FR2811660A1 - Bending of thin glass sheets in a device incorporating a cooling station with a frame of rollers to conserve the shape of the bent glass sheets and eliminate deformation during cooling - Google Patents

Abstract

Bending a glass sheet comprises heating the glass to a softening temperature, conveying the glass sheet along an essentially horizontal path (19) to a bending station (18) between two frames (20,21), shaping the glass sheet by pressing between the two frames and cooling the glass sheet in an suitable station. This cooling station (16) is made up of a frame (24) of rollers adapted to receive the bent glass sheet with the rollers (25) oriented parallel to the direction given to the glass sheet by the direction in which it is fed into the bending station. An Independent claim is included for the glass sheet bending device for implementing this process.

Description

- 1. -

  METHOD AND DEVICE FOR BOMBING A GLASS SHEET

  The invention relates to a technique for bending a glass sheet, followed by a cooling step. The technique according to the invention is either adapted to the bending of a glass sheet especially intended to be tempered, or to the bending of glass sheets then cooled and then

  assembled in pairs to form a laminated glazing.

  Although not limited to such applications, the invention will be more particularly described with reference to the formation of

  glass intended to equip the lateral parts of motor vehicles.

  More particularly, the invention relates to those techniques in which the glass sheets are fed one by one through a heating furnace to raise their temperature to a temperature close to the softening temperature, the glass sheets being conveyed on a bed of rollers. The glass sheets are then led, right out of the oven, to a bending station in which a lower shape is raised a sheet of glass to press it against a higher shape to obtain the desired shape. The glass sheet is then redeposited on the conveyor to be driven

  at the cooling station such as a quenching station.

  These bending techniques are described in particular in US 4,872,898. This document describes in particular a technique according to which a glass sheet is transported on a roller conveyor through a tunnel furnace in which its temperature is brought to its softening temperature, and then is conducted 2 - to a station bending. In the bending station the glass sheet is lifted from the conveyor by a frame having the shape that is to be imparted to the glass sheet. The frame is discontinuous so as to cross the bed of rollers on which initially rests the glass sheet. The frame then raises the glass sheet to press against an upper solid shape whose shape is complementary to that of the frame and therefore corresponds to the desired shape for the glass sheet. After pressing, the lower frame descends to a level below the roll bed and thus redeposits the glass sheet on said bed of rollers. The rollers then start moving again to

  drive the glass sheet to the quenching station.

  Other documents describe variants of this type of technique.

  In particular with regard to the lower frame and more particularly

  its configuration to allow its passage through the bed of rollers.

  Other documents still describe alternative designs of the rollers within the bending station always to facilitate the

passage of the lower frame.

  In addition to the particularity of the lower frame which crosses the roll bed which acts as a conveyor, this type of technique is characterized by the fact that the bending operation takes place outside the oven or at least a maintained chamber in temperature. This type of technique must be considered as a cold technology, this qualifier defining the location of the bending station outside a chamber held in temperature; this means that the control of the positioning of the bending tools is simpler than in the case of hot technologies, and that in return the bending process is a race against time since as soon as the oven leaves, the glass sheet goes cool down; modifications of the bending operation or its

  conditions are therefore delicate and limited.

  In addition, recent developments, particularly in the automobile industry, tend towards an ever increasing demand for glazing of complex shapes, with in particular very pronounced curvatures; At the same time, the optical quality required is higher and higher. In

  in addition, the thickness of the glazing is also reduced.

  Regarding the forming of side windows for the automotive industry on a tool according to this technology, the direction of travel of the glass sheets during their passage in the oven on the roller conveyor is imposed by the subsequent constraints of use. Indeed, it is not desirable to see the marks, in a substantially vertical direction when the glass sheet is in use condition, that can leave the rollers during the rise in temperature; if such marks exist, they actually become very visible according to certain incidences for an observer who is for example facing the motor vehicle. Therefore the direction of travel of said glass sheets is imposed to see these marks in a substantially horizontal direction and therefore almost invisible to

1 5 an observer.

  The current demands of manufacturers also require significant bending in the vertical direction after mounting the glass sheet on the motor vehicle. This large bending will therefore correspond to a bending direction corresponding to that of the conveyor in the oven. It is thus delicate to be able to transport the glass sheets after bending on a roller conveyor, these being perpendicular to the bending direction, without risk of breakage or deformation of the glass sheets, these being no longer then supported only by their central part. It is furthermore desirable, particularly for a good reproducibility of the process, to preserve the shape obtained after pressing and not to see it evolve between the pressing station and the

cooling station.

  Solutions to prevent deformation of the glass sheet after passing through the pressing station have already been proposed. The document EP 523 017 notably describes the use of a shuttle or mobile frame which has the final shape of the glass sheet for

  drive it from the bending station to the cooling station.

  Document US Pat. No. 4,433,993 furthermore provides a shuttle which follows a direction transverse to the direction of the conveyor passing through the furnace. These techniques make it possible to take charge of the glass sheet immediately after pressing so as to maintain the shape obtained and rapidly drive the glass sheet towards the cooling zone. These techniques, however, have disadvantages; first of all the movement of the shuttle requires indexing at each transfer so that the glass sheet is perfectly received. On the other hand, the glass sheet being supported at its periphery by a frame, the cooling is not homogeneous; this disadvantage is particularly disadvantageous when the glass sheets are annealed or semi-tempered for the production of laminated glazing, or when soaked. Indeed, it appears in these different cases

  level of the edges which lead to a fragility of the glazing.

  The inventors have thus set themselves the task of developing a bending technique, particularly well suited to bending thin glass sheet, which has the advantages of the techniques mentioned above, especially the absence of visible markings when the glazing is used, but which does not have the disadvantages thereof, and in particular which makes it possible to carry out a subsequent cooling of

  glass sheets without problems around the edges of the glass sheets.

  This object has been achieved according to the invention by a method of bending a glass sheet comprising heating the glass sheet; transporting the glass sheet along a substantially horizontal path to a bending station between two shapes, shaping the glass sheet by pressing between the two forms, cooling the glass sheet in a suitable station , means comprising shaped rollers receiving the glass sheet after bending, said shaped rollers being oriented parallel to the direction defined on the

  glass sheet by its feeding direction in the bending station.

  According to a preferred embodiment of the invention, the means comprising the shaped rollers are at least one shuttle, advantageously

  moving between the bending station and a cooling station.

  According to the invention, after the pressing phase, the glass sheet is redeposited after pressing and therefore after its forming on rollers themselves in shape that will allow to retain the shape obtained and avoid undesirable complementary deformation. To satisfy this result, the rollers are oriented parallel to the direction defined on the glass sheet by its feeding direction in the bending station; that is, in the case of automobile side windows which have a principal bending in the vertical direction when in use and which run in the oven in this vertical direction, the shaped rollers which receive the sheet of glass after pressing are oriented perpendicular to the vertical direction of the glass sheet

  when it is mounted on a motor vehicle.

  The use as means comprising the rollers in the form of a shuttle which is preferably movable between the bending station and a cooling station makes it possible to interpose, in an easy manner, the shaped rollers between the upper form and the bed of rollers which convey the glass sheet from the heating furnace to the bending station. According to a first embodiment of the invention, the glass sheet is transported to the cooling station in a direction lateral to the direction of supply of said glass sheet to the bending station. According to this embodiment, the shaped rollers are thus arranged to form a lateral receiving bed and preferably perpendicular to the supply conveyor in the bending station. According to such an embodiment, the invention can also provide a cooling station on either side of the supply conveyor. Such an embodiment then consists of either alternately conveying the glass sheets of each of the sides, for example using the same shuttle, or for example using two shuttles -6 - each having shaped rollers. This last achievement

  can in particular make it possible to increase production rates.

  According to a second variant embodiment according to the invention, the glass sheet is kept in contact with the upper bending mold after pressing and is rotated by an angle of 90 to then be transported to the cooling station in its direction. feeding to the bending station. The invention thus provides according to this variant to position the rollers shaped parallel to the rollers of the supply conveyor from the oven to the bending station. Such a configuration allows a linear design that has the advantage of essentially modifying existing installations.

  simply adding a rotation element.

  According to a last variant of the invention, it is intended to combine the first two variants, that is to say that it is expected to be able to convey the glass sheets after pressing to a cooling station aligned with the conveyor of brought to the bending station

  and to at least one cooling station positioned laterally.

  The glass sheets are then advantageously conveyed by shuttles each associated with a cooling station, in particular

  to increase production rates.

  An advantageous embodiment of the invention provides that the glass sheet is movable on the shuttle comprising the shaped rollers. Such an embodiment also makes it possible to limit the risks of marking on the glass, the sheet of glass not remaining stationary on the shaped rolls. Indeed, at this stage of the process, the glass sheet is still hot enough to risk being marked if it remains stationary on rollers. Although such marking is not oriented in an apparent direction in an inconvenient manner for an observer, it may still be desirable to prevent the appearance of such marks for

better optical quality.

  Concerning the movement of the shuttle or, more exactly, means carrying the shaped rollers, the invention provides two possibilities; in a first embodiment, said shuttle makes a movement from the bending station to the entrance of the cooling station to deposit the glass sheet on a new conveyor, for example with rollers. According to a second embodiment more particularly adapted to the case of several cooling stations, the shuttle enters the cooling station and supports the glass sheet during at least part of the cooling time; the frozen glass sheet is then taken up by a conveyor, for example with rollers, these being no longer necessarily shaped. In both cases, the passage of the shuttle to the conveyor of the cooling station is done naturally by driving the rollers in the form of the shuttle that drives the glass sheet on the conveyor of the cooling station. In a preferred embodiment of the invention, it is provided that the glass sheet will move back and forth on the shuttle. This embodiment can in particular make it possible to have a shuttle of limited length and on which the glass sheet will not remain stationary until

  its transfer on the conveyor of the cooling station.

  The invention also proposes a device for implementing the previously described method. This bending device according to the invention comprises a furnace for heating a glass sheet, a device for supporting and transporting the glass sheet in a substantially horizontal plane passing through the furnace to a bending station which itself comprises even two forms of bending, a lower form passing through the transport device to press the glass sheet against an upper form, the latter comprising means for retaining a glass sheet after its forming, and said bending device further comprising at least one cooling station, at least one shuttle, carrying shaped rollers receiving a glass sheet after pressing, movable between the bending station and a cooling station, and the shaped rollers being oriented parallel to the -8 - direction defined on the glass sheet by its direction of supply into the

bending station.

  The device for supporting and transporting the glass sheet is advantageously a roller conveyor, which eventually terminates with an air cushion system in the bending station. The bending device thus described allows after the step of pressing a glass sheet to maintain it in contact with the upper form, to penetrate a shuttle having shaped rollers in the bending station to receive the sheet curved glass

  and keep the shape of it until the cooling station.

  According to a first embodiment of the invention, the direction of movement of the shuttle is lateral to the direction

  feeding the glass sheet from the furnace to the bending station.

  According to this embodiment, the shaped rollers are for example arranged in a direction perpendicular to the conveyor rollers

  supplying the glass sheet from the heating furnace.

  According to a second embodiment of the invention, the direction of movement of the shuttle is in the extension of the direction of supply of the glass sheet from the oven to the bending station and the upper shape pivots an angle 90 after pressing. This other embodiment therefore consists, after pressing, while the glass sheet is held against the upper shape, to rotate said upper shape to then redeposit the curved glass sheet on the rollers in the form of the shuttle, said rollers being parallel to the

  supply conveyor rollers from the oven.

  A preferred embodiment of the invention provides that the shuttle-shaped rollers are motor rollers; this embodiment allows the glass sheet to be set in motion as soon as it is deposited on the shuttle. More preferably, the shaped rolls have an alternating rotational movement to allow a back-and-forth movement of the sheet

  of glass on the shuttle, especially during the movement of it.

  In an alternative embodiment of the invention, the shuttle enters the cooling station. The alternating rotation of shaped rollers is

  so particularly interesting.

  As regards the upper bending mold, it advantageously comprises suction means for retaining the glass sheet after pressing. It is still possible to provide blowing means

  in particular to accelerate the removal of the glass sheet on the shuttle.

  Such blowing means are of course used only when the

  suction means are no longer.

  The device and the method thus described according to the invention make it possible to bend glass sheets according to the cold technology previously described, in particular by allowing a good bending accuracy and a good optical quality of the glass sheets more particularly intended to be used. used as side windows on

motor vehicles.

  The device and the method according to the invention in fact allow to receive the glass sheets after pressing on the rollers in the shape of the shuttle and thus to keep very precisely the desired shape and to avoid the markings visible by an observer after mounting on a vehicle. Such sheets of glass will thus be able to be used as monolithic glazing or assembled in pairs to form laminated glazings. In addition, in order to optimize the production rates, the invention advantageously proposes a device which comprises a cooling station in the extension of the direction of the device for transporting the glass sheet from the furnace to the bending station and / or at least a cooling station oriented laterally with respect to the previous direction. According to a preferred embodiment of the invention, it is in particular provided to have three cooling stations, each associated with a shuttle, and the upper form of

  bending being movable about an axis to allow a rotation of 90.

- 10 -

  Other details and advantageous features of the invention

  will appear below from the description of exemplary embodiments of

  1 to 4, which show,> FIG. 1, a schematic view of a bending and cooling line illustrating the technology to which the invention relates,> FIG. 2 and 2a, a diagram of FIG. a first embodiment of a device according to the invention,> Figure 3, a diagram of a second embodiment of the invention,> Figure 4, a diagram of the second embodiment shown in Figure 3 after the step pressing,

  > Figure 5, a diagram of a fourth embodiment of the invention.

  The different figures are not represented on the scale for

simplify understanding.

  FIG. 1 shows the furnace 1 in which a glass sheet 2 runs on a roller conveyor 3. During its stay in the oven 1, the glass sheet 2 is brought to its softening temperature. The glass sheet 2 is then driven still supported by the conveyor 3 to a bending station 4. In the bending station 4, is disposed a frame 5 in the plane defined by the roller conveyor 3. When the sheet of glass 2 is glass 2 arrives above this frame, bodies not shown in the figures allow to ensure precise positioning of said glass sheet, then its movement is stopped by stopping the rollers in the bending zone. The bending frame 5 then passes through the bed of rollers 3 to lift the glass sheet. As mentioned above, the bending frame 5 has the shape that is to be imparted to the glass sheet and is designed so as to pass through the roll bed 3; either the frame 5 is interrupted or the rollers of the bending zone are adapted to allow the frame 5 to pass from a position to a high position, for example using systems of the hydraulic cylinder type. Such embodiments are known to those skilled in the art. The bending frame 5 having supported the sheet

- 11 -

  of glass 2 presses it against a bending form 6,

  advantageously fully positioned above the frame 5.

  In the case of glass sheet 2 intended to equip the lateral parts of motor vehicles, the direction of travel of the glass sheets 2 on the roller conveyor 3 is imposed so that an observer looking at a motor vehicle from the front does not can see any marks left by the rollers of the conveyor 3 and this regardless of the incidence of observation. As explained above, it should not be possible to observe marks that would have a vertical direction on the glass sheet 2 when it is put in place on a motor vehicle. This means that the axis of rotation of the rollers of the conveyor 3 must correspond to the horizontal direction of the

  glass sheet 2 when it is mounted on a motor vehicle.

  Furthermore, the main bending to be imparted to the glass sheet 2 is oriented in the vertical direction of the glass sheet when it is on a motor vehicle. This means that the main direction of bending imparted to the glass sheet 2 after pressing is perpendicular to the orientation of the rollers of the conveyor 3. If the glass sheet 2 were to be redeposited after pressing on the conveyor 3, said conveyor 3 would not not able to receive said glass sheet 2 satisfactorily to retain its shape and not risk a breakage thereof, said glass sheet 2 can be supported only by its central portion; such a position would inevitably lead either to a complementary deformation of the glass sheet 2 which is not fully supported and still at an elevated temperature, or to a tilting of the glass sheet 2 leading to a probable breakage during

  contact on a conveyor roll.

  The technique of the invention particularly described in Figures 2 to 5 to prevent these risks and to maintain the desired shape already conferred on the glass sheet 2 during pressing in the bending station. The invention consists in receiving the glass sheet on a shuttle comprising shaped rollers whose provision is provided

- 12 -

  so that the concave shape of the rollers supports the bending form

main part of the glass sheet.

  FIG. 2 illustrates a device according to the invention in which, the glass sheet 2 is deposited after pressing on a shuttle 7 comprising shaped rollers 8, and is then led to a cooling station 9 arranged along a trajectory perpendicular to the conveyor 10 and passing the glass sheet 2 to the bending station 12. The shuttle 7 and its shaped rollers 8 is better illustrated in Figure 2a. The operating principle of the invention is when the glass sheet 2 arrives in the bending station 12 to take charge of it by the bending frame 13 which presses against the upper shape 14. Suction means, not represented in the figures, then retain the glass sheet in contact with the upper form while the bending frame 13 back down to its lower position and the shuttle 7 is interposed between the conveyor 10 and the upper form 14. The means suction are then stopped and the glass sheet is received by the shaped rollers 8 of the shuttle 7. Optionally, there may be provided blowing means to assist the deposition of the glass sheet. It can further be provided a vertical downward movement of the upper form 14 before releasing the glass sheet on the shuttle 7. The shuttle 7 is then moved to the cooling station 9 and the glass sheet 2 is transferred from the shuttle 7 to the cooling conveyor 15 which passes through said cooling station 9. The transfer is carried out by a driving rotation of the rollers 8, using any means known to those skilled in the art and not shown in the figures. In addition, these means causing the rotation of the shaped rollers 8 can be actuated upon removal of the glass sheet 2 on the shuttle 7 to prevent the glass sheet remains stationary and thus prevent any risk of marking the glass by the rollers 8. It is also possible to foresee

  an alternating rotation of the rollers 8 to obtain a movement of va-et-

  comes on the shuttle 7 during the movement of it to the station

- 13 -

  9. Regarding the displacement of the shuttle 7, it can be done to the entrance of the cooling station 9 or the shuttle 7 can enter said cooling station and transfer the glass sheet to the conveyor 15, for example when the glass sheet 2 is perfectly fixed. Of course, the representation made in FIG. 2 can be carried out symmetrically, that is to say that the station of

  cooling 9 could be on the left of the supply conveyor 10.

  The invention further provides the possibility of having two cooling stations 7, one on the left and the other on the right, then associated with two

shuttles 7.

  Figures 3 and 4 illustrate another embodiment of the invention according to which the cooling station 16 is installed in the alignment of the furnace 17, the bending station 18 and the conveyor 19 passing through the furnace 17 and bringing the sheet 2 to the bending station 18. The operating principle of the tools is identical to that of the embodiment of Figure 2; the essential difference is

  rotate the angle of 90 of the glass sheet while

  it is still in contact with the upper form 20 and immediately after pressing between said upper form 20 and the lower frame 21. The rotation of the glass sheet is obtained by a rotation of the upper shape around a support axis 22, illustrated by the arrow 23. The sheet is then redeposited, as in the case of Figure 2 on the shuttle 24 having shaped rollers 25. The shuttle 24 then moves to the cooling station 16 and the glass sheet 2 is transferred to the cooling conveyor 26. FIG. 3 thus illustrates this embodiment when the upper form 20 is in the pressing position and FIG. 4 illustrates the same embodiment, the upper form having

turned from an angle of 90.

  FIG. 5 is a final embodiment in which three shuttles 27, 28, 29 associated with three cooling stations, not shown in this figure, are provided. The three shuttles

- 14 -

  allow for two of them 27 and 28 to laterally transfer the glass sheets as shown in Figure 2 and the third 29 allowing a transfer of the glass sheets in alignment with the conveyor 30, the oven 31, and the station bending 32, as illustrated in Figures 3 and 4. The shuttle 29 works of course with an upper form of bending 33 associated with an axis 34 allowing a

  rotation of 90 indicated by the arrow 35.

  The representation made in this FIG. 5 makes it possible in particular to optimize the production rates, the travel times of the

  shuttles can no longer be limiting.

  Moreover, whatever the embodiment of the invention, the movements of the shuttles and possibly that of the upper form, as well as the triggering of the suction to hold the sheet against the upper shape and the rotation of the rollers in the form of Shuttle can be automated like any other step during

  bending and cooling of the glass sheets.

- 15 -

Claims (11)

claims   1) A method of bending a glass sheet comprising heating the glass sheet to a softening temperature, transporting the glass sheet along a substantially horizontal path to a bending station between two shapes, forming the glass sheet by pressing between the two forms, cooling the glass sheet in a suitable station, characterized in that means comprising shaped rollers receive the glass sheet after bending and in that the rollers are oriented parallel to the direction defined on the glass sheet by its   feeding direction in the bending station.   2) Method according to claim 1 characterized in that the means are at least one shuttle, preferably mobile between the station   bending and a cooling station.   3) Process according to claim 1 or 2 characterized in that the glass sheet is transported to the cooling station in a direction lateral to the direction of supply of said sheet of glass towards the bending station.   4) Method according to one of claims 1 or 2 characterized in that   that the glass sheet is kept in contact with the upper bending form after pressing, in that it is rotated by an angle of, and that it is transported to the cooling station   according to its direction of supply to the bending station.    Method according to one of Claims 2 to 4, characterized in that   that the glass sheet is mobile on the shuttle.   6) Method according to claim 5 characterized in that the sheet   of glass obeys a movement back and forth on the shuttle.   7) A bending device comprising a heating furnace of a glass sheet, a device for supporting and transporting the glass sheet in a substantially horizontal plane passing through the furnace to a bending station comprising two forms of bending, a lower shape passing through the transport device for pressing the glass sheet against an upper shape, the latter comprising means for retaining a glass sheet after it has been shaped, and at least one cooling station characterized in that at least one shuttle carrying shaped rolls receives a glass sheet after bending, in that it is movable between the bending station and a cooling station and in that the shaped rollers are oriented parallel to the direction defined on the glass sheet by his   feeding direction in the bending station.   8) Device according to claim 7 characterized in that the direction of movement of the shuttle is lateral to the direction of supply of the glass sheet from the oven to the bending station. 9) Device according to claim 7 characterized in that the direction of movement of the shuttle is in the extension of the direction of supply of the glass sheet from the oven to the bending station and in that the upper form pivots d an angle of 90 after pressing.    ) Device according to one of claims 7 to 9 characterized in that   that shaped rollers are driving rollers.   11) Device according to one of claims 7 to 10 characterized in   the shaped rollers have an alternating rotational movement.   12) Device according to one of claims 7 to 11 characterized in   that the shuttle enters the cooling station.   13) Device according to one of claims 7 to 12 characterized in   the upper form has suction means.   14) Device according to one of claims 7 to 13 characterized in   it comprises a cooling station in the extension of the direction of the transport device of the glass sheet and / or at least one cooling station disposed laterally with respect to said transport device.