Note: Descriptions are shown in the official language in which they were submitted.
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BOARD POSITIONING SYSTEM AND METHOD, AND
FENCE ASSEMBLY
FIELD
The specification generally relates to positioning boards lengthwisely as they
are being
conveyed in a longitudinal direction, the boards being transversally-oriented.
BACKGROUND
The dimensional lumber industry has seen a continuous increase in the
automation ratio of
production processes in the last decades. Manual interventions are thus
progressively
eliminated from these processes, in a continuous struggle to lower production
costs.
One process which has been the subject of such automation is often referred to
in the art as
optimization. In this process, parallel and transversally oriented wood boards
are scanned as
they are longitudinally conveyed on a production line. A system referred to as
an optimizer
uses the scanning data to identify imperfections in each particular wood
board, and
calculates a trimming solution to optimize the monetary value of the wood
board. For
example, a board of a given length could have some imperfections trimmed off
one or both
ends to yield a board having a higher grade, and therefore having a higher
monetary value,
although it is not as long as its original length.
The trimming can be done in different ways. One way trimming can be done is by
using one
or more saws at fixed transversal positions at a given longitudinal location
along the
conveyance path of the boards. Each board is then displaced lengthwisely (in
the transversal
orientation), to be positioned in alignment with the particular saw or saws
which will trim it
in accordance with the trimming solution.
Although known processes and methods to lengthwisely displace such boards have
been
satisfactory to a certain degree, there remains a need to obtain even more
accuracy in
positioning the board, and to further increase the longitudinal conveyance
speed at which
the lengthwise displacement takes place, to further increase production rate.
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SUMMARY
In accordance with one aspect, there is provided a system and a method for
lengthwise
positioning of transversally-oriented elongated articles as they are being
longitudinally
conveyed, the system and method comprising sliding a laterally extending end
of the
elongated article against a fence oriented in a converging angle relative to
the conveyor, to
thereby displace the elongated article lengthwisely. The fence is comprised of
a plurality of
adjacent gates which can be moved into and out of interference with the
elongated article
individually, to allow free passage of the elongated article once the desired
amount of
lengthwise displacement has been reached.
The fence can be provided as a fence assembly having the plurality of gates
mounted to a
common base and being positioned in the conveyance path of the elongated
articles. A
plurality of actuators can be connected between the base and the respective
gates for moving
the gates.
In accordance with another aspect, there is provided a board positioning
system, the system
comprising : a conveyor having a plurality of longitudinally interspaced
pushing elements,
each pushing element being configured and adapted to receive a transversally-
oriented
board, and to exert a longitudinal conveyance force on the received board to
convey the
board along a conveyance path, with an end of the board extending laterally
from the
conveyor, when the conveyor is in operation; and a fence, adjacent the
conveyor, positioned
in the conveyance path, in interference with the laterally-extending end of
the board, and
defining a converging angle with the conveyor, the fence being configured and
adapted to
exert a positioning force, reactive of the conveyance force, to move the board
lengthwisely
as the laterally-extending end of the board is being slidingly conveyed
against the fence
when the conveyor is in operation, the fence having a plurality of adjacent
gates, each gate
being individually movable out of the conveyance path, when the positioning
force has
imparted a given lengthwise displacement to the board, and movable back into a
fence
position after the board has passed by the respective gate.
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In accordance with another aspect, there is provided a method of positioning a
transversally-
oriented board being conveyed in a longitudinal direction, the method
comprising :
obtaining a desired transversal position for the board; sliding a laterally
extending end of the
board against a fence having a plurality of adjacent gates positioned in a
common plane, the
common plane defining a converging angle relative to the longitudinal
direction, the fence
thereby imparting a lengthwise displacement to the board; converting the
desired transversal
position to a longitudinal position of the board relative to the fence; during
the sliding,
determining when the board reaches the longitudinal position; upon said
determining,
moving the one of the gates which is in contact with the board out from
longitudinal
interference with the board; after said moving the one of the gates, moving
any subsequent
gate or gates of the fence out from interference with the board; and replacing
the one of the
gates, and the any subsequent gate or gates back into the common plane once
the board has
passed by each respective gate.
In accordance with another aspect, there is provided a fence assembly for use
in a
longitudinal elongated article conveyance path of a lug conveyor, to
individually displace
transversally-oriented and longitudinally-interspaced elongated articles
lengthwisely as the
elongated articles are being carried by the lug conveyor, the fence assembly
comprising : a
support body; a plurality of adjacent gates, each gate being movable between a
respective
fence position and a respective recessed position, the fence positions being
immediately
adjacent in a common fence plane, and fixedly positioned relative to the
support body; a
plurality of actuators, each actuator connected between the support body and a
respective
one of the adjacent gates to actuate the movement of the respective gate; the
fence assembly
being fixedly positionable relative to the lug conveyor with the fence
positions in the
elongated article conveyance path, the recessed positions out of the elongated
article
conveyance path, and the fence plane defining a converging angle relative to
the lug
conveyor.
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DESCRIPTION OF THE FIGURES
Fig. 1 is a perspective view of an example of a board positioning system;
Figs. 2A, 2B and 2C are schematic diagrams showing : forces acting on a board
during
lengthwise displacement; movement components; and force components,
respectively;
Figs. 3, 4 and 5 are top plan views showing successive images of boards being
lengthwisely
displaced by the system of Fig. 1;
Fig. 6 is a side view of a portion of a fence assembly used in the system of
Fig. 1;
Fig. 7 is a perspective view of the portion shown in Fig. 5;
Fig. 8 is a side view of a portion of a lengthwise-friction-applying assembly
used in the
system of Fig. 1;
Fig. 9 is a perspective view a portion of the friction applying assembly used
in the system of
Fig. 1.
DETAILED DESCRIPTION
Fig. 1 shows an example of a board positioning system 10. The system 10
includes a
conveyor 12 which conveys interspaced boards 14a, 14b, 14c ... 14i, along a
conveyance
path 16. For ease of reference, a longitudinal direction 18 will be defined as
the direction of
the conveyor 12. Hence, the boards 14a to 14i are longitudinally interspaced
and are
oriented transversally 20. In this example, the conveyor 12 is a lug chain
conveyor 12a
having two lug chains 22, 24 each carried on a respective guide rail 26, 28.
Longitudinally
interspaced pairs of lugs 23, 25 are provided on the lug chains 22, 24 to push
the boards 14a
to 14i, with each lug 23, 25 of each lug pair being associated with a
respective lug
chain 22, 24. Each board 14a to 14i has at least one end 30 which extends
laterally from the
conveyor 12, and an opposite end 32.
The system 10 also includes a fence 34 comprised of a plurality of gates 36
which are
normally positioned in respective fence positions 38 along a common fence
plane. The fence
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34 is positioned in the conveyance path 16, at a converging angle relative to
the conveyor
12, and in interference with the laterally-extending end 30 of the boards 14a
to 14i such that
when a board comes into sliding contact with the fence 34, it is pushed by the
fence and
displaced lengthwisely to a different transversal position. This will be
detailed further
below. A main focus in the dimensional lumber production industry is to
increase
production rate, and therefore, the longitudinal speed at which the boards 14a
to 14i are
carried by the conveyor 12 in this example can be quite high.
A plurality of actuators 40 are provided, each actuator 40 being associated
with a respective
gate 36, to move the gate out from the fence position 38, into a recessed
position 42, in
which it is no longer in interference with the laterally-extending end of the
board 14d, to
thereby allow the board 14d to maintain its transversal position once a
desired amount of
transversal displacement has been imparted to the board 14d using previous
gates.
In this example, the system 10 also includes a friction applying assembly 44
which acts to
exert a lengthwise frictional force on the boards 14a to 14i when they are
being lengthwisely
displaced by the fence 34. The friction applying assembly 44 helps control the
lengthwise
displacement of the boards.
The system 10 can advantageously be used in an optimizing process. In such a
process, each
board is scanned and analyzed to identify the location of imperfections (not
shown). Then, a
trimming solution is calculated. The trimming solution is based on the
scanning data
analysis, and specifies at which one or two transversal positions the board
should be
trimmed to obtain a board of the highest value. One or more trimming saws (not
shown) are
positioned after the fence in the conveyance path of the boards, at known
transversal
positions. The fence 34 can thus be used to displace each board lengthwisely
into alignment
with the respective fixed-positioned saws for one end or both ends of the
board to be
trimmed in accordance with the trimming solution.
The action of the fence 34 on a board 14 is schematized in a simplified manner
in Fig. 2A.
The conveyor (not shown) exerts a longitudinal conveyance force 46 on the
board 14. The
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longitudinal conveyance force 46 acts to convey the board 14 along the
conveyance path 16.
The fence 34 is positioned at a fixed position in the conveyance path 16, in
interference with
the laterally-extending end 30 of the board 14. The plane of the fence 48 is
oriented in a
converging angle a relative to the conveyor, or conveyance path 16. In Fig.
2A, the
converging angle a is exaggerated to ease illustration and comprehension.
Typically, before
coming into contact with the fence 34, all the boards 14 have their laterally
extending end 30
aligned at a common datum transversal position 50, and the fence 34 is
positioned for the
first gate 36a to slightly exceed that datum, outwardly of the conveyance path
16.
The longitudinal conveyance force 46 exerted by the conveyor brings the board
14 into
contact with the fence 34. The fence 34 is fixedly positioned, and therefore
resists the
longitudinal conveyance force 46 of the conveyor by exerting a fence friction
force 52
parallel to the fence 34, and a positioning force 54, normal to the fence 34,
both of which
forces 52, 54 are reactive to the longitudinal conveyance force 46. At the
moment of
contact, the positioning force 54 rapidly accelerates the board 14 into a
lengthwise
movement. At this moment, the lengthwise friction force 56 which can be
exerted by the
friction applying assembly (44 - Fig. 1) can help smoothen the impact. As the
board 14 is
slid against the first gates 36a, 36b, 36c of the fence 34, its overall
movement 58 is in the
direction of the converging angle a of the fence plane 48, and includes both a
longitudinal
component 60 and a lengthwise (transversal) component 62, as schematized in
Fig. 2B.
The scanning data of the board 14 can be used to determine the contact point
64 at which the
board 14 will come into contact with the fence 34. Typically, the lug chains
22, 24 of the
conveyor 12 (Fig. 1) are meshed with gears, and it is possible to know the
longitudinal
position of each lug pair, and thus the longitudinal position of the contact
point 64, with a
relatively high degree of precision. This can be achieved by using an optical
encoder on the
gears, for example. Using this information, a controller (not shown) of the
actuators 40 (Fig.
1), can determine with a relatively high degree of precision at which moment
the action of
the fence 34 on the board 14 will have produced the desired lengthwise
displacement for the
board 14 to be correctly aligned with the trimming saws. At this moment, the
controller
commands the actuator of the gate 36c which is in contact with the board to
move the gate
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to the recessed position (42 - Fig. 1). While the longitudinal movement
component 60 of the
board is driven by the conveyor and does not change, the lengthwise movement
component
decelerates and comes to a halt, because the fence 34 no longer acts on the
board 14. As the
board 14 is continued to be carried longitudinally by the conveyor, the
controller commands
all the subsequent gates 36d to 36g to the recessed position 42, and back into
the fence
position 38 in cascade, to allow free passage of the board 14 which has
reached the desired
lengthwise position.
Due to the lengthwise inertia of the board 14, the lengthwise deceleration is
not
instantaneous. This can cause a certain degree of imprecision. The use of a
lengthwise
friction applying element which produces a lengthwise friction force 56 known
with a
relatively high degree of precision can help control this factor of
imprecision. In one aspect,
the lengthwise friction force 56 increases the rate of deceleration of the
board 14, and
thereby reduces the extra amount of lengthwise distance the board 14 travels
after being
freed from the positioning force 54 of the fence 34. In another aspect, if the
extra amount of
lengthwise distance traveled by the board 14 is relatively constant whatever
the longitudinal
position along the fence 34, the controller can be programmed to take this
variable into
account and to move the gate 36c into the recessed position 42 slightly before
the board 14
has reached the desired transversal position, and the inertia of the board
will then take the
board the rest of the way while it decelerates.
Fig. 2C shows the force diagram of the forces acting on the board in Fig. 2A
while the board
14 is slid against the fence 34 at a constant speed. During the constant speed
displacement,
the forces 46, 52, 54, 56 acting on the board add up to zero. It will be
understood that Fig.
2A is simplified, the moments acting on the board not being shown, for
instance.
Nevertheless, Fig. 2A can be helpful in understanding the forces at play.
Fig. 2B can helps understanding the influence of the converging angle a of the
fence 34. At
a given conveyor speed 60, the greater the angle a, the greater the lengthwise
movement
speed 62 will be, and so will the lengthwise acceleration and deceleration of
the board.
Therefore, reducing the angle a can help obtaining a higher degree of
precision in the
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lengthwise displacement. However, the maximum amount of lengthwise
displacement
which can be achieved using the fence 34 is approximately equal to the length
of the
longitudinal projection of the fence 66, which is reduced when the angle a is
reduced.
Therefore, a fence 34 of a greater length can be required to achieve a given
maximum
amount of lengthwise displacement 66 with a lower angle a, for example.
Figs. 3 to 5 are successive views showing boards 14a to 14k being conveyed
longitudinally
by the conveyor 12 while they are being individually positioned lengthwisely
by the fence
34. Fig. 3 shows how the boards 14h and 14i are first being carried at the
datum transversal
position 50 until they reach the fence 34. Board 14f has already reached its
desired
transversal position, and has been freed by the fence 34, the gate 36c being
in the recessed
position. Board 14e is being slid against the fence 34 to be taken to another
transversal
position. During the displacement of board 14f, the gates move into the
recessed position
and back into the fence position in cascade to let it pass, this is shown by
referring
successively to Figs. 3 to 5. In Fig. 4, board 14f is still free from the
fence 34, gates 36e and
36f being in the recessed position, and board 14e is still being slid against
the respective
gates 36g and 36h of the fence 34 which are in the fence position. In Fig. 5,
both board 14f
and board 14e are freed from the fence, both at their respective desired
transversal position,
while subsequent boards 14h and 14g are being slid against the fence. Little
or no
lengthwise displacement was required for board 14i, and even the first gate
36a is letting it
pass by, by being in the recessed position.
Figs. 6 and 7 show a gate 36 of the fence 34 in greater detail. All the other
gates are similar
in design. The gate 36 has a planar surface 68 adapted to slidingly receive
the boards, when
the gate 36 is in the fence position 38, the planar surface 68 is positioned
in the fence plane
48 where it is in interference with the conveyance path 16 of the boards. The
gate 36 is
movable out from the conveyance path 16, into the recessed position 42. In
this example, the
gate 36 is movable between the two positions 38, 42 by pivoting around a
common gate
pivot axis 70. The gate pivot axis 70 is received on a common support body 72.
The gate's
respective actuator is extendible in this case, and is more particularly a
piston-cylinder
assembly 40a (hereinafter "piston 40a" for simplicity) which has one end 74
pivotally
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mounted to an extension 76 on the back side 78 of the gate 36, and the other
end 79
pivotally mounted to the support body 72. The gate 36, support body 72, and
actuator 40 are
provided as parts of a fence assembly 80. Of course, the support body 72 can
include a
plurality of assembled components such as a frame and support plates for the
gates, as it is
shown in the Figs. 6 and 7. In alternate embodiments, the gates can be movable
by
translation instead of by pivoting, for example. Pivoting was selected in this
example
because it allowed to obtain a faster rate of movement out of the conveyance
path for a
given displacement of the piston shaft as compared to translation, by a
judicious positioning
of the extension on the gate. Pneumatic pistons were used in the example, but
other pistons
such as electrical pistons can alternately be used.
In Fig. 7 the first gate 36a has a deflector 82. The deflector 82 can serve to
reposition a
board 14 in the event where it accidentally exceeds the datum (see Fig. 2A).
The width of the gates can be adapted in view of specific applications. If the
gates are
specifically designed for use with larger boards, they can typically be made
wider than if
they are designed for use with thinner boards. Therefore, having more gates
per fence length
gives more flexibility. However, it also typically results in being more
expensive, because of
the extra actuators which are associated therewith. The gates are made thinner
than the
transversal projection of the spacing between the boards on the fence, so that
they can be
raised between two subsequent boards without contacting either one. In the
illustrated
embodiment, the gates all have the same width for simplicity, but can
alternately be
provided of different widths.
Fig. 8 shows one friction-applying skate 83 which forms part of the friction-
applying
assembly shown in Fig. 1. The friction-applying skate 83 includes a skate body
84 which is
pivotally mounted to a skate pivot shaft 85. The lower edge 86 and upstream
edge 87 of the
skate body 84 are covered by a friction-exerting material 88, such as rubber
for instance. A
skate actuator 89, or more particularly a piston 89a in this example, acts on
the skate pivot
shaft 85 and pivotally biases the skate body 84 into the conveyance path 16 of
the boards 14.
The upstream edge 87 of the skate body 84 is slanted, and the pivotally
biasing force is
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adjusted, such that the friction skate 83 pivotally yields to the board 14 as
the board 14 is
pushed thereunder by the lugs 25 of the conveyor 12, but maintains a
compressive force
against the board 14 in opposition to the conveyor 12 while the board 14 is
slid thereunder.
In this example, the maximal pivoting of the skate 83 is determined by the
maximal
extension of the piston 89a.
As shown in Fig. 9, the skates 83, 90 are positioned in pairs in succession on
the common
skate base 91, in a manner that there is always a skate in contact with a
board which is being
slidingly conveyed against the fence.
Turning back to Fig. 1, it will be understood that the friction applying
assembly 44 and the
fence assembly 80 are positioned at fixed positions relative to one another,
and relative to
the guide rails 26, 28 of the conveyor 12. In this example, the converging
angle of the fence
34 relative to the conveyor 12 can be modified by sliding the fence assembly
80 along
guides 92, 93, 94, and securing the fence assembly 80 into a fixed position on
the guides 92,
93, 94.
It will be understood that the fence assembly can be sold as a stand-alone
component
intended for mountin adjacent a previously existing conveyor. The fence
assembly can also
be sold in combination with a friction applying assembly, for example.
The illustrated embodiment is provided only as an example. Alternate
embodiments are
possible and can depart from that which has been illustrated.
For instance, the system or method can be used with boards of various
dimensions. Also, the
boards can be of a different material than wood. Further, the subsequent
boards carried
along the conveyor can have different lengths, and can even have different
widths and
thicknesses, instead of all being of substantially similar major dimensions.
Even further, the
method or system can be used with other elongated articles than boards, in any
suitable
alternate application.
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Also, the conveyor can be any suitable conveyor in view of the given
application. Typically,
the conveyor will include pushing elements which exert a longitudinal pushing
force on the
elongated articles. The pushing elements can be longitudinally interspaced
regularly or
irregularly. In the example illustrated in the attached figures, each pushing
element was
provided as a pair of lugs, each one of the two lugs of the pair being
associated with a
respective lug chain, and the pairs of lugs are regularly interspaced. An
alternate pushing
element can consist of a transversally elongated flange extending normally
from a conveyor
belt, for example.
The surface of the gates which is intended to slidingly receive the boards
have a low friction
coefficient, to ease the sliding action. The gates can be made of stainless
steel, or another
similar material, to that effect. Stoppers can be used with the gates to limit
the maximum
extent of movement of the gates. Alternately, the maximum extension of a
piston in a
cylinder can serve to limit the maximum extent of movement. In alternate
embodiments, the
gates can move by sliding along guides instead of by pivoting, for example.
A lengthwise friction element can be used to limit or control the lengthwise
freedom of
movement of the boards. In the illustrated example, the lengthwise friction
element is
provided as a plurality of friction applying skates which subsequently come
into frictional
contact with the board, in opposition with the conveyor. Alternately, the
lengthwise friction
element can take the form of a component provided as part of the conveyor
immediately
upstream of the respective pushing element, and on which the elongated article
rests as it is
pushed by the pushing element. Such a component can be made of rubber or
another
material which has a relatively high friction coefficient. A lengthwise
friction element which
is part of the conveyor will typically provide less friction than a lengthwise
friction element
which acts in compression on the board, in opposition to the conveyor, but may
nevertheless
provide a satisfactory degree of friction for certain applications.
It will be understood that the examples described above and illustrated are
exemplary only.
The scope is indicated by the appended claims.
