Note: Descriptions are shown in the official language in which they were submitted.
1328800
BACKGROUND OF THE INVENTION
Field o~ the Invention
This invention relates to anti-lacerative window panels
. especially for automobiles.
Review of the Art
It is customary to make some windows, especially
windshield for automobiles, from strengthened glass.
, Often toughened glass is used which is glass that has
been subjected to a tempering treatment. Although such
glass is stronger than untempered glass, it can shatter
under some circumstances, for example when a stone hits
a car windscreen. When it shatters, it crazes over its
surface almost totally obscuring the transparancy. The
driver of the car, under these circumstances, cannot see
the road and an accident may occur. -
.~ .
Laminated glass is made by sandwich laminating a layer
of polyvinyl butyral between two pieces of tempered or
non-tempered formed glass. Laminated glass has the
advantage over toughened glass that, if it shatters, it
does no~ completely craze the surface but cracks in
. lines. Rarely, if ever is visibility completely lost.
However, laminated glass can splinter and, if the impact
is sufficiently severe that the windscreen or other
window breaks into pieces, the splinters can cause
, 25 severe injuries. Even so, laminated glass windscreens
are considered preferable to toughened glass windscreens
,
~, ~ ' :'
' '
132880-0
and are ~andatory in some countries.
More recently it has ~ecome customary to la~inate a film
of plastics material onto the inner surface of a
windscreen to provide some anti-lacerative properties.
The film has some effect in maintaining the integrity of
the windscreen when it splinters so that sharp splinters
are not so likely to fall in onto any occupant of the
car. Moreover, it may have some effect in dulling the
sharp edges and points of discrete splinters in the
lC event that they do, indeed, separate from the
windscreen.
Such films on the surface of the glass should be free
from wrinkles and air bubbles and, for good optical
properties, should be formed from non-oriented
~ 15 transparan~ plastics material which may be tinted if
¦ desired. Considerable research is being done as to the
1~ best materials from which to form the film and,
~ -, . . .
currently, polypropylene and polyesters are considered ~ :
I ~ suitable.
!~ 20 Whatever plastics material is used, a problem exists in
. .
applying it to curved glass surfaces such as are used in
: many car windscreens and side screens. It has not
heretofore been found possible to laminate the film to
~ the glass in any way other than manually and - -
¦ ~5 individually for each piece of curved glass. The ~-
l~ operation has called for par~icular skill and care but,
:: .-
~ 2
,: ' ' "
'~
132~800
even so many of the resulting glass-film laminates have
had to be rejected due to wrinkles, air bubbles or poor
optical characteristics. The commercial products have,
as a result of both the skilled manual labour and the
number of reiects, been very ex~ensive.
A somewhat similar problem has existed in connection
with coated lenses for spectacles. It has, however, not
been nearly so acute since it is possible to dip
spectacle lenses for coating. This is not possible for
1~ car windows since the coating is required on the
interior surface only.
SUMMARY OF THE INVENTION
It is an aim of this invention to provide an apparatus
and method for laminating plastics material ilm onto
curved surfaces with a view to mitigating the present
difficultLes in providing acceptable products.
Accordingly, the invention provides apparatus for
laminating a film of non-oriented plastics material onto
~3 the surface of a curved glass sheet having both concave
and complementary convex surfaces comprising; a platen,
the platen having a surface substantially compLementary
to said convex surface and generally horizontal
comprising a first liner of support material for said
:, ~
sheet lining the platen surface; a ram having a
' 25 resiliently deformable buffer layer to provide a ~ -
'-~` 3
' ' ~.-'':
- 1328800
i
deformable working surface which, before contact with
said sheet, is generally complementary to said concave
surfacve of said sheet and being more tightly curved
than said concave surface;
~ 5 clamp means around the platen adapted to hold
¦ substantially horizontal a film of plastics material
adapted to adhere to said concave surface between the
ram and the platen;
means to move the ram towards the platen to carry said
film under tension to contact a sheet located on the
platen first in its deepest region and to progressively
increase the area contacted from said deepest part
towardfs edges of the sheet;
the clamping means adapted to tension the film such that
stretching of the film to contact the sheet is in the
same proportion for all radiating shortest ~ stances
l from said deepest part of said sheet to the clamping
¦~ means; and means to adhere the film contacting the film
contacting the sheet to the sheet.
~ 20 Suitably, alternate platens and rams for differently
j~ curved glass sheets are provided.
i Also provided is a method of laminating a film of non-
oriented plastics material onto the surface of a curved
'. glass sheet having both concave and complementary convex
surfaces comprising; locating the curved glass sheet on
a platen, the platen having a generally horizontal
l~ surface substantially complementary to said convex
:~;; 4
,!, .
1328800
surface and having a first buffer layer of resiliently
deformable material lining the platen surface; locating
a film of plastics materiaL adapted to adhere to said
concave surface substantially horizontally above the
curved glass sheet and tensioning the film in clamping
means; stretching of the film towards the deepest
portion of the sheet in the same proportion of stretch
for all radiating shortest distances from said deepest
part of said sheet to the clamping means, the stretching
being accomplished by moving a ram downwardly from a
first position above the film, the ram having a
- generally horizontal working surface provided with a
second buffer layer of resiliently deformable material
~ and being generally complementary to said concave
ci 15 surface and being more tightly curved than said concave
surface, the ram carrying the film under tension
downwardly to first contact the curved glass sheet
located on the platen first in its deepest region and to
progresslvely increase the area contacted from said
deepest part towards the edges of the sheet; and
adhering the film contacting the sheet to the sheet.
~ Although a pressure sensitive adhesive or other adhesive
.J may be used to laminate the f~lm to the sheet, it is
suitable to use a heat sensitive adhesive. The use of
is~ 25 polyvinyl butyral as the film material ~tself may be
.~ being considered. The film may be pre-heated, for
example, before it is stretched downwardly toward the
sheet or it may be heated while in contact with the
,
1328800
.. .
sheet. In this latter case the platen may be heated, for
example by heating elements in a bed carrying it.
SHORT DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described by
1 5 way of example with reference to the drawings, in which:
Figure 1 is a diagrammatic vertical section through an
apparatus of the invention with the ram raised;
Figure 2 is a similar section with the ram lowered; and
~ Figure 3 is a plan view of a sheet showing some clamping
^~ 10 devices.
DESCRIPTION OF PREFERRED EMBODIMENTS
In the drawings, a sheet of curved glass 10 is located
on a platen 12 having a concave surface 14 lined with a
liner 16 of support material, such as rubber, rubberlike
materials, felts, etc. which will stand up to amounts
of heat used in adhering plastics material film to the
. ...
curved glass sheet as will be described hereafter.
~ The convex surface 18 of the sheet 10 rests on the
., ~ .
liner 16. The curvature of the concave surface 14 of
platen 12 is formed to correspond to the curvature of
the curved glass sheet 10. Conveniently, the platen 12
JI is removably locatable in bed 20 so that alternate
platens may be used, each contoured indivdually to fit
l~ different glass sheets having different curves.
^j~ 25 A ram 30 Ls adapted to cooperate with platen 12 and has
a surface 31 generally corresponding to the s,hape of
.~ , . . .
`` ~328800
concave surface 16 of platen 12 and the shape of the
curved glass sheet 10. The surface 31 of ram 30 is,
however, lined with buffer layer 34 of resiliently
deformable ma~erial. The buffer layer 34 is so shaped
S that its lower surface 32 constitutes a working surface
of the combined ram 30 and buffer lay 34 which is more
tightly curved than the curved glass sheet so that, if
it were rigid, it would, when located in the concavity
of curved glass sheet 10, only touch the deepest part of
I lO the sheet with its lowermost part.
However, buffer layer 34 is deformable, formed for
example from soft rubber or rubber-like material or from
an air bag or similar device. Thus, when ram 30 is
moved down to bear against the curved sheet 10, firstly
the working surface 32 of buffer layer 34 will contact
the deepest part of the sheet, and the further descent
of ram 30 will cause deformation of the buffer layer 34
in the first contacted region 36 permitting gradual and
progressive contact of further regions of the buffer
~, 20 layer radiating outwardly to the edges of the sheet.
Clamping devices 40 are arranged above and about the
periphe~y of platen 12 to hold a film 42 of non-oriented
plastics material horizontally interposed between ram 30
in a raised position (see Figure 1) and the curved glass
sheet 10. When tbe ram 30 is moved downwardly it carries
; with it film 42 to stretch it and bring it into contact
i~ with the curved glass sheet 10 first at the deepest part
~ 7
f ~ . "; '. ',. ~
~' ';: '
1328~00
and then gradually and progrzssively outwardly therefrom
to the edges of the sheet 10.
Sufficient clamping devices 40 are located about the
platen 12 to substantially hold the film horizontal
without waves or wrinkles. The degree of tension imposed
on the film in different directions is such that, on
stretching towards the sheet 10, the proportion of
stretch is the same in every direction. For example,
referring to Figure 3, where X indicates the deepest
part of sheet 10, it can be seen that the distances L
are considerably greater than the distances L . However,
the clampLng devices 40 are arranged to hold the film 42
I such that the percentage stretch in each of the
¦ distances L and L is the same when the film 42 is in
contact with the sheet 10.
Figure 3, for simplicity, shows only two pairs of
opposed clamping devices 40. It will be appreciated,
that in practice a very much greater number will be
necessary.
The arrangement by whLch the film 42 contacts sheet 10
at its deepest part and thereafter spreads gradually and
progresslvely towards the edges of the sheet is intended
~' for the purpose of minimising or eliminating air bubbles
J~ between the film and the sheet. The arran8ement of the
l~ 25 clamping devices such that the percentage of strtch is
the same in all directions from the deepest part of the
sheet is intended to minimise or eliminate wrinkles in
, ~ . .
'J~ ' ` ' "
~ :
1328800
the film on the sheet.
Once in contact with the sheet 10, the film 42 may be
laminated to it by any suitable means. As shown in
Figures 1 and 2, the bed 20 carrying platen 12 is
S provided with heating elements 44 by which the sheet 10
may be heated to bond the film thereto. In this case the
film may suitably be polypropylene or a polyester coated
with a suitable heat sensitive adhesive on the side
, which is to contact the sheet 10. Alternatively the film
may be preheated.
In practice, the sheet 10 is seated on the buffer layer
~, 16 of a suitably configured platen 12. A similarly
suitably configured ram 30 is mounted on a head (not
shown) for reciprocal up ant down movement. A film 42 is
located horizontally between the ram 30 and the sheet 10
¦~ in clamping devices 40. By location of the clamping
~t,~ devices 40 and adjustment of tension in the film 42, the
,, .
film is adjusted that the percentage stretch in all
diréctions from the deepest part of the sheet 10 will be ~ - -
the same.
i The ram 30 is moved downwardly to contact the film 42
: , .
and carry it downwardly to contact first the deepest
part of sheet 12 and then to gradually and progressively
, continue to contact the sheet towards the edges. When
all the sheet 10 is in contact with film 42, heat may be
applied from heating elements 44 in the bed 20 or
preferably from heating elements 45 in the ram 30 or by
~, , .
., ~
~,' - ':
~328800
other means to laminate the film to the sheet.
Thereafter, the ram 30 may be lifted and the laminated
curved sheet of glass, for example. a car windscreen or
side screen, may be removed from the platen.
If the next sheet of glass to be laminated is a
different shape, then the platen mày be changed for one
suitable or the des-red p~rpose.
1`
,,~
: ' . ' -
' 10 ,
, .
