MXPA98010223A - Glass plate bending method and apparatus - Google Patents

Abstract

A glass plate molding apparatus, in which a residence time in a heating zone, which is immediately before a slow cooling zone, in a furnace body of a heating furnace to which a mold on which a glass plate is placed, is intermittently transferred, is set variable with a lift means for separating the mold from a transfer means provided in the slow cooling zone. This enables a job change time to be reduced greatly, and glass plates of different bent shapes to be continuously produced.

Description

METHOD AND APPARATUS FOR FOLDING GLASS LEAVES TECHNICAL FIELD The present invention relates to a method and apparatus for bending glass sheets.

TECHNICAL BACKGROUND The glass sheets are heated to a bending temperature (usually around 600 ° C-700 ° C) to be formed into a folded form from a flat shape. The training can be carried out by several measures. As an example of the measurements, there is a method in which glass sheets carried on ring molds are transported in a heating furnace until flexed under their own weight in order to be bent, following the profile of the molds (hereinafter, referred to as gravity using the bending method). EP-A-621244 contains a reference for a gravity forming apparatus using the bending method applied thereto. The glass sheet forming apparatus controls a starting position of the transmission of dies in a heating furnace in an annealing zone, when glass sheets are transported in the annealing zone provided subsequently to the heating furnace.

Said control allows to adjust the degree of deformation of the glass sheets between the heating furnace and the annealing zone, and provides the glass sheets with a certain bent form. On the other hand, the folded forms of glass sheets for automobile windows are required to be suitable for the production of multiple products in small quantities to cope with the tendency for automobiles to be manufactured under multiple product production in small quantities. . Since a heated and softened glass sheet follows the profile of its related mold, the folded shape of each glass sheet is modified by changing its related mold. The glass sheets are deformed even when they are transported from the heating furnace to the annealing zone. This means that the shape of each sheet of glass can also be changed by modifying the starting position of the transmission that each of the glass sheets starts moving towards the annealing zone in the heating oven, and thus modifying the period in which each of them is moving. However, in order to use the apparatus described in the publication to meet the demand for production of multiple products in small quantities, it is required that the starting position of the transport of the heating oven molds to the annealing zone be modified. , depending on the desired shape of the glass sheets.

Modifying the starting position of the transport as required implies some complication in the drive device for the modification. Furthermore, since the glass sheets are successively transported in the heating furnace, a previous glass sheet interferes with the movement of the next glass sheet if the position of the beginning of the transport of each of the glass sheets is modified . In the case of the apparatus and the method described in the publication, it has been difficult to cope with the frequent modification of the shape of the glass sheets, which are required for the production of multiple products of glass sheets in small quantities. The heating temperature in the heating furnace for bending the glass sheets has been empirically established based on a stated degree of curvature of the glass sheets. Before bending glass sheets for mass production, sample glass sheets are formed in a folded form in the heating furnace, and the folded shape of the formed glass sample sheets is compared to a designated degree of curvature . When the bent form is outside an acceptable range, the heating temperature is modified by feedback. Said method for bending glass sheets requires verifying a real apparatus if the folded shape of the glass sheets is required to be in the acceptable range, since the heating temperature in the heating zone has been established experimentally. The conventional method for bending glass sheets has the disadvantage that considerable labor is required until the glass sheets are actually mass produced. In particular, considerable unlimited manpower is required to cope with the production of multiple products in small quantities, since it is required to verify in a real device for each of the indicated forms. It takes a long time to change the shape of the glass sheets to another one (change of manpower). An object of the present invention is to solve the disadvantages of the conventional technique, and to provide a novel method and apparatus for bending glass sheets that have not been previously known.

BRIEF DESCRIPTION OF THE INVENTION The present invention has been provided to solve the problem, and to provide a method for folding glass sheets, wherein a plurality of molds are provided, the respective molds having glass sheets carried thereon, and the molds are transported successively in a heating furnace for bending the glass sheets; and wherein the heating furnace includes a plurality of divided heating zones that heat the glass sheets to a forming temperature, and an annealing zone that is provided downstream of the heating zones for annealing the glass sheets, and the molds are transported successively in the heating furnace from upstream of the heating zones to downstream of the annealing zone through the divided heating zones and the annealing zone to bend the glass sheets following the molds, fold the glass sheets successively; characterized in that the molds are transported intermittently between the respective heating zones, so that the molds remain for a certain period TQ in the respective heating zones, except the heating zone between them, shortly before the annealing zone; and because a period T] _, where the molds remain in the heating zone shortly before the annealing zone, is variable and no greater than TQ, and the moles are transported intermittently between the heating zone and the annealing zone , so that the molds remain during the period j_ depending on the indicated curvature of the glass sheets. The present invention also provides a method for bending glass sheets, wherein a plurality of molds are provided, the respective molds having glass sheets carried thereon, and the molds are transported successively in a heating furnace to bend the sheets of glass. glass; and wherein the heating furnace includes a plurality of divided heating zones that heat the glass sheets to a forming temperature, and an annealing zone that is provided downstream of the heating zones for annealing the glass sheets, and the molds are transported successively in the heating furnace from upstream of the heating zones to downstream of the annealing zone through the divided heating zones and the annealing zone for bending the glass sheets following the molds; characterized in that before transporting the glass sheets in the heating furnace to actually bend the glass sheets, a simulated shape of a glass sheet is found by calculating a degree of curvature of a glass sheet in its entirety in accordance with a method to calculate a degree of curvature of the glass sheet, including a first step to establish the dimensions of the glass sheet and preset the temperatures of the heaters provided in the respective heating zones, a second step to divide the glass sheet into a plurality of elements, and calculating a glass temperature in each of the elements in the respective heating zones based on a heating amount received by each of the elements in the respective heating zones and a period of stay of the elements of the glass sheet in the respective heating zones, a third step to calculate a degree of bending d e each of the elements of the glass sheet in the respective heating zones based on the glass temperature calculated in each of the elements in the respective heating zones, considering a relationship between the bending speeds and the temperatures of glass of the previously found glass sheet, and a fourth step to calculate a degree of curvature of the complete glass sheet transported through the complete heating zones based on the calculated degree of flexing of each of the elements of the glass sheet in the respective heating zones; and because the simulated shape of the glass sheet is compared to a pre-established shape of the desired design of the glass sheet, and the temperatures of the heaters are determined by modifying the preset temperatures of the respective heaters in order to carry the simulated shape of the glass sheet. the sheet of glass almost to the desired design form, and because the molds with the respective glass sheets carried thereon are transported through the respective heating zones. The present invention also provides an apparatus for bending glass sheets, including a plurality of molds with glass sheets carried thereon, a heating oven including a plurality of divided heating zones for heating the glass sheets to a temperature of forming, and an annealing zone provided downstream of the heating zones for annealing the glass sheets, and a conveying device for transporting the molds from upstream of the heating zones to downstream of the annealing zone through of the divided heating zones and the annealing zone, and which successively transports the molds in the heating furnace to bend the glass sheets following the molds; characterized in that the molds are transported intermittently between the heating zones and between the heating zones and the annealing zone, so that the molds remain for a certain period TQ in the respective heating zones, except the heating zone between them , shortly before the annealing zone; and because a period T ^, where the molds remain in the heating zone shortly before the annealing zone, is variable and not greater than Tg.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic cross-sectional view of an example of the complete apparatus for forming glass sheets according to the present invention. Fig. 2 is a schematic front view of an example of the annealing zone of Fig. 1. Fig. 3 is a schematic cross-sectional front view (a) showing the details of a door and its surroundings in Fig. 1, and a schematic cross-sectional view (b) showing the details thereof. Figure 4 is a partial schematic cross-sectional view of an upper portion of the oven structure in Figure 1. Figure 5 is an exposure diagram of heaters provided in the respective zones in Figure 1. Figure 6 is a schematic view of the arrangement of ceiling heaters in the heating zone 103 in Figure 1. Figure 7 is a block diagram of a heating temperature controller for ceiling heaters. Figure 8 is a schematic view explaining the division of blocks based on the arrangement of the heaters. Figure 9 is a model view of a glass sheet to explain the simulation in accordance with the present invention. Figure 10 is a schematic view explaining the specific heat received by the elements of the glass sheet in accordance with the simulation of the present invention. Figure 11 is a schematic view explaining the specific heat received by one of the elements of the glass sheet in accordance with the simulation of the present invention. Figure 12 is a graph of the relationship between glass temperatures and bending speeds. Figure 13 is a schematic view explaining the simulation finding of a bending speed. Figure 14 is a diagram showing how to find a degree of curvature of the glass sheet according to the present invention.

BEST WAY TO CARRY OUT THE INVENTION Now, the present invention will be described in relation to the accompanying drawings. In Figure 1 a schematic cross-sectional view of an example of the complete apparatus for forming glass sheets according to the present invention is shown. A heating furnace comprises a tunnel formed by an oven structure 11 having an internal wall provided with a plurality of heaters heated by energizing towards resistors, a mold return zone 12 which is provided under the furnace structure 11, and vertical transport 14, 14 'including elevators 13, 13' for transporting glass sheets between the oven structure 11 and the mold return zone 12. The oven structure 11 includes four divided heating zones 101-104 and a annealing zone 105, and vertical transportation zones 14, 14 'on an upstream side of heating zone 101 and on a downstream side of annealing zone 105. In heating oven 10, molds 30 with leaves of glass carried on them, they travel intermittently from the vertical transportation zone 14 to the vertical transportation zone 14 '. By means of said arrangement, the glass sheets are heated up to be folded, following the profile of the molds 30. The molds 30 are ring-shaped molds, each of which has a contour substantially coupled to a desired bent form of the sheets of glass, and each one of which is formed in a convex form downwards. The glass sheets have peripheral portions thereof held by the molds 30. The molds 30 are carried on a transport device 25 comprising a traction chain, a conveyor belt, etc., and are carried intermittently in each of the heating zones and the annealing zone in the furnace structure 11, driven by the transportation device 25. Each of the molds 30 normally has a glass sheet or two sheets of glass carried thereon. In particular, the formation of glass sheets according to the present invention can be effective for bending two sheets of glass to be used for laminated glass for a windshield. The laminated glass is prepared by laminating two sheets of glass with an intermediate layer interposed therebetween. Bending shapes of the two sheets of glass are required to conform to each other. The coupling of the folded shapes of both sheets of glass can be obtained by placing the two sheets of glass on a mold, one on top of the other. The respective molds 30 remain for a certain period Tg in the heating zones 101-103 between said zones, which are located up to the third of the vertical transportation zone 14. On the other hand, the period of stay T] _, in where the molds 30 remain in the heating zone 104 shortly before the annealing zone 105, it is appropriately variable, depending on the types of glass sheet. Although the period of stay is variable, T ^ _ is not greater than TQ. By means of said arrangement, the heating period is modified, depending on the indicated bending shape of the glass sheets. The glass sheets can be made to have a desired bent form for each of the types of glass sheet, by prolonging the period of stay T] _ in the heating zone 104 to greatly bend the glass sheets (making the radius of curvature is small), and shortening the residence period T] _ in the heating zone 104 to slightly bend the glass sheet (making the radius of curvature large). The oven structure 11 has certain positions thereof provided with doors 15, 15 'and 15". Specifically, the doors 15, 15 'and 15"are provided between the heating zone 101 and the vertical transportation zone 14 at a front end of the heating zone 101, between the heating zone 104 and the annealing zone 105. and between the annealing zone 105 and the vertical transportation zone 13 'at a rear end of the annealing zone 105, to provide closed spaces in the oven. The doors 15, 15 'and 15"open only when the molds 30 pass therein, since otherwise the doors close. The doors 15, 15 'and 15"open and close vertically, and the oven structure has compartments provided on an upper portion thereof that includes guides for opening the door. The provision of the doors prevents the temperature in the oven from being removed from it. The compartments will be explained in detail later. The molds 30 with the glass sheets carried on them are transported from an entrance of the furnace structure 11 in said structure by the elevator 13 in the vertical transportation area 14. At that moment, the door 15 that is provided in the front end of the furnace structure 11 opens, being coupled to the advancement of the molds 30. When each of the molds 30 has advanced in the furnace structure 11, the door 15 is closed. Only when each of the molds 30 is transported, the door 15 is opened to prevent the heat in the furnace structure 11 from escaping therefrom. The molds 30 are thus transported to the heating zone 104 of the oven structure 11. When each of the molds moves in the annealing zone 105 after having been transferred in the heating zone 104, the door 15 This is provided between the annealing zone 105 and the heating zone 104 shortly before it is opened, being coupled to the advance of each of the molds 30. The temperature in the annealing zone 105 is smaller than that of the heating zone 104. The reason for the provision of the door 15 'is that it is required that different temperatures be maintained in the respective enclosed zones. The door 15 '' is also provided between the annealing zone 105 and the vertical transport zone 14 'to maintain the temperature in the oven structure 11. The door 15' 'is also opened only when each of the molds 30 is removed from the annealing zone 105 to the vertical transportation zone 14 '. The glass sheets that have been folded in this way and have been transported to the vertical transportation area 14 ', are moved downwardly by the elevator 13 ', being carried on the molds 30. After that, only the glass sheets are transported in a subsequent process, and the molds 30 are transported to the vertical transportation zone 14 through the mold return zone 12. The heating furnace has upper, lower, right and left walls provided with heaters, which heat the interior of the heating zones 101 to 104 at a temperature such that the glass sheets can be heated and softened to be deformed into a folded shape. The heaters in the annealing zone 105 heat the interior of the annealing zone 105 to a temperature such that the glass sheets heated in the heating zones 101 to 104 can be annealed. After the glass sheet has remained in the annealing zone 105 for a certain period, the glass sheets are transported from the annealing zone 105 out of the oven structure 11, carried by a conveying device 25.

As mentioned above, a plural number of molds 30 are provided that are to be transported, and the glass sheets are transported successively in the heating oven 10, being carried on the molds. The molds 30 are transported successively, so that each of the molds remains in principle in each of the zones of the furnace structure 11. Although an area does not contain any mold 30 in an exceptional case, there is no case that an area contains a plural number of the molds 30. When the molds 30 have remained in the respective heating zones 101 to 103 for a certain period TQ, the molds 30 are transported successively to the subsequent zones. At that time, another mold 30 outside of the furnace structure 11 is transported in the heating zone 101. After that, the subsequent molds 30 are transported in the heating zone. The molds 30 in the heating zone 104 and the annealing zone 105 do not always remain there for a certain period (the residence period T ^ in the heating zone 104 is variable to no more than TQ, as already explained above. The state of permanence in the annealing zone will be explained). However, the respective molds 30 in the heating zone 104 and the annealing zone are transported successively in the subsequent zones, such as the molds 30 in the other zones. Each of the molds 30 remains during the period TQ in each of the heating zones 101 to 103 of Figure 1. On the other hand, the period of stay T] _ of each of the molds 30 in the heating zone 104 has a maximum value of TQ, and the residence period T- \ is reduced, depending on the desired bent form of the glass sheets. When a mold is transported from the heating zone 104 in the annealing zone 105 under T] _ < TQ, there is a situation where the heating zone 104 does not contain any mold 30. A mold 30 is transported from the heating zone 103 in the heating zone 104, when a period of (TQ -T ±) = T2 has passed after the lapse of T ^. Since the transport device for this transport is driven, the transport device in the heating zone 104 without a mold contained therein is also driven. In addition, the conveying device in the annealing zone 105 is also driven. Without taking any action, the glass sheet or the glass sheets on the previous mold 30 which has been transported in the annealing zone 105, are not subjected to sufficient annealing, since the annealing period is only T ^ -. A provision can be provided to prevent such intertrawn operation. Figure 2 shows a device that has a simpler structure than said arrangement. Specifically, it is preferred that the annealing zone includes a lifting device 16 that can temporarily prevent movement of the conveyed device 25 'to be transmitted to the mold 30 in that area.

When the glass sheets are bent into a certain type, the molds 30 in the heating zones 101 to 103 remain there during the period of TQ. At that time, the mold in the heating zone 104 remains there during the period of T] _. The mold in the heating zone 104 is transported in the annealing zone after the period of time elapses. Under T] _ < Q, the molds in the heating zones 101 to 103 still remain there. After the period T2 has elapsed, the respective molds 30 in the heating zones 101 to 103 are transported to the respective subsequent heating zones. At that time, the glass sheet in the annealing zone 105 has been subjected to annealing only during the period of T2. To cope with this problem, the mold 30 in the annealing zone is lifted from the conveying device 25 'by the lifting device 16 to prevent the glass sheet in the annealing zone 105 from being transported out of the oven structure eleven, carried by the transportation device. Said arrangement allows the transport device 25 'and the mold 30 to be separated to prevent the movement of the transport device 25' from being transmitted to the mold 30. After that, the mold 30 separated from the transport device 25 'is placed in the conveying device 25 'while the movement of the conveying device 25' ceases, and the movement of the conveying device 25 'is transmitted to the mold 30 when said mold is conveyed from the annealing zone 105 to the furnace structure 11. When the subsequent mold 30 in the heating zone 104 is transported in the annealing zone 105, the mold 30 in the annealing zone 105 is transported out of the oven structure 11 (the lifting zone) by the transport device 25 ' . After that, the mold 30 in the lifting zone 14 'is transported downwards under the furnace structure 11 by the elevator, and the formed glass sheet is conveyed in a direction opposite to the mold return zone 12. mold 30 is transferred to the lifting zone 14 shortly before the heating zone 105 through the mold return zone 12, and a new glass sheet is placed on the mold therein. The transport devices according to the present invention can comprise any preferred device that can intermittently transport molds placed thereon from the respective zones to the subsequent zones, such as a device where a transmission chain, conveyor belt or push roller coupled to a driving device, for example, of an electric motor, are driven. Although the transportation device that is located to correspond to the heating zones 101, 102 and 103 can be driven simultaneously by a single endless belt or individual transmission chain, the transportation device is located to correspond with the heating zone 104. it is driven independently of the movement in the heating zone 101, and so on. Since a mold is transported from the heating zone 103 to the heating zone 104, the conveying device in the heating zone 104 is also actuated, following the movement of the mold which has remained in the heating zone 103. This is also applies to the annealing zone 105. In the heating zones and the annealing zone, the kiln wall including thermal insulating materials has a plurality of heaters provided thereon to heat the respective zones to certain temperatures. In the example shown, the furnace structure has the roof wall provided with five heaters in each of the zones, the side wall provided with a heater in each of the zones, and the lower wall provided with three heaters in each of the zones, whereby the present invention is not limited to the arrangement of the heaters in the example shown. Although there are the four divided heating zones, the present invention is not limited to said division arrangement, and said arrangement can be appropriately modified, depending on the capacity of the heaters, the period of stay and the installation location. It is preferable that the heating zones comprise from about 4 to 7 divided zones to change the temperature distribution of the heaters in each of the heating zones in order to obtain certain curvatures in respective portions of a glass sheet, "giving different Temperature distributions to the glass sheets The heating zones have the temperatures established therein, depending on the type of glass sheets, to be able to be heated normally from around 600 ° C to approximately 750 ° C. The annealing zone has the temperature normally set therein of about 400 ° C to about 450 ° C, depending on the temperature and type of heated glass sheets. A burner can be provided in place of the heaters to heat the interior of the zones. All and some of the heaters can be replaced by burners. The lifting device that separates a mold from the transport device and places it back on said device in the annealing zone may comprise an appropriate device such as a device where pistons in the area are moved vertically, for example, by pneumatic cylinders , from outside the area. The glass sheet forming apparatus according to the present invention is particularly effective when the period of stay of the mold 30 in the heating zone 104 in the example shown is frequently modified. The modification of the period of stay of the mold 30 in the heating zone 104 is carried out to successively produce glass sheets having different dimensions, including a folded shape thereof. This is effective as a measure to cope with the production of multiple products of glass sheets in small quantities for automobile windows in terms of the tendency towards the production of multiple products of automobiles in small quantities. By modifying the period of stay of the mold 30 in the heating zone 104, the period for heating glass sheets can be modified to modify the curvature of the glass sheets accordingly, providing glass sheets with many types of folded shapes. In other words, the production of glass sheets of many types can be done by adjusting the heating period, depending on the types of glass sheets. The modification of the period to heat glass sheets in accordance with the types thereof can be done by modifying the set temperatures of the heaters. When successively glass sheets having different types are produced, the period of stay in the heating zone shortly before the annealing zone can be appropriately modified, depending on the types, in accordance with the forming apparatus of the present invention, to obtain bent glass sheets having various types of desired curvature. In particular, when a mold has been transported in the annealing zone in an early time setting, the following initially established arrangement is preferably provided to obtain a sufficient annealing without the provision of a complicated driving device. The provision of the lifting device in the annealing zone that temporarily raises a mold of the conveying device is preferred to prevent the movement of said device to the mold being transmitted in order to actually effect the modification in the period of stay in the heating zone. referred to in this paragraph. To cope with such production of multiple products in small amounts, it is required that the temperatures in the respective heating zones be maintained at the set temperatures. The following arrangement can be mentioned as a preferable arrangement for performing a stable temperature adjustment. (1) Compartments are provided at the doors. (2) Ceiling wall heaters are separated from the wall of the oven. The provision (1) will be explained. It has been described that the doors 15, 15 'and 15"are provided in certain positions of the furnace structure 11. It is preferred that the compartments are provided in the furnace structure to prevent the temperature in the furnace from being removed from the furnace. same when the doors open. The details of a compartment and its surroundings are shown in Figure 3. Figure 3 (a) shows a schematic cross-sectional front view of essential portions of the compartment and its surroundings, and in Figure 3 (b) it is shown a schematic view in cross section of the essential portions. Although the opening and closing devices of the respective doors may comprise any preferred device, the opening and closing devices of the respective doors in the example shown comprise devices having the same structure. In Figure 3 the device for the door 15 'is shown between the heating zone 104 and the annealing zone 105 as a typical example. The heating zone 104 and the annealing zone 105 have a boundary between them provided by the door 15 '. The upper baking wall 84 has a door entry opening 82 formed therein at the boundary between the heating zone 104 and the annealing zone 105 to communicate between the interior of the heating oven and the interior of the compartment 80, so that the door 15 'is vertically movable. The compartment 80 is formed in a vertically extended box configuration having a compartment opening towards the door entry opening 82. The compartment opening has an opening end portion thereof abutting an external surface of the wall of the door. oven 84 through thermal insulating material, to contain the door entry opening 82 at an internal periphery of the compartment opening. When the door 15 'is opened, said door is housed in the box. The compartment 80 abuts the outer surface of the furnace wall 84 through thermal insulating material, and is bolted to the furnace wall 84 in clamps thereof (not shown). The thermal insulating material that is interposed between the compartment 80 and the furnace wall 84 functions as a thermal seal for the bearing portion of both members. The compartment 80 is made of cardboard, with thermal insulating material included therein. The door 15 'has a top portion thereon coupled to an actuator 81 through coupling members 83, such as chains and wires. The door is moved vertically, driven by the driving device 81, to open and close the communication between the heating zone 104 and the annealing zone 105. Although the driving device 81 may comprise any preferred device, the example shown takes a such arrangement that the sprocket is rotated using a pneumatic cylinder as a source of thrust to wind and unwind the coupling members, opening and closing the door 15 '. The provision of the doors is effective to maintain the interior of the heating furnace at a certain temperature in a stable manner. In particular, the door 15 'which is provided between the heating zone 104 and the annealing zone 105, is effective to maintain the interior of the heating oven at a certain temperature. To control the stress exerted on the glass sheets, it is required that said sheets be properly annealed. For this reason, it is necessary to maintain the temperature in the annealing zone at a certain temperature. On the other hand, when the heat in the heating zone is conducted into the annealing zone adjacent to the heating zone, the temperature in the annealing zone can not be maintained at a certain temperature. From this point of view, it is effective that a door provided between the heating zone and the annealing zone closes the communication between them, and that the door opens and closes (when a mold is transported) as in the example shown . To maintain the interior of the annealing zone at a certain temperature, it is particularly effective to interlock the movement of the door opening device with the movement of the mold transport device, so that the door opens and closes, equalizing the regulation of time to transport the mold from the heating zone to the annealing zone. This intertraining greatly contributes to maintaining the interior of the annealing zone at a certain temperature in an apparatus that is particularly effective in coping with the production of multiple products of glass sheets in small quantities, wherein the period of stay in the heating zone 104 changes as adjusted. The separation of the heaters for the roof wall of the furnace wall in the arrangement of (2) will be explained. In Figure 4 a partial cross-sectional schematic view of the upper portion of the furnace structure 11 is shown, which is seen on the same side as Figure 1. The heaters 20 have a flat shape, and a number of them are provided. in each of the heating zones. Figure 4 shows one of the heaters and another heater adjacent to them in the transportation direction. The heaters are suspended from the ceiling wall by support members 50 to provide a first air layer 60 between an inner surface 111 of the furnace wall 84 and the heaters 20. Each of the support members comprises a suspension member 51 passed through a through hole 112 formed in the furnace wall 84 and supported on the external surface of the furnace wall 84, a support plate 52 fixed to the suspension member 51, for example, by screws, and spacers 53 made of glass. The support plate 52 is made, for example, of thermal insulation material, and the support plate is suspended in a fixed manner from the suspension member 51 to be separated from the interior surface 111 of the oven wall 84. The space between the support plate 52 and the interior surface of the furnace wall 84 functions substantially like the first air layer 60. Each of the heaters 20 and each of its related support plates 52, have the spacers 53 interposed in peripheral portions. between them, to provide a second layer of air 61 therebetween. Each of the heaters 20 has both ends provided with energizing leads, which pass through holes in the furnace wall 84 and are connected to a power source outside the furnace. The reason why such an arrangement of the heaters is effective for the production of multiple products of glass sheets in small quantities, is as follows. When a glass sheet has different curvatures in portions thereof, a temperature distribution is given to the glass sheet to be heated in the heating furnace. Various patterns can be provided with the temperature distribution to obtain glass sheets having many different bent shapes. In other words, the production of glass sheets of many different types can be achieved by giving an appropriate temperature distribution to each of the different types. To provide an adequate temperature distribution to each of the different types, the temperature setting for the heaters is modified for each of the different types. When successively glass sheets having different dimensions including folded shapes are successively produced, the temperature setting for the heaters provided on the interior surface of the furnace wall is often modified. When the heaters are embedded in the furnace wall as usual, the heat is absorbed in the furnace wall, or the heat in the furnace wall is absorbed even when the temperature setting for the heaters is modified. This creates a phenomenon which consists in that the interior of the furnace can not be adjusted to a certain temperature, or a phenomenon that takes some time for the interior of the furnace to be adjusted to a certain temperature due to a poor response capacity. The arrangement of the heaters, as noted above, provides the first and second air layers between the interior surface of the furnace wall and the heaters. This allows the temperature in the furnace to be modified with good response capacity in accordance with the change in the temperature setting for the heaters, by modifying the temperature of the glass sheets. Now, a preferred embodiment for adjusting and controlling the temperature of the heaters will be explained. The usefulness of the temperature distributions according to the different types has been pointed out. If a fine temperature distribution is provided, the diversification of the shape of the glass sheets is achieved accordingly. In order to provide this fine distribution, it is proposed that the heaters be subdivided. However, if the heaters are subdivided, the temperature control system for the heaters is therefore complicated. Next, a preferred way to simplify the temperature control system will be explained. Figure 5 shows an arrangement of the heaters that are provided in the heating zones 101-104 and the annealing zone 105. Each of the zones includes ceiling heaters 40, side heaters 42 and floor heaters 44. roof heaters 40A-40D in each of the respective heating zones include five split group heaters AE, and the respective ceiling heaters have different layout patterns. In particular, the ceiling heaters 40C and D in the heating zones 103 and 104 have the heater groups A and B divided into two blocks. Consequently, each of the heating zones 103 and 104 includes six blocks. The heating group A of the ceiling heater 40E in the annealing zone 105 is made of a single heater, which is fixed at a lower temperature than the heater groups in the other zones. The respective heater groups in the respective zones are fixed at independent temperatures. Each of the side heaters 42A-42E in each of the heating zones is made of a single heater A, and each of the side heaters have the same layout pattern to each other. The floor heaters 44A-44E in the respective heating zones are divided into three heaters A-C, and the floor heaters have the same layout pattern. The control for the ceiling heaters will be described with respect to the ceiling heaters 40C as a typical example (an amplified view of the ceiling heaters 40C is shown in figure 6). As stated at the beginning, the 40C ceiling heaters are divided into six blocks numbered from No. 1 to No. 6. In Figure 6, the ceiling heaters include heating group A, heating group B, heating group C, heating group D, heating group E, heating group A from the upper part. In other words, the ceiling heaters 40C include the two heater groups A, A set at the same temperature, and each of these heater groups A, A is made of heating elements, the number of which is half the number of heaters. the heating elements in each of the other heating groups BE. In Figure 7 a block diagram of a heating temperature controller 70 for the ceiling heaters 40C is shown. The heating temperature controller 40 shown in this figure includes a CPU 72 for collectively controlling the ceiling heaters 40C. The CPU 72 controls five current controllers (five temperature control systems) 73, 74, 75, 76 and 77 based on the information supplied to heat each of the heating groups AE at certain temperatures set via a keypad 140. With such an arrangement, a certain temperature distribution for bending the glass sheets is provided in the heating zone 103.

The current controller 73 is a temperature control system for heating the heating groups A for heating the heating groups A, A numbered 1 and 6, the current controller 74 is a temperature control system for the heating group B , the current controller 75 is a temperature control system for the heater group C, the current control system 76 is a temperature control system for the heater group D, and the current controller 77 is a control system of temperature for the heating group E. In the heating temperature controller 70 shown in FIG. 7, the two heating groups A, A which are fixed at the same temperature are controlled by the single current controller 73. In accordance with the heating temperature controller 70 thus constructed, it is sufficient to provide the five current controllers 73-77 for the heater groups AE, di vididos in six blocks. With such an arrangement, a temperature distribution with fine differences in temperature can be provided without increasing the number of current controllers to correspond to the number of heater groups, and the glass sheets can be folded in a form close to the dimensions designed Although the explanation has been made with respect to the heating temperature controller 70 for the ceiling heaters 40C in the heating zone 103, the ceiling heaters 40D in another zone can also be of controlled temperature. The ceiling heaters 40D shown in Figure 5 include two heater groups B, B divided fixed at the same temperature, and the heater groups B, B are shown as being controlled in temperature by a single current controller. The ceiling heaters 40A, 40C provided in the heating zones 101, 103 shown in Figure 5 have the same number of control systems although the ceiling heaters have different layout patterns of the heater groups thereof. Likewise, the ceiling heaters 40B, 40D provided in the heating zones 102, 104 have the same number of control systems although the ceiling heaters have different patterns of arrangement of the heater groups thereof. By intermittently transporting glass sheets through the respective heating zones with different heating group arrangement patterns as established, the distribution of the amount of heat received from the heating zones by the glass sheets can be finely divided without increasing the number of temperature control systems. Specifically, the distribution of the received heat quantity can be divided into 40 divisions on a surface of a glass sheet as shown in Figure 8 (the divisions of the heating groups in the respective heating zones can be covered to provide the 40 divisions in figure 8). In this way, a fine temperature distribution can be produced without increasing the number of control systems. As a result, it is possible to bend the glass sheets in a thin form in an economical way. The glass sheets are carried on the mold in the heating furnace, and the glass sheets are bent under their own weight to follow the profile of the molds. Not only curvatures with finely divided divisions within the 40 divisions can be given to the glass sheets but also a fine temperature distribution can be synergistically given to the glass sheets by applying various types of temperature hysteresis to respective portions of the sheets of glass. glass, such as a control according to which the temperatures in the respective heating zones are controlled so that the glass sheets have a portion thereof supported on the related molds and a peripheral portion of the supported portion provided with increased temperatures more quickly than the other portions, a control according to which the glass sheets have a portion away from the serving portion provided with an increased temperature faster than the other portions, and a control according to which a temperature is gradually increased or increased rapidly after the temperature has been increased to a certain level.

When the heaters are provided on the floor of the wall or the side walls, it is preferable that these heaters are separated from the internal surface of the furnace. Because the glass sheets are placed on the molds, the temperature control on a lower side of the glass sheets must be done, considering the existence of the molds, in some cases. On the other hand, the set temperatures and the temperature distribution of the heaters can be more accurately reflected on an upper side of the glass sheets because there is no obstacle between the heaters and the upper side of the glass sheets. It is desirable that the heaters provided on the roof of the furnace can set temperatures with better precision than the heaters provided on the floor of the furnace. From this point of view, it is recommended that at least the heaters on the roof have a good responsibility for the temperature of the glass sheets in terms of temperature setting, and it is preferable that the air layer be provided between the heaters on the glass. roof and the internal surface of the roof of the furnace as in the example. A preferred bending control for glass sheets in accordance with the fine synergistic temperature distribution set forth above will now be described. Specifically, a discovery simulation program which is installed in a main computer frame 160 shown in figure 1 will now be explained. This is a technique capable of setting heater temperatures in a simple way, in particular, for the production of small quantities or multiple products, which is different from the conventional technique according to which the temperatures of the heater in the heating zones are experimentally fixed and checked on a current apparatus whether the form of bending of a sheet of glass is in an acceptable scale. The technique according to the present invention is one for discovering the temperatures of a glass sheet and the degrees of bending in the glass sheets in the respective zones, the accuracy in the simulated results is valued in consideration of the temperatures of the sheet of glass and the bending speed on the glass sheet in the preceding areas. A computer 120 which collectively controls the heating furnace 10 was shown in Figure 1. The computer 120 has the keypad 140 for setting the heater temperatures in the respective heating zones of the heating furnace 10 and for providing conditions for a heating sheet. glass to be folded, the main frame of the computer has the discovery simulation program installed therein to find degrees of curvature on the glass sheet, and a display 180 to display the calculated results, and various functions and operational status of the glass. heating furnace 10. The heating furnace 10 and the computer 120 can be connected to exchange different information between them, and the heaters in the respective heating zones are controlled in temperature based on the temperatures of the heater supplied through the keyboard 140. Information on current temperatures of these temperatures Adores is transmitted to the display 180 to be displayed therein. The program divides a sheet of glass 26 into a plurality of elements (nxn) as shown in figure 9 when a desired size and thickness of the glass sheet 26 and heating temperatures in the respective zones are supplied through the keyboard 140. Figures 10 and 11 showed schematic views to explain how to find the amount of heat received by each of the elements in the glass sheet 26In Figure 10 shows an area that has the ceiling heaters of the same divided in No.l-No. 13 of divisions for simplification in the explanation. The zone includes side heaters and floor heaters not shown. The glass sheet 26 heated by these heaters is divided into n x n elements. The specific heat received by an element on a calculated surface (i, j) shown in Figure 11 is noted. The main frame of the computer 160 finds the specific heat C according to the following formula: C'dTG / dt = Qrl + Qr2 + Qr2 + Qr4 ~ Qcl ~ Qc2 W • • • (1) TQ: temperature of the element of a glass sheet (an element on a calculated surface is treated as a specific heat body concentrate). Qrl: amount of heat radiation received from all heaters, which is in accordance with the following formula. m Qrl = a? g A g d a T k4? nFgn • • • (2) n = 1 Qr2: amount of convection heat received from an ambient temperature, which is discovered according to the following formula. m Qr2 = a? g A g o a T k4? nFgn • • • (3) n = 1 Qr3: amount of heat radiation received from a chimney, which is discovered according to the following formula. m Qr3 = a? g A g o a T k4? nFgn • • • (4) Qr4: heat of auto-radiation of the glass sheet, which is discovered in accordance with the following formula. Qr4 = 2i-g í Tk4? _g • • • (5) QC] _: convection on an upper surface of the glass sheet, which is discovered according to the following formula. Qcl = Ag (tg-tu) k • '' (6) QC2: Convection on a lower surface of the glass sheet, which is discovered according to the following formula. Qc2 = Ag (Tg-TD) k • • • (6) a: constant Stefan-Boltzumann. Tn: surface temperature of an oven element No. n. ? n: heat radiation of the oven element No. n. An: area of the oven element No. n. Fgn: geometric factor of the furnace element No. n seen from a glass element. ? g: heat radiation of the glass. Tg: absolute temperature of a glass element. Ag: area of the glass element. Tu: room temperature in a higher portion in an oven (absolute temperature). Tr > : room temperature in a lower portion in the oven (absolute temperature). K: heat transfer coefficient due to convection in the furnace. The glass sheet is transported intermittently through the respective heating zones. The period of stay in the respective heating zones is preset, depending on a pre-established touch time. The glass temperatures of the respective glass sheet elements that are given during the stay in the heating zone 101 are discovered based on the specific heat received by each of the elements in the heating zone 101 and the residence period of the glass sheet in the heating zone 101. Such a discovery is carried out sequentially with respect to the heating and annealing zone 102-105 in consideration of the glass temperatures of the respective elements in the preceding zones to obtain the temperatures of glass of the respective elements in the respective zones (at respective times). Next, the degree of bending for each of the elements is discovered based on the glass temperatures. This discovery is carried out by a simulation technique as in the specific heat discovery as follows. First, it is necessary to take the bending speeds of the glass with respect to the temperatures of the glass before discovering the degree of bending. This is because the degree of flexion of each of the elements can be seen by adding the bending speeds based on a warm-up period. In Figure 12 a relationship between glass temperatures and glass bending speeds was shown. This figure shows that a bending speed is almost 0 when a glass temperature is substantially below 580 ° C although a bending speed has a tendency to increase rapidly when a glass temperature is beyond 580 ° C. This relationship is obtained by simulating a glass sheet 1 having dimensions shown in Figure 13. Specifically, the degrees of flexion of a measured point P in a central portion of the glass sheet 26 shown in this drawing were discovered while the sheet of glass was gradually heated to a forming temperature. A) Yes, the relationship between the glass temperatures and the glass bending speeds of Figure 12 was obtained. The degrees of bending of the respective elements of the glass sheets that have been transported through all the zones can be obtained by calculating the degree of flexion of each one of the elements based on the discovered temperatures of the glass of each one of the elements in each of the zones (in each of the times) in accordance with the relationships shown in figure 12 and adding the degree of flexion of each of the elements in each of the zones. Without carrying out calculations in the respective zones to obtain the total degree of flexion, the degree of flexion of each of the elements in each of the times that are obtained through all the zones can be seen directly. The degree of bending of the entire sheet of glass can be discovered by adding the degrees of flexion of the respective elements thus calculated. By such arrangement, the degree of curvature of the glass sheet 26 can be seen without checking on a current apparatus. When two sheets of glass are stacked and carried on a mold to be folded simultaneously, the provision of the two sheets of glass must be reflected on the simulation. Specifically, there is a technique according to which the provision of two stacked glass sheets is taken into account in the calculation, and a technique according to which the provision of a glass sheet with a thickness equal to the total thickness of the two sheets of glass Glass is taken into account in the calculation for simplification. Although the current technique provides simulated results close to a current fold shape, the latter technique can provide simulated results that are practical enough. Right away. the operation of a device to discover the degrees of curvature of a glass sheet constructed in accordance with the present invention as initially established will be explained, referring to the flow chart of Figure 14. First, the size and thickness of a glass sheet 26 to be folded are supplied through the keyboard 140, and preliminarily temperatures are set for each of the ceiling heaters 40, the side heaters 42 and the floor heaters 44 in the respective zones through the keypad 140. Thus, the initial fix is completed (step 100). When the initial fixation has been completed, the main frame of the computer 160 divides the sheets of glass into a plurality of elements (nxn) as shown in Figure 9. Next, the amount of heat radiation from the heaters and the The amount of convection heat from the ambient temperatures that are received by each of the elements in each of the zones are discovered in accordance with formula (1) based on the preliminarily set temperatures supplied for the heaters. If needed, the amount of heating received by each of the elements in each of the zones is discovered by discovering a quantity of heat transferred in the thickness direction of the glass sheet (step 200). On the other hand, the initial temperature of the glass sheet in the heating zone 101 is set at a normal temperature, and an unstable detection is carried out to see how the temperature of each of the elements of the glass sheet changes. under the temperature in the heating zone 101. According to the unstable detection, the final temperatures of the elements of the glass sheet in the heating zone 101 are discovered based on the period of stay of the glass sheet in this zone because the amount of heat received by the respective elements in this area has been discovered. Next, the initial temperatures of the elements of the glass sheet in the heating zone 102 are set at the final temperatures in the heating zone 101, the unstable detection is carried out to see the temperatures of the respective elements of the glass sheet change under the temperature in the heating zone 102. Then, the unstable discovery is also carried out with respect to the heating and recoating zones 103-105. "Thus, the glass temperatures of the respective elements of the glass sheet in the respective heating zones can be discovered (step 300). Because the touch transport time for the glass sheet has been fixed, the glass temperatures can be treated as glass temperatures in the times Then, the degrees of the curvature of the respective elements are calculated based on the temperature of the bare glass of the elements s in accordance with the glass temperature ratio and bending speeds (V) shown in Figure 2 (step 400). The degrees of curvature in the entire sheet of glass are discovered based on the calculated degrees of flexure of the respective elements (step 500). Thus, the required discovery can be made without checking the degrees of curvature of the glass sheet on a current apparatus. The uncovered shape of the glass sheet is compared to a desired designed shape of the glass sheet to find a shape deviation (step 600), and the results discovered are displayed on the display 180 (step 700). It is determined whether the shape deviation found is on an acceptable scale, and if so, the folding of the glass sheets under the initially established supplied conditions begins. Conversely, if it is negative, the preliminarily set temperatures of the heaters between the supplied conditions are modified, and the discovery is made in the procedure initially established until the deviation in the discovered form is in the acceptable range. Thus, the glass sheets can be provided with a desired designed shape in accordance with this embodiment. In the previous explanation, the color of the glass sheets is not considered. Several types of colors of automotive glass sheets have recently been adopted due to the diversification in the types of automobiles, and not only the usual transparent glass sheets but also bronzed or green glass leaves have been frequently seen. Because such colored glass sheets necessarily have different heat absorbance depending on their colors, the bending speed of the colored glass sheets is faster than that of the transparent glass sheets. If a relationship between glass temperatures and bending speeds has been obtained with respect to many sheets of colored glass in advance, it is possible to find the degree of curvature for many types of colored glass sheets. The explanation of the simulation has been made with respect to a case in which the glass sheets are transported intermittently in the respective heating zones. The simulation can also be applied to a house according to which the glass sheets are transported continuously at a substantially constant speed through all the zones. In the latter case, the degrees of bending of the respective elements that have been transported through all the zones can be discovered by discovering the glass temperatures of the respective elements at respective times instead of the glass temperatures of the respective elements in the respective zones. The arrangement of the heating groups and the number of heaters in the respective zones can be determined suitably. With regard to the profile of the molds, any profile such as a profile ring shape and a non-ring shape of solid profile can be determined suitably, being matched to a designated shape of glass sheets. A profile ring shape is preferred because a solid profile is required to have the profile of a solid portion determined with good accuracy for each type of glass sheet. In particular, in the case of a profile ring shape, a portion of the profile supporting a glass sheet and a portion thereof that does not support the glass sheet can be clearly differentiated. The fine shape control for glass sheets can be carried out by properly determining the amount of heat received by each of the portions with a glass sheet resting thereon and a portion thereof without the glass sheet resting on the glass. same (including the amount of heat received by each of the portions with the lapse of time). Although the mold return zone 12 is provided under the furnace structure 11 in the example, the position of the mold return zone can be suitably modified. For example, the position of the mold return zone and the position of the furnace structure can be reversed. The mold return zone and the furnace structure can be located side by side in the horizontal direction. Considering the heat efficiency and the limitation on the installation of the location of the apparatus, it is preferable that the return zone of the mold 12 be provided under the structure of the furnace 11. With regard to the technique that prevents the movement of the transportation device is transmitted to the mold 30 in the annealing zone 105, any preferred technique can be adopted. Instead of lifting the mold above the transport device as in the example, the mold can be lifted in a horizontal direction. Considering the simplification in the mechanism and the limitation in the installation space, it is preferable to lift the mold since it is sufficient to disengage the mold from the transportation device.

INDUSTRIAL APPLICATION In accordance with the apparatus for forming glass sheets according to the present invention, the period of stay of the mold with a glass sheet conveyed therein in the heating zone before the annealing zone is variable. This arrangement can successfully produce glass sheets having different forms of bending, depending on different types, without using a complicated conductive device. In particular, a sufficient annealing period can be ensured without interference between the molds by adopting a treatment such that the mold that has been transported within the annealing zone from the preceding heating zone in an initial time is temporarily separated from the device. transportation to be isolated from the movement of the mold in the preceding heating zone. Because the period of mold stay in the heating zone before the annealing zone is variable, a ired movement of the mold can be performed in the preferable mode. In addition, the following discovery in a degree of curvature of a sheet of glass can perform a simulation close to the check on a current apparatus without checking a degree of curvature of a sheet of glass on a current apparatus. The degree of curvature of a glass sheet is found by dividing the glass sheet into a plurality of elements and finding the amount of heat received by the respective elements and the glass temperatures of the respective elements after having fixed sheet dimensions of glass and the heater temperatures in the respective zones, and calculating the degree of bending of the respective elements based on the glass temperatures in the respective zones in consideration of the amount of heat received from the previous zones in the respective zones. By feedback the bending form thus found to the setting of the temperature of the heaters, the formation of glass sheets having a desired shape can be done without bending sample glass sheets or with the formation number for decreased sampling.

Claims (9)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for folding glass sheets according to which a plurality of molds are provided, the respective molds have glass sheets carried therein and the molds are transported successively inside a heating furnace to bend the glass sheets; and according to which the heating furnace includes a plurality of divided heating zones which heat the glass sheets to a forming temperature and an annealing zone which is provided downstream of the heating zones for annealing the glass sheets, and the molds are successively transported into the heating furnace from upstream of the heating zones downstream of the annealing zones through divided heating zones and the annealing zone for bending the glass sheets, following the molds, as to fold the glass sheets successively; characterized in that the molds are transported intermittently between the respective heating zones, in such a way that the molds remain for a certain period T0 in the respective heating zones except the heating zones between them shortly before the annealing zone; and because a period T ± according to which the molds remain in the heating zone shortly before the annealing zone is variable to no larger than T0, and the molds are transported intermittently between the heating zone and the annealing zone, in such a way that the molds remain for the period T] _ dependent on a marked curvature of the glass sheets.

2. A method for folding sheets of glass according to claim 1, further characterized in that the molds are carried on a transportation device and are transported by the transportation device; and because when the molds are transported within the annealing zone in the period T ^ set to be shorter than the period TQ, a mold in the annealing zone that has remained in the heating zone shortly before the annealing zone for a short period it is retracted in a disengaged position from the conveying device in the annealing zones until the next mold on an upstream side is transported into the heating zone shortly before the annealing zone.

3. A method for folding glass sheets according to claim 1 or 2, further characterized in that before transporting the glass sheets inside the heating oven to actually bend the glass sheets, a simulated shape of a glass sheet it is discovered to calculate a degree of curvature of a whole sheet of glass in accordance with a method for calculating a degree of curvature of the glass sheet including a first step for fixing dimensions of the glass sheet and presetting temperatures of intended heaters in the respective heating zones, a second step for dividing the glass sheet into a plurality of elements and for calculating a glass temperature in each of the elements in the respective heating zones based on a quantity of heat received by each one of the elements in the respective heating zones and a period of stay of the glass sheet in the heating zones respective, a third step to calculate a degree of bending of each of the elements of the glass sheet in the respective heating zones based on the glass temperature calculated in each of the elements in the respective heating zones in consideration of a relationship between bending speeds and glass temperatures of the previously uncovered glass sheets, and a fourth step to calculate a degree of curvature of the entire glass sheet conveyed through all the heating zones based on the calculated degree of bending of each of the elements of the glass sheet in the respective heating zones, and because the simulated shape of the glass sheet is compared with a desired pre-set design of the glass sheet and set temperatures of the heaters are determined to modify the preset temperatures of the respective heaters as to bring the simulated form the v-sheet idrio near the desired design form; because the molds with the respective glass sheets transported therein are transported through respective heating zones.

4. A method for folding glass sheets, further characterized in that a plurality of molds are provided, the respective molds have glass sheets transported therein, and the molds are successively transported inside a heating furnace to bend the sheets of glass. glass; and according to which the heating furnace includes a plurality of divided heating zones which heat the glass sheets to a forming temperature and an annealing zone which is provided downstream of the heating zones for annealing the glass sheets, and the molds are successively conveyed into the heating furnace from upstream of the heating zones downstream of the annealing zone through the divided heating zones and the annealing zone to bend the glass sheets, following the molds, as to fold the glass sheets; characterized in that before transporting the glass sheets inside the heating furnace to in fact bend the glass sheets, a simulated shape of a glass sheet is discovered by calculating a degree of curvature of a glass sheet in its entirety in accordance with a method for calculating a degree of curvature of the glass sheet including a first step for establishing dimensions of the glass sheet and presetting temperatures of heaters provided in the respective heating zones, a second step for dividing the glass sheet into a plurality of elements and calculating a glass temperature in each of the elements in the respective heating zones based on a quantity of heat received by each of the elements in the respective heating zones and a period of stay of the elements of the sheet of glass in the respective heating zones, a third step to calculate a degree of flexion of each of the elements of the glass sheet in the respective heating zones based on the calculated temperature of the glass in each of the elements in the respective heating zones in consideration of a relationship between bending speeds and glass temperatures of the glass sheet found preliminarily and a fourth step to calculate a degree of curvature of the entire glass sheet transported through all the heating zones based on the calculated degree of bending of each of the elements of the glass sheet in the zones of respective heating; that the simulated shape of the glass sheet is compared to a desired pre-set design of the glass sheet and set temperatures of the heaters are determined by modifying the pre-set temperatures of the respective heaters as to bring the simulated shape of the sheet glass near the design of desired shape, because the molds with the respective glass sheets transported therein are transported through the respective heating zones.

5. A method for bending glass sheets according to claim 4, further characterized in that when the temperature of the glass in each of the elements in the respective heating zones is calculated in the second step, the temperature of the glass in each one of the elements in the zones shortly before the respective heating zones is set as an initial temperature.

6. An apparatus for bending glass sheets including a plurality of molds with glass sheets conveyed therein, a heating furnace including a plurality of divided heating zones for heating the glass sheets to a forming temperature and an annealing zone provided downstream of the heating zones for annealing the glass sheets, and a transportation device for transporting the molds from upstream of the heating zones downstream of the annealing zone through the zones of divided heating and the annealing zone, and which successively transports the molds inside the heating furnace to bend the glass sheets as to follow the molds; characterized in that the molds are transported intermittently between the heating zones and between the heating zones and the annealing zone, that the molds remain for a certain period TQ in the respective heating zones except the heating zone between them shortly before the annealing zone, because a period T ^ according to which the molds remain in the heating zone shortly before the annealing zone is variable to no larger than TQ.

7. - An apparatus for bending glass sheets according to claim 6, further characterized in that the molds are carried on a transport device such as to be transported driven by the conveying device, and the annealing zone is provided with a device Lifting to temporarily lift a mold from the transportation device.

8. An apparatus for bending glass sheets according to claim 6 or 7, further characterized in that a wall of the heating furnace which is located between the heating zones and the annealing zone is provided with a door opening of entrance, through which a first door enters or leaves the heating oven to be opened and closed in association with the entrance of a mold, a box-shaped annex which has an opening of an annex on one side of the the inlet port opening is provided on an outer surface of the heating furnace at an outer periphery of the inlet port opening to support the outer surface such as to contain the inlet port opening in an inner periphery of the opening of the annex and to project outward from the heating furnace; and the door is housed in the annex in the form of a box in an open state.

9. An apparatus for bending glass sheets according to claim 6, 7 or 8, further characterized in that a return zone for returning a mold with a formed glass sheet removed for an inlet of the heating oven is provided to the oven heating side by side, the heating furnace has an outer side of the inlet provided with a second door to be opened and closed in association with the entrance of a mold inside the heating furnace, and the heating furnace has an outer side of an outlet provided with a second door to be opened and closed in association with removal of a mold from the heating furnace.