GB2132062A

GB2132062A - Soil cultivating implements

Info

Publication number: GB2132062A
Application number: GB08333093A
Authority: GB
Inventors: Der Lely Olaf Van
Original assignee: Texas Industries Inc
Current assignee: Texas Industries Inc
Priority date: 1982-12-20
Filing date: 1983-12-12
Publication date: 1984-07-04
Also published as: NL192496C; GB2132062B; JPS59118003A; FR2542563A1; GB8333093D0; DE3345774C2; IT1170013B; FR2542563B1; NL192496B; IT8324244A0; DE3345774A1; NL8204896A

Abstract

In a soil cultivating implement, such as a rotary harrow, of the kind which comprises a hollow frame portion 1 extending substantially horizontally perpendicular to the intended direction of operative travel of the implement and a plurality of soil working members 3 supported thereby so as to be rotatable about the axes of corresponding shafts 2, each member 3 is releasably securable to the lower end of the corresponding shaft 2 and comprises a carrier 4 having a central hub 6 and two diametrically opposed arm-like portions 5 radiating from the hub 6. Sleeve- like holders 10 for tines 12 comprise fastening portions 9 releasably securable to the lower surfaces of the carrier portions 5 by pairs of bolts 8 that lie at opposite sides of upper ribs 7 and lower ribs 11, each tine 12 being releasably securable in the corresponding holder 10. This construction allows a single form of carrier 4 to co-operate with different tine holders 10 or to co- operate directly with fastening portions of tines of other forms. An alternative form of tine holder and an alternative form of directly fastened tine are both described and illustrated. <IMAGE>

Description

SPECIFICATION Soil cultivating implements This invention relates to soil cultivating implements or machines, such as rotary harrows intended for the preparation of seedbeds, of the kind which comprise a frame portion movable over the ground and a plurality of soil working member that are rotatable about substantially vertical, or at least upwardly extending, axes, each such member including a carrier to which at least one soil working tool is directly or indirectly connected. The term "implement(s) or machine(s)" is shortened to "implement(s)" alone throughout the remainder of this document for the sake of brevity.

It is desirable that implements of this kind should be able to have their soil working tools quickly and easily replaced when worn or damaged and that they should be similarly replaceable by alternative tools to enable them to deal with differing soils, operating conditions and specific cultivating tasks.

Many known implements of the kind set forth are inadequate in these respects and the present invention seeks to overcome, or very significantly to reduce, these shortcomings. According to one aspect of the invention, there is provided a soil cultivating implementofthe kind set forth, wherein the or each tool of each soil working member is received in a holder which holder is releasably secured to the corresponding carrier.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a somewhat diagrammatic plan view of a soil cultivating implement in accordance with the invention shown connected to the rear of an argricultural tractor, Figure2 is a part-sectional view to an enlarged scale, the section being taken on the line il-ll in Figure 1, Figure 3 is a section taken on the line Ill-Ill in Figure 2, Figure 4 is an elevation as seen in the direction indicated by an arrow IV in Figure 3, Figure is part-sectional elevation to the same scale as Figures 2,3 and 4 but illustrates an alternative construction in accordance with the invention, Figure 6 is an elevation as seen in the direction indicated by an arrow VI in Figure 5, Figure 7 is a similar view to that of Figure 2 of the drawings but illustrates another alternative embodiment in accordance with the invention, and Figure 8 is a section taken on the line VIII-VIII in Figure 7.

Referring firstly to Figures 1 to 4 of the accompanying drawings, the soil cultivating implement that is illustrated in those Figures is in the form of a rotary harrow and comprises an elongate hollow frame portion 1 that extends substantially horizontally transverse and usually, as illustrated, substantially horizontally perpendicular, to the intended direction of operative travel of the implement that is indicated in Figure 1 by an arrow A.A plurality, of which there are twelve in the example that is being described, of substantially vertical, or at least up wardly extending, shafts 2 are rotatably journalled in bearings carried by upper and lower walls of the frame portion 1 (see Figure 2) so as to lie in a single row that is parallel to the transverse length of the hollow frame portion 1,the longitudinal axes/axes of rotation of the twelve shafts 2 being parallel to one another and being spaced apart at regular intervals which advantageously, but not essentially, each have a magnitude of substantially 25 cm. Each shaft 2 projects downwardly from beneath the bottom of the hollow frame portion 1 and is there provided with a corresponding soil working member that is generally indicated by the reference 3.Each soil working member3 comprises a substantially horizontally disposed support or carrier 4 having two arm-like portions 5 that project in substantially diametrically opposite directions from a central hub 6 of the carrier 4 which hub 6 has internal splines arranged to co-operate with matching external splines on a downwardly projecting portion of the corresponding shaft 2 to prevent the carrier 4 and the shaft 2 from being rotationally displaceable relative to one another.Axial displacement of each carrier 4 relative to the corresponding shaft 2 is prevented in a known manner that is not the subject of the present invention but which includes providing a screw-threaded lowermost end portion of each shaft 2 with a co-operating retaining nut that, when installed, is prevented from becoming loose by the provision of a split pin or the like entered through a transverse bore in the screw-threaded shaft portion and through aligned openings in the nut itself.

Each substantially horizontally extending arm-like portion 5 has a flat lower surface whereas the top thereof is provided with a substantially central upright rib 7 which extends lengthwise of the portion 5 concerned from the hub 6 to the outer end of that portion, each rib 7 being substantially regularly tapered from the hub 6 concerned to the outer end of the portion 5 above which it lies. This taper can be seen best in the plan view of Figure 3 of the drawings. Each rib 7 also decreases in its vertical extent considered from the hub 6 concerned to the outer end thereof and this feature can be seen best in Figure 2 of the drawings from which it will also be apparent that each rib 7 is rounded off at its radially outermost end so that the upper surface thereof meets the top of the corresponding portion 5 at the outer end of that portion 5.Each portion is formed, at opposite sides of the corresponding rib 7, with a hole through which the shank of a corresponding bolt 8 is entered (preferably upwardly, as illustrated) to secure a fastening portion 9 of a corresponding tine holder 10 to the arm-like portion 5 concerned. The upper ends of the two bolts 8 of each pair are, of course, provided with corresponding fastening nuts and may also carry washers or the like (not shown) designed to prevent the bolts 8 from working loose during the operation of the implement.The upper flat surface of the fastening portion 9 of each holder 10 is in contact with the lower flat surface of the corresponding arm-like portion 5 throughout the radial length of that portion 5, the radially inner end of the fastening portion 9 being of flat and straight configuration and bearing against a matching flat on an otherwise cylindrical portion of the hub 6 concerned. It will be realised that this portion of each hub 6 thus has two diametrically opposed flats whose surfaces contact the innerendsofthecorres- ponding fastening portions 9, each such contact surface being in substantially tangential relationship with an imaginary cylindrical surface whose longitudinal axis coincides with the longitudinal axis of the respective shaft 2.

The lower surface of each fastening portion 9 is provided with a corresponding centrally positioned rib 11 that extends radially with respect to the longitudinal axis of the corresponding shaft 2, said rib lying between the heads of the corresponding pair of fastening bolts 8 and progressively increasing in vertical extent from a rounded off inner end that adjoins the surface of the hub 6 concerned to an oppositely rounded off outer end that is integral with, or rigidly secured to, the outer surface of one of the tine holders 10.The fastening portion 9 of each sleeve-like tine holder 10 joins that holder 10, proper, at a horizontal level which is substantially mid-way between the top and the bottom of said holder 10 and it will be noted from Figures 2, 3 and 4 ofthe drawings that each tine holder 10 tapers relatively steeply upwardly from the level of the portion 9 and also tapers somewhat less steeply downwardly from that level at an angle which, as seen Figure 2 of the drawings, is relatively small but which, as seen in the direction of Figure 4 of the drawings is considerably greater.

Each substantially sleeve-like tine holder 10 receives a fastening portion of a corresponding rigid soil working tool in the form of a tine 12 and it will be seen from the drawings that each tine 12 also has a soil working portion that projects downwardly from the lower end of the fastening portion in a direction which trails rearwardly with respect to the intended direction of operative rotation B (Figures 1 and 3 of the drawings) of the corresponding soil working member 3. The upper end of the fastening portion of each tine 12 is screw-threaded and projects above the flat top of the holder 10 concerned where it co-operates with a retaining nut 13 which conveniently incorporates, or co-operates with, known means designed to prevent the nut 13 from working loose as the result of vibration during operation of the implement.Each tine holder 10 is provided, at the level of the upper surface of its fastening portion 9, with an upwardly inclined shield 14 that is at the front of said tine holder 10 with respect to the intended direction of operative rotation B of the soil working member 3 of which said holder 10 forms a part. The shields 14 lie in advance of the nuts 13 with respect to the direction B and thus tend to protect those nuts 13 from potentially damaging direct impacts against stones and other hard objects that may be met with in or on the ground when the implement is in use.The foot of each shield 14 is shaped to match the curvature of the corresponding holder 10 at the horizontal level at which it is integrally or rigidly secured to that holder 10 (see Figure 3) and the radially outermost obliquely upright edge of each shield 14 is slightly bevelled at the lower end thereof (see Figure 2) which lower end terminates at a point close to the longitudinal axis or centre line of the whole carrier 4 concerned. The two arm-like portions 5 of each carrier 4 are each provided at the front thereof, with respect to the corresponding intended direction of operative rotation B, with an upwardly and forwardly (relative to the same direction) inclined shield 16 whose radially outer end adjoins the matchingiy inclined and neighbouring shield 14 (see Figures 2 and 3).

However, each shield 16 has an upwardly inclined height which is only approximately three quarters of that of the immediately neighbouring shield 14, said shield 16 having an upper edge which is in substan tialiy parallel relationship with the longitudinal axis or centre line of the whole carrier 4, this edge being connected to a steep 90 bend with an edge which abuts against an edge of the neighbouring shield 14.

The opposite radially inner end of the upper edge of each shield 16 is connected by a substantially 135 bend to a substantially straight downwardly inclined edge whose lowermost radially inner end meets the corresponding arm-like portion 5 at a location in very close proximity to the hub 6. The shields 16 lie in advance of the nuts which co-operate with the bolts 8, with respect to the direction B, and thus tend to protect those nuts from direct collisions with potentially damaging stones and other hard objects in the same way as the shields 14 co-operate protectively with the nuts 13.

The opposite ends of the hollow frame portion 1 are closed by corresponding side plates 17 (Figure 1) which are substantially vertically parallel to one another and to the direction A. The fronts of the side plates 17, with respect to the direction A, carry substantially horizontally aligned pivot bolts or other strong pivots 18 about which arms 19 are upwardly and downwardlyturnable alongside the plates 17.

The arms 19 extend rearwardly from the pivots 18 with respect to the direction A and their rearmost ends lie well behind the hollow frame portion 1 considered in the direction A. The rearmost ends of the two arms 19 carry substantially horizontal bearings in which the opposite ends of an open-work, cage-formation ground roller 20 are rotatably journalled. The angular positions of the arms 19 about the axis defined by the pivots 18 can be changed, as may be required, by entering retaining members, such as bolts 21, in holes in the arms 19 themselves and chosen aligned holes in curved rows thereof that are formed in rear portions of the side plates 17 which project behind the frame portion 1 with respect to the direction A, the centres of curvature of these curved rows of holes being co-incident with the axis defined by the pivots 18. The holes that are chosen for co-operation with the bolts 21 or the like determine the level of the axis of rotation of the ground roller 20 relative to that of the frame portion 1 and the single row of soil working members 3 and thus the maximum depth to which the tines 12 of those soil working members 3 can penetrate into the ground when the implement is in use. The construction of the ground roller 20 is not the subject of the present invention but it will be seen from Figure 1 of the drawings that it comprises a central preferably tubular shaft to which a plurality of regularly spaced apart support plates are secured so as to be parallel to one another and substantially parallel to the direction A.Elongate elements of tubular or solid rod formation are entered through regularly spaced apart holes around the edges of the preferably circular support plates of the roller 20 and preferably, as illustrated, extend helically around the axis of rotation of that roller to define skeletally a cylindrical ground-engaging surface so that, during use of the implement, the roller 20 will act in its own right as a soil working member which will crush any stubborn lumps or clods or earth that have resisted crumbling by the immediately foregoing soil working members 3 as well as performing a gentle levelling and consolidating action upon the ground surface.

Each shaft 2 is provided, inside the hollow frame portion 1,with a corresponding straight- or spurtoothed pinion 22 which is of such a size that its teeth are in mesh with those of the or each immediately neighbouring pinion 22 in the single row thereof.

The shaft 2 which corresponds to one of the centre pair of soil working members 3 in the single row thereof has an upward extension through the top or cover plate of the hollow frame portion 1 into a gear box 23 that is mounted on top of said frame portion 1. Shafts and bevel pinions (not visible) inside the gear box 23 place the upward extension of the shaft 2 that has just been mentioned in driven connection with a rotary input shaft 25 of the gear box 23 whose leading splined or otherwise keyed end projects substantially horizontally forwards from the front of the gear box in substantially the direction A where it can be connected to the rear power take-off shaft of an agricultural tractor or other operating vehicle by way of a telescopic transmission shaft 26, which is of a construction that is known per se, having universal joints at its opposite ends.The back of the gear box 23, with respect to the direction A, is provided with a change-speed gear 24 whose construction is not the subject of the present invention. It suffices to say that the splined ends of two shafts project into the casing of the change-speed gear 24 and can cooperate with the internally splined hubs of cooperating pairs of toothed pin ions of different sizes.

These pairs of pinions can be interchanged, or be exchanged for other pairs, to give differenttransmission ratios and thus allow the speed of rotation of the soil working members 3 to be increased or decreased in response to substantially the same speed of driving rotation that is applied to the rotary input shaft 25 of the gear box 23.The front of the hollow frame portion 1, with respect to the direction A, is provided with a coupling member or trestle 27 at a location substantially mid-way between the two frame portion side plates 17, said coupling member ortrestle 27 being of approximately triangular configuration as seen in either front or rear elevation and being constructed for co-operation with the upper and lower lifting links of a three-point lifting device or hitch mounted at the rear of the agricultural tractor or other vehicle which both moves and operates the implement when the latter is in use.

In the alternative embodiment of Figures 5 and 6 of the drawings, the carrier 4 that has already been described forms part of each of a plurality of rotary soil working members 3A that occupy similar positions to the rotary soil working members 3 that have already been described. However, in this case, each soil working member 3A comprises diametrically opposed sleeve-like tine holders 28 that are provided with fastening portions 29 substantially equivalent in construction and mounting to the fastening portions 9 that have already been described. The lower surface of each fastening portion 29 carries a corresponding rib 11 A whose radially outermost end is integrally or rigidly secured to the respective tine holder 28 at substantially the top of that tine holder.

Although being of sleeve-like formation, each tine holder 28 is of angular shape having front and rear surfaces (with respect to the intended direction of operation rotation of the corresponding soil working member 3A which is from left to right as seen in Figure 6) that are inclined generally downwardly and rearwardly relative to that direction, the radially outer ends of these front and rear surfaces meeting an angular outer side surface whose shape can be seen in Figure 6. The top of each tine holder 28 is substantially flat but is inclined downwardly and outwardly with respect to the corresponding shaft 2 away from its angular junction with the outer end of the corresponding fastening portion 29.This construction provides increased clearance between immediately neighbouring soil working members 3A of the implement when it is in use and thus enables stones and other hard objects to pass between the members 3A with a reduced risk of damage to those members.

The hollow interior of each sleeve-like tine holder 28 receives a fastening portion of a corresponding soil working tool in the form of a tine 30. The axial length of this hollow interior may advantageously have a magnitude of substantially 80 mm. It will be seen from Figures 5 a nd 6 of the drawings that each tine 30 is formed from a length of metallic rod that is of basically circular cross-section but that also defines two diametrically opposed ribs 30A which lie at the front and rear of each tine with respect to the intended direction of operative rotation of the corresponding soil working member 3A. As well as enhancing the soil crumbling action, the ribs 30A assist in retaining the tines 30 in their appointed working positions since the hollow interiors of the holders 28 are of matching cross-section. The opposite ends of each tine 30 are perpendicular to the longitudinal axis of the tine which facilitates cutting the tines from long lengths of the rod material, that material advantageously having a diameter of substantially 22 mms in the example that is being described. The fastening portion of each tine 30 is retained in the co-operating holder 28 by a resilient or other retaining pin 31 entered substantially hori zontallythrough a bore at the front of that holder 28 with respect to the intended direction of operative rotation of the corresponding soil working member 3A.The bore intrudes into that portion of the hollow interior of the same holder 28 which registers with the leading rib 30A of the tine 30 and said rib is formed with a substantially semi-circular recess 32 that receives the retaining pin 31, thus preventing the tine 30 from being moved either upwardly or downwardly in the holder 28 until the retaining pin 31 is withdrawn. It will be seen from Figures 5 and 6 of the drawings that each tine 30 has a second similar recess in its rear rib 30A so that, when the tine 30 has become worn to such an extent as significantly to reduce its operating efficiency, the retaining pin 31 concerned can be temporarily removed and the tine 30 be withdrawn and replaced in an inverted position in which its fastening and soil working portions are interchanged and the fresh "rear" recess 32 co-operates with the retaining pin 31.It is noted that the "rear" recess 32 as illustrated in Figures 5 and 6 of the drawings is further from the neighbouring end of the tine 30 than is the "leading" recess 32 that is shown as co-operating with the retaining 31. This is because the initial wear inevitably shortens the length of the lower fastening portion of the tine 30 to some extent and is required to ensure that sufficient length of the tine remains for proper co-operation with the hollow interior of the tine holder 28 when the tine is removed and inverted to restore its working efficiency. This arrangement can substantially double the effective working life of each tine 30 before continuing wear renders eventual replacement unavoidable.The hollow interior of each holder 28 is in substantially parallel relationship with the front and rear surfaces of that holder 28, the inclination of each installed tine 30 preferably being not less than substantially 8 and not more than substantially 10 relative to a plane containing the longitudinal axis of the corresponding shaft 2 and a point on the longitudinal axis of the straight tine 30 concerned. Each holder 28 comprises more material at the front thereof, with respect to the intended direction of operative rotation of the corresponding soil working member 3A, than it does at the rear thereof since the holders 28, as well as the tines 30, inevitably suffer wear during operation which wear is much more marked at the front, in the direction of operative rotation, than it is at the rear.

In the use of the soil cultivating implement that has been described with reference to Figures 1 to 4 of the drawings or with reference to Figures 1,5 and 6 thereof, the coupling member or trestle 27 is connected to the lifting links of the three-point lifting device or hitch at the rear of the agricultural tractor or other vehicle which both moves and operates the implement and the rotary input shaft 25 of the gear box 23 is placed in driven connection with the rear power take-off shaft of the same tractor or other vehicle by way of the known telescopic transmission shaft 26 which has universal joints at its opposite ends.The speed at which the soil working members 3 or 3A will revolve in response to a predetermined speed of driving rotation applied to the input shaft 25 is increased or decreased, if necessary, before work commences by an appropriate adjustment of the change-speed gear 24. Similarly, the maximum depth to the which the tines 12 or 30 can penetrate into the ground is increased or decreased, if required, by changing the bodily level of the ground roller 20 relative to that of the frame portion 1 and soil working members 3 or 3A. The implement embodiments which are being described are intended primarily for use in preparing seedbeds from previously worked soil in which seedbeds seeds can germinate and, after appropriate thinning of the seedlings, if required, can grow on to maturity.The adjustments indicated will normally be made in the light of the nature and condition of the soil that is to be cultivated and the particular purpose for which that soil is required after treatment by the implement. As the implement moves operatively over the ground in the direction A, each pinion 22, shaft 2 and soil working member 3 or 3A will revolve in the direction B which direction is opposite to that of the or each immediately neighbouring similar assembly in the single row of twelve, in this embodiment, such assemblies.Each soil working member 3 or 3A works an individual strip of ground whose width is equal to, or a little greater than, 25 cm so that these individual strips of ground overlap or at least adjoin one another to produce a single broad strip of worked soil that will have a width of substantially, although not necessarily exactly, three metres when there are twelve of the soil working members 3 or 3A. It will readily be apparent that greater or smaller working widths are possible by increasing or decreasing the number of rotary soil working members. The tines 12 or 30 move very rapidly through the soil and provide a well crumbled homogeneous seedbed and any stubborn lumps or clods of soil that remain unbroken by the tines 12 or 30 are usually crushed by the immediately following freely rotatable ground roller 20 which also gently levels and consolidates the worked soil.

The construction of the soil working members 3 and 3A is such that alternative tine holders, such as the holders 10 or 28, can readily be used with the same structure that comprises the hub 6 and the carrier 4. This versatility is desirable since some constructions are more suitable for dealing with soft, wet and relatively stone-free soil whilst others are more suitable for dealing with dry, abrasive, stony soil. Figures 7 and 8 of the drawings illustrate a further alternative in which fastening portions of tines 33 formed from flat strip-shaped material can be secured to the arm-like portions of the carrier4 by the bolts 8. The soil working portions of such tines 33 move through the ground with a knife-like action and can, if desired, have their leading edges, with respect to the direction B (Figure 8), sharpened to increase the cutting action thereof. The fastening portions of the tines 33 have flat substantially horizontally extending upper surfaces which abut throughout a large area of contact against the flat lower surfaces of the arm-like portions 5 of each carrier 4, these fastening portions of the tines 33 being integrally joined to the downwardly projecting soil working portions thereof by bends which have magnitudes of substantially 90 . It will be noted from Figures 7 and 8 of the drawings, and particularly from Figure 8 thereof, that the soil working portions of the tines 33 are not in perpendicular relationship with the longitudinal axis or centre line of the whole carrier 4 but are so inclined to that longitudinal axis or centre line that the fronts thereof, relative to the direction B, are further from the longitudinal axis of the corresponding shaft 2 than are the rears thereof.

In addition to the versatility that is provided by the invention as regards directly or indirectly connecting soil working tools of different constructions to a single form of carrier 4 and its hub 6, worn or damaged tines or other soil working tools can quickly and easily be released and be replaced by fresh parts with the facility, in one described and illustrated construction, of substantially doubling the life of worn tines before eventual replacement is no longer avoidable.

The ribs 7 on the upper surfaces of the arm-like portions 5 of the carriers 4 strengtheningly stiffen those portions 5 to a very significant extent and assist in guarding the nuts which co-operate with the bolts 8 against direct impacts against stones and other hard objects. This is also true of the ribs 11 and 1 that are provided on the lower surfaces of the holder fastening portions 9 and 29, respectively, these ribs 11 and 11A offering some anti-damage protection to the heads of the bolts 8. In the embodiments of Figures 1 to 6 of the drawings, the shields 16 alone or the shields 14 and 16, encounter stones or other hard objects before they strike the bolts 8 and their nuts and, when provided, the fastening nuts 13 of the tines 12.The upwardly and forwardly oblique dispositions of the shields 14 and 16 tend to urge any stones or other hard objects which they may encounter downwardly into the soil that is being dealt with and protect the lower surface of the hollow frame portion 1 from denting damage, the upper edges of the shields 14 of the first embodiment being located at a horizontal level only a little beneath that of the bottom of the hollow frame portion 1. In the embodiments of Figures 5 to 8 of the drawings, the shields 14 are not provided but the shields 16 which form parts of the carriers 4 remain to act in the way that has just been described.

The tines 33 which are provided in the embodiment of Figures 7 and 8 of the drawings are particularly useful when dealing with sandy or other light soil that is badly infested with weeds and/or which contains many unwanted roots or root remnants.

Although certain features of the implement embo dimentsthat have been described and/or that are illustrated in the accompanying drawings will be set forth in the following claims as inventive features, it is emphasized that the invention is not necessarily limited to those features and that it includes within its scope each of the parts of each implement embodiment that has been described, and/or that is illustrated in the accompanying drawings, both individually and in various combinations.

Claims

1. A soil cultivating implement of the kind set forth, wherein the or each tool of each soil working member is received in a holder which holder is releasably secured to the corresponding carrier.

2. An implement as claimed in claim 1, wherein each holder comprises a fastening portion by which it is releasably secured to the corresponding carrier.

3. An implement as claimed in claim 2, wherein the fastening portion of each holder is constructed and arranged to be releasably securable to the lower surface of the corresponding carrier.

4. An implement as claimed in any preceding claim, wherein each rotary soil working member is provided with at least one protective shield that extends obliquely upwardly and forwardly therefrom, with respect to the intended direction of operative rotation of that soil working member, in such a way as to tend downwardly to displace stones and other hard objects encountered thereby during the operation of the implement.

5. An implement as claimed in claim 2 or claim 3 or in claim 4 when read as appendant to either claim 2 or claim 3, wherein the fastening portion of each holder is releasably securable to the lower surface of the corresponding carrier by a pair of relatively spaced bolts.

6. An implement as claimed in claim 5, wherein the fastening portion of each holder has a free end which is arranged to abut against a contact surface exhibited by a central hub of the corresponding carrier.

7. An implement as claimed in claim 2 or claim 3 or in any one of claims to 6 when read as appendant to either claim 2 or claim 3, wherein the lower surface of the fastening portion of each holder is provided with a substantially centrally located rib.

8. An implement as claimed in claim 7 when read as appendant to either claim 5 or claim 6, wherein holes formed in the fastening portion of each holder for the reception of said pair of bolts are located at opposite sides of said rib.

9. An implement as claimed in claim 2 or claim 3 or in any one of claims 4 to 8 when read as appendant to either claim 2 or claim 3, wherein the fastening portion of each holder is integrally or rigidly secured to the remainder of that holder at a location disposed approximately centrally of the upright length of the latter.

10. An implement as claimed in claim 2 or claim 3 or in any one of claims 4 to 8 when read as appendant to either claim 2 or claim 3, wherein the fastening portion of each holder is integrally or rigidly secured to the remainder of that holder at a location disposed at or adjacent to the top of the upright length of the latter.

11. An implement as claimed in claim 9, wherein each holder tapers both upwardly and downwardly from substantially the horizontal level at which the fastening portion ofthat holder is located.

12. An implement as claimed in claim 10, wherein at least the front of each holder, with respect to the intended direction of operative rotation of the corresponding soil working member, has a surface which is inclined downwardly and rearwardly relative to the same direction.

13. An implement as claimed in claim 12, wherein at least the front and the rear of each holder, with respect to the intended direction of operative rotation of the corresponding soil working member, are in parallel or substantially parallel relationship with one another.

14. An implement as claimed in any preceding claim, wherein each holder has a hollow interior constructed and arranged to receive a fastening portion of a corresponding soil working tool.

15. An implement as claimed in claim 14, wherein said hollow interior is upwardly and forwardly inclined with respect to the intended direction of operative rotation of the corresponding soil working member.

16. An implement as claimed in any preceding claim, wherein each of at least a plurality of the soil working tools is in the form of a tine made from rod material.

17. An implement as claimed in claim 16, wherein the fastening portion of each such tine comprises two diametrically opposed ribs that are employed in releasably securing that portion of the tine in the corresponding holder.

18. An implement as claimed in claim 17, wherein the fastening portion and a soil working portion of each such tine are in alignment with one another, said ribs extending to the free end of the fastening portion.

19. An implement as claimed in claim 17 or 18, wherein the fastening portions of said tines cooperate with the corresponding holders by mounting retaining pins in bores that are formed in the holders at the fronts thereof with respect to the intended directions of operative rotation of the corresponding soil working members, said bores intruding into the hollow interiors of the holders that received the fastening portions of the tines and those fastening portions being formed with recesses which receive the retaining pins, when so installed.

20. An implement as claimed in claim 19, wherein the recesses in the tines which co-operate with the retaining pins are formed in said ribs of those tines.

21. An implement as claimed in claim 19 or 20, wherein both the fastening portion and the soil working portion of each tine is formed with one of said recesses whereby the tine can be inverted to interchange its fastening and soil working portions, either recess being capable of co-operation with the corresponding retaining pin.

22. A soil cultivating implement of the kind set forth, wherein the lower surface of each carrier is provided with fastening means for co-operation with a corresponding soil working tool, each carrier also comprising at least one protective shield that extends obliquely upwardly and forwardly therefrom with respect to the intended direction of operative rotation of the corresponding soil working member.

23. An implement as claimed in claim 22, wherein each soil working tool is in the form of a strip-shaped tine having a fastening portion which is bent over at an angle of substantially 90 relative to a soil working portion thereof, the fastening portion of each such knife-like tine being constructed and arranged for releasable connection to the lower surface of the corresponding carrier.

24. An implement as claimed in claim 23, wherein the soil working portion of each tine is in non-tangential relationship with an imaginary cylindrical surface centred upon the axis of rotation of the corresponding soil working member in such a way that the leading edge thereof, relative to the intended direction of operative rotation of that soil working member, is spaced further from the axis of rotation of that member than is the rear edge thereof.

25. An implement of the kind set forth substantially as hereinbefore described with reference to Figures 1 to 4, or with reference to Figures 1,5 and 6, or with reference to Figures 1, 7 and 8 of the accompanying drawings.

26. A soil working tool destined for use in a soil cultivating implement of the kind set forth, wherein said tool is provided at locations towards both its opposite ends with means that can be employed releasably to secure that tool in an operative position in a corresponding rotary soil working member.

27. A holder for a tine or other soil working tool and destined for use in a soil cultivating implement as claimed in any one of claims 1 to 25, wherein said holder exhibits fastening means for releasably securing a corresponding tine or other soil working tool thereto and a fastening portion releasably securable to a carrier of a corresponding rotary soil working member.

28. A holder for a tine or other soil working tool of a soil cultivating implement, wherein said holder comprises means for releasably securing a tine or other soil working tool thereto and also a fastening portion by which the holder can be releasably secured to a carrier of a corresponding rotary soil working member.