WO2001030711A1

WO2001030711A1 - A method of and a device for bending a ductile sheet material

Info

Publication number: WO2001030711A1
Application number: PCT/DK2000/000593
Authority: WO
Inventors: Torben Asbjørn MADSEN
Original assignee: Wave Glass Technology Aps
Priority date: 1999-10-26
Filing date: 2000-10-25
Publication date: 2001-05-03
Also published as: DK173562B1; DK199901530A; AU1018601A

Abstract

By the method a sheet (1) is moved in a device by means of a row of rollers (2), the surfaces of which form a rolling path (11) and a shaping curve for the sheet (1). The rollers move so that the shaping curve gradually changes from a substantially plane initial shape to a desired curved shape and that the shaping curve is displaced along the rolling path (11).

Description

A METHOD OF AND A DEVICE FOR BENDING A DUCTILE SHEET MATERIAL

The present invention relates to a method of bending a ductile sheet material, in which a sheet is moved by means of a row of rollers, the surfaces of which form a rolling path and a shaping curve for the sheet, the rollers being moved so that the shaping curve gradually changes from a substantially plane initial shape to a desired curved shape.

US 4,881,962 discloses a method of bending and tempering glass sheets. A glass sheet, which has been heated in a furnace, is moved during bending on a row of rollers forming a rolling path for the glass. The rolling path is gradually curved from a horizontal plane into a curved plane, the rollers being suspended in a device which makes it possible to displace the roller axes so as to be positioned on an arc of a circle. However, this method suffers from the drawback that only sheets with a cylindrical curvature can be manufactured.

The object of the present invention is to provide a method of the kind mentioned by way of introduction, in which sheets may also be bent into other curved shapes than cylindrical curvatures.

To meet this object, the method according to the invention is characterized in that the rollers are moved so that the shaping curve is displaced along the rolling path. In this manner, the ductile sheet may move like a wave over the row of rollers, the sheet following the shaping curve formed by the surfaces of the rollers. As the curvature of the shaping curve increases gradually, and the ductile sheet follows this curve all the time, many different complex curvatures may be obtained, like for instance oval or S-shaped curvatures. As, moreover, the ductile material constantly rolls on the surfaces of the rollers and in this manner is supported by them, a fairly soft material may be shaped without undesired marks being left in the surface thereof. If the ductile material after shaping needs a treatment, like for instance chilling or tempering, for retention of the desired shape, the sheet may be moved for a suitable time in contact with the rollers, the final, desired, curved shape being kept, until the sheet is able to retain this shape.

The method according to the invention may advantageously be used for bending heated glass. According to the invention, glass sheets may be manufactured with complex curvatures, which have only been possible up till now by use of fixed moulds which are very costly in manufacture. The result has been high prices per piece when producing small series of glass with a specific curvature. By constant movement of a soft glass sheet on rollers, unintentional bending and marks being left on the glass are prevented, both during shaping and chilling/tempering, and therefore, a higher optic quality is obtained compared to what has been possible by use of conventional methods. The shaping curve may during bending be reciprocated along the rolling path, whereby the sheet may be kept in movement in the time required for bending and the possible additional treatment by use of a shorter rolling path. The installation thus becomes less costly and less space demanding.

In an embodiment of the method the rolling path extends into a chilling and/or tempering device, after shaping of the glass sheet, the shaping curve is displaced along the rolling path into the chilling and/or tempering device, and the glass sheet remains in rolling contact with the rollers until it has been sufficiently cooled to retain the curved shape. By using a separate chilling device, shaping may take place in a hot area, and the subsequent chilling may take place quickly thereafter in an already chilled area. By the method the bent glass may be transported from a shaping device to a separate chilling or tempering device and treated therein, the bent glass being all the time retained in the curved shape obtained, and it is in this manner ensured that the glass after chilling keeps the desired shape with good accuracy. The glass sheet may be reciprocated during the entire above-mentioned course, or only during bending and chilling, respectively, and consequently a shorter installation may be used.

In an advantageous embodiment a number of rows of cooling air nozzles directed towards the rolling path is provided in the chilling and/or tempering device on either side of and along the rolling path, and the cooling air nozzles are, prior to the shaping curve being moved into the chilling and/or tempering device, kept in a retracted position, in which the shaping curve may pass between the rows of cooling air nozzles and subsequently, the cooling air nozzles are displaced to an active position, in which the rows of cooling air nozzles follow the contour of the shaping curve while being simultaneously displaced together with the shaping curve along the rolling path. In this way an effective chilling is attained and consequently a good tempering of the glass, as the cooling air nozzles can be brought near to the surface of the glass.

Bending of the glass sheet may advantageously take place in a furnace, the glass sheet being heated to its transformation temperature in advance during movement in contact with the rollers. In this way undesired chilling during bending of the glass is avoided, and consequently, it is not necessary to heat the glass to a higher temperature than the one possibly necessary for a subsequent tempering. Such an additional heating may impair the optic quality and the tempering properties of the glass.

Moreover, the invention relates to a device for bending a ductile sheet material, said device having a row of rollers, the surfaces of which form a rolling path for the sheet to be bent, the rollers being from an initial position mutually displaceable in a transverse direction of the rolling path for the formation of a shaping area.

The apparatus according to the invention is characterized in that the displacement of the rollers is controlled so that the position of the shaping area is displaceable along the rolling path. In this way the advantages described above are obtained.

Preferably the rotational speed of the rollers is controlled so that a ductile sheet in contact with the rollers in the shaping area may follow this area by displacement of the area along the rolling path. In this manner the movement of the sheet may be controlled at different shapes of the shaping area, the sheet may for instance roll on an area in the form of a crest of a wave .

In an embodiment the roller control comprises a template surface which is displaceable, both in the transverse direction of the rollers into abutment against the rollers and in the longitudinal direction of the rolling path. In this way a simple and well functioning control of the relative displacement and rotation of the rollers may be obtained, as they, by movement of the template surface towards the rollers and in the longitudinal direction of the rolling path, simply may be brought to roll against the template surface, whereby the rollers may follow the contour of the template surface. The rollers thus achieve a movement and a rotation which make it possible for a ductile sheet to roll on the rollers and to obtain a shape corresponding to the template surface, the sheet following the movement of the template surface.

The rollers may at the longitudinal movements of the shaping area be displaceable in a direction perpen- dicular to the rolling path in its initial position, and may be preloaded in this direction towards the initial position, preferably pneumatically loaded, suitably spring-loaded. The preloading ensures that the rollers may accurately follow the template surface, also at a high velocity. Pneumatic preloading makes a preloading force possible which is substantially independent of the displacement of the rollers, and in this manner a more accurate performance of the wave motion of the rollers may be attained. The rollers have preferably the form of cylinders, and the template surface may abut on and roll on an end area thereof .

In an embodiment, the template surface is positioned on one side of a flexible flat band stretched between two points, for instance by means of pneumatic actuators, and the template surface may be curved by displacement of one or more form members in abutment against the flat band, preferably by means of electric motors . If a form member having a curved shape corresponding to the desired curvature of the ductile sheet is used, then it is advantageous to press it gradually against the flat band, so that the band gradually takes up the curved shape of the form member during the rolling on the rollers. The form member might also be rolled directly against the rollers, but then a possible sharp curvature might be too abruptly transferred to the ductile sheet, which could have a negative effect on the quality of the finished product. If several, individually positionable form members are used side by side, the flat band offers a template surface with a continuous course in spite of the discrete positions of the form members. By adjusting the positions of the form members many different shapes of the template surface may be obtained without the necessity of producing a permanent template. Furthermore, the desired curvature may by positioning of the form members be gradually adjusted during bending of the sheet, so that a possible sharp curvature is not transferred too quickly to the ductile material. If the form members furthermore are flexibly fastened to the flat band, the template surface may obtain more complex shapes, like for instance S-curves, the form members being able both to press against and pull the flat band.

In a further embodiment, a roller together with a counter-roller constitutes a roller pair, between which the sheet may pass, the rollers of the roller pair are retained by a roller holder in an adjustable distance in relation to each other and the roller holder is pivotal about the axis of the roller against which the template surface may roll. By letting the ductile sheet pass through such roller pairs, the sheet is forced to follow the rolling path irrespective of the force of gravity and the acceleration of the rollers. The shaping area of the rolling path may thus be moved faster and consequently shaping of the sheet may take place faster. Making the roller holder pivotal makes it adaptable to the curvature of the sheet. The roller distance may be adjustable for operation with differing sheet thickness.

Each roller holder may have an abutment, preferably in the form of two or more guide rollers, against which the template surface may abut so that the orien- tation of the roller holder may be controlled relative to the template surface. In this way the orientation of the roller pair may be controlled so that a line through the axes of the roller pair is perpendicular to the tangent of the ductile sheet. In this way, the rollers do not have to follow the ductile sheet by their own action, and consequently a better quality of the finished product is obtained.

Each roller holder may have a counterweight, which may retain the roller holder in a rest position, so that the template surface may engage the abutment on the roller holder. When the abutment on the roller holder is not in contact with the template surface, the holder may swing freely, and the counterweight may in this situation ensure an adequate initial position of the roller holder, so that the template surface may engage the abutment, when it reaches that position, irrespective of the actual position of the template surface.

As an alternative to the above mentioned counterweights, and possibly also to the above discussed abutment on the roller holders, the roller holders may be interconnected by means of springs, such as compression or tension springs, acting on each roller holder at a distance from the axis around which the roller holder is pivotal. In this way neighbour roller holders will tend to adapt their rotational positions mutually and thereby stabilize their movement so that the above mentioned counterweight may be omitted. When the template surface is in contact with the abutment on a first roller holder, but not with the abutment of a neighbour holder to this first holder, the neighbour holder will be stabilized by the first holder in an adequate position for the template surface to contact the abutment on the neighbour holder. Furthermore, the above mentioned abutment on the roller holders might be omitted, because each roller as a result of the spring force does not have to follow the ductile sheet material by its own action only. On the contrary, the rollers may assist each other to follow the sheet material and thereby facilitate their action. As an alternative and/or a supplement to the above explained interconnection of the roller holders by means of springs, the roller holders may be guided in relation to each other by means of a flat elastic band, such as a flat spring, which extends between the rollers of each roller pair and thereby constitutes an elastic interconnection between the roller holders. Thereby advantages are obtained which are similar to those of the interconnection by means of pressure or tension springs.

If a section of the rolling path extends through a furnace, the rollers in this section may be arranged within the furnace so that each end of the rollers protrudes through a flexible sealing in a furnace wall, and the template surface may abut against the protruding ends. In this manner the required number of heat- resistant mechanical parts in the furnace is reduced, the device being more safe from a functional point of view and less costly in manufacture. In an advantageous embodiment substantially all positioning and movements are controlled by a computer via actuators. In this manner, among other things, a quick readjustment between different forms of curvature is made possible, as well as optimization of patterns of movement. Alternatively to the use of a template surface, it is furthermore possible to let the position and/or the rotation of each roller be controlled by a computer, possibly by means of servo controls and/or step motors .

The invention will now be explained in detail in the following by means of examples of embodiments with reference to the accompanying drawings, in which

Fig. 1 is an outline showing the principle of the method according to the invention for bending of a ductile sheet, the rollers being seen in their axial direction,

Fig. 2 an outline showing the principle of an embodiment of the method of Fig. 1, Fig. 3 a production line for bending and tempering glass sheets according to the invention,

Fig. 4 the bending and tempering section of the production line of Fig. 3,

Fig. 5 a template device for the bending section of Fig. 4,

Fig. 6 another embodiment of the template device of Fig. 5,

Figs 7 and 8 a roller holder for a roller pair, shown in two different positions, Fig. 9 an outline showing a section along the line IX- IX through the bending device of Fig. 4,

Fig. 10 an embodiment of a connection between a form member and the flat band,

Fig. 11 an outline of a template surface which has been lowered particularly far relative to the rolling path, and

Fig. 12 an embodiment of an interconnection between two roller holders.

Fig. 1 shows the basic principle of the method according to the invention by way of six successive instantaneous views a, b, c, d, e, f of a ductile sheet 1, which is being bent. In the following description, the method will be described in respect of a glass sheet which is heated to its transformation tempera- ture, but it goes without saying that the method may be applied to sheets of many different materials which are ductile or may be brought into a ductile condition. For instance thin, ductile metal sheets, rubber or thermosetting plastics may advantageously be shaped by the method. The sheet 1 is reciprocated by rolling on a row of rollers 2, which at the beginning are positioned in a horizontal plane, see Fig. la. The sheet may also be rolled continuously in the same direction, but then a longer row of rollers 2 is required, depend- ing on the rate of advance of the sheet and the time needed for bending. By keeping the sheet 1 in movement on the rollers 2, the plate is prevented from taking the shape thereof, even though it is soft. The sheet is moved by the rotation of the rollers, but may in principle also be moved by another suitable device, in which case the rollers may be freely rotatable.

During bending of the sheet 1, the rollers 2 are displaced in vertical direction so that the rollers which at a given time are situated in the shaping area below the sheet form a shaping curve, the curvature of which increases gradually. The shaping curve is formed by a line connecting the points, in which the rollers 2 are in contact with the sheet 1, and which coincides with the lower surface of the sheet. The sheet will therefore move from side to side, as if riding on a wave, the shape of the wave changing gradually from a substantially right line to a curved shape. In Fig. lb, the sheet 1 is on its way towards the right, and it has been bent slightly. In Fig. lc, it has nearly reached the right side and has been bent somewhat more and moves then towards the left, see Fig. Id, where it has been more curved. In Fig. le, the sheet has been once more at the left side and is once more on its way towards the right, and in Fig. If it has attained its final curvature.

The sheet shown in Fig. 1 moves in a trough of a wave, i.e. on a shaping curve, which is curved in a downward direction, and it will therefore in principle be movable simply as a result of the vertical displace- ment of the rollers, as, all the time, it will tend to seek downwards as a result of gravitation, but in practice it is preferred to control the rotation of the rollers, as the movement of the sheet may be controlled better in this way. Even though the rollers 2 here are shown displaceable in a direction perpendicular to their horizontal initial plane, they may be arranged in other ways, they might for instance be suspended in a chain, where each roller would be pivotal about the axis of a chain link. In this way, the rollers would be displaceable both in vertical and horizontal directions. It is of importance that the shaping curve can be moved so that it moves in the direction of the rolling path simultaneously with a gradual increase of its curvature, so that shaping of the glass sheet may occur gently.

When the sheet 1 has attained the desired curvature, see Fig. If, the shaping curve is reciprocated under retention of this curvature, while the sheet is being chilled, until it is able to retain its final shape. Not until then does the sheet leave the support from the rollers 2.

In Fig. 1 the sheet is moved on top of the row of rollers 2 and assume the shape of the shaping curve as a consequence of the effect of gravity. Therefore, the rollers cannot be moved with a greater velocity than that by which the soft sheet 1 is able to follow the shaping area. In Fig. 2, another embodiment of the invention is shown, where each roller 2 below the glass sheet has a corresponding counter-roller 3 above the glass sheet. The upper roller 3 of a pair of rollers is connected with the lower roller 2 so that the glass sheet may just pass between them, and the roller pairs are all the time oriented in such manner that a line through the axes of the rollers is substantially perpendicular to the tangent of the glass sheet between the rollers. The upper roller 3 thus follows the movement of the lower roller 2 and thereby ensures that the glass sheet 1 abuts against the lower roller 2 and therefore follows the shaping curve without being dependent on the effect of gravity. Consequently, the rate of advance of the shaping area may be increased, and furthermore the shaping device may be differently oriented in space, for instance the axes of the rollers 2, 3 could be vertical.

It is also possible to link the upper rollers 3 to the movement of the lower rollers 2 in another manner, for instance the upper rollers 3 may be displaceable along the same vertical axes 4, which are followed by the lower rollers 2. In this case, the distance between the rollers of a roller pair may, however, be varied depending on the steepness of the shaping curve when it passes the roller pair, as the glass sheet not always passes between the roller pair perpendicularly to the connection line between the roller axes. The link shown in Fig. 2 of the rollers 2, 3 in a roller pair is, however, preferred, as the contact points of the rollers with the glass sheet will thus be opposite one another relative to the glass sheet, whereby a pressing force perpendicular to the glass sheet will be attained. This pressing force will consequently not be able to induce a possible undesired deformation on the glass sheet.

Fig. 3 is a schematic view of a production line 5 according to the invention for bending and tempering sheets 1 of plane glass. The production line 5 comprises in order from the left an introduction section 6, a preheating section 7, a bending section 8, a tempering section 9 and a discharge section 10. All sections 6, 7, 8, 9, 10 are traversed by a rolling path 11, which is made up of a row of rollers 2, and which forms a conveyor for the glass sheets 1 to be bent. As mentioned above, each roller 2 in the bending section 8 and possibly also in other ones of the sections 6, 7, 9, 10 has a corresponding upper counter-roller 3 (not shown in the figure) . In the introduction section 6 plane glass sheets to be bent may in a manner known per se be introduced in the production line in cold state and disposed on the rolling path 11. One sheet at a time may be introduced or possibly more next to each other both in the longitudinal direction and in the transverse direction of the rolling path 11, but in the following, only a single sheet 1 will be described for the sake of convenience .

When the rollers 2 are rotated, the sheet 2 moves into the preheating section 7, where it is then reciprocated on the rollers 2, while it is being heated to its transformation temperature. The rotation of the rollers 2 may here take place in various manners, for instance they may be rotated by means of a chain drive, or a plane surface may be rolled over them. The latter solution is preferred, as this device after the heating advantageously may be used also for introducing the glass sheet into the bending device 8, which is also a furnace . The rollers 2, 3 within the furnaces 7, 8 are sintered silicium rollers, which at both ends protrude through a furnace wall 55. Around the rollers 2, 3, a flexible sealing has been arranged, for instance comprising a ceramic sealing wall 56, through which the rollers 2, 3 extend, and which may be raised and lowered together with the rollers, said wall sliding sealingly against a second ceramic surface 57 secured to the furnace wall 55, see Fig. 9. A transport device 12 situated outside the furnaces 7, 8 has a downwards facing side which is coated with a plane rubber surface 13, which may be pressed downwards against and moved over the protruding roller ends 36 in rolling contact therewith, the transport device 12 being suspended displaceably along the rolling path 11 in an upper rail 15 extending above the rolling path 11. The roller ends 36 are knurled to ensure good contact with the rubber surface, as the rubber during the rolling may be pressed down into the knurled surface, so that a contact free from slippage is attained and consequently a pure rolling. In this manner, when the sheet 1 has been heated, the transport device 12 moves from the preheating section 7 to the bending section 8, the rollers 2 being rotated, and the sheet 1 therefore comes along into the furnace 8. In the bending section 8, the template device 14 takes over the movement of the rollers 2, the rubber surface 13 on the transport device 12 being raised from the roller ends 36 at the same time or somewhat before a template surface 21 of the template device 14 is lowered against them. Then the transport device 12 is taken back to the introduction section 6, from where it may straight away guide yet another sheet 1 into the preheating section 7 and start the movement of this sheet, while it is being preheated. The transport device 12 and the template device 14 may pass each other, the rubber surface 13 on the transport device 12 and the template surface 21 on the template device 14 rolling against the roller ends 36 at various points in the longitudinal direction of the roller ends, see Fig. 9. It should be noted that if the rollers 2 in the introduction section 6 and the preheating section 7 are rotated by means of for instance a chain instead of the transport device 12, then the latter may be omitted, as it will be possible to guide the template device 14 into the preheating section 7, from where it may move the glass sheet 1 into the bending section 8.

The template device 14 is suspended displaceably along the rolling path 11 in a lower rail 28 extending below and in parallel with the upper rail 15, see Fig. 9. In the template device 14 a flat band 18 is suspended between two rollers 16, 17, so that the lower surface of the band in an initial position extends in parallel with and faces the rolling path 11. The ends of the band extend over the rollers 16, 17 and are then connected with the plungers in their respective pneumatic actuators 19, 20, which are all the time being fed by compressed air and thus keeping the band 18 stretched. The pneumatic actuators 19, 20 may be replaced by springs or other resilient means, and by suitable design of these, the rollers 16, 17 may also be omitted. The band 18 might instead be rolled around the rollers 16, 17, and the rollers could then be preloaded by torsion springs.

The lower surface of the band is coated with a rubber coating constituting the template surface 21 and which like the rubber surface 13 on the transport device 12 may roll steadily towards the knurled roller ends 36 protruding from the furnace wall 55. The band 18 with the rollers 16, 17 and the pneumatic actuators 19, 20 are suspended in a frame 22 which by means of linear actuators 23, 24 can be vertically displaced relative to a glide 25, which by means of an electric motor (not shown) can be displaced along the rolling path 11 on the lower rail 28. With reference to Fig. 5 a row of linear actuators 26 has been arranged on the frame 22 along the band 18, said actuators being driven by electric motors, like for instance servo motors or step motors, and being each able to displace a form member 27 in vertical direction. The form members 27 are secured to the upper surface of the flat band 18 in such manner that they are displaceable in the longitudinal direction of the band 18 and be tilted relative to the band, for instance, they may be secured by means of a hinge 58, in which a first hinge member 59 in the form of a pin on the form member 27 is in engagement with an elongated hole 60 in a second hinge member 61, which is mounted on the upper surface of the flat band 18, see Fig. 10. The members 27 may also be connected with the flat band 18 in other ways, for instance, they may have a rounded downwards facing surface for abutment against the band 18. The flat band 18 may be deformed by vertical displacement of the form members 27. It appears from Fig. 5 that the template surface 21 on the lower surface of the band 18 by mutually differing positionings of the form members 27 may be brought to assume many different curved shapes, like for instance the S-curve shown. Such an S-curve is not possible if the form members 27 are not secured to the band 18, but merely abut against it.

In the bending section 8 and the subsequent tempering section 9, the rollers 2 are vertically displaceable and preloaded by means of pneumatic cylinders 54 to an upper initial position, in which they are positioned in a plane in extension of the rollers in the preceding sections 6, 7. The rollers 2 may also be preloaded in other ways , for instance by means of springs, but by means of pneumatic cylinders a homogenous, upwards directed load is attained which is independent of the actual position of the roller.

When the template device 14, as mentioned above, takes over the movement of the glass sheet 1 on the rollers 2, all form members 27 are first adjusted to the same height position, so that the template surface 21 follows a straight line, and the template surface is pressed down against the roller ends 36 by means of the actuators 23, 24. The actuators 23, 24 might be omitted, as the initial position of the template surface may be close to the rollers 2, so that a slight displacement downwards of the form members 27 is sufficient for the template surface 21 to abut against the roller ends 36 of the rollers 2. The glass sheet 1 is now reciprocated, the template device 14 being reciprocated on the lower rail 28, and the form members 27 are gradually displaced relative to each other, so that they finally take up a position, in which the shape of the template surface corresponds to the desired shape of the actual glass sheet 1. The downwards movement of the form members may advantageously be controlled so that each member is moved at a constant speed, and that all members within the same period of time reach their final positions. When the template surface 21 starts curving, the rollers 2 will by being displaced in downward direction transfer the curved shape to the glass sheet 1, the roller ends 36 rolling all the time against the template surface, as they are preloaded thereagainst . When for instance a downwards facing top of the template surface passes a roller end 36, then the whole roller 2 will be displaced by parallel motion in downward direction. As the roller ends 36 roll against the template surface, the rotational speed of each individual roller will vary depending on the inclination of the template surface when it passes the roller. The shape of the glass sheet follows that of the template surface, and, therefore, the roller will have a rotational speed, which also results in pure rolling of the roller against the glass sheet .

In Fig. 6 another embodiment is shown of the template device 14 according to Fig. 5. The band 18 is here suspended resiliently stretched in the frame 22 in the same way as in Fig. 5. For providing the curved shape of the template surface 21, a single form member 29 is, however, used here in the form of a block with a lower surface 30, the shape of which corresponds to the desired curved shape of the glass sheet 1. Such a form member may be manufactured cheaply and simply, as for instance it may be cut out from plastics by means of a computer-controlled machine tool. The form member 29 may be vertically displaced relative to the band 18 by means of actuators 31. During bending of the glass sheet 1, the form member is at the beginning raised so much that the band 18 extends rectilinearly, and the template surface is brought to roll against the roller ends 36, the frame 22 being lowered by means of the actuators 23, 24. Then the form member 29 is gradually lowered relative to the band 18, so that finally the band abuts along the entire lower surface 30 of the form member 29, whereby the template surface 21 obtains a shape corresponding to the shape of the lower surface 30 of the form member 29. In this manner, like in the embodiment shown in Fig. 5, a gradual shaping of the sheet 1 is obtained. If the form member 29 for instance has a top 32, it will only gradually be transferred to the shaping curve on the rolling path 11. By shaping of certain materials, the band 18 may sometimes be omitted, as the lower surface 30 of the form member 29 is then lowered gradually directly towards the roller ends 36. The top 32 shown will then be more quickly transferred to the sheet 1. To obtain the parallel displacement of the rollers 2, it is in consideration of stability preferred that identical template surfaces 21 roll against the rollers 2 at both ends 36 thereof, but it is also possible to use only one template surface at one end, if the rollers are mounted in a steady parallelism.

Fig. 7 shows a roller holder 33 connecting one roller end 36 of the roller 2, which rolls against the lower surface of the glass sheet 1, with a counter- roller 3 rolling against the upper surface of the glass sheet 1. As described above, each roller 2 in the bending section is associated with a counter-roller 3, these counter-rollers 3 being, however, not shown in Figs 3 to 6, and being not necessary according to the invention. The roller 2 is at each end 36 pivotally mounted in the upper end of a piston rod 34 in the pneumatic cylinder 54, which establishes the preloading of the roller 2 towards the initial position as described above. The roller holder 33 proper is pivotally mounted on the piston rod 34 around the axis of rotation of the roller 2.

The counter-roller 3 is pivotally mounted about an axis which is parallel with the axis of the roller 2 and which may be displaced by parallel motion relative thereto by turning of an adjustment screw 35 on the two roller holders 33 at each end 36 of the rollers 2, 3 for adjustment of the gap between the rollers to different glass thicknesses. The adjustment by displacement of the roller 3 relative to the roller 2 may take place in a manner known per se, the shaft of the roller 3 being displaceable in an elongate hole 38 in the roller holder 33, where the screw 35 abuts a shaft bushing 39 for the roller 3. Moreover, the adjustment of the gap between the rollers 2, 3 may advantageously take place by means of an actuator, like for instance an electric actuator, mounted on the roller holder 33, so that all roller pairs may at the same time be automatically adjusted from a central control. The roller 3 may further be preloaded against the roller 2, for instance a pressure spring (not shown) may be arranged between said shaft bushing and the roller holder 33. The counter-roller 3 is at the holder 33 in driving connection with the roller 2 via a toothed gearing (not shown) , which is flexible in respect of the mentioned adjustment of the gap between the two rollers 2, 3, so that the rollers 2, 3 always rotate at the same speed.

The flat band 18 rolls at bending of the glass sheet 1 against the roller end 36 of the roller 2 and furthermore against two guide rollers 37, 42 mounted on the roller holder 33 at either side of the roller end 36 of the roller 2. In Fig. 7 a situation is seen, in which the flat band 18 stands fairly steeply relative to horizontal, and it appears that the guide rollers 37, 42 take care of orienting the roller holder 33 so that a line 40 through the axes of the rollers 2, 3 is perpendicular to a tangent 41 to the glass sheet 1 between the rollers 2, 3 (the glass sheet 1 is not shown, as it is situated behind the band 18 and follows the band) .

In Fig. 8 a situation is shown, in which the template surface 21 does not yet abut against the roller end 36 of the roller 2, and also the glass sheet 1 has therefore not yet reached abutment against the rollers 2, 3. The roller holder 33 may therefore swing freely, and a counterweight 43, which is made as a part of the holder 33, therefore hangs downwards so that the guide rollers 37, 42 are located in a horizontal plane. In the situation shown, the template surface 21 moves from the left towards the right in the direction of the arrow and will therefore first get into abutment against the left guide roller 37, whereby the roller holder will turn anti-clockwise, until the template surface 21 also abuts against the roller end 36 and the guide roller 42, following which the holder 33 is in the position shown in Fig. 7. Fig. 12 shows two roller holders 33 interconnected by means of a spring 62 which acts on points 63 of the holders 33. The point 63 to which the spring is attached is situated at a distance from the axis of the roller 2 about which the holder 33 is pivotal. The spring 62 stabilizes the rotational positions of the holders 33 in relation to each other in such a way, that a first holder 33 will always be in an adequate position to contact the template surface 21 by means of the guide rollers 37, 42, because a neighbour holder 33 to said first holder will contact the template surface 21 first and thereby by means of the spring 62 move said first holder 33 in position before the template surface 21 reaches said first holder.

Furthermore, the roller holders 33 are guided in relation to each other by means of a flat elastic band 64 which is extended between the roller 2 and its counter roller 3 of each roller pair. Another possibility is to let the band 64 extend between separate guide rollers (not shown) mounted on each roller pair. The flat band 64 guide the roller holders 33 in an position adequate for abutment of the template surface 21 against the guide rollers 37, 42 in a manner similar to that of the above discussed interconnection springs 62.

If a glass sheet 1 is to be bent, the shape of which has a relatively steep course at an edge of the sheet 1, the roller holder 33 is to turn quickly at the abutment of the template surface 21 against the guide rollers 37, 42, the holder may for instance have to turn from the position shown in Fig. 8 to the position shown in Fig. 7 immediately at the abutment. To avoid this quick turning, the template surface may, however, be flattened outside the edge of the glass sheet, as indicated in Fig. 11, where the glass sheet 1 is shown with a broken line. The template surface 21 is in view of this lowered relative to the rolling path 11, so that the rolling path extends in level b, instead of in level a, relative to the glass sheet, which has been indicated with broken lines. The inclination of the template surface 21 outside the edge of the glass sheet 1, i.e. between the line a and the line b, gradually decreases until the surface 21 is horizontal. When the template surface 21 moves along the rolling path 11, the roller holders 33 therefore gradually take up the turned position which is necessary at the edge of the glass sheet. If several form members 17 are used, like in the embodiment in Fig. 5, they may be positioned so that the template surface follows a course as shown in Fig. 11. If an embodiment with a single form member 29 is used, as shown in Fig. 6, this member 29 must be lowered an extra distance relative to the flat band 18, which may then flatten gradually next to the form member 29.

When the glass sheet has acquired its final curved shape, it is moved out of the bending section 8 and into the tempering device 9, the template device 14 sliding on the rail 28 into the tempering device 9, so that the shaping curve is displaced along the rolling path 11, and the curved glass sheet 1 is therefore supported during the whole movement . In the tempering device 9 an upper cooling sledge 44 is displaceable on the rail 15, and a lower cooling sledge 45 is displaceable on a rail 46 positioned below and along the rolling path 11. On the upper cooling sledge 44 a cooling air manifold 47 is vertically displaceable by means of actuators 52 in a downward direction towards the rolling path 11, and on the lower cooling sledge 45, a cooling air manifold 48 is vertically displaceable in an upward direction towards the rolling path 11 by means of actuators 53. The cooling air manifolds 47, 48 distribute cooling air from inlets 49, 50 to cooling air nozzles 51, which on the manifolds are directed towards the rolling path 11. The cooling air nozzles 51 are disposed in rows which extends in direction of the rollers 2 forming the rolling path 11, and each row may be means of linear actuator (not shown) be displaced in vertical direction relative to the rolling path 11.

While the glass sheet 1 is moved into the tempering device 9, the cooling manifolds 47, 48 are in a retracted position, in which the shaped glass sheet may pass between the cooling nozzles 51. When the sheet has arrived in the tempering device 9, the cooling sledges 44, 45 are brought to reciprocate along the rolling path 11 together with the shaping curve, which the glass sheet 1 follows, the cooling air manifolds 47, 48 being simultaneously lowered and raised, respectively, so that the cooling air nozzles 51 approach the rolling path 11. At the same time, the height of the cooling air nozzles 51 is furthermore adjusted to an active position so that the apertures of the nozzles 51 form a contour which follows the shaping curve, and cooling gas is by means of a ventilator and/or compressor blown from the inlets 49, 50 and through the nozzles 51. In this way the nozzles 51 are brought near to the glass sheet 1 for quick chilling. In view of a chill- ing/tempering, which is more evenly distributed over the glass surface, the rows of cooling air nozzles 51 may further be reciprocated in their longitudinal direction during chilling. The glass may be chilled in view of tempering and subsequently in view of chilling to handling temperature.

After tempering/chilling, the cooling manifolds 47, 48 are led away from the rolling path 11, and the template surface 21 is flattened to a flat curve and is led out of the chilling device 9 and into the discharge section 10, from where the finished bent sheet 1 can be removed. Alternatively, the template surface may just be raised from the rolling path 11, and the rollers 2 may rotate by means of another transport device, for instance one similar to the one 14 used for introducing the glass in the production line 5.

Though the embodiment of the invention shown has rollers 2, 3 in the form of cylinders, it would be possible instead of each cylinder to use a row of rollers mounted spaced on a shaft. It is moreover possible, within the scope of the invention, to superimpose the said bending of the sheet around axes perpendicular to the travelling direction of the sheet with a bending around axes in parallel with the travelling direction of the sheet. This superimposed bending may for instance occur by means of complementary shaping rollers, of which a lower roller may be thinner in the middle, and an upper roller may be thicker in the middle. It may also take place by means of rollers, of which a middle section may be lowered relative to the remaining part of the roller.

All movements made in the production line may be made by various kinds of actuators, for instance pneumatic actuators, or electrical actuators, for example servo motors or step motors, and these actuators may advantageously be controlled by a central computer. In this way, a desired curve shape, which it is desired to impart to a piece, may easily be encoded in the computer, i.e only a few points may be entered, following which the computer calculates a suitable curve through these points.

After the tempering section, a detecting device may advantageously be provided, in which the shape of the finished, bent sheet 1 may be registered, for instance electronically, like in a computer. This may for instance take place by optical scanning, such as infrared sensors, or possibly by ultrasound. Such a device may be used for quality control of the bent sheets 1, but it may also be placed at another point relative to the production line 5 and used for detecting an already bent element, the shape of which is to be used for new bent sheet pieces . In this manner a bent glass sheet may quickly and simply be copied.

Claims

P A T E N T C L A I M S

1. A method of bending a ductile sheet material, in which a sheet (1) is moved by means of a row of rollers, the surfaces of which form a rolling path (11) and a shaping curve for the sheet (1) , the rollers being moved so that the shaping curve gradually changes from a substantially plane initial shape to a desired curved shape, c h a r a c t e r i z e d in that the rollers (2) are moved so that the shaping curve is displaced along the rolling path (11) .

2. A method according to claim 1, c h a r a c t e r i z e d in that the ductile sheet material (1) is heated glass.

3. A method according to claim 1 or 2, c h a r a c t e r i z e d in that the shaping curve is reciprocated along the rolling path (11) .

4. A method according to any one of the preceding claims, c h a r a c t e r i z e d in that the rolling path (11) extends into a chilling and/or tempering device (9) , that the shaping curve after shaping of the glass sheet (1) is displaced along the rolling path

(11) into the chilling and/or tempering device (9) , and that the glass sheet (1) remains in rolling contact with the rollers (2) until it has been sufficiently cooled to retain the curved shape.

5. A method according to claim 4, c h a r a c t e r i z e d in that a number of rows of cooling air nozzles (51) directed towards the rolling path (11) is provided in the chilling and/or tempering device (9) on either side of and along the rolling path (11) , that the cooling air nozzles (51) , prior to the shaping curve being moved into the chilling and/or tempering device (9) , are kept in a retracted position, in which the shaping curve may pass between the rows of cooling air nozzles (51) , and that subsequently, the cooling air nozzles (51) are displaced to an active position, in which the rows of cooling air nozzles (51) follow the contour of the shaping curve while being simultaneously displaced together with the shaping curve along the rolling path (11) .

6. A method according to any one of the preceding claims, c h a r a c t e r i z e d in that bending of the glass sheet (1) takes place in a furnace (8) , the glass sheet (1) being heated to its transformation temperature in advance during movement in contact with the rollers (2, 3) .

7. A method according to any one of the preceding claims, c h a r a c t e r i z e d in that the shaping curve is first reciprocated in the furnace (7, 8) during the heating and during bending of the glass sheet (1) , then displaced along the rolling path (11) to the chilling and/or tempering device (9) , and finally reciprocated in the chilling and/or tempering device (9) during chilling of the sheet (1) .

8. A method according to any one of the preceding claims, c h a r a c t e r i z e d in that during bending of the sheet, a number of the rollers (2, 3) is reciprocated a number of times in a transverse direction relative to the rolling path (11) .

9. A device (5) for bending a ductile sheet material, said device having a row of rollers (2) , the surfaces of which form a rolling path (11) for the sheet (1) to be bent, the rollers (2) being from an initial position mutually displaceable in a transverse direction of the rolling path (11) for the formation of a shaping area, c h a r a c t e r i z e d in that the displacement of the rollers (2) is controlled so that the position of the shaping area is displaceable along the rolling path (11) .

10. A device (5) according to claim 9, c h a r a c t e r i z e d in that the rotational speed of the rollers (2) is controlled so that a ductile sheet (1) in contact with the rollers (2) in the shaping area may follow this area by displacement of the area along the rolling path (11) .

11. A device (5) according to claim 9 or 10, c h a r a c t e r i z e d in that the rollers (2) at the longitudinal movements of the shaping area are displaceable in a direction perpendicular to the rolling path (11) in its initial position, and that they are preloaded in this direction towards the initial position, preferably pneumatically loaded, suitably spring-loaded.

12. A device (5) according to any one of the claims 9 to 11, c h a r a c t e r i z e d in that the roller control comprises a template surface (21) which is displaceable, both in the transverse direction of the rollers (2) into abutment against the rollers (2) and in the longitudinal direction of the rolling path (11) .

13. A device (5) according to claim 12, c h a r a c t e r i z e d in that the rollers (2) have the form of cylinders and that the template surface (21) may abut on and roll on an end area (36) thereof.

14. A device (5) according to claim 13, c h a r a c t e r i z e d in that the template surface (21) is a coating of a resilient material, for instance rubber, and that the end area (36) of the rollers (2) has a finish which can roll steadily on the template surface (21), for instance a knurled surface.

15. A device (5) according to any one of the claims 12 to 14, c h a r a c t e r i z e d in that the template surface (21) is situated on one side of a flexible flat band (18) stretched between two points, for instance by means of pneumatic actuators (19, 20), and that the template surface (21) may be curved by displacement of one or more form members (27) in abutment against the flat band (18) , preferably by means of electric motors (26) .

16. A device (5) according to claim 15, c h a r a c t e r i z e d in that a form member (29) with a curved shape corresponding substantially to the desired curvature of the ductile sheet (1) is position controlled to press against the flat band (18) .

17. A device (5) according to any one of the claims 9 to 16, c h a r a c t e r i z e d in that a roller (2) together with a counter-roller (3) constitutes a roller pair, between which the sheet (1) may pass, that the rollers (2, 3) of the roller pair are retained by a roller holder (33) in an adjustable distance in relation to each other and that the roller holder (33) is pivotal about the axis of the roller (2) against which the template surface (21) may roll.

18. A device (5) according to claim 17, c h a r a c t e r i z e d in that each roller holder

(33) has an abutment, preferably in the form of two or more guide rollers (37, 42) against which the template surface (21) may abut, so that the orientation of the roller holder (33) may be controlled relative to the template surface (21) .

19. A device (5) according to claim 17 or 18, c h a r a c t e r i z e d in that each roller holder (33) has a counterweight (43) , which may retain the roller holder (33) in a rest position, so that the template surface (21) may engage the abutment on the roller holder (33) .

20. A device (5) according to any one of the claims 17 to 19, c h a r a c t e r i z e d in that the roller holders (33) are interconnected by means of springs (62), such as compression or tension springs, acting on each roller holder (33) at a distance from the axis around which the roller holder (33) is pivotal .

21. A device (5) according to any one of the claims 17 to 20, c h a r a c t e r i z e d in that the roller holders (33) are guided in relation to each other by means of a flat elastic band (64) , such as a flat spring, which extends between the rollers of each roller pair.

22. A device (5) according to any one of the claims 9 to 21, c h a r a c t e r i z e d in that a section of the rolling path (11) extends through a furnace (7, 8), that the rollers (2, 3) in this section are arranged within the furnace (7, 8) so that each end (36) of the rollers protrudes through a flexible sealing (56, 57) in a furnace wall (55) , and that the template surface (21) may abut against the protruding ends (36) .

23. A device (5) according to any one of the claims 9 to 22, c h a r a c t e r i z e d in that a section of the rolling path (11) extends through a chilling and/or tempering device (9) , that on either side of and along the rolling path (11) a number of rows of cooling air nozzles (51) is arranged, said nozzles being directed towards the rolling path (11) , and that the cooling air nozzles (51) are controlled so that they, for instance by means of electric motors, may be displaced from a retracted position to an active position, in which the rows of cooling air nozzles (51) follow the contour of the rolling path (11) in the shaping area.

24. A device (5) according to claim 23, c h a r a c t e r i z e d in that the rows of cooling air nozzles (51) are suspended in a cooling sledge (44, 45) which can be reciprocated along the rolling path (11) •

25. A device according to any one of the claims 9 to 24, c h a r a c t e r i z e d in that substantially all positioning and movements are controlled by a computer via actuators .

26. A device (5) according to claim 9 or 10, c h a r a c t e r i z e d in that each roller in the form of a cylinder (2) together with a counter-cylinder (3) constitutes a cylinder pair, of which each cylinder may roll on either side of a ductile sheet (1) , and that the position and/or the rotation of each cylinder (2, 3) is/are controlled by a computer, possibly by means of servo controls and/or step motors .