GB1591169A

GB1591169A - Vegetation cutting machine

Info

Publication number: GB1591169A
Application number: GB2773377A
Authority: GB
Original assignee: BRITISH LELY Ltd
Current assignee: BRITISH LELY Ltd
Priority date: 1977-07-01
Filing date: 1977-07-01
Publication date: 1981-06-17
Also published as: FR2395693A1

Description

(54) VEGETATION CUTTING MACHINE (71) We, BRITISH LELY LIMITED, a British company, of Wootton Bassett, Swindon, Wiltshire, SN4 7DB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to vegetation cutting machines. By vegetation cutting in the present context is meant the cutting of hedges, grass verges and slopes at the edges of ditches, tree trimming and so on.

The invention provides a vegetation cutting machine comprising a framework adapted for mounting on a tractor or other operating vehicle, and a boom arrangement including a first boom part carried by the framework for pivoting about a first axis, and a second boom part pivotably connected to the first boom part for pivoting movement relative to the first boom part and carrying remote from the first boom part a cutting head, said first and second axes extending substantially in the intended direction of operative travel over the ground of the machine when mounted on an operating vehicle; the machine further comprising transmission mechanism carried by the boom arrangement for transmitting drive, in use ofthe machine, from the operating vehicle on which the machine is mounted to the cutting head, this transmission mechanism including first and second belt transmissions carried by the first boom part and the second boom part respectively, a pulley mechanism of the first transmission and a pulley mechanism of the second transmission being disposed at the interconnection of the two boom parts in overlapping relationship with one pulley mechanism ahead of the other relative to said direction of operative travel. Both belt transmissions can be multiple V-belt transmissions. Alternatively the first can be a multiple V-belt transmission and the second a toothed belt transmission. The cutting head may be carried by the boom arrangement for pivoting relative to the second boom part about an axis extending substantially in the intended direction of operative travel of the machine.

The cutting head may be pivotable relative to the boom arrangement through a range of less than 360" and may be connected to the boom arrangement via an adjustable coupling permitting selection of the disposition of this range about the pivotal axis of the cutting head.

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 diagrammatic rear view of a vegetation cutting machine illustrating the operative disposition of the machine relative to the rear wheels of a tractor or other operating vehicle and showing different operating positions of the machine, Figure 1A is a view of part of the machine as shown in Figure 1 but illustrating components omitted from Figure 1 for the sake of clarity, Figure 2 is a sectional view of part of the machine of Figure 1 taken on line II-II of Figure 1 but with the machine disposed in a position not illustrated in Figure 1, Figure 2A is a sectional view of a portion of part of a machine as illustrated in Figure 2 but showing a modified form of the machine, Figure 3 is a detail of the machine of Figures 1 and 2 on a larger scale and showing different operating positions, Figure 4 is a sectional view of a further detail of a particular form of the machine of Figures 1 and 2, also on a larger scale, and Figure 5 is a view taken on the line V-V of Figure 4.

The vegetation cutting machine shown in the Figures has a framework 1 that includes a coupling member or trestle 2 adapted for mounting on a tractor or other operating vehicle, the rear wheels 3 of which are shown in Figure 1. The framework 1 carries a boom arrangement 4, a first boom part 4A of which is connected at one end to the upper part of the trestle 2 for pivoting about a first axis 5 that extends substantially in the intended direction of operative travel over the ground of the machine when mounted on an operating vehicle. The other end of the first boom part 4A is connected to one end of a second boom part 4B for relative pivoting movement of the two boom parts 4A, 4B about a second axis 6 that also extends substantially in the intended direction of operative travel just mentioned. The other end of the second boom part 4B carries a cutting head 7 that is pivotable relative to the second boom part 4B about a third axis 8 that extends substantially in the intended direction of operative travel just mentioned.

The cylinder of a first single acting hydraulic piston and cylinder assembly 9 is pivotably connected to the trestle 2 at a mounting point 10 in the bottom part of the trestle and to one side of the plane that contains the first and second pivot axes 5 and 6.

The end of the piston rod of the assembly 9 that is free of the cylinder of the assembly is pivotably connected at a point 11 to the boom part 4A, this point 11 lying in the plane that contains the first and scco.ld pivot axes 5 and 6. The cylinder of a double acting hydraulic piston and cylinder assembly 12 is pivotably connected to a bracket 13 on the boom part 4A. The end of the piston rod of the assembly 12 that is free of the cylinder of this assembly is pivotably connected at a point 14 to the boom part 4B, this point 14 lying in the plane that contains the second and third pivotal axes 6 and 8.

As will be seen from Figure 1, the boom arrangement 4 as a whole extends on one side of the trestle 2, on the same side of the first pivot axis 5 as the mounting point 10 is disposed, and hence the boom arrangement 4 extends on one side of the operating vehicle. It will also be noted that the bracket 13 is offset from the plane containing the first and second pivot axes 5 and 6, the bracket being to the same side of this plane as the mounting point 10. If desired the boom arrangement 4 can be positioned on the other side of the vehicle, in which case the cylinder of the assembly 9 is attached to an alternative mounting point 10' which is on the other side of the plane of the pivot axes 5 and 6, and the cylinder of the assembly 12 is attached to an alternative bracket 13' which is also on the other side of the plane of the axes 5 and 6. It will be appreciated that in both positions of the boom arrangement the point of connection of the cylinder of the assembly 12 to the boom part 4A is disposed below the plane containing the axes 5 and 6. As the mounting points 11 and 14 are respectively in the plane containing the axes 5 and 6 and in the plane containing the axes 6 and 8 there is no need to alter these mounting points.

The boom arrangement 4B carries a third piston and cylinder assembly 15 (Figure 1A), the cylinder of which is pivotably connected to the boom part 4B at a mounting point 16 offset from the plane containing the second and third pivot axes 6 and 8. This assembly 15 is double-acting. As best shown in Figure 3 but illustrated also in Figure 1A, the end of the piston rod of the assembly 15 that is free of the cylinder of this assembly is pivotably connected at a point 17 to a bellcrank lever 18, the fulcrum point 19 of which is at the free end of a lever 20 the other end of which is pivotted at 21 to the boom part 4B. The pivot point 21 is offset from the plane containing the second and third pivot axes 6 and 8, to the same side as the mounting point 16.

The bellcrank lever 18 serves to link the piston rod of the assembly 15 to a cutting head rotating lug 22 that is rotationally fast with the cutting head, the pivotal connection of the bellcrank lever 18 to the lug 22 being at a point 23 offset from the plane containing the second and third pivotal axes 6 and 8.

Each boom part 4A, 4B is hollow andof a substantially closed construction to minimise the risk of penetration of dirt, clippings and the like into its interior. With respect to the intended direction of operative travel of the machine over the ground the outer boom part 4B is ahead of the inner boom part 4A so that at the interconnection of the two boom parts there is an overlapping relationship between the two boom parts. The arrangement 4 carries belts of a transmission mechanism for transmitting drive from the operating vehicle on which the machine is mounted in use to the cutting head. To this end (Figures 2 and 2A) there is within the boom part 4A a first belt transmission 24 which in the form illustrated is a multiple V-belt transmission and within the boom part 4B a second belt transmission 25 which in the form illustrated in Figure 2A is also a multiple V-belt transmission. Alternatively, and as illustrated in Figure 2, the transmission 25 can be a toothed belt transmission.

Referring to Figure 2, at the interconnection of the two boom parts 4A, 4B there is a pulley mechanism 26 of the first transmission 24 which includes a multiple-pulley for the V-belt, and a pulley mechanism 27 of the second transmission 25 which includes either a multiple-pulley for the V-belts (Figure 2A) or a toothed pulley for the toothed belt (Figure 2). These pulleys 26, 27 are in overlapping relationship with one ahead of the other relative to the direction of operative travel of the machine over the ground (arrow A in Figure 2) and they are drivingly interconnected by a common lay shaft 28 coaxial with the pulleys and rotatably carried by an inner journal 29 fast with the inner boom part 4A.

Figure 2 also illustrates the pivotal inter connection between the two boom parts 4A, 4B, the inner journal 29 fast with the inner boom part 4A pivotably supporting an outer journal 30 fast with the outer boom 4B. It will be appreciated that the shaft 28 is coaxial with the second pivotal axis 6, this being the axis about which relative pivotal movement of the two journals 29,30 takes place.

In addition Figure 2 shows reinforcing members (omitted from the other Figures) which are provided to the rear of the boom parts 4A, 4B with respect to the direction of operative travel A. These members include an inner strut 50 which is pivoted to the trestle 2 on the axis 5 at one end and that is secured to the inner boom part 4A by spaced brackets one of which is shown at 51; and an outer strut 52 which is pivotably connected at one end (at 53 in Figure 2) to the outer end of the strut 50. At its other end the strut 52 is fast with the outer boom parts 4B and there is also a bracket connection like the bracket 51. The pivotable connection at 53 is on the axis 6.

Where a belt transmission is a V-belt transmission it comprises four V-belts.

Openings closed by covers are provided in the boom parts so that access may be gained to the belts and the pulleys around which they run, and to tensioning mechanism (not shown) acting on the belts.

At the end of the boom part 4B remote from the boom part 4A a pulley (not visible in the Figures) of the transmission 25 is mounted on a cutting head drive shaft 31 (Figure 4) rotatably disposed in a housing 32. This drive shaft 31 is in splined connection with a stub shaft 33 rotatably mounted in a housing 34 that is fast with a casing 35 (see also Figure 1) of the cutting head. It will be appreciated that the shafts 31 and 33 are coaxial with the third pivotal axis 8. The stub shaft 33 is in driving connection via bevel pinions 36, 37 with a shaft 38 extending at right angles to the shafts 31 and 33. In the illustrated machine the cutting head is in the form of a flail head and the shaft 36 drives, via belts not shown, the flail rotor, also not shown, of this head. Alternatively some other form of cutting head, such as a saw head could be fitted to the beam arrangement 4 to be driven by the shafts 31 and 33.

The housings 32 and 34 are made fast with one another through a coupling which can be released to enable alteration about the axis 8 of the angular position of the housing 34 (and hence of the cutting head as a whole) relative to the boom part 4B. This coupling is illustrated in one form at 39 in Figures 4 and 5, and in another form at 139 in Figure 1. As illustrated in Figures 4 and 5 the coupling 39 includes a clamp 40 having internal cam surfaces 41A, 41B respectively co-operating with flanges 42 and 43 fast with the housing 32 and 34 respectively.

The clamp 40 can be released from the flanges 42, 43 by unscrewing a bolt 44 (Figure 5) utilising a tommy bar 45, two opposed parts 40A, 40B of the clamp 40 being thereby freed to pivot apart about a pivot 46. In the clamp-released condition the cutting head can be rotated, about the axis 8, relative to the housing 32 to any desired position and fixed thereat by retightening the bolt 44. Upon re-tightening the bolt 44 the cam surfaces 41A, 41B of the clamp 40 grip the flanges 42 and 43 with a wedging action. As an alternative, the pivot 46 can be replaced by a further bolt similar to the bolt 44.

In the form illustrated in Figure 1 flanges equivalent to the flanges 42 and 43 have co-operating kidney-shaped slots 140 through which bolts, not shown, are passed.

This coupling 139 is released by slackening nuts on these bolts thereby permitting angular movement of the cutting head to an extent determined by the length of the slots 140. Further angular movement can be obtained by removing the bolts completely, rotating the head further to bring different slots 140 into co-operation, and replacing the bolts.

In use of the vegetation cutting machine which has been described, its framework 1 is connected to the tractor or other operating vehicle by the coupling member or trestle 2 so that the boom arrangement 4 extends to a desired side of the tractor. A driving shaft for the belt transmission 24 is placed in driven connection with the power take-off of the same tractor by way of an intermediate telescopic transmission shaft having universal joints at its opposite ends. Appropriate fluid pressure connections are made to the hydraulic system of the tractor in a manner which is know per se. The operating vehicle will normally be an agricultural tractor.

It will be noted that the cutting head hangs at one side of the rear ground wheels 3 of the tractor and is in front of the axis of the wheels 3, this being an operating position which is most advantageous with respect to manoeuvring the tractor. The tractor driver can watch the operation of the head readily from his driving seat without turning round and hedges and the like can be cut quickly and with optimum efficiency by the head due to the advantageous operating position thereof. It is here to be emphasized that the machine can be utilised for hedge cutting or for cutting grass verges, slopes at the edges of ditches and the like, tree trimming and so on. The speed of travel of the mounted machine over the ground may vary, in accordance with operating conditions, between substantially 800 metres per hour and substantially 8 kilometers per hour. Where the cutting head is a flail head it can have a working width of the order of 107 centimetres and its flail rotor which is not illustrated in the accompanying drawings can comprise three rows of nine hardened flails each. Such a head is capable of cutting hedge shoots and branches that are up to approximately 3 years in age. The cutting material is completely pulverised so that it is not necessary to make an additional traverse to collect the cut material. Generally speaking, the cut material can be left lying on the ground where it falls since the machine will have brought it to a condition in which it will compost naturally and enhance the humus content of the soil upon which it is lying.

The angle of the first boom part 4A relative to the ground surface as viewed in the intended direction of operative travel (Figure 1), may be varied by employing the first single acting hydraulic and piston cylinder assembly 9. Similarly the angle of the second boom part 4B relative to the first boom part 4A may be varied by employing the double acting piston and cylinder assembly 12. By utilising combinations of these two ranges of movement the configuration of the boom arrangement as a whole can be varied from one on which the two boom parts are in line to one in which the two arrangements are nearly side-by-side. The extent of the range of relative movement that can take place between the two boom parts is facilitated by the overlapping relationship of the two parts and the provision of the two-part belt transmission, the extent of this range of relative movement being of the order of 142". The range of the angular movement which the first boom part can make relative to the ground surface is of the order of 68".

The most upright position that can be reached by the boom arrangement is with the two parts thereof in line, this being a fully extended configuration of the boom arrangement which is not illustrated in the drawings but there is illustrated in Figure 1, in full lines, a fully folded configuration of the boom arrangement as there is also illustrated in Figure 1 in dotted lines, a configuration intermediate the fully extended and fully folded configurations.

In every possible angular setting of the boom parts 4A, 4B the cutting head 7 is itself angularly adjustable with respect to the boom 4B by employing the double acting hydraulic piston and cylinder assembly 15. The linkage between the assembly 15 and the cutting head rotating lug 22 permits of the order of 1900 rotation of the head to be achieved by operation of the assembly 15, alternative positions of this linkage being illustrated in full, chain and chain dot lines in Figure 3. By suitably selecting the disposition and configuration of the boom arrangement, and the disposition of the cutting head, optimum operating positions of the head can be attained for all cutting, mowing and like operations that the machine may have to perform. In particular, the machine can cut the top of a hedge (dotted line position of the cutting head 7 in Figure 1), both sides of the hedge (full line position of the cutting head 7 in Figure 1), grass and weeds beneath the hedge and any neighbouring verge or bank. However, as by operation of the assembly 18 alone the head can only be rotated through a range of less than 360 , movement of the head from one extreme position (shown in full lines in Figure 1) in which the boom arrangement is fully folded and the cutting head is close both to the ground and to the tractor wheels with the axis of rotation of the flail rotor vertical, to another extreme position in which the boom arrangement is fully extended and almost upright and the axis of rotation of the flail rotor is horizontal, can only be obtained by releasing the coupling 39 or 139 and rotating the head about the axis 8 to select the disposition, about this axis, of the range of movement that can be achieved by operation of the assembly 18. It will be appreciated, however, that the nature of the coupling 39 or 139 is such that this adjustment can be simply effected and it is to be noted (see Figure 1) that the provision of the possibility of setting the flail rotor vertical close to the ground and to the tractor enables the machine to be operated very close to a hedge whilst cutting the side of the hedge. This is an important feature where access is limited, for example in a narrow lane.

It is to be noted that the transmission mechanism in the machine described is a belt mechanism at least part of which is a multi V-belt transmission. Such a transmission has the advantages that it is to some extent shock-absorbing by virtue of the use of slippable and resilient belts and cooperating pulleys (rather than, for example, chains and sprocket wheels or toothed belts throughout), and yet constitutes a relatively simple drive transmission (as compared with, for example, a hydraulic motor operated transmission) which does not hinder pivotal movements of the boom parts.

As previously indicated, the machine can be mounted to operate on the other side of the tractor as compared with Figure 1 by utilising the mounting points 10' and 13'in place of the points 10 and 13.

WHAT WE CLAIM IS: 1. A vegetation cutting machine comprising a framework adapted for mounting on a tractor or other operating vehicle, and a boom arrangement including a first boom part carried by the framework for pivoting about a first axis, and a second boom part pivotably connected to the first boom part

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. is a flail head it can have a working width of the order of 107 centimetres and its flail rotor which is not illustrated in the accompanying drawings can comprise three rows of nine hardened flails each. Such a head is capable of cutting hedge shoots and branches that are up to approximately 3 years in age. The cutting material is completely pulverised so that it is not necessary to make an additional traverse to collect the cut material. Generally speaking, the cut material can be left lying on the ground where it falls since the machine will have brought it to a condition in which it will compost naturally and enhance the humus content of the soil upon which it is lying. The angle of the first boom part 4A relative to the ground surface as viewed in the intended direction of operative travel (Figure 1), may be varied by employing the first single acting hydraulic and piston cylinder assembly 9. Similarly the angle of the second boom part 4B relative to the first boom part 4A may be varied by employing the double acting piston and cylinder assembly 12. By utilising combinations of these two ranges of movement the configuration of the boom arrangement as a whole can be varied from one on which the two boom parts are in line to one in which the two arrangements are nearly side-by-side. The extent of the range of relative movement that can take place between the two boom parts is facilitated by the overlapping relationship of the two parts and the provision of the two-part belt transmission, the extent of this range of relative movement being of the order of 142". The range of the angular movement which the first boom part can make relative to the ground surface is of the order of 68". The most upright position that can be reached by the boom arrangement is with the two parts thereof in line, this being a fully extended configuration of the boom arrangement which is not illustrated in the drawings but there is illustrated in Figure 1, in full lines, a fully folded configuration of the boom arrangement as there is also illustrated in Figure 1 in dotted lines, a configuration intermediate the fully extended and fully folded configurations. In every possible angular setting of the boom parts 4A, 4B the cutting head 7 is itself angularly adjustable with respect to the boom 4B by employing the double acting hydraulic piston and cylinder assembly 15. The linkage between the assembly 15 and the cutting head rotating lug 22 permits of the order of 1900 rotation of the head to be achieved by operation of the assembly 15, alternative positions of this linkage being illustrated in full, chain and chain dot lines in Figure 3. By suitably selecting the disposition and configuration of the boom arrangement, and the disposition of the cutting head, optimum operating positions of the head can be attained for all cutting, mowing and like operations that the machine may have to perform. In particular, the machine can cut the top of a hedge (dotted line position of the cutting head 7 in Figure 1), both sides of the hedge (full line position of the cutting head 7 in Figure 1), grass and weeds beneath the hedge and any neighbouring verge or bank. However, as by operation of the assembly 18 alone the head can only be rotated through a range of less than 360 , movement of the head from one extreme position (shown in full lines in Figure 1) in which the boom arrangement is fully folded and the cutting head is close both to the ground and to the tractor wheels with the axis of rotation of the flail rotor vertical, to another extreme position in which the boom arrangement is fully extended and almost upright and the axis of rotation of the flail rotor is horizontal, can only be obtained by releasing the coupling 39 or 139 and rotating the head about the axis 8 to select the disposition, about this axis, of the range of movement that can be achieved by operation of the assembly 18. It will be appreciated, however, that the nature of the coupling 39 or 139 is such that this adjustment can be simply effected and it is to be noted (see Figure 1) that the provision of the possibility of setting the flail rotor vertical close to the ground and to the tractor enables the machine to be operated very close to a hedge whilst cutting the side of the hedge. This is an important feature where access is limited, for example in a narrow lane. It is to be noted that the transmission mechanism in the machine described is a belt mechanism at least part of which is a multi V-belt transmission. Such a transmission has the advantages that it is to some extent shock-absorbing by virtue of the use of slippable and resilient belts and cooperating pulleys (rather than, for example, chains and sprocket wheels or toothed belts throughout), and yet constitutes a relatively simple drive transmission (as compared with, for example, a hydraulic motor operated transmission) which does not hinder pivotal movements of the boom parts. As previously indicated, the machine can be mounted to operate on the other side of the tractor as compared with Figure 1 by utilising the mounting points 10' and 13'in place of the points 10 and 13. WHAT WE CLAIM IS:

1. A vegetation cutting machine comprising a framework adapted for mounting on a tractor or other operating vehicle, and a boom arrangement including a first boom part carried by the framework for pivoting about a first axis, and a second boom part pivotably connected to the first boom part

for pivoting movement relative to the first boom part and carrying remote from the first boom part a cutting head, said first and second axes extending substantially in the intended direction of operative travel over the ground of the machine when mounted on an operating vehicle; the machine further comprising transmission mechanism carried by the boom arrangement for transmitting drive, in use of the machine, from the operating vehicle on which the machine is mounted to the cutting head, this transmission mechanism including first and second belt transmissions carried by the first boom part and the second boom part respectively, a pulley mechanism of the first transmission and a pulley mechanism of the second transmission being disposed at the interconnection of the two boom parts in overlapping relationship with one pulley mechanism ahead of the other relative to said direction of operative travel.

2. A vegetation cutting machine as claimed in claim 1, wherein both belt transmissions are multiple V-belt transmissions.

3. A vegetation cutting machine as claimed in claim 1, wherein said first belt transmission is a multiple V-belt transmission and said second belt transmission is a toothed belt transmission.

4. A vegetation cutting machine as claimed in claim 1, 2 or 3, wherein the pulleys of said pulley mechanisms are drivingly interconnected by a common shaft coaxial with the axis about which the two boom parts are relatively pivotable.

5. A vegetation cutting machine as claimed in claim 4, wherein said common shaft is rotatably supported in the first boom part by an inner journal that is fast with the first boom part and that pivotably supports an outer journal fast with the second boom part.

6. A vegetation cutting machine as claimed in claim 4, wherein said common shaft is rotatably supported in the first boom part by an outer journal that is fast with the first boom part and that pivotably supports an inner journal fast with the second boom part.

7. A vegetation cutting machine as claimed in any one of the preceding claims, wherein a first hydraulic piston and cylinder assembly is pivotably connected to the framework to one side of a plane containing said first and second pivot axes, and to the first boom part at a point lying in this plane, this assembly being operable for pivoting the first boom part relative to the framework.

8. A vegetation cutting machine as claimed in claim 7, wherein a second hydraulic piston and cylinder assembly is pivotably connected to the first boom part on said one side of the said plane, and to the second boom part at a point lying in this plane, this assembly being operable for pivoting the second boom part relative to the first boom part.

9. A vegetation cutting machine as claimed in claim 8, wherein said first and second hydraulic piston and cylinder assemblies can be selectively connected to the framework and to the first boom part respectively both to said one side of said first axis, or both to said other side of this axis.

10. A vegetation cutting machine as claimed in any one of the preceding claims, wherein the cutting head is carried by the boom arrangement for pivoting relative to the second boom part about a third axis extending substantially in the intended direction of operative travel of the machine.

11. A vegetation cutting machine as claimed in claim 10, as appendant to claim 7, 8 or 9, wherein the second boom part carries a third piston and cylinder assembly connected to the second boom part at a point offset from a plane containing the second and third pivot axes, and to a bell crank lever having its fulcrum point at the free end of a lever the other end of which is pivoted to the second boom part at a point offset from said plane containing the second and third pivot axes to the same side as the connection of the third piston and cylinder assembly to the second boom part; the bell crank lever being pivotably connected at a point offset from the plane containing the second and third pivot axes to a member rotationally fast with the cutting head; the third piston and cylinder assembly being operable to actuate the bell crank lever to pivot the cutting head about said third axis.

12. A vegetation cutting machine as claimed in claim 10 or 11, wherein the cutting head is pivotable relative to the boom arrangement through a range of less than 360C and is connected to the boom arrangement via an adjustable coupling permitting selection of the disposition of this range about the pivotal axis of the cutting head.

13. A vegetation cutting machine as claimed in claim 12, wherein said adjustable coupling is between two housing parts of a drive shaft arrangment of the cutting head, one of these housing parts being fast with the boom arrangement and the other being fast with a casing of the cutting head, the coupling including a clamp having cam surfaces cooperating with flanges of the housing parts to secure the housing parts rotationally fast, this clamp being releasable to permit relative rotation of the two housing parts.

14. A vegetation cutting machine as claimed in claim 12, wherein said adjustable coupling is between two housing parts of a drive shaft arrangement of the cutting head, one of these housing parts being fast with the boom arrangement and the other being fast with a casing of the cutting head, the coupling including slots in the flanges and bolts passed through the slots to secure the housing parts rotationally fast, these bolts being releasable to permit relative rotation of the two housing parts.

15. A vegetation cutting machine substantially as hereinbefore described with reference to Figures 1, 1 A and 2 to 5 of the accompanying drawings.

16. A vegetation cutting machine substantiallv as hereinbefore described with reference to Figures 1, 1A, 2A and 3 to 5 of the accompanying drawings.