FI57248B - REFERENCE FOUNDATION FOR LAMINATION OF GLASS ARTICLES - Google Patents

Description

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England-England (GB) 26U80 / 73 (71) Triplex Safety Glass Company Limited, 1 Albemarle Street, Piccadilly, London W.l, England-England (GB) (72) John Pickard, Studley, Warwickshire, Richard Melling, Hollywood,

Birmingham, Atrhur Joseph Nobbs, Alvechurch, Birmingham, England-England (GB) (7U) Oy Kolster Ab (5U) Method and apparatus for forming a laminated glass article - Förfarande och anordning för framställning av en laminerad glasartikel

The invention relates to a method of making laminated glass articles and to an apparatus used herein.

The laminated glass article, i.e. the laminated glass article, may comprise two or more sheets of glass and in each case a layer of transparent plastic material between the two sheets of glass. The plastic material is normally thermoplastic and, when placed between glass sheets, is bonded to them by heat and pressure. Such a laminated glass sheet is usually used as a safety glass, e.g. in windscreens and windows of vehicles. To obtain a satisfactory laminated product, the glass sheets and the plastic interlayer must adhere together over the entire surface of the glass sheets and the bond must be such that the lamination does not disintegrate in use. The plastic interlayer must therefore fill the entire space between the glass sheets and the glass sheets must be pulled together over their entire surface area during the bonding process. In the manufacture of such a laminated glass article, it has previously been proposed to apply a vacuum at the peripheral edge of the sheet group at the exposed point of the joint between the glass sheets and the intermediate layer before starting the bonding operation. In a known process, the group is subjected to ambient pressure and temperature, and during this step B 32 B 31/00 (vpr »!. $> 2 57248, the trapped air is sucked out of the interlayer between the glass sheets.

The array is then heated to a temperature at which the interlayer becomes tacky, e.g., 90 ° C, during which time further removal of air from the interlayer occurs, and pre-bonding is provided between the glass sheets and the interlayer such that ambient pressure pulls the glass sheets together around the interlayer.

However, this has been a pretreatment, called a pre-compression process, which is performed as the first stage of a two-stage process, and the entire binding effect is obtained in the second stage of the process. In the second step, a group of 1 wolf plate is further heated to achieve proper bonding and then cooled. In some cases, it is desirable to transfer the glass sheet assembly to a suitable pressure vessel in a second step where the temperature and pressure are raised to provide the entire bonding operation.

It is an object of the present invention to improve the manufacture of laminated glass articles and to reduce the risk of unsatisfactory bonding between the plastic interlayer and the glass sheets.

According to the invention, there is provided a method of forming a laminated glass article comprising two sheets of glass and a thermoplastic transparent plastic interlayer therebetween, the method comprising assembling the two glass sheets together with a thermoplastic transparent plastic interlayer, heating the group to an elevated temperature when a pressure is applied to the main surfaces of the glass sheets such that the glass sheets and the plastic interlayer become completely bonded together, applying a pressure less than the pressure applied to the main surfaces of the glass sheets to the bare periphery of the interlayer and cooling of the array. The method is characterized in that the lower pressure applied to the bare circumference of the interlayer is adjusted as a function of the pressure applied to the main surfaces of the glass sheets so as to remain below the required amount of pressure applied to the plate surfaces for at least part of said elevated temperature.

The pressure applied to the main surfaces of the sheets during the bonding process depends on the plastic material used in the interlayer. When using, for example, polyvinyl butyral, an elevated pressure, i.e. above atmospheric pressure, must be used while heating to the first temperature. In this case, the pressure at the bare circumference of the intermediate layer is also an elevated pressure, although it is lower than the pressure applied to the main surfaces. On the other hand, it is possible to use, for example, an ethylene polymer polymerizing agent as a plastic material, which can be completely bound to the glass by heating at atmospheric pressure. In this case, the major surfaces of the 3,524,248 glass sheets are maintained at atmospheric pressure during heating, while a controlled negative pressure is applied to the circumference of the intermediate layer.

By applying a lower pressure around the circumferential edge of the array, the glass sheets becoming the heating pig are kept in close contact with the intermediate layer and, in particular, the edge areas of the glass sheets are compressed together after the thermoplastic has softened and bonded. The lower pressure is preferably applied before the group reaches its maximum temperature and can be maintained at least until cooling begins and further until cooling has occurred. The compression of the edges of the glass sheets has many effects: '(a) The interlayer flows laterally from points where the distance between the edges of the glass sheets is smaller to points where the distance between the edges of the glass sheets is greater and where areas of poor bonding would normally occur.

, b) The intermediate layer is extruded outwards between the edges of the glass sheets while step a) takes place and also later until the end of step a).

c) The tendency to reduce the edge waves of the glass sheets puts the edges of the glass sheets in a more parallel position relative to each other.

The extrusion of the intermediate layer between the edges of the glass sheets creates a wedge effect in which the glass sheets taper inwards towards each other along the circumference of the group. Extrusion until the end of step a) is acceptable, but continuous extrusion must be limited to reduce the wedge effect that could cause optical distortion at the edges of the array.

In a preferred embodiment of the invention, a controlled pressure difference is maintained during the initial heating of the array and during the increase in pressure applied to the surfaces of the glass sheets. The pressure difference is also maintained when the group has reached its maximum temperature and during the period during which the group is subjected to full pressure on the surfaces of the glass sheets. The pressure difference should also be maintained when the assembly is finally cooled and the pressure is reduced so that the glass sheets and the interlayer remain securely bonded.

However, it may be possible to use the pressure difference only during part of the bonding cycle, e.g. long enough to complete step a). Once step a) has been completed, the continuous squeezing of the intermediate layer between the edges of the glass sheets can be detrimental if it results in an excessive wedge effect.

For example, the pressure difference can be stopped at some point during the period in which the group is subjected to full temperature and pressure, i.e. at the time when step a) is completed. However, the differential pressure can be used at some point after the stage of applying full temperature and pressure to the array and maintained while maintaining the array at a maximum temperature of c? Iot1 57248 u and subsequently cooling and depressurizing the glass sheet surfaces. Again, the pressure difference is applied long enough to complete step a) described.

The methods described involve the use of a constant pressure difference during all or part of the full bonding step. In the second method, a variable differential pressure can be used during the full bonding step, starting e.g. with a small differential pressure at the beginning of the cycle and gradually increasing the differential pressure during the cycle to the final first differential pressure binding cycle. This method is believed to be advantageous because it reduces the extrusion of the intermediate layer between the edges of the plates, which in turn reduces the subsequent wedge effect.

The reduced pressure may suitably be applied to the edges of the group by enclosing a hollow, flexible ring around which the edge region of the group protrudes so as to communicate with the hollow interior of the ring and connecting the interior of the ring to a source of controlled pressure. This ring may be similar to those rings previously used to apply vacuum to the circumferential regions of the Lamina-1as group during the precompression phase prior to performing the next full bonding. In this way, a vacuum can initially be applied to the array along its circumference, which is already known, and the ring can be held in place when heat and pressure are subsequently applied to perform the bonding.

The glass sheets and the interlayer preferably have the same shape and size when assembled. It is desirable not to use an intermediate layer that is oversized relative to the glass sheets because the protruding edge of the intermediate layer tends to fill the interior of the pressure relief chamber surrounding the group during the bonding operation.

The pressure difference is preferably kept between 0.1 U and 1.05 kg / cm 2, most preferably between 0.26 and 0.7 kg / cm 3.

In most cases, it is desirable that the array be installed in a closed pressure vessel using heat and pressure to bond the interlayer and the glass sheets 2 together. The pressure in the vessel can be increased to 2.0-1.0 kg / cm depending on the material of the intermediate layer. The temperature in the vessel is preferably raised to a value above 100 ° C, · e.g. to 120-160 ° C, during bonding.

The intermediate layer preferably consists of a polyvinyl butyral sheet, although other known, transparent and thermoplastic laminating articles having the same properties are suitable. When using polyvinyl butyral, can the pressure in the vessel be 7.0-1U.0 kg / cm? and the temperature may be raised to 130-1 i * 5 ° C. The intermediate layer may alternatively consist of a sheet of ethylene copolymer laminating agent, in which case the outer surfaces of the group may be subjected to atmospheric pressure during full bonding and the temperature may be raised to about 100 ° C.

The invention includes a laminated glass sheet material which may be flat or curved when made by the methods described above.

The invention also provides an apparatus for use in the manufacture of a laminated glass article, the apparatus being characterized by a closed pressure vessel containing one or more groups of glass sheets having an intermediate layer of thermoplastic transparent plastic material, support means placed in the vessel to support one or more groups, and means for increasing the pressure in the vessel and applying heat to or to each group in the vessel to bond the glass sheets and interlayer together, a gas supply passage leading to the vessel to connect it to the group or each group to provide an elevated pressure around the peripheral edge of the group or each group elsewhere, and means for maintaining a controlled pressure difference between the pressures in the gas supply passage and the vessel.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of an apparatus implementing the present invention; Figure 2 shows an enlarged cross-sectional view the part where the laminated glass panel assembly is in place; and Figure 5 shows a cross-sectional view of the ring surrounding the laminate array. This example relates to the manufacture of a laminated glass article comprising two sheets of glass and an intermediate layer of a thermoplastic, transparent plastic material therebetween, in which case polyvinyl butyral is used as the plastic material. Figure 2 shows that a polyvinyl butyral sheet 11 is interposed between two glass sheets 12 to form a laminated glass sheet array 13. The manufacturing process applies heat and pressure to the array to bond the interlayer 11 and the glass sheets 12 together. Although the panels shown in Figure 2 are flat, the panels may alternatively be curved, and the invention may be particularly well used to make laminated windshields or windows for vehicles. Such windshields are normally curved, especially towards the edge areas of the windshield.

The following describes the manufacturing process in more detail. Two glass sheets of the same size and compatible shape are assembled with the intervening C.Jf'1 to 57248 polyvinyl butyral layer 11. The edge of the intermediate layer 11 is then cut flat with the edge of the glass, which intermediate layer can extend past the plates 12. According to the known practice, a pressure reduction chamber is mounted in the form of a silicone rubber ring 1U around the entire circumference of the group 13. A ring 15 is made in the ring 1k, in which the edge areas of the group fit, so that the ring 1U seals against the main surface of the plates 12. The hollow ring chamber 16 then extends around the ring in contact with the edge of the group at the point where the junction of the plates 12 and the intermediate layer is bellows. In one target ring, the vacuum supply passage 17 extends from the hollow chamber 16 to the outside of the ring and is designed to be connected to a source of vacuum or other vacuum. The group then undergoes a pre-compression process in which the duct 17 is connected to a source of vacuum so that the hollow chamber 16 becomes emptied while the main surfaces of the glass sheets 12 are subjected to atmospheric pressure for 10 minutes to ensure deaeration. The whole group is then heated to 90-110 ° C during vacuum operation. This process provides, air is removed from the interlayer and causes the glass sheets 12 to retract into intimate surface contact with the interlayer 11. The group is then allowed to cool and, while the ring 1U is still in place, the group is placed in a basket 18, as shown in Figure 3. This basket comprises a base body 19 and two vertical arms 20 at one end of the basket. Two rows of uprights 21 and 22 are attached to the base frame 19. Ten groups of laminates can be mounted, each vertically, side by side in one basket, with one end of each group being placed between the two supports 21 and the other end between the two supports 22. A V-shaped mounting piece 23 is attached to the bottom of the basket 18 between the two vertical bars 21 and between the two vertical bars 22. One piece is shown in more detail in Figure U. The piece comprises a rectangular metal shell 2kt from the bottom

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57248 projects the pivot pin 25 downwards. The pin 25 fits into a corresponding hole in the base body 19 and allows the orientation of the piece 23 to be adjusted. A V-shaped piece 26 made of silicone rubber is tightly fitted to the shell 2k and the V-channel at the top of the rubber piece is designed to connect the conical outer surfaces of the ring 1U when the laminate sheet array is vertical. In this way, all the groups of laminates are stacked vertically in the basket 18. At the upper end of the two arms 20 is mounted a horizontal protective tube 28, the other end of which is closed and provided with a self-closing nozzle 29 which can later be connected to a controlled pressure source. The manifold 28 has ten self-closing supply nozzles 30, so that each nozzle 30 can be connected by a pipeline to a vacuum supply channel 17 on each rubber ring 1U. A pressure sensing line 31 leads from the manifold pipe 28. Before the groups are placed in the basket, a vacuum pump is connected to the inlet side 29 of the manifold pipe 28 and the vacuum system is checked for leaks. Laminate groups 13 which have undergone a pre-compression process are also inspected for vacuum leaks and then each group 13 is stacked in a basket and the vacuum channel 17 of each ring is connected to a corresponding nozzle 30 in the manifold 28. The filled basket is inspected for vacuum leaks and two similar baskets 18 are then autoclaved. 1 through the door (not shown). The autoclave 32 is a normally closed pressure vessel with steam inlet and outlet pipes 33 and 3¾ for supplying steam to the heating coils inside the autoclave. The compressed air inlet branch 35 leads to the autoclave to pressurize the surrounding space in the autoclave. A second pressure supply line 36, which can be connected to a vacuum pump, also leads to the autoclave and is connected to the inlet side 29 of each body. i ..; „.F '·: · e 57248 pressure into the interior of the tire 16 and isolating it from the ambient pressure in the autoclave. The pressure sensing line 37 extends from the autoclave together with the manifold pressure sensing line 31 and the manifold pressure supply line 36 to the pressure regulator 36 *

By means of the pressure control device 36, the ambient pressure in the rings 14 can be adjusted so as to provide a pressure difference between the pressure of the autoclave and the pressure of the hollow interior 16 of each ring 14. The pressure control device 36 includes a compressed air line 39 »leading from the autoclave inlet 33 * The line 39 extends through the valve 40 to the condensate trap 30. The air from the trap 30 passes to an adjustable differential pressure control valve 35» designed to control the pressure difference in each body 18 and manifold 28 between the ambient pressure in the autoclave. Valve 33 has an inlet 34 to which a pressure sensing line 37 leading to the autoclave is connected. * Line 37 is connected to a first pressure gauge 38 which shows the pressure used inside the autoclave. Valve 33 also has an outlet side 33 connected through a second condensate trap 56 and valve 37 to manifold pressure supply line 36. A second pressure gauge 39 is connected to valve 33 outlet 35 and indicates the pressure supplied to each basket 18 manifold 20 via line 36. A differential pressure gauge 60 is connected between line 37 and line 31 and indicates the pressure difference between the interior of each hollow ring 14 and the ambient pressure in the autoclave.

Once the baskets 16 have been autoclaved as shown in Figure 1, the necessary connections are made between Lines 31,36 and the baskets 18. The valve 57 is closed and the vacuum line is connected to the vacuum inlet 61 leading to the line *> 6. This clears the interior of each tire 14 and inspects the system for leaks. The vacuum line connected to the inlet 61 may be provided with a flow meter indicating the flow of gas through the line 36 in the event of a ring 14 leaking. Alternatively, a leak can be detected using a Manometer or vacuum gauge in the vacuum line. When this is done, the autoclave is closed and compressed air is supplied to it through the inlet branch 35. When the pressure inside the autoclave is partially elevated, the vacuum pump is disconnected from the inlet 61 and the valve 57 is opened so that the pressure determined by the differential pressure valve 53 is now supplied through lines 55 and 36 to each manifold 28 and thus inside each ring 14. The required pressure difference is controlled by valve 53 »And a flow meter 62 connected to the differential air control valve 53 can be used to check the system for leaks. If a ring 14 leaks, air under higher autoclave pressure will be supplied through lines $ 6 and 55 to valve 53 and will discharge through flow meter 62, indicating the presence of a leaking ring. If a leak occurs, the autoclave must be opened again and the 9 57248 leaking ring 14 repaired. If no leakage is detected, the pressure in the autoclave is raised to a first value, which can be e.g. 2.0-14 * 0 kg / cm. Heating is then initiated by passing steam through the steam inlet pipes 33 to the heating coils of the autoclave and using a circulation of blown air. The temperature is raised to 120-160 ° C and maintained, for example, at 133 ° C for 43 minutes, while maintaining the required ambient pressure in the autoclave and the pressure difference. The temperature is then reduced to about 40 ° C before the internal pressure of the autoclave is removed and the pressure difference is removed. During the period of elevated pressure in the autoclave, the pressure difference determined by the valve 33 can be adjusted to, for example, 0.14-1.03 kg / cm and preferably 0.28-0, depending on the laminate group to be manufactured. 7 kg / cm. Once the array has been cooled to below 40 ° C and the pressure has been released, the autoclave door can be opened and the internal piping disconnected to remove the baskets 18. The heat and pressure treatment inside the autoclave causes the plastic intermediate layer 11 to bond to the glass sheets 12 so that the laminate groups can then be removed from the baskets 18, whereby the sub-sheets of each group are bonded together.

It has been found that by maintaining the pressure difference during bonding, a vacuum is applied to the bare edge of the polyvinyl butyral interlayer while the plastic material has softened and the edges of the glass sheets have retracted inwardly toward each other in a manner that causes the plastic material to extrude and flow outwardly. After removal of the bonded groups, the extruded part of the intermediate layer is removed by cutting with a knife, so that in the finished product no part of the plastic material protrudes past the glass sheets. Removal of the extruded part prevents the lamination from starting to dissipate due to moisture entering the laminate through the bead, or physical damage to the laminate.

It has been found that the extrusion of the plastic interlayer occurs only within the circumferential region of the group and the wedge effect occurs in the outer regions of the group. That is, the glass sheets taper inwardly toward each other by the edge alloy. It has been found that the given differential pressure achieves the same wedge effect in the laminar group when a glass sheet of a certain thickness is used.

The following describes a particular lamination process by way of example and in more detail. The two glass sheets are assembled together with a polyvinyl-butyral interlayer to form a glass laminate. The thickness of the glass sheets is either 3 mm or 2.2 mm and the thickness of the polyvinyl butyral layer is 0.76 mm. A silicone bellows ring 14, the type of which is shown in Figure 3, is mounted around the laminate structure and a vacuum is applied inside the ring for 10-13 minutes at room temperature to remove air from the interlayer. The group is then heated to 90-100 ° C in an oven and at atmospheric pressure while maintaining a vacuum in the ring. This makes the plastic layer sticky as the plastic material softens slightly, in which case a small pre-bonding takes place, as well as further air leaving the intermediate layer. This completes the first step of the pre-compression process or lamination process and the vacuum is turned off. With the ring 14 still in place, the laninate structure is placed in the autoclave basket 1Θ and the autoclave for the second stage, which provides a complete bond between the glass sheets and the intermediate layer. Various connections are made to the autoclave and ring 14 is left to rest. A pressure of 1.73-2.1 kg / cm is developed in the autoclave and here the vacuum in the ring 14 is replaced by the required, adjusted pressure difference JP relative to the pressure inside the autoclave. The internal pressure of the autoclave is then raised to 8.4 kg / cm and the temperature is raised to 140 ° C for 45 minutes while maintaining the required pressure difference. The temperature is then reduced to 40 ° C while maintaining the pressure difference, and finally the pressure is removed from the autoclave and the laminate group is removed. The results obtained in this example are as follows:

Eg No. Glass thickness (for each plate) AP Wedge effect, mm / 50 mm 1 2.2 mm 0.14 kg / cnu 0.03-0.05 2 2.2 mm 0.35 kg / cnu 0.07 -0.09 3 2.2 mm 0.44 kg / cm9 0.09-0.11 4 3 mm 0.175 kg / cm 0.10-0.15 5 3 πωι 0.35 kg / cm 0.20-0 , 25

The amount of wedge effect in the finished laminate depends on the following parameters: i) thickness of the glass sheets, ii) thickness and material of the interlayer iii) design and dimensions of the ring 14, iv) autoclave pressure and temperature, v) autoclave treatment time, vi) differential and operating pressure used.

Since the amount of wedge effect depends on the time of application of the differential pressure, in some cases it is possible to reduce the amount of wedge effect by using the differential pressure only during part of the period during which the laminate is maintained at the temperature and pressure required for final bonding. For example, in the example given, the differential pressure can be applied during the last 30 minutes of the 45 minute period during which the group is maintained at the final bonding temperature of 140 ° C, and the differential pressure is maintained during subsequent cooling of the group.

An example of the silicone rubber ring 14 shown in Figure 5 is shown prior to installation on the laminate structure. The angle A is 140 °. When a 3 mm glass plate is used, the total thickness h of the glass group is 7 mm and in this case the dimension B of the ring is also 7 mm. When using 2.2 mm glass, dimension B can be 5 * 5-6 mm and the thickness D of the group is about 5 * 4 mm. In m> ponds, the opening C is about 2-2.5 mm before mounting on the glass group. The shape of the rubber changes to open the gap when it is mounted on a group of glass. An important feature of the rings is the tapered shape inside the sidewalls prior to installation on the laminate. Once installed on the array, the sidewalls bend to an almost parallel shape and the greatest seal is at the inner and outer 57248 points where the sidewalls of the ring contact the glass sheets.

The invention is not limited to the details of the examples given. Instead of polyvinyl-butyral, an ethylene copolymer as described in British Patent Specification No. 1,166,443 can be used as the interlayer plastic material. In this case, said atmospheric pressure must be applied to the main surfaces of the glass sheets to achieve full bonding. The process is roughly similar to that used with polyvinyl butyral, with the difference that the second step of full bonding does not need to be performed in an autoclave. Atmospheric pressure is applied to the array during the second stage, and a vacuum is maintained at the bare circumference of the interlayer, which is adjusted lower than the atmospheric pressure applied to the glass sheets. An example using an ethylene copolymer is described in more detail below. First, two glass sheets and an ethylene copolymer lamination sheet between them are assembled. To perform the first step of the process, a rubber ring is installed around the edges of the group as described above and a vacuum (less than 20 Torr) is connected inside the ring while maintaining the group at room temperature and pressure. The group is then heated in an oven at 120 ° C and atmospheric pressure for 10 minutes. During this time, a vacuum is maintained in the ring. During this step, the material of the intermediate layer begins to soften and become sticky, so that pre-deposition takes place, and since a vacuum is used in the ring, more air becomes removed from the intermediate layer. At the end of this first stage, the group does not need to be cooled to remove the ring, but can be heated to the higher total bonding temperature required in the second stage of the lamination process. The group is heated in an oven at 140 ° C atmospheric pressure for 16 minutes, during which time a partial vacuum is applied to the ring so that the pressure at the bare circumference of the interlayer remains below the atmospheric pressure applied to the major surfaces of the glass sheets. This pressure difference can be 0.4-1.05 kg / cm 'and preferably 0.20-0.7 kg / cm'. The pressure difference can be used during the whole heating in the second stage or only during the initial stage of the heating process or at some point after the start of the heating, e.g. during the last eight minutes of the 16 minutes of said heating period. The group is then allowed to cool to 40 ° C or even room temperature and a partial vacuum, if used at the end of the heating step, is preferably maintained in the ring throughout the cooling step. The ring is then removed and the group is heated again to 100 ° C and then cooled in water at 50 ° C. This cooling avoids the formation of mist in the interlayer.

As stated above, the differential pressure can only be applied at the beginning of the heating process, e.g. during the first 6 ml of the 16 minutes during which the group is maintained at 140 ° C in the previous example. After the first 8 minutes of operation of the differential pressure, the group is in this case cooled to 40 ° C or room temperature to remove the ring from the group. During this cooling, a differential pressure of preferably 57 578 is maintained. Once the ring is removed from the array, it is reheated to 140 ° C during the remaining Θ minutes of the heating cycle. The group is then cooled to 100 ° C to finally cool in 50 ° C water.

In all of the above examples, a controlled pressure difference is used between the bare circumference of the intermediate layer and the major surfaces of the plates during the entire critical part of the bonding. This is the period in which the group is at its hottest temperature at its temperature for complete bonding, so that the effect of the pressure difference is achieved when the plastic material is in its softest state.

When using the autoclave 52 described with reference to Figure 1, it is possible to mount the laminar arrays on the baskets 18 and place the baskets in the autoclave before performing the pre-compression cycle. In this case, the plate groups are assembled in the usual way, the rings 14 are placed around each group and these are placed in baskets 18. Once the baskets are in a closed autoclave, a vacuum is applied to the rings 14 at room temperature and pressure for 10 minutes. The pressure in the chamber is then raised to 2.1 kg / cm and heating is started. The vacuum connected to the rings 14 is replaced by the required differential pressure when the chamber temperature is about 90 ° C. The chamber pressure is then raised to a maximum value, e.g. 8.4 kg / cm, as described above, and the rest of the cycle is performed as described above.

It has been found that by maintaining a relative vacuum at the edge of the laminate array where the junction of the glass sheets and the interlayer is exposed, when heat is used to achieve complete bonding, better lamination occurs between the glass sheets and the interlayer. The examples described above result in improved lamination, especially for curved windshields, where the extrusion effect of the plastic interlayer has eliminated a few problems that would otherwise result from poor compatibility between the two glass sheets, especially in the edge areas of the sheets. In this way, a higher yield of good laminated windscreens or windows is obtained.

Claims (7)

13 57248 A method of forming a laminated glass article comprising two sheets of glass and an interlayer of thermoplastic transparent plastic material therebetween, the method comprising assembling two sheets of glass together with an interlayer of thermoplastic transparent plastic material, heating the group to an elevated temperature and maintaining the group at a temperature when a pressure is applied to the main surfaces of the glass sheets such that the glass sheets and the plastic intermediate layer are completely bonded together, applying a pressure lower than the pressure applied to the main surfaces of the glass sheets and after cooling of the array, characterized in that the intermediate layer is subjected to a lower pressure depending on the pressure applied to the main surfaces of the glass panes so that it remains below the required amount of pressure applied to the surfaces of the plates for at least part of the period during which the group is maintained at said elevated temperature. A method according to claim 1, characterized in that the pressure applied to the main surfaces of the plates is increased above atmospheric pressure and the pressure at the periphery of the interlayer is also an elevated pressure which is varied depending on the pressure applied to the main surfaces of the glass sheets. at least a portion of the time the group is maintained at elevated temperature. A method according to claim 1 or 2, characterized in that a vacuum is applied to the edges of the group by enclosing a hollow, flexible ring projecting around the periphery of the group so as to communicate with the hollow interior of the ring and connecting the interior of the ring to a controlled pressure source. . A method according to claim 1, characterized in that the pressure applied to the main surfaces of the glass sheets is increased slightly before the pressure in the chamber is raised to an atmospheric pressure or higher. Method according to Claim 2, characterized in that the pressure difference is kept between 0.1 U and 1.05 kg / cm, in particular between 0.28 and 0.7 kg / cm. A method according to claim 1, characterized in that an atmospheric pressure is applied to the main surfaces of the glass sheets and a controlled pressure lower than the atmospheric pressure is maintained at the circumference of the intermediate layer during heating to achieve full bonding. ”* 57248 Device for carrying out the method according to claim 1, characterized in that it has a closed pressure vessel (32) in which one or more groups of glass sheets with an intermediate layer of thermoplastic, transparent plastic material are placed, support means (18) placed in the vessel to support one or more groups, and the vessel has means (37-35) for increasing pressure in the vessel and applying heat to the group or each group in the vessel to bond the glass sheets and interlayer together, a gas supply passage (36) leading to the vessel to connect it to the group or each group to provide increased pressure to the group or around the peripheral edge of each group, which pressure is lower than the elevated pressure in the rest of the vessel, and means (60) for maintaining a controlled pressure difference between the pressures in the gas supply passage and the vessel. 57248 15