Glass manufacturing – Processes – Reshaping or surface deformation of glass preform
Patent
1992-12-31
1994-03-08
Woodard, Joye L.
Glass manufacturing
Processes
Reshaping or surface deformation of glass preform
65 254, 65104, 651822, 65268, 65273, C03B 23025
Patent
active
052923550
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method for bending a glass sheet, said method comprising the following steps: temperature,
The invention relates also to an apparatus for bending a glass sheet, said apparatus including: temperature sufficiently high for bending a glass sheet and
The invention can be applied in association with various types of furnace plants. In one main type, a glass sheet supported on a ring mould is carried from on furnace section into another by increasing temperature in successive furnace sections. In the final section, a sufficiently high temperature is reached for bending. In another main type, a glass sheet is heated in a furnace fitted with rollers and is then lifted from the rollers e.g. by means of an overhead vacuum pick-up and lowered on top of a ring mould brought thereunder, whereafter the bending can be effected upon the ring mould in the furnace or in a separate bending section downstream of the furnace.
Regardless of a type furnace employed, a problem with bending effected on ring moulds has been the control of temperature and bending in various sections of a glass sheet. If the overall temperature of a glass sheet is increased to a sufficient level in order to effect the bending of difficult-to-bend margianl sections, the central section of a glass sheet is also softened to the extent that it bends and sags too far downwards.
It is prior known to overcome this problem by applying a more powerful heating effect to the marginal sections of a glass sheet for the sufficient bending thereof, but the central area of a glass sheet is left to be substantially colder (e.g. 580.degree. C.) for avoiding its excessive bending and sagging downwards. However, a resulting drawback in this method is that it is not possible to produce properly tempered glass since for a proper tempering effect the entire area of a glass sheet should be heated to over 600.degree. C., preferably to the temperature of appr. 610.degree.-620.degree. C.
An object of the invention is to provide a method and apparatus for bending a glass sheet on a ring mould substantially gravitationally while simultaneously heating the entire area of a glass sheet to a sufficient temperature for bending and, if necessary, also for tempering.
A particular object of the invention is to provide a method and apparatus for controlling and regulating the gravitational bending of the entire area of a glass sheet in a manner independent of the normal interrelation between gravity and temperature. An additional feature of the invention is a possibility of focusing the heating effect on the areas critical in terms of bending.
These and other objects of the invention to be described in more detail hereinafter can be achieved on the basis of the characterizing features set forth in the annexed claims.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
A few embodiments of the invention will be described in more detail with reference made to the accompanying drawings, in which
FIG. 1 is a schematic and axonometric and partially cutout view of an apparatus for carrying out a method of the invention.
FIG. 2 shows a bent glass sheet.
FIGS. 3A-C illustrate schematically in a side view the bending of a glass sheet by means of a method and apparatus of the invention at various stages of bending.
FIG. 4 is a schematic side view of a mould assembly fitted with means for facilitating the bending of a glass sheet mechanically.
FIG. 5 shows a schematic vertical section of an apparatus for carrying a bent glass sheet into a tempering section after heating said glass sheet to a tempering temperature.
FIG. 6 shows a schematic vertical section of a bending furnace, wherein an intensified heating effect is focused on the marginal sections of a glass sheet by using the same blast air that is used to create a glass-sheet supporting pressure difference.
FIG. 7 shows a schematic section of yet another mould assembly, wherein holes or slots 11 in a mould are utilized for controlling an air flow created by a pressure differen
REFERENCES:
patent: 3431095 (1969-03-01), Ross
patent: 3526489 (1970-09-01), McPhail
patent: 4119424 (1978-10-01), Comperatore
patent: 4300935 (1981-11-01), Seymour
patent: 4356018 (1982-10-01), McMaster
patent: 4755204 (1988-07-01), Boardman et al.
patent: 4986842 (1991-01-01), Peltonen
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