CA1072338A - Glass manufacture - Google Patents
Glass manufactureInfo
- Publication number
- CA1072338A CA1072338A CA220,513A CA220513A CA1072338A CA 1072338 A CA1072338 A CA 1072338A CA 220513 A CA220513 A CA 220513A CA 1072338 A CA1072338 A CA 1072338A
- Authority
- CA
- Canada
- Prior art keywords
- boom
- trough
- glass
- furnace
- furnace according
- 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
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
- C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
- C03B5/18—Stirring devices; Homogenisation
- C03B5/187—Stirring devices; Homogenisation with moving elements
Abstract
GLASS MANUFACTURE
Abstract of the Disclosure A trough-shaped glass molting furnace is provided, approximately mid-way of the length of the trough, with a partial barrier to the downstream flowing surface current of glass. The barrier is suspended from the roof of the furnace and extends over the central portion of the width of the furnace only part-way toward the sides thereof and only part-way from the surface of the glass bath to the bottom. The barrier may be made of station-ary or rotating refrigerated loop-shaped conduits.
Abstract of the Disclosure A trough-shaped glass molting furnace is provided, approximately mid-way of the length of the trough, with a partial barrier to the downstream flowing surface current of glass. The barrier is suspended from the roof of the furnace and extends over the central portion of the width of the furnace only part-way toward the sides thereof and only part-way from the surface of the glass bath to the bottom. The barrier may be made of station-ary or rotating refrigerated loop-shaped conduits.
Description
Z.3~8 The present invention pertains to a method and apparatus for the manufacture of glass, especially flat glass, and more particularly to a glass melting furnace and a method of operating the same. Glass melting furnaces of one known form comprise essentially two parts: firstly, a high tempe-rature melting and refining zone, at the upstream end of which the raw materials are introduced so as to be melted by heating means such as burners and, secondly, a somewhat cooler conditioning zone downstream of the first, in which the glass is brought to a suitable temperature for withdrawal at the downstream end of that second zone, as a preliminary to subsequent operations.
The currents which develop in the molten glass in ; the furnace, as convection currents by reason of temperature differences from point to point and also due to the withdrawal of glass at ~he downstream end, produce and overall streaming of the glass through the furnace. Especially in the conditioning zone however there develops a downstream current which occupies approximately the uppermost one-third of the depth of the glass bath, beneath which a return or upstream current exists occupying the deeper two-thirds of the bath depth.
It has been heretofore proposed to introduce into .
the furnace mëchanical or thermal barriers, fixed or floating, which extend across the entire width of the furnace so as to separate the glass bath into two parts and in particular to ~` block flow of the surface layers, and to permit withdrawal of glass from the cooler, bottom portions of the bath. One such construction is shown in U.S. patent No. 2,081,595.
It has further been proposed to force the glass to .
A~
~ bm.
~ , flow through openings,disposed through such barriers deep beneath~the surface of the bath, and it has also been proposed to effect a stirring of a downs-tream flow which has been mechanically separated by means of a partition from the returning upstream flow. The partition is however subjected to corrosion and its replacement is difficult and costly.
It has also been proposed in U.S. patent No. 1,923,942 to provide a glass melting furnace with forebays extending therefrom, within which the glass is caused to flow in a circular or oval pattern around a central cooled portion of the forebay by the action of glass gathering molds which are ,~ .
carried across an exposed gathering area at the outer limit of the forebay. One means to cool the central area of the fore-bay proposed in this patent is a box-like structure of refractory material which extends downwardly through an open-ing in the roof over the forebay, with the lower surface of ~h'at structure eith'e'r above or below the level of the glass, air or otheL heat regulating medium being circulated through the structure. This structure is concerned however only with maintaining the finished glass at the proper temperature' at~the, actual point of its removal from the furnace, The applicant has found that the quality of the glass being made can be improved by blocking, by means of a barrier or boom extending only part-way crosswise of the furnace, the center portion of the surface downs~ream glass current and deflecting it downward to be joined with the underlying upstream return current. The boom permits however a perfectly free downstream flow of the lateral or e~ge portions of the bath, in amount sufficient to meet the needs for withdrawal of glass for use and also to permit .
' ~ - 2 -bm.
~7;~:338 ,~
continued existence of the return current even downstream of the boom.
The position of the boom must be correctly chosen.
A certain degree of devitrification of the melted glass particles may take place downstream of the boom, after contact with the boom structure, and it is necessary that the temperature of the bath downstream of the boom be sufficiently high so that these crystalline particles will be completely remelted there before `~ :
`
- 2a -bm.
.' , .
.
; ;
~'; ' :.. ' ;
:` ' ,. ~ - ' .
3~8 withdrawal fram the furnace.
In addition, the visc~sity of the glass at the location of the koom is of importan oe . In order that the hydrodynamic action of the bcom shall be as effective as possible, the viscosity of the glass in the vicinity thereof should not exceed 102 5 or 316 poises.
Ihe boom provided by the invention is thus particulæ ly effective when the bemperature of the glass is not belcw 1300C., for the glass compositions of ordinary ccmmerce.
In acc~rdance with the invention, the boom is disposed in a mid-portion of a cross-section of the bath, desirably across the axis or median line of the sufaoe thereof. In order to avoid all in~erference with the downstream flow along the edges of the ~th at the surfaoe there-of and with the upstream flow at the bottc~, the boom is made up of elements of structure which are suspended frcm the loof or crGwn of the fu~nace. Its length crosswise of the furnace depends on its position lengthwise of the furnaoe and amounts substantially to the ~7idth of that portion of the dcwnstream surfaae c;urrent which it is desired to in~errupt.
In a preferred eniodiment of the invention, the boom is given a length between one-quarter and two thirds the cross-sectional width of the bath and preferably between one-third and one-half thereof.
The vertical eXtenSiQn and, in a pre~erred emkodime~t, the tempera~une of the bocm are adjusted-so-as to pro wke a return upstream o~
the desired fraction of the downstream current otherwise existing at the location of the boom. Desirably the boom extends vertically or the bath dcwnwards fr~m the surfa oe thereof between about one-fifth and one-half of the glass bath depth. It may be deeper in the oenter portion than at ~he la~eral ends thereof and may thus have at its lower limit a downwardly oQnvex :
.
:' .. .
'`'' : ': . ' . :
:
profile.
Advantageously the boom is made of separate parts which act both as a discontinuous mechanical obstacle and as an obstacle by thermal action on the surrounding mass of glass.
The boom of the invention thus possesses two independently var-iable properties or parameters which can be selected for optimum effect.
Desirably, the boom is thus made up of refrigerated tubes or conduits having a loop or hairpin shape, the tubes lQ being mounted to permit adjustment of their orientation. Addi-tionally, it is possible to rotate these members so as to superimpose a mixing effect on the blockage effect.
This supplementary homogenization action mav be desirable when the furnace is being operated with maximum throughput. It also may effect a desirable economy of time in the production of colored glasses upon passage from one ` color to another, and it may aid in surmounting perturbations or irregularities of flow which sometimes occur when there are excessive departures from homogeneity in the starting materials.
It will be understood that the foregoing includes a general description of secondary as well as primary aspects of the invention. The primary aspects of the invention are defined below.
:
The apparatus of the present invention is defined as a glass melting furnace comprising means defining a trough, ; a boom extending part-way crosswise of the trough at a location intermediate the upstream and downstream ends of the trough, the boom being disposed above the bottom of the trough, a ~ `
roof above the trough, and means dependent from the roof to `. 30 support the boom.
u The method of the present invention is defined as , ~ a method of conditioning molten glass which comprises flowing . .
~Y rw ~
. ' : ............... : . . . : ~
, ~ '7~
., the molten qlass lengthwise of a trou~h, between upstream . and downstream ends thereo~, obstructing at a location between those ends a barrier, flow-impeding means extending . partway crosswise of the trough from the surface of the glass : part-way of the bottom of the trough, and circulating a cooling fluid through the flow-impeding means.
Brief Description of the Drawings The invention will now be further described in terms of a number of presently preferred embodiments and by reference to the accompanying drawings in which:
FIG. 1 is a plan diagrammatic view of a melting furnace in accordance with the invention as seen beneath the roof thereof;
.~ FIG. 2 is a longitudinal vertical axial sectional ~` view through the furnace of F~G. 1, taken on the line 2-2 of : FIG. l;
FIG. 3 is a transverse sectional view of the furnace of FIGS. 1 and 2, taken on the line 3-3 of FIG. 2 but showing roof thereof;
FIG. 4 is a view similar to that of FIG. 3 but illustra-.~
~.
`''' .
.,, - 4a -. ~ r~7/ ~:
, .
33~
ting a modified form of furnace in accordance with the invention:
FIG. 5 is a diagrammatic representation of a boom according to the invention made up of plural elements;
FIG. 6 is a plan diagrammatic view of the boom of FIG. 5 with, however, the boom elements shown in inclined position and showing also the pattern of glass flow in the vicinity of the boom;
FIG. 7 is a sectional view similar to FIG. 3 but showing still another form of furnace in accordance with the invention;
FIG. 8 is a perspective view of a boom made up of rotatable elements.
FIG. 9 is a diagram illustrating the support of the elements of the boom of FIG. 8 from the roof of the furnace;
and FIG. 10 is a diagram showing the support and rotating means for one of those elements.
Description of Preferred Embodiments ;, 20 The furnace of FIGS. 1 to 3 includes side walls 50 and 51, ena walls 52 and 53, a bottom 54, and a roof 55.
Heating means such as burners 56 are distributed lengthwise of the trough thus formed and maintain a suitable distr~bution ` or gradient of temperatures lengthwise of the furnace, i.e.
~` from left to right in FIG. 1, with the upstream zone 1 being ,~ hotter and constituting a melting and refining zone, whereas a cooler zone 2, downstream of zone 1, may be regarded as a `',!; conditioning or tempering zone. The raw materials are charged in at the upstream, left end as indicated at 3, and ;~ 30 withdrawal of the prepared glass is effected at the downstream '' . :
- bm/
. :
. ` . .
~OqZ33 right end 4, over a sill 57.
A boom 5 according to the invention is disposed in the bath on the central portion of the downstream current, with the burners 56 being partly upstream and partly down-stream of the position of the boom. As indicated in FIG. 1, the boom extends across the median line or longitudinal axis of the furnace, indicated as the section line 2-2 in FIG. 1.
The boom operates on approximately two-fifths of the width of the bath so that lateral downstream or edge currents 6 are permitted to flow unobstructedly toward the outlet end.
FIG. 2 shows the vertical position of the boom 5, extending downwardly approximately to the upper limit of the ` return glass current 7.
FIG. 3 is a transverse sectional view of the furnace ~ of FIGS. 1 and 2. The boom may comprise a plurality of ; ~ elements, diagrammatically and collectively indicated at 8, ; supported by tubes 9 which are cooled by water jackets 10 in order to prevent corrosion thereof at the high temperatures obtaining in the furnace.
FIG. 4 illustrates another embodiment of the furnace of the invention in which the boom takes the shape of a serpentine coil, disposed similarly however to the boom of FIGS. 1 to 3 in the central downstream flow portion of the bath cross-section. The operation of this boom is to increase the viscosity of the glass in the vicinity thereof so that that portion of the downstream current of glass which ~;
encounters it strikes a chilled zone and is entrained by the deeper portions of the bath so as to be carried upstream again.
FIGS. 5 and 6 illustrate a plural-element, '' ' ' bm/
.
discontinuous boom in accordance with the invention made up of metallic tubes 13 which are cooled by water circulated through them via suspensory portions 12 of the kubes. The tubes may thus be formed into rectangular or other 1QP
shapes as indicated. These tubes are effective as a boom ox barrier primarily by thermal action. They cool a portion of the bath in the region which they occupy and thereby produce a substantially continuous barrier or retarding screen over that region Each loop can be individually controlled in orientation by rotation about a vertical axis.
By such rotation the boom acquires, as indicated in FIG. 6, a thickness in the direction of flow lengthwise of the furnace which is greater than the thlckness of the loops themselves. The resulting action may be similar to that of a series of inclined shutters.
The arrows 14 in FIG. 6 show that the side flow - (at the surface of the bath) continues downstream for feed ~ of the plunger or other glass withdrawal mechanism of the ;
furnace (not shown) whereas the central portion of the downstream surface current, encountering the boom formed ~y the loops 13, is turned backward to join the upstream current at the bottom of the bath. The arrows 15, while shown in a horizontal plane, are intended diagrammatically to indicate that the central surface portion of the current is turned downwardly and then back upstream.
The tubes 13 of FIG. 5 may be mounted for adjust-~` ment in height so as to permit achievin~ optimum form of ~r~ the boom. Those nearest the side walls of the furnace may ,~ 30 be less deeply immersed in the glass bath than those in the ;`~ middle so as to provide a more effective action in the :'' . .
: _ 7 bm/
':
. . .
middle portion than at the edges.
FIG. 7 illustrates still another embodi~ent of the furnace of the invention including an essentially thermal boom made up of bubbling elements 16 from the roof. Such elements are known in and of themselves. They comprise tubes, usually disposed with an open end near the bottom of the furnace, through which bubbles can be blown into the mass of glass so as to effect a mixing or stirring thereof.
According to the present invention instead, each tube for the supply of gas bubbles extends down into the bath only to the dividing line, approximately between the upstxeam and downstream currents, the emission of bubbles being effected over the desired fraction of the width of the furnace by the provision of a suitable member of bubbling tubes.
The rate of production of bubbles must be a sub-; stantial one in order to achieve by partial blockage of the downstream flow a return thereof as part of the deeper upstream flow.
Control of the flow pattern of the glass in ~,~ accordance with the invention is particularly advantageous .
for the manufacture of glass in furnaces operating at or near capacity. In such a case, the hydrodynamic flow pattern which is developed in the bath by reason of the geometry of the furnace, the rate of glass withdrawal and the various th~rmally induced currents of convection may result in a flow pattern which departs materially from the optimum for the desired quality of glass. Corrective action may then be taken, especially with respect to the central downstream portions of the downstream cuxrent flow by imposing on them bm/
' . . .
%3~
a modified flow pattern by interposition of a boom in accordance with the invention. In this way, a more uniform flow pattern can be obtained with a resulting more homogene-ous quality for the glass.
FIG. 8 is a figure similar to FIG. 6 but showing in perspective another boom according to the invention made up of individually adjustable and rotatable loop-shaped cooled tubes 17. The source of coolant, which may include a water-tight rotating joint for each tube, is not shown. The tubes may have each approximately the shape of a twisted figure eight, the upper and lower lobes of which are crosswise to each other. Means, such as for example those shown in FIG. 10, may be pro~ided to rotate the tubes so that they will function as stirring or agitating as well as cooling and blocking elements.
Each of the tubes 17, when rotated, carries with ;~. .
it a quantity of glass whose viscosity is increased by the cooling effect exerted by the tube.
The downstream glass current engages the tubes 17 and they therefore play a double role of blocking and mixing, varying directly with their speed of rotation.
' The number of tubes employed depends upon the ~ lateral width desired for the boom. Speed may vary from 0 ,~ to a maximum at which bubbles become impxisoned in the glass ~` or at which cavitation takes place.
The speed of the rotation of the tubes may, for example~ be ten revolutions per minute, corresponding to a , ,.
: linear speed at the radially outermost portions of the tubes amounting to about 300 meters per hour.
~` 30 The tubes 17 may be of such size and may be so .
9, bm/
.-. - ~ .
~.
. . ~
cooled as to extract on the average from the glass a quanti~y of heat between 50 and 100 therms per hour, and preferably of the order of 75 therms per hour. This requires at least 25 liters per minute of water flow and preferably some 50 liters per minute for a tube, the diameter of whose loop is of the oxder of from 0.25 to 0.30 meters.
- - The direction of ro~ation of the stirring elements or tubes may be chosen to achieve the following effects:
l. To gather the glass toward the axis or median line of the furnace. In this case, the stirring elements on each side of that median line will rotate in the same direction, those on one side rotating in the direction opposite to those - on the other side and the direction of motion being toward the median line on the upstream side of the stirring elements.
The currents which develop in the molten glass in ; the furnace, as convection currents by reason of temperature differences from point to point and also due to the withdrawal of glass at ~he downstream end, produce and overall streaming of the glass through the furnace. Especially in the conditioning zone however there develops a downstream current which occupies approximately the uppermost one-third of the depth of the glass bath, beneath which a return or upstream current exists occupying the deeper two-thirds of the bath depth.
It has been heretofore proposed to introduce into .
the furnace mëchanical or thermal barriers, fixed or floating, which extend across the entire width of the furnace so as to separate the glass bath into two parts and in particular to ~` block flow of the surface layers, and to permit withdrawal of glass from the cooler, bottom portions of the bath. One such construction is shown in U.S. patent No. 2,081,595.
It has further been proposed to force the glass to .
A~
~ bm.
~ , flow through openings,disposed through such barriers deep beneath~the surface of the bath, and it has also been proposed to effect a stirring of a downs-tream flow which has been mechanically separated by means of a partition from the returning upstream flow. The partition is however subjected to corrosion and its replacement is difficult and costly.
It has also been proposed in U.S. patent No. 1,923,942 to provide a glass melting furnace with forebays extending therefrom, within which the glass is caused to flow in a circular or oval pattern around a central cooled portion of the forebay by the action of glass gathering molds which are ,~ .
carried across an exposed gathering area at the outer limit of the forebay. One means to cool the central area of the fore-bay proposed in this patent is a box-like structure of refractory material which extends downwardly through an open-ing in the roof over the forebay, with the lower surface of ~h'at structure eith'e'r above or below the level of the glass, air or otheL heat regulating medium being circulated through the structure. This structure is concerned however only with maintaining the finished glass at the proper temperature' at~the, actual point of its removal from the furnace, The applicant has found that the quality of the glass being made can be improved by blocking, by means of a barrier or boom extending only part-way crosswise of the furnace, the center portion of the surface downs~ream glass current and deflecting it downward to be joined with the underlying upstream return current. The boom permits however a perfectly free downstream flow of the lateral or e~ge portions of the bath, in amount sufficient to meet the needs for withdrawal of glass for use and also to permit .
' ~ - 2 -bm.
~7;~:338 ,~
continued existence of the return current even downstream of the boom.
The position of the boom must be correctly chosen.
A certain degree of devitrification of the melted glass particles may take place downstream of the boom, after contact with the boom structure, and it is necessary that the temperature of the bath downstream of the boom be sufficiently high so that these crystalline particles will be completely remelted there before `~ :
`
- 2a -bm.
.' , .
.
; ;
~'; ' :.. ' ;
:` ' ,. ~ - ' .
3~8 withdrawal fram the furnace.
In addition, the visc~sity of the glass at the location of the koom is of importan oe . In order that the hydrodynamic action of the bcom shall be as effective as possible, the viscosity of the glass in the vicinity thereof should not exceed 102 5 or 316 poises.
Ihe boom provided by the invention is thus particulæ ly effective when the bemperature of the glass is not belcw 1300C., for the glass compositions of ordinary ccmmerce.
In acc~rdance with the invention, the boom is disposed in a mid-portion of a cross-section of the bath, desirably across the axis or median line of the sufaoe thereof. In order to avoid all in~erference with the downstream flow along the edges of the ~th at the surfaoe there-of and with the upstream flow at the bottc~, the boom is made up of elements of structure which are suspended frcm the loof or crGwn of the fu~nace. Its length crosswise of the furnace depends on its position lengthwise of the furnaoe and amounts substantially to the ~7idth of that portion of the dcwnstream surfaae c;urrent which it is desired to in~errupt.
In a preferred eniodiment of the invention, the boom is given a length between one-quarter and two thirds the cross-sectional width of the bath and preferably between one-third and one-half thereof.
The vertical eXtenSiQn and, in a pre~erred emkodime~t, the tempera~une of the bocm are adjusted-so-as to pro wke a return upstream o~
the desired fraction of the downstream current otherwise existing at the location of the boom. Desirably the boom extends vertically or the bath dcwnwards fr~m the surfa oe thereof between about one-fifth and one-half of the glass bath depth. It may be deeper in the oenter portion than at ~he la~eral ends thereof and may thus have at its lower limit a downwardly oQnvex :
.
:' .. .
'`'' : ': . ' . :
:
profile.
Advantageously the boom is made of separate parts which act both as a discontinuous mechanical obstacle and as an obstacle by thermal action on the surrounding mass of glass.
The boom of the invention thus possesses two independently var-iable properties or parameters which can be selected for optimum effect.
Desirably, the boom is thus made up of refrigerated tubes or conduits having a loop or hairpin shape, the tubes lQ being mounted to permit adjustment of their orientation. Addi-tionally, it is possible to rotate these members so as to superimpose a mixing effect on the blockage effect.
This supplementary homogenization action mav be desirable when the furnace is being operated with maximum throughput. It also may effect a desirable economy of time in the production of colored glasses upon passage from one ` color to another, and it may aid in surmounting perturbations or irregularities of flow which sometimes occur when there are excessive departures from homogeneity in the starting materials.
It will be understood that the foregoing includes a general description of secondary as well as primary aspects of the invention. The primary aspects of the invention are defined below.
:
The apparatus of the present invention is defined as a glass melting furnace comprising means defining a trough, ; a boom extending part-way crosswise of the trough at a location intermediate the upstream and downstream ends of the trough, the boom being disposed above the bottom of the trough, a ~ `
roof above the trough, and means dependent from the roof to `. 30 support the boom.
u The method of the present invention is defined as , ~ a method of conditioning molten glass which comprises flowing . .
~Y rw ~
. ' : ............... : . . . : ~
, ~ '7~
., the molten qlass lengthwise of a trou~h, between upstream . and downstream ends thereo~, obstructing at a location between those ends a barrier, flow-impeding means extending . partway crosswise of the trough from the surface of the glass : part-way of the bottom of the trough, and circulating a cooling fluid through the flow-impeding means.
Brief Description of the Drawings The invention will now be further described in terms of a number of presently preferred embodiments and by reference to the accompanying drawings in which:
FIG. 1 is a plan diagrammatic view of a melting furnace in accordance with the invention as seen beneath the roof thereof;
.~ FIG. 2 is a longitudinal vertical axial sectional ~` view through the furnace of F~G. 1, taken on the line 2-2 of : FIG. l;
FIG. 3 is a transverse sectional view of the furnace of FIGS. 1 and 2, taken on the line 3-3 of FIG. 2 but showing roof thereof;
FIG. 4 is a view similar to that of FIG. 3 but illustra-.~
~.
`''' .
.,, - 4a -. ~ r~7/ ~:
, .
33~
ting a modified form of furnace in accordance with the invention:
FIG. 5 is a diagrammatic representation of a boom according to the invention made up of plural elements;
FIG. 6 is a plan diagrammatic view of the boom of FIG. 5 with, however, the boom elements shown in inclined position and showing also the pattern of glass flow in the vicinity of the boom;
FIG. 7 is a sectional view similar to FIG. 3 but showing still another form of furnace in accordance with the invention;
FIG. 8 is a perspective view of a boom made up of rotatable elements.
FIG. 9 is a diagram illustrating the support of the elements of the boom of FIG. 8 from the roof of the furnace;
and FIG. 10 is a diagram showing the support and rotating means for one of those elements.
Description of Preferred Embodiments ;, 20 The furnace of FIGS. 1 to 3 includes side walls 50 and 51, ena walls 52 and 53, a bottom 54, and a roof 55.
Heating means such as burners 56 are distributed lengthwise of the trough thus formed and maintain a suitable distr~bution ` or gradient of temperatures lengthwise of the furnace, i.e.
~` from left to right in FIG. 1, with the upstream zone 1 being ,~ hotter and constituting a melting and refining zone, whereas a cooler zone 2, downstream of zone 1, may be regarded as a `',!; conditioning or tempering zone. The raw materials are charged in at the upstream, left end as indicated at 3, and ;~ 30 withdrawal of the prepared glass is effected at the downstream '' . :
- bm/
. :
. ` . .
~OqZ33 right end 4, over a sill 57.
A boom 5 according to the invention is disposed in the bath on the central portion of the downstream current, with the burners 56 being partly upstream and partly down-stream of the position of the boom. As indicated in FIG. 1, the boom extends across the median line or longitudinal axis of the furnace, indicated as the section line 2-2 in FIG. 1.
The boom operates on approximately two-fifths of the width of the bath so that lateral downstream or edge currents 6 are permitted to flow unobstructedly toward the outlet end.
FIG. 2 shows the vertical position of the boom 5, extending downwardly approximately to the upper limit of the ` return glass current 7.
FIG. 3 is a transverse sectional view of the furnace ~ of FIGS. 1 and 2. The boom may comprise a plurality of ; ~ elements, diagrammatically and collectively indicated at 8, ; supported by tubes 9 which are cooled by water jackets 10 in order to prevent corrosion thereof at the high temperatures obtaining in the furnace.
FIG. 4 illustrates another embodiment of the furnace of the invention in which the boom takes the shape of a serpentine coil, disposed similarly however to the boom of FIGS. 1 to 3 in the central downstream flow portion of the bath cross-section. The operation of this boom is to increase the viscosity of the glass in the vicinity thereof so that that portion of the downstream current of glass which ~;
encounters it strikes a chilled zone and is entrained by the deeper portions of the bath so as to be carried upstream again.
FIGS. 5 and 6 illustrate a plural-element, '' ' ' bm/
.
discontinuous boom in accordance with the invention made up of metallic tubes 13 which are cooled by water circulated through them via suspensory portions 12 of the kubes. The tubes may thus be formed into rectangular or other 1QP
shapes as indicated. These tubes are effective as a boom ox barrier primarily by thermal action. They cool a portion of the bath in the region which they occupy and thereby produce a substantially continuous barrier or retarding screen over that region Each loop can be individually controlled in orientation by rotation about a vertical axis.
By such rotation the boom acquires, as indicated in FIG. 6, a thickness in the direction of flow lengthwise of the furnace which is greater than the thlckness of the loops themselves. The resulting action may be similar to that of a series of inclined shutters.
The arrows 14 in FIG. 6 show that the side flow - (at the surface of the bath) continues downstream for feed ~ of the plunger or other glass withdrawal mechanism of the ;
furnace (not shown) whereas the central portion of the downstream surface current, encountering the boom formed ~y the loops 13, is turned backward to join the upstream current at the bottom of the bath. The arrows 15, while shown in a horizontal plane, are intended diagrammatically to indicate that the central surface portion of the current is turned downwardly and then back upstream.
The tubes 13 of FIG. 5 may be mounted for adjust-~` ment in height so as to permit achievin~ optimum form of ~r~ the boom. Those nearest the side walls of the furnace may ,~ 30 be less deeply immersed in the glass bath than those in the ;`~ middle so as to provide a more effective action in the :'' . .
: _ 7 bm/
':
. . .
middle portion than at the edges.
FIG. 7 illustrates still another embodi~ent of the furnace of the invention including an essentially thermal boom made up of bubbling elements 16 from the roof. Such elements are known in and of themselves. They comprise tubes, usually disposed with an open end near the bottom of the furnace, through which bubbles can be blown into the mass of glass so as to effect a mixing or stirring thereof.
According to the present invention instead, each tube for the supply of gas bubbles extends down into the bath only to the dividing line, approximately between the upstxeam and downstream currents, the emission of bubbles being effected over the desired fraction of the width of the furnace by the provision of a suitable member of bubbling tubes.
The rate of production of bubbles must be a sub-; stantial one in order to achieve by partial blockage of the downstream flow a return thereof as part of the deeper upstream flow.
Control of the flow pattern of the glass in ~,~ accordance with the invention is particularly advantageous .
for the manufacture of glass in furnaces operating at or near capacity. In such a case, the hydrodynamic flow pattern which is developed in the bath by reason of the geometry of the furnace, the rate of glass withdrawal and the various th~rmally induced currents of convection may result in a flow pattern which departs materially from the optimum for the desired quality of glass. Corrective action may then be taken, especially with respect to the central downstream portions of the downstream cuxrent flow by imposing on them bm/
' . . .
%3~
a modified flow pattern by interposition of a boom in accordance with the invention. In this way, a more uniform flow pattern can be obtained with a resulting more homogene-ous quality for the glass.
FIG. 8 is a figure similar to FIG. 6 but showing in perspective another boom according to the invention made up of individually adjustable and rotatable loop-shaped cooled tubes 17. The source of coolant, which may include a water-tight rotating joint for each tube, is not shown. The tubes may have each approximately the shape of a twisted figure eight, the upper and lower lobes of which are crosswise to each other. Means, such as for example those shown in FIG. 10, may be pro~ided to rotate the tubes so that they will function as stirring or agitating as well as cooling and blocking elements.
Each of the tubes 17, when rotated, carries with ;~. .
it a quantity of glass whose viscosity is increased by the cooling effect exerted by the tube.
The downstream glass current engages the tubes 17 and they therefore play a double role of blocking and mixing, varying directly with their speed of rotation.
' The number of tubes employed depends upon the ~ lateral width desired for the boom. Speed may vary from 0 ,~ to a maximum at which bubbles become impxisoned in the glass ~` or at which cavitation takes place.
The speed of the rotation of the tubes may, for example~ be ten revolutions per minute, corresponding to a , ,.
: linear speed at the radially outermost portions of the tubes amounting to about 300 meters per hour.
~` 30 The tubes 17 may be of such size and may be so .
9, bm/
.-. - ~ .
~.
. . ~
cooled as to extract on the average from the glass a quanti~y of heat between 50 and 100 therms per hour, and preferably of the order of 75 therms per hour. This requires at least 25 liters per minute of water flow and preferably some 50 liters per minute for a tube, the diameter of whose loop is of the oxder of from 0.25 to 0.30 meters.
- - The direction of ro~ation of the stirring elements or tubes may be chosen to achieve the following effects:
l. To gather the glass toward the axis or median line of the furnace. In this case, the stirring elements on each side of that median line will rotate in the same direction, those on one side rotating in the direction opposite to those - on the other side and the direction of motion being toward the median line on the upstream side of the stirring elements.
2. Instead, the stirring elements can be employed to disperse the glass away from the median line of the furnace.
The sense of rotation of the stirring elements will then be ` opposite to that described in the immediately preceding ; paragraph.
The sense of rotation of the stirring elements will then be ` opposite to that described in the immediately preceding ; paragraph.
3. A stirring action may be imposed by pairs of the stirring elements each one turning in a direction opposite to that of its neighbors.
It is also possible in accordance with the invention to employ alternate fixed and rotative boom elements or to have rotating elements in the center and stationary ones at ``
the lateral extremities of the boomO
FIG. 8 illustrates a series of stirring and cooling elements disposed in large and rotating in the same direction but dephased successively 90 with respect to each other. The space between adjacent elements is such that the xegion o~
, .
, -- 1 0 -- .
bm/
, 233~
effective action of each one overlaps at least slightly with the correspon~ing zone of action of the adjacent stirring element. The crossed or twisted figure eight shape illustrated is favorable to achieving this result.
FIG. 9 shows half of the roof 18 of a melting furnace and the position of the stirring elements 17 by reference thereto. Successive or adjacent stirring elements are displaced angularly by 90 and their zones of operation overlap, as in the construction of FIG. 8 just described.
The upper limit of the stirring, cooling and blocking tubes 17 is no higher than the surface of the glass bath 4. The lower limit is preferably no lower than the neutral interface surface or zone which separates the down-stream surface current and the bottom upstream current. It is in general desired not to perturb the upstream current.
FIG. 10 shows a device for control adjustment and optionally for rotation of the stirring tubes. The tube 17 is supported in a sleeve 18 held in two bearings 19. These bearings are fixed to a frame 20 connected by fastening , means 21 and 22, which may be conventional, to a beam 23 which ,` is parallel to the longitudinal slot 24 in the furnace roo~
The sleeve 18 carries a conical gear 25 which is driven by a pinion 26, which in turn receives it motion from a motor 27 via a shaft 28. To permit control of the phase angle of the separate tubes 17, the pinion 26 can be disengaged from the pinion 25 by rotation of the sha~t 28 about a vertical axis 29 by means not shown. The assembly comprising the tube 17, its sleeve and support 20 may be raised or lowered by means of a tackle (not shown). Refractory plugs 30 ana 31 close the opening 24. The loop-shaped portion of the : .
~ .
.
-:
., ~:
:
. - 11 -bm/
. . .
' ~ 7Z338 stirring element 17 grazes at its upper limit the surface of the glass bath 32. Selection of the number of elements in the boom, the speed (when rotated) ana the disposition of the elements and the degree of their immersion depends upon the dimensions of the furnace and the composition of the glass being made.
It will thus be seen that the invention provides a glass melting furnace comprising means defining a trough, illustrated in FIGS. 1 and 2 at the side, end and ~ottom walls of the furnace thereshown, and a boom as generally indicated :.
at 5 in those figures, extending part-way crosswise of the trough astride the median line thereof, at a location inter-mediate the upstream and downstream ends 3 and 4 of the ~
trough, the boom being disposed above the bottom of the trough as particularly illustrated in FIG. 2~ The invention like wise provides a method of conditioning molten glass which comprises flowing the glass lengthwise of a trough between .
upstream and downstream ends thereof, and obstructing the ~ownstream flow of glass at a location between those.ends ' ,~
and part-way only across the width of the trou~h and part-way only from the surface of the glass to the bottom of the trough. The obstructing action may be combined,with a cooling action and with a stirring actionr the cooling desirably bein~
carried out at a rate substantially between fifty a~d .one hundred therms per hour and per square meter of obstructed width of glass flow.
While the invention has been hereinabove described in terms of a number of presently preferred embodiments of the apparatus thereof, and in terms of a number of presently ' .
; 30 preferred modes of practice of the method thereo-f, the .
;
.:, .
"' bm/
.
. .
.. ~ . . , , . . " , . . .
233~
invention itself is not limited thereto but rather comprehends all modifications of and departures fxom those preferred embodiments and modes properly falling within the scope of ~ the appended claims.
-~ As used herein, the term "therm" means one thousand kilogram calories.
, "
' ' :
.
, .
.`.~ i .
, .,. ~
bm/
.~
... .
.
`" ~ ' . ' .
It is also possible in accordance with the invention to employ alternate fixed and rotative boom elements or to have rotating elements in the center and stationary ones at ``
the lateral extremities of the boomO
FIG. 8 illustrates a series of stirring and cooling elements disposed in large and rotating in the same direction but dephased successively 90 with respect to each other. The space between adjacent elements is such that the xegion o~
, .
, -- 1 0 -- .
bm/
, 233~
effective action of each one overlaps at least slightly with the correspon~ing zone of action of the adjacent stirring element. The crossed or twisted figure eight shape illustrated is favorable to achieving this result.
FIG. 9 shows half of the roof 18 of a melting furnace and the position of the stirring elements 17 by reference thereto. Successive or adjacent stirring elements are displaced angularly by 90 and their zones of operation overlap, as in the construction of FIG. 8 just described.
The upper limit of the stirring, cooling and blocking tubes 17 is no higher than the surface of the glass bath 4. The lower limit is preferably no lower than the neutral interface surface or zone which separates the down-stream surface current and the bottom upstream current. It is in general desired not to perturb the upstream current.
FIG. 10 shows a device for control adjustment and optionally for rotation of the stirring tubes. The tube 17 is supported in a sleeve 18 held in two bearings 19. These bearings are fixed to a frame 20 connected by fastening , means 21 and 22, which may be conventional, to a beam 23 which ,` is parallel to the longitudinal slot 24 in the furnace roo~
The sleeve 18 carries a conical gear 25 which is driven by a pinion 26, which in turn receives it motion from a motor 27 via a shaft 28. To permit control of the phase angle of the separate tubes 17, the pinion 26 can be disengaged from the pinion 25 by rotation of the sha~t 28 about a vertical axis 29 by means not shown. The assembly comprising the tube 17, its sleeve and support 20 may be raised or lowered by means of a tackle (not shown). Refractory plugs 30 ana 31 close the opening 24. The loop-shaped portion of the : .
~ .
.
-:
., ~:
:
. - 11 -bm/
. . .
' ~ 7Z338 stirring element 17 grazes at its upper limit the surface of the glass bath 32. Selection of the number of elements in the boom, the speed (when rotated) ana the disposition of the elements and the degree of their immersion depends upon the dimensions of the furnace and the composition of the glass being made.
It will thus be seen that the invention provides a glass melting furnace comprising means defining a trough, illustrated in FIGS. 1 and 2 at the side, end and ~ottom walls of the furnace thereshown, and a boom as generally indicated :.
at 5 in those figures, extending part-way crosswise of the trough astride the median line thereof, at a location inter-mediate the upstream and downstream ends 3 and 4 of the ~
trough, the boom being disposed above the bottom of the trough as particularly illustrated in FIG. 2~ The invention like wise provides a method of conditioning molten glass which comprises flowing the glass lengthwise of a trough between .
upstream and downstream ends thereof, and obstructing the ~ownstream flow of glass at a location between those.ends ' ,~
and part-way only across the width of the trou~h and part-way only from the surface of the glass to the bottom of the trough. The obstructing action may be combined,with a cooling action and with a stirring actionr the cooling desirably bein~
carried out at a rate substantially between fifty a~d .one hundred therms per hour and per square meter of obstructed width of glass flow.
While the invention has been hereinabove described in terms of a number of presently preferred embodiments of the apparatus thereof, and in terms of a number of presently ' .
; 30 preferred modes of practice of the method thereo-f, the .
;
.:, .
"' bm/
.
. .
.. ~ . . , , . . " , . . .
233~
invention itself is not limited thereto but rather comprehends all modifications of and departures fxom those preferred embodiments and modes properly falling within the scope of ~ the appended claims.
-~ As used herein, the term "therm" means one thousand kilogram calories.
, "
' ' :
.
, .
.`.~ i .
, .,. ~
bm/
.~
... .
.
`" ~ ' . ' .
Claims (16)
1. A glass melting furnace comprising means defining a trough which contains a molten glass bath, a boom extending part-way crosswise of the trough at a location intermediate the upstream and downstream ends of the trough, said boom being dis-posed above the bottom of the trough, a roof above the trough, and means dependent from the roof to support the boom.
2. A furnace according to claim 1 wherein said boom pos-sesses crosswise of the trough a length between one-quarter and two-thirds the width of the trough at the location of the boom and a height below the surface of the molten bath between one-fifth and one-half the depth of the molten bath in the trough at that location.
3. A furnace according to claim 1 wherein the length of said boom is between one-half and one-third the width of the trough at the location of the boom and wherein the height of the boom below the surface of the molten bath is substantially one-third the depth of the molten bath at that location.
4. A furnace according to claim 1 wherein the lower limit of said boom is convexly curved downwards.
5. A furnace according to claim 1 wherein said boom is made up of spaced elements.
6. A furnace according to claim 5 in which each of said elements includes a hollow tube of loop shape, said furnace further comprising means to drive a refrigerant fluid through said tubes.
7. A furnace according to claim 6 wherein said furnace further comprises means to rotate said tubes.
8. A furnace according to claim 1 in which said boom com-prises a plurality of tubes each having an open end beneath the surface of the molten glass bath, said furnace further compris-ing means to force a gaseous fluid through said tubes.
9. A furnace according to claim 6 in which said tubes have substantially the shape of figure eight, the upper and lower lobes of which are twisted with respect to each other.
10. A furnace according to claim 7 in which adjacent tubes are rotatable in opposite directions.
11. A furnace according to claim 7 in which pairs of said tubes on opposite sides of the median line of said trough are rotatable in opposite directions.
12. A method of conditioning molten glass which comprises flowing the molten glass lengthwise of a trough, between up-stream and downstream ends thereof, obstructing the molten glass flow by a flow-impending means located between those ends, said flow-impending means extending partway crosswise of the trough and partway from the surface of the glass to the bottom of the trough, and circulating a cooling fluid through said flow-impending means.
13. A method according to claim 12 in which the cooling fluid is circulated at a rate effecting withdrawal of heat from the molten glass at a rate substantially between fifty and one hundred therms per hour and per square meter of obstructed width of glass flow.
14. A glass melting furnace comprising an elongated trough extending from an upstream charging end to a downstream discharge end, means to maintain a temperature gradient within the trough with higher temperature adjacent the charging end and lower temperatures adjacent the discharge end, a boom disposed at a location intermediate said upstream and downstream ends, said boom extending across the longitudinal axis of the trough part-way only towards the sides thereof and partway from the surface of a molten glass bath therein to the bottom thereof, a roof above the trough and means dependent from the roof to support the boom.
15. A furnace according to claim 14 wherein said boom comprises a cooled conduit.
16. A furnace according to claim 14 wherein said means to maintain the temperature gradient include burners disposed both upstream and downstream of said boom.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7406062A FR2261987A1 (en) | 1974-02-22 | 1974-02-22 | Glass melting tank - with barrier across the central part of the homogenising zone, to turn back the surface glass layer |
| FR7433624A FR2287423A2 (en) | 1974-10-07 | 1974-10-07 | Glass melting tank - with barrier across the central part of the homogenising zone, to turn back the surface glass layer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1072338A true CA1072338A (en) | 1980-02-26 |
Family
ID=26218184
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA220,513A Expired CA1072338A (en) | 1974-02-22 | 1975-02-20 | Glass manufacture |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5839777B2 (en) |
| BR (1) | BR7501080A (en) |
| CA (1) | CA1072338A (en) |
| DE (1) | DE2507015C2 (en) |
| DK (1) | DK67475A (en) |
| ES (1) | ES434996A1 (en) |
| GB (1) | GB1490426A (en) |
| LU (1) | LU71895A1 (en) |
| NL (1) | NL176161C (en) |
| NO (1) | NO137721C (en) |
| SE (1) | SE409321B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103102058A (en) * | 2013-02-07 | 2013-05-15 | 蚌埠玻璃工业设计研究院 | Stirring device used for plate glass melting kiln neck |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2478064A1 (en) * | 1980-03-11 | 1981-09-18 | Saint Gobain Vitrage | PROCESS AND OVEN FOR THE PRODUCTION OF MOLTEN GLASS |
| US4339261A (en) * | 1980-09-08 | 1982-07-13 | Libbey-Owens-Ford Company | Drive system for glass furnace stirrers |
| DE4411038C2 (en) * | 1993-06-15 | 1995-12-07 | Sorg Gmbh & Co Kg | Method and device for conditioning and homogenizing a glass stream |
| US5630860A (en) * | 1993-06-15 | 1997-05-20 | Beteiligungen Sorg Gmbh & Co. Kg | Method and apparatus for conditioning and homogenizing a glass stream |
| US5573569A (en) * | 1993-06-15 | 1996-11-12 | Beteiligungen Sorg Gmbh & Co. Kg | Method for conditioning and homogenizing a glass stream |
| US5634958A (en) * | 1993-06-15 | 1997-06-03 | Beteiligungen Sorg Gmbh & Co. Kg | Method and apparatus for conditioning and homogenizing a glass stream |
| FR2774085B3 (en) | 1998-01-26 | 2000-02-25 | Saint Gobain Vitrage | PROCESS FOR MELTING AND REFINING VITRIFIABLE MATERIALS |
| WO2012093183A1 (en) * | 2011-01-05 | 2012-07-12 | Luis Grijalba Goicoechea | Method and unit for melting glass at low temperatures |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2888781A (en) * | 1955-08-30 | 1959-06-02 | Owens Illinois Glass Co | Water cooled skimmer for glass furnace forehearth |
| BE553325A (en) * | 1956-12-12 | |||
| US3149952A (en) * | 1959-06-26 | 1964-09-22 | Henry Georges | Apparatus for adjusting the operating conditions of tank furnaces |
| US3350187A (en) * | 1963-01-08 | 1967-10-31 | Glaverbel | Process and apparatus for the homogenisation of molten glass in the chamber connecting the refining furnace to the working compartment |
| FR1404753A (en) * | 1964-06-05 | 1965-07-02 | Glaverbel | Process for homogenizing a stream of molten glass and furnace for carrying out the process |
| FR1410601A (en) * | 1964-10-02 | 1965-09-10 | Ver Glasfabrieken Nv | Bridge glass furnace |
| DE1596424B1 (en) * | 1967-06-07 | 1970-12-23 | Floatglas Gmbh | Device for homogenizing a glass melt |
| JPS495604A (en) * | 1972-05-04 | 1974-01-18 | ||
| AR204404A1 (en) * | 1973-01-12 | 1976-02-06 | Pilkington Brothers Ltd | METHOD TO PRODUCE GLASS IN A GLASS MELTING TANK AND TANK FOR ITS REALIZATION |
-
1975
- 1975-02-18 SE SE7501793A patent/SE409321B/en unknown
- 1975-02-19 DE DE2507015A patent/DE2507015C2/en not_active Expired
- 1975-02-20 CA CA220,513A patent/CA1072338A/en not_active Expired
- 1975-02-21 GB GB7370/75A patent/GB1490426A/en not_active Expired
- 1975-02-21 NO NO750603A patent/NO137721C/en unknown
- 1975-02-21 NL NLAANVRAGE7502090,A patent/NL176161C/en not_active IP Right Cessation
- 1975-02-21 LU LU71895A patent/LU71895A1/xx unknown
- 1975-02-21 BR BR1080/75A patent/BR7501080A/en unknown
- 1975-02-21 DK DK67475*#A patent/DK67475A/da not_active Application Discontinuation
- 1975-02-22 ES ES434996A patent/ES434996A1/en not_active Expired
- 1975-02-22 JP JP50021465A patent/JPS5839777B2/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103102058A (en) * | 2013-02-07 | 2013-05-15 | 蚌埠玻璃工业设计研究院 | Stirring device used for plate glass melting kiln neck |
| CN103102058B (en) * | 2013-02-07 | 2015-10-07 | 蚌埠玻璃工业设计研究院 | A kind of whipping appts for Flat Glass Furnace card neck place |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS50124910A (en) | 1975-10-01 |
| AU7844175A (en) | 1976-08-26 |
| DK67475A (en) | 1975-10-27 |
| LU71895A1 (en) | 1975-12-09 |
| NL7502090A (en) | 1975-08-26 |
| BR7501080A (en) | 1975-12-02 |
| JPS5839777B2 (en) | 1983-09-01 |
| NL176161C (en) | 1985-03-01 |
| DE2507015A1 (en) | 1975-09-04 |
| ES434996A1 (en) | 1976-12-16 |
| NL176161B (en) | 1984-10-01 |
| SE7501793L (en) | 1975-08-25 |
| GB1490426A (en) | 1977-11-02 |
| NO137721C (en) | 1978-04-12 |
| NO137721B (en) | 1978-01-02 |
| NO750603L (en) | 1975-08-25 |
| SE409321B (en) | 1979-08-13 |
| DE2507015C2 (en) | 1983-04-21 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |