Tree delimbing apparatus

A delimber suitable for mounting on a logging skidder. The delimber comprises a series of delimbing/clamping elements and hydraulic actuators for moving the delimbing/clamping elements between an open and a closed position. Each of the delimbing elements comprises a clamping surface and a cutting edge. In the closed position, the delimbing elements hold a bunch of trees and the cutting edges penetrate the trees. Moving the delimber along the trees causes the cutting edges to cut the limbs off the trunks. In another aspect, the delimber includes a tilt feature for topping the trees.

FIELD OF THE INVENTION 
The present invention relates to a delimber apparatus for logging, and more 
particularly to a multiple head delimber which is mounted on a logging 
skidder. 
BACKGROUND OF THE INVENTION 
Delimbing in the logging field comprises removing or cutting off the 
branches from a felled tree. In the days of old, logging was strictly a 
manual endeavour and a logger would chop the limbs from a felled tree 
using a hand axe. The advent of large-scale logging operations has lead to 
the development of logging machinery to improve the efficiency and output 
of a logging operation. 
In U.S. Pat. No. 4,462,438, Gaudreault discloses a dual head delimber which 
is mounted to one end of a boom on a logging vehicle. The dual head 
delimber comprises a cradle having two sets of pivotally mounted clamps 
which are juxtaposed to one another and mounted at an angle to define a 
V-shaped arrangement in relation to the longitudinal axis of the boom. The 
dual head delimber also includes a separate delimbing knife for each 
clamp. In operation, the operator moves the boom to bring the dual head 
delimber near a pile of felled trees and the delimber is lowered with the 
clamps opened around the felled trees. The clamps are then closed to grasp 
one or more of the felled trees and the boom is retracted so that the butt 
ends of the trees can also be grasped by another clamping element. The 
clamps are then slightly loosened and the delimbing knives are brought 
into contact with the trees, and the boom is moved longitudinally along 
the trees to delimb the trees. Once delimbed, the first clamps are 
engaged, while the second clamps are disengaged, and the boom is moved to 
unload the delimbed trees. 
While the dual head delimber taught by Gaudreault provides a means for 
delimbing trees, there are shortcomings. First, the arrangement of the 
dual head delimber and boom requires a vehicle with an adequate flat-bed 
to accommodate the boom and the clamp elements for clamping the butt ends 
of the trees. Secondly, the felled trees cannot be delimbed as they lay on 
the ground. The trees must be gathered into a bundle and loaded on the 
vehicle with the delimber as taught by Gaudreault. In practical terms, 
this means that such a vehicle will only be suitable for roadside 
delimbing operations and not in the field. In another aspect, the 
arrangement of the clamping elements and delimbing knives limits the 
effectiveness of the dual head delimber, and also the number of trees 
which can be delimbed at one time. 
The present invention addresses these shortcomings by providing a 
multiple-head delimber apparatus suitable for mounting on a grapple 
skidder or line skidder, which allows a bundle of felled trees to be 
delimbed on the ground without the need to move or lift the trees off the 
ground. 
BRIEF SUMMARY OF THE INVENTION 
The present invention provides a multiple-head delimber apparatus 
comprising a series of delimbing/clamping elements. The delimber apparatus 
includes hydraulic or pneumatic actuators for opening and closing the 
delimbing/clamping elements. Each of the delimbing/clamping elements 
includes integrated blade members. According to the invention, the 
delimbing/clamping elements and blade members are curved to cut the limbs 
from around the trunk of the tree including the underside. 
The multiple-head delimber is adapted for mounting on a grapple skidder, 
line skidder, or other suitable logging vehicle, and for operation on-site 
at the logging lot. The delimber is suitable for delimbing trees as they 
lay on the ground at a logging site. 
In another aspect, the hydraulic actuators provide the capability to press 
the blades into the bark of the felled tree in order to efficiently cut 
the branches as the skidder is moved along the length of the felled trees. 
The delimber apparatus according to the invention also includes a hydraulic 
or pneumatic actuated tilt movement. The tilt feature allows the felled 
trees to be topped by simply engaging the delimbing blades and tilting the 
delimber to snap-off the top of the trees with the delimber blades 
engaged. 
In a first aspect, the present invention provides a delimber apparatus 
suitable for mounting on a logging vehicle, said delimber apparatus 
comprising: (a) a frame member having mounts for connecting to the 
vehicle; (b) a plurality of delimbing elements, said delimbing elements 
being movably coupled to said frame member; (c) actuators coupled to each 
of said delimbing elements for moving said delimbing elements between a 
closed position and an open position; and (d) each of said delimbing 
elements having a clamping portion for clamping one or more trees and a 
cutting edge for cutting limbs from the trees.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is first made to FIG. 1, which shows in diagrammatic form a 
delimber apparatus 1 according to the present invention. In FIGS. 1 to 7, 
like references indicate like elements. 
As shown in FIG. 1, the delimber apparatus 1 is mounted on a logging 
vehicle or tractor 2, for example a skidder of known design. It is a 
feature of the present invention that the delimber apparatus 1 may be 
mounted on a wide variety of logging vehicles thereby providing the 
capability for delimbing a bundle of trees at a logging site instead from 
a roadside location to where the felled trees must be first be 
transported. In FIG. 1, the felled trees, indicated generally by 4, are 
delimbed as they lay on the ground. The felled trees 4 are held by their 
butt ends B by a grappler 6 of known design. The grappler 6 is attached to 
a movable boom 8 mounted on a suitable vehicle (not shown), for example, 
another skidder. The skidder 2 with the delimber 1 straddles the bundle of 
trees 4 and moves forward to the grappler 6. The operator engages the 
bundle of trees 4 with the delimber 1 and moves back and forth over the 
trees 4 to delimb or strip the branches 5. 
As will be described, the delimber 1 includes hydraulic actuators to adjust 
the attitude of the delimber 1 and maintain full contact with the trees 4. 
This feature is particularly useful because the felled trees 4 are often 
strewn on uneven ground. The delimber 1 also includes a tilt feature so 
that the trees 4 can be topped, i.e. the tops T of the trees 4 removed. 
As shown in FIG. 1, the delimber apparatus 1 is coupled to the skidder 2 
and includes hydraulic lift, tilt and steering actuators denoted generally 
by 10 for controlling the position and attitude of the delimber 1. The 
hydraulic actuators 10 allow the attitude of the delimber 1 to be adjusted 
to maintain full contact with the bundle of the trees 4 on even ground. As 
shown in FIGS. 1 and 3, the delimber 1 comprises a centre portion 12b and 
respective end portions 12a, 12c which are inclined downwards. The 
downward attitude of the end portions 12a, 12c allows the delimber 1 to 
embrace the trees 4 and delimb the sides of the bundle 4. 
Reference is next made to FIGS. 2 to 5 which show the delimber 1 according 
to the present invention in more detail. The delimber 1 comprises a main 
frame 14 and two rows 16, 18 of blade members 20. As shown in FIG. 2(a), 
the blade members 20 for the first row 16 are shown individually as 20a, 
20b, 20c and 20d. The blade members 20 for the second row are shown 
individually as 20e, 20f, 20g and 20h. 
As shown in FIG. 3, the blade members 20 are grouped into four 
delimbing/clamping elements 22a, 22b, 22c, 22d. Each delimbing/clamping 
element 22 comprises one blade member 20 from the first row 16 and one 
blade member 20 from the second row 18. For example, the 
delimbing/clamping element 22a comprises blade members 20a and 20e. In 
FIG. 3(a), the delimbing elements 22 are in a closed position, and in FIG. 
3(b), the delimbing elements 22 are in an open position. The 
delimbing/clamping elements 22 are moved between the open and closed 
positions by hydraulic (or pneumatic actuators) as described below. The 
hydraulic actuated delimbing elements 22 provide the capability to gather 
and hold the bundle of trees 4 at the same time the blade members 20 cut 
the limbs. 
As shown FIG. 7, each blade member 20 comprises a planar blade 24 and a 
mounting shoulder 26. The blade 24 is curved and has a leading cutting 
edge denoted by 28. The planar blade 24 provides a reinforced cutting 
surface which can be moved backwards and forwards over the felled trees 
without being deflected, or damaged by rocks or stumps on the ground. The 
blade members 20 are preferably made from a high tensile steel such as CHT 
100 steel. The planar blade 24 particularly in the inside curved surface 
provides a clamping surface for grasping the trees 4. The shoulder 26 is 
bored for receiving a pin or shaft 27 (FIG. 3(a)) and mounting the blade 
20 on the frame 14 through corresponding bosses 29 as shown in FIG. 5(b). 
As also shown in FIG. 5(b), the end portions 12a, 12c of the frame 14 are 
inclined at approximately 15 degrees from horizontal. 
FIG. 2(a) shows the arrangement of the blade elements 20 in the main frame 
14 with the hydraulic cylinders and link arms removed for greater clarity. 
As also shown in FIG. 2(a), the delimber 1 preferably includes stationary 
blade members 25. The stationary blade members 25 are mounted on the main 
frame 14 and denoted individually as 25a, 25b, 25c, . . . and provide an 
additional cutting surface for delimbing the trees being held in delimbing 
elements 22. The stationary blade members 25 are also preferably made from 
a high tensile steel. 
The delimbing/clamping elements 22 are moved between the open and closed 
positions by a series of hydraulic actuators 30 and link arms 32. 
Referring to FIG. 2(b), the hydraulic actuators 30 are shown individually 
as hydraulic cylinder 30a, 30b, 30c, and 30d. The link arms 32 are shown 
individually as 32a, 32b, 32c and 32d. The first link arm 32a is connected 
to hydraulic cylinder 30a, and coupled to the blade members 20a and 20f. 
The second link arm 32b is connected to hydraulic cylinder 30b, and 
coupled to the blade members 20b and 20e. The third link arm 32c is 
connected to hydraulic cylinder 30c, and coupled to the blade members 20c 
and 20h. The fourth link arm 32d is connected to the hydraulic cylinder 
30d, and coupled to the blade members 20d and 20g. 
In FIG. 2(b), the linkage between the hydraulic cylinders 30, the link arms 
32 and the blade members 20 is shown. According to this aspect of the 
invention, the delimbing/clamping elements 22 comprise blade members 20 
connected to separate link arms 32. For example, delimbing element 22a 
comprises blade members 20a, 20e, with blade 20a being connected to link 
arm 32a, and blade 20e being connected to link arm 32b. 
As shown in FIG. 6, the link arm 32 is asymmetrical. By utilizing separate 
asymmetrical link arms 32 to couple blade members 20 for each delimbing 
element 22, the opening and closing of the delimbing elements 22 is 
achieved with an abbreviated travel length for the link arms 32. This 
arrangement has the advantage of keeping the moving link arms 32 above the 
main frame 14 and away from tree limbs and possible damage. The operation 
of the hydraulic cylinders 30 to synchronize the opening and closing of 
the delimbing elements 22 is controlled by a hydraulic control system 
which is described below with reference to FIG. 4. 
Reference is next made to FIG. 4 which shows in schematic form a hydraulic 
control system 100 for the delimber 1. The hydraulic system 100 comprises 
a pump 102, a reservoir 104, hydraulic valve banks 106, flow dividers 108, 
and synchronizing valves 110. The reservoir 104 comprises a tank which 
holds hydraulic fluid for operating the system 100. The reservoir 104 is 
coupled to the pump 102 through a suction line 112. The pump 102 
pressurizes hydraulic fluid from the tank 104 and outputs the pressurized 
fluid through a pressure line 114a. 
As shown in FIG. 4, the pressure line 114a provides the hydraulic fluid 
input for the hydraulic valve bank 106a. The hydraulic valve 106a is 
coupled to the reservoir 104 through a return line 116a. The hydraulic 
valve bank 106a is coupled to the second hydraulic valve bank 106b through 
another pressure line 114b. The second valve bank 106b is also coupled to 
the reservoir 104 through a return line 116b. The hydraulic valves 106a, 
106b comprise conventional devices of the type with two spools, one with 
float. 
The first hydraulic valve bank 106a is coupled to hydraulic actuators 10a, 
10b for the controlling the lift of the delimber 1, and hydraulic 
actuators 10c, 10d for steering control. As shown in FIG. 4, the hydraulic 
lift cylinders 10a, 10b are coupled to a port 107a on the valve bank 106a 
through a pressurized line 118a and a return line 118b. The hydraulic 
fluid flow between the two cylinders 10a, 10b is split by two tee valves 
119a, 119b. Similarly, the hydraulic steering cylinders 10c, 10d are 
coupled to another port 107b on the valve bank 106a through a pressurized 
line 118c and a return line 118d. The hydraulic fluid flow between the two 
cylinders 10c, 10d is split by two tee valves 119c and 119d. The hydraulic 
cylinders 10 are actuated by controlling the flow of hydraulic fluid to 
the cylinders 10 through the valve bank 106a. 
As shown in FIG. 4, the hydraulic cylinders 10e, 10f for controlling the 
tilt of the delimber 1 are coupled to port 109a on the hydraulic valve 
bank 106b through a pressurized line 120a and a return line 120b. The 
hydraulic fluid flow between the tilt cylinders 10e, 10 f is split by two 
tee valves 121a, 121b. 
Referring to FIG. 4, the hydraulic cylinders 30 for actuating the 
delimbing/clamping elements 22 are coupled to port 109b on the hydraulic 
valve bank 106b through flow dividers 108a, 108b and synchronizing valves 
110a, 110b. The first flow divider 108a is coupled to the port 109b on the 
valve bank 106b through pressurized line 120c. The second flow divider 
108b is coupled to the port 109b on the valve bank 106b through return 
line 120d. The output of the first flow divider 108a is coupled to the 
synchronizing valves 110a, 110b and together they control the flow of 
hydraulic fluid to move the blades 20 and synchronize the opening and 
closing of the clamping elements 22. The second flow divider 108a is 
coupled to the return lines through tee valves 123a, 123 and collects the 
hydraulic fluid flow between the cylinders 30a to 30d. 
The hydraulic cylinders 30 for the delimbing/clamping elements 22 are 
implemented using conventional hydraulic cylinders specified as follows: 
2" Bore, 8" Stroke, 16" Retracted Length and 24" Extended Length. The tilt 
hydraulic cylinders 10e, 10f are implemented utilizing conventional 
hydraulic cylinders specified as follows: 2' Bore, 16' Stroke, 24' 
Retracted Length and 40' Extended Length. 
In operation, the skidder 2 with the delimber 1 is moved over a number of 
trees to be delimbed. The butt ends of the trees are held by a grappler 6 
mounted on another skidder. The operator actuates the hydraulic cylinders 
30 to close the delimbing/clamping elements 22 around the bundle of trees 
so that the blades 20 penetrate the bark of the trees and grasp the trees. 
The operator then moves the skidder 2 towards the grappler 6 and the 
leading edge of the first row 16 of blades 20 and the stationary blades 25 
cut the limbs from the trees. After the forward pass to the grappler 6, 
the operator reverses the skidder 2 and moves back to the tops of the 
trees so that the second row 18 of blades (and the stationary blades 25) 
cut the limbs from the trees. At the top of the trees, the delimber 1 can 
be tilted to snap off the tops of the trees, or another forward/backward 
pass can be made. The arrangement of the delimbing elements 22a and 22d at 
the respective ends 12a, 12c of the delimber 1 allows the sides of the 
trees to be delimbed as the blades 20 move along the length of the trees. 
It has been found that the delimber 1 is suitable for delimbing 
approximately 40 trees at a time having a butt diameter of around 6 
inches, and approximately 8 trees at a time having a butt diameter of 
around 18 inches. 
From the foregoing, it will be appreciated that a feature of the delimber 1 
according to the present invention that the delimbing blades 20 both hold 
the felled trees and cut the limbs from the trees. The hydraulic actuation 
of the delimbing elements 22 allows the blade elements 20 to penetrate 
into the bark of the trees while the trees are held in the closed 
position. The capability to open and close the delimbing blades 20 around 
a number of trees can be used to gather individual felled trees into a 
bundle. In another aspect, the adaptability of the delimber 1 to most 
logging vehicles, for example, skidders, provides the capability to delimb 
trees "on-site" with the need to the move the trees to a road-side 
location where much larger and heavier conventional delimbers would be 
situated. In another aspect, the hydraulic cylinders 10e, 10f allow the 
delimber 1 to be tilted on an angle in order to top the trees which are 
being held by the delimbing/clamping elements 22. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential characteristics thereof. Therefore, 
the presently discussed embodiments are considered to be illustrative and 
not restrictive, the scope of the invention being indicated by the 
appended claims rather than the foregoing description, and all changes 
which come within the meaning and range of equivalency of the claims are 
therefore intended to be embraced therein.