Abstract: An apparatus for bend-shaping a glass sheet is disclosed, which comprises a heating furnace, a plurality of in-furnace beds disposed within the heating furnace, at least one out-furnace bed disposed externally of the heating furnace proximately to an outlet of the heating furnace, and an elevating mechanism disposed below that one of the in-furnace beds which is positioned proximately to the outlet and the out-furnace bed. The in- and out-furnace beds have upper surfaces curved transversely and capable of jetting air to floatingly support a glass sheet. For producing a dual curved glass sheet, the elevating mechanism is operated to elevate opposed ends of the one in-furnace bed and the out-furnace bed so that these beds jointly form a hill. For producing a single-curved glass sheet, the elevating mechanism is operated to lower the opposed ends of those beds to their original flat positions.

Abstract: An apparatus for press-forming a molten gob made of meltable material, especially of glass or glass ceramics, into a body of specific shape with compression moulds which form with each other a form cavity for receiving the gob. The compression moulds consist at least in the zone of the forming surfaces of an open-pore material and the compression moulds are connected to a pressure gas source in order to produce a gas stream which emerges from the forming surfaces. The open-pore material of the forming surfaces the pores close to the forming surfaces are smaller than the pores remote from the forming surfaces.

Abstract: While periphery or peripheries of workpiece(s) W lifted in floating fashion by simultaneous suction and expulsion of gas(es) between pair(s) of first and second, or upper and lower, transport stages 14, 15 is/are retained by plurality of elevator pins 16, respective transport stage(s) is/are inverted vertically and workpiece(s) is/are transferred from upper first transport stage(s) to lower second transport stage(s) such that workpiece(s) W is/are lifted in floating fashion thereabove by simultaneous suction and expulsion of gas(es) in accompaniment to lowering of respective elevator pin(s) at said first transport stage(s).

Abstract: A transfer arm holds a plurality of preforms arranged in a single line and simultaneously drops and supplies the preforms downward. A positioning arm has a pair of arm split members split in its widthwise direction. The arm split members have positioning surfaces formed on their contact surfaces to be brought into contact with outer peripheries of the preforms. After the preforms are dropped and supplied from the transfer arm, the arm split members of the positioning arm are opened and closed so that the positioning surfaces are brought into contact with the outer peripheries of the preforms. Thus, the performs are properly positioned.

Abstract: The method of supporting and transporting hot flat glass on a gas bed for ceramicizing includes arranging a number of spaced-apart porous or perforated planar segments to form a base with a gas-permeable support surface so that slits, which are narrower than the planar segments, are formed between them, forcing gas through the porous or perforated planar segments and conducting the gas away through the slits between them so as to form the gas bed with no static pressure zones and with a parabolic pressure distribution and producing a predetermined temperature profile for ceramicizing through which the hot flat glass is transported on the gas bed without deformation and without any contact between it and the base. The resulting glass ceramic has smoother surfaces without pits or deformations.

Abstract: An apparatus for bending a glass sheet includes a final hearth bed. This final hearth bed has a top surface that is upwardly convexly curved along a plane perpendicular to an axis of the glass sheet. The top surface has an upstream end, a downstream end that is at a level lower than that of the upstream end, and an intermediate point defined therebetween. The top surface has (a) a first section that extends from the upstream end to the intermediate point and that is parallel with the axis or upwardly inclined relative to the axis and (b) a second section that extends from the intermediate point to the downstream end and that is downwardly inclined relative to the axis. The final hearth bed has a bottom surface that is along the first direction or inclined downwardly relative to the first direction.

Abstract: The invention concerns a device for supporting a horizontal guided, continuous glass strand; with a number of supporting blocks, which each exhibits a supporting area, facing the glass strand; the individual supporting block in the area of the supporting area is made from a porous, gas-impermeable diaphragm body; the diaphragm body is connected to a source of compressed gas for conveying gas through the supporting area.

Abstract: For bending a glass sheet so that the glass sheet has a compound curvature, an apparatus comprises a furnace including hearth beds on a bed support and a quenching unit provided with upper and lower air blowers. The final hearth bed may have a top surface with a simple curvature, be provided with one upstream corner cut away thereby defining a cut surface section and arranged in such a manner that the cut surface section is nearly parallel to the hearth bed adjacent to the final hearth bed. Alternatively, the final hearth bed may have a top surface with a compound curvature, so that the glass sheet is bent under the conditions set by controlling a temperature in a downstream part of the furnace, adjusting the inclination of the lower air blower and/or rotating final hearth bed so as to reverse the upstream and downstream ends thereof.

Abstract: A device for supporting a ribbon of glass, having at least one roller arranged in an area of an underside of the ribbon of glass. In order to keep a ribbon of glass as free as possible of mechanical damage during production, at least one support device is assigned to the roller. With an actuating device the roller or the support device can selectively be contacted with the underside of the ribbon of glass, wherein the support device is in contact, at least in some areas, with the underside of the ribbon of glass by way of a gas cushion. The rollers are then employed at the start of production or after a ribbon of glass has snapped off in order to transmit an advancement force to the ribbon of glass.

Abstract: A roller table for supporting and transporting a hot glass strand. A plurality of rollers arranged parallel to each other and perpendicular to the transport direction of the glass strand are capable of being selectively rotated in the direction of transport of the glass strand. At least some of the rollers are sleeves, the casings of which are which are gas-permeable on at least a portion of their surfaces and the casings are provided with a supply of pressurized gas which is emitted through the openings of the gas-permeable surfaces.

Abstract: A device for manufacturing glass gobs includes a membrane body of a porous gas transmitting material. Channels for introducing compressed gas into the membrane body extend through the membrane body material and are spaced at a distance from the gas outlet surface of the membrane body. The channels run parallel to or are at an acute angle to the outlet surface. In an alternate embodiment, the channels are open channels at the opposite surface from the outlet surface.

Abstract: A porous wall through which a flow of gas is established forming a layer supporting a liquid mass is strengthened partly to stiffen it and partly to control the shape of the lower surface of the supported liquid. Chambers containing different pressures can be formed, and possibly, separated by some of these strengthening parts to improve the equalisation by reducing the pressure at the center. Finally, capillaries may pass through the plate to measure the pressure or provide additional equalisation of the thickness of the layer by a suction device.

Abstract: The present invention generally relates to a method of making halogen lamps and halogen lamp bulbs, as well as other analogous lamps and objects. The present invention also relates to apparatus used in a method of making halogen lamps and halogen lamp bulbs, as well as other analogous lamps and objects. The method minimizes contamination in the body of the glass and minimizes reaction of lamp halogen with the interior of a halogen lamp.

Abstract: The invention relates to a method for heating up and shaping a preform consisting of glass or glass ceramic. According to the invention, a preform, formed using conventional methods, is heated to a temperature that is below the adhesion temperature of the gas, i.e. to below critical viscosity; in a second heating phase the preform is put into a hovering state through the supply of levitation gas; in the hovering state the preform is heated by a microwave heating apparatus to a temperature that permits its shaping; and the preform is delivered to a shaping station.

Abstract: An apparatus for shaping heat softened glass sheets includes an upper mold having a full surface press face with a shaping surface generally contoured to the desired curvature of the sheets; a support device to support the sheets below the upper mold; a shaping rail having an upper sheet supporting surface that supports selected peripheral portions of the sheets, the sheet supporting surface having a profile corresponding to desired elevational contours of the selected peripheral portions of the sheets and complimenting corresponding portions of the upper mold shaping surface; a chamber positioned below the sheets; a moving device for moving the upper mold and the shaping rail relative to each other so as to press at least a periphery of the sheets against the upper mold shaping surface, and a connector to direct pressurized gas into the chamber to urge the sheets towards the upper mold press face.

Abstract: Disclosed are processes for manufacturing glass optical elements by press molding a heated and softened glass material in preheated molds. In the process, the glass material is heated while it is floated by a gas blow and the heated and softened glass material is transferred to the preheated molds and then subjected to press molding. Alternatively, the process comprises: heating a glass material at a temperature at which the glass material has a viscosity of lower than 109 poises, preheating molds at a temperature at which the glass material has a viscosity of from 109 to 1012 poises, subjecting the heated and softened glass material to initial press in the preheated molds for 3 to 60 seconds, starting to cool the vicinity of molding surfaces of the molds at a rate of 20° C.

Abstract: A microstructure is formed in a viscous glass or plastic substrate by pressing a structured surface of a forming tool corresponding to a negative of the microstructure to be produced in the viscous glass or plastic substrate. After the microstructure has been formed, the forming tool is removed from the surface. In order to help form the microstructure and remove the forming tool from the substrate the forming tool has an at least partially porous base body (1) and an operative layer (2) structured with a negative structure consisting of grooves (11) extending to the porous base body (1). The forming of the microstructure in the substrate is assisted by applying suction to the porous base body (1) so that the grooves (11) fill more easily and completely with melted glass or plastic material. The removal of the forming tool after forming the microstructure is assisted by applying an overpressure to the porous body to help release the solidified glass or plastic material from the forming tool.

Abstract: An apparatus for bend-shaping a glass sheet is disclosed, which comprises a heating furnace, a plurality of in-furnace beds disposed within the heating furnace, at least one out-furnace bed disposed externally of the heating furnace proximately to an outlet of the heating furnace, and an elevating mechanism disposed below that one of the in-furnace beds which is positioned proximately to the outlet and the out-furnace bed. The in- and out-furnace beds have upper surfaces curved transversely and capable of jetting air to floatingly support a glass sheet. For producing a dual curved glass sheet, the elevating mechanism is operated to elevate opposed ends of the one in-furnace bed and the out-furnace bed so that these beds jointly form a hill. For producing a single-curved glass sheet, the elevating mechanism is operated to lower the opposed ends of those beds to their original flat positions.

Abstract: The method of making globular or spherical bodies of optical quality includes filling receptacles (2) in a heat-resistant support (3) made of a porous material with glass gobs (1); conducting gas through the heat-resistant support so that a gas flow (4) passes through the support in a direction (14) opposite to a direction in which gravity acts; heating the heat-resistant support (3) to a temperature at which the glass gobs (1) have a viscosity of up to about 106 poise; maintaining the support (3) at this temperature for a predetermined time interval; and then cooling the support (3) to ambient temperature while continuing to provide the gas flow (4) through the support (3).

Abstract: A method and apparatus for making cylindrical glass preforms with convex, optical quality convex end surfaces is taught. A glass ball preform is placed on a heated lower platen. The temperature of the glass ball preform is raised to a temperature above the glass transition temperature of the glass ball preform. The glass ball preform is engaged with an upper platen. At least one of the upper platen and the lower platen is moved vertically to cause the gap between the upper platen and the lower platen to narrow to a predetermined dimension. Simultaneously, at least one of the upper platen and the lower platen is moved horizontally relative to the other platen to cause the glass ball preform to roll between the upper platen and the lower platen and form a cylindrical preform having a predetermined diameter, the cylindrical preform having convex, optical quality end surfaces.

Abstract: A heated and softened glass sheet is put on a bending surface of a frame unit to be preliminarily bent by gravity before the glass sheet is pressed by an upper mold and the frame unit. There are steps for using a certain means for controlling an amount of preliminary bending to control deformation of the glass sheet caused by the preliminary bending; and pressing the preliminarily bent glass sheet by the upper mold and the frame unit.

Abstract: The invention concerns a method and a device for heating glass sheets in an oven, which are transported therein by a conveyor with horizontal rollers and wherein their surfaces are heated by heating means arranged above and beneath the sheets, by radiation and by forced convection by injecting hot gas into the oven, the gas injected beneath being in the form of jets whereof the axis of symmetry is oblique relative to the forward moving direction of the sheets on the conveyor and directed towards their lower surface.

Abstract: A method of forming a glass sheet includes obtaining a preform generated from a glass composition and conveying the preform through a channel having a temperature that decreases along a length of the channel to form a glass sheet having a predetermined width and thickness.

Abstract: A method of floating glass gobs by means of a gas flow. A method of manufacturing glass gobs by floating a molten glass gob and simultaneously cooling it. A method of manufacturing glass spheres by floating a softened glass gob and simultaneously rendering it spherical. These methods employ a device having a depression for floating and holding a glass gob or the like, with a gas flow being supplied along all or part of the inner surface of the depression from the opening side of the depression toward the bottom. A manufacturing method comprising the steps of adjusting a glass gob to a temperature suited to press molding while floating said glass gob by means of a gas flow injected along part or all of the depression-shaped forming surface of a lower mold from the opening side of the lower mold toward the bottom of the lower mold; and a step of press forming the glass gob.

Abstract: The invention relates to a method and a device for storing and transporting hot flat glass in a contactless manner during glass production, said storage and transportation being carried out on a gas bed which is constructed over a gas permeable bearing surface pertaining to a base (2). Pressurised gas is supplied to the base via a connection (5), said gas being guided through the gas permeable base and then re-evacuated. The aim of the invention is to obtain an optimum pressure distribution above the bearing surface, without any static pressure. In order to achieve this, the base (2) consists of a plurality of interspaced segments (21, 22 . . . 2n) respectively comprising a porous and/or perforated bearing surface (7a) as a gas outlet surface. Evacuation openings (61, 62 . . . 6n) are formed between said segments for evacuating the gas. The segments are preferably formed by bars (7) having a box profile.

Abstract: An apparatus for bending a glass sheet includes a final hearth bed. This final hearth bed has a top surface that is upwardly convexly curved along a plane perpendicular to an axis of the glass sheet. The top surface has an upstream end, a downstream end that is at a level lower than that of the upstream end, and an intermediate point defined therebetween. The top surface has (a) a first section that extends from the upstream end to the intermediate point and that is parallel with the axis or upwardly inclined relative to the axis and (b) a second section that extends from the intermediate point to the downstream end and that is downwardly inclined relative to the axis. The final hearth bed has a bottom surface that is along the first direction or inclined downwardly relative to the first direction.

Abstract: An extrusion system for producing a desired extrusion profile on a continuously moving work piece has a die containing two or more pressurized fluid extrusion cells therein, through which the work piece passes. Fluid under pressure id directed against the work piece to shape it without physical contact between the die and the work piece. The individual extrusion cells are configured to produce the desired profile, which is monitored by a non-contact metering member which applies signals to a processing unit which, in turn, applies correction signals to a pressured fluid supply module to control the pressurized fluid supply to each of the extrusion cells.

Abstract: Processes for manufacturing glass optical elements by press molding a heated and softened glass material in preheated molds. In the process, the glass material is heated while it is floated by a gas blow and the heated and softened glass material is transferred to the preheated molds and then subjected to press molding. Alternatively, the process comprises: heating a glass material at a temperature at which the glass material has a viscosity of lower than 109 poises, preheating molds at a temperature at which the glass material has a viscosity of from 109 to 1012 poises, subjecting the heated and softened glass material to initial press in the preheated molds for 3 to 60 seconds, starting to cool the vicinity of molding surfaces of the molds at a rate of 20° C.

Abstract: A method and device for the manufacture of a hollow cone (37) with a cone tip (31) whereby a parison of viscous material (35) is moulded into the shape of the hollow cone. An escape space (11) becomes accessible to the material in the vicinity of a cone tip to be formed. The moment the pressure present in the material in the vicinity of the cone tip to be formed exceeds a previously defined value. Breaking-off of the cone tip during or after moulding is prevented by this. The hollow cone is suitable inter alia for use in a cathode ray tube.

Abstract: A transfer arm holds a plurality of preforms arranged in a single line and simultaneously drops and supplies the preforms downward. A positioning arm has a pair of arm split members split in its widthwise direction. The arm split members have positioning surfaces formed on their contact surfaces to be brought into contact with outer peripheries of the preforms. After the preforms are dropped and supplied from the transfer arm, the arm split members of the positioning arm are opened and closed so that the positioning surfaces are brought into contact with the outer peripheries of the preforms. Thus, the performs are properly positioned.

Abstract: A method and apparatus for forming a planar layer on a surface of a microelectronic substrate. The method comprises controlling a temperature of a liquid support material to be at least an annealing temperature of material comprising the planar layer. In one embodiment, the planar layer material has a lower density than the liquid support material and the method further comprises floating the planar layer material upon the liquid support material so that the planar layer material attains a temperature of at least its annealing temperature. The planar layer material forms a planar surface at an interface with the support material and is adhered at an opposite surface to the substrate to form a planar layer thereon. In another embodiment, the planar layer material is adhered to a surface of the substrate.

Abstract: The invention relates to an apparatus for press-forming a molten gob made of meltable material, especially of glass or glass ceramics, into a body of specific shape;

Abstract: The invention concerns a roller table for carrying and transporting a hot glass band.

Abstract: A glass sheet quench station (16) includes first and second quench sections (24 and 26) that cooperate with a three position shuttle (28) and a control (30) to transfer glass sheets through the quench station with partial quenching performed at the first quench station and completion of the quenching at the second quench section. This glass sheet quenching method with two stage quenching shortens the cycle time to provide increased production.

Abstract: A pressure pad array is used to float glass sheets from a glass heating furnace to a ring mold in a press bending station. The pressure pads have transversely spaced, longitudinally-extending slotted nozzles angled towards one another to provide a static pressure area for floating the glass sheet. The slotted nozzles are aligned with the direction of glass sheet travel and the space between adjacent pressure pads is covered by a spacer baffle to generate additional static pressure flotation areas. The static pressure areas formed by the slotted nozzles generally produce uniform pressure profiles extending longitudinally and transversely against the sheet's underside to stably float the glass sheets on a heated gas cushion.

Abstract: A pressure pad array is used to float glass sheets from a glass heating furnace to a ring mold in a press bending station. The pressure pads have transversely spaced, longitudinally-extending slotted nozzles angled towards one another to provide a static pressure area for floating the glass sheet. The slotted nozzles are aligned with the direction of glass sheet travel and the space between adjacent pressure pads is covered by a spacer baffle to generate additional static pressure flotation areas. The static pressure areas formed by the slotted nozzles generally produce uniform pressure profiles extending longitudinally and transversely against the sheet's underside to stably float the glass sheets on a heated gas cushion.

Abstract: The invention relates to a method for the hot shaping of molten gobs on a mold base by interposing a gas bed, comprising the following method steps.

Abstract: A glass sheet quench station (16) includes first and second quench sections (24 and 26) that cooperate with a three position shuttle (28) and a control (30) to transfer glass sheets through the quench station with partial quenching performed at the first quench station and completion of the quenching at the second quench section. This glass sheet quenching method with two stage quenching shortens the cycle time to provide increased production.

Abstract: An inclined trough assembly (10) for conveying, by gravity, formable gobs of glass at an elevated temperature to a section of a glass container forming machine of the I.S. type, the trough assembly having a trough member (12) configured, in cross-section, generally corresponding to that of an upwardly facing V and a manifold (14) at least partly underlying the trough member and having a configuration, in cross-section, generally corresponding to that of an upwardly facing U. The trough member 12 is inserted into the manifold partly to the bottom thereof, and the manifold has a compressed air inlet (14a) for receiving compressed or fan air to flow along the manifold in cooling contact with the trough member to cool the trough member and thereby reduce the coefficient of friction between the gobs of glass flowing through the trough assembly and the trough member thereof.

Abstract: The invention concerns a device for supporting a horizontal guided, continuous glass strand;

Abstract: For bending a glass sheet so that the glass sheet has a compound curvature, an apparatus comprises a furnace including hearth beds on a bed support and a quenching unit provided with upper and lower air blowers. The final hearth bed may have a top surface with a simple curvature, be provided with one upstream corner cut away thereby defining a cut surface section and arranged in such a manner that the cut surface section is nearly parallel to the hearth bed adjacent to the final hearth bed. Alternatively, the final hearth bed may have a top surface with a compound curvature, so that the glass sheet is bent under the conditions set by controlling a temperature in a downstream part of the furnace, adjusting the inclination of the lower air blower and/or rotating final hearth bed so as to reverse the upstream and downstream ends thereof.

Abstract: A process for cutting glass sheets (10) includes the steps of: scoring each glass sheet on an automatic scoring table (12) having a scoring head (14) moveable on a bridge (16) and a track (18); transporting each scored glass sheet to a breaking table (22) via conveyor (20); floating each scored sheet on a fluid medium on the breaking table; and impacting each scored sheet from above the floated scored sheet to fracture the scored sheet along the score lines (40 and 44). An apparatus for cutting glass sheets includes mechanisms for performing the steps of this process. The fluid medium may be air with the impacting performed by a vacuum workholder (26) consisting of an arm (30) raised and lowered by pneumatic cylinders (32), the arm supporting a plurality of vacuum cups (28) engaging the workpiece (42) for subsequent transportation.

Abstract: Disclosed are processes for manufacturing glass optical elements by press molding a heated and softened glass material in preheated molds. In the process, the glass material is heated while it is floated by a gas blow and the heated and softened glass material is transferred to the preheated molds and then subjected to press molding. Alternatively, the process comprises: heating a glass material at a temperature at which the glass material has a viscosity of lower than 109 poises, preheating molds at a temperature at which the glass material has a viscosity of from 109 to 1012 poises, subjecting the heated and softened glass material to initial press in the preheated molds for 3 to 60 seconds, starting to cool the vicinity of molding surfaces of the molds at a rate of 20° C.

Abstract: A method for forming glass sheets is performed by a system (10) that includes a furnace (12) having a heating chamber (14) in which a topside transfer device (20) has a downwardly facing surface (22) to which vacuum and pressurized air are supplied to receive and support a heated glass sheet from a conveyor (16) without any direct contact. A forming station (24) located externally of the furnace has a vertically movable upper mold (28) whose temperature is not greater than 500° C. The upper mold (28) cooperates with a horizontally movable lower ring (34) that transfers the heated glass sheet from the topside transfer device (20) to the forming station under the control of a first actuator (40). A second actuator (42) moves the upper mold (28) downwardly to cooperate with the lower ring (34) in forming the glass sheet. The external forming station (24) includes heat loss reducing apparatus (43) for reducing heat loss of the hot glass sheet during the forming.

Abstract: An apparatus for bend-shaping a glass sheet is disclosed, which comprises a heating furnace, a plurality of in-furnace beds disposed within the heating furnace, at least one out-furnace bed disposed externally of the heating furnace proximately to an outlet of the heating furnace, and an elevating mechanism disposed below that one of the in-furnace beds which is positioned proximately to the outlet and the out-furnace bed. The in- and out-furnace beds have upper surfaces curved transversely and capable of jetting air to floatingly support a glass sheet. For producing a dual curved glass sheet, the elevating mechanism is operated to elevate opposed ends of the one in-furnace bed and the out-furnace bed so that these beds jointly form a hill For producing a single-curved glass sheet, the elevating mechanism is operated to lower the opposed ends of those beds to their original flat positions.

Abstract: A method for forming glass sheets is performed by a system (10) that includes a furnace (12) having a heating chamber (14) in which a vacuum platen (20) has a downwardly facing surface (22) to which a vacuum is supplied to support a heated glass sheet received from a conveyor (16). A forming station (24) located externally of the furnace has a vertically movable upper mold (28) whose temperature is not greater than 500° C. The upper mold (28) cooperates with a horizontally movable lower ring (34). A first actuator (39) moves the vacuum platen (20) vertically to transfer a heated glass sheet from the conveyor (16) to the lower ring (34) which is then moved by a second actuator (40) to the forming station (24). A third actuator (42) then moves the upper mold (28) downwardly to cooperate with the lower ring (34) in forming the glass sheet. The forming station (24) includes apparatus (43) for reducing heat loss of the glass sheet during the forming.

Abstract: A device for manufacturing glass gobs includes a membrane body of a porous gas transmitting material. Channels for introducing compressed gas into the membrane body extend through the membrane body material and are spaced at a distance from the gas outlet surface of the membrane body. The channels run parallel to or are at an acute angle to the outlet surface. In an alternate embodiment, the channels are open channels at the opposite surface from the outlet surface.

Abstract: A glass quenching apparatus for quenching a glass sheet heated to a predetermined temperature, includes a first nozzle group for jetting blower air onto opposite surfaces of the glass sheet, and a second nozzle group for jetting compressor air onto at least one of the opposite surfaces of the glass sheet. The first nozzle group is comprised of stationary nozzles, and the second nozzle group is comprised of movable nozzles which are capable of moving parallel to a plane of the glass sheet. The glass quenching apparatus of the foregoing construction is able to quench the glass sheet uniformly over the entire area thereof without undue wastage of quenching air.

Abstract: A method and device for the manufacture of a hollow cone (37) with a cone tip (31) whereby a parison of viscous material (35) is moulded into the shape of the hollow cone. An escape space (11) becomes accessible to the material in the vicinity of a cone tip to be formed. The moment the pressure present in the material in the vicinity of the cone tip to be formed exceeds a previously defined value. Breaking-off of the cone tip during or after moulding is prevented by this. The hollow cone is suitable inter alia for use in a cathode ray tube.

Abstract: A gas is supplied to the surface of the glass sheet transferred between a heating furnace and a cooling apparatus for tempering the glass sheet. The gas is supplied from the upstream side with respect to the direction of transfer of the glass sheet by an air curtain device. This gas runs along the glass sheet surface (upper surface) downstream with respect to the direction of transfer to obstruct the flow of cooling gas from the cooling apparatus in the upstream direction. The gas prevents cooling air from the cooling apparatus from invading the heating furnace so that the difference of the curvature of the glass sheet on the front and rear part can be eliminated.