Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a novel method ~or
~orming a coating of a metal oxide on the sur~ace o~ a
glass sheet by heat deco~position, and an apparatus
therefor in order to impart electric conductivity to the
glass surface or to improve its optical properties.
As is wel.l known, -the heat decomposition method
provides a coating of a ~etal oxide by adhering a metal
compound convertible to the metal oxide by hea-t decomposition
to the surface of a glass sheet kept at a temperature above
the heat decomposition temperature o~ the metal compound.
Generally, the metal compound is d~ssolved in a ~uit;able
solvent9 and the solu-tion is sprayed onto the glass
sur~ace or the glass is immersed in the solution.
One procedure ~or treating glass sheet in -the
~bove manner involves spraying the metal compound solution
to the glass surface be~ore the glass sheet fo~ned in a
continuous ribbon in a forming apparatus enters a lehr,
or while the temperature o~ the glass in the lehr is
still sufficiently high (more than 550C.).
It has been the conventional practice to move a
spray gun jetting out the metal compound solu-tion reciprocally
in the widthwise direc-tion o~ the glass sheet abo~e the
continuously moving glass shee-t, and thus to spray the
solution to the entire sur~ace of the glass sheet. However,
the conventional method suffers from the following dis-
advantages ~hen the moving direction o~ the spray gun
changes near both ends of the glass sheet, the spray gun
stops momentarily (~or example, ~or about 0~2 second), but
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the solution is still being jetted out during the stoppage
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Accordingly, a larger amount of the solu-tion is sprayed
onto both side ends o~ the glass sheet at w~ich the gun
stops than onto the central portion of the glass sheet in
its widthwise direction. Furthermore, the solution
sprayed from the stopping gun scatters over a considerably
wide range, and consequently, a thicker coating is ~ormed
on both side end portions o~ the glass sheet than on the ;~
central part. Naturally, there~ore, the effective width
over which a coating of uniform -thickness is fo~ed is
10 considerably smaller than the stroke of the spray g~.- ;
It may be thought that in order to increase the effective
~ wid-th, it would be feas~ble to increase the ~ of -the
t ~ spray gun to the width of the glass sheet or lar~er. Such
an idea, however, cannot avoid the serious de~ect that the
sprayed solution markedly contaminates the glass sheet-
conveying rolls and their vicinity at a part near the ends
o~ the width of the glass sheet, and is therefore infeasible.
Moreover J in the method involving the spraying
o~ the metal compound solution, the solvent (mainly,
an organic solvent) wh.ich constitutes a grea-ter part of
the solution, and a par-t oP the metal compound are gasified
on th0 surface o~ the glass sheet main-tained at a high
-temperature, and become noxious exhaust gases. In order ~
to remove these exhaust gases, a suction duct is provided ~ - - -
near the moving path of the spray ~un. Furthermore~ in
the conventiona~ appara-tus shown in Figure 5~ a side 3uction
duct 21 is disposed also above bo-th ends of glass sheet l
so that the ducts can suck and remove great amounts of e~aust
gases generated ~rom -the sprayed solution jetted out from
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spray gun 6 at halt. In view of the arrangement of the side suction ducts
21, the stroke of the spray gun 6 cannot be increased.
When the stroke of the spray gun 6 is increased, the sprayed
solution at the stroke end adheres to the side suction ducts 21, and drops
onto the glass sheet 1. Since the gun 6 is near the duct 21, a splash of
the sprayed solution leaks outside through beneath the duct 21 to cause
environmental pollution. From this standpoint, too, the stroke of the spray
gun 6 cannot be increased.
The maximum effective width over which a coating of uniform thick-
ness can be formed is about 30 inches smaller than the stroke of the spraygun, and the current practice is to cut off large portions of both sides of
the glass sheet, and therefore, in order to obtain a sheet glass with a
coating of the desired width, the original glass sheet should have a consider-
ably large width, and the yield obtainable is low.
Accordingly, it would be advantageous if the effective width over
which a uniform coating can be formed is increased, and the sprayed solution
can be utilized economically.
Accordingly, the present invention provides a method for forming a
metal oxide coating on a surface of a glass sheet continuously moving at a
~0 constant speed and held at a high temperature by spraying onto the surface
of the glass sheet a solution comprising at least one metal compouncl con-
vertible to a metal oxide upon heat decomposition, by means of a spray
gun moving reciprocally at a substantially constant speed in a direction
substantially crossing the moving direGtion of the glass sheet, characterized
in that the amount of solution being sprayed in the central part of the re-
ciprocating path is kept at a substantially cons~ant amount and the amount
of solution being sprayed in the vicinity of each extreme end of the recipro-
cating path is restricted with respect to said constant amount by diverting
at least a part of the flow of solution to the spray gun into a flow path
separ~te from the ~low path to the spray gun so as to prevent ~xcessive metal
oxide build-up on the ends of the surface of the glass sheet and to produce
a glass sheet having a metal oxide film of uDiform thickness coated in the
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surface thereof.
In order to perform the method of this invention, there is provided :
an apparatus for forming a coating of a metal oxide on the surface of a glass
sheet, which comprises a means for continuously advancing a glass sheet kept .. .. .
at a high temperature; at least one spray gun disposed above the surface of -.
said glass sheet and containing a jet nozzle for spraying a solution compris- .. -. .
ing at least one metal compound onto the surface of the glass sheet; means
for reciprocating said spray gun in a direction crossing the advancing
direction of said glass sheet; means for feeding said metal compound solution
under pressure steadily into said spray gun; a three-way valve attached to
said spray gun for restricting the amount of the spray solution in order to
change the amount of the spray solution between a first sta.te in which all
tho solut:ion -eed to the spray gun is jetted out from said nozzle and a
sccond stato in which the amount of the spray solution fed to the spray gun
is restricted and the non-sprayed solution is conducted to a flow path
separate from a path to the jet nozzle a detection-operation mechanism for
detecting the arrival of said spray gun at a predetermined position in the
vicinity of each extreme end of the reciprocating path away from the central ~:
part to each extreme end and operating said three-way valve on the basis of . .:this detection thereby to effect the change from the first state to the :.
socond state, and for detecting the departure of the spray gun from said
predetermined position to the central part of the reciprocating path and .
operating said three-way valve on the basis of this detection thereby to
effect the change from the second state to the first state.
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10'~193~3
Figures 1 to 4 of the accompanying drawings
illustra~e one embodiment o~ the apparatus for performing
the method of this invention. Figure 1 is a front elevation
of the entire apparatus; Figure 2 is a schematic side
elevation thereof; Figure 3 is an enlarged side elevation
of the principal part of *he apparatus; and Figure 4 is
an enlarged top plan of the principal parts of the
apparatus. Figure 5 is a schematic front elevation of the
conventional apparatus.
One preferred embodiment of the present invention
will be described in detail with reference to the accompany-
ing drawings.
Referring to Figure 2, a ribbon-like glass sheet
1 withdrawn continuously from a Eloat-type plate glass form-
ing apparatus (not shown) is delivered to a lehr by means
of conveyor rolls 2. While the glass sheet 1 passes over
the conveyor rolls 2, a solution of a metal compound is
sprayed onto the upper surface of the glass sheet.
Above the conveyor rolls 2, a beam 3 riding over the
advancing path of the glass sheet 1 is provided. A solution
spraying device ~ is mounted on the beam 3 so that it can
reciprocate sideways along the beam 3 while it is pulled by
a chain 5. A pair of spray guns 6 spaced from each other at
a suitable distance in the advancing direction of the glass
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sheet e~tend from the spray device ~ to a poin-t near the
upper surface of the sheet glass 1. A suction duct 20 is
provided on bo~h sides of the moving path of spray guns 6
to suck and remove noxious exhaust gases.
As is shown in Figure 3, each of the spray guns
is composed of a feed pipe 7 for the metal compound
solution and a feed pipe 8 for pressurized air in a double
tube fashion, and a jet nozzle 9 for the solution at its
lower end. Solution feed openings 10 are opened at the
upper ends of the solution feed pipes 7 of the spray guns,
and the upper ends of the two air feed pipes ~ are connected . .
to each other to form a common air feed opening 11.
At the upper part of each of the solution feed
pipes 7, a three-way valve 13 for restricting the
.amoun~.of the spray is provided which can change ~he amount .
of the metal compound solution to be sprayed from the first
state to the second state, or from the second state to the .
first state. .~ :
The first state,.referred to herein, denotes . :
the state in which all the solution.fed into the feed pipes
7 is conveyed to the nozzle 9, and therefore, all the :.
solution fed is jetted out from the nozzle 9. The second
state, referred to herein, denotes the state in which the ~:.
flowing of the solution fed into the feed pipes 7 to the :
nozzle 9 is res*ricted, and either a part of the solution is ..
conveyed to the nozzle 9 or the solution is not at all . .
conveyed to the nozzle 9, and any remainder of the solution
is sent to a return pipe 12 thereby to restrict the amount
of the solution to be jetted out from the nozzle 9.
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In the preferred embodiment of ihe present
invention, the second state is one in which the total
amount of the solution fed into the solution feed pipes 7
is sant to the return pipe 12, and no solution is jetted
out from the nozzle g.
The change of the amount of spray jet from the
nozzle is performed by means of the three-way valve
13 utilizing the oscillating motion bf a
lever 14. On both side ends of the beam 3, a plate-like
stopper 15 having a suitable length in the moving
direction A of the spray gun is disposed abuttably against ` ` `the lever 14. When the lever 14 is released from the
stopper 15, the above-mentioned first state is realized.
When the lever 14 abuts against the stopper 15, the
irst state is changed to the second state. This is shown
in Figure 4.
The stopper 15 is securred to a bracket 1~ which
is screwed into a screw shaft 16 supported in parallel to
the moving direction of the spray gun and anchored by
projections 18 of an auxiliary frame 17. By the manual
rotating operation of the screw shaft 16, the stopper 15
can be adjusted at a predetermined position by screwing in
the moving direction of *he spray gun.
Now, the operation of the apparatus of this -
invention will be described in detail. Simultaneously
with the delivering of the glass sheet 1, the solution
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spraying device 4 is reciprocated in the widthwise direction
of the sheet glass at a suitable speed corresponding to
the speed of the sheet glass. During this time, the
metal compound soluiion and pressurized air are fed
respectively from the feed openings 10 and 11, and the
solutlon is sprayed ~the first state) from the noæzles 9
of the spray guns 6 against the high tempera-ture glass sheet
utilizing the pressurized air. The metal compound of the
solution sprayed onto the high temperature glass decomposes
by heat to become a coating of a metal oxide on the glass
sheet. A part of the solvent and the metal compound is
gasified to form exhaust gases which are then removed ~hrough
the suction ducts 20.
When the spray gUIlS 6 reach a point near the
upper part of the side ends of the glass sheet 1, the lever
14 of the three-way valve 13 abuts the stopper 15
which has been adjusted in advance as to its position.
Ihus, the three-way valve 13 operates and the amount of the
spray jet from the nozzles 9 changes to the second state.
All the fed solution is let away through the return pipes 12,
and collected at a pressurized solution feeding section
(not shown). Accordingly, the spraying of the solution
from the nozzles 9 is stopped momentarily.
When the advancing direction of the spray guns 6
changes and the l-ever 14 of the restricting mechanism 13
is disengaged from the stopper 15, the restricting mechanism
13 operates to change the amount of the spray jet from the
nozzles 9 to the first state, and all the solution is again
flowed through the nozzles 9 and sprayed against the glass
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surface.
The above operation is repeated at both side ends
of the glass sheet 1, and the spraying of the solution by
the spray gun 6 is effected substantially only over the
width of the glass sheet. At both side ends, the
spraying is momentarily stopped, and no excessive solution
is sprayed against the glass sheet.
In operating the apparatus of the above construction,
the following considerations should be given.
(1) Desirably, the distance between the three~way
valve 13 and the nozzle 9 is as short as possible.
If the distance from the three-way valve 13 to the
nozzle 9 is large, the solution in the flow path from the
three-way valve 13 to the nozzle 9 still flows out even when the
supply of the solution toward the nozzle 9 is interrupted
at the three-way valve 13. This results in a delay in the
complete stoppage of the spraying. Especially when the
speed of the spray gun 6 is considerably high, the stopping
of spraying requires extreme rapidity. For example, when
the moving speed of the spray gun is 2 meterlsec., the
precision oE the timing of the spray stopping must be
adjusted to about 0.1 sec.
If, on the other hand, the three-way valve 13 is caused
to approach too near the nozzle 9, there is a likelihood~ ~ -
that the three-way valve 13 itself is damaged, for example~ by
the heat of radiation from the high tempera-ture glass, or
the metal compound coagulates within the mechanism by the
action of heat, thereby causing troubles to the three-way valve 13.
Accordingly, the distance between the three-way valve 13 and the
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glass sheet 1 musl be determined appropriately.
(2) The three-way valve 13 must be adapted ~ .
to maintain the flow of the solution even during its opera-
tion. . .
In order to effect uniform spraying, the solution
is automatically controlled so that its amount of feed is
al~ays constant. Thus, when the flow of the solution is .~
impeded even momen-tarily, the flow amount of the solution :.
varies abruptly upon the interruption or resumption of the : .
flowing of the solution, and accordingly the automatic : ~:
control of the flow rate at a predetermined value becomes ..
impossible. Accordingly, a device which merely impedes
the flow of the solution, suc}l as a shut-of:E valve, cannot
be used in place of the three-way valve 13.
~3) When the first state should be changed to the
second state with regard to the position of the spray gun
cannot bedetermined in general terms because it differs
depending upon variables such as the advancing speed of
the glass sheet, the moving speed of the spray gun or the
amount of the solution to be fed to the feed pipe. However,
once the operating conditions have been set, those skilled
in the art can easily detect, for example, by a preliminary
experiment, the best position of the spray gun near both
side ends of the.glass sheet 1 which will provide a
substantially uniform coating of a metal oxide on the
surface of the sheet glass if the change From the first
state to the second state is effected when the spray gun :.:
stays at that position. Thus, the position of the spray gun . .
for effecting this change should be determined on the above
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standard.
For example, when a glass sheet having a width of ~ -
145 inches advances at a rate of 200 inches/min. 9 the
spray gun moves at a rate of 4080 inches/min., and the
amount of the solution to be fed is 1000 cc/min.,
the maximum effective width can be obtained by changing
the amount of the solution from the first state to the
second state when the spray gun has reached a position
within 5 to 10 inches from the side end of the glass sheet.
(4) The metal compound used in this invention may
generally be any metal compounds which decompose to metal
oxides when heated and adhere to glass. Examples of
suitable metal compounds are ~diketone salts, alkoxy
compounds~ and alk~l compounds of cobalt~ iron, chromium~
nickel, tin, titanium, manganese, calcium, and magnesium.
The acetyl acetonato complex salts of the above metals are
especially preferred. The solvent used to form solutions
of the above metal compounds may be any solvents which
dissolve the above metal compounds. Generally, methanol,
butanol, isopropanol, benzene, toluene~ and heptane are used~
Since excessive spraying does not take place at
both ends of the solution sprayed width in the above-
described treatment, the sprayed width substantially becomes
an effective width, and a substantial amount of the solution
which would be wasted at both ends of the sprayed width
according to the conventional techniques can now be saved.
For example, in order to obtain an effective width of 100
inches, a sprayed width of 130 inches is required accorcling
to the conventional apparatus, whereas according to the
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apparatus of the present invention, the sprayed width can
be 100 inches. Thus, in order to obtain the same effective
width, the amount of the solution required in accordance
with the apparatus of this invention is only about 78% of
that required in the conventional apparatus, thus providing
a saving of 22%.
Since there is no excessive spraying of the
solution, the rolls 2 and their vicinity are not contaminated.
Thus, the sprayed width can be substantially equal to the
width of the glass sheet, and the effective width can be
a maximum with regard to the starting glass sheet. Further-
more, because the sprayed width can be changed by adjusting
the position of the stopper, the eEfect:ive width can be
set optionally. Por example, when it is desired to obtain a
glass sheet having a small effective width, the speed of
withdrawing the glass from a float glass forming apparatus
is increased to reduce the width of the glass sheet and the
sprayed width. This gives rise to increased productivity
corresponding to the increase of the speed of withdrawing
the glass sheet.
When the lever 1~ of the three-way valve 13
contacts the stopper lS, the spraying is stopped. Accordingly,
the stroke of the spray gun 6 can be made equal to, or larger
than, the width of the glass sheet.
Since the spraying of the solution stops at both
ends of the sprayed width, the generation of exhaust gases ;~
at this part is reduced, and it is not particularly necessary
to provide side suction ducts. Even when such a side duct
i.s required, it may be of a small size with a reduced amount ~ -
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of air suction. The stroke of the spray gun can thus be
increased accordingly, and the sprayed width can also be
increased.
In the preferred embodiment of the present inven-
tion described in detail above, the jetting of the solution
from the nozzle 9 is completely shut off at both ends of
the sprayed width. If desired, the amount of spray can be
merely reduced instead of completely shutting off the
spraying from the nozzle 9, and the excessive feed can be
let away through the return pipe 12.
The method of this invention has the following
advantages over the prior art.
~1) Since the excessive sparying is prevented by
restricting the spraying of the sOlueion at predetenmined
positions on both side ends of the sprayed widthl the
sprayed width can substantially become an effective width
over whirh a uniform coating is formed. Coated glass sheets
can be obtained in good yields by increasing the stroke of
the spray gun to the width of the glass sheet or greater~
and thus increasing the effective width to nearly the entire
width of the glass sheet.
(2) Since the excessive spraying at both ends of -
the sprayed width is restricted, the solution can be saved
correspondingly. The amount of the solution per unit effec-
tive width can be reduced, and the cost of treatment can be
curtailed.
When the method of this invention is performed by
the apparatus of this invention, the following adv~ntages
are further exhibited.
~07193~
(1) When the spraying of the solution from the
spray guns is restricted ae both ends of the sprayed width,
the restricted solution is let away through a separate flow
path. Thus, the solution is continuously fed in a steady
state even when the restriction of spraying is effected.
Thus, when the spraying is resumed, the original steady
spraying state can be instantaneously caused by a simple
switch-over of the flow path without involving any great
change in the flow rate. As a result, the flow rate of the
feed solution can be easily controlled~ and uniform spraying
can be performed over the entire sprayed width whlle the
amount of the feed solution is being maintained always
constant.
(2) As the excessive feed solution resulting from
the restriction of the amount of spray is let away through
a separate flow path, this solution can be re-utilized.
This brings about an overall increase ln the efficiency of
utilizing the spray solution.
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