U.S. patent application number 09/874326 was filed with the patent office on 2001-11-22 for method for producing a compound glazing sheet and method for implementing the same.
This patent application is currently assigned to SAINT-GOBAIN VITRAGE. Invention is credited to Balduin, Michael, Havenith, Hubert, Labrot, Michael.
Application Number | 20010042585 09/874326 |
Document ID | / |
Family ID | 7824341 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042585 |
Kind Code |
A1 |
Balduin, Michael ; et
al. |
November 22, 2001 |
Method for producing a compound glazing sheet and method for
implementing the same
Abstract
The present document describes a process for manufacturing a
pane of laminated glass without recourse to an autoclave. The pack
of layers are composed of stacked layers (6, 7, 8), is raised to
the softening temperature of the thermoplastic interlayer of the
pack of layers in a preheat channel (1). The preheated pack of
layers is put under vacuum in a vacuum assembly station (2) for the
purpose of extracting the gas from the spaces separating the layers
(6, 7, 8). After the gas has been extracted, the edge of the pack
of layers, which is held under vacuum, is mechanically compressed
inside the vacuum box and is thus sealed. Finally, the pack of
layers is brought to atmospheric pressure and its temperature
further increased in a postheat channel (4).
Inventors: |
Balduin, Michael; (Alsdorf,
DE) ; Havenith, Hubert; (Wuerselen, DE) ;
Labrot, Michael; (Aachen, DE) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
SAINT-GOBAIN VITRAGE
18, avenue d'Alsace
Courbevoie
JP
F-92400
|
Family ID: |
7824341 |
Appl. No.: |
09/874326 |
Filed: |
June 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09874326 |
Jun 6, 2001 |
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09147278 |
Aug 27, 1999 |
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6280547 |
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09147278 |
Aug 27, 1999 |
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PCT/FR98/00548 |
Mar 19, 1998 |
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Current U.S.
Class: |
156/104 ;
156/107 |
Current CPC
Class: |
B32B 37/0007 20130101;
B32B 17/10761 20130101; B32B 17/10036 20130101; B32B 37/10
20130101; B32B 17/10954 20130101; B32B 2309/68 20130101; B32B
2315/08 20130101 |
Class at
Publication: |
156/104 ;
156/107 |
International
Class: |
B32B 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 1997 |
DE |
197 12 145.4 |
Claims
1. Process for the manufacture of a pane of laminated glass
comprising at least one external layer of glass and at least one
interlayer of thermoplastic polymer, in which the various layers
are stacked, the pack of layers is put under vacuum in a vacuum box
for the purpose of extracting gas from the spaces separating the
layers and, finally, the pack of layers is brought to atmospheric
pressure and its temperature increased, characterized in that the
pack of layers is first of all heated to a temperature close to the
softening temperature of the thermoplastic polymer, in that the gas
is extracted from the spaces separating the layers of the pack of
layers directly through those edges of the pack of layers which are
not covered, due to the effect of the pressure which exists inside
the vacuum box, and in that, after completing the extraction of the
gas, the edges of the pack of layers are, for the purpose of
sealing them, bonded inside the vacuum box by means of mechanical
pressure exerted around the edge of the pack of layers.
2. Process according to claim 1, characterized in that the vacuum
box used has a proportionally smaller internal volume
3. Process according to claim 1 or claim 2, characterized in that
the pack of layers in the vacuum box is heated to and/or maintained
at a temperature close to the softening temperature of the
thermoplastic polymer.
4. Process according to claims 1 to 3, characterized in that the
air is removed from the vacuum box by connecting the vacuum box to
a chamber in which there is a high vacuum and the internal volume
of which is greater than the internal volume of the vacuum box.
5. Process according to any one of claims 1 to 4, characterized in
that the pack of layers is arranged horizontally in the vacuum box
during the gas extraction, the upper glass sheet resting freely on
the lower layers.
6. Process according to one of claims 1 to 5, characterized in that
the pack of layers is removed from the vacuum box after venting the
vacuum box and is subjected, in a postheat channel, to an
additional heat treatment at a temperature close to the melting
point of the thermoplastic polymer.
7. Apparatus for the implementation of the process according to
claim 1, characterized in that it comprises a preheat channel (1),
a postheat channel (4) and a vacuum box (20) consisting of a bottom
(22) supporting a pack of layers (6, 7, 8) and of a cover (22), in
that a frame (23), corresponding to the contour and to the shape of
the lower glass sheet (6), is fitted into the bottom (21) and a
frame (33), also corresponding to the contour and to the shape of
the upper glass sheet (8) is fitted into the cover (22) and in that
pressing means are connected to the frame (23) and or to thee frame
(33), using which means a mechanical pressure can be exerted around
the edge of the pack of layers after removing the air from the
vacuum box (20).
8. Apparatus according to claim 7, characterized in that the
pressing means connected to the frame (23) and/or to the frame (33)
consist of elastomeric forcing tubes (24, 34) which can be
connected to a compressed-air line (27).
9. Apparatus according to claim 7 or 8, characterized in that the
vacuum box (20) can be connected to a vacuum chamber (42) of
greater internal volume than the internal volume of the vacuum box
(20).
Description
[0001] The present invention relates to a process for the
manufacture of a pane of laminated glass comprising at least one
external layer of glass and at least one interlayer of
thermoplastic polymer, in which the various layers are stacked, the
pack of layers is put under vacuum in a vacuum box for the purpose
of extracting gas from the spaces separating the layers and,
finally, the pack of layers, the edge of which is sealed, is
brought to atmospheric pressure and its temperature increased. The
invention also relates to an apparatus for the implementation of
the process according to the invention.
[0002] Hitherto, it was standard practice, in the manufacture of
laminated glass, to produce beforehand a primary laminate, based on
the stack of layers, by means of a calendering operation or a
vacuum treatment so as to extract, to a large extent, the air
trapped between the layers, and subsequently to subject this
primary laminate to a high overpressure, generally of between 10
and 14 bar, in an autoclave. These so-called autoclaving processes
are expensive and tiresome.
[0003] Processes for manufacturing laminated glass are also known
in which an autoclaving operation is not essential for the final
bonding, rather the latter is carried out at atmospheric pressure.
A process of this type has been described for example, in document
DE-3,044,717 C2. According to this known process, a rubber frame is
laid around the edge of the pack of layers, which frame is provided
with a suction channel which is continuous and comprises a suction
line. The pack of layers fitted with this rubber frame is placed in
a vacuum box and the suction line is brought to the outside through
the wall of the box. Then, a different high vacuum is applied, on
the one hand, to the spaces separating the various layers, by means
of the suction line and the rubber frame, and, on the other hand,
to the box in such a way that, under the effect of the vacuum in
the vacuum box, the layers move apart, while the gas is extracted
simultaneously from the spaces separating the layers under the
effect of the vacuum transmitted by the rubber frame. After the gas
has been extracted from the spaces separating the various layers,
the temperature is increased and the pressure in the vacuum box is
brought to atmospheric pressure, while the pressure in the rubber
frame remains, during this time, at a level below atmospheric
pressure.
[0004] Document DE-2,209,643 C3 also describes a process for the
manufacture of laminated glass which does not require autoclaving
and which is suitable for a continuous production cycle. In this
known process too, the pack of layers is surrounded by an
elastomeric sealed profiled frame through which the air and gas
present between the layers are sucked out, while the pack of layers
is subjected simultaneously to an external vacuum in a vacuum box.
In this case, the pack of layers is heated at the same time as
being put under vacuum, and is subsequently brought to atmospheric
pressure, while still being heated, and bonded in this
situation.
[0005] These known processes involve two separate vacuum systems
and require a frame in order to seal the edge of the pack of layers
not only during the phase of creating the vacuum but also during
the following phase of assembly at atmospheric pressure.
[0006] The object of the invention is to simplify further a process
of this kind so as to be able to integrate it even better in a
continuous manufacturing process.
[0007] According to the invention, this object is achieved by the
fact that the pack of layers is first of all heated to a
temperature close to the softening temperature of the thermoplastic
polymer, that the gas is extracted directly from the spaces
separating the layers of the pack of layers, due to the effect of
the vacuum which exists inside the vacuum box, through those edges
of the pack of layers which are not covered and that, after
completing the extraction of the gas inside the vacuum box, the
vacuum being maintained, the edge of the pack of layers is, for the
purpose of sealing it, bonded by means of mechanical pressure
exerted around the edge of the pack of layers.
[0008] The process according to the invention consequently requires
neither an additional sealed profiled frame, the shape and size of
which depends moreover on each glazing model, nor an additional
means for separate suction through these sealed profiled frames.
Rather the invention exploits the observation that better removal
of air and better extraction of gas from the spaces separating the
layers are achieved when the pack of layers is subjected merely to
the vacuum in the vacuum box without any clamping or retaining
components around its edge. This is because the film used as
thermoplastic interlayer is provided with a surface structure. As
the pack of layers is being preheated up to a level close to the
softening temperature of the thermoplastic interlayer, the layers
are not yet completely bonded to each other because of its surface
structure, and thus the contact surface between the structured film
and the adjacent layers is sufficiently permeable to allow
effective air removal and gas extraction simply by the effect of
the external vacuum.
[0009] Moreover, given that the temperature of the pack of layers
is already sufficiently high at this moment to cause a sealed bond
with the surface of the glass due to the effect of sufficiently
high mechanical pressure, good sealing around the edges is achieved
by means of the subsequent mechanical pressing operation, which is
limited to the immediate marginal region of the external layers.
The atmospheric pressure which is subsequently exerted on the pack
of layers thus sealed around their edges has the effect of pressing
the layers against each other over their entire surface. This
treatment is simply followed by an additional heat treatment at
atmospheric pressure in which the thermoplastic polymer of the
interlayer is further softened and the ultimate transparency of the
pane of laminated glass is achieved by complete impregnation of the
glass surfaces.
[0010] According to another variant, the invention does not
exclude, after bringing the laminate to atmospheric pressure and
optionally after the additional heat treatment at atmospheric
pressure, passing the laminate into an autoclave where it is
subjected to a high overpressure. According to this variant of the
invention, the time spent in the autoclave is advantageously less
than that of the known techniques.
[0011] Other features and advantages of the invention will emerge
from the dependent claims and from the description below of the
process according to the invention and of the apparatus according
to the invention, with reference to the appended drawings in
which:
[0012] FIG. 1 shows a complete installation for executing the
process according to the invention; and
[0013] FIG. 2 is a view, with partial cutaway and in perspective,
of a vacuum box produced according to the invention.
[0014] As may be seen in FIG. 1, the installation for manufacturing
panes of laminated glass using the process according to the
invention comprises a preheat channel 1, a vacuum assembly station
2 and a postheat channel 4 from which the completed pane of
laminated glass is withdrawn.
[0015] The preheat channel 1 has the purpose of raising the pack of
layers consisting of the layers to be joined together to the
temperature required for the treatment in the vacuum assembly
station 2. It consists of a heated channel comprising a chain
transporter 11 provided with support fingers 12, by means of which
transporter the pack of layers is transported through the heating
channel. The temperature of the pack of layers leaving the heating
channel depends on the thermoplastic polymer which is used as
interlayer for the pane of laminated glass. In general, a film of
polyvinyl butyral is used as interlayer, the assembly temperature
of which is approximately 140.degree. C. in the conventional
autoclaving process. The films of polyvinyl butyral of this type
are raised to a temperature of approximately 100 to 120.degree. C.
in the preheat channel. At this temperature, the films must-be
sufficiently softened so that, because of their surface structure,
a partial bond occurs in any case at the point where the layers
adhere to each other, so that, where appropriate, the pack of
layers can be lifted off the chain transporter and moved by means
of suckers which grip the upper layer.
[0016] Next, the pack of layers thus heated is brought by means of
a transfer device, not shown, to the vacuum assembly station 2
where it is subjected to the next operation in the vacuum box 20.
The vacuum box 20, the complete construction of which is
illustrated in detail in FIG. 2, comprises a bottom 21 and a cover
22, which allows vacuum-type closure of the box. Placed inside the
bottom 21 on the bottom proper are supports 29 on which the pack of
layers is deposited. Furthermore, a frame 23 having perforations 47
is fitted around the bottom proper, its upper bearing surface
corresponding to the geometrical shape and to the contour of the
glass sheet 6 which has to be joined to the upper glass sheet 7 of
the pack of layers by means of the thermoplastic film of polyvinyl
butyral B. The perforations 47 made in the frame 23 ensure that the
inside and the outside of the frame 23, around the edges of the
pane, are at the same pressure. Fitted around the carrier frame 23
is an elastomeric tube 24 which also forms a closed frame
corresponding to the contour of the pane. The tube 24 is connected
to a hose 25 which passes through the side wall of the bottom 21
and leads to a three-way valve 26. By means of this three-way valve
26, the tube 24 can be connected either to a compressed-air line 27
or to a venting line 28. The height of the supports 29 is chosen so
that, when the tube 24 is under no pressure, the pack of layers
rests only on the said supports 29 so that no pressure is exerted
around the edge of the pack of layers.
[0017] In the same way as on the bottom 21, a frame 33 provided
with perforations 46 is also fixed to the cover 22 of the vacuum
box 20. The geometrical shape of the lower face of this frame 33
also corresponds to the shape and to the contour of the upper glass
sheet 7 of the pack of layers. Also fitted to the bearing surface
is an elastomeric tube 34 which can be connected by means of the
hose 35 both to the compressed-air line 27 and to a venting
line.
[0018] In the apparatus shown here, pneumatic pressing means having
the shape of pressing tubes are provided on both sides of the pack
of layers. Of course, it is possible, however, to use rigid or
semi-rigid pressing frames instead, these being pressed against the
edge of the pack of layers by a mechanical or pneumatic means.
Likewise, it is possible to fit, rigidly in the apparatus on one
side of the pack of layers, a forming frame provided with a bearing
surface having elastic flexibility and to provide a pressing device
only on the other side of the pack of layers, for example a driving
tube fitted to a frame, by means of which the edge of the pack of
layers is pressed against the rigid forming frame.
[0019] However, the vacuum box illustrated and described may also
be designed so that the frames 23 and 33 do not have perforations
so that, as soon as the pressing means start to act and good
sealing with respect to the glass sheets 6 and 7 is thus achieved,
entirely closed empty spaces separated from each other appear,
namely, on the one hand, the two empty spaces inside the frames 23
and 33 and, on the other hand, the empty space outside the frames
23 and 33. If the empty spaces inside the frames 23 and 33 are
provided, according to this embodiment, with separate delivery
lines emerging in a common line, it is possible to subject the
surface of the pane and the edge of the pack of layers to different
pressures. This may have advantages for executing the process in
certain circumstances. For example, the pack of layers may already
be subjected to overpressure over its surface while the vacuum is
still being exerted around its edge.
[0020] The vacuum box 20 has a proportionally small internal volume
so that the air can be rapidly removed from the vacuum box. For the
purpose of rapidly removing the air, the box is connected to a
vacuum chamber 42 via the aperture 38, a line 39 and a shutoff
valve 40. The vacuum chamber 42 has a volume substantially greater
than that of the vacuum box 20. The vacuum in this chamber is
obtained by means of the vacuum pump 43. When the vacuum box 20 is
connected by means of the valve 40, a high vacuum is created in the
latter in an extremely short time.
[0021] According to a preferred embodiment of the invention, the
vacuum box 20 furthermore includes heaters, such as infrared
radiators, not shown in the figures. Advantageously, these heaters
are provided for maintaining the temperature reached in the preheat
channel 1, where the temperature of the pack of layers may
decrease, in particular when transferring it from the preheat
channel 1 to the vacuum box 20.
[0022] The manufacturing plant, i.e. the entire installation, also
includes the postheat channel 4. The postheat channel 4, like the
preheat channel 1, is provided with a transport system--in the case
shown again a chain transporter 46--for the purpose of transporting
the panes of laminated glass horizontally. Of course, the postheat
channel and the transport system may also be designed in such a way
that the panes of laminated glass can also be transported through
the postheat channel vertically. The postheat channel is
furthermore equipped with an electrically controllable heating
system, not shown, so that the panes of laminated glass can be
subjected to a post-treatment at a precise temperature in the
postheat channel.
[0023] Of course, the manufacturing plant also includes suitable
transport systems by means of which the packs of layers are taken
into the preheat channel 1, from the latter into the vacuum box 20,
from the vacuum box 20 to the postheat channel 4 and from the exit
of the postheat channel 4 to the next treatment station.
[0024] With this installation, the process according to the
invention may, for examples be implemented in the following manner
for manufacturing a curved windscreen for vehicles: the layers, for
example three layers, intended for making up the pane of laminated
glass are placed, one on top of the other, to form a pack of
layers, namely a curved glass sheet 6 having a thickness of 3 mm, a
sheet of polyvinyl butyral 8 having a thickness of 0.76 mm and the
second curved glass sheet 7 having a thickness of 2 mm. The pack of
layers thus formed is placed on the chain transporter 11 of the
preheat channel 1 and transported through the preheat channel.
Inside this preheat channel, the pack of layers is heated to a
temperature of 115.degree. C.
[0025] Next, the pack of layers thus preheated is placed on the
supports 29 of the open vacuum box 20. The vacuum box 20 is then
closed by fitting the cover 22. In the closed arrangement, the
flexible tube 34 lies above the edge of the upper glass sheet 7 of
the pack of layers. The two tubes 24 and 34 are initially under no
pressure, so that the two glass sheets 6 and 7 do not come into
contact with the tubes 24 and 34.
[0026] As soon as the vacuum box 20 is sealably closed, it is
connected to the evacuated vacuum chamber 42 by actuating the valve
40. Thus, a vacuum of less than 40 mbar is created in the vacuum
box 20 in the space of a few seconds. At this level of vacuum, the
enclosed air, the enclosed gas and the volatile constituents of the
thermoplastic film are rapidly sucked out through the edge of the
pack of layers.
[0027] Approximately 20 seconds after complete vacuum has been
achieved, the two tubes 24 and 34 are filled with compressed air to
approximately 4 bar by actuating the corresponding three-way valve
26. Thus, the edge of the pack of layers is pressed uniformly over
its entire perimeter such that the pack of layers are sealably
bonded around the edges. The pressure in the tubes 24, 34 is
maintained for approximately 5 to 10 seconds. Next, the
communication with the vacuum chamber 42 is broken by actuating the
valve 40 and the vent-forming aperture 41 of the vacuum box 20 is
exposed to atmosphere so that, by virtue of the perforations 47, 48
in the frames 23, 33, atmospheric pressure is exerted over the
entire surface of the pack of layers. The lid 22 is then removed
from the vacuum box. Since the edge is sealed, atmospheric pressure
is now exerted on both faces of the pane of laminated glass.
[0028] The pane of laminated glass thus subjected to atmospheric
pressure is removed from the vacuum box and placed on the transport
system of the postheat channel. In this postheat channel, the pane
is maintained at a temperature of approximately 135.degree. C. for
some 15 minutes. At this temperature, the thermoplastic polyvinyl
butyral melts to an extent such that it fully adheres to the glass
sheets due to the effect of atmospheric pressure. The pane of
laminated glass rendered totally transparent in this way is removed
from the transport system 46 at the end of the postheat channel
4.
[0029] A pane of laminated glass manufactured according to this
process was subjected to the usual tests. It fully satisfied all
the requirements of the tests.
* * * * *