AU664487B2 - Method and apparatus for producing printed glass sheet - Google Patents

Description

664487

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): CERAMIC COATINGS RESEARCH PTY LTD A.C.N. 050 236 185 Invention Title: METHOD AND APPARATUS FOR PRODUCING PRINTED GLASS SHEET The following statement is a full description of this invention, including the best method of performing it known to me/us: METHOD AND APPARATUS FOR PRODUCING PRINTED GLASS SHEET This invention relates to a method and apparatus for printing glass sheet and, in particular, to a method and apparatus for screen printing glass sheet which is kilnfired.

Glass sheet is printed with a variety of different patterns both for aesthetic purposes and also to provide a degree a safety so that the glass can be clearly seen. The glass sheet may be conventional clear glass sheet or tinted glass sheet which is produced by the well known float process.

Conventional processes for providing a printed glass sheet suffer from difficulties in handling the glass sheet and also kiln-.firing the glass sheet in ordar to cure the printed pattern. The major disadvantage for conventional processes are due to the temperatures which are used in the kiln and the sheer weight of the glass sheets which create sheet distortion or bending of the glass sheets.

Furthermore, glass sheets can be damaged by vibration caused by the movement of air in the kiln. For this reason conventional methods have been restricted to the use of a minimum glass gauge of 4 millimetres and also require the glass format size to be restricted.

0 The object of this invention is to provide a method and apparatus for producing a printed glass cheet in which a minimum gauge of 3 millimetres can be used and also which provides for a larger range of glass format size than has i been possible in the past.

The invention may be said to reside in a method for producing a printed glass sheet including: 35 printing the glass sheet with a printing material 00 which will form a substantially permanent pattern on the glass sheet and which cures at a lower temperature than the temperature at which the glass sheet becomes plastic or supple; supporting the glass sheet substantially vertically in a heating device; and heating the glass sheet in the heating device to a temperature less than the temperature at which the glass sheet become plastic or supple and at least to the temperature at which the printing medium will fire to produce the substantially permanent pattern on the glass sheet.

The invention may also be said to reside in an apparatus for producing a printed glass sheet made from a glass sheet which has been printed with a printing medium to form a substantially permanent pattern on the glass sheet, including: a heating device having heating means for heating the device to a temperature which is less than the temperature at which the glass sheet becomes plastic or supple and at least to the temperature at which the printing medium will fire to produce the substantially permanent pattern on the glass sheet; and a glass support device having: a plurality of billets arranged in side by side relationship, each billet including a plurality of slots o. each for receiving a bottom edge of a sheet of glass; a plurality of removable upright support members o :at one end of each billet; :i a plurality of second upright support members at the other end of each billet; and a plurality of glass location members each removably connectable between a respective removable upright support member and a second upright support member, the glass location members including a locater member 35 having a plurality of slots for receiving an upper edge of each sheet of glass, the glass locating member being adjustable in a substantially horizontal direction so that the slots in the glass locating member can be substantially vertically aligned above the slots in the billets so that the glass sheets can be substantially vertically retained in the glass support device.

The use of a printing medium which has a firing temperature below the temperature at which the glass sheet become plastic or supple overcomes problems with distortion or bending of the glass sheet during firing of the printing medium. The method and apparatus of the invention therefore enables glass sheet of minimum gauge of 3 millimetres and format size larger than conventional printed glass sheets to be printed and fired without the glass sheet exhibiting any substantial sheet distortion or

C.

a o C o 4 bending.

In one form of the invention the glass sheet is supported in a vertical plane and is heated in a stationery kiln.

However the invention could be practised in a continuous process where the glass sheet is printed and passed through a furnace to heat the glass sheet. The furnace could be a compartmentised Annealing Lehr wherein the compartments are heated to different temperatures to raise and then lower the temperature of the glass sheet as the glass sheet moves through the Lehr.

Preferably the printing medium comprises a ceramic enamel.

Conveptional ceramic enamels which are used for printing glass sheet have a firing range which is above the temperature at which glass sheet becomes plastic or supple.

We have jointly developed a ceramic enamel which has a firing range which is less than the temperature at which the glass sheet becomes plastic or supple and preferably the ceramic enamel used is that supplied by Johnson Matthey Colour (Australia) Pty. Ltd. product code AEG 1289/63/532 which has been specifically formulated to operate at a temperature of 495 0 C. If desirable the ceramic enamels may be viscosity modified to adjust the viscosity of the enamel by mixing the enamel with a base thinner such as pine oil.

S" Mixing the enamel with up to 2% pine oil has been found sufficient to snitably modify the viscosity of the enamel.

Preferably the kiln includes an electric heating means for heating the kiln and at least one fan for circulating heated air within the kiln.

Preferably the at least one fan circulates a volume of 8,911 cubic meters per hour of air within the kiln.

Preferably the kiln includes a vent for venting off biproducts during low temperature firing.

Preferably the glass support device includes a hearth upon which the glass support device is located, said hearth including casters so that the hearth can be rolled into and out of the kiln.

Preferably the kiln includes tracks upon which the hearth can be moved so that the hearth can be rolled into and out of the kiln.

The invention may also be said to reside in a glass support *oo* device including: at least one billet including a plurality of slots each for receiving a bottom edge of a sheet of glass; at least one removable upright support member at one end of the at least one billet; at least one second upright support member at the other end of the at least one billet; and at least one glass location member removably connectable between the at least one removable upright support member and the at least one second upright support member, the glass location member including a locater member having a plurality of slots for receiving an upper edge of each sheet of glass, the glass locating member being adjustable in a substantially horizontal dijrection so that the slots in the glass locating member can be substantially vertically aligned above the slot in the billet so that the glass sheets can be substantially "vertically retained in the glass support device.

o o Preferably there is a plurality of spaced apart billets each including a plurality of slots wherein the plurality of slots in the billets are aligned to form semicontinuous grooves for receiving the bottom edge of each sheet of glass, a plurality of removable uprights, a plurality of •coo 25 second upright support members and a plurality of glass location members.

In a further aspect of the invention there is provided a laminated glass product comprising a first glass sheet having a printed pattern applied thereto, a second glass sheet laminated to the first glass sheet with a interlayer between the first and second glass sheets, said pattern being on an internal surface of the laminated product so that the pattern is encapsulated in the laminated product.

A preferred embodiment of the invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side view of a kiln and glass support device according to one embodiment of the invention; Figure 2 is a cross sectional view through a kiln with the glass support device arranged within the kiln; Figure 3 is a detailed view of the glass support device; Figure 4 is a view along the line IV-IV of figure 3; Figure 5 is a plan view of a glass locating member; Figure 6 is a view along the line VI-VI of figure 3; and "Figure 7 is a diagram showing firing temperatures and time periods for firing printed glass sheet.

With reference to figure 1, the apparatus embodying the invention includes a kiln 10 which is a generally cuboid housing having a front opening 12. A flue 14 extends from the kiln 10 and has a damper 16 for selectively closing the flue 14. A pair of fans 18 are provided for circulating air within the kiln.

A kiln hearth 20 is provided with casters 22 which roll on tracks 24 (only one shown) which extend into the kiln The hearth 20 supports a glass support device 40 which is arranged to support a plurality of glass sheets 50 in a substantially vertical plane.

The glass support device 40 comprises a plurality of 8 billets 42 which are fixed to the hearth 20. As shown in figure 4 the billets 42 preferably comprise I beam support members 47 and beams 49 which include slots 43 which extend transversely across the beams 49. A plurality of removable uprights 44 extend upwardly from the hearth As is best shown in figure 3 the uprights 44 are received in brackets 46 so that they can be removed from the brackets to provide access to the billets 42. As is best shown in figures 2 and 3 the uprights 44 are arranged at one end of the billets 42 and a plurality of second uprights 60 (only one shown in figure 3) are arranged at the other end of the billets 42. Each of the second uprights 60 is aligned with one of the removable uprights 15 44 and the upright 60 comprise an mainframe 62 of the 9*9 hearth 20 which supports an upright member 64 which is connected to the mainframe 62 by connecting rods 66.

As is best shown in figure 6 the removable uprights 44 each comprise a pair of posts 44' and 44'' which are spaced apart a small distance from one another. A limiting plate 48 is arranged between the posts 44' and 44'' to provide an adjustment limit for a locating member 70. The upright member 64 also comprised of a pair of posts (not shown) which are similar to the posts 44' and 44'' and also S* include a plate (not shown) similar to the plate 48 for limiting the adjustment height of the glass location member As is best shown in figure 3 and figure 5 the glass location member 70 comprises a rod 72 which supports a beam 74. The rod 72 also support6 a pair of guides 76 and 76' which are arranged at the end of the beam 74 and the ends of the rods 72 are screw threaded and provided with nuts 78 and 78'.

Each slot 43 in billets 42 is adapted to receive a bottom edge 51 of a respective glass sheet 50. The beams 74 also include a plurality of slots 75 which are adapted to receive a top edge 53 of the glass sheets Before the glass sheets 50 are arranged in the device the ,)lass sheets are screen printed to provide the desired pattern on the glass sheets. The screen printing process is conventional and therefore will not be described herein in detail other than to say that the glass sheets are prepared by application of rough arris edgework to both faces of the sheets 50 and the print face is determined by a high intensity short wave UV lamp. Due to a chemical reaction between the tin face of float glass and the ceramic enamels it is required to utilise/print the "opposite face to *void discolouration of the print image.

The glass sheet once prepared is then cleaned and dried via a horizontal industrial flat glass washing machine. The screens used for the screen printing are of mild steel construction using 90 to 100 T mono nylon type meshes mechanically stretched onto the metal frame utilising direct emulsion type stencils. Printing technique applied via mechanical one-man screen printing table using offcontact procedure.

The glass sheets 50 are screen printed with the desired pattern using ceramic frost enamel product code AEG 1289/63/532 made by Johnson Matthey Colour (Australia) Pty.

Ltd. and which may be viscosity modified by mixing it with up to 2% of a base thinner such as pine oil. The ceramic enamel operated at a temperature of approximately 4950°C which is below the temperature which the glass sheets become plastic or supple.

In order to arrange the glass sheets in the glass support means 40 the removable uprights 44 are removed from the brackets 46 to thereby gain access to the billets 42. The slots 43 of adjacent billets are aligned with one another so that the slots 43 form a plurality of semicontinuous grooves which are able to receive the bottom edge 51 of the glass sheets 50. The glass sheets 50 are loaded into the billets with a respective glass sheet being arranged in the aligned slots 43 of the billets 42. The removable uprights 44 are then located in place in their brackets 46 and a respective glass location member 70 is arranged between each pair of removable uprights 44 and second uprights The glass location members 70 are located in place by arranging the guides 76 between the post 44' and 44'' of the uprights 44 and between the pair of posts which make up "the uprights 64 so that the location member 70 can slide dow.wardly between the pair of posts and so that the top edges of the glass sheets 50 can be located in the respective slots 75 in the beam 74. The beam 74 may be adjusted in the direction of double headed arrow A to ensure that the slots 75 are vertically aligned above t slots 43 and therefore the glass sheets supported between the slots 75 and 43 are vertically aligned, by rotating the nut 78' so that it abuts the guide 76' and drives the beam 74 to the right in figure 3 until the glass sheets are :vertically aligned.

The billets 42, uprights 44, glass location members 70 and second uprights 64 form a rigid framework in which the glass sheets are securely held in a vertical plane on the kiln hearth 20. The kiln hearth 20 can then be rolled into the kiln As is shown in figure 2 the kiln hearth 20 can include a base 21 which includes a pair of side flanges 23 which are received in grooves 25 of base sections 27 to guide the kiln hearth 20 and to basically complete the floor of the kiln 10 when the hearth is rolled into the kiln.

As is also shown in figure 2, the hearth 20 can include two sets of glass supporting devices labelled 40A and 40B in figure 2. The two supporting devices 40A and 40B being symmetrically arranged around the mainframe 62 of the hearth 20 so that two glass support devices are arranged on the hearth 15 The kiln 12 has insulation 90 which forms the side walls,

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of and rear of the kiln and an insulated door 92 which is S..closed to seal the kiln. The kiln also has internal side walls 94 and upper baffles 96 which form a cavity 99 in the kiln. A pair of electrical heaters 98 extend the length of the kiln and are electrically heated to heat air within'the kiln. The twin fans 18 circulate a volume of air of approximately 8,911 cubic meters per hour through the kiln.

The fans 18 are operated to draw air in the direction of the arrow shown in figure 2 so that air is drawn from internal space 100 into fan 18 and then out of fan into cavity 99 and downwardly in the space between internal walls 94 and the kiln insulation 90. The air then travels through space 102 at the bottom of walls 94 and between the billets 42 to rise upwardly between the glass sheets which are supported in the glass support devices 40A and 403 to thereby heat the glass sheets and cure the printed enamel applied to the glass sheets.

The billets 42 and the beams 74 may be formed from ~11~1~ _1 stainless steels and preferably an insulation member (not shown) is arranged between the top and bottom edges 53 and 51 of the glass sheets and the billets 42 and beams 74.

The insulation may comprise aluminium HT braid insulation or any other suitable insulation for insulating the glass sheets from the stainless steel billets and beams.

Figure 7 shows the preferred heating cycle and time periods for heating within the kiln 10. As best shown in figure 7 the kiln is initially heated up to a temperature of 200 0

C

for a period of one hour then maintained at a temperature of 200°C for 15 minutes. The temperature then rises to 495 0 C over the next 6 hours and is maintained at a temperature of 495 0 C for 45 minutes. The temperature then drops to 465 0 C over the next 35 minutes and is maintained i. at a temperature 465 0 C for the next 15 minutes. The temperature is then dropped to 440 0 C over the next hour and is then dropped to a temperature of 80 0 C over the next 6 hours.

The damper 16 in flue 14 is operated when the temperature in the kiln is below 250 0 C so that biproducts produced be extracted from the kiln. When the kiln is operating at above a temperature of 250 0 C the damper 16 is closed.

*o The kiln 10 is preferably computer controlled to maintain o* :the temperature profile described with reference to figure 6.

Since the glass location members 70 are supported between the posts 44' and 44'' and the corresponding posts of the upright member 64 the members 70 are free to float and therefore glass sheets of any height, within the adjustable height limit of the uprights 44 and 60, can be accommodated in the supporting mechanisms 40. The adjustable height limit extends from the plates 48 up to the top end of the uprights 44 and therefore a large amount of adjustment for a variety of different size glass sheets is provided.

Similarly, the length of the glass sheets can be such that the glass sheets extend all of the way across all of the billets 42 as shown in figure 1 or cross only some of the billets 42 shown in figure 1 thereby also providing a large range of glass sheet sizes which can be accommodated.

In one preferred form of the invention a pair of glass sheets can be arranged in each of the respective slots and 43 by arranging the printed glass sheets in back to back relationship so that the printing on the glass sheets is on the outside of each glass sheet in the pair.

0:0* o :The preferred form of the invention which rigidly supports "the glass sheets in a substantially vertical plane and S"which uses a firing temperature for the ceramic enamel which is below the temperature at which the glass sheets become plastic or supple has been found suitable to produce 9" Sprinted glass sheets which are of thinner gauge, for s e example 3 millimetres, than conventional methods and also has been able to produce glass sheets which are of a .99.

25 variety of different sizes and in particular considerably larger than those made with conventional methods. The volume of air supplied according to the preferred embodiment has also been found to be sufficient to circulate hot air to fire the ceramic enamel which does not provide any substantial buffeting or movement of the glass sheets retained in a glass support mechanism and therefore does not tend to cause any distortion or bending of the glass sheets due to vibration during firing.

i-i 14 Printed glass sheets made according to the preferred embodiment of the invention which can utilise glass sheets of a gauge of 3 millimetres, can be used in further value added processes such as in laminated processes or in other processes for toughening the glass sheets. The ability to print glass sheet of gauge 3 millimetres is of particular importance in lamination because it enables glass sheets of that gauge to be laminated together with the printed surface being an internal laminated surface. Thus, the laminating process encapsulates the decorative screen printed face of the glass internal lamination product thereby providing a fully sealed and protected printed glass product. Conventional methods have not been able to produce printed glass sheets of this type which can be laminated due to unevenness or inappropriate coatings.

^The laminated product can include two sheets of glass at "least one of which has the printed pattern applied to it so that the printed pattern is on an internal surface and the glass sheets are laminated together with a PVB interlayer between the laminated sheets to produce a laminated glass product.

o* C Since modifications within the spirit and scope of the see& 25 invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hzreinabove.

printing medium will fire to produce the substantially permanent pattern on the glass sheet; and a glass support device having: a plurality of billets arranged in side by side relationship, each billet including a plurality of slots each for receiving a bottom edge of a sheet of glass; a plurality of removable upright support members at one end of each billet; a plurality of second upright support members at the other end of each billet; and a plurality of glass location members each removably connectable between a respective removable upright support member and a second upright support member, the glass location members including a locater member having a plurality of slots for receiving an upper edge of each sheet of glass, the glass locating member being adjustable in a substantially horizontal direction so that the slots in the glass locating member can be substantially vertically aligned above the slots in the billets so that the glass sheets can be substantially vertically retained in the glass support device.

6. The apparatus of claim 5 wherein the heating device is a kiln and includes an electric heating means for heating the kiln and at least one fan for circulating heated air within the kiln.

7. The apparatus of claim 6 wherein the at least one fan circulates a volume of 8,911 cubic meters per hour of air within the kiln.

8. The apparatus of claim 5, 6 or 7 wherein the kiln includes a vent for venting off biproducts during low temperature firing.

9. The apparatus of any one of claims 5 to 8 wherein the glass support device further includes a hearth upon

Claims (4)

1. A method for producing a printed glass sheet including: printing the glass sheet with a printing material which will form a substantially permanent pattern on the glass sheet and which cures at a lower temperature than the temperature at which the glass sheet becomes plastic or supple; supporting the glass sheet substantially vertically in a heating device; and heating the glass sheet in the heating device to a temperature less than the temperature at which the glass sheet become plastic or supple and at least to the temperature at which the printing medium will fire to produce the substantially permanent pattern on the glass sheet.

2. The method of claim 1 wherein the heating device is a stationery kiln.

3. The method of claim 1 or claim 2 wherein the printing medium comprises a ceramic enamel formulated to cure at a temperature of 495 0 C.

4. The method of claim 3 wherein the ceramic enamel Sis viscosity modified to adjust the viscosity of the enamel by mixing the enamel with a base thinner. An apparatus for producing a printed glass sheet *made from a glass sheet which has been printed with a printing medium to form a substantially permanent pattern on the glass sheet, including: a heating device having heating means for heating the device to a temperature which is less than the temperature at which the glass sheet becomes plastic or /tsupple and at least to the temperature at which the 17 which the glass support device is located, said hearth including casters so that the hearth can be rolled into and out of the kiln. The apparatus of claim 9 wherein the kiln includes tiacks upon which the hearth can be moved so that the hearth can be rolled into and out of the kiln. Dated this 12th day of September 1995 CERAMIC COATINGS RESEARCH PTY. LTD. By Its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. C S S. o *o *g* S S S S SC S *SSS.S S ABSTRACT A method and apparatus for producing printed glass sheet is disclosed. The method includes printing the glass sheet with a printing material which will form a substantially permanent pattern on the sheet and which has a firing range which is of lower temperature than the temperature at which the glass sheet becomes plastic or supple and heating the glass sheet to a temperature less than the temperature at which the glass sheet becomes plastic or supple and at least to the temperature at which the printing medium will fire. A kiln (10) is provided for heating the printed sheet and the printed sheet of glass is supported on glass support device which comprises a plurality of removable 15 uprights (44) arranged at one end of a plurality of billets (42) and uprights (60) at the other end of the billets The billets (42) include slots (43) for receiving an edge of the glass sheet (50) and a plurality of glass location members are removable connected between the removable upright members (44) and upright members The location member (70) is adjustable in the horizontal direction so that slots (75) in the member (70) can be aligned with slots (43) in the billets (42) so that the glass sheets (50) can be vertically aligned between the 25 location member (70) and the billets (42). 0