METHOD AND APPARATUS FOR PREVENTING THE DEFLECTION OF THE BEARING RAILS OF A MOULD WAGON IN A GLASS SHEET BENDING FURNACE

Abstract: The invention relates to a method and an apparatus in a glass sheet bending furnace for preventing the deflection of a mould wagon (5) bearing rail (5a) as the mould wagon is carried along a conveyor track (8) comprising rollers (8a) for resting said bearing rails (5a) thereupon, the furnace including a top array of successive heating sections (2) and a bottom array of successive cooling sections (4). The deflection of bearing rails (5a) is prevented by blasting cooling air to the top surfaces of bearing rails (5a) of mould wagons (5) in a cool­ ing section (4).

Description: The present invention relates to a method and an apparatus for preventing the deflection of the bearing rails of a mould wagon in a glass sheet bending furnace including a top array of successive heating sections and a bottom array of successive cooling sections and in which the mould wagon is carried along a conveyor track comprising rollers for resting said bearing rails thereupon. A glass sheet bending furnace and wagons of the above described type are disclosed in US-A-4 497 645. A problem encountered in a glass sheet bending furnace as described in US-A-4 497 645 is the considerable deflection of the bearing rails mounted alongside a mould wagon during a cooling cycle. The resulting deflection remains in the rails even as the wagon is advancing along the top track from one heating section to the next. The deflection of bearing rails results in a shaking or "jolting" movement of the wagon which is why especially rather large glass sheets are easily broken even before a bending section on the top track. The deflection of wagon bearing rails occurs on the bottom track as a result of temperature differences. First of all, the hot bearing rails deliver heat through their bottom surfaces to conveyor track supporting rollers. Secondly, the hot glass and mould deliver radiation heat to the top surface of a bearing rail. It has been realised in this invention that this deflection of bearing rails as a result of temperature differences can be prevented by blowing cooling air to the top surface of bearing rails on the bottom track. The characterizing features of the invention are set forth in the annexed claims. The invention will now be described with reference made to the accompanying drawings, in which fig. 1 shows schematically a bending furnace in a side view. Fig. 2 is a perspective view of a slice of one bending furnace section, comprising a top heating section and a bottom cooling section. Fig. 3 shows a bending furnace in a cross-section. Fig. 4 shows schematically the deflection of a hot bearing rail 5a as it delivers heat to cooler supporting rollers 8a. Fig. 5 shows a condition in which the deflection shown in fig. 4 has been straightened by means of a cooling blast of the invention. The bending furnace shown in fig. 1 includes a top array of successive heating sections 2 and a bottom array of successive cooling sections 4. The arrows indicate the traveling path of glass sheets along a top conveyor track 7 and a bottom conveyor track 8. The first heating sections 2 are so-called preheating sections, followed by the actual heating sections and then by one or two bending sections. At least the preheating sections 2 along with their cooling sections 4 underneath consist of section slices 1 as shown in fig. 2. The glass sheets are placed on top of bending moulds 6 supported by carrier wagons 5 shown in fig. 3. The rails 5a of bending moulds 5 are supported upon the top track rollers 7a and the bottom track rollers 8a respectively. The successive wagons 5 are advanced on the top conveyor track 7 from one heating section 2 to the next. The same way, wagons 5 are advanced on the bottom conveyor track 8 from one cooling section 4 to the next. The transfer can be effected the same way as disclosed in US Patent 4 497 645. The heat transfer between successive sections 4 and 2 is intensified by means of an arrangement described hereinbelow. As shown in figs. 2 and 3, the ceiling and floor of heating section 2 as well as those of cooling section 4 are fitted with blast air supply boxes 13, 15, 16, provided with blast orifices 14, 17 which are distributed substantially over the surface area of the sections. Both side walls of cooling sections 4 are fitted with fans 11 whose suction inlets 10 open into the cooling section. The pressure sides of fans 11 are connected by means of air passages 12 to said supply boxes 13, 15, 16. The fans 10 are used for the continuous suction of air out of cooling section 4, whereby a bent hot glass sheet HG delivers heat to this air upon cooling. The blast orifices 14, 17 of supply boxes 13, 15, 16 serve to discharge air as substantially vertical jets to the top and bottom surface of a glass sheet CG as well as to the top and bottom surface of a glass sheet HG. The air coming into section 2 finds its way back into section 4 through the gaps between box beams 13. In order to maintain thermal equilibrium, some hot air is discharged from at least one section 2 outside the furnace and, respectively, some cold replacement air is supplied into at least one section 4, the latter being distributed in the lengthwise direction of the furnace from one section 4 to another section 4. Preferably, the cold replacement air is supplied into section 4a and hot air is withdrawn from section 2a (fig. 1). The above-described heat transfer system is typically effected e.g. in the first three heating sections 2 (depending on the furnace capacity) and, correspondingly, in as many last cooling sections 4. The end walls 18 of wagons 5 provide partitions between successive sections 2, 2 or 4, 4 whenever the wagons 5 are stopped inside the sections. At the junctions between successive heating sections 2 there is provided a resilient sealing 19 which comes in contact with end walls 18 of the wagons and which is e.g. a brush made of artificial fibers/hair and which provides a barrier for air flows between successive sections. This makes it easier to maintain the temperature differences between successive sections 2. On the other hand, the temperature differences between superimposed sections should be equalized as effectively as possible. Fig. 3 illustrates the flat rails 5a running alongside wagons 5 and carrying said wagons 5 so as to rest them upon conveyor rollers 7a. On the bottom track 8, the advancing direction of wagons 5 is from hot to cold. Thus, the hot rails 5a deliver heat at their bottom surfaces to rollers 8a and take up radiation heat at their top surfaces from hot glass sheet HG and its mould 6. This results in the deflection of rail 5a, as shown in fig. 4. Rail 5a retains its deflected condition even after the wagon has advanced onto top track 7 for bending of another glass sheet. The deflected rail 5a results in a shaking or "jolting" movement of the wagon which is why especially rather large glasses are easily broken even before reaching a bending section 3 (fig. 1) on the top track. As shown in figs. 3 and 5, the air passages 12 alongside a cooling section 4 are provided with drilled holes 20 for blasting cooling air to the top surface of rails 5a. The cooling air jets equalize effectively the resulting temperature differences and rail 5a remains straight. The necessary size for blasting holes 20 can be experimentally determined. If desired, the holes 20 can also be made adjustable. The blasting holes 20 can be made in one or a plurality of successive cooling sections 4.

Claims: A method for preventing the deflection of the bearing rail (5a) of a mould wagon (5) in a glass sheet bending furnace including a top array of successive heating sections (2) and a bottom array of successive cooling sections (4) and in which the mould wagon is carried along a conveyor track (7,8) comprising rollers (7a,8a) for resting said bearing rails (5a) thereupon, by blasting cooling air to the top surfaces of the bearing rails (5a) of said mould wagons (5) in at least one cooling section (4). A method as set forth in claim 1, in which the cooling air is sucked by means of a fan (11) from said at least one cooling section (4) and passed through an array of air passages (12) on the one hand to said blasting openings (20) above the conveyor rollers (8a) of said at least one cooling section (4) and on the other hand to air supply boxes (13,15,16), made in said at least one cooling section (4) and the overlaying heating section (2) and provided with blasting orifices (eg. 14,17), said boxes being located above and below glass sheets (HG, CG) to be cooled and heated, respectively, in a particular section. Glass sheet bending furnace including a top array of successive heating sections (2) and a bottom array of successive cooling sections (4) and in which a mould wagon (5) provided with bearing rails (5a) is carried through said furnace along a conveyor track (7,8) comprising rollers (7a, 8a) for resting said bearing rails (5a) thereupon, the furnace also comprising an air passage (12) above the rollers (8a) of at least one cooling section (4), which air passage is provided with blasting openings (20) for blasting cooling air to the top surfaces of said bearing rails (5a) and is connected to a source of pressurised air. Apparatus as set forth in claim 3, in which said air passage (12) is provided with a fan (11) whose suction inlet (10) opens into said at least one cooling section (4). Apparatus as set forth in claim 4, in which said air passage (12) is in communication with air supply boxes (13,15,16) which are located on the ceiling and floor of said at least one cooling section (4) and the overlaying heating section (2).

Inventors: PELTONEN, ESKO JUHANI
Applicants: TAMGLASS ENGINEERING OY
Application year: 1989
Main classification: C03B25
IPC codes: C03B23, C03B25, C03B29, C03B35