BE550294A - - Google Patents

Description

       

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   The present invention relates to the preliminary pressing of multilayer assemblies or laminated assemblies of glass comprising two sheets of glass, each of which is planar or curved, and of a thermoplastic interlayer. It is especially useful for the simultaneous preliminary pressing of a group of flat or curved laminated glass assemblies of small dimensions and finds special application in the preliminary pressing of large curved laminated assemblies of glass, for example. those which survive, are to be used in the windshields of automobiles.



   For laminating glass assemblies, it is common practice to seal, or bond, the thermoplastic interlayer to the two sheets of glass by applying heat and pressure for example in an autoclave using a fluid, such as oil, at high temperature and subjected to high pressure. To perform this pressing or sealing of the interlayer to the two sheets of glass, it is first necessary to press beforehand, or to seal beforehand, a marginal zone of the assembly before placing it in the fluid contained in the autoclave. ; otherwise, the fluid enters the laminate assembly and becomes trapped there during lamination, which spoils the appearance of the laminate assembly.

   In addition, the prior pressing operation is necessary to remove as far as possible the air between the interlayer and the two sheets of glass; otherwise, the air would be trapped in the final product in the form of bubbles and this would also adversely affect the

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 the appearance of the whole laminated.



   In order to pre-press at least a marginal area of the laminated glass assembly in order to prepare it for the final pressing in the autoclave, methods have heretofore been proposed to exclude air from the interlayer of plastic material. and leaves. the glass and for pre-pressing, or pre-bonding, at least one marginal zone of the laminated glass assembly. To produce this pre-pressing of a flat laminated assembly, the latter was heated and passed between two elastic nip rollers, the product obtained then being subjected to the treatment in the autoclave.

   For a flat laminated assembly, when the latter comprises more than two sheets of glass and more than one sheet of the thermoplastic interlayer, or else for a laminated assembly which was bent or bent, it was found that it was necessary to place this laminated set in an oil resistant bag. The bag was then sealed and the air expelled. The bag thus emptied of air and its contents which were sealed therein was immersed in oil contained in the autoclave for the final pressing. Can the manufacture of a large number of small laminated assemblies, the process of placing in the bag, sealing, expelling air and processing in the autoclave, was labor intensive.



   When large curved laminated glass assemblies, such as windshields, were pre-pressed in the marginal area by heating and passing between two resilient pinch rollers, difficulties were encountered necessitating the adoption of protective devices. complex pre-pressing. For the wraparound or panoramic windshield in which the portion

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 ,., her. :; = t - ..,: to the central sec'cion. riaô IJ "c5.,": '1.:--:,YO!1 of curvature, with or without a court # bvrc-.: ,,'. U, li ;;, 'c \' '(: h 3-5ii.;> Progressive in section; :(: ", -.



  '1;'; [-:;, 1,., Dac <.,) /:, -, ¯ ,,) J.3 even more complete; G1s, utili5 <:; fr cl; .- :: " = t? ¯: ¯..¯¯-¯3: vi; à = a ... jji:! 3 "d't: were necessary-- ::::. 3 turn the p; Kg- 0é, t6 : prior "t: 3 worst-breeze so 6dryī" ¯.w: .. ': ... the need 4u, 3 ..; ¯, c!: -,' -. # fr.iiuei (the these windbreaks :, iu.i 'both r01 "ÜI;: f? L1 ...: f. de, JJ..r: ç";' or.5);) 'i; ,, A complexity eucor-3 plus gan- appeared qL2: i.rd we modified the pave-screens The sections e.tr8os were "4X.éâ '' 'u'o-r'9 to a twist around the longitudinal axis during the curvature of the planar structure with a view to producing a park-breeze having a cylindrical centric part and end sections ,:

       A new difficulty for the proper pressing of at least a marginal area of breakage arose when producing windshields of the composite curvature type. These windshields,,% no transverse curvature as well as a curvature. longitudinal in had minus the central section with or without torsion. extreme sections around the longitudinal axis A number of modifications to the pressure apparatus
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 preliminary age resulted in a pr c> 5 =:

  ..ja satisfactory preliminary of some of the last models of parebrisc 9: ¯: .10rlî:;: iCl):. :: S and. composites, Niais eus 2: - [tl) .ie;: J. born-.



  4.â.nn .. <.: -: T> 1't .. "yt; .J (lj-ii ('; -:"; t 011S or some -; 11 Í, - -' "Jf: : i1.t when '1J; 5 :: i. v! .Ji. pre-pressing éwC.:'.. f, .. ¯ 3: 'r. a!.; ï c's for 1: - fX1: - - i? l.: # :.> '#:) r2éJ ..,' ;; 1ble dtUl1 type t '= z 1 "' :-( '';) 1." 188 to \ ci ç .-: 3¯ - # '".> ## -" - ¯¯¯¯¯m .... ¯ This requires) b 1 (. "'! T .a ':. If4'C r:'. '.: l ,:; .., #: -. \ ¯-jih-: l ';, f;': 'L:': .. 23l:, ion d2J.ll 1J: l () d81; .'- .. .- :. 5 or cl; a, '.i!' -. -3- cc-nn-é de. .J ::. 3.S.1.11S de tJ c5 "tJ, ',. i' l :.'. at.

   H> .-,!. Lttia..È û 7.i = 1 ¯- = ii-i:; '-: * ##;!. #. ± / ##; .-èi. '. <i5;!, -. da curvature during us! ¯0PS us ces '' -. - ..,> I 0 ::. - :::.;. s: L'5.ü ci, ;;;; reduce to a minimum 1 "t JI) ';. JE; poi-da 9;: - ::.; J' ;.".:. {; 2, t (Jn necessary of the% lù "L.1 :. for the ctSl

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 gement for the pre-pressing of a significantly different model of curved windshield.



   Before making the modifications of the pre-pressing machine using two rollers, so that the pre-pressing apparatus could satisfactorily pre-press such curved windshields, it was necessary to subject them to the process. The pre-pressing process described above in which the assembly was placed in an oil-resistant bag, after which the air was expelled after sealing and subjected to the autoclave. The yield in satisfactorily pressed curved windshields with such an operation was not high enough for economical work.

   On account of the pronounced curvatures of the windshields at the junction point of the end sections and the central section, and on account of the torsion of the end sections around the longitudinal axis, the assemblies which were so supported - Re defective on their concave face during expulsion of air from the bags, there was a considerable degree of rupture of these curved windshields. This rupture included a fracture or cracking of the glass. This resulted in an expensive operation because such deterioration of the curved windshields could not be detected until the curved windshield contained in the bag had been subjected to the complete cycle of operations including the pressing in the bag. autoclave.



   Such an apparatus, which has been implemented for the preliminary pressing of curved windshields, uses an upper frame and a lower frame having a fixed structure determined by the windshields to be previously pressed, which necessitates the expensive construction of a number of frames for the pre-pressing of

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 various models of curved windshields. The change of frames is also necessary for the change of the design of the windshield moving in the production line.



   Relatively small assemblies of laminated glass are produced in quantities and many of these assemblies are produced for the manufacture of safety glasses. Some of these safety glasses have a spheroidal type curvature. Such small-sized curved laminated glass assemblies cannot be pre-pressed in a satisfactory manner in the apparatus comprising the two resilient pinch rollers.



   The present invention relates to a method and apparatus for pre-pressing at least a marginal area of a laminated assembly of glass such that it can be satisfactorily pressed by direct immersion in an autoclave full of glass. fluid, for example oil, and subjected to heat and pressure; - a method and an apparatus requiring only a slight inexpensive change during a change of windshield design in the production line4.



   According to the present invention, the method of pre-pressing at least the marginal zone of an assembly comprising two paired sheets of glass and a thermoplastic interlayer consists in supporting the assembly on a flexible sheet in a area of the sheet defined by a continuous rib on the upper surface of the sheet and spaced from the rib around the periphery of the assembly; placing a flexible covering sheet over the assembly and the rib to cover the entire area of the flexible sheet defined by the rib and maintaining a conduit

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 around the periphery of the set; expelling air from the duct through the rib while maintaining passages; air from the periphery of the assembly to the point of discharge at the rib;

   maintaining the vacuum during the heating of at least the marginal zone of the glass sheets and the interlayer, after which the vacuum can be stopped, the cover sheet as well as all the glass sheets and the interlayer having undergone the prior pressing.



   To enable those skilled in the art to understand the invention, it will now be described with reference to the appended drawing which illustrates a preferred embodiment of its implementation, and in which: FIG. 1 is a view from front in elevation of the preferred embodiment of the apparatus object of the present invention, apparatus especially suitable for the preliminary pressing of curved laminated assemblies; - Figure 2 is a top plan view, partially cut away, of the apparatus of Figure 1; - Figure 3 is an end elevational view of the apparatus of Figure 1; - Figure 4 is a partial cross section at most. large scale of the preliminary pressing apparatus in which is placed a laminated assembly of glass, the cut being made by 4-4 of Fig. 2;

   - Figure 5 is a partial cross section taken substantially at 5-5 of Figure 4, showing in more detail the nature of the various flexible sheets, part of the view showing the spacing. holes in the peripheral piping; - Figure 6 is a cross section on a larger scale of a variant of the pipework.

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 ripheric mounted on a flexible sheet having a flat face for easy sealing of the upper surface of one of the flexible sheets of the apparatus;

   Figure 7 is a partial cross section of one embodiment constituting a variant of the present invention, this view being a cross section similar to that of Figure 5, but showing the use of a different sheet material for providing air passages from the peripheral piping to the periphery of the laminate assembly; - Figure 8 is a schematic view of a variant of the apparatus of Figure 1, in which the two upper sheets are integral, one end of the sheet thus formed being fixed so that it can only perform a movement limited and the other end connected to a device for mechanically lifting the sheet to allow easy insertion and removal of the laminate assembly;

   - Figure 9 is a partial plan view from above of the apparatus according to the invention with partial cutaway! to show an embodiment, constituting a variation of the peripheral flexible band heater using two devices. ae electrically banded heater in parallel so.à constitute two sections of the peripheral phanth heating element.



   In practicing the present invention, a laminated glass assembly comprising two sheets of glass and a thermoplastic interlayer is supported by a flexible sheet in the area of the sheet which is defined by a continuous rib.

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 on its upper surface. The assembly is placed so that it is spaced from the rib. A flexible cover sheet having dimensions large enough to completely cover even during exhaustion of the air, the entire area occupied by the rib is placed on the laminate assembly. The two flexible sheets cooperate with the rib to form a conduit between the latter and the periphery of the laminated assembly.

   In the method which is the subject of the invention, the air is evacuated from this duct via the rib while maintaining at least part of the duct in order to evacuate the air from the space between the plastic interlayer and the elements. glass sheets. The assembly is then heated at least in the marginal zone while maintaining the vacuum between the two flexible sheets. After heating the assembly sufficiently to seal at least the marginal area, the vacuum is terminated and the flexible cover sheet is removed, followed by the glass laminate assembly. In this process, the assembly is sufficiently pressed beforehand so that it can be placed in the autoclave in the fluid for the final pressing under heat and pressure without penetration of the fluid between the sheets of glass and the layer. plastic interlayer.



     In the process which is the subject of the invention, very variable values of temperature and vacuum can be adopted as conditions for the pre-pressing without sacrificing a high yield of laminated assemblies which have been previously pressed in a satisfactory manner. For example, the temperature. heating can be between 93 3 and 260. and the degree of vacuum can drop to 508 mm of mercury. It is preferable that the heating temperature is between 163 and

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 236 C. It is also preferable that the vacuum be at least 635 mm of mercury.

   With this method, any of the various types of laminate assemblies described above can be satisfactorily pre-pressed, including panoramic windscreens and windscreens having appreciable transverse composite curvature with or without without torsion of the end sections around the longitudinal axis. As will be seen below, the process comprises the prior pressing of a group of laminated assemblies of small relative dimensions, whether they are curved planes. The process will be described below in greater detail with respect to the preferred embodiment in which the apparatus which is the subject of the present invention is used, and this for the purpose of illustration.



   In the drawing, which illustrates the preferred embodiment of the apparatus which is the subject of the invention, the apparatus comprises a support table generally designated by 11 and comprising two spaced vertical support pieces 12 and 13. which are kept apart by horizontal pieces 14. The support table 11 is provided with a flexible upper surface.
15 by stretching a flexible sheet 16 over the upper surfaces of the support pieces 12 and 13, surfaces which are convex in the longitudinal direction, and securing the sheet 16 to the pieces 12 and 13 by nails 17.

   The longitudinal curvature of the top edge of the support pieces 12 and 13 is approximately determined by projecting the profile of a curved laminate assembly, such as a windshield, from the approximate location where the windshield is to be placed. on sheet 16 on the support pieces. However, due to the flexibility of the upper surface, it is sufficient that the profile

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 top of the support pieces 12 and 13 is roughly approached. This apparatus has been found to be suitable for the preliminary pressing of the wide variety of windshield designs without any change in the curvature of the support table 11.



   The curved upper surface 15 formed by the sheet 16 is covered with a flexible sheet 20. The sheet 20 has on its upper surface a peripheral tubing 22 which is flat in a longitudinal part of its lower surface so as to avoid seal with the top surface of the sheet 20. Outlet tubes 23 are connected to opposite sides of the continuous peripheral tubing 22 and tubes 23 are connected to a vacuum pump (not shown). A flexible corrugated sheet resides on flexible sheet 20 in the area defined by tubing 22. The periphery of sheet 25 is adjacent to tubing 22. As seen in Figures 4 and 5, the corrugations of the sheet 25 prevail transversely to the longitudinal axis of the support table 11.

   The tubing 22 is pierced with holes 27 spaced apart along its length and going from the inside of the tubing downwards, passing through the internal wall 28 of this tubing.



  A heat-insulating flexible sheet 29 is disposed over the sheet 25 and its periphery, just as the sheet 25e is adjacent to the tubing 22. The sheet 29 is sufficiently porous to provide air passages upwardly from the tubes. hollow 30 formed by the corrugated sheet 25.



   A flexible sheet 34 of a heat resistant material, preferably a heat insulating material is disposed on the heat insulating sheet 29. The sheet 34 has approximately the outline of the assembly.

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 of curved laminated glass generally designated by 40 and comprising two curved sheets of glass 41 and 42 separated by a thermoplastic interlayer 43- An electric heater @ ormated by a flexible strip 45 is attached to the sheet 34,

  and the ze @e occupied by the heater 45 extends at least to the marginal area of the sheet assembly 40. A flexible sheet 48 having an overhead slightly greater than the area of the assembly: laminated 40 and having approximately the same contour is disposed above the flexible sheet 34. There is a flexible sheet 48. flexible sheet 50, the degree of flexibility of which is much greater than that of sheet 48.

   The sheet 50 completely covers the area defined by the tubing 22 and extends sufficiently beyond the latter before the air is removed from the apparatus that when a part of the sheet is drawn down into the air defined by the rib, a sufficient amount of the foil 50 extends at least as far as the tubing 22 to be pulled against it, in order to maintain the vacuum exercised.

   Since the edges of the sheet 50 are pulled inward a considerable distance, when vacuum is applied due to the sheet being pulled down within the area adjacent to it. the tubing 22 etc. above the sheet 25, it is preferred that the sheet 50 extend at least 76.2 or 101.6 mm beyond the tubing 22 when the apparatus is not subjected to the empty.



   The flexible band heater 45 extends around the desired perimeter to provide the proper marginal heating of the assembly 40. Con. detectors 52 and 53 of the heater 45 are re

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 linked, as seen in Fig. 2, to conductors 54 and 55 which rest on sheet 34 and extend outwardly onto sheet 20 and between tubing 22 and the latter sheet. The ends of conductors 54 and 55 are connected to an electric source (not shown). The passage between tubing 22 and foil 20 is sealed around conduits 54 and 55 to prevent air leakage through this tubing when vacuum is applied to the apparatus.



   As seen in Figure 4, the laminate assembly 40 is placed between the sheet 48 and the band heater 45, the latter coinciding with or abutting the marginal area of the laminate assembly 40. -this.



   We see in Figure 6 an alternative form of the tube 22 which can be used in place of the tube 22 shown in Figure 6. It is seen that the tube 22 of Figure 6 has a substantially triangular cross section and that it is also pierced with holes 27 directed downwards in the interior wall 28. As for the pipe 22 of FIG. 4, that of FIG. 6 has a structure such that it does not does not collapse when you empty it.



   FIG. 7 shows an alternative construction of part of the apparatus which is the subject of the invention.



  The only difference to the construction shown in Fig. 5 is the application of a cotton lined rubber liner 56 with the cotton liner 57 facing upward so as to provide air passages from the legs. holes 27 to the periphery of the laminate assembly 40.



   In figure 8, there is schematically represented in its general outline the apparatus of figure 1,

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 with the exception that a flexible sheet 60 replaces the sheets 48 and 50 and is the equivalent of the arrangement in which the sheets 48 and 50 are integral by gluing their facing faces. We can, of course; obtain it by making a sheet material having a greater thickness in the central area. One of the ends of the sheet 60 is fixed or roll 61 mounted, so as to be able to turn on a support fixed (not shown).

   The other end of the sheet 60 is attached to a large jaw extensible clamp 62 connected by a spring 63 rotatably mounted on the piston rod 64 which is raised and lowered by a hydraulic cylinder 65 mounted on a fixed support 66.



   In the foregoing description of the band heater 45, it has been indicated that it is constituted by a single band. It has been found to be particularly advantageous to achieve the perimeter heating using two band devices 45a and 45b, each of which occupies a section of the periphery. These band heaters are connected in parallel as seen in Figure 9. The extre conductors. mes 67 and 68 of the heating devices 45a and 45b are connected in parallel to conductors 69 and 70 connected to a source of electricity (not shown).



   OPERATION
Although the invention is not limited to particular materials and particular thicknesses and other dimensions except to the extent that they affect the desired properties of particular components of the apparatus, it will be appreciated. give details below for illustration purposes only.



   Support parts 12 and 13 and parts

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 horizontal 14 are made of wood. Support pieces 12 and 13 are spaced approximately 889mm apart. On parts 12-and 13 is stretched and nailed a 1.58 mm section of a rubberized canvas 915 mm wide. The double braided continuous or peripheral tubing has a round cross section with an inside diameter of 12.7 mm. Holes 27, each 3.2 mm in diameter, are drilled at 50.8 mm intervals in the tubing 22.



  The bottom of the latter is cut flat and the flat surface is sealed with rubber dissolution to the sheet 20. Tubing 22 is made continuous by sliding its two ends on two arms of a copper tee. (not shown) forming part of the outlet ducts with an internal diameter of 12.7 mm. In other words, two sections of tubing 22 are used so that their ends are connected to the copper tee forming part of the outlet ducts 23. The tubing 22 is sealed to the sheet 20 in such a way that when the The assembly 40 is placed on sheet 34 within the area defined by tubing 22, the periphery of the curved laminated glass assembly being spaced from tubing 22 by approximately 100mm at the ends. - moths of the whole and about 50 mm on the sides of the latter.

   Sheet 25 is a corrugated rubber sheet having a thickness of 3.2 mm and having about eight corrugations every 25 mm.



   Sheet 29 is a sheet of asbestos cloth with a thickness of 1.6 mm. Sheets 25 and 29 are of such size and shape that their peripheries fit tightly over tubing 22 to prevent sheet 59 from coming in between them and shutting off the supply of air from holes 27 to. at the periphery of the laminated assembly 40. A

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 Cotton-lined rubber sheet 56 shown in Fig. 7, constituting an alternative to flexible corrugated sheet 25, has a thickness of 32mm and is flexible.



   The sheet 34, to which the heater 45 is sewn, is a 1.6 mm asbestos cloth. The flexible band heater 45 used is a normal flexible band heater 25.4 mm wide flexible in all directions. It consists of a glass fiber fabric inside which is sewn a copper wire insulated by the glass fiber which follows a zigzag path along the strip in the longitudinal direction.



   Sheet 48 is 3.2mm thick rubber. Its size is chosen such that it extends from 25.4 mm to 50.8 mm beyond the edge of the windshield laminate assembly to provide marginal toe-in. Although flexible, the rubber sheet is stiff enough to produce this nip. The flexible sheet 50 is a 0.8 mm 787 x 2032 mm rubber sheet and thus extends several times 25 mm beyond the tubing 22 when the apparatus is assembled and immediately before the start of the operation. 'evacuation.



   The apparatus is assembled as shown in Figure 4, except that sheets 48 and 50 are not in place. A laminated glass assembly 40 is disposed as shown, such that the marginal area of this assembly is above the band heater 45. The sheet 48 is then applied to the assembly 40 so that it extends from 25 to 50 mm beyond the assembly 40 at all points around the periphery of said assembly. Then we have

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 the sheet 50 over the entire assembly thus formed, so that the marginal air of the sheet 50 extends several times 25 mm beyond the entire periphery of the tubing 22.



   A vacuum pump connected to the outlet tube 23 is started in order to evacuate the air between the sheets 50 and 20 in the zone delimited by the tube 22.



  As will be seen below, the time during which the vacuum is created can be varied. The best duration depends on the number of conditions which are also mentioned; below. With the evacuation of the air from the chamber delimited by the pipe 22 and the sheets 50 and 20, the pressure difference between this chamber and the atmosphere above the sheet 50 forces the latter, which was 'applied loosely to the area occupied by the continuous tubularity, to move downward and come into contact with the sheet 29.

   Sheet 50 also pulls sheet 48 downward to produce marginal nip by sheet 48 on the top edge of laminate assembly 40. As soon as the desired degree of vacuum has been reached, the vacuum is passed through. electric current in the flexible heater 45 to heat the marginal area of the laminate assembly 40 to the desired temperature mentioned above. After heating the marginal zone for the desired time, the heating is stopped and the vacuum is turned off. The sheets 50 and 48 are removed and then the laminated assembly 40 from the apparatus.



   The assembly 40 is examined to see whether or not any part of the margin requires a treatment known as edge rolling. This type of edge lamination involves inserting a thin roll between the two glass sheets at the edge at the point where the

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 marginal part is not completely cleared as a result of incomplete union. By inserting this thin roll into the space between the two sheets of glass and moving the roll back and forth, the thermoplastic material is forced inward and against the hot glass surfaces to produce l 'union. Rolling the edge ensures that the entire marginal portion has sufficient union so that oil cannot penetrate during subsequent autoclaving.

   Edge rolling has heretofore been used to correct preliminary pressing defects using two resilient nip rollers.



   In testing the method and apparatus according to the present invention, the effect of the air removal time and the heating time after the execution of the heating was investigated. evacuation, as well as the effect of the temperature of the laminated assembly placed in the apparatus, on the quality of this assembly obtained by use of the pre-pressing apparatus followed by the normal treatment at the autoclave. The evaluation or appreciation of the laminated assemblies from the process and the apparatus which is the subject of the invention in combination with the subsequent treatment in the autoclave included the standard test of two hours at boiling which is a test. described in "American Standards Association Code for Safety Glazing Materials" Z26.1. - 1950, Test n 4.



   Tests were also made using widely varying temperatures between the peripheral heater 45 and the exterior surface of the glass assembly 40, at its marginal portion at the end of the heating cycle. It was determined by these tests that

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 best results are obtained when the temperature at the end of the cycle is at least about 215 ° C.



   In using the apparatus as described above, it has been found that it is possible to pre-press satisfactorily a considerable number of different types of windshields. For example, satisfactory results have been obtained using the apparatus with the dimensions described above for the pre-pressing of laminated assemblies for the protection of panoramic windscreens from two different manufacturers of motor vehicles. . There is a considerable difference in the dimensions and in the degrees of curvature of these windshields. In one of the types of windshields in question, the end sections were curved around the longitudinal axis.

   The other just had a much smaller radius of curvature at the end sections near the center section.



  With the same apparatus it was even possible to carry out the satisfactory pre-pressing of panoramic windscreens which also had a transverse curvature in their central section. Thus, the great flexibility of the apparatus and the method object of the present invention is evident.



   This pre-pressing followed by the usual autoclave operation has given satisfactory results for windshields of various types when using the peripheral tubes 22 shown in Figures 4 and 6 and either sheet 25 , either the leaf
56.



   By using the apparatus shown in Figures 1 to 4, a large number of curved windshields can be pre-pressed. Some

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 of these windshields were of the usual panoramic type.



  Others included those with end sections curved around the longitudinal axis. To switch from the pre-pressing of one windshield design to another, even with appreciable differences in curvature, it was sufficient to change the peripheral heating device 45 by removing it, together with the sheet 34 on which it is sewn. , after disconnecting the conductors 52 and 53 from the conductors 54 and 55. The foil can be quickly replaced by another flexible foil 34 to which is sewn a flexible peripheral heater 45 having the appropriate arrangement to provide heating on the marginal region of the new windshield design which has to be pressed beforehand.

   The conductors 52 and 53 are connected to the conductors 54 and 55 and the apparatus is then ready for the pre-pressing of the model substantially different from that which was previously pre-pressed. The device can be operated by one man
In the evacuation phase, the vacuum is maintained for approximately one minute before activating the peripheral heating device 45. The heating is then carried out for approximately 3 to 4 minutes, the actual time depending on the model of the barrier. -broken. A total cycle of 4 to 5 minutes has been recognized as giving optimum use of the device.



   It has been found that the windshields which have undergone the prior pressing in the manner described above have, after their removal from the apparatus, a central part not heated and incompletely united, but in which a vacuum has been made, surrounded by a clear part completely united around the edge. Windshields that have undergone the prior pressing required only one

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 low degree of edge lamination, around 75 mm per windshield, due to occasional marginal points which do not seal neatly.

   Unclear marginal spots were not observed which, after edge rolling, were insufficiently sealed in the central area to the point of allowing fluid to penetrate the laminate and result in an unsatisfactory assembly when an assembly The pre-pressing wandering was subjected to the treatment at elevated temperature and pressure, for example by autoclaving.



   The autoclave operation consists in immersing the assembly having undergone the prior pressing directly in the fluid, for example oil at a high temperature, such as 288 C., in subjecting the oil to a high pressure such as that from 7 to 17.5 kg / cm2, preferably about 14 kg / cm2; heating the fluid under this pressure and at this temperature, for example between 38 and 163 ° C. for a few minutes, for example 30 minutes. The fluid is cooled, for example to 288 ° C. and the pressure is released. The assembly is removed and the fluid is removed from its surfaces.



   EXAMPLE I
In the apparatus according to the invention, in accordance with the method of the invention, more than one hundred of the panoramic windshields of the various types were treated. After pre-pressing and rolling the edge when necessary, they were subjected to final pressing in the autoclave under standard conditions, namely: 30 minutes at 135 C and 14 kg / cm2. Sheet 25 was used in the apparatus instead of sheet 56 in some of the tests.

   Seventy windshields of those treated were a model of each of

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 two different automobile manufacturers, namely windshields for the 1955 Plymouths and the 1955 F @ rd Thunderbirc None of the windshields from the final autoclave operation were to be discarded as containing air bubbles or fluid that has entered the puff pastry
EXAMPLE II
Vacuum was pre-evacuated for periods ranging from 0 to 5 minutes followed by 3 minutes of heating while maintaining vacuum conditions in 28 panoramic windshields and then subjected to standard final pressing in an autoclave. . The apparatus included a rubber sheet 56 lined with cotton.

   The windshields were then subjected to the two hour ASA boiling test, mentioned above.



  This heat stability test determines the efficiency of the removal of air from between the sheets in the exhaust phase. The results are shown in the table below. In these tests, the vacuum used during the vacuum generation phase was approximately 635 mm Hg. The temperature between the peripheral heater 45 and the outer surface of the adjacent glass sheet was at the end of the cycle on average about 2040 ° C.
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 <Desc / Clms Page number 22>

 not the vacuum beforehand. The results can be compared with the same test on eight windscreens of the same model which had been previously pressed by means of a machine using two elastic pinch rollers mounted so as to be able to rotate in a housing. ter, then having undergone the rolling of the edge and finally the standardized treatment in the autoclave. In the two-hour boiling test of these windshields, six exhibited bubbles.

   The average number of bubbles in these six windshields was six on the driver's side of the vehicle, zero in the mid-section, and three in the passenger's side end. Thus, by pre-emptying the apparatus of the present invention for one minute, products are obtained which are as good or better than those for which the type of pinch roller apparatus is used for the pre-pressing.



   When curved windshields are passed consecutively through the apparatus, the heating time drops from a value of three to four times to a value of two to two and a half minutes as a result of the heat retained in the apparatus. the prior pressing apparatus and which comes from the previous operation.



  Of course, the heater 45 is cut before removing the vacuum. If it were otherwise, the next assembly which would be placed at the top of the band heater 45 would undergo partial marginal band sealing at least before the vacuum was started. For best results, it is preferred that the glass laminate assembly 40 does not have a temperature above about 21 when placed in the apparatus.

 <Desc / Clms Page number 23>

 
 EMI23.1
 heat.nt L5 to b- ndo 8 (; "- ¯4i.;: .. i- \: co -.- x'.J, - * -.- # *, - ¯ .-": '. IU - '. ((2- the desired zone yt tr1j..4.sr; i, lG a court? -; rc #. #: ".:" 3 under 120 volts.

   Cvi found eus, 1o:. '::>:' "'2 ,. i-cc was chs .; ¯¯" ï.LT. by two devices at bc .....:; ' "L¯, a -:,: lî5b) each of them occupying a half of 1-1 bÓ: 'I sensitive: nen: continuous and being connected in parallel with lines under a voltage of 2oü volts, it was possible to heat more x'i ccmx.; ni, the marginal zone do J i nB0.:. ' ble. As a result, 3. 'one obtains a pressa8:;' t ...! ¯; 'tJ C satisfactory with v.'3 heating duration t :. ". ; 2 ', minutes and a half only, preceded by empty tin made for only one minute for a total cycle time of about two and a half minutes. Of course, the change in the diameter of the wire in the heater 45 results a change in voltage may shorten the heating time.



   In another variation of the heater, an electric blanket heater, which is flexible in all directions, has been found to be satisfactory. It seals the marginal area sufficiently to prevent the ingress of fluid, and the central area is completely sealed by the operation in the autoclave. Other variations have been tried with success, for example two strip heaters attached side by side so as to widen the area of the continuous strip to be heated, making the location of a laminated glass assembly less critical. relative to the flexible heater 45.



   EXAMPLE III
Using a hatch heater
 EMI23.2
 ture instead of. band heater 45 on e y2 ..:,? Has three curved laminated lenses for glasses-

 <Desc / Clms Page number 24>

   They were protected in the electric woven blanket and covered with sheets 48 and 50 as previously described for the curved sets.



  The goggle glass samples had a pronounced wrap-around curvature at each end and were made of 1.58mm glass and 0.381mm thick "vinal". They had a cord of 152 mm 4, a width of 82.5 mm and a length of 190.5 mm on the glass surface. They were supported on sheet 16, in a position such that their convexity was oriented downwards, on a rib support made of laminated asbestos cloth. The evacuation time was 2 minutes. The total cycle time was 10 minutes. Several lots of three curved laminated protective eyewear lenses were treated in this way. Satisfactory pre-pressing has been obtained with this multiple treatment of small laminated assemblies.

   Of course, with a better heating system, we could have
 EMI24.1
 shorten considerrab-1-th -., - L, duration.



   In the lamination of small flat laminated assemblies, a number of them may be laminated together, or pre-pressed together, using the apparatus and method described above, but in such a case As in the laminating of a large assembly of planar laminated glass, the resilient sheet 16 is preferably planar.



   In the preceding description of the pre-pressing in accordance with the present invention, it was noted that the sheet 48 is pulled downwards while the vacuum is being made and that it ensures the clamping of the upper edge of the assembly 40. to produce a better seal of the marginal area of this assembly. We have

 <Desc / Clms Page number 25>

 also indicated that the sheet 50 is pulled down against the sheet 46 where they occupy a common area, and beyond this area it is pulled down against the sheet 29. The sheets 25 or 56 ensure the passage of air from the holes 27 towards the edge of the laminate assembly 40 by cooperation with the passages of the sheet 29.

   It follows that the leaves
25 and 29 cooperate to provide air passages from holes 27 and the periphery of the laminate assembly 40 during the evacuation phase. The holes 27 are preferably directed downward in order to ensure that the sheet 50, when pulled down tightly against the tubing 22, is not pulled far enough downward. point to plug the holes in question and thus prevent evacuation of the laminate assembly 40. The undersurface of the foil 50 and the surface of the tubing 22 are preferably smooth, which provides a tensile strength. leaf
50 downwardly bringing it in an airtight manner against the tubing 22 during evacuation.



   In the preceding examples, the sheet 34 and the heater 45 sewn to its upper surface were located under the laminated glass assembly.
40 as seen in Figure 4. Tests were carried out with the flexible sheet 34 inverted so that the heater 45 was on its lower surface. The laminated glass assembly 40 was placed directly on the sheet 29. The sheet 34 was placed on the assembly 40 with the heater 45 in contact therewith. Leaves 48 and
50 were applied from above in the usual order.



   The apparatus, etc., is then evacuated, as described above. We got windshields

 <Desc / Clms Page number 26>

 satisfactory laminated glass curves with this modified procedure.



   In the foregoing description, the support table 11 had a convex upper surface 15 and the assemblies 40 were subjected to pre-pressing with the ends facing downwards. The surface 15 may be concave and the curved windshield may be placed in the apparatus with its ends facing upward.



   Various modifications of the support table 11 can provide improved support by the flexible sheet 16 of a composite curved windshield. For example, the entire support table can be made to form a chamber with a flexible sheet 16 constituting the roof. Air can be pumped into the chamber after placing the assembly on sheet 34.



   The increased pressure pushes the sheet 16 back into contact with a larger surface of the windshield.



   Of course, the chamber and the sheet 16 constituting its roof can occupy only an upper part of the support table 11.



   Although the foregoing description gives a description of the invention relating to the preferred embodiment, various other modifications may be suggested by those skilled in the art. For example, the apparatus for bringing a laminated assembly and holding it in place with subsequent mechanical movement of the sheets 48 and 50, integral or not, in place prior to vacuum application and heating, may be used as partially shown in Figure 8 and as described above. A mechanism for an adjustment cycle over time is clearly suggested by the foregoing description of the method and apparatus.

 <Desc / Clms Page number 27>

 reil object of the invention. The sheet 20 can also be omitted by mounting the tubing 22 directly on the sheet 16.



    CLAIMS 1. A method for the pre-pressing of at least the marginal zone of an assembly comprising two matched glass sheets and a thermoplastic interlayer, this process consisting in supporting the assembly on a flexible sheet inside the assembly. an area of the lights] the delimited by a continuous rib on the upper surface of this sheet and providing spacing of the periphery of the assembly from the rib; placing a flexible cover sheet over the assembly and over the rib to cover the entire area of the flexible sheet delimited by the rib and to maintain a conduit around the periphery of the assembly;

   in flanging the duct through the rib while maintaining air passages from the periphery of the assembly to the point of air discharge at the location of the rib ; maintaining the vacuum while at least the marginal zone of the glass sheets and the interlayer is heated, after which the vacuum can be stopped, the cover sheet and also the entire glass sheet can be removed and of the interlayer having undergone the prior pressing.


    

Claims (1)

2. The method of claim 1, wherein the two paired glass sheets are curved and a correspondingly curved flexible sheet is used to support the assembly. 3. A method according to either of claims 1 and 2, wherein only the marginal area of the assembly is heated. <Desc / Clms Page number 28> 4. A method according to either of the preceding claims, wherein the heating step is carried out entirely at substantially atmospheric pressure. 5. A method according to IL; either of the preceding claims, wherein the curved sheets of glass have a longitudinal curvature with a minimum radius of curvature in those of the end sections adjacent to the central section of the sheets of glass. glass. 6. The method of claim 5, wherein the end sections of the glass sheets are subjected to twist about the longitudinal axis to form an assembly having a cylindrical central section and tapered end sections. 7. A method according to either of the preceding claims, wherein the curved sheets of glass have a transverse curvature at least in their central section. 8. Apparatus for the pre-pressing of a laminated assembly comprising two matched sheets of glass and a thermoplastic interlayer, this apparatus comprising a support surface, a first flexible sheet mounted on this support surface so as to constitute. an elastic upper surface, a rib mounted on said part of the upper surface delimiting an area on this upper surface, to determine the position of the set of sheets. or laminated set, at least part of this rib comprising a longitudinal duct and a permeable side wall in the part of the rib comprising the duct allowing the evacuation of air towards this duct from the aforementioned defined zone, a heating device arranged so as to <Desc / Clms Page number 29> heating at least the marginal zone of the laminate assembly, a second flexible sheet within the area delimited by the rib and extending entirely to and beyond the defined area by said marginal heating zone, and a third flexible sheet disposed on the second flexible sheet and having a flexibility substantially greater than that of the second flexible sheet and extending entirely in line with the area defined by the rib, the .second and third flexible sheets being spaced with respect to the aforesaid upper surface so as to provide air passages from the permeable side wall of the rib towards the periphery of the defined area, to determine the position of the laminate assembly, the third flexible sheet being large enough to come into tight contact with the aforementioned rib above the aforementioned permeable wall during the evacuation of air between them. first and third flexible sheet. 9. Apparatus according to claim 8, for the preliminary pressing of a set of curved sheets, wherein the resilient top surface is curved, preferably convex. 10. Apparatus according to claim 9, wherein the support surface is a support table with two spaced vertical posts having longitudinally convex upper surfaces to which a flexible support sheet is attached. . 11. Device following '+' one or the other of the resells !. cations $ to 10, wherein the heater is a flexible electric heater mounted above the aforementioned portion of the upper surface <Desc / Clms Page number 30> and within the area defined by the aforementioned rib. 12. Apparatus according to claim 11, wherein the electric heater is a flexible woven band heater. 13. Apparatus according to either of claims 8 to 12, wherein the rib is a continuous tubing sealed at its lower part to the first flexible sheet and having holes directed towards the defined area. 14. Apparatus according to either of claims 8 to 13, comprising an intermediate flexible sheet mounted above the first flexible sheet, within the area defined by the aforementioned tubing and under the heating device, the periphery of this intermediate flexible sheet being adjacent to the rib and its upper surface being irregular so as to provide air passages from the permeable wall of the rib to the rib. periphery of the laminated assembly. 15. The apparatus of claim 14-, wherein the upper surface of the intermediate flexible sheet is corrugated. 16. Apparatus according to either of claims 14 and 15, wherein the intermediate flexible sheet is a rubber sheet and a heat-insulating flexible woven sheet is provided between the intermediate flexible sheet and the inner flexible sheet. heating device. 17. Apparatus according to either of claims 14 to 16, wherein the intermediate flexible sheet is a cotton-lined rubber sheet, the cotton liner forming the top surface.