GB2526830A - Timber harvester and billet-former - Google Patents

Abstract

A timber harvesting machine comprising a gripper 6 with laterally opposed jaws for gripping standing timber and a rotary cutting device 4 arranged to cut down the standing timber. The gripper may be mounted on the end of a forwardly projecting extendable arm 1 and may be articulated about a horizontal axis. The cutting device may be arranged to travel in a predetermined path beneath the gripper. The cutting device may comprise two laterally spaced horizontal rotary cutting blades (11 figure 2). Also disclosed is a billet forming machine 30 comprising a cutting wheel 7 and means for feeding lengths of timber towards the cutting wheel to form aculeate billets. Also disclosed is a timber harvesting vehicle comprising a projecting cutting device, an onboard timber cutting machine, a means for feeding the timber to the cutting machine and a discharge conveyer 80. Also disclosed is a timber harvesting machine comprising a gripper, a rotary cutting device a billet forming machine, a means for conveying timber to the billet machine and a discharge conveyor to discharge billets to a bagging device. Also disclosed is a container 100 or pile of timber billets.

Description

I

Timber Harvester and Billet-former The present invention relates to timber harvesting, to billet forming, to a pile or container of timber billets and to a timber-harvesting vehicle. The invention relates particularly but not exclusively to a vehicle for timber harvesting (eg short rotation coppice harvesting) which cuts standing timber, forms the cut timber into billets and/orbags the cuttimber.

In recent years there has been considerable interest in coppice harvesting of timber to provide a sustainable fuel, eg for power stations.

GB 2,357,4l7A discloses a combined timber harvester/baler vehicle which includes a cutting head (eg a circular saw) for cutting coppice stems at the base. The stems are guided with a pusher bar but fall freely, after which they are fed to a baler. The stems are cut to length, compressed and baled in the baler and are then deposited at a suitable roadside location for drying and subsequent collection.

The vehicle described above can safely access coppiced timber and can be fully operated by one person. In particular, it can replace manual coppice harvesting using hand-held chainsaws, a procedure which involves risks to the operatives which are often commercially unacceptable.

However the vehicle disclosed in GB 2,357,417A has certain drawbacks. It is not always easy in practice to collect the cut stems. The baled timber, being compressed and tightly packed, does not always dry out quickly, and moreover requires further processing before it can be used as fuel eg in power stations. In particular, it must be cut and processed into pellets, a process requiring significant energy input.

The BioChip 50 tracked harvester vehicle was designed by the present applicant to pick up felled timber or forest residue from the forest floor and has a conventional grab mounted onto a crowd action arm with tines hanging in the vertical plane. The grab feeds the collected timber into a conventional chipper which blows the fine chips into a bag or heap. However it has no timber felling capability and the chipper requires a lot of energy.

Furthermore the storage of wood pellets in large silos can be problematic, since air circulation through the pellets is limited and heat build up can occuç with a consequent fire risk.

In its various aspects, the present invention overcomes or alleviates various of the above drawbacks.

In one aspect the invention provides a timber harvesting machine comprising a gripper provided with laterally opposed jaws for gripping standing timber and a rotary cutting device arranged to cut down said standing timber, said gripper being arranged to support the timber being cut.

Preferably the jaws project forwardly.

The gripper reduces movement of the timber whilst it is being cut (an important safety feature) and also facilitates retrieval of the cut timber.

Preferably said gripper is arranged to bend said standing timber so as to tension a region thereof exposed to said cutting device.

This feature facilitates cutting of the timber by tending to prevent binding of the timber against the cutting device (eg a rotary saw blade).

Preferably said gripper is mounted at the forward end of a forwardly-projecting arm and is articulated about a horizontal axis to enable it to swing cut timber rearwardly.

This feature (which is particularly useful for coppice harvesting) enables the vehicle to remain stationary during retrieval of the cut thnber and in preferred embodiments allows the cut timber to be processed on board the vehicle, eg in a billet-former.

Preferably the cutting device is mounted for travel in a predetermined path beneath said gripper This feature tends to ensure that the cutting device remains in a safe zone defined by the gripper Preferably said cutting device comprises two laterally spaced substantially horizontal rotaty cutting blades mounted for travel in parallel paths beneath said gripper so as to cut said standing timber This feature tends to balance the forces applied to the gripper by the action of the cutting blades on the stems.

Preferably said rotaiy cutting device is mounted between two laterally-spaced arms of a substantially horizontal frame, said frame being open at a forward end thereof; the region between said aims including a cutting zone of said rotaiy cutting device and said frame being advanceable to admit standing timber between said arms and cut it in said cutting zone.

The laterally-spaced arms, which isolate the cutting zone, are an important safety feature.

Preferably said cutting device is arranged in use to cut at an inclination (eg 5° to 15°) to the ground surface.

This feature ensures that rain does not collect on the cut surfaces of the stems and thereby prevents rot.

Other preferred features are defined in the dependent claims.

In another aspect the invention provides a billet-forming machine comprising a cutter wheel having a circumferential array of cuffing heads, the cutting heads having axially-extending cutting edges, and means for feeding lengths of timber toward the rotating cutter wheel into the path of said cutting edges, whereby in use, S circumferentially adjacent cutting heads make spaced-apart arcuate cuts in the timber to form generally arcuate billets.

Arcuate billets have an advantage over straight (or cylindrical) billets or logs that they tend to pack more loosely in a pile or container, forming air circulation passages between them. This facilitates drying and also tends to prevent heat build-up which can represent a fire hazard.

Additionally, arcuate billets tend to crack at the arcuate surfaces during drying, and the cracks allow egress of moisture which aids further drying.

Preferably an anvil is disposed adjacent said cutter wheel and provides an anvil surface which in use supports an end of a length of timber being fed into the path of said cutting edges.

This feature assists in shearing off the billets.

Preferably said cutting heads are in the form of plates, each having opposite leading and trailing cutting edges, and being reversible to interchange the leading and trailing cutting edges.

This feature avoids the need to sharpen the cutting heads until both cutting edges of each blade have been used as the leading edges.

Preferably the billet-forming machine comprises a plurality of axially adjacent circumferential arrays of cuffing heads, the axially adjacent arrays being mutually angularly offset to enable them to form respective streams of billets in parallel.

S

This feature enhances the output of the machine and also evens out the load on the motor driving the cutting wheel.

Preferably the or each array of cuffing heads is shaped and dimensioned to form billets having minimum dimension of 10 mm, more preferably a minimum dimension of 15 mm, most preferably a minimum dimension of 20mm.

The machine can be used for forming timber billets by feeding it with cut coppice stems.

In another aspect the invention provides a timber-harvesting vehicle comprising a projecting cutting device for cutting down standing timber, an on-board timber-cutting machine, means for feeding the cut-down timber to an intake of the on-board timber-cuffing machine, and a discharge conveyor arranged to discharge pieces of timber from the timber-cutting machine to a bagging device.

in this aspect the invention enables timber to be harvested easily and provided in bags which can be transported to a central location for drying and optionally further processing.

Preferably said discharge conveyor is arranged to lift the timber pieces from the timber-cuffing machine and to feed them into the mouth of a bag.

This feature enables a deeper bag to be used.

Preferably said on-board timber-cuffing machine is a billet-forming machine.

Preferably the timber-harvesting vehicle is an off-road vehicle, said projecting cutting device, on-board timber-cuffing machine and bagging device being operable by the driver.

Other preferred features are defined in the dependent claims.

In another aspect the invention provides a timber-harvesting vehicle comprising: a gripper for gripping standing timber; a rotary cutting device arranged to cut down said standing timber, said gripper being arranged to support the timber being cut; a billet-forming machine; means for feeding the cut-down timber to an intake of the billet-forming machine, and a discharge conveyor arranged to discharge billets from the billet-forming machine to a bagging device.

The above combination of features enables timber to be harvested expeditiously and provided in bagged form suitable for use directly as fuel after a suitable drying period.

The timber-harvesting machine, billet-forming machine and timber-harvesting vehicle in accordance with the different aspects of the invention, and their preferred features, can be combined, as will become apparent from the description of the preferred embodiment.

Finally, in another aspect the invention provides a container or pile of timber billets, the billets being elongate, arcuate in the longitudinal direction, and having a generally rectangular transverse cross-section.

As noted above in connection with the second aspect of the invention, such arcuate billets have important advantages in terms of packing and consequent ease of drying.

Preferably said rectangular transverse cross-section has dimensions in the range 20 mm to 80 mm, preferably 30mm to 60mm, most preferably 45 mm to 55 mm, The above dimensional ranges represent a good compromise between the energy needed to form the billets, their rate of drying and their combustion performance.

Preferably said billets have a radius of curvature of less than 1 metre, preferably less than 0.5 metre, most preferably less than 0.3 metre.

Preferably said billets have a length along their arcuate longitudinal axis of less than 0.5 metre, preferably less than 0.3 metre.

Lower radii of curvature (greater deviations from straightness) and shorter lengths lead to a greater irregularity in packing and hence larger air passages between the billets, The billets are typically randomly oriented to provide channels for air circulation between them.

Preferred embodiments of the invention are described below by way of example only with reference to Figures 1 to 15 of the accompanying drawings, wherein: Figure 1 is a side elevation of a timber-harvesting vehicle in accordance with the first four aspects of the invention, in use for coppice-harvesting; Figure 2 is a top plan view of the grapple and circular saw blades of the vehicle of Figure 1; Figure 3 is a side elevation of the main components of the rotary cutting assembly of the vehicle of Figure 1; Figure 4 is a front elevation (ie viewed from the left in Figure 1) of the rotary cutting assembly of the vehicle of Figure 1; Figure 5 is a top plan view of the grapple of the vehicle of Figure 1 showing its extreme open and closed positions; Figure 6 is a side elevation of the grapple of Figure 5; Figure 7 is a somewhat schematic side elevation of the billet-forming machine used in thevehicle of Figure 1; Figure 8 is a transverse cross-section of a cutting head utilised in the cutter wheel of the billet-forming machine of Figure 7; Figure 9 is a schematic top plan view of the cutter heads of the cutter wheel of the billet-forming machine of Figure 7; Figure 10 is a schematic side elevation showing the action of the cutter wheel of the machine of Figure 7 in forming a billet; Figure 11 is an end elevation showing the action of the cutter wheel on a log fed into the billet-forming machine of Figure 7; Figure 121s a perspective view of a billet formed by the machine of Figure 7; Figure 13 is a somewhat diagrammatic elevation showing a container (and alternatively a pile) of billets in accordance with the fifth aspect of the invention; Figure 14 is a top plan view of the forklift device utilised in the bagging device of the timber-harvesting vehicle of Figure 1. and Figure 15 is a side elevation of the forklift device of Figure 14.

Referring to Figure 1, the timber-harvesting vehicle shown is provided with left and right tracks 15 which are independently tiltable (using eg the ALTOSH system of Richard Smalley Technical Services Ltd) to maximise their contact with the ground G and thereby provide optimum stability to a platform 9 which is maintained horizontal by hydraulic jacks and mounted on a turntable for rotation in the horizontal plane. Vehicles as described thus far (eg the BioChip 50) are commercially available from Richard Smalley Technical Services Ltd and described and illustrated in WO 97/4349 IA for example.

Platform 9 carries the driver's cabin, a forwardly-projecting telescopic arm 1 which carries a grapple comprising laterally opposed gripperjaws 6 at its forward end, and an on-board billet-forming machine 30 which is fed by an internal conveyor (not shown in Figure 1 but described in detail with reference to Figure 7 below) . Billets from billet-forming machine 30 are carried upwardly and rearwardly by an inclined discharge conveyor 80 to a bag 100 carried on a forklift mechanism 31.

A frame 4 is canied in front of the vehicle beneath grapple 6 and is supported at mounting points 21 by hydraulic jacks which are controlled to allow the frame to float at or near ground level. Frame 4 is open at the front and includes forwardly-extending lateral aims which, as described below (and illustrated in Figures 3 and 4) include slide mountings for two rotary saw blades which define a cutting zone between the lateral arms, Accordingly, as shown in Figure 1, the frame 4 fits around coppice C, the stems of which are gripped by grapple 6 and then cut near ground level by the rotary saw blades as they traverse the cufting zone. The cut stems can then be swung downwardly and rearwardly into billet-former 30 by rotation of grapple 6 about articulation axis X at the forward end of telescopic arm 1.

The above gripping and cutting operations are shown diagrammatically in Figure 2.

The gripper jaws 6 are shown closed around coppice stems Cl to C7 and are advanced (by extension of telescopic arm 1) to bend the coppice stems forwardly as well as inwardly. The bending of the stems creates outer regions in tension as shown by the shaded cross-sections in the drawing, and counter-rotating circular saw blades 11 are advanced as shown by the arrows A to cut, initially these regions, and then the complete stems. The jaws 6 can be closed further during this process to S maintain grip on the cut stems.

Further constmctional details of the cutting assembly and the grapple are shown in Figures 3 to 6.

Referring to Figures 3 and 4, the frame 4 comprises two lateral, forwardly-extending arm portions 43 which are connected at their rear ends by upper and lower cross beams 13. Thus the frame is open at the front and can admit coppice stems into a cutting zone between arm portions 43, As is also shown in Figure 1, the frame is carried at four rear mounting points 21 and can be lifted clear of the coppice stumps (by hydraulic jacks on the vehicle) once the cutting process has been completed.

Twin counter-rotating circular saw blades 11, driven by hydraulic motors 12, are supported on carriages 13 which mn forwardly and rearwardly within arm portions 43. The saw blades 11 are driven by motors 22 via mulit-vee belts 14. For ease of maintenance, the saw blades 11 are retained by quick-change domed keepers (not shown).

The saw blades are inclined outwardly at angles of eg 70 or 100 to the horizontal to ensure that rainwater does not collect on the stumps of the cut coppice stems.

The carriages 13 are supported on conical rollers 18 and can be advanced (in the direction of arrow A) and retracted by roller chains 17 which mn around front and rear sprockets. The rear sprockets are driven via further roller chains 19 which are coupled to a common hydraulic motor 12 by a transverse drive shaft 16 (Figure 4).

Thus the saw blades 11 are advanced and retracted in unison. Forward and rearward travel of the carriages 13 is limited automatically by stop plates housing conventional hydraulic or electrical sensors (not referenced).

In order to stabilise the frame 4 on uneven ground during cutting operations, jacks 16, controlled by double-acting hydraulic rams (not shown), are provided at the forward ends of arms 43.

Figures 5 and 6 show the grapple assembly in detail.

Referring to Figure 5, the jaws 6A, 6B are shown in the fully open orientation and, in phantom (6N 6B'), in the fully closed orientation, the angle between these extremes being 1210, As best seen in Figure 6, the jaw 6A is divided into upper and lower portions with a central gap which accommodates opposing jaw 6B to allow the jaws to cross over as shown by configuration 6A' 6B' in Figure 5. The jaws are operated in the lateral plane by hydraulic cylinders 20 acting on linkages 23 and in preferred embodiments can gather a coppice up to 3 metres in diameter into a bundle of stems of diameter as little as 200 mm, Referring to Figure 6, the jaw assembly can be swung about axis X by hydraulic cylinder 24 and an associated linkage, the angle of travel being 27° as shown, In use, once the coppice stems have been cut, the hydraulic cylinder 24 is operated to swing the jaws and their gripped coppice stems rearwardly and downwardly (anticlockwise in Figure 6) until the coppice stems are horizontal, The arm I can then be retracted to feed the stems into billet-forming machine 30 (Figure 1).

Billet-forming machine 30 is shown in detail in Figures 7 to 10.

Figure 7 shows a group of horizontal coppice stems (or cut timber in other forms) being fed by a powered spiked conveyor S to a cutter drum 7. The coppice stems are held against the conveyor by a toothed wheel 3 which is urged downwardly by a linkage arm connected to its axle and pivoting about rotary axis L of cutter wheel 7.

The linkage arm is acted on by a hydraulic cylinder 2, pivotally supported at axis I The retracted position of the toothed wheel is shown in phantom at 3'.

Cutter drum 7, also shown diagrammatically in plan view in Figure 9, carries angularly offset circumferential arrays of cuffing heads CH, each array being shown with different shading for clarity in Figures 7 and 9. As shown, each circumferential array of cutting heads comprises a regular array of eg three cuffing heads 120° apart, each array being mounted on a rotor (not shown) and angularly offset from its preceding axially neighbouring array by the angle subtended by one cutter blade 7, forming helical tracks of cutting heads as shown in Figure 9. For the sake of clarity, only four circumferential arrays of cutting heads are shown in Figures 7 and 9 but in a preferred embodiment, cutter drum 7, which is 375 mm long (in the axial direction), accommodates five circumferential arrays of three cutting heads CH, each array being mounted on a respective rotor. Each of the five rotors, having 15 cutting heads in total, is mounted on the centre drive shaft at 72° to the previous rotor to provide a spiral cutting action. In this example a 200 mm diameter log would have three blades cutting at one time as shown in Figure 11.

Any suitable number of circumferential arrays of cutting heads may be employed, eg three, four (as shown in Figures 7 and 9) five (as noted above) or six or more.

As shown in Figure 8, each cuffing head is substantially trapezoidal in transverse cross-section, having axially-extending cuffing edges CE at the leading and trailing ends of its radially outer (longer) face, A machined channel S with an associated counter bore is provided to enable the cuffing head to be bolted to a spoke of cuff er drum 7. To this end each spoke has a machined top hat step running parallel to the drive shaft of drum 7 to fit recess S. Each spoke has a leading surface whose profile is concave, in order to apply a curvature to the billets during operation.

The blade angle at each cutting edge is 27°. Each cutting head CH can be removed and reversed (interchanging the leading and trailing cutting edges CE) when the leading cutting edge becomes blunt.

A shear blade or anvil 8 is provided beneath cutting drum 7, narrowly spaced from the path of the cuffing edges of the cuffing heads CH, This co-operates with the cutting heads to form billets 26 which are guided to an inclined discharge conveyor 80.

The operation of the billet-forming machine is illustrated diagrammatically in Figure 10. The end of the cut timber 25 advances (from left to right as shown in the Figure) into the the cutter drum 7 (whilst the cutter drum is rotating anticlockwise) and towards the associated anvil.

The arrangement is shown in end elevation in Figure 11. Cuffing heads CH of axially adjacent arrays are shown, each array forming its own series of billets. For the sake of simplicity, the action of only two cutting heads of one array is shown in Figure 10. At any one time at least one cutting head (eg C112) will stop the stems 25 from progressing until a billet has been completely sheared off which allows the conveyor 5 (Figure 7) to complete a certain travel until the next cutting head strikes the stems. That travel is suitably adjusted to match the speed of the cutting drum 7 and the desired billet thickness. For example one half a revolution of the cutting drum 7 may cut a billet 50 mm thick so one complete revolution would correspond to a travel (of conveyor 5) of 100 mm, Referring to Figure 9, it will be seen that a helical gap C between the cutting heads CG is formed, The width of each bundle of stems 25 will be less than the longitudinal dimension of cuffing drum 7 but greater than the width (in the longitudinal direction) of an individual cutting head CH. Accordingly as each successive portion of bundle 25 is fed into cutting drum 7 a number of streams of billets will be cut off in parallel, each array cutting off its own stream of billets. For the sake of simplicity however, Figure 10 and the following description refer to the action of two cutting heads of one array only in producing one stream of billets, Referring to Figure 10, a first cutting head Cilt has made a first cut (CUT!) in the timber 25 and this is a radially inner concave surface of the forming billet. In the position shown in Figure 10, a second cutting head CH2 is starting a second cut (CUT 2) and this is a radially outer convex surface of the forming billet. The second cut shears off the billet, The shearing effect of the leading face of culling head CH2 bends the forming billet radially inwards and this is enhanced by the concave profile of the leading surface 90 of the spoke carrying the cutting head.

In other words, as the timber is fed into the cutter wheel 7, it enters a gap between circumferentially adjacent leading and trailing cutting heads Cl-TI and CH2 and the portion of timber in the gap is cut off and bent radially inwardly by the trailing cutting head CH2 to form a billet 26.

Furthermore the concave leading surface 90 disposed radially inwardly of the cutting head forms cracked convex surfaces of the billets during use.

The resulting billet 26 is shown in Figure 12. The shearing and bending described above result in cracks 26A which facilitate drying of the billet and also combustion when drying has been completed and the billet is used as fuel. The dimensions a (width) and b (thickness) are preferably in the range 10 mm to 150 mm, more preferably 5 mm to 150 mm, most preferably 20mm to 00 mm, Preferably thickness dimension b is in the range 10 mm to 50 mm and width dimension a is in the range 50 mm to 150 mm, The dimension c (the length along the arcuate longitudinal axis) is preferably less than 0.5 metre, more preferably less than 0.3 metre. This dimension is limited by the diameter of the stems in bundle 25 -for example a log of diameter 200 mm will produce a billet of length approximately 200 mm (or less if the timber breaks during billet formation).

Preferably the billets have a radius of curvature of less than 1 metre, more preferably less than 0.5 metre, most preferably less than 0.3 metre, Figure 13 shows, somewhat diagrammatically, a container 100 or a pile 100' of billets 26 packed randomly. Because they are curved and somewhat irregular in shape (as a result of variations in the shearing effect of the cutting heads) they do not pack closely and voids V occur which provide air passages for drying, and for dissipating any heat that might build up in the mass of billets.

The discharge conveyor 80 feeds the billets 26 to the mouth of a bag 100 (Figure 1) which is supported on a forklift device. The forklift device is shown in Figures 14 and 15 and comprises a vertically movable frame 33 having three rearwardly facing anns 31 which carry the bags of billets (not shown), In order to stop the bags of billets from falling off when working on sloping ground, hydraulically or electrically controlled pegs 32, controlled by actuators 36 are provided on the arms 3 1. The pegs can be retracted to a position flush with the upper surfaces of the arms 31 when it is desired to remove the bags of billets.

The frame 33 is mounted in a mast 41 and can be raised and lowered by a downwardly-extending hydraulic actuator 34 carrying a lower roller 39 which engages a loop in a belt or chain 35. The belt or chain 35 is connected at its ends to a fixed point, eg on mast 34, and to the frame 33 and runs over a further upper roller 39 as shown, whereby extension of the hydraulic actuator raises the forklift frame Preferably the entire forklift assembly is rotatable in a horizontal plane to enable the bags of billets to be deposited at either side of or behind the vehicle.

Claims (39)

1. Claims A timber harvesting machine comprising a gripper provided with laterally opposed jaws for gripping standing timber and a rotary cutting device arranged to cut down said standing timber, said gripper being arranged to support the timber being cut.
2. 2. A timber harvesting machine according to claim I wherein said gripper is arranged to bend said standing timber so as to tension a region thereof exposed to said cutting device.
3. 3. A timber harvesting machine according to claim 1 or claim 2 wherein said gripper is mounted at the forward end of a forwardly-projecting arm and is articulated about a horizontal axis to enable it to swing cut timber rearwardly.
4. 4. A timber harvesting machine according to any preceding claim wherein said cutting device is mounted for travel in a predetermined path beneath said gripper.
5. 5, A timber harvesting machine according to claim 4 wherein said cutting device comprises two laterally spaced substantially horizontal rotary cutting blades mounted for travel in parallel paths beneath said gripper so as to cut said standing timber.
6. 6. A timber harvesting machine according to any preceding claim wherein said cutting device is mounted between two laterally-spaced arms of a substantially horizontal frame, said frame being open at a forward end thereof the region between said arms including a cutting zone of said cutting device and said frame being advanceable to admit standing timber between said arms and cut it in said cutting zone.
7. 7. A timber harvesting machine according to any preceding claim wherein said cutting device is arranged in use to cut at an inclination to the ground surface.
8. 8. A timber harvesting machine according to claim 7 wherein said cutting device is arranged to cut an an inclination of 50 to 15° to the ground surface.
9. 9. A timber harvesting machine according to any preceding claim wherein said ann which projects forwardly above a caniage on which said cutting device is mounted near ground level.
10. 10. A timber harvesting machine according to claim 8 wherein said arm is extendable in a forward direction.
11. 11. A timber harvesting machine according to any preceding claim which is an off-road vehicle, said gripper and cutting device being controllable by the driver.
12. 12. A limber harvesting machine according to claim 11 wherein said gripper and/or said cutting device are powered from the vehicle engine.
13. 13. A timber harvesting machine according to claim 11 or claim 12 wherein said gripper and/or said cutting device are hydraulically or electrically driven.
14. 14. A billet-forming machine comprising a cutter wheel having a circumferential way of cutting heads, the cutting heads having axially-extending cutting edges, and means for feeding lengths of timber toward the rotating cutter wheel into the path of said cutting edges, whereby in use, circumferentially adjacent cutting heads make spaced-apart arcuate cuts in the timber to form generally arcuate billets.
15. 15. A billet-forming machine according to claim 14 wherein an anvil is disposed adjacent said cutter wheel and provides an anvil surface which in use supports an end of a length of timber being fed into the path of said cutting edges.
16. 16. A billet-forming machine according to claim 14 or claim 15 wherein said cuffing heads are in the form of plates, each having opposite leading and trailing cutting edges, and being reversible to interchange the leading and trailing cutting edges.
17. 17. A billet-forming machine according to any of claims 14 to 16 comprising a plurality of axially adjacent circumferential arrays of cutting heads, the axially adjacent arrays being mutually angularly offset to enable them to form respective streams of billets in parallel.
18. 18. A billet-forming machine according to any of claims 14 to 17 wherein said cutter wheel is provided with rotating concave leading surfaces disposed radially inwardly of respective cutting heads, said concave leading surfaces forming cracked convex surfaces of the billets during use,
19. 19. A billet-forming machine according to any of claims 14 to 18 wherein the or each array of cutting heads is shaped and dimensioned to form billets having minimum dimension of 10mm..
20. 20. A method of forming timber billets comprising feeding cut coppice stems to a billet-forming machine as claimed in any of claims 14 to 19.
21. 21. A timber-harvesting vehicle comprising a projecting cutting device for cutting down standing timber, an on-board timber-cuffing machine, means for feeding the cut-down timber to an intake of the on-board timber-cutting machine, and a discharge conveyor arranged to discharge pieces of timber from the timber-cutting machine to a bagging device.
22. 22. A timber-harvesting vehicle according to claim 2 wherein said discharge conveyor is arranged to lift the timber pieces from the timber-cutting machine and to feed them into the mouth of a bag.
23. 23. A timber-harvesting vehicle according to claim 21 or claim 22 wherein said bagging device includes a forklift device adjacent an outlet end of the conveyor.
24. 24. A timber-harvesting vehicle according to claim 23 wherein said forklift device is operated by a hydraulic ram acting on a 1oop of a lifting chain or belt coupled between a fixed point and the fork assembly of the forklift device, whereby travel of the hydraulic ram is amplified.
25. 25, A timber-harvesting vehicle according to claim 23 or claim 24 wherein said forklift device is mounted for rotation in a horizontal plane.
26. 26. A timber-harvesting vehicle according to any of claims 21 to 25 wherein said forklift device has vertically retractable retaining pegs on a fork assembly thereof for engaging the underside of a bag of timber pieces.
27. 27. A timber-harvesting vehicle according to any of claims 21 to 26 wherein said on-board timber-cufting machine is a billet-forming machine,
28. 28. A timber-harvesting vehicle according to claim 27 wherein said billet-forming machine is as claimed in any of claims 14 to 19.
29. 29. A timber-harvesting vehicle according to any of claims 21 to 28 which is an off-road vehicle, said projecting cutting device, on-board timber-cutting machine and bagging device being operable by the driver.
30. 30. A timber-harvesting vehicle comprising: a gripper for gripping standing timber; a rotary cutting device arranged to cut down said standing timber, said gripper being arranged to support the timber being cut; a billet-forming machine; means for feeding the cut-down timber to an intake of the billet-forming machine, and a discharge conveyor arranged to discharge billets from the billet-forming machine to a bagging device.
31. 3]. A timber harvesting vehicle according to claim 30 wherein said gripper is as defined in any of claims 2, 3 or 9 to H.
32. 32. A timber harvesting vehicle according to claim 30 or claim 3] wherein said rotary cutting device is as defined in any of claims 4 to 8, ]2 and]3.
33. 33. A timber harvesting vehicle according to any of claims 30 to 32 wherein said billet-forming machine is as defined in any of claims 14 to 19.
34. 34. A timber harvesting vehicle according to any of claims 30 to 33 wherein said bagging device is as defined in any of claims 23 to 26.
35. 35. A container or pile of timber billets, the billets being elongate, arcuate in the longitudinal direction, and having a generally rectangular transverse cross-section.
36. 36. A container or pile of timber billets according to claim 35, wherein said rectangular transverse cross-section has dimensions in the range 10 mm to 50 mm, preferably 15mm to 150 mm, most preferably 20mm to too mm.
37. 37. A container or pile of timber billets according to claim 35 or claim 36, wherein said billets have a radius of curvature of less than 1 metre, preferably less than 0.5 metre, most preferably less than 0.3 metre.
38. 38. A container or pile of timber billets according to claim 35 or claim 36 or claim 37, wherein said billets have a length along their arcuate longitudinal axis of less than 0.5 metre, preferably less than 0.3 metre,
39. 39. A container or pile of timber billets according to any of claims 35 to 38 wherein said billets are randomly oriented to provide channels for air circulation between them. 2]40. A container or pile of timber billets, the timber billets being substantially as described hereinabove with reference to Figures 12 and 13 of the accompanying drawings.4] A billet-forming machine substantially as described hereinabove with reference to Figures 7 to 11 of the accompanying drawings.42. A timber harvesting machine substantially as described hereinabove with reference to Figures Ito 15 of the accompanying drawings.