Note: Descriptions are shown in the official language in which they were submitted.
~.~t9~i14
BACKGROUND OF THE I NVENT I ON
1. Field of the Invention
The present invention relates to the manufacture of a moldec
wooden product by introducing into a mold wood fibers to which a
binder containing a synthetic resin or the like has been added,
and shaping this material by hot compression molding to obtain
the molded wooden product.
2. Descri~tion of the Related Art
In general, the manufacture of molded wooden products has
been carried out by molding wood fibers obtained by
disintegrating wood chips by splitting or the like, and then by
utilizing the bindability of the wood fibers themselves during
molding. The molded wooden products are called hardboards, and
the products themselves are uniform and light and have few
defects. These products have been widely utilized as interiorl
construction materials, furniture, interior substrates for cars,
and television and stereo cabinets, for example, since the
surface thereof is smooth and has high heat-resistance, high
water-repellency and high moisture-resistance, and the strength
is relatively high for the thickness of the plate.
The molded wooden products are manufactured, for example, by
a wet molding method where wood chips are digested and
disintegrated to form wood fibers, a synthetic resin and a
cellulose paper are then incorporated into the wood fibers, and
this material is dispersed in water and then filtered under
pressure and compressed under vacuum to form a mat. This mat or
soft fiber plate is compression molded under heat.
I ~ ~
~ 1 ~`9~L~14
Alternatively, a dry mattinq method can be used where a binder
such as a synthetic resin is added to bond the wood fibers which
are then formed into a stack and pressed under heat with a roll
press to obtain a mat, and the mat is compression molded under
heat into the desired shape.
The manufacture of molded wooden products, by reference to
an example of a conventional dry matting method, is as follows.
Wood chips are put in a digesting tank of a fiber-disintegrating
machine and are loosened therein by steam to soften the chips so
that the fibers may be disintegrated or split with ease. Next
these chips are put into a disintegrating disk and pulverized and
disintegrated therein to obtain wood fibers. The wood fibers are
dried with hot air, and then these are fully blended with long
fibers for the purpose of improving their drawability. As an
example, these long fibers can comprise 17% of hemp fibers and,7%
of polypropylene fibers. Also added is 8% of a binder, such as a
phenol-type thermosetting resin, a thermoplastic resin or the
like, and 1 to 5% of a water-repelling agent such as rosin,
paraffin or the like. Next, the wood fibers to which the binder
and other additives have been added are stacked and compressed
under heat with a roll press to form an easily portable mat Ml
having a thickness of about 10 to 40 mm.
Next, the mat to be molded is cut to a siæe which is
somewhat larger than the size of the final article and set on the
lower half Of a compression mold. The
lower mold half and the upper mold half are heated to a
temperature in the range of 180C to 220C by the hot plates.
~-
The mold halves are clos~d in alignment with e~ch other
by lowering the upper mold half. A gas is generated during
this step, and the gas is removed by opening the mold, and
thereafter, the upper and lower mold halves are again closed.
These pre-compression and gas-removal steps are repeated several
times, and then the mat is finally compressed by the upper mold
half and the lower mold half.
Afterwards, the mold is opened, and the product is removed
therefrom as a molded wooden product.
~,
The above-described conventional method for the manufacture
of molded wooden products has several problems. The dry matting
method requires the step of forming the wood fibers into a mat
which can be easily handled and the step of cutting the mat into
: a desired shape. These steps are required so that the mat can be
applied to the compression mold with ease. Thus, the method
requires additional steps, making it unnecessarily complex. In
addition, a binder such as thermoplastic resin or the like is
required to form the wood fibers into mats. Further, when the
I mat is molded under compression, the mat is apt to be drawn into
the mold especially in the deep-drawn portion thereof, and,
therefore, the mat is re~uired to be cut in a somewhat larger
size than the size of the final molded product. This is
uneconomical because the resulting excess material must be cut
away and discarded after molding of the product. Thus, the yield
of the process is reduced, and the manufacturing cost is
increased. In addition, the need for a cutting step after molding
1 !
J.~
the product creates an additional burden. In molding wooden
products to have a deeply-drawn portion, long fibers such as
expensive hemp fibers and a binder such as a thermoplastic resin
are required to be incorporated into the material which forms the
mats, in addition to the woods fibers, in order to improve the
deep-drawability of the mats. When hemp fibers having no
adhesiveness are used, an extra amount of thermosetting resin or
like binder is required. This results in an increase in the
manufacturing costs, making the product expensive.
'; In the case of the manufacture of molded products having a
deeply-drawn portion, when the amount of wood fibers contained in
the mat is large, the mat is required to be softened with steam
and then pre-shaped into the shape of the article to be obtained,
in order to improve the deep-drawability of the mat. In this
q case, not only an extra step is required but the edge of the m,at
which is stretched by the deep-drawing is made thin. Nhen the
pre-shaped mat is molded under compression, the thinner edge will
have a low density, and the strength of the final molded wooden
product is decreased, especially at the edge thereof. This
creates a problem for the manufacturer. In the case where a
molded wooden product in the shape of a large plate having a
deep-drawn portion is to be formed from a single mat, the mat
when drawn into the deep-drawn portion may be broken or folded in
the portion near the deep-drawn portion. The density of the
folded portion increases, the folded portion becomes blistered,
and a wooden product having the desired shape is not obtained.
In order to solve these problems, patches made of the same
... ... ,-.-.5 -- . .. .. .....
- . -
~ . .
: ' ' : ~ ... .
;~ ~?,~
material as that of ~he mat are applied to the mat in the portionto be deep-drawn prior to molding. This makes the operation
burdensome and unduly complicated.
When the wet molding method is used, a large amount of water
is required for the mat-making step, and, therefore, a large-
scale drainage system is necessary. Furthermore, the manufacture
of a wooden product having a deep-drawn portion from a mat formed
by the wet-molding method is as at least as difficult as the
. above-discussed dry matting method, since the fibers become
entangled in the formed mat. Thus, the wet-molding method has
the same types of problems as the dry matting method, e.g., the
deep-drawn portion and the peripheral portion of the final
product are thinner or broken.
A method has been considered for the direct compression
molding of wood fibers where wood fibers are directly put in a
mold of a desired shape and molded therein under compression.
; When a molded product in the shape of a plate is manufactured by
such a molding method, almost all the above-mentioned problems
can be solved. However, in the molding of deep-drawn portions,
special attention is required regarding the molding procedure
because, if the compression molding is carried out merely under a
conventional process, sufficient deep-drawability is not
attained.
Under these circumstances, the present inventors have
I previously proposed a method for the manufacture of molded wooden
products where ~od Pibers to be molded ~re Porred in ~
I
~ ~?~ 4
predetermined shape of low density and the shaped mass is put in
a mold and compre`ssion molded under heat. This proposal has
solved many of the above-mentioned problems in the use of mats.
However, where the mass of material contains wood fibers which
have not been completely disentangled, once compression starts
the wood fibers are found to be lacking in fluidity within the
mold. Accordingly, in the case of molding deep-drawn portions,
the edge of the deep-drawn portion is thinner and the molded
product is of reduced quality.
SUMMARY OF THE I NVENT I ON
It is an object of the present invention to solve the above-
mentioned problems, to improve the yield of molded wooden
products and the manufacture thereof, and to ensure that the
molding process has a deep-drawing capability. The present
invention provides a method for the manufacture of molded wooden
products of an improved quality, and which does not require a
mat-forming step.
Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of
the invention. The objects and advantages of the invention may
be realized and obtained by means of the steps and combinations
particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of
the invention, as embodied and broadly described herein, the
molding process of this invention relates to the manufacture of a
molded wooden product made of wood fiber and having a deep-drawn
x~
portion, and comprises the steps of introducing wood fibers into
a compression mold, initially compressing the wood fibers other
than those used to form the deep-drawn portion to an extent that
the compressed fibers are prevented from further movement, and
then compression molding under heat both the wood fibers which
were initially compressed and the wood fibers used to form the
deep-drawn portion to produce the molded wooden product.
Preferably, in the method of the present invention, wood
fibers to which a binder or the like has been added are placed
directly into a mold, and either the part of the mold to
accomplish deep-drawing or the other part is first closed to
initially compress the associated fibers. Then all of the wood
fibers in the mold are compression molded under heat.
Alternatively, wood fibers to which a binder containing a
synthetic resin or the like has been added are formed into a mass
of a predetermined shape, the resulting mass is put into a mold,
and either the part of the mold where deep-drawing occurs or the
remaining part is firs~ closed to initially compress the
associated fibers. Thereafter the whole mass is compression
molded under heat.
The fibers to be used in the present invention are obtained,
for example, by disintegrating wood. The wood used is not
specifically limited to a specific type and may be, for example,
an akamatsu (Japanese red pine), a sugi (Japanese cedar), a
lauan, a Japanese beech, etc. In addition, rice straws, flax
husks, bagasse, etc. can also be used.
Conventional processes for the preparation of wood fibers by
disintegration of wood chips or the like can be employed by
anyone skilled in the art, and can include, for example, the
method of digesting wood under pressure and mechanically
disintegrating the wood into fibers under the same pressure or
under normal pressure.
The b;nder to be added to the wood fibers is preferably one
that complements the bonding properties of the wood fibers
themselves and the amount added is not specifically limited,
provided the wood fibers are bound together to form a molded
wooden product having desired strength. Examples include a
synthetic resin, including a thermoplastic resin such as a croman
resin or a thermosetting resin such as a phenol resin or an urea
resin, and preferably a water-soluble phenol resin. These resins
may be used singly or in the form of a mixture thereof. In
addition to the binder, other additives such as a water-repelling
agent for improving water-resistance can be added to the wood
fibers.
In the manufacturing method of the present invention, the
wood fibers are placed directly into the shaping mold, without
being formed into a mat. The manner of introduction of the wood
fibers directly into the mold is not limited to a specific
technique. For instance, the wood fibers to which a binder has
been added can be introduced into the mold along with a gas such
as air or the like, with the fibers being introduced at one side
of the mold under pressure and vacuum being applied at the other
side, or by vacuum alone at one side or introduced under pressure
r ~ 9~
alone. The wood fibers can also be directly dropped into the
mold and accumula~ed therein; or the wood fibers can be formed in
a pile on a support such as a net or the like and transported
into the mold, the wood fibers being kept on the support by
vacuum.
In another embodiment of the method of the present
invention, the wood fibers to be shaped are formed into a
predetermined mass and introduced into a mold. ~he method for
thus forming this mass and the method for the transportation of
the mass into a mold are not specifically limited to any
particular technique. For instance, a laminating container is
provided with a metal net therein and the fibrous material is
introduced into the container under vacuum so that the material
forms in a pile on the metal net. Thereafter, the material piled
on the net is carried bn a holder under vacuum, transported into
a shaping mold, and, once the preferred positioning of the
material is determined, the vacuum in the holder is released to
drop the fibrous material into position in the mold.
For the compression molding of the fibrous material where
either the part of the mold used for deep-drawing or the
remaining part is first closed and then all of the fibrous
material is molded under pressure, the mold is divided into
several parts in the direction that compression is to occur,
e.g., in the vertical direction, into a part used for deep-
drawing, and the remaining part of the mold. The wood fibers
residing in either of these thus-divided parts are first closed,
and thereafter, the whole mass of fibers is molded under
-- . ,.. . ..... , ~,
.; ., . . - . , .
~ ` ~?,~
pressure. In this process, the operation of "closing~ means to
firmly press the wood fibers to such an extent that the fibers
cannot move.
Since a time interval is to occur between the compression of
the portion of the fibrous material to be deep-drawn and that of
the remaining part which is not to be deep drawn, either the
upper mold or the lower mold constituting the entire mold is
divided into the corresponding part used for deep-drawing and the
other part or parts not used for deep drawing. One of the thus
divided parts is vertically movable relative to the other part or
parts. The movable part is actuated by a moving means such as a
spring which applies an appropriate force. The molding
parameters in this case are based upon and determined in
accordance with the wood fibers used, the type of binder, the
size or shape of the article to be produced, and the desired
strength of the final product. For instance, compression molding
can be carried out at a temperature of 150C to 220C, a molding
pressure of 20 to 80 kg/cm2, and a molding time of 20 seconds to
5 minutes.
In the method for manufacturing molded wooden products of
the present invention, the wood fibers to which a binder has been
added are compression molded, and, therefore, the wood fibers are
integrally bonded. In addition, since the wood fibers can be
directly introduced into the mold, for example, by an air-flow,
without being formed into a mat, the fibers are not entangled but
are unconnected and dispersed at random. Therefore, the wood
fibers are fully disintegrated and entrained in the fluid, and
only a small amount of binder need be used.
..... , -11-
.~. . .
. ~; , .
',~ '~,?.9~
In deep-draw molding, where the wood fibers in the portion
to be deep-drawn àre first closed or compresssed in the mold, the
wood fibers in this part of the mold are stably fixed in the
mold, as in the case of a pre-shaped material. Alternatively,
where the other part of the mold -- other than the part to
accomplish deep-drawing -- is first closed to compress the wood
fibers therein, the excess wood fibers shift to the part of the
mold where deep-drawing is to occur, and the latter part is
sufficiently filled with wood fibers so that the subsequent deep-
drawing step can be carried out without the deep-drawn portion of
the final product being cracked or thinly formed.
Accordingly, the method of the present invention is not
dependent upon a step of forming the wood fibers into a mat and a
step of cutting the mat to a determined shape. In addition, the
present method does not require binder in the formation of the
mat. Further, long fibers such as hemp fibers for the
improvement of deep-drawability as well as thermosetting resins
for binding such fibers and extra amounts of thermoplastic resins
are unnecessary. The additional steps of pre-shaping, of
reinforcing the portion to be deep-drawn by applying patch
materials thereto, and of applying steam to the wood fibers in
the portion to be deep-drawn, are unnnecessary in the manufacture
of molded products in accordance with the present invention, and
the resulting molded products have satisfactory strength.
In accordance with the method of the present invention,
deep-drawability is improved and high-strength molded wooden
products can easily be obtained, as noted above. In addition,
some steps typically required in conventional matting methods car
be omitted in the method of the present invention. Therefore,
complexity and the cost of raw materials can be reduced, and
productivity can be improved.
In the method of the present invention, the fibrous material
to be molded can be formed into a mass having a predetermined
shape and the resulting mass introduced into a shaping mold,
making the process of forming a mat from the wood fibers
unnecessary. Again, the yield of the products is improved and
the manufacturing process is simplified. Furthermore,
compression occurs when the wood fibers are in an untanqled
state, and therefore, the wood fibers in the peripheral portions
of the article are prevented from moving inside the mold during
compression molding. The forming of the external shape of the
molded product results only from compression molding, and, thus,
the step of afterworking the article for improving the surface
characteristics of the final product can be omitted.
A time interval occurs between the compression step of the
portion of the fibrous material to be deep-drawn and that of the
remaining portions not to be deep-drawn, thereby ensuring that a
sufficient amount of wood fibers reside at the edge of the
portion to be deep-drawn so that the deep-drawing capability is
improved.
The accompanying drawings, which constitute part
of the specification, illustrate the prior art and preferred
embodiments of the invention and, together with tne general
jl description given above and the detailed description of the
-13-
,.~ ~L~??~
preferred embodiments given belowr serve to explain the
principles of thè invention.
BRIEF DESCRIPTION OF THE DRAWIN~S
Fig. 1 shows a sectional view in elevation of a mold (in
open position) which can be used in compression molding wood
fibers in accordance with a first embodiment of the method of the
present invention;
Fig. 2 shows a sectional view in elevation of the mold of
Fig. 1 in initially compressed and partially closed position;
Fig. 3 shows a sectional view in elevation of the mold of
Fig. 1 in fully compressed and closed position with the wood
fibers under compression;
Fig. ~ shows a plan view of a side plate of the mold used in
the first embodiment of the method of the present invention;
:~ Fig. 5 shows a sectional view in elevation of a mold which
can be used in compression molding of wood fibers in accordance
with a second embodiment of the method of the invention;
Fig. 6 shows a view of an apparatus suitable for feeding
wood fibers in the first embodiment of the method of the present
invention;
Fig. 7 is a schematic view showing an apparatus for forming
a mass of wood fibers;
Figs. 8 and 9 are schematic views showing an apparatus for
transporting a mass of fibrous material formed by the apparatus
of Fig. 7 and an embodiment for the use therof;
Fig. 10 is a perspective view of a molded wooden product
manufactured in accordance with a first embodiment of the method
of the present invention;
~9~
Fig. ll shows a perspective view of a mat of wood fibers used in prlor art
processes;
Fi~. 12 ~hows a sectlonal view in elevation of a prior art mold in whlch a
mat of the type shown in ~ig. 11 has been placed; and
Fi~. 13 shows a sectional view in elevation of the mold of Fig. 12 with
the mat of Fi8. 11 under compression.
In the prior art, as shown in Fig. 12, the mat Nl to be moldeA i5 sst on
the lower half 2 of compression mold 1. The upper half 3 and the lower half 2
are both heated by hot plates 4. Fig. 13 shows the mat being finally
compressed to a molded wooden product ~2. In Fig. 13, M2' represents excess
material derived during molding.
DESCRIPTION OF THE PREFERRED EHBODInEUT
Reference will now be made in detail to the present preferred embodiments
of the invention as illustrsted in the accompanying drawings. The present
invention will be explained in the following examples in which the processes
of the present invention are adapted, by way of example, to the molding of a
door trim substrate with an arm rest, this product finding utility in the
manufacture of automobiles.
EXANPLE 1:
An example of the manufacture of wood f~bers wlll be flrst explainsd.
Chips comprising small pieces of wood obtained by chipping wooden mater~als
are digested and disintegrated at 160C to 180C. The wetted wood fibers thus
obtained are dried with hot air.
Next, the dried wood fibers are put into a blender and stlrred while they
are ~imultaneously sprayed with 1 to 5% of paraffln as a water-repellent
agent, 2 to 10% ~by dry weight) of phenol resin-aqueous solution (resin
content, for example, 50~) as a binder, and a mold lubricant or the like.
During the stirring and spraying process, the fibers are well blended while
- 15 -
.~
the water content in the wood fibers is appropriately regulated
to obtain binder-`containing wood fibers.
The wood fibers to which the binder has been added are
directly introduced into a shaping mold, without being formed
into a mat. This step is carried out as follows.
The above-mentioned wood fibers M3 to which the binder has
been added are put in a feeding container 21 of filling apparatus
20, as shown in Fig. 6. The filling apparatus 20 is composed of
the feeding container 21 and a pressure container 22. The two
3~ containers are linked with each other via the opening 23 located
at the bottom part of the feeding container 21 and the aligned
opening 23' at the upper part of the pressure container 22. The
aligned openings 23 and 23' are blocked by the masking plate 24
which can be opened and shut by the action of cylinder 26. The
masking plate 24 is reciprocated by the action of cylinder 26 so
that a hole in the masking plate can be brought into and out of
alignment with the openings 23 and 23'. When the masking
plate 24 is opened, i.e., its hole is brought into alignment with
holes 23 and 23', the wood fibers M3 to which the binder and the
like have been added fall down to the pressure container 22
through the openings 23 and 23'. A pair of rotatable brush
wheels are provided in the lower part of the feeding container 21
where the wood fibers M3 have been kept. These brushes when
rotated cause the top of the brushes to engage with each other
which tend to untangle any entangled fibers of the wood fibers M3
that are contacted.
. . . ..... .
~ I ~;?,9161~ ~
The pressure container 22 is provided with a weighinq
plate 27 below the opening 23', and the wood fibers M3 which fall
through this opening pile up on this weighing plate 27. The
weight of the wood fibers M3 on the weighing plate 27 is measured
by a load cell (not shown~ connected to the weighing plate 27,
and when the weight has reached a predetermined value, the brush
wheels are stopped and the masking plate 24 is shut, thereby
terminating the feeding of the wood fibers M3 into the pressure
container 22.
With reference to Fig. 1, the mold 30 comprises an upper
mold 31 and lower mold 32. The mold faces are inclined at an
angle such that the angle for compression of the portion to be
deep-drawn is not too large. The lower mold 32 comprises several
parts including the fixed lower mold part 32a, positioned in the
center of the mold for the portion of the fibrous material,tolbe
deep-drawn, and the movable lower mold parts 32b which are
supported by the springs 48 and are adjacent to the fixed part
32a. The mold parts 32b are designed to compress the fibrous
material surrounding the portion of the fibrous material to be
deep-drawn. In the state where the upper mold 31 and the lower
mold 32 are open, the movable mold parts 32b positioned adjacent
to the deep-drawing part of the lower mold 32 are elevated by the
springs 48 to a height higher than the fixed lower mold part 32a,
but the stopper plates 46 connected at the bottom of the lower
mold parts 32b act to limit the upward movement of these parts by
contact with the top of stoppers 47.
-17-
. I ,. . .
:
The upper mold 31 has a deep-drawing part in concave form.
When opened, the shaping mold 30 forms a defined cavity, where
the distance across the mold at the deep-drawing part is wider
than the other parts of the mold. The periphery of the mold 30
is surrounded by side plates 33 and 34 so that the wood fibers M
once fed into the mold do not escape out of the mold 30. The
side plates 33 and 34, which face each other, are movable along
the side surfaces of the mold 30. One side plate 33 has a
feeding port 35 (see also Fig. 4) opening to a position
corresponding to the opening in the side of the opened mold 30,
and the other side plate 34 has a net 36 to hold the wood
fibers M3 within the opened mold 30.
The discharge opening 28 provided in the pressure
container 22 (Fig. 6) is designed to be aligned with the feeding
port 35 of the side plate 33 of mold 3Q tFig. 1). As air is
introduced into the pres-sure container 22 from the opening
opposite to opening 28, the wood fibers M3 accumulated on the
weighing plate 27 in the pressure container 22 are transported
into the mold 30 by the air. In this procedure, the air passes
through the net 36 of the outer plate 34, while the wood
fibers M3 are contained by the net 36 and thus fill the cavity of
mold 30.
During this introduction of the fibers under pressure,
negative or a vacuum is also applied at the downstream side of
the net 36. The wood fibers M3 introduced into the mold 30 under
such pressure and vacuum collect from the mold side of the net 36
inwardly without entangling the fibers. In this step, air
-18-
.... .
~?,~
contained in the wood fibers M3 are degassed by vacuum via the
air-removal holes 42 provided in the upper mold 31 and the lower
mold 32, and the vacuum ducts 43, to aid in uniformly filling the
mold with the wood fibers M3. In the air-removal procedure, the
vacuum in the air-removal holes in the side of the lower flow (in
upper mold 32) may be varied relative to that of the holes in the
side of the upper flow (in upper mold 31) as the filling of the
wood fibers M3 in the mold 30 progresses. The quantity of wood
fibers M3 admitted into the mold 30 may be determined on the
basis of their weight, as mentioned above, or, alternatively, it
may be determined on the basis of the pressure imparted during
the introduction of the fibers into the mold while the density o
the fibers as they fill the mold is appropriately regulated or
monitored.
The wood fibers M3 to which the binder and other additiv,e~s
have been added are now ready to be compression molded. First,
the side plate 33 arranged on the side surface of mold 30 is
moved to cover the mold opening with the use of the rack 37 and
pinion 39 gearing. The rack 37 is provided below the side
plate 33, whi:Le the pinion 39 is rotated by the motor 38 fixed t
the bracket 40, so that the opening in mold 30 is covered by the
part of the side plate 33 (Fig. 4) adjacent to the feeding
port 35 thereof, as shown in Fig. 2. In the same manner, the
side plate 34 containing net 36 is also moved by a side-plate
sliding means (not shown), so that this opening in mold 30 is
covered by the part of the side plate 34 adjacent to the net 36,
as also shown in Fig. 2. Thus, the position of these side
~ -19-
plates 33 and 34 are fixed with respect to the position of the
lower mold 32.
Next, the wood fibers M3 are molded into the desired shape
under compression created between the upper mold 31 and the lowe~
mold 32, which have been heated to a temperature in the range of
150C to 220C by the hot plates 41, by downward movement of
upper mold 31 as shown in Fig. 2. The molding surfaces of the
parts 32b of the lower mold 32 around the deep-drawing part 45
are elevated due to the springs 48, and thus, the wood fibers M3
are sandwiched between the descending upper mold 31 and the lower
mold parts 32b, and pressed together. ~he lower mold parts 32b
are supported by the springs 48 and, thus, the force exerted by
the springs 48 is imparted as pressure to the wood fibers M3.
However, the height of the springs 48 is reduced under pressure
created by upper mold 31, and the lower mold parts 32b descend as
the upper mold 31 descends further. The descent of the lower
mold parts 32b stops when the stopper plates 46 provided below
these mold parts reach the hot plate 41 at the bottom of the
mold. In this state, the wood fibers M3 are closed or compacted
in the area around the deep-drawing part 45, but because a high
level of pressure has not yet been imparted, the fibers are not
yet formed into a molded product. Any excess of wood fibers
resulting from this step flow into the deep-drawing part of the
mold so that it is completely filled.
The upper mold 31 is now lowered further so that the wood
fibers M3 across the entire mold 30 are molded into the desired
shape by the pressure created by the the upper mold 31 and the
,~ ' ~19~
lower mold 32 and the applied heat, as shown in Fig. 3. During
this step, any gas generated is removed under vacuum by the gas-
removal holes 42 via the vacuum ducts 43 and the valve 44 at the
position approximately 10 mm before the bottom dead point of the
upper mold 31. The molding parameters can include, for example, a
molding pressure of 20 to 80 kg/cm2 and a molding time of
20 seconds to 5 minutes.
In this process as just described, the peripheral part of
the mold 30 adjacent to the deep-drawîng part 45 is first
partially closed to initially compress the wood fibers in the
non-deep-drawn region, thereby preventing further movement of
these fibers. Afterwards, the entire mass of fibers is
compression molded under heat into the desired shape. This deep-
drawn molding process operates in a stable ~anner without the
formation of thin regions in the final product or the
susceptibility of the product to breakage or fracture during
manufacture. ~n addition, that part of the product other than
the deep-drawn portion is shaped in the initial compressing stage
of the molding process, and, therefore, the manufacturing yield
is improved by eliminating the waste encountered in the use of
the mats.
When the mold is opened, vacuum applied through the gas-
removal holes 42 in the upper mold 31 holds the molded wooden
product M4 against the upper mold 31 and it is thus lifted up
therewith. After the valve 44 is closed and vacuum is released,
the molded wooden product M4 is removed. The product has the
shape of a door trim substrate in which the deep-drawn part 45 is
an arm rest, as shown in Fig. 10. This product is free from
defects and has a`thickness of 2.5 mm and a bending strength of
200 to 350 kg/cm2 or higher.
Since the molding is carried out with the interior mold
surfaces being inclined, in the present example, the compression
angle and the drawing angle in the deep-drawn portion are small.
Therefore, molding can be achieved without the deep-drawn portior
being broken, and further, the final product can easily be
removed from the mold.
EXAMPLE 2:
In this second example of the invention, the wood chips are
digested, disintegrated and dried to obtain wood fibers, in the
same manner as in Example 1. The wood fibers are preferably
blended with the same binder, water-repellant agent, mold
lubricant and the like as in Example 1. The wood fibers to which
the binder and other additives have been added are put into the
compression mold 50 shown in Fig. 5 by use of the same techniques
used in describing Example 1.
The mold 50 comprises an upper mold 51 and a lower mold 52.
The upper mold 51 is divided into a separately movable upper mold
part 51a for use in deep-drawing and the adjacent or surrounding
upper mold parts 51b. With the wood fibers inside the mold 50,
the side plates 33 and 34 are closed to enclose the mold 50 as
described in Example 1. Next, the deep-drawing upper mold part
51a is lowered by the action of the rod 49 so that the wood
fibers M3 of the portion to be deep-drawn 45 are firmly pressed
together in this closing step. Afterwards, the upper mold parts
-22-
. . ... __.. . .... . .. .... ~ . ..
. . .
., . , . .. ~ .
- , .. .
~?~9~
51b are lowered~ and all of the fibers M3 in the mold 50 are
molded into the desired shape under hot compression molding by
the upper mold 51 and the lower mold 52. The wood fibers in the
deep-drawn part 45 have been pressed together during the closing
step and correspond to a pre-shaped mass. Therefore, this
portion of the final product is stably deep-drawn without being
broken or made made unduly thin. The molding parameters may be
the same as used in Example 1. The final product obtained has
equally superior strength as that obtained in Example 1. In the
;~ process of the present example, additional steps such as
pre-compression are unnecessary, and the same or an improved
result can be attained as if these steps had been taken.
One embodiment of the mass-forming apparatus for the
preparation of the fibrous mass W is shown in Fig. 7. The mass-
forming apparatus 60 is principally comprised of a spraying
container 61 which has an angled roof-like form made of iron
plate or the like and a laminating container 62 for laminating
c.~ the fibrous mixture M comprising wood fibers, binder and other
additives. Container 62 is positioned below container 61. The
spraying container 61 has an opening 63 in the top thereof, and a
nozzle 64 is provided above opening 63 for spraying the fibrous
mixture M fed through a pressure duct (not shown) to the nozzle.
Air containers 65 are provided on both sides of opening 63, with
each having an orifice in the inside thereof (not shown) for
directing a jet of air against the spray. These jets are used
for regulating the direction in which the mixture is sprayed.
Each of these containers 65 is constructed to receive air fed
through air-feeding ducts 66 as switched by switch valve 67.
~ `
A vacuum duct 68 for applying vacuum to the interior of the
laminating container 62 is connected to the bottom side of
laminating container 62. A form-imparting part 69, which, for
example, comprises a metal net, punched metal or the like and
which functions to form the bottom surface of the mass into a
predetermined shape, is provided above the vacuum duct 68. The
laminating container 62 has height sensors 70 on the side wall
above the form-imparting part 69 for detecting the levels and
thus the amount of the mixture M and to form the upper surface of
the mass W into a desired shape.
The operation of the mass-forming apparatus 60 is as
follows. The switch valve 67 is opened to feed air into one or
both of the air containers 65 through the air-feeding ducts 66,
and provide air-flow from the spraying container 61 to the
laminating container 62. Thereafter, mixture M is released from
the nozzle 64 and passes through the opening 63 The released
mixture M descends from the opening 63 of the spraying
container 61 along with the air, in a floating manner, into the
laminating container 62 to form a predetermined accumulation on
the form-imparting part 69. In this step, the air jets provided
by container 65 are appropriately regulated by switching the
switching valve 67, or by shutting both the valve and the
orifices, so that the direction of the falling mixture M is
controlled and the fibers fall on predetermined positions of the
form-imparting part 69 where they quickly accumulate to the
desired thickness~ In this procedure, air in the mixture is
drawn from the bottom of the laminating container 62 by the
vacuum duct 68, and the lamination of the mixture M is
accelerated.
As the lamination of the mixture M proceeds, certain of the
height sensors 70 provided on the side wall of the container 62
detect that levels of the mixture M have reached predetermined
heights. The switch valve 67 is appropriately controlled so that
the direction of the fall of the fibrous mixture is changed.
Eventually, all the sensors 70 will detect that the desired
levels of the m;xture M have been attained. At this stage, the
feeding of the mixture M is stopped and, at the same time, the
feeding of the air from the air-feeding duct 66 is also stopped.
The mass of material W having a predetermined shape is thus
obtained. The mass W, constituted as a lamination of fibers, has
an extremely low density, and, generally, its thickness is
selected to be 20 to 120 times that of the final molded product.
In order to transport the fibrous mass W to the mold, the
above-described laminating container 62 is released from the
spraying container 61, and is aligned with a holder 71, for
example, as shown in Fig. 8. The holder 71 has a configuration
capable of receiving the laminating container 62, and is provided
on the inside with a form-imparting part 72 comprising a metal
net or the like and shaped to correspond to the thickened part WI
of the material mass W. The top of holder 71 above part 72 is
connected with a vacuum tube 73. When a vacuum is applied to the
vacuum duct 73, the fibrous mass W is elevated by virtue of
having a light specific gravity, and closely adheres to the form-
imparting part 72 in the holder 71, and with the vacuum
.~ ` ~ ?,~
maintained, the holder is also lifted up with the fibrous mass
and can now be moved by a conveying means (not shown), in the
direction shown in Fig. 9, to a predetermined position within a
mold, e.g., mold 30 or mold 50 of the present invention, where
the mass is dropped into the inside of the mold, in contrast to
the feeding means used in the mold of Fig. 1, and thereafter the
vacuum is released and the mass W is set in the mold.
Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader
aspects is, therefore, not limited to the specific details,
representative apparatus and illustrative examples shown and
described. Accordingly, departures may be made from such details
without departing from the spirit or scope of the applicant's
general inventive concept, provided they come within the scope of
the appended claims and their equivalents.
