Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS FOR DETECTING DEFECTS IN WOOD PROCESSED BY
A PLANER
Field of the invention
The present invention relates to an apparatus for detecting defects in wood,
particularly wood which has been processed with a planer.
Description of the prior art
It is known presently to visually inspect pieces of wood after they
have been processed with a planer, in order to categorise them. This
process is labour-intensive and time consuming, and requires considerable
experience in order to properly grade the wood. Defects such as wane,
twist, crook, skip and bow are evaluated.
Canadian patent application no. 2,237,640 describes an apparatus
and method for detecting surface defects. The apparatus includes surface
shape detection means for obtaining profile trace data of at least one
surface of the article at a cross-section, the profile trace data being
referenced to a reference system, data processing means for deriving a
base reference curve from generally rectangular portions of the profile trace
data and defect detecting means comparing the trace data with the base
reference curve to recognise a defect induced departure of the trace data
with respect to the base reference curve and to produce a defect output
signal.
However, the apparatus described in this application does not
necessarily work as expected since there are no means provided tc
maintain the article in a given position while the article is being scanned.
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Accordingly, the error margin is considerable, and it is extremely difficult
for
the apparatus to provide accurate results.
Summary of the invention
It is an object of the invention to provide an apparatus for detecting
defects which reduces the computational power required to properly
analyse an article by maintaining the article in a predetermined position
while it is being scanned.
In accordance with the invention, this object is achieved with an
apparatus for detecting defects in wood comprising:
- a frame comprising
- an inlet for loading and conveying the piece of wood in the apparatus
in the scanning direction,
- an outlet for releasing the piece of wood from the apparatus;
- scanning means located between the inlet and the outlet for
scanning said piece of wood, the scanning means including an
output for scanned data;
- computer means operatively connected to the scanning means for
receiving the scanned data and processing said data; and
- control means for controlling the inlet and the scanning means and
insuring proper synchronization.
The inlet and outlet of the apparatus according to the present invention
each comprise at least one roller assembly. Each roller assembly is
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designed to hold two opposite surfaces of the piece of wood so that the
piece of wood is conveyed between said roller assembly. The apparatus is
characterized in that each roller assembly is positioned so that when the
piece of wood passes by said scanning means, it is held and guided by at
least two points.
Another object of the present invention is concerned with a method for
detecting defects in wood by using the apparatus of the present invention.
Brief description of the drawings
The present invention and its advantages will be more easily
understood after reading the following non-restrictive description of
preferred embodiments thereof, made with reference to the following
drawings in which:
Figure 1 is a side elevational view of the apparatus according to a
preferred embodiment of the present invention;
Figure 2 is a top plan view of the apparatus of Fig. 1;
Figure 3 is a front elevational view of the apparatus of Fig. 1; and
Figures 4a, 4b, 4c, 4d and 4e are schematic representations of the
defects in wood the present invention can detect.
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Description of a preferred embodiment of the invention
The present invention is directed to an apparatus for detecting
defects in wood. Such an apparatus is preferably placed at the output of a
typical wood planer.
As can be seen in Figure 1, the apparatus 1 includes a frame 10
comprising an inlet 20, an outlet 30 and scanning means 40 located
between the inlet 20 and the outlet 30. The scanning means 40 includes an
output for scanned data.
The inlet 20 comprises at least one roller assembly 21 for securing
the piece of wood as it is being fed into the scanning means 40. The inlet
may further comprise conveyor means for conveying the piece of wood
towards the scanning means.
The outlet 30 also includes at least one roller assembly 31 for
securing the piece of wood as it is being fed out of the scanning means 40.
The outlet may also comprise a platform for receiving the piece of wood
when it is exiting from the scanning means 40.
The apparatus 1 also includes computer means (not shown)
operatively connected to the scanning means 40 for receiving the scanned
data and processing the data; and control means for controlling the
conveyor means and the scanning means to insure proper synchronisation.
One important aspect of the apparatus according to the present
invention is that the inlet and outlet roller assemblies 21, 31 are arranged
so that at any one time, the piece of wood is being held by at least two
points, as will be hereinafter detailed.
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In a preferred embodiment, the inlet includes two roller assemblies
21, as better shown in Figure 1. The roller assemblies each comprises
components for holding and guiding the piece of wood at two opposite
location on the piece of wood, i.e. two points. Therefore, the piece of wood
5 may be held at its upper and bottom surfaces or at its two opposite side
surfaces. This insures proper alignment of the piece of wood throughout its
passing in the apparatus. Therefore, according to the preferred
embodiment illustrated in figure 1, the components of the roller assemblies
21 of the inlet each comprise a top roller and a bottom roller. In this way,
the piece of wood is held and guided on its top and bottom surface by the
top and bottom rollers, i.e. two points. Since the inlet 20 preferably
includes
two roller assemblies, the distance between each of the roller assemblies is
such that it is smaller that the smallest length of the piece of wood that is
to
be fed in the apparatus of the present invention. Advantageously, the roller
assemblies are longitudinally adjustable, so that the apparatus can analyse
pieces of wood of varying lengths.
The inlet includes a U-shaped trough 23 for receiving and guiding a
piece of wood. The U-shaped trough is in direct communication with the
outlet of the planer. The U-shaped trough has a top and a bottom. Each of
them may be provided with roller means (not shown). The width of the
trough and the height thereof are adapted to guide and receive a piece of
wood. Advantageously, the width and the height can be adjusted so that the
apparatus according to the invention can handle pieces of wood of various
size. Consequently, the rollers must be adjustable also to account for
variations in the thickness of the piece of wood.
In the illustrated embodiment, the outlet 30 has the same
configuration as the inlet, except for the fact that the outlet does not
include
the conveyor means since once the piece of wood has passed through the
scanning means, it is ejected at considerable speed. As for the inlet, the
outlet may comprise components for holding and guiding the piece of wood
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at any two opposite location on the piece of wood. Thus, the latter may be
held at its upper and bottom surfaces or at its two opposite side surfaces.
As detailed above, this insures the proper alignment of the piece of wood
throughout its passing in the apparatus. Therefore, according with the
preferred embodiment illustrated in figure 1, the components of the roller
assemblies of the outlet each comprise a top roller and a bottom roller. In
this way, the piece of wood is held and guided on its top and bottom
surface by the top and bottom rollers, i.e. at two points. Further seen in the
illustrated embodiment of figure 1 the outlet comprises two roller
assemblies. It should be noted that the distance between each of the roller
assemblies is preferably such that it is smaller than the smallest length of
the piece of wood that is fed in the apparatus of the present invention.
Advantageously, the roller assemblies are longitudinally adjustable, so that
the apparatus can analyse pieces of wood of varying lengths.
The outlet has a U-shaped trough 33 having a width and a height in
direct communication with the scanning means 40. The width and the
height of the trough (33) are adapted to guide and receive a piece of wood,
and are also preferably adjustable. The U-shaped trough (33) may also
include roller means 31.
Consequently, the invention provides an apparatus which holds and
guides a piece of wood by at least two points as it passes through the
apparatus' top and bottom rollers at the inlet or top and bottom rollers at
the
outlet. In a preferred embodiment of the invention, the piece of wood is held
and guided by at least four points at any time. Therefore, the inlet and the
outlet each include two sets of rollers, each set being separated by a
distance D,, D3 less than the length of a piece of wood. Further preferably,
the distance between the inlet roller adjacent the scanning means and the
outlet roller adjacent the scanning means (D2) is less than the length of a
piece of wood
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It should be noted that in the event where the spacing between two
consecutive pieces of wood fed in the apparatus is not sufficient, the
apparatus may not be able to detect the piece of wood as two separate
entities and provide adequate results. Accordingly, the rollers are driven at
a speed approximately 5% higher than the speed at which said piece of
wood is ejected from the planer.
As mentioned above, the apparatus also includes control means for
controlling the roller assemblies 21, 31 and the scanning means 40 to
insure proper synchronisation. To that effect, the rollers are driven either
directly or through gears or straps 11 by a motor, which is synchronised
with the planer, so that the surface speed of the rollers corresponds to the
speed at which the piece of wood is being ejected from the planer (see
Figure 3). If the inlet means also includes conveyor means, the conveyor
means also are controlled and synchronised with the motor.
In use, the piece of wood is ejected from the planer and engaged by
the inlet means. The inlet means hold the piece of wood and guide it into
the scanning means. The piece of wood travels through the scanning
means and then is guided into the outlet means, which in turn engage the
piece of wood and eject it therefrom for further processing.
The scanning means includes optical means for projecting a beam of
light onto the piece of wood as it travels through the scanning means and
detection means for receiving the beam of light. The detection means are
connected to the output means of the scanning means.
The scanning means preferably include four lasers 41, each of the
lasers being oriented at an angle with respect to each of the four surfaces
of the piece of wood (see Figs. 1 and 2). Therefore, the scanning means is
able to view simultaneously all four surfaces of the piece of wood. Each of
the lasers has associated therewith a detector, for receiving the light shined
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on the corresponding surface of the piece of wood. The data collected by
each of the detectors is transmitted to a computer means which analyses
the data and produces useful information.
More specifically, the data is used to produce a three-dimensional
representation of the piece of wood as it is scanned. The three-dimensional
representation is then analysed according to various defects (Figs. 4a to 4e
are representative of the various defects which can be recognised by the
present invention), and a grading of the piece of wood is then obtained.
The scanning means scan a profile of the piece of wood every one
half inch (1.7 cm) with a tolerance of 1011000 of an inch.
The purpose of the provision of the roller means is to hold the piece
of wood firmly as it is being scanned, which increases considerably the
reliability of the scanning means. More specifically, the accuracy of the
wane, twist and bow of the piece of wood is far better evaluated when the
piece of wood is held as opposed to scanning the piece of wood in a free-
standing mode.
In order to further optimise the apparatus of the present invention and
subsequent processing of the wood, the apparatus may further be provided
with a printer at the outlet thereof, the printed being connected to the
computer means and printing a code on the piece of wood for identification
purposes. Preferably, the printer is an inkjet printer, and even more
preferably an ultraviolet ink printer, so that the wood does not become
visibly marked by the printing operation.
It should be noted that the present apparatus can scan
approximately 150 pieces of ten feet long wood a minute, or at a rate of
approximately 2000 feet a minute.
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It should be also noted that the scanning means can further
advantageously be provided with an X-ray means for evaluating the degree
of rot within the piece of wood or for detecting knots on the piece of wood.
It
should be understood that additional types of sensors can also be used.
The present invention is also concerned with a process for detecting
defects in a piece of wood. The process comprises the steps of
- feeding a piece of wood in the apparatus according to the present
invention;
- measuring the length of the wood and registering defects of the
wood through the scanning means; and
- processing data through the computer means.
Preferably, the results are printed in the form of a code on the piece of
wood at the exit of the scanning means.
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 of change the nature and scope of
the present invention.
