BACKGROUND OF THE INVENTION

1 . Field of the Invention

[0001 ] This invention relates to tree harvesters.

[0002] The invention particularly relates, but is not limited to, tree harvesters suitable for harvesting shrubs, coppice, or tall single stem trees, where such trees are planted at preferably regular spacing in rows.

2. Dictionary

[0003] The term "trees" shall be used throughout the specification to describe shrubs and trees which have either a single-stemmed form; or a plurality of coppice stems extending generally upwards from a tree stump or lignotuber; and by example, includes trees of the Eucalyptus and Acacia genera indigenous to Australia; and of the Salix and Populus genera indigenous to Europe and North America.

[0004] The term "in a substantially vertical position" will be used throughout the specification to indicate that a stem of a tree is inclined at an angle (preferably) no more than 30° to the vertical Z axis.

[0005] The term "harvester" will be used throughout the specification to define a chipper device, mounted to a mobile vehicle that moves along row of trees, continuously chipping each stem into a desired particle size.

[0006] The term "pour rate" will be used throughout the specification to define the speed that chipped material flows through the harvester and is measured in green metric tonnes per hour. This is an important measurement of performance of the tree harvesters.

3. Prior Art

[0007] NB: The following discussion is by way of background information only, and is not to be considered a statement of the common general knowledge (CGK) in the area of technology, anywhere in the world.

[0008] It has been proposed, internationally, to grow trees (as hereinbefore defined) of the Eucalyptus, Populus and Salix genera as an ecologically- based energy and fiber feedstock. [0009] As the Eucalyptus, Populus and Salix genera are fast-growing, their biomass can be used as a "renewable" source of energy, fibreboard or paper pulp, as the trees can be harvested every 2-6 years.

[0010] The key challenge has been the ability to economically chip the trees and transport the chipped biomass from the tree growing areas to industry processors e.g., fiberboard and paper manufacturers, electricity generators, heat users and biofuel convertors.

[001 1 ] Efforts to solve this challenge have initiated research to develop efficient continuous tree chipper harvesters in Australia to improve pour rate productivity measured in terms of weight or volume per hour, thereby reducing the cost of chipping trees.

[0012] Example of two such "PRIOR ART" prototype continuous tree chipper harvesters will now be described.

[0013] International Patent application PCT/AUOO/00171 (= International Publication WO 00/52998) (Oil Mallee Company of Australia Pty Ltd) discloses a tree harvester ("the Giles harvester") mounted on a tractor, where transport means, in the form of vertically-spaced endless chain conveyors, engage the substantially vertical tree stems just before the trees are cut adjacent the bases of the stems by a rotary saw. The transport means convey the tree stems, in a substantially vertical position, towards a chipper drum rotating about a substantially horizontal axis. Counter-rotating feed rollers, and an adjustable anvil, mounted adjacent to the chipper drum, direct the stems of the trees into the chipper drum at an angle between 90° and 30° from the vertical, with the stems being guided and supported by a pair of adjustable plates while being chipped. By adjusting the location of the plates and the anvil relative to the (conventional) chipper drum, a wide range of trees can be harvested.

[0014] International Patent Application PCT/AU2010/000403 (= International Publication WO 2010/129986) (Future Farm Industries CRC Limited) discloses a tree harvester ("the Sulman harvester") which has advantages over the Giles harvester, in that the tree stems are fed substantially vertically to a chipper drum, rotating about an axis inclined at a small angle to the horizontal axis, and parallel with the direction of travel of the tree harvester. At least one pair of opposed nip rollers feed the tree stems downwardly, and rearwardly, to the chipper drum, so that the tree stems are progressively chipped as they are fed into, and along, the full length of the chipper drum. Unlike the Giles harvester, no energy and time is wasted in tipping the tree stems from the original orientation in which they are feed to the chipper drum, and the wear on the knives of the chipper drum is more evenly spread along the length of the chipper knives, extending the periods between re- sharpening. In addition, the parallel orientation of the chipper drum enables the simultaneous chipping of two or more stems in single file. This results in greater operational and energy efficiency, leading to a higher pour rate for the Sulman harvester than is possible by the Giles harvester.

[0015] Both the Giles and Sulman harvesters have advantages over previous tree harvesters for smaller trees, where many of those harvesters were based on forage harvesters, originally designed for harvesting thin stemmed cereal and grass crops, and horizontal disc chippers for discrete vertical chipping of individual tree stems. However, with both those harvesters, there can be difficulties in maintaining control over the lower ends of the tree stems when transitioning between the conveyor and nip rollers that feed the lower ends of the tree stems to the chipper drum. Both harvesters were designed to release the lower ends of the tree stems from the inclined linear grip of the conveyor, then drop them to the opposing nip rollers positioned, above (Sulman harvester), or adjacent (Giles harvester), the chipper drum. This brief disconnection of the lower ends of the tree stems between the inclined linear pinch of the conveyor and the rotational pinch of the of the nip rollers, for feeding the tree stems substantially vertically to the chipper drum of a tree harvester, provided opportunity for the tree stems to escape grip and rotate about the top conveyor or auger feed means, resulting in the lower ends of the tree stems to miss engagement with the nip rollers. This was particularly prevalent during episodes of high wind velocity, causing the tree stems to tip over and block the harvester, and detrimentally affect the pour rate. [0016] Another limitation, of both the Sulman and the Giles harvesters, was that the axes of the opposing nip rollers were held parallel between being the fully closed to fully open positions, affecting the ability of the nip rollers to positively pinch multiple tree stem diameters simultaneously.

[0017] Commercial chipping machines come in two main types: disc chippers and drum chippers. Moveable disc chippers are most commonly used for the production of pulp chips; whereas moveable drum chippers are found to be better suited to chipping tree forms, with more branches, due to their relatively larger feed aperture. Larger static disc- and drum chippers are used on terminals for chipping cut-to-length logs.

[0018] Both disc- and drum chippers serve different chipping functions, due their cutting geometry and physical construction. Both have positive and negative attributes, depending on the material required to be chipped, and the relative priority between energy efficiency and chip quality.

[0019] While disc chippers provide superior control over their cutting geometry; and more importantly, their ability to maintain a consistent cutting angle throughout each cut; their aperture is limited in length to less than half the disc radius;, whereas, with a drum chipper, the aperture can be as long as the drum itself. This gives drum chippers an advantage over the types and volume of material they can process.

[0020] Basically, disc chippers have the advantage of controlling optimum cutting angles for maximising energy efficiency versus chip quality; while drum chippers provide more opportunity for higher chipping productivity. In disc chippers, there is a trade-off between low chipping energy and high quality chips at the expense of volume.

[0021 ] A key criticism of drum chippers is the higher range of cutting angles between the start of the cut and the final stage of cut, as the knife-edge approaches the counter knife, or anvil. This issue is exacerbated in drum chippers when multiple layers of stems are vertically dropped or horizontally fed simultaneously to the drum chipper. While the aperture may be of a size that enables multiple layers of stems to be chipped simultaneously, there is a serious penalty in both energy efficiency and chip quality. This results in higher processing costs, while lowering the merchantable value of the wood chips.

[0022] The geometry behind chipping:

[0023] Chips are formed due to a compression force of the leading knife face against the wood. When the chipper knife enters the tree stem or log, compression stress occurs parallel to the fibre (wood grain) orientation. This compression force, and the wood's resistance to longitudinal splitting into individual chips, determines the chip thickness to chip length ratio produced; as well as the relative degree of generation of pin chips and fines.

[0024] The compression force is produced by the chipper's Lambda angle (λ) and has a significant impact on chip quality. The λ angle is the complementary angle to the angle of the log and the cutting surface of the knife. Mathematically, this is defined as λ = 90° - (α+β+ε), where a is the clearance angle, β is the knife sharpness angle and ε is the spout angle (see FIG.15). A higher λ, at a constant chip length, results in thinner chips and lower fines content.

[0025] In disc chippers, the λ angle can only be controlled by physical adjustment of either the spout angle (ε), clearance angle (a) or the knife sharpness angle (β). Once these three angles are determined and fixed, the disc chipper will maintain the λ angle consistently.

[0026] However, this is not the same for drum chippers. Large variations in λ are normal and are created when multiple logs are vertically dropped or horizontally fed simultaneously into the drum chipper. Multiple layers of logs increase the cutting height, at which the chipper knife begins cutting the logs, above (horizontal feed), or beside (vertical feed), the counter-knife or anvil.. Typically, in standard drum chippers, when the knife begins cutting the top layer of logs, the λ angle is not only dramatically lower than desired, it is often starting at a negative angle (see FIG.16, resulting in detrimental outcomes, such as, significantly higher energy consumption per volume chipped (specific energy); plastic deformation causing damage to the wood fibres; and-or a wide distribution of chip size uniformity; all contributing to lowering the economic value of the chips produced. [0027] One design constraint with a mobile chipper (i.e. tree harvester) is that the chipper means needs to be sufficiently compact to fit within a vehicle. Disc chippers are constructed with a large disc, and have a relatively small aperture compared to drum chippers. Productivity is a key factor in reducing commercial cost -; therefore, the need for a chipping means to have a sufficiently large aperture to process multiple tree stems simultaneously in single file is critical. Thereby, a drum chipping means orientated parallel to the direction of travel is the preferred chipping means for mobile chipper harvesters.

[0028] Regardless of whether the tree stems are feed to the d:rum chipper vertically or horizontally, the key challenges include:

1 . Aligning and forcing the stems to be presented in single plane along the axis of the drum, to minimise the angle variation of the spout angle (ε) and lambda angle (λ) between the start and finish of the cut, thereby holding the spout angle (ε) and lambda angle (λ) closer to the desired optimal angles required to increase energy efficiency and increase chip uniformity.

2. Maximising the productivity of the drum chipper by chipping multiple stems fed inwardly and rearwardly along the full length of the chipper drum (i.e. axial flow), thereby maximising the available blade length per cut.

OBJECTS OF THE PRESENT INVENTION

[0029] It is an object of the present invention to provide an efficient method for controlling the lower ends of the tree stems being fed to the chipper drum of a tree harvester.

[0018] It is a preferred object to provide suitable apparatus to affect the method.

[0030] Other preferred objects will become apparent from the following description. SUMMARY OF THE PRESENT INVENTION:

[0031 ] In one aspect, the present invention resides in a method of feeding tree stems to a chipper drum of a tree harvester of the type having a pair of opposed nip rollers provided above a chipper drum, the method including the steps of:

a) conveying the tree stems by a conveyor in a substantially vertical orientation to a transitional feeding position upstream of the pair of opposed nip rollers;

b) engaging the tree stems by at least lower feed means of transitional feed means at the transitional feeding position; and

c) feeding the tree stems by the transitional feed means to the pair of nip rollers, so that the lower ends of the tree stems are located at least below the rotational axes of the pair of nip rollers.

[0032] Preferably, the lower ends of the tree stems are fed so as to be intermediate the pair of nip rollers and the chipper drum, so that the lower ends can be fed downwardly towards, and rearwardly along, the chipper drum by the pair of nip rollers.

[0033] Preferably, when there are two or more, vertically-spaced, pairs of opposed nip rollers, the lower ends of the tree stems are at least below the rotational axes of the lowermost pair of the pairs of nip rollers.

[0034] Preferably, the tree stems are engaged by the lower feed means above their lower ends, where the lower feed means include at least one pair of opposed rotating spirals or helixes, which are downstream convergent, and which rotate with the pitches of the spirals or helixes in unison with a horizontal linear speed of the conveyor conveying the tree stems.

[0035] Preferably, in step a), the lower ends of the tree stems are engaged in a linear pinch grip between opposed inclined endless chains of the conveyor; and

in step b), the lower ends of the tree stems transition directly to a rotational pinch grip of the pair of nip rollers before the linear pinch grip is released.

[0036] Preferably, in at least step c), secondary feed means of the transitional feed means engage the tree stems, above the lower feed means of the transitional feed means, to assist in maintaining the tree stems substantially vertically as the tree stems are fed to the chipper drum. [0037] In a second aspect, the present invention resides in a tree harvester including:

a chipper drum operable to rotate about an axis substantially aligned with the direction of travel of the tree harvester;

a pair of opposed nip rollers spaced above the chipper drum, rotatable about respective rotational axes, and operable to apply a rotational pinch grip to the lower ends of the tree stems; and

conveying means operable to convey tree stems in a substantially vertical orientation to a transitional feeding position upstream of the pair of nip rollers, wherein:

at least lower feed means of transitional feed means engage the tree stems at the transitional feeding position and are operable to feed the tree stems to the pair of nip rollers so that the lower ends of the tree stems are located at least below the rotational axes of the pair of nip rollers.

[0038] Preferably, the transitional feed means are operable to feed the lower ends of the tree stems intermediate the pair of nip rollers and the chipper drum, so that the lower ends are fed downwardly towards, and rearwardly along, the chipper drum by the pair of nip rollers.

[0039] Preferably, when there are two or more, vertically-spaced, pairs of opposed nip rollers, the lower ends of the tree stems are fed by the lower feed means to be at least below the rotational axes of the lowermost pair of the pairs of nip rollers.

[0040] Preferably, the lower feed means includes at least one pair of opposed rotating spirals or helixes which are downstream convergent, and which rotate with the pitches of the spirals or helixes in unison with the horizontal linear speed of the conveyor conveying the tree stems.

[0041 ] Preferably, the conveyor includes a pair of opposed inclined endless chains which apply a linear pinch grip to the lower ends of the tree stems; and

the rotational pinch grip of the pair of nip rollers is applied to the lower ends of the tree stems before the linear pinch grip is released by the endless chains. [0042] Preferably, secondary feed means of the transitional feed means engage the tree stems, above the lower feed means, to assist in maintaining the tree stems substantially vertically as the tree stems are fed to chipper drum.

[0043] Preferably, the respective rotational axes of the chipper drum and the pairs of nip rollers are parallel in side view, and are upwardly inclined to the horizontal, in the downstream direction.

[0044] Preferably the angle of inclination of the rotational axes to the horizontal is in the range 1 °≤a<10°, where more preferably, 1 °<a<5°.

[0045] Preferably, the feed rotating spirals or helixes of the feed means are provided about cones, which rotate about rotational axes at a greater angle of inclination than the respective nip rollers i.e. the angle of inclination β≥α.

[0046] Preferably, each nip roller has a forward portion, adjacent a respective rotating spiral or helix, where the forward portion is divergent in a downstream direction, to provide a transitional feeding portion for the tree stems from the feeding means to the pair of nip rollers.

[0047] Preferably, the pair of nip rollers and the chipper drum are of axial lengths greater than at least the spacing's between adjacent trees in a row of trees being harvested by the tree harvester, so that two or more tree stems can be fed to the chipper drum simultaneously.

[0048] Preferably, the respective rotational axes of the pair of nip rollers are displaceable laterally to receive, and engage, plurality of tree stems of different diameters.

[0049] Other preferred features of the present invention will become apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0050] To enable the invention to be fully understood, and to enable the skilled addressee to put the invention into practice, a number of preferred embodiments will now be described, with reference to the accompanying illustrations, in which: FIG. 1 is a schematic side view of the path of the trees being harvested in the PRIOR ART Sulman harvester; in accordance with the present invention;

FIG. 2 is a similar schematic side view showing the path of the trees being harvested in a tree harvester in accordance with a generic embodiment of the present invention;

FIG. 3 is a time-lapse schematic view of the path of the lower ends of the tree stems of FIG. 2;

FIG. 4 is a schematic top plan view showing the tree harvester feeding tree stems of different diameters along the conveyor and through the nip rollers of the tree harvester;

FIG. 5 is a schematic side view of a first embodiment of the tree harvester of the present invention;

FIG. 6 is a similar view of a second embodiment of the tree harvester of the present invention;

FIG. 7 is a schematic top plan view of the elevator arms of the conveyor of FIG. 6;

FIG. 8 is a schematic side view of a third embodiment of the tree harvester of the present invention;

FIG. 9 is a schematic top plan view of the elevator arms of the conveyor of FIG. 8;

FIG. 10 is a schematic top plan view of the adjustable mounting of one of the nip rollers;

FIG. 1 1 is a part-sectional view the nip roller with an independently driven conical auger; and

FIGS. 12 to 14 are respective top plan views showing the pair of nip rollers fully open; fully closed; and gripping multiple sized tree stems; respectively.

FIGS. 15 and 16 illustrate the relative geometry between the cutting edges of the chipping drum knives to the anvil and the tree stems being chipped; FIG. 17 is a schematic end view illustrating the alternative methods for feeding multiple logs (i.e. 8) to a drum chipper in double- or single file;

FIGS. 18 to 20 illustrate the relative geometry between the cutting edges of the chipping drum knives to the tree stems (and anvil) when the tree stems are fed in double file; and

FIGS. 21 to 23 show similar views when the tree stems are fed in single file in accordance with the present invention..

[0051 ] NB: Any annotations on the drawings are by way of illustration only, and are not limiting to, the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

[0052] The tree harvester (H) illustrated in FIG. 1 is a schematic example of a PRIOR ART Sulman tree harvester disclosed in International Publication WO 2010/129986 A1 , the contents of which are incorporated into the present Specification by way of reference.

[0053] The PRIOR ART tree harvester (H) has a base cutter (BC) which cuts the lower ends of the stems (TS) of the trees (T) grown in rows (R). A conveyor (C), with upper- and lower elevator arms (EA) and an upwardly- inclined conveyor floor (CF), guide the lower ends of the tree stems (TS) to a location above a pair of nip rollers (NR) which are located above a chipper drum (CD). The trees (T) are conveyed substantially vertically, assisted by an auger (A) on the upper elevator arms (EA) and a pair of feed rollers (FR) associated with the lower elevator arms (EA).

[0054] The lower ends of the tree stems (TS) are momentarily released from the conveyor (C) before they are engaged by the nip rollers (NR); and can change orientation which e.g. prevents clean feeding to the nip rollers (NR); even resulting in blockages in the harvester (H).

[0055] FIGS. 2 and 3 illustrate the paths of the tree stems TS; and more particularly in FIG. 3, the paths of the lower ends E of the stems TS; of the trees T, being harvested by the embodiments of the tree harvester of the present invention, to be hereinafter described in more detail. In particular, and as will be appreciated by the skilled addressee, the lower ends E of the tree stems TS are feed to the nip rollers below their axes of rotation; and more preferably, intermediate the nip rollers and the chipper drum; and are engaged by transitional feed means associated with the nip rollers at least momentarily before the tree stems TS are released by the conveyor (including the continuous chains on the pairs of elevator arms associated with the conveyor.) This ensures that the lower ends E of the tree stems TS are always constrained during the transfer from the conveyor to the nip rollers.

[0056] The generic embodiment of the tree harvester 10, illustrated in FIGS. 2 to 4, has features omitted for clarity; but is generally similar to the PRIOR ART Sulman harvester (H) of FIG. 1 except as specifically described. NB: Wherever possible throughout the following description, the same reference numeral xx will be used to denote the same feature in the different embodiments, where these will be denoted by respective prefixes e.g. xx, 1xx, 2xx, 3xx etc.

[0057] The harvester 10 has a base cutter 20, driven by a hydraulic motor 21 , mounted at the forward end of a conveyor 30. The conveyor 30 has an upwardly-inclined floor 31 defined by the top run 32 of a continuous conveyor 33 having transverse cleats or slats interconnecting side chains.

[0058] Opposed pairs of upper- and lower- elevator arms 40, 41 are provided vertically spaced above the conveyor 30 and co-operate therewith to convey the tree stems TS substantially vertically as they are advanced rearwardly to a transitional feeding zone 50. Each elevator arm 40, 41 is provided with a continuous chain 42, provided with spaced cleats 43. The tree stems TS are engaged between opposed, rearwardly-moving runs 44 of the chains 42 on each pair of elevator arms 40, 41 . The chains 42 pass around drive- and idler sprockets 45, 46 at the ends of the elevator arms 40, 41 ; and are driven via suitable hydraulic motor / transmission units 47. In this embodiment, the upper portions of the tree stems TS are engaged by a pair of opposed substantially horizontal augers 48, each driven by the adjacent motor / transmission unit 47, to stabilize the upper ends of the trees T as the tree stems TS enter the transitional feed zone 50 and are then fed downwardly and rearwardly to the chipper drum 70 by a pair of opposed (counter- rotating) nip rollers 60.

[0059] The chipper drum 70 rotates about a shaft 71 , driven by a hydraulic motor not illustrated, with a rotational axis aligned with, but inclined at a small angle to the horizontal from front to rear. Removable chipper knives 72 are provided around the chipper drum 70 and co-operate with an anvil (not shown).

[0060] The opposed pair of nip rollers 60 are mounted on respective drive shafts 61 , driven by suitable hydraulic motors (not shown). The shafts 61 rotate about similar inclined rotational axes, spaced above and laterally offset from, the rotational axis of the chipper drum 70. The rotational axes of the nip rollers 60 and of the chipper drum 70 are all upwardly inclined at an angle a, to the horizontal, in the downstream direction. The angle a is in the range 1 °<a<10°; but more preferably 1 °<a<5°; with a=3° the most preferred.

[0061 ] In the transitional feeding zone 50, a lower feed means 51 has a pair of spaced conical augers 52, each conical auger 52 being mounted immediately upstream of a respective nip roller 60. Each conical auger 52 has a divergent conical body 53 around which is provided a spiral or helix 54. Each conical auger 52 may be driven by a hydraulic motor (not shown) enclosed in a shroud at the distal end of the conical auger 52; or via a drive from the adjacent nip roller 60. The skilled addressee will note that the inclination (β) of the rotational axis of each conical auger 52 is greater than the inclination (a) of the adjacent nip rollers 60 (and of the chipper drum 70) ; and that each conical auger 52 is rotated to provide a (horizontal) linear pinch grip to the tree stems TS at the same rate as for the conveyor 30 (and chains 42). In addition, the divergent conical augers 52 begin to progressively apply a rotational pinch grip to the tree stems TS in the transitional feed zone 50 as the tree stems TS are transferred to the leading (or upstream) ends of the nip rollers 60.

[0062] As illustrated by the dashed (time-lapse) line TL in FIG. 3, the lower ends E of the tree stems TS are always controlled by the harvester 10 as they are transferred from the conveyor 30 to the nip rollers 60 & chipper drum 70.

[0063] In the first embodiment of the tree harvester 1 10, illustrated in FIG. 5, the overall arrangement is substantially identical to that of the generic embodiment 10 hereinbefore described, except that the transitional feeding zone 150 is provided with secondary feed means 155 located above the pair of conical augers 152 and the pair of nip rollers 160, at the downstream ends of the lower elevator arms 141 . The secondary feed means 155 has a laterally spaced pair of secondary feed units 156, each with a tapered nose portion 157 which leads to a secondary conical auger 158, followed by a transitional portion 159 (with a helix of reduced pitch) and a secondary nip roller 160A, all driven by a hydraulic motor 162.

[0064] As will be appreciated by the skilled addressee, the secondary feed means 155 engages the tree stems TS intermediate their length, and provides further guidance / control of the movement of the tree stems TS in the transitional feed zone 150. The rotational speed of the secondary feed means 155 is adjusted to match the linear and vertical speeds of the tree stems TS as they are advanced to, and through, the nip rollers 160.

[0065] In the second embodiment illustrated in FIG. 6, the secondary feed means 255 is provided by a pair of augers 256, each with a spiral or helix 257 about a shaft 258 which rotates about a rotational axis inclined to the horizontal at angle a. The rotational speed of the augers 256 is matched with the conical augers 252 and nip rollers 260 so that the spiral or helix 257 engage the tree stems TS with a linear speed matched to the conical augers 252 and nip rollers 260.

[0066] FIG. 7 illustrates the relationship of the elevator arms, and continuous chains, of the upper elevator arms 141 of the first embodiment; and of both the upper and lower elevator arms 240, 241 , of the second embodiment. However, the detailed description will be now directed to the lower elevator arms 241 , and secondary feed means 250, of the second embodiment of FIG. 6. [0067] Referring now to FIG. 7, the lower elevator arms 241 are provided as a mirror-image pair. The arms 241 have a frame 280 with a rearward-run support section 281 , leading to a divergently-angled distal portion 282. The outer end of the distal portion 282 is connected to the return-run support section 283, which is connected to the rearward-run support section 281 via a mounting frame 284 which is movably mounted on the harvester chassis 201 . The continuous chain 242 passes around a drive sprocket (not illustrated), driven by the motor / transmission unit 247 mounted on the support frame 284. The rearward run 244 of each continuous chain 242 passes around idler sprockets 246, 246A at each end of the distal portion 282 to assist in guiding the tree stems TS into the gap between the continuous chains 242 to be conveyed towards the transitional feed zone 250. The trailing ends of the elevator arms 241 are supported on support arms 285 mounted on sliding blocks 286 on the chassis 201 , and which are laterally movable by hydraulic rams 287 to adjust the spacing between the chains 242 to receive / engage tree stems TS of different diameters. The elevator arms 241 are hingedly mounted on the support arms 286 and are laterally movable by hydraulic rams 288, interconnecting the chassis 201 to hinged support arms 289, The rams 288 operate, to selectively swing the elevators arms 241 , as shown by the arrows, to adjust the gap between the chains 242 to receive tree stems of different diameters. By selective operation of the hydraulic rams 287, 288, the continuous chains 242 can convey a plurality of tree stems TS, of different diameters, simultaneously.

[0068] In the tree harvester 310 of the third embodiment, illustrated in FIGS. 8 and 9, the pairs of opposed augers 48 adjacent the upper elevator arms 40 are replaced by feed units 156 of the secondary feed means 155 of the first embodiment of FIG. 5. The elevator arms 340 are arranged substantially as hereinbefore described with reference to FIG 7; but the respective feed units 356 are also mounted on the sliding blocks 386, movable by the hydraulic rams 387, to allow lateral adjustment of the spacing between the feed units 356 to receive,/ engage / advance tree stems TS of different diameters. [0069] The skilled addressee will appreciate the descriptions and illustration of the embodiments of FIGS. 2 to 9 are somewhat schematic; and that e.g. details have been omitted from the illustrations for clarity. The specific design features, including drive- and control- systems will vary to suit the particular intended applications; and these, in turn, will depend on the tree species being harvested, the tree stem diameters, the spacing's between the trees in the rows R, and other factors which must be taken into account when establishing the specific design criteria for a harvester.

[0070] The mounting and drive for the nip rollers, and associated conical augers of the transitional feed means, will now be described in more detail with reference to FIGS. 10 to 14.

[0071 ] Of each opposed pair of nip rollers 60 and conical augers 52, generally one of each pair will be fixed relative to the chassis 01 of the tree harvester 10; while the other of the pair is movably mounted relative to the chassis 01 to enable the gaps between the opposed pairs to be selectively adjusted. The adjustable mountings for each will now be described.

[0072] Chassis 01 has vertical posts 02 and horizontal rails 03 .A rocker arm 04 is hingedly mounted between brackets 05 and is selectively swung through a horizontal plane, in the direction of arrow A, by a hydraulic ram 06. A support cradle 07 is hingedly mounted, intermediate its length, to the distal end of the rocker arm 04 and is selectively movable, also in the horizontal plane, in the direction of arrow B, by a hydraulic ram 08 interconnecting support brackets 09 on the proximal end of the cradle 07 to the chassis 01 .

[0073] The nip roller 60 has the proximal end of its shaft 61 journalled in bearings 65 mounted on the support brackets 09, and its drive shaft is connected to a drive motor 62. The distal end of the drive shaft 61 is journalled in bearings, mounted on the cradle 07, but enclosed by the conical body 53 of the conical auger 52.

[0074] As illustrated in FIG. 1 1 , the conical auger 52 is driven at its distal end by a hydraulic drive motor 58 enclosed within a shroud 91 at the distal end of the cradle 07. [0075] As illustrated in FIGS. 12 to 14, by selective extension / retraction of the hydraulic rams 06, 08, the rocker arm 04 and/or cradle 07 can be moved relative to the chassis 01 , so that the gaps between the pair of nip rollers 60, and the pair of conical augers 52, can be varied. FIG. 12 illustrates the pair of nip rollers 60 at their maximum spacing; while FIG. 13 illustrates the minimum spacing; and FIG. 14 illustrates an example spacing for tree stems TS of different diameters.

[0076] The skilled addressee will appreciate that the hydraulic system controlling the operation of the rams 06, 08, can be configured / programmed to automatically operate the rams 06, 08 to compensate for the different tree stem diameters. For example, hydraulic line pressure sensors can send signals to controller(s) to ensure constant gripping pressures on the tree stems TS by the nip rollers 60, conical augers 52 and/or any of the other feed means, especially as the tree stems TS pass through the transitional feed zone 50.

[0077] FIGS. 15 and 16, which illustrate the theory of chipping, have been hereinbefore described in the PRIOT ART.

[0078] As illustrated in FIG. 18, multiple logs tree stems TS - in this example, 8 tree stems TS - may be fed to the drum chipper SDC. Where the tree stems TS are in double file, the tree stems TS are advanced to the chipping drum CD in a "packet" with a length L1 and a width W1 _. However, in accordance with the present invention, the tree stems TS are fed in single file, in a corresponding "packet" with a length L2 and width W2 _, (i.e. where L2 = 2@L1 & W1 = 2@W2).

[0079] As hereinbefore described, the compression force on the tree stems TS is produced by the chipper's knife's Lambda angle (λ), where the λ angle is the complementary angle to the angle of the log and the cutting surface of the knife. Mathematically, this is defined as λ = 90° - (α+β+ε), where a is the clearance angle, β is the knife sharpness angle and ε is the spout angle (see FIGS.15 and 16). A higher λ, at a constant chip length, results in thinner chips and lower fines content. [0080] As illustrated in FIGS. 18 to 20, when the tree stems TS are fed in double file, the knives CK may strike the uppermost log L at an angle of approximately, or even greater than, 90°; and with a negative λ angle. This means that the cutting edges KE of the knives CK will move in a path substantially transverse to, or even inclined against, the travel of the tree stems TS through the chipping drum CD over the anvil CA.

[0081 ] When the tree stems TS are fed to the chipping drum CD in single file, in accordance with the present invention, and as illustrated in FIGS 21 to 23, the λ angle is positive, and the knives CK move in a "slicing" path across and along the wood fibres. This results in higher quality chips, with less fines; and reduced power input to enable the knives CK o cut through the tree stems TS.

[0082] The higher the positive λ angle, the easier the cutting edges KE of the knives CK will pass thought the tree stems TS.

[0083] The skilled addressee will appreciate the present invention enables the tree stems TS to be fed sequentially, in single file, into, and along, the chipping drum CD to produce higher quality chips, with reduced fines, while minimizing the fuel consumption / energy input for a given mass of logs chipped.

[0084] Advantages of the present invention include, but are not limited to: a) To provide a method to transition the lower ends of tree stems from the inclined linear pinch grip of the conveyors directly to the rotational pinch grip of nip rollers for feeding the stems of trees substantially vertically and rearwardly to the leading chipper drum knife edge of a tree harvester; b) To provide a method to directly connect powered augers or nip rollers to the rear end of the inclined conveyor to transition the lower ends of tree stems from the inclined linear pinch grip of the conveyors directly to the rotational guide of spirals or helix or the rotational pinch grip of nip rollers for feeding the stems of trees substantially vertically and rearwardly to the leading chipper drum knife edge of a tree harvester; c) To provide a flexible means to adjust the opposing nip roller horizontal axis, providing simultaneous positive rotational pinch on multiple stems of multiple diameters; and

d) To provide apparatus for affecting the methods, and thereby maximise the pour rate of the tree harvester and minimize the energy inputs to the harvester.

[0085] Other advantages will become apparent when comparing the output of the tree harvesters of the present invention with those of the PRIOR ART.

[0086] Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

[0087] In this specification, the terms 'comprises', 'comprising', 'includes', 'including', or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.