GB2051542A - Combine harvesters - Google Patents

Abstract

A combine harvester comprises a threshing mechanism (13), a rotary separating mechanism (19) extending transversely of the machine and having opposed ends extending transversely beyond the opposite ends of the threshing mechanism (13), a cleaning mechanism (7) of a width substantially corresponding to the width of the threshing mechanism (13) and disposed vertically below the threshing mechanism (13) and a central portion of the separating mechanism (19) to receive separated crop material therefrom, rethreshing means (45) associated with the cleaning mechanism (7) and disposed at each side thereof for rethreshing tailings separated in the cleaning mechanism (7), and conveyor means (67) extending between the associated rethresher means (45) and the cleaning mechanism (7) underneath an end portion of the separating mechanism (19). The conveyor means (67) is adapted to recycle rethreshed tailings from the associated rethresher means (45) to the cleaning mechanism (7) and to receive crop material separated in the separating mechanism end portion thereabove and to direct it, together with the rethreshed tailings, to the cleaning mechanism (7). <IMAGE>

Description

SPECIFICATION Combine harvesters The present invention relates to combine harvesters and has particular reference to conveyor means employed in such machines.

While the terms "grain", "straw" and "tailings" are used principally throughout this specification for convenience, it should be understood that these terms are not intended to be limiting. Thus "grain" refers to that part of the crop material which is threshed and separated from the discardable part of the crop material which is referred to as "straw".

Incompletely threshed ears are referred to as "tailings". Also, the terms "forward", "rear ward", "left", and "right" when cited in connection with the combine harvester and/or components thereof are determined with reference to the direction of operative travel of the combine harvester in the field and should not be taken as limiting.

In known combine harvesters, grain is threshed and separated in a threshing and separating mechanism and the separated grain, together with impurities of all sorts, such as chaff, dust, straw particles, and tailings, is fed to a cleaning mechanism for cleaning. Clean grain is collected below the cleaning mechanism and fed to a grain tank for temporary storage. The tailings are separated from the clean grain and impurities for reprocessing. This reprocessing either involves recycling the tailings through the threshing and separating mechanism or treating them in a separate tailings rethreshing means. In both cases the tailings are conveyed through an elevator which usually is of the paddle type.

The present invention is concerned with combine harvesters having a tailings return elevator, preferably in combination with a separate tailings rethresher mechanism.

Whilst the invention conceivably can be applied either to conventional combine harvesters with separating means comprising straw walkers and to so-called rotary combine harvesters with axial flow type threshing and separating rotors, the invention is particularly useful on rotary combines of the type comprising one or more transversely-extending threshing and/or separating rotors of which at least one end extends beyond the side edge of the cleaning mechanism disposed therebelow.

In conventional combine harvesters, wherein the tailings are recycled through the threshing and separating mechanisms, a tailings elevator, which usually is of the paddle type, extends at one side of the machine between a location beneath the cleaning mechanism, where tailings are collected, and a location forwardly and generally above the level of the threshing means at one side thereof and at which location the elevator supplies tailings to a transverse tailings distributing auger. This arrangement of the tailings elevator and distributing auger is relatively long and hence is expensive and takes up much room, whereby it is cumbersome and access to other components of the machine and drive means therefor is hampered considerably.

Furthermore, in rotary combine harvesters of the type comprising one or more transversely extending threshing and/or separating rotor assemblies of which at least one end extends beyond the corresponding side edge of the cleaning mechanism which is disposed therebelow, additional conveyor means are required for conveying crop material which is separated at said end to the cleaning device.

This again takes up space and increases the cost of the machine. Also the material separated in these separator portions is not evenly spread over the full width of the cleaning mechanism, whereby uneven loading and/or overloading of the latter may occur. Such a combine harvester is disclosed in the British Patent Specification No. 1,460,715.

Also, during recent years, the size, and especially the capacity, of combines have increased considerably which means that the threshing, separating and cleaning means have to be capable of handling considerably increased volumes of crop material. With the present large capacity machines, even small percentages of tailings represent considerable volumes. Hence the tailings return elevator and tailings distributor auger must be sized accordingly and also recycling of these volumes of tailings through the threshing, separating and cleaning means often leads to un-even loading and/or overloading of the various components both of which are disadvantageous as both ultimately result in considerable grain losses.

In other known combine harvesters, independent tailings rethreshers have been provided which are normally arranged to receive the tailings from the cleaning mechanism and to discharge the rethreshed tailings onto the grain pan of the cleaning mechanism to recycle the tailings therethrough. This arrangement is advantageous in as far as the main threshing and separating mechanism can be used to its full capacity without any risk of unevenly loading or overloading it with tailings. These separate tailings rethreshers have proven to be advantageous especially in combination with high capacity combine harvesters since they enable components to operate with a maximum efficiency.

Nevertheless, these separate tailings rethreshers also have some disadvantages, a major one being that certain arrangements are complicated and hence expensive. One such arrangement combines a conventional type elevator with rethresher means. Another arrangement combines rethresher means with a vertical auger for feeding the tailings to the rethresher located thereabove. This arrangement is driven via a drive transmission including conical gears which add to the expense.

In the latter arrangement tailings are not forcibly moved through the entire length of the tailings rethreshing means in the rethresher and hence a certain percentage of tailings is discharged from the rethresher prematurely, whereby these tailings once again have to pass through the rethresher after separation in the cleaning mechanism.

All known tailings rethreshers comprise a rotor cooperable with stationary elements to rethresh the tailings and operable to discharge the rethreshed tailings and spread them substantially evenly over the grain pan. Therefore the design of the rotor is a compromise to fulfil both functions to an acceptable degree.

In operation, the rotor moves the tailings over an aggressive surface thereby effecting rethreshing. The aggressive surface in some of the known tailings rethreshers extends only over a small arc so as to accommodate an inlet and an outlet opening. Thus the efficiency of such a rethresher is relatively low. In other arrangements, the aggressive surface is larger but, as already explained above, the rotor is incapable of moving all of the tailings over the entire surface, whereby maximum efficiency is not realised.

Another disadvantage is that the tailings are supplied to the tailings rethresher rotor either co-axially or in a direction generally parallel to the rotor axis. Thus the tailings are not evenly spread over the entire width of the rethreshing rotor and the associated aggressive surface which again reduces the efficiency. Also, such tailings rethreshers are unable to handle difficult crops such as wet and weed-infested crops as well as crops mixed with wet, sticky soil. Indeed, in these conditions crop material no longer fluently flows and tends to stick in the inlet area of the rethresher as well as in the free spaces between the adjacent paddles of the rethresher rotor. This causes the capacity and the efficiency of the rethresher to drop considerably and eventually plugging or blocking may occur.

It is the object of the present invention to eliminate or to attenuate one or more of the aformentioned drawbacks and to provide a combine harvester with a minimum of crop conveying elements.

According to the invention, a combine harvester is provided comprising a threshing and separating mechanism, a cleaning mechanism disposed to receive threshed and separated crop material from the threshing and separating mechanism, tailings rethresher means associated with the cleaning mechanism for rethreshing tailings separated therein and conveyor means for recycling rethreshed tailings from the rethresher means to the cleaning mechanism and adapted also to receive material separated in at least a portion of the threshing and separating mechanism to direct that material, together with rethreshed tailings, to the cleaning mechanism.

The invention is particularly suited to a combine harvester of the rotary type wherein a rotary threshing mechanism and a rotary separating mechanism extend parallel to each other transversely of the machine, and wherein the separating mechanism has a width exceeding the width of the threshing mechanism with the opposed ends of the separating mechanism being disposed beyond the corresponding ends of the threshing mechanism. In such combines, the layer of crop material is, in operation, first fed through the rotary threshing mechanism and subsequently, substantially half the mat is conveyed in one spiral pattern through the separating mechanism toward one end thereof, whilst the remainder of the crop material is conveyed in an opposite spiral path to the opposite end of the separating mechanism. All material is discharged onto the ground at said opposite ends.Grain mixed with impurities separated in the threshing mechanism, and in the central portion of the separating mechanism, is conveyed directly to the cleaning mechanism disposed vertically therebelow and which has a width substantially corresponding to the width of the threshing mechanism. Thus, portions at the opposed sides of the central portion of the separating mechanism extend beyond the side edges of the cleaning mechanism which usually comprises a forward grain pan and a pair of cleaning sieves disposed rearwardly thereof, one above the other.

The conveyor means preferably extend from the rethreshing mechanism to a location above the level of the grain pan alongside one side of the cleaning mechanism and below one end portion of the separating mechanism.

Preferably such a conveyor mechanism is provided at each side of the cleaning mechanism below the opposed outer ends of the separating mechanism. In one arrangement, each conveyor mechanism comprises an auger tube with an auger therein. A grain collecting chute is provided below each of the opposed end portions of the separating mechanism and is adapted to receive separated grain from said end portions and to direct it to the conveyor mechanisms at locations intermediate the ends thereof. The diameter of the auger tube and auger downstream of the corresponding chute exceeds the diameter of the other portions of the auger tube and auger. Preferably, the two portions of the auger tube and auger extend coaxially. In this arrangement an impeller may be provided coaxially with the auger at the discharge end thereof and be operable to impel grain mixed with impurities transversely across the grain pan. Deflector means may be provided above the grain pan in the path of the crop material issuing from the impeller.

In an alternative arrangement, each conveyor mechanism comprises a first portion in the form of an auger tube with an auger therein which extends alongside the cleaning mechanism, and a second portion oriented substantially at right angles to the first portion and extending transversely of the machine.

The second portion is formed by an auger which is provided at the bottom end of the associated collecting chute which is shaped to form an auger trough. The second portion of the conveyor mechanism has its discharge end above the level of the grain pan.

Combine harvesters embodying the present invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a first embodiment, Figure 2 is a sectional view, to a larger scale, of the components indicated at II in Fig.

1, Figures 3 and 4 are sectional views to different scales, taken along the line Ill-Ill and IV-IV, respectively, of Fig. 2, Figure 5 is a sectional view taken along the line V-V in Fig. 3, and Figure 6 is a view similar to Fig. 1 illustrating an alternative embodiment.

With reference to Fig. 1, the combine harvester embodying the present invention is generally indicated at 1 and comprises a main frame or chassis 2 supported on a pair of drive wheels 3 and a pair of steerable wheels 4 (only one wheel of each pair being shown).

Supported on the main frame 2 are an operator's platform 5, a grain tank 6, a grain cleaning mechanism 7 and an engine 8. A conventional header 9 and a feed conveyor 10 extend forwardly of the machine. The main frame 2 also supports a threshing and separating mechanism, generally indicated at 12, and the threshing portion 1 3 thereof comprises a conventional rotatable threshing cylinder 14 cooperable with a conventional stationary threshing concave 15, the operation of which is generally known in the art.

Rearwardly of the threshing cylinder 14 and the associated concave 1 5 there is provided a conventional deflector or so-called straw beater 1 6 with a cooperable beater grate 1 7.

These components have substantially the same width as the threshing cylinder 1 4 and concave 1 5 disposed in front thereof and are arranged to deflect the straw mat issuing from the threshing mechanism.

Rearwardly of the straw beater 1 6 there is provided a separating mechanism 1 9 which basically is composed of a single, transverselyextending casing or housing 20 with a pair of separator rotors 21, 22 mounted therein. The width of the separating mechanism 1 9 exceeds the width of the threshing mechanism 13, whilst the plane of symmetry thereof coincides with the plane of symmetry of the threshing mechanism 13, whereby the outer ends of the separating mechanism 1 9 extend beyond the respective ends of the threshing mechanism 1 3. Preferably, the separating mechanism 1 9 has a width of about three meters.

The transversely-extending separating rotors 21, are arranged in parallel, one behind the other, inside the casing 20 part of which is defined by a concave 25. The rotors 21, 22 are driven in the same direction and comprise crop-treating and crop-conveying elements cooperable with the concave 25 and operable in use to separate grain from the straw whilst conveying approximately half the straw mat in a first spiral path around both rotors 21, 22 at the inner side of the casing 20 and to one end of the separator mechanism 1 9 for discharge, and the remainder of the straw mat in an opposite spiral path, again around both rotors 21, 22, to the opposite end for discharge.For a more detailed description of the threshing and separating means 1 2 and the operation thereof, reference is made to our British Patent Specification No. 1,460,715.

The cleaning mechanism 7 is disposed underneath the threshing and separating mechanism 1 2 with its longitudinal plane of symmetry coinciding with the plane of symmetry of the threshing and separating mechanism. The cleaning mechanism 7 has a width which substantially corresponds to the width of the threshing cylinder 14 and associated concave 1 5 and thus the separating mechanism 1 9 has opposite ends which extend beyond the side edges of the cleaning device disposed therebelow. The cleaning device 7 comprises a grain pan 30 for collecting grain separated in the threshing and separating mechanism 12, cleaning sieves 31, 32 located rearwardly thereof, and a cleaning fan 33 disposed forwardly of the sieves 31, 32 and below the grain pan 30.The cleaning sieves 31, 32 and the grain pan 30 are mounted for reciprocatory movement on the combine harvester chassis 2. A clean grain collecting chute 35 and a tailings collecting chute 36, which are generally known in the art, are disposed below the cleaning sieves 31 and 32 and are arranged to discharge clean grain and tailings received from the cleaning sieves 31, 32 into a clean grain auger trough 37 and a tailings auger trough 38, respectively. The clean grain auger trough 37 extends transversely of the combine harvester and contains a clean grain auger 40 have a discharge end adjacent one side of the cleaning mechanism 7 to which collected grain is conveyed. A clean grain elevator 41 extends from said discharge end, alongside the threshing mechanism 1 3 and forwardly of the separating mechanism 1 9 to the grain tank 6.

The tailings auger trough 38 also extends transversely of the machine and comprises opposed discharge ends 42 adjacent the op posite sides of the cleaning device 7. A tailings auger 43 is disposed in the tailings auger trough 38 and comprises auger flights which are wound in opposite directions from the centre of the auger. Identical tailings transfer means 44 and tailings rethreshers 45 are provided at the opposite ends of the tailings auger trough 38. Each tailings rethresher 45 is coupled to an elevator conveyor 46, to be described in more detail hereinafter. Only one tailings transfer means 44, one tailings rethresher 45 and one elevator conveyor 46 are shown in the drawings. As can be seen in the drawings, the tailings transfer means 44 and the tailings rethreshers 45 extend coaxially with the auger axis 48 and are immediately adjacent each other.

Each tailings transfer means 44 comprises a housing 47 arranged coaxially with the auger axis 48 and having an outer diameter which is greater than the diameter of the tailings auger 43. The housing 47 comprises a generally frusto-conical portion 49 which is coupled at its smaller diameter end to the auger trough 38 and connected at its larger diameter end to a generally cylindrical portion 50. A pair of spiral fins 51 are arranged on the inner side of the housing 47 and are disposed to direct tailings toward a rethresher inlet 52 in a spiral path. A tailings auger shaft 53 is extended into the tailings transfer means 44 and into the tailings rethresher 45 and carries an impeller 54 within the transfer means 44.The impeller 54 is composed of generally radiallyoutwardly-extending impeller blades 55 with portions 39 located adjacent the rethresher 45 and at the outer circumference of the impeller being inclined rearwardly as seen in the direction of rotation 56 (Fig. 4). The portions 39 are inclined rearwardly about crease lines 57 which are directed outwardly away from the axis 48 and at an angle relative to, and away from, the rethresher 45 so that the portions help to direct material towards the rethresher 45.

Each tailings rethresher 45 comprises a generally cylindrical housing 58 with opposed end walls 59 and 60 and a generally cylindrical wall 61. A rethresher rotor 62 is mounted in the housing 58 on the shaft 53 which extends therethrough. The rethresher inlet 52 is provided in the end wall 59 which also forms a partition wall between the tailings transfer means 44 and the tailings rethresher 45. The inlet 52 is arranged eccentrically with respect to the shaft 53 and spans a sector of no more than 180 .

Downstream relative to the inlet 52, as seen in the direction of rotation 56 of the shaft 53, stationary aggressive rethresher means in the form of rethresher rasps 63 are mounted in a particular pattern on a section of the inside of the cylindrical wall 61 of the rethresher hous ing 58. Rearwardly thereof, as seen in the direction of rotation 56, there is provided in the wall 61 an outlet 64 which faces upwardly.

The rethresher rotor 62 comprises a number of radially-outwardly-extending vanes 65 secured to the shaft 53 and carrying at their outer ends side-by-side extending aggressive rethresher rasps 66 which are so disposed relative to the stationary rethresher rasps 63 that, in operation, each rotary rethresher rasp 66 moves in between two adjacent stationary rethresher rasps 66.

A tailings return conveyor 67 extends between the outlet 64 of each tailings rethresher 45 and an aperture in the combine side wall above the level of the grain pan 30. Each such return conveyor 67 is inclined upwardly in a forward direction and passes below an outer end of the separating mechanism 1 9.

Each return conveyor 67 comprises an auger tube 68 to which is coupled a collecting chute 69 intermediate its ends. The diameter of the auger tube 68 downstream of the collecting chute 69, i.e. forwardly of the chute, as seen in the direction of operative travel, exceeds the diameter of the auger tube portion which is coupled to the rethresher 45. An auger 70 comprising two portions of different diameters is installed in the auger tube 68, with the portion having the larger diameter being positioned in the downstream auger tube section.

The collecting chute 69 has an upwardlyfacing opening adapted to receive material separated in the portion of the separating mechanism 1 9 extending beyond the adjacent side edge of the cleaning mechanism 7 therebelow, and tapers downwardly, the smaller area end being coupled to the auger tube 68 in a manner to lead all material received therein from the separating mechanism 1 9 towards the auger tube.

At the discharge end, each auger tube 68 flares outwardly and is coupled to an impeller housing 71 which extends coaxially with the auger tube and has a discharge opening 72 coinciding with the opening in the combine side wall above the grain pan 30. A rotor 73 having impeller blades 74 mounted on an extension of the auger shaft 75 is provided in the housing 71 and is operable to throw material onto and across the grain pan 30.

Deflector plates 76 are installed underneath the separator concave 25 in the path of crop material issuing from the impellers at both sides of the combine main body.

As the combine harvester 1 is propelled forwardly over a field, the crop material to be harvested is severed from the stubble by a sickle bar 11 on the header 9 and is conveyed by the header 9 and the feed conveyor 10 to the threshing and separating mechanism 1 2.

The crop material is conveyed over the thresh ing concave 1 5 and grate 1 7 by the threshing cylinder 14 and the straw beater 1 6 whilst being threshed. The crop material (which may be wheat, corn, rice, soy beans, rye, rape seed, barley, etc.) is thus rubbed and beaten, whereby the grain, seed, etc. is loosened and separated from the straw stalks, coils, or other discardable part of the crop material.In the separating mechanism 19, approximately half the straw mat is conveyed in a first spiral path around the rotors 21, 22 at the inner side of the casing 20 to one end of the separator mechanism 1 9 for discharge onto the ground whilst the remainder of the straw mat is conveyed in an opposite spiral path, again around the rotors 21, 22 and at the inner side of the casing 20, to the opposite end of the separator mechanism 1 9 for discharge. During this spiral movement of the crop material, grain not yet separated in the threshing mechanism 1 3 and by the action of the straw beater grate 17, is separated through the separator concave 25. Together with the separated grain there is mixed all sorts of impurities such as chaff, dust, short straw particles and tailings.Material separated in the threshing mechanism 13, the straw beater and associated grates 1 6 and 1 7 and the central portion of the separating mechanism 19, which are all disposed immediately above the cleaning mechanism 7, is dropped directly onto the cleaning mechanism 7. Material separated in the outer ends of the separating mechanism 1 9 is received in the collecting chutes 69 and directed towards the associated auger tubes 68.

Most, if not all, of the material directed to the cleaning mechanism 7 is received on the grain pan 30 which conveys it stepwise in a rearward direction to the cleaning sieves 31, 32. The cleaning sieves 31, 32 and the cleaning fan 33 are arranged to discharge light impurities such as chaff and dust in a rearward direction onto the ground, whilst collecting clean grain on the clean grain collecting chute 35 for conveyance to the clean grain auger 40. Clean grain is transported by the clean grain elevator 41 to the grain tank 6 on top of the machine for temporary storage therein.

The tailings are separated from the clean grain, on the one hand, and the discardable material, on the other hand, at the rearward end of the cleaning mechanism 7 and are collected on the tailings collecting chute 36 for conveyance to the tailings auger 43. The operation of the threshing, separating and cleaning mechanisms as briefly described above is known in the art and is described, for example, in British Patent Specification No.

1,460,715 and, therefore, further detailed description is not necessary.

The tailings auger 43 is driven in the direction 56 and due to its oppositely wound auger flights 43 about half the amount of tailings is conveyed to one end and the remainder to the opposite end for recycling. As the tailings transfer means 44, the tailings rethreshers 45 and the tailings return conveyors 67 on both sides of the combine are identical to each other, the operation of the components on one side only will now be described in more detail.

As the auger 43 feeds material into the tailings transfer means 44, the impeller 54 thereof immediately forces the tailings towards the outer circumference of the housing 47 which, as described, has a larger diameter than the tailings auger 43. As the material is impelled by the impeller 54 along the inner side of the housing 47, the fins 51 and the bent portions 39 of the impeller blades 55 lead the tailings axially toward the associated rethresher 45 in a spiral path. This movement axially of the tailings transfer means 44 is also induced to some degree by the shape of the conical portion 49 of the housing 47. The tailings are fed by the impeller 54 through the rethresher inlet 52 into the rethresher housing 58. It is thus clear that all tailings enter the rethresher housing 58 at about one and the same location substantially at the outer circumference thereof.More precisely, all tailings are forcibly fed to the rethresher 45 substantially at the outer circumference thereof and forwardly of the stationary rethresher rasps 63 when seen in the direction of rotation 56. Thus all tailings are forcibly moved over the entire length of the aggressive surface formed by the stationary rethreshed rasps 63 and hence no tailings are discharged prematurely. Also, as all tailings enter the tailings rethresher 45 at about its outer circumference, virtually none thereof escape from the aggressive rethresher action by moving therethrough between adjacent rethresher rasps. When entering the rethresher housing 58, the tailings are generally evenly spread over its width.The rethresher rotor 62 deflects the stream of tailings in the direction of rotation 57 and causes the same to pass between the stationary and the movable rethresher rasps 63 and 66, whereby they are submitted to a thorough rethreshing.

The impetus imparted to the tailings by the rethresher rotor 62 causes them to leave the rethresher 45 and to enter the tailings return conveyor 67 in an upward direction through the opening 64 after they have passed over the full length of the aggressive rethresher means on the inside of the rethresher housing 58. Re-threshed tailings (comprising a mixture of grain, chaff and dust) entering the conveyor 67 are caught by the flights of the auger 70 and conveyed thereby towards the upper end thereof. Material separated in the outer end of the separating mechanism 1 9 above the conveyor 67 and collected in the collecting chute 69 is added to the rethreshed tailings in the conveyor 67 and is transported together therewith to the impeller 73 which throws this mixture across the grain pan 30.The deflectors 76 in the streams of crop material entering the area above the grain pan 30 from opposed sides, help in spreading the material substantially evenly across the grain pan 30.

This material, which comes either from the rethreshers 45 or from the outer ends of the separating mechanism 19, is processed in the cleaning mechanism 7, together with the crop material received on the grain pan directly from the threshing and separating mechanism 12.

The drive for the various components of the tailings rethreshers is very simple and is composed of a chain 80 extending around a first sprocket 81 on an intermediate driven shaft 82 mounted on the chassis 2, a second sprocket 83 mounted on the tailings auger shaft 53 to drive the tailings auger 43, the tailings impellers 54 and the rethreshers 45 in the direction 56, and finally a third sprocket 84 on the input shaft of a gearbox 85. The gearbox 85 is attached to the lower end of the tailings return conveyor 67 and the output shaft thereof is drivingly coupled to the return auger 70.

In a combine harvester constructed in accordance with the present invention, all components such as the threshing and separating mechanisms, for example, can be used to their maximum design capacity and without any undue risk of unevenly loading and/or overloading the same as a result of being supplied with tailings which would result in unacceptable grain losses. Thus, the threshing and separating efficiency of such machines is considerably improved. Also, the risk of unevenly loading the cleaning mechanism with tailings is reduced substantially as tailings are returned to the grain pan in substantially equal amounts from opposed sides thereof spread across the width of the grain pan, the deflectors 76 helping in this connection.Furthermore, material separated in the outer portions of the separating means 1 9 is also more or less evenly spread across the grain pan.

The efficiency of the separate tailings rethreshers is equally extremely high for several reasons. A major reason is the provision of the separate transfer means between each tailings auger portion and the associated rethresher which moves the tailings from the vicinity of the rotary axis of the auger to a spiral path with a diameter which is about the same as the diameter of the rethresher. Thus the tailings enter the rethresher right at a point where actual rethreshing takes place so that rethreshing starts as soon as the tailings have entered the rethresher. Another reason is the fact that tailings are smoothly transferred from the auger to the rethresher, whereby no hesitation in the flow of material occurs and uneven loading is avoided.In addition, the tailings are more or less evenly spread across the full width of the rethresher, which is again helpful in improving efficiency.

Furthermore, all tailings enter the rethresher at about the same point, whereby all tailings are submitted to a rethreshing action of substantially the same length and aggressiveness as they pass over the full length of the stationary aggressive rethresher means. Thus substantially no tailings are discharged prematurely.

Finally, as rethreshed tailings leave the stationary rethresher means, they are immediately discharged in a tangential direction towards the return conveyor. This prevents any tailings being recycled in the tailings rethresher. This discharge of tailings from the rethresher to the conveyor is very smooth without any abrupt changes in the direction of movement, whereby again hesitation in the movement of the material is avoided. This is especially so as the return auger which receives the tailings from the rethresher rotor is positioned closely adjacent the latter at the transfer area. Thus the tailings are passed continously, fluently and quickly through the various components without any substantial risk of jamming and, as all components can be driven at a relatively high speed, large volumes of tailings can be processed with components of comparatively small dimensions.

Nevertheless, the tailings collecting auger, the transfer means and the rethreshers are very simple in design as they all extend coaxially with and adjacent each other. Thus only one shaft with associated bearings is required and the housings can be of sheet metal. For the same reason, the drive for the various components is very simple. Finally, the tailings collecting auger, the tailings transfer means and the tailings rethreshers remain very compact and for all these reasons the arrangement is relatively cheap to manufacture even though all main components are provided in duplicate in the sense that there is one set on each side of the cleaning mechanism.

The tailings return conveyors are very short in comparison to known tailings return conveyors and the conveyors with the impellers at the discharge ends thereof are very simple in design. Also the drive means therefor are very simple and accordingly the tailings return means are also comparatively cheap to manufacture. The tailings return means serve a dual purpose, namely the recycling of rethreshed tailings and the transport of material separated in portions of the separating mechanism to the cleaning mechanism and the distribution thereof across the width of the cleaning mechanism. Hence no separate conveyors are required to accomplish this transport and distribution and thus the arrangement is not at all cumbersome. Instead, good access to all other combine components is provided.

Finally the tailings rethreshers and tailings return conveyors are capable of handling all types of crop without any serious risks of plugging, even those crops which in many prior art designs inveriably cause problems.

With reference to Fig. 6, an alternative embodiment is illustrated. Each tailings return conveyor 67 is basically composed of a first and a second auger 77 and 78, respectively which are disposed at right angles to each other. As in the preferred embodiment of Figs.

1 to 5, the first auger 77 conveys rethreshed tailings received from the tailings rethresher upwardly in a forward direction. This auger 77 supplies the rethreshed tailings to the second auger 78 which is disposed transversely of the machine underneath one end of the separating mechanism 1 9 and arranged at the bottom of a collecting trough 79 which itself is adapted to receive material separated from the straw in said end portion of the separating mechanism. The second auger 78 thus conveys to the cleaning mechanism rethreshed tailings as well as material separated in a portion to the separating mechanism.

Claims (14)

1. A combine harvester comprising a threshing and separating mechanism, a cleaning mechanism disposed to receive threshed and separated crop material from the threshing and separating mechanism, tailings rethresher means asscociated with the cleaning mechanism for rethreshing tailings separated therein, and conveyor means for recycling rethreshed tailings from the rethresher means to the cleaning mechanism and adapted also to receive material separated in at least a portion of the threshing and separating mechanism to direct that material, together with rethreshed tailings, to the cleaning mechanism.

2. A combine harvester according to claim 1, wherein the cleaning mechanism is disposed below the threshing and separating mechanism and is adapted to receive a portion of the material separated in the threshing and separating mechanism directly therefrom.

3. A combine harvester according to claim 2, wherein the threshing and separating mechanism extends beyond a side edge of the cleaning mechanism arranged therebelow.

4. A combine harvester according to claim 3, wherein the conveyor means extend between the rethresher means and the cleaning mechanism adjacent one side of the cleaning mechanism and passes underneath the portion of the threshing and separating mechanism which extends beyond said side edge of the cleaning mechanism.

5. A combine harvester according to claim 4 and further comprising a collecting chute extending between said portion of the threshing and separating mechanism and a point intermediate the ends of the conveyor means and adapted to direct crop material separated in said portion of the threshing and separating mechanism to the conveyor means.

6. A combine harvester according to claim 5, wherein the conveyor means are in the form of an auger conveyor.

7. A combine harvester according to claim 6, wherein the diameter of the auger conveyor portion downstream of the collecting chute is larger than the diameter of the other portion of the auger conveyor.

8. A combine harvester according to claim 7, wherein both auger conveyor portions are coaxial and have a common auger shaft.

9. A combine harvester according to any of claims 6 to 8 and further comprising impeller means mounted coaxially with the auger conveyor at the discharge end thereof for impelling material received from the rethresher means and the threshing and separating mechanism transversely of the cleaning mechanism.

10. A combine harvester according to claim 9, wherein the cleaning mechanism comprises a grain pan and cleaning sieves, the grain pan being disposed to receive separated crop material directly from the threshing and separating mechanism and to convey it to the cleaning sieves, and the impeller means being adapted to spread material received from the conveyor means transversely across the grain pan.

11. A combine harvester according to claim 10 and further comprising deflector means disposed above the grain pan in the stream of crop material issuing from the impeller means and operable to assist in evenly spreading the crop material across the grain pan.

1 2. A combine harvester according to claim 6, wherein the auger conveyor comprises a first portion and a second portion disposed at substantially right angles to each other, with the first portion comprising an auger tube with an auger therein and extending from the rethresher means at one side of the cleaning mechanism, and the second portion comprising an auger arranged within the collecting chute at the bottom end thereof and having a discharge end disposed above the cleaning mechanism.

1 3. A combine harvester according to any of the preceding claims, wherein the threshing and separating mechanism is of the rotary type.

14. A combine harvester according to claim 13, wherein the threshing and separating mechanism comprises a rotary threshing mechanism and a rotary separating mechanism disposed parallel to each other and extending transversely of the machine, and wherein the separating mechanism extends partially transversely beyond a fore-and-aft extending side edge of the cleaning mechanism therebelow.

1 5. A combine harvester according to claim 14, wherein the separating mechanism has a width exceeding the width of the threshing mechanism and is disposed rearwardly thereof with its opposed ends at substantially equal distances beyond the adjacent ends of the threshing mechanism, and wherein the cleaning mechanism has a width substantially corresponding to the width of the threshing mechanism and is disposed vertically therebelow and below a central portion of the separating mechanism, the arrangement being such that material separated in the threshing mechanism and the central portion of the separating mechanism falls directly onto the cleaning mechanism, the combine harvester further comprising tailings rethresher means and conveyor means at each side of the cleaning mechanism and below and adjacent end portion of the separating mechanism, with each conveyor means adapted to receive crop material separated in the end portion of the separating mechanism thereabove.

1 6. A combine harvester according to claim 15, wherein the separating mechanism comprises a separator casing with at least one separator rotor therein, the arrangement being such that, in operation, substantially half the mat of crop material received from the threshing mechanism is conveyed in a first spiral path around said at least one rotor inside the casing to one end of the separating mechanism for discharge, and that the remainder of the straw mat is conveyed in an opposite spiral path around said at least one rotor inside the casing to the opposite end of the separating mechanism for discharge.

1 7. A combine harvester substantially as herein-particularly described with reference to Fig. 6 of the accompanying drawings.