Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/02—Re-forming glass sheets
  • C03B23/023—Re-forming glass sheets by bending
  • C03B23/025—Re-forming glass sheets by bending by gravity
  • C03B23/027—Re-forming glass sheets by bending by gravity with moulds having at least two upward pivotable mould sections

Definitions

• the invention relates to a method and apparatus , by means of which bending produced by the force of gravity in a glass sheet bending furnace is controlled by restricting the increase of temperature on a required area in the glass sheet.
• the problem has been that due to gravity the glass sheet bends too much, generally in the centre of the sheet before the glass sheet edge areas have even reached the required degree of bending. That is the case especially on bending big size glass sheets with an edge mould.
• That kind of glass sheets are typically bent in a one-chamber or multi-chamber furnace, where heating is carried out with radiation elements above the glass sheet.
• the problem is reduced in connecting radiation elements above the area of strongest bending only.
• the object of this invention is to produce a small-mass cooling surface, which is at least in the bending section and in connection with the bending glass sheet causing differences of temperature into the glass.
• a box type horizontal surface made for instance of two metal sheets and placed under the glass sheet, does not hinder the glass sheet from getting heated.
• the surface can be set in function advantageously only by blasting compressed air at a certain time. When fed air is steered into and out of the box type construction, it does not cause any interference of flow in the furnace. By means of the temperature and quantity of compressed air the surface temperature can be adjusted and thus the effect on the glass sheet. Cooling by the box is used only at the final stage of heating, when harmful bending would begin, at a temperature over 550°C. Thus real heating phase can be done quickly.
• the most advantageous embodiment is a box underneath the glass sheet, whereat much surface is achieved with as little mass as possible.
• a box can be fixed in the edge mould, the edge mould chassis or the bending section of the furnace. It can be also built in the bending section of a series furnace, into which the edge moulds move, for instance, in turns along a track and whereby mould and glass sheet can stop at it and move across it.
• Fig. 1 is a side view of a glass sheet in an edge mould.
• Fig. 2 is a diagonal view of a bent glass sheet in an edge mould in the furnace.
• Figure 1 shows a hinged edge mould on which glass sheet l is installed. Holders 4 of the mould edges are by means of joints 5 hinged to be turning in a way known as such. Due to weights 6 the glass sheet rests at first on several points till the glass sheet bending and proper design of the weights 6 finally turn holders 4 up to their overrunning stops, whereat the edges of the glass sheet middle portion sink onto the mould holders 8.
• a box according to the invention is placed in the mould so that it is under the glass sheet about in the glass sheet middle portion.
• Figure 2 is a diagonal representation of the mould in a 1- chamber furnace, which is a typical bending furnace of large windshields.
• the glass has got bent to its final shape according to the edge mould.
• both glass sheet edges there is a small bending radius due to which heat must have been directed at the most to these glass edge portions, so that bending has been possible by the force of gravity.
• the glass sheet gets heated excessively also in its middle portion which is still without support.
• a cooled box 3 as per this invention excessive bending of the glass sheet from its middle portion has been prevented in keeping the glass temperature lower. Then the glass sheet stiffness in its middle portion has been retained and there has been no excessive sagging. Cooling compressed air has been conveyed into box 3 when the temperature of glass middle portion has exceeded 550°C.
• connection 7 For conveyance of compressed air there are connections 7 in the box.
• the compressed air is steered off the box along a tube to the outside of the furnace in order to avoid disturbing flows in the furnace.
• the box causes a cooling effect and heat radiation that is shifted over from the glass to the box and, to a low degree, as convection between these two.
• the distance of box 3 can be adjusted with respect to the glass sheet, whereat a certain adjustment of capacity is achieved. It is also possible to adjust the compressed air quantity or the temperature and achieve different cooling effects on the glass. If necessary, with the shape and size of the box different cooling effects are produced, likewise in using several boxes disposed in required spots, if necessary.
• a box as per the invention can be used in a series furnace. It can be installed firmly into the bending section, whereat the mould and glass sheet get along a track to its upper side or, transferably, into the bending section, whereat it is moved, when needed, to the glass lower side by a mechanism.
• a box as per the invention can also be fixed to an edge mould moving along the track in a series furnace, where in the bending section compressed air is connected to it. It can also be in the mould chassis and from there be adjusted into different levels.
• a plate can be used with a heat conductive coil underneath, through which the compressed air passes.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=8556677

Family Applications (1)

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• 1997
  • 1997-03-04 AU AU20969/97A patent/AU725900B2/en not_active Ceased
  • 1997-03-04 EP EP97906197A patent/EP0970023A1/de not_active Withdrawn
  • 1997-03-04 WO PCT/FI1997/000141 patent/WO1998039261A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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