Note: Descriptions are shown in the official language in which they were submitted.
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MHO 96113137 PCT/CA95/00588
VEHICLE WINDOW AND METHOD OF MAKING THE SAME
BACKGROUND Or THE INVENTION
1. Field of the Invention
This invention relates to windows and more
particularly to windows having electrical defrosting
grids embodied therein such as the rear windows of
motor vehicles.
2. Description of the Related Art
Motor vehicle designs particularly for'
passenger vehicles require a great latitude in the
curvatures which are considered desirable from a
design standpoint and often such curvatures are
desired in the windows provided. Recent designs
have more and more gone to the round look at the
front and rear ends of the car. Particularly, in
rear windows where defrosting is of great
importance, the curvatures desired are becoming
greater and greater. A cost problem in producing
severely curved rear windows is in embodying the
electrical resistance heating elements in the final
product because heretofore it has not been possible
to utilize the more cost effective silk screening
methods to provide the heating elements because of
the necessity to silk screen onto an essentially
flat surface.
It is well known that glass has been the
material of choice in motor vehicle rear windows for
many years. It is also well known that plastic
materials, such as polycarbonates, if employed in
lieu of glass, could reduce the weight of the rear
r window. Nevertheless, glass continues to be used.
It is apparent that, in order for motor vehicle
y makers to shift from glass to plastics, the plastic
window must be cost effective in other ways besides
weight reduction.
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One way in which additional cost
effectiveness can be achieved relates to the way the '
electrical defrosting system is embodied in the
window construction. For example, it would be
desirably effective to have the electrical grid
quite close to the exterior surface but still
protected by being mounted inwardly of the exterior
surface. With an arrangement of this type, the
electrical grid can be made to effectively operate
with less power requirement with the resultant
advantages in the characteristics and amount of
conductive material needed to provide the system.
SUMMARY OF THE INVENTION
It is an object of the present invention
to provide a vehicle window which meets the cost
effectiveness requirements set forth above. In
accordance with the principles of the present
invention, this objective is achieved by providing a
vehicle window which comprises the combination of
three components: one, a thin clear sheet; two, an
electrically operable defrosting grid; and three, a
relatively thick clear substrate layer. The
relatively thin clear sheet is of a plastic material
having opposed surfaces. The electrically operable
defrosting grid is adhered to one surface of the
thin sheet. The relatively thick clear substrate
layer is of a plastic material having opposed
surfaces curved into a vehicle window configuration.
The relatively thick substrate layer is adhered to
the one surface of the relatively thin sheet and the
electrically operable defrosting grid attached
thereto while in contact therewith in a molten state
under heat and pressure within a cavity defined by
two generally parallel curved die surfaces of
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cooperating injection molding dies so that, upon
" solidification, the surfaces of said relatively thin
sheet are retained in a curved configuration in
generally parallel coextensive relation to
corresponding curved surfaces of said relatively
thick substrate layer.
The provision of the thin c7.ear sheet as a
basic component o.f the window enables the
particularly cost effective silk screening process
to be used in making the window because the
relatively thin sheet can have the silk screening of
the grid performed while in a planar condition and
then subsequently curved during the injection
molding of the relatively thick substrate layer.
Accordingly, another object of the present invention
is to provide a method of making a window which can
have fairly severe curvatures in two planes
sufficient to accommodate a wide variety of designs
having an electrical defrosting system which is
2o provided by a conventional silk screening process.
In accordance with the principles of the present
invention, this objective is achieved by providing a
method of forming a window which comprises providing
a relatively thin sheet of clear plastic material
having opposed surfaces and silk screening onto one
surface of the relatively thin sheet while in a
substantially flat planar condition a curable
electrically conductive ink in the form of a
defrosting grid. The curable electrically
. 30 conductive ink is cured on the one surface of the
relatively thin sheet so that the defrosting grid is
. stably adhered thereto. The relatively thin sheet
with the defrosting grid adhered to one surface
thereof is mounted adjacent a curved die surface of
?.5 a molding die arranged to be disposed in cooperating
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relation with a second molding die having a
similarly shaped curved die surface. The first and
second molding dies are disposed in cooperating
relation so as to bring the two curved die surfaces
into generally parallel relation to form a die
cavity with a spacing between the two curved die
surfaces substantially greater than the thickness of
the thin sheet. Finally, a clear plastic material
is injection molded under heat and pressure within
the die cavity between the two generally parallel
curved die surfaces so as to form a window having
curved exterior surfaces comprising a curved
relatively thin clear sheet having the electrically
conductive grid adhered to one surface thereof and a
relatively thicker substrate layer of clear plastic
molded in adhered relation to the relatively thin
clear sheet.
Another object of the present invention is
the provision of a vehicle window which comprises a
relatively thin sheet of clear plastic material
having opposed surfaces, an electrically operable
defrosting grid adhered to one surface of the
relatively thin sheet, and a relatively thick
substrate layer of clear plastic material having
opposed surfaces curved into a vehicle window
configuration. The relatively thick substrate layer
is adhered to one surface of the relatively thin
sheet and the electrically operable defrosting grid
adhered thereto while in contact therewith in a
molten state under heat and pressure within a cavity
of an injection molding device so that upon
solidification the surfaces of the relatively thin
sheet are retained in a curved configuration in
generally parallel coextensive relation to
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S
corresponding curved surfaces of the relatively
- thick substrate layer.
These and other objects of the present
invention will become more apparent during the
course of the following detailed description and
appended claims.
The invention may best be understood with
reference to the accompanying drawings wherein an
illustrative embodiment is shown.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 is a perspective view of a
vehicle rear window constructed in accordance with
the principles of the present invention;
Figure 2 is a generally schematic view
illustrating a step in the process of making the
window shown in Figure 1;
Figure 3 is a view similar to Figure 2
illustrating a further step in the method; and
Figure 4 is a view similar to Figure 2
showing a still further step in the method of making
the window of Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now more particularly to the
drawings, there is shown in Figure 1 a vehicle
window, generally indicated at 10, which embodies
the principles of the present invention. The window
consists essentially of three components: a
' relatively thin sheet of clear plastic material 12,
an electrically operable defrosting grid, generally
indicated at 14, and a relatively thick substrate
layer of clear plastic material 16.
The relatively thin sheet 12 is formed
from any suitable thermoplastic material. Preferred
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6
materials are taken from the group consisting of
polycarbonate or polyester resin, with polycarbonate
being a preferred embodiment. The relatively thin
sheet 12 may be formed by any appropriate method, '
such as extrusion or molding. The relatively thin
sheet 12 has a thickness within an operative range
of 5 to 40 mils and a preferred range of 10 to 30
mils. A preferred thickness for the relatively thin
sheet 12 is approximately 20 mils.
The electrically operable defrosting grid
14 is of conventional form including a series of
parallel wire-like elements 18 and a pair of buss
bars 20 at opposite ends thereof. In the broadest
aspects of the present invention, grid 14 may be
formed in any suitable manner from any suitable
conductive material. However, in a preferred
embodiment, the defrosting grid 14 is formed by a
conductive material in the form of an ink applied to
one surface of the thin sheet 12 through a silk
screen. The ink is subsequently cured by heat. It
will be understood, however, that the ink may be an
ink which is capable of being cured by exposure to
ultraviolet light or other means. A preferred
example is epoxy material loaded with silver
particles which is cured by heat in accordance with
conventional practice.
It will also be understood that the silk
screening process which is utilized for applying the
electrically operable defrosting grid 14 to one
surface of the thin sheet 12 can also be utilized to
provide the thin sheet with a border of black
material provided by loading the epoxy. material with
carbon particles rather than the silver particles,
all in accordance with conventional silk screening
practice.
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It is also possible to provide the surface
' of the thin sheet 12 opposed to the surface which
receives the electrically operable defrosting grid
' 16 with an abrasive resistant coating. The coating
is applied before the silk screening process and
preferably by a dipping procedure. This preferred
procedure has the effect of coating both surfaces of
the relatively thin sheet 12. Where the one surface
which is to receive the silk screening material is
provided with an abrasive resistant coating, the
coating serves to enable the silk screening inks to
adhere more tenaciously thereto. The abrasive
resistant coating preferably comprises a thermoset
material taken from the group consisting of
polysiloxane, acrylic resin or aliphatic
polyurethane.
The relatively thick substrate layer 16 is
preferably formed from thermoplastic material taken
from the group consisting of polycarbonate, cyclic
polyolefin and polymethyl methacrylate. The
relatively thick substrate layer has a thickness
within an operative range of 50 to 500 mils and a
preferred range of from 100 to 150 mils. A
preferred example of the thickness of the relatively
thick substrate layer is approximately 125 mils.
Figure 2 illustrates the preferred method
of applying the electrically operable defrosting
grid 14 to one surface of the relatively thin sheet
12. As shown, the relatively thin sheet 12 is
mounted on a support 22 having a flat planar support
surface 24. The thin sheet 12 is mounted on the
flat surface 24 so as to be supported in a planar
condition during the silk screening process. The
silk screening itself is of a conventional nature
and includes a silk screen assembly, generally
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'WU 96113137 PCT/CA95/00588
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indicated at 26, which includes a peripheral frame
28 and a silk screen 30 having openings formed
therein which define the parallel wire elements 18
and buss bars 20 of the electrically operable
defrosting grid 14. The silk screen 30 is loaded
with an ink comprising an epoxy plastic material
capable of being cured which is loaded with
electrically conductive particles, such as silver
particles. After the ink has been applied to the
silk screen 30, a squeegee device 32 is moved over
the silk screen so as to pass the ink on the silk
screen through the openings thereof and deposit the
same on the upper surface of the thin sheet 12.
After both the wire elements 18 and buss bars 20 of
the grid 14 have been applied to the surface of the
relatively thin sheet 12, the applied ink is then
cured in accordance with conventional practice by
heating the same.
As previously indicated, the exterior of
the relatively thin sheet 12 can also be silk
screened to provide a black marginal edge also in
accordance with conventional practice. This silk
screening would be accomplished with the use of a
different ink where the silver particles are
replaced by carbon particles or the like.
It will be understood that while Figure 2
illustrates the silk screening process to be
accomplished while the thin sheet 12 is in a planar
condition which is flat, it is within the
contemplation of the present invention in the
broadest aspects thereof to accomplish the silk
screening procedure on a continuous web in which
case the planar surface would be cylindrical.
After the electrically operable defrosting
grid has been applied and cured to the one surface
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of the thin sheet 12, the Chin ~,hcet 12 i~ then mounted within a
molding die, such as shown at 32 in Figure 3. The molding die 32
includes a curved die surface 34 and the thin sheet 13 is mounted with
respect to the melding die 32 so that it is adjacent to the curved
s nurfaae 34. As shcwn in Figure 3, the curved surface may have
curvature in two planes which ie a prevalent practice wiCh respect to
motar, vehicle type rear windows.
zt i" contemplated that the relatively thin sheet 12 has a
thickness which when mounted in the molding die 32, would simply
conform generally to the cuxved die surface 34. Preferably the
relatively thin sheet X2 is mounted wi~llin the molding die 32, adjacent
the die aurfaa~! 32 go that a marginal edge extends beyond the die's
molding surface 34. The outwardly extending marginal Cdge portion has
its upper eurCace engaged by a cooperating marginal edge o~ a second
molding die 36 which Cooparater with thA molding die 32 when moved into
cooperating relation ~rith ehe die 32.
As bast shown in figure 4, the cooperating molding die 36
includes a curved die surface 38 which is gGnera.lly parallel with the
curved die surface 34 of the molding die 32. The curved die surfaces
ao 34 and 38 form a die cavity when the molding dies 32 and 36 are moved
into cooperating relation. The diP cavity has a thiclmer~rs between the
curved die surfaces 34 and 3B which is subgtantiall.y greater than the
thickriez~s of the relatively thin sheet 12.
..4
After the da.e membare~ 32 and 36 have 3~eon moved into
cooperating relation, the plastic material which is to foam the
nubatrate layer 16 is introduced into the die cavity above the
marginally ;
AMENDED SHEET
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grip thin sheet 12 and injection molded under heat
and pressure in accordance with conventional
practice. During the injection molding the opposite
surface of the relatively thin sheet is forced
5 against the die surface 34 if it has not already
been engaged therewith. If desired, the thin sheet
12 can be preformed to engaged the die surface 34
just before being mounted therein.
The resulting window 10 includes exterior
10 surfaces which are curved to conform with the die
surfaces 34 and 38. The electrically operable
defrosting grid 14 is captured between the
relatively thick substrate layer 16 and the
relatively thin sheet 12 which now has a curvature
corresponding to that of the substrate layer 16,
retained by the adherence of the relatively thin
sheet 12 to the substrate layer 16.
It thus will be seen that the objects of
this invention have been fully and effectively
accomplished. It will be realized, however, that
the foregoing preferred specific embodiment has been
shown and described for the purpose of this
invention and is subject to change without departure
from such principles. Therefore, this invention
includes all modifications encompassed within the
spirit and scope of the following claims.
