HEAT TRANSFER METHOD IN GLASS SHEET BENDING OVEN AND A BENDING OVEN

Abstract: A heat transfer method in a glass bending furnace, which has a top array of successive heating sections (2) and under it a bottom array of successive cooling sections (3), and in which method glass sheets are conveyed on bending moulds in mould carrying wagons on the top conveyor track from one section (2) to the next and on the bottom conveyor track from one section (3) to the next and the air heated by the bent hot glasses is sucked from cooling section (3) and blasted to the not-bent colder glasses in the heating sections (2). In order to intensify heat transfer, air sucked from the cooling section (3) is blasted as such, against the travel direction of carrying mould wagons, to a top section (2) next after the section upon cooling section (3), from which air is sucked, or to the adjacent top section of the said section.

Description: HEAT TRANSFER METHOD IN GLASS SHEET BENDING OVEN AND A BENDING OVEN The invention relates to a heat transfer method and an applicable glass bending furnace as per the introductory chapter of patent claim 1. Previously known from the Finnish patent 68390 is intensification of heat transfer in a double-decker glass bending furnace, where heat transfer is effected vertically between sections one on top of another by means of radiation and gravitational convection. The bottom of the mould carrier wagons is open enabling radiation and convection from the hot glass sheet on the bottom track section to the colder glass sheet on the top track section. Further, a method to intensify heat transfer is known from patent FI-81331, where in comparison with the above solution fans are installed to increase heat transfer from the bottom track section to the top track section. Not even the last mentioned solution has turned out effective, enough, because it works effectively only for a few seconds when the mould carrier wagons have reached a new position. There is then during this short moment enough difference of temperature for significant heat transfer. However, since the mould carrying wagons always stay for a time span of 1.5 - 3 minutes in a section before they are shifted over to the next section, the use of fans is quite useless. A method and bending furnace as per this invention offer a significant improvement of heat transfer and significantly longer lasting heat transfer per each cycle. These advantages and improvements are achieved by the inventive characteristics presented in the enclosed patent claims. By means of the method and bending furnace of this invention the transfer of heat from the bottom track section to the top track section and the glass therein is instensified to a considerable extent. A substantial portion of intensification is based on the increased available temperature difference between the bottom track glass and the top track glass, to which air is blasted from the bottom track section. In the following the invention is disclosed with reference to the enclosed drawing, where Fig. 1 shows a bending furnace schematically in a side view. Fig. 2 shows a diagonal view of successive bending furnace sections with bottom track and top track. The arrows in the schematic view of figure 1 show the travel direction of mould carrying wagons and the glass sheets upon them in furnace 1. For instance, on the top track there are six sections 2, where the glass sheet is heated, and a section, where bending takes place and where the mould carrying wagon is lowered onto the bottom track. There are, for instance, on the bottom track six cooling sections 3. In the figure two mould carrying wagons 13 are illustrated by way of example. Figure 2 is a view of some sections 6 and 7, which are individually built successive segments joined together to form a successive furnace. There is a floor 4 between the top track and the bottom track. On both sides of sections 6,7 there are wheels 11 partly embedded in insulation 10 and fastened by bearings to roll for conveyance of the mould carrying wagons 13. At least as one wagon end, the mould carrying wagons 13 have an insulated partition wall dividing the top track lengthwise into sections 2 and the bottom track into sections 3. Most advantageously, the wagon has an insulated bottom, whereby the illustrated floor is not needed to cover the whole furnace length. If wagon 13 is without bottom, a floor 14 is needed. In the figure a fan 9 assembly is shown where, as per prior art, air from the bottom section 3 is not blasted to the top section 2 upon it but to its adjacent section against the travel direction of the carrier wagons. From top section 2, into which air is blasted, air is discharged downward along channel 12 either back to the same section from where it was sucked or to the section under it or its adjacent section 3. Thanks to this solution greater transfer of heat from the glass on the bottom track to the glass on the top track glass is achieved, since the temperature difference between sections is even 100 C higher than the difference of temperature between face-to-face sections. If blasting is channelled to the top track so slantly that one section is passed, an even greater difference of temperature is achieved. It is possible to steer the blasting in full from the top track to one or several random sections, but it is also possible to discharge a portion of the blast out from the furnace completely.

Claims: PATENT CLAIMS 1. A heat transfer method in a glass sheet bending furnace, which has a top array of successive heating sections (2) and under it a bottom array of successive cooling sections (3), and in which method glass sheets are conveyed on bending moulds in mould carrying wagons (13) on the top conveyor track from one section (2) to the next and on the bottom conveyor track from one section (3) to the next and the air heated by the bent hot glasses is sucked from cooling section (3) and blasted to the not-bent colder glasses in heating sections (2), characterized in that in order to intensify heat transfer, air sucked from cooling section (3) is blasted as such, against the travel direction of mould carrying wagons (13), to a top section (2) next after the section upon the cooling section (3) from which air is sucked, or to the adjacent top section of the said section. 2. A method according to patent claim 1 characterized in that the substantially greatest portion of air blasted into the top track section (2) is returned to a section (3) under the top section on the bottom track or to its adjacent section 3. A glass sheet bending furnace for carrying out the method set forth in patent claim 1 characterized in that between the top track sections (2) and bottom track sections (3) there are air channels (8) with a fan (9) so arranged that the air sucked from the bottom track section (3) can be blasted, against the travel direction of carrying mould wagons (13), to a top track section (2) next after the section upon said section (3) or its adjacent section on the top track and that there is from section (2) a return air channel system (12) into section (3) under it or its adjacent section on the bottom track. 4. A bending furnace according to patent claim 3 characterized in that the successive sections are separated by the back wall of the carrying mould wagons (13)

Inventors: KARISOLA JUHA, VAEHAE-ANTILA KARI, KARISOLA, JUHA, VAEHAE-ANTILA, KARI
Applicants: GLASSROBOTS OY, KARISOLA JUHA, VAEHAE ANTILA KARI, KARISOLA, JUHA, VAEHAE-ANTILA, KARI
Application year: 1996
Main classification: C03B23
IPC codes: C03B23, C03B27, C03B29, C03B35