WO2004113241A1

WO2004113241A1 - Method and furnace device for hardening and cooling of a glass

Info

Publication number: WO2004113241A1
Application number: PCT/FI2004/000383
Authority: WO
Inventors: Risto Nikander
Original assignee: Feracitas Oy
Priority date: 2003-06-25
Filing date: 2004-06-24
Publication date: 2004-12-29
Also published as: EP1651579A1

Abstract

Method for tempering and cooling of glass in tempering machine, which includes a separate tempering section (TS) and a separate cooling section (CS), which is little longer than glass, including at least one tempering blower and air channels and nozzle arrangements (CHP) to aim the air blow onto the glass. During tempering the method divides the air from the blower/blowers in between the tempering and cooling sections in such a way, that high enough cooling effect is achieved in the tempering section for the glass being tempered.

Description

METHOD AND FURNACE DEVICE FOR HARDENING AND COOLING OF A

GLASS

Present technology

For flat glass tempering machines there are two different main methods

1) A separate tempering section

Tempering takes place normally in about 1200 long tempering section, through which a thin glass, thickness generally 2,8 - 4,0 mm, is driven by relatively fast speed, at about 600 rnm s, during which time the tempering takes place. Final cooling takes place only in cooling section located after tempering section. As thin glasses require high cooling power, the method is advantageous, since only relatively short length requires high cooling power. In majority of cases glasses are loaded at the length of about 3 — 5 metres and if tempering pressure should be applied to such a length, the needed tempering power would be even up to 3 - 4 times higher, that in tempering section, the length of which is about 1200 mm, (not considering the power needed for the cooling section). This method thus allows reduction of peak power during tempering.

After tempering the glass is cooled in cooling section, which is generally 200 — 400 mm longer than glass. During cooling is it not sensible to use as high cooling power as during tempering and, on the other hand, when cooling section area is large, also the required air flow is high so tempering blower is not well suited for final cooling. Additionally high pressure tempering blower specific pressure curve is unsuitable and energy wasteful if it is used for low pressure after cooling.

The disadvantage of the method is that tempering and after cooling sections both require their own blowers, which increase expenses. As tempering blower is used only during tempering and there is no time enough to stop the blower in between the tempering phases, all the energy it uses in between tempering phases is a waste. Even though the energy it draws during these periods can be reduced in various ways, still the waste is remarkable.

2) Combined tempering and cooling section The glass is tempered and cooled in the same section so that nozzle arrangement is the same for the whole of tempering section. The advantage of this method is that the machine is shorter about 1200 mm, as no separate tempering section is required. The disadvantage of this method is that the whole tempering section is supplied with high pressure, which leads to unreasonably large blowers, motors and power feeds. Alternatively special arrangements like "compressor boost" must be used, in which the glass is tempered by combined effect of blower- and compressor air. This method is expensive.

As this method includes combined tempering and after cooling sections and optimum nozzle arrangement for thin glass tempering is quite different from after cooling nozzle arrangement;, the whole area requires nozzle arrangements, which can be used for tempering and for after cooling. Normally these arrangements involve high counter pressure, turbulence around exit of the nozzle and badly directed blowing towards rollers. Thus these nozzle arrangements are compromises which mean they are not best possible for either one.

One way to reduce tempering peak power in this combined tempering and cooling method is to divide the section into two parts. The first part is now tempering section, into which two blowers blow in series so that sufficient tempering pressure for thin glass is reached. This method is described in publication FI 100525 B. Also this involves use of earlier mentioned compromise nozzle arrangements. It can be noted, that method of the publication FI 100525 B leads into the situation, in which the leading end of the glass is driven through high pressure section and it is totally tempered and cooled into certain temperature and now gate 10 is opened in the situation, when the trailing end of the glass has not yet cooled into the temperature of the leading end of the glass. Uneven cooling of the glass can cause the glass to break. It is not possible to drive the glass through the whole of the high pressure section, as in most cases there is still glass on unloading table. Additionally it can be noted, that the manufacturing of blower ducting into the tempering/cooling sections is not advantageous, as ducts become complicated and energy wasteful during the time when glass is cooled. In both earlier mentioned cases it can be noted, that thick glasses are generally driven into the tempering with much lower speed and the tempering process with them is much slower than with thin glasses, so it is not worthwhile to handle tempering process of thick glasses in this connection. As very low pressure, even natural convection, is sufficient to temper thick glasses, it may be even difficult to reach low enough tempering pressure with high pressure blowers. So with thick glasses it is only advantageous if blower blows into tempering and cooling sections during tempering, because in this way free open area is larger and produced tempering pressure can be lowered in a natural way.

Description of novel technology:

The method here described eliminates the disadvantages of the earlier mentioned systems as follows;

As such known thin glass tendering section, designed to cool thin glass quickly with optimum nozzles, is used. After tempering section a cooling section, also known as such and well designed to cool glass after tempering, is used.

Characteristic for the method according to the invention is that the air produced by tempering section blower/blowers can be directed during tempering wholly into tempering section or part of the air can be directed into after cooling section. During after cooling the air from same blower/blowers is, instead, directed at least mainly into after cooling section.

In this way it is possible to reach tempering pressure required for thin glasses with lower connected power and saving manufacturing expenses. Tempering of thicker glasses becomes also easier, as open area of nozzles is larger and thus reaching low tempering effects becomes easier. Depending on thickness of glass, selection of blower(s) and length of glass loading even the whole blower for after cooling section may be eliminated.

Division of air in between tempering section and after cooling section can be made either after the discharge opening of blower/blowers or by a device located either in tempering section or in after cooling section. With the thinnest glasses and larger loading areas two tempering blowers are used. Blowers Bl and B2 can be typically medium pressure blowers. When air pressure of tempering section is produced by two of this kind of blowers Bl and B2, connected in series during tempering, high enough tempering pressure even for thin glasses, such as 2,8 mm, can be reached without increasing the connected power. If desired, tempering section could even be made longer, for example by 300 mm, which would typically increase cooling time 0,5 seconds. This would assist cooling of glass enough below its annealing temperature so that the glass could be totally driven into the after cooling section, which would be completely without blowing in this case, until the blo ing is switched from tempering section into after cooling section. If the tempering machine produces blower air in some other section, for example suction removes over pressure from tempering section, it is useful to lead this air into after cooling section to cool glass during tempering.

When looking at different loading lengths and assuming ordinary length of tempering section to be 1200 mm and glass exit speed 600 mmls and loading length range to be from 2000 mm to 6400, the following can be noted;

a) When tempering thin glass all air is good to blow into tempering section. With short loads, the rvrrjnϊng of glass through tempering section takes 3 -4 seconds time only. If there is no blowing into after cooling section, the glass is just so short time without forced convection. On the other hand, since after cooling section length is just about 3000 mm, the air flow needed for after cooling section may not be even as large as needed for tempering considering the open area and needed air exit speed in the sections. Thus, with short loadings it is possible to use just one blower. If the blower selection leads into two blowers, the whole of air produced by blower Bl can be conducted into blower B2 and begin after cooling only when the whole of the glass load is in after cooling section. The glass has been without final cooling only a short period of time and it has no time to lose it degree of tempering if and when it has been cooled just below necessary tempering temperature. With shorter loadings the gate G can totally close entering of air into after cooling section or gate Gl can lead all air of blower Bl into blower B2 in order to reach necessary tempering pressure. b) With long loading running of glass trough the tempering section, which means tempering of glass load, takes time 6 - 10 seconds but, on the other hand, length of after cooling section compared to tempering section is multiple. In this case the air produced by blower B 1 to cool glass advantageously can be much higher compared to tempering section blower B2. As the loading gets longer, the glass should be cooled more and more below tempering temperature, but on the other hand also blower Bl has more extra air, which does not need to be conducted into blower B2 in order to reach sufficient tempering pressure. Depending on necessary tempering pressure the gate Gl should now be opened just enough so that necessary tempering pressure is achieved and all surplus air is conducted into the cooling section, (gate opening positions Gl', Gl", Gl'" etc.) In this way all air production of blowers is utilized for tempering and cooling of glass and nothing would be wasted, which would be the case with vane- and throttling control.

The arrangement in question facilitates tempering and cooling of glass which;

- allows use of optimum tempering section for tempering,

- allows use of optimum cooling section for cooling, - is tempering and cooling in such a way, that it gives glass very even temperature over the full length of glass

- is economic to make and saves energy and works well with short and long loadings

- produces high enough tempering pressure also for thin glass with relatively low connected power, - makes possible to select optimum blower for glass cooling

- allows use of one only, more suitable blower for thick glasses, as with 15 -20 mm glasses the tempering pressure should be especially low and it is more easy to achieve when ducts are open to tempering section and cooling section, (so called free open area is large). - makes possible to use straight forward, energy saving and inexpensive ducts

- allows normally use of one less blower than with conventional systems

The invention is described below with reference to attached figures 1 - 5. Figures 1 — 5 are schematic drawings of tempering section seen from above. The furnace part and unloading section are excluded. In all figures blowers B, Bl and B2 blow into lower and upper nozzles in tempering and cooling sections. However, it is possible to use the invention with one or more blowers. The figures have following markings;

- B is combined blower for tempering- and cooling sections

- M is the drive motor for the above

- Bl is the feed blower of tempering section but it may also be called blower for cooling section

- Ml is the drive motor for the previous

- B2 is blower for tempering section

- M2 is drive motor for the terrrpering section blower

- TS is tempering section - CS is cooling section

- G is division device, which divides air in between tempering-and cooling sections. It is located in upper and lower nozzle blocks and it can be alternatively located in cooling section, too.

- Ga is similar device as G, but it divides air directly from blower B in between tempering and cooling sections.

- C is movable duct or alternatively closing gate

- Gl is division plate, which divides the air production of blower Bl either into the blower B2 or into the cooling section CS or shares the air in between them as described.

Fig. 1 describes the alternative, in which only one blower B is used and the air produced by it is conducted into tempering section TS and/or cooling section CS by adjusting division device G or alternative device Ga to the wanted position. This arrangement is suitable particularly for short loadings and 4 mm and thicker glasses. If the device Ga is used, the air ducts of tempering section and cooling section must be totally separated during tempering. Instead a separate air channel from Ga into cooling section CS is needed.

Fig. 2 describes an arrangement to temper thin glasses, when high pressures are needed and often 2 blowers are used in series. Channel C is attached on to the intake opening of blower B2 and device Gl divides at least majority of the air from the blower Bl in to the blower B2. Gate G closes the connection from tempering section into the cooling section so that the tempering section has high pressure and cooling section low pressure or is without pressure. There is a free access of the air from nozzle blocks into the nozzles in both sections. The pressure produced by the hlowers can be controlled primarily by the position of the gate Gl but also by other known methods.

Figure 3 describes an arrangement which is typical for tempering of thin glass during the beginning of the cooling stage, when both blowers still run. The gate G has opened access into the cooling section, but prevents the air access into the tempering section nozzles, (darkened). The gate Gl now conducts the air from blower Bl directly into the cooling section CS and channel C has been opened up so that the blower B2 has free suction from open air and also it blows all of its air into the cooling section. Cooling continues optimally so, that both blowers or just one of them is used at such a speed, which, with minimum power consumption, cools the glass to a low enough unloading temperature. Especially with long loadings the air volume required by cooling section can be so high, that also the air of blower B2 is needed for glass cooling. This is possible, if blowers Bl and B2, when working independently, can run at the same point of blower curve.

Figure 4 shows an arrangement, in which tempering of thin glass is in progress and in which a part of the air from blower Bl is conducted into the air channels into the nozzle blocks according to the figure 6. Leading of such an air, for example, under the rollers and possibly similarly into the upper nozzle blocks, into the low pressure air channel CLP and through the openings onto the feet of the high pressure nozzles would improve ihe ejector effect, which is caused by high pressure, fast moving air jets JHP. In the tempering section particularly important is increase of the cooling power. Partially this "secondary air" ensures that ejector air is in sufficient quantity in every place so that the cooling effect is similar on the whole width of the glass.

Figure 5 shows a method in which the air received from tempering section by blower B3 can be lead into the cooling section nozzles, figure 6, through the channels CHP. In this way the cooling effect of this air can be utilized during the tempering and initial stages of cooling.

During the final cooling of glass the air from blower B3 or other similar air can be lead through low pressure channels CLP of picture 6 into the foot of the nozzles. In this case the secondary air should produce more ejector air to the space between the high pressure nozzles and rollers, which would further secure transfer of possible broken glasses away from between the rollers and the nozzles. In this way optimal tempering nozzles could be better used also in cooling section. In typical 1,2 metres long tempering sections, through which the glass is driven, the glass normally has no time to break so that this arrangement in tempering section is not so important.

Claims

1. A method for tempering and cooling of glass in furnace, which has a separate tempering section (TS) and a separate cooling section (CS), which is little longer than the glass, and which includes at least one tempering blower and air ducts and nozzle arrangements (CHP) to conduct the air onto the glass, characterized in that during tempering of glass the air flow from blower/blowers is divided in between the tempering and cooling sections in such a way, that in tempering section sufficiently high cooling effect is achieved, as required by the thickness of glass being tempered.

2. A method according to claim 1 characterized in that the device (G) in tempering section (TS) divides the air in suitable proportion between the nozzles in tempering section (TS) and in cooling section (CS).

3. A method according to claim 1 characterized in that the air production of at least one tempering blower (B, Bl) is divided by devices (Ga, Gl) into the air channels, one of which leads into the tempering section (TS) and the other in to the cooling section (CS).

4. A method according to claims 2 and 3 characterized in that the gate (G, Ga) can close the entrance of air totally either into tempering section (TS) nozzles or cooling section (CS) nozzles.

5. A method according to claim 2 characterized in that gate is mounted in cooling section (CS).

6. A method according to claim 1 characterized in that the pressure of the air lead into the tempering section (TS) is adjusted to the wanted level by directing part of the air from tempering blower into the cooling section (CS) by gate (G, Ga, Gl).

7. A method according to claim 1 characterized in that during tempering the air from blower B3 is lead into the nozzles (CHP).

8. A method according to claim 1 characterized in that during cooling the air from blower B3 is lead to the vicinity of the feet of nozzles (CHP).

9. A furnace device according to the claim 1, in order to accomplish the method which has a separate tempering section (TS) and cooling section (CS) and which includes at least one tempering blower and air ducts and nozzles (CHP) to aim the air blown onto the glass, characterized in that the device includes ducts from at least one blower into the tempering section and cooling section and division device, (G, Ga, Gl) or respective system, by which the air delivery from blower/ blowers can be divided between the tempering section and cooling section or just into one of them.

10. A furnace device according to the claim 9 characterized in that tempering section (TS) and cooling section (CS) can be united or separated from each other by gate G or equal closing element.

11. A furnace device according to claims 9 and 10 characterized in that closing gates are included in tempering section or in cooling section ducts by which the air entrance into nozzles can be prevented.