Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR PRODUCING CERAMIC FRIT-COATED GLASS
This application is based on, and claims priority to, United States
provisional
application number 60/978,437, having a filing date of October 7, 2007, and
entitled Method and
Apparatus for Producing Ceramic Frit-Coated Glass.
BACKGROUND OF THE INVENTION
The current manufacturing process for producing ceramic frit-coated glass
includes first scoring or cutting flat glass to the customer's prescribed
dimensions, applying
ceramic frit in a reverse direction of movement, heat processing, and
delivering the product to
the customer or passing it through additional value added processes. The
process generally
spans three days to several weeks from the customer request to product
delivery. Existing
technology has not allowed for coating of flat glass stock sheet sizes with
ceramic frit for
shipment to offsite fabrication facilities where they would subsequently be
cut to smaller
customer specific dimensions for immediate heat treatment processing.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a novel
method of
producing ceramic frit-coated glass in a shortened time frame. The invention
discloses a method
of producing ceramic frit-coated glass in stock sheets thereby allowing the
manufacturer to hold
such in its inventory for quick final processing. Further, it is an objective
of this invention to
provide novel methods of scoring (cutting) sheets, or lites, of ceramic frit-
coated glass to a
predetermined size as required by the consumer. In certain embodiments, the
methods of the
invention greatly reduce the lead time in producing ceramic frit-coated glass.
Some
embodiments of the present invention reduce the customer lead time to one day
or less.
Furthermore, some embodiments of the present invention can easily allow cut
size product
specific to a customer's requested dimensions.
In one illustrative embodiment of the invention, stock sheets of ceramic frit-
coated glass are created by using a rotating roller or a rubber drum. The
roller or rubber drum
picks up liquid ceramic frit from a reservoir and deposits it onto a lite of
glass that is passing
underneath the roller. In contrast to the prior art, the roller deposits the
liquid ceramic frit in a
forward direction of movement. In another illustrative embodiment, a curtain
coater is used to
apply the liquid ceramic frit onto the plate of glass. Again, the liquid
ceramic frit is applied in a
forward direction of movement in contrast to the prior art. Adjusting the
height of the roller or
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the speed at which the lite of glass moves underneath the curtain coater will
allow the operator to
control the thickness of the ceramic frit coating. The coated glass is then
heat treated to the
desired cure and cooled.
In certain embodiments, the ceramic frit-coated glass is scored (cut) to a
customer
specified size prior to final heat treating. In certain embodiments, the
ceramic frit coating is
eliminated using a ceramic frit removal wheel, and the glass substrate is
scored with
conventional glass scoring wheel. In a further embodiment, ceramic frit having
a green strength
of at least a pencil hardness of HB is used to make the stock sheet glass, and
the coated glass is
laid frit side down and scored into custom sizes.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a glass cutting device with an edge deletion motorized device and
a
stock sheet of glass with ceramic frit being removed according to an
illustrative embodiment of
the invention.
Fig. 2 shows a ceramic frit removal wheel with modified periphery according to
an illustrative embodiment of the invention.
Fig. 3 shows a ceramic Mt removal wheel mounted on an edge deletion
motorized device according to an illustrative embodiment of the invention.
Fig. 4 shows a side view of a conventional glass cutting wheel mounted on a
glass cutting device with a sheet of ceramic frit-coated glass being scored
for cutting according
to an illustrative embodiment of the invention.
Fig. 5 shows a sheet of glass with the ceramic frit removed and a void area on
the
lite of glass according to an illustrative embodiment of the invention
Fig. 6 shows a lite of glass cut from the stoce lite with ceramic frit removed
along
the outer edges according to an illustrative embodiment of the invention.
Fig. 7 shows a uncoated upper surface of a sheet of ceramic frit-coated glass
being scored according to an illustrative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In certain embodiments, the method of this invention allows for more efficient
production of ceramic frit-coated glass. Unlike traditional methods where the
glass is made to
the dimension specified by the customer, the inventive method contemplates
making ceramic
frit-coated stock sheets of glass that can be cured to green strength to
either be packaged and
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stored in inventory or to be shipped out to another facility in stoces to be
heat treated at a later
point. When required, the stock sheets will be processed to the cut size
required by the
customer. This stock-sheet method allows a supplier to have an inventory of
ceramic frit-coated
glass stock sheets that can be immediately scored to the customers' specified
sizes, heat
processed to bond the ceramic frit-coating to the glass, and delivered to the
customer. The stock-
sheet method reduces the customer lead-time from days to within a single day.
Additionally,
this process can efficiently provide a product of a specific cut size or to
customer specified
dimensions.
Through embodiments of the invention, full stock sheet, such as sheets ranging
from about 12" x 24" to 100" x 144", can be created or can be formed or cut to
pre-determined
sizes.
In one illustrative embodiment of the invention, a rotating roller or rubber
drum is
positioned perpendicular to the axis of a glass-transferring conveyor. The
rotating roller or
rubber drum picks up liquid ceramic frit from a reservoir during its rotation.
As a pane of glass
passes under a roller coater on the conveyor line, the roller deposits the
liquid ceramic frit onto
the glass surface. The coated glass is then conveyed through an electrically
heated drying section
(vented) or is dried by any other suitable method. Thereafter, the coated
glass is conveyed
through a "cool down" section. The liquid ceramic frit is prepared by any
conventional method
well-known to those skilled in the art. In one embodiment, the ceramic frit is
ground into
powder, which is suspended in an oil-based or water soluble emulsion.
In an illustrative embodiment of the invention, the rotating roller is a
rubber roller
having a durometer within a range of from 50 to 70 durometer. Additional
illustrative durometer
ranges include from 40 to 80 durometer and from 55 to 65 durometer.
In another illustrative embodiment of the invention, a curtain coater
comprising
an upper trough is filled with liquid ceramic frit. The upper trough has an
opening or a series of
openings along the bottom to allow the liquid ceramic frit to flow out in a
"waterfall." A lower
collection trough is provided to collect excess liquid ceramic frit to be
returned to the upper
trough. As a pane of glass passes under the "waterfall" of liquid ceramic
frit, a layer of frit is
applied to the upper surface of the pane of glass. The coated glass is then
conveyed through an
electrically heated drying section (vented) or is dried by any other suitable
method. Thereafter,
the coated glass is conveyed through a "cool down" section.
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The thickness, density, and viscosity of the ceramic frit material is
controlled
through the "roller coater" roll height adjustments and conveyor transfer
speeds or controlled by
the line speed and material density being applied through the "curtain
coater". The ceramic frit-
coated glass is heat cured to green strength to achieve durability so that the
frit and glass can be
handled. The cooling process employs conventional methods to cool down the
coated glass,
including ample mass air cooling. The coated glass is control cooled to room
or ambient
temperature, or to an acceptable glass handling gradient.
Once formed, the ceramic frit-coated stock sheets may be packaged as a stoce
and
transported to another location for final processing, stored as inventory, or
immediately
processed to the customer-specified cut size. To the best of the inventor's
knowledge there is
currently no accurate means of scoring/cutting glass with cured/green strength
ceramic frit
material applied to glass for purposes of reducing the overall larger/stoce
dimensional size to a
smaller dimensional size. The invention contemplates novel methods of
scoring/cutting the
ceramic frit-coated glass to a smaller size as required by the customer. FIGS.
1-7 depict
illustrative embodiments of the inventive method and products. The methods
allow high volume
use of various sizes of stock sheets of ceramic frit-coated glass to be cut to
small
sizes/dimensions according to customer order for immediate heat processing and
delivery.
In one embodiment, a ceramic frit removal wheel 201 is used to remove the frit
coating. A diamond angled cutting or scoring wheel is used to score or cut the
glass. In this
embodiment, a flat glass cutting system, for example a cutting system equipped
with an edge
deletion motorized device, is used. In a preferred embodiment, the cutting
device is a computer
numerical control device. Fig. 1 shows a flat glass cutting system 101 with
the stock sheet of
coated glass 102. The edge deletion motorized device 103 removes the coated
ceramic frit from
the glass surface. Where the coating has been removed, a shallow channel 104
through ceramic
frit revealing the glass surface is formed.
When the edge deletion device is fitted with a ceramic frit deletion wheel 201
that
is capable of removing the appropriate composition with a certain green
strength, the periphery
of which has been modified in accordance with this invention 202, the deletion
wheel can
eliminate the ceramic frit coating that has been cured to green strength on
the surface of the
coated glass along an approximate 1/8" band width. The band width size is
variable and may be
narrower or wider than 1/8". Illustrative wheel dimensions include: 200mm x
20mm x 76.2mm
(diameter x thickness x arbor) with a modified periphery 202 producing a 5mm
outer diameter
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flat. After the removal of the green strength ceramic frit from the glass, the
glass can be scored
within the removed ceramic frit surface area using a standard conventional
glass cutting wheel or
any glass scoring device.
As shown in the Figs 3 and 4, a wheel 301 is used to remove the ceramic frit
401
from the glass 402 and then a standard diamond cutting wheel 403 is used to
score the glass so it
can be sized to a customer's specifications. The score line 404 is made in the
area where the
ceramic frit has been removed. The modified periphery includes a cut side
shoulder of
approximately 1/2 inch. Other dimensions are within the spirit and scope of
the invention
provided they allow for the desired cutting of the coated glass. In an
illustrative embodiment of
the invention, the ceramic frit removal wheel is a resinoid bonded aluminum
oxide abrasive grit
(ALO) grinding wheel with a modified periphery. Edgeworks Co. markets such a
wheel, in
unmodified form, under part number 131-8203-150. Other wheel materials or a
combination of
wheel materials can be used, provided they can remove the ceramic frit where
desired and score
the glass as needed.
Fig. 5 shows a partial sheet of glass 501 with ceramic frit 502 removed. A
void
area 503 is shown on the sheet of glass. The void area allows the cutting head
sensor of the edge
deletion device to detect the glass surface to align the edge trip and to
center the computer
numerical control (CNC) cutting device. Fig. 6 shows a final cut size sheet of
coated glass 601
with a border where the frit coating was removed 602 while the remainder of
the plate is coated
with ceramic frit 603.
As illustrated in Fig. 7, in another embodiment of the invention, the ceramic
frit-
coated glass is positioned frit-surface 703 down on a conveyor belt 703 or air
floatation table of
the glass cutting device. The opposing uncoated glass surface 702 is scored
using a diamond
angled cutting or scoring wheel 701. The score line 704 is made directly on
the uncoated surface
702. This method requires the use of fit that is sufficiently durable or which
has sufficient
green strength to withstand being placed against such a conveyor belt or air
floatation table. The
green strength of the ceramic frit material must be sufficient to withstand a
pencil hardness test.
Pencil hardness varies from 9H (the hardest) to 6B (the softest). The pencil
test is modeled after
the ASTM D 3363 test. In this test, the tester holds the pencil with the point
positioned away
from the tester. The pencil is positioned firmly against the ceramic frit
coating at about a 45
angle. The tester pushes the pencil away from himself in a short stroke, for
example a stroke of
0.256 inches or 6.5 mm. The tester begins the process with the hardest pencil
(9H) and
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continued down the scale of hardness to either of two end points: either
pencil hardness, i.e.
where the pencil does not cut into or gouge the ceramic frit coating; or
scratch hardness, where
the pencil scratches the coating. Ceramic fit usable for the methods of this
invention should be
at a pencil hardness of at least HB. Any ceramic frit material exhibiting
hardness at this range
would be suitable to be placed frit-surface down to be scored and cut from the
uncoated surface.
Such ceramic frit material is also available commercially; for e.g., through
Glass Coatings and
Concepts. Conventional, known glass cutting machines can be used in this
process.
Those skilled in the art will appreciate that the methods of this invention is
applicable to a wide variety of glass, including uncoated glass and
pyrolytically coated solar-
control reflective glass. Suitable frit materials include bismuth borosilicate
glasses and zinc
borosilicate glasses.
While the invention has been described by illustrative embodiments, additional
advantages and modifications will occur to those skilled in the art.
Therefore, the invention in its
broader aspects is not limited to specific details shown and described herein.
Modifications, for
example, to the wheel and roller dimensions/specifications may be made without
departing from
the spirit and scope of the invention. Accordingly, it is intended that the
invention not be limited
to the specific illustrative embodiments, but be interpreted within the full
spirit and scope of the
described embodiments and their equivalents.
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