CA1161348A - Forming and assembly process for two or more curved glass panes having different physical-chemical properties and/or different thickness, especially suitable for windscreens and other safety glass items for motor vehicles and the like - Google Patents
Forming and assembly process for two or more curved glass panes having different physical-chemical properties and/or different thickness, especially suitable for windscreens and other safety glass items for motor vehicles and the likeInfo
- Publication number
- CA1161348A CA1161348A CA000379689A CA379689A CA1161348A CA 1161348 A CA1161348 A CA 1161348A CA 000379689 A CA000379689 A CA 000379689A CA 379689 A CA379689 A CA 379689A CA 1161348 A CA1161348 A CA 1161348A
- Authority
- CA
- Canada
- Prior art keywords
- pane
- panes
- curved
- glass
- mould
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000011521 glass Substances 0.000 title claims abstract description 152
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000000126 substance Substances 0.000 title claims abstract description 13
- 239000005336 safety glass Substances 0.000 title claims abstract description 6
- 230000008569 process Effects 0.000 title description 20
- 239000002985 plastic film Substances 0.000 claims abstract description 10
- 230000005855 radiation Effects 0.000 claims description 13
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000003513 alkali Substances 0.000 claims description 3
- 229910052681 coesite Inorganic materials 0.000 claims description 3
- 229910052906 cristobalite Inorganic materials 0.000 claims description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- 229910052682 stishovite Inorganic materials 0.000 claims description 3
- 238000005496 tempering Methods 0.000 claims description 3
- 229910052905 tridymite Inorganic materials 0.000 claims description 3
- 238000009966 trimming Methods 0.000 claims description 3
- 239000003086 colorant Substances 0.000 claims 1
- 229910052593 corundum Inorganic materials 0.000 claims 1
- 229910001845 yogo sapphire Inorganic materials 0.000 claims 1
- 230000005540 biological transmission Effects 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 10
- 239000004033 plastic Substances 0.000 description 8
- 238000005516 engineering process Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 239000004571 lime Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 2
- 230000000284 resting effect Effects 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000005357 flat glass Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/10009—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets
- B32B17/10036—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the number, the constitution or treatment of glass sheets comprising two outer glass sheets
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
- B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
- B32B17/10807—Making laminated safety glass or glazing; Apparatus therefor
- B32B17/10889—Making laminated safety glass or glazing; Apparatus therefor shaping the sheets, e.g. by using a mould
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
- C03B23/025—Re-forming glass sheets by bending by gravity
- C03B23/0258—Gravity bending involving applying local or additional heating, cooling or insulating means
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
- C03B23/025—Re-forming glass sheets by bending by gravity
- C03B23/027—Re-forming glass sheets by bending by gravity with moulds having at least two upward pivotable mould sections
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/40—Properties of the layers or laminate having particular optical properties
- B32B2307/402—Coloured
- B32B2307/404—Multi-coloured
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2605/00—Vehicles
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Joining Of Glass To Other Materials (AREA)
- Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
- Laminated Bodies (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
A method of forming and bonding at least two curved glass panes having different physical-chemical prop-erties and/or different thicknesses, especially suitable for use as windshields and other safety glass items for motor vehicles and the like, one pane having a lesser degree of curvability than the other when loaded on a concave surface of a horizontal mould and curved in a furnace. The panes are loaded on a horizontal mould having a concave surface which faces upward, the pane of lesser curvability being in direct contact with the concave surface of the mould, the other pane being loaded on the one. The panes are then curved in a furnace and trimmed. A plastic sheet is then inserted between the curved panes, with the positions of the curved panes being reversed. The curved panes and plastic sheet are then bonded in an autoclave.
A method of forming and bonding at least two curved glass panes having different physical-chemical prop-erties and/or different thicknesses, especially suitable for use as windshields and other safety glass items for motor vehicles and the like, one pane having a lesser degree of curvability than the other when loaded on a concave surface of a horizontal mould and curved in a furnace. The panes are loaded on a horizontal mould having a concave surface which faces upward, the pane of lesser curvability being in direct contact with the concave surface of the mould, the other pane being loaded on the one. The panes are then curved in a furnace and trimmed. A plastic sheet is then inserted between the curved panes, with the positions of the curved panes being reversed. The curved panes and plastic sheet are then bonded in an autoclave.
Description
1 16~3d~8 The present invention relates to a manufacturing process for curved and bonded glass panes, especially suit-able for use as windshields or other safety glass items in motor vehicles or the like. More precisely, the present invention relates to a manufacturing process for bonded and curved glass panes which can be used in cases where the physical-chemical properties and/or thickness of the glass panes to be bonded and curved are not the same.
Processes for forming and assembling two curved glass panes having different physical-chemical properties and/or different thicknesses, especially suitable for wind-shields and other safety glass items for motor vehicles and the like, are already known, such processes comprising the consecutive steps of ~1) loading the glass panes on a rigid horizontal mould with concave surface facing upwards, (2) curving of the two glass panes simultaneously in a furnace, ~3) trimming the glas~ panes to shape and, if required, sub~equent by temperlng the glass panes, (4) placing a sheet of plastic material between the matched glass panes, and (5) lastly bonding the panes an~ plastic togethe in an auto-clave under special temperature and pressure conditions.
The applicant proposes, in order to eliminate the faults occuring in the above-described prior processes, that of the two glass panes to be bonded, the one with the smaller degrée of curvature, be placed in direct contact with mould itself, and that during the assembly phase, the position of the two glass panes be inverted. Hence the glass pane originally placed in direct contact with the mould will go to form the inner part, that is, the concave part of the finished product.
Furthermore, the Applicant suggests that the glass pane of the two to be bonded having the smaller degree of curvability should ascribe such property wholly or mainly to a higher softening temperature or a higher radiant heat ,. ~
1 16~348 transmission coefficient (in relation to the radiation chiefly present in the furnace) or yet again to a greater thickness of the actual glass pane.
In order to understand the progress achieved by the process in accordance with the invention, it is first of all necessary to consider in more detail the procedures and limitations of manufacturing processes for bonded and curved glass panes already known until now. In such processes, two consecutive phases can be distinguished, namely: forming and assembly, with these phases being repeated in the process concerned.
During the forming phase, two operations are per-formed: the glass panes are curved in the furnace and trimmed to shape. These operations can be perforned accord-ing to two different technologies. In one technology, the two operations are performed in the order indicated above, the proce~s being known as an expan~ion process. ~n the other technology, the operations are performed in the reverse order, the process being known as a contour process. The process in accordance with the invention can be carried out using either of the two forming technologies.
During the assembly phase, a sheet of plastic material is first placed between each pair of glass panes to be bonded; next the so-formed sandwich (glass plus plastic) is pressed under given temperature conditions to expel most the air trapped between the plastic material and the glass;
lastly the sandwich is placed for a sufficiently long period in an autoclave, where the bonding operation is carried oùt under controlled temperature and pressure conditions.
For successful results in the manufacturing pro-cess, the glass panes must be curved in such a way that the surfaces in contact properly match each other or, i.e., there must be no appreciable differences in local curvature between the two surfaces to be bonded.
, ,,,, . , ... .. ,, _ ., _, ~ , 3A~
While, in fact, if the manufacturing process upstream and downstream to the curving phase is properly carried out, slightly different curvatures between the two surfaces to be bonded will not a?ter the final result, very different is the case, for the purposes of achieving proper bonding, when there is a great local difference of curvature on one of the two surfaces to be bonded. Such a case would lead to delamination after assembly (poor bonding with inter-ruptions occurring) along the edges of the sandwich and/or inside the sandwich.
Adequate matching of the curvatures of the two surfaces to be assembled is still today generally accom-plished by simultaneous curving in a furnace of the glass panes to be subsequently bonded together. For this purpose the glass panes are placed, during the curving phase, on a horizontal mould with concave surface facing upwards, in th~ same po~ition that they will as~ume in the finished product, For example, in the manufacture of a windshield with two layers of glass having the same physical-chemical properties and the same thickness, the pair of glass panes to be curved is loaded on the horizontal mould with concave surface facing upwards, whereby the glass pane which will form the outer part of the windshield ~convex part), is positioned in contact with the mould (that is, underneath), and then over this (that is, on top) is placed the glass pane which will form the inner part (concave part) of the windshield. The pair of glass panes loaded on the mould will then be placed in the heating furnace where the glass will be gradually raised to the softening temperature Con-sequently the glass panes assume, thanks to the effect of temperature and gravity, the final mould shape. More par-ticularly, the lower surface of the lower glass pane in direct contact with the mould, tends to assume the shape of ' 1' ' ~ - 3 -1 16~3~8 the latter while the lower surface of the upper glass pane tends, in turn, if suitably heated, to assume the shape of the upper surface of the lower glass pane.
It ls found that, in order to achieve a good matching of the surfaces in contact, the upper glass pane must be raised to an average temperature which is higher than that of the lower glass pane; in fact, the resultant lower viscosity reached by the glass of the upper pane per-mits this pane to be laid down on the lower glass pane. In order to accomplish these heat conditions, the heating furnaces for glass panes of equal thickness are generally operated so that, especially in the curving zone, the quan-tity of heat provided to the upper glass pane, mainly by radiation, is greater than the quantity given up to the lower glass pane.
It should also be observed that, still in order to obtain a correct final shape of the glass pane in the curving phase, the curve forming moul~ can either be of the rigid type (in the sense that its geometry does not vary in the furnace apart from the inevitable elastic and thermal defor-matlons), or else it can be of the ar~iculated type (that is, suitable hinge arrangements which permit the mould geometry to change inside the furnace). The rigid type moulds are mainly used for parts with small curvature, while the articu-lated type is mainly used in the other cases.
After curving, the glass panes undergo a suitableannealing treatment which, by lowering the glass temperature - without setting up consistent states of tension in it, permits the panes to maintain their shape already reached in the curving phase.
In the case of forming and bonding a pair of glass panes with the same physical-chemical properties, the above described curving process certainly gives rise to good results on glass panes of the samé thickness ~symmetrical ,~; ,.~, -- _ ,,,,. ~ .
1 16i3~
bonding) or else on glass panes of different thickness (assymetrical bonding), always provided that the thinner glass pane forms the upper part of the pair to be curved, that is, it is on the concave part of the finished product.
In fact, in the latter case, the lesser thermal capacity of the upper glass pane (thinner pane) favours its reaching higher average temperatures, and therefore its laying down on the lower glass pane. The laying down of this pane is also facilitated by the greater deformability of the thinner glass pane with respect to that of the thicker glass pane.
The Applicant has noticed that if the thinner glass pane is placed, instead, in the lower part o~ the pair, that is, in the convex part of the finished product, the greater thermal capacity and greater rigidity of the upper glass pane tends to render the correct curving and bonding without su~sequent del~mination more difficult Analogous difficultie~ can arise, in both symmetrical an~ assymetrical bonding, when the glass panes to be bonded have different physical-chemical properties. More particularly, as stated previously, if the glass pane placed on the concave part of the finished product has a higher softening temperature and/
or higher transmission coefficient of the radiation mainly present in the curving furnace, it is not possible to cor-rectly lay down this pane on the lower pane by using conven-tional technology. In fact, assuming equal quantities ofheat are absorbed, the glass pane with the higher softening temperature undergoes a lesser degree of curving than that of the other glass pane, just as, for equal radiant heat flow, the pane with the higher radiant heat transmission coefficient reaches lower average temperatures than does the other pane.
As a result, in conventional technology, unless very strict control is kept over the heat flow and the method of heat transfer in the furnace, if the glass pane with ~ ., l 16~3~8 higher softening temperature and/or higher radiant heat transmission coefficient is positioned in the upper part of the pair ~because it must be in the concave part of the finished product), it will prove very difficult to lay it down on the lower glass pane.
The Applicant has found that after carry-out suit-able experiments, the difficulties described in the preceding cases are to be ascribed to the smaller degree of curvature of the upper glass pane with respect to the lower pane, whereby the degree of curvability of a glass pane placed in a curving furnace and submitted to the force of its own weight, is understood to be the permanent deformation (vis-cous) reached by the pane within a certain time under given ambient furnace conditions.
The degree of curvability of a glass pane therefore is a measure of its ability to conform more or less easily to the constraining geometry and substantially depends on the geometry of the pane ltself and on the physical-chernical prop-erties of the glass of which it is made.
Concerning the latter properties, of particularly importance, as already stated, is the softening temperature of the glass and its total radiant heat transmission coeffi-cient relative to the wavelength range of the radiation.
For a given part (that is for a given contour con-figuration), the dependence of the degree of curvability of a glass pane on its geometry is also essentially linked to its thickness. More precisely, the degree of curvability of a glass pane decreases the higher is its thickness, the higher is its radiant heat transmission coefficient, the 3~ higher is the softening temperature of the glass of which it is made.
In order to solve the dificulties in curving met with in the previously described cases, the ~pplicant first of all carried out experiments involving the separate curving 1 16i3~8 of the glass panes to be bonded. However, this process gave poor yualitative results in the assembly phase and therefore a higher number of rejects.
In those cases where -the smaller degree of cur-vability of the glass pane essentially depends on its highertotal radiant heat transmission coefficient (in relation to the radiation mainly present in the curving furnace), attempts were then made to increase this degree of curvability by modifying the heat transfer procedure in the furnace, particu-larly by increasing the heat transfer component by convectionat the expense of that by radiation. However, this entails appreciable and troublesome modifications to the glass pane curving furnace.
With thé manufacturing process in accordance with the present invention, the Applicant has finally succeeded in overcoming the difficulties in manufacture encountered in the previ~usly descri~ed case~.
The process in question is applied, as stated in the title and in the background portion of this specification, particularly to the manufacture of curved and bonded glass panes whose physical-chemical properties and/or thickness are not the same.
The process is essentially characterized by the fact that during the curving phase, the order in which the glass panes are positioned on the mould is the reverse of that during the assembly phase, as it was surprizingly found that this is sufficient to offset the difficulties encoun-tered in the previous above listed processes.
Hence, more especially with the process in accord-ance with the invention, the glass pane with the lesserdeyreé of curvability, that is, the glass pane with the higher softening temperature, or the ~lass pane with the greater total radiant heat transmission coefficient (in relation to the radiation mainly present in the furnace) or the thicker glass 116-13d~
pane is placed in direct contac-t with the mould during the curving phase, when it is to be subsequently placed in the concave part, that is the inner part of the finished product.
~f s~lch factors influencing the degree of curvability are present, but are not common to the same glass pane, obviously it will be the pane with the lesser degree of curvability to be placed in direct contact with the mould during the curving phase, when it is to be placed in the concave part, that is, the inner part of the finished product. Likewise, in the case of a product entailing the use of more than two glass panes having different degrees of curvability, it also follows that the glass pane with the lesser degree of curvability, when it is to be placed in an inside position in the finished product, will be placed in direct contact with the mould lS during the curving phase.
Accordingly, the invention is broadly claimed here-in as a method for forming and bonding at least two curved ~lass panes includlng first and second curved glass panes having diferént physical-chemical properties and/or differ-ent thic~.ness, especially suital~le for use as a windshieldor other safety glass item for a motor vehicle or the like, the first pane having a lesser degree of curvability than the second pane when loaded on a concave surface of a horizontal mould and curved in a furnace, the method comprising the steps of:
(1) loading the first and second panes on a hori-zontal mould having a first concave surface which faces up-wards; the first pane being in direct contact with said first - concave surface, the second pane being loaded on said first pane;
~ 2) after step ~1), curving the first and second panes in said furnace on said mould to form first and second curved panes, respectively, each having an inner concave surface and an outer convex surface;
', i1 ~, .
1 16~3J~8 (3) trimming the first and second panes;
(4) placing the first curved pane over the second curved pane, with a plastic sheet sandwiched therebetween such that one side of said plastic sheet is in direct con-tact with said concave surface of the second curved pane andthe c~ther side of said plastic sheet is in direct contact with said convex surfacé of the first curved pane; and (5) following step (4), bonding the first and second curved panes and said plastic sheet in an autoclave.
The advantages to be derived from the manufacturing process of curved and bonded glass panes in accordance with the invention will appear clear from the examples of applica-tion described below.
TABLE 1 (Average composition) Glass pane no. 1 Glass pane no. 2 SiO2 70 - 74 % -50 - 70 ~
CaO 8 - 10 ~ 0.5 - 1.0 %
MgO 2 - 4 % 2 - 4 %
A123 0 1 - 1 5 ~ 5 - 25 Fe2O3 0 10 - 0 60 % 0 02 - 0 6 TiO2 0 05 - 0 06 % 0 05 - 0 2 Alkalies 12 - 15 % 12 - 15 A glass pane of mainly silica-lime composition, designated by the letter A, in Fig-~res 1 and 2, is to be bonded with a glass pane with a mainly silica-alumina com-position, designated by the letter B.
The two glass panes, initially flat and of the same thickness, before the assembly phase, must first undergo a forming phase, as they are to bc used as a curved windshield for a motor vehicle The silica-lime glass pane A is to form the outer g _ ., . ..... ~, .. .... ..
' 1 16~348 part of the windshield, that is, it will be in the convex part of the finished product, while the silica-alumina glass pane B is to form the inner part of the windshield (the con-cave part of the finished product).
The two glass panes have different physical-chemical properties, Their average compositions are given in table 1. The viscosity curves, covering the concerned range for the two types of glass, are given by way of expla-nation only in figure 1. It can be seen from the figure that the glass pane B has, at the same temperature, a higher vis-cosity than that of glass pane A, and therefore it has a higher softening point. The latter can be defined as the temperature at which the viscosity assumes a certain given vaiue (for example n=108 poise). Figure 2 gives, also by way of explanation, the monochromatic radiant heat transmis-sion coefficient curves of the two glass panes in relation to the wavelength of the radiation in the range concerned. The higher monochromatic radiant heat transmission coefficient of glass pane B with respect to glass pane ~ for the differ-ent wavelengths mean~ that the total radiant heat transmission coefficient (in relation to the radiation mainly present in the furnace) of the silica-alumina glass pane is higher than that of the silica-lime glass pane. In certain zones of the glass curving furnaces, the ratio of the two total heat transmission coefficient is in the region of about 2.
The two glass panes are placed on a mould which will than be advanced along the glass curving furnace. In accordance with the present invention, glass pane B will be -placed in direct contact with the mould (whose concave sur-- face faces upwards), and glass pane A will be laid on glass pane B.
The mould-pair of gl~ss pancs assembly will then enter the heating tunnel and glass pane A will, also on account of its lower radiant heat transmission coefficient, 7~' - 10 -"~
1 1613~8 reach its softening temperature (which is, among other thinys, lower than that of glass pane B) before the under-lyinc3 ylass pane B. Inspite of this, glass pane A will start to curve only when glass pane B will also have reached its softening temperature.
Curving will then continue until glass pane B con-forms to the curve forming mould.
Curving of ylass pane B, besides being favoured by the force of its own weight, will also be favoured by the weiyht of the overlying glass pane A which, having reached its softening temperature first, will be fully resting on glass pane B.
Heating of g~ass pane B is favoured by its contact with glass pane A which, being more opaque to radiation from the furnace, will tend to capture it more rapidly. In fact, the contact between the two glass panes favours heat transfer by conduction between them.
After the required annealln~ treatment is performed, the gla5s pané~ are separated and bonded together with an interposed sheet of plastic. In accordance with the present invention, the position of the two glass panes will be reversed in this operation, in the sense that the silica-limé glass pane A will go to the outer position (convex partl while the silica-alumina glass pane B will go to the inner position (concave part).
The position reversing operation gives rise to a slight difference in curvature between the surfaces which, during the assembly phase, will be placed in contact with the sheet of plastic.
It has been found that in the case of windshields with small or medium curvature, this slight difference in ` curvature of surfaces in contact with the sheet is such as not to alter the successful result of the bonding process.
In fact, in such a case, the différence between the radii of , ", ... ..
I 16~3~8 .
curvature is in the region of 0.1 - 1% of the ideal radius of curvature.
It has also be found that the operation according to the invention does not impair the good quality of the bondi.ng, even in the case of windshields with an appreciable degr~e of curvature, provided that the mould shape is properly corrected.
The same glass pane of mainly silica-lime composi-tion, according to the precedin~3 example, which will be designated by the letter A, is to be bonded to a thinner - glass pane, of mainly silica-alumina composition, which will be designated by the letter B.
The two initially flat glass panes, before the assembly phase, must first undergo a forming phase as they are to be used as a curved windshield for a motor vehicle.
Furthermore, the silica-alumina glass pane, which will form the inner part of the windshield (concave part of the finished product) must unde~go, before assembly, a che-mica~ tempering treatment.
This treatment is designed to impart greater mechanical strength to the inner part of the windshield, and above all, to impart a greater degree of passive safety in the event of fracture caused by impact.
The physical-chemical properties of the two glass panes correspond to those already given in the preceding example 1, with the possible exception that the monochromatic radiant heat transmission coefficient of glass pane B can be - even higher in certain ranges of the radiation wavelengths because of the smaller thickness of glass pane B.
It has been found experimentally than, in spite of the smaller thickness (which can be, by way of example, between two thirds and a quarter the thickness of glass pane A), glass pane B possesses a deyree of curvability which, r,4~ ~ 12 .
1 16~ 8 under the usual ambient conditions of the glass curving furnace, is less than that of glass pane A. This means that in this case, the influence of the softening temperature and the total radiant heat transmission coefficient is greater than that of the thickness.
Also in this case, it is convenient to adopt the process in accordance with the invention if good qualitative standards of bonding are to be achieved. Hence the forming and assembly process is identical to that of the preceding example.
It should also be noticed that in this case, if glass pane B has an appreciably smaller thickness than that of glass pane A, its lower resistance to bending does not lead in practice to deformations in the assembly phase even for windshield of appreciably large curvature and consequently the mould shape does not have to be significantly correct.
EXAMPLÉ 3 Two glass panes ~ the same composition ~for e~ample silica-alumina) and having the same physical-chemical properties but different thickne~s, are to be curved and bonded in such a manner that the thinner glass pane, desig-nated hy letter A, will form the outer part of the windshield (convex part), while the thicker glass pane, designated by the letter B, will form the inner part of the windshield (concave part).
- The two glass panes are places on a mould which will then be advanced along the glass curving furnace. In accordance with the present invention, glass pane B will be placed in direct contact with the mould, and gl~ss pane A
will be laid down on glass pane B.
The glass panes assembled on the mould will then enter the heating tunnel and glass pane A, on account of its lower heat capacity, will reach its softening temperature before the underlying glass pane B. In spite of this, glass ~ ' 1 16~3~
pane A will start to curve only when glass pane B will have also reached its softening temperature.
Curving will then continue until glass pane B con-forms to the curve forming mould.
Curving of glass pane B, besides being favoured by the force of its own weight, will also be favoured by the weight of the overlying glass pane A which, having reached its softening temperature first, will be fully resting on glass pane B.
After the required annealing treatment is per-formed, the glass panes are separated and bonded together with an interposed sheet of plastic. In accordance with the present invention, the position of the two glass will be reversed in this operation with respect to the curving phase, in the sensé that that thinner glass pane A will go to the outer position (convex part) and the thicker glass pane B
will go to the inner posi*ion (concave part).
It has been found that sUch an operation does not impair the good ~uality of the bonding, even in the case of windshields with appreciably large curvature ana without significant modifications to the mould shape because of the lower rigidity of the thinner glass pane with respect to the thicker glass pane.
It will be understood that what has been described and illustrated above is only by way of example and that numerous variations and modifications may be effected in carrying out the invention without departing from the true scope of the invention. Such modifications and variations will therefore fall within the scope of the claims.
''!' ': -- ], 4 ~ .
Processes for forming and assembling two curved glass panes having different physical-chemical properties and/or different thicknesses, especially suitable for wind-shields and other safety glass items for motor vehicles and the like, are already known, such processes comprising the consecutive steps of ~1) loading the glass panes on a rigid horizontal mould with concave surface facing upwards, (2) curving of the two glass panes simultaneously in a furnace, ~3) trimming the glas~ panes to shape and, if required, sub~equent by temperlng the glass panes, (4) placing a sheet of plastic material between the matched glass panes, and (5) lastly bonding the panes an~ plastic togethe in an auto-clave under special temperature and pressure conditions.
The applicant proposes, in order to eliminate the faults occuring in the above-described prior processes, that of the two glass panes to be bonded, the one with the smaller degrée of curvature, be placed in direct contact with mould itself, and that during the assembly phase, the position of the two glass panes be inverted. Hence the glass pane originally placed in direct contact with the mould will go to form the inner part, that is, the concave part of the finished product.
Furthermore, the Applicant suggests that the glass pane of the two to be bonded having the smaller degree of curvability should ascribe such property wholly or mainly to a higher softening temperature or a higher radiant heat ,. ~
1 16~348 transmission coefficient (in relation to the radiation chiefly present in the furnace) or yet again to a greater thickness of the actual glass pane.
In order to understand the progress achieved by the process in accordance with the invention, it is first of all necessary to consider in more detail the procedures and limitations of manufacturing processes for bonded and curved glass panes already known until now. In such processes, two consecutive phases can be distinguished, namely: forming and assembly, with these phases being repeated in the process concerned.
During the forming phase, two operations are per-formed: the glass panes are curved in the furnace and trimmed to shape. These operations can be perforned accord-ing to two different technologies. In one technology, the two operations are performed in the order indicated above, the proce~s being known as an expan~ion process. ~n the other technology, the operations are performed in the reverse order, the process being known as a contour process. The process in accordance with the invention can be carried out using either of the two forming technologies.
During the assembly phase, a sheet of plastic material is first placed between each pair of glass panes to be bonded; next the so-formed sandwich (glass plus plastic) is pressed under given temperature conditions to expel most the air trapped between the plastic material and the glass;
lastly the sandwich is placed for a sufficiently long period in an autoclave, where the bonding operation is carried oùt under controlled temperature and pressure conditions.
For successful results in the manufacturing pro-cess, the glass panes must be curved in such a way that the surfaces in contact properly match each other or, i.e., there must be no appreciable differences in local curvature between the two surfaces to be bonded.
, ,,,, . , ... .. ,, _ ., _, ~ , 3A~
While, in fact, if the manufacturing process upstream and downstream to the curving phase is properly carried out, slightly different curvatures between the two surfaces to be bonded will not a?ter the final result, very different is the case, for the purposes of achieving proper bonding, when there is a great local difference of curvature on one of the two surfaces to be bonded. Such a case would lead to delamination after assembly (poor bonding with inter-ruptions occurring) along the edges of the sandwich and/or inside the sandwich.
Adequate matching of the curvatures of the two surfaces to be assembled is still today generally accom-plished by simultaneous curving in a furnace of the glass panes to be subsequently bonded together. For this purpose the glass panes are placed, during the curving phase, on a horizontal mould with concave surface facing upwards, in th~ same po~ition that they will as~ume in the finished product, For example, in the manufacture of a windshield with two layers of glass having the same physical-chemical properties and the same thickness, the pair of glass panes to be curved is loaded on the horizontal mould with concave surface facing upwards, whereby the glass pane which will form the outer part of the windshield ~convex part), is positioned in contact with the mould (that is, underneath), and then over this (that is, on top) is placed the glass pane which will form the inner part (concave part) of the windshield. The pair of glass panes loaded on the mould will then be placed in the heating furnace where the glass will be gradually raised to the softening temperature Con-sequently the glass panes assume, thanks to the effect of temperature and gravity, the final mould shape. More par-ticularly, the lower surface of the lower glass pane in direct contact with the mould, tends to assume the shape of ' 1' ' ~ - 3 -1 16~3~8 the latter while the lower surface of the upper glass pane tends, in turn, if suitably heated, to assume the shape of the upper surface of the lower glass pane.
It ls found that, in order to achieve a good matching of the surfaces in contact, the upper glass pane must be raised to an average temperature which is higher than that of the lower glass pane; in fact, the resultant lower viscosity reached by the glass of the upper pane per-mits this pane to be laid down on the lower glass pane. In order to accomplish these heat conditions, the heating furnaces for glass panes of equal thickness are generally operated so that, especially in the curving zone, the quan-tity of heat provided to the upper glass pane, mainly by radiation, is greater than the quantity given up to the lower glass pane.
It should also be observed that, still in order to obtain a correct final shape of the glass pane in the curving phase, the curve forming moul~ can either be of the rigid type (in the sense that its geometry does not vary in the furnace apart from the inevitable elastic and thermal defor-matlons), or else it can be of the ar~iculated type (that is, suitable hinge arrangements which permit the mould geometry to change inside the furnace). The rigid type moulds are mainly used for parts with small curvature, while the articu-lated type is mainly used in the other cases.
After curving, the glass panes undergo a suitableannealing treatment which, by lowering the glass temperature - without setting up consistent states of tension in it, permits the panes to maintain their shape already reached in the curving phase.
In the case of forming and bonding a pair of glass panes with the same physical-chemical properties, the above described curving process certainly gives rise to good results on glass panes of the samé thickness ~symmetrical ,~; ,.~, -- _ ,,,,. ~ .
1 16i3~
bonding) or else on glass panes of different thickness (assymetrical bonding), always provided that the thinner glass pane forms the upper part of the pair to be curved, that is, it is on the concave part of the finished product.
In fact, in the latter case, the lesser thermal capacity of the upper glass pane (thinner pane) favours its reaching higher average temperatures, and therefore its laying down on the lower glass pane. The laying down of this pane is also facilitated by the greater deformability of the thinner glass pane with respect to that of the thicker glass pane.
The Applicant has noticed that if the thinner glass pane is placed, instead, in the lower part o~ the pair, that is, in the convex part of the finished product, the greater thermal capacity and greater rigidity of the upper glass pane tends to render the correct curving and bonding without su~sequent del~mination more difficult Analogous difficultie~ can arise, in both symmetrical an~ assymetrical bonding, when the glass panes to be bonded have different physical-chemical properties. More particularly, as stated previously, if the glass pane placed on the concave part of the finished product has a higher softening temperature and/
or higher transmission coefficient of the radiation mainly present in the curving furnace, it is not possible to cor-rectly lay down this pane on the lower pane by using conven-tional technology. In fact, assuming equal quantities ofheat are absorbed, the glass pane with the higher softening temperature undergoes a lesser degree of curving than that of the other glass pane, just as, for equal radiant heat flow, the pane with the higher radiant heat transmission coefficient reaches lower average temperatures than does the other pane.
As a result, in conventional technology, unless very strict control is kept over the heat flow and the method of heat transfer in the furnace, if the glass pane with ~ ., l 16~3~8 higher softening temperature and/or higher radiant heat transmission coefficient is positioned in the upper part of the pair ~because it must be in the concave part of the finished product), it will prove very difficult to lay it down on the lower glass pane.
The Applicant has found that after carry-out suit-able experiments, the difficulties described in the preceding cases are to be ascribed to the smaller degree of curvature of the upper glass pane with respect to the lower pane, whereby the degree of curvability of a glass pane placed in a curving furnace and submitted to the force of its own weight, is understood to be the permanent deformation (vis-cous) reached by the pane within a certain time under given ambient furnace conditions.
The degree of curvability of a glass pane therefore is a measure of its ability to conform more or less easily to the constraining geometry and substantially depends on the geometry of the pane ltself and on the physical-chernical prop-erties of the glass of which it is made.
Concerning the latter properties, of particularly importance, as already stated, is the softening temperature of the glass and its total radiant heat transmission coeffi-cient relative to the wavelength range of the radiation.
For a given part (that is for a given contour con-figuration), the dependence of the degree of curvability of a glass pane on its geometry is also essentially linked to its thickness. More precisely, the degree of curvability of a glass pane decreases the higher is its thickness, the higher is its radiant heat transmission coefficient, the 3~ higher is the softening temperature of the glass of which it is made.
In order to solve the dificulties in curving met with in the previously described cases, the ~pplicant first of all carried out experiments involving the separate curving 1 16i3~8 of the glass panes to be bonded. However, this process gave poor yualitative results in the assembly phase and therefore a higher number of rejects.
In those cases where -the smaller degree of cur-vability of the glass pane essentially depends on its highertotal radiant heat transmission coefficient (in relation to the radiation mainly present in the curving furnace), attempts were then made to increase this degree of curvability by modifying the heat transfer procedure in the furnace, particu-larly by increasing the heat transfer component by convectionat the expense of that by radiation. However, this entails appreciable and troublesome modifications to the glass pane curving furnace.
With thé manufacturing process in accordance with the present invention, the Applicant has finally succeeded in overcoming the difficulties in manufacture encountered in the previ~usly descri~ed case~.
The process in question is applied, as stated in the title and in the background portion of this specification, particularly to the manufacture of curved and bonded glass panes whose physical-chemical properties and/or thickness are not the same.
The process is essentially characterized by the fact that during the curving phase, the order in which the glass panes are positioned on the mould is the reverse of that during the assembly phase, as it was surprizingly found that this is sufficient to offset the difficulties encoun-tered in the previous above listed processes.
Hence, more especially with the process in accord-ance with the invention, the glass pane with the lesserdeyreé of curvability, that is, the glass pane with the higher softening temperature, or the ~lass pane with the greater total radiant heat transmission coefficient (in relation to the radiation mainly present in the furnace) or the thicker glass 116-13d~
pane is placed in direct contac-t with the mould during the curving phase, when it is to be subsequently placed in the concave part, that is the inner part of the finished product.
~f s~lch factors influencing the degree of curvability are present, but are not common to the same glass pane, obviously it will be the pane with the lesser degree of curvability to be placed in direct contact with the mould during the curving phase, when it is to be placed in the concave part, that is, the inner part of the finished product. Likewise, in the case of a product entailing the use of more than two glass panes having different degrees of curvability, it also follows that the glass pane with the lesser degree of curvability, when it is to be placed in an inside position in the finished product, will be placed in direct contact with the mould lS during the curving phase.
Accordingly, the invention is broadly claimed here-in as a method for forming and bonding at least two curved ~lass panes includlng first and second curved glass panes having diferént physical-chemical properties and/or differ-ent thic~.ness, especially suital~le for use as a windshieldor other safety glass item for a motor vehicle or the like, the first pane having a lesser degree of curvability than the second pane when loaded on a concave surface of a horizontal mould and curved in a furnace, the method comprising the steps of:
(1) loading the first and second panes on a hori-zontal mould having a first concave surface which faces up-wards; the first pane being in direct contact with said first - concave surface, the second pane being loaded on said first pane;
~ 2) after step ~1), curving the first and second panes in said furnace on said mould to form first and second curved panes, respectively, each having an inner concave surface and an outer convex surface;
', i1 ~, .
1 16~3J~8 (3) trimming the first and second panes;
(4) placing the first curved pane over the second curved pane, with a plastic sheet sandwiched therebetween such that one side of said plastic sheet is in direct con-tact with said concave surface of the second curved pane andthe c~ther side of said plastic sheet is in direct contact with said convex surfacé of the first curved pane; and (5) following step (4), bonding the first and second curved panes and said plastic sheet in an autoclave.
The advantages to be derived from the manufacturing process of curved and bonded glass panes in accordance with the invention will appear clear from the examples of applica-tion described below.
TABLE 1 (Average composition) Glass pane no. 1 Glass pane no. 2 SiO2 70 - 74 % -50 - 70 ~
CaO 8 - 10 ~ 0.5 - 1.0 %
MgO 2 - 4 % 2 - 4 %
A123 0 1 - 1 5 ~ 5 - 25 Fe2O3 0 10 - 0 60 % 0 02 - 0 6 TiO2 0 05 - 0 06 % 0 05 - 0 2 Alkalies 12 - 15 % 12 - 15 A glass pane of mainly silica-lime composition, designated by the letter A, in Fig-~res 1 and 2, is to be bonded with a glass pane with a mainly silica-alumina com-position, designated by the letter B.
The two glass panes, initially flat and of the same thickness, before the assembly phase, must first undergo a forming phase, as they are to bc used as a curved windshield for a motor vehicle The silica-lime glass pane A is to form the outer g _ ., . ..... ~, .. .... ..
' 1 16~348 part of the windshield, that is, it will be in the convex part of the finished product, while the silica-alumina glass pane B is to form the inner part of the windshield (the con-cave part of the finished product).
The two glass panes have different physical-chemical properties, Their average compositions are given in table 1. The viscosity curves, covering the concerned range for the two types of glass, are given by way of expla-nation only in figure 1. It can be seen from the figure that the glass pane B has, at the same temperature, a higher vis-cosity than that of glass pane A, and therefore it has a higher softening point. The latter can be defined as the temperature at which the viscosity assumes a certain given vaiue (for example n=108 poise). Figure 2 gives, also by way of explanation, the monochromatic radiant heat transmis-sion coefficient curves of the two glass panes in relation to the wavelength of the radiation in the range concerned. The higher monochromatic radiant heat transmission coefficient of glass pane B with respect to glass pane ~ for the differ-ent wavelengths mean~ that the total radiant heat transmission coefficient (in relation to the radiation mainly present in the furnace) of the silica-alumina glass pane is higher than that of the silica-lime glass pane. In certain zones of the glass curving furnaces, the ratio of the two total heat transmission coefficient is in the region of about 2.
The two glass panes are placed on a mould which will than be advanced along the glass curving furnace. In accordance with the present invention, glass pane B will be -placed in direct contact with the mould (whose concave sur-- face faces upwards), and glass pane A will be laid on glass pane B.
The mould-pair of gl~ss pancs assembly will then enter the heating tunnel and glass pane A will, also on account of its lower radiant heat transmission coefficient, 7~' - 10 -"~
1 1613~8 reach its softening temperature (which is, among other thinys, lower than that of glass pane B) before the under-lyinc3 ylass pane B. Inspite of this, glass pane A will start to curve only when glass pane B will also have reached its softening temperature.
Curving will then continue until glass pane B con-forms to the curve forming mould.
Curving of ylass pane B, besides being favoured by the force of its own weight, will also be favoured by the weiyht of the overlying glass pane A which, having reached its softening temperature first, will be fully resting on glass pane B.
Heating of g~ass pane B is favoured by its contact with glass pane A which, being more opaque to radiation from the furnace, will tend to capture it more rapidly. In fact, the contact between the two glass panes favours heat transfer by conduction between them.
After the required annealln~ treatment is performed, the gla5s pané~ are separated and bonded together with an interposed sheet of plastic. In accordance with the present invention, the position of the two glass panes will be reversed in this operation, in the sense that the silica-limé glass pane A will go to the outer position (convex partl while the silica-alumina glass pane B will go to the inner position (concave part).
The position reversing operation gives rise to a slight difference in curvature between the surfaces which, during the assembly phase, will be placed in contact with the sheet of plastic.
It has been found that in the case of windshields with small or medium curvature, this slight difference in ` curvature of surfaces in contact with the sheet is such as not to alter the successful result of the bonding process.
In fact, in such a case, the différence between the radii of , ", ... ..
I 16~3~8 .
curvature is in the region of 0.1 - 1% of the ideal radius of curvature.
It has also be found that the operation according to the invention does not impair the good quality of the bondi.ng, even in the case of windshields with an appreciable degr~e of curvature, provided that the mould shape is properly corrected.
The same glass pane of mainly silica-lime composi-tion, according to the precedin~3 example, which will be designated by the letter A, is to be bonded to a thinner - glass pane, of mainly silica-alumina composition, which will be designated by the letter B.
The two initially flat glass panes, before the assembly phase, must first undergo a forming phase as they are to be used as a curved windshield for a motor vehicle.
Furthermore, the silica-alumina glass pane, which will form the inner part of the windshield (concave part of the finished product) must unde~go, before assembly, a che-mica~ tempering treatment.
This treatment is designed to impart greater mechanical strength to the inner part of the windshield, and above all, to impart a greater degree of passive safety in the event of fracture caused by impact.
The physical-chemical properties of the two glass panes correspond to those already given in the preceding example 1, with the possible exception that the monochromatic radiant heat transmission coefficient of glass pane B can be - even higher in certain ranges of the radiation wavelengths because of the smaller thickness of glass pane B.
It has been found experimentally than, in spite of the smaller thickness (which can be, by way of example, between two thirds and a quarter the thickness of glass pane A), glass pane B possesses a deyree of curvability which, r,4~ ~ 12 .
1 16~ 8 under the usual ambient conditions of the glass curving furnace, is less than that of glass pane A. This means that in this case, the influence of the softening temperature and the total radiant heat transmission coefficient is greater than that of the thickness.
Also in this case, it is convenient to adopt the process in accordance with the invention if good qualitative standards of bonding are to be achieved. Hence the forming and assembly process is identical to that of the preceding example.
It should also be noticed that in this case, if glass pane B has an appreciably smaller thickness than that of glass pane A, its lower resistance to bending does not lead in practice to deformations in the assembly phase even for windshield of appreciably large curvature and consequently the mould shape does not have to be significantly correct.
EXAMPLÉ 3 Two glass panes ~ the same composition ~for e~ample silica-alumina) and having the same physical-chemical properties but different thickne~s, are to be curved and bonded in such a manner that the thinner glass pane, desig-nated hy letter A, will form the outer part of the windshield (convex part), while the thicker glass pane, designated by the letter B, will form the inner part of the windshield (concave part).
- The two glass panes are places on a mould which will then be advanced along the glass curving furnace. In accordance with the present invention, glass pane B will be placed in direct contact with the mould, and gl~ss pane A
will be laid down on glass pane B.
The glass panes assembled on the mould will then enter the heating tunnel and glass pane A, on account of its lower heat capacity, will reach its softening temperature before the underlying glass pane B. In spite of this, glass ~ ' 1 16~3~
pane A will start to curve only when glass pane B will have also reached its softening temperature.
Curving will then continue until glass pane B con-forms to the curve forming mould.
Curving of glass pane B, besides being favoured by the force of its own weight, will also be favoured by the weight of the overlying glass pane A which, having reached its softening temperature first, will be fully resting on glass pane B.
After the required annealing treatment is per-formed, the glass panes are separated and bonded together with an interposed sheet of plastic. In accordance with the present invention, the position of the two glass will be reversed in this operation with respect to the curving phase, in the sensé that that thinner glass pane A will go to the outer position (convex part) and the thicker glass pane B
will go to the inner posi*ion (concave part).
It has been found that sUch an operation does not impair the good ~uality of the bonding, even in the case of windshields with appreciably large curvature ana without significant modifications to the mould shape because of the lower rigidity of the thinner glass pane with respect to the thicker glass pane.
It will be understood that what has been described and illustrated above is only by way of example and that numerous variations and modifications may be effected in carrying out the invention without departing from the true scope of the invention. Such modifications and variations will therefore fall within the scope of the claims.
''!' ': -- ], 4 ~ .
Claims (13)
1. Method for forming and bonding at least two curved glass panes including first and second curved glass panes having different physical-chemical properties and/or different thickness, especially suitable for use as a wind-shield or other safety glass item for a motor vehicle or the like, the first pane having a lesser degree of curvability than the second pane when loaded on a-concave surface of a horizontal mould and curved in a furnace, the method com-prising the steps of:
(1) loading the first and second panes on a hori-zontal mould having a first concave surface which faces upwards; the first pane being in direct contact with said first concave surface, the second pane being loaded on said first pane;
(2) after step (1), curving the first and second panes in said furnace on said mould to form first and second curved panes, respectively, each having an inner concave surface and an outer convex surface;
(3) trimming the first and second panes;
(4) placing the first curved pane over the second curved pane, with a plastic sheet sandwiched therebetween such that one side of said plastic sheet is in direct contact with said concave surface of the second curved pane and the other side of said plastic sheet is in direct contact with said convex surface of the first curved pane; and.
(5) following step (4), bonding the first and second curved panes and said plastic sheet in an autoclave.
(1) loading the first and second panes on a hori-zontal mould having a first concave surface which faces upwards; the first pane being in direct contact with said first concave surface, the second pane being loaded on said first pane;
(2) after step (1), curving the first and second panes in said furnace on said mould to form first and second curved panes, respectively, each having an inner concave surface and an outer convex surface;
(3) trimming the first and second panes;
(4) placing the first curved pane over the second curved pane, with a plastic sheet sandwiched therebetween such that one side of said plastic sheet is in direct contact with said concave surface of the second curved pane and the other side of said plastic sheet is in direct contact with said convex surface of the first curved pane; and.
(5) following step (4), bonding the first and second curved panes and said plastic sheet in an autoclave.
2. Method as in claim 1, wherein the softening temperature of the first pane is higher than the softening temperature of the second pane, the difference in degrees of curvability of the first and second panes being mainly due to the difference in softening temperatures of the first and second panes.
3. Method as in claim 1, wherein the total radiant heat coefficient with respect to the radiation in the furnace of the first pane is higher than that of the second pane, the difference in degrees of curvability of the first and second panes being mainly due to the difference in total radiant heat coefficients with respect to the radiation in the furnace of the first and second panes.
4. Method as in claim 1, wherein the first pane has a greater thickness than does the second pane, the dif-ference in degrees of curvability of the first and second panes being mainly due to the difference in thickness of the first and second panes.
5. Method as in claim 1, further comprising the step of tempering the first and second curved glass panes prior to step (4).
6. Method as in claims 1, 2 or 3, wherein said mould comprises an articulated mould.
7. Method as in claims 1, 2 or 3, wherein said step (3) preceeds said step (2).
8. Method as in claim 1, wherein the first and second panes have different colours.
g. Method as in claim 1, wherein the second pane is composed of 70-74% SiO2, 8-10% CaO, 2-4% MgO, 0,1-1.5 A2O3, 0.10-0.60% Fe2O3, 0.05-0.06% TiO2, and 12-15% alkalies;
and the first pane is composed of 50-70% SiO2, 0.5-1.0% CaO, 2-4% MgO, 5-25% Al2O3, 0.02-0.6% Fe2O3, 0.05-0.2% TiO2, and 12-15% alkalies.
and the first pane is composed of 50-70% SiO2, 0.5-1.0% CaO, 2-4% MgO, 5-25% Al2O3, 0.02-0.6% Fe2O3, 0.05-0.2% TiO2, and 12-15% alkalies.
10. Method as in claim 9, wherein the first and second panes have the same thickness.
11. Method as in claim 9, wherein the first pane is thicker than the second pane, said method further compris-ing the step of chemically tempering the second pane.
12. Method as in claim 1, wherein the first and second panes have substantially identical silica-alumina compositions, the first pane being thicker than the second pane.
13. Method as in claim 1, wherein step (1) includes the step of loading a third glass pane having a greater degree of curvability than the first and second panes when loaded on a concave surface of a horizontal mould and curved in a furnace on the second pane, said method further comprising the steps of curving the third pane in said furnace concurrent with said step (2) on the second pane to form a third curved pane and placing the third curved pane on the convex side of the second curved pane so as to be bonded thereto during said step (5).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT22.759A/80 | 1980-06-13 | ||
| IT22759/80A IT1131319B (en) | 1980-06-13 | 1980-06-13 | PROCESS OF FORMING AND ASSEMBLY OF TWO OR MORE CURVED GLASS SHEETS WITH PHYSICAL-CHEMICAL CHARACTERISTICS AND / OR DIFFERENT THICKNESSES, PARTICULARLY SUITABLE FOR WINDSHIELDS AND OTHER SAFETY GLASSES FOR VEHICLES AND SIMILARS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1161348A true CA1161348A (en) | 1984-01-31 |
Family
ID=11200112
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379689A Expired CA1161348A (en) | 1980-06-13 | 1981-06-12 | Forming and assembly process for two or more curved glass panes having different physical-chemical properties and/or different thickness, especially suitable for windscreens and other safety glass items for motor vehicles and the like |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5761646A (en) |
| BE (1) | BE889213A (en) |
| CA (1) | CA1161348A (en) |
| DE (1) | DE3124067A1 (en) |
| ES (1) | ES8203713A1 (en) |
| FR (1) | FR2484398A1 (en) |
| GB (1) | GB2078169B (en) |
| IT (1) | IT1131319B (en) |
| LU (1) | LU83428A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110382228A (en) * | 2018-02-14 | 2019-10-25 | 法国圣戈班玻璃厂 | Laminated glazing |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61139910U (en) * | 1985-02-18 | 1986-08-29 | ||
| GB2174334B (en) * | 1985-04-16 | 1989-06-21 | Hickman James A A | Architectural bends of laminated glazing material |
| JPH02307833A (en) * | 1989-05-19 | 1990-12-21 | Nippon Sheet Glass Co Ltd | Heating of plate glass for laminated glass |
| US4952227A (en) * | 1989-05-22 | 1990-08-28 | Libbey-Owens-Ford Co. | Apparatus for processing glass |
| JP2727745B2 (en) * | 1989-08-24 | 1998-03-18 | 旭硝子株式会社 | Bending method for bent laminated glass and raw glass for laminated glass |
| KR101113457B1 (en) * | 2010-05-10 | 2012-03-05 | 삼성모바일디스플레이주식회사 | Curved Touch Screen Panel and Fabricating Method for the Same |
| DE102010032092A1 (en) * | 2010-07-23 | 2012-01-26 | Schott Ag | Laminated, transparent disc set, method for its production and bending and its use |
| WO2012137742A1 (en) * | 2011-04-01 | 2012-10-11 | 旭硝子株式会社 | Laminated glass and process for producing same |
| KR20140026553A (en) * | 2011-06-20 | 2014-03-05 | 아사히 가라스 가부시키가이샤 | Method for producing laminated glass, and laminated glass |
| BE1020051A3 (en) * | 2011-07-04 | 2013-04-02 | Agc Glass Europe | AUTOMOBILE GLAZING. |
| WO2014054468A1 (en) * | 2012-10-02 | 2014-04-10 | 旭硝子株式会社 | Method for producing laminated glass |
| FR3012071B1 (en) * | 2013-10-23 | 2021-01-01 | Saint Gobain | THIN LAMINATED GLASS |
| FR3012072B1 (en) * | 2013-10-23 | 2021-01-01 | Saint Gobain | THIN LAMINATED GLASS FOR WINDSHIELD |
| GB201322240D0 (en) | 2013-12-16 | 2014-01-29 | Pilkington Group Ltd | Laminated glazing |
| TWI649277B (en) | 2014-05-07 | 2019-02-01 | 美商康寧公司 | Formed glass article and method of forming same |
| CN106536432A (en) | 2014-05-23 | 2017-03-22 | 康宁股份有限公司 | Thin Glass Formed for Radiation Shielding |
| JP2017190271A (en) * | 2016-04-15 | 2017-10-19 | 日本電気硝子株式会社 | Laminated glass and method for producing the same |
| CN106183329B (en) * | 2016-07-06 | 2018-01-30 | 和县晶晶玻璃制品有限公司 | A kind of curved surface stained glass preparation technology |
| CN110461781B (en) * | 2017-02-20 | 2022-11-15 | 康宁公司 | Shaped glass laminates and methods of forming the same |
| JP7308189B2 (en) | 2017-10-18 | 2023-07-13 | コーニング インコーポレイテッド | How to control separation between glasses during simultaneous droop to reduce final shape mismatch between glasses |
| WO2019200203A1 (en) | 2018-04-13 | 2019-10-17 | Corning Incorporated | Uniformly pair sagged glass articles and hybrid laminates |
| US10981357B2 (en) | 2018-05-31 | 2021-04-20 | Agc Automotive Americas Co. | Glass article |
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Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1068865B (en) * | 1959-11-12 | |||
| FR328121A (en) * | 1902-10-27 | 1903-12-30 | Wytenhove Gustave | Process of doubling ice creams in white using colored glasses |
| US2314325A (en) * | 1942-01-24 | 1943-03-23 | Libbey Owens Ford Glass Co | Method of producing bent laminated safety glass |
| LU33391A1 (en) * | 1954-10-27 | |||
| FR1113950A (en) * | 1954-11-04 | 1956-04-05 | Glass sheet decoration process | |
| DE1153494B (en) * | 1960-06-07 | 1963-08-29 | Pittsburgh Plate Glass Co | Use of an upper glass sheet with a heat absorption higher than that of the lower glass sheet when bending glass sheets in pairs |
| JPS5567549A (en) * | 1978-11-09 | 1980-05-21 | Nippon Sheet Glass Co Ltd | Production of curved laminated glass with joined surface printed |
-
1980
- 1980-06-13 IT IT22759/80A patent/IT1131319B/en active
-
1981
- 1981-06-03 GB GB8116972A patent/GB2078169B/en not_active Expired
- 1981-06-10 ES ES502926A patent/ES8203713A1/en not_active Expired
- 1981-06-12 BE BE0/205090A patent/BE889213A/en not_active IP Right Cessation
- 1981-06-12 CA CA000379689A patent/CA1161348A/en not_active Expired
- 1981-06-12 LU LU83428A patent/LU83428A1/en unknown
- 1981-06-12 JP JP56090696A patent/JPS5761646A/en active Granted
- 1981-06-12 FR FR8111661A patent/FR2484398A1/en active Granted
- 1981-06-15 DE DE19813124067 patent/DE3124067A1/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110382228A (en) * | 2018-02-14 | 2019-10-25 | 法国圣戈班玻璃厂 | Laminated glazing |
| US11230088B2 (en) * | 2018-02-14 | 2022-01-25 | Saint-Gobain Glass France | Laminated glazing |
| CN110382228B (en) * | 2018-02-14 | 2022-09-27 | 法国圣戈班玻璃厂 | Laminated glazing |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3124067A1 (en) | 1982-03-18 |
| ES502926A0 (en) | 1982-04-01 |
| GB2078169B (en) | 1984-11-21 |
| JPS5761646A (en) | 1982-04-14 |
| IT1131319B (en) | 1986-06-18 |
| GB2078169A (en) | 1982-01-06 |
| FR2484398B1 (en) | 1985-01-11 |
| BE889213A (en) | 1981-12-14 |
| JPH0327499B2 (en) | 1991-04-16 |
| LU83428A1 (en) | 1983-04-06 |
| ES8203713A1 (en) | 1982-04-01 |
| FR2484398A1 (en) | 1981-12-18 |
| IT8022759A0 (en) | 1980-06-13 |
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