Glass manufacturing – Product cooling means
Reexamination Certificate
2000-07-12
2002-07-02
Derrington, James (Department: 1731)
Glass manufacturing
Product cooling means
C065S114000, C065S115000, C065S182200, C065S351000
Reexamination Certificate
active
06412309
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement in a glass quenching apparatus for quenching a heated glass sheet to manufacture tempered glass.
2. Description of Related Art
FIG. 14
hereof diagrammatically illustrates a conventional glass manufacturing method which is designed to manufacture tempered glass sheets of a thickness in the range of 3 mm to 5 mm. In general, such glass sheets of a 3 mm to 5 mm thickness are called normal-thickness glass sheets.
In the glass manufacturing method of
FIG. 14
, air jets
102
are emitted upward from a floating bed
101
within a heating furnace
100
so that a glass sheet
104
is floated above the floating bed
101
by the pressure of air jets, and the floated glass sheet
104
is heated to a predetermined temperature higher than its softening point or temperature while it is transferred as indicated by a profiled arrow.
Then, the heated glass sheet
104
is delivered from the heating furnace
100
to a glass quenching station
106
, where air
108
is blown onto opposite surfaces of the glass sheet
104
to thereby quench the heated glass sheet
104
. With this quenching, a compressive layer is formed in and along the surface of the glass sheet
104
, which increases the strength of the glass sheet
104
.
Subsequently, the thus-quenched or tempered glass sheet
104
is conveyed to a next station by a bed of rollers
109
.
As is known in the art, the quenched glass sheet has an increased strength by virtue of a compressive layer formed in and along its surface by rapidly cooling, i.e., quenching, the surface of a glass sheet heated up to a predetermined temperature to thereby produce a temperature difference between the surface and interior of the glass sheet. Thus, a glass sheet having a smaller thickness, such as 1.5 mm−3.0 mm, than that of the normal-thickness glass sheet (hereinafter referred to as “small-thickness glass sheet”) is cooled in the interior more readily than the normal-thickness glass sheet.
Accordingly, for such small-thickness glass sheets, it is necessary to quench their surface within an even shorter time than for the normal-thickness glass sheets.
One example of the conventionally-known methods for quenching the small-thickness glass sheets is shown in Japanese Patent Publication No. HEI 6-24995 under the title of “Method of Manufacturing Tempered Glass Sheets”. According to the disclosed method, a small-thickness glass sheet is quenched within a short time period by a combined use of compressor air and blower air. Specifically, the air supplied from the compressor (compressor air) is rapidly decompressed in a nozzle to produce a shock wave, so that the compressor air with the shock wave produced therein is blown onto the small-thickness glass sheet and simultaneously the air supplied from the blower (blower air) is blown onto the small-thickness glass sheet to thereby quench the glass sheet.
With the known quenching methods, however, various inconveniences are encountered when small-thickness glass sheets of different sizes are to be quenched, as set forth below in relation to a case where small-thickness glass sheets of two different sizes are each formed into a curved tempered glass sheet.
FIGS. 15A and 15B
are schematic views explanatory of basic operating principles of a conventionally-known glass quenching apparatus. More specifically,
FIG. 15A
illustrates an example where a small-thickness glass sheet
110
of a relatively large size (width W
1
) is quenched, and
FIG. 15B
illustrates an example where a small-thickness glass sheet
120
of a relatively small size (width W
2
) is quenched.
In the example shown in
FIG. 15A
, air jets are emitted upward from a floating bed
109
of the glass quenching apparatus so that the small-thickness and large-size glass sheet
110
previously curved at a preceding stage is floated above the floating bed
109
by the pressure of air jets. Then, the floated glass sheet
110
is retained at one edge (right edge in
FIG. 15A
)
110
a
by a holder
112
of a transfer arm
111
. During emission of the air jets from the floating bed
109
, air is jetted downward through a plurality of nozzles
113
.
Under these conditions, a conveyor chain
114
is driven to move the glass sheet
110
, via the transfer arm
111
, in a direction normal to the plane of the sheet of
FIG. 15A
, so that the glass sheet
110
is quenched during the movement by the chain
114
.
It is also generally known that a central region of glass sheets is hard to cool while edge regions of glass sheets are easy to cool. Because of this physical principle, there is a need to enhance the cooling capability of the quenching apparatus at a position P
1
corresponding to a central region
110
b
of the small-thickness and large-size glass sheet
110
. The terms “cooling capability” refer to a degree at which the heat of the heated glass can be absorbed by the air jets. Namely, the greater cooling capability can quench the glass sheet within a shorter time.
In the example shown in
FIG. 15B
, similarly to the example of
FIG. 15A
, the small-thickness and small-size glass sheet
120
previously curved at the preceding stage is retained at its right edge
120
a
in this figure by the holder
112
of the conveyor chain
114
and moved by the conveyor chain
114
via the transfer arm
111
in the direction normal to the plane of the sheet of
FIG. 15B
, so that the glass sheet
120
is quenched during the movement by the chain
114
. Because a central region
120
b
of the glass sheet
120
is hard to cool as compared to the sheet edge portions, there is a need to enhance the cooling capability of the quenching apparatus at a position P
2
corresponding to the central region
120
b
of the small-thickness and small-size glass sheet
120
. Because, in this example, the glass sheet
120
is set on the floating bed
109
with its right edge
120
b
used as a positional reference and then moved in the direction normal to the plane of the sheet of the figure while being maintained in this positional condition, tile central region
120
b
of the small-size glass sheet
120
is displaced rightward from the central region
110
b
of the large-size glass sheet
110
.
Namely, the glass quenching apparatus shown in
FIGS. 15A and 15B
is designed to quench each of the small-thickness glass sheets
110
and
120
by retaining the reference edge (right edge)
110
a
or
120
a
of the glass sheet via the holder
112
to support the glass sheet in a predetermined place above the floating bed
109
, i.e., by setting the glass sheet on an edge-guided basis. Because the glass sheets
110
and
120
of two different (large and small) sizes are set on such an edge-guided basis, the respective central regions of the sheets
110
and
120
would be significantly displaced from each other above the floating bed
109
, so that there arises a need for the quenching apparatus to have increased cooling capabilities at two positions P
1
and P
2
. This means that for use with three or more different sizes of glass sheets, the quenching apparatus needs to have increased cooling capabilities at three or more separate portions.
Accordingly, the conventional glass quenching apparatus of the foregoing construction requires a high equipment cost, which increases the cost of tempered glass sheets.
Additionally, the conventional glass quenching apparatus, when used for quenching small-thickness glass sheets, induces an increase in manufacturing cost because a large quantity of air is wasted for quenching other regions of the small-thickness glass sheets than the central region.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a glass quenching apparatus which is capable of quenching tempered glass sheets without increasing the cost of the tempered glass sheets.
To achieve the foregoing object, the present invention provides a glass quenching apparatus for quenching a glass sheet heated to a predetermined temperature, comprising: a first nozzle group
Fujioka Norihiro
Futagami Tohru
Kajii Masuhide
Derrington James
Merchant & Gould P.C.
Nippon Sheet Glass Co. Ltd.
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