WO2008143645A1

WO2008143645A1 - Debarker head

Info

Publication number: WO2008143645A1
Application number: PCT/US2007/024192
Authority: WO
Inventors: Douglas C. Swinyard; Alex J. Stevenson; Philip J. Springhall; Boele A. De Vries
Original assignee: Waratah Nz Limited
Priority date: 2007-05-21
Filing date: 2007-11-19
Publication date: 2008-11-27
Also published as: WO2008143644A1; AU2007353829A1; ZA200908009B; AU2007353829B2

Abstract

A debarker head for use with a work machine is disclosed. The debarker head is configured for debarking a felled tree.

Description

DEBARKER HEAD

The present application claims priority to U.S. Provisional Application No. 60/939,367 filed 21 May 2007 and U.S. Provisional Application No. 60/957,928 filed 24 August 2007, both of which are hereby incorporated by reference herein.

Field of the Disclosure [0001] The present disclosure relates to debarking of a felled tree.

Background of the Disclosure

[0002] A debarker head is used to debark a felled tree. It is attachable to a work machine, such as, for example, to the free end of a boom thereof, for manipulation by the work machine. The debarker head itself does not fell any trees, as it does not have any felling device to do so. Instead, other means may be used for tree felling. However, once a tree is felled, the work machine positions the debarker head over the felled tree for the debarker head to pick up the tree and drive it along one or more debarking components so as to delimb and debark the tree.

Summary of the Disclosure

[0003] According to the present disclosure, there is provided a debarker head for use with a work machine. The debarker head is configured for debarking a felled tree.

[0004] According to an aspect of the present disclosure, the debarker head comprises a delimb arm arranged to open and close, a drive wheel, a drive arm to which the drive wheel is attached, the drive arm arranged to open and close to move the drive wheel therewith, and a grapple hydraulic circuit for operating both the delimb arm and the drive arm. The grapple hydraulic circuit is responsive to pressure from the work machine (i) that is below a predetermined threshold close pressure to close the delimb arm but not the drive arm, (ii) that is at at least the predetermined threshold close pressure to close both the delimb arm and the drive arm, (iii) that is below a predetermined threshold open pressure to open the delimb arm but not the drive arm, and (iv) that is at at least the predetermined threshold open pressure to open both the delimb arm and the drive arm. [0005] In such a case, the debarker head may be configured without any electronics for controlling the functions of the debarker head. Instead, the work machine can be outfitted with an electro-hydraulic control circuit fluidly coupled to the grapple hydraulic circuit onboard the debarker head, a delimb-close input device, a drive-close input device, a delimb-open input device, and a drive-open input device, and a controller that communicates with the input devices and the electro-hydraulic control circuit.

[0006] The controller may thus be adapted to signal the electro-hydraulic control circuit to output to the grapple hydraulic circuit a predetermined activate-delimb pressure lower than a predetermined threshold close pressure to close the delimb arm but not the drive arm in response to actuation of the delimb-close input device, signal the electro-hydraulic control circuit to output to the grapple hydraulic circuit a predetermined close-delimb-and-drive pressure above the predetermined threshold close pressure to close both the delimb arm and the drive arm in response to actuation of the drive-close input device, signal the electro-hydraulic control circuit to output to the grapple hydraulic circuit the predetermined activate-delimb pressure lower than a predetermined threshold open pressure to open the delimb arm but not the drive arm in response to actuation of the delimb-open input device, and signal the electro-hydraulic control circuit to output to the grapple hydraulic circuit a predetermined open-delimb-and-drive pressure above the predetermined threshold open pressure to open both the delimb arm and the drive arm in response to actuation of the drive-open input device.

[0007] The above and other features will become apparent from the following description and the attached drawings.

Brief Description of the Drawings

[0008] The detailed description of the drawings refers to the accompanying figures in which:

[0009] FIG. 1 is a side elevation view showing a work machine (in phantom) and a debarker head attached to a free end of a boom of the work machine; [0010] FIG. 2 is a perspective view of the debarker head; [0011] FIG. 3 is a bottom view of the debarker head; [0012] FIG. 4 is a side elevation view of the debarker head; [0013] FIG. 5 is a sectional view of the debarker head taken along lines 5-5 of FIG. 4;

[0014] FIG. 6A is a perspective view of a rotator of the debarker head;

[0015] FIG. 6B is a side elevation view of the rotator;

[0016] FIG. 6C is a top plan view of the rotator;

[0017] FIG. 7A is a sectional view taken along lines 8a-8a of FIG. 6C;

[0018] FIG. 7B is an enlarged view of region A of FIG. 8a;

[0019] FIG. 8 is a longitudinal sectional view of a rotary union of the debarker head;

[0020] FIG. 9 is an exploded perspective view of the rotary union;

[0021] FIG. 10 is an end view of the manifold body;

[0022] FIG. 11 is a bottom view of the debarker head, with some modifications;

[0023] FIG. 12 is a side elevation view of the modified debarker head, similar to

FIG. 4 but with a few changes;

[0024] FIG. 13 is a sectional view of the modified debarker head taken along lines

13-13 of FIG. 12;

[0025] FIG. 14 is a sectional view of the rotator and rotary union of the modified debarker head;

[0026] FIG. 15 is a sectional view showing the rotator, rotary union, and valve exploded from the chassis of the modified debarker head;

[0027] FIG. 16 is an enlarged detail of a shock absorbing portion of a mount for mounting the rotary union, valve, and rotator to the chassis back;

[0028] FIG. 17 is a perspective view of the rotary union and the mount attached to an end of the rotary union;

[0029] FIG. 18 is an exploded perspective view showing the mount;

[0030] FIG. 19 is a bottom view of the mount;

[0031] FIG. 20 is enlarged bottom view of a detail of the mount;

[0032] FIG. 21 is a longitudinal sectional view of the rotary union with a mounting plate of the mount attached to end thereof;

[0033] FIG. 22 is a perspective view of the rotary union with the mounting plate attached to the end thereof;

[0034] FIG. 23 is an exploded perspective view of the rotary union with the mounting plate attached to the end thereof;

[0035] FIG. 24 is an end view of the manifold body with the mounting plate attached to the end thereof; [0036] FIG. 25 is a simplified schematic view of a control system for the debarker head shown in more detail in FIGS. 25A-25C; and

[0037] FIGS. 25A-25C are schematic views of portions of the control system of FIG. 25.

Description of the Drawings

[0038] Referring to FIG. 1 , there is shown a work machine 10, illustratively a forestry excavator, and a debarker head 12 attached to a free end of a boom 14 of the work machine 10. The work machine 10 further has a base unit 16, which may take a variety of forms, for carrying and manipulating the boom 14 and debarker head 12 attached thereto. The base unit 16 has an operator's station 18 for a human operator controlling the work machine 10.

[0039] Referring to FIGS. 2-4, the debarker head 12 comprises a chassis 20 and a rotator 22. One or more debarking components 30a, 30b, 30c, 32a, 32b, 34 are mounted to the chassis 20 for use generally in front of the chassis 20. The rotator 14 is adapted to be attached to the free end of the boom 14 (e.g., via a joint 24) to attach the debarker head 12 to the boom 14. The rotator 22 is mounted on a back 26 of the chassis 20, in a manner against tiltable movement of the chassis 20 relative to the rotator 22, for rotating the chassis 20 about a yaw axis 28 to adjust a yaw angle of the chassis 20 and the debarking components mounted thereto about the yaw axis 28.

[0040] The components 30a, 30b, 30c, 32a, 32b, 34 serve to debark the tree, among other functions. In particular, components 30a, 30b, 30c are drive wheels (which may also be referred to as feed wheels) that contact the tree to drive the tree back and forth in opposite directions along a feed path 36. Such contact with the bark promotes debarking. Two of the wheels 30a, 30b are attached to respective drive arms 38a, 38b pivoted to the chassis 20 for pivotal movement about respective axes 40a, 40b to open and close the wheels 30a, 30b. A tree is gripped by wheels 30a, 30b open closure of arms 38a, 38b. As such, drive wheels 30a, 30b and drive arms 38a, 38b assist with the grapple function of the head 12. Drive wheel 30c is recessed in and mounted to the chassis 20 against pivotal movement relative thereto. [0041] Components 32a, 32b are delimb arms (which may also be referred to as grapple arms or debark arms) pivoted to the chassis 20 for pivotal movement about respective axes 42a, 42b to open and close. A tree can be gripped upon closure of the arms 32a, 32b. As such, the arms 32a, 32b assist with the grapple function of the head 12. The arms 32a, 32b have knifes formed on opposite sides thereof, configured to delimb and debark the tree upon movement of the tree along the feed path 36.

[0042] Component 34 is a knife fixed to an end of the chassis 20 against movement relative thereto. As such, the knife 34 is configured to delimb and debark the tree upon movement of the tree along the feed path 36.

[0043] As a debarker, the head 12 has no felling device. It thus has no butt saw for felling the tree . However, in some embodiments, the debarker head 12 may include a cross-cutting device (not shown) for cross-cutting a tree held by the head 12 into one or more pieces of desired length. The cross-cutting device may be, for example, a chain saw, a shearing device, or the like.

[0044] Since the debarker head 12 will not be felling trees, it need not be able to tilt relative to the rotator 22 say, for example, to an upright, harvesting position as with tree harvester heads. The head 12 thus has no tilt bracket (also known as a hanging bracket) interconnecting the rotator 22 and the chassis 20. Rather, exemplarily, the rotator 22 is mounted on the back 26 of the chassis 20 in contact therewith. [0045] The rotator 22 is configured to rotate the chassis 20 (and components mounted thereto) about the yaw axis 28 to adjust the yaw angle of the chassis 20. The rotator 22 may rotate in opposite directions indicated by double-headed arrow 44.

[0046] Referring to FIGS. 5-7B, the rotator 22 has a rotator housing 46 to which various components are mounted. At the top of the rotator 22 is a pin 48 supported on opposed side walls 50 rising from a support wall 52. A pair of walls 54 interconnect side walls 50. A motor guard 56 mounted on the support wall 52 partially surrounds a motor 58 (e.g., a hydraulic motor) also mounted on the support wall 52. A pinion gear 60 is attached to the motor 58 for rotation thereby. [0047] A slewing ring 62 of the rotator 22 has a ring gear 64 and a bearing 66. The ring gear 64 is mounted on the back 26 of the chassis 20 in contact therewith and in fixed relation thereto with fasteners 67 about a hole 68 defined in the back 26 and interfaces with the pinion gear 60 for rotation thereby. The bearing 66 is mounted on the support wall 52 in contact therewith and in fixed relation thereto via fasteners . [0048] The rotator 22 is thus configured to rotate the chassis continuously 360 degrees about the yaw axis 28. Exemplarily, three hydraulic lines (supply - rotate clockwise, return - rotate anti-clockwise, and case drain which is returned via a port in the rotary union) routed from the work machine 10 serve the motor 58 for operation thereof to rotate the pinion gear 60. Such rotation of the pinion gear 60 rotates the ring gear 64 about the bearing 66 and the yaw axis 28. Rotation of the ring gear 64 causes the chassis 20 to rotate about the yaw axis 28 also. [0049] Referring back to FIG. 5, the debarker head 12 has a valve unit or block or just valve unit 70 onboard the chassis 20 for controlling hydraulic flow to operate various functions, such as those functions associated with the drive wheels 30a, 30b, 30c, the drive arms 38a, 38b, and the delimb arms 32a, 32b. The valve unit 70 is mounted within and to the chassis 20 in register with the hole 68. A valve mounting plate 75 attached to the bottom (as viewed in FIG. 5) of the valve unit 70 is coupled to an internal portion 77 of the chassis 20 via a number of fasteners 81 (e.g., bolts). [0050] Referring to FIGS. 5 and 8-10, the debarker head 12 has a rotary union 72 for routing hydraulic fluid between hoses, or other types of hydraulic lines, from the work machine 10 and the valve unit 70. The rotary union 72 extends from the rotator 22 through a non-circular hole 74 (illustratively, generally square) defined in the support wall 52, the slewing ring 62, and the hole 68 defined in the back 26 to the valve unit 70. The rotary union 72 is attached to the valve unit 70 without the use of any hoses.

[0051] The rotary union 72 has a manifold housing 76 and a manifold body 78. The manifold body 78 is rotatably received in a bore 79 of the manifold housing 76 in fluid communication therewith.

[0052] The manifold housing 76 is fixed to the support wall 52 against movement relative thereto. In particular, it exemplarily has a non-circular profile (illustratively, generally square as in FIG. 9) that fits in the non-circular hole 74 (illustratively, generally square as in FIG. 6C) defined in the support wall 52 so as to be constrained against rotation about the yaw axis 28.

[0053] A locking plate or key 80 (FIGS. 7A and 14) fixed to the support wall 52 locks against a side of the generally square manifold housing 76 to retain the housing 76 axially in place. The key 80 is received in a keyway 71 formed in a side of the manifold housing 76 to retain the manifold housing 76 in place (FIG. 14). [0054] The manifold body 78 extends from the manifold housing 76 to the valve unit 70. In particular, it extends out of the manifold housing 76 through the slewing ring 62 and the hole 68 defined in the back 26 of the chassis 20 to the valve unit 70 and is attached thereto by fasteners 95 for rotation therewith about the yaw axis 28. [0055] During assembly of the head 12, the valve unit 70 and the rotary union 72 are attached to one another as a sub-assembly. This sub-assembly is then inserted through the hole 68 of the back 26 into the chassis 20, after which the valve unit 70 is fastened to the chassis 20. The rotator 22 is then mounted onto the back 26 so as to surround the rotary union 72 by fastening the ring gear 64 of the slewing ring 62 to the back 26 about the hole 68 in fixed relation thereto. Hoses (not shown) are then attached to a number of ports 82 (or, more specifically, identified sometimes as ports 82a-82e) of the manifold housing 76 for routing hydraulic fluid to/from the rotary union 72.

[0056] Each of the ports 82 is aligned in register with a respective annular housing passageway 84, the housing passageways 84 being spaced longitudinally along the length of the manifold housing 76. In turn, each housing passageway 84 is aligned in register with a respective body passageway 86 defined in the manifold body 78 for fluid communication therewith during rotation of the manifold body 78 in the manifold housing 76. The body passageways 86 are spaced circumferentially relative to one another.

[0057] Exemplahly, there are five of each of the ports 82, the housing passageways 84, and the body passageways 86, forming portions of five separate hydraulic lines. Such lines are provided, for example, for the following: grapple closed for closing the delimb and drive arms 32a, 32b, 38a, 38b (as discussed in more detail herein), grapple open for opening the delimb and drive arms 32a, 32b, 38a, 38b (as discussed in more detail below), drive/feed forward for the drive motors 150, drive/feed reverse for the drive motors 150, and motor case drain. Two other lines routed to the head 12 from the work machine 10 include motor supply and motor return for the motor 58.

[0058] Referring to FIGS. 8-10, other details of the rotary union 72 are shown. A sealed connection is established between the manifold housing 76 and the manifold body 78. There is an annular seal 87 positioned on either side of each housing passageway 84 between the housing 76 and body 78 to prevent leakage from one passageway 84 to another. Further, there is a plain bearing or bushing 89 mounted at either end of the manifold housing 76. A thrust washer 83 and O-ring seal 85 are positioned between a retainer plate or cap 75 and a first end of the manifold housing 76, the cap 75 being attached to the manifold housing by use of a number of fasteners 77. Another thrust washer 83 and O-ring seal 85 are positioned between the a spacer sleeve 93 and an opposite, second end of the manifold housing 76. A valve mounting plate 73 is fixed (e.g., welded) to an end of the manifold body 78, and the valve unit 70 is attached to the plate 73 by use of a number of fasteners 95. [0059] Referring to FIGS. 11-16, a mount 90 may be used with the head 12 to attach the rotator 22, rotary union 72, and valve unit 70 to the back 26 of the chassis 20. Use of the mount 90 simplifies assembly of the rotary union 72 and valve unit 70 to the chassis 20. The head 12 may have additional features, such as, for example, a rub plate 213 for sliding of the tree along the rub plate 213 and a wider drive wheel 30c.

[0060] Referring to FIGS. 13-20, the mount 90 comprises a first mounting plate or ring 91 (which may also be referred to as a valve mounting plate) and a second mounting plate or ring 92. The first mounting plate 91 , shown also in FIGS. 20-24, is attached to an end portion of the manifold body 78 so as to surround and be fixed thereto. A spacer sleeve 93 spaces the manifold housing 76 from the first mounting plate 91. The valve unit 70 is attached to a radially inner hub 94 (FIG. 14) of the first mounting plate 91 via fasteners 95.

[0061] The first mounting plate 91 is attached to the second mounting plate via fasteners 96. Fasteners 96 attach a radially outer, annular flange 97 of the first mounting plate 91 to a radially inner hub 98 of the second mounting plate 92. The flange 97 is stepped axially from the hub 94 away from the valve unit 70, and a radially outer, annular flange 99 of the second mounting plate 92 is stepped axially from the hub 98 away from the valve unit 70.

[0062] Plate 91 is mounted to plate 92 in a manner that minimizes shock loading on the valve unit 70 and manifold body 78. Exemplarily, the mount 90 comprises four fastening units 106B, 106b, 106c, 106d spaced angularly (e.g., about 90 degrees) about the flange 97. Each fastening unit has two fasteners 96, first and second shock absorbers 102a, 102b positioned on opposite sides of the first mounting plate 91 and made of, for example, polyurethane (e.g., PU40) having a hardness of, for example, Shore 90, a lock plate 103, a press plate 104, and two bushings 105 made of, for example, nyoil. There are four first shock absorbers 102a, each one dedicated to a respective fastening unit 106B, 106b, 106c, 106d, whereas there are only two second shock absorbers 102b. Each second shock absorber 102b is semicircular or otherwise arcuately elongated so as to be associated with three fastening units: an intermediate fastening unit 106B or 106c and half of each fastening unit 106b, 106d adjacent thereto. For example, for each intermediate fastening unit 106B, 106c, one of the second shock absorbers 102b is associated with the two fasteners 96 of such fastening unit 106B, 106c but with only one of the fasteners 96 of the adjacent units 106b, 106d.

[0063] In each fastening unit 106B, 106b, 106c, 106d, each first shock absorber 102a is sandwiched between the press plate 104 and the flange 97 of the first mounting plate 91. Further, the second shock absorber 102b is sandwiched between the first and second mounting plates 91 , 92. Each bushing 105 extends through a hole formed in the first mounting plate 91 into holes formed in the first and second shock absorbers 102a, 102b. The lock plate 103 lies against the press plate 104.

[0064] Each fastener 96 extends through holes formed in the lock plate 103, the press plate 104, and a bushing 105 to the hub 98 of the second mounting plate 92 so as to fasten the mounting plate 91 to the mounting plate 92. Since the fastener 96 extends through a bushing 105, it also extends through the first shock absorber 102a, the flange 97 of the first mounting plate 91 , and the second shock absorber 102b. A pair of dowel pins 107 facilitate alignment of the holes formed in the plates 91 , 92 during assembly.

[0065] After a fastener 96 has been torqued into place, a corner portion 340 of the associated lock plate 103 next to the fastener 96 is folded away from the press plate 104 so as to lie against a side face of the head of the fastener 96. The thus-folded corner portions 340 lock the fasteners 96 in place.

[0066] Referring back to FIGS. 13-15, to attach the rotary union 72 to the chassis back 26, holes formed in the flange 99 are aligned with holes formed in the chassis back 26 such that the flange 99 extends between the ring gear 64 and the chassis back 26. Fasteners 67 (e.g., bolts) spaced about and extending from the ring gear 64 are passed through the holes formed in the flange 99 into the holes formed in the chassis back 26, thereby attaching the rotary union 72 to the chassis back 26. [0067] Referring to FIG. 25, there is a shown an electro-hydraulic control system 110 for controlling operation of the debarker head 12. The control system 110 is configured such that the electronics for control of the debarker head functions are onboard the work machine 10 rather than head 12, resulting in a simplified head 12. [0068] Referring to FIGS. 25A-25C, the control system 110 exemplarily has an electronic controller 112, a delimb-close input device 114, a delimb-open input device 116, a drive-close input device 118, a drive-open input device 120, an electro- hydraulic first control circuit 122, and an electro-hydraulic second control circuit 123. The first control circuit 122 is fluidly coupled to the rotator 22 and a grapple hydraulic circuit 124 onboard the debarker head 12, and the second control circuit 123 is fluidly coupled to a feed hydraulic circuit 152 onboard the debarker head 12. Exemplarily, the first control circuit 122 may be configured as a valve unit or block ("operation control valve" in FIG. 25A) mounted at the base of the boom 14 near where the boom 14 is mounted on the base unit 16, and the second control circuit 123 may be configured as a valve unit or block mounted ("main excavator valve" in FIG. 25B) on the base unit 16 for controlling excavator-type functions of the work machine 10.

[0069] The controller 112 communicates with the input devices 114, 116, 118, 120 and the control circuits 122, 123. Exemplarily, the controller 112 signals the electro- hydraulic control circuit 122 to output to the grapple hydraulic circuit 124 a predetermined activate-delimb pressure (e.g., 7.5 MPa) lower than a predetermined threshold close pressure (e.g., 8.5 MPa) to close the delimb arms 32a, 32b but not the drive arms 38a, 38b in response to actuation of the delimb-close input device 114, signals the electro-hydraulic control circuit 122 to output to the grapple hydraulic circuit 124 a predetermined close-delimb-and-drive pressure (e.g., 20 MPa) above the predetermined threshold close pressure to close the delimb arms 32a, 32b and the drive arms 38a, 38b in response to actuation of the drive-close input device 118, signals the electro-hydraulic control circuit 122 to output to the grapple hydraulic circuit 124 the predetermined activate-delimb pressure (e.g., 7.5 MPa) below a predetermined threshold open pressure (e.g., 9.5 MPa) to open the delimb arms 32a, 32b but not the drive arms 38a, 38b in response to actuation of the delimb-open input device 116, and signals the electro-hydraulic control circuit 122 to output to the grapple hydraulic circuit 124 the predetermined open-delimb-and-drive pressure (e.g., 12 MPa) above the predetermined threshold open pressure to open the delimb arms 32a, 32b and the drive arms 38a, 38b in response to actuation of the drive- open input device 120.

[0070] Although the predetermined threshold open pressure is exemplarily greater than the predetermined threshold close pressure, it is within the scope of this disclosure for the predetermined threshold open and close pressures to be equal to a predetermined threshold pressure. Further, although the predetermined close- delimb-and-drive pressure is greater than the predetermined open-delimb-and-drive pressure, it is within the scope of this disclosure for the predetermined close- and open-delimb-and-drive pressure to be equal to a predetermined activate-delimb-and- drive pressure.

[0071] As alluded to above, there are seven hydraulic hoses or lines routed from the base unit 16 to the head 12. Those hoses are provided for the following functions: (1 ) grapple closed for closing the delimb and drive arms 32a, 32b, 38a, 38b, (2) grapple open for opening the delimb and drive arms 32a, 32b, 38a, 38b, (3) drive/feed forward for the drive motors 150, (4) drive/feed reverse for the drive motors 150, (5) drive motor and rotator motor case drain, (6) rotator motor - clockwise, and (7) rotator motor - anti-clockwise. The first five of those hoses are fluidly coupled to the ports 82a, 82b, 82c, 82d, 82e (FIG. 25B), respectively, whereas the last two are routed directly to the rotator motor 58.

[0072] Referring to FIGS. 25A and 25B, there is shown the first control circuit 122 (FIG. 25A) and the second control circuit 123 (FIG. 25B). Pressurized fluid from a pressure source 311 (FIG. 25A) is routed to a pressure line 312 of the circuit 122 via, for example, valving of the circuit 123 associated with various excavator-type functions of the work machine 10 in response to energization of a valve 312 by the controller 112 (FIG. 25A).

[0073] Referring to FIG. 25A, pressurized fluid provided by pressure line 310 is routed to directional control valves 314a, 314b via respective compensators 316B, 316b. Control valve 314a directs flow of pressurized fluid to and from rotator motor 58 via ports 318a, 318b. Control valve 314b directs flow of pressurized fluid to and from ports 82a, 82b onboard the head 12 via ports 320a, 320b. [0074] The control circuit 122 comprises a pressure-setting section 322 for setting the pressures outputted from the ports 320a, 320b to the head 12. In response to actuation of the delimb-close input device 114, the control valve 314b shifts upwardly from its neutral position (as viewed in FIG. 25A) to its close-function position, and the controller 112 energizes the valve 324a so as to close the valve 324a. As a result, the pressure level associated with the pressure setting of the pressure-limit valve 326B (e.g., 7.5 MPa) is communicated to the compensator 316b, which sets the pressure communicated via the control valve 314b to close-function port 82a at this pressure level in order to close the delimb arms 32a, 32b but not the drive arms 38a, 38b. This pressure level may thus also be referred to as the predetermined activate- delimb pressure, the purpose of which is discussed in more detail in connection with FIG. 25B.

[0075] In response to actuation of the drive-close input device 118, the control valve 314b shifts upwardly from its neutral position (as viewed in FIG. 25A) to its close-function position, and the controller 112 energizes the valves 324a, 324b so as to close the valves 324a, 324b. As a result, the pressure level associated with the pressure setting of the pressure-limit valve 328a (e.g., 20 MPa) is communicated to the compensator 316b, which sets the pressure communicated via the control valve 314b to close-function port 82a at this pressure level in order to close both the delimb arms 32a, 32b and the drive arms 38a, 38b. This pressure level may thus also be referred to as the predetermined close-delimb-and-drive pressure, the purpose of which is discussed in more detail in connection with FIG. 25B. [0076] In response to actuation of the delimb-open input device 116, the control valve 314b shifts downwardly from its neutral position (as viewed in FIG. 25A) to its open-function position, and the controller 112 energizes the valve 324a so as to close the valve 324a. As a result, the pressure level of the pressure setting of the pressure-limit valve 328a (e.g., 7.5 MPa) is communicated to the compensator 316b, which sets the pressure communicated via the control valve 314b to open-function port 82b at this pressure level in order to open the delimb arms 32a, 32b but not the drive arms 38a, 38b. As mentioned above, this pressure level may also be referred to as the predetermined activate-delimb pressure.

[0077] In response to actuation of the drive-open input device 120, the control valve 314b shifts downwardly from its neutral position (as viewed in FIG. 25A) to its open- function position, and the controller 112 energizes the valves 324a, 324b so as to close the valves 324a, 324b. As a result, the pressure level associated with the pressure setting of the pressure-limit valve 328b (e.g., 12 MPa) is communicated to the compensator 316b, which sets the pressure communicated via the control valve 314b to open-function port 82b at this pressure level in order to open both the delimb arms 32a, 32b and the drive arms 38a, 38b. This pressure level may thus also be referred to as the predetermined close-delimb-and-drive pressure, the purpose of which is discussed in more detail in connection with FIG. 25B. [0078] Referring to FIG. 25C, there is shown the grapple hydraulic circuit 124. The grapple hydraulic circuit 124 comprises a delimb actuator 126 (e.g., hydraulic cylinder) attached to the delimb arms 32a, 32b to open and close them, a drive actuator 128 (e.g., hydraulic cylinder) attached to the drive arms 38a, 38b to open and close the drive arms 38a, 38b, close-function port 82a fluidly coupled to a first delimb port 130a of the delimb actuator 126 (e.g., head side thereof) such that pressure at the close-function port 82a is communicated to the first delimb port 130a and fluidly coupleable to a first drive port 132a of the drive actuator 128 (e.g., head side thereof) in response to at least the predetermined threshold close pressure (e.g., 8.5 MPa), and open-function port 82b fluidly coupled to a second delimb port 130b of the delimb actuator 126 (e.g., rod side thereof) such that pressure at the open-function port 82b is communicated to the second delimb port 130b and fluidly coupleable to a second drive port 132b of the drive actuator 128 (e.g., rod side thereof) in response to the predetermined threshold open pressure (e.g., 9.5 MPa). [0079] The grapple hydraulic circuit 124 comprises a first delimb line 134a, a second delimb line 134b, a first drive line 136B, and a second drive line 136b. The first drive line 134a interconnects the close-function port 82a and the first delimb port 130a. The second delimb line 134b interconnects the open-function port 82b and the second delimb port 130b. The first drive line 134a interconnects the first delimb line 134a and the first drive port 132a. The second drive line 136b interconnects the second delimb line 134b and the second drive port 132b. [0080] The first drive line 134a comprises a pilot-operated, normally closed first valve 138. The first valve 138 is openable in response to piloting of the predetermined threshold pressure to a pilot port 138a of the first valve 138 from the first delimb line 134a or the second delimb line 134b. A shuttle valve 140 of the circuit 124 comprises opposite inlets respectively fluidly coupled to the first and second delimb lines 134a, 134b and an outlet fluidly coupled to the pilot port 138a of the first valve 138 to transmit the greater pressure within the lines 134a, 134b to the valve 138 for pilot control thereof.

[0081] The second drive line 134b comprises a pilot-operated, normally closed second valve 142. The second valve 142 is openable in response to piloting of at least the predetermined threshold open pressure to a pilot port 142a of the second valve 142 from the second drive line 136b.

[0082] The first drive line 136B comprises a pressure-reducing/relief valve 144. The valve 144 is set to reduce the pressure in the line 136B to a predetermined reduced pressure (e.g., 10 MPa). A check valve 158 is arranged in parallel with the valve 144.

[0083] A pilot-operated, normally closed exhaust valve or counter-balance valve 146 is fluidly coupled to the first drive line 136B and the second drive line 136b. A pilot port 146B of the valve 146 is fluidly coupled to the first drive line 136B such that the valve 146 is pilot-operated by pressure from the first drive line 136B. A main port 146b of the valve 146 is fluidly coupled to the second drive line 136b so as to exhaust flow from the second drive line 132b upon opening of the counter-balance valve 146 by sufficient pressure from the first drive line 136B. The exhausted flow is then directed to the first and second delimb lines 134a, 134b via check valves 148a, 148b. Since the hydraulic fluid from the rod side 132b of the drive actuator 128 cannot exhaust through valve 142, it exhaust via counter-balance valve 146 and check valve 148b during closing of the drive actuator 128.

[0084] When feeding the tree through the head 12 it is possible to open the delimb arms 32a, 32b. At the same time the drive actuator 128 may become over- pressurized (e.g., +10 MPa). In such a case, the hydraulic fluid will exhaust from the drive actuator 128 via valve 144 and check valve 148a. Check valve 148b will have high pressure against it during such an event.

[0085] The debarker head 12 has a feed hydraulic circuit 152 for operating a number of feed motors 150. For example, there are four feed motors 150, which keep the drive wheels 30a, 30b, 30c synchronized.

[0086] The feed hydraulic circuit 152 has a feed-forward line 154a and a feed- reverse line 154b. The feed-forward line 154a is in fluid communication with the feed-forward port 82c and the feed motors 150 to feed the tree in a forward direction when hydraulic fluid is routed from the work machine 10 to the feed-forward port 82c. The feed-reverse line 154b is in fluid communication with the feed-reverse port 82d and the feed motors 150 to feed the tree in a reverse direction when hydraulic fluid is routed from the work machine 10 to the feed-reverse port 82d. [0087] Exemplarily, the control circuit 123 supplies the hydraulic fluid to the feedforward and feed-reverse ports 82c, 82d. In particular, one of the directional control valves 330 is responsible for directing hydraulic fluid between the ports 82c, 82d. [0088] The feed hydraulic circuit 152 is fluidly coupled to the grapple hydraulic circuit to provide fluid and pressure thereto. The circuit 152 has a first check valve 156B and a second check valve 156b. The first check valve 156B is fluidly coupled to the feed-forward line 154a and the first drive line 136B to allow flow and pressure from the feed-forward line 154a to the first drive line 136B. The second check valve 156b is fluidly coupled to the feed-reverse line 154b and the first drive line 136B to allow flow and pressure from the feed-reverse line 154b to the first drive line 136B. [0089] The fluid and pressure communicated from the feed hydraulic circuit 152 to the first drive line 136B can help with extension of the drive actuator 128 and, thus, grip of the tree by the drive arms 38a, 38b during feeding of the tree, in either direction. This may be especially helpful when the operator flicks open the delimb arms 32a, 32b by brief operation of the delimb-open input device 116 during feeding to, for example, un-jam the tree. It may be of further help in the event that there may be leakage from either drive line 136B, 136b (e.g., across the valve 144) after the operator releases the drive-close input device 116. This can result in a pressure reduction for the drive arms 38a, 38b. The feed hydraulic circuit 152 is configured to make up for the hydraulic fluid that may have leaked upon operation of the drive motor(s) 150 in either the forward or reverse directions. In so doing, it increases the pressure at the drive actuator 128 and thus the grip of the drive arms 38a, 38b. The feed hydraulic circuit 152 is fluidly coupled to the first drive line 136B to provide this fluid and pressure.

[0090] In use, a human operator desiring to debark a particular felled tree will operate the work machine 10 so as to position the head 12 over that tree. With the delimb arms 32a, 32b and drive arms 38a, 38b already open, the operator will then actuate the delimb-close input device 114 so that the controller 112 causes the activatθ-delimb pressure (e.g., 7.5 MPa) to be outputted from the work machine 10 to the close-function port 82a of the circuit 124 in the manner disclosed herein causing the delimb arms 32a, 32b to close around the tree, lifting the tree toward the chassis 20. Hydraulic fluid and the activate-delimb pressure are communicated to the port 130a of the delimb actuator 126 via the line 134a so as to extend the actuator 126 and close the delimb arms 32a, 32b. Fluid discharged from the port 130b is routed to the port 82b via the line 134b for return to tank. [0091] Next, the operator will actuate the drive-close input device 118 so that the controller 112 causes the larger close-delimb-and-drive pressure (e.g., 8.5 MPa) to be outputted from the work machine 10 to the close-function port 82a of the circuit 124 in the manner disclosed herein causing the delimb arms 32a, 32b to remain closed and the drive arms 38a, 38b to close bringing the drive wheels 30a, 30b, 30c into contact with the tree so as to grip the tree. The close-delimb-and-drive pressure is communicated to the port 130a via the line 134a, maintaining extension of the delimb actuator 126 and closure of the delimb arms 32a, 32b. Further, the close- delimb-and-drive pressure is communicated to the pilot port 138a of the valve 138 via the shuttle valve 140 so as to open the valve 138. The valve 144 in the line 136B reduces the close-delimb-and-drive pressure to the predetermined reduced pressure (e.g., 10 MPa) so that hydraulic fluid and the predetermined reduced pressure are communicated to the port 132a of the drive actuator 128, thereby extending the drive actuator 128 causing the drive arms 38a, 38b to close.

[0092] The close-delimb-and-drive pressure in line 136B upstream from the valve 144 is communicated to the pilot port 146B opening the valve 146, thereby allowing fluid discharged into the line 136b from the port 132b of the drive actuator 128 to exhaust through the valves 146, 148b and line 134b to the port 82b for return to tank. The delimb arms 32a, 32b and the drive arms 38a, 38b thus close in response to actuation of the drive-close input device 118.

[0093] Once the tree has been picked up and gripped by the head, the operator will actuate respective input devices to operate the feed circuit 152 so as to drive the tree in forward and reverse directions along the path 36, resulting in debarking of the tree by the debarking components. To feed the tree in a forward direction, fluid is supplied to the feed-forward line 154a via the feed-forward port 82c. To feed the tree in a reverse direction, fluid is supplied to the feed-reverse line 154b via the feed- reverse port 82d.

[0094] During feeding in either direction, the delimb arms 32a, 32b relax their grip on the tree for effective feeding of the tree by the drive wheels 30a, 30b, 30c. A pressure switch 332 (FIG. 25B) senses feeding of a tree. The controller 112 communicates electrically with the pressure switch 332 so as to receive feeding information from the pressure switch 332. The controller 112 signals the control circuit 122 to output a predetermined softclamp pressure (e.g., 3.5 MPA) lower than the activate-delimb pressure (e.g., 7.5 MPa) to the close-function port 82a of the circuit 124 upon feeding of a tree. The delimb line 134a, in turn, communicates the softclamp pressure to the port 130a so as to extend the delimb actuator 126 accordingly.

[0095] The pressure switch 332 is arranged to sense hydraulically a feed command from a human operator upon operation of an input device 334 (e.g., joystick), as shown in FIG. 25B. For example, the input device 334 commands operation of the directional control valve 330 via pilot lines 336B, 336b. The pilot line 336B transmits a feed forward pilot signal from the input device 334 to a forward pilot port of the valve 330, and the pilot line 336b transmits a feed reverse pilot signal from the input device 334 to a reverse pilot port of the valve 330. A shuttle valve 338 is coupled fluidly to the lines 336B, 336b and the pressure switch 332 to communicate any pilot signal present in the lines 336B, 336b to the pressure switch 332. Thus, any time there is command to feed in either direction, the pressure switch 332 senses this feed command and so informs the controller 112.

[0096] In response to such feeding information, the control valve 314b shifts upwardly from its neutral position (as viewed in FIG. 25A) to its close-function position, and the controller 112 energizes the valve 324b so as to close the valve 324b. As a result, the pressure level associated with the pressure setting of the pressure-limit valve 326b (e.g., 3.5 MPa) is communicated to the compensator 316b, which sets the pressure communicated via the control valve 314b to close-function port 82a at this pressure level in order to extend the drive actuator 126 and close the delimb arms 32a, 32b, but not the drive arms 38a, 38b, with this pressure level. This pressure level is the predetermined softclamp pressure.

[0097] It is within the scope of this disclosure to use a hydraulic device, in place of the pressure switch 332, for directing valve 324a hydraulically, so as to engage the predetermined softclamp pressure.

[0098] During the feeding process, the tree may become jammed, in which case the operator may actuate the delimb-open input device 116 to briefly open the delimb arms 32a, 32b and un-jam the tree. Upon operation of the delimb-open input device 116, the controller 112 causes the activate-delimb pressure (e.g., 7.5 MPa) to be outputted from the work machine 10 to the open-function port 82b of the circuit 124 in the manner disclosed herein so that the delimb arms 32a, 32b open, but not the drive arms 38a, 38b. The line 134b communicates hydraulic fluid and the activate- delimb pressure to the port 130b of the delimb actuator 126 so as to retract the actuator 126 and thereby open the delimb arms 32a, 32b. Fluid discharged from the port 130a upon retraction of the delimb actuator 126 is routed through the line 134a to the port 82a for return to tank. Since the activate-delimb pressure is below the predetermined threshold open pressure (e.g., 9.5 MPa), the valves 138, 142, as well as the drive arms 38a, 38b, remain closed.

[0099] After completion of the debarking, delimbing, and any repositioning of the debarked tree over a different area, the operator will actuate the drive-open input device 120 so that the controller 112 causes the open-delimb-and-drive pressure (e.g., 12 MPa) to be outputted from the work machine 10 to the open-function port 82b of the circuit 124 in the manner disclosed herein causing the delimb arms 32a, 32b and the drive arms 38a, 38b to open and release the felled tree. The open- delimb-and-drive pressure is communicated to the port 130b via the line 134b, retracting the delimb actuator 126 so as to open the delimb arms 32a, 32b. Fluid discharged from the port 130a upon retraction of the delimb actuator 126 is routed through the line 134a to the port 82a for return to tank.

[00100] Further, the open-delimb-and-drive pressure is communicated to the pilot port 138a of the valve 138 via the shuttle valve 140, and is communicated to the pilot port 142a of the valve 142. Since the open-delimb-and-drive pressure is greater than the predetermined threshold open pressure (e.g., 9.5 MPa), it opens the valves 138, 142. Upon opening of the valve 142, hydraulic fluid and the open-delimb-and- drive pressure is communicated to the port 132b of the drive actuator 128 via the line 136b, retracting the drive actuator 128 and opening the drive arms 38a, 38b. Fluid discharged from the port 132a upon retraction of the drive actuator 128 is routed through the line 136B, the open valve 138 of the line 136B, and the line 134a to the port 82a for return to tank. The delimb arms 32a, 32b and the drive arms 38a, 38b thus open in response to actuation of the drive-open input device 120 to release the debarked and delimbed log.

[00101] It is within the scope of this disclosure for the head 12 to include one or more electrical components. In such an alternative embodiment, the head 12 may include slip rings and an electrical port(s), in addition to the hydraulic ports disclosed herein, for electrically powering such component(s).

[00102] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A debarker head for use with a work machine, comprising: a delimb arm arranged to open and close, a drive wheel, a drive arm to which the drive wheel is attached, the drive arm arranged to open and close to move the drive wheel therewith, and a grapple hydraulic circuit for operating both the delimb arm and the drive arm, wherein the grapple hydraulic circuit is responsive to pressure from the work machine (i) below a predetermined threshold close pressure to close the delimb arm but not the drive arm, (ii) at at least the predetermined threshold close pressure to close both the delimb arm and the drive arm, (iii) below a predetermined threshold open pressure to open the delimb arm but not the drive arm, and (iv) at at least the predetermined threshold open pressure to open both the delimb arm and the drive arm.

2. The debarker head of claim 1 , wherein the predetermined threshold close pressure and the predetermined threshold open pressure are different from one another.

3. The debarker head of claim 1 , wherein the predetermined threshold open pressure is greater than the predetermined threshold close pressure.

4. The debarker head of claim 1 , wherein the grapple hydraulic circuit comprises a pilot-operated, normally closed valve that remains closed in response to pressure below the predetermined threshold close pressure and opens in response to pressure at at least the predetermined threshold close pressure.

5. The debarker head of claim 4, wherein the grapple hydraulic circuit comprises another pilot-operated, normally closed valve that remains closed in response to pressure below the predetermined threshold open pressure and opens in response to pressure at at least the predetermined threshold open pressure.

6. The debarker head of claim 1 , wherein the grapple hydraulic circuit comprises a pilot-operated, normally closed first valve that remains closed in response to pressure below the predetermined threshold close pressure and opens in response to pressure at at least the predetermined threshold close pressure, and a pilot-operated, normally closed second valve that remains closed in response to pressure below the predetermined threshold open pressure and opens in response to pressure at at least the predetermined threshold open pressure.

7. The debarker head of claim 1 , wherein the grapple hydraulic circuit comprises a delimb actuator attached to the delimb arm to open and close the delimb arm, a drive actuator attached to the drive arm to open and close the drive arm, a pilot-operated, normally closed first valve, a pilot-operated, normally closed second valve, a close-function port fluidly coupled to a first delimb port of the delimb actuator such that pressure at the close-function port is communicated to the first delimb port and fluidly coupleable to a first drive port of the drive actuator via the first valve in response to piloting of at least the predetermined threshold close pressure to the first valve, and an open-function port fluidly coupled to a second delimb port of the delimb actuator such that pressure at the open-function port is communicated to the second delimb port and fluidly coupleable to a second drive port of the drive actuator via the second valve in response to piloting of at least the predetermined threshold open pressure to the second valve.

8. The debarker head of claim 7, wherein the grapple hydraulic circuit comprises a first delimb line interconnecting the close-function port and the first delimb port, a second delimb line interconnecting the open-function port and the second delimb port, a first drive line interconnecting the first delimb line and the first drive port, and a second drive line interconnecting the second delimb line and the second drive port.

9. The debarker head of claim 8, wherein the first drive line comprises the first valve, and the second drive line comprises the second valve.

10. The debarker head of claim 9, wherein the grapple hydraulic circuit comprises a shuttle valve comprising inlets respectively fluidly coupled to the first and second delimb lines and an outlet fluidly coupled to a pilot port of the first valve such that the first valve is openable in response to piloting of at least the predetermined threshold close pressure to the first valve from the first delimb line or the second delimb line.

11. The debarker head of claim 9, wherein the second valve is openable in response to piloting of at least the predetermined threshold pressure to the second valve from the second drive line.

12. The debarker head of claim 9, wherein the grapple hydraulic circuit comprises a pilot-operated, normally closed counter-balance valve comprising a pilot port fluidly coupled to the first drive line so as to be pilot-operated by pressure from the first drive line and another port fluidly coupled to the second drive line so as to exhaust flow from the second drive port upon opening of the counter-balance valve by sufficient pressure from the first drive line.

13. The debarker head of claim 8, comprising a feed hydraulic circuit comprising a feed motor for operating the drive wheel, wherein the feed hydraulic circuit is fluidly coupled to the first drive line.

14. The debarker head of claim 13, wherein the feed hydraulic circuit comprises a feed-forward line, a feed-reverse line, a first check valve fluidly coupled to the feed-forward line and the first drive line to allow flow from the feed-forward line to the first drive line, and a second check valve fluidly coupled to the feed-reverse line and the first drive line to allow flow from the feed-reverse line to the first drive line.

15. A work machine in combination with the debarker head of claim 1 , wherein the work machine comprises an electro-hydraulic control circuit fluidly coupled to the grapple hydraulic circuit onboard the debarker head, a controller that communicates with the electro-hydraulic control circuit, a delimb-close input device, and a drive-close input device, and the controller signals the electro-hydraulic control circuit to output to the grapple hydraulic circuit a predetermined activate-delimb pressure lower than the predetermined threshold close pressure to close the delimb arm but not the drive arm in response to actuation of the delimb-close input device, and signals the electro-hydraulic control circuit to output to the grapple hydraulic circuit a predetermined close-delimb-and-drive pressure above the predetermined threshold close pressure to close the delimb arm and the drive arm in response to actuation of the drive-close input device.

16. The work machine of claim 15, wherein the work machine comprises a delimb-open input device and a drive-open input device, and the controller signals the electro-hydraulic control circuit to output to the grapple hydraulic circuit the predetermined activate-delimb pressure to open the delimb arm but not the drive arm in response to actuation of the delimb-open input device, and signals the electro- hydraulic control circuit to output to the grapple hydraulic circuit a predetermined open-delimb-and-drive pressure above the predetermined threshold open pressure to open the delimb arm and the drive arm in response to actuation of the drive-open input device.

17. The work machine of claim 15, wherein the work machine comprises a pressure switch for sensing feeding of a tree, and the controller receives feeding information from the pressure switch and signals the electro-hydraulic control circuit to output to the grapple hydraulic circuit a predetermined softclamp pressure lower than the predetermined activate-delimb pressure upon feeding of a tree.