U.S. patent application number 11/142861 was filed with the patent office on 2005-12-15 for decorative components for motor vehicle interiors.
This patent application is currently assigned to Key Safety Systems, Inc.. Invention is credited to Menaldo, Lorenzo, Ridolfi, Adolfo, Salvoro, Roberto, Testa, Giuseppe.
Application Number | 20050276874 11/142861 |
Document ID | / |
Family ID | 34932548 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050276874 |
Kind Code |
A1 |
Menaldo, Lorenzo ; et
al. |
December 15, 2005 |
Decorative components for motor vehicle interiors
Abstract
A method of manufacturing a decorative components for vehicle
interiors, comprises the steps of pre-forming a sheet of formable
veneer material under pressure and heath, positioning the
pre-formed sheet in a mold half of an injection mold comprising a
cavity; holding the sheet in position on the mold half, closing
said mold and injecting into the cavity one or more thermoplastic
materials on the back of the veneer sheet to provide a support
layer.
Inventors: |
Menaldo, Lorenzo;
(Villafranca, IT) ; Testa, Giuseppe; (Illasi,
IT) ; Ridolfi, Adolfo; (Tregnago, IT) ;
Salvoro, Roberto; (Illasi, IT) |
Correspondence
Address: |
KEY SAFETY SYSTEMS, INC.
PATENT DEPARTMENT
5300 ALLEN K BREED HIGHWAY
LAKELAND
FL
33811-1130
US
|
Assignee: |
Key Safety Systems, Inc.
|
Family ID: |
34932548 |
Appl. No.: |
11/142861 |
Filed: |
June 1, 2005 |
Current U.S.
Class: |
425/129.1 ;
264/250; 264/255; 428/34.1 |
Current CPC
Class: |
B29C 2045/14237
20130101; B32B 21/14 20130101; B29C 51/145 20130101; B29K 2711/14
20130101; B29C 45/14065 20130101; B29C 69/02 20130101; B29L
2031/3047 20130101; B29C 45/14778 20130101; B29C 2791/001 20130101;
B29K 2027/06 20130101; B32B 27/12 20130101; B32B 27/08 20130101;
B29C 51/28 20130101; B29K 2055/02 20130101; B32B 2605/08 20130101;
B29L 2031/3005 20130101; B32B 21/08 20130101; Y10T 428/13 20150115;
B29C 45/1679 20130101; B32B 2605/003 20130101; B32B 2451/00
20130101 |
Class at
Publication: |
425/129.1 ;
428/034.1; 264/250; 264/255 |
International
Class: |
B65D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2004 |
EP |
04425423.3 |
Claims
We claim:
1. A method of manufacturing a component for a vehicle interior
comprising the steps of: (a) preparing a laminate layer comprising
a veneer layer and a formable and form-retaining layer selected
from thermoplastic and thermosetting plastic materials; (b)
pre-forming said laminate layer in a mold having a cavity and a
male portion, said male portion comprising a deformable element to
shape said laminate layer according to said cavity; (c) positioning
said pre-formed laminate layer in an injection mold and injecting
into said mold one or more thermoplastic materials on the back of
the said pre-formed laminate to provide a laminate having a support
and coupling layer.
2. The method of manufacturing a component for a vehicle interior
according to claim 1, wherein said laminate comprises a peripheral
rim or step.
3. The method of manufacturing a component for a vehicle interior
according to claim 1 or 2, wherein said laminate comprises a veneer
layer bonded to a transparent film material.
4. The method of manufacturing a component for a vehicle interior
according to claim 1 or 2 wherein said laminate comprises a layer
of resistive material.
5. The method of manufacturing a component for a vehicle interior
according to claim 3 wherein said laminate comprises a layer of
resistive material.
6. The method of manufacturing a component for a vehicle interior
according to claim 1 or 2 wherein said veneer material comprises
wood.
7. The method of manufacturing a component for a vehicle interior
according to claim 3 wherein said veneer material comprises
wood.
8. The method of manufacturing a component for a vehicle interior
according to claim 4 wherein said veneer material comprises
wood.
9. The method of manufacturing a component for a vehicle interior
according to claim 1 wherein means of attachment of the decorative
component are molded integral with said injected support layer.
10. The method of manufacturing a component for a vehicle interior
according to claim 1 wherein said veneer material comprises at
least one material selected from a group consisting of wood,
fabrics, carbon fiber, and aramid fiber.
11. The method of manufacturing a component for a vehicle interior
according to claim 1 further comprising an "In-Mold Paint"
step.
12. A component for a vehicle interior manufactured by the method
of claim 1 comprising a veneer material bonded to a first layer of
formable and form retaining material selected from thermosetting or
thermoplastic material, said thermoplastic film being bonded with
one layer of thermoplastic material produced by injection
molding.
13. The component for a vehicle interior according to claim 12 that
is a shell for a steering wheel.
14. The component for a vehicle interior according to claim 12
wherein said veneer material comprises wood.
15. The component for a vehicle interior according to claim 13
wherein said veneer material comprises wood.
16. A mold for pre-forming sheets of formable veneer material for a
component for a vehicle interior comprising two mold halves
defining a cavity, expandable means located on one of said mold
halves and projecting into said cavity when the mold is closed, and
means of expanding said expandable means and causing it to occupy
substantially all said cavity.
17. The mold according to claim 16, further comprising at least one
insert for the production of undercuts, steps and locking rims.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to decorative components for
motor vehicle interiors, as well as to a method and devices for
their production.
[0002] 1. Background of the Invention
[0003] In the automotive field the demand for decorative parts or
components, in particular made of wood, continues to rise. It is
known to cover an aluminum or plastic core with a layer of wood or
other decorative layer that is glued and finished manually.
[0004] To reduce the time required by such manual operations,
techniques have been developed that produce a laminated shell in a
one-step method with a wood veneer and a supporting layer of a
thermosetting resin. A disadvantage of this technique is that
pieces with hooks, locking rims and other mechanical attachment
means cannot be produced. Another disadvantage is the long
production times.
[0005] 2. Discussion of the Prior Art
[0006] U.S. Pat. No. 5,792,302 discloses a process for the
production of steering wheels with a wood veneer as a surface
layer. Two layers of wood are pre-formed in two half-shells that
are placed in a mold with the metal armature of the steering wheel.
An expansion resin is then injected into a space between the metal
armature and the half-shells, according to the Reaction Injection
Molding technique, in order to force the half-shells against the
mold and bond them together. Alternatively, two half-shells already
supplied with the expanded resin portion are produced separately
and glued to the metal armature of the steering wheel. This
technique has several drawbacks because pieces with means of
attachment or locking rims or undercuts cannot be produced. During
the foaming Reaction Injection Molding flash is formed that must be
removed by hand. The pre-forming and Reaction Injection Molding
molding times are particularly long, reaching 40 minutes each.
Moreover, like in the thermosetting-resin molding technique, it
also requires a manual finishing step.
[0007] U.S. Pat. No. 5,264,062 discloses production methods for a
composite molded article having a wood overlay surface material.
This document teaches to laminate the wood overlay surface to a
metal or resin sheet that is backed on the other side to a porous
or fibrous material; the wood overlay veneer of the thus obtained
laminate is then coated, possibly after polishing. According to one
of the disclosed production methods, the coated laminated material
is preliminary molded (formed) by press working before a
thermoplastic supporting layer is injection molded to the back of
the material.
[0008] U.S. Pat. No. 5,863,479 discloses a method of producing a
laminated or composite material having a wood overlay veneer
wherein the wood veneer is backed with a thin aluminium sheet,
treated with a primer-based colorant and coated with a resin layer
before being pre-formed in a conventional mold using a press. The
thus obtained piece is placed into a mold and a backing resin
supporting layer and a front transparent coating layer are injected
into the mold.
[0009] The above methods are long and complex, involving several
coupling and coating steps and are limited to pre-forming of very
simple shapes, thus resulting in expensive production
processes.
[0010] It is an aim of the present invention to solve the
aforementioned problems and provide a process and a device to
produce decorative parts or components with a veneer layer of wood,
fabrics or other decorative materials, in a reliable and economic
way that gives very good aesthetic results and that reduces the
manual finishing times.
SUMMARY OF THE INVENTION
[0011] The present invention addresses the aforementioned problems.
According to one aspect of the invention, the veneer layer sheet
comprises one layer of wood veneer or other decorative material
bonded to one layer of backing material selected from thermoplastic
or thermosetting materials and is pre-formed prior to the final
thermoplastic-material injection step that provides the required
supporting and coupling layer. According to a further aspect, the
layer of rigid material is transparent and is located on the
external side of the decorative material layer.
[0012] According to a still further aspect of the invention, the
pre-forming step is carried out in a mold having a male and a
female part, wherein the male part comprises a projecting element
that is at least in part deformable to adapt its shape to the shape
of the female part and to accordingly shape the decorative layer.
The male part projecting element is made of rubber, e.g. silicone
rubber, that can be full or provided with an internal cavity that
can be expanded upon feeding of a pressurized fluid.
[0013] According to another aspect of the invention, one of the
layers of the decorative layer is provided with electrically
resistant means, such as a layer of electrically resistant coating,
to act as heating means for a steering wheel or similar
component.
[0014] During the closing of the mold or at the beginning of the
injection step, the veneer layer sheet is held in position against
the respective mold half. This holding in position action can be
carried out with retaining means such as jacks, struts, needles or
similar moving elements, or by the mentioned pre-forming of the
veneer layer. Because the layer is pre-formed accurately, it
already has a shape that is almost the final one and will therefore
fit snugly in the mold half without requiring any mechanical means.
If, because of the final shape a self-retaining effect cannot be
achieved and mechanical means are required, such as those
previously mentioned, they project from the mold half that does not
house the veneer layer and are mobile between an extended position
and a retracted position; the force applied by said projecting
elements to the covering sheet is such as to maintain the sheet in
position at least during the initial step of the molding process.
Thus, for the present invention the wording "holding in position"
refers to both the above ways only through the shape or with
mechanical means.
[0015] According to a further aspect of the invention, a varnish or
a coating layer is injected on the side of the cavity that
corresponds to the face of the decorative sheet, after the
thermoplastic-material injection step.
[0016] A further aspect of the invention is a mold for pre-forming
the decorative components, comprising two mold halves, a cavity and
a deformable forming means positioned in one of said mold
halves.
[0017] A further aspect of the invention is a decorative component
as obtainable with the method of manufacturing described above,
comprising a veneer layer, at least one layer of backing material
selected from thermoplastic or thermosetting materials, at least
one coupling layer of thermoplastic material having means of
attachment and/or undercuts provided into said thermoplastic
material.
[0018] A still further aspect of the invention is steering wheel
shells having a veneer layer as obtainable according to the
invention method of manufacturing.
[0019] Preferably, the decorative components obtained according to
the invention comprise a first layer of thermoplastic glued to the
decorative material layer and a second layer of thermoplastic
injected onto the said first layer. A layer of fabric or non-woven
fabric may be bonded externally to the layer of thermoplastic glued
to the decorative material layer in order to improve flexibility
and the adhesion of the injected material on the decorative
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a perspective view in partial section of two
half-shells according to the invention.
[0021] FIGS. 2, 3 and 4 are schematic cross sectional views of the
method of molding half-shells according to the invention.
[0022] FIG. 5 is a schematic cross sectional view of a liner sheet
to be used in the method of manufacturing according to the
invention.
[0023] FIG. 6 is a partially magnified cross sectional view of the
bonded half-shells of FIG. 1.
[0024] FIGS. 7 and 8 are schematic cross sectional views of a
pre-forming mold during two steps of the pre-forming process.
[0025] FIG. 9 is an enlarged exploded view of a veneer element
after preforming of FIGS. 7 and 8 and injection molding.
[0026] FIG. 10 is a perspective view of the veneer element of FIG.
9.
[0027] FIG. 11 is a cross sectional view of a rim of a steering
wheel manufactured in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] As used herein and in the claims the term decorative
components for motor vehicle interiors refers to steering wheel
shells, handles, gear-change lever knobs, inserts for door interior
panels, dashboards and similar articles.
[0029] With reference to FIGS. 2-4, a mold 1 according to the
present invention comprises mold halves 2, 3, which when closed
define a cavity 4 having a shape corresponding to the design of a
decorative component for a car interior, for example a knob for a
gear-change lever; a shell for a steering wheel; an insert for a
dashboard or for an interior panel for a door. In the embodiment
shown and discussed herein, reference is made to a pair of
half-shells for a steering wheel, but the same remarks are valid
for other decorative components. Similarly, the decorative
component disclosed hereinafter is provided with a wood veneer, but
instead of wood, the veneer could be made of a fabric, e.g. carbon
fiber fabric or aramid fibers, leather and other materials.
[0030] A pre-shaped layer 5 comprising a layer of veneer material
(wood, fabric or other) 12 (FIG. 5) and a backing layer 14 of
thermoplastic or thermosetting material, is placed in the mold,
held in position and an amount of a thermoplastic material 6 is
injected onto the back of the layer 5. To maintain the layer of
wood 5 in position during the closing of the mold and to prevent it
from moving from the desired position, in one embodiment of the
invention the mold is provided with a means of retaining the layer
5 in position. In FIGS. 2-4 such a means of retaining position is
exemplified by retractable small rods or needles 7, which move
between an extended position with the mold open (FIG. 2), a
partially retracted one at the beginning of the injection step, and
a retracted one, in which they are positioned when the injection of
thermoplastic support material is partially completed (FIG. 4).
[0031] FIG. 3 shows the mold-closing step, in which rods 7 hold in
position the steering wheel half-shell 5 in the mold half 2 before
being retracted in the last step of the injection molding process.
Alternatively, other known means such as for example needles,
clips, suction pads, temporary adhesives can be used to hold in
position the veneer layer sheet 5.
[0032] The injection molding conditions are e.g. those used in the
technique known as "In Mold Labeling (IML)" or "In Mold Dekorieren
(IMD)" and involve low injection pressures; in the inventive method
injection pressures are related to the dimension of the decorative
component. For example, injection molding of wood veneered steering
wheel rim sectors, using a 30% glass reinforced polyamide, is
carried out at a pressure within the range of 1.100 and 1.500
Kg/cm.sup.2, depending upon the shell length. In spite of the
injection pressure being relatively low, the pressure is however
sufficient to press the pre-shaped sheet 5 against the mold half 2
and to give the sheet or layer 5 the desired shape and dimensions.
Thermoplastic materials suitable for injection molding of layer 6
are polyolefins and polypropylene in particular, polyamides, ABS
and vinyl polymers.
[0033] The mold half 3 is designed to mold hooks 8 or similar means
of attachment of the half-shell to a steering wheel, dashboard or
panel, as well as reinforcing ribs and other structural components
as required. In FIG. 1 the two half-shells L and R are used for
covering a steering wheel all the way around its circumference,
i.e. for 360.degree.. To enable an overlap without showing gaps,
the half-shell L is provided with a locking step 9 and with a
portion 10 of the thermoplastic layer of 6 protruding with respect
to the layer of wood 5. The corresponding half-shell R presents a
portion 11 of the sheet 5 that projects beyond the injected
thermoplastic layer 6 in order to provide a complementary shape to
the locking step 9. Once the half-shells L and R are joined, as
shown in FIG. 6, a portion 10 of layer 6 of the half-shell L
overlaps layer 6 of the half-shell R; the two half-shells can be
welded using ultrasonic energy, vibration, "hot gas" and other
known techniques of welding thermoplastic. In this way, the use of
adhesives and the problems associated therewith are avoided.
[0034] The mold half 3 is provided with at least one nozzle 16 for
injecting the thermoplastic layer. In the simplest embodiment shown
in FIGS. 1-5, the sheet 5 is backed by a layer 6 comprising a
thermoplastic material that provides the structural and coupling
layer required. If the dimensions of the sheet are reduced one
nozzle may be sufficient, but it is often preferred to inject
through two or more nozzles in order to use low injection
pressures. The nozzles can feed one or more thermoplastic materials
according to the type of decorative component being produced.
Different materials can be injected in various portions of the mold
to give a portion of decorative component where the veneer is a
wood sheet and a portion where the "veneer" is an imitation leather
thermoplastic material, that was injection molded in that area.
[0035] The technique of using different injection molding materials
is known and used in the production of car trim panels and will
make possible e.g. car dashboards and door panels to be produced,
in which the wood veneer is bonded to the panel as a single
piece.
[0036] It is also possible to use the invention's laminates to
produce panels or other products having a "simple" shape by
compression molding; with this method the decorative material,
possibly or preferably pre-formed, is shaped and bonded to a
supporting layer of thermoplastic material by compression in a
mold.
[0037] The wood or other material veneer sheet 5, on the back of
which the thermoplastic 6 is injected, is sufficiently formable to
be initially pre-formed and to be later imparted the final shape,
completely, as a result of the of injection molding step. Such a
sheet 5 is preferably made of a laminate of thermoplastic and a
veneer material such as wood or fabric or leather or other
material. FIG. 5 shows an example of such a laminate, with a wood
veneer.
[0038] The sheet 5 in FIG. 5 comprises a layer of wood 12 (but
other materials may be used) bonded by means of a thin layer of
glue 13 to a layer of thermoplastic or thermosetting material 14
that ensures the necessary support and form (i.e. shape) retaining
properties to the wood layer in order to retain the shape imparted
to the laminate sheet 5 with the pre-forming step. In other
embodiments the sheet 5 is comprising a layer of resistive material
15 such as e.g. an electrically resistive coating or varnish
located externally to the film 14 or, alternatively, the resistive
coating 15 is applied directly to the layer of wood 12 and
thermoplastic layer 14 is bonded to the varnish 15. Electric
contacts will be provided in a known way, e.g. by means of laminae
provided in correspondence of hooks 8 (FIG. 1).
[0039] FIG. 5 also depicts a further layer 23 of transparent
plastics such as a polycarbonate or polyester film that is bonded
by means of an adhesive layer 24 to the external side of layer 12.
The use of this transparent film results in ready to use shells
after injection molding has been carried out as above disclosed,
i.e. there is no need of coating the wood or fabric layer after
injection molding. Film layer 23 is either thin and used in
addition to layer 14, that is in this case the form-retaining
means, or film layer 23 is thick enough to be used as an
alternative to layer 14, i.e. film layer 23 acts both as a coating
and as a form retaining element.
[0040] The product thus obtained is formable and resistant to
stretching and can be easily pre-formed into the desired shape
without the wood veneer surface cracking. The layer 12 of wood (or
fabric or other decorative material) that has to be laminated with
the remaining layers 15 and 23 is known in the art, is described,
for example, in EP 0 376 993 B, U.S. Pat. No. 4,430,371 A, and
[0041] U.S. Pat. No. 4,205,107 A and is commercially available.
[0042] The thickness of the wood veneer 12 is between 0.1 and 1.2
mm and preferably between 0.4 and 0.8 mm; the adhesive has a
minimal thickness, for example around 0.01-0.05 mm, the transparent
layer 23 has thickness within the range of 0.1 to 0.3 mm and the
sheet or film of thermoplastic 14 has thickness of between 0.08 and
0.8 mm and preferably between 0.1 and 0.4 mm. Suitable adhesives
are hot-melt adhesives, for example vinyl or polyester, and acrylic
or neoprene adhesive. Materials for the thermoplastic film are
selected from PVC, polyolefins, ABS and similar materials suitable
to provide a formable support. The laminate is obtained as a flat
sheet that is cut as necessary and is subsequently pre-formed into
the required shape.
[0043] By using the formable, and pre-formed, laminates, in
particular those having a wood veneer, above described, it is
possible to produce by injection or compression molding decorative
components for car interiors that range from gear lever knobs to
steering wheels and from door panels to dashboards.
[0044] An advantage of the invention is the use of formable
laminates having a thickness of 1.8 mm or less, comprising one
veneer layer and at least one layer of thermoplastic material, for
the production of decorative components for car interiors.
[0045] FIGS. 7 and 8 show a mold for pre-forming the laminates
according to the invention. Such a mold comprises two mold halves
30, 31 that define a cavity that has the shape required. The two
mold halves are provided with a means 18 of regulating the
temperature, such as e.g. a circuit for oil, to increase and to
reduce the temperature in the shortest possible time.
[0046] A mold half 31 is provided with a male portion comprising a
projecting portion 19 that is at least partially deformable and
that is housed in the cavity 26 of the mold half 30 when the mold
is closed. This deformable projecting portion 19. In the shown
embodiment the deformable means has a cavity 25 and is formed by
expandable means that can increase its volume, i.e. by an
inflatable silicone rubber bladder that can be pressurized to
increase its volume. To pressurize the bladder 19 it is connected
to a duct 20, that is connected to a source of pressure, e.g. of
compressed air (not shown). FIG. 7 also shows an insert 21 (i.e. an
intermediate or additional mold portion) that is located between
the two mold halves 30, 31 to form a locking step or rim 32. The
insert 21 has an opening 17 therein that generally corresponds to
the shape of the cross-section of the cavity 26 of the mold halves
30, but with a smaller area. In other words, the distance 27
between the sides 29 of the opening 17 for inflatable element 19 is
greater than the distance between the corresponding edges of cavity
26 of mold half 30. Thus, when the insert 21 is positioned on mold
half 30, a step is formed that will produce the required locking
rim (FIG. 8); the pre-formed laminate layer L (FIG. 1) is thus
produced. When the pre-formed laminate layer R of FIG. 1 is to be
produced, the insert 21 is replaced by an insert wherein the
distance 27 and the distance 28 are the same, to avoid the forming
of a step.
[0047] Instead of a bladder, the deformable element 19 can be made
of a solid, deformable material, such as silicone rubber or a
foamed polymer having density sufficient to press the laminate
layer 5 against the mold cavity walls to impart the required, and
exact, shape to laminate 5. In other words, the element 19 is
deformed to follow the shape of the cavity 26 and of the insert 21.
The deformed element 19 compresses laminate 5 against the walls of
cavity 26 and insert 21 to reproduce the required exact shape to be
obtained.
[0048] The operation of the pre-forming mold will now be described.
The insert 21 is positioned on the mold half 30 by guides 22
present on the mold half 30. Then a sheet 5, cut to the desired
size and shape, is positioned in the cavity of the mold half 30
from above i.e. through opening 17 of insert 21. As the mold is
closed the deformable protruding portion 19 is inserted into the
cavity 26 of the mold half 30, through the insert 21. Then, the
mold halves 30, 31 are heated and the bladder 19 is pressurized by
feeding compressed air through a conduit. The bladder 19 is
inflated until it firmly presses the sheet 5 against the walls of
the mold half 30 and a part of the insert 21. By the combined
action of heat and pressure a laminate sheet 5 is formed into a
shape that can be very close to the final one. In fact, it is
possible to obtain parts pre-formed so well that in the following
co-molding step there is no need for additional retaining means to
retain the sheet 5 in the injection mold.
[0049] When the sheet 5 is of the type laminated with a
thermoplastic film, the temperature of the mold halves 30, 31 has
to be lower than the melting point or degradation temperature of
the glue present in the laminate, while trying to make pre-forming
cycles as fast as possible. For the sheets used for the present
invention the temperature used is between 50 and 200.degree. C. and
preferably between 55 and 100.degree. C.; the pressure is between 4
and 6 bars, usually approximately 5 bars and the cycle time between
3 and 60 seconds.
[0050] The same mold and the same process can be used for the mold
preparation of products in carbon fiber; in this case the times are
of approximately 20 minutes and the pressure used is approximately
3-4 bar, with a temperature between 70.degree. C. and 180.degree.
C., applied in different steps, depending upon the dimensions and
the shape of the decorative component.
[0051] FIGS. 9 and 10 show a veneer element for steering wheels
that is smaller than the half shell above disclosed, said element
being an insert for a steering wheel having a main surface made
e.g. of leather. The insert is to be housed in a seat provided in
the leather coating. The net, exact shape of the insert obtained
thanks to the process of the invention is clearly visible in these
figures. Layer 5 has been pre-formed as above discussed to result
in a shape comprising peripheral steps or rims 32. After injection
molding of thermoplastic layer 6 (FIGS. 3-4) the resulting veneer
element comprises a decorative layer 5 that ends with step 32 and a
supporting layer 6 that comprises a peripheral "counter-step" 33
that matches step 32 to provide an even peripheral edge 34. No
further steps are required to bring the peripheral edges into the
required shape. This is a great advantage when considering that
inserts and half shells for steering wheels are in fact curved in
two directions: transversally to the steering wheel and along its
circumference. In other words, the pre-forming of the veneer layer
into a form that is retained makes it possible to shape it to
follow the shape of the steering wheel and to avoid further
production steps for finishing the edges.
[0052] FIG. 11 is a cross sectional view of the rim of a steering
wheel manufactured according to the present invention showing
insert 35 in place on a steering wheel armature 40, an expansion
resin (PUR foam) 39, and a first partial coating 41 covering more
or less half of the circumference of the steering wheel section and
comprising an inner layer 38 of foam material glued or coupled to
an outer layer 37 made of leather. On the steering wheel side
opposite to that covered by the leather layer coating 41 the PUR
foam 39 is shaped into at least one seat 42 that acts as a
retaining means for hook 8 of the insert 35. Glue 43 is provided in
seat 42 and around hook 8 to firmly retain it to the PUR foam 39.
In the shown embodiment, a heating element 44 is located between
PUR foam 39 and plastic supporting layer 6 of insert 35;
alternatively, a heating element such as a resistive layer can be
located between the plastic layer 6 and the laminate layer 5, as
previously discussed.
[0053] The invention will now be further disclosed with reference
to the following example.
EXAMPLE
[0054] A formable laminate comprising a wood veneer layer 0.75 mm
thick, a thermoplastic material layer 0.21 mm thick and a backing
fabric layer, having a total thickness of 1.1 mm is cut to an
arched shape of 130.degree. C. The thus cut laminate is preformed
in a pre-forming mold as above disclosed for 50 sec at 90.degree.
C. and 4.8 bar (pressure of the fluid fed to the inflatable
bladder). The pre-formed laminate was then positioned in a mold and
retained in position by suction means. A 30% fiberglass reinforced
polyamide was injected on the back of the laminate to give a half
shell with a perfect shape and without cracks of the wood layer.
The injected supporting layer of thermoplastic material is provided
with integral hooks for mounting on the steering wheel structure.
After finishing and light sanding the shell is lacquered and
polished to give an excellent decorative component that can be fit
to a steering wheel.
[0055] Returning to the "In Mold" molding step of the pre-formed
sheet, it has been mentioned that this allows hooks, webbing and
similar details to be obtained in a single piece. If no transparent
layer 23 is present, the invention makes it possible to directly
paint the part in the mold for injection molding, according to the
known "In-mold paint" techniques, such as by injection either of a
transparent polyurethane varnish or of a coating layer.
[0056] The invention shows several advantages over the prior art.
The invention solves the problem for open and closed shape parts in
steering wheels shells lowering the cost of production. The
invention enables the production in one-shot co-molding process of
decorative components with a wood, leather or fabric finish,
already provided with undercuts, rims and means of attachment such
as hooks and similar, as necessary for their final use. The
pre-forming and molding times are reduced and the temperature and
pressure requirements are moderated.
[0057] The method of manufacturing is simple and reliable and the
parts produced are aesthetically very attractive. Moreover, by
co-molding by injection molding the thermoplastic support a "net
shape" part is obtained, i.e. no machining is required to achieve
the final shape of the part.
[0058] Although several preferred embodiments are illustrated and
described above, there are possible combinations using other
geometries, materials and different dimensions for the components
that perform the same functions. This invention is not limited to
the above embodiments and should be determined by the following
claims.
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