WO2003106358A1

WO2003106358A1 - An oven and method for the treatment of glass articles

Info

Publication number: WO2003106358A1
Application number: PCT/GB2003/002587
Authority: WO
Inventors: Harry King
Original assignee: Gemco Furnaces B.V.
Priority date: 2002-06-15
Filing date: 2003-06-16
Publication date: 2003-12-24
Also published as: AU2003277080A1; TW200409736A; GB0213847D0

Abstract

An oven (10) for treatment of glass articles, most preferably planar pieces of glass (50) for use in PDP screens comprises an elongate housing (12) defining a plurality of heat treatment zones (16a-16g). An array of nozzles (42a-42f) connected to an air inlet manifold (34) define inlet means. A corresponding array of outlet pipes (44a-44f) connected to an exhaust manifold (32) define fluid outlet means. Between them, the inlet and outlet means define a fluid flow means and air flowing from the inlet passes directly to the outlet and parallel to the article, without impinging upon the article to be treated. A method of treating glass articles comprises the steps of arranging the article (50) in a chamber to be heated, flowing heated fluid over the article, without impinging thereon, the flow being substantially parallel with the article. A further method comprises the steps of passing heating fluid over an upper part of an article (50) in a first direction and at the same time passing fluid over the lower part of the article in a substantially opposite direction.

Description

AN OVEN AND METHOD FOR THE TREATMENT OF GLASS ARTICLES

The present invention relates to an oven for the treatment of glass articles and a method of treatment of glass articles, particularly Cathode ray tubes (CRT) and plasma display panels (PDP).

Ovens for heat treating glass articles are known. One such known oven comprises a chamber in which glass articles to be treated are located and an air circulation system which is arranged to blow air against the glass article, h one particular form of oven, a number of baffles are provided to direct air against selected parts of the article being treated. In such known ovens, an air outlet is located, often at the base of the chamber to extract all of the air blown into the chamber. Known ovens suffer from problems of uneven temperature distribution.

It is an object of the invention to provide an improved oven.

According to one aspect of the invention there is provided an oven for the heat treatment of one or more glass articles comprising a heat treatment chamber and fluid flow means for passing fluid through the chamber, the fluid flow means comprising a fluid inlet arranged to admit fluid into the chamber and a fluid outlet arranged to allow egress of fluid from the chamber, the outlet being arranged substantially in line with the fluid inlet so that fluid entering the chamber passes substantially directly to the outlet. By "directly" we mean that the fluid does not impinge upon the article to be heat treated. In use, the fluid flow means is arranged to promote flow of fluid substantially parallel with the surface of an article to be treated.

In a preferred embodiment there is provided a support for glass articles, the support defining a support plane. In such a case, the fluid flow means preferably promotes a flow of fluid substantially parallel with the support plane.

Preferably, the oven comprises a first fluid inlet/fluid outlet pair arranged so as to cause fluid flow in one direction and a second fluid inlet/fluid outlet pair arranged to cause fluid flow in a substantially opposite direction.

Preferably, for each article to be treated, there is provided first and second fluid inlet/fluid outlet pairs arranged to cause fluid flow in respectively opposite directions. For the avoidance of doubt, where two articles are to be treated, one of the fluid inlet/fluid outlet pairs may be "shared" between the two articles.

Preferably the article to be treated is substantially planar. In such a case, the first fluid inlet/fluid outlet pair may be arranged to direct flow over one face of the planar article whilst the second fluid inlet/fluid outlet pair may be arranged to direct flow over the opposite face of the planar article.

Preferably, the oven is arranged to treat a plurality of articles. In such a case, the oven may be provided with at least one fluid inlet/fluid outlet pair per article to be treated. Most preferably, as described above, for each article to be treated there is provided a first fluid inlet/fluid outlet pair for directing fluid flow over one part of the article and the second fluid inlet/fluid outlet pair for directing flow over another part of the article. In a preferred embodiment, the plurality of articles are arranged in a stack with spacing between neighbouring articles, the second fluid inlet/fluid outlet pair of one article comprising the first fluid inlet/fluid outlet pair of the neighbouring article.

In the most preferred embodiment, the oven is arranged to treat a stack of five articles, the oven being provided with six fluid inlet/fluid outlet pairs, three pairs being arranged to direct flow in a first direction and the other three fluid inlet/fluid outlet pairs being arranged to direct flow in a second, opposite direction, the sets of fluid inlet/fluid outlet pairs being interleaved with one another so that neighbouring fluid inlet/fluid outlet pairs direct air flow in opposite directions.

The oven preferably includes first and second zones, the first zone having fluid flow means arranged to direct fluid flow in a first direction and the second zone having fluid flow means arranged to direct flow in second, substantially opposite direction. Where the oven comprises a first fluid inlet/fluid outlet pair directing flow in a first direction and a second fluid inlet/fluid outlet pair directing flow in a second substantially opposite direction, the oven may comprise first and second zones, the sense of air flow in one zone being opposite to that of the other zones. Most preferably, there is provided an oven in accordance with the first aspect of the invention, the chamber having a first zone including a first fluid inlet and a first fluid outlet arranged to direct an air flow in a first direction and a second zone including a second fluid inlet and a second fluid outlet arranged so as to direct flow in a second substantially opposite direction to the first. Preferably, in each further zone, fluid flow is reversed. According to another aspect of the invention there is provided a method of treating a substantially planar glass article comprising the steps of arranging the article in a chamber to be heated, arranging the flow of fluid over the article, the flow being substantially parallel with the article.

In that way, the heated air does not impinge upon the article and thus this avoids the occurrence of hot spots which are undesirable.

h a preferred embodiment, the method comprises the steps of arranging a flow of fluid over a part of the article in a first direction and arranging a flow of fluid over another part of the article in a second substantially opposite direction.

In a further preferred embodiment, the method further comprises the steps of subjecting the article to treatment in a first zone, moving the article into a second zone, and reversing the direction of fluid flow over the article from the first zone to the second zone.

According to a third aspect of the invention there is provided a method of treating a substantially planar glass article comprising the steps of passing fluid over one part of an article in a first direction, passing fluid over another part of the article in a substantially opposite direction. The arrangement of the fluid inlet and the fluid outlet such that air passes directly from one to another without substantially impinging upon an article to be heated results in a substantially even distribution of heat across the article to be treated.

An embodiment of the invention will now be described in detail by way of example and with reference to the accompanying drawings in which:

Fig.l is a side elevation of an oven in accordance with the invention; Fig.2a is an end elevation of the oven of Fig.l, Fig.2b is a view similar to Fig.2a but with a vacuum cart carrying glass panels shown in the oven,

Fig.3 is an end elevation of part of the oven of Figs.1 and 2 shown to a larger scale, Fig.4a is an elevation of an array of nozzles used in the oven of Figs.1 and 2, Fig.4b is a schematic perspective view of an outlet pipe used in the oven of Figs.1 and 2, and

Fig.5 is a graph showing a temperature profile of a treatment of a glass article.

In Figs.l and 2, an oven 10 comprises an elongate housing 12 enclosing an elongate heating chamber 14, the heating chamber comprising a plurality of zones 16a-g.

The housing comprises a top wall 18, side walls 20, 22 and a base 24 supported above ground level by legs 25. The base 24 has an opening 26 running centrally and longitudinally thereof. The elongate heating chamber 14 comprises an outer skin 28 having a top wall 28a, side walls 28b and c and an open base and end so as to define an inverted channel and an inner skin 30 having a top wall 30a, side wall 30b, 30c and an open base and ends to define an inverted channel.

An exhaust manifold 32 is defined between the inner surface of the walls of the housing 12 and the outer surface of the outer skin 28. An exhaust port 33 is formed through the top wall 18 of the housing 12.

An inlet manifold 34 is defined between the inner surface of the outer skin 28 and the outer surface of the inner skin 30.

A recirculating fan 36 is arranged in respective openings in the top walls 18, 28a and 30a of the housing 12, outer skin 28 and inner skin 30 respectively. A gas-tight seal is provided at each opening to ensure gas tightness of the inlet and exhaust manifolds.

The fan 36 has an inlet 38 which is in fluid communication with atmosphere mounted above an impeller 40. The impeller 40 is arranged within the inlet manifold and is arranged to draw air from atmosphere via the inlet 38 and to provide a positive pressure in inlet manifold 34.

A radiant tube heater 42 extends from outside the housing 12, through the side wall 20 of the housing 12, the side wall 28b of the outer skin 28, through the inlet manifold 34, above the top wall 30a of the inner skin 30 and out through respective side wall 28c and 22 respectively.

Three gas nozzle arrays 42a, b and c are provided through the side wall 30b of inner skin 30 and three gas nozzle arrays 42d, e, f are provided through side wall 30c of the inner skin 30. The nozzle arrays 42a-f are in fluid communication with the inlet manifold 34.

Three outlet pipe arrays 44a, b, c are provided and are arranged so as to extend through the side wall 30b of inner skin 30, through the inlet manifold 34 and into the exhaust manifold 32. Three outlet pipe arrays 44d, e and f are provided and are arranged to extend through the side wall 30c of the inner skin 30, through the inlet manifold 34 and opening out into the exhaust manifold 32.

It will be noted from Fig.2 that the gas nozzle arrays 42a, b, c, d, e and f are arranged alternatingly in the respective opposite side walls 30b, 30c with the outlet pipe arrays 44a, b, c, d, e and f. More particularly, the gas nozzle array 42a is arranged at the same vertical position in the side wall 30b as the outlet pipe array 44d in the opposite side wall 30c. The same is true, mutatis mutandis for the nozzle array/outlet pipe array pairs 42b, 44e; 42c, 44f; 42d, 44a; 42e, 44b; and 42f, 44c.

As can be seen in Fig.4a, a gas nozzle array 42a-f comprises six nozzles arranged in a horizontal line, regularly spaced from one another. In a most preferred embodiment, the respective opposite outlet pipe arrays 44a-f also comprise an array of six outlet pipes in a horizontal line, regularly spaced from one another, most preferably having the same regular spacing therebetween as the gas nozzles of the gas nozzle array. The outlet pipes of pipe arrays 44a-f preferably have a diameter of 30mm.

Two further outlet openings 46a, b are formed, one each side of the chamber 14 of the respective bases of the side walls 28b, 30b, 28c, 30c of the outer and inner skins 28, 30. Those openings are selectively closable by means of respective adjustable vanes 48a, 48b which are arranged pivotally within the openings 46a, 46b.

In use, the radiant tube 41 is operated to generate heat within the oven 10. The fan 36 is operated so as to create a flow of air through the heating chamber 14. The impeller 40 generates a positive pressure within the inlet manifold 34 and air flows over the radiant tube 41, becoming heated in that process. The air then flows down between the side walls 28b, 28c of the outer skin 28 and the side walls 30b, 30c of the inner skin 30 and out through nozzles 42a-f. Air flows directly from nozzle arrays 42a-f through the respective opposite outlet pipes 44a-f into the exhaust manifold 32 and out through exhaust port 33. Such an arrangement promotes gas flow in a substantially straight line from the nozzle array 42 to the outlet pipe 44. Because of the arrangement of alternating nozzles and outlet pipes, a "layered" air flow is provided with air flow in opposite directions in alternating layers.

The air flow described above is illustrated in detail in Fig.2b which shows the oven 10 in operation treating a stack of flat plasma display panels 50 arranged on a support 52 carried by a vacuum cart 54 which, simultaneous with the heat treatment formed by the oven 10, evacuates the interior of the plasma display panels. The detailed pipe work of the vacuum cart 54 is not shown. Fig.3 shows the layered airflow in detail with the vacuum cart and other details omitted for clarity.

As can be seen in Fig.2b, air flows in opposite directions in alternating layers above and below the glass panels 50 on the support 52. In that way, as the temperature profile of the air flow decreases from nozzle to outlet, each panel receives a substantially "even" heating across its width.

As can be seen in Fig.l, the oven 10 is divided into multiple heating zones 16a-g. Each zone has its own air flow regime and temperature profile. The purpose of the zones is to effect a particular heat treatment profile as the panels move through the oven on the vacuum carts 54.

Fig.5 shows a typical heat treatment profile in graphical form corresponding to the zones 16a to 9 in the oven.

h zones 16a and b the panels are heated at 5-10°C/min to a temperature of approximately 450°C. h zones 16c and d the temperature is maintained at 450°C for approximately 20-30 mins. In zones e and f the temperature is reduced by 5-10°C/nιin to approximately 380°C and in zone g the temperature is maintained at 380°C for several hours before the panels are removed for cooling to ambient.

Claims

1. An oven for the heat treatment of one or more glass articles comprising a heat treatment chamber and fluid flow means for passing fluid through the chamber, the fluid flow means comprising a fluid inlet arranged to admit fluid into the chamber and a fluid outlet arranged to allow egress of fluid from the chamber, the outlet being arranged substantially in line with the fluid inlet so that fluid entering the chamber passes substantially directly to the outlet.

2. An oven for the heat treatment of one or more glass articles according to claim

1, in which a support for glass articles is provided, the support defining a support plane.

3. An oven for the heat treatment of one or more glass articles according to claim

2, in which the fluid flow means promotes a flow of fluid substantially parallel with the support plane.

4. An oven for the heat treatment of one or more glass articles according to any preceding claim, in which the oven comprises a first fluid inlet/fluid outlet pair arranged so as to cause fluid flow in one direction and a second fluid inlet/fluid outlet pair arranged to cause fluid flow in a substantially opposite direction.

5. An oven for the heat treatment of one or more glass articles according to claim 4, in which, for each article to be treated, there is provided first and second fluid inlet/fluid outlet pairs arranged to cause fluid flow in respectively opposite directions.

6. An oven for the heat treatment of one or more glass articles according to claim 4 or 5, in which the article to be treated is substantially planar.

7. An oven for the heat treatment of one or more glass articles according to claim 6, in which the first fluid inlet/fluid outlet pair is arranged to direct flow over one face of the planar article whilst the second fluid inlet/fluid outlet pair may be arranged to direct flow over the opposite face of the planar article.

8. An oven for the heat treatment of one or more glass articles according to any preceding claim, in which the oven is arranged to treat a plurality of articles.

9. An oven for the heat treatment of one or more glass articles according to claim 8, in which the oven is provided with at least one fluid inlet/fluid outlet pair per article to be treated.

10. An oven for the heat treatment of one or more glass articles according to claim 8, in which for each article to be treated there is provided a first fluid inlet/fluid outlet pair for directing fluid flow over one part of the article and the second fluid inlet/fluid outlet pair for directing flow over another part of the article.

11. An oven for the heat treatment of one or more glass articles according to claim 10, in which the plurality of articles are arranged in a stack with spacing between neighbouring articles, the second fluid inlet/fluid outlet pair of one article comprising the first fluid inlet/fluid outlet pair of the neighbouring article.

12. An oven for the heat treatment of one or more glass articles according to any preceding claim, in which the oven is arranged to treat a stack of five articles, the oven being provided with six fluid inlet/fluid outlet pairs, three pairs being arranged to direct flow in a first direction and the other three fluid inlet/fluid outlet pairs being arranged to direct flow in a second, opposite direction, the sets of fluid inlet/fluid outlet pairs being interleaved with one another so that neighbouring fluid inlet/fluid outlet pairs direct air flow in opposite directions.

13. An oven for the heat treatment of one or more glass articles according to any preceding claim, in which the oven includes first and second zones, the first zone having fluid flow means arranged to direct fluid flow in a first direction and the second zone having fluid flow means arranged to direct flow in second, substantially opposite direction.

14. An oven for the heat treatment of one or more glass articles according to any preceding claim, in which the oven comprises a fluid inlet/fluid outlet pair directing flow in a first direction and the oven comprises first and second zones, the sense of air flow in one zone being opposite to that of the other zone so that the fluid inlet in one zone becomes the fluid outlet in the other zone and vice versa.

15. An oven for the heat treatment of one or more glass articles according to claim 14, in which the oven comprises a first fluid inlet/fluid outlet pair directing flow in a first direction and a second fluid inlet/fluid outlet pair directing flow in a second substantially opposite direction, the oven comprising first and second zones, the sense of air flow in one zone being opposite to that of other zone so that each fluid inlet in one zone becomes a respective fluid outlet in the other zone and vice versa.

16. An oven for the heat treatment of one or more glass articles according to claim 1, in which the chamber has a first zone including a first fluid inlet and a first fluid outlet arranged to direct an air flow in a first direction and a second zone including a second fluid inlet and a second fluid outlet arranged so as to direct flow in a second substantially opposite direction to the first.

17. An oven for the heat treatment of one or more glass articles according to claim 16, in which further zones are provided, each zone having specific fluid flow and temperature characteristics.

18. An oven for the heat treatment of one or more glass articles according to claim 17, in which the fluid flow is successively reversed in each subsequent zone.

19. An oven for the heat treatment of one or more glass articles according to claim 17 in which, in a first zone, the article temperature of the article to be treated is elevated at a temperature elevation rate to a first temperature then in a second zone is maintained at that temperature for a predetermined period before being allowed to cool to ambient temperature.

20. An oven for the heat treatment of one or more glass articles according to claim 19 in which the temperature elevation rate is from 5 to 10 degrees Celsius per minute.

21. An oven for the heat treatment of one or more glass articles according to claim 19 or 20 in which the first temperature is 450 degrees Celsius.

22. An oven for the heat treatment of one or more glass articles according to claim 19, 20 or 21 in which the article is maintained at the first temperature for 20 to 30 minutes.

23. An oven for the heat treatment of one or more glass articles according to claim 19, 20, 21 or 22 in which a third zone is provided in which the article temperature is reduced at a temperature reduction rate from the first temperature to a second lower temperature and, in a fourth zone, the article is maintained at the second temperature before being allowed to cool to ambient.

24. An oven for the heat treatment of one or more glass articles according to claim 23 in which the temperature reduction rate is from 5 to 10 degrees Celsius per minute.

25. An oven for the heat treatment of one or more glass articles according to claim 23 or 24 in which the second temperature is 380 degrees Celsius.

26. An oven for the heat treatment of one or more glass articles according to claim 23, 24 or 25, in which the article is maintained at the second temperature for a period from 2 to 12 hours.

27. A method of treating a substantially planar glass article comprising the steps of arranging the article in a chamber to be heated, arranging the flow of fluid over the article, the flow being substantially parallel with the article

28. A method of treating a substantially planar glass article according to claim 27, in which the method comprises the steps of arranging a flow of fluid over a part of the article in a first direction and arranging a flow of fluid over another part of the article in a second substantially opposite direction.

29. A method of treating a substantially planar glass article according to claim 28, in which the method further comprises the steps of subjecting the article to treatment in a first zone, moving the article into a second zone, and reversing the direction of fluid flow over the article from the first zone to the second zone.

30. A method of treating a substantially planar glass article comprising the steps of passing fluid over one part of an article in a first direction, passing fluid over another part of the article in a substantially opposite direction.

31. A method of treating a substantially planar glass article according to any of claims 27 to 30 further comprising the steps of heating the article at 5-10°C/min to a temperature of approximately 450°C, maintaining the article at 450°C for approximately 20-30 mins, reducing the temperature by 5-10°C/min to approximately 380°C and maintaining the temperature at 380°C for several hours before cooling to ambient.