Note: Descriptions are shown in the official language in which they were submitted.
CA 02518681 2005-11-16
SYSTEM FOR POSITIONING A WORKPIECE
Field of the Invention
This invention relates to the field of devices for positioning a workpiece in
a
sawmill, and more particularly, it relates to a system for positioning a
workpiece into an optimized
position to produce the highest value or yield of lumber.
Background of the Invention
Conventional log turners known as "flying log turners", typically comprise a
pair of
four to five foot long vertically oriented spiked rolls which are located on
each side of a
transporting conveyor. The log turner rotates a workpiece, such as a log, as
the workpiece travels
towards the infeed of a primary breakdown machine, such as canters, bandmills
or circular Scragg
saws. The spiked rolls of the log turner are movable laterally towards and
away from the
centreline of a workpiece, longitudinally along the length of the workpiece in
an open-and-close
operation, and vertically upwards and downwards to engage, manipulate, and
rotate the workpiece.
The pair of rolls moves in an open-and-close operation to control the location
along the length of
the log where the rolls contact and manipulate the log position. Each roll, or
set of rolls also moves
in the vertical direction.
Other conventional log turners known as knuckle turners provide a less
accurate
method of turning logs. If accurate turning feedback was achieved, this would
be a more cost-
effective method of turning the logs as compared to flying log turners.
As a workpiece travels along the conveyor en route to the primary breakdown
machines, an optimizer, using data from a scanner, determines an optimized
position of the
workpiece such that the workpiece, when processed in accordance with the
desired angular
CA 02518681 2005-09-09
rotation of the optimized position, may generate the highest value or yield of
lumber. To position
the workpiece in the optimized position, motion control data generated by the
optimizer and
associated programmable logic controller (PLC) initiates movement of the log
turner to rotate the
workpiece in order to attain the optimized position. In flying log turners
lateral and longitudinal
displacement of the spiked turning rolls brings the rolls into contact with
the surface of the
workpiece. The vertical displacement of each spiked roll allows the workpiece
to be rotated about
its longitudinal axis. The log turner rotates the workpiece until the
optimized position is achieved.
During the turning process, surface irregularities such as protruding knots or
indentations on the surface of the workpiece may affect proper contact of the
spiked rolls with the
1B workpiece, thereby inhibiting proper rotation of the workpiece to
position it in the optimized
position. This turning inaccuracy results in a significant reduction in lumber
recovery.
Furthermore, even if the optimized position is achieved, movement of the
transport conveyor on
which the workpiece travels may not maintain the workpiece in the optimized
position. Precision
in workpiece rotation and workpiece positioning is made even more difficult
given the high speed
at which the log turner performs its function. By providing a system to
improve the accuracy of
workpiece positioning, lumber volume and value will thereby increase.
The scanner/optimizer decides what angular orientation the log needs to be in
to get
the highest value breakdown solution from the log. Motion control data is sent
from the Optimizer
to the PLC control system allowing the rolls to contact the log, and by moving
the rolls in opposite
vertical directions; the log can be rotated to the desired angular position.
During the log turning process, approximately eight feet along the length of
the log
is in contact with the turning rolls. Because the outer surface of the log
typically exhibits many
geometric defects such as knots, cat-face, etc., smooth & consistent contact
with the turning rolls
is impeded. This in turn results in the target angular position of the log not
being reached. For
example, as the rolls pass over a knot that is sticking out, optimal contact
with the log is sacrificed
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and therefore the targeted position is not achieved. Depending on log
geometry, log diameter and
products being manufactured, this turning inaccuracy can have a significant
impact on lumber
recovery.
Summary of the Invention
It is an object of the present invention to provide a system of positioning a
workpiece into an optimized position whereby rotational accuracy of a
workpiece may be
monitored, maintained, and/or corrected so that positional or rotational
errors at primary
breakdown may be avoided, thereby improving overall lumber recovery.
It is another object of the present invention to provide a marking device to
place a
mark on an end of the workpiece to assist the system in monitoring,
maintaining, and/or correcting
the position of the workpiece such that the optimized position may be achieved
and maintained.
It is another object of the present invention to provide a means for
identifying the
orientation of the mark in real-time as the workpiece is transported through
the turning mechanism
such that any necessary corrective angular repositioning may be timely
performed to ensure that
the orientation of the mark prior to the workpiece leaving the turning
mechanism coincides with
the optimized position of the workpiece.
It is another object of the present invention to provide a evaluator to
determine in
real-time if there are any positional differences between the orientation of
the mark and the
optimized position while the workpiece is being rotated and transported
towards the primary
breakdown machine.
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It is a further object of this invention to provide a mechanism for
transmitting
corrective positioning information to control the operation of the turning
mechanism to adjust the
position of the workpiece such that the optimized position may be achieved and
maintained.
The present invention is a system for positioning a workpiece into an
optimized
position. The system includes a marking device adapted to place a mark on the
workpiece prior to
the workpiece passing through an optimizer. A first identifying means
identifies the orientation of
the mark as a point of reference such that the workpiece may be positioned
into the workpiece's
optimized position by rotating the workpiece relative to the orientation of
the mark. A turning
mechanism rotates the workpiece. A second identifying means identifies the
orientation of the
mark while the workpiece is being rotated. An optimizer or other processor
receives information
from the first identifying means and from the second identifying means to
determine if the
workpiece is in the optimized position. A PLC or other processor controls
rotation of the
workpiece such that the optimized position of the workpiece may be achieved.
The marking device may be a spray paint marking device for placing a spray
paint
line on an end of the workpiece. A first camera identifies the orientation of
the mark. This maybe
prior to the workpiece exiting the optimizer. The optimizer determines the
optimized position of
the workpiece. A workpiece turning mechanism such as one including a pair of
turning rolls, one
turning roll on each side of a conveyor, rotates the workpiece to its
optimized position. The
turning rolls may be spiked to grasp the workpiece without slipping. The
turning rolls may also
displace horizontally to engage the workpiece. They may also rotate about a
vertical axis to assist
in transporting the workpiece along the conveyor. The pair of turning rolls
displace vertically
relative to one another, upwards and downwards, causing the workpiece to
rotate where
sandwiched between the rolls. A second camera may be positioned within the
turning mechanism.
A third camera may be positioned adjacent to the turning mechanism. The second
and third
cameras identify the orientation of the mark in real-time, continually or at
predetermined time
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intervals while the workpiece is being rotated. The real time orientation of
the mark is transmitted
to the processor which compares the real time orientation of the mark with the
desired optimized
position of the workpiece to determine if the workpiece is in the optimized
position. To position
or maintain the workpiece in the optimized position, the processor transmits
information to the
turning mechanism to control rotation of the workpiece such that the optimized
position of the
workpiece may be achieved and maintained.
Brief Description of the Drawings
Various other objects, features and attendant advantages of the present
invention
will become fully appreciated as the same becomes better understood when
considered in
conjunction with the accompanying drawings, in which like reference characters
designate the
same or similar parts throughout the several views, and wherein:
Figure 1 is a detailed plan view of the infeed, scanner/optimizer, conveyor
and
turning roll portions of the present invention;
Figure 1 a is a schematic plan view of the present invention;
Figure 2 is a detailed side elevational view of the invention illustrated in
Figure 1;
Figure 3 is an enlarged plan view of a portion of the turning roll mechanism;
Figure 4 is a sectional view taken on line 4-4 of Figure 3; and
Figure 5 is an enlarged view of a portion of Figure 3.
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Detailed Description of Embodiments of the Invention
With reference to the Figures wherein similar characters of reference denote
corresponding parts in each view, a system 10 according to the present
invention includes a
scanner/optimizer 15, a processor 20, a marking device 25, a first and a
second mark orientation
identifying means 30 and 35, and a turning mechanism 40.
As seen in Figures 1 and la, a plurality of logs, referred to herein
alternatively as
workpieces 5, located on an infeed 12 are transported by suitable means, such
as a chainway or
other conveyor, in downstream direction of flow A on a feedpath towards a
conveyor 14. Marking
device 25 mounted along infeed 12 makes or places a mark 28 on each workpiece
5.
Alternatively, marking device 25 may be positionable along conveyor 14 so that
marking device
25 places mark 28 on workpiece 5 prior to workpiece 5 passing through
scanner/optimizer 15. In
one embodiment, not intended to be limiting, marking device 25 is a spray
paint marking device
for placing a visually observable spray paint line on an end 7 of workpiece 5.
Alternatively,
marking device 25 may be a cutting means for making a superficial visual cut
mark on end 7 of
workpiece 5. It will be recognized that there are many different marks and
marking devices within
the scope of the present invention that may be used to provide a suitable mark
on workpiece 5 as a
reference point to provide information regarding the rotational position of
workpiece 5. Further,
as better described below, natural features or objects or irregular shapes
occurring on or along the
workpiece may serve as a mark for the purposes of tracking the rotational
orientation of the
workpiece.
Workpieces 5, which are marked on ends 7, are then transported on conveyor 14
in
downstream direction B towards and through scanner/optimizer 15.
Scanner/optimizer 15 detects,
analyzes, and classifies the geometrical information and surface
characteristics or features of each
workpiece 5 and determines an optimized cutting solution to obtain optimal
lumber production
from each workpiece 5. Based on the optimized cutting solution,
scanner/optimizer 15 calculates
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an optimized position for each workpiece 5 such that workpiece 5 may be
rotated into its position
prior to processing in a downstream machine center such as a canter, gangsaw,
etc. The optimizer
=
may determine the optimized position of workpiece 5 simultaneously with first
identifying means
30 identifying the orientation of mark 28 on end 7 of workpiece 5. In one
embodiment, first
identifying means 30 is a first vision camera such as a video camera mounted
adjacent to and in
proximity with scanner/optimizer 15 such that end 7 of workpiece 5 may be
photographed or
scanned prior to end 7 passing through scanner/optimizer 15. Data relating to
the orientation of
mark 28 identified by first identifying means 30 is then transmitted to
processor 20. The
optimized position calculated by scanner/optimizer 15 is also transmitted to
processor 20.
Typically, processor 20 is a computer or a PLC system capable of controlling
turning mechanism
40 to rotate and position workpiece 5 into its optimized position. The
orientation and position of
mark 28 identified by first identifying means 30 serves as a reference point
to assist processor 20
in controlling the rotation of turning mechanism 40 to position workpiece 5 in
the optimized
position, as described below.
As seen in Figures 3 to 5, turning mechanism 40 comprises a plurality of
turning
rolls 45 located on each side of conveyor 14. Turning rolls 45 are typically
spiked to enable
turning rolls 45 to engage the surface of workpiece 5 to rotate workpiece 5.
As seen in Figure 3,
only two pairs of turning rolls 45, one pair on each side of conveyor 14, are
illustrated and is not
intended to be limiting as two turning rolls 45, one on each side of conveyor
14, or four or more
even numbered pairs of turning rolls 45 may be employed. Each pair of turning
rolls 45 may
simulta eously rotate about their vertical axis C and/or displace in direction
D laterally of the
direction of flow B, towards and away from the centreline of workpiece 5.
Rotation of turning
rolls 45 about veitical axis C assists with the transport of workpiece 5 along
conveyor 14. Lateral
displacement of turning rolls 45 in direction B allows turning rolls 45 to
engage the surface of
workpiece 5 of varying widths. To rotate workpiece 5, turning rolls 45 may
also independently
displace vertically upwards and downwards in direction E along their
corresponding vertical axes
C, to thereby rotate workpiece 22 in a clockwise or counter-clockwise
direction about its
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longitudinal axis G, as shown by arrow F. Turning rolls 45 are actuated by
conventional actuator
means such as hydraulic means while the rotational, lateral, and vertical
movement of turning rolls
45 are controlled by processor 20. Processor 20 transmits information by
conventional means to
turning mechanism 40 to control actuation of rolls 45 so as to selectively
rotate and position
workpiece 5 into the optimized position.
Second identifying means 35 monitors the position of mark 28 as workpiece 5 is
rotated by turning mechanism 40. Second identifying means 35 may include a
second vision
camera such as a video camera, wherein the second camera may be mounted within
turning
mechanism 40. In another embodiment, at least two second identifying means 35
are mounted
within turning mechanism 40, as seen in Figure 3. A third identifying means
50, in a preferred
embodiment including a third vision camera, is positioned along conveyor 14
where workpiece 5
exits turning mechanism 40. For simplicity, and not intending to be limiting,
only a single second
identifying means 35 and a single third identifying means 50 are illustrated
in Figure la.
Second and third identifying means 35 and 50 identify the orientation of mark
28
continually or at predetermined length or time intervals, such as every 5
seconds, and transmits the
orientation information for the mark such as mark 28 to processor 20.
Processor 20 performs an
evaluation in real time of any positional differences between the desired
optimized position of
workpiece 5 and the real time position of workpiece 5, as indicated by
reference to the orientation
of the mark such as mark 28. If the orientation of the mark indicates that
workpiece 5 is not in the
optimized position, processor 20 calculates the required angular rotation of
workpiece 5 so as to
position workpiece 5 into the optimized position and transmits such corrective
information to
turning mechanism 40. Any positional errors of workpiece 5 are thus corrected
on a continual
basis until workpiece 5 exits turning mechanism 40. If the orientation of mark
28 indicates
workpiece 5 is in the optimized position, processor 20 and turning mechanism
40 cooperates to
maintain workpiece 5 in the optimized position by making any necessary
adjustments if workpiece
5 is displaced, for example, by the movement of conveyor 14.
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Video images may be used to track the movement of the log or workpiece by
identification of an object or other feature such as a patch of bark 5a in the
image and tracking the
relative movement of that object or feature or unique characteristic of the
log, frame to frame.
This may also be accomplished using mathematical techniques such as
correlation or phase
correlation, or object tracking techniques known in the art. To obtain a
correct movement a range
measurement must be added to determine if translation is occurring. This range
measurement can
also provide log diameter for side to side translation and geometric
correction to the video image.
If video information is taken in several locations the log can be tracked very
accurately and the log
can be rotated to the correct optimized location for log breakdown in the
downstream machine
center. The tools can also be adjusted to correct for translations that the
log has made during
rotation and transportation process before the machine center.
The same can be done using the three-dimensional shape of the log. The
original
log is scanned using a three-dimensional scanning system and that data
correlated with the original
three-dimensional shape data to determine rotation and location.
These are just examples and many methods may be used to measure the log
rotation
and provide feedback to allow for precise rotation and correct tool placement
of the machine
center.
The system would then, in real time, calculate and communicate corrective
positioning information to the motion control system that is controlling the
log turners, so any
potential angular orientation error could be corrected on a continuous basis
during the log turn
process. If tracked further in the process, exact location of the log may be
determined and the
cutting tools adjusted accordingly.
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In interpreting both this specification and the claims that follow, all terms
should
be interpreted in the broadest possible manner consistent with the context. In
particular, the terms
"comprises" and "comprising" should be interpreted as referring to elements,
components, or
steps in a non-exclusive manner, indicating that the referenced elements,
components, or steps
may be present, or utilized, or combined with other elements, components, or
steps that are not
expressly referenced. The term "mark" is meant to include orientation marks
added to a log, and
to other inherent orientation objects and features including unique or non-
symmetrical log shape
which may be tracked to determine if a rotational orientation of a log has
changed or if a preferred
or optimized rotational orientation of a log has been obtained.
In this fashion, rotation position and location errors are reduced to thereby
improve overall lumber value recovery. Placing a reference mark on the log
prior to the turner
rolls is described above. This may be in the form of a vertical line painted
on the end of the
log somewhere on the log infeed. A camera reads the orientation of the paint
mark at frequent
intervals during the turn process. The sub-system that looks at the vertical
paint spray mark
calculates an angular orientation and communicates this to the optimization
system at
predetermined intervals (every 6" to 12", for example along the log). The same
error rotation
correction could be accomplished using log image or shape recognition. Other
methods would
also work.
As will be apparent to those skilled in the art in the light of the foregoing
disclosure, many alterations and modifications are possible in the practice of
this invention.
The scope of the claims should not be limited by the preferred embodiments set
forth in the
examples, but should be given the broadest interpretation consistent with the
description as a
whole.
