Improvements in combine harvesters

Abstract

A threshing apparatus includes a threshing drum 4 and a receiving hopper comprising a containment wall 9. A containment wall trough 9a has an opening 9a’ for passing threshed material to a grain separator 20. A rotary valve 10 is rotationally driven in the trough and comprises a shaft and plural radial vanes 10a, each having a free and shaft ends, the trough and the vanes being shaped and dimensioned so the free end of each vane abuts an inner trough surface and the vanes are spaced on the shaft so that at any point during valve revolution the free ends of at least two vanes abut the inner trough surface to seal between the trough opening and the threshing drum to isolate the separator from the draught caused by thresher drum rotation. The drum is fed crop by a first feeder e.g., belt 7 running at a first surface speed and a second feeder e.g., feed roller 7, above and apart from the first feeder which runs at a greater speed than the first e.g., 1.01-1.2 times. The separator may involve an air knife generating a narrow airstream in a separator upper region.

Description

Field of the Invention The present invention relates to combine harvesters and in particular to combine harvesters having a threshing drum of substantially the same width as the crop gathering header. Background of the Invention Typically, a combine harvester comprises a header, which includes a knife, a reel, a bed and an auger. The reel presents the crop to the knife, which cuts the crop. The cut crop falls on to the bed of the header where it is gathered by the auger. The header comprises an outlet at a point where the header is attached to an enclosed elevator. The auger feeds the crop through the outlet to the elevator, which feeds the gathered crop into a threshing drum. In the threshing drum most of the seed is separated from the crop residues. Some combine harvesters have straw walkers to separate any seed not separated from the crop residue in the threshing drum. Others have secondary threshing drums with or without straw walkers. Some other combine harvesters have one long threshing drum and no straw walkers. A number of different headers are also known. Some have belts instead of or in addition to an auger to feed the gathered crop to the elevator. Some headers strip the seed from the standing crop so that most of the crop residue does not pass through the combine harvester. Stripper headers do not have a reel or a knife. Other headers use air jets or belts in place of a reel to feed the crop into the header. A common feature of modern headers is that the width of crop gathered by the header is wider than the outlet of the header and that the crop is fed from the header outlet to the threshing drum by an elevator. Gathering the crop into a width smaller than the width of the header creates two problems. First, the volume of material presented to the threshing drum is comparatively thick. Second, if the residue is not to be collected after harvest, the residue must be spread out, preferably over as much of the width of the header as possible. This consumes substantial power and is often ineffective, to the extent that it is common to complete a pass of a field with a straw rake to better spread out the chopped crop residue. In his United Kingdom Patent number GB2351219 the Applicant describes a harvesting machine in which a threshing drum is a part of the header and the elevator is eliminated from the harvesting machine. The threshing drum is the full width of the header which provides the advantage that only a thin layer of material is presented to the threshing drum and the residue falls from the threshing drum across substantially the full width of the header. The harvesting machine described in the Applicant’s patent GB2351219 requires substantially less power than a conventional combine harvester having the same width of header. Nevertheless, some improvements to the harvesting machine described in GB2351219 would be desirable. A threshing drum comprises a beater and a concave. The beater is of a slightly smaller radius than the concave. Harvested material passes through the small space between the beater and the concave, the beater rubbing the material against bars of the concave to separate seed from crop residue. The beater rotates at high speed, typically between 600 rpm and 1200 rpm. This creates a significant draught, including in a direction opposite to the direction of travel of material through the drum. In a conventional combine harvester this is not an issue because the elevator is enclosed and filled with a significant volume of material (for a combine harvester having a 10m cutting width the width of the elevator may be around 1,5m). In the Applicant’s harvesting machine there is a tendency for the draught created by the beater to blow the cut material away from the threshing drum, thereby creating an uneven flow of material into the threshing drum. It is known to use rollers to compress a windrow of material prior to such a windrow of material undergoing a harvesting operation, for example some forage harvesters are provided with a roller as are some balers. In each case the function of the roller is to compress the windrow and the rollers are free-wheeling. A combine harvester having a drum of approximately the same width as the header is described in GB477872. In this combine harvester material cut by the header’s knife is transported towards the drum by a conveyor belt and in the region proximate the inlet of the threshing drum a second belt is mounted above the conveyor belt, the crop being compressed between the two belts, which are driven at even speed. It would be desirable to improve the presentation of harvested crop to the threshing drum. Combine harvesters of the prior art also comprise grain separating equipment, which usually comprises a series of sieves and fans. The Applicant’s earlier patent GB2351219 did not include grain separation equipment. The Applicant’s earlier patent application WO2006 / 064288 described a modular combine harvesting machine where a grain separation apparatus was contained in a grain cart, typical towed behind a tractor. It would be desirable to provide grain separation equipment within the harvesting machine. Summary of the Invention According to a first aspect of the invention there is provided a threshing apparatus including a threshing means, and a hopper comprising a containment wall that is so shaped, dimensioned and located as to receive threshed material from the threshing means, wherein a trough is formed in the containment wall, the trough having an opening therein which provides an outlet from the containment wall for the received threshed material, the threshing apparatus further comprising a rotary valve mounted in the trough for rotation relative to said trough, drive means for driving the rotary valve about its axis of rotation, the rotary valve comprising a shaft and a plurality of vanes extending radially from the shaft, each vane having a free end and a shaft end, wherein the trough and the vanes are shaped and dimensioned such that in a part of one complete revolution of the rotary shaft the free end of each vane abuts an inner surface of the trough and wherein the number of vanes and their radial spacing on the shaft provides that at any point during one revolution of the rotary valve the free ends of at least two of the vanes are in abutment with the inner surface of the trough to provide a substantial seal between the opening in the trough and the threshing drum. According to a second aspect of the invention there is provided a harvesting machine comprising a threshing drum and a first crop feeder, the threshing drum and the crop feeder being of substantially the same width, said first crop feeder situated upstream of the threshing drum in the direction of travel of harvested material through the harvesting machine and disposed to feed harvested material into the threshing drum, wherein the said first crop feeder includes at least one first drivable element and a first drive means arranged to drive the at least one drivable element at a first surface speed, the harvesting machine further comprising a second crop feeder including at least one second drivable element disposed upstream of the threshing drum and above and spaced apart from the crop feeder, the second crop feeder being of substantially the same width as the first crop feeder, wherein the at least one second drivable element is driven by a second drive means arranged to drive the second drivable element at a second surface speed, wherein the second surface speed is greater than the first surface speed. Advantageously, between the first crop feeder and the threshing drum, and beneath the second crop feeder there is situated a plate, a feeder roller or a plate and a feeder roller. Preferably, the at least one drivable element of the crop feeder comprises a belt and the drive means is arranged such that the belt moves towards the threshing drum. The belt may include a plurality of spaced apart cleats. Advantageously, the cleats lie parallel with the longitudinal axis of the threshing drum. In use, harvested crop falls on to the first crop feeder and is moved towards the threshing drum while being supported on said first crop feeder. Preferably, the at least one second drivable element comprises at least one roller. Alternatively, the at least one second drivable element may comprise a belt. The at least one second drivable element may comprise a plurality of protrusions extending outward from the surface of at least one second drivable element. It is preferred that the protrusions extend across the at least one second drivable element in a direction substantially perpendicular to the direction of travel of the harvesting machine. Where the at least one second drivable element comprises a roller, the roller may comprise a plurality of spaced apart protrusions disposed about the roller’s circumference, preferably equidistantly. Where the at least one second drivable element comprises a belt, the belt may comprise a plurality of spaced apart protrusions, such as cleats, each protrusion extending across the width of the belt. Preferably the protrusions are spaced apart equidistantly. Advantageously the distance between opposing surfaces of the at least one first drivable element and the at least one second drivable element of the first and second crop feeders is adjustable. To this end, the at least one second drivable element may be mounted such that it may slide towards and away from the at least one first drivable element, or the at least one second drivable element may be mounted between spaced apart arms which are mounted pivotably, thereby allowing the at least one second drivable element to move in an arc, towards and away from the at least one first drivable element. Preferably, the distance between opposing surfaces of the at least one first drivable element and the at least one second drivable element is between 20 and 120mm, more preferably between 20 and 100mm, still more preferably between 40 and 80mm. Advantageously the distance between the at least one second drivable element and the threshing drum is adjustable. To this end, the at least one second drivable element may be mounted such that it may slide towards and away from the threshing drum, the at least one second drivable element may be mounted between spaced apart arms which are mounted pivotably, thereby allowing the at least one second drivable element to move in an arc, towards and away from the threshing drum. Preferably, the free end of each vane is formed from a flexible material. The flexible material forming the free end of each vane is either an integral part of the vane or a removable part of the vane. Suitable materials for forming the flexible material may be plastic, rubber, or natural fibre for example. The flexible material may be formed by a brush. Advantageously, the rotary valve comprises at least three vanes spaced equidistantly around the shaft. The inner surface of the trough may be curved and the centre of the trough may be colocated with the centre of the rotary valve. The threshing apparatus may further comprise a separator situated downstream of the opening in the trough. The grain separator may extend across substantially the full width of the containment wall. The separator may comprise a chamber formed by a plurality of walls joined together, wherein one of the walls is perforated and the other walls are sealed against egress of air, and an air knife arranged to generate a narrow stream of air above the perforated wall. The separator may comprise a belt arranged to travel around the chamber, wherein the belt is perforated and overlies the perforated wall. The spaced apart runners may be mounted between the perforated wall and an underside of the belt, the underside of the belt being supported by the runners above the surface of the perforated wall. Preferably, the runners are shaped so as to align the belt with the perforated wall as the belt travels around the chamber. Advantageously, the underside of the belt has runners attached thereto, and wherein the belt runners mesh with the chamber runners. Preferably, the belt runners and chamber runners have correspondingly shaped mating surfaces. The mating surfaces may be angled so that the belt self-centres in the chamber. The grain separator may further include guards situated above the belt and arranged to guide threshed material away from the edges of the belt. Preferably, the separator comprises an open top auger trough, an auger mounted in the auger trough for rotation relative thereto, and an air knife mounted above the open top of the auger trough and arranged to direct air across and away from the open top of the auger trough. The auger trough may include walls each wall including a plurality of openings therein for the passage of air therethrough. The auger trough may be mounted in an air box to form a plenum chamber between inner surfaces of the air box and outer surfaces of the auger trough, the plenum chamber connected to a source of pressurise fluid. The openings are preferably shaped to direct air ingressing the auger trough from the plenum chamber towards the open top of the auger trough and may be in the form of louvres. The openings need to be large enough to permit air to pass therethrough, but small enough to prevent most of the material other than grain (MOG) from passing therethrough. Pressurisation of the plenum chamber will however self-clean the plenum chamber to a large extent. The threshing means may include a threshing drum comprising a concave and a beater. The threshing means may include a stripper header. The harvesting machine of the second aspect of the invention may comprise a threshing apparatus according to the first aspect of the invention. The harvesting machine may include a cutting means, such as a sickle bar, upstream of the first crop conveyor in the direction of travel of harvested material through the harvesting machine. The harvesting machine may include a reel mounted above the first crop conveyor and upstream of the second crop feeder in the direction of travel of harvested material through the harvesting machine. According to a third aspect of the invention there is provided a harvesting machine comprising a threshing apparatus including a threshing means and a grain separator situated downstream of the threshing means, wherein the grain separator comprises an air knife arranged to generate a narrow stream of air in an upper region of the grain separator. The separator may comprise a chamber formed by a plurality of walls joined together, wherein one of the walls is perforated and the other walls are sealed against egress of air, and wherein the air knife is arranged to generate a narrow stream of air above the perforated wall. The separator may comprise an open top auger trough, an auger mounted in the auger trough for rotation relative thereto, and wherein the air knife is mounted above the open top of the auger trough and arranged to direct air across and away from the open top of the auger trough. Brief Description of the Drawings In the Drawings, which illustrate preferred embodiment of the invention, and which are by way of example: Figure 1 a is schematic representation of a combine harvester according to an aspect of the invention; Figure 1 b is a cross-sectional elevation of the combine harvester illustrated in Figure 1 a; Figure 1c is schematic cross-section of the combine harvester illustrated in Figure 1a at a larger scale; Figure 2a is a schematic representation of crop separation apparatus; Figure 3a is a schematic representation of crop separation apparatus illustrated in Figure 2a; Figure 3b is an exploded view of a part of the crop separation apparatus illustrated in Figure 3a; Figure 3c is a plan view of the crop separation apparatus illustrated in Figure 3a; Figure 3d is a front view of the crop separation apparatus illustrated in Figure 3a; Figure 3e is cross sectional elevation on the axis A-A of the of the crop separation apparatus illustrated in Figure 3d; Figure 3f is a detail view of certain components of the crop separation apparatus illustrated in Figure 3a; Figure 4 is a schematic plan view of the combination of a combine harvester and a walk behind tractor, the combine harvester mounted on the walk behind tractor; Figure 5 is a schematic plan view of the combination of a combine harvester of the invention, a four wheeled tractor and a collection trailer, the combine harvester mounted on the tractor and the collection trailer towed by the tractor; Figure 6 is a schematic plan view of the combination of a combine harvester of the invention, a four wheeled tractor and a self unloading trailer, the combine harvester mounted on the tractor and the self unloading trailer towed by the tractor; Figure 7 is a schematic plan view of the combination of two combine harvesters of the invention, a four wheeled tractor, a support and drive module and a self unloading trailer, the combine harvesters mounted on the tractor and the support and drive module, and the self unloading trailer towed connected to the support and drive module; Figure 8 is a schematic plan view of the combination of three combine harvesters of the invention, a four wheeled tractor, a support and drive module and a self unloading trailer, the combine harvesters mounted on the tractor and the support and drive module, and the self unloading trailer towed connected to the support and drive module; Figure 9 is a schematic plan view of the combination of five combine harvesters of the invention, a four wheeled tractor, a support and drive module and a self unloading trailer, the combine harvesters mounted on the tractor and the support and drive module, and the self unloading trailer towed connected to the support and drive module; Figure 10 is a schematic representation of the support and drive module of the invention; Figure 11a is a schematic representation of a part of another type of crop separation apparatus; Figure 11 b is schematic representation of a part of the crop separation apparatus illustrated in Figure 11a; Figure 11c is a schematic representation of the component illustrated in Figure 11b; Figure 11 d is a schematic representation of the component illustrated in Figure 11c illustrating different parts of the crop separation apparatus; Figure 11e is a schematic cross-section of the part illustrated in Figure 11a; Figure 12 is a schematic representation of an alternative crop feeder arrangement; and Figure 13 is a side view of the crop feeder arrangement illustrated in Figure 12. Detailed Description of the Preferred Embodiments Referring now to Figures 1 a to 1c, there is shown a combine harvester 1 comprising a feed conveyor 2, a bed having side walls 3 and a threshing drum 4 mounted on and extending between the side walls 3. The feed conveyor 2 comprises a belt having a plurality of spaced apart cleats, the cleats lying substantially perpendicular to the direction of travel of harvested material through the harvesting machine. A feeder roller 6 is mounted on the header 1 above the feed conveyor 2 and in front of the threshing drum 4. Figures 1 b and 1c illustrate the combine harvester 1 in greater detail. The threshing drum 4 comprises a beater 4a and a concave 4b, each of which comprise protrusions 4a’, 4b’ respectively, and engage with crop flowing through a space ’s’ between the outermost parts of the beater and the innermost parts of the concave. The protrusions of the threshing drum 4a’ are often referred to as rasp bars. The protrusions 4b’ of the concave may be known as bars or wires. The concave is open between the bars 4b’, so that grain threshed free may fall through the concave 4b. The threshing drum 4 rotates in the direction of arrow ‘x’. This draws harvested crop into the threshing drum 4 from the feed conveyor 2. However, as mentioned above, the typical drum speed may be between 600 and 1200 revolutions per minute. This causes a significant draught blowing away from the the threshing drum 4 towards the feed conveyor 2, in essence blowing harvested, but not yet threshed, crop material away from the entrance to the threshing drum 4. The combine harvester of the invention is provided with a stuffer roller 6 situated above the feed conveyor and forward of the entrance to the threshing drum 4. The stuffer roller 6 may be mounted on arms (not shown) to provide for movement of the roller in an arc indicated by arrow ‘y’ from the position shown in Figure 1b to a position more distant from the feed conveyor 2. For some crops, the distance between the surface of the stuffer roller 6 and the adjacent surface of the feed conveyor 2 may be between 30mm and 500mm. Typically, the distance between the surface of the stuffer roller 6 and the adjacent surface of the feed conveyor 2 may be 60mm when harvesting a cereal crop, or 500mm when harvesting a crop of oilseed rape for example. The stuffer roller 6 may be mounted to permit movement back and forth along the axis indicated by arrow ‘z’, for example over a distance of up to 200mm. In this way the stuffer roller 6 may be moved closer to the threshing drum 4 and further away from the feed conveyor 2, or closer to the feed conveyor 2 and further away from the threshing drum 4. The stuffer roller 6 is provided with a drive mechanism, for example a hydraulic motor or a belt drive. The stuffer roller 6 is driven at a number of revolutions per minute that result in a surface velocity somewhat in excess of the surface velocity of the feed conveyor 2. Typically, the rotational speed of the stuffer roller 6 is either set or controlled such that the surface velocity of the stuffer roller 6 is between 1.01 and 1.20 times the surface velocity of the feed conveyor 2. In this way the stuffer roller 6 pulls the harvested material from the feed conveyor 2 and presents the harvested material to the threshing drum 4. As the differential between the surface velocity of the stuffer roller 6 and the feed conveyor 2 is increased, the more the harvested material will appear to be pulled from the feed conveyor 2 and stuffed into the threshing drum 4. For this reason, the differential in surface velocities is small, so that an uneven feed of harvested material into the threshing drum 4 is avoided. The drive mechanism may be arranged to provide a fixed speed of rotation of the stuffer roller 6, or a variable speed. Where the drive mechanism is a belt drive, a variator may be used to provide for varying the rotational speed of the stuffer roller 6. A feed roller 7 is situated immediately behind the feed conveyor 2 and below and partially to the rear of the staffer roller 6. The rotational speed of feed roller 7 is either set or controlled such that the surface velocity of the feed roller 7 is between 1.01 and 1.20 times the surface velocity of the feed conveyor 2. Together, the stuffer roller 6 and feed roller 7 gently pull harvested material from the conveyor 2 to feed harvested material into the threshing drum 4. The position of the arms may be controlled by suitable actuators, such as hydraulic rams, electrically operated linear drives, or manually operated levers. The adjustments provided allow the settings of the combine harvester to be optimised for the crop type and or conditions encountered. The stuffer roller 6 serves to both hold the harvester material against the back draught generated by rotation of the threshing drum 4, and in combination with the feed roller 7, to present the harvested material to the drum 4 in an even manner. A secondary threshing drum 8 is situated immediately to the rear of the threshing drum 4, the secondary threshing drum being fed directly with the material that has not passed through the concave 4b. The secondary threshing drum 8 is similar to the threshing drum 4 and comprises a beater 8a and a concave 8b. Threshed seeds fall through the concave 8b, while the material from which the seed has been threshed passes out of the secondary threshing drum either to: fall back to the ground; be gathered into a windrow; or be gathered into a straw chopper. Where a straw chopper is provided, the chopper may be moveable between a position in which straw passing out of the secondary threshing drum passes through the chopper and a position where the chopper is bypassed. Similarly, a windrowing apparatus may have a working and non-working position. Below the primary and secondary threshing drums 4, 8 there is situated a hopper H comprising a containment wall 9 and a rotary valve 10. The containment wall 9 and the rotary valve 10 work together to capture threshed grain and material other than grain (MOG) such as chaff, awns, stalk parts, seed shells, broken seeds and the like which is small enough to fall through the spaces between the bars of the concave. The rotary valve 10 sits in a trough 9a formed in the base of the containment wall 10. The trough 9a has an opening 9a’ in the bottom of the trough 9a, the opening 9a’ being located above a grain separator 20 which is described in greater detail below. Combine harvesters of the prior art generally include sieves and a fan for separating MOG from threshed grain and deliver a sample of grain that is substantially clean of MOG. Hence, there is an expectation of the standard of the sample of grain that a combine harvester should produce in terms of separation quality. Previous versions of the type of combine harvester that is described herein, that is one where the concave extends substantially the full width of the header, have conducted the separation process in another apparatus, such as a trailer vehicle towed behind the combine harvester as described in WO2006 / 064288. The present invention provides an apparatus in which grain separation is integrated into the crop harvesting machine. In addition to catching threshed grain and MOG entrained therewith, the containment wall 9 and rotary valve 10 of hopper H, together form a substantially airtight seal between the threshing apparatus (threshing drums 4 and 8) and the grain separator 20. As discussed above, threshing drums operate at significant rotational speeds, creating substantial draught. By forming a substantially airtight seal between the rotary valve 10 and the containment wall 9, the grain separation apparatus down stream of the rotary valve 10 is effectively isolated from the draught created by the threshing drum 4. Typically, separators use an arrangement of forced air. As can be seen from Figure 1 b, the rotary valve comprises a plurality of vanes 10a. The spaces between these vanes 10a form pockets which receive threshed grain and MOG from the threshing drums 4, 8, the containment wall 9 having sloping walls which guide the grain and MOG to the rotary valve under the force of gravity. The vanes 10a of the rotary valve 10 form a seal between their tips and the inner surface of the trough 9a formed in the containment wall 9. The vanes 10a indicated in Figure 1 b, together with the vanes of the rotary valve 10 below the vanes marked 10a, and the grain and MOG in the pockets between those vanes provide an effective seal between the threshing drums 4, 8 and the opening 9a’. The separator 20 is therefore isolated from influence by the threshing drums 4, 8. Figures 2 illustrates the separator 20. Figures 3a to 3f illustrate the separator 20 in greater detail. The shape and configuration of the walls of the trough 9a and the vanes 10a of rotary valve 10 ensure that at any one moment there are always two vanes in contact with trough 9a, one to each side of the trough 9a, thereby isolating the hopper H and the threshing drum from the separator 20. The separator 20 extends across substantially the full width of the bed between the side walls 3 and is situated beneath the hopper H and the threshing drums 4, 8. The separator comprises chamber 20 that, in use, is filled with pressurised air by a fan. The separator comprises lower and upper walls and side walls, which together form the enclosed chamber 20. The upper wall comprises a perforated panel 23. The size of individual perforations and the density of perforations across the surface of the panel 23 may be varied to suit the crop type and / or harvesting conditions. Variation of the perforations may be achieved by having a plurality of panels 23 with different perforation sizes and / or densities, or by providing a panel 23 where the size and / or density of the perforations may be adjusted. Such perforated panels are known to the skilled person and will not be described in greater detail here. Spaced apart runners 28 are provided on the upper surface of the chamber 20, the function of which is described below. A transit belt 30 is arranged around the chamber 21. As can be seen from Figure 3a, rollers 22a, 22b are provided at each end of the separator 20, the roller 22a having a fixed position whilst the roller 22b is moveable to allow for tensioning and slackening of the belt 30. Industry standard belt tensioning mechanisms are used and hence not described in detail. The belt 30 is itself perforated. The perforation size, shape and density is selected to match the crop type being harvested. Attached to the underside of the belt 30 are runners 31. The runners 31 engage with the runners 28 which are mounted on the upper surface of the perforated panel 23 to ensure that the belt 30 stays aligned over the chamber 21. As can be seen from Figure 3f, the runners 28 have an angled surface 28’. The belt runners have corresponding angled surfaces. These ensure alignment of the belt 30 over the chamber 21. Air exiting the chamber 21 through the perforated panel 23 pressurises the space between the underside of the belt 30 and the upper surface of the perforated panel 23. In use the belt 30 is covered with threshed crop material which has passed through the concave comprising grain and MOG, which is fed to the conveyor by the rotary valve 10. Since grain is heavier than MOG, the MOG is blown upwards out of the layer of grain and MOG on the belt 30. The grain remains on the belt so that it may be transported to another part of the harvesting machine. The flow of air through the belt 30 is indicated by the arrows ‘a’ in Figure 1 b. The separator 20 includes a deflector plate 26 as showing Figures 1 b, 2, 3a, 3b, 3e and 3f. The deflector plate lies on an axis substantially parallel with the axis k-k of the air knife 25 and interacts with the air flow produced by the air knife to ensure that MOG is blown out of the separator 20. Both the air knife and the deflector plate may be mounted such that their positions may be varied independently of one another. For example, axes on which the air knife and the deflector plate each lie may be varied. The length of the deflector plate 26 may be varied so that the distance of the free edge of the deflector plate is further away or closer to the wall 22. Immediately above the belt 30 are crop guards 24. These crop guards cause the grain and entrained MOG to be placed on the surface of the belt away from the edges thereof, and hence prevented from falling into the space between the perforated panel of the air chamber 21 and the underside of the conveyor. The separator comprises an air knife 25 which is located to one side of the belt 30. The air knife 25 produces a high velocity air stream which directs MOG lifted from the bed of grain and MOG on the belt 30 to the rear of the separator where it may fall to the ground or be collected by a collection device. The air knife 25 also provides an initial separation function when the grain and entrained MOG falls from the rotary valve 10 to the separator 20. The belt 30 is driven to move in a direction towards an outlet. The outlet is typically another conveyor means, for example another belt, an auger or a pneumatic conveyor. Where the combine harvester 1 is mounted on one end of a tractor, a tank for receiving the grain from the belt 30 and conveying means may be mounted at the other end of the tractor. The tank may be part of a towed vehicle or mounted on one of the three point linkages of the tractor. In other examples, the combine harvester includes a discharge means such as an auger for discharging to a trailer and a comparatively small tank so that grain may be stored for a short period during trailer change overs. In such an arrangement, discharge would be substantially continuous. The separator 20 has been described with reference to the combine harvester 1, which includes a threshing drum and a feed conveyor. However, the separator 20 could be used with other types of combine header, such as a stripper header. The stripper rotor of a stripper header creates very significant draught, and hence the separation of airflow in the region of the stripper header from the separator provided by the invention would be useful. A combine harvester of the invention utilising a stripper header may also include a secondary threshing drum, such as the secondary threshing drum 8 to release any grain that was not threshed free by the stripper rotor. Referring now to Figure 4, there is shown a combine harvester 1 mounted on a walk behind tractor 30. Typically, the combine harvester 1 for mounting on a walk behind tractor would be between 0.6m and 2m wide. Figure 5 illustrates the combination of a standard agricultural tractor 40, which in the illustrated embodiment is mounted on wheels 41,42 (although the tractor could be mounted on tracks instead of wheels), a combine harvester 1 mounted on the front of the tractor 40, typically by means of a three point linkage, and a collection trailer 50. The trailer comprises a draw bar 51 which attaches to a towing hitch 43 of the tractor 40, wheels 53 which support the trailer 50 and a container 52 for receiving threshed material from the combine harvester 1. In this embodiment, the trailer may be a tipping trailer or a gravity bin. Figure 6 differs from the combination illustrated in Figure 5 in that the collection trailer has been replaced by a self-unloading trailer 60 comprising a drawbar 61 for connection to the tractor 40, a collection bin 62 and an unloading auger 63. The collection bin 62 is filled via conveyor pipe 1 a which is supported off the combine harvester 1 and the tractor 40 by support strut 1 b. Threshed material is conveyed through the conveyor pipe 1a by pressurised air. Such conveyor systems are well known in the art and as such are not described herein in greater detail. Figure 7 illustrates the combination of two combine harvesters 1, a tractor 40, a support and drive vehicle 70 and a self-unloading trailer 60. One of the combine harvesters 1 is mounted on the front of the tractor 40, and the other is mounted on the support and drive vehicle 70 and extends to one side thereof. The support and drive vehicle 70 comprises front and rear drawbars 71a, 71b. The front drawbar 71a is attached to the tractor 40. Thedrawbar61 oftheself unloading trailer is connected to the rear drawbar 71 b of the support and drive unit 70. Typically, the collection bin 62 is filled via a conveyor pipe 1 a of the type shown Figure 6. Figures 8 and 9 illustrate similar arrangements to that shown in Figure 7, except that in Figure 8 the combination comprises three combine harvesters 1, two being mounted on the support and drive vehicle 70, one to each side thereof. In the embodiment illustrated in Figure 9, the combination comprises five combine harvesters 1, four of which are mounted on the support and drive vehicle 70. Figure 10 illustrates the support and drive vehicle 70, which is mounted on wheels 73. The vehicle 70 comprises front and rear draw bars 71 a, 71 b and a body 72. The body 72 may mount linkages to support combine harvesters 1, hydraulic power packs for driving the combine harvesters 1. The vehicle 70 may include an engine and the wheels 73 may be driven. The wheels 73 and / or hydraulic power pack may be driven by the towing tractor 40, for example by the tractor’s power take off or the tractor’s hydraulic system. Alternatively, an engine mounted on the body 72 may drive a hydraulic power and / or the wheels 73. Wheels 73 may of course be replaced by tracks, as is common in crop harvesting machines. Figures 11 a to 11 e illustrate an alternative type of crop separation apparatus. Instead of the conveyor belt system illustrated in Figures 1 to 3, the harvested material is moved by an auger as described below. The separator comprises four principal parts, an auger trough 100, an auger 107, an air box 110 and an air knife 25. The auger trough has an open top which serves two functions. First, the open top allows material to be received into the trough along the whole length thereof. Such material could be material exiting the rotary valve 10 described above. Second, MOG may be removed from the material in the auger trough via the open top. The lower part of the trough is substantially semi-circular in cross-section, having a diameter slightly larger than the auger 107 that sits in the trough. The detail of the relative dimensions of the auger trough 100 and the auger 107 will not be described in detail here as the rudimentary design of augers and their housings are well understood in the art. The auger trough 100 comprises a wall 101 which includes the substantially semi-circular lower part and substantially vertical elements extending from the lower part. The substantially vertical elements include louvres 106, which preferably, and as shown in Figure 11 e, comprise a plurality of spaced apart and substantially parallel guide vanes 106a. These guide vanes 106a are angled upward from the outside of the wall 101 to the inside, so that air passing through the louvres 106 is directed towards the open top of the auger trough. The wall 101 also comprises a flange 104 which comprises a substantially horizontal surface 104a and a substantially vertical surface 104b, the surface 104b including a plurality of holes 105. The auger 107 is mounted on a shaft 108 in a bearing (not shown) which is attached to an end plate 102 of the auger trough 101. Figure 11 d illustrates the air box 110. The air box 110 comprises a bottom wall 110b from which extend side walls 110a. The free end of each side wall 110a is provided with a flange 110c in which a plurality of holes 110d are located. The spacing and diameter of the holes 110d corresponds substantially with the spacing and diameter of the holes 105 in the flange 104 of the auger trough 101, such that the auger trough may be attached to the air box 110. The auger trough 101 sits in the air box 110, the surface 104b of the auger trough 101 being adjacent and attached to a flange 110c by bolts or rivets passing through the holes 105, 110d. A sealant may be provided between the surface 104b and the surface of flange 110c in order to provide an airtight seal. Alternatively, the auger trough 101 could be attached to the air box by welding. As can be seen from Figure 11 d, an plenum chamber 112 is formed between the inner surface of the air box 110 and the outer surface of the auger trough 101. The air box 110 includes an air feed 111. The air knife 25 is located above the auger trough 101, in the illustrated example immediately above the auger trough. The crop separation apparatus illustrated in Figures 11a to 11e works as follows: Threshed material containing MOG is presented to the open top of the auger trough 101 above the air knife 25, and preferably across substantially the full length of the auger trough 101. As such the crop separation apparatus is being fed constantly with a narrow stream of threshed material containing MOG. An initial separation is performed by the air knife 25 which blows some MOG out of the stream of threshed material containing MOG. The remaining material falls into the auger trough 101. The auger 107 moves threshed material from one end of the auger trough 101 to the other. As it does so, the threshed material is agitated and more MOG finds itself in the path of the air knife 25, which blows the MOG away from the auger trough 101. Additional separation capacity is provided by pressurised air that is introduced to the material within the auger trough 101 through the plenum chamber 112 and louvres 106. The orientation of the elements 106a of the louvres 106 direct MOG towards the air knife 25, which moves the separated MOG away from the auger trough 101. Figure 12 illustrates an alternative crop feeder apparatus in a combine harvester 1 ’. The combine harvester 1 ’ differs in some respects to the combine harvester 1 illustrated in the earlier figures. In particular, the stuffer roller 6’ is mounted on swing arms 6a’ for rotation about the pivot attachment of the swing arms 6a’ to the header body (not shown). The feed roller 7 is replaced by a plate 6b’, which extends between the conveyor 2’ and the concave 4b’. The plate 6b’ may be spring loaded and function as a stone trap. For example, the plate 6b’ may be attached pivotably to the header frame at the concave end of the plate 6b’, with a spring or springs 6c’ biasing the plate 6b’ into the position shown in Figures 12 and 13. If stone of sufficient size enters the space between the plate 6b’ and the stuffer roller 6’, the plate 6b’ may pivot downwards, allowing the stone to fall from the plate 6b’ under gravity. The threshing apparatus of the invention provides a number of advantageous features. First, the rotary valve allows the draft created by the threshing drum to be isolated from other parts of the apparatus in terms of airflow. Second, the separator provides for material other than grain to be separated from the desired threshed material. Third, the roller that sits ahead of the drum and above the conveyor provides for an even flow of harvest material into the threshing drum.

Claims

1. A threshing apparatus including a threshing means, and a hopper comprising a containment wall that is so shaped, dimensioned and located as to receive threshed material from the threshing means, wherein a trough is formed in the containment wall, the trough having an opening therein which provides an outlet from the containment wall for the received threshed material, the threshing apparatus further comprising a rotary valve mounted in the trough for rotation relative to said trough, drive means for driving the rotary valve about its axis of rotation, the rotary valve comprising a shaft and a plurality of vanes extending radially from the shaft, each vane having a free end and a shaft end, wherein the trough and the vanes are shaped and dimensioned such that during one complete revolution of the rotary shaft the free end of each vane abuts an inner surface of the trough and wherein the number of vanes and their radial spacing on the shaft provides that at any point during one revolution of the rotary valve the free ends of at least two of the vanes are in abutment with the inner surface of the trough to provide a substantial seal between the opening in the trough and the threshing drum.

2. A threshing apparatus according to Claim 1, wherein at least the free end of each vane is formed from a flexible material.

3. A threshing apparatus according to Claim 1 or 2, wherein the rotary valve comprises at least three vanes spaced equidistantly around the shaft.

4. A threshing apparatus according to any preceding claim, wherein the inner said surface of the trough is curved and the centre of the trough is co-located with the centre of the rotary valve.

5. A threshing apparatus according to Claim 2, wherein the flexible material forming the free end of each vane is either an integral part of the vane or a removable part of the vane.

6. A threshing apparatus according to any preceding claim further comprising a separator situated downstream of the opening in the trough.

7. A threshing apparatus according to Claim 6, wherein the grain separator extends across substantially the full width of the containment wall.

8. A threshing apparatus according to Claim 6 or 7, wherein the separator comprises a chamber formed by a plurality of walls joined together, wherein one of the walls is perforated andthe other walls are sealed against egress of air, and an air knife arranged to generate a narrow stream of air above the perforated wall.

9. A threshing apparatus according to Claim 8, further comprising a belt arranged to travel around the chamber, wherein the belt is perforated and overlies the perforated wall.

10. A threshing apparatus according to Claim 9, wherein spaced apart runners are mounted between the perforated wall and an underside of the belt, the underside of the belt being supported by the runners above the surface of the perforated wall.

11. A threshing apparatus according to Claim 10, wherein the runners are shaped so as to align the belt with the perforated wall as the belt travels around the chamber.

12. A threshing apparatus according to Claim 10 or 11, wherein the underside of the belt has runners attached thereto, and wherein the belt runners mesh with the chamber runners.

13. A threshing apparatus according to Claim 12 when dependent on Claim 11, wherein the belt runners and chamber runners have correspondingly shaped mating surfaces.

14. A threshing apparatus according to Claim 14, wherein the mating surfaces are angled.

15. A threshing apparatus according to any of Claims 9 to 14, wherein the grain separator further includes guards situated above the belt and arranged to guide threshed material away from the edges of the belt.

16. A threshing apparatus according to Claim 6 or 7, wherein the separator comprises an open top auger trough, an auger mounted in the auger trough for rotation relative thereto, and an air knife mounted above the open top of the auger trough and arranged to direct air across and away from the open top of the auger trough.

17. A threshing apparatus according to Claim 16, wherein the auger trough includes walls each wall including a plurality of openings therein for the passage of air therethrough.

18. A threshing apparatus according to Claim 17, wherein the auger trough is mounted in an air box to form a plenum chamber between inner surfaces of the air box and outer surfaces of the auger trough, the plenum chamber connected to a source of pressurise fluid.

19. A threshing apparatus according to Claim 19, wherein the openings are shaped to direct air ingressing the auger trough from the plenum chamber towards the open top of the auger trough.

20. A threshing apparatus according to Claim 19, wherein the openings are in the form of louvres.

21. A threshing apparatus according to any preceding claim, wherein the threshing means includes a threshing drum comprising a concave and a beater.

22. A threshing apparatus according to any preceding claim, wherein the threshing means includes a stripper header.

23. A harvesting machine comprising a threshing drum and a first crop feeder, the threshing drum and the crop feeder being of substantially the same width, said first crop feeder situated upstream of the threshing drum in the direction of travel of harvested material through the harvesting machine and disposed to feed harvested material into the threshing drum, wherein the said first crop feeder includes at least one first drivable element and a first drive means arranged to drive the at least one drivable element at a first surface speed, the harvesting machine further comprising a second crop feeder including at least one second drivable element disposed upstream of the threshing drum and above and spaced apart from the crop feeder, the second crop feeder being of substantially the same width as the first crop feeder, wherein the at least one second drivable element is driven by a second drive means arranged to drive the second drivable element at a second surface speed, wherein the second surface speed is greater than the first surface speed.

24. A harvesting machine according to Claim 23, wherein between the first crop feeder and the threshing drum, and beneath the second crop feeder there is situated a plate, a feeder roller or a plate and a feeder roller.

25. A harvesting machine according to Claim 23 or 24, comprising a threshing apparatus according to any of Claims 1 to 22.

26. A harvesting machine comprising a threshing apparatus including a threshing means and a grain separator situated downstream of the threshing means, wherein the grain separator comprises an air knife arranged to generate a narrow stream of air in an upper region of the grain separator.

27. A harvesting machine according to Claim 26, wherein the separator comprises a chamber formed by a plurality of walls joined together, wherein one of the walls is perforated and the otherwalls are sealed against egress of air, and wherein the air knife is arranged to generate a narrow stream of air above the perforated wall.

28. A harvesting machine according to Claim 27, further comprising a belt arranged to travel around the chamber, wherein the belt is perforated and overlies the perforated wall.

29. A harvesting machine according to Claim 28, wherein spaced apart runners are mounted between the perforated wall and an underside of the belt, the underside of the belt being supported by the runners above the surface of the perforated wall.

30. A harvesting machine according to Claim 29, wherein the runners are shaped so as to align the belt with the perforated wall as the belt travels around the chamber.

31. A harvesting machine according to Claim 30, wherein the underside of the belt has runners attached thereto, and wherein the belt runners mesh with the chamber runners.

32. A harvesting machine according to Claim 31 when dependent on Claim 31, wherein the belt runners and chamber runners have correspondingly shaped mating surfaces.

33. A harvesting machine according to Claim 32, wherein the mating surfaces are angled.

34. A harvesting machine according to any of Claims 28 to 33, wherein the grain separator further includes guards situated above the belt and arranged to guide threshed material away from the edges of the belt.

35. A harvesting machine according to Claim 26, wherein the separator comprises an open top auger trough, an auger mounted in the auger trough for rotation relative thereto, and wherein the air knife is mounted above the open top of the auger trough and arranged to direct air across and away from the open top of the auger trough.

36. A harvesting machine according to Claim 35, wherein the auger trough includes walls each wall including a plurality of openings therein for the passage of air therethrough.

37. A harvesting machine according to Claim 36, wherein the auger trough is mounted in an air box to form a plenum chamber between inner surfaces of the air box and outer surfaces of the auger trough, the plenum chamber connected to a source of pressurise fluid.

38. A harvesting machine according to Claim 37, wherein the openings are shaped to direct air ingressing the auger trough from the plenum chamber towards the open top of the auger trough.

39. A harvesting machine according to Claim 38, wherein the openings are in the form oflouvres.

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