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Патент USA US3094588

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June 18, 1963
Filed Nov. 18, 1959
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United States Patent O rrace
. Patented June 18, 1963
description when taken in connection with the accompany
ing drawings.
In the drawings, wherein like numerals are employed to
designate like parts throughout the same:
Henry R. Meriwethe?', Jr., and Curtis A. Mewbourne,
Shreveport, La., and Richard E. Warren, Toledo, and
Alfred E. Badger, Maumce, Ohio, assignors to Libbey
Owens-Ford Glass Company, Toledo, Ohio, a corpora
tion of Ohio
FIG. 1 is a longitudinal, vertical, sectional view through
a draw pot and the end of a cooling chamber of a sheet
glass furnace showing the heating means of this inven
Filed Nov. 18, 1959, Ser. No. 853,977
8 Claims. (Cl. 13-6)
tion associated therewith;
'FIG. 2 is a fragmentary plan view taken substantially
10 along the line 2-2 of FIG. l;
The present invention relates to a method and apparatus
for treating glass and more particularly to a method and
that may be used in the practice of this invention; and
FIG. 3 is a perspective view of one form of electrode
FIG. 4 is a circuit diagram illustratíng a means for
apparatus for treating molten glass prior to its introduc
controlling the amount of electrical energy and thereby
tion into a working receptacle.
This is a continua?tion-in-part of our co-pending appli 15 controlling the amount of heat being added to the molten
cation Serial No. 499,434, ?led April 5, 1955, now aban
The present invention is here disclosed in connection
with a type of sheet glass drawing machine known in the
Although this invention is by no means restricted there
art as the Colburn machine, and is particularly applicable
to, it has proved to be particularly valuable in connection
with the continuous production of sheet glass and will be 20 to machines where the glass is drawn from a meniscus of
controlled visc'osity as is done in the ordinary window glass
described in that connection here. In the present day
manufacture of sheet or window glass, the batch is melted
The sheet glass drawing apparatus herein illustrated in
and the resultant molten glass re?ned in a continuous
cludes a relatively shallow working receptacle or draw pot
'type tank furnace. The molten glass moves from the
re?ning end of the tank into and through a so-called 25 10 containing a mass of molten glass i1:1, preferably sup
plied theretvo from the exit end 112 of the cooling or condi
cooling or conditioning chamber and, from there, into a
tioning chamber having conditioned molten glass 13 con
relatively shallow working receptacle or draw pot from
tained therein. A sheet 14 is continuously drawn from
which a ribbon of glass is continuously drawn. Molten
the mass 11, the said sheet being held rto width by Width
glass supplied to -the draw pot through the cooling cham
ber is preferably kept at a controlled temperature so that 30 maintaining knurls or similar edge engaging members 1-5.
Arranged over the glass is .a pair of lip tiles 16 and 17.
› the glass in the draw pot has the desired víscosity for the
The thíckness and character of the sheet 14 is determined
drawing operation.
by the temperature and quality of -the glass 111 which makes
Certain dif?cult-ies have been encountered in maintain
up .the meniscus '18 at the surface of the molten glassin
ing the desired temperature at all points throughout the
- draw pot in prior known installatíons. Thus, because the 35 the draw pot and extending across the draw pot for a
distance equal to the Iwidth of the sheet :14.
e walls at the exit end of the conditioning chamber, and the
It is particularly important that the glass .in the meniscus
walls of the draw pot, have a tendency to cool the glass;
18 is all at the same temperature in order that the drawn
(and because glass has a tendency to ?ow in the centrally
located areas more rapidly than near the walls, the glass 40 sheet may be of uniform -thickness Moreover, ?if exces«
sive cooling is allowed near the width maintaining knurls,
in the central portion of the draw pot is normally hotter
semi-solid gobs of glass often referred to as knots are
'than the' glass near the side walls.
formed which causes losses due to the fact that these gobs
In the past, various heating devices have been employed
of glass must -be removed and after removal it take some
in an attempt to maintain uniformity of the temperature
time to put the machine back into proper operation. i
of the glass in the draw pot, but none of these has proved
Due to the fact that .the glass at the sides of the draw
entirely satisfactory. (For one thing most of the combus
pot has a tendency to cool› oif faster than the glass at the
tion heating devices of the prior art have caused convec
' tion currents which prevented proper control and intro
center of the same, we have found it is necessary to add
heat to the glass ?owing along the :side walls of the draw
in order .to compensate for the heat losses occurring
dirt losses.
the walls thereof. It is also important to supply
It is the primary object of this invention to properly
the heat within the glass -andto provide means for sup
condition a moving stream of molten glass for working or
plying the heat that may be accurately controlled. Ac
drawing by selective temperature regulation before the
cording to this invention, the heat is supplied to the molten
the glass reaches the forming zone of the working recep
glass at a point near the exit end of the conditioning
tacle or draw pot.
55 chamber and just ahead of the entrance end of the draw
Another object of this invention is to provide a special
pot. In the apparatus shown in FIG. l, there is an arch
heating means for heating the glass ?owing into the sides
19 which represents such a point, and the heat is prefer
of the working receptacle near the entrance end thereof
_ ably applied at points in the glass where it ?ows under this
so thata uniform temperature may be maintained at the
arch and near the ?side walls of said arch. Generally the
zone of formation.
60 glass in the draw pot is relatively „shallow compared to the
A further object of this invention is to provide a type
glass in the conditioning chamberas is shown in FIG. l.
of heating means which applies heat directly in the molten
This means that the amount of glass in the draw pot is
glass at points on each side of the glass as it moves into
comparatively ?sm-all thereby making it more d?i?icult to
the draw pot whereby a quantity of glass may be suitably
control variations of the temperature of the glass in said
duced products of combustion which frequently caused top
treated by the action of heat before it is drawn into a 65
A further 'object isto provide a controlled uniform
We have found that the heat losses through the side
wallsof the draw pot\ may be compensated for and the
temperature _of the/glass in? the zone of formation so that i
a better grade of sheet. glass may be drawn at a greater
temperature _in therdraw pot accurately controlled by elec
glass sheet.
trically heating the gl-assíby passing -an electric current
_ speed of operation than has been heretofore possible.
70 throughthe molten glass ?owing toward each side of the
Other objects and advantages of the_ invention will be
i' draw. pot before it reaches the entrance end. The elec
tríc energy dissipated in the glass causes the glass to be
come more apparentduring the course of the following
heated by the Joule e?ect. This electric current is sup
was also found that dirt and `smear losses were reduced
plied to the molten glass by two pair-s of similar electrodes
due to the fact that :some of the combustion heating was
20 .and 21. Especially good results have been obtained
eliminated by being replaced with the heating means of
when the distance between the electrodes is about one
this invention. The increased stability of operation pro
foot and preferably the electrodes are spaced betwee
vided better capping and allowed other subsequent pro
about 8 and 18 inches.
duction processes to be performed more e?íiciently. There
was also a reduction in clean-ups due to formations of
semi-solid gobs of glass in front of the knurls, less knurl
'The preferred electrode, as best shown in FIG. 3, is
made up 'of anangular bar 22 made of an electrically
conducting material which is adaptedto extend through
troubles, and less clean-up losses. Therefore, it is seen
the walls of the condítioning chamber and extend down 10 that the controlled heating means of this invention pro
duces a ?ner grade of window glass with less cost than
wardly into the molten glass. lPreferably, this bar is
was achieved by the control means ofthe prior art.
made of ra heat-resistant alloy which is satisfactory in
It is to be understood that the form of the invention
operation both above 'and ;?submcrged inthe glass. At
disclosed herein is to be taken as the preferred embodiment
tached to this lead-in bar is. another bar`23v which is com
pletely submerged'in the 'glass whilein Operating posi
thereof, and that various changes in the shape, size and
tion an'd'it is 'rbetweenthe bars'23` 'ofeelectrodes 20 and
arrangement of parts as well -as various procedural changes
21, as best shown'in FIG. 2, that'the electrici?ty ?ows
through the ;molten glass. -Preferably, these bars are
may be resorted to without departing-from the spirit of
the invention or the scope 'of the following claims.
We claim:
1. In apparatus for drawing a sheet from a mass of
As has been stated, it istparticularly important to con 20
molten glass including a draw pot and a cooling chamber
trol :the amount of'heat added to thegl-ass to provide a
through which a stream of molten?glass ?ows to said draw
'uniform temperature at the forming'zone, and due to
pot, electric heating means within the?cooling chamber
`the'fact that relatively small amountsof glass are present
composed of molybdenum.
"in-the' drawpot, it is particularly important to have means
for accurately controlling the heat supplied bythe elec
and positioned along* opposíte side walls at the exit end of
said cooling chamber for internally heating the edge por
tions of the stream of molten glass in said cooling cham
ber and before said molten glass reaches said. draw pot.
2. Apparatus as de?ned in claim 1 in whichvsaidcool
ing chamber includes an arch substantially closing the exit
;plicdbetween the 'electrodes,vmore current would ?ow
'as theglass 'gets'hotterthereby causing the 'glass to heat 30 end of said chamber above the stream of molten glass mov
ing therethrough, and said „electric heating means are
still faster. For .this reason, an automatic controlling
located beneath said arch along opposite side walls thereof.
circuit is' employe'd to keepthe 'amount of current ?owing
3. Apparatus as de?nedrin claim 1 in which said elec
:substantially constant as' illustrated in FIG. 4. The cir
tric heating means comprises a pair of electrodesat oppo
cuit consists 'of a 'two "pole safety switch 24“for dis_
connecting leadwiresZS and'26, which are connected 35 -site sides of said cooling chamber ,with each electrode
having a portion thereof submergedv in themoltenglass
`to a sui-table ' power .source. The lead w?'re 26 is con
.nected to a coilinsthe saturable reactor 2.7 with-the s ?and means for controlling the amount of electrical current
supplied to said electrodes.
'other end of 'the'coil 'being connected to the primary i
4. An apparatus as de?nedin claim 3, wherein the dis
coil ofíthetransformer ``28\,`the.other lead'wire 25 being
connected ?to'the other end “of'the primary coil of the 40 tance between electrodes of each_ pair is within the range
-of eight inches to eighteen inches.
'transformer 28. The control coil of the saturable re
5. An apparatus as de?ned in claim. 3, wherein the dis
›actor is supplied =by 'lead?wires'29and :30' which are con
tance betweenthe electrodes of eachpair is about twelve
nected to a 125 Volt D.C. _shop- source. A safety switch
'31, fuses 32 and ?xed resistorí?íš` are'located as shown in
6. Apparatus as de?ned in claim 3 in which the sub
*the D.C. controlcircuit. This circuit islled through a
merged portions of said electrodes are, inthe form` of bars
potentiometer rheostat 34 “and from'there into the' sat
_substantially parallel'withthe adjacent side wall of said
'urable reactor'27, therebycontrolling the amount of cur
tric current ?owing :between ?the electrodes '20` and 21.
'Itiswell known thatas'glass'getshotter its electric re
sistance gets lower so that if a constant voltage is ap
cooling .chamber.
rent'which ?ows throughtthe primary coil of` thetrans
former .28.
7. Apparatus as de?ned in claim 6 in which said .bars
The current which?ows through the secondary coil of 50 are of molybdenum and serve as electrode faces.
'the transformer 28 .is directlyproportional to .the current
?owing'throughtthe primary coil which is controlled as
.hereinbefore set, forth. From the secondary coil the
current is led' through a variac and choke`35- and through
the .di-pole safety switch 36 to the electrodes '20 and
'21. Ammeter '3-7 `and voltmeter 338\ are located in the
heating circuit so that ,the electric ,energy passing into
the molten glass may be measured, and -ammeter 39 is
locatedin the D.C. ,control circuit so that the operator
may observe the amount of current ?owing therethrough.
The control apparatus provides a substantially constant
current ?ow through the glass, and in operation it is
usually .left a-t a set position as .soon as uniform oper
ating conditions are achieved. ~If changes in the cur
rent are desired, the operator may make the necessary ad
justment by appropríately setting the potentiometer 34.
It is .also contemplated that the potentiomete?- may be
adjused by a suitable thermostat to maintain the desired
~ temperature, but this is not essential.
~When the apparatus herein disclosed was installed 70
in a window glass machine similar to :the one shown in
FIG. 1, it was found that the sheet could be drawn from
the draw pot at amore rapid rate and a steadier pull
maintained than 'had been possible beforethe installation
of the controlled heating means ofthis invention. It 75
8. In a method of drawing ,a sheet from a mass of
molten glass in a draw pot, the steps of ?owing a stream
of mol-ten glass into said draw pot through acooling
chamber, and heating the edge portions of the molten glass
,stream in the exit end of _said cooling chamberas it ?ows
therethrough along narrow bands at the sides of` said
stream and substantially parallel with the direction of ?ow
before the molten glass reaches the draw pot.
References Cited in the ?le of this patent
Ferngren ______________ ..`_Oct. 3, 1925
Hitner _______________ __ Dec. 14, 1926
Drake _______________ __ Nov. 18, 1930
Henry ______________ __ Sept. 26, 1933
Koupal et al ___________ __ Apr. 19, 1938
2,348,67 8
Adam _______________ __ Jan. 31, 1939
-Kilian et al. ___________ _.. Mar. 3, 1942
Great Britain _________ __ Dec. 30, .19335
Great Britain ________ __ Nov. 29, 1940
Rolnickv ______________ __ May 23, 1944
Labino ______________ __ Sept. 19, 1950
La Burthe ____________ _.. Nov. 3, 1955
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