Note: Descriptions are shown in the official language in which they were submitted.
A TIMBER-WORKING DEVICE AND METHOD OF OPERATION
FIELD OF THE DISCLOSURE
The present invention relates to a timber-working device and method of
operation.
BACKGROUND
It is well-known to mount timber-working devices, commonly referred to as
forestry or harvester
heads, to a carrier vehicle in order to perform a number of operations in
connection with timber
processing. These operations may include one, or a combination of, grappling
and felling a
standing tree, delimbing a felled stem, debarking the stem, and cutting the
stem into logs ¨
commonly using at least one chainsaw.
Feeding the stem along its length relative to the head is typically achieved
using arm mounted
rotary drives having a drive wheel at the end of opposing drive arms, while
delimbing is
performed by blades on opposing delimb arms.
It is known to control the extent to which the chainsaw travels when cutting a
stem, based on
a diameter measurement of the stem made by the head based on the angle of
rotation of the
feed and/or delimb arms as they close on the stem. Limiting the travel
increases machine
productivity by avoiding wasteful movement, and avoids damage to the saw
caused where the
saw passes beyond the stem into other matter such as the ground.
However, to date such saw limiting assumes that the diameter measurement
relates to a single
stem held by the head. Where the head is used to process multiple stems
simultaneously,
particularly two stems held side by side, the diameter measurement obtained
from the angle
of the feed and/or delimb arms indicates the presence of a much deeper cross-
section of wood
than is actually held by the head. This causes excessive saw travel
requirements to be set.
It is an object of the present invention to address the foregoing problems or
at least to provide
the public with a useful choice.
No admission is made that any reference cited herein constitutes prior art.
The discussion of
the references states what their authors assert, and the applicants reserve
the right to
challenge the accuracy and pertinency of the cited documents. It will be
clearly understood
that, although a number of prior art publications are referred to herein, this
reference does not
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constitute an admission that any of these documents form part of the common
general
knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word "comprise" or "include", or variations
thereof such as
"comprises", "includes", "comprising" or "including" will be understood to
imply the inclusion of
a stated element, integer or step, or group of elements integers or steps, but
not the exclusion
of any other element, integer or step, or group of elements, integers or
steps.
Further aspects and advantages of the present invention will become apparent
from the
ensuing description which is given by way of example only.
SUMMARY
According to an embodiment of the present invention there is provided a method
of operating
a timber-working device including a cutting device, the method including the
steps of:
receiving an indication of the number of stems currently grasped by pivoting
arms of
the timber-working device;
receiving an indication of a stem thickness measurement of the at least one
stem
currently grasped by the pivoting arms, wherein the stem thickness measurement
is dependent
on the number of stems grasped; and
determining the travel required of the cutting device to sever the at least
one stem,
based at least in part on the number of stems currently being grasped and the
stem thickness
measurement.
According to another aspect of the present invention there is provided a
timber-working
device, including:
pivoting arms configured to grasp one or more stems to be processed;
a measurement device configured to output a signal indicating a stem thickness
measurement of the at least one stem currently grasped by the pivoting arms,
wherein the
stem thickness measurement is dependent on the number of stems grasped;
a stem count device configured to output a signal indicating the number of
stems
currently grasped by the pivoting arms;
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a cutting device; and
at least one controller configured to:
receive the signal indicating the stem thickness measurement and the signal
indicating the number of stems currently grasped by the pivoting arms; and
determine the travel required of the cutting device to sever the at least one
stem,
based at least in part on the indication of stem thickness measurement, and
indication
of the number of stems.
According to another aspect of the present invention there is provided an
article of manufacture
having computer storage medium storing computer readable program code
executable by a
computer to implement a method of operating a timber-working device including
a cutting
device, the code including:
computer readable program code receiving an indication of the number of stems
currently grasped by pivoting arms of the timber-working device;
computer readable program code receiving an indication of a stem thickness
measurement of the at least one stem currently grasped by the pivoting arms,
wherein the stem
thickness measurement is dependent on the number of stems grasped; and
computer readable program code determining the travel required of the cutting
device to
sever the at least one stem, based on the number of stems currently being
grasped and the
stem thickness measurement.
The timber-working device may be a forestry or harvester head, and may be
referred to as such
throughout the specification. Forestry heads typically have the capacity to
grapple and fell a
standing tree, delimb and/or debark a felled stem, and cut the stem into logs.
However, a
person skilled in the art should appreciate that the present invention may be
used with other
timber-working devices, and that reference to the timber-working device being
a forestry head
is not intended to be limiting.
One well known system for forestry heads uses opposing drive arms, one on each
side of a
feed axis. Each drive arm may include a feed wheel configured to be brought in
contact with
stem. The arms may be driven, for example by hydraulic cylinders, to pivot
relative to the frame
of the device in order to grapple the stem with the feed wheels. The feed
wheels may each
connect to a rotary drive such that they may be used to drive or feed the
stems along the feed
axis of the head.
The timber-working device may further include one or more frame mounted feed
wheels. The
drive system may include a frame mounted feed wheel on either side of the feed
axis, which
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may be controlled independently to each other. Where two stems are grasped by
the drive
arms, these frame mounted wheels may be controlled together with those of the
respective
drive arms to independently control the relative positions of the two stems
along the feed axis.
It should be appreciated that this is not intended to be limiting, and the
timber-working device
may include only a single frame mounted feed wheel, for example aligned with
the feed axis.
Where the timber-working device is processing two stems and it is desirable to
feed the stems
independently, the frame mounted wheel may be locked or permitted to spin
freely, with the
arm mounted feed wheels used to control feeding.
In another embodiment the pivoting arms include at least one pair of delimb
arms, as known in
the art. Such delimb arms are configured to be closed about the stem, and
include sharpened
edges to cut limbs from the stem as it is driven by the feed wheels.
Reference to a stem thickness measurement should be understood to mean an
indication of a
measurement of a cross-sectional dimension of a stem, or collective stems,
held by the timber-
working device. In the case of a single stem, this dimension may be diameter
of the stem, as
often referenced during processing of trees with a forestry head. While the
collective thickness
of multiple stems is not technically a diameter measurement, for convenience
the term diameter
may be used interchangeably with stem thickness measurement throughout the
application.
This measurement may be obtained using any suitable measurement device known
in the art.
In an exemplary embodiment, the indication of stem thickness is an indication
of the angular
position of at least one of the arms.
The angular position sensor may be any suitable means known to a person
skilled in the art for
determining rotation of the arm or arms ¨ whether absolute or incremental. For
example, the
angular position sensor may be a rotary encoder.
It should be appreciated that the angular position sensor may not directly
measure rotation of
the arm. For example, the angular position sensor may be configured to output
a signal
indicative of the position of a linear actuator driving the pivoting arm.
Reference to the position
of the linear actuator should be understood to mean the position of a point on
the actuator
which may be used to determine the degree to which the actuator is extended.
For example,
the linear actuator may be a hydraulic cylinder including a linear position
sensor. Various
technologies are known in the art for achieving this ¨ for example operating
using
magnetostrictive principles, or Hall-Effect. Given known geometries of the
head, the position of
the actuator may be used to derive the angular position of the arm, or arms.
=
The angular position of at least one of the arms may be used in conjunction
with the known
geometry of the frame to determine the relative position of various points on
the device, and
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thereby geometry of the stem(s) being grasped by the arms. This will be
discussed further
below.
It should be appreciated that reference to obtaining the stem thickness
measurement using the
angular position of the arm is not intended to be limiting. For example,
acoustic and optical
diameter sensing systems have been proposed.
In an embodiment the cutting device includes at least one saw. In particular
the saw may be at
least one chainsaw.
It is known for forestry heads to include a main saw which is primarily used
for the felling and
cross cutting of stems. Further, some forestry heads may include a secondary
or topping saw.
lo The topping saw is typically of a lower specification than the main saw,
and used primarily
during processing once a tree is felled.
Each chainsaw may include a saw chain, a saw bar around which the saw chain
moves, and a
saw drive gear for driving the saw chain around the saw bar. Each chainsaw may
be pivoted
about one end in order to travel though a cutting arc. The extent of the
travel may be controlled
as known in the art.
Reference to the cutting device being a chainsaw is not intended to be
limiting, as the saw may
take other forms ¨ for example a disc saw. Further, the cutting device may
take other forms
known in the art, for example a shear.
Reference to travel should be understood to mean the range of motion through
which the
cutting device moves. In the context of a pivoting chainsaw, travel is the arc
through which the
saw must pass to reach the break through point at which the stem(s) is
severed. However, it
should be appreciated that travel need not be arcuate, and that the mode of
travel will depend
on the type of cutting device.
Where more than one stem is grasped by the arms, determining the travel
required of the
cutting device to sever the stems may include reference to an effective
cutting profile of the
stems.
An effective cutting profile should be understood to mean the cross section of
the collective
stems through which the cutting device must pass to sever the stems.
Together with known geometries of the timber-working device and path of travel
of the cutting
device, the effective cutting profile may enable determination of the most
distant break though
point and thus the travel required.
For example, where the device is currently grasping two stems the effective
cutting profile of
the stems may be generally ovaline in shape. If there were no indication of
two stems being
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grasped, the stem thickness measurement could imply that the required travel
is equivalent to
that for the case of a large single stem having a circular diameter. This
could result in a much
deeper cut than actually required, creating inefficiencies.
In another example, where the device is currently grasping three stems the
effective cutting
profile of the stems may be generally triangular in shape. The smaller
diameter of the
individual stems may cause them to settle differently within the grasp of the
arms compared to
a single stem creating the same angular position reading. This may require a
travel greater
than in the case of a single stem.
Without an indication of three stems being held by the device, the determined
travel may not be
to
sufficient to completely sever one or more of the stems. Failure to completely
sever a stem
may cause complications with subsequent processing, or damage the stem due to
breakage
rather than severing.
Determination of the travel required based on the number of stems currently
being grasped and
the stem thickness measurement may be achieved by any suitable means known in
the art.
For example, look up tables may be accessed to return the value, or algorithms
applied to
calculate the value.
The indication of the number of stems may be initiated by an operator of the
timber-working
device. For example, the stem count device may be an operator input device
enabling input of
the number of stems currently grasped by the timber-working device, and
generating a signal
indicative of the input for transmission to the controller. As the operator is
continuously
observing the timber-working device and its operation, selection of the number
of stems being
processed is envisaged as being a straightforward and intuitive step.
However, it should be appreciated that this is not intended to be limiting,
and that embodiments
may be implemented with automated detection or determination of the number of
stems. In
some embodiments the stem count device may be a general purpose controller,
having other
functions within the context of operating the timber-working device.
By way of example, a first angular position sensor may be provided to output a
signal indicating
an angular position of at least one of the delimb arms, and a second angular
position sensor
may be provided to output a signal indicating an angular position of at least
one of the drive
arms. The controller may be configured to receive the signals indicating the
respective angular
positions of the delimb arm and the drive arm, and correlate the angular
position of the delimb
arm with the angular position of the drive arm to determine the number of
stems currently
grasped by the timber-working device.
Where the collective profile of the stems varies from the generally circular
shape as in the case
of a single stem, the relationship between the angular positions of the drive
and delimb arms
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may also change, This may enable correlation of these angles to determine the
number of
stems held by the arms.
The angular position sensors may be any suitable means known to a person
skilled in the art
for determining rotation of the arms ¨ whether absolute or incremental. For
example, the
angular position sensor may be a rotary encoder.
It should be appreciated that the angular position sensor may not directly
measure rotation of
the arm. For example, the angular position sensor may be configured to output
a signal
indicative of the position of a linear actuator driving the pivoting arm.
Reference to the position
of the linear actuator should be understood to mean the position of a point on
the actuator
which may be used to determine the degree to which the actuator is extended.
For example,
the linear actuator may be a hydraulic cylinder including a linear position
sensor. Various
technologies are known in the art for achieving this ¨ for example operating
using
magnetostrictive principles, or Hall-Effect. Given known geometries of the
head, the position of
the actuator may be used to derive the angular position of the arm, or arms.
The angular positions of the arms may be used in conjunction with the known
geometry of the
frame to determine the relative position of various points on the device, and
thereby geometry
of the stem or stems being grasped by the arms.
In an exemplary embodiment, the stem count device may include pressure plates
with
associated pressure switches disposed laterally across the feed axis of the
frame. Pressure
zo applied to the plates due to one or more stems bearing against them when
grasped by the drive
or delimb arms may trigger the pressure switches. The number of stems held may
be inferred
by the pattern or lateral spread of the triggered switches.
For example, where three pressure plates are positioned across the frame ¨ one
centred on the
feed axis and one laterally offset from the feed axis on either side ¨
triggering of the switch
associated with the central plate, but not the others, may be indicative of a
single stem being
processed. In contrast, triggering of the switches associated with the lateral
plates, but not the
central plate, may be indicative of two stems being processed.
The various illustrative logical blocks, modules, circuits, and algorithm
steps described in
connection with the embodiments disclosed herein may be implemented as
electronic
hardware, computer software, or combinations of both. In particular, they may
be implemented
or performed with a general purpose processor such as a microprocessor, or any
other suitable
means known in the art designed to perform the functions described.
The steps of a method or algorithm and functions described in connection with
the
embodiments disclosed herein may be embodied directly in hardware, in a
software module
executed by a processor, or in a combination of the two. If implemented in
software, the
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functions may be stored as processor readable instructions or code on a
tangible,
non-transitory processor-readable medium ¨ for example Random Access Memory
(RAM),
flash memory, Read Only Memory (ROM), hard disks, a removable disk such as a
CD ROM, or
any other suitable storage medium known to a person skilled in the art. A
storage medium may
be connected to the processor such that the processor can read information
from, and write
information to, the storage medium.
BRIEF DESCRIPTION OF DRAWINGS
Further aspects of the present invention will become apparent from the
following description
which is given by way of example only and with reference to the accompanying
drawings in
which:
FIG. 1 is a side view of an exemplary timber-working system including,
for example, a
forestry head;
FIG. 2 is an elevated view of the forestry head;
FIG. 3 is a perspective view, with portions broken away, showing an
exemplary
chainsaw of the forestry head;
FIG. 4 is a diagrammatic view of an exemplary control system for the
timber-working
system;
FIG. 5A is an end view of the forestry head in use;
FIG. 5B is another end view of the forestry head in use;
FIG. 6 is a flowchart illustrating an exemplary method for operating a
timber-working
device;
FIG. 7 is a flowchart illustrating an exemplary method for determining
the number of
stems grasped by a forestry head, and
FIG. 8 is a line graph showing an exemplary relationship between the
angular position of
a delimb arm relative to the angular position of a drive arm of a forestry
head.
DETAILED DESCRIPTION
FIG. 1 illustrates a timber-working system including a carrier 10 for use in
forest harvesting.
The carrier 10 includes an operator cab 12 from which an operator (not shown)
controls the
carrier 10. The carrier 10 further includes a boom assembly 14, to which a
timber-working
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device in the form of a forestry head 16 is connected.
Connection of the head 16 to the boom assembly 14 includes a rotator 18,
configured to rotate
the head 16 about the generally vertical axis of rotation marked by dashed
line 20. A tilt
bracket 22 further allows rotation of the head 16 between a prone position (as
illustrated) and a
standing position.
Referring to FIG. 2, the head 16 includes a frame 24 to which the tilt bracket
22 of FIG. 1 is
pivotally attached. Right hand (RH) and left hand (LH) delimb arms 26a and 26b
are pivotally
attached to the frame 24, as are opposing RH and LH feed arms 28a and 28b. RH
and LH
feed wheels 30a and 30b are attached to RH and LH feed arms 28a and 28b
respectively,
which together with RH and LH frame-mounted feed wheels 32a and 32b may be
controlled to
feed one or more stems (not illustrated) along feed axis 34 of the head 4.
Feed wheels 30a,
30b, 32a and 32b may collectively be referred to as the 'feed mechanism.' A
measuring wheel
36 may be used to measure the length of the stem as it passes.
A main chainsaw 38, and a topping chainsaw 40, are attached to the frame 24.
The main saw
38 is typically used to fell a tree when the head 16 is in a harvesting
position, and to buck stems
into logs in the processing position of the head 16 (as seen in FIG. 1). The
topping saw 40 may
be used to cut off a small-diameter top portion of the stem(s) to maximize the
value recovery of
the trees.
Referring to FIG. 3, the saw 38 is mounted to a saw housing 42 of the frame
24. The saw 38
.. includes an endless cutting chain 44, a chain support 46, a chain driver 48
in the form of a
hydraulic motor, and an attachment device 50 attaching the chain 44, the chain
support 46, and
the chain driver 48 to the saw housing 42.
The attachment device 50 includes a swing 52, which includes an arm 54 and an
arm support
ring 56 to which the arm 54 is fastened with threaded fasteners. The swing 52
enables rotation
of the chain support 46 attached to the swing 52.
The chain support 46 includes a guide bar 58 and a bar holder 60 holding the
guide bar 58.
The chain 44 is trained about the guide bar 58 and the chain driver 48. The
bar holder 60 is
attached movably to a mount 62 of the saw apparatus 38 for movement of the bar
holder 60
and the guide bar 58 relative to the mount 62.
A hydraulic swing cylinder 64 is attached to the arm 54 and the frame 24
therebetween. The
cylinder 64 is operable to pivot the swing 52, the chain support 46, and the
chain 44 between a
stowage position retracted into the saw housing 42 and a deployed position
during a sawing
event (e.g., felling, bucking).
The various operations of the head 16 may be controlled by the operator using
hand and foot
controls as known in the art. Further, certain automated functions of the
harvester head 16
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may be controlled by an electronic control system 100 as shown by FIG. 4.
The control system 100 includes one or more electronic controllers, each
controller including a
processor and memory having stored therein instructions which, when executed
by the
processor, causes the processor to perform the various operations of the
controller.
For example, the control system 100 includes a first controller 102 on board
the carrier 10 and
a second controller 104 on board the head 4. The controllers 102, 104 are
connected to one
another via a communications bus 106 (e.g., a CAN bus).
A human operator operates an operator input device 108, for example hand and
foot controls,
located at the operator's cab 12 of the carrier 10 to control the head 16.
Details of operation
are output to an output device 110 ¨ for example a monitor. Certain automated
functions may
be controlled by first controller 102 and/or second controller 104.
The system 100 includes angular position sensors ¨ for example delimb rotation
sensor 112a
mounted to one of delimb arm 26a or 26b, and feed rotation sensor 112b mounted
to feed arms
28a or 28b ¨ each configured to output a signal indicative of the angular
position of the
associated arm for transmission to first controller 102 via second controller
104 and bus 106.
The head 16 has a number of valves 114 arranged, for example, in a valve block
and coupled
electrically to the second controller 104 so as to be under its control. The
valves 114 include,
for example, a motor valve configured to control operation of the motor 48 and
a swing valve
configured to control pivotal movement of the swing 52 via extension of swing
cylinder 64.
Saw rotation sensor 116 is electronically coupled to the second controller
104, and configured
to output a signal indicative of the relative position of the chain support 46
and the chain 41
between the stowage position and fully deployed position.
The control system 100 is configured to implement method 200 of FIG. 6, which
will be
described with reference to FIGS. 1 through 4, together with FIG. 5A and FIG.
5B showing the
head 16 in use.
In step 202, a human operator operates the operator input device 108 to grasp
one or more
stems with the delimb arms 26a and 26b, and feed arms 28a and 28b, such that
the stem(s) is
positioned between the arm-mounted feed wheels 30a and 30b, and frame-mounted
feed
wheels 32a and 32b.
In step 204, the operator operates the operator input device 108 to transmit
an indication to first
controller 102 of the number of stems currently held by the head 16. In the
case of FIG. 5A this
will be a single stem 300, and two stems 302 and 304 in the case of FIG. 5B.
In step 206, rotation sensor(s) 112a and/or 112b transmits a signal indicating
the angular
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position of the associated arm to the first controller 102 via second
controller 104 over bus 106.
In step 208 the first controller 102 refers to a look up table for the
appropriate number of stems,
using the measured angular position as a reference, in order to determine the
travel required
for saw 38 to sever the stems while limiting travel.
Referring to FIG. 5A, saw 38 is illustrated at its fully deployed position,
i.e. at its greatest travel
setting. The projected end position of the saw 38 based on the indication of a
single stem at
the measured angular position is shown in dashed outline 306 (including
allowance for
measurement errors). It may be seen that the travel required to reach position
306 is less that
to achieve the fully deployed position illustrated.
la Referring to FIG. 5B, the projected end position of the saw 38 in the
dual stem case is shown in
dotted outline 308. Comparing the single stem projected end position 306 to
the dual stem
projected end position 308, it may be seen that the travel required to sever
stem 300 is greater
than that required to sever stems 302 and 304, despite the angular position of
the drive arms
28a and 28b being substantially the same.
In step 210 the first controller 102 receives from operator input device 108 a
signal indicative of
a request to operate the saw 38. In response to that signal, the first
controller 102 broadcasts
a request to operate the saw 38 on bus 106 together with control information
regarding the
determined travel limit of the saw 38.
In step 212 the second controller 104 receives the request to operate the saw
38, outputs
control signals to the two valves 114 responsible for control of the motor 48
and swing cylinder
64 respectively, and takes a position reading from saw rotation sensor 116.
In step 214 the second controller 104 monitors the position of the saw 38
using the output of
saw rotation sensor 116, and controls the valve 114 responsible for control of
the swing cylinder
64 to reverse travel once the predetermined travel limit is reached and return
the saw to its
stowage position.
In an exemplary embodiment, the act of the operator operating the operator
input device 108 to
transmit an indication to first controller 102 of the number of stems
currently held by the head
16 in step 204 may be replaced by an automated method 400 for determining the
number of
stems ¨ described herein with reference to FIG. 7.
In step 402, rotation sensors 112a and 112b transmits signals indicating the
angular positions
of the respective associated arms to the first controller 102 via second
controller 104.
In step 404 the first controller 102 correlates the angular position of the
delimb arm 26a or 26b
with the angular position of the drive arm 28a or 28b to determine the number
of stems
currently grasped by the head 16.
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FIG. 8 illustrates an exemplary relationship between the angular position of
RH delimb arm
26a and the angular position of RH feed arm 28a. The line designated at 500
represents the
relationship in the case of grasping a single stem, and the line designated at
502 represents
the relationship in the case of grasping two stems.
It may be seen that there is the relationship between the RH delimb arm 26a
and RH drive
arm 28a may be distinguished between the two cases (single stem 500 and two
stems 502).
It should be appreciated that exact angular position values may vary between
head
configurations and geometries, but that the general principle applies.
Determination of the number of stems may thus be achieved, for example, by
referencing the
angular position of the RH drive arm 28a and comparing the angular position of
the RH delimb
arm 26a with a threshold delineating the two cases (see line designated at
504).
As an example, where the angular position of the RH drive arm 28a is 25
degrees, if the angle
of the RH delimb arm 26a is less than 64 degrees the first controller 102
determines that a
single stem is currently grasped by the head 16. If the angle of the RH delimb
arm 26a is
greater than 64 degrees the first controller 102 determines that two stems are
currently
grasped by the head 16.
Reference to any prior art in this specification is not, and should not be
taken as, an
acknowledgement or any form of suggestion that that prior art forms part of
the common
general knowledge in the field of endeavour in any country in the world.
Embodiments described herein 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, in any or all combinations of two or more of said parts,
elements or features.
Where in the foregoing description reference has been made to integers or
components having
known equivalents thereof, those integers are herein incorporated as if
individually set forth.
It should be noted that various changes and modifications to the presently
preferred
embodiments described herein will be apparent to those skilled in the art.
Such changes and
modifications may be made without departing from the spirit and scope of the
disclosure and
without diminishing its attendant advantages. It is therefore intended that
such changes and
modifications be included within the present invention.
Embodiments have been described by way of example only and it should be
appreciated that
modifications and additions may be made thereto without departing from the
scope thereof as
defined in the appended claims.
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