BACKGROUND OF THE INVENTION Traditional methods of ploughing a field before seeding involve the use of a cultivator machine to turn over the entire top layer of soil. In recent years it has been found that, in order to prevent soil erosion and to obtain higher crop yields, there should be minimal soil disturbances during both the ploughing operation and the seeding operation. Several tillage devices have been designed with this object in mind. In particular, press wheels mounted one behind each tyne on tillage and seeding devices are intended to close over furrows containing seeds with minimal disturbance and press firmly down onto the soil compacting the grain underneath as soil to grain contact is important for a good crop yield. Grains sown in crumbly and cloddy soil will not germinate until the next rain, by which time the grain may have turned mouldy and has to be re-sown. For this reason the use of press wheels has become popular for compacting grain under soil ensuring grain to soil contact.

However, particularly in wet conditions and with certain types of soil, known press wheels, comprising a solid flat metal or rubber wheel, become clogged with mud and trash, that is, straw and crop waste. Consequently, instead of pressing the furrow downwardly to cover the seeds, the press wheel gouges into the soil and more mud and trash collects about the press wheel leaving clods of soil and exposed seeds. Furthermore, some known rubber press wheels leave deep furrows with smooth firm bases behind each tyne. This is known to contribute to water erosion

in fields which is detrimental to crops.

Ploughing a field also commonly involves evenly levelling the ground with a levelling harrow. For good crop germination the soil should be tined and broken up as much as possible as crops do not grow in clods of soil.

Levelling harrows consist of a row of long bent teeth that are dragged across a field to level it out. Similar to the problems with traditional press wheels, the harrow teeth collect mud and trash clogging up the harrow resulting in clods, uneven levelling of the ground and a reduced crop yield.

The aim of the present invention is to provide a wheel that can be used successfully in agriculture in any soil conditions and in a variety of soil types.

SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a cultivating wheel for drawing over ground comprising a helical coil having a first end, a second end and at least two windings therebetween; and an attachment means for mounting the first end onto a shaft having a longitudinal axis, the wheel being adapted to rotate about the longitudinal axis; wherein the coil has sufficient flexibility to allow relative movement between the windings when the wheel is made to run over ground.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings in which : Figure 1 is a side view of a cultivating wheel in

accordance with a first embodiment of the present invention; Figure 2 is an end view of the cultivating wheel shown in Figure 1; Figure 3 is a side view of a cultivating wheel in accordance with a second embodiment of the invention; Figure 4 is an end view of the cultivating wheel shown in Figure 3; and Figure 5 is a perspective view of a number of cultivating wheels mounted on an agriculture frame.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF INVENTION The cultivating wheel 10 of the present invention is illustrated in Figures 1 to 5 and is designed to be mounted on a cultivating machine and drawn over ground.

Depending on the manner in which it is used, the cultivating wheel can be suitably used as an agricultural press wheel or as a substitute for a levelling harrow.

When used as a press wheel the cultivating wheel travels behind a share mounted on a tyne of a cultivator machine.

The wheel rotates in line with the direction of travel of the cultivator, that is, about an axis perpendicular to the direction of travel. In this manner the cultivating wheel closes and presses down on the furrow formed by the cultivator share. As a levelling harrow, the cultivating wheel is mounted on an angle to the direction of travel so as to not bite the ground as deeply as when used as a press wheel, but rather to simultaneously drag and rotate over the ground covering a wider area thereby levelling the soil.

Figure 1 shows a first embodiment of a cultivating wheel 10 which can be secured to a wheel support frame 44 as illustrated in figure 5. The cultivating wheel 10 comprises a hub 12 which is mounted on bearings for rotational movement about a shaft 14.

Shaft 14 together with support 15 and vertical support arm 15a form part of the wheel support frame that is attached to the agriculture machine. The vertical arms 15a of the support frame may be spring loaded to give the frame suspension as the wheels travel over the ground.

A helical coil 16 is secured to the hub 12 so that the longitudinal axis of the helical coil 16 is parallel with the longitudinal axis of the shaft 14. The helical coil 16 is substantially a continuous, cylindrical helical spring having a free end 25 and a fixed end 27 secured to the hub by means of a plate 18 and threaded connectors 20. The plate 18 is formed as a disc and is made of metal. A fixed terminal winding 22 of the helical coil 16 is held between the plate 18 and the end face 24 of the hub 12. Threaded connectors 20 pass through the plate 18 and the hub 12 to secure the terminal winding 22 to the hub 12. The free terminal winding 26 at the free end 25 of the helical coil 16 is not secured and is free to move. Coil 16 is axially flexible or spring-like such that the free terminal winding 26 is capable of moving axially relative to fixed terminal winding 22. As the cultivating wheel rotates over ground portions of the windings reciprocally move together then separate.

Particularly with furrows, as corresponding portions of the windings come into contact with the ground the portions move closer together narrowing the gaps between the windings. Whilst the windings do not necessarily make contact, they do substantially simulate a single solid press wheel when in contact with the ground. The coming together of the windings evenly compacts the soils in the seeded furrows. Upon leaving contact with the ground the windings separate thus flicking any mud build up off the coil and rotate around once again. The winding portions are therefore constantly moving relative to one another thereby dislodging any mud build up on the wheel.

The helical coil 16 is preferably made of spring steel thereby providing the wheel with the flexibility required for relative movement of the windings. In the first embodiment the maximum outer diameter of the main windings 28 of the coil 16 is greater than the outer diameter of the hub 12. The diameter of the windings decrease such that the outer diameter of the fixed winding 22 secured to the hub 12 is less than the outer diameter of the plate 18.

Preferably the helical coil 16 has at least two or three main windings 28 of equal outer diameter. When pressing furrows these main windings 28 apply a force to the soil to close over the furrow in the soil made during the seeding operation and to also press the soil downwardly. The relative movement between the windings ensures the wheel does not become clogged with trash in dry conditions or trash and mud in wet conditions.

In the interest of keeping manufacture of the wheel simple and economical, the coil in the preferred embodiments is a continuous coil. However, it is reasonably foreseeable that the inventive concept of the cultivating wheel could be embodied in a discontinuous coil. For example, the coil could be broken so as to have separate windings or be interrupted with connecting members between the windings, provided some relative movement between the windings is still achievable.

Figures 3 and 4 illustrate a second embodiment of the cultivating wheel 10. Similar to the first embodiment, the second embodiment of the cultivating wheel is also a cylindrical helical coil having main windings 28 but has different attachment means to the shaft 14. The attachment means comprises a centre hub 30 directly clamped onto the shaft and fixed with locking bolts 32 to rotate with the shaft. The shaft 14 is mounted on sealed

bearings 34 for rotational movement on a support arm 35 of the support frame 44 (see figure 5) trailing the agriculture machine. The shaft is designed to carry a series of wheels. The fixed terminal winding 22 of the wheel 10 is fixed to hub 30 by way of a clamp plate assembly 36. In this embodiment, the coil cannot be welded to the hub because it is made of spring steel.

Aside from clamping, any other suitable means of fixing the coil to the hub can be employed. Clamp plate assembly 36 comprises a first plate (not shown) moulded adjacent to the centre hub 30 and extending radially of the hub. A second cover plate (not shown) is removably clamped to the first plate with through-bolts 38. A side aperture 39 in the clamp plate assembly 36 allows the end 40 of the terminal winding 22, which is hooked, to be received in the clamp plate assembly and fixed there by clamping.

Figure 4 illustrates the hooked end 40 in ghost line.

Hooked end 40 hooks around at least one of the through bolts 38 to prevent the end of terminal winding 22 from sliding out of the clamp plate assembly 36 during use.

The hub and clamp plate assembly is formed from cast iron.

As mentioned above, the windings of the second embodiment of the cultivating wheel are also manufactured from spring steel which gives the wheel the sideways spring or flexing quality required for it to work effectively. However, it is understood that other materials, such as mild steel, or other coil constructions may be employed provided some relative movement between the coil windings is achievable. Although annular-shaped windings are the most ideal, the present wheel would operate satisfactorily with other shapes, for instance, with octagon or decagon-shaped windings. It is also foreseeable that to maintain the structural integrity of the coil windings, the wheel may include spokes extending from hub 30 to the inner circumference of the windings.

This prevents distortion of the annular cultivating wheel

without inhibiting the relative sideways movement of the windings. Hub 30 may be extended axially through the coil windings to support multiple spokes extending radially around the wheels.

In stony conditions or when turning corners the forces acting on the cultivating wheel can cause the free terminal winding 26 to overlap the winding adjacent to it and remain caught. This restricted movement of the windings can affect the overall performance of the cultivating wheel. The size of the windings and gauge of the steel material are such that effort is required to return the terminal winding to its proper position.

Overlapping can be avoided by several means. A small tab welded towards the free end 25 and extending radially inwards of the coil will prevent the free winding 26 from overlapping adjacent winding 28. Alternatively, and an illustrated in Figures 3 and 4, the end 42 of free terminal winding 26 is bent inwards towards hub 30 forming a hooked end that will abut against the adjacent winding thereby preventing any overlap.

Embodiments of the present cultivating wheel may differ in the number of main windings depending on the purpose of the wheel and the desired effect. For example, a cultivating wheel with only two main coils forms a narrower and deeper press into the soil. As a general rule, the fewer number of coils the deeper the wheel is able to push into the soil. A deeper press is particularly suitable in wet soil conditions.

Consequently, a wheel with a larger number of windings is more suited to dry soil.

In the examples shown, a first end 27 of the cultivating wheel is fixed whilst the second end 25 is free to move. This is a simple construction because it allows relative movement between the windings and is

economical to produce. However, relative movement may be achieved by partly fixing or fully fixing the second end.

For example, the second end could be secured to a second hub mounted on the shaft but which hub is capable of sliding longitudinally along the shaft so as to not inhibit relative movement of the windings. Therefore, whilst the second end is secured to the shaft, it is effectively still free to move relative to the first fixed hub 12 or 30. This arrangement, whilst more involved than the free end construction, is an attractive alternative because the restrained second end provides stability to the wheel and also prevents the free terminal winding 26 from overlapping with the adjacent winding. Fully fixing the second end so that it does not slide along the shaft can be done when the cultivating wheel comprises a greater number of windings 28, for instance, five, six or more windings. The wheel can still operate effectively even though both terminal windings are secured to the shaft because the middle windings are capable of moving relative to one another.

In muddy conditions mud collects on the windings of the coil. As only the terminal winding 22 in the preferred embodiments is fixed to the hub 12 or 30 the main windings 28 are freely responsive to the ground travelled over and therefore the coil has a tendency to compress and expand, and to bounce up and down. This movement flicks mud and soil on the windings 28 off the helical coil 16. Soil and trash that would normally accumulate in large clumps on a traditional press wheel is flicked off as a result of the constant separation of the windings as they leave the furrow. When the cultivating wheel is mounted on an angle for levelling ground, the flexible relative movement of the windings moves the mud inside the helical coil 16 so that it passes out of the windings and through the end of the coil adjacent the terminal winding 26 as the wheel simultaneously drags and

revolves over the ground. The build up of mud and trash is avoided by the constantly moving windings.

Running cultivating wheels on an angle for levelling ground involves mounting cultivating wheels at an angle to the direction of travel of the agriculture machine. As illustrated in figure 5, the wheels are mounted on a shaft 14 that is itself mounted on sealed bearings on a wheel support frame 44 at the rear of the machine. Wheel frame 44 is pivotally mounted at pivot pin 50 to a rear axle 46 on the machine. The angle of frame 44 relative to the direction of travel, indicated by Arrow A, is fixed by a tightening bolt 47 at the pivot mounting between frame 44 and rear axle 46. Bolt 47 is dropped into one of the holes 48 provided on mounting bracket 49 on frame 44 and extends through a corresponding hole an axle 46. Bolt 47 fixes the angle of turn of frame 44 relative to rear axle 46. The angle of turn on wheel frame 44 is between 0° and 70° and normally between 30° and 40°. To level a field a machine travelling in the direction of Arrow A pulls behind it wheel support frame 44 fixed at a desired angle to the direction of travel.

The shaft 14 is therefore also angled and the cultivating wheels rotate about the longitudinal axis of the shaft.

As the angled wheels are pulled by the machine they rotate around the axis of the shaft and are simultaneously dragged in the direction of travel. Rather than running deep in a straight line as in the furrow pressing operation, the angled wheels run shallow covering more ground and thereby flattening clods and generally levelling the ground. The bite on the cultivating wheels is less deep when they are at an angle than with straight in-line rotation. The coil windings in the levelling operation oscillate relative to one another thereby preventing the build up of mud, straw and the like on the wheels. The cultivating wheels are therefore able to function cleanly and effectively in levelling the ground

for long periods and without need for maintenance.

The cultivating wheel of the present invention is able to run clean whilst pressing furrows or levelling fields owing to the flexing motion of the coil. With regular press wheels or levelling harrows, the build up of trash and mud creates blockages on the wheel which consequently transfer to blockages and clumps in the field. Crop yields fare better in evenly tilled fields and firmly pressed furrows. The present cultivating wheel dramatically reduces the trash and mud build up on the wheels. The resulting evenly level field provides a good base for smoothly planting seeds. As a pressing device the cultivating wheel packs the soil into the ground, breaks clogs and leaves a layer of tilth above the grain.

This has been found to yield better and earlier crops owing to the better soil to grain contact in the pressed furrow.

The dual purpose of the cultivating wheel both as a press wheel and a substitute for the conventional levelling harrow, lends the present cultivating wheel to be a very useful, simple and relatively inexpensive agricultural implement.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention.

For the purpose of this specification the words "comprising","comprise"or"comprises"are understood to mean the inclusion of a feature but not exclusion of any other feature.