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

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 frit 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

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.

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

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 frit 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

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 frit 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.