TECHNICAL FIELD
[0001] This invention relates to a three stage forming station and method for forming a hot
glass sheet with transverse curvature having improved optics.
BACKGROUND
[0002] United States Patent 4,661,141 Nitschke et al. discloses a glass sheet press bending
system for bending hot glass sheets by conveying a hot glass sheet to below an upper mold that is
moved downwardly to receive a hot glass sheet and provide support thereof by upwardly directed
gas jets supplied from below a plane of conveyance of a roll conveyor and by a vacuum drawn at the
upper mold, and the upper mold is then moved upwardly with the glass sheet supported thereon by
contact with two thirds or more of the downwardly facing surface along the length of the glass sheet.
When glass sheets are formed with transverse curvature, i.e., curvature in directions that cross each
other without any straight line elements, the periphery of the glass sheet has excess glass that can
cause excess pressure between the mold and the glass sheet at the center of the glass sheet and
thereby result in undesirable optics both as to reflection and to transmission in the central viewing
area of the glass.
[0003] In connection with the type of system disclosed by the aforementioned United States
Patent 4,661,141, see also United States Patents: 5,900,034 Mumford et al; 5,906,668 Mumford et
al; 5,917,107 Ducat et al; 5,925,162 Nitschke et al; 6,032,491 Nitschke et al; 6,079,094 Ducat et
al; 6,173,587 Mumford et al; 6,418,754 Nitschke et al; 6,718,798 Nitschke et al; and 6,729,160
Nitschke et al.
SUMMARY
[0004] An object of the present invention is to provide an improved forming station for three
stage forming a hot glass sheet with transverse curvature.
[0005] In carrying out the above object, a forming station constructed according to the
invention includes a downwardly facing first upper mold, that has curvature in a first direction and
straight line elements in a second direction transverse to the first direction, for initially forming the
glass sheet with curvature in the first direction while maintaining straight line elements in the second
direction. An upwardly facing lower mold of the forming station has curvature in the first direction
and permits glass sheet curvature in the second direction, and the lower mold receives the glass sheet
from the first upper mold so the glass sheet sags under gravity along the second direction to have
some curvature in the second direction as well as curvature in the first direction. A downwardly
facing second upper mold of the forming station is complementary to the upwardly facing lower
mold and cooperates with the lower mold to press form the glass sheet with transverse curvature
corresponding to the shapes of the lower mold and the second upper mold.
[0006] In one disclosed embodiment, the three stage forming station includes a conveyor
from which the first upper mold receives the glass sheet prior to being received by the lower mold
which subsequently moves the glass sheet horizontally to below the second upper mold for the press
forming. That embodiment also includes a housing having a heated chamber and has the conveyor
embodied by a roll conveyor for conveying the hot glass sheet into the heated chamber of the
housing along a horizontal plane of conveyance. The first upper mold is movable vertically within
the heated chamber between an upper position above the roll conveyor and a lower position adjacent
the roll conveyor, and the first upper mold has a downwardly facing surface of a downwardly
convex curved shape including its straight line elements. A gas lift jet array located below the plane
of conveyance supplies upwardly directed lift jets for lifting the glass sheet upwardly from the roll
conveyor to the first upper mold when located in its lower position to initially form and support the
glass sheet against the downwardly facing surface of the first upper mold, whereupon the first upper
mold is moved upwardly to its upper position with the glass sheet supported against its downwardly
facing surface. The second upper mold is spaced horizontally within the heated chamber from the
first upper mold and is movable vertically between an upper position located above the elevation of
the plane of conveyance and a lower position closer to the elevation of the plane of conveyance, and
the second upper mold has a downwardly facing surface of a downwardly convex shape with
transverse curvature. A vacuum source selectively draws a vacuum at the downwardly facing
surface of the second upper mold. The lower mold faces upwardly with an upwardly concave shape
complementary to the downwardly convex shape of the downwardly facing surface of the second
upper mold. The lower mold is movable horizontally within the heated chamber at a location above
the plane of conveyance to below the first upper mold in its upper position with the glass sheet
supported against its downwardly facing surface, and the first upper mold is then moved
downwardly to adjacent the lower mold to release the glass sheet onto the lower mold whereupon the
first upper mold is moved upwardly to its upper position and the lower mold and the glass sheet
supported thereon are moved to below the second upper mold while in its upper position. The
second upper mold is then moved downwardly from its upper position to its lower position to
cooperate with the lower mold to press form the glass sheet with curvature in transverse directions,
and the second upper mold is then moved upwardly to its upper position with the press formed glass
sheet supported on the second upper mold by vacuum drawn at its downwardly facing surface by the
vacuum source. A delivery mold is moved to below the press formed glass sheet on the second
upper mold in its upper position whereupon the vacuum is terminated and the glass sheet is released
from the second upper mold onto the delivery mold which is then moved out of the forming station
for delivery of the press formed glass sheet. A controller operates the roll conveyor, the first upper
mold, the gas lift jet array, the second upper mold, the vacuum source, the lower mold, and the
delivery mold to perform the press forming of the glass sheet and its delivery.
[0007] As disclosed by the one embodiment, the vacuum source is operated by the controller
to provide a vacuum to the downwardly facing surface of the first upper mold to cooperate with the
gas lift jet array in lifting the glass sheet from the roll conveyor into contact with the downwardly
facing surface of the first upper mold for initial forming and support of the glass sheet, and after the
glass sheet is moved upwardly and contacts the downwardly facing surface of the first upper mold,
the controller terminates the operation of the gas lift jet array while continuing to operate the vacuum
source to provide the vacuum that is then the sole support of the glass sheet on the first upper mold.
Also, the lower mold has a ring shape that supports the glass sheet as it sags by gravity, and the
lower mold is also disclosed as having a support pad within its ring shape to control sagging of the
glass sheet during movement from below the first upper mold to below the second upper mold. As
disclosed, the forming station includes at least one press member that assists the lift jet array in
initially forming the glass sheet against the downwardly facing surface of the first upper mold.
There is also disclosed a quench station to which the delivery mold moves the press formed glass
sheet for quenching.
[0008] In another disclosed embodiment, the three stage forming station includes a conveyor
from which the first upper mold receives the glass sheet prior to the first upper mold moving
horizontally to move the glass sheet above the lower mold that then receives the glass sheet for
subsequently performing the press forming with the second upper mold. That embodiment also
includes a housing having a heated chamber and has the conveyor embodied by a roll conveyor for
conveying the hot glass sheet into the heated chamber of the housing along a horizontal plane of
conveyance. The first upper mold is movable horizontally within the heated chamber between a
pickup position above the roll conveyor and a delivery position spaced horizontally from the pickup
position, and the first upper mold has a downwardly facing surface of a downwardly convex curved
shape including its straight line elements. A gas lift jet array located below the plane of conveyance
supplies upwardly directed lift jets for lifting the glass sheet upwardly from the roll conveyor to the
first upper mold when located in its pickup position to initially form and support the glass sheet
against the downwardly facing surface of the first upper mold. The second upper mold is spaced
horizontally within the heated chamber from the pickup position of the first upper mold and is
movable vertically between an upper position located above the elevation of the plane of conveyance
and a lower position closer to the elevation of the plane of conveyance, and the second upper mold
has a downwardly facing surface of a downwardly convex shape that defines its transverse
curvature. A vacuum source selectively draws a vacuum at the downwardly facing surfaces of each
of the first and second upper molds. The lower mold is located within the heated chamber below the
second upper mold and is also below the first upper mold after movement thereof to its delivery
position with the glass sheet supported thereon by vacuum drawn by the vacuum source whereupon
the vacuum is terminated to release the glass sheet onto the lower mold and the first upper mold is
moved back to its pickup position. The second upper mold is then moved downwardly from its
upper position to its lower position to cooperate with the lower mold to press form the glass sheet
with curvature in transverse directions, and the second upper mold is subsequently moved upwardly
to its upper position with the press formed glass sheet supported on the second upper mold by
vacuum drawn at its downwardly facing surface by the vacuum source. A delivery mold is moved to
below the press formed glass sheet on the second upper mold in its upper position whereupon the
vacuum is terminated and the glass sheet is released from the second upper mold onto the delivery
mold which is then moved out of the forming station for delivery of the press formed glass sheet. A
controller operates the roll conveyor, the first upper mold, the gas lift jet array, the second upper
mold, the vacuum source, the lower mold, and the delivery mold to perform the press forming of the
glass sheet and its delivery.
[0009] In the other embodiment, the vacuum source is operated by the controller to provide a
vacuum to the downwardly facing surface of the first upper mold to cooperate with the gas lift jet
array in lifting the glass sheet from the roll conveyor into contact with the downwardly facing
surface of the first upper mold for initial forming and support of the glass sheet, and after the glass
sheet is moved upwardly and contacts the downwardly facing surface of the first upper mold, the
controller terminates the operation of the gas lift jet array while continuing to operate the vacuum
source to provide the vacuum that is then the sole support of the glass sheet on the first upper mold.
Also, the lower mold has a ring shape that supports the glass sheet as it sags by gravity, and the
lower mold is also disclosed as having a support pad within its ring shape to control sagging of the
glass sheet. As disclosed, the forming station includes at least one press member that assists the lift
jet array in initially forming the glass sheet against the downwardly facing surface of the first upper
mold. There is also disclosed a quench station to which the delivery mold moves the press formed
glass sheet for quenching.
[0010] Another object of the present invention is to provide an improved method for three
stage forming a hot glass sheet with transverse curvature.
[0011] In carrying out the immediately preceding object, the three stage method for forming
a hot glass sheet with transverse curvature is performed by initially forming the glass sheet against a
downwardly facing first upper mold so as to have curvature in a first direction and straight line
elements in a second direction transverse to the first direction. The glass sheet is then transferred
from the first upper mold onto an upwardly facing lower mold having curvature in the first direction
and permitting the glass sheet to sag under gravity to have some curvature in the second direction as
well as curvature in the first direction. Thereafter the glass sheet is press formed between the lower
mold and a downwardly facing second upper mold that has transverse curvature and is
complementary to the lower mold so the glass sheet has transverse curvature corresponding to the
shapes of the lower mold and the second upper mold.
[0012] In one disclosed practice, the three stage forming method is performed on a hot glass
sheet by conveying the hot glass sheet on a conveyor into a heated chamber of a forming station to
below the first upper mold which is located within the heated chamber above the conveyor and has a
downwardly facing surface of a convex shape with the curvature in the first direction and straight
line elements in the second direction transverse to the first direction, and which is spaced
horizontally from the second upper mold which is located within the heated chamber above the
elevation of the conveyor and has a downwardly facing surface of a convex shape with its transverse
curvature. The first upper mold is moved downwardly from an upper position to a lower position
adjacent the glass sheet on the conveyor and upwardly directed gas lift jets are supplied to lift the
glass sheet from the conveyor and provide the initial forming of the glass sheet against the
downwardly facing surface of the first upper mold, and the first upper mold is then moved upwardly
to its upper position with the glass sheet supported by the first upper mold. The lower mold, which
faces upwardly with a concave shape complementary to the downwardly convex shape of the
downwardly facing surface of the second upper mold, is then moved horizontally within the heated
chamber to a location above the conveyor and below the first upper mold in its upper position with
the glass sheet supported on the first upper mold and the first upper mold is subsequently moved
downwardly and releases the glass sheet onto the lower mold and is then moved upwardly.
Subsequently the lower mold with the glass sheet thereon is moved from below the first upper mold
to below the second upper mold in an upper position thereof and the second upper mold is then
moved downwardly to a lower position thereof and a vacuum is drawn at its downwardly facing
surface during the press forming of the glass sheet between the second upper mold and the lower
mold to provide the curvature of the glass sheet in transverse directions, whereupon the second upper
mold is moved upwardly to its upper position with the press formed glass sheet supported on the
second upper mold by the vacuum drawn at its downwardly facing surface. A delivery mold is then
moved to below the press formed glass sheet on the second upper mold in its upper position
whereupon the vacuum is terminated to release the glass sheet from the second upper mold onto the
delivery mold which is then moved out of the forming station for delivery of the press formed glass
sheet.
[0013] In the one practice, a vacuum is drawn at the first upper mold to assist the gas lift jets
in forming and supporting the glass sheet on the first upper mold, and after the glass sheet is moved
upwardly from the conveyor and contacts the downwardly facing surface of the first upper mold, the
supply of the upwardly directed gas lift jets is terminated and the vacuum then provides the sole
support of the glass sheet on the first upper mold. Also, the lower mold that receives the glass sheet
from the first upper mold has a ring shape that supports the glass sheet as it sags under gravity
during its movement to the second upper mold for the press forming, and a support pad controls
sagging of the supported hot glass sheet within the ring shape of the lower mold. As disclosed, at
least one press member assists the lift jet array in initially forming the glass sheet against the
downwardly facing surface of the first upper mold. Also, the delivery mold moves the press formed
glass sheet from the forming station to a quench station for quenching.
[0014] In another disclosed practice, the three stage forming method is performed by
conveying the hot glass sheet on a conveyor into a heated chamber of a forming station to below the
first upper mold at a pickup position thereof within the heated chamber above the conveyor, with the
first upper mold having a downwardly facing surface of a convex shape with curvature in the first
direction and straight line elements in the second direction transverse to the first direction, with the
first upper mold in the pickup position being spaced horizontally from the lower mold and the
second upper mold which is located above the lower mold, and with the second upper mold located
within the heated chamber above the elevation of the conveyor and having a downwardly facing
surface of a convex shape with its transverse curvature. The first upper mold is moved downwardly
from an upper position to a lower position adjacent the glass sheet on the conveyor and upwardly
directed gas lift jets are supplied to lift the glass sheet from the conveyor and provide the initially
forming of the glass sheet against the downwardly facing surface of the first upper mold, the first
upper mold is then moved upwardly to its upper position with the glass sheet supported by the first
upper mold, and a vacuum is drawn at the first upper mold to support the glass sheet thereon. The
first upper mold and the glass sheet supported thereon are moved horizontally within the heated
chamber from the pickup position to a delivery position below the second upper mold and above the
lower mold which has an upwardly facing surface of a concave shape complementary to the convex
shape of the downwardly facing surface of the second upper mold. Subsequently the vacuum drawn
at the first upper mold is terminated in the delivery position to release the glass sheet onto the lower
mold, the first upper mold is moved back to the pickup position, the second upper mold is moved
downwardly to cooperate with the lower mold in the press forming of the glass sheet, and then the
second upper mold is moved upwardly to its upper position with the press formed glass sheet
supported on the second upper mold by vacuum drawn at its downwardly facing surface. A delivery
mold is then moved to below the press formed glass sheet on the second upper mold in its upper
position whereupon the vacuum is terminated to release the glass sheet from the second upper mold
onto the delivery mold which is then moved out of the forming station for delivery of the press
formed glass sheet.
[0015] In the other disclosed practice, the lower mold has a ring shape that supports the glass
sheet as it sags by gravity, and a support pad controls sagging of the supported hot glass sheet within
the ring shape of the lower mold. As disclosed, at least one press member assists the lift jet array in
initially forming the glass sheet against the downwardly facing surface of the first upper mold. Also,
the delivery mold moves the press formed glass sheet from the forming station to a quench station
for quenching.
[0016] According to another object, the invention is used in a three stage forming station for
forming a hot glass sheet with transverse curvature, and the invention comprises: a downwardly
facing first upper mold, that has curvature in a first direction and straight line elements in a second
direction transverse to the first direction, for initially forming the glass sheet with curvature in the
first direction while maintaining straight line elements in the second direction; an upwardly facing
lower mold, that has curvature in the first direction and permits glass sheet curvature in the second
direction, for receiving the glass sheet from the first upper mold so the glass sheet sags under gravity
along the second direction to have some curvature in the second direction as well as curvature in the
first direction; and a downwardly facing second upper mold, that has transverse curvature and is
complementary to the upwardly facing lower mold, for cooperating with the lower mold to press
form the glass sheet with transverse curvature corresponding to the shapes of the lower mold and the
second upper mold.
[0017] As disclosed, the invention further includes a delivery mold for receiving the press
formed glass sheet from the second upper mold for delivery.
[0018] As disclosed, the first and second upper molds each has a downwardly facing surface
of a downwardly convex shape, and the downwardly facing surface of each of the first and second
upper molds also includes an associated array of vacuum holes. Furthermore, the lower mold has an
upwardly concave shape provided by a ring shape that defines its upwardly concave shape and
supports the glass sheet as it sags by gravity.
[0019] Also, the lower mold as disclosed includes a support pad within its ring shape to
control sagging of the glass sheet during movement from below the first upper mold to below the
second upper mold.
[0020] The objects, features and advantages of the present invention are readily apparent
from the following detailed description of the preferred embodiment when taken in connection with
the referenced drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIGURE 1 is a schematic elevational view of a glass sheet processing system
including a three stage forming station that embodies the present invention and carries out the
method of the invention for three stage forming of a hot glass sheet.
[0022] FIGURE 2 is a sectional view taken through the forming station along the direction of
line 2-2 in Figure 1 and illustrates a forming apparatus that includes first and second upper molds, a
lower mold and a delivery mold for performing three stage forming of a hot glass sheet with
transverse curvature.
[0023] FIGURE 3 is a perspective view of the first upper mold with its normally
downwardly forming convex surface shown facing generally upwardly for purposes of illustration.
[0024] FIGURE 4 is a perspective view of the second upper mold with its normally
downwardly forming convex surface also shown facing generally upwardly for purposes of
illustration.
[0025] FIGURE 5 is a perspective view of the lower mold which receives the initially
formed glass sheet from the first upper mold for gravity sagging and movement to below the second
upper mold for subsequent press forming.
[0026] FIGURE 6 is a view taken along the direction of line 6-6 of Figure 2 to show the
initial pickup of the hot glass sheet from the conveyor by the first upper mold for the initial forming.
[0027] FIGURE 7 is an elevational view of the forming station taken in the same direction as
Figure 2 and illustrates the movement of the glass sheet on the lower mold from the first upper mold
to below the second upper mold for the press forming with transverse curvature.
[0028] FIGURE 8 is an elevational view taken in the same direction as Figure 7 and
illustrates the operation of the delivery mold for delivering the formed glass sheet from the forming
station.
[0029] FIGURE 9 is a plan view taken along the direction of line 9-9 in Figure 6 to illustrate
a gas lift jet array that operates to perform the initial pickup of the glass sheet from the conveyor by
the first upper mold.
[0030] FIGURE 10 is a flow chart that illustrates the three stage hot glass sheet forming
operation.
[0031] FIGURE 11 is a view taken in the same direction as Figure 2 but illustrating another
embodiment of the three stage forming station of the invention which also carries out the method of
the invention for three stage forming of the hot glass sheet.
[0032] FIGURES 12 and 13 are partial views of Figure 11 illustrating the glass sheet
processing during a cycle of operation of the system.
[0033] FIGURE 14 is a flow chart that illustrates the three stage hot glass sheet forming
operation of the forming station embodiment of Figures 11-13.
DETAILED DESCRIPTION
[0034] As required, a detailed embodiment of the present invention is disclosed herein;
however, it is to be understood that the disclosed embodiment is merely exemplary of the invention
that may be embodied in various and alternative forms. The figures are not necessarily to scale;
some features may be exaggerated or minimized to show details of particular components.
Therefore, specific structural and functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one skilled in the art to practice the present
invention.
[0035] With reference to Figure 1, a glass sheet forming system generally indicated by 20
includes a furnace 22 having a heating chamber 24 for providing a heated ambient for heating glass
sheets. A conveyor 26 of the system conveys the heated glass sheet in a generally horizontally
extending orientation and is preferably of the roll conveyor type including rolls 28 like those
disclosed by United States Patent Nos.: 3,806,312 McMaster; 3,934,970 McMaster et al, 3,947,242
McMaster et al.; and 3,994,71 1 McMaster et al. A three stage forming station 30 of the system 20 is
constructed according to the present invention and performs the method thereof such that both the
forming station and the forming method are described in an integrated manner to facilitate an
understanding of different aspects of the invention. The forming station 30 has a construction with a
press forming somewhat similar to that of the disclosure of the aforementioned United States Patent
4,661,141 and the other United States Patents set forth in the above Background section of this
application. Furthermore, the forming station 30 has an insulated housing 32 defining a heated
chamber 34 in which forming apparatus 36 of the forming station is located as also shown in Figure
2.
[0036] As illustrated in Figure 2, the glass sheet forming apparatus 36 includes a first upper
mold 38 that functions during a first stage of the hot glass sheet forming, a second upper mold 40
that functions during a press forming stage of the hot glass sheet forming, a lower mold 42 that
receives the glass sheet G from the first upper mold 38 for gravity sagging and moves the glass sheet
from the first upper mold to the second upper mold 40 and cooperates with the second upper mold to
provide the press forming, and a delivery mold 44 that receives the formed glass sheet from the
second upper mold 40 for delivery from the forming station 30, which delivery is to a quench station
46 as disclosed.
[0037] With continuing reference to Figure 2, a schematically indicated actuator 48 such as
one or more cylinders has a connection(s) 50 to the first upper mold 38 to provide movement thereof
between an upper position above the roll conveyor 26 and as shown in Figure 6 a lower position
adjacent the roll conveyor and a conveyed hot glass sheet G. The first upper mold 38 has a
downwardly facing surface 52 which has a downwardly convex shape shown in Figure 6 and
illustrated by the phantom line 54 in Figure 3. Mold surface 52 also has straight line elements such
as illustrated by phantom line 56 and may be provided by a cylindrical shape or a partial conical
shape.
[0038] A gas lift jet array 58 in the forming station as illustrated in Figure 6 is located below
the plane of conveyance C of the hot glass sheet and includes gas jet pumps 60 that supply upwardly
directed gas jets 62 for lifting the glass sheet G upwardly from the roll conveyor 26 to initially form
and support the glass sheet against the downwardly facing surface 52 of the first upper mold 38
which is then moved upwardly to its upper position with the glass sheet supported against its
downwardly facing surface as shown in Figure 2. The gas jet pumps 60 are of the type disclosed by
United States Patents 4,204,854 McMaster et al. and 4,356,018 McMaster et al. such that a primary
gas flow therefrom induces a secondary gas flow many times the extent of the primary gas flow in
order to provide the lifting. A downwardly facing surface 52 of the first upper mold 38 also has an
array of vacuum holes 64 through which a vacuum may be drawn to also provide initial lifting of the
glass sheet and to then support the glass sheet as is hereinafter described.
[0039] As shown in Figure 2, the second upper mold 40 is spaced horizontally within the
heated chamber 34 of the forming station housing 32 and is movable vertically by an actuator 66 and
a connection 68 like the actuator and connection associated with the first upper mold 38. This
vertical movement of the second upper mold 40 is between an upper position located above the
elevation of the plane of conveyance and a lower position (Figure 7) closer to the elevation of the
plane of conveyance. The second upper mold 40 has a downwardly facing surface 70 of a
downwardly convex shape with curvature in transverse directions without any straight line elements
as shown by the curved phantom lines 72 and 74 in Figure 4. The second upper mold 40 also has an
array of vacuum holes 76 in its downwardly facing surface 70 for forming and supporting the heated
glass sheet against the second upper mold during the forming cycle.
[0040] It should also be mentioned that the first and second upper molds 38 and 40 can also
be moved upwardly and downwardly at the same time by a single actuator instead of separate
actuators.
[0041] As shown in Figure 2, a schematically indicated vacuum source 78 is disclosed as
operable to provide a vacuum at the downwardly facing surfaces 52 and 70 of the first and second
upper molds 38 and 40. Actually, this source of vacuum can be provided by positive pressure air
supplied to gas jet pumps 80 and 8 1 on the first and second upper molds 38 and 40 and are
preferably of the type disclosed by United States Patents 4,202,681 McMaster and 4,222,763
McMaster so as to be capable of drawing greater and lesser extents of vacuums as well as providing
positive pressure air for providing glass sheet release during the forming operation as is hereinafter
more fully described.
[0042] The lower mold 42 as best illustrated in Figure 5 faces upwardly with an upwardly
concave shape in transverse directions complementary to the downwardly convex shape of the
downwardly facing surface 70 of the second upper mold 40. This lower mold 42 is movable by an
actuator 82 and connection 83 horizontally within the heated chamber 34 of the forming station
housing 32 at a location above the plane of conveyance of the glass sheet to below the first upper
mold 38 in its upper position as shown in Figure 7 with the glass sheet supported against its
downwardly facing surface 52. The first upper mold 38 is then movable downwardly to release the
glass sheet for transfer onto the lower mold 42. The release of the glass sheet can be provided by the
termination of the vacuum drawn and the termination of the upwardly directed gas jets provided by
the gas jet array 58 previously described, as well as by providing positive pressure gas to the mold
surface 52. The first upper mold 38 is then moved upwardly to its upper position and the lower mold
42 and the glass sheet supported thereon are moved horizontally to below the second upper mold 40
while in its upper position as shown in Figure 2. During this movement, the glass sheet sags by
gravity toward the shape of the lower mold 42 with curvature in transverse directions. The second
upper mold 40 is then moved downwardly from its upper position shown in Figure 2 to its lower
position shown in Figure 7 to cooperate with the lower mold 42 to press form the glass sheet with
curvature in transverse directions, and the second upper mold then has a vacuum drawn at its
downwardly facing surface 70 to support the glass sheet and is moved upwardly to its upper position
shown in Figure 8.
[0043] The glass forming operation continues by the lower mold 42 being moved out from
under the second upper mold 40 and back under the first upper mold 38 as shown by phantom line
representation in Figure 7, while the delivery mold 44 is moved from its Figure 2 position at the
quench station 46 to below the second upper mold 40 to receive the glass sheet as shown in Figure 8
as the vacuum is terminated at the second upper mold so the glass sheet drops onto the delivery mold
which is then moved by its actuator 84 and connection 85 out of the forming station for delivery of
the pressed formed glass sheet such as by quenching in the quench station 46 between lower and
upper quench heads 86 and 87 as shown in Figure 2.
[0044] A controller 88 shown in Figure 1 has a bundle of connections 90 that operate the roll
conveyor 26, the first upper mold 38, the second upper mold 40, the lower mold 42, the delivery
mold 44, the gas lift jet array 58, the vacuum source 78 and the quench station 46 to perform the
press forming of the glass sheet, its delivery and quenching.
[0045] During development of the forming station 30, the inventors have determined that
glass sheet forming with transverse curvature upon initial forming on an upper mold can cause
buckling at the central viewing area of the glass sheet due to excess glass at the glass sheet periphery
when the flat glass sheet assumes the curvature in crossing directions with no straight line elements,
and such buckling results in distorted optics as to transmission and/or reflection in the central
viewing area of the glass. It has also been determined that use of a first upper mold with straight line
elements during the initial stage of forming, then allowing the gravity sag forming on the lower mold
to begin the transverse curvature, and subsequently performing the final press forming of the glass
sheet reduces optical distortions both as to transmission and reflection in the central view area of the
formed glass sheet.
[0046] Also, for purposes of this application, the term "straight line elements" means straight
lines between two opposite extremities of the first upper mold surface 52 and of the glass sheet after
the first stage of forming, which straight lines have midpoints from which the mold surface and
initially formed glass sheet are spaced no more than about 0.5%, and preferably no more than about
0.3%, of the distance between the extremities.
[0047] In the three stage forming station disclosed, the vacuum source 78 shown in Figure 2
is operated by the controller 88 shown in Figure 1 through the bundle of connections 90 to provide a
vacuum to the downwardly facing surface 52 of the first upper mold in order to cooperate with the
gas lift jet array 58 in lifting the glass sheet G from the roll conveyor 26 into contact with the first
upper mold at its downwardly facing surface 52 for initially forming and support of the glass sheet.
After the glass sheet G is moved upwardly and contacts the downwardly facing surface 52 of the
first upper mold, the controller 88 disclosed terminates the operation of the gas lift jet array 58 while
continuing to provide the vacuum that is then the sole support of the glass sheet on the first upper
mold.
[0048] As illustrated in Figure 5, the lower mold 42 has a ring shape that defines the
upwardly concave shape in transverse directions complementary to the downwardly facing convex
shape of the second upper mold surface 70. This ring shape of the lower mold 42 defines an open
center 92 so as to contact the glass sheet at its periphery and allow gravity sagging; however, in
order to control the gravity sagging of the glass sheet during its transfer between the first and second
upper molds 38 and 40, the lower mold 42 may be provided with one or more pads 94 in its open
center.
[0049] The manner in which the forming apparatus is constructed and operates to initially
form the glass sheets with straight line elements at the first stage of forming, begin the transverse
curvature by the gravity sagging on the lower mold and subsequently completing the transverse
curvature by the press forming reduces central deformation of the formed glass both as to
transmission and reflection at its central viewing area. More specifically, during the first stage of
forming on the first upper mold, the formed glass sheet with straight line elements only has
curvature between the end portions 96 of the first upper mold 38 so that initially there is no excess
peripheral glass for causing deformation. Subsequent gravity sagging of the initially formed glass
sheet on the lower mold initiates the transverse forming without forcing deformation of the glass due
to the excess peripheral glass as the glass forms transversely. During the final press forming on the
second upper mold 40 shown in Figure 4, the end portions 100 and side portions 102 of the lower
mold 42 shown in Figure 5 press the glass sheet against the downwardly facing surface 70 of the
second upper mold 40 to provide the final transverse curvature of the glass sheet with decreased
distortion in the central viewing area of the formed glass sheet.
[0050] When the glass sheet has a generally rectangular shape, the initial forming will be in a
cylindrical shape, and when the glass sheet is of a generally trapezoidal shape the initial forming will
be of a partial conical shape, both of which have straight line elements so there is no excess glass
sheet at the periphery of the glass sheet during the first stage of forming. As described above, the
subsequent gravity sag forming on the lower mold to start forming the transverse curvature and the
final press forming complete the glass sheet forming with transverse curvature with reduced central
viewing area distortion.
[0051] With reference to Figure 9, the gas lift jet array 58 disclosed includes a pair of end
portions 104 that are aligned with the end portions G' of the glass sheet to initially provide their
lifting and support on the first upper mold 38, and the gas lift jet array also includes a central portion
108 having a pair of branches 110 for providing the support and lifting of the intermediate portion
G" of the glass sheet. Pressurized gas that is heated during its flow into and then through a heating
path in the heated chamber supply conduits 112 that supply pressurized gas to the end portions 104
and conduits 114 that supply pressurized gas to the central portion 108 in both of its branches 110.
A control generally indicated by 116 includes valves 118 that adjustably control the pressure
supplied to the conduits 112 feeding the end portions 104 and the control 116 also includes valves
120 that adjustably control the gas pressure supplied to the branches 110 of the central portion 108.
Of course, the valving and control for supplying the gas array end portions 104 and the central
portion 108 can also be constructed in different ways than the specific way shown to adjustably
control the amount of lifting and support at the end portions and intermediate portion of the glass
sheet. This operation takes place after the downward movement of the first upper mold to receive
the glass sheet for the first stage of forming and can then be terminated while the vacuum continues
to be drawn at the first upper mold surface to continue the support of the glass sheet. The vacuum is
continued until release of the glass sheet onto the lower mold 42 and such termination may be
accompanied by supply of positive pressure air supplied by the gas jet pump 80.
[0052] With reference to the flow chart of Figure 10, the press forming operation begins by
the heating 122 of the glass sheet G in the furnace and its subsequent conveyance 124 after heating
into the forming station to begin the press forming operation. Then the downward movement of the
first upper mold as illustrated at 126 and its receipt of the glass sheet G for the initial forming with
curvature in the first direction and straight line elements in the second transverse direction is
followed by the first upper mold and glass sheet upward movement 128 and subsequently by the
lower mold movement 130 under the raised first upper mold and release of the glass sheet onto the
lower mold for the gravity sagging that starts the transverse curvature. The lower mold and initially
formed glass sheet are then moved as shown by 132 to below the second upper mold which is then
moved downwardly as shown by 134 to press form the initially formed glass sheet with transverse
curvature. The second upper mold is then moved upwardly as shown at 136 and the lower mold is
moved out from below the second upper mold, followed by the delivery mold movement 138 below
the second upper mold to receive the formed glass sheet for delivery. The downward second upper
mold movement shown by 134 initiates the press forming of the glass sheet with the lower mold as
vacuum is supplied to the second upper mold to provide the press forming in transverse directions
with optics that are enhanced by the initial forming of the glass sheet with straight line elements
followed by the gravity sagging before the press forming.
[0053] With reference to Figure 11, another embodiment of a three stage forming station 30'
constructed according to the present invention operates to carry out the method of the invention and
has many of the same components that operate like those of the previously described embodiment
such that like references numerals are applied to like components and much of the previous
description is applicable and thus will not be repeated.
[0054] In the forming station 30' illustrated in Figures 11-13, a heated glass sheet G on the
conveyor 26 is received by the first mold 38 and moved horizontally from its pickup position shown
in Figure 11 to a delivery position shown in Figure 12 where the lower mold 42 is located, which is
different from the prior embodiment wherein the lower mold provides the horizontal movement. As
such, while there is gravity sagging on the lower mold in this embodiment, there is less time for such
gravity sagging so that the shape can be more accurately controlled. After the glass sheet is
deposited on the lower mold 42 by the first upper mold 38, the first upper mold 38 moves back from
its delivery position of Figure 12 to its pickup position of Figure 11 and the second upper mold 40
moves downwardly as shown in Figure 13 to cooperate with the lower mold in press forming the
glass sheet as previously described. After the press forming, the second upper mold 40 moves
upwardly with the glass sheet supported against its downwardly facing surface 70 by a drawn
vacuum as previously described and the delivery mold 44 shown in Figure 11 is moved from the
quench station 46 into the forming station 30' to receive the glass sheet for movement back out to the
quench station between the lower and upper quench heads 86 and 87 for quenching also as
previously described.
[0055] As shown in Figure 11, the first upper mold 38 has a frame 38' that is supported by
elongated beams 140 (only one shown) that are moved by an actuator 142 through a connection 144.
These beams 140 are supported by associated rollers 146 that are mounted by actuators 148 to
provide vertical movement of the beams and hence vertical movement of the first upper mold 138
during its operation. More specifically, the first upper mold 38 can be moved downwardly to about
one half inch (12 to 15 mm) from the conveyor 26 for the initial pickup of the glass sheet and can
then be moved upwardly so as to move above drive mechanism covers 150 located the ends of the
conveyor rolls 28 to reduce heat flow from the interior of the forming station to the factory ambient.
Lateral rollers 152 also contact the beams to provide lateral positioning during movement of the first
upper mold 38 between its pickup position shown in Figure 11 and its delivery position shown in
Figure 12.
[0056] The forming station 30' illustrated in Figures 11-13 thus also has three stages of
operation wherein the glass sheet is formed on the first upper mold 38 with curvature in a first
direction and straight line elements in a second direction transverse to the first direction, by gravity
on the lower mold 42 after receipt thereby from the first upper mold 38 in its delivery position
shown in Figure 12, and finally by the press forming between the second upper mold 40 and the
lower mold 42 as shown in Figure 13.
[0057] The lower mold 42 as illustrated is supported by a framework 154 that is supported
by actuators 156, such as screw jacks, for vertical movement. This vertical movement can be
downward to allow the first upper mold 38 to move over the lower mold 42 and then upward so that
the release of the glass sheet is at a more closely spaced relationship to control positioning. In
addition, the vertical movement of the lower mold 42 can also be used in cooperation with the
vertical movement of the second upper mold 40 to perform the press bending.
[0058] With reference to the flow chart of Figure 14, the embodiment of Figures 11-13
performs the press forming operation beginning by the heating 158 of the glass sheet G in the
furnace and its subsequent conveyance 160 into the forming station, followed by the first upper mold
receiving the glass sheet from the conveyance for initial forming with straight line elements in the
first stage, and then the horizontal movement 164 of the first upper mold and the glass sheet to above
the lower mold. Then, the glass sheet release 166 from the first upper mold onto the lower mold
provides gravity sagging in the second stage which can be performed in a shorter time than when the
lower mold moves horizontally, and the second upper mold is moved downwardly at 168 to the
lower mold for press forming with transverse curvature in the third stage, and the second upper mold
and glass sheet are moved upwardly at 170 followed by the delivery mold movement 172 below the
second upper mold to receive the press formed glass sheet and then move it out of the forming
station for delivery.
[0059] Both embodiments can have reduced cycle time by the vertical positioning of the
constructions disclosed. In the embodiment of Figures 1-10, the vertical positioning permits both the
lower mold 42 and the delivery mold 44 to be below the second upper mold 40 at the same time so
successive cycles overlap to reduce cycle time. In the embodiment of Figures 11-14, the vertical
positioning permits both the first upper mold 38 and the delivery mold 44 to be below the second
upper mold 40 at the same time so successive cycles overlap to reduce cycle time.
[0060] In both embodiments, it is also possible to assist the lift jets with mechanical pressing
of the glass sheet against the first upper mold 38 at its downwardly facing surface 52 so as to ensure
completed glass contact therewith even with abrupt curvature at one or more locations. This type of
pressing can be performed by having a press member, or a pair of press members, mounted on the
first upper mold 38 and operated by the controller 88 through an actuator(s) that extends between the
upper mold and the press member which may pivot or otherwise move relative to the upper mold.
See United States patent 4,514,208 Nitschke, which discloses mechanical pressing against an upper
mold.
[0061] All of the previously mentioned patents are assigned to the applicant of the present
application and are hereby incorporated by reference.
[0062] While exemplary embodiments are described above, it is not intended that these
embodiments describe all possible forms of the invention. Rather, the words used in the
specification are words of description rather than limitation, and it is understood that various
changes may be made without departing from the spirit and scope of the invention. Additionally, the
features of various implementing embodiments may be combined to form further embodiments of
the invention.

WHAT IS CLAIMED IS:
1. A three stage forming station for forming a hot glass sheet with transverse
curvature comprising:
a downwardly facing first upper mold, that has curvature in a first direction and
straight line elements in a second direction transverse to the first direction, for initially forming the
glass sheet with curvature in the first direction while maintaining straight line elements in the second
direction;
an upwardly facing lower mold, that has curvature in the first direction and permits
glass sheet curvature in the second direction, for receiving the glass sheet from the first upper mold
so the glass sheet sags under gravity along the second direction to have some curvature in the second
direction as well as curvature in the first direction; and
a downwardly facing second upper mold, that has transverse curvature and is
complementary to the upwardly facing lower mold, for cooperating with the lower mold to press
form the glass sheet with transverse curvature corresponding to the shapes of the lower mold and the
second upper mold.
2. A three stage forming station as in claim 1 which includes a conveyor from
which the first upper mold receives the glass sheet prior to being received by the lower mold which
subsequently moves the glass sheet horizontally to below the second upper mold for the press
forming.
3. A three stage forming station as in claim 2 which includes:
a housing having a heated chamber;
the conveyor being embodied by a roll conveyor for conveying the hot glass sheet
into the heated chamber of the housing along a horizontal plane of conveyance;
the first upper mold being movable vertically within the heated chamber between an
upper position above the roll conveyor and a lower position adjacent the roll conveyor, and the first
upper mold having a downwardly facing surface of a downwardly convex curved shape including its
straight line elements;
a gas lift jet array located below the plane of conveyance to supply upwardly directed
lift jets for lifting the glass sheet upwardly from the roll conveyor to the first upper mold when
located in its lower position to initially form and support the glass sheet against the downwardly
facing surface of the first upper mold, whereupon the first upper mold is moved upwardly to its
upper position with the glass sheet supported against its downwardly facing surface;
the second upper mold being spaced horizontally within the heated chamber from the
first upper mold and being movable vertically between an upper position located above the elevation
of the plane of conveyance and a lower position closer to the elevation of the plane of conveyance,
and the second upper mold having a downwardly facing surface of a downwardly convex shape with
transverse curvature;
a vacuum source for selectively drawing a vacuum at the downwardly facing surface
of the second upper mold;
the lower mold facing upwardly with an upwardly concave shape complementary to
the downwardly convex shape of the downwardly facing surface of the second upper mold, the lower
mold being movable horizontally within the heated chamber at a location above the plane of
conveyance to below the first upper mold in its upper position with the glass sheet supported against
its downwardly facing surface, and the first upper mold then being moved downwardly to adjacent
the lower mold to release the glass sheet onto the lower mold whereupon the first upper mold is
moved upwardly to its upper position and the lower mold and the glass sheet supported thereon are
moved to below the second upper mold while in its upper position;
the second upper mold then being moved downwardly from its upper position to its
lower position to cooperate with the lower mold to press form the glass sheet with curvature in
transverse directions, and the second upper mold then being moved upwardly to its upper position
with the press formed glass sheet supported on the second upper mold by vacuum drawn at its
downwardly facing surface by the vacuum source;
a delivery mold is moved to below the press formed glass sheet on the second upper
mold in its upper position whereupon the vacuum is terminated and the glass sheet is released from
the second upper mold onto the delivery mold which is then moved out of the forming station for
delivery of the press formed glass sheet; and
a controller that operates the roll conveyor, the first upper mold, the gas lift jet array,
the second upper mold, the vacuum source, the lower mold, and the delivery mold to perform the
press forming of the glass sheet and its delivery.
4. A three stage forming station as in claim 3 wherein the vacuum source is
operated by the controller to provide a vacuum to the downwardly facing surface of the first upper
mold to cooperate with the gas lift jet array in lifting the glass sheet from the roll conveyor into
contact with the downwardly facing surface of the first upper mold for initial forming and support of
the glass sheet.
5. A three stage forming station as in claim 4 wherein after the glass sheet is
moved upwardly and contacts the downwardly facing surface of the first upper mold, the controller
terminates the operation of the gas lift jet array while continuing to operate the vacuum source to
provide the vacuum that is then the sole support of the glass sheet on the first upper mold.
6. A three stage forming station as in claim 3 wherein the lower mold has a ring
shape that supports the glass sheet as it sags by gravity.
7. A three stage forming station as in claim 6 wherein the lower mold includes a
support pad within its ring shape to control sagging of the glass sheet during movement from below
the first upper mold to below the second upper mold.
8. A three stage forming stations as in claim 3 further including at least one press
member for assisting the gas lift jet array in forming the glass sheet against the downwardly facing
surface of the first upper mold.
9. A three stage forming station as in claim 3 further including a quench station
to which the delivery mold moves the press formed glass sheet for quenching.
10. A three stage forming station as in claim 1 which includes a conveyor from
which the first upper mold receives the glass sheet prior to the first upper mold moving horizontally
to move the glass sheet above the lower mold that then receives the glass sheet for subsequently
performing the press forming with the second upper mold.
11. A three stage forming station as in claim 10 which includes:
a housing having a heated chamber;
the conveyor being embodied by a roll conveyor for conveying the hot glass sheet
into the heated chamber of the housing along a horizontal plane of conveyance;
the first upper mold being movable horizontally within the heated chamber between a
pickup position above the roll conveyor and a delivery position spaced horizontally from the pickup
position, and the first upper mold having a downwardly facing surface of a downwardly convex
curved shape including its straight line elements;
a gas lift jet array located below the plane of conveyance to supply upwardly directed
lift jets for lifting the glass sheet upwardly from the roll conveyor to the first upper mold when
located in its pickup position to initially form and support the glass sheet against the downwardly
facing surface of the first upper mold;
the second upper mold being spaced horizontally within the heated chamber from the
pickup position of the first upper mold and being movable vertically between an upper position
located above the elevation of the plane of conveyance and a lower position closer to the elevation of
the plane of conveyance, and the second upper mold having a downwardly facing surface of a
downwardly convex shape that defines its transverse curvature;
a vacuum source for selectively drawing a vacuum at the downwardly facing surfaces
of each of the first and second upper molds;
the lower mold being located within the heated chamber below the second upper
mold and is also below the first upper mold after movement thereof to its delivery position with the
glass sheet supported thereon by vacuum drawn by the vacuum source whereupon the vacuum is
terminated to release the glass sheet onto the lower mold and the first upper mold is moved back to
its pickup position;
the second upper mold then being moved downwardly from its upper position to its
lower position to cooperate with the lower mold to press form the glass sheet with curvature in
transverse directions, and the second upper mold is subsequently moved upwardly to its upper
position with the press formed glass sheet supported on the second upper mold by vacuum drawn at
its downwardly facing surface by the vacuum source;
a delivery mold is moved to below the press formed glass sheet on the second upper
mold in its upper position whereupon the vacuum is terminated and the glass sheet is released from
the second upper mold onto the delivery mold which is then moved out of the forming station for
delivery of the press formed glass sheet; and
a controller that operates the roll conveyor, the first upper mold, the gas lift jet array,
the second upper mold, the vacuum source, the lower mold, and the delivery mold to perform the
press forming of the glass sheet and its delivery.
12. A three stage forming station as in claim 11 wherein the vacuum source is
operated by the controller to provide a vacuum to the downwardly facing surface of the first upper
mold to cooperate with the gas lift jet array in lifting the glass sheet from the roll conveyor into
contact with the downwardly facing surface of the first upper mold for initial forming and support of
the glass sheet.
13. A three stage forming station as in claim 12 wherein after the glass sheet is
moved upwardly and contacts the downwardly facing surface of the first upper mold, the controller
terminates the operation of the gas lift jet array while continuing to operate the vacuum source to
provide the vacuum that is then the sole support of the glass sheet on the first upper mold.
14. A three stage forming station as in claim 11 wherein lower mold has a ring
shape that supports the glass sheet as it sags by gravity.
15. A three stage forming station as in claim 14 wherein the lower mold includes
a support pad within its ring shape to control sagging of the glass sheet.
16. A three stage forming stations as in claim 11 further including at least one
press member for assisting the gas lift jet array in forming the glass sheet against the downwardly
facing surface of the first upper mold.
17. A three stage forming station as in claim 11 further including a quench station
to which the delivery mold moves the press formed glass sheet for quenching.
18. A three stage method for forming a hot glass sheet with transverse curvature
comprising:
initially forming the glass sheet against a downwardly facing first upper mold that has
curvature in a first direction and straight line elements in a second direction transverse to the first
direction;
then transferring the glass sheet from the first upper mold onto an upwardly facing
lower mold having curvature in the first direction and permitting the glass sheet to sag under gravity
to have some curvature in the second direction as well as curvature in the first direction; and
thereafter press forming the glass sheet between the lower mold and a downwardly
facing second upper mold that has transverse curvature and is complementary to the lower mold so
the glass sheet has transverse curvature corresponding to the shapes of the lower mold and the
second upper mold.
19. A three stage method for forming a hot glass sheet as in claim 18 wherein the
method is performed by:
conveying the hot glass sheet on a conveyor into a heated chamber of a forming
station to below the first upper mold which is located within the heated chamber above the conveyor
and has a downwardly facing surface of a convex shape with the curvature in the first direction and
straight line elements in the second direction transverse to the first direction, and which is spaced
horizontally from the second upper mold which is located within the heated chamber above the
elevation of the conveyor and has a downwardly facing surface of a convex shape with its transverse
curvature;
moving the first upper mold downwardly from an upper position to a lower position
adjacent the glass sheet on the conveyor and supplying upwardly directed gas lift jets to lift the glass
sheet from the conveyor and provide the initially forming of the glass sheet against the downwardly
facing surface of the first upper mold, and the first upper mold then being moved upwardly to its
upper position with the glass sheet supported by the first upper mold;
then moving the lower mold, which faces upwardly with a concave shape
complementary to the downwardly convex shape of the downwardly facing surface of the second
upper mold, horizontally within the heated chamber to a location above the conveyor and below the
first upper mold in its upper position with the glass sheet supported on the first upper mold and
subsequently moving the first upper mold downwardly and releasing the glass sheet onto the lower
mold and then moving the first upper mold upwardly;
subsequently moving the lower mold with the glass sheet thereon from below the first
upper mold to below the second upper mold in an upper position thereof and then moving the second
upper mold downwardly to a lower position thereof and drawing a vacuum at its downwardly facing
surface during the press forming of the glass sheet between the second upper mold and the lower
mold to provide the curvature of the glass sheet in transverse directions, whereupon the second upper
mold is moved upwardly to its upper position with the press formed glass sheet supported on the
second upper mold by the vacuum drawn at its downwardly facing surface; and
then moving a delivery mold to below the press formed glass sheet on the second
upper mold in its upper position whereupon the vacuum is terminated to release the glass sheet from
the second upper mold onto the delivery mold which is then moved out of the forming station for
delivery of the press formed glass sheet.
20. A three stage method for forming a hot glass sheet as in claim 19 wherein a
vacuum is drawn at the first upper mold to assist the gas lift jets in forming and supporting the glass
sheet on the first upper mold.
21. A three stage method for forming a hot glass sheet as in claim 20 wherein
after the glass sheet is moved upwardly from the conveyor and contacts the downwardly facing
surface of the first upper mold, the supply of the upwardly directed gas lift jets is terminated and the
vacuum then provides the sole support of the glass sheet on the first upper mold.
22. A three stage method for forming a hot glass sheet as in claim 2 1 wherein the
lower mold that receives the glass sheet from the first upper mold has a ring shape that supports the
glass sheet as it sags under gravity during its movement to the second upper mold for the press
forming.
23. A three stage method for forming a hot glass sheet as in claim 22 wherein a
support pad controls sagging of the supported hot glass sheet within the ring shape of the lower
mold.
24. A three stage method for forming the glass sheet as in claim 19 wherein at
least one press member assists the gas lift jets in initially forming the glass sheet against the
downwardly facing surface of the first upper mold.
25. A three stage method for forming a hot glass sheet as in claim 19 wherein the
delivery mold moves the press formed glass sheet from the forming station to a quench station for
quenching.
26. A three stage method for forming a hot glass sheet as in claim 18 wherein the
method is performed by:
conveying the hot glass sheet on a conveyor into a heated chamber of a forming
station to below the first upper mold at a pickup position thereof within the heated chamber above
the conveyor, with the first upper mold having a downwardly facing surface of a convex shape with
curvature in the first direction and straight line elements in the second direction transverse to the first
direction, with the first upper mold in the pickup position being spaced horizontally from the lower
mold and the second upper mold which is located above the lower mold, and with the second upper
mold located within the heated chamber above the elevation of the conveyor and having a
downwardly facing surface of a convex shape with its transverse curvature;
moving the first upper mold downwardly from an upper position to a lower position
adjacent the glass sheet on the conveyor and supplying upwardly directed gas lift jets to lift the glass
sheet from the conveyor and provide the initial forming of the glass sheet against the downwardly
facing surface of the first upper mold, the first upper mold then being moved upwardly to its upper
position with the glass sheet supported by the first upper mold, and a vacuum being drawn at the first
upper mold to support the glass sheet thereon;
then moving the first upper mold and the glass sheet supported thereon horizontally
within the heated chamber from the pickup position to a delivery position below the second upper
mold and above the lower mold which has an upwardly concave shape complementary to the convex
shape of the downwardly facing surface of the second upper mold;
subsequently terminating the vacuum drawn at the first upper mold in the delivery
position to transfer the glass sheet onto the lower mold, moving the first upper mold back to the
pickup position, moving the second upper mold downwardly to cooperate with the lower mold in the
press forming of the glass sheet, and then moving the second upper mold upwardly to its upper
position with the press formed glass sheet supported on the second upper mold by vacuum drawn at
its downwardly facing surface; and
then moving a delivery mold to below the press formed glass sheet on the second
upper mold in its upper position whereupon the vacuum is terminated to release the glass sheet from
the second upper mold onto the delivery mold which is then moved out of the forming station for
delivery of the press formed glass sheet.
27. A three stage method for forming a hot glass sheet as in claim 26 wherein the
lower mold has a ring shape that supports the glass sheet as it sags by gravity.
28. A three stage method for forming a hot glass sheet as in claim 27 wherein a
support pad controls sagging of the supported hot glass sheet within the ring shape of the lower
mold.
29. A three stage method for forming the glass sheet as in claim 26 wherein at
least one press member assists the gas lift jets in initially forming the glass sheet against the
downwardly facing surface of the first upper mold.
30. A three stage method for forming a hot glass sheet as in claim 26 wherein the
delivery mold moves the press formed glass sheet from the forming station to a quench station for
quenching.
31. For use in a three stage forming station for forming a hot glass sheet with
transverse curvature, the invention comprising:
a downwardly facing first upper mold, that has curvature in a first direction and
straight line elements in a second direction transverse to the first direction, for initially forming the
glass sheet with curvature in the first direction while maintaining straight line elements in the second
direction;
an upwardly facing lower mold, that has curvature in the first direction and permits
glass sheet curvature in the second direction, for receiving the glass sheet from the first upper mold
so the glass sheet sags under gravity along the second direction to have some curvature in the second
direction as well as curvature in the first direction; and
a downwardly facing second upper mold, that has transverse curvature and is
complementary to the upwardly facing lower mold, for cooperating with the lower mold to press
form the glass sheet with transverse curvature corresponding to the shapes of the lower mold and the
second upper mold.
32. The invention of claim 3 1 which further includes a delivery mold for
receiving the press formed glass sheet from the second upper mold for delivery.
33. The invention of claim 31 wherein the first and second upper molds each has a
downwardly facing surface of a downwardly convex shape.
34. The invention of claim 33 wherein the downwardly facing surface of each of
the first and second upper molds includes an associated array of vacuum holes.
35. The invention of claim 3 1 wherein the lower mold has an upwardly concave
shape.
36. The invention of claim 35 wherein the lower mold has a ring shape that
defines its upwardly concave shape and supports the glass sheet as it sags by gravity.
37. The invention of claim 36 wherein the lower mold includes a support pad
within its ring shape to control sagging of the glass sheet during movement from below the first
upper mold to below the second upper mold.
38. The invention of claim 31 wherein the first and second upper molds each has a
downwardly facing surface of a downwardly convex shape including an associated array of vacuum
holes, and the lower mold having a ring shape that defines an upwardly convex shape and supports
the glass sheet as it sags by gravity.
39. The invention of claim 3 1 wherein: the first upper mold has a downwardly
convex shape with an array of vacuum holes; the lower mold, that has a ring shape of an upwardly
convex shape that has curvature in the first direction and permits glass sheet curvature in the second
direction; and the second upper mold has a downwardly convex shape with an array of vacuum
holes.