Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Field of the Invention
Present invention relates to a panel product,
more particularly, the present invention relates to a
substantially uniform density ribbed waferboard panel
having ribs along one side and a plane surface on the
opposite side.
8ackground to the Present Invention
Structurally reinforced wood particle panels
utilizing the shape of the panel itself to provide the
reinforcement, are known. A structurally reinforced panel
is disclosed in the U.S. Patent 3,083,128 issued March 26,
1963 to Herrington et al. which disclosed a lignocellulose
hardboard panel having improved stiffness and dimensional
stability and wherein one flat surface is flat or planer
and the opposite is formed with a plurality of spaced ribs
having a density very significantly lower than the density
of the depressed areas (valleys) therebetween. The hard-
bodrd panel is produced by pressing a uniform thickness
mat so that the depressed areas are squeezed to a thinner,
final thickness and thus higher density than the ribbed
areas.
Obviously, reinforcing ribs should be as strong
as possible if they are to provide a maximum degree of
reinforcing. This was recognized by Herrington et al. and
in an attempt to provide better reinforcing, Herrington et
al operated a press in a manner to produce skins on the
surface of the hardboard so that the density adjacent both
surfaces were significantly higher than the density in the
middle of the board. Obviously, this technique would have
limited effect which, in part, would depend on -the thick-
ness of hardened surface layer.
The Herrington et al. pdtent relates to a hard-
board formed by the so-called Masonite process wherein the
sheet is formed from a specially produced pulp using a wet
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laying process which lends itself better to deformation
and the embossing techniques and the surfacing hardening
of the material as described.
Chipboard when it is to be ernbossed is yenerally
5provided with a embossing layer of fine chips as taught,
for example, in the U.S. Patent 3,793,125 issued February
19, 1974 to Kunz. In this patent, wafer or chipboard is
decorated by applying d layer of fine chips to the
surface, overlaying a fine chip layer with a decorative
10deformable layer and then pressing using a relief carrier.
U.S. Patent 4,061,813 issued December ~, 1977 to
Geimer et al. discloses the wood-based building component
made of fibers or particles adhesively secured together
and shaped in a single pressing to form a flat panel with
15a plurality of spaced specially shaped channels formed
therein.
It has also been taught to form a corrugated
shaped board by using a special press on a mat of wood
wafers to simultaneously shape and press to consolidate
20the mat into the corrugated configuration. The press
required to do this is relatively complicated (see U.S.
patent 4,616,991 isswed October 14, 1986 to Bach).
Of the above described boards only the embossed
hardboard of Herrington et al. described in U.S. Patent
253,083,128 has a flat surface on one side and reinforcing
rib on the other. However, as the above described, the
board of this patent is a hardboard made by wet processing
and has significantly different average densities in the
skins and center of the panel and in the valley and the
30rib areas.
U.S. Patent 4,084,996 issued April 18, 1978 to
Wheeler describes a plywood panel provided with a plural-
ity of embossed parallel grooves formed therein by a caul
plate having a plurality of spaced ridges corresponding to
35the desired grooves in the panel.
.
.
U.S. Patent 43308,308 describes a ribbed,
reinforced fiberous material panel formed, for example, of
fiberglass. It is not clear in the patent how the ribs are
formed. In any event, the resultant structure is consoli-
dated by heat only without the application of pressure.
The patent shows a fiberous product with integral ribs
that presumably are of essentially the same density as the
valley areas therebetween, however, as above described the
product is a cured fiberglass product not a pressed ligno-
cellulose product.
The nonuniform application of pressure when
uneven surfaced panels are being consolidated and formed
by pressing results in major differences in the densities
of various areas of the consolidated product, i.e. the
areas pressed the most (thinner areas) have the highest
densities while for reinforcing the reverse is more
desirable.
Brief Description of the Present Invention
It is an object of the present invention to
provide a rein~orced waferboard product having reinforcing
ribs consolidated therein by pressing and where in the
density of the board is essentially the same in the ribbed
areas as in the areas between the ribs or if desired the
rib areas may be of higher density than the areas there-
between.
Broadly the present invention relates to a
particleboard panel comprising a board with one surface
thereof substantially planar and an opposite surface
thereof having integral ribs separated by valleys, said
board being formed by pressing a mat of said particles
said mat having ribbed areas of greater thickness spaced
by valleys of lesser thickness, said board after pressing
and consolidating having a density in the rib areas wlthin
15% of the density ln the valley areas.
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. .
Preferably, the wood particles are wood ~lafers.
More preferably7 the wood wafers will be oriented at least
in the layers adjacent the faces of the board with their
longitudinal axis (grain direction) substantially parallel
to the longitudinal axis of the ribs.
Broadly, the present invention also relates to a
method of making consolidated wood particleboard having
one surface thereof ribbed comprising laying wood
particles coated with binder on a flat supporting caul
plate to build up a uniform mat of preselected thickness,
applying further of said wood particles coated with binder
on said mat at spaced locations thereacross to form spaced
projections of said particles on said mat, simultaneously
pressing said mat and said projections in a press having a
platen contoured to mate with the said projections and
said mat between said projections to simultaneously
compress and consolidate the wood particles and binder in
said mat and said projections substantially to the same
degree to produce a board having one substantially planar
~0 surface and the opposite surface thereof with ribs, said
board in the area of said ribs having an average density
within 15% of the average density of the said board in the
areas between said ribs and preferably within 10%.
Preferably, the projections will be in the form
of substantially parallel spaced continuous ribs.
In one embodiment of the present invention the
density in the areas of the projections or ribs on the
consolidated board will be substantially the same as the
density in the areas therebetween and in another embodi-
ment the density in the areas of the projections will begreater by between 5% and 15% (preferably 5%-10%) than the
density in the areas therebetween ~the valley areas).
Preferably, the wafers forming at least the
surface areas of the board will be oriented to substan-
tially align their longitudinal axes (grain direction)parallel with the longitudinal axes of the ribs.
Brief Description of the Drawings
Further feature objects and advantages will be
evident from the following detailed description of the
preferred embodiments of the present invention taken in
conjunction with the accompaning drawings in which:
Figure 1 is an isometric illustration of a
ribbed panel formed in accordance with the present
invention.
Figure 2 is a schematic side elevation illus-
trating the forming heads of the present invention.
Figure 3 is a schematic illustration of thedeflectors used to lay the ribs on the mat and provide the
completed layup.
Figure 4 is a section along the line 4-4 Figure
2.
Figure 5 is a section along the line of 5-5
Figure 2.
Figure 6 is an end view illustrating the press
with two different versions of upper platen showing the
ribbed layup in position for pressing.
Figure 7 indicates the dimensions of the consol-
idated board and of the upper platen used for consolida-
tion in the press.
Figure 8 is a partial end view of a laying head
for forming one of the ribs and incorporating a particle
orienting device.
Detailed Description of the Present Invention
.
Generally, the present invention is concerned
with the manufacture of a waferboard and thus the
particles used to form the board will be conventional wood
wafers as used in manufacture of waferboard or oriented
strandboard or the like. If a high strength product is to
be produced it is preferred to use relatively long wafers
or strands exceeding about 10 inch in length with their
longitudinal axis (which ~/ill normally be parallel with
the grain direction in the wafer or strand) substantially
parallel to the longitudinal axis of the board as taught,
for example, in U.S. Patent 4,610,913 issued September 9,
1986 to Barnes.
A board or panel 10 constructed in accordance
with the present invention is provided with a main body
portion 12 substantially rectangular in cross section and
having a planar surface 14 (facing do~nwardly in Figure 1)
and an opposite substantially parallel surface 16 having
ribs 18 projecting therefrom. These ribs 18 extend longi-
tudinally of panel 12 and have, in the illustrated
arrangement, an upper surface or free surface 20 substan-
tially parallel the planar surface of thè panel 12. Thefree surface 20 is connected to the surface 16 of the
panel 12 via the sidewalls 22 sloping to the surface 16
(and 20).
Interposed between the ribs 18 are valleys 24
having as their bottom surfaces the surface 16 of the
panel 12. The ribs 18 are uniformly spaced and are
substantially of uniform size as are the valleys 24, in
the arrangement illustrated.
The density of the rib areas 18 each include the
rib 18 itself plus the area 26 shown in the imaginary
rectangle illustrated or outlined by the dotted lines in
Figure 1, i.e. ~hrough the thickness of the panel 12
beneath each rib 18 is preferably substantially the same
as the density of the panel in the areds of the valley 24,
i.e. the areas between the areas 26. If desired density
in the rib areas (26 and ribs 18) may be slightly higher
than the density of the panel in the areas of the valleys
24, the differences in densities in the rib areas and the
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valleys 24 must not be too great or the integrity of the
board may be affected. In any e~ent, the density of the
rib areas of the consolidated board will be within 15% of
the average density of the consolidated board in the areas
24 between the ribs.
It is preferred that the densities of the
consolidated board in the rib and valley areas be substan-
tially or essentially the same, however, for some applica-
tions it may be appropriate to make a clear difference
between the densities (strengths) of the rib and valley
areas of the board. In some cases the ribs may be delib-
erately made of higher density, 5% to 15% higher, prefer-
ably 5%-10% higher to increase the strength in the ribbed
areas to make the board more resistant to bending without
disrupting the integrity of the board.
To produce the board of the present invention a
uniform thickness mat of wafers is first laid and then a
separate mat or projection for each of the discrete ribs
18 is superimposed thereon. This technique is illustrated
schematically in Figure 2 wherein a first forming head 28
lays the wafers to form a substantially uniform thickness
mat 30 which is eventually consolidated into the panel 12
and the second forming head 32 forms a plurality of the
spaced discrete projections or rib forming mats 34 onto
the upper surface 36 of the mat 30. These mats 30 and 34
are formed by depositing the wafers onto a plurality of
discrete caul plates 38 moving in the direction of arrow
40 beneath the laying heads 28 and 32.
It will be noted that the projections or rib
forming mats 34 are laid directly on the top surface 36 of
the mat 30 and thus the wafers of the rib projections 34
interact with the wafers of the main mat 30 as an integral
part thereof.
The projections or rib forming mats 34 are
produced by a special forming head having curved baffles
40 directing the wafers through spaced narrow openings 42
to for~ the projections 34 adapted to be consolidated to
form the ribs 18. The openings 42 are slightly narrower
than the desired base on the projections or rib forming
mats 34 so that the wafers forming the projections 34 fall
onto the surface 36 and build up a tapered projection in
accordance with the angle of repose of the wafers.
It is preferred that the wafers be oriented,
i.e. have their longitudinal axis substantially parallel
to the lcngitudinal axis of the panel 12 (and ribs 18) and
for this reason the laying head 28 may be provided with a
suitable orienting section 44 to orient the wafers as they
fall to form the mat 30. Similarly, forming head 32 may be
provided with discrete orienting devices 46 (Figure 8)
positioned beneath the opening 42 to orient the wafers
falling through the passages or slots 42 so that the
wafers forming the projections or rib forming mats 34 are
also oriented in the same manner as the wafers forming the
main mat 30. In many cases, a separate orienter 46 may
not be necessary as the tapered baffles 40 and the widths
of the slots 42 may combine and function as orienters and
orient the wafers passing therethrough and forming the
projections or rib forming mats 34.
The platens 38 are flat as illustrated in
Figures 2, 4, 5 and 6 and have planar surfaces so that the
bottom surface of the mat 30 (see Figures 4 and 5) corres-
ponds with the upper surface 48 of the platen 38 and forms
the planar surface 14 of the finished product 10.
It will be apparent that a special press is
necessary to press the layup of the mat formed of a combi-
nation of a substantially standard uniform thickness mat
30 having projections or rib forming mats 34 superimposed
thereon. This is provided by an insert 55 fixed to bottom
surfaces 52 of each press platen 54 which forms the top
surface of the press opening. The insert 55 is formed with
alternating lands 56 and valleys 58 positioned and shaped
so that the valleys 58 generally correspond with the
projections or rib forming mat sections 34 and the land
areas 56 are position therebetween as will be described in
more detail hereinbelow.
The bottom surface of the upper press in Figure
6 has an insert 55 in which the lands are provided by
discrete land inserts 56 secured directly to the platen 54
with the surface of platen 54 forming the top of the
grooves or valleys. The insert 55A shown on the bottom
surface of the upper platen for the lower press opening is
a continuous insert with grooves formed therein to form
the lands 56 and valleys 58.
It will be apparent that it is important to
align the projections or rib forming mat sections 34 with
the grooves or valleys 58 to obtain proper pressing and
consolidation of the mat 30 (34) into the consolidated
panel. It is important to apply heat to the mat 30 (34) as
uniformly as possible so that the adhesive which typically
will be a phenol formaldehyde-type adhesive coating the
~5 wafers may cure uniformly through the mat and form a
uniformly cured board or panel 10. Thus, it is important
that the insert 55 or 55A be in and remain in direct
communication with the surface 52 of the platen 54 so that
heat may be readily transferred from the platen 54 to the
insert 55 or 55A and the insert remains at essentially the
same temperature as platen 54 and functions in effect is
an integral part of the platen for heat transfer
purposes, It is also important that the insert 55 or 55A
be a good heat conductor to ensure the proper transfer of
heat from platen 54 to mat 30 (34). If a nonuniform
thickness platen is moved in and out of the heated press
with the mat there will likely be nonuniform heating of
the mat as the thicker areas of the platen will not trans-
fer heat as quickly as the thinner areas of the platen.
The precise dimensions of the mat 30 (34) are
not critical, however, they should be matched reasonably
well with the corresponding dimensions in the insert 55.
As shown in Figure 7 the width of the top of the projec-
tions or ribbed forming mat sections 34 indicated as W
correspond with the width of the base of the groove 58 in
the insert 55 (or 55A). Similarly, the width of the
valleys between the rib forming areas 34 is indicated by
the distance X correspond with the width of the land areas
56. However3 the height h, i.e. difference in elevation
between the land areas 56 and valleys 58 is less than the
height of mat sections 34 above the mat 30 since these mat
sections 34 must be compressed to a degree generally at
least equal to that of the areas of the valleys 24 to
obtain the desired density and consolidation. In other
words the percent reduction in height of the velley areas
and rib areas will normally be about the same.
The height of the mat section 34 above the mat
30 is indicated as h+C where C corresponds the amount of
compression to occur in the rib forming mat portions 34 to
form the consolida,ted ribs 18 having the height h above
the surface 16 of the valleys 24. Similarly, the thickness
of the mat 30 will be equal to the thickness t of the
rectangular cross section portion of panel of the panel 12
(i.e. spacing between surfaces 14 and 16) plus an amount
equal to C1 to ensure that the proper consolidation occurs
in the valley portions 24 of the product.
The thicknesses C and C1 normally will be the
same if same density is required in the rib areas as in
the areas therebetween and the height h is equal to the
thickness t so that the amount of the rib forming mat
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sections 34 have to be compressed to be equal in density
to the other areas of the mat is essentially twice the
amount that the sections 56 compress the mat 30 to form
the valleys 24. If the height h is less than the thickness
t, then the value for C will generally be less than that
of C1. If a higher density is desired in the rib portions
18 and areas 26 then the proportions or relationship of
thickness dimension C1 to thickness dimension C will be
adjusted to obtain the desired difference in density.
The angle A will normally be the angle of repose
at the wafers, but the angle B is determined primarily by
the height h and will not be the same as angle A. The
width of the valleys 58 are shown equal to the width w of
the top of the mats 34 but the width of the valleys 58
could differ from that of the mats 34. For example, if
the widths of the valleys 58 are slightly wider than that
of the mats 34 it will have little consequence to the
consolidated board as long as the ribs retain their
shape. However, if the width of valleys 58 is signifi-
cantly less than that of the mats 34 (ribs) local high
density areas at the sides of the ribs would result which
if there is a large difference in density and could affect
the integrity of the consolidated board. Preferrably the
width of the land areas 56 will be equal to the width of
the valleys, if the land areas 56 are smaller than the
valleys there will be uncompressed (not properly consoli~
dated)areas adjacent the ribs and if~ the areas 56 are
wider than the valleys there may be overcompressed areas
adjacent the ribs.
It is believed that the operation of the present
invention should be apparent from the above description.
However, to briefly review, first a mat 30 is formed on
caul plates 38, then discrete rib forming mats 34 are laid
thereon via the head 32, the caul plates 38 carrying the
mats 30 (34) are then transferred to a press wherein the
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rib forming mat sections 34 align with grooves 58 formed
in a heated insert 55 (55A) in the upper platen and the
complete mat 30 (34) is pressed at elevated temperature to
form a completed consolidated product haviny ribs 18
extending along one side thereof and a substantial planar
surface 14 on the other.
As above indicated, the wafers used may be
oriented as desired, preferably, all (in the mats 30 and
34) with their longitudinal axis aligned with that of the
ribs 18. Alternatively, only the wafers forming the ribs
may be aligned in this direction with the wafers forming
the main body of the panel 12 being random oriented or the
main body of panel 12 may have discrete layers with the
wafers thereof oriented in different directions some
layers with the wafers oriented longitudinally and some
layers with the wafers oriented transverse to the longi-
tudinal axis of the ribs 18.
Having described the invention, modifications
will be evident to those skilled in the art without
departing from the spirit of the invention as defined in
the appended claims.
