Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Present Invention
The present invention relates to a method and to an apparatus for
working sheets of wood or of fibrous material having a porous structure
which is especially suitable for producing veneers of artificial wood. More
particularly the invention relates to a method which enables the porous
structure of any type of natural wcod to be recreated artificially, starting
with common wood of poorer quality in order to produce veneers or for
other purposes of use of natural wood.
Various methods have been proposed in the prior art for the production of
sheets of wood veneer imitating natural wood. The first attempts involved
the formation of suitable blocks by superimposing and glueing laminates
of wood obtained by tangentially slicing a log. The block was shaped
appropriately in a press, superimposed and glued to other identical
blocks until a final block was obtained from which sheets of wood veneer
were then cut, according to predetermined cutting angles. The shape of
the block, slant of the cutting angle, dyeing of the sheets and the possible
use of coloured glues, enabled the grains and porosity of wood to bs
imitated to a certain extent~ In practice the structure of the veneer
remained substantially similar to the wood structure of the sheets of
material used for forming blocks.
This technique is described for example in the patents US 3 312 582 andUS 3 418195.
3 2 1 9 9 7 6 3 ::
Methods of this kind provided a fairly rough imitation both of the grains
and of the porous structure of natural wood. The level of commercial
success was hence very low in relation to the obviously artificial
appearance of the individual sheets of veneer, apparent even to a non-
skilled in the art. The method was moreover extremely complex, with
negligible aesthetic results, which were not always totally repeatable.
Other methods were also proposed which involved the formation of
blocks by means of a different combination and superimposing of
different wood sheets or of laminates, some of whose fibres were
orientated perpendicular to the plane of the sheets themselves. By
means of an appropriate composition of the blocks and their configuration
in the moulds, it was possible to place in the required positions layers
with fibres orientated in various ways, longitudinally and perpendicular to
the sheets of veneer cut from the block itself, in this way achieving a
better imitation of a wood structure reproducing the various layers of
growth of a natural trunk.
Although these systems have given good results, they nevertheless
provide a porous structure of the veneer sheets whose appearance is not
entirely natural in that layers with fibres orientated perpendicular to tha
plane of the sheet itself alternate in the reconstructed block, contrarily to
the longitudinal direction of the fibres in a natural trunk. Moreover there is
no possibility of controlling the shape, arrangement or dimension of the
individual pores or of modifying these characteristics according to the
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varying production needs in order to obtain the porous structure of the
type of wood to be imitated.
Finally the process of reconstructing the block from which the final veneer
is to be cut is still relatively complex and complicated.
.
The object of the present invention is to provide a method for the
formation of sheets of fibrous material which have a porous structure of
any type whatsoever of natural wood, which can be obtained in a
repeatable and perfectly controlled manner.
More particularly the object of the present invention is to provide a
method for the formation of porous structures on sheets of fibrous
material, as a perfect imitation of the porous structures of natural wood,
by means of which the fibres of the individual sheets can be maintained
parallel in the natural planes wherein they lie, at the same time achieving
an imitation of whatsoever porous structure so as to improve the quality
of the veneer which can be obtained in this way to a considerable extent.
Yet a further object of the present invention is to provide a method and
apparatus as defined above, which not only allow high quality results to
be achieved when imitating any type of wood, but at the sama time allow
a high degree of control of the production process, and repeatability,
continuity and reliability of the result achieved.
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Summary of the Invention
The above can be obtained by means of a method for the formation of
porous structures in sheets of fibrous material to imitate porous
structures of natural wood, according to the features of the main claim. - ~;
According to the invention, a portion of a sample surface of a porous ;;
structure of a natural wood to be reproduced is analysed, taking note of
information relating to the shape and coordinates of characteristic points ;~
of the lines defining the shape of the individual pores. Said information is
stored in a process iogic unit comprising a computerised design program,
and at the same time data are provided to indicate the dimensions of the
pores. The data and information stored in this way are then converted ~ ~ ;
into control signals for a computerised engraving system, which
reproduces the memorised porous structure of the sheet of natural wood,
engraving it continuously or discontinuously on fibrous material in sheets
or in the form of a strip, which can be used later in the preparation of
artificial veneers according to systems in themselves known, for example
from the prior documents previously mentioned. ~ :
Brief Description of th~Drawings
These and further features of the method and apparatus according ta the
present invention are to be illustrated in greater detail hereinunder with
reference to the examples in the accompanying drawings, in which~
Fig. 1 represents a process diagram according to a possible embodiment n
of the present invention; -
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Fig. 2 is a plan view of an enlarged detail of a sheet of natural wood,whose porosity must be imitated by operating according to the process
diagram in figure 1;
Fig. 3 is a plan view of a further enlarged detail of a pore of the porous
structure of figure 2; ~ .
Fig. 4 is a sectional view of the pore taken along line 4-4 of figure 3;
Fig. 5 is a sectional view of the pore taken along line 5-5 of figure 3;
Fig. 6 is a plan view of a sheet of fibrous material on which the fibrous
structure of the wood type to be imitated has been reproduced, according
to the method of the invention;
Fig. 7 is a plan view of a sheet of fibrous material on which a fibrous
strcture of a wood has been reproduced according to a variant of the
~nethod according to the invention.
Detailed Description of the Invention
With reference to figure 1, A denotes a sheet of natural wood of a
generical wood type whose porous structure is to be imitated for the
production of an artifical veneer.
As can be seen in the same figure 1, and in the detail in figure 2 which
represents an enlarged view of a portion of surface B of the sheet of
natural wood A, the fibrous structure of the latter has, in the example
shown, zones B1 having a very compact fibrous structure, with few pores,
alternating with zones B2 having a high degree of porosity, according to
the wood layers belonging to the various periods of growth of a natural
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7 2 1 ~ 9 7 6 3
trunk.
After having isolated a portion C of a sample surface of a porous zone
B2, whose fibrous structure must be reproduced and used to achieve a
.
perfect imitation of the similar porous structure of the natural wood, a
determination is carried out of the positions and coordinates of
characteristic points of the lines representing individual pores P in relation
to specific reference cartesian axes, storing these data and information in
a process logic unit or microprocessor 10, indicated schematically in -~
figure 1 .
This can be achieved for example by analysing the porosity of the sample
surface C by means of a scanner, or directly by an operator who uses for
example a pen for writing 11 or by another suitable manner. -
During the manual or automatic scanning of the individual pores P of the
portion of sample surface C, all the information required for defining the
position and distribution of the individual pores is obtained by means of
the coordinates of the various points or characteristic points which form
the lines representing the pores themselves.
These data are then stored in the data memory of the process logic unit
- . .
10, into whose main memory a suitable computerised design program
(CAD) has been loaded previously and which is appropriate for this ~ ~:
purpose. ~ ~ "
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Since each pore P, as shown in figures 3, 4 and 5, is characterised, inaddition to its shape and position, also by its length L1, width L2 and
depth L3 which can be constant or vary, by means of the control
keyboard or another device, for example a mouse 12, the operator enters
into the memory of the microprocessor 10 all those necessary data which
indicate the real dimensions of the pores to be reproduced, with the
possibility of adapting them or changing them. Thus an image will
gradually be created on the screen of the porous structure to be formed,
which may be adjusted or modified from time to time until a perfect
imitation of the natural one is obtained.
Onca the process unit 10 has stored and processed, on the basis of its
design program, the information and data relating to all the pores of the
sample of area C analysed, these data must be converted into signals
suitabls for the functioning of a computerised engraving system. This
conversion may ba performed directly by the same process logic unit 10
if appropriate circuits are provided or, as indicated schematically in figure
1, it can be performed by a second process logic unit 13 provided with a
control keyboard 14, connected directly and serially to the process unit
10, as indicated by the dotted line 15, or by means of a suitable magnetic
medium 16 indicatedschematically. !
The conversion of these data into signals for controlling the computerised
engraving system may be controlled or modified if required by varying
appropnate working parameters in the second process unit (CAM) for
9 2 1 0 ~ 7 6 3
controlling the apparatus. Therefore the signals in output from the
process unit 13, by means of a suitable interface 17, are sent to the
computerised engraving system 18 to reproduce in a unique or
repeatable manner on the sheet of material C1 of a different wood type,
of poorer quality, the same porous structure of the sample of surface C of
the wood structure of the type which is to be imitated.
: `
The sheets C1 with the engraved porous structure may then be used in a
normal process of forming blocks for the production of an artificial veneer,
in a manner in itself known. Engraving of the pores (continuously or
discontinuously) may be carried out at any point of the process of
producing the vsneer, for example immediately after the tangential slicing
or the radially cutting of the log and before possible dyeing, or
subsequent to the phase of dyeing which precedes the formation of the
block from which the new veneer will in the end be cut.
. . ;.:
The engraving of the porous structure on the sheet C1 can be performed ~ m
using any computerised engraving system, be it mechanical or of another
kind. For example tests carried out have shown that it is extremely
advantageous, in terms of reliability and rapidity of execution, to use
engraving systems which adopt sources of highly concentrated light
energy in order to generate pulses of variable intensity and duration,
such as to produce localised combustion of the fibrous material in order
to achieve engraving of the sheet, faithfully copying and reproducing the
effect of porosity of the original sample according to the processing ~ ~;
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performed by the process logic units 10 and/or 13 mentioned previously.
By way of an example, good results have been achieved by using
devices capable of generating and strongly amplifying radiations of
optical frequency, of the stimulated radiation emission type. By choosing
appropriate optical frequencies of operation and the frequencies of
. ~.
emission of the pulses of light energy, it is possible to achieve excellent
results for any type of wood to be imitated. Therefore the process logic
unit 13 must control the energy generator 19 and the actuator or
actuators 20 which direct and control the ray for engraving the porous
structure on the sheet C1. Figure 6 in the drawings shows the final result
on the sheet C1.
By following the procedure described above, it is therefore possible toanalyse a whole series of samples of porosity of the same type of wood
ancUor different wood types, storing them in one of the process units or
on appropriate magnetic media which may be used from time to time
according to production needs. In every case a method and apparatus
will be provided for the formation of porous structures in sheets or strips
of fibrous material, which will enable any porous structure of natural wood
to be imitated to perfection, always maintaining a longitudinal
arrangement of the pores in substantially tangential planes in'the
reconstruction of a hypothetical trunk of wood from which an artificial
veneer is subsequently cut.
The method according to the invention therefore enables a greater
11 2.L~9763
degree of approximation to be achieved in the imitation of a veneer of
natural wood, maintaining control and a high degree of reliability in the
production process, with the possibility of adapting the method for
producing porous structures, however configured, directly on rotary-cut
wood, or on veneers forming the end product. This is shown by way of an
example in figure 7, where a porous structure F with a design of the
various grains of the wood has been reproduced on a generical sheet of
wood E. This can be achieved for example by combining data and
information of a sample of porosity of a type of wood previously stored in
the memory, with a particular grain design to imitate a specific type of
wood, specially created or copied from a sample of natural veneer.
~ - .
The intention therefore is that the general principle of the present
invention consists in reproducing by engraving porous structures of
natural wood on sheets of fibrous material of another kind, which can be
used in the production of artificial veneers with an improved appearance.
Therefore what has been said and shown has been given merely as an
illustration of the innovative principle which is claimed.
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