2
BACKGROUND OF THE INVENTION
The present invention relates to an atomized
resin binding method and system for making wood-
shaving panels.
There are already known resin binding methods
for making wood-shaving panels, which methods are
carried out in systems essentially comprising a meter-
ing hopper for metering the wood-shavings obtained
from dried wood, the hopper supplying with a continuous
type of wood shaving flow a ribbon balance which is
suspended from a load cell.
The balance continuously sends the value of
the weight of the wood shavings supplied to the re-
sin binding apparatus to an electronic processor de-
vice which, in order to hold the dry glue/dry wood
shaving weight ratio constant, as set by the operator,
drives the RPM's of a pump which supplies the resin
binding apparatus with a glue mixture comprising
water, a glue, and a curing paraffin mixture.
For making the panels there are conventional-
ly used at least two systems for each panel making
line: a system is used for resin binding the fine
wood shavings, which will form the surfaces of the
panel, whereas the other system is used for resin bind-
-_
ing the larger size wood shavings which will form
the inner portion of the panel.
Downstream of these systems there is provided
a further forming system, preferably comprising four
forming apparatus arranged with an in-line arrange-
ment.
The first forming apparatus is provided for
spreading on a forming ribbon or web a first layer
of fine resin bond wood shavings, while the second
and third forming apparatus are provided for apply-
ing two layers of resin bond wood shavings of larger
particle size, whereas the fourth forming apparatus
is provided for forming the last layer including
fine particle wood shavings.
The thus formed "mattress" is entrained, by
means of the ribbon or web which is continuously
driven under the forming apparatus, inside a conti-
nuous pressing. apparatus, comprising two steel rib-
boas sliding on two plates which are heated to a
temperature which varies from 180°C to 240°C, with
the same speed as the forming web or ribbon.
Under the combined effect of pressure and
temperature, the resin bond wood shaving mattress
is set owing to the curing of the resin, so as to
~~~~~~4~
provide a wood shaving panel.
Such a prior method, on the other hand, is
affected by several drawbacks.
In particular, in winter time, the mattress
temperature will decrease, with respect to a summer
time, of about 20°C, so as to require an increased
baking time and, accordingly, an increased operating
time of the system, in particular from 4.8 sec/mm
to 5.9 sec/mm, for a base thickness of 18 mm of the
finished wood shaving panel.
A~further drawback is that, periodically,
the operation of the system must be interrupted in
order to clean out the resin binding apparatus from
resin and wood powder scales.
Yet other drawbacks are a comparatively low
resin binding efficiency, and the requirement of
using water delivered from refrigerator assemblies
operating at about 5°C, in order to cool the resin
binding apparatus jackets, since, because of the
friction over-heating, the scales tend to set and
deposit on the inner walls of these jackets, so as
to cause the apparatus to be obstructed.
The mentioned forming apparatus, moreover,
are also fouled because of a not optimal distribution
of the binding resin on the wood shavings.
Yet another drawback is the requirement of
using an expensive paraffin emulsion in order to re-
duce the amount of water absorbed by the finished
product.
SUMMARY OF THE INVENTION
Accordingly, the aim of the present invention
is to overcome the above mentioned drawbacks, by
providing such a system and method allowing to great-
ly reduce the baking time, with a consequent great
increase of the making efficiency, and which do not
involve any interruption of the making operation in
order to clean the resin binding and forming appa-
ratus.
Within the scope of the above mentioned aim,
a main object of the present invention is to provide
such a resin binding method and system which allow
to obtain a very great operating efficiency, with
a consequent improvement of the mechanical charac-
teristics of the finished wood shaving panel.
Another object of the present invention is
to provide such a resin binding method and system
providing an improved spreading of the mattress by
the forming apparatus,. with consequent improved thick-
CA 02094940 2002-08-15
E
ness tolerances of the raw panels at t:he outlet of
the pressing machine.
Yet another object of the present. invention
is to provide such a method and system which allow
to overcome the requirement of using any paraffin
emulsion.
Yet another object of the present invention
is to provide such a method and system which do not
include refrigerators for cooling the water circula-
tion jackets of the resin binding apparatus.
According to one aspect of the present inven-
tion, the above mentioned aim anei objects, as well
as yet other objects, which will become more appa-
rent hereinafter, are achieved by an improved system
for making wood shaving panels, characterized in that
said system provides for the use of a high tempera-
ture fluid which preferably comprises pressurized
steam, said fluid being conveyed intr> a resin bind-
ing apparatus in order to increase the temperature
of the wood shavings, glue materials and chemi-
cal aids, which are so mixed as to provide a~ wood
shaving panel.
CA 02094940 2002-08-15
6a
More specifically, the present. irnvenf:ion provides a
system for maki ng wood ~:havi ng panel s c:ompri si ng feedi ng
means for feeding a wood shaving mass and a resin binding
apparatus to which the wood shaving mass is supplied to be
bound by glue materials and other chemical adjuvanis,
wherei n the system further compri ses injector mean s for
i n jecti ng a hi gh temperatrare pres ~uar°i geed f 1 ui d i nto the
wood shaving means conveyed to the resin binding apparatus
to increase the temperature of the wood shaving mass, the
g1 ue materi al s and the cl~emi ~a l ad,juvant.s , whi ch are so
mixed as to provide a wood shaving panel.
The present i event i on t~l so prvovi des an atomi zed resi n
binding method for making wood shaving panfuls, wherein the
method comprises the steps of simultaneously supplying heat
and an even and di ffused dynami c pul se to a mi xture of wood
shavings, glue and chemical adjuvants, subjected to a
turbulent motion, produced by a stirrer ope:~rating inside a
resin binding apparatus, and providing the heat and dynamic
pulse by injecting into the resin binding <apparatus a
pressuri zed water steam, t:he steam bei rag super-heated and
pre-processed upstream of the loading zone of the mixture,
with respect to a feeding direction of the mixture being
stirred.
BRIEF DESCRIPTION OF THE DRAWINGS
Further characteristics and advantages of
the invention will become more apparent hereinafter
from the following detailed disclosure of a preferred,
though not exclusive, embodiment thereof, vahich is
illustrated, by way of an indicative, but not limi-
tative example, in the accompanying drawings, where:
Figure 1 illustrates a schematic diagram of
a conventional system for continuously pressing and
making wood shaving panels;
Figure 2 illustrates a schematic diagram of
a prior resin binding system for making panels;
Figure 3 illustrates a schematic diagram of
other parts of a system for continuously making
wood shaving panels;
Figure 4 illustrates a schematic diagram of
a resin binding system for carrying out the method
according to the present invention;
Figure 5 is a schematic cross-sectioned side
view illustrating a vessel for steam processing wood
shavings according to the invention;
and
Figure 6 is a top cross-sectional view illus-
trating the above vessel coupled to a steam condensa-
to separating device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the figures of the accompany-
ing dravrings, and, more specifically to Figure 2,
prior resin binding systemsfor making wood shaving
panels conventionally comprise a dry wood shaving
metering hopper 1 vrhich supplies with a continuous
flow of dry wood shavings a ribbon balance 2, sus-
pended from a load cell 3.
The balance 2 is provided for continuously
sending the data related to the vreight of the wood
shavings supplied to the resin binding apparatus,
to an electronic processor, which, in order to hold
the dry glue/dry wood shaving weight ratio constant,
as it has been set by the operator, will control the
RPM's of a pump 5 which supplies the resin binding
apparatus 4 with a glue mixture comprising, in parti-
cular, water, a glue and a curing paraffin emulsion.
For each layer of the mattress being formed
along the making line of the wood shaving panel
there are conventionally used one or more resin bind-
ing systemsof the above disclosed type.
Some resin apparatus are used for resin bind-
ing the fine wood shavings, which will form the out-
er surfaces of the panel, and one or more of said
g
resin binding apparatus will be used for resin bind-
ing, the wood shavings having a larger particle
size, and which will form the mattress or mattresses
provided for forming the inner portion of the panel.
Downstream of the above disclosed apparatus,
there is provided a forming system 6 which essential-
ly comprises four forming apparatus 7, 8, 9, 10 ar-
ranged in an in-line arrangement.
The first forming apparatus 7 is provided
for spreading on a forming ribbon 11 a first layer
of fine resin bond wood shavings, while the second
8 and third 9 forming apparatus are provided for
forming two resin bond wood shaving layers of lar-
ger particle size, and, finally, the first forming
apparatus 10 is provided for forming the last layer
of fine wood shavings.
The thus formed mattress 12 is entrained, by
means of the forming ribbon 11 which is continuously
driven under the above forming apparatus, inside a
continuous pressing apparatus 13 comprising two steel
webs or ribbons 14 sliding on heated plates 15 with
the same speed as the forming ribbon 11.
Under the combined effect of pressure and
temperature, the resin bond wood shaving mattress 12
to
is set, owing to the curing of the resin, so as to
provide a finished wood shaving panel.
As stated, however, the above prior making
method is affected by several drawbacks.
In particular, in winter time, the tempera-
ture of the mattress 12 decreases, with respect to
the summer time temperature, of about 20°C, thereby
involving a corresponding increase of the baking
time and, accordingly, of the system operating time
from 4.8 sec/mm to 5.9 sec/mm, for a base thickness
of 18 mm of the finished wood shaving panel.
With reference to Figure 3, 4, 5 and 6, the
nebulized resin binding system and method according
to the present invention substantially provide to
simultaneously subject to heat and an additional
dynamic pulse, of even and diffused nature, the mix-
ture of wood shavings, glue and chemical aids which
is subjected to a turbulent motion provided by the
stirrer 16 operating inside the resin binding appa-
ratus 4.
In particular, the. heat is applied by inject-
ing pressurized steam (at a preset pressure from
0.1 to 13 bars) and, in a preferred embodiment, the
steam is super-heated to a temperature which can be
CA 02094940 2002-08-15
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preset by the operator (at 1?_0-2001°C1 <~nd being more-
over pre-processed.
This is preferably obtained by means of a
steel injector 17, arranged perpendim.nlarly to the
flow direction, <~nd proviried with a nozzle having
an inner diameter of 8-1() mm, at a distance of about
300 mm from the inlet hopper 18 in the resin binding
apparatus, at a short distance upstre<rrn c~f the in-
jectors ( not shown ) for 1 oath ng the g1 uei rig m. xture > wi th
respect to the material advancement direc:t:ion as impressed
by the sti rrer 16.
The mentioned pre-processing is performed in-
side a suitable ~>teel c:ylindric vessel., or turbomixer
19, which, according to a preferred, i:hough not ex-
clusive,embodiment has an inner diamei:er ~ - 350 mm,
a height of about 600 mm and a thickness of about
mm.
Thi s turbomi xer vessel 19 cornpri ses t:wo noz-
z1 es 20 and 21 vahi c:h are arranged tangenti al 1y of
the vessel surface and, in its inside, d4flet::-
ing fins 22 and 23.
~1oreover, coupled to the vessel there is pro-
vided a condensate separating device 2~, arranged up-
stream of the vessel and in which there are separated
CA 02094940 2002-08-15
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the steam fractions which v~ould deposit on the ducts
of the system.
hlore specifically, t:he nozzle 20 allows super-
heated steam to be introduced into i:he vessel, where-
as the nozzle 21 is provided for introducing the
several chemical aids or a~ljuvants.
A mixing of the super-heated steam and the
chemical adjuvants is performed at the central re-
gion of the vessel, because of the provision of the
above mentioned deflecting fins 22 and 23 which
operate so as to hold t:he chemical <idjuvants sepa-
rated from the super-heated steam flow, during the
first step in which these adjuvants are conveyed to
the vessel for processing the steam.
In particular, the chemical adjuvants com-
prise surface active agents, preferably ethylene and
methylene glyccles.
These adjuvants are used for modifying the
surface condition of the water so as to properly
control the thermal balance of this water during
the different year seasons, in the pressing step.
f~loreover, there are also used catalyzer sub-
stances in order to accelerate tfoe curing of the
glueing mixture and there are also used cleansing
CA 02094940 2002-08-15
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sub~;tanc:es.
The latter are used, in toartic:ular, vFor clean-
ing all of the downstream arranged apparatus.
There are also a~E~d water-repellent. substances, in
order to provide the wood shaving panel with an improved
resistance against water.
From the atomized mixture formed as above
disclosed, having even physical characteristics and
conveyed through said injector 17 into the resin
binding apparatus 4, there are transferred the con-
densation heat and momentum, by impact, to the dry
wood shavings, which are progressively impregnated
by the glueing mixture, under the effect of mutual
slipping, impacts and of the turbulent motion oc-
curring between the several substances introduced
into the resin binding apparatus 4.
The main feature of the present invention
consists substantially of the injection of the super-
heated steam, which allows to achieve sf_~ver<~l great
advantages.
Firstly, as it is introduced into the resin
binding machine, the steam will expand, so as to
heat the glueing mixture and render it more "malle-
able".
CA 02094940 2002-08-15
1 ~~
The steam, moreover, causes the wood pores
to also expand, so as to allow the glue and other
chemical adjuvants to properly enter these pores.
Accordingly, it is obtained an improved bind-
ing efficiency, which will provide the finished wood
shaving panel with very good mechanical character-
istics, as well as a great resistance against ageing
and moisture.
Moreover, the steam provide:; an o~otimal s;pread-
ing of the chemical adjuvants throuc3h the mattress,
without negatively affecting the catalysis of the
binding resin.
The introduction of super-heated steam into
the resin binding apparatus, provides moreover a
good lubrication of its walls, preventing them from
being fouled, and this without t:he requirement of
using cooled water, since exclusively tower water
at 30°C is used, as necessary for cooling the water
jackets of the resin binding apparatus.
Moreover, it is provided to actuate, by means
of the steam progressively condensing on the inner
wall of the cylindric jacket 4' of the resin bind-
ing apparatus 4, lubricating action on the wood shaving 'flow toward
.. - 15
the outlet 29 to the forming station 6.
One of the main advantages of the present in-
vention is that the steam provides a great reduction
of the baking time.
In fact, the super-heated steam will cause,
in a very advantageous manner, and mainly in winter
time, an increase of the mattress temperature of
about 20°C, with a corresponding increase of the
operating efficiency of about 20°/, in the term of
the amount or yield of made panels.
A further important aspect of the invention
is that the disclosed method also allows to obtain
a great reduction of the formaldehyde contents of
the finished product.
From the above disclosure it should be appa-
rent that the invention fully achieves the intended
aim and objects.
The invention as disclosed is susceptible
to several;modifications and variations, all of which
will come within the scope of the inventive idea.
Moreover, all of the details can be replaced
by other technically equivalent elements.
In practicing the invention, the used mate-
rial, provided that they are compatible to the in-
. _ is ~~~494~
tended use, as well as the contingent size and shapes
can be any according to requirements.
