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Title:
APPARATUS FOR PRUNING LIVE TREES
Document Type and Number:
WIPO Patent Application WO/2022/118181
Kind Code:
A1
Abstract:
A pruning head able to self-ascend and self-descend a tree trunk to prune branches from the trunk. Provided is a chassis supporting a driving mechanism that has a motor driven traction member to grip onto the tree trunk and control the ascend and descend. A plurality of blades are provided each to locate against a part of the circumferential surface of the trunk. The blades are independently suspended from the chassis to drive through the branches to close prune them from the trunk.

Inventors:
HUDSON DAVID MARSHALL (NZ)
Application Number:
PCT/IB2021/061094
Publication Date:
June 09, 2022
Filing Date:
November 30, 2021
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HUDSON STRATEGIC LTD (NZ)
International Classes:
A01G3/08; A01G23/02; A01G23/08; A01G23/081; B27L1/00; B66C3/04; B66C3/14; B66C3/20
Domestic Patent References:
WO2010004095A12010-01-14
WO1995000004A11995-01-05
Foreign References:
US20150144225A12015-05-28
US7802594B12010-09-28
US3688821A1972-09-05
EP0200805A11986-11-12
US20030132729A12003-07-17
SU648411A11979-02-25
Attorney, Agent or Firm:
AJ PARK (NZ)
Download PDF:
Claims:
CLAIMS

1. A tree pruning apparatus for at least partially pruning a live tree that has a trunk and a plurality of limbs extending outwardly from the trunk, said apparatus comprising: a. a dock, configured to be connected to a moveable vehicle by a boom extending from the vehicle to the dock and that can move relative the vehicle to reposition the dock relative to the vehicle, the dock comprises a tree trunk receiving region to allow the dock to register to a trunk of the tree, and b. a pruning head removably engageable with the dock, to be deployed from the dock and travel up the tree trunk parallel the elongate axis of the tree trunk and travel down the tree trunk parallel the elongate axis to be retrieved back to the dock, said pruning head comprising: i. a driving mechanism that comprises at least one motor, to grip onto the trunk and drive the pruning head up and down the tree trunk; ii. a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, each blade independently mounted by a respective arm that allows its respective blade to move radially relative to the tree trunk independently of the other blades, said blades each have a primary cutter that when said pruning head travels up a tree trunk can drive through the limbs to cut them from the trunk in close proximity to the trunk.

2. A tree pruning apparatus as claimed in claim 1 wherein the pruning head comprises at least 6 blades to each locate against the trunk at the circumference of a sector of the trunk, said at least 6 blades in concert able to locate against a substantial part of the circumferential surface of the trunk, each blade supported by a respective arm to allow the blades to move radially towards and away from the elongate axis, so as to allow each blade to follow the circumferential surface of the trunk in use independently of each other, as the pruning head travels up and down along the trunk, so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the primary cutter of the other blades are not caused to move radially outwardly by said one blade.

3. A tree pruning apparatus as claimed in claim 2 wherein each arm is mounted to a chassis of the pruning head in a pivotal manner about a rotational axis to provide for the radial movement of each blade.

4. A tree pruning apparatus as claimed in claim 3 wherein each arm is mounted to a chassis of the pruning head in a pivotal manner about a respective rotational axis that is perpendicular to the elongate axis and parallel a tangent of the trunk immediately adjacent the arm, when in use.

5. A tree pruning apparatus as claimed in anyone of claims 3 or 4 wherein each arm is an elongate arm that extends in a direction substantially parallel to the elongate axis of the trunk when in use, from the chassis at a first end of the arm where the arm is mounted to the chassis to a distal end of the arm at where a respective blade is mounted.

6. A tree pruning apparatus as claimed in anyone of claims 3 to 5 wherein each arm is elongate and extends in its elongate direction from where it is mounted to the chassis in a direction so that the cutting force of the blade causes a tensile or compression force in the arm transferred to the chassis at where the arm is mounted to the chassis.

7. A tree pruning apparatus as claimed in anyone of claims 1 to 6 wherein the pruning head comprises at least 2 pruning units each comprising a respective chassis and at least one arm.

8. A tree pruning apparatus as claimed in claim 7 wherein each said pruning unit comprises two arms mounted to each said chassis, each arm having a respective blade mounted to it.

9. A tree pruning apparatus as claimed in anyone of claims 3 to 8 wherein each blade (a) can move radially relative the trunk by rotation about the rotational axis of its respective arm and (b) is mounted to its respective arm in a swivelling manner to allow the blade to rotate about an axis substantially parallel the elongate axis of the trunk when in use.

10. A tree pruning apparatus as claimed in anyone of claims 1 to 9 wherein each arm is biased towards said trunk, in use, by a spring.

11. A tree pruning apparatus as claimed in claim 7 or 8 wherein each pruning unit comprises of a said driving mechanism mounted to the chassis.

12. A tree pruning apparatus as claimed in anyone of claims 1 to 11 wherein the pruning head is able to reconfigure between an open condition and a more closed condition, wherein in the open condition the pruning head can be engaged and removed from the trunk and when in the more closed condition the pruning head is captured to the trunk.

13. A tree pruning apparatus as claimed in claim 12 wherein the driving mechanism comprises of at least two traction belts and when the pruning head in in a closed condition, each traction belt is compressed against the trunk so that a sufficient amount of traction can be gained between the trunk and the pruning head to cause it to move up the trunk when the traction belts are motor driven.

14. A tree pruning apparatus as claimed in anyone of claim 1 to 13 wherein the pruning head weighs at least 200kg.

15. A tree pruning apparatus as claimed in claim 14 wherein the pruning head, by virtue of its weight and speed of travel along the trunk, can drive through a limb to cut limb with a force over 8KN.

16. A tree pruning apparatus as claimed in claim 14 wherein the pruning head, by virtue of its weight and speed of travel along the trunk, can drive through at least two limbs simultaneously with force of over 20KN.

17. A tree pruning apparatus as claimed in anyone of claims 14 to 16 wherein the driving mechanism is of a shape and configuration to be able to cause the pruning head to travel along the trunk at at least 4m/s.

18. A tree pruning apparatus as claimed in anyone of claims 14 to 17 wherein the driving mechanism is able to thrust the pruning head upwardly with a thrust of at least 4KN.

19. A tree pruning apparatus as claimed in anyone of claims 1 to 18 wherein, each blade has a primary cutter presented to cut limbs when the pruning head travels up the trunk and a secondary cutter presented to cut limb stubs when the pruning head travels down the trunk.

20. A tree pruning apparatus as claimed in claim 19 wherein each blade has opposed cutting ends wherein said primary cutter is defined at a first of said opposed cutting ends and the secondary cutter is defined and the other of said opposed cutting ends.

21. A tree pruning apparatus as claimed in claim 19 or 20 wherein the secondary cutter is configured to cut closer to the trunk than the primary cutter.

22. A tree pruning apparatus as claimed in claim 19 or 20 wherein the secondary cutter is configured to cut the limb from the trunk to leave a limb stub projecting a length from the trunk and the secondary cutter is configured to shave the limb stub to reduce its length projecting from the trunk.

23. A tree pruning apparatus as claimed in anyone of claims 19 to 22 wherein the blade comprises a trunk contact surface that extends between the primary and secondary cutters.

24. A tree pruning apparatus as claimed in anyone of claims 19 to 23 wherein each blade comprises a trunk contact surface configured to engage with the surface of a trunk in use, the cutters having cutting edges being at a predetermined distance from the trunk contact surface to create a predetermined limb stump length.

25. A tree pruning apparatus as claimed in anyone of claims 1 to 24 wherein the boom is moveably attached to a vehicle to allow relocation of the dock, carrying the pruning head, from one tree to another tree without the vehicle needing to move.

26. A tree pruning apparatus as claimed in anyone of claims 1 to 25 wherein there are two booms extending from the vehicle each able to move independently relative the vehicle and each carrying a respective dock and pruning head, each capable of operating independently of each other to allow pruning of two trees to occur from one ground position of the vehicle. A tree pruning apparatus as claimed in anyone of claims 1 to 26 wherein there are two booms extending from the vehicle each able to move independently of each other relative the vehicle and be operated to allow a first boom to locate its respective dock and pruning head to a first tree and be performing pruning on that first tree whilst the second boom is relocating its respective dock and pruning head from a second tree to a third tree. A tree pruning apparatus as claimed in anyone of claims 1 to 27 wherein a thinning head is supported from the vehicle by a boom able to move the thinning head within a 3 dimensional envelope relative to said vehicle, the thinning head comprising of a trunk cutter capable of cutting a tree trunk to fell trees. A tree pruning apparatus as claimed in claim 28 wherein the boom supporting the thinning head is a 3rd boom. A tree pruning apparatus as claimed in claim 28 or 29 wherein there are (a) two booms extending from the vehicle each able to move independently of each other relative the vehicle and be operated to allow a first boom to locate its respective dock and pruning head to a first tree and be performing pruning on that first tree whilst the second boom is relocating its respective dock and pruning head from a second tree to a third tree and (b) a third boom supporting a thinning head that can move independently of the two booms and be independently felling trees. A pruning head able to self-ascend and self-descend a tree trunk to at least partially prune a plurality of limbs extending outwardly from the trunk of a live tree, said pruning head comprising: a chassis supporting a driving mechanism that comprises at least one motor driven traction member to grip onto the tree trunk and control the ascend and descend of the pruning head along the tree trunk and a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, each blade independently mounted by a respective arm each arm pivotally mounted to said chassis to allow its respective blade to move radially relative to the tree trunk independently of the other blades, said blades each have a primary cutter that when said pruning head ascends the tree trunk can drive through the limbs to cut them from the trunk. A pruning head as claimed in claim 31 wherein the pruning head comprises at least 6 blades to each locate against the trunk at the circumference of a sector of the trunk, said at least 6 blades in concert able to locate against a substantial part of the circumferential surface of the trunk, each blade supported by a respective arm to allow all the blades to move radially relative to the trunk, so as to allow each blade to follow the circumferential surface of the trunk in use independently of each other, as the pruning head travels along the trunk, so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the primary cutter of the other blades are not caused to move radially outwardly by said one blade. A pruning head as claimed in claim 31 or 32 wherein each arm is mounted to said chassis in a pivotal manner about a rotational axis to provide for the radial movement of each blade. A pruning head as claimed in anyone of claims 31 to 33 wherein each arm is mounted to said chassis in a pivotal manner about a respective rotational axis that is perpendicular to the elongate axis and parallel a tangent of the trunk immediately adjacent the arm, when in use. A pruning head as claimed in anyone of claims 31 to 34 wherein each arm is an elongate arm that extends in a direction substantially parallel to the elongate direction of the trunk when in use, from the chassis at a first end of the arm where the arm is mounted to the chassis to a distal end of the arm at where a respective blade is mounted. A pruning head as claimed in anyone of claims 31 to 35 wherein each arm is elongate and extends in its elongate direction from where it is mounted to the chassis in a direction so that the cutting force of the blade causes a tensile or compression force in the arm transferred to the chassis at where the arm is mounted to the chassis. A pruning head as claimed in anyone of claims 31 to 36 wherein the pruning head comprises at least 2 pruning units each comprising a respective said chassis and at least one arm. A pruning head as claimed in claim 37 wherein each said pruning unit comprises two arms mounted to each said chassis, each arm having a respective blade mounted to it. A pruning head as claimed in anyone of claims 31 to 38 wherein each blade (a) can move radially relative the trunk by rotation about the rotational axis of its respective arm and (b) is mounted to its respective arm in a swivelling manner to allow the blade to rotate about an axis substantially parallel the elongate axis of the trunk when in use. A pruning head able to self-ascend and self-descend a tree trunk to at least partially prune a plurality of limbs extending outwardly from the trunk of a live tree, said pruning head comprising: a chassis supporting a driving mechanism that comprises at least one motor driven traction member to grip the tree trunk and control the ascend and descend of the pruning head along the tree trunk and a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, each blade comprising (a) a primary cutter operationally located at a first distance from the trunk and that when said pruning head ascends the tree trunk can drive through limbs to cut them from the trunk to leave limb stumps extending from the tree trunk and (b) a secondary cutter operationally located a second distance from the trunk that is less than the first distance and that when said pruning head descends the tree trunk can cut through limb stumps. A method of pruning a stand of trees comprising:

(a) manoeuvring in proximity to at least 3 trees of the stand, a mobile tree pruner that comprises of a ground vehicle that carries two booms each able to move independently of each other relative the vehicle, at the end of each boom there being a dock carrying a pruning head able to (i) deploy from a docked condition with the dock and self-ascend the trunk a tree and when doing so, prune limbs from the trunk of the tree and (ii) self-descend the trunk to dock with the dock, each boom adapted and configured to allow its respective dock and pruning head to be moved within a 3 dimensional envelope relative to the vehicle,

(b) whilst a first boom and its respective dock and pruning head are located to a first tree performing pruning on that first tree, relocating a second boom and its respective dock and pruning head from a second tree to a third tree. A method as claimed in claim 41 wherein the method comprises the regenerative braking of the motor of one pruning head as it descends a tree for use in the next ascend of another tree by the motor of the or the other pruning head. A mobile tree pruner for at least partially pruning a live tree that has a trunk and a plurality of limbs extending outwardly from the trunk, said pruner comprising: a. a moveable vehicle, b. a dock, connected to the moveable vehicle by a boom extending from the vehicle to the dock and that can move relative the vehicle to reposition the dock relative to the vehicle, the dock comprises a tree trunk receiving region to allow the dock to register to a trunk of the tree, and c. a pruning head removably engageable with the dock, to be deployed from the dock and travel up the tree trunk along the elongate axis of the tree trunk and travel down the tree trunk along the elongate axis to be retrieved back to the dock, said pruning head comprising: i. a driving mechanism that comprises at least one motor, to grip the trunk and drive the pruning head up and down the tree trunk; ii. a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, said blades each have a primary cutter that when said pruning head ascends the tree trunk can drive through the limbs to cut them from the trunk, d. a thinning head comprising a tree trunk cutter capable of cutting through the trunk of a tree to fell the tree, the thinning head connected to the moveable vehicle by a boom extending from the vehicle to the dock and that can move relative the vehicle to reposition the cutter relative to the vehicle.

Description:
APPARATUS FOR PRUNING LIVE TREES

The present invention relates to an apparatus for pruning live trees. In one aspect the present invention more particularly, but not exclusively, relates to an apparatus for close pruning live trees.

BACKGROUND

Trees used for the production of timber or lumber are accorded a higher value if they are straight and are substantially knot free. Knot free timber is known as clear wood. T rees that are substantially knot free, have a large collar/diameter of clear wood. Hence tree trunks with minimal knot formation are more desired for timber processing as they can be used for higher quality (and hence higher value) purposes such as veneer, timber mouldings and furniture. Knotty timber also has limited structural integrity and hence has reduced economic value in the building construction industry.

Trees can lose limbs such as branches naturally over their life. Natural pruning happens when branches do not receive enough sunlight and die. This can happen in densely populated forests. Wind may also take part in natural pruning. When this occurs, the dead branch can cause an imperfection such as a burl or knot to be generated at the surface of the trunk and this may extend some radial distance into the trunk. This reduces the clear wood diameter of the trunk.

Should a branch remain attached to the tree trunk for the duration of the life of the tree, it will also cause trunk growth imperfections such as knots.

To help reduce knot and burl formation, trees may be artificially pruned over their life. Pruning is most commonly done in a manual manner. The primary purpose of pruning is to produce clear wood. Additionally, trees such as pine and spruce trees in a densely populated forest get pruned to improve tree growth rates (height and diameter wise). Such pruning typically keeps only the upper branches (approximately the top 7m of matured tree) intact. These are located at the sunnier forest canopy and are hence most efficient to support tree growth, resulting in trees competing for sunlight with neighbouring trees. Such Silviculture practices have been developed over many years to help increase clear wood yield from a timber production forest in a safe manner.

However, manual pruning remains dangerous. It is also a skilled task that, if not done properly, can comprise the clear wood yield of a tree.

The publication Best Practice Guidelines for Silvicultural Pruning (ISBN 0-9582194- 0-0), published by Competenz (A business unit of Te Pukenga - a New Zealand Government Tertiary Education Institution) provides a guide for certain pruning procedures and techniques for the New Zealand Silviculture industry.

The Competenz guide describes several manual techniques for pruning branches from the trunk of a tree. Such involve a worker climbing a tree and using hand-held manual tools such as jacksaws or loppers to remove the lower branches of a tree. This is dangerous, physically demanding and time consuming. The advantage in the use of manual tools is that a skilled worker can ensure branch removal occurs in a way that avoids or minimises knot formation.

A common pruning fault is a coathanger. This can be caused by the branch being pruned not close to the trunk. This can lead to an increase of the size of the defect in the trunk core, hence decreasing clear wood. Another fault is collar damage where the branch is removed too close to the trunk or at the trunk itself. A quality prune creates a branch stub that will heal over with minimal knot formation.

To reduce the physical demands on a worker and to slightly speed up the pruning process, a chainsaw could also be used. The use of a chainsaw up a ladder is dangerous. A chainsaw is also heavy and also larger than loppers so it may be more restricted in its access to a branch. Chainsaws hence do not provide for a quality and consistent prune of a tree.

Silviculture operations are often recorded by approved forest managers to ensure that "best practice" is performed and resulting trees meet certain specifications. For timber to be sold as pruned timber (such as under the Pinus Radiata classification P40) , the pruning quality and audit of pruning at the time of pruning has to be recorded and documented. These specifications may be contractually defined between the forest manager and contract pruners and an audit is provided for the forest owners. Following best practice will help trees be classified as "pruned".

To help meet these specifications, the artificial pruning of established trees (such as pinus radiata) in a forest is typically done in multiple lifts of approximately 4m at two year intervals. This is desirable in order to maintain the 7m of canopy for strong growth rates. This is also desirable to help ensure the tree trunk is no larger than 170mm in diameter at the time of pruning and that the collar outside 170mm is clear wood. In accordance with the specification mentioned above, there is nothing more to be gained by pruning of larger diameter trunks as the tree will not be classified as "pruned" or "clear wood."

The number of times pruning has to occur affects the forest maintenance costs. This hence affects the financial yield of a timber production forest.

The terrain of a forest can be difficult to negotiate to get access to the trees. Especially after a number of years of growth where fallen trees and branches may hamper movement and access. This can be made even more difficult in steep terrain.

Artificial pruning of trees that avoids the need for a worker climbing a ladder and manually pruning, have been developed. Self-climbing de-limbers such as described in US7591292 and US10470382 are examples. Such de-limbers increase the speed at which tree branches may be removed, but they have limitations.

US10470382 discloses a hand transported de-delimber head with a power cable back to a ground power supply. A halfmoon cutting blade is described. As illustrated in figure 15 of the current patent specification, where reference numerals 46,70,12,72 correspond to those used in US10470382, when the blade encounters a burl indicated as 937 in figure 15, the blade 46 can deform. The deformed blade may then not cut a branch adjacent the burl at a desired distance from the trunk. Instead it may cut the limb at a distance L that may be longer than desired. As such the ability of blades to accurately follow a trunk may be reduced, and a cutting length of branches may become less accurate. Consistent quality pruning may hence not occur due to blade deformation.

Hand transported de-delimbers need to be light enough to be able to be carried by one or two people. Yet they are still be cumbersome and slow to move between trees.

As a result of their low weight (such a 50kg) hand transported de-delimbers may not generate sufficient dynamic energy required for their blades to cut through branches that may be encountered in each lift. Speed of travel can increase dynamic energy. However increased speed will require increased acceleration and deceleration and as a result, increased traction (pressure) with the trunk. This can cause damage to the bark of a tree.

Due to low dynamic energy, hand transported de-delimbers may be more suited for the first lift, of a young tree, when branches to be pruned are of a smaller diameter. However young trees are more susceptible to bark damage and hence sensitive to pressures applied by a hand transported de-delimber.

Furthermore, branches of some trees tend to grow in clusters of 3-6 branches extending from the trunk. A hand transported de-delimber striking a plurality of branches substantially simultaneously may not have sufficient dynamic energy to prune all branches.

For a Pinus Radiata tree for example, a hand transported de-limber may have a branch diameter limit of 35mm. Potentially less when multiple branches are encountered simultaneously. This equipment is hence undesirable for use in a commercial pine forest

US7591292 discloses a de-limber of live trees and teaches a light weight delimber head. For traction it teaches the use teeth that bite into the bark of the tree and, if necessary, into the trunk. This will damage the bark and may impact tree health and growth.

In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

It is an object of the present invention to provide an apparatus for pruning live trees which overcomes or at least partially ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

BRIEF DESCRIPTION OF THE INVENTION

In a first aspect the present invention may be said to be a tree pruning apparatus for at least partially pruning a live tree that has a trunk and a plurality of limbs extending outwardly from the trunk, said apparatus comprising: a. a dock, configured to be connected to a moveable vehicle by a boom extending from the vehicle to the dock and that can move relative the vehicle to reposition the dock relative to the vehicle, the dock comprises a tree trunk receiving region to allow the dock to register to a trunk of the tree, and b. a pruning head removably engageable with the dock, to be deployed from the dock and travel up the tree trunk parallel the elongate axis of the tree trunk and travel down the tree trunk parallel the elongate axis to be retrieved back to the dock, said pruning head comprising: i. a driving mechanism that comprises at least one motor, to grip the trunk and drive the pruning head up and down the tree trunk; ii. a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, each blade independently mounted by a respective arm that allows its respective blade to move radially relative to the tree trunk independently of the other blades, said blades each have a primary cutter that when said pruning head travels up a tree trunk can drive through the limbs to cut them from the trunk in close proximity to the trunk.

In a second aspect the present invention may be said to be a pruning head able to self-ascend and self-descend a tree trunk to at least partially prune a plurality of limbs extending outwardly from the trunk of a live tree, said pruning head comprising: a chassis supporting a driving mechanism that comprises at least one motor driven traction member to grip the tree trunk and control the ascend and descend of the pruning head along the tree trunk and a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, each blade independently mounted by a respective arm each arm pivotally mounted to said chassis to allow its respective blade to move radially relative to the tree trunk independently of the other blades, said blades each have a primary cutter that when said pruning head ascends the tree trunk can drive through the limbs to cut them from the trunk.

In a further aspect the present invention may be said to be a pruning head able to self-ascend and self-descend a tree trunk to at least partially prune a plurality of limbs extending outwardly from the trunk of a live tree, said pruning head comprising: a chassis supporting a driving mechanism that comprises at least one motor driven traction member to grip the tree trunk and control the ascend and descend of the pruning head along the tree trunk and a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, each blade comprising (a) a primary cutter operationally located at a first distance from the trunk and that when said pruning head ascends the tree trunk can drive through limbs to cut them from the trunk to leave limb stumps extending from the tree trunk and (b) a secondary cutter operationally located a second distance from the trunk that is less than the first distance and that when said pruning head descends the tree trunk can cut through limb stumps.

In a further aspect the present invention may be said to be a method of pruning a stand of trees comprising: (a) manoeuvring in proximity to at least 3 trees of the stand, a mobile tree pruner that comprises of a ground vehicle that carries two booms each able to move independently of each other relative the vehicle, at the end of each boom there being a dock carrying a pruning head able to (i) deploy from a docked condition with the dock and self-ascend the trunk a tree and when doing so, prune limbs from the trunk of the tree and (ii) self-descend the trunk to dock with the dock, each boom adapted and configured to allow its respective dock and pruning head to be moved within a 3 dimensional envelope relative to the vehicle,

(b) whilst a first boom and its respective dock and pruning head are located to a first tree performing pruning on that first tree, relocating a second boom and its respective dock and pruning head from a second tree to a third tree.

In a further aspect the present invention may be said to be a mobile tree pruner for at least partially pruning a live tree that has a trunk and a plurality of limbs extending outwardly from the trunk, said pruner comprising: a. a moveable vehicle, b. a dock, connected to the moveable vehicle by a boom extending from the vehicle to the dock and that can move relative the vehicle to reposition the dock relative to the vehicle, the dock comprises a tree trunk receiving region to allow the dock to register to a trunk of the tree, and c. a pruning head removably engageable with the dock, to be deployed from the dock and travel up the tree trunk along the elongate axis of the tree trunk and travel down the tree trunk along the elongate axis to be retrieved back to the dock, said pruning head comprising: i. a driving mechanism that comprises at least one motor, to grip the trunk and drive the pruning head up and down the tree trunk; ii. a plurality of blades to each locate against a part of the circumferential surface of the trunk, said plurality of blades in concert to locate against a substantial part of the circumferential surface of the trunk, said blades each have a primary cutter that when said pruning head ascends the tree trunk can drive through the limbs to cut them from the trunk, d. a thinning head comprising a tree trunk cutter capable of cutting through the trunk of a tree to fell the tree, the thinning head connected to the moveable vehicle by a boom extending from the vehicle to the dock and that can move relative the vehicle to reposition the cutter relative to the vehicle.

The present invention may also be said to be a pruning head able to self-ascend and self-descend a tree trunk to at least partially prune a plurality of limbs extending outwardly from the trunk of a live tree, said pruning head comprising: a chassis supporting a driving mechanism that comprises at least one motor driven traction member to act on the tree trunk and control the ascend and descend of the pruning head along the tree trunk and a plurality of blades to each locate adjacent a part of the circumferential surface of the trunk and be radially positioned to cut limbs from the trunk at a predetermined distance from the trunk, guided by the circumferential surface of the trunk.

Preferably the pruning head comprises at least 3 blades to each locate against the trunk at the circumference of a sector of the trunk and in concert locate against a substantial part of the circumferential surface of the trunk, each blade supported by a repetitive four-bar linkage independently of the other blades..

Preferably each blade can each locate directly against the tree trunk..

Preferably each blade can slide over the tree trunk as the pruning head travels up and down the trunk.

Preferably each blade is radially positioned to cut limbs from the trunk at a predetermined distance from the trunk, guided by the circumferential surface of the trunk adjacent the blade.

Preferably the pruning head comprises at least 6 blades to each locate against the trunk at the circumference of a sector of the trunk, said at least 6 blades in concert able to locate against a substantial part of the circumferential surface of the trunk, each blade supported by a respective arm to allow the blades to move radially towards and away from the elongate axis, so as to allow each blade to follow the circumferential surface of the trunk in use independently of each other, as the pruning head travels up and down along the trunk..

Preferably the pruning head comprises at least 6 blades to each locate against the trunk at the circumference of a sector of the trunk, said at least 6 blades in concert able to locate against a substantial part of the circumferential surface of the trunk, each blade supported by a respective arm to allow the blades to move radially towards and away from the elongate axis, so as to allow each blade to follow the circumferential surface of the trunk in use independently of each other, as the pruning head travels up and down along the trunk, so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the primary cutter of the other blades are not caused to move radially outwardly by said one blade.

Preferably each blade can move radially relative the trunk independently of the other blades so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the other blades are not caused to separate from the trunk..

Preferably each blade can move radially relative the trunk independently of the other blades so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the other blades are not caused to separate from the trunk by the one blade..

Preferably each blade can move radially relative the trunk independently of the other blades so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the primary cutter of or the other blades are not move radially outwardly from the trunk..

Preferably each arm is mounted to a chassis of the pruning head in a pivotal manner about a rotational axis to provide for the radial movement of each blade.

Preferably each arm is mounted to a chassis of the pruning head in a pivotal manner about a respective rotational axis that is perpendicular to the elongate axis and parallel a tangent of the trunk immediately adjacent the arm, when in use. Preferably each arm is an elongate arm that extends in a direction substantially parallel to the elongate axis of the trunk when in use, from the chassis at a first end of the arm where the arm is mounted to the chassis to a distal end of the arm at where a respective blade is mounted.

Preferably each arm is elongate and extends in its elongate direction from where it is mounted to the chassis in a direction so that the cutting force of the blade causes a tensile or compression force in the arm, transferred from the arm to the chassis at where the arm is mounted to the chassis.

Preferably the pruning head comprises at least 2 pruning units each comprising a respective chassis and at least one arm.

Preferably each said pruning unit comprises two arms mounted to each said chassis, each arm having a respective blade mounted to it.

Preferably each blade (a) can move radially relative the trunk by rotation about the rotational axis of its respective arm and (b) is mounted to its respective arm in a swivelling manner to allow the blade to rotate about an axis substantially parallel the elongate axis of the trunk when in use.

Preferably a notional line between rotational axis of the arm and distal end of the arm at where the blade is mounted is substantially parallel the elongate axis of the trunk..

Preferably said two arms per chassis share a common pivot axis at where they are mounted to the chassis..

Preferably each arm has a respective blade mounted to it in a swivelling manner allowing the blade to rotate in use around an axis parallel the elongate direction of the trunk..

Preferably the arm is confined in movement relative to the chassis it is mounted to only be able to rotate relative the chassis about its rotational axis..

Preferably each blade is confined in movement relative the arm it is mounted to only be able to rotate relative the arm about a swivel axis parallel the elongate axis of the trunk..

Preferably each arm is biased towards said trunk in use..

Preferably each arm is biased towards said trunk, in use, by a spring. Preferably each pruning unit comprises of a said driving mechanism mounted to the chassis.

Preferably the drive mechanism comprises a traction belt able to be driven by the motor.. Preferably the traction belt can grip onto the tree trunk upon application of a compression for of the pruning head with the trunk..

Preferably the pruning head is configured like a jaw, able to move between an open condition and a more closed condition, wherein in the open condition the pruning head can be engaged and removed from the trunk and when in the more closed condition the pruning head is captured to the trunk..

Preferably the pruning head is able to reconfigure between an open condition and a more closed condition, wherein in the open condition the pruning head can be engaged and removed from the trunk and when in the more closed condition the pruning head is captured to the trunk.

Preferably the driving mechanism, when the pruning head in in a closed condition, can gain sufficient traction with the trunk to cause the pruning head to move up the trunk driven by said at least one motor..

Preferably in the more closed condition the traction belt of each pruning unit is held in compression against the trunk so that a sufficient amount of traction can be gained between the trunk and the pruning head to cause it to move up the trunk..

Preferably the driving mechanism comprises of at least two traction belts and when the pruning head in in a closed condition, each traction belt is compressed against the trunk so that a sufficient amount of traction can be gained between the trunk and the pruning head to cause it to move up the trunk when the traction belts are motor driven.

Preferably the pruning head weighs at least 200kg.

Preferably the pruning head, by virtue of its weight and speed of travel along the trunk, can impart a cutting force of over 8KN on a limb.

Preferably the pruning head, by virtue of its weight and speed of travel along the trunk, can impart a cutting force of over 20KN on one or at least two limbs simultaneously.

Preferably the pruning head, by virtue of its weight and speed of travel along the trunk, can impart a cutting force of over 30KN on one or at least two limbs simultaneously.. Preferably the pruning head, by virtue of its weight and speed of travel along the trunk, can impart a cutting force of over 40KN on one or at least two limbs simultaneously..

Preferably the pruning head, by virtue of its weight and speed of travel along the trunk, can impart a cutting force of over 50KN on one or at least two limbs simultaneously..

Preferably the pruning head weighs at least 250kg.

Preferably the pruning head weighs at least 250kg.

Preferably the pruning head weighs are least 280kg.

Preferably the driving mechanism is of a shape and configuration to be able to cause the pruning head to travel along the trunk at at least 4m/s.

Preferably the driving mechanism is of a shape and configuration to be able to cause the pruning head to travel along the trunk at at least 5m/s..

Preferably the driving mechanism is of a shape and configuration to be able to cause the pruning head to travel along the trunk at 5m/s..

Preferably the driving mechanism is able to thrust the pruning head upwardly with a thrust of at least 4KN.

Preferably the driving mechanism is able to thrust the pruning head upwardly with a thrust of at least 5KN.

Preferably the driving mechanism is able to thrust the pruning head upwardly to an operations speed of at least 4m/s in a distance no greater than 500mm.

Preferably the driving mechanism is able to thrust the pruning head upwardly to an operations speed of at least 5m/s in a distance no greater than 500mm.

Preferably the driving mechanism is able to thrust the pruning head upwardly to an operations speed of 5m/s within a distance no greater than 500mm.

Preferably the driving mechanism is able to thrust the pruning head upwardly to an operations speed of 5m/s within a distance no greater than 250mm.

Preferably the pruning head weights around 300kg and the driving mechanism is able to thrust the pruning head upwardly to an operations speed of 5m/s within in a distance of 250mm. Preferably the trees to be pruned by the pruning apparatus are pinus radiata trees.

Preferably the limbs to be cut from the trunk are up to 60mm in diameter.

Preferably at least 3 and preferably at least 4 and preferably at least 5 limbs are able to be cut from the trunk by the blades simultaneously.

Preferably the pruning head is sprung or biased or able to expand inwards towards the elongate axis in use.

Preferably the pruning head is of a jaw configuration and is at least partially circular, with an opening able to be created and closed, configured to receive a trunk.

Preferably, each blade has a primary cutter presented to cut limbs when the pruning head travels up the trunk and a secondary cutter presented to cut limb stubs when the pruning head travels down the trunk.

Preferably each blade has opposed cutting ends wherein said primary cutter is defined at a first of said opposed cutting ends and the secondary cutter is defined and the other of said opposed cutting ends.

Preferably the secondary cutter is configured to cut closer to the trunk than the primary cutter.

Preferably the secondary cutter is configured to cut the limb from the trunk to leave a limb stub projecting a length from the trunk and the secondary cutter is configured to shave the limb stub to reduce its length projecting from the trunk.

Preferably the blade comprises a trunk contact surface that extends between the primary and secondary cutters.

Preferably each blade comprises a trunk contact surface configured to engage with the surface of a trunk in use, the cutters having cutting edges being at a predetermined distance from the trunk contact surface to create a predetermined limb stump length.

Preferably each blade comprises a trunk contact surface configured to engage with the surface of a trunk in use, the primary having a cutting edge being at a predetermined distance from the trunk contact surface to cut each limb to a predetermined limb stump length.. Preferably the pruning apparatus may have blades presented for cutting limb from the trunk when the pruning head travels upwardly and may have blades presented for cutting limb stumps when the pruning head travels downwardly..

Preferably the blades presented for cutting limb stumps cut closer to the trunk than the blades presented for cutting the limbs..

Preferably the plurality of blades each locate directly against a part of the circumferential surface of the trunk to be able to slide along the trunk over the trunk..

Preferably the plurality of blades each locate indirectly against a part of the circumferential surface of the trunk in a manner to be able to slide along the trunk guided by the trunk..

Preferably said close proximity to the trunk is less than 10mm and preferably less than 5mm and preferably between 2 and 5 mm and preferably around 3mm..

Preferably said secondary cutter will shave the limb stub to a length from the trunk less than 10mm and preferably less than 5mm and preferably between 2 and 5 mm and preferably around 3mm..

Preferably said primary cutter will cut the limb to a length from the trunk less than 10mm and preferably less than 5mm and preferably between 2 and 5 mm and preferably around 3mm..

Preferably the boom is moveably attached to a vehicle to allow relocation of the dock, carrying the pruning head, from one tree to another tree without the vehicle needing to move.

Preferably there are two booms extending from the vehicle each able to move independently relative the vehicle and each carrying a respective dock and pruning head, each capable of operating independently of each other to allow pruning of two trees to occur from one ground position of the vehicle.

Preferably there are two booms extending from the vehicle each able to move independently of each other relative the vehicle and be operated to allow a first boom to locate its respective dock and pruning head to a first tree and be performing pruning on that first tree whilst the second boom is relocating its respective dock and pruning head from a second tree to a third tree. Preferably a thinning head is supported from the vehicle by a boom able to move the thinning head within a 3 dimensional envelope relative to said vehicle, the thinning head comprising of a trunk cutter capable of cutting a tree trunk to fell trees.

Preferably the boom supporting the thinning head is a 3 rd boom.

Preferably there are (a) two booms extending from the vehicle each able to move independently of each other relative the vehicle and be operated to allow a first boom to locate its respective dock and pruning head to a first tree and be performing pruning on that first tree whilst the second boom is relocating its respective dock and pruning head from a second tree to a third tree and (b) a third boom supporting a thinning head that can move independently of the two booms and be independently felling trees.

Preferably the trees able to be felled may be up to 250mm in diameter.

Preferably the trunk cutter is a mechanical shears..

Preferably the trunk cutter is a saw..

Preferably the prune is a close prune..

Preferably the pruning head comprises at least 6 blades to each locate directly or indirectly against the trunk at the circumference of a sector of the trunk, said at least 6 blades in concert able to locate against a substantial part of the circumferential surface of the trunk, each blade supported by a respective arm to allow all the blades to move radially relative to the trunk, so as to allow each blade to follow the circumferential surface of the trunk in use independently of each other, as the pruning head travels along the trunk, so that when one blade is caused to move radially outwardly by the circumferential surface of the trunk, the primary cutter of the other blades are not caused to move radially outwardly by said one blade.

Preferably each arm is mounted to said chassis in a pivotal manner about a rotational axis to provide for the radial movement of each blade.

Preferably each arm is mounted to said chassis in a pivotal manner about a respective rotational axis that is perpendicular to the elongate axis and parallel a tangent of the trunk immediately adjacent the arm, when in use.

Preferably each arm is an elongate arm that extends in a direction substantially parallel to the elongate direction of the trunk when in use, from the chassis at a first end of the arm where the arm is mounted to the chassis to a distal end of the arm at where a respective blade is mounted.

Preferably each arm is elongate and extends in its elongate direction from where it is mounted to the chassis in a direction so that the cutting force of the blade causes a tensile or compression force in the arm transferred to the chassis at where the arm is mounted to the chassis.

Preferably the pruning head comprises at least 2 pruning units each comprising a respective said chassis and at least one arm.

Preferably each said pruning unit comprises two arms mounted to each said chassis, each arm having a respective blade mounted to it.

Preferably each blade (a) can move radially relative the trunk by rotation about the rotational axis of its respective arm and (b) is mounted to its respective arm in a swivelling manner to allow the blade to rotate about an axis substantially parallel the elongate axis of the trunk when in use.

Preferably the motor is powered by a remote power source..

Preferably each motor is powered by a remote power source..

Preferably the remote power source is located at the vehicle..

Preferably the motor is a hydraulic motor..

Preferably the vehicle comprises a hydraulic pump to power the hydraulic motor(s)..

Preferably the boom for the thinning head is moveable independently of the boom for the dock..

Preferably there are two booms each with a respective said dock and pruning head..

Preferably the pruning head is as herein defined..

Preferably the dock is as herein defined..

Preferably the mobile tree pruner is as herein defined..

Preferably the pruning apparatus may also be referred to as a mobile tree pruner.. Preferably each blade is independently mounted by a respective arm that allows its respective blade to move radially relative to the tree trunk independently of the other blades, said blades each have a primary cutter that when said pruning head travels up a tree trunk can drive through the limbs to cut them from the trunk in close proximity to the trunk..

Preferably blades are independently suspended from the chassis by a respective arm to allow each blade to drive through the limbs to close prune them from the trunk.

Preferably a cable is provided for transmitting operating power to the pruning head, the cable extending to and between the boom or vehicle and the pruning head..

In one embodiment, the method comprises the step of the apparatus automatically driving the pruning head to separate from the dock and drive up said tree once pruning head is captured to a trunkin one embodiment, the method comprises the step of the apparatus automatically measuring the girth of the trunk as soon as the apparatus determines the dock is correctly located to the tree..

In one embodiment, the method comprises the step of the apparatus automatically determining the height to prune the tree once the girth has been determined- in one embodiment, the pruning head drives to a maximum speed of 5m/s up the trunk..

Preferably the method may comprise the regenerative braking of one motor of a pruning head as it descends a tree for use in the next ascend of another tree of the or the other pruning head..

Preferably the pruning apparatus comprises of a system for delivering power to each motor of each pruning head to cause each pruning head to ascend a tree.. Preferably the system for delivering power to each motor of each pruning head to cause each pruning head to ascend a tree can receive power back from each motor by regeneratively braking the motor..

Preferably the motor is part of a regenerative braking system..

Preferably the motor on descent of a pruning head, will brake the pruning head reliant on a regenerative braking system to allows power to be extracted from a descending pruning head, to be used in powering the motor or the or another pruning head..

Preferably the pruning head can achieve a speed greater than 5m/s at impact of a and each branch to be pruned.

Preferably the tree to be pruned is a Pinus Radiata tree..

Preferably the tree to be pruned presents a plurality of limbs projecting from the trunk at a plurality of heights along the trunk..

Preferably the tree to be pruned presents a 5 limbs projecting from the trunk at a plurality of heights along the trunk..

Preferably the limbs to be pruned are at least 40mm in diameter and may be at least 50mm in diameter..

As used herein the term "and/or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

The term "comprising" as used in this specification and claims means "consisting at least in part of". When interpreting statements in this specification and claims which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner. The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.)

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described by way of example only and with reference to the drawings in which:

Figure 1a is a perspective view of a pruner showing a multi head configuration of the pruner, with one pruning head in an elevated condition and another pruning head in a docked condition,

Figure 1 b is an alternative and perspective view of figure 1a,

Figure 1c shows a variation of the preferred form of the pruner where a single head is provided and a different configuration of boom and dock is described,

Figure 2 is a perspective close-up view of the dock and pruner head of a preferred from of the present invention,

Figure 3a is a close-up perspective view of a pruning head,

Figure 3b is a side view of a pruning head,

Figure 3c is an alternative perspective view of the pruning head,

Figure 4a is a perspective view of a pruning head and a dock with the pruning head in a docked condition,

Figure 4b is an alternative perspective view of figure 4a, Figure 4c illustrates the dock engaged to a tree stump,

Figure 4d is a close-up perspective view of part of the dock shown in figure 4c,

Figure 4e is a close-up perspective view of a pruning head and dock with the pruning head in its docked condition,

Figure 5 shows a dock of a variation of the pruner as seen in figure 1c,

Figure 6a is a perspective view of 2 units of the pruning head and a hinge connecting the units together,

Figure 6b is a perspective view of the hinge,

Figure 7a is a close-up perspective view of cutter of the pruning head of the variation shown in figures 1c and 5,

Figure 7b shows further detail of the region of the pruning head of figure 7a,

Figure 7c is a perspective view of the alternative form of pruning head looking down on the cutting end of the pruning head,

Figure 7d is a perspective view of two cutting blades and their respective arms,

Figure 7e is an alternative perspective view of figure 7d,

Figure 7f has yet a further alternative perspective view of figures 7d and 7e

Figure 7h is a close-up perspective view of a plurality of blades each supported by respective arm independently of each other,

Figure 7g shows the pruning head with some components removed to illustrates aspects of the pruning head hereinafter described,

Figure 8a is a perspective view of a pruning head, partially exploded with and arm removed from a unit to illustrates feature hereinafter described, Figure 8b shows a plurality of units of the pruning head with components removed for illustrative purposes,

Figure 9a is a perspective view of a pruning head with components removed for illustrative purposes to show a traction member,

Figure 9b is a alternative perspective view of figure 9a,

Figure 9c is an alternative perspective view to show a traction member of a pruning head,

Figure 10 shows a pruner operating in steep terrain,

Figure 11 is an alternative view of the pruner of figure 10 operating in steep terrain,

Figure 12a is a schematic view of a cutting blade adjacent a tree stump,

Figure 12b-c show the cutting blade in an up stroke and down stroke respectively cutting a branch from a tree trunk,

Figure 13 is a perspective view of a variation of a pruner of the present invention that includes a thinning head,

Figure 14 is a close-up perspective view of part of the pruner of figure 13,

Figure 15 (prior art) illustrates a prior art pruner showing features to illustrate disadvantages inherent in such prior art pruning apparatus as hereinbefore described,

Figure 16 shows a graph of required peak force (in kN) to cut a branch from a trunk vs the branch diameter (in cm) to be cut for a typical Pinus Radiata tree,

Figure 17 shows a graph of cutting force (in kN) vs the mass of a pruning head (in KG) for pruning of commercial pine trees, for a pruning head travelling at 4m/s along the trunk of a tree such as a Pinus Radiata tree.

DETAILED DESCRIPTION With reference to the above drawings, in which similar features are generally indicated by similar numerals, a first example of a tree pruner is shown in figure 1 A. Figure

1C and figure 13-14 show another example.

The pruner 1 is configured to prune branches or limbs 2 off of a trunk 3 of a tree 4. The tree 4 to be pruned by the pruner 1 is alive, in situ and upright extending out of the ground 6.

The tree 4 has a base 7 nearest the ground 6, and an upper region 8 distal from the ground 6 and base 7. The tree may be a pine tree or spruce tree for example. The tree may for example be a Pinus Radiata variety of pine tree. These can grow relatively straight if appropriate silviculture is exercised. The tree 4 may hence have a notionally straight elongate axis 5 extending centrally along the trunk. This axis is usually vertical for a live tree.

The pruner 1 may comprise of a vehicle 9 which may house an operator (not shown) in an operator cage 10. The operator is safely protected from any detritus created during the pruning process by the operator cage 10. The vehicle can propel itself over the ground, including on inclined terrain. The vehicle may have traction tracks for such purposes.

The pruner 1 may comprise a boom 12 that is supported from the vehicle 9. In figures 1A and 1 B two booms are shown. Each boom is shown coupled to the vehicle in a rotational manner. Two axes of rotation are preferably provided. This allows the boom to lift and lower and to swing horizontally relative the vehicle and/or ground. This allows the boom to move relative the ground on which the vehicle is positioned. The boom 12 may also be telescopic. This allows the distal end of the boom to be positioned within a relatively large envelope of travel. This is a 3 dimensional envelope.

In figures 1 A and 1 B a preferred from of the pruner 1 is shown having 2 booms. The two booms are able to move independently of each other relative to the vehicle. The movement is preferably controlled by the operator. One or more actuators may be used for such control. These may be hydraulic actuators. In figure 1C a variation of the preferred form of pruner is shown. Here the boom 12 is not telescopic but instead is articulated and may be of a kind as typically found on tractors, diggers and other agricultural or forestry equipment. Whilst figure 1C shows an example of a pruner with one boom only, in other forms there may be two booms independently operable.

The provision of two booms allows pruning work on two adjacent trees to occur independently, from one ground position of the vehicle. The advantages of this are described below.

The vehicle 9 is capable of operating in rugged environments and step terrain. To facilitate operations on steeper terrain, the vehicle can be restrained by a variable tension hydraulic powered winch 900. The winch cable may be stationary to reduce damage to trees. A winch 900 may be attached to a vehicle.

The pruner 1 may also comprise of features such as a launch dock 100 and a pruning head 200 having a plurality of blades positioned to cut through limbs of the tree to remove them from the tree trunk. Details of these features will be set out in more detail below, after the following brief introduction.

The dock 100 comprises a receiving region 101 configured to be received by a trunk 3 of a tree 4 as shown in a first example of the dock 100 in Figure 2A. This allows the dock to register to the tree. In figure 1C and figure 5 an alternative example of the dock 100 is shown.

Typically, the receiving region 101 can extend at least partially around the base 7 of a tree 4. However, in other embodiments the pruning process may be started above the base 7. The receiving region of the dock can facilitate the registering of the dock with a tree at the base or higher.

The dock 100, as seen in figure 5, may comprise of a tree alignment guide 108 that allows alignment of the trunk 3 with the dock 100 as the dock approaches the trunk 3. An alignment guide can help ensure the dock 100 can be repeatedly and accurately aligned with each successive tree. Such alignment is preferable relative to the elongate axis 5 of the tree, so that the pruning head can then be caused to locate to the trunk. The dock may be pivotally mounted to the boom 12 at pivot axis 600 as seen in figure 2A. An operator or automatically control (such as controlled by a hydraulic ram 601) may be used to control to pivotal position between the arm and the dock. This pivotal movement (together with the arm's range of motion relative to the ground) allows the dock to be positioned in appropriate alignment with the trunk to allow the pruning head to engage and release from the trunk whilst engaged to the dock and for it to be deployed and received from/to the dock. This can be achieved by ensuring the vehicle is parked in an appreciate location adjacent a tree. The vehicle itself does not require accurate positioning to ensure the dock can engage to a tree trunk, so long as the vehicle is proximate a tree. The boom or booms can to the repositioning work of the dock after the vehicle is parked in sufficient proximity to a tree or trees to be pruned.

The pivot axis 600 may be presented to allow the dock to rotated in vertical plane. Additional pivot axes may be provided to allow the dock to rotate in at least one of the other orthogonal planes to help facilitate alignment of the dock with the trunk. This may be desirable to have, especially in sloping terrain as seen in figures 10 and 11.

Once the pruning head is located to a tree trunk, the pruning head can deploy from the dock. The pruning head can then self-ascend and self-descend along the trunk, gripping the trunk, parallel to the elongate axis of the trunk.

In the example of the pruner shown in figure 1 A and 1 B the launch dock preferably comprises a docking region 950 at where the pruning head 200 can dock and be deployed from. At the docking region 950 a plurality of rollers 951 may be presented at where a plate 952 of the pruning head can register. The plate may pass between opposed rollers and become laterally confined by the roller. The docking region may also include base 953 on which the pruning head can come to rest and be supported vertically when docked. Other modes of securing yet allowing vertical deployment from and retrieval of the pruning head to the dock are envisaged. The drawings show one of several other ways in which this can be achieved.

The dock 100 and/or the pruning head 200 may comprise a bump stop to safely and gently allow the dock to receive the pruning head 200. The pruning head 200 may have features that engage complementary features of the dock 100 to secure/lock the pruning head 200 in place with the dock during movement of the vehicle 9 and pruner 1 between trees.

The dock as in figure 1C and figure 5 may comprise of dock guide wheels or bushes or bearing strips configured to engage with the guide plate 107 of the dock. This allows the pruning head 200 to be more accurately and safely retrieved to the dock 100.

Alternative or additional funnelled configurations of components can be provided, to help accommodate slight mis-alignment between the dock and the pruning head during the retrieval of the pruning head to the dock.

The dock is preferably supported by and at the end of a boom 12. The dock 100 preferably has one or more arm attachment features 109 configured to quickly and easily allow the attachment of the dock 100 to the boom 12. A quick attachment may be used as is known in the art.

The dock 100 is configured to allow the pruning head to deploy from it and to be received by it back to its docked condition. When docked, the boom 12 and dock can carry and position and reposition the pruning head appropriately to a trunk to be pruned.

The pruning head 200 is configured to release and be deployed from the dock 100 so as to propel up the trunk 3 and whilst doing, so cut off limbs 2 from the trunk 3.

Once the pruning head 200 reaches a desired height, and has then lowered down the trunk, the dock 100 is able to receive the pruning head 200 and guide the pruning head 200 into its home location to the dock. The pruning head and its dock can then be removed from the trunk and manoeuvred to the next tree for pruning.

Hydraulic, pneumatic and/or electrical power is supplied to the pruning head for the purposes powering components of the pruning head that will hereinafter be described. The power may be transferred via an umbilical 13 such as a power cable. The umbilical 13 extends from the vehicle 9 to the pruning head and can travel with the pruning head as it climbs and descends the tree.

Preferably the vehicle 9 supplies power to the pruning head via the umbilical. The vehicle 9 may comprise a hydraulic accumulator 11. Where there are two booms dependent from the vehicle, two pruning heads are provided one at each end of a respective boom 12. Reference will hereinafter made only to one apparatus and boom but it will be obvious to apply the teachings for a two boom configuration.

In one example as seen in figure 1C, the cable 13 extends to the vehicle 9 and may be stored with a cable reel 14 either on the vehicle 9 or on the boom 12. The cable reel 14 is preferably configured to a) dispense cable, b) retract the cable, c) store cable, and d) keep tension in the cable 13.

In the example shown in figures 1A, 1 B and 2A, the umbilical 13 is preferably located in or to a telescopic arm 603. The telescopic arm 603 is preferably supported by the vehicle or its respective boom in a pivotal manner and attached to the pruning head to be able to passively travel with the pruning head at its distal end. The umbilical may be configured to allow its extension and contraction as the arm telescopically extends and retracts. A coiling or flacking or other mechanism may be provided for such purposes. In other embodiments the cable 13 may extend from the dock up to the pruning head.

In a preferred form the function of the pruning head is to close prune trunks, for the production of a large clear wood collar by appropriately removing limbs from the trunk. If not appropriately cut and closely to the trunk, substantial knots or burls can develop in the trunk at where the limbs have been removed. As will herein after be described the use of independent blade suspension aids the accurate and consistent pruning of limbs from a trunk. The use of cutting blades operational in both the upward and downward movement of the pruning head may also facilitate this. The pruning head 200 may cut limbs 2 or limb stubs during both the upward movement and downward movement of the pruning head 200 along the trunk 3. This will be described in more detail below.

The pruning head 200 can configure between an open condition and a closed condition. In an open condition the pruning head 200 is able to receive a trunk 3 and be released from the trunk and in a closed condition the pruning head 200 extends sufficiently about and securely locates and retains to the trunk 3. In the closed condition the blades are presented in their condition for cutting. The pruning head 200 comprises a chassis or a plurality of chassis. It may comprise of a base or base chassis 201 that may support a number of features of the pruning head 200. The base is preferably that part of the pruning head that facilitates the registering and holding of the pruning head with the dock.

From the base 201 there is dependent one or more pruning units 202 as shown in Figure 3A-C. In a preferred from there are 3 pruning units 202A-C. The units are connected to each other using a hinge 204 so that the units can move relative to each other and assume open and closed condition of the pruning head. Unit 202A is preferably secured to or part of the base 201. Unit 202B is dependent from unit 202A using a hinge on one side of unit 202A. Unit 202C is dependent on the other side using a hinge. The hinge defines a pivotal axis YY that is substantially parallel the elongate direction 5 of the tree, in use.

A hinge actuator 203 for one or each hinge may be used to control the rotation of the units relative each other. This may be controlled directly by the operator or by an automated process. The ability of the units 202 to pivot allows the pruning head to move between the open and closed conditions. In a jaw like manner for example. In an open condition the units 202B and 202C are more separated from each other than when in the closed condition where the units 202B and 202C are more proximate each other at the split 606. At the split the units 202B and 202C can separate to create a mouth opening for the trunk of a tree to pass through and to then become captured to the pruning head when the units 202b and 202C are caused to move towards each other by the actuators 203. In the closed condition the pruning head is captured to the trunk and cannot laterally come off the trunk. The mouth is more closed in this closed condition and of a size smaller than the diameter of the trunk. The actuators can be controlled to maintain the closed condition during tree pruning. The actuators can cause pressure of the pruning head to be applied to the trunk for the proposes of providing traction for the pruning head.

Each unit 202A-C comprises of a chassis 608. The chassis is generally elongate in the direction parallel the axis 5 when in use. Each chassis provides support to other components of its respective unit. The hinges 204 are preferably connected to respective chassis' such as by the use of threaded fasteners 609. The base 201 is preferably engaged to the chassis of the unit 202a.

Preferably each unit comprises of a driving mechanism 210. The driving mechanism 210 is supported by the chassis 608.

The driving mechanism is provided to drive the pruning head up a trunk and control its decent down the trunk. The driving mechanism is able gain sufficient traction with the trunk to allow the pruning head to be accelerated from the dock and upwardly along the trunk and generate dynamic energy in pruning head along the trunk to help ensure the blades can remove limbs from the trunk. Examples of energy, speed, acceleration, mass and sizes are set out at the end of the detailed description.

The driving mechanism may also cause the pruning head to be decelerated such as towards the top of the trunk. It may also accelerate the pruning head back down the trunk. Alternatively or in addition, gravity may cause the acceleration of the pruning head down the tree.

In one embodiment, the units preferably apply a substantially constant pressure of the drive mechanisms onto the trunk. The trunk diameter changes over the height of the trunk and the actuators can be used to adjust the relative position of the units as the trunk diameter changes so that a substantially constant pressure can be applied. The constant pressure may be within a band of pressure sufficient to keep the pruning head captured to the trunk and ensuring the blades are held in proximity to the trunk, yet not apply too much pressure to the trunk that may otherwise adversely damage the tree.

Each drive mechanism 210 is configured to act in concert with each other to control the motion of the pruning head 200 up and down the trunk 3. The drive mechanism is powered by power supplied from the vehicle by the umbilical/cable 13. In some embodiments the power may be electrical power. In other embodiments the power is hydraulic power supplied by hydraulic fluid via a hydraulic pump and accumulator located in or at the vehicle 9. In the preferred embodiment the power is hydraulic power and it supplies one or more hydraulic motors 620 that each drive one or more respective traction members 212. The motors may be part of a regenerative braking system. This allows the motors to deliver power during the descent of a pruning head to and for use by motors driving another pruning head up a different tree.

The traction members 212 may be one or more wheelsets wherein each wheelset may have two or more wheels 710 as seen in figure 1C. The wheels or wheel sets may be supported by the chassis 610 using a suspension mechanism so that the wheel can follow the uneven contour of a trunk. The wheels may be mounted for rotation on an axis that in use is horizontal and parallel to the tree trunk tangent.

Preferably the wheels have a contact surface that will contact the surface of the trunk 3. The wheel's contact surface may be formed of a thermoset polyurethane elastomer such as LURETHANE™. LURETHANE™ tyres will help reduce or eliminate the prospect of adversely damaging the tree.

In one embodiment, the traction requirement for clean pruning needs a constant applied force of ~3,000N to each wheel, irrespective of trunk irregularities.

In a more preferred form, the traction members 212 are traction belts as seen in figure 9A and 9B. Each traction belt 212 may comprise of an array of pads or grousers 621 that are presented to be able to make contact with the tree trunk. Each traction belt is driven around respective end sprockets 622A and 622B and can be held taught thereby and there between. The sprocket 622B may be directly driven by the motor 620. The sprocket 622A may be an idle sprocket. The sprockets are preferably supported on axles directly or indirectly supported to its respective chassis.

The array of pads/grousers extends parallel the direction of the axis 5 when in use.

The pads/ grousers may be made from a thermoset polyurethane elastomer such as LURETHANE™. They do not bite into the bark of a tree. They rely on a good coefficient of friction to ensure adequate traction is maintained. Being of a soft material also aids in enhancing surface contact with the trunk.

After engagement of the units 602A-C with the trunk 3 and the trunk 3 is securely retained within the pruning head 200 - the drive mechanism can then be activated and drive the pruning head 200 up the trunk 3 to start the pruning process. Limbs 2 are cut using a plurality of blades 220 of the pruning head. Two embodiments will now be described in relation to the blade configurations. The first embodiment is less preferred to the second.

In a first embodiment seen in figures 1C and 7A and 7B the apparatus comprises a blade set 221 that comprises a plurality of blades 220. There may be 10 blades provided per set. Preferably one blade set 221 is provided per unit 202. Preferably the plurality of blades 220 are joined adjacently to together via an articulated joint 222. The articulated joint may allow the blades to rotate with respect to an adjacent blade about a blade joint rotation axis which is parallel the elongate axis 5 in use.

Preferably each blade set 221 comprises a biasing jaw 223. The biasing jaw 223 holds the plurality of blades 220 together and also biases the blades 220 towards the trunk 3. This allows the blades 220 to stay close to or on the surface of the trunk 3. Preferably the jaw 223 is substantially semi-circular or circular or arcuate to naturally follow the curve of the trunk 3. The jaw is preferably sprung towards the elongate axis 5.

The jaw is preferably biased to reduce its radius. Tensile members or restraining wires 224 may be engaged to distal ends of the jaw as shown in Figure 7B. The restraining wires 224 are configured to increase the size of either or both the opening and radius of the jaw by pulling back on the distal ends of the jaw to allow easy entry of a trunk into the opening of the jaw.

In the configuration of blades described in figures 7A and 7B the blade sets are preferably supported by and presented from the chassis 610 using a four-bar linkage mechanism 230. This preferably comprises two upright arms 231 a lateral member extends from the upright arms to the biasing jaws 223 as shown in Figure 7A and 7B. The bottom "bar" of the four-bar linkage 230 is part of the chassis 610. The four-bar linkage 230 allows the movement of the blade sets 221 laterally from the elongate axis 5 to be independent of the movement of the pruning head 200. Preferably the four-bar linkage 230 comprises four rotational or revolute joints 232 each comprising rotational axes 233. Preferably the rotational axes 233 are perpendicular the elongate axis 5. As the bottom bar of the four- bar linkage is rigid, then the movement of the linkage creates lateral movement towards and away from the trunk with minimal vertical movement. The linkage 230 may be biased or spring-loaded so the blade contact surfaces apply light pressure onto trunk.

In a second embodiment the blades are preferably each independently supported by and presented from a respective chassis. This allows for more consistent pruning of trees to occur. Reference will be made to figures 7c to 7G to illustrate.

In this second embodiment there is no blade set and instead each blade is provided independently of the others. Each independent blade is supported by its own dedicated linkage (such as the arm 660 herein after described). Each pruning head may have 3 or more blades so supported independently. Preferably there are 6 of such blades per pruning head.

The blades are able to be independently positioned about circumference of a sector of the trunk. Where there are 6 blades each sector is substantially 1/6 of the circumference of the trunk. All blades in concert are able to locate about substantially the full circumference of the trunk.

The blades are preferably supported by a respective said chassis 610 about a rotational axis parallel the elongate axis and/or a rotational axis perpendicular the elongate axis. This articulation allows each blade to independently follow the varying surface profile of the trunk as the pruning head travels along the trunk.

Each blade 220 is preferably dependent from a chassis 610 by a respective arm 660. Each blade is preferably supported at a distal end 661 of a respective arm 660. Each blade is preferably secured to the arm using a bolt or axle 663 that allows the blade to rotate relative to the arm about an axis 664, that when the pruning head is captured to a trunk, extends substantially parallel the axis 5. This allows the blade some degree of freedom of movement relative to the chassis. Preferably the arm is itself supported by the chassis at the opposite distal end of the arm. Each arm is attached to a chassis in a rotational manner at pivot axis 667 with the use of a bolt or axle 668 for example. The axis 667 is preferably perpendicular to the axis 5 and parallel a tangent of the trunk, when in use. Preferably two of said arms are so supported by a chassis. So each chassis preferably supports two arms each in turn supporting a respective blade. The provision of the axis 667 allows the blades to move radially in and out relative the trunk. A spring arrangement 498 may be used to bias the blades radially inwardly and against the trunk

As can be seen the shape and configuration of the chassis and its respective arms allows for two arms to be disposed at opposed lateral sides of the chassis and at a radially outward part of the chassis. A single bolt or axle 668 may be used to secure the two arms to a chassis. The axis 667 is preferably perpendicular to the axis 5 in use. It is preferably parallel the axis of the wheels or sprockets herein before described. This allows the blade at the opposite end of the arm to the pivot 668 to move substantially radially in and out relative to the trunk in use and independent of the other blades.

The arm is substantially elongate and positions the blade at the opposite end to where the pivot is provided so that the radial movement is accompanied by negligible blade rotation about the axis 667 thereby ensuring the blade angle relative the trunk remains substantially constant. The position of the pivot axis 667 well away from where the blade is subjected to cutting forces also means a favourable angle of force F (see figure 3C) can be transmitted from the chassis (by virtue of its momentum and the traction forces from the traction belt) to the blade. This favourable angle helps reduce bending moments in components of the pruning head helping increase the cut force of the cutters applied to each limb. It is anticipated that the pruning force to each blade on impact may exceed 8kN. The design of the preferred form the pruning head takes this into account with blades and the pruning units and their chassis along with the traction tracks and arms preferably being aligned to each other and to the direction of travel to help ensure effective transfer of force with little or no elastic yielding of pruning head components and force absorption. This may be achieved by ensuring engineering design that allows transfer of momentum of a 200kg or more (preferably 300kg) pruning head to its cutting blades as will herein after be described by way of example.

The range of rotational movement of the arm relative the chassis may be limited the slot and pin arrangement. A pin 675 of the arm may be registered in a slot 676 of the chassis the slot defining end stops that limit the range of rotation of the arm relative to the chassis. The pin may be a bolt. The pin or bolt may help retain the arm, within its rotational limits, to the chassis. Each arm has its own pin so that the arms can rotate about its respective axis 667 independent of the other arms. Hence allowing the blades to independently move radially inwards and outwards relative the trunk and independent of each other.

Preferably each blade comprises a contact surface 227 configured to engage with and slide over the surface of a trunk in use. Each blade preferably has an arcuate surface of a radius that is in close proximity to the radius of trees to be pruned. The radius may for example be 90mm

The blades of the pruning head of the second embodiment just described may at least partially nest inside each other. This is clearly shown with reference to the two blades illustrated in figure 7D. In this way, in the direction of travel along the trunk, all the blades are in overlap with each other. This may help ensure that substantial if not complete circumferential enveloping of the blades occurs during pruning, ensuring that all limbs in the path of the pruning head are cut and removed from the trunk.

The blades rely on a cutting action being applied to the limb. Being cut close the trunk the cutting action does require a counter edge or other resistance to be introduced on the opposite side of the limb.

Preferably each blade has a primary cutting edge 225. This is a sharp end. The primary cutting edge 225 is preferably the leading edge of the blade as the pruning head travels up a trunk. The edge 225 may lie in plane to which the axis 5, in use, is normal to. Alternatively, the edge may be undulating or serrated as an example. The blade in use extends downwardly from the primary cutting edge. Preferably there is no other part of the blade above the cutting edge when the pruning head is traveling up a trunk. The blade so configured aligns with the direction of travel of the pruning head and helps ensure that a blade deflection is minimal or eliminated to ensure a strong cut force is imparted on the limbs. The blade acts in compression when cutting. The compression direction is parallel the cutting direction.

The primary cutting edge 225 as seen in figure 12A is radially offset outwardly from the trunk contact surface 227 of the blade. This distance (A) may be a few millimetres. The offset helps prevent the blade from biting into the trunk itself. The cutting edge may have a lead-in surface 789 that is at a slight angle to the direction of travel up the trunk so as to help avoid the blade biting into the trunk. Much like the tips of a ski that help a skier travel over the surface of the snow. Offset may be achieved in other ways also (such as by skids, wheels or a ridge extending along the trunk contact surface of the blade) and not by a lead-in at the cutting edge. The distance A may be a desired and predetermined distance from the contact surface 227 to create a desired and length of a limb stub. This distance (A) may be 5mm for example.

The provision of a plurality (at least 4 and preferably 6) independently adjusting blades about the trunk circumference allows a consistent and hence close-to-the-trunk cut to be made of the limb. Being independent, the radial position of one blade is not influenced by the radial position of another blade. For example one blade may be caused to ride over a knot of the trunk and as a result move radially outwardly. Were the blades interdependent, adjacent blades may then also move outwardly to a degree that may then not cut adjacent limbs in as close a proximity to the trunk as desired.

The primary cutting edge 225 will cut limbs from the trunk as the pruning head travels upwardly along the trunk.

Preferably the blades 220 each have two cutting ends, provided by the primary cutting edge 225 and a secondary cutting edge 226. Preferably the primary cutting edge is upper more the secondary cutting edge. The primary cutting edge 225 impacts limbs or limb stubs 2 during the upward movement of the pruning head, and the secondary cutting edge 226 may further cut the same limbs 2 a second time, during the downward movement of the pruning head 200. The secondary cutting edge of each blade is preferably the lower most part of the blade. In use, the blade generally extends upwardly from the secondary cutting edge. The secondary cutting edge may be of the same or similar configuration at the primary cutting edge. The surface 227 preferably extends continuously between the cutting ends. The surface is preferably part cylindrical and of constant profile between the two cutting ends.

Preferably the primary cutting edge 225 has a cutting edge further away from the trunk 3 than the lower cutting edge 226. This allows the blade 220, in its second pass over the trunk on the way back down toward the dock, to re-cut the stubs of a limb and this may be at more proximate distance to the trunk 3. As shown in Figure 12A the primary cutting edge 225 has a distance A from the trunk and the secondary cutting edge 226 has a distance B from the cutting edge to the trunk surface. The distance B may be 3mm.

In figures 12B and 12C there is shown the up-stroke and down-stroke of a cutter 220. In the up-stroke the cut length of the limb is a distance A from the trunk and on the down-strike the cutter 220 may trim the cut length of the limb to distance B which is less than distance A. The cut on the down stroke may be considered a shaving of the limb stub. This may require less force that a cutting through the limb on the upstroke. The blade, being subjected to less force during cutting, may therefore be subjected to less forces deforming or otherwise affecting the desired position or performance of the blade. The blade may stay sharper for longer. This in turn should lead to a more accurate and/or consistent final cut length of the limbs of a tree. Such length may be around 3mm for example.

The ability of each blade 220 to double cut, allows a consistent, regular, close and clean final cut of the limbs 2. The first cut may be considered a course cut of the limb and the second cut may be closer and more accurate cut.

The blades are preferably composed of metal.

As seen in figures 13 and 14, the pruner 1 may also provide a thinner 940. The thinner may be comprised of a thinning head 941 carried at the end of a boom 942 that is secured to the vehicle. The boom, like those earlier described may be controlled for motion relative the vehicle to allow the thinning head to be positioned relative a tree. The boom may be telescopic. When young trees, planted at 1000 per hectare, have created a canopy the weaker trees are thinned to leave 400 strong trees per hectare. Combining thinning with pruning as part of one device as herein described, provides an economical break through for forest managers. During pruning operations and whilst the vehicle 9 is manoeuvred and already brough into position for pruning sufficiently proximate trees, thinning out of trees at the same time will mean that this can be done from one ground position of the vehicle. This can be done by a hydraulic shear 945 capable of cutting and felling unwanted trees of up to around 250mm diameter at or near ground level.

The pruner 1 may have one arm for a pruner head 200 and one arm for a thinning head 941. The pruner 1 may have two arms for a pruner head and one arm for a thinning head. Whilst one head is performing its cutting operation, the vehicle operator may be manoeuvring the other head to a new location thereby improving forest management efficiencies.

The pruner 1 may have multiple sensors that allow semi-automation and/or automation of the pruner 1. For example the dock 100 may comprise one or more of a proximity sensor 103 configured to determine the proximity of the dock 100 to the trunk 3, a pitch sensor 104 configured to determine if the dock 100 and tree alignment member 108 is plumb or vertical or at least aligned with the trunk 3. Further the dock 108 may comprise of a roll sensor 105 to ensure that the lateral swing of the dock 100 is upright. The dock 100 may use both the pitch sensor 104 and the roll sensor 105 to control the position of the dock relative the tree to ensure the dock 100 is plumb with the tree trunk 3. The sensors allow the apparatus to be used on slopes as shown in Figures 10 and 11. In other embodiments the control of the apparatus is partially or fully manually controlled.

The apparatus in one embodiment is equipped with a LASER measurement tool which can be set to a fixed height. When the pruning head reaches a specified height the LASER measurement tool output reverses the upward movement of the pruning head to downward movement.

The pruner 1 may comprise an auto-start function so that as soon as the dock 100 has determined that it is in the correct position then the pruning process will begin. This process may start with the actuators 203 actuating to move the units 202 and hence the pruning head 200 to the closed condition captured to a trunk. Furthermore, once in the closed condition, the actuation of the drive mechanism 210 may be automatically started so as to start the pruning head 200 up the tree to start the pruning process.

The dock 100 may have a girth calliper or member 102 configured to help determine the girth of the trunk 3 once the trunk 3 has been received at the receiving region 101.

When pruning operations are underway, pruning time per tree may be around 4- 6 seconds. Relation time of a pruning head between trees may be 15- 20 seconds. By using a multi head pruner, productivity may be increased by 80%. In addition, hydraulic power is able to be recovered from a pruning head when descending. This can allow for a sharing of power between pruning heads by performing one pruner on up stroke followed by one pruner on downstroke. The return pressure from a descending pruning head can be used to help power the ascent of the other pruning head.

The pruner head of the present invention relies on weight to create dynamic energy so that the blades can cut through multiple branches at once. Trees in commercial forest may grow with a plurality of branches projecting from the tree trunk at the same or similar height. Pinus Radiata trees for example may up to 5 branches in a cluster each over 50mm diameter.

The pruner head needs to operate in contact with trunk being pruned without damaging the bark. Bark, in particular of young trees, can be delicate. This restricts the compression pressure that can be applied directly to bark and also the pruning head's acceleration forces acting on the bark. To help ensure effective traction is created between the pruning head and the trunk with no or minimal skidding of the traction members over the bark and detrimental shear forces being experienced by the bark, the pruning head may use tracks with soft Lurethane grousers in contact with tree. These offer a good coefficient of friction and have some compliance to the trunk surface.

The traction forces that the pruning head applies to the tree trunk are substantially less than the cutting force required for pruning. This is achieved by appropriate control of the driving members including for example the controlled hydraulic power to accelerate pruner.

The energy required for cutting a branch is the force applied to the cutting blade multiplied by the distance of the cut. By way of example, Figure 16 illustrates an example of Force v Branch Diameter for a Pinus Radiata tree. It can be seen from figure 16 that for a 3.5cm branch the force required is 3.0Kn over a distance of 3.5 cm. Work done is the cutting force 3000N x ,035m = 105 Nm = 105 joules. In commercial forests such as a Pinus Radiata forest, the pruning head may encounter 5 branches simultaneously each of 5cm diameter. Referring to figure 16, to cut a single 5cm branch requires a force of around 5.3Kn over a distance of 5.0 cm. The work done 5,300N x 0.05m = 265Nm = 265 joules. To simultaneously cut 5 x 5cm branches hence requires a blade cutting force of 26.5Kn force and energy of 1,325 N.m = 1325 joules. The preferred pruning head of the present invention is hence intentionally heavy to ensure it can:

(a) generate more than required dynamic energy for the blades to cut, before the blades strikes the first branch or set of branches above the location that the pruning head is upwardly accelerated from, and

(b) maintain sufficient dynamic energy through to the desired prune height. The desired height may be up to 24m. The pruning operation may not reach the top of the tree as it is desirable for the live tree to retain a canopy of leaves to support ongoing tree maturation.

In some embodiments the pruning head may weigh around 300 kg. As such the preferred pruning head could not be carried by one or two persons to place it onto a tree trunk.

To accelerate this mass upwards over a distance of around 250mm to an operating speed of 5 m/sec an upward hydraulic thrust of 5-6KN can be applied. Upon striking multiple 50mm branches the impact force may be 30-55KN helping ensure a clean cut of all the branches achieved.

Whilst increasing the speed of travel will increase the dynamic energy of a pruning head, with increased speed requirements undesirable bark damage may start to occur. For the preferred form of the present invention a desirable operational speed up the trunk, is around 4-5 metres per second. This could undertake a prune up to 6m in height in 1.2 to 1.5 seconds. This upward speed is preferably reached from standing start, over a distance of around 250mm.

In a preferred from as an example the pruning head may weigh 298kg and can deliver a cutting force of 55 Kn. By way of example, to provide the necessary operational required upward force, each traction member may be delivered approximately 2,000N by a respective motor 615.

This is an adequate safety margin for occasional larger branches and less than perfect blade sharpness. With reference to figure 17, lighter weight pruning heads are shown in the bottom left zone, delivering less than 20Kn force which is not adequate for required duties. A range of weight of the preferred form of the invention is show on upper right in the graph of figure 17, capable of generating 20-30Kn of cutting force. The pruning head is hence able to provide for an accurate, consistent and close pruning of trees in a forest. The pruning head's function is to close prune trunks for the production of a clear wood collar.

Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

Although the invention has been described by way of example and with reference to particular embodiments, it is to be understood that modifications and/or improvements may be made without departing from the scope or spirit of the invention.

For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.