opposite end 26 of each of the impact bars 18 of the second array 16b.

The end 20 of the impact bars 18 in the second array 16b are welded to the base plate 14. Similarly, the opposite end 26 of the impact bars 18 in the second array 16b are welded to the second support ribs 24b.

Owing to the hollow nature of the impact bars 18, the weight of the impact rotor 10a is significantly lighter to an equivalent impact rotor with solid impact bars. By way of comparison with the impact rotors used in the commercially available mill described in WO 2018/053600, an embodiment of the disclosed impact rotor 10a may weigh up to about 55% less. More specifically an embodiment of the disclosed impact rotorlO having 25 mm square section hollow bars 18 weighs approximately 24 kg compared with, about 43 kg for the impact rotor in aforementioned commercially available. The reduction in weight reduces the inertia of the impact rotor 10a thereby reducing the load on an associated drive system at start-up. The weight reduction also makes it easier to handle the material processing system during installation and maintenance, as well as reducing the: weight added to the combine; and, the startup torque on the combine engine due to a lower moment of inertia. Figure 4 illustrates an alternate embodiment of the impact rotor, designated as 10b. In describing the embodiment of the rotor 10b same reference numbers will be used as for the embodiment of the rotor 10a, described above. The impact rotor 10b is of a generally similar configuration to that of the first embodiment but the impact bars 18 are made from a hard plastics material, such as but not limited to ultra-high-molecular-weight polyethylene; high density polyethylene; or, polyetheretherketone. The impact bars 18 are arranged as an inner array 16a and an outer array 16b. The impact bars 18 are coupled at one end to the base plate 14. Each array has an associated support ring 24a, 24b to which the bars 18 are coupled. The base plate 14 and the support rings 24 in this embodiment are made of a metal or metal alloy.

Mechanical fasteners, such as bolts 30 are used to connect the bars 18 to the base plate 14 and the respective support rings 24. In one embodiment a single mechanical fastener/bolt 30 may be used to couple a corresponding impact bar 18 its support ring 24 and the base plate 14. In this arrangement the bolt 30 extends wholly through the corresponding impact bar 18. The impact bars 18 can be formed with the same cross-sectional shape as described in relation to the impact bars 18 of the first embodiment.

The impact rotor 10b provides the same benefits in terms of its lightweight and lower inertia as the first embodiment of impact rotor 10a.

The base plate 14 of either embodiment of impact rotor 10a, 10b (hereinafter referred to in general as “impact rotor(s) 10”) may be provided with one or more scrapers 39. The scrapers 39 are located on an upper face of the base plate 14 and radially outside of an outer most circular array of impact bars 18. Moreover, the base plate 14 is provided with radially outward extending lugs 15 on which respective scrapers 39 are coupled.

Figures 5-7 illustrate one embodiment of a stator arrangement S1 that may be used with embodiments of the impact rotor 10a, 10b to construct a material processing system 40 such as a multistage hammer mill.

Figures 5 and 6 illustrate an impact mechanism 41 connected to the base plate 14. In this embodiment the impact mechanism 41 forms part of the impact rotor 10. The impact mechanism 41 has a hub 37 that is centered on the rotation axis 12 and fixed to the base plate 14. Therefore, the impact mechanism 41 and hub 37 rotate together with the base plate 14, and the impact bars 18. A plurality of radially extending hammers or flails 42 are coupled to the hub 37. The flails 42 are pivotally coupled to the hub 37 by respective pivot pins 43 that are parallel to but offset from the rotation axis 12.

The stator arrangement S1 includes a first stator structure 44a that surrounds the axis 12 and is located between the axis 12 and the first circular array 16a of impact bars 18. The first stator structure 44a provides a surface or surfaces against which material is impacted by the impact mechanism 41 . The stator structure 44a also has a plurality of holes or gaps 45 through which impacted material can pass if, or when their size is reduced to be, small enough to pass through. In this embodiment the first stator structure 44a is in the form of a mesh screen or perforated plate fabricated from a plurality of (in the illustrated embodiment three) mesh segments 46. A plurality of axially extending supporting ribs 47 is provided on a radially outer side of the segments 46 immediately behind each of the screen arrangements 20 in the radial direction. The ribs 47 are evenly spaced circumferentially about the first stator structure 44a and provide structural support for the stator structure 44a. Also, there is a 48 space between mutually adjacent segments 46. The space(s) 48 allows the passage hard materials such as stones or metal bodies to minimise the risk of damage to the stator structure 44a.

A top plate 50 to which the stator structures 44 are attached has a central opening 52. The central opening 52 constitutes an inlet for material into the processing system 40. The material that enters the material processing system 40 through the opening 52 is impacted by the impact mechanism 41 and accelerated in a radial outward direction toward the first stator structure 44a. This material is: impacted by the impact mechanism 41 and against the surface of the segments 46 resulting in fragmentation, crushing or milling to particles of a size that passes through the holes or gaps 45.

In this embodiment there is a second stator structure 44b, and third stator structure 44c. Each of the stator structures 44b and 44c are of the same or similar construction, configuration and function as the first stator structure 44a. However, the diameters of the second and third stators are progressively larger. Also, optionally the holes or gaps 45 in the segments of the stator structures 44b, 44c may be formed to be progressively smaller with increasing distance from the axis 12. The second stator structure 44b surrounds the first array 16a of the impact mechanism 10. The third stator structure 44c surrounds the second array 16b of the impact rotor 10. The impact rotor 10 together with the impact mechanism 41 are rotated together as a single unit. Material entering the material processing system 40 through the opening 52 is thus subjected to multiple impacts as it travels to an outlet (not shown in this embodiment) which is formed in a housing (also not shown in this embodiment) that surrounds the impact rotor and stator arrangement. When this material is chaff containing weed seeds the weed seeds are devitalised due to being fragmented, crushed or milled.

The scraper 39 on the impact rotor 10/ base plate 14 assists in drawing material through the material processing system 40. The air is drawn from the inlet 52, and through the stator structures 44a-44c. The scrapers 39 also propel the material toward an outlet before it falls to the base plate 14. This is in contrast to having scrapers on an under surface of the plate 40 which may have an adverse effect of drawing in air from below the base plate and provide no benefit to material flow through the material processing system.

Figures 8 and 9 show an alternate stator arrangement S2 comprising a plurality of stator structures 44ax-44cx (hereinafter referred to in general as “stator 44ix” or “stators 44ix”) that may be used with the above-described impact rotors 10 to form a material processing system 40. The same reference numbers as used for denoting features in Figs 5-7 are used to denote the same feature in the state arrangement S2 shown in Figures 8-9.

The primary differences with the embodiment shown in Figures 5-7 are that in the stator arrangement S2:

• each of the stators 44ix is formed as a single piece element rather than a plurality of separate segments 46;

• there are no supporting ribs 47;

• there are no spaces 48 between adjacent segments (because there are no segments 46)

The stators 44ix are formed from a one piece planar element, such as but not limited to, a rectangular plate of metal, in which the holes or gaps 45 are formed. The holes or gaps 45 may be formed for example by stamping or cutting the element. The element is then rolled into a ring with opposite short sides of the plate adjacent each other. Thus, the stators 44ix can be made for example from one piece of steel formed as or into a ring like structure. Also, each stator 44ix is formed with enlarged holes 48x that act in a similar way to the spaces 48 of the earlier embodiment formed between separate segments 46.

Each stator 44ix may be formed with one or more parts of increased width in a circumferential direction. More specifically, the stators 44ix can be considered to be in the form of screens formed with a matrix of holes 45, 48x arranged in columns and rows. The solid material of the screens between the holes forms axially extending parts 49 and circumferentially extending parts 51 . In some embodiments, not all of the parts 49 are of the same width in the circumferential direction. For example, some of the parts 49w are wider than other parts 49n. The wider parts 49w are regularly spaced about the screens/stators 44. In the absence of the ribs 47 incorporated in the stators of Figs 5-7, support for each stator 44ix can be provided by the wider parts 49w. In the embodiments shown in Figs 8 and 9 the thickness of any one of the stators is constant in the radial direction. The parts 49w of each stator 44ix wear more slowly than the parts 49n and provide structural integrity even when other parts of the stator may be worn through.

Forming the stators 44ix in one piece means a simpler manufacture process. In addition, processing system 40 comprising the rotor 10 and the stators 44ix can be much more compact than the state of the art as the stator elements are far more compact. This means that the tip speed of the rotor impact elements is more similar than a less compact arrangement. Having a similar tip speed leads to the ability to have more efficient devitalisation of seeds. If the speed of impact is too slow, seeds are not damaged, if seeds are struck too fast then energy is wasted.

The material processing system 40 in Figures 8 and 9 is also shown with a circumferential side wall 54, outlet opening 56 and bottom housing wall 58 which together form part of an outer housing 60 for the material processing system 40. The housing 60 also has an upper cover (not shown) that overlies the plate 50 and is provided with an opening in alignment with the inlet 52. In the material processing system 40, the plate 50 and the base plate 14 are at axially opposite ends of, and inside, the housing 60.

Material enters through the opening in the housing and the inlet 52 in the top plate 50. With the impact rotor 10 rotating, the impact mechanism 41 impacts the material and accelerates the material onto the innermost stator 44ax. The material passes through the holes 45/48 in the stator 44ax is subsequently impacted by the adjacent rotating impact bars 18 of the first array 16a. These impact bars in turn accelerate the material onto the central stator 44bx, causing further fragmentation, damage and devitalisation of weed seeds. This material subsequently passes through the holes in stator 44bx and impacted by the second array 16b of impact bars 18. The successive impacts with the elements of the impact rotor 10 and the stators 44 devitalise weed seeds in the processed chaff. The processed chaff exits through the outlet opening 56 and may be spread onto the ground, fed into a straw chopper, or fed to a spreader.

Figures 10-12 show a third stator arrangement S3 that may be particularly useful for incorporation into a material processing system 40 mounted on a combine for harvesting fibrous material such as lupins, beans, and peas. The same reference numbers as used for denoting features of the stator arrangements S1 and S2 are used to denote the same feature in the stator arrangement S3 shown in Figures 10-12.

In this embodiment the stator arrangement S3 comprises a plurality of stator structures 44a-44c each composed of a plurality of segments 46e having a relatively small arc length which are arranged into a plurality of circular stator arrays. The arc length of each segment 46e may be between about 10° to 20°, and there may be between about 10 to 20 segments 46e evenly spaced about the axis 12. The stator segments 46e are coupled to and retained between a top plate 50 and respective stator rings R1-R3. A material processing system 40 may be constructed using the stator arrangement S3 in conjunction with an impact rotor which may include an embodiment of the above described impact rotors 10a and 10b, or a prior art impact rotor.

Each stator segment 46e comprises a screen 62 provided with a plurality of holes 45. The screen 62 has a generally rectangular configuration. The holes 45 are arranged in a regular matrix pattern with vertical columns and horizontal (or circumferential) rows. The screen lies in tangent plane relative to the axis 12. In this, but not necessarily all, embodiments at least one of the surfaces 66 of the holes 45 may be profiled with a plurality of serrations or ridges 68 (shown best in Figure 11). This profiling may assist in the damage, fragmentation, or attrition of material passing through the stator segments 46e. Each segment 46e also includes on opposite sides of the screen 62, blades 64. The blades 64 extend between and are coupled to the top plate 50 and respective rings R1-R3. In some embodiments the plates 64 are also fixed to the screen 62, for example by welding. The blades 64 are orientated to lie in respective radial planes relative to the axis of rotation 12.

Each blade 64 is formed with a plurality of edges 70. The edges 70 include radially inner edges 70i and radially outer edges 70j, but collectively and in general are referred to as “edge(s) 70”. The edges are exposed to material passing through the stator arrangement S3 providing aggressive impact edges for the material to promote damage, fragmentation or attrition to the material. Each blade 64 is orientated so that its opposite surfaces 72 of greatest area lie in radial planes with respect to the axis of rotation 12.

In this embodiment, and as best seen in Figure 11 , the screen 62 is arranged to lie inboard of the radially inner edges 70i of the blades 64. The edges 70i directly face material that is impacted by the impact rotor of an associated material processing system, such impacted material being accelerated in a radially out ward direction. Additionally, in this but not necessarily all embodiments the screens also lie inboard of the radially outer edges 70j

Each of the stator segments 46e are circumferentially spaced from each other leaving spaces 48 for the passage of hard objects that may be entrained in the material being processed.

Figure 13 illustrates yet a further embodiment of a stator arrangement S4. The stator arrangement S4 can be viewed as being substantially the same as the stator arrangement S3 but with the screens 62 removed. Thus, the stator arrangement S4 comprises respective stator structures 44a-44c, each having a plurality of blades 64 orientated so that their major surfaces lie in radial planes referenced to the central axis 12. So, in this embodiment each blade 64 also constitutes a segment of the corresponding stator structure. One end of each plate 64 is coupled to the top plate 50 with the opposite end being coupled to respective stator rings R1- R3. The general purpose of the stator S4 when used with embodiments of the impact rotors 10a, 10b, or indeed prior art rotors, is to form a material processing system that largely acts as a material spreader. The stator S4 will cause a degree of devitalisation of weed seeds in chaff passing through the corresponding material processing system. It is believed that the devitalisation may predominantly apply to volunteers seeds. Significantly, embodiments the present disclosure provide for a “plug and play” material processing system in which the stator arrangements S1-S4 can be interchanged easily and quickly to suit the type or characteristics of crop being harvested by a combine. In the event that no or very little weed seed or volunteers seed devitalisation is required the stator system S4 may be used with the disclosed or prior art impact rotors. When harvesting a crop such as wheat, the stator systems S1 or S2 may be most suitable. When harvesting fibrous crops such as lupins, beans or peas stator arrangement S3 may be more suitable. This is enormously beneficial

In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the mill and residue processing system as disclosed herein.