GB2183132A - Soil preparation machines - Google Patents

Abstract

A cultivator tine 25 has an upper inclined portion 23 constrained by guide rollers 14 and 15 to allow soil- induced movement of the tine substantially only along an inclined rectilinear path. In variations of this design, the resilient block 30, which counteracts upward movement of the tine, is replaced by an hour-glass shaped resilient block (67, Fig. 5) or by tension springs (50, Fig. 3). Alternatively, the tine is reciprocated along the path by a driven cam (75, Fig. 6). Also disclosed (Figs. 7-12) are machines having supports pivotally mounted on the machine frames, each support carrying a plurality of fines and being pivoted by a drive mechanism to effect substantially vertical oscillation of the tines. <IMAGE>

Description

SPECIFICATION Soil preparation machines The present invention relates to cultivators, harrows and like soil-preparation machines.

The advantages of providing cultivator shares with a component of motion additional to that corresponding solely to the forward motion of the cultivator over the ground are well known. These advantages include damage protection, enhanced soil shatter, draught reduction and reduced risk of blockages, especially in the presence in the soil (or on the surface) of appreciable quantities of long organic materials.

This additional movement of the share can be soil-induced when the share-carrying tines are resiliently mounted or when the whole or part of each tine is made of a spring material.

Alternatively, it can be achieved by vibrating the shares with a mechanical or hydraulic drive, the tines generally, but not always, then being pivotally mounted, usually at a point offset from their centre lines.

Normally, as a share moves horizontally through the soil with the forward motion of the machine, the soil resistance to yielding that it encounters will increase up to a peak value, when suddenly a relatively large volume of soil breaks out, often in the form of big aggregates or clods, to release the share from its load. Soil-induced or activated tine movement of the type discussed above in the vertical plane can reduce the forces imposed on the share in these circumstances and also the frequency of break-out, thereby leading to lower draught and smaller clods. Machines using this principle are well known and in widespread use e.g. spring-tine cultivators and harrows and machines having spring-loaded tine mountings.

Soil-preparation machines are also known in which the tines are mechanically or hydraulically oscillated, mainly in the horizontal plane as are machines using parallelogram suspensions for the share of a deep-loosening tine and for individual tine assemblies.

Further information on at least some of the systems referred to above may be had from the German publication 'Bodenbearbeitung' by H. Schulte-Karring, KTBL-Arbeitsblatt number 203, 1983.

Disadvantages of the machines so far described include variations in the depth of cultivation and in the draught of the implement.

Moreover, in those designs using only horizontal or vertical share movement, slip occurs at the soil/share interface and this leads to unnecessary wear and waste of energy. A more recent innovation has been a deep soil loosener in which the tines are optionally vibrated by a heavy eccentric weight driven from the tractor power take-off, for example.

This latter machine additionally suffers from two further defects; firstly, that provision made to limit the movement of the tines to the vertical plane cannot be totally effective, so that some lateral movement of the tines in the soil is unavoidable and, secondly, that all the tines are moved in unison and the draught requirement of the machine fluctuates with the position of the tines.

The present invention stems from the discovery that in the reduction of draught and the successive propagation of cracks, particularly in hard soils, a combination of horizontal fore and aft and vertical share movement is important and if horizontal fore and aft and vertical share movement can be made to take place simultaneously, this can enable a no-slip situation to be established at the share/soil interface which leads to reduction of wear and a much greater efficiency of energy use.

According to the present invention, a cultivator, harrow or like soil-preparation machine comprises one or more soil-working tines and constraining means effective during operation of the machine to constrain at least the share portion of the or each tine to follow a substantially rectilinear path inclined to both the horizontal and the vertical in a vertical plane containing the direction of forward motion of the machine.

Conveniently, the angle of inclination subtended by the linear path to the horizontal is between about 40 and about 10 , a value of 11-1/2 currently being preferred.

Conveniently, the or each tine conprises at least a section of the shank inclined at said angle of inclination and engaged by fixed-position guide elements. The tine can, for example, continue into the soil at the same or a slightly different angle of inclination to that of the guided section, or it can be cranked.

Conveniently, the guide elements include one or more rotary members in engagement with the adjacent inclined surfaces of the tine section.

Conveniently, the rotary members comprise two rollers disposed to engage opposite inclined faces of the tine section and also spaced apart in the length direction of said section with the top-most roller located further from the tine share than is the bottom-most roller.

Conveniently, each roller is supported on an associated link member spanning the top section of the tine.

Conveniently, the machine includes a stop means adapted to be engaged by the lower inclined surface of the tine section at least in the event that the tine is engaged with the ground during a reverse motion of the machine.

Conveniently, the rotary elements comprise a first pair of guide elements, a second pair of guide elements also being provided so as to have one of each pair of guide elements engaging each side of the tine section.

Conveniently, the second pair of guide elements are rotary elements.

Conveniently, the rotation axes of all the rotary elements are spaced apart along the length direction of the inclined section of the tine.

Conveniently, the or at least one of the rotary members is circumferentially recessed to accommodate the inclined section of the tine and thereby reduce or substantially prevent any undesired lateral movement of the tine which might otherwise take place.

Conveniently, the machine includes clamping means whereby the tine and its constraining members can be clamped to a cross-bar support of the machine.

Conveniently, upward inclined movement of the or each tine is soil-induced, the machine including biassing means operative to resist this upward movement and to urge the or each tine back down the inclined path towards its previous position.

Conveniently, the biassing means is provided by a fixed-position block or blocks of resilient material which is compressed, or further compressed, by the upward inclined movement of the or each tine.

Conveniently, the or each block presents, or together present, a mass of resilient material which diverges in a generally upwards direction parallel to the length dimension of the inclined section of the tine.

Alternatively, the or each block may present, or together present, a mass of resilient material comprising first and second cone portions disposed in a generally hour-glass configuration about a common axis lying generally parallel to the length dimension of the inclined top section of the tine.

In alternative arrangements, the biassing means is provided by a fixed-position spring which is strained, or further strained, by the upward movement of the or each tine.

Conveniently, the machine includes a backstop for the resilient block of spring, as the case may be, and adjustment means for varying the position of the back-stop to adjust the biassing forces exerted on the tine or tines by the resilient block or spring.

In alternative embodiments, instead of having the tine movement soil-induced, drive means are included for driving the tine in said upward inclined movement, either directly or through a support for the tine.

Conveniently, the drive means comprises a rotating cam engaging cam-following surfaces provided by the tine or by its support.

Alternatively, the drive means may comprise an eccentric operating through a connecting rod attached at its other end with the tine or its support.

Conveniently, there are a plurality of tines and the drive means operates to stagger the motion of the different tines or groups of tines so as substantially to avoid or significantly to reduce variations in the draught requirement of the machine.

According to another aspect of the invention, a cultivator, harrow or like soil-preparation machine comprises one or more soilworking tines and constraining means effective during operation of the machine to constrain at least the share portion of the or each tine to follow a substantially vertical path, the tines being arranged as groups of counter-reciprocating tines at the fore and aft ends of a conmon pivoted support for the tines.

Conveniently, the support is pivoted midway between two groups of tines.

Alternatively, the support may be pivoted nearer a first one of two tine groups whereby in operation of the machine the tines of said first tine group are driven into the ground to a lesser amount than the tines of the other of the two tine groups.

As an alternative, the tines might be arranged as groups of counter-reciprocating tine at the fore and aft ends of a common linkagetype support for the tines dimensioned so that in operation of the machine the tines of a first one of the tine groups are driven into the ground to a lesser amount than the tines of the other one of said tine groups.

Conveniently, where first and second groups of tines are present, then the first tine group leads a second tine group during forward motion of the machine.

In a further alternative, the tines may be arranged as two groups of counter-reciprocating tines at the fore and aft ends of a comnon parallelogram-linkage support for the tines.

In one arrangement, the tines are arranged in four groups with the tines of the leading two groups at the fore and aft ends of a first common support for these leading two groups, and the tines of the trailing two groups at the fore and aft ends of a second common support for these trailing two groups.

Conveniently, in this case, the tines of one of the two groups are shorter and/or are driven into the ground to a lesser amount than the tines of the other of the two groups.

Conveniently, the said one group of tines leads the said other group of tines during forward motion of the machine.

In its broadest aspect, the invention also extends to any of the features herein described, or their equivalents, either alone or in any novel selection or combination.

It is an advantage of machines according to the present invention that they allow individual tines, or rows of tines, to be arranged so that they will yield automaticallly at pre-set levels to the build-up of soil resistance. Alternatively, driven movement may be provided so that vertical movement is combined with forward movement at variable frequency and, optionally, amplitude.

Embodiments of the invention will now be described, by way of example only, with refer ence to the accompanying drawings in which Figures 1-6 relate to tines adapted to be driven along an inclined rectilinear path while Figures 7-12 depict cultivators in which the whole or part of the tine bar assemblies are driven up and down in a substantially vertical motion relative to at least one fixed-position frame member.In more detail: Figures 1, la and 2 are respectively schematic side, front and plan views of a first design of tine mounting; Figures 3 and 3a are respectively schematic side and back views of a second design of tine mounting; Figures 4 and 5 are schematic side views of alternative tine mountings to those depicted in Figures 1 to 3a; Figure 6 is a schematic side view of the upper part of a tine showing part of a convenient drive system for the tine; Figures 7 and 8 are respectively schematic cross-sectional side and plan views of a cultivator showing a quite different way of mounting the tines; Figure 9 is a schematic plan view of an alternative form of drive system to that shown in Figure 6; and Figures 10 and 10a are side and end views, and Figures 11 and 12 schematic side views of three further forns of cultivator according to the present invention.

Thus referring first to Figures 1, 1 a and 2, reference numeral 10 indicates a soil-actuated tine and share assembly attached to one side of a flat support member 12. Cantilevered out from and secured to the latter are an upper and a lower idling roller 14,15 and each is joined by a connecting link 17,18 to a securing bolt 20,21 on the opposite side of the upper, cranked section 23 of the cultivator tine 25. Loose collars 27,28 around the centre section of each securing bolt 20,21 protect against wear and reduce friction should the cultivator be reversed with the tine in or on the ground. Reference numeral 30 indicates a large upwardly divergent block of resilient material supported above by a strong bracket 31 which is secured to the support member 12.

A lip (not shown) at the top of the tine assembly 10 above the upper connecting link 17 prevents the leg from falling out of the mounting arrangement when the cultivator is lifted.

In normal work, the cultivator is pulled from left to right as viewed in the illustration, so thåt the soil resistance urges the upper, cranked portion 23 of the cultivator tine against the two idling rollers 14,15. With increasing soil resistance, the tine 25 is forced rearwards against the resistance of the resilient block 30 along an inclined rectilinear path set by the positions of the rollers 14,15.

The upwardly divergent shape of the block 30 means that its resistance to deformation is graduated and will change smoothly from relatively low values when the tine displacement can be wholly accommodated by compression of the narrower lower section ofthe block 30 to relatively high values when the tine displacement is such as also to require compression of the wide upper sections of the block.

Because small forces on the tine meet relatively little resistance from the block 30, the tine 25 will vibrate freely at relatively low amplitudes. However, larger forces will meet increased resistance from the block so that the tine vibrations are never allowed to become unacceptably large.

Optional adjustment of the pre-compression of the resilient block 30 allows the resistance to tine movement to be varied to suit the soil conditions. For example, for hard soils, the position of bracket 31 should be set to allow an upward share movement of up to 20 mm to be sure of forming a crack in the soil. In one such arrangement (not shown), the bracket 31 is screw-mounted and the position of the bracket is set by threaded nuts holding the bracket 31 against the resilience of the block 30.

The relative positions of the two large rollers .14,15 and the inclination of the upper tine portion 23, together determine the ratio of the rearward component of the tine movement to its upward component. Desirably the angle of inclination 32 should not exceed about 40 and values of down to about 10 are thought best, a value of 11-1/2 currently being preferred.

As with all the embodiments and variations described with reference to the accompanying drawings, features of any one or more of the designs may, where convenient, be incorporated into any one or more other such designs e.g. in some cases to replace corresponding features appearing in these other designs.

Thus it should be noted, for instance, that the roller design of Figures 1 and la, may be varied so as to be as shown in some of the later embodiments, to avoid rubbing contact at the sides of the upper tine section.

Figure 2 shows in simplified plan view an example of a tractor-mounted cultivator with tine support bars of the kind needed for the suspension arrangement of Figures 1 and 1 a.

Turning now to Figures 3 and 4, these show embodiments in which the roller tine support is applied to the more conventional hollow-section mounting bar 39. Thus in the machine of Figure 3, a two-part clamping arrangement 35 is used to secure a bracket assembly 37 to the mounting bar 39, the rear part of the bracket having two plates 41,42 between which the tine support rollers 44,45 are sandwiched.

Should the cultivator be reversed when the tine is in contact with the ground, an upper locating roll (not shown) at the rear of the tine with optional loose collar in the centre cooperates with the face of the mounting bar 39 adjacent to the upper tine section to prevent the tine from becoming dislocated.

As will be seen, on both sides of the cultivator tine 25, the lower part of the clamping arrangement 35 is formed into a bracket 47 for supporting the lower ends of two tension springs 49,50 which engage at their upper ends with a lug 52 attached transversely across the upper end of the tine. The lug 52 also provides a stop to prevent the tine 25 from sliding out of its guides.

The rear view of the mounting arrangement shown in Figure 3a shows the rollers 44,45 shaped to locate the upper section of the tine centrally thereby to avoid frictional contact with the side plates.

The spring rate of the tension springs 49,50 determines the responsiveness of the tine to soil forces, and adjustment of tension is possible by means of the threaded nuts 55,56 at both ends of the springs.

Figure 4 shows in outline form only, an alternative rollertype tine mounting arrangement using four rollers identified by reference numerals 58 to 61. In this instance, it will be observed that the cultivator frame member comprising the mounting bar 39, is turned through 45" relative to the position shown in Figure 3.

Figure 5 illustrates a three-roller tine support system using rollers 63,64,65. This system is in some respects similar to that of Figure 3.

Resistance to upward tine movement is provided by a compression spring formed of two truncated rubber cones 67,68 threaded below a fixed bracket 70 over a tension bolt 71 attached to a lug 72 at the upper end of the tine.

As already indicated, instead of relying on soil-induced movement, the tines may instead be moved in the desired fashion by an appropriate drive. One such arrangement is shown in Figure 6 which illustrates, in outline from only, a drive mechanism suitable for any of the roller-guided cultivator tines 25 herein described. The drive comprises a shaft 74 with a cam 75 attached, passing through a suitably dimensioned and located aperture (or recess) 76 in the tine.

In an alternative design to that depicted in Figure 6, accommodation for the cam 75 may be provided at the end of the tine assembly or on the leading or trailing edges of the inclined section of the tine.

On a cultivator which carries a number of tines transversely aligned, it is possible for the driven shaft 74 to pass through appropriate apertures in each tine and for successive cams to be displaced angularly to each other so that any desired timing of the tine movement is achieved, thereby to avoid significant fluctuations in the draught requirement of the machine.

In the embodiments so far described with reference to the accompanying drawings, the tines are adapted to move along an inclined linear path in a vertical plane containing the direction of forward motion of the machine. In the embodiments described below, the tines continue to move in a vertical plane containing the direction of forward motion of the machine but now their motion in this plane will be substantially vertical.

Thus turning first to Figure 7, this shows in cross-sectional side view one such tractormounted cultivator consisting essentially of a central beam 77, optionally supported on land wheels 78, to which is rigidly attached forwardly a sub-frame 79 forming the tractor headstock and supporting a pto-driven gearbox 80 and eccentric drive 81. Pivotally attached to strong, downward pointing lugs from the optionally wheel-supported main beam 77 are two channel-section or other strong longitudinally arranged members 83,84 which, together with pivoted front and rear tine mounting bars 86,87, form a pivoted cradle.

A fixed, rigid member 91 extending centrally upwards from the main beam forms the pivot for two arms 93,94, as shown in Figure 8.

These extend forwardly and rearwardly to link up pivotally with vertical extensions 96,97 attached rigidly to the front and rear pivoted tine-mounting bars 86,87 shown in Figure 8.

In this way, a parallelogram is formed, with the cultivator tines effectively becoming extensions of the vertical members 96,97. The eccentric drive 81 is connected to the front upright link or links 96 of the parallelogram.

In operation, when the front row of tines is lifted by the eccentric drive 81, the rear row of tines is forced down, and vice versa. It can be calculated that at a forward speed of 5 km/h and standard pto speed, each row of tines is lifted every 150 mm. If the output speed from the gearbox 80 to the eccentric drive is doubled, the amplitude can be halved if the tractor continues to move at the same speed or the amplitude can be maintained if the tractor speed is increased to 10 km/h.

Figure 8 shows a plan view of the embodiment shown in Figure 7 but with the central member joining the centre pillar 91 to the headstock partly cut away. It should be remembered that the construction disclosed in Figures 7 and 8 is by way of example only. A trailed cultivator may have, for example, a second fixed-position beam forward of the front tine bar and linked with the optionally wheel-supported beam 77 by rigid members to form a main frame.

Figure 9 shows details of the eccentric drive 81, illustrating in particular how the amplitude of vertical reciprocation may be changed by linking the connection rod 99 of the drive to holes 100 provided in the drive disc 101 at different distances from the centre of the drive disc.

Figures 10 and 10a show a similar but more simplified arrangement to that shown in Figure 7. In the Figure 10, 10a arrangement, the tine bars and longitudinal end plates 105,106 are rigidly joined together as a cradle with the end plates pivoted on the optionally wheel-supported centre beam 77. An eccentric drive 81 from the tractor mounting sub-frame 79 is connected to the front of the pivoted cradle to impart a rocking motion. This simplification of construction introduces a small degree of arcuate movement. For example if the foreand-aft spacing of the two rows of tines 25 is 1 m, then for a vertical share displacement of 50 mm the change in tine and share angle is only approximately +3.5 .

If the pivot 108 for the cradle is not centraly positioned between the two rows of tines, then differential reciprocatory movement may be achieved. For example it becomes possible to impart modest vertical tine movement to a front row of shallow-working tines and more pronounced movement to a set of deep-loosening tines following at the rear.

According to a preferred feature, cutting discs 110 are mounted on pivoted links 111 so as to operate on the surface region of the ground where soil heave will occur due to the lifting action of the share. As shown in Figure 10a, two or more such discs may be provided, preferably with an equal number on either side of the tine.

In the version shown, the discs 110 can, if necessary, ride up against the restraining action of a compression spring 112, a stop being provided to prevent the disc spindle from colliding with the tine in extreme circumstances. The stop might, for example, be provided by or on a rod passing through the centre of a coil spring.

In a variation (not shown), the spring 112 is omitted and the position of the discs is fixed.

The illustrated disc arrangement and its variation, may both be included for use with any of the other tine configurations appearing in the illustrated embodiments.

Figure 11 schematically shows an embodiment illustrating how optional variations in front and rear tine movement may be achieved simply by moving the pivot point for the cradle as well as for the steering arms of the parallelogram 113 which guarantee vertical share movement.

Figure 12 is a further application of the simplified drive system in which two cradles 114,115 are pivotally suspended from a main frame 117. In the embodiment of Figure 12 each rocking cradle has two rows of tines, and the drive amplitude may differ between front and rear. On each cradle the tine length and distance from the pivot may differ between the first and second row of tines.

Claims (43)

1. A cultivator, harrow or like soil-preparation machine comprising one or more soilworking tines and constraining means effective during operation of the machine to constrain at least the share portion of the or each tine to follow a substantially rectilinear path inclined to both the horizontal and the vertical in a vertical plane containing the direction of forward motion of the machine.

2. A machine as claimed in Claim 1 in which the angle of inclination subtended by the linear path to the horizontal is between about 40 and about 10 .

3. A machine as claimed in Claim 2 in which the angle of inclination is 11-1/2".

4. A machine as claimed in Claim 1 or Claim 2 in which the or each tine comprises at least a section inclined at said angle of inclination and engaged by fixed-position guide elements.

5. A machine as claimed in Claim 4 in which the guide elements include one or more rotary members in engagement with the adjacent inclined surfaces of the tine section.

6. A machine as claimed in Claim 5 in which the rotary members comprise two rollers disposed to engage opposite inclined faces of the tine section and also spaced apart in the length direction of said section with the top-most roller located further from the tine share than is the bottom-most roller.

7. A machine as claimed in Claim 6 in which each roller is supported on an associated link member spanning the top section of the tine.

8. A machine as claimed in Claim 6 or Claim 7 including a stop means adapted to be engaged by the lower inclined surface of the tine section at least in the event that the tine is engaged with the ground during a reverse motion of the machine.

9. A machine as claimed in Claim 5 or Claim 6 in which the rotary elements comprise a first pair of guide elements, a second pair of guide elements also being provided so as to have one of each pair of guide elements engaging each side of the tine section.

10. A machine as claimed in Claim 9 in which the second pair of guide elements are rotary elements.

11. A machine as claimed in Claim 10 in which the rotation axes of all the rotary elements are spaced apart along the length direction of the inclined section of the tine.

12. A machine as claimed in any of Claims 5 to 11 in which the or at least one of the rotary members is circumferentially recessed to accommodate the inclined section of the tine and thereby reduce or substantially prevent any undesired lateral movement of the tine which might otherwise take place.

13. A machine as claimed in any preceding claim comprising clamping means whereby the tine and its constraining members can be clamped to a cross-bar support of the ma chine.

14. A machine as claimed in any preceding claim in which upward inclined movement of the or each tine is soil-induced, the machine including biassing means operative to resist this upward movement and to urge the or each tine back down the inclined path towards its previous position.

15. A machine as claimed in Claim 14 in which the biassing means is provided by a fixed-position block or blocks of resilient material which is compressed, or further compressed, by the upward inclined movement of the or each tine.

16. A machine as claimed in Claim 15 when including - the limitations of Claim 4 in which the or each block presents, or together present, a mass of resilient material which diverges in a generally upwards direction parallel to the length dimension of the inclined section of the tine.

17. A machine as claimed in Claim 15 when including the limitations of Claim 4 in which the or each block presents, or together presents, a mass of resilient material comrpising first and second cone portions disposed in a generally hour-glass configuration about a common axis lying generally parallel to the length dimension of the inclined top section of the tine.

18. A machine as claimed in Claim 14 in which the biassing means is provided by a fixed-position spring which is strained, or further strained, by the upward movement of the or each tine.

19. A machine as claimed in any of Claims 14 to 17 including a back-stop for the resilient block of spring, as the case may be, and adjustment means for varying the position of the back-stop to adjust the biassing forces exerted on the tine or tines by the resilient block or spring.

20. A machine as claimed in any or Claims 1 to 13 including drive means for driving the tine in said upward inclined movement, either directly or through a support for the tine.

21. A machine as claimed in Claim 20 in which the drive means comprises a rotating cam engaging cam-following surfaces provided by the tine or by its support.

22. A machine as claimed in Claim 20 in which the drive means comprises an eccentric operating through a connecting rod attached at its other end with the tine or its support.

23. A machine as claimed in any of Claims 20 to 22 in which there are a plurality of tines and the drive means operates to stagger the motion of the different tines or groups of tines so as substantially to avoid or significantly to reduce variation in the draught requirement of the machine.

24. A cultivator, harrow or like soil-preparation machine comprising one or more soilworking tines and constraining means effective during operation of the machine to constrain at least the share portion of the or each tine to follow a substantially vertical path, the tines being arranged as groups of counterreciprocating tines at the fore and aft ends of a common pivoted support for the tines.

25. A machine as claimed in Claim 24 in which the support is pivoted mid-way between the groups of tines.

26. A machine as claimed in Claim 24 in which the support is pivoted nearer a first one of two tine groups whereby in operation of the machine the tines of said first tine group are driven into the ground to a lesser amount than the tines of the other of the two tine groups.

27. A cultivator, harrow or like soil-preparation machine comprising one or more soilworking tines and constraining means effective during operation of the machine to constrain at least the share portion of the or each tine to follow a substantially vertical path, the tines being arranged as groups of counter-reciprocating tine at the fore and aft ends of a common linkage-type support for the tines dimensioned so that in operation of the machine the tines of a first one of the tine groups are driven into the ground to a lesser anount than the tines of the other one of said tine groups.

28. A machine as claimed in Claim 26 or Claim 27 in which a first tine group leads a second tine group during forward motion of the machine.

29. A cultivator, harrow or like soil-preparation machine comprising one or more soilworking tines and constraining means effective during operation of the machine to constrain at least the share portion of the or each tine to follow a substantially vertical path, the tines being arranged as two groups of counter-reciprocating tines at the fore and aft ends of a common parallelogram-linkage support for the tines.

30. A cultivator, harrow or like soil-preparation machine comprising a plurality of soilworking tines and constraining means effective during operation of the machine to constrain at least the share portions of the tines to follow a substantially vertical path, the tines being arranged in four groups with the tines of the leading two groups at the fore and aft ends of a first common support for these leading two groups, and the tines of the trailing two groups at the fore and aft ends of a second common support for these trailing two groups.

31. A machine as claimed in Claim 30 in which the tines of one of the two groups are shorter and/or are driven into the ground to a lesser amount than the tines of the other of the two groups.

32. A machine as claimed in Claim 31 in which the said one group of tines leads the said other group of tines during forward motion of the machine.

33. A machine substantially as hereinbefore described with reference to Figures 1, 1 a and 2 of the accompanying drawings.

34. A machine substantially as hereinbefore described with reference to Figures 3 and 3a, of the accompanying drawings.

35. A machine substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

36. A machine substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

37. A machine substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.

38. A machine substantially as hereinbefore described with reference to Figures 7 and 8 of the accompanying drawings.

39. A machine substantially as hereinbefore described with reference to Figure 9 of the accompanying drawings.

40. A machine substantially as hereinbefore described with reference to Figure 10 of the accompanying drawings.

41. A machine substantially as hereinbefore described with reference to Figure 11 of the accompanying drawings.

42. A machine substantially as hereinbefore described with reference to Figure 12 of the accompanying drawings.

43. The features herein described, or their equivalents, either alone or in any novel selection or combination.