APPARATUS FOR BENDING GLASS SHEET

Abstract: An apparatus [50] for bending a glass sheet [G; g] has a heating zone [1] for heating the glass sheet [G; g], a shaping zone [3] for shaping the glass sheet [G; g], and a cooling zone [4; 8, 9] for cooling the glass sheet [G; g]. A transfer zone [2] for transferring the glass sheet [G; g] is disposed immediately before the shaping zone [3] with respect to the direction in which the glass sheet [G; g] is fed. The glass sheet [G; g] is fed through the transfer zone [2], the shaping zone [3], and the cooling zone [4; 8, 9] by a ring mold mechanism [14; 114; 214] which supports the glass sheet [G, g] from below.

Description: The present invention relates to an apparatus for bending a glass sheet, and more particularly to an apparatus for bending a laminated glass sheet and reinforced glass sheet which will be used as window glass sheets for automobiles. Apparatus for carrying out such bending of glass sheet is known. In US-A-4 666 492, a glass sheet is heated in a furnace, and thereafter transferred to a shaping station by means of a vacuum platen pickup which attracts an upper surface of the glass sheet. In the shaping station, the glass sheet is disposed on a hammok material which is arranged above a lower mold, and there the glass sheet is positioned by a vision sensor position system. Next, the glass sheet is shaped by the lower mold and an upper mold a lower surface of which is covered by a fiberglass sheet while keeping the hammok on the lower mold. Further, the shaped glass sheet is attracted by the lower surface of the upper mold so that the latter transfers the former onto a ring-like member which then moves the glass sheet to a cooling station. Thus, there remains such a possibility in US-A-4 666 492 that the vacuum platen pickup and/or the fiberglass sheet of the upper mold leave their marks on the upper surface of the glass sheet, and the hammok material leaves its mark on the lower surface of the glass sheet, while the same cannot be satisfactorily shaped into a desired shape. In US-A-4 433 993, at a shaping station, which is arranged at the end of a furnace, conveyer rolls for conveying glass sheets and an upper surface of a lower mold intersect each other so that corresponding grooves are formed on the upper surface. Thus, there remain such a possibility that the grooves leave their marks on a lower surface of the glass sheet when pressing it. It is an object of the present invention to provide an apparatus for bending a glass sheet accurately into a deep and complex configuration, as desired, without leaving unwanted marks on the glass sheet while employing the entire region of shaping molds. According to the present invention, there is provided an apparatus for bending a glass sheet comprising: a heating furnace for heating the glass sheet; a first moving mechanism for moving the glass sheet horizontally in the heating furnace; a shaping zone for shaping the glass sheet, the shaping zone being disposed downstream of the heating furnace in a direction in which the glass sheet is moved; a transfer zone disposed immediately before the shaping zone in the heating furnace; a ring support to which the glass sheet is horizontally transferred from the first moving mechanism in the transfer zone; a second moving mechanism for moving the ring support with the glass sheet supported thereon from the transfer zone to the shaping zone; upper and lower shaping molds for bendingly shaping the glass sheet in the shaping zone; and a cooling zone for cooling the glass sheet shaped in the shaping zone, the cooling zone being disposed outside of the heating furnace contiguously to the shaping zone, characterised in that the glass sheet is supported by the ring support during its shaping. the entire surface regions of the upper and lower shaping molds are used to shape the glass sheet; and the shaping molds are made of a heat resistant material which can be easily machined. The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:- FIG. 1 is a schematic plan view of a glass sheet bending apparatus according to the present invention; FIGS. 2A through 2D are fragmentary cross-sectional views showing progressive steps of bending a laminated glass sheet on the glass sheet bending apparatus of the present invention; FIG. 3 is a plan view of a transfer zone in the glass sheet bending apparatus; FIG. 4 is a cross-sectional view taken along line IV - IV of FIG. 3; FIG. 5 is a front elevational view of a jig for carrying a ring mold into the transfer zone of FIG. 3; FIGS. 6A to 6F are fragmentary cross-sectional views showing progressive steps of shaping a reinforced glass sheet on the glass sheet bending apparatus of the present invention, and FIG. 7 is a fragmentary cross-sectional view of a modified ring mold used in a quenching zone in the glass sheet bending apparatus. As shown in FIG. 1, a glass sheet bending apparatus 50 according to the present invention has a heating furnace 1 with a shaping zone 3 at its downstream end. A transfer zone 2 is disposed in the heating furnace 1 immediately in front of the shaping zone 3. The shaping zone 3 shapes two glass sheets as described later on. From the shaping zone 3, there extends a lehr 4 for annealing a laminated glass sheet thus shaped, in a direction laterally out of the heating furnace 1 and normal to the longitudinal direction thereof; The lehr 4 has a downstream end connected to the transfer zone 2 through a ring support return passage 6. The return passage 6 has an upstream end which immediately follows the downstream end of the lehr 4 and serves as a pickup station 5 for picking up the annealed glass sheet. The ring support return passage 6 has a downstream end which is positioned adjacent to the transfer zone 2 and serves as a preheating chamber 7 for heating a ring support 14 (FIGS. 2A through 2D) up to a predetermined temperature. Primary and secondary cooling zones 8, 9 extend from the shaping zone 3 out of the heating furnace 1. As described later on, the cooling zones 8, 9 are used to manufacture tempered glass sheets. The glass sheet bending apparatus 50 is constructed of the heating furnace 1, the lehr 4, the ring support return passage 6, and the cooling zones 8, 9. As shown in FIG. 2A, for example, a plurality of moving rollers 10 for moving a pair of glass sheets G horizontally in the longitudinal direction of the heating furnace 1 are disposed in the heating furnace 1. As illustrated in FIG. 3, the heating furnace 1 has a pair of side walls 11, which define the transfer zone 2 therebetween, and rotatable drive shafts 12 are rotatably supported on the side walls 11, with rollers 13 mounted on the inner ends of the shafts 11. Similar rotatable shafts are supported on the side walls of the shaping zone 3, the lehr 4, and the return passage 6 along the path of movement of the ring support 14. The ring support 14 placed on the rollers is moved from the transfer zone 2 through the shaping zone 3, the lehr 4, and the return passage 6 back to the transfer zone 2 upon rotation of the rotatable shafts. A jig 15 shown in FIG. 5 is used to carry and place the ring support 14 from the preheating chamber 7 at the downstream end of the return passage 6 onto the rollers 13 in the transfer zone 2. The jig 15 has four hooked fingers 16 for supporting an outer frame 17 of the ring support 14 from below, thus suspending the ring support 14. There are plurality of ring supports 14 circulating through the zones 2, 3, the lehr 4, and the return passage 6, and supplied one at a time to the transfer zone 2. As shown in FIG. 4, the ring support 14 has outer and inner rings 18, 19 disposed inwardly of the outer frame 17. In the transfer zone 2, the glass sheet G is transferred from the moving rollers 10 onto the inner ring 19. The inner ring 19 has wider corners 19a for supporting the corners of the glass sheet pair G, and narrower sides 19b for supporting side edges of the glass sheet pair G. Cylinder units 20 having pushers 21 for positioning the glass sheet pair G are mounted on the outer frame 17. As shown in FIG. 3, three rollers 10a out of the moving rollers 10, which are located in the transfer zone 2, are vertically movable and dimensioned such that they are positioned within the inner ring 19. The rollers 10a receive the glass sheet pair G from the feed rollers 10 when the rollers 10a are in their elevated position, and transfer the glass sheet pair G onto the ring support 14 when they are lowered. The shaping zone 3 has an upper convex mold 22 and a lower concave mold 23 which are vertically movable. The glass pair G is pressed to a bent shape by the molds 22, 23. The molds 22, 23 are made of a heat resistant material which can well be machined. More specifically, the molds 22, 23 are made of a material which can continuously withstand temperatures ranging from about 550°C to 700°C in the heating furnace 1, and which has such a hardness that it can be machined by a sintered carbide cutting tool under numerical control, i,e., a hardness ranging from 2 to 5 as measured by the Mohs scale. Specifically, the molds 22, 23 may be made of one of the following materials: Aluminous cement which contains 40 wt % of Al²O³, 25 wt % of SiO², and 35 wt % of CaO. This material can resist more than 1000°C, and can be used stably at temperatures around 700°C. The Mohs hardness of the material ranges from 2 to 3; Calcium silicate which is capable of resisting 1000°C or more and can be used stably at temperatures around 700°C. The Mohs hardness of this material ranges from 3 to 4. Fused silica which contains 99 wt % or more of SiO³. The fused silica is produced by melting and then cooling silica, and sintering it at 400°C to 800°C so that the specific gravity thereof ranges from 1.0 to 1.9. The fused silica has a Mohs hardness in the range of from 3 to 5. While the fused silica is relatively expensive, it has a thermal coefficient of expansion ranging from 5 x 10⁻⁷ to 6 x 10⁻⁷ which is smaller than those of metals and other ceramic materials. Since the fused silica is subjected to small thermal deformation during usage, the shaping molds of fused silica can shape glass sheets highly accurately. The molds 22, 23 for pressing laminated glass sheets and molds 122, 123 and 222, 223 (described later on) for pressing tempered glass sheets have curved shaping surfaces and can shape glass sheets at their softening point to which the glass sheets have been heated. Therefore, these molds can be used to shape glass sheets in the heating furnace 1 the interior of which is kept at a relatively high temperature. Webs of woven cloth or felt (nonwoven cloth) of silica fibers, glass fibers, carbon fibers, or the like are applied to the shaping surfaces of the molds 22, 23 to prevent the glass pair G from sticking to the shaping surfaces and also from developing strains. The entire upper surface region of the lower mold 23 is used as the shaping surface. A process of successively bending a pair of glass sheets G into a laminated glass sheet, using the glass sheet bending apparatus 50, will be described with reference to FIGS. 2A through 2D. As shown in FIG. 2A, the glass sheet pair G is fed horizontally by the feed rollers 10 to the transfer zone 2 in the heating furnace 1 until the glass sheet G are placed on the rollers 10a in alignment with the ring support 14. At this time, the ring support 14 has been positioned slightly lower than the rollers 10a in surrounding relationship to the rollers 10a. While the glass sheet pair G is being thus moved along, it is heated to around a glass softening temperature point. Then, as shown in FIG. 2B, the rollers 10a are lowered to place the glass sheet pair G on the inner ring 19 of the ring support 14. Immediately thereafter, the cylinder units 20 are operated to position the glass sheet pair G. As shown in FIG. 2C, the ring support 14 with the glass sheet pair G thereon is moved by the shafts 12 and the rollers 13 into the shaping zone 3 vertically between the molds 22, 23. Then, the glass sheet pair G is pressed and bent by the upper and lower molds 22, 23 as illustrated in FIGS. 2D. Immediately before the glass sheet pair G is pressed, the cylinder units 20 may be actuated again to correct the position of the glass sheet pair G. The ring support 14 which supports the shaped glass pair G is then moved from the shaping zone 3 into the lehr 4 by the shafts 12 and the rollers 13, until finally the ring support 14 reaches the glass sheet pick-up station 5 at the upstream end of the ring support return passage 6. During passage through the lehr 4, the glass sheet pair G is annealed in the lehr 4. The annealed glass sheet pair G is thereafter picked up in the pick-up station 5. After the ring support 14 has moved past the pick-up station 5, the ring support 14 is conveyed through the return passage 6 to the preheating chamber 7 at the downstream end of the return passage 6. The ring support 14 is heated to a predetermined temperature in the preheating chamber 7, and then delivered by the jig 15 into the predetermined position in the transfer zone 2 shown in FIG. 2A. The above process is specifically addressed to the formation of a laminated glass sheet for use in an automotive window. An arrangement for bending a tempered glass sheet for use in an automotive window, using the glass sheet bending apparatus 50, will be described below with reference to FIGS. 6A through 6F. In this process, an upper convex mold 122 and a lower concave mold 123 are employed in place of the molds 22, 23 and the cooling zones 8, 9 are put to use. The primary cooling zone 8 serves as a quenching zone. The upper mold 122 is connected to a vacuum pump (not shown) for attracting a shaped glass sheet g to the lower shaping surface of the upper mold 122. The shaping surface of the upper mold 122 has a plurality of holes (not shown) defined therein for exerting a vacuum pressure there through to attract the glass sheet g. The entire upper surface region of the lower mold 123 is used as a shaping surface. A first ring support 114a is disposed between the transfer zone 2 and the shaping zone 3 for reciprocating movement therebetween. The rollers 10a are vertically movable and dimensioned such that they are positioned within an inner ring (not shown) of the ring support 114a. The first ring support 114a is of a configuration shallower than the final product configuration of the glass sheet g so that the first ring support 114a pre-shapes the glass sheet g. The heating furnace 1 has an outlet 30 which is openable and closable by a vertically movable shutter 31. Between the shaping zone 3 and the primary cooling zone 8, there is disposed a second ring support 114b reciprocally movable between these zones with the shutter 31 lifted. The second ring support 114b is of a configuration identical to the final product configuration of the glass sheet g. The primary cooling zone 8 has an upper box 33 and a lower box 34 which communicate with a source of air under pressure. Nozzles 15 are mounted on the entire lower surface region of the upper box 33 and nozzles 16 are mounted on the entire upper surface region of the lower box 34. The nozzles 15, 16 apply air under pressure to the surfaces of the shaped glass sheet g. A process of bending a tempered glass sheet for use in an automotive window using the heating furnace 1 and the cooling zones 8, 9 will be described below. The first ring support 114a is substantially structurally identical to the ring support 14 shown in FIGS. 2A through 2D and 3. As shown in FIG. 6A, a single glass sheet g is fed horizontally by the feed rollers 10 to the transfer zone 2 in the heating furnace 1 until the glass sheet g is placed on the rollers 10a in alignment with the first ring support 114a. At this time, the first ring support 114a has been positioned slightly lower than the rollers 10a in surrounding relationship to the rollers 10a. While the glass sheet g is being thus fed along, it is heated to around a glass softening temperature point. Then, as shown in FIG. 6B, the rollers 10a are lowered to place the glass sheet g on the inner ring of the first ring support 114a. Immediately thereafter, the cylinder units (not shown) are operated to position the glass sheet g. As shown in FIG. 6C, the first ring support 114a with the glass sheet g placed thereon is moved by the shafts 12 and the rollers 13 between the upper and lower molds 122, 123. While the glass sheet g is being fed from the zone 2 to the zone 3, it is pre-shaped. As shown in FIG. 6D, the glass sheet g is pressed and bent by the upper and lower molds 122, 123 in the shaping zone 3. Thereafter, as shown in FIG. 6E, the shaped glass sheet g is attracted by the upper mold 122 under suction, and the upper mold 122 is lifted and the lower mold 123 is lowered. Then, the first ring support 114a is moved back into the transfer zone 2 into alignment with the rollers 10a, and at the same time the shutter 31 is temporarily opened to allow the second ring support 114b to be moved into a position between the upper and lower molds 122, 123. Then, as illustrated in FIG. 6F, the rollers 10a are elevated to a position higher than the upper surface of the first ring support 114a in the transfer zone 2. Simultaneously, the glass sheet g is released from the upper mold 122 and placed onto the second ring support 114b. Thereafter the shutter 31 is temporarily opened, and the second ring support 114b is moved into a position between the boxes 33, 34 in the quenching zone 8, as shown in FIG. 6A. As shown in FIG. 6A, air is ejected from the nozzles 35, 36 on the boxes 33, 34 and applied to the glass sheet g to temper the same. The glass sheet g is cooled until the process progresses to the condition shown in FIG. 6C, after which the glass sheet g is delivered into the second cooling zone 9 in which the glass sheet g is cooled. FIG. 7 shows a modification of the glass sheet bending apparatus 50. The modified arrangement employs a single ring support 214 instead of the two ring supports 114a, 114b shown in FIGS. 6A through 6F. The glass sheet g is fed by the single ring support 214 from the transfer zone 2 through the shaping zone 3 to the quenching zone 8. An upper mold 222 has no holes for attracting the glass sheet g under suction since the upper mold 222 is not required to attract the shaped glass sheet g. A lower mold 223 is identical in construction to the lower mold 123, and has its entire upper surface region used as a shaping surface. In the glass sheet bending apparatus 50, the glass sheet pair G or the glass sheet g is moved horizontally from the transfer zone 2 to the shaping zone 3 in the heating furnace 1 by means of the ring support 14 or the ring support 114a, 114b, or the ring support 214. The glass sheet pair G is also moved from the shaping zone 3 to the terminal end of the lehr 4 by the ring support 14. The glass sheet g is also moved from the shaping zone 3 to the zone 8, 9 by means of the ring supports 114a, 114b or the ring support 214. Therefore, the lower molds 23, 123, 223 are not required to have roller pockets. As a result, the entire surface regions of the shaping molds 22, 23, 122, 123, 222, 223 are used to shape the glass sheets G, g without leaving undesirable marks thereon. The transfer zone 2 and the shaping zone 3 are disposed in the heating furnace 1. Therefore, the glass sheets G, g can be shaped while they are kept at around the glass softening point. Even if the glass sheets G, g are to be shaped to a deep and complex configuration, the glass sheets G, g can easily and accurately be bent to the desired shape. The glass sheets G, g can thus be shaped because the shaping molds 22, 23, 122, 123, 222, 223 are made of a heat resistant material which can easily be machined, as described above. The shaping zone 3 is positioned contiguously and closely to the transfer zone 2. Thus, the time required until the glass sheets G, g are transferred onto the ring support and shaped is short. As a consequence, before the glass sheets G, g sag due to gravity, they are delivered into the shaping zone 3 without allowing their temperature to drop. This is effective in easily and accurately bending the glass sheets G, g to shape. The sagging of the glass sheets G, g due to gravity can be utilized to pre-shape the glass sheets G, g. The structure of each of the transfer zone 2 and the shaping zone 3 is simplified as these zones are individually positioned. To shape a laminated glass sheet, a pair of glass sheets G placed one on the other is shaped and the shaped glass sheet pair G is annealed while it is placed on the ring support 14. Therefore, the glass sheets of the glass sheet pair G remain closely held against each other while the glass sheet pair G is being delivered from the heating furnace 1 to the pick-up station 5. As a result, even if the shaped glass sheet pair G has a relatively complex configuration, the glass sheets of the produced laminated glass sheet are well paired. Since the glass sheet bending apparatus 50 has both the laminated glass sheet shaping section 1, 2, 3, 4, 5, 6, 7 and the tempered glass sheet shaping section 1, 2, 3, 8, 9, the single glass sheet bending apparatus 50 can selectively produce a laminated glass sheet and a tempered glass sheet. When the temperature of the glass sheet pair G is lowered to the temperature at which the configuration and residual stresses of the glass sheet pair G are determined, the glass sheet pair G may be removed from the ring support 14 and fed by rollers or the like. With this arrangement, the number of ring supports 14 used can be minimised. Depending on the shape to which a laminated glass sheet is to be bent, the lower mold 23 may be dispensed with, and the glass sheet pair G may be shaped by only the ring support 14 and the upper mold 22. Although there have been described what are at present considered to be the preferred embodiments of the present invention, it will be understood that the invention may be embodied in other specific forms without departing from the scope of the appended claims.

Claims: An apparatus (50) for bending a glass sheet (G; g), comprising: a heating furnace (1) for heating the glass sheet (G; g); a first moving mechanism (10, 10a) for moving the glass sheet (G; g) horizontally in the heating furnace (1); a shaping zone (3) for shaping the glass sheet (G; g), the shaping zone (3) being disposed downstream of the heating furnace (1) in a direction in which the glass sheet (G; g) is moved; a transfer zone (2) disposed immediately before the shaping zone (3) in the heating furnace (1); a ring support (14; 114a; 214) to which the glass sheet (G; g) is horizontally transferred from the first moving mechanism (10, 10a) in the transfer zone (2); a second moving mechanism (12, 13) for moving the ring support (14; 114a; 214) with the glass sheet (G; g) supported thereon from the transfer zone (2) to the shaping zone (3); upper and lower shaping molds (22; 122; 222), (23; 123; 223) for bendingly shaping the glass sheet (G; g) in the shaping zone (3); and a cooling zone (4; 8, 9) for cooling the glass sheet (G; g) shaped in the shaping zone (3), the cooling zone (4; 8, 9) being disposed outside of the heating furnace (1) contiguously to the shaping zone (3), characterised in that the glass sheet (G; g) is supported by the ring support (14; 114a; 214) during its shaping, the entire surface regions of the upper and lower shaping molds (22, 23; 122, 123; 222, 223) are used to shape the glass sheet (G; g) and the shaping molds (22, 23; 122, 123; 222, 223) are made of a heat resistant material which can be easily machined. An apparatus (50) according to claim 1, characterised in that for bending a laminated glass sheet (G) constructed of two sheets of glass, the ring support (14) supports the laminated glass sheet (G) horizontally which sheet (G) has been shaped in the shaping zone (3); and the apparatus (50) further comprises: a third moving mechanism (12, 13) for moving the ring support (14) with the glass sheet (G) supported thereon to the cooling zone (4); and the cooling zone (4) comprising a lehr (4) for annealing the laminated glass sheet (G). An apparatus (50) according to claim 2, further characterised by : a pick-up station (5) for picking up the annealed laminated glass (G), the pick-up station (5) being disposed immediately following a downstream end of the lehr (4); a ring support return passage (6) interconnecting the pick-up station (5) and the transfer zone (2); and a fourth moving mechanism (12, 13) for moving the ring support (14) from which the glass sheet (G) has been picked up in the pick-up station (5), to the transfer zone (2) through the ring support return passage (6); the ring support (14) circulating through the transfer zone (2), the shaping zone (3), and the lehr (4). An apparatus (50) according to claim 1, characterised in that the cooling zone (4) comprises a lehr (4) and a quenching section (8, 9) which are branched from the shaping zone (3) and are selectively usable. An apparatus (50) according to claim 1, characterised in that the cooling zone (8, 9) comprises a quenching section (8, 9) for tempering the glass sheet (g) shaped in the shaping zone (3), the quenching section (8, 9) being disposed downstream of the shaping zone (3) and outside of the heating furnace (1); and the ring support (114a; 214) is reciprocally movable between at least the transfer zone (2) and the shaping zone (3) by the second moving mechanism (12, 13). An apparatus (50) according to claim 5, characterised in that the upper mold (122) in the shaping zone (3) is arranged to attract the shaped glass sheet (g) under suction; the apparatus (50) further including another ring support (114b) for receiving the glass sheet (g) shaped in the shaping zone (3) from the upper mold (122), and a fifth moving mechanism for reciprocally moving the other ring support (114b) between the shaping zone (3) and the quenching section (8, 9). An apparatus (50) according to claim 5, characterised in that the ring support (214) is reciprocally movable between the transfer zone (2), the shaping zone (3) and the quenching section (8, 9) by the second moving mechanism (12, 13). An apparatus (50) according to any one of claims 1 to 7 characterised in that the first moving mechanism (10, 10a) comprises: a plurality of moving rollers (10) for moving the glass sheet (G; g) in the heating furnace (1); and movable rollers (10a) vertically movable between an upper position in which the rollers (10a) receive the glass sheet (G; g) from the moving rollers (10), and a lower position in which the movable rollers (10a) transfer the glass sheet (G; g) onto the ring support (14; 114a; 214). An apparatus (50) according to any one of claims 1 to 8 characterised in that the heat resistant material of the upper and lower molds (22, 122, 222; 23, 123, 223) is selected from the group consisting of aluminous cement, calcium silicate, and fused silica.

Inventors: HONJO, SEIICHIRO C/O NIPPON SHEET GLASS CO., LTD., OKAJIMA, YASUNORI C/O NIPPON SHEET GLASS CO., LTD.
Applicants: NIPPON SHEET GLASS CO. LTD.
Application year: 1989
Main classification: C03B23
IPC codes: C03B23, C03B35, C03B27, C03B29, C03B25