Method and apparatus for manufacturing a bent glass sheet

Abstract: The invention relates to a method and apparatus for manufacturing a bent glass sheet. A glass sheet (9) carried by roll­ ers (7) included in a furnace (1) is trans­ ferred onto rollers (8) of a bending mould (10) included in a mould station (3) built as a part of the furnace. By adjusting the position of rollers (8) of bending mould (10) in vertical direction a glass sheet is bent to a desired curvature while heating it in furnace mould station (3). The roller mould (10), along with its bent glass sheet (9′), is carried out of furnace (1) and into a chilling station. When using a transferable and adjustable roller mould (10), the apparatus does not set limitations for the size or degree of bending of glass sheets to be bent.

Description: The present invention relates to a method of manufacturing a bent glass sheet, said method comprising heating a glass sheet in a furnace upon rotating rollers, bringing the glass sheet onto a bending mould positioned in the furnace, bending the glass sheet in the furnace to the configuration of the bearing surface of the bending mould, and carrying the bending mould out of the furnace after the bending operation and into a chilling section together with said curved glass sheet. The invention relates also to an apparatus for manufacturing a bent glass sheet, said apparatus comprising a furnace provided with a conveyor formed by rotating rollers and heating means for heating a glass sheet carried on the rollers close to the softening temperature of the glass, and a bending station located inside the furnace and provided with a bending mould having a curveable bearing surface, said mould being transferable out of the furnace while carrying a glass sheet bent to a given curvature. The bending of architectural glass is becoming more popular, but it has been problematic to obtain a sufficient capacity due to the bending/tempering of large glasses. This problem has been solved by the subject matter of claims 1 and 10. Prior known is the bending of a glass sheet in a furnace by using curved rollers or rolls. However, such a method has been restricted to the bending of small glasses and the bending of large building glasses (e.g. 2 x 3 mm) e.g. to an arch corresponding to a 90° sector is not possible. For example, US Patent specifications 3 846 104 and 4 437 871 disclose the bending of a glass sheet in a furnace between shaping surfaces, the upper shaping surface serving also as a vacuum pickup. A glass sheet is carried upon the lower mould from the furnace to an annealing operation. Such particular mould structures are suitable for bending rather small glass sheets such as windshields but not for bending major architectural glasses to a curvature with a rather large sector angle. US Patent specification 2 223 124 discloses the bending of a glass sheet with a roller mould by adjusting the position of rollers in vertical direction. The rollers are not associated with a displaceable roller mould but are disposed in a space for effecting therein both heating and tempering. Since a glass sheet is heated and tempered in one and the same space, the apparatus is not fit for continuous production but, instead, is very slow indeed. It is not capable of a capacity required by modern production. Prior known is also a bending/tempering operation effected outside a furnace by using a curveable roller conveyor as a bending mould (EP-A-0261611). Also this method is restricted to the production of relatively small glass sheets and is not suitable for manufacturing the above-described large bent glasses. In addition, especially the bending of thin glass sheets cannot be managed with an acceptable tempering result as thin glass will be necessarily cooled before a tempering blast is started. The method and apparatus of the invention are capable of eliminating the above limitations and drawbacks. One embodiment of the invention will now be described in more detail with reference made to the accompanying drawings, in which fig. 1 shows the downstream end of a glass-bending furnace of the invention in a vertical section at the outset of a bending operation. Fig. 2 shows the same as fig. 1 but at the finishing stage of a bending operation. Fig. 3 shows the apparatus schematically in plan view and partially cut away. Fig. 4 shows a bending station included in a bending furnace in cross-section, and fig. 5 shows a driving mechanism for a bending mould roller. A furnace 1 is divided with a partition 4 into two sections 2 and 3. The furnace section 2 includes longitudianl heating resistances 5 and the furnace section 3, which serves as a bending station for receiving a bending mould 10, includes transverse heating resistances 6. The heating resistances 6 is mounted on the top section of the bending station 3 and adapted, if necessary, to be capable of applying the heat to a desired point either by using a matricewise adjustable resistance zone or movable heating resistances or a combination thereof. Naturally, it is also possible to employ convection heat (hot-gas blowing) for applying the heat to a desired area on a glass sheet 9 being bent. In the furnace section 2, a glass sheet 9 is carried on a conveyor formed by rollers 7. The rotation of rollers 7 is preferably reciprocal with glass sheet 9 also moving back and forth i.e. it is oscillating. The stroke length of this oscillating movement can be equal in both directions or the stroke can be longer in advancing direction, whereby successive glass sheets are gradually indexing forward in furnace section 2 while oscillating at the same time. Through an opening 4a said glass sheet 9 can be advanced into the bending station 3 which comprises a bending mould 10 having its rollers 8 substantially level with other rollers 7 located in furnace 1. Thus, rollers 8 participate in forwarding a glass sheet 9 and the glass sheet can be transferred directly onto the rollers 8 of the roller mould 10 with a single advancing stroke during which the rotation of the rollers 7 and 8 is synchronized to the same peripheral speed. However, the invention is not limited to this case but, instead, said rollers 8 of the roller mould 10 can also extend in the longitudinal direction of furnace 1. This requires, however, separate transfer roller systems between the rollers 7 and 8 or some other separate transfer mechanism (e.g. a suction pad carrier) for bringing a glass sheet upon the roller mould 10. The rollers 8 of the roller mould 10 are adjustable in vertical direction in a manner that the configuration thereof forms a desired arch, e.g. a segment or segments of a curcular arc. Rollers 8 are supported at the ends thereof by means of movable rods 12. Rods 12 extend through an insulating floor 11 included in the mould 10, the actuators for operating said rods 12 and for driving said rollers 8 being located beneath that floor. As shown in fig. 4, the bottom portions of rods 12 associated with the opposite ends of roller 8 are connected with a beam 19 provided with a threaded sleeve for engaging the threading of a lifting screw 18. A pulse-controlled stepped motor 17 drives said lifting screw 18 through the intermediary of a gear 17'. As shown in fig. 5, said rod 12 comprises a sleeve 13 having a shaft 14 rotatably journalled therein. The shaft 14 is driven by an electric motor 15 and the rotating motion is transmitted to the roller 8 by a bevel gear 16. Said actuators for the driving rollers 8 and for adjusting a vertical position are all mounted and fitted on a common frame for providing a separate, displaceable bending mould 10 whose rollers 8 make up a glass-sheet bearing shaping surface. The roller mould 10 is mounted by means of wheels 21 on the rails 20 for carrying the roller mould therealong out of the bending station 3 of the furnace 1 and into a tempering and chilling station 23 (fig. 3). The electric power and control required by roller mould 10 is supplied by means of a flexible cable 24. The bending station 3 is provided with side walls 22 adapted to be ascendable and descendable in vertical direction for carrying roller mould 10 out of bending station 3, When said roller mould 10 is positioned outside of the bending station 3, another roller mould 10 can be brought over to replace the first roller mould in the bending station 3. Alternatively, if just one roller mould 10 is employed, with said roller mould partially or completely outside of the bending station 3, said bending station 3 can be provided with a heat-transfer preventing flat interlayer to replace roller mould 10, said layer being located close to the level of rollers in the vertical direction of the furnace. Thus, the interlayer would primarily serve the same purpose as floor 11 (without lead-in bushings 11a). When a flat glass sheet 9 to be bent has been carried onto the rollers 8 of a bending mould 10 included in the bending station 3 (fig. 1), the lifting of rollers 8 is initiated at a lifting speed matching a desired final curvature while said rollers 8 are rotated back and forth during bending. This oscillating motion obtained in a glass sheet 9' by means of the reciprocal rotating motion of rollers 8 can be totally independent of the oscillating motion of the other section 2 of furnace 1 produced by rollers 7. Thus, a glass sheet 9' to be bent can be oscillated through a distance substantially shorter than that covered by a glass sheet supported on rollers 7. Thus, it is possible to minimize the number of rollers 8 as well as the number of separate mechanisms required for their operation. The above-described structure makes it possible to adjust the vertical position of rollers 8 independently of each other. Thus, the motors 17 are each separately controlable by means of a control program, whereby the bending can be effected to any desired curvature while the curving speed of various sections of a glass sheet can be freely selected. Thus, the only dependence between the controls of motors 17 is that required by a control program which is freely selectable and variable by means of a digital control program. It is quite obvious that the invention is not limited to the above embodiment but its structural design can be varied in many ways. For example, the lifting mechanism of rollers 8 can be provided with a motor 17 at both ends of rollers 8, or a single motor 17 can drive two lifting screws 18 which are mounted directly in connection with rods 12.

Claims: A method of manufacturing a bent glass sheet, said method comprising heating a glass sheet (9) in a furnace (1) upon rotating rollers (7,8) bringing the glass sheet (9) onto a bending mould (10) positioned in the furnace (1), bending the glass sheet (9) in the furnace (1) to the configuration of the bearing surface of the bending mould (10), and carrying the bending mould (10) out of the furnace (1) after the bending operation and into a chilling section (23) together with said curved glass sheet (9'), characterized in that during said bending operation, said glass sheet is carried upon rotating rollers (8) comprised in the bending mould (10), that the curving of said glass sheet is achieved by adjusting the position of the rollers (8) of the bending mould (10) in a substantially vertical direction in a manner that the locations of the rollers (8) match a given curved configuration, and that after the bending operation said bending mould (10) is carried out of the furnace (1) while its rollers (8) support the curved glass sheet (9'). A method as set forth in claim 1, characterized in that during the bending operation, said bending mould (10) is held in a bending station (3), located in the furnace and separated with a partition (4) from the other section (2) of the furnace (1), said bending station (3) being used for heating said glass sheet prior to and during said bending operation. A method as set forth in claim 1 or 2, characterized in that said rollers (7 and/or 8) in the furnace and/or bending station are reciprocally rotated for creating a reciprocal or oscillating motion. A method as set forth in any of claims 1, 2, or 3 characterized in that said rollers (8) of the bending mould (10) located in the bending station (3) are held substantially level with the other rollers (7) mounted in the furnace (1), said rollers (8) of the bending mould (10) also participating in forwarding the glass sheet (9). A method as set forth in any of claims 1 to 4, characterized in that during the bending operation said rollers (8) of the bending mould (10) are rotated back and forth independently of the rotating motion of the other rollers (7) of the furnace (1). A method as set forth in claim 5, characterized in that the reciprocating rotating motion of the rollers (8) of the bending mould (10) located in the furnace (1) is used to oscillate said glass sheet (9) through a substantially shorter distance than that effected by the reciprocating rotating motion of said other rollers (7) of the furnace (1). A method as set forth in claim 1, characterized in that the bending mould (10) carried outside said furnace (1) along with its bent glass sheet (9') is transferred to a tempering/chilling station (23). A method as set forth in claim 1, characterized in that as the bending mould (10) is brought outside of the bending station (3) of the furnace (1), another bending mould (10) is carried into said bending station (3) of the furnace (1) to replace the first bending mould. A method as set forth in claim 1, characterized in that as the bending mould (10) is partially or completely brought outside of the bending station (3) of the furnace (1), a heat-transfer preventing interlayer is carried into said bending station (3) of the furnace (1) to replace said bending mould (10). An apparatus for manufacturing a bent glass sheet, said apparatus comprising a furnace (1) provided with a conveyor formed by rotating rollers (7) and heating means (5) for heating a glass sheet (9) carried on the rollers (7) close to the softening temperature of the glass, and a bending station (3) located in the furnace and provided with a bending mould (10) having a curveable bending surface, said mould being transferable out of the furnace (1) while supporting a glass sheet (9') bent to a given curvature, characterized in that the curveable bearing surface of the bending mould (10) comprises rollers (8) whose position is adapted to be adjusted in a substantially vertical direction in such a manner that the rollers take up positions which match with a given curved configuration, and that said bending mould (10) along with its rollers (8) is transferable to a chilling station (23) located outside said furnace (1). An apparatus as set forth in claim 10, characterized in that said bending station (3) and the other section (2) of the furnace (1) are separated from each other with a partition (4) for reducing air circulation as the roller mould (8,10) is advancing out of said bending station (3) of the furnace (1). An apparatus as set forth in claim 10 or 11, characterized in that said roller mould (10), along with its means (14,15,16;17,18) for driving the rollers (8) and adjusting the position of the rollers (8), is transferable outside said bending station (3) of the furnace (1) along rails (20). An apparatus as set forth in claim 12, characterized in that at least one of the side walls (22) of the furnace bending station (3) is vertically ascendable and descendable and that, as the roller mould (10) is located outside of the furnace bending station (3), said bending station (3) is provided with a heat-transfer preventing interlayer which is located close to the level of the rollers in the vertical direction of the furnace. An apparatus as set forth in claim 10, characterized in that for the adjustment of the vertical position of the rollers (8) of the roller mould (10), each roller (8) is provided with its own active vertical-position adjusting means (17,18) for adjusting the vertical position of the rollers (8) independently of each other. An apparatus as set forth in claim 14, characterized in that said adjusting means (17,18) are each separately operable as dictated by a control program.

Inventors: LEPPAENEN JORMA TANELI, MIIHKINEN VEIJO TOIVO TAPANI, LEPPAENEN, JORMA TANELI, MIIHKINEN, VEIJO TOIVO TAPANI, Leppänen, Jorma Taneli
Applicants: TAMGLASS ENG OY, TAMGLASS ENGINEERING OY
Application year: 1990
Main classification: C03B23
IPC codes: C03B23