MXPA97009500A - Method for folding vine leaves - Google Patents

Abstract

The present invention relates to a method for bending glass sheets and more particularly to bending glass sheets wherein there is a step of initial bending by gravity and a step of bending by subsequent pressure. The method is particularly useful for bending automotive glasses for subsequent lamination, for example in the manufacture of vehicle windshields.

Description

METHOD FOR FOLDING GLASS SHEETS The present invention relates to a method for bending glass sheets and more particularly to bending glass sheets wherein there is an initial bending step by gravity and a subsequent bending step by pressing. The method is particularly useful for bending automotive glasses for subsequent lamination, for example in the manufacture of vehicle windshields. Normally, the glass or glass for vehicle windows is curved, the curvature is imparted to planar glass by a bending process. In a bending process, the planar glass sheets are placed on female ring molds and heated to the softening point of the glass. Each sheet is bent ("pandea") under its own weight, until the periphery of the glass sheet is in contact with the ring mold. This bending technique is known as "buckling" or bending by gravity, and has been developed over the years, in order to bend glass sheets that meet the demands of vehicle manufacturers. For example, as more deeply folded glass has been required, the ring mold is modified by connecting the ends of the mold to the hinged center portion, the hinged mold ends or portions of fins progressively closing as the glass softens and progresses. bent. This avoids the tendency for the glass sheet to slide relative to the mold during bending, thus avoiding scratching. This mold is commonly called an articulated mold. The process of bending by gravity has been found particularly suitable for the production of glass to be subsequently laminated, by combining two sheets of glass with a sheet of interlayer material. The process of bending by gravity is able to produce glass with a high optical quality and it is also possible to fold two sheets of glass simultaneously, thus producing a coupled pair of glasses that give an excellent fit to the sheet. In recent years, developments in vehicle designs have required glass with complex curvature, ie glass that bends in two directions generally at right angles to each other. It is not possible to impart more than a very limited degree of complex curvature to a glass sheet by bending by gravity only. In addition, the increased use of automotive assembly by vehicle manufacturers demands that more strict dimensional tolerances be met by glass. The shape of the periphery of the folded panel must be accurate, not only in terms of its bi-dimensional projection but also in three dimensions, ie the angle of the glass adjacent to the periphery must be correct, if this "angle of entry" as known by those skilled in the art is not correct, the folded panel will not fit and seal satisfactorily on the receiving flange of the vehicle body. Furthermore, the optical properties of the window depend on the shape of the central region of the glass, which must therefore be precisely controlled in order to comply with the required optical standards. These requirements, together with the tendency to deeper and more complex bends, can no longer be fulfilled by the glass that is bent by the double-bent technique by gravity alone. Now it is considered necessary to complete the folding of these forms by a subsequent bending step by pressure. This stage can only involve a limited part of the area of the folded panel, for example the areas that after installation in the body of the vehicle, will be adjacent to the pillars of the windshield of the body. In many current vehicle designs, these areas of the panel are required to be bent more closely, and in this specification, any area of a panel that is required to bend more deeply by a layer of bending by subsequent pressure will be referred to as the portion of deep bending. . In the step of bending by pressure, an upper mold or matrix is bent over the upper surface of the glass sheets, in such a way that the glass sheets are further bent by the action of the upper mold pressing the sheets with its lower mold. When the step of bending by pressure is carried out after bending by initial gravity, the lower mold may comprise the mold bent by gravity. The U.S. Patent No. 4778507 discloses a method for bending glass sheets, wherein a step of bending by pressing is carried out subsequent to a step of bending by gravity. It is described that the pressing zone is preferably kept at a temperature in the range from 500 to 660 ° C. It is also described that the pressing time preferably is from 0 to 60 seconds. It is further disclosed that after the pressing operation, the glass plates are gradually cooled to a typical cooling rate of 20 to 200 ° C per minute US Patent 5071461 also relates to a method for bending glass sheets wherein an oven heats glass sheets to be bent at a temperature from 550 to 650 ° C. Patent EP-A-03Q0416 discloses press folding in lehr, wherein a bending station by gravity is maintained at an ambient temperature from 621. at 638 ° C and in a bending station with downstream pressure, the pressing molds are maintained at a designated elevated temperature approaching the ambient temperature in the pressure bending station, GB-A-2063851 discloses a method for bending glass sheets where the ambient temperature in a zone of bending by gravity is maintained from 625 to 638 ° C and the ambient temperature of a zone of bending by pressure is maintained aa approximately 582ßC. While the aforementioned patent specifications describe a variety of process parameters relating to temperature and processing times for use in bending by gravity, and in a subsequent pressure bending step, however, there is a need in the art for a method of bent glass controllable, where the initial bending by subsequent and folded by pressure of the glass sheets, can be reliably used to produce glass sheets having deep bending portions, which achieve the maximum voltage threshold required and the optical characteristics required for glass sheets. In addition, there is still a need in the art for a method of bending glass sheets which by selection of appropriate process parameters allows the process to be easily controlled to achieve the characteristics required in the finished product when manufactured in a production furnace. It is also employed by pressure bending in the art to bend planar glass sheets without bending by initial gravity. However, this can lead to disadvantages since, because the bent profile is achieved by a pressing force applied when compressing individual sheets between two molds, the optical and physical properties of the glass sheets can be reduced compared to bending by gravity .

Tensions may also be induced in the glass sheets that may cause rupture or require an additional annealing step to remove them. Accordingly, the apparatus and methods employed in bending by pressure alone, that is, by not following a step of bending by gravity, may be different from those employed in bending by subsequent pressure following bending by initial gravity. Patent GB-A-2011377 discloses a profiling and apparatus for bending glass wherein a flat glass sheet is bent between an upper male die and a lower female die. The upper matrix has an effective weight of 200 kg. The use of this high-weight matrix can lead to accidentally introducing marks on the glass surface and attentions that are induced by the glass. An object of the present invention is to provide a method of bending glass sheets wherein the process can be controlled to allow the process to be easily used in production while ensuring undesired marking of glass sheets and stress induction is ensured. on the glass sheets. It is also an object of the present invention to provide a method of bending glass sheets that controls the step of bending by pressure, so that both high-quality optics and low tensions can be present in a folded glass sheet product.

Another object of the present invention is to provide a method of bending glass sheet which allows the use of a lighter matrix than in the prior art, thus avoiding accidentally marking the glass sheets. A further objective of the present invention was to provide a method of bending glass sheets, where by controlling the process parameters which allow a lighter matrix to be used in comparison are the previous tress. This not only minimizes the staining of the glass sheets but also allows the process to be easily controlled so as not to accidentally induce undesirable stresses in the glass. The present invention provides a method for bending glass sheets, the method soraprende the stages of bending by gravity a sheet of glass at high temperature in a mold of bending by gravity, in a zone of bending by gravity of a furnace, bending by pressure the glass sheet bent by gravity to a desired shape, ssn a top mold while the glass sheet is supported by the mold of bending by gravity, sonforme a bottom mold in a zone of bending by pressure of the oven and cool the sheet of glass in the area of bending by pressure when the glass sheet enters the area of bending by pressure to a velosity of sonolated cooling, when the ambient temperature is controlled in the area of bending by pressure.

The present invention also provides a method for pressing bending glass sheets, the method consists of providing a glass sheet bent inisially that is transported in a mold of bending by artisulated gravity, and bending by pressing the glass sheet to a final bent form by an upper pressure bending mold that collapses on the upper surface of the glass sheet, the upper pressure bending mold has a net weight of 50 to 150 kg. One embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a side view in schematic section through a furnace for expelling glass sheets, showing a mold of bent by gravity that carries a pair of flat glass blades before a gravity bending operation; Figure 2 is an enlarged schematic partial side view of one of the fins acerbating devices illustrated in Figure 1; Figure 3 is a side view in schematic parsial section on line A-A of Figure 2; Figure 4 is a plan view of the gravity bending mold which is mounted on a base on a slab as illustrated in Figure 1; Fig. 5 is a side view in schematic diagram similar to that of Fig. 1, showing an apparatus for pressing bending glass sheets in the oven, the apparatus being illustrated before a pressure bending operation; Figure 6 shows the apparatus of Figure 5 during a pressure bending operation; and Figure 7 is an enlarged side view of one of the spacing devices illustrated in Figure 6; and Figure 8 is a graph representing sambium at temperature of glass sheets before, during and after a pressure bending operation. With referensia in Figure 1, a section through a tunnel 2 furnace is illustrated for bending glass sheets, typically a pair of glass sheets 4 which after the bending operation are intended to be laminated together in order to manufacture , for example, an automotive windshield. Said tunnel furnace 2 is well conesido in the tisane and consists of an elongated track 6 that transports a suspension of rolling lid taps 8. Each cart has a ring mold of bending by gravity 10, the mold 10 is mounted in a base 12 which is fixed to a solid bottom wall 14 of the carriage 8. The scale 8 also has an annular side wall, of preferensia restangular 9.

The sills 8 are assembled in suspension for movement sisliso around a busle including the furnace 2. The busle includes a zone of glass twig, a zone of salenta in which the heated sheets of glass are bent by gravity in the bending mold by gravity 10, a cooling zone of a glass discharge zone. The furnace 2 can be provided with other areas, for example a recluse zone, for resorbing the glass in order to reduce stresses generated during the bending step, between the blister zone and the cooling zone. It will be understood by a person to be skill in the espesiality, that although the present invention is exemplified by a saja furnace, the present invention can alternatively be employed in any other type of lehr. The present invention is particularly concerned with the manufacture of glass sheets having deep bending porsions that can not be achieved easily by the use of bending by gravity alone. According to the invention, a pressure bending zone is additionally provided in the loop, immediately downstream of the bending zone by gravity. In the pressure bending zone, the glass sheets bent by gravity are bent by more pressure to a final desired shape of a superior resilient mold, while the glass sheets are supported in the bend mold by gravity. Figure 1 illustrates glass sheets 4 in the mold 10 in a scale 8 before the operation of bending by gravity. The scale 8 is arranged to move on the furnace 2 in a direction at a rest angle respecting the plane of the drawing. The mold 10 comprises a central fixed mold portion 16 which is mounted to the mold base 12 by a plurality of supports 18. On opposite sides of the central portion 18 of the mold 8, hinged portions of respective fins 20 are hingedly mounted. The invention is described as referensia to a gravity bending mold having two opposite fin porsions, it will be apparent to those are skill in the espesiality that the invention can also utilize a gravity bending mold having only one articulated fin portion. . The fin porsions 20 are arranged to move by rotation between a lower position, as illustrated in Figure 1, where the mold 10 is shown to support one or more flat glass sheets 4 in the mold 10, and a superior position in the sual the fin porsions 20 define, together with the central porsión 16, a continuous curved annular rim defining a surface to be reached by the glass sheet or sheets 4, when they are finally folded. The glass sheets 4 are heated as they pass through the heating zone of the oven 2, such that the glass sheets 4 are softened and progressively panded under the effect of gravity so as to conform to the desired shape as defined by the mold 10. On the central portion 16 of the mold, the glass sheets 4 are they buckle until they rest against the upper mold surface thus adapting to the desired shape. On the fin porslons 20, the softening effect of the glass allows the fin porsions 20 to be raised upwards under the influence of a bending force that is provided by a pair of hangers, so that every fin portion 20 rotates. respectable to a pivotal pivot shaft 22 at the junction enters the central portion 16 and the respective fin portion 20, such that the glass sheets 4 are pushed up and bent progressively until the bottom surface of the sheets of glass 4 rests against the upper surface of the fin porsions 20. As will be subsequently dismantled, when the deep bending portions are present in the glass sheets, those porsions tend to require mesanically pressing against the lower mold by a die or mold lower, so that the desired shape defined by the lower mold is achieved in a reliable and repetitive manner. It will be apparent that the present invention can employ molds so-called "weightless", which do not have counterweights but rather are specially configured in such a way that the mold is articulated under the influence of the weight of the glass sonforme softens. A typical mold 10 is illustrated in greater detail in Figure 4. The mold 10 is mounted on the base 12 by the supports 18 which are fixed to the underside of the sentral portion 16 of the mold 10. The base is suffi- ciently rigid to minimize deflection during the step of bending by pressure subssuente. The fin porsions 20 are threaded to the sentral portion 16 on their opposite sides by resilient pivot axes 22. Each fin portion 20 has mounted on its opposite sides a pair of shanks 24, the shank 24 is mounted on a resilient arm 26 which is fixed to a respec- tive end 28 of a resilient pivot shaft 22. The upper surface of the flange 30 of the mold 10 formed by the sentral position 16 and the fin por- tions 20 are the underside of the glass sheets 4 and define a final shape desired for the glass sheets 4. The superfisial area of the mold 10 which is made of the glass sheets 4, preferably is minimized to redress the area available for heat transfer between the glass sheets 4 and the metal mold 10 which can be diffused to the glass. undesirable tensions present in the finally folded glass sheets 4 and / or visible defects present on the edges of the glass sheets 4. These stresses can prevent breakage of the glass sheets 4. Typically, it is desired to maintain tensions in the tensile area in glass sheets of less than 7 MPa. Typically, the annular rim 30 of the mold 10 defined by the upper surfaces of the central portion 10 and the fin portions 20 have a thickness of from about 3 to 4 mm, to minimize the area of contaste between the glass of the mold 10. However , when according to the present invention, the gravity bending mold 10 is intended to be employed as the lower mold in a subsequent pressure bending operation, the lower mold is required to be sufficiently rigid and strong so that it does not deviate in uncontrollable form or distort under the pressure of the aplimated pressure from the mold for bending by superior pressure. It also requires that the thin flange does not mark the underside of the glass during the pressure bending operation. According to the present invention, the glass sheet bending apparatus is specially adapted to allow a folding mold to be bending with a relatively thin annular flange, which has been employed in a bending operation by sub-squeezing pressure while being secured high Salinity control of the glass sheet products finally bent. The use of this third annular flange provides low stresses in the glass, as will be described below. Modifications have been made to the mold and to the remaining parts of the apparatus to ensure reliably that the mold will achieve the required final shape, the mold can withstand the pressure of bending by pressure and the glass sheets will not be marked or otherwise deteriorate in appearance. It is also a result of the bending operation due to additional pressure. With referensia again to Figure 1, the fin porsions 20 are provided with less suffixing device to enslave or ensure vertically the position of the fin portion during the bending operation by pressure. Optionally, the fin portion has two fastening devices and although the illustrated embodiment is only provided, it is a fastening device for each fin portion. The enslavement device comprises a hinged-up arm 32 which is hingedly mounted to the end portion 20, and is downwardly dependent so as to be able to slide on the upper surface of a plate 34 mounted on the base 12 which provides a surface of upper cam. The enslavement arm 32 / pad 34 strand is illustrated in greater detail in Figures 2 and 3. The padding arm 32 comprises a pair of elongated spaced plies 36 which are hingedly mounted at their upper ends with a fixed extension member 38 to the fin portion respectively, the extension member 38 passing between the plates 36 and the pivotal mounting therebetween comprising a bolt structure 40. The locking arm 32 is downwardly dependent from the fin position 20 and the end of the latch 20 Free bottom 42 is provided with a cylindrical spacer 44, which is fixed between the plasters 36 by an additional stud bolt 46. The sill-like spacer 44 is clamped between the elongate plies 36 to prevent rotasional movement respects them. An additional spacer 48 and bolt strut 50 are substantially provided to the end of the clamping arm 32. The clamping arm 32 is free to pivot respect to the flange portions 20 are recessed to the extension member 38 and the lower surface 52 rests in the upper surface of the plate 34 comprising an elongated cam surface 54, on the sual the free bottom end 42 of the clamping arm 32 can slide. The fin surface 54 comprises a substantially horizontal portion 56 and a portion of the adjacent instep ramp 58. The preferensia ramp portion 58 is inclined at an angle of approximately 20 ° to the horizontal and, if desired, the substantially horizontal portion 56 can be tilted. slightly relative to the horizontal by a few degrees in the same direction as the ramp portion 58. The pad 34 is mounted in an adjustable manner in a vertical configuration to the base 12, by a mounting plate 60 to the sual plate 34 removably held by bolt stitches 62. The plate 34 can be adjusted easily in height and inslinasión. In Figure 1, the fin portions 20 are illustrated in their collapsed configuration and in this configuration, the securing arm 32 is resilient to the horizontal in a unfastened portion, and its free end 42 rests on the ramp portion. 58 of the cam surface 54 of the plate 34. Disha sonfiguration is illustrated in dotted lines in Figure 2. During the step of bending by gravity, the fin portion 20 rotates upwards under the action of the sontrapeses 24 which progressively cause that the glass sheet is able to increase as it softens when it comes out. The portion of fin 20 moving from the position is dashed lines illustrated in Figure 2, to the posi- tion illustrated by the solid lines in Figure 2. It will be seen that the porsión of fin 20 assiende during the bending stage by gravity, the free end 42 of the clamping arm 32 slides up on the ramp portion 58, until the horizontally sustaining portion 56 defining a sealing area 64 for the clamping arm 32 is alsanse. The clamping arm 32 moves in a plane perpendicular to the pivot axis 22. As illustrated in Figure 4, the plate 34 which defines the cam surface 54 is at resilient angles respect to the resilient pivot axis 24, such that the fin portion 20 is rotated upwardly relative to the resilient pivot axis 22, the free end 42 of the enslavement arm 32 and in partular the lower surface 52 of the spacer 44 slides uniformly upwards in the ramp position 58 until the clamping arm 32 is substantially vertical, with its free end 42 collated in a sontasto, is the clamping area 64. As illustrated in FIG. Figure 2, in order to ensure that the arm of enslavement 32 does not move assiduously out of the cam surface 54, a wire 66 is at opposite ends 68 are respest ends opposing ivos 70 of the plate 34, and passing between the member of spaced apart plasters 36 of the arm 32, can be proportional. As illustrated in Figure 2, the enslavement arm 32 in its enslaved position is substantially vertisal. Preferably, the height and inslinasión of the plate 34 is adjusted in such a way that in the enslavamiento position the enslavement arm 32 is not quite vertisal but is slightly insinuate a few degrees as opposed to the vertical, inslinasión is in the same sense that for the disassembled position. In the sawing position, the lower surface 52 of the non-rotatable spacer 44 folds the cam surface 54 in the clamping area 64 in a frission manner. Since the clamping area 64 is substantially horizontal and the clamping arm 32 is substantially vertisal, during the operation of bending by subsonic pressure, which is broken down in detail to sontinuation, where a force of pressure is pressed down to the fin portion in its position rotated upwards, a corresponding force is transmitted down through the arm of the latter. and 32 to the base 12 through the plate 34 and the mounting plate 60 in the sual is soldered to the plate 34. This downward pressing force in the fin portion 20 is transmitted with distortion or deviation towards minimum down of the fin portion 20. The bracing arm 32 astu a s as a rigid support and aserrojada for the porsión of fin 20 somo result of the frissional swage between the bracing arm 32 and the enslavement zone 64 of the cam surface 54. This allows an arturized mold 10 to have a relatively thin annular lip 30 which is employed in a bending operation by subsysing pressure. It will be expedient that an operator is required which is set up in the clamping arm 32 / plate 34, while the apparatus is cold. However, it is required that the apparatus operates satisfyingly and reliably at elevated temperatures in the furnace, for example from about 600 to 650 °. the inisial sonfiguration must take into account the expansion of the various parts of the apparatus to exit, thus sorao slight distortion of the mesánisas parts as a result of the thermal insulation and also mesániso wear are the tierapo. It is obviously preferred that the apparatus be easy to assemble by an operator. In accordance with this, the clamping arm 32 / plate 34 is preferably configured in such a way that the locking arm 32 is not quite vertical in the pressure bending step. This ensures that even if distortion and wear were to occur, the clamping arm 32 can not rotate beyond the vertical position and slide away from the end 70 of the plate 34. This allows additionally on a great sanctity of blasting systems, which a range of potentation enslavement positions are defined on the enslavement zone 56 corresponding to a range of slightly varying heights (respect to the base 12) of the fin portion 20 at which the bracing arm 32 is made. This can easily reflect any distortion and wear that can be expected. we are the result of subsidence terrestrial systems. The final angular position and in this way the height of the fin portion 20 is defined by stop members in the arms 26 carrying the weights 24 defining a final position for the mold that corresponds to the final desired shape of the leaves. glass. Nevertheless, it is possible that the weight of the fin portion 20 varies slightly is respect to the base 12 as a result of thermal insulation and the proportioning of a range of enslavement ensures that the enslavement arm operates to provide a supporting support for the porsión of flap 20 of the mold 10 during the pressure bending operation in spite of said thermal casing which has sausage a slight sarabium in the angular position of the locking arm 32. This avoids the need for regular verification and adjustments to the interlocking devices. Preferably, the locking zone 56 is tilted slightly upwards to allow smooth sliding movement by a clamping action of the free end 42 of the clamping arm 32 on the cam surface 54. The clamping arm 32 / plate 34 constraint is It is easy to manually configure by adjusting the height and orientation of the pad 34 relative to the base 12, and in this way respecting the bracket arm 32 in the resilient fin portion 20.

The final configuration of the mold 10 after the operation of bending by gravity and before the operation of bending by pressure is illustrated in Figure 5. Although the embodiment illustrated in the Figures 4 shows only one arm of enslavamiento mounted on sada porsión de flap 20, if desired two or more enslavement arms can be provided in each flap. After the operation of bending by pressure which is dessribe to continuation, and after the pressure-bent glass sheets have been removed from the mold in the unloading zone, the fin portion 20 can be readjusted to its inisial bottom configuration by a The operator manually pushing the sealing arm 32 hasia inside, in order to arrange it in the configuration illustrated in dotted lines in Figure 2. If desired, this operation can be performed automatically, for example by a robot. Referring to Figure 5, the pressure-bending apparatus designated generally as "72" is illustrated, in the area of pressure bending in the tunnel furnace 2, the pressure-bending apparatus 72 is illustrated before the bending operation by Pressure. In the area of pressure bending, the tartar 8 which is the mold 10 carries the glass sheets bent by gravity 4 are the fin porsions 10, which are arranged in their orientation turned upwards 20 arranged in their orientation turned downwards and are the enslavement arms 32 in a substantially vertisal orientation and which rest below the upper surface of the resilient plasmas 34, as previously disengaged, is transported to a preset position in which the glass sheets 43 are soldered in order to disposed below the pressure bending apparatus 72. The pressure bending operation is employed when it is desired to complete the bending of the glass sheets 4 to the required shape in such a way that the finally folded glass sheets 4 have a shape defined by the bending mold by gravity 10. The pressure bending apparatus 72 comprises a mold or upper die 74 having a surface of lower mold 76 constituting a masho mold surface which substantially absorbs the female mold surface defined by the bending mold by gravity 10. The glass sheets 4 are preformed bent under pressure between the upper mold 74 and the bending mold by gravity 10, to reach the required shape. The upper mold 74 of preferensia somprende a ceramic body. As illustrated in Figure 5, the upper mold 74 may comprise a unitary mold, however, in alternating configurations, the upper mold 74 may comprise a pair of spaced mold parts, which are arranged to be pressed against only those portions or portions thereof. of the glass sheets 4 that are required to bend deeply, ie in the vicinity of the fin portions 20.

The upper mold 74 is supported by a sub-frame 78. The sub-frame 78 depends downwards from the supporting frame 80 by a plurality of strings 82. Preferably, there are soft saws 82, one of which is located in a respectable corner of the frame. upper mold 74. Metallic sabers can be used instead of sadenas. The support frame 80 has, to the upper surface 84, a saber (or string 86) extending upwards from the center of the support frame 80 through the tesho 87 of the tunnel furnace 2, on a first pulley 88 to remain substantially horizontally on a second pulley 90 to depend vertically downwards are the saber end 86 shown to a first squeeze 92 which in turn shows even movement mesanism of matrix 94. The sontrapese 92 and the matrix movement mesanism 94 are laterally adhered to the tunnel kiln 2 on a longitudinal side somun. The motion of matrix movement 94 of preferensia somprende a hydraulically and pneumatic cylinder / piston shell which are conestan at its bottom end to the floor 96. In Figure 5, the upper mold 74 is illustrated in its elevated configuration is the piston / slug socket 94 which is in the retracted configuration. In the elevated configuration of the upper mold 74, the carriage 8 can move from an upstream part of the tunnel kiln 2 in position below the upper mold 74 before the subsequent pressure bending operation. The counterweight 92 is provided with a desired weight to minimize the required work that is engaged by the piston / shank shoulder 94 in raising and collapsing the upper mold 74 but it is the sounding that in the failure case of the piston strut / 54, the weight of the first counterweight 92 is sufficiently high, such that the entire apparatus surely fails to pull the upper mold structure 74 upwards, away from the carriages 8 passing underneath. A second shrinkage crust is also stretched to allow the upper mold 74 to rest on the glass sheets 4 during the bending step are pressure is a predetermined net weight, a rigid metal rod 98 extends upwards away from the center of the bend. the upper surface 100 of the subframe 78 for the upper mold 64. A second wire 102 is conestablished to the upper part of the rod 98 and extends sussively through orifices (not shown) in the upper frame 80 and the tesho of the upper frame 80. oven 88, and thence on a pair of pulleys 104, 106 to be set at its other end are a second skin 1010 that is free to move vertically. If desired, for both the first and second straps 92, 108, rails or vertical supports (not shown) can be provided to avoid lateral movement of the sleeves 92, 108. The second strand 108 has a specific weight that is chosen to provide A predetermined net weight specific to the combined structure of the upper mold 74 and sub-frame 78 to the sual is mounted to the mold 74. The net weight of the upper matrix shrinkage, typically is 50 to 10 kilograms detaching from the mold configuration partisular and the desired size and shape of the folded glass sheets. The saber 102 between the second thinner 108 and the upper mold 74 is always in tension. The metal rod 98 is provided between the saber 102 and the sub-frame 78, in order to redress the stretching or warping of the saber 102 in the case of the upper mold 74, where the ambient temperature in the pressure zone is high. The saber 86 between the mounting frame 80 and the first light weight 92 is also always in tension. As it is disengaged to sontinuation, during the bending stage they are pressure, the chains 82 are left in such a way that during the bending operation they are pressure, it is only the net weight of the upper mold 74 and its associated sub-frame 78. which is apliped to the upper surface of the glass sheets 4. On opposite sides of the upper mold 74 and adjacent there is provided a plurality of adjacent spacing devices 109. Each of the spacing devices 109 includes an upper stop member 110 which protrudes a vertical body 112 having fixed at its bottom end, a substantially horizontal plate 114. The upper stop members 110 are mounted firmly in the sub-frame 78. A corresponding plurality of lower stop members 116 of the spacing devices are mounted on the base 12. Each lower stop member 116 comprises a body extending up to 118, which has a member mounted on its upper end. vertisally adjustable passer 120. As illustrated, more detail is given to Figure 7, the spacer member 120 includes a bolt portion 122, which has a doming portion 124, substantially hemispherical and the upper portion of which is disposed , during the pressure bending operation, for leaning against the lower surface 126 of the plate portion 114 of the respective upper stop member 110. The bolt portion 122 is threaded into the upwardly extending body 118 to be easily adjustable in height and a threaded nut 128 is provided to allow fixing the domed head portion 124 at the required height. Preferably, the plate portion 114 and the head portion dome 124 are composed of steel. The upper and lower limit stop members 116 are provided in register in pairs, preferably, three pairs of stop members 110, 116 are provided. With such a configuration, as illustrated in FIG. 4, two pairs of stop members are provided on a long edge 117 of the spaced-apart mold 10 and a third pair of stop members 110, 116 are provided centrally on the opposite long edge 119. of the mold 10. The spacing devices 109 are provided to ensure that the upper and lower molds 74, 10 are substantially substantially spaced apart over their entire area by a spacing corresponding to the thickness of glass sheets 4 in their final shaped form. This ensures that any excessive pressure from the glass sheets 4, which may result in marking the glass sheets 4 by the annular rim 30, is substantially avoided. As described in detail below, three spacer devices 109 are preferably provided, such that it is ensured that the vertical position of the upper mold 74 relative to the lower gravity bending mold 10 is determined without the relative relative oscilloration of the molds 74, 10. This increases the possibility that corrected spacing is achieved reliably. Since they are the width of the bending arms 32, it is necessary that the spacing devices 109 be adjusted by an operator while the apparatus is cold, but the spacing devices 109 must ensure spacing of the upper mold 74 and the lower mold 10 at high temperatures. during the bending operation they are pressure, which may involve an asymmetric expansion or other deformation that is the result of thermal insulation. The proportioning of three pairs of stop members 110, 116 ensures that the spacing between the upper and lower molds 74, 10 can be reliably adjusted without any ossication of the upper mold 74 relative to the lower mold 10 in the configuration of bending by final pressure of the molds. molds 10, 74.

It will be expedient that in a typical tunnel furnace 2, a plurality of taps 8 is provided, each containing a mold of bending by gravity 10. A tipiso 2 furnace includes at least 20 scaffolds 8 / bending mold by gravity 10. However, only an upper pressure bent mold 74 is provided. It is necessary to perform an operation by the lower bending mold 10, and its associated carriage is suitably configured with respect to the bending mold by upper pressure 74. Accordingly, this is the spacing device 109 to define the adjustable spasm sorresto between the molds. 10, 74 are provided in conjunction with each mold bent by resurfacing gravity 10, such that each bending mold by gravity 10 can be individually configured to operate in the form of sorresta are the upper smooth mold 74. Each spacing device 109 is individually adjusted before of the furnace in-house operation such that during the pressure bending pressure, when the upper mold 64 collapses on the glass sheets 4 transported in the mold bent by gravity 10, the upper and lower molds 74, 10 are spaced apart Correspondingly to each other a distance corresponding to the thickness of the glass sheets 4 in its final folding form. The bending operation is now described as referring to Figure 6. When the lower mold 10 carrying the glass sheets 4 is presented below the upper mold 74, the piston / cylinder cussion 94 is actuated to lower the frame lower 80 supporting the upper mold 74, until the upper edge 74 is in contact with the underlying glass sheets 4 in the bending mold by gravity 10. The stroke of the piston / cylinder structure 94 is larger than just required To overcome the sontasto of the upper mold 74 are the glass sheets 4. The support frame 80 thus overstressed so as to be folded down after sontasing the upper mold 74 are the glass sheets 4 in such a way that the supporting frame 80 has collapsed in order to be closer to the subframe 78 than in the initial configuration illustrated in Figure 5. This excessive demolding of the support frame 80 is provided by the chains 82 They are slack. In this configuration, the upper mold 74 and its associated subframe 78 lie downwardly in the glass sheets 4 are the desired net weight that is chosen by appropriate selection of a particular weight for the second skin weight 108. The upper mold 74 in this way press the upper surface of the glass sheets are a pre-determined net weight. Furthermore, since the upper mold 74 is not supported from above during the pressure bending operation, at least at the end of the pressure bending operation, the weight of the upper mold 74 is evenly distributed across all the surfaces. of sound, typically over an area of about 1 m2, the upper mold 84 and the sub-acute glass sheets 4. This ensures uniform distribution of weight on the glass sheets 4 during the bending operation are pressure. The bending operation is operasión typically lasts 20 seconds. At the end of the bending operation are pressure, where the glass sheets have been pressed intimately around the entire periphery are the lower bending mold 10 by the upper mold 84, for one of the spacing devices 109 The dome is supported by the plate member 114 to define through substantially the entire area of the pressure bending mold, a pre-adjusted spacing between the upper and lower molds 74, 10 corresponding to the thickness of the sheets of glass bent by pressure. Providing the stop member ensures that no excessive pressure is exerted on the glass sheets 4 during the bending operation is pressure. This minimizes edge edging of the inner surface of the glass sheets 4 by the annular rim 30 of the bending mold by gravity 10., which is a partisan problem suando employs a mold of bending by gravity that has thin ridges are a thickness in the order of approximately 3 to 4 mm. According to the invention, the method of the preferred embodiment of the present invention, in the step of bending by pressure, the process parameters of the step of bending by pressure, for example temperature, time, etc. and the mechanical apparatus, in particular the sonfiguration of the bending mold by lower gravity and the sonfiguration and net weight of the upper bending mold, are soordinated in order to provide improvements against methods of the previous tress. These improvements are manifested not only in better sonrolability of the bending stage by pressure but also potent improvements in the output of the products that are made by the method of glass bending. Figure 8 illustrates a tipisa relation between temperature and time in a modality of a sanding glass bending process are the present invention. In Figure 8, and the following temperature reflection of the glass sheets, it will be understood that referensias at temperature are those porsiones of the sheets of glass that require to be deep folded by the process of bending are subsysuente pressure. The average glass temperature of the entire sheet will be less than the temperature speci fi ed in those porsiones that are intended for deep bending. The blowout zone is configured to allow the required distribution of temperature over the area of the glass sheets to be achieved easily, for example by differential blow-off. In a preferred embodiment prior to the pressure bending operation, the sub-eden glass sheets 4 can be vented by a tesho-scale to provide a differential temperature profile on the surface of the glass sheets 4 to assist the sheets of glass. 4 glass that reach the required shape during the operation of bending by pressure.

This teasing differential teasin is described in European Patent Application Co-pending No. 94309435.9. It will be seen from Figure 8 that the temperature varies in general are the three sonsesutive stages of (a) bending by gravity of the glass sheets in a bend zone by sorptive gravity above the furnace, (b) bent by sheet pressure bent by gravity in a bend zone by pressure downstream of the furnace; and (c) cooling the glass blades still in an adisional downstream sorbent zone. In the area of bending by gravity, the temperature of the glass sheet is inset during the bending stage by gravity and sonforme the sheets of glass folded by gravity leave the bending zone by gravity, the temperature of the porsiones of the leaves of glass that will bend deeply is maximized at a temperature Tmax. For any configuration of glass sheets are folded partisular, the value of Tmax is ensued within a relatively small range that is determined by the suitability of the glass forraa for any somposission and thickness of determined glass sheet. Typically, the deep bending portions of the glass sheet are at a maximum temperature of about 625 to 640 ° C, when the glass sheet leaves the bending zone by gravity. It is required that the temperature of the glass sheet in the area of bending by gravity be sufficiently high to ensure that the viscosity of the glass sheet is sufficiently low to allow the sheet to buckle surprisingly to its desired shape. However, if the temperature is too high, the optical savities of the resulting produst may be degraded. Typically, the ambient temperature in the bending zone by gravity is around 650 ° C. As the glass sheet enters the bending zone under pressure, the glass sheet immediately begins to cool as illustrated in Figure 8. According to the method of the present invention, the cooling velocity of the glass sheets in The area of pressure bending is controlled to maintain a relatively low value. After the glass sheets have been present in the bending zone by pressure for a period of time within the sual, the glass sheets have been soldered under the upper pressure bending mold 74 and the mold 74 has been lowered in order of being in sontasto are the upper surface of the glass sheets, this period is referred to as the stretching time T-dra, initiates the operation of bending by pressure. The pressure bending operation is continuous for a T-press period as illustrated in Figure 8, after which the matrix is removed from the glass sheets. The stretching time is determined by the mesaniso transport system for the female molds, to allow the glass sheets to move out of the bending zone by gravity and the position below the upper mold and the time to begin the operation of the upper mold. The ambient temperature in the pressure bending zone is shortened to be relatively high, typically 500 to 600 ° C, more typi- cally 550 to 580 ° C. This allows the cooling velocity of the glass sheets to be braked in a controlled manner as they are subjected to the use of a lower ambient temperature in the area of pressure bending. The pressure bending operation is optimally sampled within a relatively high temperature range for the porsiones of the glass sheets to be bent by pressure. For example, in Figure 8, bending is stressed by pressure at a temperature Tstart, and ending at a lower temperature Tstop. The range of temperature in the sual leaves are doubled by pressure controls the transient stresses induced in the glass sheets during bending by pressure. If bending by pressure is carried out at a relatively high glass temperature, then the glass tends to be softer and any induced stresses in the glass sheets during the pressure bending operation relax more easily because the constant tension relaxation time is more heavy at higher temperatures. In this way, according to the preferred method of the invention, the pressure bending step is carried out at a relatively high pressure bending temperature, in the area of pressure bending. When the matrix is removed from the glass, the glass sheet retains the desired bent form, because the transient pressure tensions have been relaxed, and also the glass temperature is sufficiently redressed, so that greater bending does not occur by gravity . This requirement for the temperature of the glass sheets which is relatively high during bending by pressure can potentially prevent the sontrol problems due to the necessity of the bending by bending the glass sheets before they have left the bending zone by gravity. , such that the glass sheets do not cool below the bend temperature zone are preferred pressure. However, by maintaining the ambient temperature in the bending zone by relatively high pressure, the cooling velocity of the glass sheets is slowed down and this in turn provides a large window of time within the area of the pressure bending operation. It can be done satisfyingly. According to this, when the cooling velosity of the glass sheets is controlled by the entrance of the glass sheets in the area of pressure bending, improved sound quality of the pressure bending operation is provided, due to the fact that There is greater freedom of time for the operation of bending by pressure to be performed. In addition, providing a relatively high temperature during bending by pressure in a time-controlled manner allows the glass to be relatively slowly bent. This is preferred due to the use of a relatively slow pressure bending step tends to provide reduced transient pressure stresses that are induce in the glass sheets. Typically, the period of pressing between T-start and Tstop as illustrated in Figure 8 is up to 20 seconds, more preferably 10 to 15 seconds. This supply of the installation for longer periods of pressed in turn, allows a relatively light weight matrix in somparasión are those typically used in bending by pressure is used. Typically, the press twill that is flattened to the upper mold is 100 ± 50 kg, more typically 50 to 100 kg. The pressure twill is chosen depending on the particular mold configuration and the desired size and shape of the folded glass sheets. The use of a relatively lightweight pressure load in turn leads to reduced incidence of glass sheet breakage or transient pressure stresses induced in the glass sheets and also reduces the tendency for the glass sheets marked by the molds , in particular the lower mold when the lower mold comprises a conventional convex bending mold having the preferred thin annular rim as previously pre-sharpened with thickness of about 3 to 4 mm. A light weight pressure load also reduces wear and maintenance of tools under pressure are the use of heavier sergers that are typically used in pressure bending devices. After the step of bending by pressure, the glass sheets are cooled in a sonolable manner in the areas of bending by pressure. The maintenance of a relatively high ambient temperature in the area of bending by pressure, controls the cooling velosity following the bending by pressure in such a way that the glass sheets are maintained at a sufficiently high temperature during this continuous cooling to allow relaxed of any kind. stresses that have been induced in the glass sheets during the bending operation by pressure and also resoser the glass sheets. This controlled cooling allows the control of residual area voltages in the glass sheets, partially on the edges of the glass sheets to allow the resulting laminated produst to meet the requirements of the vehicle manufacturer. Preferably, in the pressure bending zone, the average cooling velocity of the glass sheets is less than 50 ° C per minute, and more preferably up to about 30 ° C per minute, even more preferably from about 10 ° to 20 ° C. C per minute This supply of a cooled cooling velocity in the bending zone by pressure by the use of high ambient temperatures in the bending zone by pressure, relaxes the synchronization requirements of the bending operation by pressure and the speed within from which the pressure bending operation is initiated and carried out This also allows the glass sheets to be removed from the bending furnace by gravity at a relatively lower temperature for the deep bending portions in the range for example from 625 at 640 ° C, which would otherwise be required to maintain a range of bending temperature by partial pressure without the use of a braking cooling range, which in turn can improve the optimum output of the glass sheets. This relaxation of the requirements of synchronization allows a matrix of relatively light weight to be used, which can improve the physical and optical sarasteristisations of the resulting pressure-bent glass sheets. The glass sheet is then removed from the bending zone by pressure to a cooling zone where the glass sheets are allowed to cool to a higher cooling velocity than in the bending zone by pressure. If desired, the cooling velocity in the cooling zone can be controlled by the low level radiant heating supply. The cooling rate is controlled in such a way that any area voltages and tempering stresses induced in the glass sheets are within the predetermined ranges. However, once the glass sheets are below about 500 ° C, which is less than the glass tension point, then the cooling velosity can be relatively high without introducing undesirable stresses in the glass sheets . According to the preferred method of the present invention, the ambient temperature in the area of pressure bending is maintained at a high level. This in turn provides the upper mold with a relatively high working temperature without separate heating elements for the upper mold being required. This provides the advantage of the reduced capital cost of the upper mold. In the bending furnace by gravity and the area of bending by pressure, the ambient temperatures are sonolated. For example, by the supply of outgoing air burners or radiant showerheads. In the cooling zone, sonoside cooling configurations can be employed, for example the supply of black surfaces to receive radiation from the cooling oven sheets and the supply of air flows behind the oven tesho, to remove salor from the zone. Cooling. Again, reference is made to Figure 6, the spacing devices 109 are specially configured to allow several shifts in the lateral positions of the upper mold 74, and the lower mold 10, because the dome 124 is capable of coupling the plate member 114 on a select range of lateral positions encompassed by the area of the plate member 114. This allows precise spacing of the molds to be achieved despite possible multiple slices in the positions of the plurality of bending molds 10 around the bending busle . This stress does not restrict the lateral freedom of the solecation of the upper matrix 74 during bending by pressure. The upper mold 74 is supported by the support frame 70 by chains 72, they are what the upper mold 74 is not restricted in the lateral movement of translational and rotasional during the bending operation are pressure. Still further, the support frame 80 is suspended from the saber 86 which in turn does not restrict the upper mold 74 while the lateral movement during the bending operation is pressure. In addition, supporting the upper mold 74 on the one hand is a plurality of strings 82 to a support frame 80 and on the other hand to a saber 86 between the support frame 80 and the pulley 86, allows a vertical movement without restricting, for example inslinasión, of upper mold parts 74 during the bending operation are pressure. The upper mold 74 is required to be accurately soldered one by one of the plurality of molds bent by gravity 10 in the entire loop including the tunnel furnace. In the prastisa, the translational position, both horizontally and vertically and the position of rotation, both horizontally and the inclination of each bending mold by gravity 10, will vary from one tartar to another, not only following the inisial sonfiguration of the furnace but also also in partisular after operasión of the furnace. This is due to thermal expansion, deformation as a result of thermal insulation and wear of the appliance, for example, wear of tartar sheets on the rails. Since the upper mold 74 is allowed to lodge in the shape bent by gravity of the glass sheets 4 during the bending operation by pressure without any restriction of its insular or lateral movement, the upper mold 74 can easily sculpt its position The bending to be bent are pressure presiso are respect to the glass sheets subyasentes 4 independently of the several in position respects the upper mold 74 of those sheets of glass 4 from a mold bent by gravity 10 to another. This freedom of movement in the upper mold 74 during the pressure bending operation ensures that bending is achieved by pres- sure, regardless of any number of positions in between the plurality of lower gravity folding molds. The suspension of the upper mold 74 by bending members such as saws 82, allows this movement without restriction. In addition, the upper mold 74 is supported by the sails 82, it is that the upper edge 74 can be wound in a minor propulsion slightly in sontasto are the sub-eve glass sheets 4. This allows the required shape of the sub-eve glass sheets 4 to be achieved is a progressive push ass as a result of The upper matrix progressively progresses in sontaste to the sub-acute glass sheets 4. Preferably, the upper mold 74 is wound on the upper glass surface, so that the deep-bending porsions are first formed by the upper mold 74. The proportioning stop member in which the lower stop member includes a hemispherical dome and the upper stop member consists of a flat plate, the sual resting on the dome, ensures a reliable relative vertisal solosation of the upper mold and the lower mold, for Minimize the steepness of the glass sheets by the bending mold by gravity 10. However, this is achieved without removing or redressing the The upper mold 74 moves laterally in both the translational and rotational directions and to be vertically insensitive to the lower edge 10 and the glass sheets 4 in an unrestricted form, during the bending operation are pressure. The present invention can allow glass sheets to be fabricated are bent porsiones having spokes as small as 150 mm. This can be done with a minimum radius of 450 mm, used when bending by gravity using different blasting of the glass sheets and a minimum radius of 1000 mm suando is used by bending by gravity without differentiation. The present invention allows glass sheets to be fabricated. Deep bending porsiones are edge tensions that are compared to those that are achieved using bending techniques are soncionalesional bending. The present invention typically allows bent glass sheets to be fabricated by edge transitions below 7 MPa. This allows glass sheets to be folded, without requiring a subsequent resoside to remove stress, after the step of bending with pressure.

Claims (21)

1. RJJIVIMPICACIQWES 1. A method for bending glass sheets, the method is sarasterized because it stages the steps of: bending by gravity a sheet of glass at high temperature in a mold of bending by gravity, in a zone of bending by gravity of a furnace, bending by pressing the glass sheet bent by gravity to a desired shape are a top mold while the glass sheet is held by the mold bending by gravity as a lower mold in a zone of pressure bending of the furnace and cooling the sheet of glass in the area of bending by pressure when the glass sheet enters the area of bending by pressure to a velosity of regulated cooling, to the sontrolar the room temperature in the area of bending by pressure.
2. 2. A sonification method is claim 1, which is sarasterized because the ambient temperature in the pressure bending zone is sonroled to be in the range from 500 to 600 ° C.
3. 3. A sonicity method is claim 2, which is sarasterized because the ambient temperature in the pressure bending zone is sonroled to be within the range of 550 to 580 ° C.
4. 4. A sonicity method is any one of claims 1 to 3, sarasterized because the cooling velocity of the glass sheet in the pressure bending zone is shortened to be up to 50 ° C per minute.
5. 5. One method of sonification is the claim 4, characterized in that the cooling velocity of the glass sheet in the pressure bending zone is shortened to be up to 30 ° C per minute.
6. 6. A method of soundness is the claim 5, characterized in that the cooling rate of the glass sheet in the area of bending by pressure is controlled to be from 10 to 20 ° C per minute.
7. 7. A method of conformance to any of the preceding claims, which is sarastered because the pressure bending step is carried out for a period of up to 20 seconds.
8. 8. A method of sonification is claim 4, which is sarasterized because the pressure bending step is carried out for a period of 5 to 15 seconds.
9. 9. A sonicity method is claim 4, which is sarasterized because the pressure bending step is carried out for a period of 10 to 15 seconds.
10. 10. A sonicity method is any of the preceding claims, which is sarasterized because the upper mold applies a press twill to the upper surface of the glass sheet from 50 to 150 kg.
11. 11. A sonicity method is claim 10, which is sarasterized because the upper mold applies a pressure serge to the lower surface of the glass sheet from 50 to 100 kg.
12. 12. A method of sonification with any of the preceding claims, which is sarasterized because during the step of bending by pressure, the upper mold rests on the sheet of glass are a net weight selessionado.
13. 13. A method of soundness is any of the presedent claims, which is sarasterized because the upper mold is adapted to be folded on the upper surface of the glass sheet by a suspension system which is configured to allow lateral movement and inslination of the upper mold respecting the mold bent by gravity that transports the glass sheet.
14. 14. A sonicity method is any one of the presssing demands, sarasterized because at the end of the pressure bending step, the upper mold and the gravity-bent mold are spaced apart from one another by a plurality of spacing devices which are to allow lateral movement of the upper mold respects the mold of bending by gravity.
15. 15. A method of soundness is any of the preceding claims, characterized in that the temperature of the portion of the sheet of glass to bend, when entering the area of bending under pressure from the area of bending by gravity is 625 to 64? "C.
16. 16. A method of sonification is any of the presedent claims, sarasterized because the gravity bending mold comprises an artisulated mold having an annular rim that rests against the lower surface of the folded glass sheet, the annular bead having a thickness of 3 to 4 mm.
17. 17. A method for bending by pressing sheets of glass, the method is sarasterized because it is necessary to provide a glass sheet that is not completely bent, that is transported in a mold of bending by gravity artisulated and bending by pressing the glass sheet at an ambient temperature from 500 to 600 ° C, to a form of final bending by a bending mold are upper pressure that collapses on the upper surface of the glass sheet, the bending mold are upper pressure has a net weight from 50 to 150 kg.
18. 18. A dsformity method is claim 17, which is sarasterized because pressure bending is carried out at an ambient temperature of 500 to 580 ° C.
19. 19. A method of sonification is the claim 17 or are the claim 18, sarasterized because the step of bending by pressure is carried out for a period from 5 to 15 seconds.
20. 20. A folded sheet of glass produced by the method of any previous claim, the glass sheet is sarasterized because it has a maximum tension of the area of transssion of less than 7 MPa.
21. 21. Use in the area of bending by pressure of a glass bending furnace, this area is sorptive below a bending area by gravity of the furnace, from an ambient temperature from 500 to 600 ° C to test the cooling velosity of the glass sheet in the area of pressure bending within the range of up to 50 ° C per minute.