U.S. patent application number 10/983616 was filed with the patent office on 2005-03-24 for process for producing multilayer molded article.
This patent application is currently assigned to Sumitomo Chemical Company, Limited. Invention is credited to Kitayama, Takeo, Saitoh, Atsushi.
Application Number | 20050062197 10/983616 |
Document ID | / |
Family ID | 26609644 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050062197 |
Kind Code |
A1 |
Kitayama, Takeo ; et
al. |
March 24, 2005 |
Process for producing multilayer molded article
Abstract
A method for producing a multilayer molded article in which an
skin material having nap on the outer surface thereof is integrally
molded with a substrate of a synthetic resin, using a mold
comprising a pair of male and female mold halves. In this method,
after the fabric skin material and the molten resin are clamped in
the mold and primary cooling is carried out, the mold is opened
halfway to form a predetermined gap between the mold halves, and
the molten synthetic resin undergoes secondary cooling and hardens
while the mold is held in the half-open state. In the present
invention, the time period for the operation to open the mold
halfway is set at one second or less. By limiting the half-opening
operation time period to the short period of one second or less,
recovery of the nap is reliably achieved without the nap tending to
stay flattened. Moreover, because the transition from the primary
cooling step to the secondary cooling step occurs in a short period
of time, problems such as inadequate cooling of the molten
synthetic resin do not occur.
Inventors: |
Kitayama, Takeo; (Scarsdale,
NY) ; Saitoh, Atsushi; (Sakata-shi, JP) |
Correspondence
Address: |
FITCH, EVEN, TABIN & FLANNERY
Suite 401L
1801 K Street, N.W.
Washington
DC
20006-1201
US
|
Assignee: |
Sumitomo Chemical Company,
Limited
Tokyo
JP
|
Family ID: |
26609644 |
Appl. No.: |
10/983616 |
Filed: |
November 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10983616 |
Nov 9, 2004 |
|
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10076609 |
Feb 19, 2002 |
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6835340 |
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Current U.S.
Class: |
264/255 ;
264/328.16 |
Current CPC
Class: |
B29C 43/52 20130101;
B29C 43/14 20130101; B29C 43/58 20130101; B29C 43/184 20130101;
B29C 2043/5841 20130101; B29C 33/30 20130101 |
Class at
Publication: |
264/255 ;
264/328.16 |
International
Class: |
B29C 045/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2001 |
JP |
P2001-042234 |
Feb 19, 2001 |
JP |
P2001-042235 |
Claims
1-4: (canceled).
5: A method for producing a multilayer molded article by integrally
molding a skin material having nap on the outer surface thereof and
a substrate made of a synthetic resin, using a mold comprising a
pair of male and female mold halves that can come into contact with
or move away from each other, wherein one of said mold halves has a
movable block that is located such that it can be moved toward or
away from the other mold half, and a surface of said movable block
facing said other mold half constitutes part of a molding surface
of said one mold half, said method comprising: a first step of
supplying the skin material to a gap between said pair of male and
female mold halves of said mold in an open state and positioning
said skin material at a position facing said surface of said
movable block; a second step of supplying molten synthetic resin
between a back surface of said skin material and a molding surface
of said other mold half that faces said back surface; a third step
of clamping said mold either after said molten synthetic resin has
been supplied or while said molten synthetic resin is being
supplied; a fourth step of carrying out primary cooling of said
molten synthetic resin while said mold is being clamped under a
predetermined clamping pressure; a fifth step of moving said
movable block away from said other mold half and forming a
predetermined gap between said movable block and said other mold
half; a sixth step of carrying out secondary cooling of said molten
synthetic resin while said mold is being held in the ending state
of said fifth step; and p1 a seventh step of opening said mold
after said molten synthetic resin has hardened and extracting a
molded article as a final product; wherein the time period for
moving said movable block in said fifth step is no more than one
second.
6: The method according to claim 5, wherein said gap between said
pair of male and female mold halves in said fifth step equals or
exceeds 80% of the thickness of said final product.
7: The method according to claim 5, wherein said fourth step is
divided into a first stage and a second stage, and wherein said
mold is held at a first clamping pressure in said first stage and
said mold is held at a second clamping pressure that is smaller
than said first clamping pressure in said second stage.
8: The method according to claim 5, wherein said gap formed between
said pair of male and female mold halves in said fifth step is
determined by adjusting in increments of 0.1 mm to ensure that the
color of the outer surface of the skin material does not change
significantly after molding and to ensure that there is minimal
deformation of said molded article
9-11: (canceled).
12: A method for producing a multilayer molded article by
integrally molding a skin material having nap on the outer surface
thereof and a substrate made of a synthetic resin, using a mold
comprising a pair of male and female mold halves that can come into
contact with or move away from each other, in which one of said
mold halves has a movable block that is located such that it can be
moved toward or away from the other mold half, and a surface of
said movable block facing said other mold half constitutes part of
a molding surface of said one mold half, said method comprising: a
first step of supplying the skin material to a gap between said
pair of male and female mold halves of in an open state and
positioning said skin material at a position facing said surface of
said movable block; a second step of supplying molten synthetic
resin between a back surface of said skin material and a molding
surface of said other mold half that faces said back surface; a
third step of clamping said mold either after said molten synthetic
resin has been supplied or while said molten synthetic resin is
being supplied; a fourth step of carrying out primary cooling of
said molten synthetic resin while said mold is being clamped under
a predetermined clamping pressure; a fifth step of moving said
movable block away from said other mold half and forming a
predetermined gap between said movable block and said other mold
half; a sixth step of carrying out secondary cooling of said molten
synthetic resin while said mold is being held in the ending state
of said fifth step; and a seventh step of opening said mold after
said molten synthetic resin has hardened and extracting a molded
article as a final product; wherein said gap formed between said
movable block and said other mold half in said fifth step is
determined by adjusting in increments of 0.1 mm to ensure that the
color of the outer surface of the skin material does not change
significantly after molding and to ensure that there is minimal
deformation of said molded article.
13: The method according to claim 12, wherein said gap between said
pair of male and female mold halves in said fifth step equals or
exceeds 80% of the thickness of said final product.
14: The method according to claim 12, wherein said fourth step is
divided into a first stage and a second stage, and wherein said
mold is held at a first clamping pressure in said first stage and
said mold is held at a second clamping pressure that is smaller
than said first clamping pressure in said second stage.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for producing a
multilayer molded article in which an skin material having nap on
the outer surface, such as a fabric skin material, is attached on
the outer surface of a substrate made of synthetic resin.
[0003] 2. Description of the Related Art
[0004] A multilayer molded article that includes a fabric skin
material attached thereon is widely used, for example, as an
automobile interior component (such as in door trim or on an
instrument panel) or as an component mounted on the exterior or in
the interior of home electrical appliances.
[0005] As a method for producing such a multilayer molded article,
a method is known in which, for example, molten thermoplastic resin
is supplied to a mold comprising a pair of male and female mold
halves after a fabric skin material is placed therein and the mold
is held at a predetermined clamping pressure, so that the molten
thermoplastic resin is molded into a predetermined configuration
and that, at the same time, the fabric skin material is attached on
the outer surface of the molded resin. This method offers the
advantage that the fabric skin material is attached on the outer
surface of the substrate made of thermoplastic resin simultaneously
with the molding of the substrate, but the problem exists that the
fabric skin material becomes flattened due to the clamping
pressure, and the esthetic appeal (i.e., the appearance, feel,
etc.) of the resulted article is compromised.
[0006] Accordingly, as a method to eliminate the loss in esthetic
appeal due to the flattening of the fabric skin material in this
fashion, a method has been proposed in which the mold is opened
slightly after a clamping and primary cooling step, thereby forming
a gap between the outer surface of the fabric skin material and the
molding surface of the mold, and this condition is maintained while
the thermoplastic resin undergoes secondary cooling (Japanese
Patent Laid-Open No. 10-58485, Japanese Patent Laid-Open No.
11-314227). Using this method, a recovery space for the flattened
nap on the outer surface of the fabric skin material is maintained,
such that the previously flattened nap rises during secondary
cooling, enabling a molded article that exhibits little flattening
to be obtained.
[0007] However, even using this method, there remain the problems
that a molded article having a good appearance is not always
obtained because sufficient recovery of the flattened nap does not
always occur, and that deformation sometimes occurs in the molded
article due to inadequate cooling.
[0008] Accordingly, an object of the present invention is to
provide a method for producing a multilayer molded article in which
a fabric skin material is integrally molded with a synthetic resin
substrate using a mold comprising a pair of male and female mold
halves, wherein the loss in the appearance and feel due to the
flattening of the fabric skin material is reliably prevented and
deformation of the molded article is prevented as well.
SUMMARY OF THE INVENTION
[0009] The present invention is a method for producing a multilayer
molded article in which an skin material having nap on the outer
surface thereof is integrally molded with a synthetic resin
substrate using a mold comprising a pair of male and female mold
halves that can be moved toward and away from each other, wherein
such method includes a first step of supplying a skin material to
the gap between the pair of male and female halves of the mold
while they are in an opened state, a second step of supplying
molten synthetic resin between the back surface of the skin
material and the molding surface of one of the pair of male and
female mold halves that faces such back surface, a third step of
clamping the mold either after the thermoplastic resin has been
supplied or while it is being supplied, a fourth step of carrying
out primary cooling of the molten synthetic resin while the mold is
being clamped under a predetermined clamping pressure, a fifth step
of opening the mold halfway and forming a predetermined gap between
the pair of male and female mold halves, a sixth step of carrying
out secondary cooling of the molten synthetic resin while the mold
is being held in this half-open state, and a seventh step of
opening the mold after the molten synthetic resin has hardened and
extracting a molded article as a final product.
[0010] According to one aspect of the present invention, the time
period of the operation of the fifth step to open the mold halfway
is set at one second or less.
[0011] In other words, if the time period for the operation of the
fifth step in which the mold is opened halfway exceeds one second,
the nap tends to stay flattened during the half-opening operation,
and the rising of the nap during the sixth step in which secondary
cooling is performed does not take place completely, but if the
half-opening step is carried out in a short interval of one second
or less, the nap recovers its shape in a reliable fashion without
acquiring the tendency to stay flattened. Furthermore, because the
time period between the fourth step, i.e., the primary cooling
step, and the sixth step is no more than one second, problems such
as inadequate cooling of the molten synthetic resin do not occur.
Here, the time period for the half-opening operation is the time
period from the beginning of the reduction in the mold clamping
pressure to the point at which the mold is halfway open.
[0012] In another aspect of the present invention, the gap formed
between the pair of male and female mold halves in the fifth step
is determined by adjusting in increments of 0.1 mm to ensure that
the color of the outer surface of the skin material does not change
significantly after molding, as well as to ensure that there is
minimal deformation during molding.
[0013] The hue of the coloring of the outer surface of the fabric
skin material may change due to the degree of flattening nap.
Consequently, where the change in the color of the fabric skin
material after molding is the smallest, the state of the nap after
molding is close to the state of the nap before molding, in which
there is a minimum amount of flattening. This is due to the fact
that, because the pressure applied by the surface of the mold on
the outer surface of the fabric skin material is reduced as the
half-opening gap widens and the rising of the nap that was
flattened takes place in a more reliable fashion in the sixth
(secondary cooling) step, the change in the color of the outer
surface of the fabric skin material after molding becomes small. On
the other hand, if the half-opening gap becomes too wide, the
cooling of the molten thermoplastic resin in the secondary cooling
step becomes insufficient and deformation of the molded article can
easily occur. Accordingly, by setting the size of the half-opening
gap such that the change in the color of the outer surface of the
fabric skin material after molding is small and there is minimal
deformation in the molded article, insufficiency of cooling of the
molten thermoplastic resin is prevented during the second cooling
step and the optimal amount of recovery of the flattened nap on the
outer surface of the fabric skin material is obtained. Moreover, by
adjusting the gap in minute increments of 0.1 mm, the optimal size
of the half-opening gap in order to obtain a molded article
exhibiting the least amount of flattening and deformation can be
reliably determined.
[0014] Furthermore, the present invention comprises a method for
producing a multilayer molded article by integrally molding an skin
material having nap on the outer surface thereof and a synthetic
resin substrate using a mold comprising a pair of male and female
mold halves that can come into contact with or move away from each
other, wherein one of the mold halves has a movable block that is
located such that it can be moved closer to or farther away from
the other mold half, and the surface of the movable block facing
the other mold half comprises part of the molding surface of such
one mold half, and wherein such method includes a first step of
supplying a skin material to a gap between the pair of male and
female mold halves while the mold is in an open state and
positioning the skin material such that it faces the movable block
surface described above, a second step of supplying molten
synthetic resin to the gap between the back surface of the skin
material and the molding surface of the other mold half that faces
such back surface, a third step of clamping the mold either after
the molten synthetic resin has been supplied or while the molten
synthetic resin is being supplied, a fourth step of carrying out
primary cooling of the molten synthetic resin while the mold is
being clamped under a predetermined clamping pressure, a fifth step
of moving the movable block away from the other mold half and
forming a predetermined gap between the movable block and the other
mold half, a sixth step of carrying out secondary cooling of the
molten synthetic resin while the mold is being held in the ending
state of the fifth step, and a seventh step of opening the mold
after the molten synthetic resin has hardened and extracting a
molded article as a final product.
[0015] In this method, in another aspect of the present invention,
the time period for moving the movable block in the fifth step is
one second or less.
[0016] Using this method, by setting the time period for the moving
of the movable block to a short interval of one second or less, the
nap can be reliably restored without it acquiring the tendency to
stay flattened. Furthermore, because the time period between the
fourth step, i.e., the primary cooling step, and the sixth step is
no more than one second, problems such as inadequate cooling of the
molten synthetic resin do not occur.
[0017] In another aspect of the present invention, the gap formed
between the movable block and the other mold half in the fifth step
is adjusted and determined in increments of 0.1 mm to ensure that
the color of the outer surface of the skin material does not change
significantly after molding, as well as to ensure that there is
minimal deformation.
[0018] Using this method, because the gap between the movable block
after it is moved and the other mold half has the optimal size, the
nap can be reliably restored and problems such as inadequate
cooling of the molten synthetic resin can be prevented.
[0019] It is preferred that the gap between the pair of male and
female pair of mold halves in the half-opening step, or the gap
between the movable block and the other mold half in the movable
block movement step, be set to 80% or more of the thickness of the
final product. If the gap is less than 80% of such thickness, the
pressure applied to the outer surface of the fabric skin material
becomes large and the flattened nap may not be restored uniformly,
and if the gap exceeds 100% of the thickness of the final product,
there is insufficient cooling of the molten synthetic resin during
secondary cooling. Here, the thickness of the final product is the
sum of the preset thickness of the synthetic resin substrate and
the thickness of the skin material before molding.
[0020] Furthermore, it is preferred that the fourth step, i.e., the
primary cooling step, be divided into a first stage and a second
stage, and that the mold be held at a first clamping pressure in
the first stage and at a second clamping pressure that is smaller
than the first clamping pressure in the second stage. The reason
for this is that, if during the second stage of the primary cooling
step the pressure applied to the outer surface of the fabric skin
material is reduced relative to the pressure applied during the
first stage, the tendency of the nap to stay flattened is
mitigated. As a result, the flattened nap can be reliably restored
during the subsequent second cooling step period. Moreover, because
the mold comprising a pair of male and female mold halves is held
at the second clamping pressure in the second stage as well, the
problem of inadequate cooling of the molten synthetic resin does
not occur during primary cooling, and there is no deformation of
the obtained molded article.
[0021] These and other features and advantages of the present
invention will become apparent to those skilled in the art upon a
reading of the following detailed description when taken in
conjunction with the drawings wherein there is shown and described
an illustrative embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a side view schematically showing the molding
apparatus in which the present invention may be applied;
[0023] FIGS. 2A to 2F are views schematically showing the steps for
producing a multilayer molded article in accordance with a first
embodiment of the present invention;
[0024] FIG. 3 is a summary cross-section of the multilayer molded
article produced according to the steps shown in FIGS. 2A to
2F;
[0025] FIG. 4 is a cross-section schematically showing a multilayer
molded article having ribs;
[0026] FIGS. 5A to 5F are views schematically showing the steps for
producing a multilayer molded article pertaining to a second
embodiment of the present invention; and
[0027] FIG. 6 is a cross-section of the multilayer molded article
produced according to the steps shown in FIGS. 5A to 5F.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Embodiments of the present invention will be described below
with reference to the accompanying drawings. In the following
description, like references characters designate like or
corresponding parts throughout the several views. Furthermore, in
the following description, the multilayer molded article is a
molded article in which an skin material is attached on a
thermoplastic resin substrate, and the skin material is an outer
layer such as a fabric skin material that is made of synthetic
resin and has an outer surface with a nap having a length of at
least 1 mm. In addition, it should be understood that the
embodiments described below are only illustrations of the present
invention, which is not limited thereby.
[0029] Now, a first embodiment will be described. The method for
producing a multilayer molded article according to the first
embodiment is a method in which a fabric skin material and a
substrate are integrally formed using the injection press molding
method. This embodiment employs a vertical molding apparatus which
can opens and closes vertically. That is, the molding apparatus
includes a mold having a male and female pair of mold halves that
can come into contact with or move away from each other.
[0030] FIG. 1 is a side view of the basic construction of the
molding apparatus 100. As shown in FIG. 1, the molding apparatus
100 includes a direct pressure-type clamping mechanism 11 and a
horizontal ejection-type injector 12.
[0031] The mold 200 used in the molding apparatus 100, which is
ordinarily used in injection press molding and the like, comprises
a pair of mold halves (hereinafter termed the male mold half 1 and
the female mold half 2), between which is formed a cavity having a
desired product configuration when the mold is in the clamping
position. The mold 200 can opens and closes vertically by the
clamping mechanism 11. The male mold half 1 is stationary, while
the female mold half 2 is movable.
[0032] The clamping mechanism 11 has a clamping cylinder 13 for
opening and closing the mold 200 between a closed state and a
completely open state, and an mold opening apparatus 15 for opening
the mold halves 1 and 2 to a half-open position at which they are
separated by a predetermined gap. Both the clamping cylinder 13 and
the opening apparatus 15 are operated through hydraulic power, but
it is also acceptable if they are driven through electric power. A
plunger 14 as the output shaft for the clamping cylinder 13 is
mounted to a mounting plate 10 that is fixed to the top surface of
the female mold half 2. Through the driving of this clamping
cylinder 13, the female mold half 2 can be moved up and down,
thereby opening and closing the mold 200. The opening apparatus 15
has multiple cylinders connected in a parallel fashion to a
hydraulic circuit not shown in the drawings, and are driven
synchronously and with equal force. When controlling the opening
apparatus 15, the female mold half 2 is raised a predetermined
amount from the closed position away from the male mold half 1, and
the mold 200 thereby reaches a half-open state. In other words, the
female mold half 2 is raised from the closed position to the
half-open position by driving the opening apparatus 15 at the time
of releasing the pressure from the clamping cylinder 13 (which
includes the moment cessation begins as well as the completion
thereof), while the mold 200 is in the clamping position, or by
driving the opening apparatus 15 and subsequently reducing the
pressure exerted by the clamping cylinder 13. The gap W between the
male mold half 1 and the female mold half 2 when the mold is in the
half-open state is determined by the stroke of the mold opening
apparatus 15.
[0033] The clamping mechanism 11 may also comprise an
electric-powered device that uses a servomotor or the like as the
drive source in lieu of the clamping cylinder 13. Where an
electric-powered clamping mechanism is used, because the mold 200
can be opened to the half-open state with high precision, a
component equivalent to the mold opening apparatus 15 is not
necessary.
[0034] At the same time, the injector 12 has a screw 18 located
inside a tubular cylinder 17. An injection nozzle 19 located at the
front end of the injector 12 is connected to one end of a molten
resin path 5 formed in the male mold half 1. The other end of the
molten resin path 5 is connected to the resin supply opening 6 that
opens onto the interior molding surface of the mold 200 (see FIGS.
2A to 2F). In this way, the molten thermoplastic resin that is
plasticized in the cylinder 17 and injected from the injection
nozzle 19 is supplied to the interior of the mold 200 via the
molten resin path 5. The number of molten resin paths 5 and resin
supply openings 6 may be one or two or more, depending on the
configuration, size and the like of the ultimate product, and their
location and configuration may determined appropriately.
[0035] The method for producing a multilayer molded article using
the molding apparatus 100 will now be explained. This production
method is carried out using the following steps {circle over (1)}
to {circle over (7)}. FIGS. 2A to 2F are simplified views showing
the production steps {circle over (1)} to {circle over (7)}.
[0036] <{circle over (1)} Skin Material Supply Step>
[0037] First, the mold 200 is opened to the completely open state,
as shown in FIG. 2A. In other words, the female mold half 2 is
positioned at the completely open position at which it is located
at a predetermined distance above the male mold half 1. The fabric
skin material 3 is then supplied between the mold halves 1 and 2
while they are in the completely open state. At this time, the
fabric skin material 3 is positioned such that the surface on which
the nap 31 is formed (i.e., the outer surface) faces the female
mold half 2. It is acceptable if this fabric skin material 3 is
positioned such that it covers the molding surface, i.e., the top
surface of the male mold half 1, if it is fixed using an skin
material fixing frame (not shown) located between the male and
female mold halves 1 and 2, or if it is fixed on the molding
surface of the female mold half 2 using appropriate means (not
shown) such as pins, and any desired fixing method may be used.
[0038] <{circle over (2)} Molten Resin Supply Step>
[0039] Molten thermoplastic resin 4 is then supplied between the
fabric skin material 3 and the molding surface of the male mold
half 1, as shown in FIG. 2B. When this occurs, the molten
thermoplastic resin 4 is supplied between the molding surface on
the substrate side (i.e., the molding surface of the male mold half
1) and the surface of the fabric skin material 3 on which the nap
31 is not formed (i.e., the back surface). The molten thermoplastic
resin 4 is supplied from the injector 12 via the molten resin path
5 located inside the male mold half 1. Alternatively, the resin may
be supplied by external supply means that supplies the resin
directly to the molding surface from resin supply means such as an
injector or other mechanism located outside the mold 200.
Furthermore, the cavity clearance between the male and female mold
halves 1 and 2 when the molten thermoplastic resin is supplied is
appropriately determined by, specifically, the type and thickness
of the fabric skin material 3 used, the type of thermoplastic resin
used, the thickness of the molded substrate and the like.
[0040] <{circle over (3)} Clamping Step>
[0041] Next, the male and female mold halves 1 and 2 are closed and
the clamping step is performed, as shown in FIG. 2C.
[0042] This clamping is carried out by driving the clamping
cylinder 13 of the clamping mechanism 11 to extend the plunger 14.
But, the step may be begun after the supply of molten thermoplastic
resin 4 is completed, or synchronously with the molten resin supply
step {circle over (2)}, i.e., parallel with the supply of the
molten thermoplastic resin 4. Where clamping is carried out after
the supply of molten thermoplastic resin 4 is completed, it is
preferred that clamping begin immediately after the supply of
molten thermoplastic resin 4 is completed in order to prevent
deformation, etc. of the molded article. Through this clamping
step, the back surface of the fabric skin material 3, i.e., the
surface having no nap 31, is integrally attached on the molten
resin layer at the same time that the outer surface of the fabric
skin material 3 having the nap 31 comes into contact with the
molding surface of the female mold half 2.
[0043] <{circle over (4)} Primary Cooling Step>
[0044] The molten thermoplastic resin 4 then undergoes primary
cooling while [the mold 200] is held in the clamping state. The
primary cooling is considered achieved if the surface area of the
molten thermoplastic resin 4 has hardened slightly during
maintenance of the clamping state, and it is not necessary for the
center area of the thermoplastic resin in the direction of its
thickness to have hardened completely.
[0045] At this time, by holding the pair of male and female mold
halves 1 and 2 according to a predetermined clamping pressure, the
molten thermoplastic resin can be cooled without deformation of the
molded article. The mold 200 is held according to a first clamping
pressure during the first stage of the primary cooling step {circle
over (4)}, and is then held during the second stage according to a
second clamping pressure that is lower than the first clamping
pressure used in the first stage. In this way, because holding the
mold 200 during the second stage according to a second clamping
pressure that is lower than the first clamping pressure used in the
first stage reduces the pressure applied to the outer surface of
the fabric skin material 3 during the second stage and lessens the
pressure on the nap 31, the tendency for the nap 31 to become
flattened is mitigated. As a result, the nap 31 that becomes
flattened can recover its shape more reliably during the subsequent
secondary cooling step {circle over (6)}. Moreover, because the
primary cooling step is also conducted while the mold 200 is being
held according to the second clamping pressure during the second
stage, the problem of deformation of the molded article due to
insufficient cooling does not occur.
[0046] The switching from the first clamping pressure to the second
clamping pressure can be accomplished by reducing the hydraulic
pressure exerted on the clamping cylinder 13, or by driving the
opening apparatus 15 to apply upward pressure on the female mold
half 2 while holding constant the clamping pressure exerted by the
clamping cylinder 13. The second clamping pressure is set to the
optimal pressure as determined based on such factors as the type
and thickness of the fabric skin material 3 used, the type and
thickness of the thermoplastic resin comprising the substrate 40,
and the resin temperature during molding, but from the standpoint
of preventing deformation of the molded article, it is preferred
that the second clamping pressure be set to a value that is between
10% and 80% of the first clamping pressure.
[0047] Depending on the type of fabric skin material 3 and
substrate 40 used and the temperature of the resin during molding,
the mold 200 may be held according to a uniform clamping pressure,
without switching from a first clamping pressure to a second
clamping pressure.
[0048] If the primary cooling period is too short, significant
deformation of the molded article can result, while if the primary
cooling period is too long, substantial damage occurs to the fabric
skin material 3 and the nap does not recover its shape.
Consequently, the total time used for primary cooling, as well as
the time periods for the first and second stages, are set to the
optimal times in accordance with such factors as the type and
thickness of the used fabric skin material 3, the resin temperature
during molding and the clamping pressure. As a typical rule, where
the primary cooling period is between five and ten seconds, it is
preferred that the clamping time in the first stage not exceed
three seconds. For example, when producing a multilayer molded
article in which a fabric outer layer 3 having a 6 mm nap is
attached on a substrate 40 having a thickness of 2.5 mm, where the
mold temperature is 30.degree. C. and polypropylene resin (motel
thermoplastic resin 4) heated to 200.degree. C. is used, the
primary cooling period should range from approximately five seconds
to ten seconds.
[0049] <{circle over (5)} Half-Opening Step>
[0050] After the primary cooling step {circle over (4)} has been
completed, the pair of male and female mold halves 1 and 2 are
half-opened such that they are separated by a predetermined gap W,
as shown in FIG. 2D.
[0051] This-half-opening step is carried out by raising the female
mold half 2, the molding surface of which has been in contact with
the outer surface of the fabric skin material 3. When this
half-opening is done, a gap A is formed between the outer surface
of the fabric skin material 3 and the molding surface of the female
mold half 2. As a result, the clamping pressure exerted on the nap
31 on the outer surface of the fabric skin material 3 is reduced,
thereby permitting the flattened nap 31 to rise and recover its
shape during the subsequent secondary cooling step {circle over
(6)}.
[0052] The gap W indicates the distance between the molding surface
of the male mold half 1 and the molding surface of the female mold
half 2, while the gap A indicates the difference between the
molding surface of the female mold half 2 during the primary
cooling step {circle over (4)} and the molding surface of the
female mold half 2 when the mold 200 is in the half-open state (see
FIG. 2D).
[0053] This half-opening operation is carried out within one second
or less. If the period for the half-opening operation exceeds one
second, the nap 31 tends to get flattened even during this period
and does not completely recover, but performing the operation
within one second allows the nap 31 to recover its shape and
eliminates the tendency toward flattening.
[0054] Moreover, because the transition from the primary cooling
step {circle over (4)} to the secondary cooling step {circle over
(5)} takes place in one second or less, the problem of inadequate
cooling of the molten thermoplastic resin 4 also does not occur.
Here, the half-opening operation time period is the period that
elapses between the time that the clamping pressure on the mold 200
begins to be reduced after the primary cooling step {circle over
(4)} is completed and the time that the female mold half 2 reaches
the half-open position. This half-opening operation may be carried
out by either releasing the pressure from the clamping cylinder 13
(which includes the moment cessation begins as well as the
completion thereof) and driving the opening apparatus 15, while the
mold 200 is in the clamping position, or driving the opening
apparatus 15 and subsequently reducing the pressure from the
clamping cylinder 13. The method involving the prior driving of the
opening apparatus 15 is preferred from the standpoint of speeding
up the half-opening operation. Where the mold comprising a pair of
male and female mold halves is held at the second clamping pressure
during the second stage of the primary cooling step {circle over
(4)}, the half-opening step can be more reliably carried out within
one second. Furthermore, where an electric-powered clamping
mechanism that uses a servomotor or the like is employed as the
clamping mechanism 11, the half-opening operation can be performed
within one second by switching the polarity supplied to the
servomotor and raising the female mold half 2 to a predetermined
half-open position.
[0055] Even where the half-opening operation is carried out in one
second or less, if the gap W between the mold halves 1 and 2 is too
narrow, the nap 31 that is flattened by the clamping pressure
cannot recover its shape, and a molded article with an attractive
appearance cannot necessarily be obtained. On the other hand, if
the half-opening gap W is too wide, the problem of inadequate
cooling becomes significant, and deformation of the molded article
occurs. Therefore, the gap W must be set to the appropriate
width.
[0056] When determining the width of the half-opening gap W, it is
effective if the half-opening gap W between the male and female
mold halves 1 and 2 is adjusted in increments of 0.1 mm in order to
minimize the difference in the color of the fabric skin material 3
after molding and the degree of deformation of the molded article.
This involves performing the molding operation multiple times,
changing the width of the gap W each time in 0.1 mm increments,
observing the color difference in the outer surface of the fabric
skin material and the degree of deformation in each obtained
multilayer molded article, and selecting a gap W that results in
the smallest color difference and deformation in the molded
article.
[0057] The color difference in the outer surface of the fabric skin
material 3 is observed for the following reason: because the hue of
the outer surface of the fabric skin material 3 changes depending
on the degree of flattening of the nap 31, it is understood that
where the color difference in the outer surface of the fabric skin
material 3 after molding is smallest, the condition of the nap 31
after molding is close to the condition of the nap 31 before
molding, and the least amount of nap flattening occurs. This is due
to the fact that the color difference in the outer surface of the
fabric skin material 3 becomes smaller as the width of the
half-opening gap W increases, because the nap 31 that was flattened
rises in a reliable fashion during the secondary cooling step
{circle over (6)} when the pressure applied to the outer surface of
the fabric skin material 3 by the molding surface is mitigated.
[0058] In addition, if the half-opening gap W is too wide, there is
insufficient cooling of the molten thermoplastic resin 4 during the
secondary cooling step {circle over (6)}, and deformation of the
molded article can easily occur. Accordingly, the width of the
half-opening gap W is determined subject to the condition that
minimal deformation of the molded article occur during the molding
step.
[0059] According to the method for determining the width of the gap
W as described above, because the width of the gap W is adjusted in
small increments of 0.1 mm, the gap W can be reliably set to the
optimal width for obtaining a molded article with the smallest
possible nap flattening and deformation. This adjustment in 0.1 mm
increments is easily and reliably performed using the opening
apparatus 15. In other words, because the pressure needed to raise
the female mold half 2 to the half-open position is apportioned
among the cylinders of the opening apparatus 15, the total stroke
amount of the opening apparatus 15 as a whole can be easily
controlled, and as a result, the female mold half 2 can be stopped
at the half-open position far more precisely than when it is raised
by a single clamping cylinder 13 that has a large capacity and
relatively sluggish responsiveness. In addition, where an
electric-powered clamping mechanism that uses a servomotor is
employed, the female mold half 2 can be raised to the predetermined
half-open position with great precision by the servomotor.
[0060] It is preferred that the width of the gap W between the mold
halves 1 and 2 fall within a range between 80% of the thickness of
the final product and the total thickness of the final product.
Here, the thickness of the final product is defined as the sum of
the preset thickness of the substrate 40 and the thickness of the
fabric skin material 3 prior to molding.
[0061] By performing the half-opening step {circle over (5)} using
the half-opening gap W determined in this manner, the flattened nap
31 on the fabric outer layer 3 is restored in an optimal fashion in
the subsequent secondary cooling step {circle over (6)} while
insufficient cooling of the molten thermoplastic resin 4 is
prevented.
[0062] The optimal width of the gap W can be automatically sought
by building a software program that pre-registers the hue of the
back surface of the fabric outer layer 3 prior to molding and the
design configuration of the final product, reads, using a desired
image analyzer or other apparatus that is equipped with an image
pickup device, the hues of the outer surfaces of post-molding
fabric skin materials 3 and the configurations of the molded
articles obtained using various gaps W obtained through adjustment
in 0.1 mm increments, analyzes the color differences and degrees of
deformation of the molded articles, and automatically determines
the value that brings about the minimal color difference and
deformation, and by seeking the optimal position of the gap W based
on processing carried out by such program.
[0063] <{circle over (6)} Secondary Cooling Step>
[0064] Secondary cooling of the molten thermoplastic resin 4 is
next carried out while the mold 200 is held in the half-open state,
as shown in FIG. 2E.
[0065] This secondary cooling is performed until the center portion
of the clamped molten thermoplastic resin 4 in terms of its
thickness has hardened, as in the normal molding method.
Furthermore, with regard to the fabric skin material 3 that is
compressed by the clamping performed in the primary cooling step
{circle over (4)}, the flattened nap 31 recovers its shape during
the cooling period of the secondary cooling step {circle over
(6)}.
[0066] <{circle over (7)} Product Extraction Step>
[0067] After the molten thermoplastic resin 4 has hardened to
become the substrate 40, the mold 200 is opened and the multilayer
molded article is extracted, as shown in FIG. 2F. The resulted
article includes the fabric skin material 3 attached on the
substrate 40, and the 31 nap on the skin material 3 recovers its
shape. Thereafter, the unnecessary parts of the fabric skin
material 3 outside the substrate 46 are cut off, and the final
product 8 made of the multilayer molded article is obtained (see
FIG. 3).
[0068] As described above, according to the first embodiment,
because the time period of the half-opening operation of the
half-opening step {circle over (5)} is limited to one second or
less, the nap 31 on the outer surface of the fabric skin material 3
is reliably restored and inadequate cooling of the molten
thermoplastic resin 4 does not occur. As a result, a multilayer
molded article 8 having an attractive appearance with little
flattened nap or deformation can be reliably obtained.
[0069] Moreover, because the width of the gap W is determined
through adjustment in increments of 0.1 mm in order to minimize
both the color difference in the outer surface of the fabric skin
material 3 after molding and the degree of deformation, the
reliability of the restoration of the nap 31, as well as the effect
of preventing inadequate cooling of the thermoplastic resin 4, are
further increased. In addition, where the half-opening gap
determination method described here is used, the optimal
half-opening gap W can be obtained, and as a result, a multilayer
molded article having an attractive appearance with minimal nap
flattening or deformation can be reliably obtained even if the time
period of the half-opening operation of the half-opening step
exceeds one second.
[0070] In the method described above, the deformation of the molded
article can be controlled even more effectively where ribs 7 are
formed on the back surface of the substrate 41 as shown in FIG. 4.
This is realized by placing indentations and protrusions
corresponding to the ribs 7 on the molding surface of the male mold
half 1.
[0071] A second embodiment will now be described. The second
embodiment is a method for producing a multilayer molded article
wherein a fabric skin material is partially attached to the outer
surface of a substrate. The principal aspect in which the second
embodiment differs from the first embodiment is that in the second
embodiment a movable block that can slide to advance and retract in
the opening and closing directions is located on part of the female
mold half, and the operation to retract this movable block (the
movable block retraction step {circle over (5)} described below) is
equivalent to the half-opening step {circle over (5)} shown in FIG.
2D. Therefore, a molding apparatus having a construction
essentially identical to that of the molding apparatus 100 used in
the first embodiment can be also used in this method, except that
in lieu of the female mold half 2 shown in FIG. 1 and in FIGS. 2A
to 2F, a female mold half 20 is used in which a movable block 21 is
located at the area of the molding surface 23 that corresponds to
the skin material attaching surface in a product and comes into
contact with the fabric skin material 50, as shown in FIGS. 5A to
5F.
[0072] The size of the molding surface 24 of the movable block 21
corresponds essentially to the surface of the fabric skin material
50 to be attached. The movable block 21 is constructed such that it
is embedded in the female mold half 20 and is connected to driving
means 22, and can slide inside the mold 200A to advance and retract
in the mold opening and closing directions via the driving means
22.
[0073] The driving means 22 may comprise a hydraulic cylinder, an
electric-powered output shaft such as a servomotor, or other
means.
[0074] In the state in which the movable block 21 has advanced the
farthest, as shown in FIG. 5A, the molding surface 24 of the
movable block 21 and the molding surface 23 of the female mold half
20 in which the movable block 21 is embedded form a single
continuous molding surface. In this second embodiment, the mold
opening apparatus 15 used in the first embodiment (see FIG. 1) need
not be included in the clamping mechanism.
[0075] The multilayer molded article production method pertaining
to the second embodiment will now be explained in detail below.
This production method is carried out via the following steps
{circle over (1)} to {circle over (7)}, in that order. FIGS. 5A to
5F are simplified views showing these production steps {circle over
(1)} through {circle over (7)}.
[0076] <{circle over (1)} Skin Material Supply Step>
[0077] First, as shown in FIG. 5A, the mold 200A is opened to the
completely open state and the fabric skin material 50 is supplied
between the male mold half 1 and the female mold half 20. When this
is done, the fabric skin material 50 is supplied with the nap 51
facing upward to a position corresponding to the molding surface 24
of the movable block 21. FIG. 5A shows a situation in which the
fabric skin material 50 is placed at a position on the molding
surface of the male mold half 1 at which it faces the molding
surface 24 of the movable block 21.
[0078] The fabric skin material 50 may be simply placed on top of
the molding surface of the male mold half 1, but it is also
acceptable if the position of the fabric skin material 50 is fixed
using a fixing apparatus or other means to determine its position.
The fabric skin material 50 may be supplied and fixed using any
desired method. For example, depending on the positional
relationship between the male and female mold halves 1 and 20 and
the type, etc., of fabric skin material 50, the fabric skin
material 50 may be placed directly on the molding surface 24 of the
movable block 21, or the outer surface of the fabric skin material
50 may be temporarily affixed to the molding surface 24 of the
movable block 21 using two-sided tape or similar means.
[0079] <{circle over (2)} Molten Resin Supply Step>
[0080] The molten thermoplastic resin 4 is next supplied between
the fabric skin material 50 and the molding surface of the male
mold half 1, as shown in FIG. 5B.
[0081] This molten resin supply step {circle over (2)} is
essentially similar to that carried out in the first embodiment,
except that when the molten thermoplastic resin 4 is supplied,
normally, the position of the movable block 21 is pre-adjusted such
that the molding surface 24 of the movable block 21 and the molding
surface 23 of the female mold half 20 in which the movable block 21
is embedded form a continuous molding surface.
[0082] <{circle over (3)} Clamping Step>
[0083] The male and female mold halves 1 and 20 are then closed and
clamping is carried out, as shown in FIG. 5C. This clamping step
{circle over (3)} is also similar to that carried out in the first
embodiment, and during this clamping step, the outer surface of the
fabric skin material 50 comes into contact with the molding surface
24 of the movable block 21 at the same time that it is attached to
part of the outer surface of the molten thermoplastic resin
layer.
[0084] <{circle over (4)} Primary Cooling Step>
[0085] The molten thermoplastic resin 4 then undergoes primary
cooling while being held in the clamped state. This primary cooling
step {circle over (4)} is also similar to that carried out in the
first embodiment. In other words, the mold 200A may be held
according to a first clamping pressure during the first stage of
this primary cooling step {circle over (4)} and then held during
the subsequent second stage according to a second clamping pressure
that is smaller than the first clamping pressure, or alternatively,
the mold 200A may be held according to a uniform clamping pressure
throughout the entire primary cooling step {circle over (4)}.
[0086] <{circle over (5)} Movable Block Movement (Retraction)
Step>
[0087] Once the primary cooling step {circle over (4)} is
completed, the movable block 21 is retracted (moved upward) to form
a predetermined gap A1 between the outer surface of the fabric skin
material 50 and the molding surface 24 of the movable block 21, as
shown in FIG. 5D.
[0088] The movable block 21 is retracted through the driving of the
means 22 such as a hydraulic cylinder connected to the movable
block 21. Thus, a gap A1 is formed between the outer surface of the
fabric skin material 50 and the molding surface 24 of the movable
block 21. As a result, the clamping pressure exerted on the nap 51
on the outer surface of the fabric skin material 50 is reduced,
thereby causing the nap 51 that was flattened to rise during the
cooling period of the subsequent secondary cooling step {circle
over (6)}, enabling it to recover its shape.
[0089] The time period for the movement of the movable block 21,
i.e., the retraction operation period (the time from the
commencement to the completion of retraction) is one second or
less, as with the half-opening period of the half-opening step
{circle over (5)} in the first embodiment. Consequently, the nap 51
can reliably recover its shape during the subsequent secondary
cooling step {circle over (6)} without staying flattened, and
because the transition from the primary cooling step {circle over
(4)} to the secondary cooling step {circle over (6)} takes in no
more than one second, the problem of inadequate cooling of the
molten thermoplastic resin 4 in the attaching area of the fabric
skin material 50 does not occur.
[0090] The gap A1 formed by the retraction of the movable block 21
is the distance between the molding surface 23 of the female mold
half 20 and the molding surface 24 of the movable block 21 when the
movable block 21 has been retracted (see FIG. 5D). It is preferred
that the gap W1 formed between the molding surface of the male mold
half 1 and the molding surface 24 of the movable block 21 after
retraction of the movable block 21 have a width that falls between
80% and 100% of the thickness of the final product.
[0091] Here, it is effective if the gap W1 is determined after
adjustment in minute increments in order to minimize the color
difference in the outer surface of the fabric skin material 50
after molding and the deformation of the molded article, as with
regard to the half-opening step {circle over (5)} in the first
embodiment. In this way, the flattened nap 51 on the outer surface
of the fabric skin material 50 can recover in an optimal fashion in
the subsequent secondary cooling step {circle over (6)} while
inadequate cooling of the molten thermoplastic resin 4 is
prevented.
[0092] By adjusting the width of the gap W1 in minute 0.1 mm
increments, the optimal gap W1 that enables a molded article having
minimal nap flattening and deformation to be obtained can be
reliably determined.
[0093] Moreover, with respect to the gap W1, it is also acceptable
if essentially the same software as that used in the half-opening
step {circle over (5)} in the first embodiment is built, and if the
optimal position is automatically sought using this software.
[0094] <{circle over (6)} Secondary Cooling Step & {circle
over (7)} Product Extraction Step>
[0095] As in the first embodiment, after the molten thermoplastic
resin 4 has undergone secondary cooling while the movable block 21
is held in the retracted state (see FIG. 5E) and the molten
thermoplastic resin 4 has hardened to become the substrate 40, the
mold 200 is opened and the molded article is extracted (see FIG.
5F). In the processes {circle over (1)} through {circle over (7)}
described above, a multilayer molded article 80 is produced in
which a fabric skin material 50 having a restored nap 51 is
partially attached on a substrate 40, as shown in FIG. 6.
[0096] In this second embodiment as well, because the time period
of the operation to retract the movable block 21 in the movable
block 21 retraction step {circle over (5)} is limited to one second
or less, the nap 51 on the outer surface of the fabric skin
material 50 can be reliably restored, and such problems as
inadequate cooling of the molten thermoplastic resin 4 do not
occur. As a result, a multilayer molded article 80 that has an
attractive appearance and does not exhibit nap flattening or
deformation can be reliably obtained.
[0097] In addition, because the gap W1 between the molding surface
24 after the movable block 21 is retracted in the movable block 21
retraction step {circle over (5)} and the molding surface of the
male mold half 1 is determined through adjustment in increments of
0.1 mm so as to minimize the color difference in the outer surface
of the fabric skin material 50 after molding as well as the
deformation of the molded article, the nap 31 can be restored more
reliably and the effect of preventing inadequate cooling of the
thermoplastic resin 4 is strengthened. Where this gap determination
method is used, because an extremely accurate gap W1 is obtained, a
multilayer molded article having an attractive appearance with
minimal flattened nap or deformation can be obtained even if the
time period of the retraction operation of the retraction step
{circle over (5)} exceeds one second.
[0098] Depending on the relationship between the surface area of
the entire substrate 40 and the area of the section on which the
fabric skin material 50 is attached, the section of the substrate
40 on which the fabric skin material 50 is attached may be
inadequately cooled due to the adiabatic effect of the fabric skin
material 50, creating the risk of deformation of the molded article
due to the different rates of cooling between the attaching area of
the substrate 40 and the other areas thereof. Such deformation can
be prevented by locating ribs 7 or other means on the back of the
substrate 41, as shown in FIG. 4. Furthermore, the movable block 21
is not limited to any particular configuration and number. Its
molding surface may have various different configurations, and
multiple movable blocks 21 may be used.
[0099] While the above description is useful in understanding the
present invention and its advantages, the embodiments described
herein are merely illustrative, and needless to say, various
changes to the configuration, construction and arrangement thereof
may be made without departing from the spirit and scope of the
present invention.
[0100] For example, the opening and closing directions of the mold
200 or 200A are not essential features of the present invention,
which could be implemented in an identical manner even if the mold
were to open and close horizontally from left to right.
[0101] Furthermore, so long as the fabric skin material 3 or 50
applied in the method of the present invention has on the outer
surface thereof a synthetic resin nap 31 or 51 having a length of 1
mm or more, there is no particular limitation on the type of fabric
skin material that may be used. For example, a woven or knitted
material having nap, such as moquette or tricot, or a non-woven
fabric such as needle-punched carpet, may be used. These fabric
skin materials may be used alone, but may also be used as a
compound fabric skin material comprising two or more materials that
are attached on each other using an adhesive or other substance. In
particular, a fabric skin material that includes as the liner
material foamed polyolefin resin sheeting such as foamed
polypropylene sheeting, or foamed urethane sheeting, is often used.
With regard to foamed polyolefin resin sheeting such as foamed
polypropylene sheeting, both bridged-type foamed sheeting and
non-bridged type foamed sheeting may be used, and there are no
particular limitations regarding the expansion ratio thereof.
Furthermore, depending on the configuration of the fabric skin
material to be attached, the fabric skin material may be subject to
preliminary molding.
[0102] Moreover, for the thermoplastic resin used to form the
substrate 40 or 41 applied in the method of the present invention,
any resin may be used that is normally used in common injection
molding, injection pressure molding, extrusion molding or stamping
molding, and there is no particular restriction on the material
used. For example, such material may comprise a common
thermoplastic resin such as polyolefin resin such as polyethylene
or polypropylene, or polystyrene, acrylic resin,
acrylonitrile-styrene-butadiene block copolymer, nylon or other
polyamide, polyvinyl chloride, polycarbonate, or styrene-butadiene
block copolymer, as well as a thermoplastic elastomer such as EPM
or EPDM or a mixture thereof, or a polymer alloy that combines
these materials. These resins may be foaming or non-foaming resins,
and may include a filler consisting of an organic or inorganic
filler comprising a reinforcing fiber such as glass fiber, talc, or
Wallastonite. Naturally, various pigments, sliding materials,
anti-static agents, antioxidants, anti-UV agents or other commonly
used additives may be included where appropriate.
* * * * *