U.S. patent application number 09/790494 was filed with the patent office on 2001-07-12 for process and apparatus for laminating laminated glazing assemblies.
This patent application is currently assigned to Saint-Gobain Vitrage. Invention is credited to Balduin, Michael, Havenith, Hubert, Labrot, Michael.
Application Number | 20010007270 09/790494 |
Document ID | / |
Family ID | 7895533 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007270 |
Kind Code |
A1 |
Balduin, Michael ; et
al. |
July 12, 2001 |
Process and apparatus for laminating laminated glazing
assemblies
Abstract
A process for laminating multi-layer pre-forms into laminated
glazing assemblies is provided. The pre-forms are first subjected
to a vacuum in an inlet lock. Then, the pre-forms are heated to an
assembly or bonding temperature in a heating chamber, while still
being subjected to vacuum. Next, the pre-forms are pressed using
pressing pieces in a pressing chamber, which is also subjected to
vacuum. A greater pressure is exerted along the edges of the
laminated glazing assemblies so as to bond the edges, preferably by
using membranes. In an outlet lock which follows the pressing
chamber, the laminated glazing assemblies are again vented to
atmospheric pressure. An apparatus suitable for carrying out the
process is also provided. The apparatus has chambers which are
connected together by conveyors so as to achieve a quasi-continuous
flow of material.
Inventors: |
Balduin, Michael; (Alsdorf,
DE) ; Havenith, Hubert; (Wurselen, 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 F-924000
Courbevoie
FR
|
Family ID: |
7895533 |
Appl. No.: |
09/790494 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09790494 |
Feb 23, 2001 |
|
|
|
09492455 |
Jan 27, 2000 |
|
|
|
Current U.S.
Class: |
156/99 ; 156/285;
156/381 |
Current CPC
Class: |
B32B 37/12 20130101;
B32B 2309/68 20130101; B32B 17/10844 20130101; B32B 17/10871
20130101; B32B 37/10 20130101; B32B 39/00 20130101; B29C 2043/3647
20130101; B29C 2043/561 20130101; B29C 43/32 20130101; B32B
17/10807 20130101; B29C 2043/3649 20130101; B32B 17/10761 20130101;
B29C 43/56 20130101 |
Class at
Publication: |
156/99 ; 156/285;
156/381 |
International
Class: |
G02B 001/00; B32B
017/00; C03C 027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 1999 |
DE |
199 03 171.1-45 |
Claims
We claim:
1. A process for laminating a pre-form, wherein said pre-form
includes at least first and second solid panes superposed with
respect to each other and having a layer of adhesive in between
such that said pre-form is to be subjected to pressure and heat
differences, to form a laminated glazing assembly, said process
comprising the steps of: subjecting said pre-form to an overall
vacuum by lowering an ambient pressure; heating said pre-form to a
predetermined temperature necessary to adhesively bond said at
least first solid pane to said layer of adhesive, while maintaining
said overall vacuum; pressing said pre-form at said predetermined
temperature using flexible pressing pieces to form said laminated
glazing assembly, while maintaining said overall vacuum; and
increasing said ambient pressure to atmospheric pressure by venting
said laminated glazing assembly.
2. The process according to claim 1, further comprising heating
said laminated glazing assembly further so as to fully melt said
layer of adhesive, after increasing said ambient pressure to
atmospheric.
3. The process according to claim 1, wherein said subjecting said
pre-form an overall vacuum, said heating of said pre-form, said
pressing of said pre-form, and said increasing said ambient
pressure to atmospheric pressure are each carried out in physically
separate successive chambers, and wherein said heating of said
pre-form and said pressing of said pre-form takes place in chambers
permanently under vacuum.
4. The process according to claim 1, wherein said heating of said
pre-form is done in a heating chamber which is most preferably a
tunnel oven with radiative heating elements.
5. The process according to claim 1, wherein said pressing of said
pre-form includes applying pressing forces by at least one movable
membrane against one of main surfaces of said pre-form.
6. The process according to claim 1, wherein said pre-form is
pressed flat against a conveyor belt assembly so that a belt of
said conveyer belt assembly transfers pressing forces to a main
surface of said pre-form which faces said conveyor belt.
7. The process according to claim 5, wherein said pre-form is flat
and said one of said main surfaces of said pre-form bears away from
said at least one moveable membrane on a solid flat bearing
surface.
8. The process according to claim 5, wherein when said pre-form has
at least one curved solid pane and wherein said pressing forces are
applied using said at least one movable membrane acting on said one
of said main surfaces and at least a second movable membrane action
on a second of said main surfaces.
9. The process according to claim 5, wherein said pressing of said
pre-form is such that said at least one movable membrane is
subjected to at least atmospheric pressure on a face thereof and
away from said pre-form.
10. The process according to claim 1, wherein said layer of
adhesive has an average roughness between 80 .mu.m and 140 .mu.m,
and more preferably between 100 .mu.m and 110 .mu.m.
11. An apparatus for laminating a pre-form, wherein said pre-form
includes at least first and second solid panes superposed with
respect to each other and having a layer of adhesive in between so
that said pre-form is subjected to pressure and heat differences,
to form a laminated glazing assembly, said apparatus comprising: an
inlet lock for lowering an ambient pressure of said pre-form, after
said pre-form has been introduced into said inlet lock; a heating
chamber, in which a first vacuum is created, wherein said pre-form
is heated in said heating chamber after being introduced into said
inlet lock at an assembly temperature where said first vacuum was
created; a pressing chamber, in which a second vacuum is created
equivalent to said first vacuum, wherein said pressing chamber
includes pressing pieces so that a sufficient pressure may be
applied to main surfaces of said pre-form, and wherein said
pressing chamber follows said heating chamber in which said
pre-form has been heated to said assembly temperature necessary to
adhesively bond said at least first solid pane to said layer of
adhesive so that after said pre-form leaves said pressing chamber,
said laminated glazing assembly is finally assembled; an outlet
lock located next to said pressing chamber, wherein said laminated
glazing assembly is introduced and vented to atmospheric pressure
in said outlet lock, after said laminated glazing assembly has been
pressed in said pressing chamber; a plurality of shutters located
within said apparatus, wherein said shutters separate said inlet
lock and said outlet lock from said heating chamber and said
pressing chamber, respectively; and conveying devices located
within said apparatus, wherein said conveying devices convey said
pre-forms through said heating and pressing chambers.
12. The apparatus according to claim 11, wherein said heating
chamber includes a tunnel oven with a conveyor and radiative
heating elements.
13. The apparatus according to claim 11, wherein said laminated
glazing assembly is further heated in said outlet lock.
14. The apparatus according to claim 11, wherein said conveying
devices includes a conveying device in said pressing chamber, said
conveying device in said pressing chamber including a conveyor belt
assembly having a conveyor belt on which said pre-form is conveyed
during pressing of said pre-form.
15. The apparatus according to claim 11, wherein at least one of
said pressing pieces is provided in said pressing chamber and said
at least one of said pressing pieces includes a membrane in a
working chamber, said membrane being subjected to variable pressure
levels via a system of pipes and valves for actuating said
membrane.
16. The apparatus according to claim 15, wherein said membrane is
placed beneath said belt of said conveyor belt assembly.
17. The apparatus according to claim 15, further comprising a solid
surface which serves as a counterpart to said at least one of said
pressing pieces, wherein said at least one of said pressing pieces
is made in the form of another membrane.
18. The apparatus according to claim 15, wherein said membrane
includes two opposed membranes which can be actuated in opposite
directions and which press said pre-form, once said pre-form is
correctly positioned between said two opposed membranes.
19. The apparatus according to claim 14, further comprising a
tensioning device corresponding to said conveyor belt of said
conveyor belt assembly provided in said pressing chamber, wherein
said tensioning device allows said conveyor belt, which is
pre-tensioned, to be elastically moved away during pressing of said
pre-form.
20. The apparatus according to claim 11, further comprising a
broken-glass debris removing member, wherein said broken-glass
debris removing member is positioned near said conveyor belt in
order to remove broken-glass debris from a surface of said conveyor
belt.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a process and an apparatus
for laminating pre-forms into laminated glazing assemblies, wherein
the pre-forms include two solid panes laid on top of each other
with a layer of adhesive in between such that the two solid panes
with the layer of adhesive in between are subjected to pressure and
temperature differences to form the laminated glazing assembly.
BACKGROUND OF THE INVENTION
[0002] The expression "laminated glazing assemblies" should be
understood here to mean multi-layer products which consist of at
least two solid panes with an adhesive film in between. The
adhesive film is made of plastic or similar material for joining
the two solid panes together. The two solid panes may both be made
of glass or may both be made of plastic. However, it is also
possible for a glass pane and a plastic pane to be joined together
by an adhesive film. The individual layers (i.e., the solid panes
and the layers or films of plastic) are produced separately in a
conventional manner. The individual layers are then layered on top
of each other to form of a packet of layers (i.e., a "pre-form"),
before a final assembly into a laminated glazing assembly.
[0003] Modern glazing assemblies made of laminated glass, such as
windscreens and side windows in motor vehicles, are often finally
laminated in large autoclaves at high pressure and high
temperature. Because of the necessary increase in pressure and of
the long residence time required, a process using an autoclave step
slows down the continuous and highly mechanized sequence of
operations in the manufacture of the laminated glass assemblies,
which has already been achieved for the manufacture and conversion
of the individual layers for forming the pre-forms.
[0004] However, processes have also already been described for the
manufacture of laminated glass which dispense with the autoclaving
for the final bonding. In these autoclave-less processes, the
pre-forms are finally bonded at atmospheric pressure.
[0005] German Patent No. 2,209,642 (hereinafter "the DE '642
patent") describes a process for manufacturing three-layer
laminated-glass glazing assemblies. During the process of the DE
'642 patent, the pre-forms are put under vacuum and heated in a
chamber, while the intermediate spaces are simultaneously subjected
to vacuum using a suction frame. After having reached a certain
temperature, for example, 100.degree. C., the chamber is again
vented to atmospheric pressure. However, the lateral vacuum is
maintained by the suction frame, which continues to create a
vacuum. Consequently, a primary laminate is simply assembled
temporarily. This primary laminate is then transferred, with the
suction frame under vacuum, into another chamber which is at
atmospheric pressure. In the atmospheric pressure chamber, the
primary laminate is heated to a temperature above the melting point
of the adhesive film, which has been placed between the two solid
panes. The pressure difference between the outside and the inside
is sufficient to form the final laminated assembly.
[0006] German Patent No. 3,044,717 (hereinafter "the DE '717
patent") describes another autoclave-less process for the
manufacture of two-layer laminated products having a thermoplastic
sheet located on the outside. According to the process of the DE
'717 patent, a chamber at ambient pressure receives the pre-form.
The ambient pressure chamber has its pressure temporarily decreased
to a pressure even lower than the internal pressure obtained
between the layers of the pre-form. The pressure may be reduced
with the aid of a suction frame. The pressure difference briefly
separates the layers from each other so as to facilitate the
outgassing of the intermediate space. Next, the entirety of the
pre-form is heated to the bonding temperature. During the time the
pre-form is heated to the bonding temperature, the pressure in the
chamber is increased back up to ambient pressure so as that the
final laminated glazing assembly results and the internal pressure
within the pre-form remains below atmospheric.
[0007] The two above-described autoclave-less processes rely on
separable vacuum systems and also require a suction frame for
sealing the packet of layers around the edge. The edge sealing is
done, not only during the phase when the pre-form is under vacuum,
but also during the subsequent phase wherein the final laminated
glazing assembly is produced at atmospheric or higher pressure. For
each shape and/or size of the pre-form, depending on the case, a
specific variant of the suction frame has to be used. Since
positioning and removing the suction frame cannot presently be
mechanized, the above-described autoclave-less processes cannot be
incorporated into, or can only be incorporated insufficiently into,
an at least quasi-continuous manufacturing line. The term
"quasi-continuous" should be understood here to mean a sequence of
operations during which the flow of product material takes place,
in principle, continuously during certain pane cycle periods and
must only be interrupted for a short time for certain conversion
steps, for example, for pressing between membranes or other
pressing molds.
[0008] German Reference No. 2,424,085 (hereinafter "the DE '085
reference") also describes an autoclave-less process during which a
plastic film is laminated onto a pane using pressing membranes. In
order to carry out the process of the DE '085 reference, the pane
and the film are placed in a chamber so that the pane does not
contact the film. Next, the chamber is closed and a vacuum is
created therein. The plastic film rests on a membrane forming a
wall of the chamber. The membrane is subjected to vacuum on both
sides (i.e., on a front and rear face away from the chamber). After
a necessary vacuum has been obtained in the chamber, the rear face
of the membrane is subjected to atmospheric pressure. Because of
the pressure difference established, the membrane presses the film
against the pane. The film is made of either self-adhesive plastic
or is provided with an adhesive layer. In this way, it is possible
to produce curved glazing assemblies made of laminated glass. The
curved laminated glazing assemblies are then pressed in a similar
manner between two membranes.
[0009] When a heat-activatable adhesive is used, the pane is
pre-heated outside of the chamber and then placed in the chamber.
This process has the advantage that both a suction frame and
individual pressing molds may be dispensed with.
[0010] Finally, German Reference No. 19,712,145 (hereinafter "the
DE '145 reference") describes another laminating process during
which a pre-form, consisting of two panes and an adhesive film
interlayer, is heated to the assembly temperature. The pre-form is
then transferred into a chamber and a vacuum is created therein.
PVB adhesive films are usually employed for the manufacture of
glazing assemblies of the DE '145 reference. The PVB adhesive films
are usually made of laminated glass which has a relatively rough
and nontransparent surface so as to guarantee that, after the solid
panes and the adhesive film have been joined together, all the air
can be sucked out through the channels formed by the unevenness in
the film. In order to obtain the required high transparency of the
final product, the adhesive film must be fully melted so that the
unevenness completely disappears. In the process of the DE '145
reference, after the minimum pressure has been obtained and after
sufficient venting, the edge of the pre-form is sealed by
mechanical pressing, while the chamber is vented again. Under the
action of forces exerted on the main surfaces of the laminated
product, preferably in combination with additional heating in order
to completely melt the adhesive film, the rise in pressure causes
the panes to be joined to the adhesive film so that a virtually
continuous flow of material can be achieved.
SUMMARY OF THE INVENTION
[0011] The objective of the present invention is to provide an
apparatus and process for laminating pre-forms into laminated
glazing assemblies, wherein at least a quasi-continuous flow of
material is achieved for laminated glazing assemblies of variable
outlines and sizes.
[0012] The above-described objective is achieved according to the
present invention by providing a process for laminating pre-forms
into laminated glazing assemblies by using the effect of pressure
and heat differences on the superposed layers of the pre-forms in
order to form the laminated glazing assemblies. The process
comprising the steps of: subjecting the pre-forms to an overall
vacuum by lowering the ambient pressure; maintaining the ambient
vacuum, while both heating the pre-forms to a temperature necessary
for joining the glass to the plastic and pressing the pre-forms
between flexible pressing pieces in order to form the laminated
glazing assemblies; and increasing the ambient pressure to
atmospheric pressure by venting the laminated glazing
assemblies.
[0013] During the step of subjecting the pre-forms to the overall
vacuum, the temperature of the pre-forms is not yet increased or in
some cases, is increased only slightly. Thus, any premature bonding
is avoid so that the laminated glazing assemblies do not have any
air inclusions therein and thus, it is not necessary to scrap the
defective laminated glazing assemblies so as to reduce the
efficiency of the process.
[0014] The second and third step of heating the pre-forms to a
temperature necessary for joining the glass to the plastic and
pressing the pre-forms between flexible pressing pieces in order to
form the laminated glazing assemblies (both while maintaining
vacuum), makes it possible to dispense with a suction frame for the
pre-forms. During the heating step, the pre-forms are heated to a
temperature necessary to join the glass to the plastic. An adhesive
film of polyvinylbutyral (i.e., "PVB"), which is used for most
multi-layer laminated glazing assemblies, melts at approximately
130.degree. C. When the layer of adhesive is of another plastic
other than PVB, the layer of adhesive may be on the outside of the
solid panes, may be a heat-activatable adhesive between the solid
panes, and is usually of a type having a melting point less than
130.degree. C.
[0015] The cycle time of the process and of the corresponding
apparatus is essentially determined by the time required for the
pre-form to be subjected to vacuum during the initial step. This
cycle time has been found sufficient to heat the pre-form to the
required temperature during the heating step. It also allows enough
time for the pressing step, which may require the material between
the pressing pieces to be immobilized, at least for a short period
of time lasting a few seconds.
[0016] The rapid final cooling of the laminated glazing assembly to
normal temperatures, which occurs after the exit shutter is opened,
is not critical when the solid panes are glass because the assembly
temperatures are also significantly below the usual pre-tensioning
temperatures.
[0017] Preferably, the pre-form is reheated, in any known manner,
so to completely melt the structure of the film to assembly the
laminated glazing assembly.
[0018] In order to achieve a high efficiency, the various steps,
namely the evacuation, heating, pressing and venting, are carried
out in successive physically separate chambers, wherein the heating
chamber and the pressing chamber always remain under vacuum.
[0019] The level of vacuum created in the heating chamber and the
pressing chamber is approximately 1 to 10 hPa of absolute pressure.
The entry temperature of the pre-form is brought to approximately
50.degree. C. by pre-heating the preform. Thereafter, in the
apparatus, the heating rate is set to approximately 2.degree.
C./second until the usual assembly temperature of 130.degree. C. is
reached. The cycle time of a complete cycle is about 15 seconds,
this being imposed by the prior and subsequent processes. The
pressing time itself is only about 5 seconds.
[0020] Even when taking into account the reheating of the pre-form
in order to form the final laminated glazing assembly, the total
times for manufacturing laminated glazing assemblies according to
the process of the present invention are appreciably shorter than
the values of approximately 2.5 hours that are achieved with the
autoclaving process.
[0021] The flexible pressing pieces used in the pressing step are
most likely conventional membranes. Therefore, the plant does not
require pressing molds of any one specific type, which are set for
certain glazing models. Laminated glazing assemblies of different
outlines and sizes can be treated directly, one after another,
without having to modify the plant and therefore, without any down
time.
[0022] Flat pre-forms may be pressed between a membrane and a flat
and solid bearing surface, whereas curved glazing pre-forms are
preferably pressed in a conventional manner between two membranes
that can be pressed on both sides in order to carry out the final
assembly. Of course, flat pre-forms may also be pressed by two
membranes in a pressing chamber.
[0023] In all cases, during the pressing of the pre-forms, the
pre-forms may rest on a conveyor belt assembly in the pressing
chamber. The conveyor belt, of the conveyor belt assembly,
transfers the pressing or reaction forces to the main surface of
the pre-form facing the conveyor belt.
[0024] Of course, it is also possible to use other pressing pieces
such as, for example, resilient rollers. However, pressing
membranes transfer the pressing effect over the entire surface of
the pre-form in the most homogeneous manner. The pressing membranes
also adapt best to the surfaces and sizes of different glazing
assemblies. However, care has to be taken to ensure that the
pre-forms to be pressed are always entirely covered by the
membranes. The size of the pre-forms that can be converted
therefore depends directly on the membrane area available. In all
cases, the pressing pieces are required to provide a covering,
which reliably prevents adhesion of the glass or of the plastic, in
a conventional manner.
[0025] The pressing membranes may be subjected to atmospheric
pressure on the opposite side from the pre-form because there is a
vacuum inside the pressing chamber. In all cases, this pressure
difference is enough to generate sufficiently high assembly forces.
It is therefore possible, in principle, to avoid the need for and
the use of a high-pressure generator.
[0026] During the venting of the laminate, in order to prevent air
from getting back into the laminated product, it is necessary, in
principle, to find a way to bond the edges in a manner similar to
the process mentioned in the DE '145 reference. When membranes are
used that have working areas which extend beyond the edges of the
pre-forms on all sides thereof, a greater force is exerted on the
edges of the pre-forms during pressing to result in sufficient
bonding of the edges. This is especially so because the adhesive
film reaches its melting point along the edges rather than in the
middle of the surface. The vacuum created is as if it were trapped
in the laminate.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0027] Further details and advantages of the subject matter of the
present invention will be evident from the drawing figures of the
two illustrative embodiments which are described, as follows:
[0028] FIG. 1 is a cross-sectional view of a first embodiment of
the present invention of an entire autoclave-less apparatus for the
manufacture of flat laminated glazing assemblies;
[0029] FIG. 2 is a cross-sectional view showing the details of the
pressing chamber of the apparatus of FIG. 1, wherein a membrane is
used as the pressing piece and the membrane is shown in a working
position;
[0030] FIG. 3 is cross-sectional view showing a second embodiment
of the pressing chamber of FIG. 2, wherein the pressing chamber is
particularly for the manufacture of curved laminated products such
that the pressing chamber includes two membranes shown in the rest
position; and
[0031] FIG. 4 is a cross-sectional view showing the pressing
chamber of FIG. 3 in a working position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Referring to FIG. 1, a laminated glazing assembly apparatus
3 for laminating pre-forms 1 into laminated glazing assemblies 20
is shown. The pre-forms 1 include pre-assembled panes and
interlayer films. The pre-forms 1 are conveyed on a conveyor belt
2a of a first conveyor belt assembly 2 to the laminated glazing
assembly apparatus 3. The laminated glazing assembly apparatus 3
runs from the left to the right of FIG. 1. The pre-forms 1 are
first transferred into an inlet lock 4 via a conveyor belt 2.5a of
a second conveyor belt assembly 2.5. The inlet lock 4 serves as an
input station and may be hermetically sealed on the inlet side
(i.e., on the left) by a shutter 5 and on the outlet side by a
shutter 6. The inlet lock 4 may be subjected to vacuum and then
vented using a system of pipes (not shown). The shutters 5 and 6,
just like the conveyor belt assemblies 2 and 2.5, are motor-driven
and coordinated by a central controller (not shown). The shutter 6
seals off the inlet lock 4 from a heating chamber 7, which is
located downstream of the inlet lock 4. The heating chamber 7
includes electrical (radiative) heating elements. However, the
heating chamber 7 may instead by heated by convective heating.
During the operation of the plant, the heating chamber 7 always
remains under a vacuum of a predetermined level. Inside the heating
chamber 7, the pre-forms 1 are preferably transported on whatever
type of conveyors guarantees effective action of, either the
radiative heating or the convective heating, if required, on all
sides. The conveyors may be, for example, a conveyor assembly
having several narrow conveyor belts. However, FIG. 1 shows the
pre-forms 1 as being moved via rollers 8a of a roller conveyor 8
through the heating chamber 7.
[0033] The heating chamber 7 is followed by a pressing chamber 9.
Throughout the operation of the plant, the pressing chamber 9,
similarly to the heating chamber 7, always remains under vacuum.
The vacuum in the heating chamber 7 and in the pressing chamber 9
will always be the same so that it is not necessary for the heating
and pressing chambers 7, 9 to be pressure-separated or decoupled.
The temperature may also be the same in the heating and pressing
chambers 7, 9. Heat may be provided to the pressing chamber 7, if
required, via any suitable heating means such as, for example, a
hot-air blower (not shown). A remotely controllable shutter (not
shown) may also be provided, if necessary, between the heating and
pressing chambers 7, 9.
[0034] The pre-forms 1 advance through the pressing chamber 9 on a
conveyor belt 10a of a third conveyor belt assembly 10. The third
conveyor belt assembly 10 is guided over a bearing surface 11. In
the first embodiment shown in FIG. 1, the bearing surface 11 serves
as a passive lower pressing piece for the flat pre-forms 1. A
membrane 12 is located above the conveyor belt assembly 10 in the
roof of the pressing chamber 9. The membrane 12 constitutes an
active upper pressing piece.
[0035] A working chamber 13 is located above the membrane 12. The
working chamber 13 is hermetically isolated from the pressing
chamber 9 by the membrane 12. The working chamber 13 may be
subjected alternately to vacuum and to atmospheric pressure (or
higher pressure, if required), via a system of pneumatic pipes 14
and suitable valves 25. The vacuum available in the working chamber
13 must be slightly higher than the vacuum in the pressing chamber
9 so that the membrane 12 can be reliably raised into the roof of
the pressing chamber 9, after each pressing or venting
operation.
[0036] A separating force or a lifting force (not shown), depending
on the case, may be produced by the intrinsic elasticity of the
membrane 12 or by suitable springs 24 or other suitable
energy-storage devices (not shown).
[0037] On the output side (i.e., to the right in FIG. 1), the
pressing chamber 9 may also be hermetically isolated by a shutter
15 of an outlet lock 16. The outlet lock 16 is located downstream
of the pressing chamber 9. A fourth conveyor belt assembly 17
having a conveyor belt 17a is provided in the outlet lock 16 for
transporting the laminated glazing assemblies 20. On the output
side, the laminated glazing assemblies 20 may be isolated from the
environment by a shutter 18. In a conventional manner, a fifth
conveyor belt assembly 19 having a conveyor belt 19a transports the
finished laminated glazing assemblies 20 to a tunnel oven (not
shown). The laminated glazing assemblies 20 reside in the tunnel
oven (not shown) for a prolonged period of time, such as about 1
hour or less, at an ambient temperature of about 130.degree. C.
During entry of the pre-forms 1 into the inlet lock 4 on the first
conveyor belt assembly 2, the shutter 5 (on the left in FIG. 1) of
the inlet lock 4 is open and the shutter 6 (on the right in FIG. 1)
of the inlet lock 4 is closed. After a plurality of pre-forms 1 has
been introduced into the inlet lock 4, the shutter 5 is then closed
so that the inlet lock 4 may be subjected to vacuum. When the
vacuum in the inlet lock 4 is at the same level as the vacuum in
the heating chamber 7, the shutter 6 is opened. The shutter 6 may
be operated more easily by establishing a direct pressure
compensation via a switchable shunt pipe (not shown) before opening
the shutter 6. The plurality of pre-forms 1 are transferred into
the heating chamber 7 and then, the shutter 6 is closed again. The
inlet lock 4 can now be vented and then, after opening the shutter
5, can accept the next plurality of pre-forms 1. It goes without
saying that, during the operation of the laminated glazing assembly
apparatus 3, the two shutters 5 and 6 are never open at the same
time.
[0038] The plurality of pre-forms 1 within the heating chamber 7
are heated up to the melting point of the adhesive film or,
depending on the type of adhesive used, until the melting point is
approximately reached. If the heating chamber 7 is long enough, the
pre-forms 1 are then transported further by the rollers 8 of the
roller conveyor during the heating step. The pre-forms 1 are then
transferred onto the third conveyor belt assembly 10 of the
pressing chamber 9 without modifying the pressure level or the
temperature. If required, the pre-forms 1 are correctly position on
the bearing surface 11 beneath the membrane 12 using a positioning
system (not shown). The outlet shutter 15 of the pressing chamber 9
is now closed, as is the shutter 6. There is still vacuum in the
working chamber 13, at a position located above the membrane 12.
The third conveyor belt assembly 10 stops and the pressure in the
working chamber 13 is rapidly increased. The pressure difference
which is established presses the entire area of the membrane 12
against the upper faces of the heated pre-forms 1, as shown in FIG.
2. The pre-forms 1 are pressed against the bearing surface 11 via
the conveyor belt of the conveyor belt assembly 10. The pressure
exerted is sufficient for all the layers of the pre-forms 1 to be
solidly joined together. More particularly, a greater pressure is
exerted on the edges of the pre-forms 1. After the prescribed
pressing time of a few seconds, a vacuum is again created in the
working chamber 13 and again the membrane 12 is lifted up to the
roof of the pressing chamber 9 so that the pressed laminated
glazing assemblies 20 are released. Before opening the shutter 15
to expel the pressed laminated glazing assemblies 20 into the
outlet lock 16, the outlet shutter 18 of the outlet lock 16 must be
closed and the outlet lock 16 must be subjected to vacuum at the
vacuum level in the pressing chamber 9. If necessary, the proper
lever of vacuum in the outlet lock 16 may be achieved using a
switchable shunt pipe (not shown). The laminated glazing assemblies
20 are now transferred by the conveyor belt 10a of the third
conveyor belt assembly 10 onto the conveyor belt 17a of the fourth
conveyor belt assembly 17, which is in the output lock 16. When the
transfer is complete, the shutter 15 is again closed and the output
lock 16 is vented to atmosphere.
[0039] If a vacuum is created in the heating chamber 7 and in the
pressing chamber 9 via the systems for creating a vacuum in the
inlet and outlet locks 4, 16, the shutters 6, 15 will be closed,
during the operation of the plant, only for the time during which
the pressure level in the inlet and outlet locks 4, 16 is greater
than the working pressure in the heating and pressing chambers 7,
9. Therefore, only during the introduction and discharge of the
plurality of pre-forms 1 or the laminated glazing assemblies 20, as
the case may be. The handling capacity of the plant may be
comparatively improved if suitable means for maintaining the vacuum
are also provided in the heating and pressing chambers 7, 9.
[0040] In order to guarantee uniform cycle times, the number of
pre-forms 1 or laminated glazing assemblies 20, as the case may be,
which can be accepted into the various stations will be sized in
the same way. In other words, the inlet and outlet locks 4, 16 and
the pressing chamber 9 will each be able to accept an equivalent
number of pre-forms 1 or laminated glazing assemblies 20, as the
case may be. The heating chamber 7 or the rollers 8a of the roller
conveyor 8 which is provided in the heating chamber 7 may, in
principle, operate continuously via either a sufficient length of
the heating chamber 7 or a slower transfer rate of the pre-forms 1.
In order to reduce the length of the heating chamber 7, the inlet
lock 4 could already be equipped with heating elements (not
shown).
[0041] If necessary, special measures will be taken to remove any
broken-glass debris from the surface of the conveyor belt 10a of
the third conveyor belt assembly 10 and from the lower face of the
membrane 12. Removal of the broken-glass debris from either the
surface of the conveyor belt 10a of the third conveyor belt
assembly 10 or from the lower face of the membrane 12 may be
accomplished, for example, by a brush (not shown). In such a case,
the brush would most likely be placed near the lower side of where
the conveyor belt 10a runs.
[0042] In the alternative embodiment of the pressing chamber 9 as
is shown in FIG. 3, the main difference from the embodiment shown
in FIGS. 1 and 2 is that a second membrane 21 is provided as an
active lower pressing piece in addition to the membrane 12. The
second membrane 21 lies beneath the third conveyor belt assembly 10
and replaces the bearing surface 11. In order to actuate the second
membrane 21, a second working chamber 22 is provided. The second
working chamber 22, like the working chamber 13, may be subjected
alternately to a vacuum and to atmospheric or higher pressure via a
system of pipes 23 and may be hermetically isolated from the
pressing chamber 9 by the membrane 21. The pressure in the two
working chambers 13 and 22 will generally be controlled in a
synchronous manner. However, the pressure in the working chambers
13 and 22 may also be controlled independently of each other in a
predefined sequence of operations over time.
[0043] Normally, the two working chambers 13 and 22 are under
vacuum and therefore, the pressing pieces are in the rest position.
In this state, the third conveyor belt assembly 10 is freely
accessible for transporting the pre-forms 1 that are to be pressed
or the laminated glazing assemblies 20 that have been pressed, as
the case may be. Preferably, the lower membrane 21 does not rest on
its lower face at this time so as to minimize rubbing and wear.
Also, it is preferable that there is no sliding contact between the
upper membrane 12 and the laminated glazing assemblies 20.
[0044] After positioning the heated pre-forms 1, which may be
slightly curved, for example, for the side windows of vehicles
having a cylindrical curvature and made of laminated safety glass,
between the two membranes 12 and 21. The two working chambers 13
and 22 are vented. Then, the situation illustrated in FIG. 4 is
established. In other words, the membranes 12 and 21 both grip the
pre-forms 1 to produce a surface pressing force along two sides and
the edges of the membranes 12 and 21. Thus, in the embodiment shown
in FIG. 4, the third conveyor belt assembly 10 can present only the
least possible resistance to the full-area matching the possibly
curved glazing surface facing it. In this case, a tensioning device
24 is shown, particularly on one of the idler rollers 10b allowing
the third conveyor belt assembly 10, which is pre-tensioned, to
move elastically away during lifting by the lower membrane 21. The
membranes 12 and 21 themselves must also be sufficiently flexible
to match the full-area shape.
[0045] Thus, in a manner similar to FIG. 2, a surface pressing load
is applied to the heated pre-forms 1 subjected to vacuum. The
vacuum is maintained for a time long enough for the desired
full-area bonding of the individual layers of the pre-forms 1 to be
achieved. The flexibility of the membranes 12 and 21 is used to
obtain a greater pressing force along the edges of the pre-forms 1
and thus, in particular, to achieve reliable bonding of the outer
edge of the pre-forms 1 into the laminated glazing assemblies 20.
This again prevents any air from entering between the layers of the
laminated glazing assemblies 20, when the laminated glazing
assemblies 20 is again subsequently vented to atmospheric
pressure.
[0046] It has been found from experimentation that a layer of
adhesive, which is particularly well-adapted to the above-described
process of laminating a pre-form 1 into a laminated glazing
assembly 20 because the adhesive layer allows for better draining
of air, has a roughness more important in value than an usual
adhesive layer. More particularly, a preferred layer of adhesive
has an average roughness Rz ranging from between 80 .mu.m to 140
.mu.m, and even more preferably ranging from 100 .mu.m to 110
.mu.m. A particularly favorable adhesive layer has been found to be
a PVB film having characteristics, measured according to the norm
DIN 4768, as follows:
1 TABLE 1 SIDE 1 SIDE 2 Ra/.mu.m 18,46 16,01 Rz/.mu.m 112,42 96,86
Rmx/.mu.m 134,32 108,75 RSm/.mu.m 948,05 675,12
[0047]
2 TABLE 2 SIDE 1 SIDE 2 Ra/.mu.m 18,36 17,51 Rz/.mu.m 111,09 102,86
Rmx/.mu.m 132,99 115,25 RSm/.mu.m 1560,51 1112,86
[0048] The measures in Table 1 are realized according to the
material direction (i.e., extrusion direction) and the measures in
Table 2 are realized according to a direction perpendicular to the
material direction. In each of Table 1 and Table 2, the measures
are realized on both sides.
[0049] Such PVB films, which have a roughness more important in
value than the usual adhesive layer, are obtained by extrusion and
are submitted to a thermal treatment such as, for example, cooling
and/or to a mechanical treatment such as, for example, a lamination
with engraved rollers.
[0050] In this configuration, it goes without saying that control
of the membranes 12 and 21 by varying the pressure in the working
chambers 13 and 22 requires greater attention than when pressing
flat pre-forms 1 against a solid bearing surface 11.
* * * * *