Title of Invention	A METHOD AND DEVICE FOR THE PRODUCTION OF FLAT FLOAT GLASS WITH NO STATIONARY POINT
Abstract	The invention concerns a method and a device for the production of flat glass comprising the continuous floating of a molten glass on a float bath in a float installation, the said floated glass progressively forming a riboon running on the} said float bath without having any stationary point in the installation. To do this, the molten metal can be poured at locations capable of being stationary points and in particular at the float point furthest upstream and situated on the longitudinal axis of the bath. The glass may be glass-ceramic precursor glass. Glass-ceramic plates can be made in large dimensions, even greater than 7 5 cm and even very thin such as thinner than 3 mm.

Title of Invention

A METHOD AND DEVICE FOR THE PRODUCTION OF FLAT FLOAT GLASS WITH NO STATIONARY POINT

Abstract

The invention concerns a method and a device for the production of flat glass comprising the continuous floating of a molten glass on a float bath in a float installation, the said floated glass progressively forming a riboon running on the} said float bath without having any stationary point in the installation. To do this, the molten metal can be poured at locations capable of being stationary points and in particular at the float point furthest upstream and situated on the longitudinal axis of the bath. The glass may be glass-ceramic precursor glass. Glass-ceramic plates can be made in large dimensions, even greater than 7 5 cm and even very thin such as thinner than 3 mm.

Full Text	FLAT FLOAT GLASS WITH NO STATIONARY POINT The invention concerns the production of flat float glass, and particularly of fiat glass-ceramic. Glass-ceramics are materials rich in silica comprising at least one crystalline phase and obtained after a ceramization heat treatment from a precursor glass (or mother-glass). Glass-ceramics have a very low coefficient of linear expansion, usually less than 15xl0-7 Glass-ceramics may comprise at least 50% silica by mass. An important family of glass-ceramic is that comprising both and Li20 for which the ceramization process leads to crystals of beta- eucryptite or beta-spodumene or beta-quartz. These glass-ceramics, which may be translucent or opaque, find a use particularly as hob plates or fire- resistant plates, and more generally in uses requiring a glass with a very low coefficient of expansion. Glass-ceramics however have the disadvantage of having a strong tendency to devitrify when hot, which usually leads to many maintenance operations on the forming installations. Specifically, the plates or sheets of glass-ceramics are usually made by rolling between metal rolls and devitrification deposits damage the surface of the said rolls. The latter must therefore be periodically rectified (even every two to three days) or even replaced. The glass-ceramic forming installations are therefore usually designed to make maintenance operations easy, which involves a high degree of accessibility to the rolls, even during production. It is thus unthinkable for those skilled in the art to form glass-ceramics in gigantic installations whose core remains inaccessible during operation as is the case with float glass installations. Specifically, these installations are several tens of metres or even several hundreds of metres long and several metres wide and the transition times to start-up or to shut-down are considerable. Such installations must therefore operate non-stop and a shut-down for maintenance is catastrophic and ruled out. The conventional installations for forming glass- ceramics by rolling between rolls also do not allow the production of very large sheets. The width is limited to less than 700 mm. There is however a need today for plates of greater widths. Similarly, this rolling process cannot be used to produce very thin sheets of less than 3 mm. The applicant has effectively been able to ascertain that the floating of a glass-ceramic could not be achieved in the usual manner for a conventional glass of the soda-lime-silica type. Specifically, a devitrification always occurs in the zone where the glass is cast onto the metal float bath. Remember that, in the production of a ribbon of float glass, to produce sheets of flat glass, molten glass is poured onto a bath of molten metal, usually of tin or of a predominantly tin alloy, where it forms the said continuous ribbon which cools progressively and is extracted with the aid of extractor rollers which take it to an annealing furnace called a lehr. The zone covering the ribbon of glass when it runs onto the float bath is encumbered with heating systems and cooling systems which are provided to condition the temperature and more precisely the viscosity of the glass so that it can be drawn to the required thickness and then set. The central zone of the molten floated material situated on the longitudinal axis of the float and the furthest upstream on the float bath is in fact a zone where the speed of the floated material is low or zero. This type of zone appears to promote devitrification, in particular when glass-ceramic is involved. The devitrification causes the formation of crystals accumulating in the same location and requiring the shut-down of production. Accordinq to the invention, this problem is remedied by conceiving a float installation devoid of any stationary points for the molten floated material. The speed of the molten floated material is therefore not zero at any of its points. US3843345 teaches the floating of a conventional glass on a float bath, but without a pouring (or fall) of the glass. At the location where the glass passes over the metal, there is a glass/metal/refractory triple point (in fact a line) which is necessarily stationary. In addition, the speed of the glass at the edges seems to be zero. This device is therefore not suitable for glass-ceramic precursor glass. US3684475 teaches the passing of a ribbon of rolled glass on a float bath. It therefore does not involve a pouring of molten glass. Such rolling at these very high temperatures does not make it possible to obtain wide and/or thick sheets of glass. US2002/0023463 teaches a particular composition of glass-ceramic capable of being floated without surface crystallization. The abstract of JP2000281365 teaches the recirculation of the tin from downstream to upstream via the edges of the float bath of a float enclosure. Other documents that may be mentioned are US3539320, US4115091 and US3718450. According to the invention, use can be made of a conventional float installation normally procuring a point or a zone of low speed or zero speed glass at the location where the precursor glass is poured, but while arranging the casting also of a molten metal at this location in order to remove any stationary point for the glass. The casting of the molten metal is arranged so as to constitute a zone in motion for the glass. Molten, metal is introduced at the float points which would be fixed for the glass if there were no introduction. This molte'n metal is preferably of the same kind as that of the float bath and will mix with it. This casting of molten metal draws along the molten material in that critical zone and prevents it from being stationary. Thus, all the molten glass material introduced into the float installation is drawn along toward the outlet of the latter, without stagnation at any location, and therefore without devitrification at any location, which is particularly advantageous when the requirement is to produce glass-ceramic The casting of the molten metal intended to prevent the stationary points is carried out in a symmetrical manner relative to the longitudinal axis of the float installation so as not to disrupt the pouring symmetry of the glass relative to this axis. This casting is preferably carried out over a certain width corresponding for example to at least 50% of the width of the glass spout lip, even at least 80% of the width of the glass spout lip. It may therefore involve a veritable curtain or cascade over a large width of the installation. Preferably, the metal is poured so as not to cause turbulence in the float bath. Thus, it is preferable to pour it onto an inclined plane of refractory material (for example made of sillimanite), the said inclined plane ending at the float bath. In this manner, the metal is poured gently into the bath. According to one embodiment, to avoid the excess of molten metal due to the casting of metal at the head of the installation, molten metal is tapped from at least one point further downstream of the same float bath. Advantageously, it is at least in part this same tapped metal that is cast at the head of the bath. In this case, the metal circulates in fact at least partially in a loop from upstream to downstream and vice-versa. This recirculation may also serve to limit, or even prevent, the natural recirculations inside the bath that can disrupt the forming. Preferably, the molten metal is tapped off and reintroduced in a symmetrical manner relative to the longitudinal axis of the installation, so as not to disrupt the symmetrical operation of the assembly. Thus, if metal is tapped from one side downstream of the installation, metal is also tapped and at the same rate from the other side of the installation and at the location symmetrical to the first relative to the longitudinal axis of the installation. In this case, it can be the said that molten metal is being tapped on the lateral portions of the float bath and in a symmetrical manner relative to the longitudinal axis. The same applies for the reintroduction, it being understood that usually this is carried out via a duct whose axis is on the longitudinal axis of the installation and pours metal at least at the point furthest upstream of the glass and on the longitudinal axis. As has already been the said, this metal pouring duct is preferably fairly wide relative to the width of the float bath at this location. This symmetry of the molten metal circulation system can be assured by the use of calibrated pumps. The flow rate of these pumps may usually be adjusted by an air pressure which is supplied to them. An adjustment is sought that ensures a symmetry of the temperatures and a pulse-free drawing of the glass sheet. According to the invention, molten metal is introduced continuously at the glass float point furthest upstream and situated on the longitudinal axis of the bath. This introduced molten metal may in particular originate at least partially from a tapping point of the same bath situated further downstream. The flow rate of metal poured upstream depends on the size of the installation. The flow rate of metal is sufficient to prevent the formation of a stationary point for the glass. The flow rate at this point furthest upstream usually lies between 0.05 and 5 litres per second. In one embodiment, the vitreous composition spread out on the float bath is a glass-ceramic precursor glass. The particular structure of glass-ceramic is achieved by a specific heat treatment (called ceramization) after the forming in sheet/plate form and even usually after the longitudinal and transversal cutting of the floated ribbon. This glass-ceramic precursor glass may also be called "mother" glass. For simplicity, it may simply be called "glass" in the context of the present application. The invention relates to a method for the production of a ribbon of float glass, particularly a glass-ceramic precursor, in which the ribbon, formed on a float bath, floats along on this bath, this ribbon being removed from the bath when it has sufficiently solidified. The invention is used for the production of varied thicknesses of glass and relates more specifically to the production of a thin ribbon, and particularly thinner than 3 mm. More specifically, the invention relates to a method for the production of flat glass comprising the continuous floating of a molten glass on a float bath in a float installation, the said floated glass progressively forming a ribbon running on the said float bath without having any stationary point in the installation. The thickness of the ribbon is determined by the traction force exerted on it on the one hand by the extractor rollers and where necessary on the other hand by the action of knurled "top rolls" which act on the top edges of the ribbon. Specifically, for a given drawing, that is to say for a quantity of glass coming out of the furnace per given unit of time, the thickness of the ribbon of float glass is a function of the speed of the said ribbon in the lehr and of the width of the latter. At the moment when the glass is poured on the metal, at the entrance of the float enclosure, the glass is sufficiently fluid to spread on the metal surface under the effect of its own weight. Advantageously, the temperature at this location is such that the dynamic viscosity of the glass lies between 3 and 4.5 poise. For a glass-ceramic precursor glass, the temperature of the glass, at this location, usually lies between 1300 and 1450°C. While the ribbon of glass is running on the float bath, the said ribbon will therefore be drawn, out to reduce its thickness. This drawing process is usually obtained for outputs of between 500 and 600 tonnes per day with ribbon speeds lying between 15 and 30 metres per minute, for conventional thicknesses of the order of 2 to 5 mm. Such outputs and speeds of the glass ribbon running on the float bath furthermore cause, under the said ribbon, a current of tin directed towards the colder outlet end of the bath; this may be called a downstream current. The metal carried along by the ribbon on this downstream current hits the outlet wall of the bath and then by reflection tends to form a return current directed towards the upstream portion of the bath; this may be called an upstream current. This upstream current may be particularly strong between the edges of the ribbon of glass and the side walls of the bath. This cooler upstream current mixes with the downstream current causing disruptions such as turbulence and injects metal at a temperature lower than that of the metal of the downstream current. Then, particularly along the transverse zones, high temperature variations appear particularly in the drawing zone where the glass is particularly sensitive to these temperature variations. These temperature differences are particularly harmful because they locally change the viscosity of the glass and so the drawing may not be homogeneous. This results in deformations of the glass ribbon and also a lateral instability of the said glass ribbon which moves periodically from one side to the other of the bath. Such an instability may in particular disrupt the temperatures at the lehr and so have a harmful effect on the annealing and even be capable of causing breakages. To remedy the disadvantages arising from this upstream current, FR 2 254 527 teaches, in the case of a soda- lime-silica glass, the placing of transverse barriers beneath the ribbon of glass, in order to prevent the upstream current reflected by the outlet wall of the bath from mixing with the downstream current in the drawing zone. To do this, a first tweel is provided beneath the ribbon of glass at the downstream end of the drawing zone; this tweel allows only a portion of the downstream current to flow beneath the ribbon and forces the upstream current to travel along the edges of the said ribbon. A second tweel, spaced upstream of the first and situated in the region of maximum acceleration of the glass, acts in the same manner in this second location allowing only a portion of the downstream current to flow beneath the ribbon of glass and forcing the upstream current to travel along the edges of the said ribbon. FR 2 372 122 furthermore proposes to associate the aforementioned transverse tweel with fixed deflectors situated upstream of the tweel and having the function of intercepting the currents of metal travelling along the side walls of the bath. According to one embodiment of the invention, the float bath is fitted with one or more of these tweels and, where appropriate, with one or more of these fixed deflectors, limiting the intensity of the upstream current. According to one embodiment of the invention, the ribbon runs on the float bath, a portion of the molten metal being tapped at the downstream end of the bath and reintroduced upstream into the bath. According to a variant, the quantity of tapped molten metal corresponds substantially to the quantity of molten metal that would be drawn along by the aforementioned upstream current, that is to say by the current created by the reflection on the bath's outlet wall of the current of molten metal which accompanies the run of the ribbon of glass. According to a variant, the method according to the invention is used to virtually totally eliminate the return current in the bath and hence the disruptions which derive therefrom, particularly in terms of turbulence. Furthermore, and in combination with this effect, the molten metal being cast upstream of the bath so that it forms a moving reception zone for the glass, it prevents any devitrification in the zone furthest upstream of the floated glass. The molten metal may undergo a heat treatment before it is reintroduced into the bath. Specifically, the temperature of the tapped metal is preferably brought to a temperature corresponding to that of the metal in the zone of the bath where the tapped metal is to be reintroduced. It is thus possible not only to prevent the turbulence but also to avoid causing temperature variations at the location where the metal is reintroduced. The molten metal may be tapped from the lateral portion of the bath and preferably in a symmetrical manner on either side. The molten metal may be tapped on the surface of the bath. The molten metal may also be tapped via the bottom of the bath at the sides or via the bottom. Preferably, the tapping is carried out in a symmetrical manner relative to the longitudinal axis of the bath so as not to disrupt the trajectory of the •ribbon of glass which is running on the molten metal. The tapping may be carried out totally at the end of the bath or further upstream of this end. According to a variant, the tapped molten metal may be reintroduced, simultaneously: - on the one hand, partially in the zone furthest upstream of the mass of glass in order to prevent devitrification, and - on the other hand, at at least one second point between the inlet and the outlet of the float installation. According to a variant, this second point (in fact preferably a pair of second points placed symmetrically relative to the longitudinal axis of the bath) is situated at the end of the glass drawing zone. This choice first makes it possible to carry out this operation in a zone with few encumbrances since this is after the last top rolls which draw along the ribbon of glass from above. In addition, the choice of this zone makes it possible to limit the energy necessary to increase the temperature of the metal which in this zone is usually at a temperature lying between 1200 and 800°C. Thus, according to a variant, the flow of tapped and reintroduced metal is divided, on the one hand, in order to supply the float point the furthest upstream and situated on the longitudinal axis of the bath, and, on the other hand, in order to supply at least one other reintroduction point situated between the preceding point and the tapping point. According to a variant of the invention, the molten metal is reintroduced into the bath at this second point (and naturally this is not the case for the zone furthest upstream) at a virtually zero speed and preferably in a symmetrical manner relative to the longitudinal axis of the float installation. According to this variant, it is possible to prevent or at the least limit the creation of a new current due to the volume of reintroduced molten metal. The preferred choice of a symmetrical reintroduction also makes it possible not to disrupt the trajectory of the ribbon of glass by a unilateral addition of material. The invention also proposes a device for applying the method that has just been presented. This device for the production of a ribbon of float glass comprises a float bath on which the ribbon runs, a means of pouring the glass upstream of the bath and a means of casting molten metal, upstream and on the longitudinal axis of the bath. According to a variant, this device also comprises at least one system of tapping the molten metal and at least one pipe connecting the tapping orifice to at least one reintroduction point or zone. The system for tapping metal may be an orifice in the floor of the float bath. According to a variant, the system of tapping the molten metal is an overflow at the downstream end of the bath, at least one pipe connecting the overflow system to at least one reintroduction point or zone. The overflow system may consist of a tank, or reserve close-coupled to the bath and connected thereto by a spillway in which case the pipe is outside the bath. This also allows reintroduction of the metal at at least one second point (the first point, as has already been said, being the zone furthest upstream of the floated glass and on the longitudinal axis) advantageously either side of the bath, which is carried out from above. Again advantageously, the invention provides for the use of a device of the spillway type with flared surface which allows the metal reintroduced at this second point to flow into the bath at a virtually zero speed. The external pipe is resistant to the corrosion due to the molten metal; it is made for example of refractory material of the zircon/alumina type. According to another variant embodiment of the invention, an overflow system and a pipe are produced within the bath. This pipe may in particular be formed by the presence in the bath of a wall which therefore allows a return current in the bath without contact with the current of molten metal created by the run of the ribbon of glass. Preferably, according to one or other of these variants, the invention makes provision for associating the pipe with heating elements. The latter will advantageously be heating means of the induction type, particularly in the case of a pipe outside the bath made of a refractory material. In the case of the provision of a return channel in the bath, it is again possible to provide heating means such as electrodes indirectly heating the said channel. Thus the invention also concerns a float method on a float bath recirculating at least partially from downstream to upstream via at least one external duct, the metal tapped downstream being reheated before being reintroduced upstream. The invention again advantageously provides for a pumping system such as at least one graphite pump, introduced between the tapping system and the zone and the point or points of reintroduction. The pumping system will allow a circulation of the molten metal in the pipe such that the leve of molten metal in the bath remains constant. If there are several pumps, a system of controlling the flow rate of recirculated metal can be provided to ensure the symmetry of the system. According to a variant embodiment and particularly when the pipe is of reduced length, the variation of density of the molten metal linked to the heat treatment that it undergoes for example within the pipe is used to give a speed to the molten metal leading to the same result. Other details and advantageous features of the invention will emerge hereinafter from the description of exemplary embodiments of the invention with reference to Figures 1 to 8 which represent, - Figure 1, a schematic side view (a) and top view (b) of the upstream portion of a conventional tank (prior art), comprising a float bath for the production of a glass ribbon by floating, - Figure 2, a schematic side view of the device according to the invention, - Figure 3, a schematic general view from above of a conventional float installation (prior art), - Figure 4, a schematic top view of one embodiment of the invention, - Figure 5, a schematic side view of another embodiment according to the invention, - Figure 6, a schematic top view of another embodiment of the invention, - Figure 7, a partial side view in section of a diagram of a portion of a device corresponding to the case in Figure 4, - Figure 8, a top view of the representation of Figure 7. Figure 1 shows the upstream portion of a tank elongated for the production of float glass according to prior art, seen from the side (a) and seen from above (b) . The glass i flows on a spoutl.p 2 after adjustment of the thickness and of load between the said spoutlip and a vertical front tweel 3, then floats on the metal 5. It can be seen that the glass forms a heel 4 beneath the spoutlip. Arrows suggest the movement of the molten glass. The zone furthest upstream 6 of this heel situated symmetrically on the longitudinal axis AA' is a zone of stationary points. This zone is situated symmetrically on the axis AA' between two flows of glass travelling either side of the installation. Figure 2 shows a device according to the invention seen from the side. As hereinabove, the glass runs on a spoutlip 2 after thickness calibration by a front tweel 3 to float thereafter on the float bath 5. A heel 4 forms beneath the spoutlip 2. According to the invention, molten unetal of the same kind as that of the bath 5 constantly flows in the zone 6 preventing the formation of a stationary point for the molten glass. The duct 7 brings this molten metal which, is made to flow on an inclined plane 201 before it reaches the float bath itself, so doing to prevent turbulence in the bath of liquid metal. Figure 3 shows a conventional float installation without the particular device according to the invention. The invention provides an adaptation of this type of installation for floating glass of the glass- ceramic type. The invention may therefore make use of the same installation with the addition of a molten metal inlet at the zone or at the point furthest upstream and in a symmetrical manner relative to the longitudinal axis AA' of the installation and therefore also of the float glass. The tank comprises side walls 8 and end walls 9 and 10, respectively at the inlet and at the outlet of the tank. The tank, containing a bath 5 of molten tin, has a narrower downstream portion 11. The molten glass is poured onto the bath at its inlet end, from a distribution channel 12 ending in the spoutlip and placed above the inlet wall of the tank. Temperature regulators, not shown in the figures, are incorporated into the roof that surmounts the bath. These regulators establish the heat conditions of the glass while keeping it in the deformable state until the end of the drawing zone. In glass production, the bath comprises several zones shown in Figure 3 which may be distinguished in the following manner: - a zone I for spreading out the glass after it has been cast onto the float bath, upstream. - a zone II in which the ribbon of glass being formed is subjected to longitudinal forces directed outwards under the actions of lift-out rollers 12 and top rolls 13. In this zone, the drawing of the glass begins and the latter becomes thinner; - a zone III in which the ribbon of glass takes its definitive form under the action of the lift-out rollers 12. Zones II and III together form the drawing zone. - a consolidation zone IV in which the set ribbon of glass cools progressively. After having been poured onto the float bath, the glass spreads out freely to the maximum in zone I. It thus forms a ribbon 14 which moves downstream under the effect of the traction of the lift-out rollers 12 outside the tank. The desired thickness is then obtained by the combined action of the traction of the lift-out rollers 12 and the knurled top rolls 13, usually made of steel, slightly oblique relative to the perpendicular to the direction of travel of the ribbon. These top rolls are connected by shaft 15 to motors 16 which drive them usually at speeds differing depending on their position and increasing downstream. These rolls apply to the edges of the ribbon of glass being formed forces opposing a narrowing of the ribbon of glass. The ribbon of glass is thus drawn out in the zone of these top roils. The ribbon of glass is then brought to the desired thickness by a drawing due to the lift-out rollers. The movement of the ribbon of glass on the bath causes beneath the ribbon a current of molten metal directed downstream of the tank and called the downstream current. This downstream current butts against the outlet face of the tank and rebounds to form an upstream current. The downstream current is schematized in the figure by a full arrow and the upstream current is schematized by dashed arrows (in zone IV). Figure 4 shows a partial top view of a diagram representing half of a float bath 17 . According to the invention, a portion of the molten metal may be tapped off at the downstream end of the bath and transported by a pipe 18. The metal is partially reintroduced in zone 6 across the whole width upstream of the bath (the flow of metal at 6 is represented by arrows), symmetrically relative to the longitudinal axis AA' (Figure 4 therefore shows only half of the width of reintroduction of the molten metal). Another reintroduction zone may be situated at different points 19 of the bath. The invention also makes provision for the possibility of carrying out a heat treatment and more precisely a raising of the temperature to bring the tapped metal to a temperature closer to that of the reintroduction zone; such an operation is used to further limit the disruption due to temperature variations. In the case of Figure 4 and of a division into two reintroduction points 6 and 19, it is possible to make provision for example for a progressive heat treatment all along the pipe; according to this embodiment, the heat regulation is adapted to obtain at point 19 a temperature of the tapped molten metal corresponding to the temperature of the bath at this reintroduction point 19 in the bath and the heat treatment continues, while the rest of the molten metal is on its journey, up to point 6 so that the temperature of the metal at this point; 6 corresponds to the temperature in the bath in this reintroduction zone. According to another embodiment, it is possible to provide a heat treatment only for the metal taken up to point 6, considering that the metal reintroduced at point 19 is at such a temperature that it will not disrupt the reintroduction zone of the bath, the temperature difference being slight. The heating means used may be any means known to those skilled in the art and advantageously means of heating by induction particularly when a pipe 18 is made of a refractory material. According to the invention, the device illustrated in this Figure 4 is advantageously made in a symmetrical manner on the two edges of the bath so that the tapping and reintroduction of the molten metal do not disrupt the trajectory of travel of the ribbon of glass. It is again possible to provide a pumping device such as a graphite pump as previously stated. Such a pump will ensure that the tapped metal travels in the pipe 18. According to another embodiment and more particularly when heating is provided, the variation of density of the molten metal inside the pipe 18 may be sufficient to ensure that the tapped metal travels as has also already been stated previously. Figure 5, which shows a partial schematic side view of a float bath, illustrates a device similar to the previous one according to which the molten metal is no longer tapped through the side of the bath but through the bottom thereof, via a pipe 18. This figure shows a pump 20 and a heating device, but the latter are optional as in the case of Figure 4. The pump 20 is advantageously provided at the beginning of the pipe 18 and the heating device 51 is for its part provided at the end of the said pipe 18 just before the reintroduction zone 6. The reintroduced metal runs on an inclined plane 52 before rejoining the float bath 53. Figure 6 illustrates another embodiment of the invention according to which the tapped molten metal is brought back upstream, on the one hand, by a pipe 27 created inside the bath 5 by the presence of a wall 23 and, on the other hand, by a duct 18 returning the molten metal all the way upstream to zone 6 in order to prevent the formation of a stationary point of glass. A pump 61 returns the molten metal through the duct 18. This Figure 6 shows first of all the ribbon of glass 1 which is running on the float bath 5 delimited by the walls 8. The molten metal is drawn along by the ribbon of glass which creates a downstream current indicated by the arrows 26. At the end of the bath, this downstream current is transformed into an upstream current. This transformation occurs naturally as previously explained by the rebound on the end of the. bath and the molten metal is channelled in the pipe 27 by a bath-bottom geometry judiciously provided for this purpose. This Figure 6 again shows heating elements such as radiant elements positioned above the bath to thermally recondition the tapped molten metal and bring it to the point 29 for reintroduction into the bath at a temperature as close as possible to that of the bath at this point. As in the case of the previous embodiments, these heating elements are optional and advantageously present when the reintroduction point is far upstream. Similarly, it is possible to add to such an embodiment a pump which would be advantageously placed at the beginning of the pipe 27 . Figures 7 and 8 represent a diagram of an installation that may correspond to an embodiment according to Figure 4, that is to say a lateral tapping of the molten metal. These figures show the downstream portion of the bath 37, the molten metal tapping point 30 and further upstream a reintroduction point 31. An overflow device 33 is made in close-coupled manner in the wall 32 of the bath. This device 33 will naturally receive the molten metal which is drawn along by the ribbon of glass and which butts against the downstream end of the bath, then takes it to the pump 34 and finally into the pipe 35. The overflow device 33 consists essentially of an inclined plane 36 which helps the excess molten metal to be drawn along so that no upstream current appears within the bath 37. The pump 34 is advantageously a graphite pump and, as in all the previously presented embodiments, is optional. It is again possible to add to this device a heating system that is also optional. At the point 31 of reintroduction into the bath 37, there is advantageously provided a device, not shown in the figures, used to reintroduce the molten metal at a virtually zero speed; it is for example a spoutlip with flared surface. The duct returning the molten metal is divided in order to supply the reintroduction point 6 furthest upstream and is placed on the axis to prevent the glass from forming a stationary point. In the same manner as the other embodiments according to the invention, the system shown in Figures 7 and 8 is advantageously produced either side of the bath in particular so as not to disrupt the trajectory of the ribbon of glass both at the tapping zone and at the reintroduction zone. Naturally, irrespective of which embodiment of the invention is chosen, the greatest volume created particularly by the molten metal circulation device is taken into account to determine the total volume of molten metal necessary for the correct operation of the device for producing the ribbon of float glass. These embodiments according to the invention have further advantages; it is known that, in the system of producing a ribbon of float glass, impurities are created which are found in the downstream zone of the bath and may contaminate the bottom surface of the ribbon of glass. The invention will make it possible at the same time as the tapping of the molten metal in the downstream zone to tap off these impurities and either remove them or subsequently reintroduce them into the bath further upstream, the latter following the route of the tapped molten metal. The reintroduction of these impurities upstream of the bath and hence in a hotter zone at reduced atmosphere will cause them to be reduced and hence disappear. The method according to the invention therefore also makes possible a treatment of the molten metal that removes the impurities. The method according to the invention has the further advantage of being simple to implement and being able in particular to be adapted to existing installations without requiring major implementation work. The ribbon of floated glass, particularly glass-ceramic precursor, may be from 1 mm to 30 mm thick, and more particularly from 1.5 mm to 25 mm and from 50 to 500 cm wide and more particularly from 60 to 4 60 cm. On leaving the forming installation, the ribbon passes into a lehr to cool progressively, after which the ribbon is cut up into sheets comprising two main faces and one sheared edge. Each main face of these sheets may have a surface area of 0.15 m to 20 m . In particular, each main face may be from 0.4 m to 6 m long and from 0.4 m to 3.5 m wide. These sheets then undergo the ceramization heat treatment specific to transforming them into glass- ceramic. As an example, for a glass-ceramic based on Si02-Li20, the ceramzation treatment may usually be carried out in the following manner: a) raising the temperature at the rate of 30 to 80C/minute to the nucleation domain, usually situated in the vicinity of the glass transformation domain; b) passing through the nucleation range (670-800°C) in 15 to 25 minutes; c) raising the temperature at the rate of 15 to 30°C/minute up to the temperature of the ceramization level usually lying between 900 and 1100°C ; d) maintaining the temperature of the ceramization level for a period of 10 to 25 minutes; e) rapid cooling to the ambient temperature. After the ceramization cycle, the sheet of glass comprises the crystalline phase characteristic of the glass-ceramic structure. The invention also concerns a flat glass-ceramic preparation method comprising the float process according to the invention with no stationary point, leading to a flat glass, which then undergoes a ceramization treatment leading to the said flat glass- ceramic . The invention also concerns the device for applying the method that has been described and more particularly a device for producing a ribbon of float glass, according to which the ribbon runs on a float bath, characterized in that it comprises a means of introducing molten metal substantially at the point furthest upstream of the float glass and situated on the longitudinal axis of the bath. The means of introduction is preferably such that the molten metal is in motion at the point of meeting with the float bath. More particularly, the means of introduction may comprise an inclined plane of refractory material, the said inclined plane ending at the float bath, such that the molten metal to be introduced first runs onto the inclined plane before pouring into the bath. In particular, the device may comprise at least one duct supplied with metal tapped from the bath and returning the said tapped metal to the point furthest upstream of the glass and situated on the longitudinal axis of the bath. It may also comprise at least one overflow system at the downstream end of the bath to tap off molten metal and connected to the duct. The overflow system may be a tank close- coupled to the bath and connected thereto by a spillway, the pipe being outside the bath. Preferably, the metal is withdrawn and reintroduced in a symmetrical manner relative to the longitudinal axis of the float installation. The invention also relates to a (flat) sheet of glass- ceramic at least one dimension of which (width or length) is greater than 75 cm, and even greater than 80 cm and even greater than 100 cm and even greater than 200 cm, usually less than 600 cm. In particular, the sheet may be thin, that is to say thinner than 3 mm and even thinner than 2.5 mm, even thinner than 2 mm, furthermore usually thicker than 0.8 mm. Any type of glass-ceramic precursor glass may be worked according to the invention, including those comprising more than 1.5% ZnO and even more than 1.6% by weight of ZnO. It is clearly understood that this invention, described more particularly for producing glass-ceramic, also applies to glass of a non glass-ceramic type. It is also well understood that the metal in the float bath may be recirculated independently of the reintroduction at the head of the float bath. The recirculation of the molten metal (usually tin-based) is more particularly described in relation with the production of glass for glass-ceramic and other glasses sensitive to crystallization, but this recirculation method applies also to any float chamber, whatever the glass produced, so as to benefit from advantages other than that of preventing crystallization. WE CLAIM: 1. Method for the production of flat glass comprising the continuous floating of a molten glass (1) on a bath of molten metal (5) in a float installation, the said glass being poured in the molten state onto the molten metal and progressively forming a ribbon (14) running over the said metal bath without having any stationary point in the installation, characterized in that molten metal is introduced into the installation so that it forms a moving reception zone (6) for the molten glass. 2. Method as claimed in the preceding claim, wherein the glass floating on the molten metal bath is a glass-ceramic precursor glass. 3. Method as claimed in one of the preceding claims, wherein the molten metal is introduced at the float points that would be stationary for the glass if there were no introduction. 4. Method as claimed in one of the preceding claims, wherein the molten metal is introduced at the float point furthest upstream and situated on the longitudinal axis of the bath. 5. Method as claimed in claim 1 to the preceding claim wherein the molten metal introduced originates at least partially from a tap-off point of the same bath situated further downstream. 6. Method as claimed in the preceding claim, wherein the flow of tapped- off and reintroduced metal is divided, on the one hand, in order to supply the float point further upstream and situated on the longitudinal axis of the bath, and, on the other hand, in order to supply at least one other reintroduction point situated between the preceding point and the tap-off point. 7. Method as claimed in one of the two preceding claims, wherein the tapped-off metal is reheated before it is reintroduced. 8. Method as claimed in one of claims 5 to the preceding claims, wherein molten metal is tapped off from the lateral portions of the float bath and in a symmetrical manner relative to its longitudinal axis. 9. Method as claimed in one of claims 5 to the preceding claim, wherein the molten metal is reintroduced partially on the lateral portions of the bath with a virtually zero speed and in a symmetrical manner relative to the longitudinal axis. 10. Method of preparing a flat glass-ceramic comprising the method of one of the preceding claims leading to a flat glass, which then undergoes a ceramization process leading to the said flat glass-ceramic. 11. Method as claimed in one of the preceding claims, wherein at the location where the glass is poured, its dynamic viscosity lies between 3 and 4.5 poise. 12. Method as claimed in one of the preceding claims, wherein at the location where the glass is poured, its temperature lies between 1300 and 1450°C. 13. Device for forming molten glass for the production of a ribbon (14) of float glass, which device comprises a molten glass pouring zone followed by a glass drawing zone, according to which the ribbon runs on a float bath, characterized in that it comprises a means of introducing molten metal substantially at the point furthest upstream of the floated glass and situated on the longitudinal axis of the bath. 14. Device as claimed in the preceding claims, wherein the introduction means is such that the molten metal is in motion at the point of meeting with the metal bath. 15. Device as claimed in one of the preceding device claims, wherein it comprises an inclined plane (201) of refractory material, the said inclined plane ending at the metal bath (5), such that the molten metal to be introduced first runs onto the inclined plane (201) before pouring into the bath. 16. Device as claimed in the preceding claim, wherein it comprises at least one duct (7) supplied with metal tapped-off from the bath and returning the same tapped-off metal to the point furthest upstream of the glass and situated on the longitudinal axis of the bath. 17. Device as claimed in the preceding claim, wherein it comprises at least one overflow system (33) at the downstream end of the bath, in order to tap off molten metal, and connected to the duct. 18. Device as claimed in the preceding claim, wherein the overflow system is a tank close-coupled to the bath and connected thereto by a spillway and in that the pipe is outside the bath. 19. Device as claimed in one of claims 16, to the preceding claim, wherein the metal is drawn and reintroduced in a symmetrical manner relative to the longitudinal axis of the float installation. 20. Ribbon of floated flat glass of the glass-ceramic precursor type containing more than 1.5% ZnO. 21. Glass-ceramic plate, at least one dimension of which is greater than 200 cm. 22. Glass-ceramic plate as claimed in the preceding plate claim, the thickness of which is less than 3 mm. 23. Glass-ceramic plate as claimed in one of claims 21 or 22, wherein it contains more than 1.5% ZnO. The invention concerns a method and a device for the production of flat glass comprising the continuous floating of a molten glass on a float bath in a float installation, the said floated glass progressively forming a riboon running on the} said float bath without having any stationary point in the installation. To do this, the molten metal can be poured at locations capable of being stationary points and in particular at the float point furthest upstream and situated on the longitudinal axis of the bath. The glass may be glass- ceramic precursor glass. Glass-ceramic plates can be made in large dimensions, even greater than 7 5 cm and even very thin such as thinner than 3 mm.

Full Text

FLAT FLOAT GLASS WITH NO STATIONARY POINT
The invention concerns the production of flat float
glass, and particularly of fiat glass-ceramic.
Glass-ceramics are materials rich in silica comprising
at least one crystalline phase and obtained after a
ceramization heat treatment from a precursor glass (or
mother-glass). Glass-ceramics have a very low
coefficient of linear expansion, usually less than
15xl0-7 Glass-ceramics may comprise at least 50%
silica by mass. An important family of glass-ceramic is
that comprising both and Li20 for which the
ceramization process leads to crystals of beta-
eucryptite or beta-spodumene or beta-quartz.
These glass-ceramics, which may be translucent or
opaque, find a use particularly as hob plates or fire-
resistant plates, and more generally in uses requiring
a glass with a very low coefficient of expansion.
Glass-ceramics however have the disadvantage of having
a strong tendency to devitrify when hot, which usually
leads to many maintenance operations on the forming
installations. Specifically, the plates or sheets of
glass-ceramics are usually made by rolling between
metal rolls and devitrification deposits damage the
surface of the said rolls. The latter must therefore be
periodically rectified (even every two to three days)
or even replaced. The glass-ceramic forming
installations are therefore usually designed to make
maintenance operations easy, which involves a high
degree of accessibility to the rolls, even during
production. It is thus unthinkable for those skilled in
the art to form glass-ceramics in gigantic
installations whose core remains inaccessible during
operation as is the case with float glass
installations. Specifically, these installations are
several tens of metres or even several hundreds of
metres long and several metres wide and the transition
times to start-up or to shut-down are considerable.
Such installations must therefore operate non-stop and
a shut-down for maintenance is catastrophic and ruled
out. The conventional installations for forming glass-
ceramics by rolling between rolls also do not allow the
production of very large sheets. The width is limited
to less than 700 mm. There is however a need today for
plates of greater widths. Similarly, this rolling
process cannot be used to produce very thin sheets of
less than 3 mm.
The applicant has effectively been able to ascertain
that the floating of a glass-ceramic could not be
achieved in the usual manner for a conventional glass
of the soda-lime-silica type. Specifically, a
devitrification always occurs in the zone where the
glass is cast onto the metal float bath. Remember that,
in the production of a ribbon of float glass, to
produce sheets of flat glass, molten glass is poured
onto a bath of molten metal, usually of tin or of a
predominantly tin alloy, where it forms the said
continuous ribbon which cools progressively and is
extracted with the aid of extractor rollers which take
it to an annealing furnace called a lehr. The zone
covering the ribbon of glass when it runs onto the
float bath is encumbered with heating systems and
cooling systems which are provided to condition the
temperature and more precisely the viscosity of the
glass so that it can be drawn to the required thickness
and then set.
The central zone of the molten floated material
situated on the longitudinal axis of the float and the
furthest upstream on the float bath is in fact a zone
where the speed of the floated material is low or zero.
This type of zone appears to promote devitrification,
in particular when glass-ceramic is involved. The
devitrification causes the formation of crystals
accumulating in the same location and requiring the
shut-down of production.
Accordinq to the invention, this problem is remedied by
conceiving a float installation devoid of any
stationary points for the molten floated material. The
speed of the molten floated material is therefore not
zero at any of its points.
US3843345 teaches the floating of a conventional glass
on a float bath, but without a pouring (or fall) of the
glass. At the location where the glass passes over the
metal, there is a glass/metal/refractory triple point
(in fact a line) which is necessarily stationary. In
addition, the speed of the glass at the edges seems to
be zero. This device is therefore not suitable for
glass-ceramic precursor glass.
US3684475 teaches the passing of a ribbon of rolled
glass on a float bath. It therefore does not involve a
pouring of molten glass. Such rolling at these very
high temperatures does not make it possible to obtain
wide and/or thick sheets of glass.
US2002/0023463 teaches a particular composition of
glass-ceramic capable of being floated without surface
crystallization.
The abstract of JP2000281365 teaches the recirculation
of the tin from downstream to upstream via the edges of
the float bath of a float enclosure.
Other documents that may be mentioned are US3539320,
US4115091 and US3718450.
According to the invention, use can be made of a
conventional float installation normally procuring a
point or a zone of low speed or zero speed glass at the
location where the precursor glass is poured, but while
arranging the casting also of a molten metal at this
location in order to remove any stationary point for
the glass. The casting of the molten metal is arranged
so as to constitute a zone in motion for the glass.
Molten, metal is introduced at the float points which
would be fixed for the glass if there were no
introduction. This molte'n metal is preferably of the
same kind as that of the float bath and will mix with
it. This casting of molten metal draws along the molten
material in that critical zone and prevents it from
being stationary. Thus, all the molten glass material
introduced into the float installation is drawn along
toward the outlet of the latter, without stagnation at
any location, and therefore without devitrification at
any location, which is particularly advantageous when
the requirement is to produce glass-ceramic The
casting of the molten metal intended to prevent the
stationary points is carried out in a symmetrical
manner relative to the longitudinal axis of the float
installation so as not to disrupt the pouring symmetry
of the glass relative to this axis. This casting is
preferably carried out over a certain width
corresponding for example to at least 50% of the width
of the glass spout lip, even at least 80% of the width
of the glass spout lip. It may therefore involve a
veritable curtain or cascade over a large width of the
installation. Preferably, the metal is poured so as not
to cause turbulence in the float bath. Thus, it is
preferable to pour it onto an inclined plane of
refractory material (for example made of sillimanite),
the said inclined plane ending at the float bath. In
this manner, the metal is poured gently into the bath.
According to one embodiment, to avoid the excess of
molten metal due to the casting of metal at the head of
the installation, molten metal is tapped from at least
one point further downstream of the same float bath.
Advantageously, it is at least in part this same tapped
metal that is cast at the head of the bath. In this
case, the metal circulates in fact at least partially
in a loop from upstream to downstream and vice-versa.
This recirculation may also serve to limit, or even
prevent, the natural recirculations inside the bath
that can disrupt the forming. Preferably, the molten
metal is tapped off and reintroduced in a symmetrical
manner relative to the longitudinal axis of the
installation, so as not to disrupt the symmetrical
operation of the assembly. Thus, if metal is tapped
from one side downstream of the installation, metal is
also tapped and at the same rate from the other side of
the installation and at the location symmetrical to the
first relative to the longitudinal axis of the
installation. In this case, it can be the said that
molten metal is being tapped on the lateral portions of
the float bath and in a symmetrical manner relative to
the longitudinal axis. The same applies for the
reintroduction, it being understood that usually this
is carried out via a duct whose axis is on the
longitudinal axis of the installation and pours metal
at least at the point furthest upstream of the glass
and on the longitudinal axis. As has already been the
said, this metal pouring duct is preferably fairly wide
relative to the width of the float bath at this
location. This symmetry of the molten metal circulation
system can be assured by the use of calibrated pumps.
The flow rate of these pumps may usually be adjusted by
an air pressure which is supplied to them. An
adjustment is sought that ensures a symmetry of the
temperatures and a pulse-free drawing of the glass
sheet.
According to the invention, molten metal is introduced
continuously at the glass float point furthest upstream
and situated on the longitudinal axis of the bath. This
introduced molten metal may in particular originate at
least partially from a tapping point of the same bath
situated further downstream.
The flow rate of metal poured upstream depends on the
size of the installation. The flow rate of metal is
sufficient to prevent the formation of a stationary
point for the glass. The flow rate at this point
furthest upstream usually lies between 0.05 and
5 litres per second.
In one embodiment, the vitreous composition spread out
on the float bath is a glass-ceramic precursor glass.
The particular structure of glass-ceramic is achieved
by a specific heat treatment (called ceramization)
after the forming in sheet/plate form and even usually
after the longitudinal and transversal cutting of the
floated ribbon. This glass-ceramic precursor glass may
also be called "mother" glass. For simplicity, it may
simply be called "glass" in the context of the present
application.
The invention relates to a method for the production of
a ribbon of float glass, particularly a glass-ceramic
precursor, in which the ribbon, formed on a float bath,
floats along on this bath, this ribbon being removed
from the bath when it has sufficiently solidified. The
invention is used for the production of varied
thicknesses of glass and relates more specifically to
the production of a thin ribbon, and particularly
thinner than 3 mm.
More specifically, the invention relates to a method
for the production of flat glass comprising the
continuous floating of a molten glass on a float bath
in a float installation, the said floated glass
progressively forming a ribbon running on the said
float bath without having any stationary point in the
installation.
The thickness of the ribbon is determined by the
traction force exerted on it on the one hand by the
extractor rollers and where necessary on the other hand
by the action of knurled "top rolls" which act on the
top edges of the ribbon. Specifically, for a given
drawing, that is to say for a quantity of glass coming
out of the furnace per given unit of time, the
thickness of the ribbon of float glass is a function of
the speed of the said ribbon in the lehr and of the
width of the latter.
At the moment when the glass is poured on the metal, at
the entrance of the float enclosure, the glass is
sufficiently fluid to spread on the metal surface under
the effect of its own weight. Advantageously, the
temperature at this location is such that the dynamic
viscosity of the glass lies between 3 and 4.5 poise.
For a glass-ceramic precursor glass, the temperature of
the glass, at this location, usually lies between 1300
and 1450°C.
While the ribbon of glass is running on the float bath,
the said ribbon will therefore be drawn, out to reduce
its thickness. This drawing process is usually obtained
for outputs of between 500 and 600 tonnes per day with
ribbon speeds lying between 15 and 30 metres per
minute, for conventional thicknesses of the order of 2
to 5 mm. Such outputs and speeds of the glass ribbon
running on the float bath furthermore cause, under the
said ribbon, a current of tin directed towards the
colder outlet end of the bath; this may be called a
downstream current. The metal carried along by the
ribbon on this downstream current hits the outlet wall
of the bath and then by reflection tends to form a
return current directed towards the upstream portion of
the bath; this may be called an upstream current. This
upstream current may be particularly strong between the
edges of the ribbon of glass and the side walls of the
bath. This cooler upstream current mixes with the
downstream current causing disruptions such as
turbulence and injects metal at a temperature lower
than that of the metal of the downstream current. Then,
particularly along the transverse zones, high
temperature variations appear particularly in the
drawing zone where the glass is particularly sensitive
to these temperature variations. These temperature
differences are particularly harmful because they
locally change the viscosity of the glass and so the
drawing may not be homogeneous. This results in
deformations of the glass ribbon and also a lateral
instability of the said glass ribbon which moves
periodically from one side to the other of the bath.
Such an instability may in particular disrupt the
temperatures at the lehr and so have a harmful effect
on the annealing and even be capable of causing
breakages.
To remedy the disadvantages arising from this upstream
current, FR 2 254 527 teaches, in the case of a soda-
lime-silica glass, the placing of transverse barriers
beneath the ribbon of glass, in order to prevent the
upstream current reflected by the outlet wall of the
bath from mixing with the downstream current in the
drawing zone. To do this, a first tweel is provided
beneath the ribbon of glass at the downstream end of
the drawing zone; this tweel allows only a portion of
the downstream current to flow beneath the ribbon and
forces the upstream current to travel along the edges
of the said ribbon. A second tweel, spaced upstream of
the first and situated in the region of maximum
acceleration of the glass, acts in the same manner in
this second location allowing only a portion of the
downstream current to flow beneath the ribbon of glass
and forcing the upstream current to travel along the
edges of the said ribbon. FR 2 372 122 furthermore
proposes to associate the aforementioned transverse
tweel with fixed deflectors situated upstream of the
tweel and having the function of intercepting the
currents of metal travelling along the side walls of
the bath.
According to one embodiment of the invention, the float
bath is fitted with one or more of these tweels and,
where appropriate, with one or more of these fixed
deflectors, limiting the intensity of the upstream
current.
According to one embodiment of the invention, the
ribbon runs on the float bath, a portion of the molten
metal being tapped at the downstream end of the bath
and reintroduced upstream into the bath. According to a
variant, the quantity of tapped molten metal
corresponds substantially to the quantity of molten
metal that would be drawn along by the aforementioned
upstream current, that is to say by the current created
by the reflection on the bath's outlet wall of the
current of molten metal which accompanies the run of
the ribbon of glass. According to a variant, the method
according to the invention is used to virtually totally
eliminate the return current in the bath and hence the
disruptions which derive therefrom, particularly in
terms of turbulence. Furthermore, and in combination
with this effect, the molten metal being cast upstream
of the bath so that it forms a moving reception zone
for the glass, it prevents any devitrification in the
zone furthest upstream of the floated glass.
The molten metal may undergo a heat treatment before it
is reintroduced into the bath. Specifically, the
temperature of the tapped metal is preferably brought
to a temperature corresponding to that of the metal in
the zone of the bath where the tapped metal is to be
reintroduced. It is thus possible not only to prevent
the turbulence but also to avoid causing temperature
variations at the location where the metal is
reintroduced.
The molten metal may be tapped from the lateral portion
of the bath and preferably in a symmetrical manner on
either side. The molten metal may be tapped on the
surface of the bath. The molten metal may also be
tapped via the bottom of the bath at the sides or via
the bottom. Preferably, the tapping is carried out in a
symmetrical manner relative to the longitudinal axis of
the bath so as not to disrupt the trajectory of the
•ribbon of glass which is running on the molten metal.
The tapping may be carried out totally at the end of
the bath or further upstream of this end.
According to a variant, the tapped molten metal may be
reintroduced, simultaneously:
- on the one hand, partially in the zone furthest
upstream of the mass of glass in order to prevent
devitrification, and
- on the other hand, at at least one second point
between the inlet and the outlet of the float
installation. According to a variant, this second
point (in fact preferably a pair of second points
placed symmetrically relative to the longitudinal
axis of the bath) is situated at the end of the glass
drawing zone. This choice first makes it possible to
carry out this operation in a zone with few
encumbrances since this is after the last top rolls
which draw along the ribbon of glass from above. In
addition, the choice of this zone makes it possible
to limit the energy necessary to increase the
temperature of the metal which in this zone is
usually at a temperature lying between 1200 and
800°C.
Thus, according to a variant, the flow of tapped and
reintroduced metal is divided, on the one hand, in
order to supply the float point the furthest upstream
and situated on the longitudinal axis of the bath, and,
on the other hand, in order to supply at least one
other reintroduction point situated between the
preceding point and the tapping point.
According to a variant of the invention, the molten
metal is reintroduced into the bath at this second
point (and naturally this is not the case for the zone
furthest upstream) at a virtually zero speed and
preferably in a symmetrical manner relative to the
longitudinal axis of the float installation. According
to this variant, it is possible to prevent or at the
least limit the creation of a new current due to the
volume of reintroduced molten metal. The preferred
choice of a symmetrical reintroduction also makes it
possible not to disrupt the trajectory of the ribbon of
glass by a unilateral addition of material.
The invention also proposes a device for applying the
method that has just been presented. This device for
the production of a ribbon of float glass comprises a
float bath on which the ribbon runs, a means of pouring
the glass upstream of the bath and a means of casting
molten metal, upstream and on the longitudinal axis of
the bath.
According to a variant, this device also comprises at
least one system of tapping the molten metal and at
least one pipe connecting the tapping orifice to at
least one reintroduction point or zone.
The system for tapping metal may be an orifice in the
floor of the float bath.
According to a variant, the system of tapping the
molten metal is an overflow at the downstream end of
the bath, at least one pipe connecting the overflow
system to at least one reintroduction point or zone.
The overflow system may consist of a tank, or reserve
close-coupled to the bath and connected thereto by a
spillway in which case the pipe is outside the bath.
This also allows reintroduction of the metal at at
least one second point (the first point, as has already
been said, being the zone furthest upstream of the
floated glass and on the longitudinal axis)
advantageously either side of the bath, which is
carried out from above. Again advantageously, the
invention provides for the use of a device of the
spillway type with flared surface which allows the
metal reintroduced at this second point to flow into
the bath at a virtually zero speed. The external pipe
is resistant to the corrosion due to the molten metal;
it is made for example of refractory material of the
zircon/alumina type.
According to another variant embodiment of the
invention, an overflow system and a pipe are produced
within the bath. This pipe may in particular be formed
by the presence in the bath of a wall which therefore
allows a return current in the bath without contact
with the current of molten metal created by the run of
the ribbon of glass.
Preferably, according to one or other of these
variants, the invention makes provision for associating
the pipe with heating elements. The latter will
advantageously be heating means of the induction type,
particularly in the case of a pipe outside the bath
made of a refractory material. In the case of the
provision of a return channel in the bath, it is again
possible to provide heating means such as electrodes
indirectly heating the said channel.
Thus the invention also concerns a float method on a
float bath recirculating at least partially from
downstream to upstream via at least one external duct,
the metal tapped downstream being reheated before being
reintroduced upstream.
The invention again advantageously provides for a
pumping system such as at least one graphite pump,
introduced between the tapping system and the zone and
the point or points of reintroduction. The pumping
system will allow a circulation of the molten metal in
the pipe such that the leve of molten metal in the
bath remains constant. If there are several pumps, a
system of controlling the flow rate of recirculated
metal can be provided to ensure the symmetry of the
system. According to a variant embodiment and
particularly when the pipe is of reduced length, the
variation of density of the molten metal linked to the
heat treatment that it undergoes for example within the
pipe is used to give a speed to the molten metal
leading to the same result.
Other details and advantageous features of the
invention will emerge hereinafter from the description
of exemplary embodiments of the invention with
reference to Figures 1 to 8 which represent,
- Figure 1, a schematic side view (a) and top view (b)
of the upstream portion of a conventional tank (prior
art), comprising a float bath for the production of a
glass ribbon by floating,
- Figure 2, a schematic side view of the device
according to the invention,
- Figure 3, a schematic general view from above of a
conventional float installation (prior art),
- Figure 4, a schematic top view of one embodiment of
the invention,
- Figure 5, a schematic side view of another embodiment
according to the invention,
- Figure 6, a schematic top view of another embodiment
of the invention,
- Figure 7, a partial side view in section of a diagram
of a portion of a device corresponding to the case in
Figure 4,
- Figure 8, a top view of the representation of
Figure 7.
Figure 1 shows the upstream portion of a tank elongated
for the production of float glass according to prior
art, seen from the side (a) and seen from above (b) .
The glass i flows on a spoutl.p 2 after adjustment of
the thickness and of load between the said spoutlip and
a vertical front tweel 3, then floats on the metal 5.
It can be seen that the glass forms a heel 4 beneath
the spoutlip. Arrows suggest the movement of the molten
glass. The zone furthest upstream 6 of this heel
situated symmetrically on the longitudinal axis AA' is
a zone of stationary points. This zone is situated
symmetrically on the axis AA' between two flows of
glass travelling either side of the installation.
Figure 2 shows a device according to the invention seen
from the side. As hereinabove, the glass runs on a
spoutlip 2 after thickness calibration by a front tweel
3 to float thereafter on the float bath 5. A heel 4
forms beneath the spoutlip 2. According to the
invention, molten unetal of the same kind as that of the
bath 5 constantly flows in the zone 6 preventing the
formation of a stationary point for the molten glass.
The duct 7 brings this molten metal which, is made to
flow on an inclined plane 201 before it reaches the
float bath itself, so doing to prevent turbulence in
the bath of liquid metal.
Figure 3 shows a conventional float installation
without the particular device according to the
invention. The invention provides an adaptation of this
type of installation for floating glass of the glass-
ceramic type. The invention may therefore make use of
the same installation with the addition of a molten
metal inlet at the zone or at the point furthest
upstream and in a symmetrical manner relative to the
longitudinal axis AA' of the installation and therefore
also of the float glass. The tank comprises side walls
8 and end walls 9 and 10, respectively at the inlet and
at the outlet of the tank. The tank, containing a bath
5 of molten tin, has a narrower downstream portion 11.
The molten glass is poured onto the bath at its inlet
end, from a distribution channel 12 ending in the
spoutlip and placed above the inlet wall of the tank.
Temperature regulators, not shown in the figures, are
incorporated into the roof that surmounts the bath.
These regulators establish the heat conditions of the
glass while keeping it in the deformable state until
the end of the drawing zone.
In glass production, the bath comprises several zones
shown in Figure 3 which may be distinguished in the
following manner:
- a zone I for spreading out the glass after it has
been cast onto the float bath, upstream.
- a zone II in which the ribbon of glass being formed
is subjected to longitudinal forces directed outwards
under the actions of lift-out rollers 12 and top
rolls 13. In this zone, the drawing of the glass
begins and the latter becomes thinner;
- a zone III in which the ribbon of glass takes its
definitive form under the action of the lift-out
rollers 12.
Zones II and III together form the drawing zone.
- a consolidation zone IV in which the set ribbon of
glass cools progressively.
After having been poured onto the float bath, the glass
spreads out freely to the maximum in zone I. It thus
forms a ribbon 14 which moves downstream under the
effect of the traction of the lift-out rollers 12
outside the tank.
The desired thickness is then obtained by the combined
action of the traction of the lift-out rollers 12 and
the knurled top rolls 13, usually made of steel,
slightly oblique relative to the perpendicular to the
direction of travel of the ribbon. These top rolls are
connected by shaft 15 to motors 16 which drive them
usually at speeds differing depending on their position
and increasing downstream. These rolls apply to the
edges of the ribbon of glass being formed forces
opposing a narrowing of the ribbon of glass. The ribbon
of glass is thus drawn out in the zone of these top
roils. The ribbon of glass is then brought to the
desired thickness by a drawing due to the lift-out
rollers.
The movement of the ribbon of glass on the bath causes
beneath the ribbon a current of molten metal directed
downstream of the tank and called the downstream
current. This downstream current butts against the
outlet face of the tank and rebounds to form an
upstream current. The downstream current is schematized
in the figure by a full arrow and the upstream current
is schematized by dashed arrows (in zone IV).
Figure 4 shows a partial top view of a diagram
representing half of a float bath 17 . According to the
invention, a portion of the molten metal may be tapped
off at the downstream end of the bath and transported
by a pipe 18. The metal is partially reintroduced in
zone 6 across the whole width upstream of the bath (the
flow of metal at 6 is represented by arrows),
symmetrically relative to the longitudinal axis AA'
(Figure 4 therefore shows only half of the width of
reintroduction of the molten metal). Another
reintroduction zone may be situated at different points
19 of the bath. The invention also makes provision for
the possibility of carrying out a heat treatment and
more precisely a raising of the temperature to bring
the tapped metal to a temperature closer to that of the
reintroduction zone; such an operation is used to
further limit the disruption due to temperature
variations. In the case of Figure 4 and of a division
into two reintroduction points 6 and 19, it is possible
to make provision for example for a progressive heat
treatment all along the pipe; according to this
embodiment, the heat regulation is adapted to obtain at
point 19 a temperature of the tapped molten metal
corresponding to the temperature of the bath at this
reintroduction point 19 in the bath and the heat
treatment continues, while the rest of the molten metal
is on its journey, up to point 6 so that the
temperature of the metal at this point; 6 corresponds to
the temperature in the bath in this reintroduction
zone. According to another embodiment, it is possible
to provide a heat treatment only for the metal taken up
to point 6, considering that the metal reintroduced at
point 19 is at such a temperature that it will not
disrupt the reintroduction zone of the bath, the
temperature difference being slight. The heating means
used may be any means known to those skilled in the art
and advantageously means of heating by induction
particularly when a pipe 18 is made of a refractory
material. According to the invention, the device
illustrated in this Figure 4 is advantageously made in
a symmetrical manner on the two edges of the bath so
that the tapping and reintroduction of the molten metal
do not disrupt the trajectory of travel of the ribbon
of glass.
It is again possible to provide a pumping device such
as a graphite pump as previously stated. Such a pump
will ensure that the tapped metal travels in the pipe
18. According to another embodiment and more
particularly when heating is provided, the variation of
density of the molten metal inside the pipe 18 may be
sufficient to ensure that the tapped metal travels as
has also already been stated previously.
Figure 5, which shows a partial schematic side view of
a float bath, illustrates a device similar to the
previous one according to which the molten metal is no
longer tapped through the side of the bath but through
the bottom thereof, via a pipe 18. This figure shows a
pump 20 and a heating device, but the latter are
optional as in the case of Figure 4. The pump 20 is
advantageously provided at the beginning of the pipe 18
and the heating device 51 is for its part provided at
the end of the said pipe 18 just before the
reintroduction zone 6. The reintroduced metal runs on
an inclined plane 52 before rejoining the float bath
53.
Figure 6 illustrates another embodiment of the
invention according to which the tapped molten metal is
brought back upstream, on the one hand, by a pipe 27
created inside the bath 5 by the presence of a wall 23
and, on the other hand, by a duct 18 returning the
molten metal all the way upstream to zone 6 in order to
prevent the formation of a stationary point of glass. A
pump 61 returns the molten metal through the duct 18.
This Figure 6 shows first of all the ribbon of glass 1
which is running on the float bath 5 delimited by the
walls 8. The molten metal is drawn along by the ribbon
of glass which creates a downstream current indicated
by the arrows 26. At the end of the bath, this
downstream current is transformed into an upstream
current. This transformation occurs naturally as
previously explained by the rebound on the end of the.
bath and the molten metal is channelled in the pipe 27
by a bath-bottom geometry judiciously provided for this
purpose. This Figure 6 again shows heating elements
such as radiant elements positioned above the bath to
thermally recondition the tapped molten metal and bring
it to the point 29 for reintroduction into the bath at
a temperature as close as possible to that of the bath
at this point. As in the case of the previous
embodiments, these heating elements are optional and
advantageously present when the reintroduction point is
far upstream. Similarly, it is possible to add to such
an embodiment a pump which would be advantageously
placed at the beginning of the pipe 27 .
Figures 7 and 8 represent a diagram of an installation
that may correspond to an embodiment according to
Figure 4, that is to say a lateral tapping of the
molten metal. These figures show the downstream portion
of the bath 37, the molten metal tapping point 30 and
further upstream a reintroduction point 31. An overflow
device 33 is made in close-coupled manner in the wall
32 of the bath. This device 33 will naturally receive
the molten metal which is drawn along by the ribbon of
glass and which butts against the downstream end of the
bath, then takes it to the pump 34 and finally into the
pipe 35. The overflow device 33 consists essentially of
an inclined plane 36 which helps the excess molten
metal to be drawn along so that no upstream current
appears within the bath 37. The pump 34 is
advantageously a graphite pump and, as in all the
previously presented embodiments, is optional. It is
again possible to add to this device a heating system
that is also optional.
At the point 31 of reintroduction into the bath 37,
there is advantageously provided a device, not shown in
the figures, used to reintroduce the molten metal at a
virtually zero speed; it is for example a spoutlip with
flared surface.
The duct returning the molten metal is divided in order
to supply the reintroduction point 6 furthest upstream
and is placed on the axis to prevent the glass from
forming a stationary point.
In the same manner as the other embodiments according
to the invention, the system shown in Figures 7 and 8
is advantageously produced either side of the bath in
particular so as not to disrupt the trajectory of the
ribbon of glass both at the tapping zone and at the
reintroduction zone.
Naturally, irrespective of which embodiment of the
invention is chosen, the greatest volume created
particularly by the molten metal circulation device is
taken into account to determine the total volume of
molten metal necessary for the correct operation of the
device for producing the ribbon of float glass.
These embodiments according to the invention have
further advantages; it is known that, in the system of
producing a ribbon of float glass, impurities are
created which are found in the downstream zone of the
bath and may contaminate the bottom surface of the
ribbon of glass. The invention will make it possible at
the same time as the tapping of the molten metal in the
downstream zone to tap off these impurities and either
remove them or subsequently reintroduce them into the
bath further upstream, the latter following the route
of the tapped molten metal. The reintroduction of these
impurities upstream of the bath and hence in a hotter
zone at reduced atmosphere will cause them to be
reduced and hence disappear. The method according to
the invention therefore also makes possible a treatment
of the molten metal that removes the impurities.
The method according to the invention has the further
advantage of being simple to implement and being able
in particular to be adapted to existing installations
without requiring major implementation work.
The ribbon of floated glass, particularly glass-ceramic
precursor, may be from 1 mm to 30 mm thick, and more
particularly from 1.5 mm to 25 mm and from 50 to 500 cm
wide and more particularly from 60 to 4 60 cm.
On leaving the forming installation, the ribbon passes
into a lehr to cool progressively, after which the
ribbon is cut up into sheets comprising two main faces
and one sheared edge. Each main face of these sheets
may have a surface area of 0.15 m to 20 m . In
particular, each main face may be from 0.4 m to 6 m
long and from 0.4 m to 3.5 m wide.
These sheets then undergo the ceramization heat
treatment specific to transforming them into glass-
ceramic. As an example, for a glass-ceramic based on
Si02-Li20, the ceramzation treatment may usually
be carried out in the following manner:
a) raising the temperature at the rate of 30 to
80C/minute to the nucleation domain, usually
situated in the vicinity of the glass transformation
domain;
b) passing through the nucleation range (670-800°C) in
15 to 25 minutes;
c) raising the temperature at the rate of 15 to
30°C/minute up to the temperature of the
ceramization level usually lying between 900 and
1100°C ;
d) maintaining the temperature of the ceramization
level for a period of 10 to 25 minutes;
e) rapid cooling to the ambient temperature.
After the ceramization cycle, the sheet of glass
comprises the crystalline phase characteristic of the
glass-ceramic structure.
The invention also concerns a flat glass-ceramic
preparation method comprising the float process
according to the invention with no stationary point,
leading to a flat glass, which then undergoes a
ceramization treatment leading to the said flat glass-
ceramic .
The invention also concerns the device for applying the
method that has been described and more particularly a
device for producing a ribbon of float glass, according
to which the ribbon runs on a float bath, characterized
in that it comprises a means of introducing molten
metal substantially at the point furthest upstream of
the float glass and situated on the longitudinal axis
of the bath. The means of introduction is preferably
such that the molten metal is in motion at the point of
meeting with the float bath. More particularly, the
means of introduction may comprise an inclined plane of
refractory material, the said inclined plane ending at
the float bath, such that the molten metal to be
introduced first runs onto the inclined plane before
pouring into the bath. In particular, the device may
comprise at least one duct supplied with metal tapped
from the bath and returning the said tapped metal to
the point furthest upstream of the glass and situated
on the longitudinal axis of the bath. It may also
comprise at least one overflow system at the downstream
end of the bath to tap off molten metal and connected
to the duct. The overflow system may be a tank close-
coupled to the bath and connected thereto by a
spillway, the pipe being outside the bath. Preferably,
the metal is withdrawn and reintroduced in a
symmetrical manner relative to the longitudinal axis of
the float installation.
The invention also relates to a (flat) sheet of glass-
ceramic at least one dimension of which (width or
length) is greater than 75 cm, and even greater than
80 cm and even greater than 100 cm and even greater
than 200 cm, usually less than 600 cm. In particular,
the sheet may be thin, that is to say thinner than 3 mm
and even thinner than 2.5 mm, even thinner than 2 mm,
furthermore usually thicker than 0.8 mm.
Any type of glass-ceramic precursor glass may be worked
according to the invention, including those comprising
more than 1.5% ZnO and even more than 1.6% by weight of
ZnO.
It is clearly understood that this invention, described
more particularly for producing glass-ceramic, also
applies to glass of a non glass-ceramic type. It is
also well understood that the metal in the float bath
may be recirculated independently of the reintroduction
at the head of the float bath. The recirculation of the
molten metal (usually tin-based) is more particularly
described in relation with the production of glass for
glass-ceramic and other glasses sensitive to
crystallization, but this recirculation method applies
also to any float chamber, whatever the glass produced,
so as to benefit from advantages other than that of
preventing crystallization.
WE CLAIM:
1. Method for the production of flat glass comprising the continuous
floating of a molten glass (1) on a bath of molten metal (5) in a float
installation, the said glass being poured in the molten state onto the
molten metal and progressively forming a ribbon (14) running over the
said metal bath without having any stationary point in the installation,
characterized in that molten metal is introduced into the installation so
that it forms a moving reception zone (6) for the molten glass.
2. Method as claimed in the preceding claim, wherein the glass floating
on the molten metal bath is a glass-ceramic precursor glass.
3. Method as claimed in one of the preceding claims, wherein the molten
metal is introduced at the float points that would be stationary for the
glass if there were no introduction.
4. Method as claimed in one of the preceding claims, wherein the molten
metal is introduced at the float point furthest upstream and situated
on the longitudinal axis of the bath.
5. Method as claimed in claim 1 to the preceding claim wherein the
molten metal introduced originates at least partially from a tap-off
point of the same bath situated further downstream.
6. Method as claimed in the preceding claim, wherein the flow of tapped-
off and reintroduced metal is divided, on the one hand, in order to
supply the float point further upstream and situated on the longitudinal
axis of the bath, and, on the other hand, in order to supply at least
one other reintroduction point situated between the preceding point
and the tap-off point.
7. Method as claimed in one of the two preceding claims, wherein the
tapped-off metal is reheated before it is reintroduced.
8. Method as claimed in one of claims 5 to the preceding claims, wherein
molten metal is tapped off from the lateral portions of the float bath
and in a symmetrical manner relative to its longitudinal axis.
9. Method as claimed in one of claims 5 to the preceding claim, wherein
the molten metal is reintroduced partially on the lateral portions of the
bath with a virtually zero speed and in a symmetrical manner relative
to the longitudinal axis.
10. Method of preparing a flat glass-ceramic comprising the method of one
of the preceding claims leading to a flat glass, which then undergoes a
ceramization process leading to the said flat glass-ceramic.
11. Method as claimed in one of the preceding claims, wherein at the
location where the glass is poured, its dynamic viscosity lies between 3
and 4.5 poise.
12. Method as claimed in one of the preceding claims, wherein at the
location where the glass is poured, its temperature lies between 1300
and 1450°C.
13. Device for forming molten glass for the production of a ribbon (14) of
float glass, which device comprises a molten glass pouring zone
followed by a glass drawing zone, according to which the ribbon runs
on a float bath, characterized in that it comprises a means of
introducing molten metal substantially at the point furthest upstream
of the floated glass and situated on the longitudinal axis of the bath.
14. Device as claimed in the preceding claims, wherein the introduction
means is such that the molten metal is in motion at the point of
meeting with the metal bath.
15. Device as claimed in one of the preceding device claims, wherein it
comprises an inclined plane (201) of refractory material, the said
inclined plane ending at the metal bath (5), such that the molten metal
to be introduced first runs onto the inclined plane (201) before pouring
into the bath.
16. Device as claimed in the preceding claim, wherein it comprises at least
one duct (7) supplied with metal tapped-off from the bath and
returning the same tapped-off metal to the point furthest upstream of
the glass and situated on the longitudinal axis of the bath.
17. Device as claimed in the preceding claim, wherein it comprises at least
one overflow system (33) at the downstream end of the bath, in order
to tap off molten metal, and connected to the duct.
18. Device as claimed in the preceding claim, wherein the overflow
system is a tank close-coupled to the bath and connected thereto by a
spillway and in that the pipe is outside the bath.
19. Device as claimed in one of claims 16, to the preceding claim, wherein
the metal is drawn and reintroduced in a symmetrical manner relative
to the longitudinal axis of the float installation.
20. Ribbon of floated flat glass of the glass-ceramic precursor type
containing more than 1.5% ZnO.
21. Glass-ceramic plate, at least one dimension of which is greater than
200 cm.
22. Glass-ceramic plate as claimed in the preceding plate claim, the
thickness of which is less than 3 mm.
23. Glass-ceramic plate as claimed in one of claims 21 or 22, wherein it
contains more than 1.5% ZnO.

The invention concerns a method and a device for the
production of flat glass comprising the continuous
floating of a molten glass on a float bath in a float
installation, the said floated glass progressively
forming a riboon running on the} said float bath without
having any stationary point in the installation. To do
this, the molten metal can be poured at locations
capable of being stationary points and in particular at
the float point furthest upstream and situated on the
longitudinal axis of the bath. The glass may be glass-
ceramic precursor glass. Glass-ceramic plates can be
made in large dimensions, even greater than 7 5 cm and
even very thin such as thinner than 3 mm.

Documents:

01872-kolnp-2006 abstract.pdf

01872-kolnp-2006 assignment.pdf

01872-kolnp-2006 claims.pdf

01872-kolnp-2006 correspondence others.pdf

01872-kolnp-2006 description(complete).pdf

01872-kolnp-2006 drawings.pdf

01872-kolnp-2006 form-1.pdf

01872-kolnp-2006 form-2.pdf

01872-kolnp-2006 form-3.pdf

01872-kolnp-2006 form-5.pdf

01872-kolnp-2006 international publication.pdf

01872-kolnp-2006 international search authority report.pdf

01872-kolnp-2006 pct form.pdf

01872-kolnp-2006-correspondence others-1.1.pdf

01872-kolnp-2006-correspondence-1.2.pdf

01872-kolnp-2006-form-18.pdf

01872-kolnp-2006-priority document.pdf

1872-KOLNP-2006-ABSTRACT.pdf

1872-KOLNP-2006-AMENDED DOCUMENT.pdf

1872-KOLNP-2006-CLAIMS.pdf

1872-KOLNP-2006-CORRESPONDENCE 1.1.pdf

1872-KOLNP-2006-DESCRIPTION COMPLETE.pdf

1872-KOLNP-2006-DRAWINGS.pdf

1872-KOLNP-2006-FORM 1.pdf

1872-KOLNP-2006-FORM 2.pdf

1872-kolnp-2006-form 27.pdf

1872-KOLNP-2006-FORM 3.pdf

1872-KOLNP-2006-FORM 5.pdf

1872-KOLNP-2006-FORM-27.pdf

1872-kolnp-2006-granted-abstract.pdf

1872-kolnp-2006-granted-claims.pdf

1872-kolnp-2006-granted-correspondence.pdf

1872-kolnp-2006-granted-description (complete).pdf

1872-kolnp-2006-granted-drawings.pdf

1872-kolnp-2006-granted-examination report.pdf

1872-kolnp-2006-granted-form 1.pdf

1872-kolnp-2006-granted-form 18.pdf

1872-kolnp-2006-granted-form 2.pdf

1872-kolnp-2006-granted-form 3.pdf

1872-kolnp-2006-granted-form 5.pdf

1872-kolnp-2006-granted-gpa.pdf

1872-kolnp-2006-granted-reply to examination report.pdf

1872-kolnp-2006-granted-specification.pdf

1872-kolnp-2006-granted-translated copy of priority document.pdf

1872-KOLNP-2006-OTHERS.pdf

1872-KOLNP-2006-PETITION UNDER RULE 137.pdf

1872-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

abstract-01872-kolnp-2006.jpg

« Previous Patent

Next Patent »

Patent Number

234042

Indian Patent Application Number

1872/KOLNP/2006

PG Journal Number

24/2009

Publication Date

12-Jun-2009

Grant Date

01-May-2009

Date of Filing

05-Jul-2006

Name of Patentee

SAINT-GOBAIN GLASS FRANCE

Applicant Address

LES MIROIRS, 18 AVENUE D'ALSACE, F-92400 COURBEVOIE

Inventors:

#	Inventor's Name	Inventor's Address
1	GOULAS, CATHERINE	SAINT-GOBAIN RECHERCHE 39 QUAI LUCIEN, LEFRANC, 93300 AUBERVILLIERS
2	COBO HEDILLA, ANGEL-FRANCISCO	SAINT-GOBAIN GLASS ESPANA AVDA DE LUGO, 110 33400 AVILES (ASTURIAS)
3	LEMAILLE, MAURICE	SAINT-GOBAIN GLASS ESPANA AVDA DE LUGO, 100, E-33400 AVILES
4	GOULAS, CATHERINE	SAINT-GOBAIN RECHERCHE 39 QUAI LUCIEN, LEFRANC, 93300 AUBERVILLIERS
5	COBO HEDILLA, ANGEL-FRANCISCO	SAINT-GOBAIN GLASS ESPANA AVDA DE LUGO, 110 33400 AVILES (ASTURIAS)
6	LEMAILLE, MAURICE	SAINT-GOBAIN GLASS ESPANA AVDA DE LUGO, 100, E-33400 AVILES

PCT International Classification Number

C03B 18/02

PCT International Application Number

PCT/FR2005/050041

PCT International Filing date

2005-01-24

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0400788	2004-01-28	France