Note: Descriptions are shown in the official language in which they were submitted.
CA 02519245 2005-09-15
WO 2004/082947 PCT/CA2004/000423
1
SYSTEM AND METHOD FOR PRINTING A CODE ON AN
ELONGATE ARTICLE AND THE CODE SO PRINTED
FIELD OF THE INVENTION
The present invention relates to a system and method for printing a code on an
elongate article, particularly a piece of wood, and the code so printed.
BACKGROUND OF THE INVENTION
Recently, there have been developments in the field of wood processing in
order
to autoniate the various processes involved therein. More particularly, it has
become more prevalent to optimize planers, and to automate wood grading
stations.
In this context, automatic grading systems using linear scanner need a method
to
identify each board and retrieve board data down the line on the lug chain.
Previously, when a board is scanned, an identification code is printed on the
board, which is read later on the lug chain with a machine adapted to read the
code, the code is then used to retrieved the grading decision previously
saved.
One of the disadvantages of such systems is that the code so printed on the
piece
of wood takes up too much space, or is printed with a large quantity of ink.
This
results in an unsightly mark, which wi!l not come off. Alternative embodiments
have used UV ink to print the code, but the UV ink has a tendency to fade to
yellow in time, again resulting in unsightliness.
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Finally, since the code must be printed on the piece of wood at high speeds,
it can
result it sloppy marks, which are unreadable by the code reading apparatus.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and apparatus for marking
a
piece of wood which obviates the disadvantages of the prior art mentioned
above.
It is also an object of the invention to provide a code which is discreet, and
which
is redundant, increasing the accuracy of the reading apparatus.
In accordance with a preferred embodiment of the invention, this object is
achieved with an apparatus for printing a code on elongate articles passing
through a printing station in a longitudinal direction, said apparatus
comprising:
an ink unit for storing ink to be delivered;
at least one printing head, said printing head being operatively
connected to said ink unit, said printing head including at least two valves,
said
valves being laterally spaced from each other; and
a controller for controlling said ink unit and said at least one printing
head, so that said controller is adapted to actuate said valves in order to
print a
longitudinally oriented code on each at least one lateral surface of said
elongate articles as said articles pass through said printing station, said
code
being printed at least twice on each of said elongate articles and said code
being unique to each of said elongate articles.
In accordance with another object of the invention, there is provided a method
for
printing a redundant code on an elongate article as said elongate article
passes
through a printing station, comprising the steps of:
(a) providing an ink unit;
(b) providing at least one printing head, said printing head including at
least two valves being laterally spaced from each other;
(c) providing a controller operatively associated with said ink unit and
said at least one printing head; and
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(d) actuating said valves with said controller in order to print said code.
BRIEF DESCRIPTION OF THE FIGURES
The present invention will be better understood after reading a description of
a
preferred embodiment thereof, made in reference to the following drawings in
which:
Figure 1 is a schematic representation of the printing system according to a
preferred embodiment of the invention;
Figure 2 is a photograph of a plurality of wood boards printed with the system
of
Figure 1;
Figure 3 is a representation of a code word according to a preferred
embodiment of the invention; and
Figure 4 is a representation of the system including a second print head.
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Referring now to Fig. 1, there is shown a schematic representation of the
system
for printing a code on an elongate article.
As mentioned in the prior art, printing a code on an elongate article has been
done
previously. However, the codes so printed are generally large, and there has
not
been previously a motivation to print a redundant code on the article.
However,
with an increase in speed of wood processing plants, and with an increase in,
the
unreadability of the previous codes, there is now a need to provide a system
and
apparatus for printing a redundant code on a elongate article which obviates
the
prior art deficiencies mentioned above.
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Thus, the system 10 of the present invention comprises an ink urvit; at least
one printing head 13 and a controller 15.
The ink unit, in a preferred embodiment, includes an ink reservoir 21,
preferably
of the type "bag-in-box". Other components include a return valve 23, filter
25,
pump 24, air eliminator 29, bleeding valve 31 associated with reservoir 33,
pressure transducer 35, pressure reservoir 37 and main valve 39, all
interconnected in the usual manner. A person skilled in the art will
appreciate that
the above description is for a standard printing circuit, and that variations
are well
within the scope of the present invention.
The printing head 13 includes a filter 41 and at least two, preferably three,
valves
43. In a preferred embodiment, the valves 43 are micro-valves, which are
adapted
to open and close rapidly, spraying droplets of ink. The valves are also
preferably
aligned with each other, and laterally spaced apart.
A controller 15 controls all of the elements of the ink unit 11, and the
printing head
13.
The code that is to be printed takes up a predetermined length (footprint) on
the
piece of wood. The code word is comprised of a plurality of "bits", which may
be on
(presence of the bit) or off (absence of the bit). In a preferred embodiment,
each
bit is a longitudinal line, preferably printed with UV ink. The bits are
printed by the
CA 02519245 2005-09-15
WO 2004/082947 PCT/CA2004/000423
controller sending a signal to the valves to open for a predetermined amount
of
time. In the context of processing wood in a wood processing plant, the valves
are
only open for a few microseconds. However, given the speed at which the wood
travels, this results in each bit being approximately 1 cm long. The footprint
of the
5 code is approximately 25 cm, leaving sufficient time (or space) between
successive bits that there would not be confusion between two successive "on"
bits.
The code word according to a preferred embodiment of the invention is
comprised
of ten bits. However, it will be appreciated that more or less bits may also
fulfill the
objects of the present invention, according to the needs of the particular
user.
As mentioned previously, and as shown in Fig. 2, the code word is printed at
least
twice simultaneously, where each code is laterally spaced from the other one.
In a
more preferred embodiment, the code is printed three times, insuring better
redundancy.
Referring now to Fig. 3, there is shown three code words 51 printed
simultaneously on a piece of wood 100. As can be seen, bit 1 is on, bit 2 is
off, bit
3 is off, bit 4 is on, etc. If the code word were printed only once, errors
could occur
due to variations on the texture of the wood, presence of knots, etc. By
printing the
code at least twice, and preferably three times, the accuracy when reading the
code downstream is further increased.
The ink used for the apparatus is preferably UV as mentioned previously.
Furthermore, advantageous characteristics of the ink include fast drying, so
that
less ink is required, and the ink must be adapted to be readable on wood.
In another preferred embodiment of the invention, the apparatus of the present
invention comprises two print heads.
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The second print head is useful to mark square boards, i.e. boards that have
tendency to rotate 90 degrees, in which situation the printed mark stays on
the
side and cannot be detected by the code reader. The second print head is
preferably mounted at a 90 degrees angle from the first print head.
If the second print head is used, a second main valve 39' is also provided.
Although the present invention has been explained hereinabove by way of a
preferred embodiment thereof, it should be pointed out that any modifications
to
this preferred embodiment within the scope of the appended claims is not
deemed
to alter or change the nature and scope of the present invention.
