Soil cultivation and stone/clod separation

The present invention relates to a combined soil cultivator and stone/clod separator. The present invention also relates to a soil cultivator, to a stone and clod separator, and to a method of cultivating soil and/or separating stones/clods. In particular, but not exclusively, the present invention relates to a combined soil cultivator and stone/clod separator comprising at least one soil crumbling assembly.

Stone and clod separators and cultivators are used in agriculture and horticulture to produce fine soil conditions free of large clods of soil and stones, in preparation for the planting of, for example, vegetables such as potatoes. This often requires a number of passes of a cultivator/separator and successive operations of the cultivator/separator in order to sufficiently break down heavy soils.

European Patent Publication Number 0410808 (Richard Pearson Limited) and European Patent Publication Number 1332656 (Reekie Manufacturing Limited) disclose a prior proposed lifting conveyor and agricultural separator, and a soil cultivator, respectively. Whilst the lifting conveyor/separator of EP 0410808 and the soil cultivator of EP 1332656 are effective in, respectively, lifting and separating a root crop, bulbs or stones/clods and in cultivating soil, it is generally desired to improve upon the structures and operation of such known equipment.

It is therefore amongst the objects of at least one embodiment of the present invention to obviate or mitigate disadvantages associated with prior soil cultivators and/or stone and clod separators.

It is also amongst the objects of at least one embodiment of the present invention to provide a soil separating, cultivating device capable of producing sufficiently clod free soil conditions whilst minimising preparatory soil cultivations, resulting in increased speed of operation, reduced overall power requirement and less damage to soil structure.

It is a further object of at least one embodiment of the present invention to provide a clod and stone separator which sieves loose soil more effectively.

According to a first aspect of the present invention, there is provided a combined soil cultivator and stone/clod separator comprising:

• a digging device;
• a first soil sieving conveyor;
• at least one soil crumbling assembly; and
• at least one further soil sieving conveyor;

wherein the digging device is arranged to dig up material and to transfer the material rearwardly, relative to a direction of travel, to the first soil sieving conveyor; and wherein the at least one soil crumbling assembly is positioned downstream of the first sieving conveyor, for receiving material from the first soil sieving conveyor; and further wherein the at least one further soil sieving conveyor is positioned to receive substantially all of the material passing down through the at least one soil crumbling assembly.

It will be understood that the material which the digging device digs up and transfers to the first soil sieving conveyor comprises soil particles and clods or clod material of various sizes, as well as stones of varying sizes.

The invention provides a combined soil cultivator and stone/clod separator which exerts a combined cultivating and stone/clod separating action on soil in a single pass across the surface of a field or the like. This avoids or at least minimises a requirement to carry out separate stone/clod separating and cultivating operations, when compared with prior equipment.

The at least one further soil sieving conveyor may also be positioned to receive substantially all of the material delivered rearwardly from the at least one soil crumbling assembly.

Preferably, the first soil sieving conveyor is arranged to carry out a sieving action on material transferred to the conveyor by the digging device, and may be arranged to transfer material above a first size along a length of the conveyor for discharge onto or into the soil crumbling assembly. Thus the first soil sieving conveyor may be arranged to allow material below said first size to fall down through the conveyor back to the ground, effectively carrying out a sieving action on the material. It will therefore be understood that stones and clods which are oversized are prevented from falling down through the first soil sieving conveyor to the ground, and are discharged onto or into the soil crumbling assembly for further working. The first soil sieving conveyor may define a plurality of sieving spaces, the dimensions of each sieving space determining the maximum, first size of material permitted to fall down through the conveyor. The first soil sieving conveyor may be arranged to transfer or transport material which is oversized relative to the dimensions of said sieving spaces along a length of the first soil sieving assembly, and to discharge said material onto or into the at least one soil crumbling assembly. The first soil sieving conveyor may be configured such that, during passage of oversized material along the length of the conveyor, the oversized material is at least partially broken down or crumbled, such that a portion of the oversized material is broken down and falls down through the conveyor before it reaches the end thereof.

Preferably also, the at least one soil crumbling assembly is arranged to exert a crumbling action on clods received from the first soil sieving conveyor, to break-down or crumble the clods to a smaller size. The at least one soil crumbling assembly may also be arranged to permit clods/stones below a second size, larger than said first size of material permitted to fall down through the first soil sieving conveyor, to pass down through the assembly. The at least one soil crumbling assembly may define a plurality of sieving spaces, the dimensions of each space determining the maximum, second size of material passing down through the assembly, and may be arranged to exert a crumbling action on clods which are oversized relative to the sieving spaces, to break-down or crumble the clods. Additionally, the soil crumbling assembly may define an opening for each sieve space through which material to be crumbled is received, and the openings may be sized to prevent entry of material above a third size, greater than said second size. Clod material above said third size will typically be broken down by the soil crumbling assembly to a smaller size, through repeated impact of the soil crumbling assembly against the clods, such that the clod material can subsequently pass into the openings and down through the soil crumbling assembly. However, excessively large clods may be transferred along a length of the assembly and discharged from the assembly. Other, harder material above said third size, such as stones or rocks, may be transferred along a length of the assembly and discharged from the assembly. In this fashion, large clods/stones which are oversized relative to the openings and thus too large to be handled by the soil crumbling assembly may be discharged from the assembly.

It will be understood that the soil crumbling assembly is positioned downstream of the first soil sieving conveyor in that it is positioned so as to receive material discharged from, optionally, an end of said conveyor. The soil crumbling assembly is preferably located rearwardly of the first soil sieving conveyor, relative to the direction of travel, and is preferably also positioned such that a main plane or axis of the soil crumbling assembly is on the same plane or coaxial with a main plane or axis of the first soil sieving conveyor.

The at least one further soil sieving conveyor may be arranged to exert a further sieving action on material passing down through and delivered rearwardly from the at least one soil crumbling assembly, and may be arranged to transfer material above said first size along a length of the conveyor for discharge. Preferably, the at least one further soil sieving conveyor is arranged to discharge material above the first size on to a discharge device such as a lateral conveyor, which may be adapted to discharge the material into wheel ruts formed during passage of the cultivator. Alternatively, the material may be collected and removed off-site. It will therefore be understood that material which is broken-down or crumbled by the soil crumbling assembly to a size above said first size may be transferred along the at least one further soil sieving conveyor, whilst material broken-down or crumbled to a size below said first size may fall down through the conveyor to the ground, as described above with respect to the first soil sieving conveyor. Furthermore, during passage of the material above said first size along the at least one further soil sieving conveyor, at least a portion of the material may be further broken down and may fall through the at least one further soil sieving conveyor prior to discharge from the end of the conveyor.

Providing a cultivator and stone/clod separator having two such sets of conveyors and a soil crumbling assembly enables crumbling of oversized clods and stone separation without hampering or negating work previously carried out by the first soil sieving conveyor. This is because the further conveyor receives substantially all of the material passing down through and discharged rearwardly from the soil crumbling assembly, and effectively performs a grading action of the material output from the soil crumbling assembly.

In a preferred embodiment of the invention, the first and at least one further soil sieving conveyors each comprise a plurality of rotatable members spaced apart with respect to the direction of travel. Each rotatable member may comprise a plurality of generally parallel star wheels. Each star wheel may comprise a plurality of fingers and may be shaped to rotate material in an opposite direction to a direction of rotation of the star wheels. In an alternative embodiment, the first and at least one further soil sieving conveyor may comprise a web defining a plurality of discharge apertures, the web taking the form of an endless belt.

In a preferred embodiment, the soil crumbling assembly comprises a plurality of generally parallel star wheel members spaced apart with respect to the direction of travel, each rotatably mounted on a frame of the cultivator and stone/clod separator. Each rotatable member may comprise a row of star wheels having outwardly extending fingers. The star wheels of adjacent rows may cooperate to define sieving spaces therebetween through which soil particles can pass downwardly, and the fingers of each star wheel of one row of star wheels may cooperate with the fingers of a corresponding star wheel of an adjacent row in order to exert a combined working action on soil particles and clod material which is oversized relative to said sieving spaces, in order to break-down or crumble such material prior to discharge from the assembly.

In embodiments of the invention, the cultivator and stone/clod separator may comprise a further soil crumbling assembly and a further soil sieving conveyor. The cultivator may therefore comprise a first soil crumbling assembly positioned downstream of the first soil sieving conveyor; a second soil sieving conveyor positioned to receive substantially all of the material passing down through and delivered rearwardly from the first soil crumbling assembly; a second soil crumbing assembly positioned downstream of the second soil sieving conveyor, for receiving material from the second soil sieving conveyor; and a third soil sieving conveyor positioned to receive substantially all of the material passing down through and delivered rearwardly from the second soil crumbling assembly.

It will therefore be understood that a two-stage crumbling action may be exerted on dug-up material, enhancing the crumbling-separating action. This may further reduce the number of passes or operations of the cultivator required in order to achieve a satisfactory result.

The first soil crumbling assembly may be arranged to carry out a first crumbling of the material and the second soil crumbling assembly to carry out a second, finer crumbling of the material. Accordingly, sieving spaces of the second crumbling assembly may be smaller than those defined by the first soil crumbling assembly.

The digging device may comprise a share blade or the like and a conveyor such as a roller, for digging-up and transferring material to the first soil sieving conveyor. Alternatively, any other suitable digging device may be utilised.

The cultivator and stone/clod separator may comprise a frame on which the digging device, first soil sieving conveyor, at least one soil crumbling assembly, and at least one further soil sieving conveyor are mounted, movement of the frame along or relative to the surface of a field or the like causing the digging device to dig up material to be transferred to the first soil sieving conveyor.

The first soil sieving conveyor may define the or a soil crumbling assembly. This may be achieved by forming the first soil sieving conveyor from a plurality of star wheel arrays defining a soil sieving portion and a soil crumbling portion, and by spacing star wheel arrays of the soil crumbling portion so as to define soil sieving spaces larger than soil sieving spaces defined by star wheel arrays of the soil sieving portion.

According to a second aspect of the present invention, there is provided a soil cultivator comprising:

• a digging device;
• a first soil sieving conveyor;
• at least one soil crumbling assembly; and
• at least one further soil sieving conveyor;

wherein the digging device is arranged to dig up material and to transfer the material rearwardly, relative to a direction of travel, to the first soil sieving conveyor; and wherein the at least one soil crumbling assembly is positioned downstream of the first sieving conveyor, for receiving material from the first soil sieving conveyor; and further wherein the at least one further soil sieving conveyor is positioned to receive substantially all of the material passing down through the at least one soil crumbling assembly.

According to a third aspect of the present invention, there is provided a stone and clod separator comprising:

• a digging device;
• a first soil sieving conveyor;
• at least one soil crumbling assembly; and
• at least one further soil sieving conveyor;

wherein the digging device is arranged to dig up material and to transfer the material rearwardly, relative to a direction of travel, to the first soil sieving conveyor; and wherein the at least one soil crumbling assembly is positioned downstream of the first sieving conveyor, for receiving material from the first soil sieving conveyor; and further wherein the at least one further soil sieving conveyor is positioned to receive substantially all of the material passing down through the at least one soil crumbling assembly.

Further features of the soil cultivator and the stone/clod separator of the second and third aspects of the invention in common with the combined soil cultivator and stone/clod separator of the first aspect are defined above.

According to a fourth aspect of the present invention, there is provided a method of cultivating soil and separating stones/clods, the method comprising the steps of:

• digging-up material to be cultivated and from which stones and clods are to be separated and transferring the dug-up material on to a first soil sieving conveyor; activating the first soil sieving conveyor to transfer the material to a soil crumbling assembly positioned downstream of the first sieving conveyor;
• activating the at least one soil crumbling assembly; discharging substantially all of the material passing down through the at least one soil crumbling assembly onto an at least one further soil sieving conveyor.

Material delivered rearwardly from the at least one soil crumbling assembly may also be discharged on to the at least one further soil sieving conveyor. However, in an alternative, a barrier may be formed to encourage material to pass down through the soil crumbling assembly.

Activating the first soil sieving conveyor both transfers material to the soil crumbling assembly and sieves the material, such that material below a size defined by sieving spaces of the conveyor passes down through the conveyor. It will be understood that the further conveyor carries out a similar sieving operation.

According to a fifth aspect of the present invention, there is provided a stone and clod separator, soil cultivator having a frame which is pulled forwardly in order to dig up soil via a share blade and a conveyor roller which transfers material rearwardly to the soil sieving conveyor, soil crumbling means down stream of sieving conveyor, and a further soil sieving conveyor positioned to accept all material passing down through and delivered rearwardly from the soil crumbling means.

The soil conveyor, the soil crumbling means and the further soil sieving conveyor may each consist of a series of star wheel rotatable members. The soil sieving conveyor and the further soil sieving conveyor may both consist of a web type soil sieving conveyor.

According to a sixth aspect of the present invention, there is provided a stone and clod separator comprising:

• a digging device;
• a first soil sieving conveyor for carrying out a first sieving action on soil dug up by the digging device and
• transferred rearwardly, relative to a direction of
• travel, to the first soil sieving conveyor; and
• at least one further soil sieving conveyor positioned to receive material passing downwardly through the first soil sieving conveyor, for carrying out a further sieving action on the soil.

The soil sieving conveyors act, in use, to sieve out and thus separate stones/clods from soil dug up by the digging device.

The first and further soil sieving conveyors may define respective soil sieving spaces, and the dimensions of the soil sieving spaces of the first soil sieving conveyor may be larger than the dimensions of the soil sieving spaces of the further soil sieving conveyor.

One or both of the soil sieving conveyors may comprise a plurality of arrays of spaced star wheels, or one or both of the soil sieving conveyors may comprise a web defining a plurality of discharge apertures, the web taking the form of an endless belt.

The at least one further soil sieving conveyor may also be positioned to receive substantially all of the material delivered rearwardly from the first soil sieving conveyor.

The further soil sieving conveyor may be positioned such that a substantial part of the further conveyor overlaps the first conveyor. In this fashion, a large part of the material sieved by the first conveyor may fall on to the further conveyor, where the material may be further sieved.

The separator may comprise the first soil sieving conveyor; a second soil sieving conveyor positioned to receive material passing downwardly through the first soil sieving conveyor, for carrying out a second sieving action on the soil; and a third soil sieving conveyor positioned to receive material passing downwardly through the second soil sieving conveyor, for carrying out a third sieving action on the soil. The second and third soil sieving conveyors may define respective soil sieving spaces, and the dimensions of the soil sieving spaces of the second soil sieving conveyor may be larger than the dimensions of the soil sieving spaces of the third soil sieving conveyor. The third soil sieving conveyor may be positioned such that a substantial part of the third conveyor overlaps the second conveyor. In this fashion, a large part of the material sieved by the second conveyor may fall on to the third conveyor, where the material may be further sieved.

According to a seventh aspect of the present invention, there is provided a method of separating stones and/or clods from soil, the method comprising the steps of:

• digging-up material from which stones and/or clods are to be separated and transferring the dug-up material on to a first soil sieving conveyor;
• activating the first soil sieving conveyor to carry out a first soil sieving action on the material;
• discharging at least part of the material passing down through the first soil sieving conveyor onto an at least one further soil sieving conveyor; and
• activating the further soil sieving conveyor to carry out a further soil sieving action on the material.

Stones and/or clods which are oversized and do not pass down through either the first or further soil sieving conveyors may be discharged from an end of the further conveyor, and may be collected for disposal or discharged into wheel ruts formed during the separating process.

Further features of the method of the seventh aspect of the invention may be derived from and with reference to the separator of the sixth aspect of the invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

• Figure 1 shows in diagrammatic side view a soil cultivator and stone/clod separator, in accordance with an embodiment of the present invention;
• Figure 2 shows in diagrammatic side view a soil cultivator and stone/clod separator, in accordance with an alternative embodiment of the present invention;
• Figure 3 shows in diagrammatic side view a soil cultivator and stone/clod separator, in accordance with a further alternative embodiment of the present invention; and
• Figure 4 shows in diagrammatic side view a stone and clod separator, in accordance with a further alternative embodiment of the present invention.

In Figure 1 a preferred embodiment of soil cultivator and stone/clod separator according to the invention is shown, and is designated generally by reference numeral 7. The soil cultivator and stone/clod separator 7 has a frame 6 which is pulled forwardly in the direction of arrow 8, in order to dig up soil via a share blade 1 and a conveying roller 2 which transfers material rearwardly to soil sieving conveyor 3, soil crumbling means 4 and a further soil sieving conveyor 5.

The sieving action of conveyor 3 allows fine soil particles and small clods to fall back to the ground and delivers oversize clods to the downstream soil crumbling means 4 to be broken down into further fine soil particles and small clods, which are then delivered onto the surface of the further soil sieving conveyor 5.

The soil sieving conveyor 3, the soil crumbling device 4 and the further soil sieving conveyor 5 each consist of a series of arrays of rotatable star wheel members 3a, 4a and 5a, respectively. The star wheel members 3a, 4a and 5a in each array are mounted spaced along respective shafts 14, 15 and 16, by which the star wheel members are driven and rotated. The rotatable members 4a of the soil crumbling device 4 have star wheels which, by design or spacing, in order to facilitate effective crumbling of oversize clods of soil, could not be used in the sieving conveyors 3 or 5 without allowing oversize material to fall back onto the ground. The background use of star wheel rotatable members for soil sieving and soil cultivation, and the construction and arrangement of such star wheel members, are described in detail in EP 0410808 and in EP 1332656, and the star wheel members in the soil sieving conveyors 3, 5 and the soil crumbling device 4 are constructed, arranged and operated in a similar fashion. Indeed, it will be understood that the star wheels 3a, 4a and 5a of the arrays 3, 4 and 5 are spaced along lengths of their respective shafts 14, 15 and 16 to define sieving spaces between the adjacent star wheels on the shafts, and the star wheels on the adjacent shafts. The dimensions of these sieving spaces, at least along the length of the shafts 14, 15 and 16, can be varied by mounting spacers (not shown) between adjacent star wheels on the shafts.

In more detail, material below a first size, defined by sieving spaces of the star wheels 3a of the soil sieving conveyor 3, is permitted to fall down through the star wheels 3a to the ground. Material larger than the first size is transferred along the conveyor 3 for discharge on to the soil crumbling device 4. During movement along the soil sieving conveyor 3, the action of the star wheels 3a tends to cause a reduction in the size of the material, breaking down the material such that portions fall down through the sieving spaces to the ground. This breaking-down action can result in the size of the material being reduced to a level sufficient for the material to enter the sieving spaces, passing down through the soil sieving conveyor 3 to the ground.

Any material remaining above the first size is, however, discharged on to the crumbling device 4. Material which is above the first size, but below a second size defined by sieving spaces of the star wheels 4a of the soil crumbling device 4, falls down into the sieving spaces and is crushed by resilient fingers of the star wheels 4a. The crushed material then falls down through the star wheels 4a on to the second soil sieving conveyor 5, which carries out a similar sieving action to the first conveyor 3.

Following working of the dug-up material using the conveyor 3, the crumbling device 4 and the second conveyor 5, a majority of the material has been finely crumbled and 'sieved', ready for planting. However, any large clods or hard items such as rocks or stones above a third size defined by an opening 17 of the star wheel members 4a is transferred along a length of the assembly, and discharged on to a lateral conveyor 18. The lateral conveyor 18 transports the material laterally and deposits it in ruts (not shown) made by wheels of the soil cultivator and stone/clod separator 7, into a collection area (not shown) on the cultivator/separator 7, or into a tractor trailer or the like.

It will be understood, however, that many soil clods above the second size will be broken down by the soil crumbling assembly 4 to a smaller size, through repeated impact of the fingers of the star wheels 4a against the clods. This will enable much of the large clod material to pass into the openings 17 and down through the soil crumbling assembly 4. Other, harder material above said third size, such as stones or rocks, will simply be discharged as described above.

A further embodiment of the invention is shown in Figure 2, designated generally by reference 11, and differs from the stone and clod separator 7 shown in Figure 1 in that the soil sieving conveyors 3 and 5, consisting of rotatable star wheel members, are replaced by web type soil sieving conveyors 9 and 10. The illustration of the cultivator/separator 11 has been simplified somewhat compared to Figure 1, and thus a lateral conveyor, like the conveyor 18, has been omitted, for ease of illustration.

Turning now to Figure 3, there is shown a combined soil cultivator and stone/clod separator in accordance with a further alternative embodiment of the present invention, the combined soil cultivator and stone/clod separator indicated generally by reference numeral 13. The cultivator/separator 13 is essentially of similar structure to the cultivator/separator 7 shown in Figure 1, with certain additional components. Like components of the cultivator/separator 13 with the cultivator/separator 7 share the same reference numerals, with the addition of the suffix '.

The cultivator/separator 13 includes a first soil sieving conveyor 3, and a first soil crumbling assembly 4. A second soil sieving conveyor 5 is positioned to receive material discharged from the soil crumbling assembly 4 and carries out a sieving action on the material, allowing fine soil particles and small clods to fall back to the ground and delivering oversize clods to a second, downstream soil crumbling assembly 4' to be broken down. The cultivator/ separator 13 also includes a third soil sieving conveyor 5', which is positioned to receive material discharged from the second soil crumbling assembly 4'. The third soil sieving conveyor 5' carries out a final sieving action on the material, allowing fine soil particles and small clods discharged from the second crumbling assembly 4' to fall back to the ground.

The sieving spaces of the star wheels in the first soil crumbling assembly 4 are larger than those of the second soil crumbling assembly 4', so that the first assembly 4 carries out an initial crumbling action, discharging broken-down material on to the second soil sieving conveyor 5, for sieving and transport of larger material to the second soil crumbling assembly 4' for further working. It will therefore be understood that the first soil crumbling assembly 4 carries out a rough crumbling of oversized material, and that the second soil crumbling assembly 4' carries out a finer crumbling. Providing the cultivator/separator 13 with two such soil crumbling assemblies 4 and 4' maximises the volume of material that can be processed to a desired degree in a single pass, and enhances the quality of the finished, worked soil surface. It will be understood, however, that the soil sieving spaces of the first and second soil crumbling assemblies 4 and 4' may be the same, such that the cultivator/separator simply carries out a double-crumbling action.

The cultivator/separator 13 optionally includes a barrier comprising a roller 12 provided above and downstream of the soil crumbling assembly 4, which is arranged to increase the residence time of oversized clods as they pass over the top of the star wheel members of the assembly 4. Similar barriers having rollers 12' and 12" , respectively, are optionally provided above and downstream of the second soil crumbling assembly 4' and the third soil sieving conveyor 5'. Barriers of this type are disclosed in the above European Patent publication 1332656.

Turning now to Figure 4, there is shown a stone and/or clod separator in accordance with a further alternative embodiment of the present invention, the separator indicated generally by reference numeral 19. The separator 19 has a first soil sieving conveyor 20, of similar construction to the conveyor 3 of the cultivator and stone/clod separator 7 shown in Figure 1. Indeed, like components of the separator 19 with the cultivator 7 share the same reference numerals. The conveyor 20 comprises a number of arrays of star wheels 21 and, in use, material dug up by a share blade 1 is transferred on to the conveyor 20 by a roller 2.

The separator 19 also includes a second soil sieving conveyor 23, which takes the form of a web type soil sieving conveyor similar to the conveyors 9 and 10 of Figure 2. The web conveyor 23 overlaps a large portion of the first, star wheel conveyor 20 such that a large portion of the material sieved by the first conveyor 20, passing down through sieving spaces of the conveyor 20, falls on to the web conveyor 23. Apertures (not shown) in an endless belt 24 of the conveyor 23 carry out a further sieving action on the material falling on to the conveyor 23. Typically, the apertures in the belt 24 will define sieving spaces of smaller dimensions than sieving spaces defined by the star wheel arrays of the conveyor 20. In this way, a finer sieving action is carried out on the material falling from the star wheel conveyor 20 on to the web conveyor 23. However, the sieving spaces of the star wheel conveyor 20 and the web conveyor 23 may be of similar dimensions.

Any stones or clods which are too large to fall down through the sieving spaces of the first conveyor 20 are discharged from an end 25 of the star wheel conveyor 20 on to the web conveyor 23, are carried along the web conveyor 23, and then discharged from an end 26 of the conveyor 23 on to a lateral conveyor 18, for collection or deposit into wheel ruts. However, it will be appreciated that transit of the material along the web conveyor 23 may further break-down the material, the broken-down material falling down through the sieving spaces to the ground.

The separator 19 is of particular utility with relatively clod-free soils, such as sandy soils, in which there is no or little requirement to break down heavy soil clods. The primary function of the separator 19 is, therefore, to separate out stones from soil.

In a variation on the separator 19, sieving spaces of the final four arrays of star wheels 21 adjacent the end 25 the conveyor 20 are larger than those defined by the remainder of the arrays of star wheels 21. This is achieved by spacing the star wheels 21 in these final four arrays farther apart along respective shafts 22 of the conveyor 20, using suitable spacers on the shafts 22. In this fashion, the sieving spaces of the final four arrays are sufficiently large such that the star wheels in these arrays act to crumble large clods transferred along the conveyor 20 from the end adjacent the share blade 1. This broken-up material then passes down through the larger sieving spaces and on to the web conveyor 23 for subsequent sieving. Any especially large clods/stones are passed over the end 25 on to the web conveyor 23, and then into the discharge conveyor 18.

In this fashion, an initial sieving of the large volumes of soil transferred on to the conveyor 20 by the roller 2 is carried out by the star wheel arrays defining the smaller sieving spaces. This has the effect of first sieving out significant volumes of finer material through the conveyor 20 on to the ground or on to the web conveyor 23. Accordingly, when the larger clods reach the star wheel arrays defining the larger sieving spaces, the fingers of the star wheels 21 in these arrays are better able to work on the clods, to break the clods down for subsequent sieving on the web conveyor 23. It will therefore be understood that, in this variation, a cultivator and stone/clod separator 19 is provided which essentially operates in a similar fashion to the cultivators/separators 7, 11 and 13. The essential difference is that the final four star wheel arrays define a soil crumbling device, and thus the first soil sieving conveyor and the soil crumbling device includes star wheels of similar shape.

Whilst the cultivator and stone/clod separator 19 is described as having larger sieving spaces in the final four star wheel arrays, it will be appreciated that a larger or smaller number of arrays may have these larger spaces, depending upon factors including overall dimensions of the cultivator and stone/clod separator and the number of star wheel arrays.

Various modifications may be made to the foregoing without departing from the spirit and scope of the present invention.

For example, one or more of the above described features of the cultivators/separators 7, 11, 13 and/or 19 may be provided in combination in modifications to the cultivators/separators, or in further alternative embodiments. Thus, by way of example, the cultivator/separator 7 may include a roller like the roller 12 shown in Figure 3; or one of the soil sieving conveyors 3, 5 or 5' may be replaced with a web like the web 9 shown in Figure 2. In a further variation on the separator 19, the web conveyor 23 may be replaced with a star wheel type conveyor, such as the conveyor 20.