CA1070951A - Method and tunnel furnace for the thermal treatment of glass products, in particular envelopes for display tubes - Google Patents
Method and tunnel furnace for the thermal treatment of glass products, in particular envelopes for display tubesInfo
- Publication number
- CA1070951A CA1070951A CA235,899A CA235899A CA1070951A CA 1070951 A CA1070951 A CA 1070951A CA 235899 A CA235899 A CA 235899A CA 1070951 A CA1070951 A CA 1070951A
- Authority
- CA
- Canada
- Prior art keywords
- zone
- tunnel
- zones
- temperature
- products
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000007669 thermal treatment Methods 0.000 title claims description 4
- 239000011521 glass Substances 0.000 title abstract description 15
- 238000000034 method Methods 0.000 title abstract description 10
- 238000001816 cooling Methods 0.000 abstract description 15
- 238000010438 heat treatment Methods 0.000 abstract description 15
- 238000005192 partition Methods 0.000 abstract description 8
- 238000011282 treatment Methods 0.000 description 2
- 101150007148 THI5 gene Proteins 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B25/00—Annealing glass products
- C03B25/04—Annealing glass products in a continuous way
- C03B25/06—Annealing glass products in a continuous way with horizontal displacement of the glass products
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
Abstract
ABSTRACT:
A method of thermally treating glass products in which the products are conveyed through a number of heating zones and/or cooling zones of a tunnel furnace and are heated and cooled, respectively, by means of an airflow maintained in each zone in a direction transverse to the direction of transport; according the invention, the velocity of the airflow increases gradually both in the heating zones and in the cooling zones; for that purpose, two perforated partitions having gradually increasing flow apertures for the airflow are provided in each zone.
A method of thermally treating glass products in which the products are conveyed through a number of heating zones and/or cooling zones of a tunnel furnace and are heated and cooled, respectively, by means of an airflow maintained in each zone in a direction transverse to the direction of transport; according the invention, the velocity of the airflow increases gradually both in the heating zones and in the cooling zones; for that purpose, two perforated partitions having gradually increasing flow apertures for the airflow are provided in each zone.
Description
~7~9~
Method and tunnel Eurnace for the thermal treatment of glass products, in particular envelopes for display tubes.
The invention relates to a method for the the~lal treatment of glass products, in particular env010pes for display tubes, in which the products are conveyed through a tunnel furnace which is divided into zones and are exposed in the successive zones to the action of a temperature-controlled air flow which is maintained throughout the length of each zone in a direction transverse to the direction of tranSport of the products, the air flows in the individual zones being controllable independently of each other. Such method5 are used for removing glass stresses in glass products.
In such a method which is known from the British patent specification 701 095, a previously determined temperature variation from the inlet end to the outlet end of the tunnel urnace can be maintained due to the independent control of the air temperature in each zone. Since, however, the temperature of the air flows varies stepwise from zone to zone and since the velocity of the air flow within one and the same zone and hence the coefficient of heat tr~nsfer in thi5 zone is constant, the products are subjected to a stepwise temperature variation from zone to zone. Said stepwise temperature variations result in considerable, undesired temperature differences between the inside and the outside of the products.
These drawbacks could be avoided partly by short stays of the products in the individual zones and/or by a low co-efficient of heat transferJ that is to say low velocities of the air flows. However, short stays require an expensive
Method and tunnel Eurnace for the thermal treatment of glass products, in particular envelopes for display tubes.
The invention relates to a method for the the~lal treatment of glass products, in particular env010pes for display tubes, in which the products are conveyed through a tunnel furnace which is divided into zones and are exposed in the successive zones to the action of a temperature-controlled air flow which is maintained throughout the length of each zone in a direction transverse to the direction of tranSport of the products, the air flows in the individual zones being controllable independently of each other. Such method5 are used for removing glass stresses in glass products.
In such a method which is known from the British patent specification 701 095, a previously determined temperature variation from the inlet end to the outlet end of the tunnel urnace can be maintained due to the independent control of the air temperature in each zone. Since, however, the temperature of the air flows varies stepwise from zone to zone and since the velocity of the air flow within one and the same zone and hence the coefficient of heat tr~nsfer in thi5 zone is constant, the products are subjected to a stepwise temperature variation from zone to zone. Said stepwise temperature variations result in considerable, undesired temperature differences between the inside and the outside of the products.
These drawbacks could be avoided partly by short stays of the products in the individual zones and/or by a low co-efficient of heat transferJ that is to say low velocities of the air flows. However, short stays require an expensive
2 ~ ~
~-'IIN. 7675 19.~ 75 ~7~
furnace hclving a coInparatively large number of zoIles; a low coeff`icient of heat transeer has the drawback that large -teIllperature d:ifferences across -the surface occur in products hav:ing large differences in wall thickness, as a result of which extra stresses occur in the product.
It :is the object of the invention to provide a methocI which does not exhibit -the said drawbacks and which enables the products to be treated to be subjected to a gradually occurring -temperature variation during their transport through the tunnel furnace.
According to the invention, this object is achieved main:Ly :in that, vie~Yed in the direction of transport, the air flow :Ln each zone has a continuously variable velocity.
Since the velocity of the air flow in a given zone is variable, the coefficient of heat transfer in said zone also varies. Since the coefficient of heat transfer is variable~ temperature variations of the products within the same zone take place gradually.
The measure according -to the invention may be used both for heating glass products and for cooling because with these treatments extra stresses are apt to occur in the products.
A preferred embodiment of the method according to the invention is charac-terized by such a distribution of the velocity of the air flow that temperature variations of the products occur at a constant rate. By a suitable choice of the velocity of the air flow within the same zone, the coefficient of hea-t transfer can be varied so that a linearly varying temperature gradient is main-tained in said zone, ~7~5~
temperature variations of the produc~s taking place throughout the length of the zone at a constant rate.
In another preferred embodiment of the method according to the invention the velocity of the air flow increases gradually in each zone. As a result of this measure a gradually increasing coefficient of heat transfer and a gradual temperature increase or temperature decrease o the pToducts are realized within each zone of the heating track and/or the cooling track of the tunnel furnace.
In accordance with this invention there is provided a tunnel furnace for the thermal treatment of an associated article which comprises: a housing defining a tunnel which includes a plurality of zones, each zone having an inlet and an outlet for the associated article, the inlet for the associated article for each zone after the first zone being the outlet of the preceding zone, a transport apparatus for the transport of the associated articles in a longitudinal direc-tion through said tunnel from an inlet side to an outlet side of each successive zone, each zone extending ov0r longitudinal section of said tunnel, means for generating an airflow in a direction transverse to the longitudinal direction of the tunnel with each zone and means for controlling the temperature of the airflow in each zone, said housing including first and second walls having therein flow apertures, said first and second walls in any one zone being disposed in opposed relationship, each of said walls being disposed in generally parallel relationship to said longitudinal direction, ~he total area of the flow apertures on opposed sides of any one zone being equal, the area of the flow apertures in each zone being inversely related to the longitudinal distance from the outlet of each of said zones.
The tunnel furnace~ may be construc*ed as a cooling furnace - having only a cooling section for the controlled cooling of blown or moulded glass products which are still hot.
:
. 7~75 19.6.1975 ~7~5~
Such -t~lnneL furnaces usually comprise botll a heating section and a cool:ing ~section, already cooled glass products being first heated and then cooled agaln. In special cases such a tunnel furnace may be constructed only as a heating furnace.
The invention will ~e described in greater detail with reference to the drawing. In the clrawing:
Figure 1 is a longitudinal sectional view of an embodiment o~ the tunnel furnace according to the invention taken on the line I-I of Fig. 2;
Figure 2 is a cross sectional view o~ the tunnel furnace talcen on the line II-II of Fig. 1;
Figures 3 ancl l~ show time temperature graphs.
The tunnel furnace 1 shown in I~ ures 1 and 2 comprises a heating section 3 which is subdivided into 1S heating zones 5, and a cooling section 7 which is divided into cooling zones 9. A -transport device, in the embodiment shown an endless transport belt 11 of metal grating work, serves for the transport of glass products to be treated thermally through the tunnel 13 of the furnace in the direction denoted by the arrow X from the inlet side to the out]et side of the furnace. The zones 5 and 9 each comprise a fan 15, a recirculation duct 17, and a number o control-lable heating elements 19. A partition 21 having flow apertures 23 is provided in each heating zone on the lower 2$ side and on the upper side of the tunnel 13. Partitions 25 having flow apertures 27 are provided in a corresponding manner in -the cooling zones 9.
By means of the fan 15, an airflow A is main-tained in each zone 5 and 9, in a direction transverse to .
Pl-IN. 7~75 1~.6.1~75 ~7~1951 the d.il~cc-tion of` tran.spor-t of the procIucts, vertically upwards through the r10~ apertures 23 ancl 27 of the partitions 21 and 25 and through -the transpor-t belt 11. Via the recirculation duc-t l7, said air is conveyed bacl~ to the lower side of the zones. The a:ir, during i-ts f:low through the recirculation duct 17, is hea-ted again at the desired temperature by means of the controllable heating elements 19. The air temperature is indivldually controllable in each zone independently of the temperature control in the other zones. As is shown in the drawing, the cross-section of the flow aperture 23 in the partit:ions 21 which are placed in the heating zones 5, gradually increases viewed in the di.rection of` transport X.
As a result of this the velocity of` the air flow be-tween the two parti-tions, viewed in the direction of transport X, also increases as a result of` which the coefficient of heat transfer becomes larger in the direction of transport. By a suitable choice of the cross-section of the flow apertures 21, the variation of the coefficient of heat transfer can be adapted to the thickness of the glass products to be treated in such manner that a constant heating rate of the prr,duct is obtained.
A gradual cooling of the product is obtained in a simi].ar manner in the zones 9 of the cooling section 7 in that the velocity of the air flow as well as the coefficient of hea-t transfer, viewed in the direction of transport, gradually increases in each zone. For that purpose, the flow apertures 27 in the partitions 25 which are placed in the - cooling zones 9 are also proportioned so tha-t their cross-section, viewed in the direction of t:ransport, increases ~197~gS~
gradually.
In the embodiment the partitions 21 and 25, respectively, are provid-ed on the lower side and on the upper side of each zone. In a similar, althOugh less favourable, manner, the partitions 21 and 25, respectively~
could be arranged on either side of the tunnel 13.
The graphs shown in Figures 3 and 4 clearly show the advantages ~ ;
o~tained by means of the method according to the invention. In these graphs, T is the air temperature, To is the surace temperature of the glass - ~;
products to be treated, TM is the average temperature of the products and a T is the difference between the surface temperature To and the average temperature TM of the glass products during traversing successive heating zones Zl, Z2 and Z3.
Figure 3 shows the temperature variation if the glass products are treated according to the known method; from this it appears that the surface ~ ,~
temperature T0 as well as the temperature difference ~T of the glass pro- ;
ducts fluctuates considerably both within the same zone and between succes-sive zones, which means that large temperature differences occur betweèn the inside and the outside of the products.
Figure 4 shows the situation if the products are treated with the ~ ;
method according to the in~ention. Both the surface temperature To and the average temperature TM vary linearly, as a result of a constant heating rate, the temperature difference ~T reaching a constant value in a comparatively short period of time.
In the cooling zone, the cooling of the products occurs in a similar manner with a gradually decreasing temperature variation and with a stabilised temperature difference.
~-'IIN. 7675 19.~ 75 ~7~
furnace hclving a coInparatively large number of zoIles; a low coeff`icient of heat transeer has the drawback that large -teIllperature d:ifferences across -the surface occur in products hav:ing large differences in wall thickness, as a result of which extra stresses occur in the product.
It :is the object of the invention to provide a methocI which does not exhibit -the said drawbacks and which enables the products to be treated to be subjected to a gradually occurring -temperature variation during their transport through the tunnel furnace.
According to the invention, this object is achieved main:Ly :in that, vie~Yed in the direction of transport, the air flow :Ln each zone has a continuously variable velocity.
Since the velocity of the air flow in a given zone is variable, the coefficient of heat transfer in said zone also varies. Since the coefficient of heat transfer is variable~ temperature variations of the products within the same zone take place gradually.
The measure according -to the invention may be used both for heating glass products and for cooling because with these treatments extra stresses are apt to occur in the products.
A preferred embodiment of the method according to the invention is charac-terized by such a distribution of the velocity of the air flow that temperature variations of the products occur at a constant rate. By a suitable choice of the velocity of the air flow within the same zone, the coefficient of hea-t transfer can be varied so that a linearly varying temperature gradient is main-tained in said zone, ~7~5~
temperature variations of the produc~s taking place throughout the length of the zone at a constant rate.
In another preferred embodiment of the method according to the invention the velocity of the air flow increases gradually in each zone. As a result of this measure a gradually increasing coefficient of heat transfer and a gradual temperature increase or temperature decrease o the pToducts are realized within each zone of the heating track and/or the cooling track of the tunnel furnace.
In accordance with this invention there is provided a tunnel furnace for the thermal treatment of an associated article which comprises: a housing defining a tunnel which includes a plurality of zones, each zone having an inlet and an outlet for the associated article, the inlet for the associated article for each zone after the first zone being the outlet of the preceding zone, a transport apparatus for the transport of the associated articles in a longitudinal direc-tion through said tunnel from an inlet side to an outlet side of each successive zone, each zone extending ov0r longitudinal section of said tunnel, means for generating an airflow in a direction transverse to the longitudinal direction of the tunnel with each zone and means for controlling the temperature of the airflow in each zone, said housing including first and second walls having therein flow apertures, said first and second walls in any one zone being disposed in opposed relationship, each of said walls being disposed in generally parallel relationship to said longitudinal direction, ~he total area of the flow apertures on opposed sides of any one zone being equal, the area of the flow apertures in each zone being inversely related to the longitudinal distance from the outlet of each of said zones.
The tunnel furnace~ may be construc*ed as a cooling furnace - having only a cooling section for the controlled cooling of blown or moulded glass products which are still hot.
:
. 7~75 19.6.1975 ~7~5~
Such -t~lnneL furnaces usually comprise botll a heating section and a cool:ing ~section, already cooled glass products being first heated and then cooled agaln. In special cases such a tunnel furnace may be constructed only as a heating furnace.
The invention will ~e described in greater detail with reference to the drawing. In the clrawing:
Figure 1 is a longitudinal sectional view of an embodiment o~ the tunnel furnace according to the invention taken on the line I-I of Fig. 2;
Figure 2 is a cross sectional view o~ the tunnel furnace talcen on the line II-II of Fig. 1;
Figures 3 ancl l~ show time temperature graphs.
The tunnel furnace 1 shown in I~ ures 1 and 2 comprises a heating section 3 which is subdivided into 1S heating zones 5, and a cooling section 7 which is divided into cooling zones 9. A -transport device, in the embodiment shown an endless transport belt 11 of metal grating work, serves for the transport of glass products to be treated thermally through the tunnel 13 of the furnace in the direction denoted by the arrow X from the inlet side to the out]et side of the furnace. The zones 5 and 9 each comprise a fan 15, a recirculation duct 17, and a number o control-lable heating elements 19. A partition 21 having flow apertures 23 is provided in each heating zone on the lower 2$ side and on the upper side of the tunnel 13. Partitions 25 having flow apertures 27 are provided in a corresponding manner in -the cooling zones 9.
By means of the fan 15, an airflow A is main-tained in each zone 5 and 9, in a direction transverse to .
Pl-IN. 7~75 1~.6.1~75 ~7~1951 the d.il~cc-tion of` tran.spor-t of the procIucts, vertically upwards through the r10~ apertures 23 ancl 27 of the partitions 21 and 25 and through -the transpor-t belt 11. Via the recirculation duc-t l7, said air is conveyed bacl~ to the lower side of the zones. The a:ir, during i-ts f:low through the recirculation duct 17, is hea-ted again at the desired temperature by means of the controllable heating elements 19. The air temperature is indivldually controllable in each zone independently of the temperature control in the other zones. As is shown in the drawing, the cross-section of the flow aperture 23 in the partit:ions 21 which are placed in the heating zones 5, gradually increases viewed in the di.rection of` transport X.
As a result of this the velocity of` the air flow be-tween the two parti-tions, viewed in the direction of transport X, also increases as a result of` which the coefficient of heat transfer becomes larger in the direction of transport. By a suitable choice of the cross-section of the flow apertures 21, the variation of the coefficient of heat transfer can be adapted to the thickness of the glass products to be treated in such manner that a constant heating rate of the prr,duct is obtained.
A gradual cooling of the product is obtained in a simi].ar manner in the zones 9 of the cooling section 7 in that the velocity of the air flow as well as the coefficient of hea-t transfer, viewed in the direction of transport, gradually increases in each zone. For that purpose, the flow apertures 27 in the partitions 25 which are placed in the - cooling zones 9 are also proportioned so tha-t their cross-section, viewed in the direction of t:ransport, increases ~197~gS~
gradually.
In the embodiment the partitions 21 and 25, respectively, are provid-ed on the lower side and on the upper side of each zone. In a similar, althOugh less favourable, manner, the partitions 21 and 25, respectively~
could be arranged on either side of the tunnel 13.
The graphs shown in Figures 3 and 4 clearly show the advantages ~ ;
o~tained by means of the method according to the invention. In these graphs, T is the air temperature, To is the surace temperature of the glass - ~;
products to be treated, TM is the average temperature of the products and a T is the difference between the surface temperature To and the average temperature TM of the glass products during traversing successive heating zones Zl, Z2 and Z3.
Figure 3 shows the temperature variation if the glass products are treated according to the known method; from this it appears that the surface ~ ,~
temperature T0 as well as the temperature difference ~T of the glass pro- ;
ducts fluctuates considerably both within the same zone and between succes-sive zones, which means that large temperature differences occur betweèn the inside and the outside of the products.
Figure 4 shows the situation if the products are treated with the ~ ;
method according to the in~ention. Both the surface temperature To and the average temperature TM vary linearly, as a result of a constant heating rate, the temperature difference ~T reaching a constant value in a comparatively short period of time.
In the cooling zone, the cooling of the products occurs in a similar manner with a gradually decreasing temperature variation and with a stabilised temperature difference.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A tunnel furnace for the thermal treatment of an associated article which comprises: a housing defining a tunnel which includes a plurality of zones, each zone having an inlet and an outlet for the associated article, the inlet for the associated article for each zone after the first zone being the outlet of the preceding zone, a transport apparatus for the transport of the associated articles in a longitudinal direction through said tunnel from an inlet side to an outlet side of each successive zone, each zone extending over longitudinal section of said tunnel, means for generating an airflow in a direction transverse to the longitudinal direction of the tunnel with each zone and means for controlling the temperature of the air-flow in each zone, said housing including first and second walls having therein flow apertures, said first and second walls in any one zone being disposed in opposed relationship, each of said walls being disposed in generally parallel relationship to said longitudinal direction, the total area of the flow apertures on opposed sides of any one zone being equal, the area of the flow apertures in each zone being inversely related to the longitudinal distance from the outlet of each of said zones.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7412568A NL7412568A (en) | 1974-09-24 | 1974-09-24 | METHOD AND TUNNEL OVEN FOR THE THERMAL TREATMENT OF GLASS PRODUCTS, ESPECIALLY OF BALLOONS FOR IMAGE TUBES. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070951A true CA1070951A (en) | 1980-02-05 |
Family
ID=19822151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA235,899A Expired CA1070951A (en) | 1974-09-24 | 1975-09-19 | Method and tunnel furnace for the thermal treatment of glass products, in particular envelopes for display tubes |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5157706A (en) |
| BE (1) | BE833723A (en) |
| BR (1) | BR7506112A (en) |
| CA (1) | CA1070951A (en) |
| DE (1) | DE2542044A1 (en) |
| FR (1) | FR2325613A1 (en) |
| GB (1) | GB1495190A (en) |
| NL (1) | NL7412568A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56162451A (en) * | 1980-05-19 | 1981-12-14 | Hitachi Ltd | Manufacture of color-picture tube and its device |
| GB2152647B (en) * | 1984-01-07 | 1987-07-08 | Stein Atkinson Strody Ltd | Furnace with sub-zones having air flow control device |
| JPH01169314U (en) * | 1988-05-20 | 1989-11-29 | ||
| JP2521386B2 (en) * | 1991-10-31 | 1996-08-07 | 日本ファーネス工業株式会社 | Steel heating furnace |
| DE19721334C2 (en) * | 1997-05-22 | 1999-07-29 | Horn Glasanlagenbau Gmbh & Co | Cooling track, especially for cooling glass objects |
| RU2151109C1 (en) * | 1998-03-24 | 2000-06-20 | Белгородская государственная технологическая академия строительных материалов | Method of annealing glass in lehr |
| CN104016576A (en) * | 2014-06-24 | 2014-09-03 | 中国建材国际工程集团有限公司 | Constant temperature reduction speed cooling method and device of forced convection area of lier |
| CN112050630B (en) * | 2019-06-06 | 2022-12-30 | 欧佩德伺服电机节能系统有限公司 | Kiln capable of effectively utilizing heat energy and implementation method |
-
1974
- 1974-09-24 NL NL7412568A patent/NL7412568A/en not_active Application Discontinuation
-
1975
- 1975-09-19 GB GB3858875A patent/GB1495190A/en not_active Expired
- 1975-09-19 CA CA235,899A patent/CA1070951A/en not_active Expired
- 1975-09-20 JP JP11315875A patent/JPS5157706A/en active Pending
- 1975-09-20 DE DE19752542044 patent/DE2542044A1/en not_active Withdrawn
- 1975-09-22 BR BR7506112A patent/BR7506112A/en unknown
- 1975-09-23 BE BE160298A patent/BE833723A/en unknown
- 1975-09-23 FR FR7529103A patent/FR2325613A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5157706A (en) | 1976-05-20 |
| FR2325613A1 (en) | 1977-04-22 |
| BR7506112A (en) | 1976-08-03 |
| BE833723A (en) | 1976-03-23 |
| GB1495190A (en) | 1977-12-14 |
| DE2542044A1 (en) | 1976-04-01 |
| NL7412568A (en) | 1976-03-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |