Conveyor roll device for preliminarily bending sheet glass

Abstract: A glass sheet (G) that has been heated nearly to a softening point thereof is preliminarily bent by a conveyor roll device (10) while being fed along a feed path to a bending press (2). The conveyor roll device has a succession of first straight rolls (11) spaced along the feed path for supporting a central region of the glass sheet, and a succession of second straight rolls (12) spaced along the feed path for supporting a marginal edge portion of the glass sheet. The second straight rolls are vertically tilted with respect to the first straight rolls. The first and second straight rolls alternate with each other along the feed path.

Description: The present invention relates to a conveyor roll device that is positioned between a heating furnace and a bending press, for preliminarily bending a sheet of glass that has been heated by and fed from the heating furnace and which will be fed into and pressed to a bent shape by the bending press. Bent glass sheets such as automobile window glass panels are produced by feeding a glass sheet heated by a heating furnace to a bending press having upper and lower press dies, between which the heated glass sheet is pressed to a desired bent shape. If, however, a flat glass sheet were pressed directly to a final bent shape, the bent glass sheet would tend to crack or would not be bent accurately to desired shape. One solution to the above problem is disclosed in U.S. patent No. 4,749,399. According to the disclosed solution, the peripheral edge of a heated glass sheet fed from a heating furnace is supported on a separable ring mold, and after the peripheral edge of the glass sheet is preliminarily shaped by the ring mold, the glass sheet is pressed to a desired bent shape between upper and lower dies. If the glass sheet is to be bent to a relatively large curvature, only the peripheral edge of the heated glass sheet is supported by the ring mold for a relatively long period of time until the glass sheet is pressed by the upper and lower dies. Therefore, the heated glass sheet is liable to be undesirably deformed due to gravity before it is pressed to shape. Patent publication No. US-A-3 905 794 shows a succession of conveyor rolls for feeding a glass sheet from a heating furnace into a bending press. Each of the conveyor rolls comprises a curved core and a flexible sleeve rotatably fitted over the curved core. When the heated glass sheet is fed by the conveyor rolls, the glass sheet is preliminarily bent to a curved shape by the conveyor rolls. The conveyor rolls thus serve as bending rolls for preliminarily bending the glass sheet. The flexible sleeves are loosely fitted over the corresponding cores in order for the flexible sleeves to be able to rotate on the respective cores for feeding the glass sheet. Consequently, when the conveyor rolls feed the glass sheet, the flexible sleeves vibrate on rotation around the cores, straining the glass sheet to the point where some undesirable optical distortions may develop in the finally bent glass sheet. Another problem is that a different set of curved conveyor rolls must be used when glass sheets of a different curvature are to be produced. Other conveyor roll arrangements are disclosed in EP-A-0,364,415 and EP-A-0,143,691. The first of these uses a series of rollers to provide a cradle for a bent sheet of glass whilst it is still in a soft state. The second uses curved rollers of the type having a flexible tube rotatable about a curved core to support a sheet of glass. Another known conveyor roll arrangement for bending glass sheets is described in FR-A-2,221,409. This document discloses a roller arrangement having two sets of rolls arranged one above the other. Heated glass carried by the upper set of rolls is lowered to the lower set of rolls during a sag bending operation, by the action of the upper set of rolls pivoting about a fixed outmost end. It is therefore an object of the present invention to provide a conveyor roll device which can preliminarily bend a sheet of glass to an accurate shape without deformations and optical distortions. According to the present invention there is provided a glass bending apparatus comprising: a press for bending a glass sheet; and a conveyor roll device for feeding the glass sheet which has been heated to a temperature near its softening point by a furnace along a direction to said press and for preliminary bending the glass sheet prior to pressing of the glass sheet by said press; said conveyor roll device comprising a sequence of rolls which are rectilinear where they contact the glass sheet and arranged with their axes at differing angles of inclination to a horizontal plane so as to give the glass sheet a required prebend as the glass sheet is fed to said press, wherein said sequence of rolls includes a series of rolls for supporting an underside of the glass sheet at a peripheral edge thereof, said series of rolls being mounted to allow reciprocating translatory movement toward and away from a central axis of the conveyor roll device in synchronism with feeding of the glass sheet along said direction. Some preferred embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: FIG. 1 is a front elevational view of a glass sheet bending system including a conveyor roll device which is disposed between a heating furnace and a bending press; FIG. 2 is a schematic plan view of the conveyor roll device of FIG. 1; FIG. 3 is a side elevational view taken along line III-III of FIG. 2; FIG. 4 is a side elevational view of a conveyor roll of a conveyor roll device; FIG. 5 is a side elevational view of a second conveyor roll of a conveyor roll device, the conveyor roll having a fixed pivot point; FIG. 5A is a perspective view of a glass sheet that is preliminarily bent by the conveyor roll device shown in FIG. 5; FIG. 6 is a plan view of a power transmitting system for the conveyor roll device according to the first embodiment; FIG. 7 is a side elevational view showing the manner in which a glass sheet is preliminarily bent by the conveyor roll device according to the first embodiment; FIG. 8 is a side elevational view showing the manner in which the glass sheet is transferred to transfer rolls; FIG. 9 is a side elevational view of a conveyor roll device according to a first embodiment of the present invention; FIG. 9A is a perspective view of a glass sheet that is preliminarily bent by the conveyor roll device shown in FIG. 9; FIGS. 10A through 10C are schematic plan views showing the manner in which the conveyor roll device shown in FIG. 9 operates to preliminary bend a glass sheet; FIG. 11 is a fragmentary perspective view of a conveyor roll device according to a second embodiment of the present invention; FIG. 12 is a side elevational view of a conveyor roll device according to a third embodiment of the present invention; and FIG. 12A is a perspective view of a glass sheet that is preliminarily bent by the conveyor roll device shown in FIG. 12. As shown in FIG. 1, a glass sheet bending system includes a conveyor roll device 10 according to an embodiment of the present invention for preliminarily bending a glass sheet. The glass sheet bending system also has a heating furnace 1 for heating a glass sheet nearly to its softening point and a bending press 2 for pressing the heated glass sheet to a desired bend shape. The bending press 2 is positioned downstream of the heating furnace 1 with respect to the direction in which the heated glass sheet is fed from the heating furnace 1 along a feed path A. The bending press 2 comprises a vertically movable upper die 3, a vertically movable lower die 4 disposed below the upper die 3, a vertically movable concave ring mold 5 extending around the lower die 4 for supporting the peripheral edge of a glass sheet G, and a plurality of transfer rolls 6 vertically movably located in the ring mold 5 for supporting the glass sheet G that has been preliminarily bent by the conveyor roll device 10. The transfer rolls 6 are composed of inner rolls 6a and outer rolls 6b (see FIG. 2) that are arranged to provide an upper support surface complementary in shape to the preliminarily bent glass sheet G. The heated glass sheet G discharged from the heating furnace 1 is fed by the conveyor roll device 10 onto the transfer rolls 6. Then, the peripheral edge of the glass sheet G is supported by the ring mold 5, after which the glass sheet G is pressed to shape between the upper and lower dies 3, 4. The conveyor roll device 10 will be described in detail below with reference to FIGS. 2 through 6. The conveyor roll device 10 has a pair of left and right conveyor roll assemblies disposed one on each side of the central axis B of the feed path A. Since the left and right conveyor roll assemblies are symmetrical in configuration, only one of the left and right conveyor roll assemblies will be described below with reference to FIGS. 2 through 5. As shown in FIG. 2, the conveyor roll assembly comprises a plurality of first spaced straight conveyor rolls 11 extending perpendicularly to the feed path A and a plurality of second spaced straight conveyor rolls 12 also extending perpendicularly to the feed path A. The first and second conveyor rolls 11, 12 alternate with each other along the feed path A. As shown in FIGS. 2 and 3, the second conveyor rolls 12 are tilted about their inner ends that are closer to the center of the feed path A, successively through differing angles with respect to a horizontal plane. More specifically, the second conveyor rolls 12 are tilted through progressively greater angles in the direction away from the heating furnace 1. As shown in FIG. 4, each of the first conveyor rolls 11 is rotatably mounted on an arm 15 that is supported on a frame 13 for angular adjustment about a shaft 14 on the outer end of the first conveyor roll 11 with respect to the frame 13. Rotation of a main shaft 17 that is rotated by a motor 16 (see FIG. 6) is transmitted to each of the first conveyor rolls 11 through successive bevel gears 18 and a universal joint 19. As shown in FIG. 5, but not being claimed in the present invention, each of the second conveyor rolls 12 is rotatably mounted on an arm 21 that is supported on the frame 13 for angular adjustment about a shaft 20 on the inner end of the second conveyor roll 12 with respect to the frame 13. A vertical arcuate guide plate 22 having an arcuate guide groove 23 defined therein is attached to an outer edge of the arm 21. The frame 13 supports a bracket 24 with a setscrew 25 supported thereon which extends through the arcuate guide groove 23. When the setscrew 25 is loosened, the arm 21 and hence the second conveyor roll 12 can be angularly adjusted with respect to the frame 13. When the setscrew 25 is tightened, the arm 21 and the second conveyor roll 12 are fixed at a desired angle with respect to the frame 13. Rotation of the main shaft 17 rotated by the motor 16 is transmitted to the second conveyor roll 12 through bevel gears 26 and a flexible shaft 27. Actually, as shown in FIG. 6, the rotation of the main shaft 17 of the right conveyor roll assembly is transmitted through the bevel gears 26 and the flexible shafts 27 to the second conveyor rolls 12 of the left conveyor roll assembly, and the rotation of the main shaft 17 of the left conveyor roll assembly is transmitted through the bevel gears 26 and the flexible shafts 27 to the second conveyor rolls 12 of the right conveyor roll assembly. In this manner, the flexible shafts 27 are not required to be sharply bent in transmitting the rotation to the second conveyor rolls 12. The glass sheet G that has been heated by the heating furnace 1 is preliminarily bent by the conveyor roll device 10 as follows: The first conveyor rolls 11 are held substantially horizontally, and the second conveyor rolls 12 are tilted successively through progressively greater angles in the direction away from the heating furnace 1. Thus, the second conveyor roll 12 closest to the heating furnace 1 is tilted through the smallest angle, and the second conveyor roll 12 closest to the bending press 2 is tilted through the greatest angle. The heated glass sheet G discharged from the heating furnace 1 is then fed by the conveyor roll device 10. As the heated glass sheet G travels on the first and second conveyor rolls 11, 12, it is progressively preliminarily shaped thereby as shown in FIG. 7. More specifically, opposite marginal edge portions of the glass sheet G are bent upwardly through progressively greater angles by the second conveyor rolls 12 of the left and right conveyor roll assemblies. The glass sheet G that has been preliminarily bent by the conveyor roll device 10 is then delivered onto the transfer rolls 6. As shown in FIG. 8, the outer rolls 6b of the transfer rolls 6 are tilted upwardly with respect to the inner rolls 6a thereof so that they jointly provide an upper support surface for snugly supporting the glass sheet G in a manner to keep the preliminarily bent configuration thereof. After the glass sheet G has been placed on the transfer rolls 6, the transfer rolls 6 are lowered to an imaginary-line position C (FIG. 8), transferring the glass sheet G onto the ring mold 5. At this time, the transfer rolls 6 are retracted in recesses 4a (see FIG. 1) defined in the lower die 4. Thereafter, the upper die 3 is lowered, and the lower die 4 and the ring mold 5 are lifted for pressing the glass sheet G to a desired final bent shape. The conveyor roll device 10 is suitable for preliminarily bending rectangular glass sheets into a shape whose opposite marginal edges are bent with a uniform radius of curvature (i.e., R 1 = R 2 in FIG. 5A). The first conveyor rolls 11 may not be angularly adjustable, but may be fixed in a completely horizontal direction. In this case, the first conveyor rolls 11 of the left and right conveyor roll assemblies may be joined together. Since the second conveyor rolls 12 are independently tiltable through desired angles, the conveyor roll device 10 can be adjusted to preliminarily bend a glass sheet G highly accurately to a desired curved shape. As the first and second conveyor rolls 11, 12 support the underside of the glass sheet G without vibrations, the glass sheet G is substantially free from deformations and optical distortions after it is preliminarily bent. The conveyor roll device 10 is also capable of adjusting the speed at which a glass sheet G is preliminarily bent, by altering the angles of the second conveyor rolls 12. FIG. 9 shows a conveyor roll device according to a first embodiment of the present invention. The conveyor roll device shown in FIG. 9 differs from the conveyor roll device shown in FIG. 5 in that each of the second conveyor rolls 12 is rectilinearly movable perpendicularly toward and away from the central axis B of the feed path A. As shown in FIG. 9, the arm 21 is angularly movably mounted on a bracket 30 that is connected to the bracket 24 by a horizontal plate 31. The bracket 24 is not connected to the frame 13. The brackets 30, 24 have respective lead screw nuts threaded over a horizontal lead screw 32 rotatably mounted on the frame 13. The horizontal lead screw 32 extends perpendicularly to the central axis B of the feed path A. The horizontal lead screw 32 has an outer end connected to the main shaft 17 through bevel gears 26. When a glass sheet G is fed by the conveyor roll device, the second conveyor rolls 12 are synchronously moved perpendicularly to the feed path A by the lead screw 32. Specifically, before the glass sheet G is fed by the conveyor roll device, the second conveyor rolls 12 are positioned in an inner position as shown in FIG. 10A. When the glass sheet G is fed by the conveyor roll device, the second conveyor rolls 12 of the left and right conveyor roll assemblies move away from each other as shown in FIG. 10B. After the glass sheet G enters the bending press, the second conveyor rolls 12 return to the inner position as shown in FIG. 10C. The conveyor roll device shown in FIG. 9 is suitable for preliminarily bending trapezoidal glass sheets into a shape whose opposite marginal edges are bent with a uniform radius of curvature (i.e., R 1 = R 2 in FIG. 9A). The lead screws 32 may be connected to a different motor so that they may be rotated independently of the motor 16 which rotates the second conveyor rolls 12. Therefore, the lead screws 32 may be used to adjust the position of the second conveyor rolls 12 with respect to, or the distance thereof from, the central axis B of the feed path A, rather than moving them in synchronism with the feeding of the glass sheet G. The conveyor roll device with the lead screws 32 used to adjust the position of the second conveyor rolls 12 is suitable for preliminarily bending rectangular glass sheets of different sizes into a shape whose opposite marginal edges are bent with a unifrom radius of curvature. FIG. 11 shows a conveyor roll device according to another embodiment of the present invention. In FIG. 11, the arm 21 is angularly movably mounted on the bracket 30, and the lead screw 32 is threaded through the lead screw nut in the bracket 30 and a lead screw nut 33 on the plate 31. The bracket 24 is mounted on a base 34 movably disposed on the horizontal plate 31. The horizontal plate 31 has a pair of parallel arcuate guide grooves 35 defined therein, and the base 34 is positionally adjustably fastened to the horizontal plate 31 by setscrews 36 that extend through the guide grooves 35. The arcuate guide grooves 35 extend about the vertical axis of the bracket 30 around which the arm 21 can be turned. Therefore, when the setscrews 36 are loosened, the arm 21 and hence the conveyor roll 12 can be angularly moved about the vertical axis of the bracket 30, i.e., the angle between the central axis B of the feed path A and the vertical plane in which the conveyor roll 12 is tiltable can be varied. When the setscrews 36 are tightened, the vertical plane in which the conveyor roll 12 is tiltable is angularly fixed with respect to the central axis B of the feed path A. FIG. 12 shows a conveyor roll device according to yet another embodiment of the present invention. The conveyor roll device shown in FIG. 12 differs from the conveyor roll device shown in FIG. 9 in that the arm 21 is angularly movable about its inner end in synchronism with the feeding of the glass sheet G. More specifically, the arm 21 is operatively coupled to the motor 16 through bevel gears 37, a worm gear mechanism 38, and the lead screw 32. One of the bevel gears 37 is fixed to the inner end of the arm 21, and the other bevel gear 37 meshing therewith is coupled to the worm gear mechanism 38 that is mounted on the bracket 30. The worm gear mechanism 38 is operatively connected to the lead screw 32. Therefore, when the glass sheet G is fed by the conveyor roll device, the second conveyor rolls 12 are moved away from the central axis B of the feed path A by the lead screws 32, and at the same time are tilted, i.e., vertically angularly moved with respect to the first conveyor rolls 12. The conveyor roll device shown in FIG. 12 is suitable for preliminarily bending trapezoidal glass sheets into a shape whose opposite marginal edges are bent with different radii of curvature (i.e., R 1 ≠ R 2 in FIG. 12A). In FIG. 1, the bending press 2 is positioned outside of the heating furnace 1. However, the principles of the present invention are also applicable to a glass sheet bending system in which a bending press is positioned within a heating furnace. The present embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description.

Claims: A glass bending apparatus comprising: a press (2) for bending a glass sheet (G); and a conveyor roll device (10) for feeding the glass sheet which has been heated to a temperature near its softening point by a furnace (1) along a direction to said press and for preliminary bending the glass sheet prior to pressing of the glass sheet by said press; said conveyor roll device comprising a sequence of rolls (11,12) which are rectilinear where they contact the glass sheet and arranged with their axes at differing angles of inclination to a horizontal plane so as to give the glass sheet a required prebend as the glass sheet is fed to said press, wherein said sequence of rolls (11,12) includes a series of rolls (12) for supporting an underside of the glass sheet at a peripheral edge thereof, said series of rolls being mounted to allow reciprocating translatory movement toward and away from a central axis (B) of the conveyor roll device (10) in synchronism with feeding of the glass sheet (G) along said direction. A glass bending apparatus according to claim 1, wherein said series of rolls (12) for supporting the peripheral edge of the glass sheet are arrangable with their axes at increasing angles of inclination to axes of the rolls of another series (11) so as to provide the required prebend. A glass bending apparatus according to claim 2, wherein said series of rolls include a first series of rolls (11) for supporting an underside of the glass sheet (G) over its region spanning from a central portion thereof to an outer peripheral portion thereof, and a second series of rolls (12) for supporting an underside of the glass sheet at the outer peripheral portion thereof, the rolls of said first and second series being arranged alternately in said direction, and the rolls of said second series being set to have angles of inclination relatively to the rolls of said first series, said angles of inclination being adjustable. A glass bending apparatus according to any of claims 1 to 3, wherein at least some of the rolls (11,12) of said sequence and said press (2) are located outside said furnace (1). A glass bending apparatus according to any of the preceding claims, wherein said series of rolls (12) for supporting an underside of the glass sheet at a peripheral edge is mounted so that angles between vertical planes containing axes of the rolls are adjustable.

Inventors: MIZUSUGI TETSUYA, MIZUSUGI, TETSUYA, MIZUSUGI, TETSUYA, C/O NIPPON SHEET GLASS CO. LTD.
Applicants: NIPPON SHEET GLASS CO LTD, NIPPON SHEET GLASS CO., LTD.
Application year: 1993
Main classification: C03B23
IPC codes: C03B35, C03B23